RU2466192C2 - Method to convert end gas produced in metallurgical furnace, method to produce converted gas, device for reforming of end gas, device to convert end gas, method to cool end gas and device to cool end gas - Google Patents

Abstract

FIELD: oil and gas production.

SUBSTANCE: method is realised by addition of a recovery agent into end gas, containing a high-temperature gaseous carbon dioxide, leaving the metallurgical furnace, in order to provide interaction of gaseous carbon dioxide with a recovery agent to convert end gas. The recovery agent is added, when oxygen concentration in end gas is 1 vol.% or below. The process of end gas conversion is completed, when temperature of end gas makes 800°C or higher. To implement this method, two versions of the device are used.

EFFECT: reduced emissions of gaseous carbon dioxide together with higher heat content of end gas.

29 cl, 10 dwg, 4 ex

Description

The technical field to which the invention relates.

The invention relates to a method for converting exhaust gas generated in a metallurgical furnace, a method for producing converted gas, to a method for cooling exhaust gas generated in a metallurgical furnace, and also to an exhaust gas reforming device, an exhaust gas conversion device and an exhaust gas cooling device. In particular, the invention relates to a conversion method and to a method for cooling off-gas containing carbon dioxide gas formed in a metallurgical furnace, such as an oxygen converter or a reduction melting furnace, and to corresponding devices.

State of the art

In recent years, the reduction of carbon dioxide gas emissions has become an important issue in the framework of global environmental protection and the prevention of global warming. In metallurgical plants in particular, reducing carbon dioxide gas emissions is the most important issue related to firm viability. Traditional solutions have been proposed to reduce emissions. However, a full-scale technology to reduce carbon dioxide gas emissions has not yet been developed.

Typically, exhaust gases having a high temperature and containing a significant amount of carbon dioxide gas are generated in an oxygen converter, a reduction smelter, and the like in metallurgical plants. These flue gases contain carbon monoxide and hydrogen, in addition to gaseous carbon dioxide, and are therefore used as an energy source for various equipment in metallurgical plants. In addition, from the point of view of utilizing the heat content of such off-gas, typically the high-temperature off-gas is sent to the boiler to generate low pressure steam, and thus, off-heat is recovered. However, low pressure steam is not a valuable source of energy in metallurgical plants, and it is therefore highly desirable to find the chemical use of high temperature off-gas.

At the same time, it is known that various hydrocarbons, such as methane, and oxygen-containing compounds, such as methanol and dimethyl ether, react with gaseous carbon dioxide or water vapor and turn into carbon monoxide and hydrogen. As a waste heat recovery technology using this process, Japanese Patent Laid-Open Publication JP-A 2000-212615 discloses a method of attempting to “increase heat content” in which a gas and / or liquid containing hydrocarbons is mixed with a high temperature waste gas, containing carbon dioxide and / or water vapor generated in conversion equipment, such as an oxygen converter, to carry out the reforming process, while increasing the concentration of carbon monoxide as well as hydrogen in the exhaust gas, and thus, the latent heat of the exhaust gas increases.

In the method described in JP-A 2000-212615, when natural gas is pumped into the gas leaving the oxygen converter to carry out the reforming process according to the following equation (1), the temperature drops to about 375 ° C. at the time this process considered complete. However, as shown by the studies of the authors of the present invention, when the temperature of the completion of the reforming process is lower than 800 ° C, the problem of significant carbon formation arises, which leads to the deposition of carbon and dust in the gas recovery system of the oxygen converter. In addition, lowering the temperature of completion of the reforming process leads to a decrease in the efficiency of the reforming process, which leads to a decrease in the degree of conversion of carbon dioxide.

JP-A 5-117668 (1993) describes a method of attempting to increase the heat of an exhaust gas, in which coal is supplied to a location where the temperature of the gas leaving the oxygen converter is 600 ° C or higher, and the exhaust gas and coal are driven contact in countercurrent, to carry out the reforming process according to the following equation (2), and thus, to obtain carbon monoxide.

JP-A 5-117668 (1993) describes an excellent method since low-cost coal is used in the conversion process, but the problem is that non-combustible materials (SiO ₂ , AlO ₃ and the like) contained in the coal precipitate in the channel or precipitate in an oxygen converter, which leads to an increase in the amount of sludge.

JP-A 2-11715 (1990) discloses a method and apparatus for increasing the content of carbon monoxide and hydrogen in the exhaust gas, in which methane and water vapor are introduced in a place where the temperature of the exhaust gas generated in the oxygen converter is 1300 ° C or higher, thus, the steam reforming process is carried out according to the following equation (3):

The method disclosed in JP-A 2-11715 (1990) has the problem that when water vapor is added, CO and H _{2 are released} , the reforming process involving carbon dioxide does not proceed, and therefore this method does not contribute to the reduction CO ₂ .

As described above, in traditional technologies that increase the heat content, where the value of the latent heat of the exhaust gas increases (the heat of the endothermic reaction according to equation (1) is stored as the heat of combustion of the reaction products) by using the heat content of the exhaust gas containing gaseous carbon dioxide released from Metallurgical furnaces, such as an oxygen converter and a reduction smelter, have problems with carbon deposition and gas reactivity shaped carbon dioxide, the deposition of incombustible materials such as SiO _2, Al ₂ O ₃ and the like, and in addition, the gaseous carbon dioxide does not react, and there are no effects of improving the heat content of the exhaust gas and reducing carbon dioxide gas emissions.

Traditionally, a typical method for cooling high-temperature off-gas generated in a metallurgical furnace, such as an oxygen converter and a reduction melting furnace, is a mechanical method in which the off-gas is cooled using an aqueous cooling jacket (water cooling pipe) located in a channel (s) oxygen converter gas extraction systems, the waste heat being recovered using a heat exchanger (see publication of the above ki Japanese Patent JP-B 57-10930 and the publication of Japanese Laid-Open Patent Application JP-A 62-074018 (1987)).

However, in the case of the prior art described above, the channel, for example, the radiating part (channel), in the case of a gas extraction system of an oxygen converter, must have the structure of an aqueous cooling jacket. In this regard, problems arise, such as the need to construct a cooling device having a complex and large-sized structure, and in addition, it is necessary to mount a boiler in a heat utilization system. Moreover, the target exhaust gas (which must be cooled) is a gas leaving the metallurgical furnace and having a high temperature of 800 ° C or higher, and when trying to cool the exhaust gas using the above cooling device, materials that withstand high temperature.

A cooling method using atomized water is considered as another cooling method. However, it is necessary to construct a large-sized cooling device for atomization and contact between water and gas. In addition, the gas after cooling contains water vapor, which is a disadvantage in the case when the gas after processing will be used as combustible gas.

SUMMARY OF THE INVENTION

It is an object of the present invention to provide a method for converting high temperature off-gas. The technical result achieved in this invention is to reduce emissions of gaseous carbon dioxide, along with an increase in the heat content of the exhaust gas, due to the efficient process of reforming carbon dioxide, without deposition of carbon and non-combustible materials, and a device for this method.

To achieve this technical result, the present invention has developed a method for converting exhaust gas emitted from a metallurgical furnace, which comprises adding a reducing agent to an exhaust gas containing high temperature carbon dioxide gas leaving the metallurgical furnace, reacting carbon dioxide gas with a reducing agent, and reforming the exhaust gas where a reducing agent is added when the oxygen concentration in the exhaust gas is 1 vol.% or lower, and the reforming process ends when the temperature of the exhaust gas is 800 ° C or higher.

The reducing agent is selected from compounds such as fossil resources and compounds such as non-fossil resources. In the case of compounds such as fossil resources, the reducing agent is preferably selected from at least the group consisting of natural gas, liquefied petroleum gas, methane, ethane, light gasoline, raffinate, methanol, ethanol, dimethyl ether and diethyl ether. In the case of compounds such as non-fossil resources, the reducing agent is preferably selected from at least the group consisting of bioethanol, biodiesel and a mixture of bioethanol and biodiesel.

The high temperature exhaust gas discharged from the metallurgical furnace preferably has a temperature of from 800 to 1800 ° C, and more preferably from 1000 to 1800 ° C.

The high temperature off-gas emitted from the metallurgical furnace preferably has a carbon dioxide concentration of from 3 to 30 vol.%.

Preferably, the reducing agent is added when the concentration of oxygen in the exhaust gas is 0.5 vol.% Or less.

The reforming process is completed when the temperature of the exhaust gas is preferably from 800 to 1100 ° C, and more preferably from 850 to 1050 ° C.

Preferably, the reforming process is carried out at an exhaust gas temperature of 800 ° C. or higher, for a residence time of from 0.01 to 50 seconds, and more preferably is carried out at an exhaust gas temperature of 800 ° C. or higher, for a residence time of from 0.1 to 20 seconds.

In the case where the metallurgical furnace is an oxygen converter with a long residence time, it is desirable to add a reducing agent from the side pipe of the upper tube to blow air into the oxygen converter. In the case where the metallurgical furnace is an oxygen converter with a reduced residence time, preferably a reducing agent is added between the fence device and the primary dust collector in the gas recovery system of the oxygen converter.

In addition, the present invention relates to a method for producing a converted gas, which comprises adding a reducing agent to an exhaust gas containing high temperature carbon dioxide gas discharged from a metallurgical furnace, and reacting carbon dioxide gas with a reducing agent, wherein the reducing agent is added when the oxygen concentration in the exhaust gas gas is 1 vol.% or less, and the reforming process ends when the temperature of the exhaust gas is 800 ° C or higher.

Preferably, the reducing agent is at least one fossil resource type compound selected from the group consisting of natural gas, liquefied petroleum gas, methane, ethane, light gasoline, raffinate, methanol, ethanol, dimethyl ether and diethyl ether.

Preferably, the reducing agent is at least one non-fossil resource type compound selected from the group consisting of bioethanol, biodiesel and a mixture of bioethanol and biodiesel.

In addition, the present invention relates to an exhaust gas reforming apparatus in an oxygen converter gas extraction system in which a reducing agent is added to an exhaust gas containing high temperature carbon dioxide gas ejected from a metallurgical furnace, the carbon dioxide gas reacting with the reducing agent, and thus flue gas is converted; this device includes means for measuring the concentration of oxygen in the exhaust gas in the gas extraction system; a cross-section switching device for switching the cross-section of the exhaust gas pipelines under the action of the output signal of the concentration measuring means; means for measuring the temperature of the exhaust gas, the heat content of which increases as a result of the reforming process; flow rate control means that controls the amount of reducing agent added, operating under the influence of the output signal from the temperature measuring means and the output signal from the concentration measuring means; and a purge device for a reducing agent.

A preferred means of measuring concentration is as follows.

(A) A gas analyzer mounted on the inlet side of a primary dust collector in an oxygen converter gas recovery system.

(B) A gas analyzer mounted on the discharge side of a secondary dust collector in an oxygen converter gas recovery system.

(C) The analyzer (A), as well as the analyzer (B).

Preferably, the cross-section switching device is a valve that switches the gas cross-section, operating in accordance with the output signal of the oxygen concentration from the concentration measuring means, and selects the cross-section in the direction of the torch or gas holder.

Preferably, the temperature measuring means is a thermometer inserted on the input side of the primary dust collector in the oxygen converter gas extraction system.

