HK1118596A1 - Method and system of material combustion - Google Patents

Abstract

The invention relates to a substance burning method, comprising the steps that: the substance is added with a first reaction gas to generate bottom ashes and a first product below the theoretical oxygen demand, and the first product comprises a first gaseous substance and fly ashes; the first product is added with a second reaction gas below the theoretical oxygen demand, and the temperature of the first product is increased above the melting point of the fly ashes so as to generate melten slag and a second product, and the second product comprises a second gaseous substance; the second product is recycled thermally at least once, and at least one oxidation burning is carried out by the second product so as to achieve the fundamentally full burning of the second product, wherein, a large amount of nitrogen oxide can not be produced in the last step.

Description

Method and system for burning substance

Technical Field

The invention relates to a combustion method and a system for substances, in particular to a combustion method and a system for converting combustible substances into gaseous combustible gas after gasification.

Background

One of the ways in which human beings today obtain energy is to generate heat energy by burning combustibles, and the goal sought is to increase the efficiency of the use of heat energy and to reduce the pollutants produced by the combustion during the combustion process.

Theoretically, if high thermal efficiency is required, the lower the amount of excess reactant gas (e.g., pure oxygen, air, etc.), the better to reduce the exhaust heat loss derived from the excess reactant gas. However, too low an amount of excess reactant gas tends to result in incomplete combustion of the fuel, resulting in not only loss of the fuel but also generation of pollutants such as Hydrocarbons (HC), carbon monoxide (CO), etc. In addition, the theoretical adiabatic temperature decreases with the increase of the amount of excess reactant gas, and the fuel with high calorific value is easily combusted at the excessively low amount of excess reactant gas, and a large amount of Nitrogen Oxides (NO) is easily generated due to high temperature_x)。

For example, when fuel (e.g., natural gas, fuel oil, pulverized coal, etc.) is highly miscible with reactant gases, lower excess combustion air is often given to reduce exhaust heat losses, but the temperature of the combustion products is higher, resulting in the production of nitrogen oxide pollutants.

When fuel (e.g., lump coal, waste, etc.) is not easily mixed with the reaction gas, a large amount of excess gas is often supplied for sufficient combustion of the fuel, thereby increasing exhaust heat loss and lowering thermal efficiency. For example, incinerators typically produce at least twice the theoretical oxygen demand in order to burn the waste sufficiently.

In addition, fly ash from the combustion process often contains harmful substances, if reducedPollution and feasibility of material recycling are improved, the fly ash must be melted to form molten slag, and the combustion temperature must be raised to above the melting point of ash (generally up to about 1300-1500 ℃). At such high temperatures, Nitrogen Oxides (NO) are produced if oxygen and nitrogen are present simultaneously_x) A contaminant.

In the case of a waste incinerator, a large amount of combustion air must be supplied to sufficiently burn the waste, and therefore the temperature of the combustion exhaust gas (about 800 to 1000 ℃) cannot be set to a temperature at which the fly ash is melted. If fly ash is to be melted, a melter must be placed after the incinerator and additional auxiliary fuel added to raise the temperature of the combustion products. This approach requires additional external energy and also derives a significant amount of nitrogen oxide pollution from operating in the presence of excess air.

The combustion mode of the known technology often fails to compromise between thermal efficiency and pollutant reduction. Therefore, there is a need for a method and system for combusting a substance to improve the problems of the prior art.

Disclosure of Invention

The object of the present invention is to provide a method for combustion of substances which achieves high combustion efficiency and high thermal efficiency with an extremely low amount of excess reactant gas.

Another object of the present invention is to melt the fly ash of combustible materials at high temperature without generating nitrogen oxide pollutants due to high temperature.

It is yet another object of the present invention to provide a system for combustion of a substance that achieves high combustion efficiency and high thermal efficiency with a very low amount of excess reactant gas.

