TW202504676A - Ammonia mixed fuel supply method and device - Google Patents

Abstract

The present invention provides a technology for supplying ammonia mixed fuel without generating precipitates. A method includes: a step of removing CO2 from a fuel gas containing _CO2 ; a step of dehumidifying the fuel gas from which _CO2 has been removed; and a step of mixing ammonia in the piping system when the fuel gas _from which _CO2 has been removed and dehumidified is transported to a fuel gas using device using the piping system, wherein the method heats the piping system from the location where the ammonia is mixed to the fuel gas using device to maintain the temperature of the fuel gas at 60°C or above. A device includes: a mixer for mixing ammonia in the middle of a piping system for transporting a fuel gas containing _CO2 ; a heating device for heating the piping system from the mixer to a fuel gas using device to make the temperature of the fuel gas above 60°C; a _CO2 removal device, which is arranged in the piping system upstream of the mixer and removes _CO2 from the fuel gas containing _CO2 ; and a dehumidifier, which is arranged between the _CO2 removal device and the mixer.

Description

Ammonia mixed fuel supply method and device

The present invention relates to a method for mixing ammonia with a fuel gas containing _CO2, such as by-product gas from a steel plant, and supplying the mixture to a fuel gas using equipment, and an apparatus for the method. Here, the symbol "N" for the volume unit of the gas indicates a standard state, and the standard state indicates a state of a temperature of 0°C and a pressure of 101325 Pa.

In steel mills, byproduct gases containing combustible components such as hydrogen ( _H2 ), hydrocarbons, and CO, which are generated during the refining process of raw materials such as iron ore and coal, are widely used as fuel. The byproduct gases also contain a large amount of impurities. For example, even after desulfurization treatment in chemical equipment for the purpose of cleaning, the byproduct gases contain about 200 Vol.ppm to 3000 Vol.ppm of _H2S . In addition, the byproduct gases contain about 2 Vol.% to 25 Vol.% of _CO2 and also contain water equivalent to a saturated state.

In recent years, the goal of carbon neutrality has become popular, and research on the use of fuels other than fossil fuels has been underway. As we are in the transition period of completely switching fuel gas to renewable energy, there is a growing demand for mixing non-fossil fuels such as hydrogen and ammonia with by-product gas for use as fuel.

Hydrogen fuel is generally chemically stable and very difficult to react with components in by-product gas, and has been widely tested as a mixed fuel. However, ammonia (NH ₃ ), which has attracted attention as a carbon neutral fuel along with hydrogen, is known to be easily soluble in water and easily reacts with components in by-product gas. For example, ammonium carbonate (NH ₄ ) ₂ CO ₃ ·H ₂ O or ammonium bicarbonate (NH ₄ )HCO ₃ is easily generated as a precipitate, so it can be confirmed that it is difficult to handle.

As a countermeasure, Patent Document 1 discloses the following method: when analyzing ammonia in a gas containing carbon dioxide, ammonia, and water, an inert gas such as nitrogen or argon is injected and diluted to 3 to 10 times to suppress the precipitation of ammonium carbonate at room temperature. In addition, Patent Document 2 discloses that when continuously sampling coal gas, a scrubber is set to remove ammonium bicarbonate. [Prior art document] [Patent document]

Patent document 1: Japanese Patent Publication No. 54-070095 Patent document 2: Japanese Patent Publication No. 08-122228 Patent document 3: Japanese Patent Publication No. 5939189

[Problems to be solved by the invention] However, the existing technology has the following problems. Even if the method disclosed in Patent Document 1 can be used for gas analysis, there is a risk that the fuel gas will be diluted and cannot be used as fuel. In addition, if the purpose of the technology disclosed in Patent Document 2 is simply to perform gas analysis, the method can be used to remove precipitates, but in the case of mixing ammonia in the fuel gas, there is a problem that the device structure cannot be directly applied.

The present invention is made in view of the above situation, and its purpose is to provide a method and a device for supplying ammonia mixed with _CO2 -containing fuel gas to fuel gas using equipment without generating precipitates. [Means for Solving the Problem]

The ammonia mixed fuel supply method of the present invention, which is helpful in solving the above-mentioned problem, is characterized in that it includes: a step of removing _{CO2 from} a fuel gas containing CO2; a step of dehumidifying the fuel gas from which _CO2 has been removed _; and a step of mixing ammonia in the piping system when the piping system is used to transport the dehumidified fuel gas from which CO2 has been removed to a fuel gas using device. The method heats the piping system from the position where the ammonia is mixed to the fuel gas using device to maintain the temperature of the fuel gas above 60°C.