Preferably, the flow rate control means of the reducing agent is triggered in accordance with at least one output of the concentration measuring means and the temperature measuring means.

It is desirable that the purge device of the reducing agent be mounted at least in one place between the upper tube for blowing air of the oxygen converter, or the barrier device in the gas extraction system of the oxygen converter, and the inlet side of the primary dust collector in the radiating part of the gas extraction system.

In addition, the present invention relates to a device for converting exhaust gas emitted from a metallurgical furnace, which is used for reforming the exhaust gas during the interaction between the carbon dioxide gas contained in the exhaust gas and the reducing agent by adding a reducing agent to the high-temperature exhaust gas emitted from metallurgical furnace, where the nozzle for injecting a reducing agent having the structure of a double concentric pipe, soda neighing the outer pipe for injecting diluted nitrogen and the inner pipe for injecting a reducing agent, mounted together by insertion into the outer pipe, is installed in the exhaust gas channel of the gas extraction system of the metallurgical furnace.

The metallurgical furnace is preferably an oxygen converter.

It is desirable that the exhaust gas channel contains a lower hood, an upper hood and a radiating portion in a gas recovery system.

Preferably, at least one nozzle for injecting a reducing agent is mounted in a circumferential direction below the radiative portion of the exhaust gas channel.

It is preferred that the nozzle for injecting the reducing agent spray the reducing agent from the central opening of the inner tube, the diluted nitrogen being ejected from the annular channel formed between the inner tube and the outer tube.

The outer pipe may be a pipe for blowing diluted nitrogen during an emergency stop by diluting the exhaust gas generated in a metallurgical furnace integrated in the exhaust gas channel. The diluted nitrogen discharged by the jet from the annular channel of the outer pipe may be diluted with nitrogen for emergency shutdown by diluting the exhaust gas generated in the metallurgical furnace.

Preferably, the reducing agent contains at least one fossil resource type compound selected from the group consisting of natural gas, liquefied petroleum gas, methane, ethane, light gasoline, raffinate, methanol, ethanol, dimethyl ether and diethyl ether.

Preferably, the reducing agent comprises at least one non-fossil resource type compound selected from the group consisting of bioethanol, biodiesel and a mixture of bioethanol and biodiesel.

Another objective of the present invention is to develop a convenient method for cooling high-temperature off-gas, with a temperature of 800 ° C or higher, using a chemical process in which the heat content of metallurgical off-gas is used without building large cooling equipment, and a cooling device for this method.

To achieve the above objectives, the present invention has developed a method of cooling the exhaust gas generated in the metallurgical furnace, which consists in adding a reducing agent to the exhaust gas generated in the metallurgical furnace and containing high temperature gases - carbon monoxide and carbon dioxide, to cause an endothermic reaction between the reducing agent and carbon dioxide in the exhaust gas; and cooling of the exhaust gas itself through an endothermic reaction.

Preferably, the reducing agent is purged in the channel up to the inlet side of the dust collector, an endothermic reaction occurs in the channel, and the reaction is completed when the gas temperature after the reaction is 800 ° C. or higher. This channel is preferably an emitting part between the upper cap of the oxygen converter and the inlet side of the primary dust collector.

Preferably, the off-gas is an off-gas from an oxygen converter containing converter dust emitted from the oxygen converter. The catalyst for the endothermic reaction are dust particles of iron oxide in the dust of the converter.

Preferably, the reducing agent is at least one selected from the group consisting of natural gas, liquefied petroleum gas, methane, ethane, light gasoline, raffinate, methanol, ethanol, dimethyl ether and diethyl ether.

In addition, the present invention provides a device for cooling an exhaust gas generated in a metallurgical furnace, which comprises a nozzle for injecting a reducing agent that enters an endothermic reaction with carbon dioxide gas in a high temperature exhaust gas containing carbon dioxide and carbon monoxide that is mounted in one or several places of the channel part in the oxygen converter gas extraction system.

Preferably, a portion of the channel is located between the upper tube for blowing air of the oxygen converter or the lower cap in the oxygen converter of the gas recovery system and the inlet side of the primary dust collector.

The off-gas is preferably an off-gas from an oxygen converter that contains converter dust emitted from the oxygen converter. The catalyst for the endothermic reaction are dust particles of iron oxide in the dust of the converter.

The interaction between the gaseous carbon dioxide in the exhaust gas and the reducing agent is preferably an endothermic reaction, the catalyst of which is the dusty particles of iron oxide in the dust of the converter.

Preferably, the reducing agent is at least one selected from the group consisting of natural gas, liquefied petroleum gas, methane, ethane, light gasoline, raffinate, methanol, ethanol, dimethyl ether and diethyl ether.

Brief Description of the Drawings

Figure 1 is a schematic drawing of an exhaust gas conversion device of a converter according to a first embodiment.

The figure 2 shows a graph of the degree of conversion of CO ₂ and CH ₄ and the amount of carbon according to the 1st variant implementation from the temperature of the output of the modeling gas, which increases the heat content.

The figure 3 shows a graph of the degree of conversion of CO ₂ and CO ₄ and a reduced heating value according to the 1st embodiment, on the oxygen concentration in the modeling gas, which increases the heat content.

Figure 4 is a schematic drawing of an exhaust gas conversion device of an oxygen converter according to the 1st embodiment.

Figure 5 is a schematic drawing of an exhaust gas conversion device of an oxygen converter according to the 2nd embodiment.

Figure 6 shows a cross-sectional view of a nozzle for injecting a reducing agent according to the 2nd embodiment.

Figure 7 is a schematic drawing of an exhaust gas cooling device of an oxygen converter according to a 3rd embodiment.

Figure 8 is a schematic drawing of an exhaust gas cooling device equipped with a blowing agent injection unit according to the 3rd embodiment.

Figure 9 is another schematic drawing of an exhaust gas cooling device equipped with a blowing agent injection unit according to the 3rd embodiment.

The figure 10 shows a graph of the dependence of the rate constant on the reaction temperature for the channel of the oxygen converter according to the 3rd embodiment.

Embodiments of the invention

Embodiment 1

Embodiment 1 is a method for converting a high-temperature off-gas to achieve an effective increase in the heat content of the off-gas and to reduce carbon dioxide gas emissions by fully developing the carbon dioxide gas reforming process without depositing carbon, non-combustible materials and the like, in the channel. Specifically, a reducing agent is added to the exhaust gas at a high temperature of the order of 800 ° C. or higher, and preferably 1000 ° C. or higher, leaving the metallurgical furnace. Further, the metallurgical furnace is described by the example of an "oxygen converter". The high temperature off-gas is hereinafter referred to as “off-gas”. The addition of a reducing agent causes a reforming process to occur between the carbon dioxide gas contained in the exhaust gas and the reducing agent, such as natural gas, as shown in equation (1)

The heat of the exhaust gas is increased by controlling any of the factors: the added amount, the period of addition and the place of addition of the reducing agent, so that the start time for adding the reducing agent occurs when the oxygen concentration in the exhaust gas becomes 1 vol.% Or less, and the reforming process is completed when the temperature of the exhaust gas is 800 ° C or higher.

Typically, the exhaust gas emitted from the oxygen converter contains from about 10 to 20 vol.% CO ₂ and from about 50 to 80 vol.% CO, has a calorific value of from about 1,500 to 2,000 kcal / nm ³ , and the neck temperature during operation is approximately from 1200 to 1800 ° C. In the 1 m embodiment, an increase in the heat content of the exhaust gas and a decrease in carbon dioxide gas emissions are achieved simultaneously by adding a reducing agent, such as natural gas, to the exhaust gas of the oxygen converter and carrying out the reforming process according to equation (1) between the reducing agent and the carbon dioxide gas. In other words, since the exhaust gas with a high heat content, that is, the converted exhaust gas, is used as various heat sources in metallurgical plants (for combustion), gaseous carbon dioxide is finally released. However, the amount of auxiliary fuel, such as boiler fuel used in metallurgical plants, can be reduced in accordance with the increase in heat content, and as a result, carbon dioxide gas emissions can be reduced in an appropriate amount.

Figure 1 is a schematic drawing of a system for extracting gas from an oxygen converter to explain an exhaust gas conversion method according to a first embodiment of the invention. As shown in the drawing, the exhaust gas generated in the oxygen converter 1 is discharged through the hollow cylinder 2, the lower hood 3, the upper hood 4, the primary dust collector (wet dust collector) 5, the secondary dust collector 13, and the like, and the concentration is measured along the gas oxygen using a gas analyzer 6 provided on the output pipe (downstream) of the secondary dust collector 13, in continuous, semi-continuous or periodically. When the oxygen concentration in the exhaust gas is more than 1 vol.%, The control valve 7 controlling the addition (introduction) of the amount of reducing agent during the reforming process is closed, and at the same time, the valve 8 switching the gaseous flow channels is closed, so that the exhaust gas goes towards the torch 9.

Figure 1 shows an embodiment where a gas analyzer 6 is provided on the outlet of the secondary dust collector 13. However, the gas analyzer 6 may be located on the inlet side of the primary dust collector 5, which is adjacent to the thermometer 10, or the analyzer 6 may be provided as on the intake side of the primary dust collector. 5 and on the outlet pipe of the secondary dust collector 13.

The type of gas analyzer 6 is not specifically specified, but an analyzer is preferably used that can measure the concentration of carbon dioxide gas (flow rate) and the flow rate of the exhaust gas, in addition to the oxygen concentration. The flow rate of gaseous carbon dioxide can be determined from the measurement data of the gas analyzer 6, and therefore, it is possible to determine the amount of reducing agent introduced in the reforming process.

For example, when the oxygen concentration decreases to 1 vol.% Or less and the temperature of the exhaust gas, measured using a thermometer 10 located on the inlet side of the primary dust collector, is 800 ° C or higher, a valve 8 opens, switching the gaseous flow channels, so that the exhaust gas is directed towards the gas holder (not shown), and at the same time, valve 7 is opened, and, for example, a reducing agent for the reforming process is added through the side pipe of the upper tube for injecting oxygen 11. Perhaps in there is a need for continuous measurement of gas temperature using a thermometer 10, and the introduced amount of the reducing agent and / or the place of addition (injection) of the agent is regulated so that the reforming process is completed at the temperature of the exhaust gas with high heat content of 800 ° C or higher.

A reducing agent is added when the oxygen concentration in the exhaust gas is 1 vol.% Or less. The reason for this limitation is outlined below. When there is more than 1 vol% oxygen in the exhaust gas, hydrogen gas in the exhaust gas and hydrogen atoms in the reducing agent are able to interact with oxygen to form water vapor, and the reforming process involving water vapor proceeds due to the addition of the reducing agent. As a result, the degree of conversion of gaseous carbon dioxide is reduced, which reduces the effect of reducing the content of gaseous carbon dioxide. When adding a reducing agent at a time when the concentration of oxygen in the exhaust gas is more than 1 vol.%, There is a danger of ignition and explosion.

Preferably, the concentration of oxygen in the exhaust gas approaches zero whenever possible in order to efficiently carry out the carbon dioxide gas reforming process represented by equation (1). However, the administration of up to about 1 vol.% Oxygen is an acceptable range. The reason for this limitation is outlined below. The system for extracting gas from an oxygen converter is designed so that air is supplied to a small extent. Therefore, it takes a long time to reduce the oxygen concentration to the detection limit or less. If a reducing agent cannot be added during this period, then not only does the effect of increasing the heat content decrease, but the burning of gas on the flare 9 also increases, which adversely affects the increase in emissions of gaseous carbon dioxide. Therefore, a necessary condition of the 1st embodiment is that the concentration of oxygen in the exhaust gas is 1 vol.% Or less when the addition of the reducing agent begins.

