JPH0790137B2 - Refining method for high temperature reducing gas - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for refining a high-temperature reducing gas, for example, hydrogen sulfide and carbonyl sulfide contained in a high-temperature reducing gas such as a product gas of a coal gasification process. Etc. to a method for rationally removing sulfur compounds.

[Conventional technology]

In recent years, due to depletion of petroleum resources and soaring prices, the diversification of fuels (or raw materials) has been called for, and the use of coal and heavy oil (tar sand oil, oil shale oil, Daqing crude oil, Maya crude oil, vacuum residual oil, etc.) Technology is being developed. However, this gasification product gas contains sulfur compounds such as hydrogen sulfide (H ₂ S) and carbonyl sulfide (COS) in the range of several hundreds to several thousand ppm, depending on the raw material coal or heavy oil, but it does not prevent pollution. It must be removed to prevent corrosion of the upstream or downstream equipment. As a method for removing this, the dry method is also advantageous in terms of thermo-economics, and the process configuration is simple. Therefore, the method of absorbing and removing the sorbent containing a metal oxide as the main component as a sulfide at a high temperature is generally used. There is.

As the absorbent, metal oxides such as Fe, Zn, Mn, Cu, Mo, W are used, and it reacts with hydrogen sulfide (H ₂ S) and carbonyl sulfide (COS) at 250 to 500 ℃, but H ₂ S In the case of Fe ₂ O ₃ and Fe ₂ O ₃ , for example, it is said that the absorption reaction proceeds as shown in equations (1) to (4).

3Fe ₂ O ₃ ＋ H ₂ → 2Fe ₃ O ₄ ＋ H ₂ O …… (1) 3Fe ₂ O ₃ ＋ CO → 2Fe ₃ O ₄ ＋ CO ₂ …… (2) Fe ₃ O ₄ ＋ H ₂ ＋ 3H ₂ S → 3FeS ＋ 4H ₂ O… … (3) Fe ₃ O ₄ + CO + 3H ₂ S → 3FeS + 3H ₂ O + CO ₂ …… (4) Next, the absorbent after the absorption reaction is regenerated into the original metal oxide with oxygen-containing gas as shown in equation (5). , Sulfur compounds in high temperature reducing gas are SO _{2 by} repeating this absorption and regeneration reaction.
It is recovered and removed as gas.

4FeS + 7O ₂ → 2Fe ₂ O ₃ + 4SO ₂ (5) The absorbent used in this process is the above-mentioned metal oxide, either alone or supported on a heat-resistant porous material.
In the case of the moving bed system, those formed in a spherical shape or in a cylindrical shape are usually used, and in the case of the fixed bed system, those formed in a honeycomb shape are usually used. Since a gas purified by removing sulfur compounds from a reducing gas such as coal gasification gas is used as an energy source, a process for producing stable CO and H ₂ concentrations is preferable. The reaction of equation (2) must be suppressed as much as possible. In the fluidized bed and moving bed systems, the absorption process and the regeneration process are repeated continuously, so this technical problem is easy to overcome, but in the fixed bed system, the absorption process and the regeneration process are repeated intermittently, so the absorption reaction after regeneration starts. Sometimes in the purified gas
The CO and H ₂ concentrations are temporarily reduced, which is not practically preferable as a refining method for high-temperature reducing gas.

Therefore, the present inventors have proposed a method in which a sulfur compound contained in a high-temperature reducing gas is adsorbed and removed by an adsorbent containing a metal oxide as a main component, and the adsorbent adsorbing the sulfur compound is regenerated with an oxygen-containing gas. And then reducing the regenerated absorbent with a high temperature reducing gas until the concentration of the reducing gas before and after the absorbent becomes the same, and then by aeration of the high temperature reducing gas Proposed a method for refining high-temperature reducing gas, characterized in that the reducing gas concentration in the purified gas is stabilized by continuously repeating the step of adsorbing and removing the sulfur compound (Japanese Patent Application No. 60-85412).
issue).