To achieve the above object, the combustion method of matter of the present invention comprises the steps of: adding the material to a first reaction gas at a level below its theoretical oxygen demand to produce bottom ash and a first product comprising a first gaseous material and fly ash; adding the first product to a second reactant gas at a temperature below its theoretical oxygen demand to raise the temperature of the first product above the melting point of the fly ash to produce a molten slag and a second product comprising a second gaseous material; and subjecting the second product to a plurality of heat recoveries and a plurality of oxidative combustions, wherein the plurality of heat recoveries alternate with the plurality of oxidative combustions to achieve substantially complete combustion of the second product.

To achieve the above object, a substance combustion system of the present invention includes a gasification furnace, a melting furnace, a plurality of heat recovery devices, and a plurality of reaction gas supply devices. Wherein the gasifier adds the material to the first reaction gas below its theoretical oxygen demand to produce bottom ash and a first product comprising the first gaseous material and fly ash. The melter adds the first product to a second reactant gas at a temperature below its theoretical oxygen demand to raise the temperature of the first product above the melting point of the fly ash to produce a molten slag and a second product comprising a second gaseous material. The heat recovery devices are used for carrying out heat recovery on the second product for multiple times. The reaction gas supply devices are used for carrying out multiple times of oxidation combustion on the second product, wherein the multiple times of heat recovery and the multiple times of oxidation combustion are alternately carried out, so that the second product is substantially fully combusted, and nitrogen oxides are not generated in a large amount.

The present invention has the beneficial effects of complete combustion of matter, lowering the temperature of the combustion product to below the temperature of the produced NOx to reach high heat efficiency and controlling pollutant effectively.

Drawings

FIG. 1 is a graph of combustion product temperature versus reactant gas equivalence ratio for a substance;

FIG. 2 is a schematic view of a first embodiment of a combustion system of matter of the present invention; and

FIG. 3 is a schematic view of a second embodiment of a combustion system of matter of the present invention.

Wherein the reference numerals are as follows:

1 gasification furnace of combustion heat utilization system 10 of substance

20 melting furnace 31, 32 heat recovery device

41. 42, 43, 44, 45 reaction gas supply device

50 device 81 fuel feeder

82 vibration screening machine 83 magnetic separator

84. 85 storage tank 86 slag outlet

87 cooling water tank

Detailed Description

In order to better understand the technical content of the present invention, the present invention is described below with reference to preferred embodiments as examples.

Referring now to fig. 1-2, a first embodiment of the present invention is shown. FIG. 1 is a graph of combustion product temperature versus reactant gas equivalence ratio for a substance (calorific value LHV about 3,300 kcal/kg). Fig. 2 is a schematic view of a combustion system 1 of the substance of the present invention.

Referring first to fig. 1, in the graph of fig. 1, the horizontal axis represents the equivalence ratio of reactant gas, which is the ratio (ER) of the actual amount of reactant gas to the theoretical amount of oxygen demand, and the vertical axis represents the temperature of the combustion products, which is expressed in degrees celsius, when ER ═ 1, which represents the actual amount of reactant gas equal to the theoretical amount of oxygen demand, the temperature of the combustion products can reach the maximum theoretical combustion temperature, when ER < 1, which represents the amount of reactant gas supplied being less than the theoretical amount of oxygen demand, at which time the fuel cannot be completely combusted, the temperature of the combustion products increases as ER increases, when ER > 1, which represents the actual amount of reactant gas being greater than the theoretical amount of oxygen demand, at which time the excess reactant gas lowers the temperature of the combustion products, and the temperature of the combustion products decreases as ER increases.

Fig. 1 shows three curves in total, representing the relationship between the combustion products of a combustible substance and ER in different states, wherein the uppermost curve represents the temperature curve of the combustible substance in the adiabatic state, the second curve represents the temperature curve of the first curve after the temperature of the combustion products has been reduced by the heat recovery device, and the third curve represents the temperature curve of the second curve after the temperature of the combustion products has been reduced again by the heat recovery device. In the figure, Q1, Q2, Q3, Q4 and Q5 represent the amounts of the reaction gases obtained before A, between A and B, between B and C, between D and E and between F and G, respectively. The hatched area in the figure indicates the nitrogen oxide generation region, and this region is formed in a high-temperature oxygen-containing environment.