In the 1st embodiment, it is important that the amount of reducing agent added and / or the place of addition of the agent is controlled so that the reforming process is completed when the temperature of the cooled reforming exhaust gas, i.e., the exhaust gas in a state of increased heat content, is in the form of latent heat of combustion of the reaction product , is 800 ° C or higher due to the reforming process using the heat content of the exhaust gas. Thus, it is required that the temperature of the exhaust gas at the time the reforming process is completed is 800 ° C. or higher, and more preferably this temperature is 850 ° C. or higher. The reason for this limitation is outlined below. When the temperature of the exhaust gas at the time of the completion of the reforming process is less than 800 ° C, not only carbon, such as fly ash, is deposited in the channel, but also the conversion of gaseous carbon dioxide is reduced, which leads to a deterioration in the effect of increasing heat content, as well as the effect of reducing the emission of gaseous carbon dioxide.

In other words, the idea of the first embodiment is not to regulate the reforming process due to the flow rate of carbon dioxide gas in the exhaust gas, but that the increase in the heat content of the exhaust gas is controlled by the temperature of the exhaust gas (> 800 ° C) by the time the process is completed reforming. The reason for this limitation is outlined below. Typically, an oxygen converter is a batch furnace, and the temperature characteristic of the exhaust gas fluctuates significantly when abnormal blowing occurs, such as an increase in the iron oxide content of molten steel. In other words, the method of the present invention conveniently eliminates the resulting fluctuations in the temperature of the exhaust gas.

For the above reason, the added amount and place of addition of the reducing agent is determined so that the reforming process is completed when the temperature of the exhaust gas with high heat content (stored thermal energy) is 800 ° C or higher. For example, in the case of a reducing agent, the added amount preferably varies depending on the flow rate of the carbon dioxide gas, such as the reducing agent, the stoichiometry of the carbon dioxide gas reforming process, the temperature of the exhaust gas at the point of addition and the residence time of the gas from the point of addition of this agent to thermometer 10.

The term “completion of the reforming process” as defined above means that the interaction between the added reducing agent, such as methane, and gaseous carbon dioxide in the exhaust gas proceeds near equilibrium in such an atmosphere. To bring the reaction to full equilibrium theoretically, an infinite residence time is required. Therefore, the term near equilibrium cannot be defined unambiguously. For this reason, in the 1st embodiment, the term “completion of the reforming process” is used, defined by increasing the concentration of hydrogen gas, as described hereinafter, with respect to the concentration of hydrogen in the exhaust gas prior to reforming.

For example, with decarburization purging, the hydrogen concentration in the exhaust gas is usually low - about 1 vol.%, And due to reforming, the hydrogen concentration in the exhaust gas increases from about 2 to 25 times, compared with the hydrogen content before reforming. Therefore, it is easy to control. For this reason, with decarburization blowing, it is preferable to determine "completion of the reforming process" by increasing the content of gaseous hydrogen by two or more times compared to the hydrogen content before reforming.

On the other hand, in dephosphoric purge, when the exhaust gas flow rate is usually low and the exhaust gas extraction rate is also low, in recent years this operation is carried out with the introduction of plastic waste or the like in order to increase the exhaust gas flow rate in order to increase the extraction rate . In this case, the concentration of gaseous hydrogen in the exhaust gas prior to reforming is from about 10 to 15 vol.% Due to the evolution of hydrogen from additional materials, such as plastic waste. Moreover, liquefied petroleum gas (LPG) or the like is supplied to the bottom-blowing converter as cooling gas to prevent damage to the tuyeres, and for this reason, a large amount of hydrogen gas is released upon decomposition of the LPG. In the case of the release of such a large amount of hydrogen gas, a quantitative increase in the concentration of hydrogen in the exhaust gas after reforming is from about 1 to 5 vol.% Compared with the concentration of hydrogen gas before reforming. Therefore, in dephosphoric purge and bottom purge of the furnace, it is preferable to define “completion of the reforming process” by increasing the gaseous hydrogen content by 1 vol.% Or more, compared with the hydrogen content before reforming.

The temperature of the exhaust gas decreases as the reforming process proceeds. Therefore, the term completion of the reforming process, when the temperature of the exhaust gas after 800 ° C or higher, has a physical meaning. On the other hand, the hydrogen atom in the added reducing agent is converted to hydrogen gas through a reforming process. In a method where the off-gas is recovered as an energy source, analysis of the off-gas composition is essential, and controlling the completion of the reaction by the concentration of hydrogen gas is important both for chemistry and as an operational control.

In the above description, the stoichiometry of the carbon dioxide gas reforming process means that (X-Z) moles of carbon dioxide gas interact with 1 mole of reducing agent, as shown in the following equation (4). Typically, the introduction of an equivalent amount of a reducing agent is preferred. However, in the case where the temperature of the exhaust gas at the point of addition is not high enough, as compared to 800 ° C, that is, the lower limit of the reaction completion temperature at the position of thermometer 10, preferably the reducing agent is added in an amount less than an equivalent amount. For example, in the case where the concentration of gaseous carbon dioxide in the exhaust gas of the converter is 15 vol% and methane is used as a reducing agent, the value (X-Z) = 1 corresponds to an equivalent amount. Therefore, when the temperature of the exhaust gas at the inlet is 1600 ° C or higher, methane is added in an amount equivalent to the amount of carbon dioxide gas. On the other hand, when the temperature of the exhaust gas at the inlet is 1200 ° C., the corresponding amount added is approximately 2/3 of the equivalent amount. As used herein, the term “appropriate addition amount” means an amount of a reforming agent terminated at a position where the temperature of the high heat exhaust gas is 800 ° C. or higher.

In the reforming process corresponding to equation (1) or the following equation (4), the lower concentration range of gaseous carbon dioxide does not correspond to the theoretical one. However, it is obvious that the effect of purging with a reducing agent, that is, the effect of increasing heat content, decreases with decreasing concentration of carbon dioxide gas. The reality is that the effect of increasing the heat content is negligible when the concentration of gaseous carbon dioxide is less than 3 vol.%, And it is unprofitable. On the other hand, the local reaction rate increases significantly near the purge of the reducing agent with increasing concentration of carbon dioxide gas. As a result, the local temperature of the exhaust gas is significantly reduced and there is a likelihood of damage to the oxygen converter gas extraction system due to heat stroke and the like. The concentration of gaseous carbon dioxide above 30 vol.% Is undesirable from the point of view of stable operation of the oxygen converter and maintenance of equipment:

The residence time of the gas from the place of addition of the reducing agent to the position of the thermometer 10 is preferably in the range from 0.01 to 50 seconds, and more preferably from 0.1 to 20 seconds. The residence time is 0.01 seconds or more due to the provision of sufficient interaction time to complete the reforming process. There is no leakage of a reducing agent for economic reasons. The reason that the gas dwell time is 50 seconds or less is because 50 seconds or less is the upper limit of the time for which the reaction is complete, and there is no need for a long channel, and the costs of the waste gas equipment can be reduced.

For example, in order to add methane in an equivalent amount to carbon dioxide gas in the case where the concentration of carbon dioxide gas in the off-gas converter is 15 vol%, methane is used as the reducing agent and the temperature of the off-gas at the point of addition is 1600 ° C or higher , with a residence time of 0.5 to 5 seconds, the reforming process can be completed, and the gas temperature at the time of completion of the reaction is 800 ° C or higher.

Preferably, the place of addition of the reducing agent is determined taking into account the residence time of the gas and the temperature of the exhaust gas at the place of addition. For example, in the case where the residence time is from 0.01 to 50 seconds, and preferably from 0.1 to 20 seconds, as described above, the place of addition of the reducing agent is preferably chosen where the exhaust gas has the highest temperature.

The figure 1 shows an example of the introduction of a reducing agent through the side tube of the upper pipe for blowing air. Thus, the reason that the tube 11 is designated in the 1st embodiment as the place of addition is because the tube 11 is a mandatory equipment when operating the converter with an overflow, and it is convenient to use it to add a reducing agent. However, the place of addition is not limited only to the side pipe in the 1st embodiment. For example, a reducing agent may be introduced through a nozzle that is mounted in a hollow cylinder 2 or in the upper part of the upper cap 4 and the lower cap 3.

Specifically, in the case of a relatively small amount of carbon dioxide gas in the off-gas converter, the reaction time may be short. Therefore, a reducing agent can be added at a location that is even higher than the lower cap 3 or the upper cap 4, for example, at the lower end of the first radiating part. The place of addition is not limited to one point, and the agent can be added from many points. For example, a reducing agent may be added at two places in the side pipe tube 11 and the upper part of the lower cap 3.

Preferably, as a reducing agent that can be used in the first embodiment, at least one fossil resource type compound selected from materials such as natural gas, liquefied petroleum gas, methane, ethane, light gasoline, raffinate, methanol is used ethanol, dimethyl ether and diethyl ether. Of these, natural gas, liquefied petroleum gas, light gasoline, raffinate and diethyl ether are preferred, since they have good reactivity with respect to carbon dioxide gas, are cheap and readily available in large quantities.

As the reducing agent, organic compounds such as non-fossil resources can be used along with or instead of compounds such as fossil resources. The use of organic compounds such as non-fossil resources is particularly preferred due to the fact that the reforming process is carried out using a carbon-neutral reducing agent, in addition to the fact that the heat content of the exhaust gas is increased due to the reforming process of gaseous carbon dioxide, and this can make a significant contribution in reducing carbon dioxide gas emissions. Examples of organic compounds such as non-fossil resources include bioethanol, biodiesel and mixtures thereof.

In the case of using a reducing agent, which is a gas at room temperature, such as natural gas or liquefied petroleum gas, a nozzle suitable for gas purging is used, the shape and number of nozzles being not particularly limited. In the case where the reducing agent is a liquid at room temperature, such as raffinate, bioethanol or biodiesel, this reducing agent can be sprayed and introduced, or it can be gasified and introduced in gaseous form. When sprayed, the droplet diameter of the agent is such as to provide effective contact with carbon dioxide gas, and is preferably from 0.01 to 1000 μm, and more preferably from 0.1 to 100 μm.

When using a liquefied gas, such as dimethyl ether, or a liquefied gas of an organic compound such as a non-fossil resource, the reducing agent can be pre-gasified and introduced as a gas, or the reducing agent can be supplied in the form of a liquid, and the reducing agent is gasified near the nozzle or in the nozzle. In this case, the gasification of the reducing agent near the nozzle or in the nozzle cools the nozzle due to the heat of vaporization, which is preferred to protect the nozzle.

In addition, the present invention provides a method for producing a converted gas, which comprises adding a reducing agent to an exhaust gas containing high temperature carbon dioxide gas discharged from a metallurgical furnace, whereby carbon dioxide gas interacts with the reducing agent, wherein the reducing agent is added when the oxygen concentration in the exhaust gas is 1 vol.% or less, and the reforming process is completed when the temperature is from odyaschego gas is 800 ° C or higher.