In addition, the inventors of the present invention have a method of absorbing and removing a sulfur compound such as hydrogen sulfide and carbonyl sulfide contained in a high-temperature reducing gas with an absorbent, thereby recovering a regenerated absorbent with a high-temperature reducing gas before and after the absorbent. After reducing until the target reducing gas concentration becomes constant, in a method for refining a high-temperature reducing gas in which the step of absorbing and removing the sulfur compound is continuously repeated, at least three reactors packed with an absorbent are used. Absorption, pre-regeneration,
A high-temperature reducing property characterized by comprising four steps of regeneration and reduction and stabilizing the absorption and regeneration performance by aerating the high-temperature reducing gas and absorbing and removing the sulfur compound with the absorbent. Gas purification method (Japanese Patent Application No. 62-167814)
Or a method of absorbing and removing a sulfur compound such as hydrogen sulfide and carbonyl sulfide contained in a high-temperature reducing gas in a step of absorbing and removing the sulfur compound with an absorbent, and absorbing the sulfur compound into a regeneration reaction. Preliminary regeneration step of raising the temperature to reach the required temperature, step of regenerating the absorbent that has reached the regeneration reaction temperature with an oxygen-containing gas, reducing the regenerated absorbent with a high temperature reducing gas before and after the absorbent It consists of four steps of reducing until the gas concentration becomes the same,
By adjusting the amount of gas circulated in the regeneration process, or by adjusting the amount of the recycle gas and utilizing the combustion heat of the high-temperature reducing gas supplied to the regeneration process, absorption and regeneration performance at low load can be improved. We have proposed a refining method for high-temperature reducing gas, which is characterized by stabilization (Japanese Patent Application No. 62-167815).

The normal process gas temperature in the absorption process is 300 to 500 ° C, but in the case of the regeneration process, the oxygen gas (O ₂ ) in the regeneration gas is sulfided in the absorption process and the iron sulfide in the absorbent and the above (5). The reaction takes place according to the formula, and due to the heat of reaction generated at that time, it reaches 500 to 900 ° C. Since the absorbent that comes into contact with high-temperature gas causes a heat storage phenomenon and becomes an abnormally high temperature, which may result in the destruction of the absorbent, it is expected to introduce a regeneration system that alleviates the abnormal accumulation in the absorbent. ing. O ₂ concentration in the regeneration reactor inlet gases associated with the magnitude of the reaction heat in the case of a fixed bed system is usually 1-3%, increasing the O ₂ concentration in the gas, regeneration recycle gas volume is inversely proportional to it Since there is less, there is an advantage that the equipment and power consumption in the regeneration system become economical,
On the other hand, if the concentration exceeds a certain level, the above-mentioned unfavorable phenomenon will occur with the absorbent, and it is difficult to say that it is an economical and effective method simply by controlling the O ₂ concentration in the gas at the inlet of the regeneration reactor. . A tower switching system in which the desulfurization regeneration cycle consisting of absorption, regeneration, and reduction steps is continuously and smoothly performed, and moreover stable absorption and regeneration performance is obtained and the load fluctuation of the S recovery system in the latter stage is the smallest. It is necessary to adopt a method of refining a high-temperature reducing gas that adopts.

[Problems to be Solved by the Invention]

The present invention provides a method capable of eliminating the above-mentioned drawbacks associated with a method for purifying a high-temperature reducing gas in a system in which absorption, regeneration, and reduction steps are operated one tower at a time, particularly in the regeneration step. It is intended to provide a method for alleviating abnormal heat storage in an absorbent due to heat of regeneration reaction, eventually protecting the life of the absorbent and obtaining stable absorption and regeneration performance.

[Means for Solving the Problems] The present invention is a method of absorbing and removing a sulfur compound such as hydrogen sulfide and carbonyl sulfide contained in a high-temperature reducing gas with an absorbent, in which at least four reactors are filled with the absorbent. An absorption step of absorbing and removing the sulfur compound with an absorbent, a regeneration step of regenerating the absorbent with an oxygen-containing gas, a cooling step after completion of the regeneration step, a regeneration step of the regenerated absorbent with a high-temperature reducing gas. Part of the reactor that consists of four steps of reduction process that reduces until the reducing gas concentration before and after the absorbent becomes the same and starts the next regeneration process before the regeneration in the reactor in the regeneration process is completed In addition to performing parallel regeneration, the outlet gas of the reactor in the cooling step after the regeneration is introduced into the reactor in the regeneration step to be a part of the regeneration gas, and in the regeneration step, the regeneration reactor High temperature outlet It is a method for refining a high-temperature reducing gas, characterized in that heat is continuously recovered from the gas to stabilize absorption and regeneration performance.

