JPS63291986A - Purification of high-temperature reducing gas - Google Patents

Abstract

PURPOSE:To stably purify the titled gas without decreasing fuel source, by regenerating an adsorbent containing adsorbed sulfur compound with an oxygen-containing gas, reducing the adsorbent with a part of a high-temperature reducing gas and removing sulfur compound in the high-temperature reducing gas using the adsorbent. CONSTITUTION:A high-temperature reducing gas 1 partially burnt and gasified in a gasification furnace is introduced through a change-over valve 10 into an adsorption column 6 which is a first reactor filled with an adsorbent 9. After removing sulfur compound in the reducing gas by the above treatment, the pressure of the gas is reduced using a gas vent and the gas is passed through a gas cooler 31 and stored in a gas holder 33. An oxygen-containing gas 2 is introduced through a valve 16 into the reducing gas to a prescribed pressure to regenerate the adsorbent 9. The high- temperature regenerated gas left in a reactor is extracted under reduced pressure and a part of the high-temperature reducing gas is introduced through a valve 13 into the reactor to a prescribed pressure to reduce the adsorbent and reuse the adsorbent for the adsorption of sulfur compound. The high-temperature reducing gas 1 can be continuously refined to obtain refined gas 3 by successively performing the adsorption, regeneration and reduction in the 1st-3rd reactors 6, 7, 8.

Description

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

[Conventional technology]

In recent years, there has been a call for diversification of fuels (or raw materials) due to the depletion of oil resources and soaring prices.
Techniques for utilizing oil, Daqing heavy oil, Maya crude oil, vacuum residual oil bottles, etc. are being developed. The method of gasifying coal and heavy oil to use for power generation, fuel, and synthetic raw materials is a typical example of the seven methods.

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 necessary to prevent pollution, corrosion of downstream equipment, and poisoning of catalysts. , removal is necessary.

The necessary conditions for this hydrogen sulfide removal process are as follows.

(1) Gasification product gas is at high temperature (furnace outlet, 1000~
2000℃, 300-500℃ even with partial heat recovery) high pressure (in the case of a pressurized gas furnace), downstream power generation (combined cycle power generation method combining a gas turbine and a steam turbine), fuel and When it is used as a synthetic raw material, it is often used at high temperature and high pressure, so a dry method using high temperature and high pressure for the hydrogen sulfide removal process that occurs during that process is advantageous from a thermoeconomic standpoint. Incidentally, in the case of coal gasification power generation, it is said that there is a difference of 4 to 5 times in power generation efficiency between the dry method and the wet method.

(2) From the viewpoint of handling and marketability, it is preferable to use by-products that meet the needs.

When the gasification process begins to be used for power generation, fuel, and synthetic raw materials, the amount of by-products will be enormous, and the impact on related markets will be large, and the form of the by-products will be an important factor.

(3) The process must be simple and rational. When it comes to practical application, the economic efficiency of Plan F (fixed cost + operating cost) will ultimately be evaluated, so it is most important that the process be simple and economical.

(4) It is necessary to have high reliability in terms of stable operation of the plant. Since it is incorporated into a power generation plant or a chemical plant, it is necessary to have high reliability in terms of stable operation of the plant. be.

Furthermore, the following methods are already known as methods for treating hydrogen sulfide gas.

1) Wet method a) Absorption/desorption method: Absorb with a solvent such as methanol or polyethylene glycol-μ at low temperature and high pressure, and desorb at high temperature and low pressure. be.

b) Absorption oxidation method: A method in which elemental sulfur is produced by absorbing it in an alkaline aqueous solution such as potassium carbonate and partially oxidizing it with air in the presence of a catalyst. Examples include the Takahax method and the Stretford method.

ii) Dry method a) A method in which metal oxides such as iron or zinc are adsorbed and removed as sulfides at high temperatures, such as the iron box method.

b) A method of partially oxidizing hydrogen sulfide to form a mixed gas with sulfur dioxide gas and reacting it at high temperature in the presence of a catalyst to form elemental sulfur, such as the Claus method.