As used herein, the term "converted gas" as a product means gas generated from the completion of a reforming process between gaseous carbon dioxide in the exhaust gas and a reducing agent. The term “completion of the reforming process” was previously defined. Therefore, in a decarburization purge, a gas in which the hydrogen gas content is doubled or more than the amount before reforming is called “converted gas”, which is a product of the present invention. In a dephosphoric purge or in a converter with a lower purge, a gas in which the hydrogen content increases by 1 vol.% Or more, compared with the amount before reforming, is called "converted gas", which is a product of the present invention.

In a "converted gas", the concentration of gaseous carbon dioxide decreases and the concentration of hydrogen and carbon monoxide increases due to the reforming process. Therefore, the heat of combustion of the gas increases from about 5 to 30% compared with the original exhaust gas. However, the calorific value is not a measurable quantity, but is usually a value calculated from the composition of the gas. Therefore, the "converted gas" is preferably determined by the change in the concentration of gaseous hydrogen, as described previously.

Preferably, the reducing agent is at least one fossil resource type compound selected from the group consisting of natural gas, liquefied petroleum gas, methane, ethane, light gasoline, raffinate, methanol, ethanol, dimethyl ether and diethyl ether.

Preferably, the reducing agent is at least one non-fossil resource type compound selected from the group consisting of bioethanol, biodiesel and a mixture of bioethanol and biodiesel ;.

In the implementation of the above method of converting the exhaust gas, in the first embodiment, as a conversion device accelerating the reforming process between the carbon dioxide gas contained in the exhaust gas and the reducing agent, there is provided a device for converting the exhaust gas generated in a metallurgical furnace, which includes a measuring means the concentration of oxygen in the exhaust gas in the gas recovery system of the oxygen converter; a cross-section switching device that switches the cross-section in the line of the exhaust gas pipeline in accordance with the oxygen concentration in the reforming exhaust gas based on the output signal from the concentration measuring means, that is, depending on whether the oxygen concentration is more than 1% or less than 1 vol.%; means for measuring the temperature of the reforming effluent gas having an increased heat content due to the reforming process; flow rate control means that controls the addition (introduction) of the amount of a reducing agent and is driven from the output of the temperature measuring means and from the output of the concentration measuring means; and a blowing agent with a reducing agent for adding a reducing agent, which is controlled by means of flow rate control means, to the exhaust gas at a predetermined location, for example, from a nozzle mounted in the side of the pipeline of the upper air injection tube or in a hollow cylinder.

In the first embodiment, the gas analyzer 6, mounted on the inlet side of the primary dust collector 5 or secondary dust collector 13, for example, inside the passageway of the second dust collector (downstream), or in both places, is used as a means of measuring concentration; a device in which a valve 8, a switching channel for a gaseous flow, is controlled in such a way that it opens or closes under the action of the output signal about the oxygen concentration from the gas analyzer 6, is mounted in the branched part of the passage section in the direction of the torch 9 and the passage section to the gas holder (not shown), so that any of the directions to the torch 9 and to the gas holder can be selected, this device is used to switch the flow area; and the temperature measuring means consists of a thermometer 10 mounted on the boundary with the radiating part of the output channel, which is mated with the input side of the primary dust collector 5. A gas flow meter 15 measuring the flow rate of the exhaust gas is preferably provided on the output side of the secondary dust collector in the gas recovery system of the oxygen converter.

The control system of the above conversion device is shown by the dashed line in figure 1. This diagram shows only one valve 7 that controls the flow rate for supplying a reducing agent, and this valve is driven by one (or two) output signal from the gas analyzer 6 for measuring oxygen concentration and an output signal from a thermometer 10 measuring the temperature. However, two control valves (not shown) can be used that are separately controlled by the computing device 12, and the valve 8, the switching channel for the gaseous stream, can be driven by the output signal from the gas analyzer 6, and at the same time can be controlled from the output signal thermometer 10 using another control valve provided on the output side of the switching valve.

Example 1

In this example, an experiment was conducted in which natural gas was added to the exhaust gas from the top cap 4 using a 300-ton top-purged converter. When natural gas is not blown in, the exhaust gas has a flow rate of 79,000 nm ³ / hr and the composition of the gas is CO: 50 vol.%, CO ₂ : 15 vol.%, H ₂ : 1 vol.% And N ₂ : 34 vol.% . This means that the amount of CO ₂ emitted is 11850 nm ³ / h.

This corresponds to a mass of 122,000 tons of gaseous carbon dioxide during the year. Natural gas is added in an amount of 11850 nm ³ / hour, equal to the flow rate of CO ₂ . The content of CH ₄ in natural gas is 92 vol.%. Therefore, the molar ratio between CO ₂ and CO ₄ can be estimated approximately equal to 1: 1. The temperature of the exhaust gas near the mouth of the Converter is about 1700 ° C.

The flue gas meter 15 and gas analyzer 6 are mounted on the output side of the secondary dust collector (dust collector) 13, and the thermometer 10 is mounted on the inlet side of the primary dust collector (wet dust collector), so that the amount of added natural gas can be controlled by the oxygen concentration in the exhaust gas and by the temperature of the reforming off-gas. Oxygen seeps immediately after the start of purging. Therefore, the addition of natural gas begins when the oxygen concentration becomes equal to 1 vol.% Or less, while determining the temperature, flow rate and composition of the reforming waste gas. As a result, the exhaust gas has a temperature of 980 ° C and a flow rate of 114400 nm ³ / h, and has a composition of CO: 55 vol.%, CO ₂ : 0.1 vol.%, N ₂ : 21 vol.%, N ₂ : 23.5 vol.%, CH ₄ : 0.1 vol.% and the amount of O ₂ less than 0.1 vol.%. Given equilibrium, the reforming process ends at the point of temperature measurement. The formation and deposition of dust, such as carbon in the channel, is not observed, and the exhaust gas can be reformed without any difficulty. The amount of hydrogen gas increases by 21 times due to the reforming process, and the reforming process is completed at 980 ° C. The residence time of the gas from the point of addition of natural gas to the temperature measuring point is about 4.5 seconds.

The heat of combustion of the exhaust gas before reforming is 1537 kcal / nm ³ , and the heat of combustion of the gas after reforming is 2220 kcal / nm ³ , that is, the increase in heat content is 44% in the standard volume of exhaust gas. The exhaust gas flow rate increases by 1.45 times. Thus, it is obvious that a very large amount of gas with a high heat content is obtained. However, this increase in heat content includes the amount of heat introduced with natural gas as a reducing agent. Therefore, the degree of true increase in heat content, with the exception of the amount of heat introduced, is 29%. An estimate of the reduction of carbon dioxide gas emissions due to a decrease in the need for auxiliary fuel and corresponding to this partial increase in heat content gives a value of 105,000 t / year.

Comparative Example 1

The experiment with the addition of a reducing agent is carried out in the same manner as in example 1, except that the place of addition of natural gas is transferred to the point where the temperature of the exhaust gas is 1300 ° C, that is, downstream than in example 1. Outgoing the gas after reforming has a temperature of 770 ° C, and has a composition of CO: 47 vol.%, CO ₂ : 4 vol.%, N ₂ : 20 vol.%, N ₂ : 23.5 vol.%, CH ₄ : 0.3 vol. % and O ₂ : less than 0.1% vol. Thus, the loss of CO ₂ is 4 vol.%. Moreover, carbon is formed in an amount of about 4 wt.%, Which is deposited in the channel. The amount of gaseous hydrogen increases by 20 times due to the reforming process, and the reforming process is completed at 770 ° C. The residence time of the gas from the point of addition of natural gas to the point of temperature measurement is approximately 3.5 seconds.

Example 2

In this example, an experiment was conducted in which a simulating laboratory furnace was used, which includes an aluminum oxide tube having an inner diameter of 12 mm and a length of 5 m. In this modeling experimental furnace, the gas inlet pipe is mounted on the inlet flange of the aluminum oxide tube, the methane gas injection tube has an outer diameter of 3 mm, and the thermocouple protective cover is mounted on the inlet flange. The methane gas addition site is located 1.5 m from the inlet flange, the gas temperature measuring means is 1 m away from the inlet flange, the methane gas tube and thermocouple protective cover passing through this flange. The thermocouple input assembly and the gas cooling device using cooling water are mounted on the output flange, and the summing gas flow meter and gas analyzer are mounted on the output side of the gas cooling device. An electric heater coil is wound around the entire aluminum oxide tube. The current is supplied only to 1 meter of the heater on the inlet side, and this part is designed as a heating zone for the modeling gas of an oxygen converter. Electric current is not supplied to the part of the heater located below the heater, and this part plays the role of an adiabatic reaction zone. Methane is introduced at a point approximately 0.5 m below the heating zone described above. Therefore, the actual length of the adiabatic reaction zone is 3.5 m.

The modeling gas of the oxygen converter is obtained by mixing CO: 50 vol.%, CO ₂ : 15 vol.%, H ₂ : 1 vol.% And N ₂ : 34%. The flow rate of the modeling gas is set equal to 1 l / min, the flow rate of methane gas is set to 150 ml / min, which is equivalent to the flow rate of CO ₂ , and the experimental reforming process is carried out with varying the temperature of the heating zone in the range of 1800 ° C, 1500 ° C, 1300 ° C, 1100 ° C and 900 ° C. In this example, as a result of measuring the temperature at the outlet of the adiabatic reaction zone using a thermocouple mounted on the outlet flange, it was found that the outlet temperature is 1060 ° C, 840 ° C, 775 ° C, 735 ° C and 705 ° C, respectively for the temperature in each heating zone 1800 ° С, 1500 ° С, 1300 ° С, 1100 ° С and 900 ° С. The corresponding concentration of hydrogen gas at the outlet is 21 vol.%, 20 vol.%, 19 vol.%, 18 vol.% And 17 vol.%. The gas residence time in the adiabatic zone is from 2 to 6 seconds.

The degree of conversion and material balance are calculated according to the flow rate of the outgoing gas and analysis of the gas composition. Carbon formation is evaluated by visual inspection of the internal channel of the tube after the experiment. Due to the laboratory scale of the experiment, it is difficult to quantify carbon production. Therefore, the amount of carbon formed was estimated by the difference between the material balance data for carbon atoms (%) and 100%. In figure 2, the temperature at the outlet of the furnace (in figure 2 is indicated as the temperature of the modeling gas with increased heat content) is shown on the abscissa axis, and the degrees of conversion of CO ₂ and CH ₄ are shown on the left on the ordinate axis, and the amount of carbon formed is shown on the right on the ordinate axis. As can be seen from figure 2, the formation of carbon is practically not observed in the experiment, when the temperature of the modeling gas with high heat content is 1060 ° C (in this case, the temperature of the heating zone is 1800 ° C). However, carbon formation becomes significant when the temperature of the simulated gas with increased heat content is less than 800 ° C (in this case, the temperature of the heating zone is from 1300 ° C to 900 ° C).

From figure 2 it is obvious that by adjusting the reforming process so that the process ends when the temperature of the exhaust gas, with increased heat content due to the reforming process, is 800 ° C. or higher, a high degree of carbon dioxide gas conversion and a significant the effect of increasing heat content, and in addition, it is possible to suppress the process of carbon formation, which is the cause of clogging of the channel.