Furthermore, for the ammonia mixed fuel supply method of the present invention, "further comprising the step of desulfurizing the fuel gas containing CO ₂ " can be a better solution. Furthermore, the fuel gas containing CO ₂ includes by-product gas from a steel plant.

The ammonia mixed fuel supply device of the present invention, which is helpful in solving the above-mentioned problem, is characterized in that it includes: a mixer, which mixes ammonia in the middle of the piping system for transporting _CO2 -containing fuel gas; a heating device, which heats the piping system from the mixer to the fuel gas use equipment to make the temperature of the fuel gas above 60°C; a _CO2 removal device, which is arranged in the piping system more upstream than the mixer, and removes _CO2 from the _CO2- containing fuel gas; and a dehumidifier, which is arranged between the _CO2 removal device and the mixer.

Furthermore, a desulfurization device for removing sulfur components from the fuel gas containing _CO2 in advance may be a better solution for the ammonia mixed fuel supply device of the present invention. [Effect of the Invention]

According to the present invention, in the piping system for mixing ammonia with _CO2 -containing fuel gas such as by-product gas of steel mills, the precipitation of ammonium carbonate or ammonium bicarbonate and the clogging of the piping can be suppressed. Therefore, ammonia-mixed fuel can be stably supplied as a fuel gas that contributes to carbon neutralization. In addition, by removing _CO2 , it is also expected that the calorific value of the fuel gas will increase, thereby producing an added value effect. Furthermore, in the case where the _CO2 -containing fuel gas contains sulfur components, by using a desulfurization device for desulfurization, the catalytic effect of the precipitation of ammonium carbonate due to the sulfur component can be reduced.

The following is a detailed description of the embodiments of the present invention. In addition, each figure is a schematic diagram and sometimes differs from the actual situation. In addition, the following embodiments are illustrative of the device or method used to embody the technical idea of the present invention, and the structure is not specifically specified as the following content. That is, the technical idea of the present invention can be added with various changes within the technical scope described in the patent application scope.

The inventors conducted a composition analysis of byproduct gas from a steel plant and found that the byproduct gas contains a large amount of impurities in addition to combustible components such as hydrogen (H ₂ ), hydrocarbons, and CO. In particular, even after desulfurization treatment in a chemical plant for the purpose of cleaning the byproduct gas, the byproduct gas contains sulfur (S) components derived from H ₂ S at about 100 Vol.ppm to 3000 Vol.ppm, and contains saturated water.

Here, first, a case will be described in which ammonia is mixed in the by-product gas, and a precipitate is generated in the coexistence of ammonia NH ₃ , water H ₂ O, and carbon dioxide CO ₂ , and further a gas containing sulfur components such as H ₂ S also coexists.

<Ammonium carbonate (NH ₄ ) ₂ CO ₃ ·H ₂ O> When sulfur (S) or the like is present as a catalyst in the precipitation reaction and the gas is cooled to room temperature, ammonium carbonate is precipitated as colorless crystals with an ammonia odor. As its properties, ammonium carbonate decomposes at 58°C to form ammonia NH ₃ , water H ₂ O, and carbonic acid gas CO ₂ .

<Ammonium bicarbonate (NH ₄ )HCO ₃ > When carbon dioxide is allowed to act on concentrated ammonia water while cooling, ammonium bicarbonate is precipitated as colorless crystals. As its properties, ammonium bicarbonate decomposes at 60°C to form ammonia NH ₃ , water H ₂ O, and carbonic acid gas CO ₂ .

<Ammonium carbamate NH ₂ COONH ₄ > It is formed by the reaction of dry ice and liquid ammonia, or by passing CO ₂ into an alcoholic ammonia solution. It precipitates as colorless crystals. It is stable in dry air. It decomposes into ammonia NH ₃ and carbonic acid gas CO ₂ when heated to 60°C. It loses water and becomes urea when heated to about 130°C in a closed tube.

Focusing on the properties of the precipitates as described above, a method of suppressing the precipitation of ammonium carbonate, ammonium bicarbonate, etc. when ammonia is mixed with a fuel gas containing CO ₂ has been studied. As an ammonia mixed fuel supply device 1, a device such as that shown in FIG. 1 is exemplified.