The method a) sb) in 1) above has been put into practical use for refining coke oven gas (COG) and gas in oil refining processes, but it is generally used for cooling the gas, removing dust, and removing contaminating impurities (tar, μ, etc.). naphthalene, halogen, Numa, HCN,
In order to prevent clogging by Cog, etc.), contamination and deterioration of the absorption liquid, the pretreatment equipment is extremely complicated, and as already mentioned, it is disadvantageous in terms of thermoeconomics because it cools the gas. There is also the issue of wastewater treatment.

The dry method (ji) is an advantageous method for treating the gasification product gas. However, although the Claus method (b) is widely used in oil refining processes, it is generally applied to high concentration gases of several tens of percent or more, and in the normal Claus method, a small amount of hydrogen sulfide or sulfur dioxide gas is added to the treated gas due to the reaction equilibrium. Since it contains steel gas, it is necessary to further treat the steel gas, and it is difficult to apply it as it is.

Method a) is an advantageous method for treating high-temperature gasification product gas, but there are problems with powdering and deterioration when reusing the adsorbent.
Furthermore, since there was little need for high-temperature dry processing, there have been few full-scale practical devices that regenerate and recirculate adsorbents.

In response to the above-mentioned needs regarding the treatment method of gasified gas, the present inventors have been conducting research on the development of dry desulfurization agents and reduction catalysts and optimization of the treatment process as a method for removing hydrogen sulfide from reducing gas. , a step of regenerating the absorbent that has adsorbed sulfur compounds with an oxygen-containing gas, and then a step of reducing the regenerated absorbent with a high-temperature reducing gas until the concentration of the reducing gas to be purified before and after the absorbent becomes the same. , and then continuously repeating the steps of aerating the high-temperature reducing gas and adsorbing and removing the sulfur compound with the absorbent, thereby stabilizing the reducing gas concentration in the purified gas. A method for purifying reducing gases was proposed. (Special application 1986-0
No. 85412) [Problems to be solved by the invention] In the invention of Japanese Patent Application No. 60-085412, a reduction step is added between the switching of the reactor from the regeneration step to the adsorption desulfurization step, and a part of the process gas is added. By doing so, the iron oxide oxidized with Fe snow 03t in the regeneration process is converted into Fe3 in advance.
By reducing with O4 and FeOt, the next time the reactor is switched to the adsorption desulfurization process, the FefiO
This is intended to prevent temporary fluctuations in gas concentration due to consumption of I(l, CO gas in the process gas due to reduction of =).

However, in a final operation, if the adsorption desulfurization, regeneration, and reduction processes are simply switched, the residual gases from each process will mix, causing temporary fluctuations in the gas composition.
Furthermore, since the pressurization conditions are different, temporary fluctuations in gas flow rate may occur, so it is necessary to take measures to prevent this.

Next, ■ High pressure inside the reactor at the completion of the adsorption desulfurization process (for example, 2
0 kll/d G) The remaining gas needs to be recovered and used. Normally, purging is performed with N1 gas, etc., but the recovery rate is low (it is not a good idea as it requires a large amount of purge gas, and it is desirable to omit the purge operation to improve economic efficiency).

In addition, there is gasified gas in the reactor where adsorption desulfurization was performed and oxidizing gas containing oxygen in the reactor where regeneration was performed, so if they are mixed as is, the temperature will rise due to combustion. Doing so may cause problems such as pressure increase or pressure increase.
Normally, a gas purge with an inert gas such as N or gas is performed at the time of process switching, but this requires a large amount of purge gas and is not a good idea.To improve economic efficiency, it is desirable to omit the purge operation.

[Purpose of the invention]

The present invention is an attempt to study in detail the unexamined points (1) to (2) in these conventional methods, and to improve their performance.