Example 3

The experimental reforming process is carried out in the same manner as in example 2, except that gases are used that simulate the composition of the converter gas, as shown in table 1, and the temperature of the heating zone of the modeling gas is 1600 ° C. In all cases, the temperature of the simulated gas with high heat content is 800 ° C or higher. In figure 3, the oxygen concentration in the modeling gas is shown on the abscissa axis, the degrees of conversion of CO ₂ and CH ₄ are shown on the left on the ordinate axis, and the value of lower calorific value calculated by the gas composition is shown on the right on the ordinate axis. As can be seen from figure 3 and table 1, in experiments No. 3-4 to No. 3-6, where the oxygen concentration in the modeling gas is more than 1%, the degree of conversion of CH ₄ is high, however, the degree of conversion of CO _{2 is} significantly reduced and it turns out low calorific value gas. This means that as a result of the formation of H ₂ O due to the presence of oxygen in the modeling gas, the process of reforming of CH ₄ with the participation of water proceeds. For ease of comparison, Table 1 shows the concentration of hydrogen gas at the outlet.

Table 1 (vol.%) Experiment No. 3-1 3-2 3-3 3-4 3-5 3-6 With fifty fifty fifty fifty fifty fifty CO ₂ fifteen fifteen fifteen fifteen fifteen fifteen H ₂ one one one one one one N ₂ 34 33.5 33 32,5 32 29th O ₂ 0 0.5 one 1,5 2 5 H ₂ at the exit 21 21 21 21 20.5 eighteen

As can be seen from figure 3, it was found that a high degree of conversion of gaseous carbon dioxide and a significant effect of increasing heat content by controlling the start of adding a reducing agent at a time when the oxygen concentration in the exhaust gas is 1 vol.% Can be achieved.

Example 4

In this example, an experiment was performed using bioethanol as a reducing agent, gasified by heating in a heater, using a simulating laboratory furnace containing the same aluminum oxide tube as in Example 1. In this modeling experimental furnace, the gas inlet is mounted on the inlet flange of the alumina tube, the tube for introducing vaporous bioethanol has an outer diameter of 3 mm, and a thermocouple protective cover is mounted on the inlet flange. A tube for adding vaporous bioethanol and a protective sleeve for the thermocouple pass through this flange, so that the place where the bioethanol vapor is introduced is 1.5 m from the inlet flange, and the gas temperature measuring device is 1 m from the inlet flange. A thermocouple input pocket and a device for cooling gas with cooling water are mounted on the outlet flange, and a summing gas flow meter and gas analyzer are mounted on the output side of the gas cooling device. An electric heater coil is wound around the entire aluminum oxide tube. However, the current is supplied only to 1 m of the heater on the inlet side, and this part is designed as a heating zone for the modeling gas of an oxygen converter. Electric current is not supplied to the part of the heater located below the heater, and this part plays the role of an adiabatic reaction zone. Bioethanol vapors are introduced at a point approximately 0.5 m below the previously described heating zone. Therefore, the actual length of the adiabatic reaction zone is 3.5 m.

The modeling gas of the oxygen converter is obtained by mixing CO: 50 vol.%, CO ₂ : 15 vol.%, H ₂ : 1 vol.% And N ₂ : 34%. The flow rate of the simulating gas is set to 1 l / min, the flow rate of the bioethanol vapor is set to 150 ml / min, which is equivalent to the flow rate of CO ₂ , and the temperature of the heating zone is set to 1500 ° C. In this case, the temperature in the adiabatic reaction zone, measured by a thermocouple mounted on the outlet flange, is 820 ° C. Moreover, the concentration of hydrogen gas at the outlet is 20 vol.%. The gas dwell time in the adiabatic zone is 3 seconds. As a result of calculating the degree of conversion and material balance according to the gas flow rate at the outlet and gas analysis, it was found that the degree of conversion of bioethanol is 99%, the conversion of CO ₂ is 89%, and the degree of carbon formation is 1.5%. Carbon formation is evaluated by visual inspection of the internal channel of the tube after the experiment. The amount of carbon formed is estimated by the difference between the material balance data for carbon atoms (%) and 100%. This reaction can be represented by equation (5), and it was found that 2/3 of the resulting CO comes from non-fossil resources. Therefore, even if the synthesis gas is burned as fuel, the emission of carbon dioxide gas is only 1/3, and this is likely to be of great importance in reducing emissions of carbon dioxide gas.

Example 5

The experiment with the addition of the reducing agent was carried out in the same manner as in example 1, except that the hole 16 for purging the reducing agent is provided at the lower end of the first radiating part in the upper part of the upper cap 4, and the amount of added natural gas is 3360 nm ³ / hour. The temperature of the exhaust gas at the point of addition is about 1300 ° C, which is equivalent to the temperature in comparative example 1, but this example differs from comparative example 1 in that a small amount of natural gas is added. The exhaust gas after reforming has a temperature of 940 ° C, a flow rate of 77280 nm ³ / h, and the following composition: CO - 63 vol.%, CO ₂ -7 vol.%, H ₂ - 8 vol.%, N ₂ - 21 vol. %, CH ₄ : less than 0.1 vol.% And O ₂ : less than 0.1 vol.%. The amount of gaseous hydrogen increases by 8 times due to the reforming process, and the reforming process ends at 940 ° C at the temperature measurement site. In contrast to comparative example 1, the formation and deposition of dust, such as carbon on the surface of the channel, is not observed, and the exhaust gas can be converted without difficulty. The residence time of the gas from the point of addition of natural gas to the temperature measuring point is about 4 seconds.

Embodiment 2

An exhaust gas conversion device of a metallurgical furnace according to the 2nd embodiment is a device in which a reducing agent and the like are added to high temperature exhaust gas at a temperature of 800 ° C or higher, and preferably 1000 ° C or higher, discharged from the metallurgical furnace, such as an oxygen converter or a reduction melting furnace, in order to carry out a reforming process between the gaseous carbon dioxide contained in the exhaust gas and the reducing a In this way, the exhaust gas is converted, and characterized in that the blowing nozzle of the reducing agent having the structure of a double concentric pipe containing an outer tube for blowing diluted nitrogen and an inner tube for blowing a reducing agent, selected together by insertion into the outer tube, is mounted in the channel exhaust gas metallurgical furnace.

The structure of the 2nd embodiment is described below with reference to an example of using an oxygen converter as a metallurgical furnace.

The high-temperature off-gas emitted from the oxygen converter typically contains from about 10 to 20 vol.% CO ₂ and from about 50 to 80 vol.% CO, the calorific value of the gas is from about 1500 to 2000 kcal / nm ³ , and the neck temperature the oxygen converter during operation is approximately 1200 to 1800 ° C. In the device of the 2nd embodiment, the heat content of the exhaust gas and the reduction of carbon dioxide gas emissions are simultaneously and safely achieved by adding a reducing agent such as natural gas to the exhaust gas converter in order to carry out a reforming process between the reducing agent and carbon dioxide gas in accordance with equation (1):

In other words, since metallurgical plants (for combustion) use high heat content exhaust gas and converted gas as various heat sources, carbon dioxide gas is finally emitted. However, it is possible to reduce the consumption of auxiliary fuel, such as boiler fuel used in metallurgical plants, in an amount corresponding to a partial increase in heat content, and as a result, the amount of carbon dioxide gas formed can accordingly be reduced.

5 is a schematic drawing of an oxygen converter gas extraction system for explaining an exhaust gas conversion device of a metallurgical furnace according to the 2nd embodiment. As shown in FIG. 5, the exhaust gas generated in the oxygen converter 1 is discharged through the hollow cylinder 2, the lower hood 3, the upper hood 4, the first emitting part 25, the primary dust collector (wet dust collector) 5, the secondary dust collector 13 and the like.

Figure 6 is an example of a preferred nozzle for injecting a reducing agent N used in the 2nd embodiment.

According to a second embodiment, the conversion device is preferably such that a nozzle for injecting a reducing agent N having a double concentric pipe structure that includes an outer tube 8 for injecting diluted nitrogen and an inner tube 9 for purging a reducing agent such as natural gas preferably mounted in the exhaust gas channel of the oxygen converter, that is, in any position of the lower hood 4, the upper hood 4 and the radiating part 25, in one of ultiple places in the duct in a circumferential direction. For example, the total number of nozzles installed in two places is four, since the nozzles are paired.

The injector N for injecting a reducing agent can spray the reducing agent described hereinafter from a central hole 29a formed by the inner tube, and can spray diluted nitrogen, such as diluted nitrogen for emergency shutdown, from the annular channel 28a, which is the space between the outer tube 28 and inner tube 29.

Appropriate atomization of diluted nitrogen and atomization of a reducing agent, such as natural gas, are carried out independently. For example, nitrogen atomization is the case at the time of the introduction of diluted nitrogen for emergency shutdown of the process when there is a danger of explosion due to a rise in temperature of the exhaust gas of the converter. On the other hand, the second case is the spraying of a reducing agent supplied during reforming and increasing the heat content of the exhaust gas. Of course, you can spray both gases at the same time, and this option is used to control the concentration of the reducing agent in the purge gas.

Typically, in an oxygen converter gas extraction system having such a converter exhaust gas channel, an injector 32 is provided in the lower part of the first emitting part 25, near the upper edge of the upper cap 4, as shown in the example, for supplying diluted nitrogen during an emergency shutdown. The present invention preferably uses the existing nozzle 32 for supplying diluted nitrogen, which nozzle used as the outer tube 28 and the inner tube 29 to purge the reducing agent are assembled by insertion in the central part, inside the outer tube 28, thereby forming a nozzle N for injecting a reducing agent having a double concentric pipe structure. In this case, since the existing nozzle 12 for supplying diluted nitrogen is used as such, installation costs can be significantly reduced.

The reason for using the emergency stop nozzle 32 for injecting a reducing agent is that diluted emergency stop nitrogen is usually used to supply a large amount of nitrogen to the converter exhaust gas channel, from the hollow cylinder 2 to the radiating part 25, in order to prevent explosion under the influence of high temperature off-gas at the time of the accident during the operation of the oxygen converter. Typically, a diluted nitrogen nozzle unit includes about 2 to 8 nozzles having a large inner diameter, about 200 to 300 mm, located on the peripheral wall, and is usually used only in the event of an accident. The present invention is an embodiment where, in such a nozzle for supplying diluted nitrogen having a large diameter, that is, the outer pipe 28, a tube 9 for purging a reducing agent having a diameter smaller than the nozzle is inserted in the axial direction of the central part of the nozzle, and thus, a double tubular structure is formed.

The above nozzle 32 for supplying diluted nitrogen is already available. Therefore, there is no need to prepare the nozzle by adding the function of supplying a reducing agent to the gas recovery system of the oxygen converter and the injection tube 11, as well as a new nozzle design, but simply the inner tube 29 for purging the reducing agent is simply mounted inside the outer pipe 28 as a nozzle for supplying diluted nitrogen. This is beneficial due to ease of installation and low cost.

Typically, the equipment of the converter exhaust gas channel differs from the above nozzle 12 for supplying diluted nitrogen during an emergency stop, and the projections for mounting scaffolding at the entrance to the channel for inspection are installed in several places, in addition to the inspection openings for inspection. In the above example of the present invention, it is contemplated to use a purge pipe of an existing nozzle 32 for supplying diluted nitrogen during an emergency shutdown as an outer nozzle pipe for purging a reducing agent. However, it is possible to insert the nozzle N for injecting a reducing agent having the structure of a double concentric pipe according to the 2nd embodiment into the existing inspection openings and scaffolding.

