JPH11314021A - Method for combustion of hydrogen sulfide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the generation of sulfuric anhydride in a method wherein hydrogen sulfide is burnt with combustion air to produce sulfurous acid gas by keeping the oxygen concentration in the combustion air at more that a specific volume percent and an air ratio at a specific value so that a high concentration hydrogen sulfide is completely burnt. SOLUTION: Coal gas containing hydrogen sulfide generated in a coal gasification furnace is introduced into a hydrogen sulfide absorption tower 2, and hydrogen sulfide in the coal gas is absorbed by using alkanolamine absorption liquid. The desulfurized coal gas is introduced to a gas turbine from a refined gas line 3. Then, an absorbed liquid 8 is introduced into a desorption tower 4, and the hydrogen sulfide is desorbed. The highly concentrated hydrogen sulfide desorbed from the absorbed liquid 8 is introduced into a hydrogen sulfide combustion furnace 11 from a hydrogen sulfide line 10, and burnt. The sulfurous acid gas generated by combustion is introduced into the absorption tower from a combustion exhaust gas line 15. Herein, an oxygen concentration of the air for combustion is allowed to be at least 25 Vol.%, and its air ratio is allowed to be 1.0 to 1.2.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for burning hydrogen sulfide, and more particularly to a method for burning high-concentration hydrogen sulfide from a coal gasifier to produce sulfurous acid gas.

[0002]

2. Description of the Related Art Conventionally, gasifiers for gasifying coal include:
Each system of a fixed bed, a fluidized bed, and an airflow bed has been proposed. Among these methods, the airflow layer is formed by converting coal into fine powder together with an oxidizing agent at a temperature equal to or higher than the melting point of coal ash (1300 to 160).
The gasification efficiency is higher than that of other methods because the gas is supplied to the gasification furnace at 0 ° C.) and gasified. In addition, there are many types of charcoal that can be used, and they are excellent in environmental compatibility, and are suitable for synthesis gas, combined power generation, fuel and fuel of fuel cells, and are being developed. Coal contains sulfur,
This sulfur is converted into hydrogen sulfide and carbonyl sulfide in the gasifier. Its concentration is governed by the sulfur content in the coal, but is in the range of several hundred to several thousand ppm. When the gas generated by gasification is used as fuel and raw material for synthesis gas, combined cycle power generation, and fuel cells, it is necessary to remove hydrogen sulfide and carbonyl sulfide in the generated gas. It has been known. In the dry method, after hydrogen sulfide is reacted with iron and nickel oxides as desulfurizing agents and then oxidized with a gas containing oxygen, sulfur is liberated and the desulfurizing agent is regenerated. Yes. On the other hand, in the wet method, hydrogen sulfide is absorbed using an alkanolamine absorption liquid, and then hydrogen sulfide is desorbed from the absorption liquid to recover elemental sulfur by the Claus reaction. However, the demand for recovered sulfur is sluggish, and there are many problems because it is a flammable dangerous substance. Therefore, if the sulfur content in coal is recovered as gypsum by the lime-gypsum desulfurization method, it is suitable for a plant that consumes a large amount of coal, such as a coal gasification combined cycle power plant, because it has demand and has stable properties. In order to apply the lime-gypsum desulfurization method to coal gasification, instead of the undesired Claus method, high-concentration hydrogen sulfide from a wet method may be oxidized to sulfur dioxide gas and then treated by a lime-gypsum desulfurization method. As a method of burning hydrogen sulfide, hydrogen sulfide is partially oxidized in the first step of the Claus method to obtain a sulfur dioxide gas that is half the hydrogen sulfide in a molar ratio. 2H ₂ S + 3O ₂ → 2SO ₂ + 2H ₂ O (1) 2H ₂ S + SO ₂ → 3S + 2H ₂ O (2)

[0003]