[Action]

When the absorbent after the absorption reaction is regenerated so that the sulfur compound can be absorbed, the following (6) to
The sulfate-forming reaction as in the formula (9) is likely to occur.
If these sulfates remain inside the absorbent and block the pores, they cannot be completely desorbed even when they are regenerated at a high temperature, resulting in deterioration of the performance of the absorbent.

FeS + 2O ₂ → FeSO ₄ …… (6) 2FeS + SO ₂ ＋ 5O ₂ → Fe ₂ (SO ₄ ) ₃ …… (7) 2Fe ₂ O ₃ ＋ 4SO ₂ ＋ O ₂ → 4FeSO ₂ …… (8) 2Fe ₂ O ₃ ＋ 6SO ₂ ＋ 3O ₂ → 2Fe ₂ (SO ₄ ) ₃ (9) Therefore, the regeneration reaction temperature must be raised to some extent in order to prevent the above-mentioned sulfate from being produced as a by-product. However, if the temperature becomes too high than necessary, the absorbent will be destroyed, and the regeneration system becomes important together with the selection of the regeneration temperature and the O ₂ gas concentration in the regeneration gas.

In a continuous desulfurization regeneration system consisting of absorption, regeneration, and reduction, various tower switching patterns are conceivable depending on the number of towers, and the regeneration system also differs, but the regeneration treatment of the reactor that completed the absorption process is performed for each tower. , In many cases, it is done independently. At that time, since the introduction of the regeneration gas is either co-current or countercurrent with the absorption operation, the gas tends to reach a higher temperature due to the transfer of reaction heat and the heat storage phenomenon of the absorbent toward the outlet side, and the atmosphere is harsh for the absorbent. Becomes On the other hand, it is difficult to adopt the split regeneration operation in which gas is introduced from the middle stage of the regeneration reactor when the regeneration tower is one. As the absorbent is regenerated, O ₂ gas tends to come out in the reactor outlet gas, but it is necessary to prevent this O ₂ gas from mixing with the SO ₂ reduction reactor in the subsequent stage. Considering the entire tower switching time system including time management, absorption, and reduction, it can be said that it is poor for practical use.

Therefore, the method of the present invention is one in which two regeneration reactors are installed to solve the above technical problems. The method of the present invention alleviates the abnormal heat storage in the absorbent due to the heat of the regeneration reaction, and consequently protects the life of the absorbent and produces it in the regeneration reactor.
It has the advantage of suppressing fluctuations in the concentration of SO ₂ gas.

In the method of the present invention, at least four reactors packed with an absorbent are used, and the steps of absorption, regeneration, cooling, and reduction are carried out by, for example, 4,
It is characterized in that it is carried out in a cycle consisting of 6,2,4 time distribution, and particularly in the regeneration process including the cooling process, two regeneration reactors are installed and partial regeneration is performed. That is, in order to sufficiently perform the regeneration of the absorbent that has completed the absorption step, O ₂ is supplied to the reactor even during the cooling step after the completion of the regeneration.
Aerate the contained gas. However, O _{2 is not}
Since no gas is required, O ₂ gas will come out from the outlet of the regeneration reactor, but introduce this gas into the middle stage of the other regeneration reactor so that O ₂ gas will not be mixed in the S recovery system gas. To

In this way, the cooling process outlet gas after the regeneration is introduced to the middle stage of the other regeneration reactor, but the regeneration gas is introduced from the inlet to the regeneration reactor before that, and the cooling process outlet gas is introduced. And the regeneration gas waits for a while, and the regeneration operation proceeds by a series of these operations. Since the temperature of the outlet gas of the cooling process after the completion of regeneration introduced into the middle stage of the other regeneration reactor is higher than the temperature of the gas at the inlet of the regeneration reactor, the temperature of the gas at the inlet of the regeneration reactor is about the same as the temperature at the inlet of the regeneration reactor. Introduce into the vessel By partially adopting the divisional regeneration method in this way, avoiding abnormally high temperatures resulting from the reaction heat of the absorbent,
Can protect the absorbent from destruction.