Typically, a plurality of nozzles N for injecting a reducing agent are installed in the direction along the circumference of the exhaust gas channel. However, only part of the available nozzles 32 for supplying diluted nitrogen can be used, and nozzle N can be installed there, and nozzles N can be mounted in all nozzles 12. The installation of nozzles N for purging the reducing agent is the same, even in the case of using the above viewing holes and flange.

The blowing of the reducing agent into the converter exhaust gas channel when it is filled with high-temperature exhaust gas is preferably carried out from the nozzle N for blowing the reducing agent mounted in the lower part of the first radiating part 25, where the exhaust gas has a high temperature of 800 ° C or higher. This example is shown in FIG. 5. The temperature of the exhaust gas at the bottom of the first emitting part 5 in the converter exhaust gas channel is usually from about 1100 to 1400 ° C., and this temperature is sufficient for the reforming process to proceed. On the other hand, oxygen is completely consumed during the combustion of carbon monoxide in this place, and the flame does not soar up to this place. Therefore, the off-gas can be reformed to increase the heat content in a safe and efficient manner, and in some cases, gas concentration can be adjusted using diluted nitrogen.

A reducing agent, such as natural gas, is introduced into the high-temperature off-gas of the oxygen converter from the nozzle N to blow the reducing agent and interacts with carbon dioxide gas in the off-gas to initiate a reaction according to equation (1), which absorbs the heat content of the off-gas. Therefore, the temperature of the exhaust gas decreases during the process. As the process proceeds, the exhaust gas flow rate, the concentration of carbon monoxide and the concentration of hydrogen increase, and on the other hand, the concentration of gaseous carbon dioxide decreases. In figure 5, the process is controlled using a thermometer 10, a gas analyzer 6, a gas flow meter (not shown), and the like. A valve 7 controlling the flow rate of the reducing agent and the pressure of the supplied reducing agent (not shown) can be controlled using these measured parameters. The first dust collector 5 is a wet dust collector. Consequently, the exhaust gas is rapidly cooled in the dust collector, the zone immediately up to the first dust collector 5 being a space that can be used in this process.

The reducing agent that can be used in the present invention is preferably at least one material selected from natural gas, liquefied petroleum gas, methane, ethane, light gasoline, raffinate, methanol, ethanol, dimethyl ether, diethyl ether, organic compounds such as non-mineral resources, such as bioethanol and biodiesel, and mixtures thereof. Of these, natural gas, liquefied petroleum gas, light gasoline, raffinate and dimethyl ether are preferred since they are highly reactive with respect to carbon dioxide gas and readily available in large quantities. In the case of using a reducing agent, which is a gas at room temperature, such as natural gas and liquefied petroleum gas, a nozzle suitable for purging the gas is used, and the shape of the nozzle and the number of nozzles are not particularly limited. In the case where the reducing agent at room temperature is a liquid, such as a raffinate, the reducing agent can be introduced by spraying the reducing agent in the form of an aerosol and can be gasified and introduced in the form of a gas. In the case of an aerosol delivery, the diameter of the droplets is such as to ensure effective contact of the droplets with gaseous carbon dioxide, and is preferably from 0.01 to 1000 μm, and more preferably from 0.1 to 100 μm. If liquefied gas, such as dimethyl ether, is used as a reducing agent, this reducing agent can be pre-gasified and introduced in the form of a gas, and can be supplied in the form of a liquid, wherein the gasification of the reducing agent occurs near the nozzle or in the nozzle. In this case, the gasification near the nozzle or in the nozzle is cooled by the heat of vaporization, which is preferable from the point of view of protection of the nozzle.

In the reducing agent, organic compounds such as non-fossil resources can be used along with organic compounds such as fossil resources instead. When organic compounds such as non-fossil resources are selected as the reducing agent, the reforming process is carried out using a carbon-neutral reducing agent, in addition to the fact that the heat content of part of the exhaust gas is increased due to the reforming process of gaseous carbon dioxide, and this is preferable from the point of view of the possibility of significant reduction of gaseous carbon dioxide emissions. Examples of organic compounds such as non-fossil resources include bioethanol, biodiesel and mixtures thereof. Bioethanol and biodiesel are usually liquid at room temperature. Therefore, they are preferably introduced by spraying in the form of an aerosol or gasified and then introduced in the form of gas. In the case of liquefied gas, as an organic compound such as non-fossil resources, preferably liquefied gas is used in the same manner as described above for dimethyl ether.

Example 1

In this example, an experiment was carried out with the addition of natural gas as a reducing agent in the exhaust gas of an oxygen converter (exhaust gas) from the nozzle N to blow the reducing agent installed using the nozzle 32 for supplying diluted nitrogen during an emergency stop provided in the lower part of the radiating part 25 as shown in FIG. 5, using a 300 t top-purge converter 1. N nozzles for injecting a reducing agent in the conversion device used in in this example, are installed with an equivalent width in all four places, at almost the same height in the direction of the axis of the converter exhaust gas channel (radiating part), the inner diameter of its outer pipe 28 being 200 mm. All nozzles N for purging the reducing agent, mounted in four places, are equipped with an inner tube 29 with an inner diameter of 35 mm for purging the reducing agent, as shown in figure 6, with the valve regulating the total pressure and the valve regulating the flow rate (not shown shown), fitted to the inside of the upstream pipeline of the inner tube 29 to purge the reducing agent.

Prior to purging natural gas as a reducing agent, confirmation is received as to whether there are difficulties with the flow of nitrogen gas for emergency shutdown or they are absent. As a preset, the flow rate of injected nitrogen could be 27,000 nm ³ / h, and it was found that there were no difficulties in operating the oxygen converter. The flow rate of the exhaust gas, without purging natural gas is 67,000 nm ³ / h, and the gas has a composition of CO: 60 vol.%, CO ₂ : 15 vol.%, H ₂ : 1 vol.% And N ₂ : 24 vol.% . It follows that the amount of CO ₂ emitted is 10,050 nm ³ / hour. Natural gas is added in a total amount of 3600 nm ³ / hour to four N nozzles to inject a reducing agent. Since the content of CH ₄ in natural gas is 92 vol.%, The molar ratio between CO ₂ and CH ₄ can be approximately 3: 1. Although the temperature of the exhaust gas near the N nozzle for injecting a reducing agent is not actually measured, an estimate based on numerical analysis gives a value of about 1300 ° C.

Under operating conditions, the overpressure of the supplied natural gas is set to 200 kPa, and the flow rate from each nozzle N for injection of the reducing agent is maintained at 900 nm ³ / h. Oxygen is exhausted immediately after the start of purging. Therefore, when the oxygen concentration becomes equal to 1 vol.% Or less, the addition of natural gas begins and the values of temperature, flow rate and composition of the converted exhaust gas are recorded. As a result, the exhaust gas has a temperature of 910 ° C, a flow rate of 78000 nm ³ / h, and the composition of CO: 64 vol.%, CO ₂ : 6 vol.%, H ₂ : 8 vol.%, N ₂ : 22 vol.% moreover, the content of CH ₄ and O _{2 is} less than the detection limit. All the introduced amount of natural gas reacts with gaseous carbon dioxide, and there is no danger of burning and explosion. In addition, it is noted that the formation and deposition of dust from the exhaust gas, such as carbon in the channel (s), does not occur, and that the exhaust gas is effectively converted. The calorific value of the exhaust gas before reforming is 1840 kcal / nm ³ , however, the calorific value after reforming is 2140 kcal / nm ³ . Thus, the increase in heat content of the standard volume of exhaust gas is 16%. The calculated carbon dioxide gas flow rate in the exhaust gas after reforming is 4680 nm ³ / h, and the carbon dioxide gas conversion rate is 53%. Thus, the effectiveness of the use of the device according to the present invention is confirmed.

In a second embodiment, the following effects are obtained.

1. An apparatus for reforming an exhaust gas of a metallurgical furnace may be inexpensive equipment having a simple structure. In addition, a safe reforming process can be carried out with an increase in the heat content of the exhaust gas, and a final reduction in carbon dioxide gas emissions with high efficiency is achieved.

2. Since a pipeline is used for purging with diluted nitrogen during an emergency shutdown, which was originally provided in the gas extraction system of the oxygen converter of a metallurgical furnace, a completely new device for mounting the exhaust gas channel is not required, and the cost of installing the device can be reduced.

3. Due to the use of the natural structure of the heat content of the high-temperature exhaust gas emitted from the metallurgical furnace, during the process of reforming gaseous carbon dioxide by adding a reducing agent, the formation and deposition of carbon and non-combustible materials do not occur and the heat content in the exhaust gas can be increased. In addition, at the same time, increased use of exhaust gas and reduced emissions of gaseous carbon dioxide can be achieved.

4. In connection with the use of a nozzle having the structure of a double concentric pipe including an external tube for injecting diluted nitrogen and an internal tube for injecting a reducing agent, it is possible to control the temperature of the reducing agent, and, in addition, it is convenient and efficient to prevent the danger of rapid combustion and explosion, due to purging with diluted nitrogen.

5. Since the double concentric pipe arrangement uses natural gas or the like as a reducing agent, which are cheap and available in large quantities, the reforming process is economically viable. In particular, if organic compounds such as non-fossil resources such as bioethanol and biodiesel are used as a reducing agent, the process can make a significant contribution to reducing carbon dioxide gas emissions.

Embodiment 3

In metallurgical plants, in an oxygen converter, a reduction smelting furnace and the like, a large amount of off-gas is generated with a high temperature of about 1000 ° C. or higher, which contains gaseous carbon dioxide. Waste gases contain combustible components such as carbon monoxide, which are different from gaseous carbon dioxide, and therefore these gases are used as an energy source when operating various equipment in metallurgical plants.

In this regard, it is known that various hydrocarbons, such as methane, and oxygen-containing compounds, such as methanol and dimethyl ether, interact with gaseous carbon dioxide to form carbon monoxide and hydrogen. In such a system, various hydrocarbons, such as methane, are a reducing agent for gaseous carbon dioxide. This process is an endothermic reaction, and when methane and gaseous carbon dioxide interact during the reforming process, heat is absorbed in the amount of ΔН _298к = 247 kJ. Specifically, when the exhaust gas containing carbon dioxide gas is contacted with a reducing agent, such as methane, initiating the reforming process according to equation (1), the temperature of the exhaust gas spontaneously decreases.

Carbon monoxide and hydrogen formed in the reaction shown by equation (1) are combustible gases. In the case when the gas is considered as an energy source, the heat content of the exhaust gas increases due to the reaction according to equation (1). In other words, the high-temperature off-gas is converted to fuel gas containing combustible components such as carbon monoxide and hydrogen, and the gaseous material obtained by cooling the gas can be used as an energy source. Consequently, the product of the reforming process is a useful fuel gas.

It is known that the course of the reforming process shown as equation (1) is promoted by an increase in temperature, the equilibrium conversion of gaseous carbon dioxide in this reaction at 900 ° C being about 95%, and the equilibrium degree of conversion reaching almost 100% at approximately 1000 ° C or higher.