Next, please refer to fig. 1 and fig. 2 together, wherein points a to G in fig. 1 and points a to G in fig. 2 are completely corresponding to each other. The invention can treat various combustible substances, including solid, liquid and gaseous combustible substances. Substances of different nature are fed into the gasifier 10 via a suitable fuel feeder 81. For example, the fuel feeder 81 that transports solid fuel may be a screw conveyor, and the fuel feeder 81 that transports liquid and gaseous fuel may be a nozzle. The gasification furnace 10, which may be various types of hearths, is located at a corresponding position between points a to B in fig. 2, and for example, the gasification furnace 10 may be a fluidized bed.

When the combustible material in solid or liquid state is in the condition of ER < 1, the reaction gas (such as oxygen, air, water vapor, etc.) with the reaction gas amount of Q1 is added through the reaction gas supply device 41, and then the point A in FIG. 1 and FIG. 2 is reached. The reaction process comprises the following steps: of substancesSome of them oxidize and release chemical energy, and at the same time, the substances which can not be oxidized are cracked and converted into gaseous substances due to high temperature. As shown in fig. 1, when the reaction gas amount Q1 of the reaction gas is given higher, the temperature of the product is also higher, and the reaction gas amount Q1 may be adjusted depending on the nature of the combustible to control the reaction temperature entering the gasification furnace 10. Generally, the temperature entering the gasifier 10 (point a) is between 500 ℃ and 900 ℃. The material is acted by the gasification furnace 10 to generate bottom ash and a first product, and the first product comprises a first gaseous material and fly ash. The gasified substances are mostly converted into low molecular weight gas such as CO and CO₂、H₂、H₂O、CH₄、N₂And the like, as well as minor amounts of Tar (Tar), unburned carbon, ash, and the like. These substances flow out of the gasification furnace 10 in the direction of the gas flow, and large unburned carbon and incombustibles (such as metals, sand, etc.) remain at the bottom of the gasification furnace 10. The remaining larger unburned carbon may continue to react with the injected reaction gas (reaction gas amount Q1), be converted into gaseous matter, or until it exits the furnace 10 with the combustion products. The non-combustible material (collectively referred to as bottom ash) which is not reacted can be effectively separated from the combustible material in this high temperature state, can be discharged from the bottom of the gasification furnace 10, and then sorted by the vibratory screening machine 82 and the magnetic separator 83 and stored in the storage tanks 84 and 85, respectively, and the finer material is mostly bed sand which can be recycled and reused, and for the remaining material with a larger particle size, the metal material contained in the fuel can be separated by using an appropriate sorting apparatus, such as a magnetic separator and a vortex separator. Because the metal material is in an oxygen-deficient environment in this state, the metal material is not easily oxidized into metal oxide, and has a high recovery value. The other remaining non-combustible substances are non-metallic inorganic substances and can also be recovered as a grading composition for reuse.

As shown in fig. 2, a proper amount of reaction gas (reaction gas amount Q2) can be supplied through the reaction gas supply means 42 at the end of the gasification furnace 10 (located between point a and point B near point B), and at this time, part of the gaseous combustible material reacts further with the injected reaction gas, and the temperature of the resultant can be increased. And can further convert high molecular weight gaseous substances, tar, unburned carbon and the like into low molecular weight gaseous forms effectively. In this case, the temperature in the gasification furnace 10 is usually maintained at 500 to 1000 ℃ to prevent ash from softening and slagging on the furnace wall.

