JPS63122790A - Purification of high-temperature reducing gas - Google Patents

Abstract

PURPOSE:To purify the titled gas efficiently, by removing sulfides from a high- temperature reducing gas with an adsorbent, introducing an O2-containing regenerating gas to the adsorbent and making the sulfides flow as SO2 and converting the SO2 with an SO2 reducing catalyst set at the rear flow side of the adsorbent. CONSTITUTION:Coal 1 and oxygen 2 are fed to a gasifying furnace 3 to give crude gas 4, from which dust is removed by a dust collector 5 to give a high- temperature reducing gas 6. The gas is passed through an adsorption reactors 17-19 packed with an adsorbent to adsorb sulfides and then an oxygen- containing regenerating gas 40 is introduced to the adsorbent 20 and a sulfurous acid-containing gas is made to flow. Then, the flow gas and the high- temperature reducing gas flowing from the adsorbent 20 are fed to reactors 24-26 packed with a sulfurous acid reducing catalyst set at the rear flow side of the adsorbent 20, the sulfurous acid gas in the flow gas is converted into sulfur of single substance, a gas flowing from the reducing catalyst 27 is fed to a separator 38, sulfur of single substance is separated, the residual gas 39 is recycled as part of the regenerating gas for the adsorbent.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a method for purifying high-temperature reducing gases, such as hydrogen sulfide contained in a high-temperature reducing gas mixture, such as the product gas of a coal gasification process. etc., and how to rationally remove them.

[Conventional technology]

In recent years, due to the depletion of oil resources and soaring prices, there has been a call for diversification of fuels (or raw materials), such as coal and heavy oil (tar sand oil, oil shale oil, Daqing heavy oil, Maya crude oil, vacuum residual oil, etc.). Development of utilization technology is progressing. A typical example is the method of gasifying coal or heavy oil to use as power generation, fuel, or synthetic raw material.

However, this gasification product gas contains hydrogen sulfide ranging from several hundred ppm to several 11,000 ppp, depending on the raw material coal and heavy oil, and this is used to prevent pollution, corrosion of backlight equipment, and poisoning of catalysts. , it is necessary to remove it.

There are wet and dry methods for this removal, but the wet method requires cooling the process gas, which is disadvantageous in terms of thermoeconomics, and coexisting components (tar, naphthalene, halogen, NH
,,FIIC! N, C! The process becomes complicated because it requires equipment for pretreatment and wastewater treatment to remove OEI media (e.g., OEI media and dust) or to prevent contamination and deterioration of the absorption liquid.

On the other hand, the dry method is thermoeconomically advantageous and has a simple process configuration, so it has become common to adsorb and remove sulfides at high temperatures using an adsorbent containing metal oxides as the main component. Adsorbents include Fe, Zn, Mo, Mn, Cu, and W.
Metal oxides such as H
In the case of Fe, o, the adsorption reaction is said to proceed as shown in equations (1) to (7).

Fe,03 +H,-+2FeO+horse o------(1
)51F8,0. -)-4+2Fe, 04+H
,O---(2)F'e,O,+Co→2FeO+0
0. ”-(3)5Fe, 03 +CO-
+ 2Fel○, +(! O, -----・(4) Fe
O + horse E? -+FeS+H,O--(5)Fe,O
,-1-H,-)-5FItS-45Fes-4-aH
,O---・-(6)Fes 04 + Co+5
HtB →5 Fe S + 5% O+ C!
OH-”-” (7) Next, the adsorbent after the adsorption reaction is regenerated into metal oxide with oxygen-containing gas as shown in equation (8), and by repeating this adsorption and regeneration reaction, the sulfur compound in the high-temperature reducing gas is is collected and removed as sulfur dioxide gas.

4FeEl+ yo, 42Fe, O8+aso,
+++ (s) The adsorbent used in this process is the metal oxide mentioned above, either alone or supported on a heat-resistant porous material, which is formed into a spherical or cylindrical shape in the case of a moving bed method. In the case of fixed bed systems, honeycomb-shaped molds have traditionally been used.