On the other hand, when a reducing agent, such as methane, is added to the gas leaving the metallurgical furnace and containing combustible gas with a high temperature of about 800 ° C. or higher, and preferably 1000 ° C. or higher, which includes gaseous carbon dioxide and additional combustible components such as carbon monoxide and hydrogen, for example a converter gas, wherein a reducing agent and gaseous carbon dioxide in the exhaust gas enter into the above endothermic reaction, high temperature dyaschy gas is rapidly cooled by the flow of the endothermic reaction, without the need for refrigeration equipment.

However, according to the studies of the inventors, it was found that when the completion temperature of the above endothermic reforming reaction is less than 800 ° C, the problem of significant formation of solid carbon occurs, which leads to the deposition of the solid product on the equipment. For this reason, it is desirable to complete the endothermic reaction when the gas temperature after the reaction is 800 ° C. or higher. If it is intended to cool the gas to a temperature lower than 800 ° C, this can be done by simultaneously using a common cooling method, for example in a heat exchanger.

The term “endothermic ^: reforming reaction” used in the invention means that the reaction between the added reducing agent, such as methane, and gaseous carbon dioxide in the exhaust gas proceeds almost to equilibrium under these conditions. Theoretically, to achieve complete equilibrium, an infinite residence time is required and the expression “almost to equilibrium” does not have a strict definition. In the present invention, “completion of the endothermic reforming reaction” is defined at a time when the concentration of hydrogen gas increases compared to the concentration of hydrogen in the exhaust gas before reforming. The temperature of the exhaust gas is reduced due to the reforming process. Therefore, this expression has physical meaning: the reforming process ends when the gas temperature after the reaction is 800 ° C or higher.

On the other hand, the hydrogen atoms in the added reducing agent are converted to hydrogen gas in the reforming process. An analysis of the composition of the exhaust gas is essential in the process of recovering the exhaust gas as an energy source. Monitoring the completion of the reaction by the concentration of hydrogen gas is of chemical importance and is important for the quality of the control operation.

In decarburization purging, since the initial concentration of hydrogen gas in the exhaust gas is small, of the order of 1 vol%, the hydrogen gas content in the gas after reforming increases from about 2 to 25 times, compared with the amount of hydrogen before reforming, and therefore the current control is a simple task. Therefore, with decarburization blowing, the “completion of the endothermic reforming reaction” preferably corresponds to the moment when the concentration of gaseous hydrogen increases by 2 times or more compared to the initial one, before reforming.

On the other hand, in dephosphoric purging, when the initial exhaust gas flow rate is small and the exhaust gas extraction rate is low, the amount of exhaust gas has recently been increased by introducing plastic waste, thereby increasing the extraction rate. The concentration of gaseous hydrogen in the exhaust gas prior to reforming is from about 10 to 15 vol.%, Due to the gaseous hydrogen formed from additional materials, such as plastic waste. Moreover, since a LPG or the like is supplied as a cooling gas to prevent damage to the tuyeres by fire to purge the converter from below, a large amount of hydrogen gas is generated even by decomposition of the LPG. In this case, the formation of a large amount of gaseous hydrogen, the concentration of hydrogen in the gas, the exhaust gas after reforming, increases only from 1 to 5%, compared with its concentration before reforming. Therefore, when dephosphoric purging and purging from the bottom of the converter, “completion of the endothermic reforming reaction” preferably corresponds to the moment when the concentration of hydrogen gas increases by 1% or more compared with the concentration before reforming. Therefore, the analytical accuracy of the gas analyzer of 0.5% or less is preferable, and the accuracy of 0.1% or less is more preferable. An example of such a gas analyzer is an analyzer that continuously measures thermal conductivity and a gas chromatograph.

A characteristic feature of the cooling method in the 3rd embodiment is, for example, that in the case of the exhaust gas of the converter, it contains dust, comprising as a main component highly dispersed iron oxide powder (particles of a size of 0.5 mm or less and exceeding 100 microns , and particulate smoke 100 μm or less), called converter dust. A highly dispersed iron oxide powder (a mixture containing at least one of the oxides FeO, Fe ₂ O ₄ , Fe ₃ O ₄ or iron oxyhydroxides) plays the role of a reforming catalyst that stimulates the endothermic reaction (methane oxidation reaction) according to the above equation ( 1) at a lower temperature. Due to the presence of a finely divided iron oxide powder, the endothermic reaction according to equation (1) proceeds even if the temperature of the exhaust gas is less than 1000 ° C and 800 ° C or higher, and effective cooling of the exhaust gas is achieved. This makes it possible in the present invention to efficiently cool the high-temperature off-gas due to the endothermic chemical reaction according to equation (1), but not mechanically, without using a cooling device such as a water cooling jacket. Since the converter dust is contacted at high temperature with a reducing gas discharged from the oxygen converter, part of the dust is restored when the endothermic reaction proceeds according to equation (1), and iron oxide is formed. However, this does not affect its function as a reforming catalyst.

One embodiment of the third embodiment is described below based on an example of the use of high temperature off-gas emitted from an oxygen converter.

The high-temperature off-gas emitted from the oxygen converter typically contains from about 10 to 20 vol.% CO ₂ and from about 50 to 80 vol.% CO, the calorific value is from about 1500 to 2000 kcal / nm ³ , and the temperature in the neck operating time is from about 1200 to 1800 ° C. In the 3rd embodiment, the required amount of a reducing agent, such as methane or natural gas, is added to the exhaust gas of the converter in any one place, or two or more places on the upper part of the tube for blowing air or the radiating part of the channel, i.e. the lower cap, on the inlet side of the first dust collector in order to carry out an endothermic reaction between the reducing agent and gaseous carbon dioxide, as shown above in equation (1), thus, the exhaust gas is spontaneously cooled, discharged from an oxygen converter.

The amount of added reducing agent for the implementation of the endothermic reaction is determined depending on the molecular ratio between CO ₂ and CH ₄ , taking into account the amount (m ³ / h) of exhaust gas generated in the converter. For example, when the molecular ratio between CO ₂ and CH ₄ is 1: 1, when the concentration of CO ₂ in the gas leaving the converter is 15 vol.%, The amount of this gas is 79,000 m ³ / h, with the amount of methane added as reducing agent is about 11850 m ³ / hour.

Adding a reducing agent can reduce the temperature of the exhaust gas from about 1600 ° C to 1000 ° C on the inlet side of the primary dust collector, for example in the lower hood, in the absence of a cooling water jacket in the radiating part. At the same time, a mechanically initiated cooling method with the formation of a water cooling structure in the radiating part can be used.

FIG. 7 is a schematic drawing of an oxygen converter gas recovery system for explaining a method for cooling exhaust gas generated in a metallurgical furnace in accordance with a 3rd embodiment. As shown in the drawing, the gas generated in the oxygen converter 1 passes through the hollow cylinder 2, the lower hood 3 and the radiating part (channel) containing the upper hood 4, and is discharged into the primary dust collector 5.

In the 3rd embodiment, the site of addition of the reducing agent for carrying out the endothermic reaction is where the nozzle with the supply of the reducing agent can be provided, in any position of the blowing tube 11, the lower cap 3, the upper cap 4 and the subsequent radiating part, as described previously .

Preferably, the reducing agent that can be used in the 2nd embodiment is at least one selected from fossil resource compounds such as natural gas, liquefied petroleum gas, methane, ethane, light gasoline, raffinate, methanol, ethanol, dimethyl ether and diethyl ether. Of all these agents, natural gas, liquefied petroleum gas, light gasoline, raffinate and diethyl ether are preferred, since they have good reactivity with respect to carbon dioxide gas, are cheap and readily available in large quantities. In the case of using a reducing agent, which is a gas at room temperature, such as natural gas and liquefied petroleum gas, a nozzle suitable for gas purging is used, the shape and number of nozzles being not particularly limited. In the case where the reducing agent is a liquid at room temperature, such as a raffinate, this reducing agent can be administered by spraying in the form of an aerosol, or it can be gasified and introduced in gaseous form. When sprayed, the droplet diameter of the agent is such as to provide effective contact with carbon dioxide gas, and is preferably from 0.01 to 1000 μm, and more preferably from 0.1 to 100 μm.

In the case of using liquefied gas, such as dimethyl ether, as a reducing agent, this agent can be pre-gasified and introduced in the form of gas and can be introduced in the form of a liquid, while the gasification of the reducing agent occurs near the nozzle or in the nozzle. In this case, the gasification near the nozzle or in the nozzle, the nozzle itself is cooled by the heat of vaporization, which is preferable from the point of view of protection of the nozzle.

In the reducing agent, organic compounds such as non-fossil resources can be used along with organic compounds such as fossil resources instead. The use of organic compounds such as non-fossil resources is particularly preferred due to the fact that the reforming process is carried out using a carbon-neutral reducing agent, in addition to the fact that the heat content of part of the exhaust gas is increased due to the reforming process of gaseous carbon dioxide, and this is preferable from the point of view of view of the possibility of a significant reduction in gaseous carbon dioxide emissions. Examples of organic compounds such as non-fossil resources include bioethanol, biodiesel and mixtures thereof. Bioethanol and biodiesel are usually liquid at room temperature and are used in the same way as the raffinate described above. Liquefied gases as an organic compound such as non-fossil resources are used in the same manner as described above for dimethyl ether.

Example 1

In this example, an experiment was conducted in which a simulating laboratory furnace was used, which includes an aluminum oxide tube having an inner diameter of 12 mm and a length of 5 m. In this modeling experimental furnace, the gas inlet pipe is mounted on the inlet flange of the aluminum oxide tube, the methane gas injection tube has an outer diameter of 3 mm and the thermocouple protective cover is mounted on the inlet flange; the methane gas addition site is 1.5 m from the inlet flange, the gas temperature measuring means is 1 m away from the inlet flange, the methane gas tube and thermocouple protective cover passing through this flange. The thermocouple input assembly and the gas cooling device using cooling water are mounted on the outlet flange, and the summing gas flow meter and gas analyzer are mounted on the output side of the gas cooling device. An electric heater coil is wound around the entire aluminum oxide tube. The current is supplied only to 1 meter of the heater on the inlet side, and this part is designed as a heating zone for the modeling gas of an oxygen converter. Electric current is not supplied to the part of the heater located below the heater, and this part plays the role of an adiabatic reaction zone.

Methane is introduced at a point approximately 0.5 m below the heating zone described above. Therefore, the actual length of the adiabatic reaction zone is 3.5 m.

The modeling gas of the oxygen converter is obtained by mixing CO: 50 vol.%, CO ₂ : 15 vol.%, H ₂ : 1 vol.% And N ₂ : 34%. The flow rate of the modeling gas is set equal to 1 l / min, the flow rate of methane gas is 150 ml / min, which is equivalent to the flow rate of CO ₂ , and the experimental reforming process is carried out with varying the temperature of the heating zone in the range of 1800 ° C, 1500 ° C and 1300 ° FROM. In this example, as a result of measuring the temperature at the outlet of the adiabatic reaction zone using a thermocouple mounted on the outlet flange, the outlet temperature decreases to 1060 ° C, 840 ° C, and 775 ° C in each experiment with a heating zone temperature of 1800 ° C, respectively , 1500 ° C and 1300 ° C. The concentration of hydrogen gas at the outlet is 21 vol.%, 20 vol.% And 19 vol.%, Respectively. The gas residence time in the adiabatic zone is from 2 to 6 seconds.