Then, high temperature combustible gas from the outlet of the gasification furnace 10 (at point B in FIG. 2) is introduced into the high temperature melting furnace 20. the melting furnace 20 is located at a corresponding position between point B and point C in FIG. 2. after the combustible gas enters the melting furnace 20, an appropriate amount of reaction gas (reaction gas amount Q3) is injected above the combustible gas through the reaction gas supply device 43 (located between point B and point C in FIG. 2). The temperature of the melting furnace 20 can be controlled by controlling the amount of the injected reaction gas, and the temperature of the reacted product is raised above the melting point of ash (e.g., point C in FIG. 1) to produce slag and a second product including a second gaseous material. this step is different from the conventional combustion melting furnace that operates with an excess gas (point C' in FIG. 1). when the fuel has a certain calorific value (about 2,000kcal/kg or more), the fly ash temperature of the melting furnace 20 above the melting point ER < 1 can be controlled with air as the reaction gas Referring to fig. 1, in order to reach a temperature above the melting point of fly ash, the temperature is raised to a point C, where the ER value is about 0.6 and the temperature is about 1400 ℃, and the ER value is about 1.4 and the temperature is about 1400 ℃ when reaching the point C 'of fig. 1, compared to the prior art, the volume of the melting furnace 20 of the present invention is less than half of that of the prior art combustion melting furnace under the same residence time, and besides, the prior art generates nitrogen oxides (as shown by the area indicated by the oblique lines in fig. 1, the point C' is located in the area), the method of the present invention does not generate nitrogen oxides, and other high molecular weight organic substances are converted into a second product with low molecular weight due to high temperature, the molten ash slag can flow to a cooling water tank 87 below the melting furnace 20 through a slag outlet 86 below the melting furnace, the slag may be cooled and discharged for reuse, and the temperature of the slag outlet 86 may be increased by injecting a suitable amount of reactant gas to allow the slag to flow out of the melter 20 without the need for additional fuel as in the prior art, and the temperature within the melter 20 is typically maintained between 1000 c and 1600 c.

It should be noted that the reaction gas supply device 42 may not be provided at the end of the gasification furnace 10, and the required reaction gas may be added to the required amount at a time only by the reaction gas supply device 43 located in the melting furnace 20.

The product (at point C in fig. 1) passing through the melting furnace 20 is a high-temperature combustible gas product, and if the reaction gas is continuously supplied to be sufficiently combusted, it will enter the nitrogen oxide production zone. Thus, in order to avoid the production of nitrogen oxides, the second product is then subjected to at least one heat recovery and at least one oxidative combustion to achieve substantially complete combustion of the second product. The process achieves the purpose of not generating a large amount of nitrogen oxides by controlling the temperature or controlling the oxygen supply amount. Wherein sufficient reactant gas is supplied for the final oxidative combustion to substantially complete combustion of the second product. This process is further described below.

And the sensible heat of the second product is absorbed by a heat recovery device so as to achieve the purpose of reducing the temperature. The combustible gas (at point D in fig. 1) having the reduced temperature is supplied with an appropriate amount of reaction gas (reaction gas amount Q4) through the reaction gas supply means, and the combustible portion contained in the combustible gas is further oxidized while converting its chemical energy into sensible heat of the combustion products, thereby increasing the temperature of the combustion products (at point E in fig. 1).

At this time, if the ER value is already slightly greater than 1, it means that the supplied reaction gas is sufficient and the fuel is sufficiently burned, and the temperature is still lower than the nitrogen oxide generation region, and at this time, all the steps of the present invention can be completed. Thereafter, sensible heat in the combustion products continues to be recovered using heat recovery devices of known art. However, if the ER value is still less than 1 and the temperature approaches the nitrogen oxide generation region after a proper amount of the reaction gas is supplied through the reaction gas supply device 44, if the reaction gas is continuously supplied to complete combustion, the temperature of the combustion product reaches the temperature at which the nitrogen oxide is generated (e.g., the top of the second curve), and at this time, the sensible heat of the combustible gas is absorbed again, and after the temperature is lowered (e.g., point F in fig. 1), a proper amount of the reaction gas is introduced. The two steps are repeated until the combustible components are completely combusted when the actual amount of reactant gas in the combustion products is greater than the theoretical oxygen demand, and the temperature is lower than the temperature at which nitrogen oxides are generated (e.g., point G in fig. 1) although excess oxygen is present, so that the generation of nitrogen oxides is avoided.