However, various problems are expected when high-concentration hydrogen sulfide is burned into sulfur dioxide to be treated by a lime-gypsum desulfurization method. 1) Since conventional hydrogen sulfide combustion technology is partial oxidation, there is no consideration that unburned hydrogen sulfide does not remain in the combustion exhaust gas, and toxic hydrogen sulfide in the exhaust gas is not absorbed by the absorption tower of the lime gypsum desulfurization method. Released into the environment along with the exhaust gases. 2) In order to prevent unburned hydrogen sulfide from remaining in the combustion exhaust gas, excess oxygen may be supplied to the hydrogen sulfide in the formula (1). For example, burning hydrogen sulfide at an air ratio of 1.5 solves the problem of unburned components, but excess oxygen further oxidizes the sulfur dioxide gas generated by burning hydrogen sulfide as shown in equation (3). Sulfuric anhydride is converted into fine sulfuric acid mist by reacting with water as shown in formula (4), and is not absorbed by the absorption tower in the lime gypsum desulfurization method and is released to the environment together with exhaust gas. It may also cause the flue of the desulfurization unit to corrode. 2SO ₂ + O ₂ → 2SO ₃ (3) SO ₃ + H ₂ O → H ₂ SO ₄ (4) An object of the present invention is to provide a high-concentration hydrogen sulfide. In order to prevent the generation of sulfuric anhydride.

[0004]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for burning hydrogen sulfide, in which hydrogen sulfide is combusted with combustion air to produce sulfurous acid gas.
It is achieved by setting the air ratio to 1.0% to 1.2% by volume or more. The above object is a coal having a hydrogen sulfide combustion step in which hydrogen sulfide separated from coal gas obtained by gasifying coal is burned with combustion air to produce sulfurous acid gas, and a desulfurization step of absorbing sulfurous acid gas with limestone slurry. In the gasification method, the oxygen concentration of the combustion air is 25 V
ol% or more and an air ratio of 1.0 to 1.2. It is desirable that the oxygen concentration of the combustion air be 25 vol% or more using oxygen obtained by air separation. The oxygen concentration of the combustion air was adjusted to 2 using the oxidant oxygen.
It is desirable to be 5 Vol% or more. According to the above configuration, by increasing the oxygen partial pressure, hydrogen sulfide can be completely oxidized, and residual hydrogen sulfide can be eliminated. Also, by increasing the oxygen partial pressure, the reaction temperature rises and the oxidation reaction is promoted. By minimizing the amount of oxygen remaining after the oxidation of hydrogen sulfide, the production of sulfuric anhydride can be prevented.

[0005]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a flowchart showing the configuration of the embodiment of the present invention. 1 is a coal gasifier 3 not shown
A coal gas line for introducing coal gas containing hydrogen sulfide generated in 0, a hydrogen sulfide absorption tower for absorbing hydrogen sulfide in coal gas using an alkanolamine absorbent, and a gas not shown for desulfurized coal gas A purified gas line leading to the turbine 90, 4 is a desorption tower for desorbing hydrogen sulfide from the absorbent 8, 11 is a hydrogen sulfide combustion furnace for burning high-concentration hydrogen sulfide desorbed from the absorbent 8, and 15 is a combustion sulfide furnace. A flue gas line that guides the generated sulfurous acid gas to an absorption tower 70 (not shown), a combustion air line 16 that guides combustion air from a fan 14 to a hydrogen sulfide combustion furnace 11, and a combustion air line 12 that flows from an oxygen source to a combustion air line 16. An oxygen line for injecting oxygen at a concentration. In this embodiment, the oxygen concentration of the combustion air is set to 25 Vol% or more and the air ratio is set to 1.0 to 1.
It is 2. According to the combustion method of the present embodiment, high-concentration hydrogen sulfide is converted into sulfur dioxide gas without generating unburned hydrogen sulfide and sulfuric anhydride in the hydrogen sulfide combustion furnace 11. The control of the hydrogen sulfide combustion furnace 11 detects the oxygen concentration of the combustion air in the combustion air line 16 and adjusts the amount of oxygen injected from the oxygen line 12 so that the oxygen concentration becomes 25 Vol% or more. Alternatively, the opening of the valve for adjusting the amount of oxygen injected from the oxygen line 12 may be linked to the opening of the valve for adjusting the combustion air supplied from the fan 14 to the hydrogen sulfide combustion furnace 11. Further, the amount of oxygen injected from the oxygen line 12 may be adjusted according to the supply amount of hydrogen sulfide. In short, any means can be used as long as the condition that the oxygen concentration of the combustion air is 25% by volume or more and the air ratio is 1.0 to 1.2 can be satisfied.