Carbon formation is practically not observed in experiments when the temperature of the modeling gas with increased heat content is 1060 ° C (in this case, the temperature of the heating zone is 1800 ° C) and when the temperature of the modeling gas with increased heat content is 840 ° C (in this case, the temperature of the heating zone is 1500 ° C). However, significant carbon formation occurs in the experiment, when the temperature of the modeling gas with high heat content is less than 800 ° C (in this case, the temperature of the heating zone is 1300 ° C).

Example 2

In this example, an experiment was carried out using a 300-ton top-purged converter and an inlet 16 was provided for purging a reducing agent (natural gas) into the converter exhaust gas (exhaust gas) containing converter dust (highly dispersed iron oxide powder) from the lower edge of the upper cap 4 in order to cool the radiating part, that is, the outlet passage (channel), as shown in figure 8. In normal operation of the converter, the lower cap 3 and the upper cap 4, which are the outlet passages, and eyut cooled pipe structure, and offgas is cooled by water. The experiment is carried out: by stopping water cooling. When natural gas is not blown in, the exhaust gas has a flow rate of 79,000 nm ³ / hr and the composition of the gas is CO: 50 vol.%, CO ₂ : 15 vol.%, H ₂ : 1 vol.% And N ₂ : 34 vol.% . Natural gas is added in an amount of 11850 nm ³ / hour, which is equivalent to the flow rate of CO ₂ . Since the content of CH ₄ in natural gas is 92 vol.%, The molar ratio between CO ₂ and CO ₄ can be estimated approximately equal to 1: 1. The temperature of the exhaust gas near the mouth of the Converter is about 1700 ° C.

The exhaust gas flow meter and gas analyzer 6 are mounted on the output side of the secondary dust collector (dust collector) 13 and a thermometer 10 is mounted on the inlet side of the primary dust collector (wet dust collector). After this, the addition of natural gas begins, and the temperature, flow rate and composition of the reforming off-gas are determined. As a result, the exhaust gas has a temperature of 980 ° C and a flow rate of 114400 nm ³ / hour and has a composition of CO: 55 vol.%, CO ₂ : 0.1 vol.%, H ₂ : 21 vol.%, N ₂ : 23.5 about %, CH ₄ : 0.1 vol.% And the amount of O ₂ less than 0.1 vol.%. Due to the built-in opening for purging natural gas, the exhaust gas can be cooled in the discharge channel without any difficulties. The amount of gaseous hydrogen increases by 21 times due to the reforming process, and the endothermic reforming process is completed at 980 ° C.

Example 3

The experiment was carried out in the same manner as in example 2, except that a purge hole was provided at the lower end of the first radiating part in the upper part of the upper cap 4, as shown in figure 9. The temperature of the exhaust gas at the purge site is about 1300 ° C. .

Analogously to example 1, begins the addition of natural gas and determines the temperature, flow rate and composition of the exhaust gas reforming. As a result, the exhaust gas after reforming has a temperature of 940 ° C, a flow rate of 77280 nm ³ / h, and the following composition: CO - 63 vol.%, CO ₂ - 7 vol.%, H ₂ - 8 vol.%, N ₂ - 21 vol.%, CH ₄ less than 0.1 vol.% And O ₂ less than 0.1 vol.%. The exhaust gas can be cooled in the exhaust duct without any difficulty. The amount of hydrogen gas increases by 8 times due to the reforming process, and the endothermic reforming process is completed at 940 ° C.

Example 4

Preparation of dust particles

Water is introduced into the exhaust gas emitted from 300 tons of the overhead converter with two stages of the primary dust collector 5 and into the secondary dust collector 13 and the dust of the converter is collected. Large dust particles larger than 100 μm are separated from the spent water containing the collected dust from the converter using a large particle separator. A coagulator is added to the remaining spent water, and small particles precipitate after aggregation and concentrate. After that, the concentrate is dehydrated with a filter press to obtain a finely divided powder.

The coarse particles and fine particles thus obtained are dried at 105 ° C. overnight and ground to a size of 0.5 mm or less using a mortar and pestle, respectively. These particles are dried again at 105 ° C. for 2 hours and then used in an activity evaluation experiment.

The results of an experimental assessment of activity

This experimental example is carried out using a quartz modeling laboratory furnace having an inner diameter of 7 mm and a length of 200 cm. A gas mixture containing CO: 60 vol.%, CO ₂ : 15 vol.%, H ₂ : 1 is used as a simulating converter gas. vol.% and N ₂ : 24 vol.%. The flow rate of the simulating gas is maintained at 850 ml / min and the flow rate of methane gas is maintained at 127.5 ml / min, which is equivalent to the flow rate of CO ₂ . Modeling gas is introduced into a laboratory furnace, inside of which 19 ml of dust is loaded. The heating is carried out using an electric furnace, and thus, during the reforming process, the temperature of the modeling gas changes from 700 ° C, 800 ° C, 900 ° C and 1000 ° C. The gas composition is analyzed in the corresponding outlet openings and the observed rate constant K 'is calculated from the obtained gas composition and gas contact time with dust.

The evaluation results, including a blank experiment in which dust is not added, are shown in Figure 10. These data confirm the conclusion that dust plays the role of a catalyst and has high activity in the reforming process.

Claims (29)

1. A method of converting exhaust gas generated in a metallurgical furnace by adding a reducing agent to the exhaust gas containing high temperature carbon dioxide gas exiting the metallurgical furnace to allow the interaction of carbon dioxide gas with a reducing agent to convert the exhaust gas, the reducing agent being added, when the oxygen concentration in the exhaust gas is 1 vol.% or lower, the exhaust gas conversion process is completed to where the flue gas temperature is 800 ° C or higher. 2. The method according to claim 1, characterized in that the reducing agent is at least one fossil resource type compound selected from the group consisting of natural gas, liquefied petroleum gas, methane, ethane, light gasoline, raffinate, methanol, ethanol dimethyl ether and diethyl ether. 3. The method according to claim 1, characterized in that the reducing agent is at least one non-fossil resource type compound selected from the group consisting of bioethanol, biodiesel and a mixture of bioethanol and biodiesel. 4. The method according to claim 1, characterized in that the high-temperature off-gas emitted from the metallurgical furnace has a temperature of from 800 to 1800 ° C. 5. The method according to claim 4, characterized in that the high-temperature off-gas emitted from the metallurgical furnace has a temperature of from 1000 to 1800 ° C. 6. The method according to claim 1, characterized in that the high-temperature off-gas emitted from the metallurgical furnace has a carbon dioxide concentration of from 3 to 30 vol.%. 7. The method according to claim 1, characterized in that the reducing agent is added when the concentration of oxygen in the exhaust gas is 0.5 vol.% Or less. 8. The method according to claim 1, characterized in that the process of converting the exhaust gas is completed when the temperature of the exhaust gas is from 800 to 1100 ° C. 9. The method according to claim 1, characterized in that the process of converting the exhaust gas is completed when the temperature of the exhaust gas is from 850 to 1050 ° C. 10. The method according to claim 1, characterized in that the process of converting the exhaust gas is carried out at an exhaust gas temperature of 800 ° C or higher, during a residence time of from 0.01 to 50 seconds. 11. The method according to claim 1, characterized in that the process of converting the exhaust gas is carried out at an exhaust gas temperature of 800 ° C or higher, during a residence time of from 0.1 to 20 s. 12. The method according to claim 1, characterized in that the metallurgical furnace is made in the form of an oxygen converter, into which, to inject air, a reducing agent is added from the side pipe of the upper tube. 13. The method according to claim 1, characterized in that the metallurgical furnace is made in the form of an oxygen converter, in the gas extraction system of which a reducing agent is added between the fence device and the primary dust collector. 14. A device for converting exhaust gas generated in a metallurgical furnace, such as an oxygen converter, by the method according to one of claims 1 to 13, comprising means for measuring the concentration of oxygen in the exhaust gas in a gas extraction system of an oxygen converter, a switching device of the cross-section that performs switching the cross section of the exhaust gas pipelines under the action of the output signal of the concentration measuring means, a means of measuring the temperature of the exhaust gas, the heat content of which As a result of the process of converting the exhaust gas, a means for controlling the flow rate for controlling the amount of reducing agent added is operated by the output signal from the temperature measuring means and the output signal from the concentration measuring means. 15. The device according to 14, characterized in that the concentration measuring means is made in the form of a gas analyzer mounted on the inlet side of the primary dust collector in the gas recovery system of the oxygen converter. 16. The device according to 14, characterized in that the means for measuring the concentration is made in the form of a gas analyzer mounted on the outlet side of the secondary dust collector in the gas recovery system of the oxygen converter. 17. The device according to 14, characterized in that the switching device of the cross-section is made in the form of a valve that operates in accordance with the output signal of the oxygen concentration from the concentration measuring means, and selects the cross-section in the direction of the torch or gas holder. 18. The device according to 14, characterized in that the temperature measuring means is in the form of a thermometer mounted on the input side of the primary dust collector in the gas recovery system of the oxygen converter. 19. The device according to 14, characterized in that the means for controlling the flow rate of the reducing agent is triggered in accordance with at least one output signal of the concentration measuring means and temperature measuring means. 20. The device according to 14, characterized in that the blowing agent of the reducing agent is installed at least in one place between the upper tube for blowing air of the oxygen converter, or the fence device in the gas extraction system of the oxygen converter, and the inlet side of the primary dust collector in the radiating part gas recovery systems. 21. A device for converting exhaust gas generated in a metallurgical furnace, the method according to one of claims 1 to 13, containing a nozzle for injecting a reducing agent, made in the form of a double concentric pipe containing an outer pipe for injecting diluted nitrogen and an inner tube for injecting a reducing an agent installed together by insertion into an external pipe installed in an exhaust gas channel of a metallurgical furnace gas extraction system. 22. The device according to item 21, characterized in that the metallurgical furnace is made in the form of an oxygen converter. 23. The device according to item 21, characterized in that the channel in the wall contains a lower hood, an upper hood and a radiating part in the gas recovery system of an oxygen converter. 24. The device according to item 21, characterized in that at least one nozzle for injecting a reducing agent is installed in the direction along the circumference, below the radiative part of the exhaust gas channel of the oxygen converter. 25. The device according to item 21, characterized in that the nozzle for injecting a reducing agent is made with the possibility of spraying the reducing agent from the Central hole of the inner tube, and diluted nitrogen is discharged by a jet from the annular channel formed between the inner tube and the outer pipe. 26. The device according to item 21, characterized in that the outer pipe is made in the form of a pipe for blowing diluted nitrogen during an emergency stop by diluting the exhaust gas generated in a metallurgical furnace integrated in the exhaust gas channel. 27. The device according to item 21, characterized in that the diluted nitrogen discharged by the jet from the annular channel of the outer pipe is diluted nitrogen for emergency shutdown by diluting the exhaust gas generated in the metallurgical furnace. 28. The device according to item 21, characterized in that the reducing agent contains at least one compound such as fossil resources, which is selected from the group consisting of natural gas, liquefied petroleum gas, methane, ethane, light gasoline, raffinate, methanol, ethanol dimethyl ether and diethyl ether. 29. The device according to item 21, characterized in that the reducing agent contains at least one compound such as non-fossil resources, which is selected from the group consisting of bioethanol, biodiesel and a mixture of bioethanol and biodiesel.

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