In this embodiment, in the state of point C in fig. 1, the combustion product is brought to the state of point D in fig. 1 through the heat recovery device 31, and then to the state of point E in fig. 1 through the reaction gas supply device 44, and then to the state of point E in fig. 1, and then its ER value is still less than 1, at which point if the reaction gas is continuously added, the combustion product will reach the temperature for generating nitrogen oxides, and therefore, the combustible gas will absorb the sensible heat of the combustible gas through another heat recovery device 32, and reduce its temperature (e.g. point E in fig. 1 is reduced to point F), and then an appropriate amount of reaction gas (reaction gas amount Q5) will be introduced through the reaction gas supply device 45, so that the combustion product is further oxidized to release chemical energy to raise the temperature to point G in fig. 1, at which point G the combustion product will be completely combusted under extremely low excess reaction gas because the high temperature gas fuel and the reaction gas are very easily mixed, the excess gas content of the final combustion product is only about 10%, thus effectively reducing the heat emission loss of the excess reaction gas, the thermal efficiency of which is the same as that of the conventional combustion mode G', but the method of the present invention does not have the disadvantage that the conventional combustion mode generates nitrogen oxide pollutants.

It should be noted that the heat recovery device and the reaction gas supply device may be provided in two sets (as in the first embodiment of fig. 2), only one set, or three or more sets according to actual needs. The number of the heat recovery means and the reaction gas supply means is set in relation to the characteristics of the substance to be treated.

It should be noted that, in addition to the above steps of performing heat recovery and performing oxidation combustion sequentially, heat absorption and combustion may be performed simultaneously, in which case the heat recovery device and the reaction gas supply device are integrated into the same device. The devices for simultaneous heat absorption and combustion can also be provided in more than two numbers, the number of which is related to the characteristics of the substance to be treated.

Please refer to fig. 2. The combustion system 1 of the substance of the present invention includes a gasification furnace 10, a melting furnace 20, heat recovery devices 31, 32, and reaction gas supply devices 44, 45. Wherein the gasifier 10 is capable of adding a first reaction gas at a temperature lower than the theoretical oxygen demand of the combustible material to produce bottom ash and a first product, the first product comprising a first gaseous material and fly ash. Melter 20 may add the first product to the second reactant gas at a temperature below its theoretical oxygen demand to raise the temperature of the first product above the melting point of the fly ash to produce molten slag and a second product, the second product comprising a second gaseous material. The heat recovery means 31, 32 may reduce the temperature of gaseous species in the second product. The reactant gas supply means 44, 45 may add reactant gas to further combust the combustible gaseous material in the second product to increase the temperature. The second product is subjected to at least one heat recovery and at least one oxidative combustion by the heat recovery means 31, 32 and the reaction gas supply means 44, 45 to achieve substantially sufficient combustion of the second product. The process achieves the purpose of not generating a large amount of nitrogen oxides by controlling the temperature or controlling the amount of oxygen supplied. Wherein sufficient reactant gas is supplied to substantially fully combust the second product at the time of the last oxidative combustion. Since the functions of each device are the same as those of each step of the method for burning the related substances, the description thereof is omitted.

It should be noted that the heat recovery device and the reaction gas supply device may be provided in two sets (as in the embodiment of fig. 2), only one set, or three or more sets according to actual needs. The number of the heat recovery means and the reaction gas supply means is set in relation to the characteristics of the substance to be treated.

Each group of heat recovery device and the reaction gas supply device can be integrated into a whole besides being arranged in sequence. FIG. 3 is a schematic view of a second embodiment of a combustion system of matter of the present invention. Unlike the first embodiment, the present embodiment has the apparatus 50 that can perform heat recovery and oxidative combustion simultaneously. For example, the apparatus 50 may be constructed with water walls or boiler tubes around the reaction gas supply apparatus for heat recovery. It should be noted that more than two devices 50 may be provided, the number of devices 50 provided being dependent on the nature of the substance to be treated.