Since gas purified by removing sulfur compounds from reducing gas such as coal gasification gas is used as an energy source, it is preferable to use a process that produces it stably by degrees of co, Tita. 4) The reaction of formula must be suppressed as much as possible. In the moving bed system, the adsorption process and regeneration process are repeated continuously, so the above technical issues are easy to overcome, but in the fixed bed system, the adsorption process and regeneration process are repeated intermittently, so it is difficult to switch between the adsorption layer and the regeneration layer. However, since the Co, H, and concentration in the purified gas decreases at the start of the adsorption reaction, this method is not practically preferred as a method for purifying high-temperature reducing gases.

Therefore, the present applicant sequentially switched three fixed bed reactors to regenerate the adsorbent that had adsorbed sulfur compounds with an oxygen-containing gas, and then purified the regenerated adsorbent before and after the adsorbent using a high-temperature reducing gas. Reduction in the purified gas is achieved by continuously repeating the steps of reducing the target reducing gas concentration until they become the same, and then aerating the high-temperature reducing gas and adsorbing and removing the sulfur compounds with the adsorbent. He proposed a method for purifying high-temperature reducing gases that stabilizes the concentration of reactive gases. (Japanese Patent Application No. 60-085412) On the other hand, in the regeneration process, in order to reduce the amount of gas to be processed, the regeneration reaction of equation (8) is carried out sequentially in a circulation system, and the SO produced and the concentration are concentrated, and then the sulfur is recovered. ing. However, in this method, the regenerating gas containing about 14 to 10 parts of 5O comes into contact with the adsorbent in a high-temperature atmosphere of 400 to 800°C, and the amount of by-product SO increases, which puts the adsorbent in an extremely harsh state. Therefore, long-term use of the adsorbent cannot be expected.

The adsorbent after adsorbing S is regenerated according to equation (8), but since this reaction is usually carried out at 400 to 800° C. and is an exothermic reaction, the adsorbent is required to have heat resistance. Furthermore, SO generated in the regeneration reaction and Bo that partially becomes So on the adsorbent.
Durability against x-containing gas is also required, and adsorbents are selected from these viewpoints. However, in order to reduce as much as possible the amount of gas to be treated when the SO produced in the regeneration reaction is recovered as a solid such as elemental sulfur or calcium sulfate, the regeneration process is usually carried out in a circulation system.
is concentrated to about 4 to 10 inches. Therefore, the adsorbent is 40
Since it is used under extremely harsh conditions, such as contacting gas containing high concentrations of So at high temperatures of 0 to 800 degrees Celsius, the concentration of SO in the recycled regeneration gas should be kept as low as possible to use the adsorbent in a better environment. It is desirable to do so, and since the adsorbent cannot be replaced during use in a fixed bed type, this is particularly strongly desired from the viewpoint of improving process reliability.

[Problem that the invention seeks to solve]

The present invention eliminates the disadvantages of conventional high-temperature reducing gas purification methods by decomposition, recovers sulfur dioxide gas as elemental sulfur from the gas flowing out from the adsorbent in the regeneration process, and reduces the load on the recovery process. By circulating the gas to the regeneration process, the concentration of sulfur dioxide gas in the recycled regeneration gas is reduced,
The present invention aims to provide a method for purifying high-temperature reducing gases that enables long-term use of adsorbents.

[Means for solving problems]

The present invention is a gas purification method that adsorbs and separates sulfides in a high-temperature reducing gas, in which a sulfur dioxide gas reduction catalyst is arranged on the downstream side of an adsorbent, and an oxygen-containing regeneration gas is introduced into the adsorbent in the regeneration process to reduce sulfur dioxide. The gas-containing gas is discharged, and the discharged gas and the high-temperature reducing gas discharged from the adsorbent in the adsorption step are introduced into the reduction catalyst to convert the sulfurous acid gas in the discharged gas into elemental sulfur. This is a method for purifying a high-temperature reducing gas, which is characterized in that after separating elemental sulfur from the outflowing gas, the remaining gas is used as part of the regeneration gas of the adsorbent.

〔Example〕

FIG. 1 is a flow diagram of a rounding apparatus implementing the present invention. Coal 1 and a small amount of air or oxygen 2 are supplied to a gasification furnace S for partial combustion and gasification, and the crude gas 4 whose main components are CO is reduced to a dust concentration of 10 g/g"N by a dust collector 5. The gasification gas 6 reduced to below is supplied to the dry desulfurization equipment.This gasification gas 6 differs depending on the type of coal and gasification conditions, but in addition to dust, it contains several 1a to several thousand pp.
m's horse El, C! O8, ME, and trace amounts of HF.