Next, data serving as a basis of the present invention will be described. FIG. 2 is a chart showing data of the embodiment of the present invention. This figure is a chart showing the results of the combustion test, in which the horizontal axis represents the oxygen concentration of the supplied combustion air, and the vertical axis represents the concentrations of residual hydrogen sulfide and the produced sulfuric anhydride in the combustion gas. In the combustion test, the oxygen concentration of the combustion air was changed for each of the four cases where the air ratio was 1.1 to 2.0 with respect to 50% by volume of hydrogen sulfide, and the residual hydrogen sulfide and the generated sulfuric anhydride in the combustion gas were changed. The concentration was analyzed. Oxygen concentration 21 Vo
For 1% or more, oxygen was injected into the air from an oxygen cylinder. As a result of the test, the oxygen concentration was 25 Vol% regardless of the air ratio.
With the above, the residual hydrogen sulfide was below the detection limit, and when the air ratio was 1.0 to 1.2, the generated sulfuric anhydride was below the detection limit regardless of the oxygen concentration. Therefore, it is possible to suppress the generation of sulfuric anhydride due to excess oxygen by setting the air ratio to 1.0 to 1.2, and to completely oxidize hydrogen sulfide by setting the oxygen concentration to 25 vol% or more, thereby suppressing the residual hydrogen sulfide.

Next, another embodiment of the present invention will be described.
FIG. 3 is a flowchart showing the configuration of another embodiment of the present invention. The basic configuration shown in this figure is the same as that of FIG. 1 except that the atmosphere is supplied to an air separation device 20 to separate nitrogen and increase the oxygen concentration to 25 Vol% or more, and the hydrogen sulfide combustion furnace 1
1 combustion air. When the oxygen concentration of the air separation device 20 is increased to 25% by volume, the adsorption type using the molecular sieve reduces both the equipment cost and the operation cost.

FIG. 4 is a flowchart showing the configuration of another embodiment of the present invention. This diagram shows the coal gasifier
An example in which the embodiment shown in FIG. The oxidant oxygen of the coal gasifier is removed from the air separation device 50 to the oxygen line 53.
This is an example in which the oxygen concentration is increased to 25% by volume or more by injecting the oxygen from the oxygen line 12 into the combustion air line 16 by the following method. Although the drawing shows the fan 14 for supplying the combustion air, the compressed air by the air compressor 80 may be supplied. Also, instead of combustion air, a cryogenic air separation device 5
Only the oxygen separated at 0 may be supplied to the hydrogen sulfide combustion furnace 11.

[0009]

According to the present invention, hydrogen sulfide is completely oxidized by increasing the oxygen partial pressure to eliminate residual hydrogen sulfide, and oxygen remaining after oxidation of hydrogen sulfide is minimized. Can be prevented from being generated.

[Brief description of the drawings]

FIG. 1 is a flowchart showing a configuration of an embodiment of the present invention.

FIG. 2 is a table showing data of the embodiment of the present invention.

FIG. 3 is a flowchart showing a configuration of another embodiment of the present invention.

FIG. 4 is a flowchart showing a configuration of another embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Coal gas line 2 Hydrogen sulfide absorption tower 3 Purification gas line 4 Desorption tower 8 Absorbent 10 Hydrogen sulfide line 11 Hydrogen sulfide combustion furnace 12 Oxygen line 13 Air line 14 Fan 15 Combustion exhaust gas line 16 Combustion air line 20 Air separation device 21 Nitrogen Line 30 Coal Gasifier 40 Coal 50 Air Separator 53 Oxygen Line 60 Deduster 62 Desulfurizer 70 Absorption Tower 71 Exhaust Gas Line 80 Air Compressor 81 Compressed Air Line 82 Compressed Air Line 90 Gas Turbine 100 Waste Heat Recovery Boiler 110 chimney

Claims (4)

[Claims] 1. A method for combusting hydrogen sulfide with combustion air to generate sulfurous acid gas, wherein the combustion air has an oxygen concentration of 25 vol% or more and an air ratio of 1.0 to 1.2. A method for burning hydrogen sulfide. 2. A hydrogen sulfide combustion step in which hydrogen sulfide separated from coal gas obtained by gasifying coal is burned with combustion air to produce sulfurous acid gas, and a desulfurization step in which the sulfurous acid gas is absorbed by limestone slurry. A coal gasification method, comprising: setting the oxygen concentration of the combustion air to 25 Vol% or more and setting the air ratio to 1.0 to 1.2. 3. The coal gasification method according to claim 2, wherein the oxygen concentration of the combustion air is adjusted to 25% by volume or more using oxygen obtained by air separation. 4. The coal gasification method according to claim 2, wherein the oxygen concentration of the combustion air is set to 25% by volume or more using oxygen as an oxidizing agent.