In summary, the method and system for utilizing combustion heat of combustible materials of the present invention utilize melting ash in the absence of oxygen to avoid the generation of pollutants such as nitrogen oxides and dioxin, and further convert the combustible materials into combustible gaseous materials with low molecular weight, which are easily mixed with reaction gas, and gradually combust the gaseous fuel at high temperature, so that not only the materials can be effectively and completely combusted, but also the temperature of the combustion products can be reduced below the temperature of the generated nitrogen oxides when excessive reaction gas is generated, thereby achieving the purpose of high thermal efficiency and effectively controlling the generation of pollutants.

In summary, the present invention has characteristics that are quite different from the prior art in terms of the purpose, means and effect. It is to be noted that the above-mentioned embodiments are merely illustrative of the principles of the present invention and its efficacy, and are not to be construed as limiting the scope of the present invention. Those skilled in the art can make modifications and variations to the embodiments without departing from the technical principles and spirit of the present invention. The scope of the invention is to be construed in accordance with the substance defined by the following claims.

Claims (12)

1. A method of combusting matter, comprising the steps of:

step (A): adding a material to the first reaction gas below its theoretical oxygen demand to produce bottom ash and a first product comprising the first gaseous material and fly ash;

step (B): adding the first product to a second reaction gas at a temperature below its theoretical oxygen demand to raise the temperature of the first product above the melting point of the fly ash to produce a molten slag and a second product comprising a second gaseous material;

step (C): performing a plurality of heat recoveries on the second product, and performing a plurality of oxidative combustions on the second product, wherein the plurality of heat recoveries and the plurality of oxidative combustions are performed alternately to achieve substantially complete combustion of the second product;

wherein no substantial amount of nitrogen oxides are produced during step (C).

2. The method of combusting substance of claim 1, wherein sufficient third reactant gas is supplied to combust the second product substantially completely at the time of oxidative combustion carried out at the last time of said multiple oxidative combustion of step (C).

3. The method of combustion of matter as claimed in claim 1 or 2 wherein the substantial production of nitrogen oxides during step (C) is achieved by controlling temperature or controlling oxygen supply.

4. A method of combusting substance according to claim 3, wherein the heat recovery in step (C) is carried out sequentially with the oxidative combustion.

5. The method of burning substances as set forth in claim 1, wherein the temperature in the step (a) is between 500 ℃ and 1000 ℃.

6. The method of burning substances as set forth in claim 1, wherein the temperature in the step (B) is between 1000 ℃ and 1600 ℃.

7. A system for combustion of a substance, comprising:

a gasifier that adds a material below its theoretical oxygen demand to a first reaction gas to produce bottom ash and a first product, the first product comprising a first gaseous material and fly ash;

a melting furnace that adds the first product to a second reactant gas at a temperature below its theoretical oxygen demand to raise the temperature of the first product above the melting point of the fly ash to produce a molten slag and a second product, the second product comprising a second gaseous material;

a plurality of heat recovery devices for heat recovering the second product a plurality of times; and

a plurality of reactant gas supply means for subjecting the second product to a plurality of oxidative combustions, wherein said plurality of heat recoveries alternate with said plurality of oxidative combustions to achieve substantially complete combustion of the second product;

wherein the second product does not substantially produce nitrogen oxides during the heat recovery and the oxidative combustion.

8. The system for combustion of matter recited in claim 7, wherein the last oxidative combustion of said plurality of oxidative combustions supplies sufficient third reactant gas to substantially fully combust said second product.

9. The system of claim 7 or 8, wherein the substantial reduction of nitrogen oxides is achieved by controlling temperature or controlling oxygen supply.

10. The material combustion system of claim 9, wherein said heat recovery is performed in tandem with oxidative combustion.

11. The system of claim 7, wherein the temperature in the gasifier ranges from 500 ℃ to 1000 ℃.

12. The system for combustion of matter recited in claim 7, wherein the temperature in the melting furnace is between 1000 ℃ and 1600 ℃.