According to the above method, heat can be continuously and effectively recovered from the hot gas at the outlet of the regeneration reactor, and the heat balance of the entire system regarding absorption and regeneration can be maintained accordingly. It helps stabilize the playback performance.

〔Example〕

 FIG. 1 shows an embodiment of the method of the present invention.

In FIG. 1, 1 and 2 are dedusting high-temperature reducing gas lines containing sulfur compounds such as H ₂ S and COS, 3,4,5,6,7,8,10,12 and 1
4 is the same gas flow path switching valve, 9, 11, 13 and 15 are gas switching valves containing high-concentration sulfur compounds from the reactor of the regeneration process, 16, 17, 18 and 19 are reactions filled with adsorbent Bowl, 20
Is an adsorbent, and 21, 22, 23 and 24 are for supplying a gas obtained by mixing a part of a relatively low-temperature circulating gas to the outlet gas of the reactor in the cooling process to the middle stage of the reactor performing the regeneration process. The flow path switching valves of 25, 26, 27 and 28 are flow path switching valves for supplying the outlet gas of the reactor in the reduction step to the middle stage of the reactor in the absorption step, and 29, 32, 35 and 38 are Reactor outlet gas flow path switching valve in the reduction step, 30, 33, 36 and 39 are purified gas flow path switching valve from the absorption step reactor, 31, 34, 37 and 40 are in the regeneration step A flow passage switching valve for supplying a regeneration gas to a certain reactor, 41 is a regeneration gas circulation line, 42 is a purified gas extraction line, 43 is a reducing gas flow passage switching valve, 44 is a reducing gas line, and 45 is Line 50 below
A branch line, 46 is the same flow path switching valve, 47 is an air or oxygen-containing gas supply line, 48 is a heat exchanger, 49 is a branch line of a line 50 described below, 50 is sulfur from the high-concentration sulfur compound-containing gas. The remaining gas line, 51 is a branch line of 50, 52 is a cooled high-concentration sulfur compound-containing gas line,
53 is a sulfur recovery device, 54 is a heat exchanger, 55 is a gas line, 56
Is a heat exchanger, 57 is a sulfur recovery device, 58 and 59 are gas lines, 6
0 is a blower.

Note that * 1, * 2, and * 3 are lines corresponding to the line 51.

In FIG. 1, the reactor 16 of the same structure filled with the absorbent 20
19 is the reduction step according to the equations (1) and (2), the equation (3),
An embodiment in which the absorption step according to the formula (4) and the regeneration step according to the formula (5) are sequentially switched is shown, but the present invention is not limited to the fixed bed type, and H ₂ S, COS
A process of repeating regeneration by the formula (5) after absorbing and removing sulfur compounds such as the above can be applied to both the fluidized bed system and the moving bed system. Needless to say, it can be applied to a fixed bed type with four or more towers. Further, although the composition and shape of the absorbent are not particularly limited, here, the case where Fe ₂ O ₃ is used as the absorbent will be described.

High temperature reducing gas containing sulfur compounds such as H ₂ S and COS 1
For example, if the coal gasification gas has a dust concentration of 10
mg / Nm ³ about to is obtained by dedusting, of different but several tens to several hundreds of 1000ppm besides dust coal types and gasification conditions H ₂ S, C
It contains OS, NH _3, halogen, etc., the gas temperature is 250 to 500 ° C due to the fuel recovery at the gasifier outlet, and the pressure varies from atmospheric pressure to 25 kg / cm ² G depending on the type of gasifier. is there.

The first is the absorption step in the reactor 16 and the reduction step in the reactor 17,
The state in which the regeneration process is being performed in the reactors 18 and 19 is shown.

FIG. 2 shows the time schedule of the absorption, regeneration, cooling, and reduction cycles when the present invention is carried out, and FIG. 3 shows the absorption gas temperature of 450.
The graph shows an example of the temporal change of the regeneration tower outlet gas temperature when the regeneration inlet gas temperature is 500 ° C and the regeneration inlet gas temperature is 500 ° C.