Carbon dioxide CO ₂ in the by-product gas 2 not only causes precipitates but also does not contribute to the combustion reaction. Therefore, by removing carbon dioxide CO ₂ from the by-product gas 2, the calorific value per unit volume of the fuel gas can also be increased. As a dry gas, CO ₂ is preferably set to less than 1 Vol.%. As a CO ₂ removal device 4, for example, carbon dioxide CO ₂ can be absorbed as carbonate by contacting with an alkali or the like. In addition, methanation can also be used to convert carbon dioxide CO ₂ or carbon monoxide CO in the by-product gas 2 into methane CH ₄ , hydrogen H ₂ or nitrogen N ₂ by reacting with ammonia NH _3. As an example of methanation, the example disclosed in patent document 3 can be cited.

The dehumidifier 5 is used to remove saturated water in the byproduct gas 2 or water generated by methanation. The dehumidifier 5 usually cools the gas to dehumidify, so it needs to be installed before mixing ammonia. If cooling is performed after mixing ammonia, there is a possibility that the precipitate will precipitate in the dehumidifier 5 and cause clogging of the piping. In addition, it is preferably installed in the rear section of the _CO2 removal device 4. Regarding the amount of water after dehumidification, it is preferably below the dew point of 10°C.

Furthermore, it includes a mixer 8, which mixes ammonia 6 in a piping system 7 that supplies the byproduct gas 2 to a fuel gas using device 10. The mixer 8 is preferably capable of controlling the flow rate. A heating device 9 is provided in the piping system, and the heating device 9 heats the fuel gas after the position where the ammonia 6 is mixed so that the temperature becomes 60°C or above. As the heating device 9, a heater using resistance heating or an outer coil of a steam piping can be listed. It is preferable to heat the fuel gas flowing into the mixer or the supplied ammonia 6 to 60°C or above. Thereby, the temperature drop in the ammonia mixing section can be suppressed. Although the upper limit of the temperature is not specified, considering the energy cost, it is preferable to make the fuel gas after the position where the ammonia 6 is mixed to be below 100°C.

If the sulfur content in the by-product gas is 200 Vol.ppm or more in terms of H ₂ S, it is preferred to include a desulfurization device 3. Furthermore, it is preferred to make the sulfur content in the by-product gas in a dry state less than 200 Vol.ppm in terms of H ₂ S. Examples of the desulfurization device 3 include the limestone method, the magnesium hydroxide method, the ammonia method, the electron beam method, the sodium method, etc. Any method may be used as long as the H ₂ S concentration after treatment is less than 200 Vol.ppm.

<Example 1> In the device structure shown in Figure 2, a simulated by-product gas 2A is supplied as a fuel gas containing _CO2 , and an ammonia mixed fuel supply test is carried out. The pipe diameter is set to 20A. As a heating device 9, a steam trace in which a steam pipe is installed along the piping system 7, and the gas temperature is adjusted to 68°C. The length of the piping system 7 from the ammonia mixer 8 to the burner (burner) as the fuel gas using equipment 10 is set to 2 m. The simulated by-product gas 2A is configured to remove moisture using a dehumidifier 5 upstream of the ammonia mixer 8. The flow rate of the simulated by-product gas 2A is set to 4.9 ^Nm3 /h, and the flow rate of the mixed ammonia is set to 0.7 ^Nm3 /h. The composition of the simulated byproduct gas 2A is H ₂ : 25 Vol.%, N ₂ : 27 Vol.%, CO: 21 Vol.%, CO ₂ : 12 Vol.%, CH ₄ : 15 Vol.%, H ₂ S: less than 200 Vol.ppm in a dry state. The lower calorific value of the simulated byproduct gas 2A is 2563 kcal/Nm ³ (10.72 MJ/Nm ³ ). In addition, the dew point of the simulated byproduct gas 2A after dehumidification is 9°C.

After the 100-hour ventilation test, a small amount of precipitates such as ammonium carbonate or ammonium bicarbonate were found in the piping system.