[Means for solving problems]

The present invention provides a method for adsorbing and removing sulfur compounds contained in a high-temperature reducing gas, including: (1) a regeneration step of regenerating an absorbent that has adsorbed the sulfur compound with an oxygen-containing gas; A method of continuously repeating a reduction step in which a part of the sulfur compound is used to reduce the sulfur compound, followed by a desulfurization step in which the sulfur compound in the high-temperature reducing gas is adsorbed and removed using a reduced absorbent, and includes: (1) a desulfurization step by adsorption; In the switching operation to the regeneration process, the high-temperature reducing gas remaining in the reactor at a predetermined pressure was extracted from the system by depressurization and recovered, and then oxygen-containing regeneration gas was added until the predetermined pressure was reached to adsorb sulfur compounds. Regeneration of the absorbent is started, and ■ In the switching operation from the regeneration process to the reduction process, the high temperature regeneration gas having a predetermined pressure remaining in the reactor is extracted to the post-treatment process by reducing the pressure, and then the regeneration process is switched from the absorption process to the regeneration process. This method of purifying high-temperature reducing gas is characterized by adding high-temperature reducing gas recovered outside the yarn until a predetermined pressure is reached at the time of switching to the regenerated absorbent to start reduction of the regenerated absorbent.

One embodiment of the method of the present invention will be explained with reference to FIG.

The gasified gas 1 mainly composed of CO and CO that has been partially burned and gasified in the gasifier is removed and led to a step of removing sulfur compounds. The gasified gas 1 after this dust removal differs depending on the type of coal and gasification conditions, but it contains 10 to several thousand ppm of hydrogen, CO8, nitrogen, HCN, etc. The temperature is 250 to 10°C due to heat recovery by steam and a portion of the gasifier outlet, and the pressure is normal pressure to 2.5 ata, although it varies depending on the type of gasifier.

In the present invention, the gasified gas 1 after dust removal is Fe.

An absorption tower 6 which is a first reactor filled with an absorbent 9 made of metal oxides such as Zn, Mo, Mn, Cu, W, etc.
The sulfur compounds in the gasification gas 1 are adsorbed and removed as sulfides by venting through the flow path switching valve 10, while in the regeneration tower 7, which is the second reactor, the same absorbent 9 as in the absorption tower 6 is used. Oxygen-containing gas (for example, air) 2 is passed through the flow path switching pulp 17 to the absorbent 9 which has reached breakthrough due to the adsorption of sulfur compounds (filled with sulfur compounds), and is roasted as shown in the following equation. The absorbent 9 is regenerated by the calcination reaction, and at the same time, rich So is generated through the flow path switching pulp 20.

Get gas 5. At this time, the flow path switching valve 11.14°25
．． 26 is closed.

4F*S+701→2Fe30s+480.
・(1) The above reaction is an exothermic reaction and oxygen-containing gas 20
Since this occurs rapidly at the same time as ventilation, the temperature can be controlled by circulating the outlet gas of the regeneration tower 7 through the circulation fins 4 and uniformly supplying the oxygen necessary for the regeneration reaction throughout the entire body at a low concentration. It is preferable to do so. This playback temperature is 250~
The process was carried out at 600°C, and the concentrated So
, the gas 5 is used as a raw material for producing sulfuric acid, or is led to a process where it is recovered as elemental sulfur or solid sulfur compounds. It can also be recovered as gypsum using a wet desulfurization method.

The absorbent 9 may be in any shape such as granules, cylinders, honeycombs, or plates. A porous heat-resistant base material such as mina, titania, silica, or zeolite is used that supports the above-mentioned metal oxide.

Fe! The desulfurization reaction formula when 01 is used as an absorbent component is as follows: FeB04+CO+3I(18-+3Fe8+3'H1
0+CO1-123Fe104+H1+5H1S→3F
eS+4H,O.f31 A trace amount of COS coexisting in the gasified gas 1 is converted into E and S and adsorbed and removed by the reaction shown in the following formula, or is removed by an adsorption reaction with Fe104.