In FIG. 1, the dedusted gasified gas 1 is absorbed by the reactor 16 via the flow path switching valve 4, and the sulfur compound in the gas is usually 300 to 500 ° C. according to the formulas (3) and (4). Then, it is absorbed and removed by the absorbent 20, becomes purified gas 42 through the flow path switching valve 30, and is supplied to the gas turbine in the downstream.

In the time schedule of FIG. 2, the explanation will be given below on the assumption that the reactor 18 starts regeneration 4 hours before the reactor 19.

The reactor 19 that has completed the absorption step moves to the regeneration step, but air or oxygen-containing gas is supplied to the line 50 from the line 47,
Flow path switching valve via line 49, heat exchanger 48, line 41
It is introduced into reactors 18 and 19 via 37 and 40. The gas used to regenerate the absorbent is passed through the flow path switching valves 13 and 15 and the SO ₂ reduction and sulfur recovery device 53, the heat exchanger 54, the line 55, and the heat exchanger 48 and the line 52 through the line 52. It is led to the sulfur separator 57 via 56 and the sulfur is recovered via the line 64. After that, the gas from which sulfur has been separated is supplied with air or an oxygen-containing gas from a line 47 through a blower 60, and the line is supplied.
After being heated to the required temperature for the regeneration reaction in the heat exchanger 48 through the line 50 and the line 49, it is returned to the circulating gas line 41.

The gas returned to the gas line 41 flows through the flow path switching valves 37 and 40.
After being introduced into the reactors 18 and 19 during regeneration and contributing to promotion of the regeneration reaction, it becomes a circulating gas through the flow path switching valves 13 and 15 as described above.

Assuming that a continuous desulfurization regeneration cycle is formed by the time schedule shown in FIG.
Circulate and vent for a period of time to complete the regeneration of the absorbent,
Regeneration is almost complete within the first 6 hours, and the remaining 2 hours serve to complete regeneration and cool down. Since the outlet gas of this cooling step is higher than the inlet gas temperature of the regeneration reactor, a part of the relatively low temperature (200-300 ° C) regeneration circulation gas from the blower 60 is mixed with this gas via lines 50 and 51. The mixed gas is cooled to about the inlet gas temperature of the reactors 18 and 19, and then introduced into the middle stage of the other reactor 19 via the flow path switching valve 24.

Regeneration gas is introduced into the reactor 19 from 2 hours before the gas in the cooling step of the reactor 18 is introduced into the middle stage thereof, and the gas is the gas that has passed through the S recovery system and contains air or oxygen from the line 47. Gas is supplied to line 50 and line as described above.
It is introduced through the flow path 49, the heat exchanger 48, and the line 41 through the flow path switching valve 40. Reactor 19 is regenerated in a similar manner to that of reactor 18. That is, the gas in the circulation line 41 supplied with the air or the oxygen-containing gas from the line 47 is introduced from the reactor inlet through the flow path switching valve 40 for 8 hours, but the regeneration reactor 18 is introduced 2 hours after the introduction is started. The gas in the cooling step of 2 is introduced through the flow path switching valve 24 for 2 hours. Gas is passed through the reactor 19 inlet for 8 hours, but the last 2
As described above, the cooling process is aimed at cooling the reactor, the gas in the low temperature side inlet line 49 of the heat exchanger 48 is mixed, and the gas that has reached a temperature almost the same as the reactor inlet is already 2 times. It is introduced through the flow path switching valve 21 into the middle stage of the reactor 16 which has been moved to the regeneration process from the time before, and a series of regeneration and cooling processes is completed.

An example of the behavior of the gas temperature at the outlet of the regeneration reactor during this period is shown in FIG.

When the regeneration reactor is operated independently for each tower, the outlet gas temperature at the time of disclosure of the regeneration step shows the temperature of A and is almost close to the inlet gas temperature, but as the regeneration proceeds, the exothermic reaction of iron sulfide and oxygen The outlet gas temperature gradually increases with the progress, heat, and movement, and shows the temperature of B. In this case, the temperature difference between A and B is about 200 ° C.