<Example 2> The same apparatus structure as that of Example 1 is used, and as the simulated by-product gas 2A, a fuel gas from which carbon dioxide gas CO ₂ is removed by methanation is used. The pipe diameter and gas flow rate are set to be the same as those of Example 1. The composition of the simulated by-product gas 2A is H ₂ : 18 Vol.%, N ₂ : 47 Vol.%, CO: 0 Vol.%, CO ₂ : less than 1 Vol.%, CH ₄ : 35 Vol.%, H ₂ S: less than 200 Vol.ppm in a dry state. The lower calorific value of the simulated by-product gas 2A is 3474 kcal/Nm ³ (14.53 MJ/Nm ³ ). In addition, the dew point of the simulated by-product gas 2A after dehumidification is 9°C.

After the 100-hour ventilation test, no precipitates such as ammonium carbonate or ammonium bicarbonate were found in the piping system.

<Example 3> In the device structure shown in Figure 3, a simulated by-product gas 2A is supplied as a fuel gas containing _CO2 , and an ammonia mixed fuel supply test is carried out. The piping diameter is set to 20A. The piping is not heated but the test is carried out in an environment of normal temperature, i.e., 15°C to 25°C. The length of the piping system 7 from the ammonia mixer 8 to the burner of the fuel gas using equipment 10 is set to 2 m. The gas flow rate is set to the same as Example 1. The simulated by-product gas 2A is in a saturated water state. The composition of the simulated byproduct gas 2A is H ₂ : 25 Vol.%, N ₂ : 27 Vol.%, CO: 21 Vol.%, CO ₂ : 12 Vol.%, CH ₄ : 15 Vol.%, H ₂ S: 1250 Vol.ppm in a dry state. The lower calorific value of the simulated byproduct gas 2A is 2563 kcal/Nm ³ (10.72 MJ/Nm ³ ).

In the 5-hour ventilation test, the pipe was clogged by the precipitate of ammonium carbonate. [Industrial Applicability]

The technology of the present invention enables the supply of ammonia mixed with _CO2 -containing fuel gas to fuel gas-using equipment without generating precipitates, thereby stably supplying carbon-neutral fuel and reducing environmental load, which is therefore useful in industry.

1: Ammonia mixed fuel supply device 2: Byproduct gas (fuel gas containing CO ₂ ) 2A: Simulated byproduct gas 3: Desulfurization device 4: CO ₂ removal device 5: Dehumidifier 6: Ammonia 7: Piping system 8: (Ammonia) mixer/ammonia mixer 9: Heating device 10: Fuel gas use equipment (burner)

FIG. 1 is a schematic diagram showing the schematic structure of an ammonia mixed fuel supply device of an embodiment of the present invention. FIG. 2 is a schematic diagram showing the schematic structure of an ammonia mixed fuel supply device used in Embodiment 1 and Embodiment 2. FIG. 3 is a schematic diagram showing the schematic structure of an ammonia mixed fuel supply device used in Embodiment 3.

1: Ammonia mixed fuel supply device

2: Byproduct gas (fuel gas containing CO ₂ )

3: Desulfurization device

4:CO ₂ removal device

5: Dehumidifier

6: Ammonia

7: Piping system

8: (Ammonia) mixer/ammonia mixer

9: Heating device

10: Fuel gas use equipment (burner)

Claims (5)

A method for supplying an ammonia mixed fuel comprises: a step of removing _CO2 from a fuel gas containing _CO2 ; a step of dehumidifying the fuel gas from which _CO2 has been removed; and a step of mixing ammonia in the piping system when the piping system is used to transport the dehumidified fuel gas from which _CO2 has been removed to a fuel gas using device. The method for supplying an ammonia mixed fuel heats the piping system from the position where the ammonia is mixed to the fuel gas using device to maintain the temperature of the fuel gas above 60°C. The method for supplying an ammonia mixed fuel as described in claim 1 further comprises a step of desulfurizing the _CO2 -containing fuel gas. The method for supplying an ammonia mixed fuel as described in claim 1 or 2, wherein the _CO2- containing fuel gas is set to be a by-product gas of a steel plant. A supply device for an ammonia mixed fuel comprises: a mixer for mixing ammonia in the middle of a piping system for transporting a fuel gas containing _CO2 ; a heating device for heating the piping system from the mixer to a fuel gas using equipment to make the temperature of the fuel gas above 60°C; a _CO2 removal device, disposed in the piping system upstream of the mixer, for removing _CO2 from the _CO2 -containing fuel gas; and a dehumidifier, disposed between the _CO2 removal device and the mixer. The ammonia mixed fuel supply device as described in claim 4 further includes a desulfurization device for removing the sulfur component of the _CO2 -containing fuel gas in advance.