CO8+ Hl0-4Co snow+ EIIS= (4)F
e104+1(1+3CO8→3FeS+H10+5C
O1” (5JFb104+CO+3CO8-IFe8+
4cO1...(6) Desulfurization reaction temperature ffi is 250 to 45
0℃, SV value (gas flow rate Nm”/h/absorbent capacity ms
) is about to00~2 CL OOO1/h, more than 90% f)'H@BF) in the waste is removed, and purified gas 3 is obtained via the flow path switching pulp 25 of the absorption tower 6. At this time, the flow path switching valves 13.14 and 19.22 are closed.

Furthermore, the reduction tower 8, which is the fifth reactor, is filled with the same absorbent 9 as the absorption tower 6 and the regeneration tower 7. A part (about several percent) of the gasified gas 1 is vented through the flow path switching valve 15 to mainly perform the following (method reduction reaction).

This reduction reaction is a preliminary reduction reaction until the concentration of H, CO in the purified gas 3 becomes constant, and is returned to the gasified gas 1 after dust removal via the flow path switching pulp 24.

At this time, the flow path switching valves 12, 18, and 21 are closed.

3FelO1+ Hl 42Fe104 + Ego
-'' (7) At the stage of such a preliminary reduction reaction (2), (3).

(5), (6))! ms, COB adsorption reaction is also performed at the same time, (method reaction is 12), +3
), (5), +6) Since this reaction is faster than the reactions of equations 1 and 6), after the preliminary reduction reaction is completed, the ventilation of the gasified gas 10 after removal is stopped to allow time for the start of the adsorption reaction in the next step.

Now, in this final embodiment, each reactor (absorption tower, regeneration tower, reduction tower) is used repeatedly by switching valves.

In order to prevent the flow rate and composition of the gasification gas 1 from changing when switching gases, the following method is adopted for gas replacement (or purging) in the reactor.

(1) That is, the high pressure (for example, 20 kg/am" G) remaining gas in the absorption tower 6 at the completion of the gas absorption process is degassed until the pressure becomes below a predetermined pressure (for example, 5 kliJ/m" G).

In this case, the pulp 25 is closed and the pulp 22 is open. The residual gas 28 discharged from the absorption tower 6 passes through the gas cooler 51 to the compressor 32, at original pressure (20kg15
IsG ) and stored in the gas holder 33GC. The log gas 29 from the gas holder 55 is appropriately combined with the purified gas 2.

After the gas is discharged from the absorption tower 6, about 5 kg/a11G of gasified gas 1 remains, but this gas enters the next regeneration step without being purged. Although the initial pressure inside the absorption tower 6 is below 5 kg 7al G, the oxygen-containing gas 2 is gradually introduced into the regeneration fin until the pressure rises to a predetermined pressure (for example, 20:00/a, "G"). is circulated through the regeneration system to promote the oxidation (regeneration) reaction of the absorbent 9, and the absorption tower 6
When the temperature reaches 400℃ or higher, the main components Co and H in the remaining gas
, etc. react and are converted to C'O,, I(, 0, etc.). After all the combustibles in the remaining gas have reacted, full-scale regeneration operation is performed. That is, the circulation fins 4, the pulp 16, Absorption tower 6, absorbent!, oxygen-containing gas 2 to the fins of bypass 19
is circulated, and a portion of the gas 5 is treated in a downstream O wet desulfurization system.

(In FIG. 1, this state is illustrated in the regeneration tower 7t. In this case, the circulation of the oxygen-containing gas 2 is as follows.
Circulation line 4, pulp 17, regeneration tower 7, absorbent 9, paper μ
This is done by the driver 20. ) (2) On the other hand, in the absorption tower 6 at the completion of the regeneration process, concentrated 9 SO gas (approximately 7 to 8% 80=) is under high pressure (e.g. 2
0 kg/allG).