The gas temperature is 250 to 500°C, which is recovered by a steam heater at the outlet of the gasifier 5, and the pressure is normal pressure to 25 ata, although it varies depending on the type of gasifier 5.
It is.

In FIG. 1, an adsorption reactor 17, 18, 1? of the same structure filled with an adsorbent 20 is shown. Although an example of a fixed bed type has been shown in which the process is sequentially switched between the adsorption process according to formulas (5) to (7), the regeneration process according to formula (8), and the reduction process according to formulas (1) to (4), the present invention It is not limited to a fixed bed type, but a fluidized bed type or a moving bed type is used when regenerating according to the formula (8) after adsorbing and removing sulfur compounds such as 'H, s, and oos in the reducing gas with an adsorbent. It is also possible to adopt a formula. It is also a fixed bed type with gas flow path switching.

It goes without saying that a multi-column fixed bed system other than the three-unit switching system can also be applied. Further, the present invention relates to a method for regenerating an adsorbent, and is not limited to the composition or shape of the adsorbent.

First, a state in which the adsorption reactor 17 performs an adsorption process, the adsorption reactor 18 performs a reduction process, and the adsorption reactor 19 performs a regeneration process will be described.

By ventilating the gasified gas 6 through the flow path switching valve 8 to the adsorption reactor 17 in the adsorption step, sulfur compounds are adsorbed and removed by the adsorbent 20, and the purified gas containing dangerous sulfur compounds undergoes a reduction reaction. The SO in the vessel 24 is used to activate the reduction catalyst 27, and is supplied to a gas turbine or the like in the halo as a purified gas 34 via a flow path switching valve 51. The reduction process is to perform a reduction reaction according to equations (1) to (4) as a pretreatment for the adsorption process, and a part of the gasified gas 6 is adjusted in flow rate to pass through the flow path switching valve 12 and the regenerated adsorbent 20. Reduction processing of the adsorbent is performed by ventilating the adsorption reactor 18 filled with EIO, the reduction reactor 25, and the flow path switching valve 32.

After the adsorption reaction is completed, the adsorbent 20a is regenerated with the oxygen-containing gas 40, and the regeneration step is preferably carried out in a circulation system in order to reduce the amount of gas to be treated. Also, the regeneration reaction is 400 to 800
Although the process is carried out at a temperature of 250°C, since a simple sulfur recovery process is incorporated into the circulation system, heat exchanger-1 is used to restore the gas temperature in the system from 250°C or lower to a predetermined temperature during sulfur separation. , adsorption reactor 1 via flow path switching pulp 16f
Ventilate to 9. 0.0 to suppress heat generation during regeneration reaction.
It is preferable to keep the concentration as low as possible within the range of [11 to 1], and S at the outlet of the adsorption reactor 19 due to the regeneration reaction.
O, is generated and 0. is mostly consumed in the regeneration reaction, so it becomes zero. Therefore, So during the regeneration reaction, reduction reactor 2
6 is EIO discharged from the adsorption reactor 19;

It becomes a mixed gas of containing N and gas and a reducing gas that does not contain sulfur compounds such as a, s, and cos, which is vented through the flow rate switching valve 25, and has a gas property that functions as a So and reduction catalyst. SO, reduction catalyst is Tie, ,
5iO1, ZrO, etc. N
Those supporting oxides such as i, Co, Mo, and W are used. These SO1 reduction catalysts can be used at a reaction temperature of 350 to 500°C according to equations (9) to (6).

Reacts with CO, theoretical mole/so, , (!O/S
When o is 2, it is converted to elemental sulfur, and when it is 3, it is converted to H and S, so it is possible to recover any elemental sulfur by adjusting the flow rate of the containing gas to a, CO-containing reducing gas and S after regeneration. becomes.

2E] O, -) -4 horse → S, +AII! O・−・−・
(9) 2SO, +400→day, + aao,
−・・・・・・ α1BOt +
5 H! 4H,S-)-2H,O----
--α and SO, +5CO+H, 04% day +5CO, -・
- (If the reaction temperature becomes high due to the regeneration reaction of the IJ adsorbent, the optimum temperature for the SO8 reduction reaction can be achieved by lowering the gas temperature between the adsorption reactor 19 and the reduction reactor 26. The shape of the So reduction catalyst is preferably honeycomb-shaped in a fixed bed type, but any shape such as granular, cylindrical, powder, etc. is acceptable.

Next, an example of the performance of the So reduction catalyst will be shown. T10゜85
Coo a wt.
4 tMob, prepared with 8 wt% supported catalyst;
Performance evaluation was performed at 5V, 2500h-1, reaction temperature of 550 to 500°C, and gas composition changed, resulting in the results shown in the table below. When CO coexists, (cojuma)/So becomes -5, which is larger than the theoretical reaction equivalent of equations (9) to (b), so
Although the %S concentration in the exit gas is increasing, SO! The concentration is 9
The temperature is about 0.5% lower, and 50% of the SO in the inlet gas.
Since the amount of sulfur has disappeared, it is presumed that it has been converted to elemental sulfur.

From this test result, elemental sulfur can be arbitrarily produced by injecting an appropriate amount of the purified gas 54 from the adsorption process in accordance with the concentration of SO, 80% of the reduction catalyst 27 population. Then, the gas 55 after the So and reduction reaction passes through the flow path switching pulp 30 and is lowered to 250° C. or lower in a cooler 56, and the elemental sulfur is stored in a separator 58. The regenerating gas 59 from which elemental sulfur has been removed is extracted from the gas extraction line 44 in an amount equivalent to the injection of the oxygen-containing gas 40, and the final sulfur is recovered by an existing process such as dry sulfur recovery using Claus reaction or wet lime-gypsum method. Together with the remaining gas, the heat exchanger 41
The circulating regeneration gas 45 is heated to the temperature required for the regeneration reaction.
As a result, it is circulated to the adsorption reactor 19 via the flow path switching pulp 16.

Since this example has been explained using a fixed bed type three-way switching method, the flow path switching pulps 9, 10°, 11, 15, 14 which are not mentioned above are
, 15, 21. 22, 28, 29.55 are adsorption reactor 1
When 7 is performing an adsorption process, the adsorption reactor 18 is performing a reduction process, and the adsorption reactor 19 is performing a regeneration process, they are in a closed state. a cooler 56 provided in the regeneration gas circulation line;
The cooling gas 37 and high temperature gas 42 sources of the heat exchanger 41 are not limited in any way as long as they satisfy the heat exchange conditions.

Furthermore, in the embodiment, the SO□ reduction reactors are installed on the downstream side of the adsorbent reactor, but it is of course possible to install them all together in the circulating regeneration gas line.

〔Effect of the invention〕

By employing the above configuration, the present invention has the following effects.

(1) Since the concentration of sulfur dioxide gas in the circulating regeneration gas could be reduced, the adsorbent could be used for a long period of time.

(2) By using the high temperature reducing gas from the adsorption process to reduce the sulfur dioxide gas in the gas flowing out from the adsorbent regeneration process to elemental sulfur, it was possible to reduce the load on the sulfur recovery process.

(3) By passing the reducing gas flowing out from the adsorption process through the sulfur dioxide gas reduction catalyst, it was useful for imparting activity to the catalyst.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a flow diagram of an apparatus for carrying out the present invention. Temporary Agents 1) Meifuku Agent Ryo Hagiwara - Sub-Agent Atsuo Anzai

Claims (1)

[Claims] In a gas purification method that adsorbs and separates sulfides in high-temperature reducing gases, a sulfur dioxide gas reduction catalyst is placed on the downstream side of the adsorbent, and oxygen-containing regeneration gas is introduced into the adsorbent in the regeneration process to generate sulfur dioxide-containing gas. The outflow gas and the high-temperature reducing gas flowing out from the adsorbent in the adsorption step are introduced into the reduction catalyst to convert the sulfurous acid gas in the outflow gas into elemental sulfur, and the gas flowing out from the reduction catalyst. A method for purifying a high-temperature reducing gas, characterized in that after separating elemental sulfur from the sulfur, the remaining gas is used as part of the regeneration gas of the adsorbent.