If the process is switched to the reduction step without this degassing, it will be mixed into the purified gas 5 temporarily, resulting in a decrease in the desulfurization rate.

Therefore, immediately before the end of the regeneration process, it is necessary to reduce the pressure inside the absorption tower 6 to near atmospheric pressure and extract 80 m of gas. The released So and gas 5 are introduced into a post-treatment process such as a downstream wet evacuation system.

(3) After the regeneration step is completed, the process proceeds to the reduction step.

Initially, the inside of the absorption tower 6 is under reduced pressure (atmospheric pressure), so the gasification gas 1 is introduced until the pressure rises to a predetermined pressure (for example, 20 kg/al G). After that, the operation of the reduction process will begin. Although the gas absorption operation is continuously switched to avoid fluctuations in the gas flow rate and composition, there is a slight decrease in the gas amount at the beginning of the regeneration → reduction process (while the pressure inside the absorption tower 6 is increased to 20 kg/-G). However, this problem can be solved by the method described below.

As mentioned above, the high-pressure residual gas in the absorption tower at the completion of the gas absorption process is degassed to a predetermined pressure (for example, 5 k19 /
After the pressure is reduced to below (at”
d G ) and stored in the gas holder 33 .

This gas holder 33 gas is returned to purified gas 3 or crude gas 1 fin using line 29 or line 34 by timer operation when switching the reduction process (increasing the pressure inside the reactor). By performing the above operation, it is possible to prevent the gas jfk from decreasing during the transition from regeneration to reduction.

(4) Repeat absorption → regeneration → reduction → absorption. Absorption and reduction are always operated continuously, and as a result, some discontinuity of the son gas flow occurs in the regeneration process, but air is sent in the downstream wet desulfurization to ensure a continuous gas flow. You can deal with it by getting in trouble.

The gasification gas introduced in the reduction process should be kept to the minimum necessary (for example, about 5x), and the reduction of the absorbent (Fan
Ql-+Fe504) was the main objective.

〔Effect of the invention〕

As stated above, according to the method of the present invention, 4. This is a method for removing and refining sulfur compounds that can be stably supplied to the next process without temporarily reducing the fuel source such as CO or changing the gasification gas flow rate.

[Brief explanation of drawings]

FIG. 1 is a diagram for explaining an embodiment of the method of the present invention. 5...Purified gas 4...Circulation fin 5...SO gas! -NIL 1 Absorption tower 7-H & 2 Regeneration tower 8... Ugly 3 Reduction tower! ... Absorbent 10 to 27 - ... Flow path switching pulp 28 ... Absorption tower residual gas 2 ? -...Gas holder output log gas 30...Reducing gasification gas SL...Gas cooler s2...Gas compressor 33...Gas 1hfi/der 34-...Return gas line

Claims (1)

[Claims] A method for adsorbing and removing sulfur compounds contained in a high-temperature reducing gas, comprising: (1) a regeneration step of regenerating an absorbent that has adsorbed the sulfur compound with an oxygen-containing gas, and then the regenerated absorbent. A method of continuously repeating a reduction step in which sulfur compounds are reduced using a part of a high-temperature reducing gas, and then a desulfurization step in which the sulfur compounds in the high-temperature reducing gas are adsorbed and removed using a reduced absorbent, 2) In the switching operation from the desulfurization process by adsorption to the regeneration process, the high-temperature reducing gas with a predetermined pressure remaining in the reactor is extracted out of the system by depressurization and recovered, and then the oxygen-containing regeneration gas is brought to the predetermined pressure. (3) In the switching operation from the regeneration process to the reduction process, the high-temperature regeneration gas remaining in the reactor at a predetermined pressure is depressurized. High-temperature reduction characterized in that after being extracted to the treatment process, the high-temperature reducing gas recovered outside the system at the time of switching from the absorption process to the regeneration process is added to a predetermined pressure to start reduction of the regenerated absorbent. Method for purifying sexual gases.