On the other hand, in the case of the method of the present invention, since the regeneration reactor is operated in a two-column series, the outlet gas temperature exhibits the following behavior. That is, in the regeneration reactor 19, the outlet gas temperature exhibits the behavior of D to E. It is calculated that at the point D where the reactor 19 starts regeneration, the reactor 18 has already passed 4 hours after the start of the regeneration operation, and the outlet gas temperature of the reactor 18 has reached point D. It Therefore, since the gas in which the outlet gases of the reactors 19 and 18 merge is introduced into the high temperature side inlet of the heat exchanger 48, the high temperature side inlet gas temperature of the heat exchanger 48 shows the average temperature of D and D. It will be. As the regeneration operation of the reactors 18 and 19 progresses, the outlet gas temperature of each reactor rises, and the hot side inlet gas temperature of the heat exchanger 48 rises accordingly. The point B at which the regeneration operation of the reactor 18 is completed becomes the highest and indicates the temperature of the gas. However, the reactor 18 moves to the cooling step, and the middle stage of the reactor 19 is a gas cooled to about the inlet gas temperature. Since the reactor 18 is introduced, the temperature of the outlet gas of the reactor 19 reaches a temperature of K when the cooling operation is started, and the other gas enters the heat exchanger 48 without being mixed. Thereafter, as the regeneration operation of the reactor 19 progresses, the outlet gas temperature rises from K to K and enters the heat exchanger 48 as it is. Since the regeneration of the reactor 16 is started at the time when the outlet gas of the reactor 19 shows the temperature of K, the temperature of the gas on the high temperature side of the heat exchanger 48 shows the average temperature of K and G. As the above-described operation is repeated, the temperature of the gas at the high temperature side inlet of the heat exchanger 48 changes from one to another.

Thus, in the case of the method of the present invention, the difference in height of the high temperature side inlet gas temperature (= outlet gas average temperature in FIG. 3) of the heat exchanger 48 is about
Compared to the case of 120 ° C and independent regeneration of each tower, it is much smaller and stable operation is possible.

On the other hand, by operating the two columns of the regeneration reactor in a part of series operation, regeneration of the absorbent can be sufficiently completed, and O ₂ gas in the reactor outlet gas after the regeneration is completed is mixed with the S recovery system in the subsequent stage. There is no concern and it can be said that the merits are great.

For removal of SO ₂ gas generated by regeneration reaction, SO ₂ reduction reaction alone, recovery and removal as elemental sulfur by combination with SO ₂ reduction reaction and Claus reaction, recovery and removal as gypsum by reaction with wet lime, etc. There is no limitation on the method.

Here, a method for recovering and removing SO as a simple substance by combining the SO ₂ reduction reaction of the formulas (10) to (13), the Claus reaction of the formula (14) and the hydrolysis reaction of the formula (15) will be described.

SO ₂ ＋ 3H ₂ → H ₂ S ＋ 2H ₂ O …… (10) SO ₂ ＋ 3CO → COS ＋ 2CO ₂ …… (11) 2SO ₂ ＋ 4H ₂ → S ₂ ＋ 4H ₂ O …… (12) 2SO ₂ ＋ 4CO → S ₂ ＋ 4H ₂ O …… (13) 2H ₂ S + SO ₂ → 3 / xS _X ＋ 2H ₂ O (x = 2-8) …… (14) COS + H ₂ O → H ₂ S + CO ₂ …… (15) Line required for SO ₂ reduction reaction The reducing gas of No. 2 is a part of the dedusting gas ratio gas of the line 1 via the flow path switching valve 3.
Is supplied to the SO ₂ reduction and sulfur recovery device 53, SO ₂ gas contained in the gas after the regeneration step of the line 52, (10) - (13)
According to the formula, it becomes H ₂ S, COS, and elemental sulfur. Then, (14),
After the reaction of the formula (15), it was cooled to 130 to 250 ° C and the sulfur content of 64
By recovering and removing the SO3 out of the system, a processing gas (gas in line 58) is obtained by removing most of SO ₂ gas generated in the regeneration reaction. It is a matter of course that the reducing gas used here is more preferably a gasified gas in the line 42 after purification.

A part 45 of the gas in the line 50 at the outlet of the blower 60 is recovered and removed outside the system together with the amount of the reducing gas in the line 2, the supply amount of air or oxygen-containing gas supplied as an oxygen source for the regeneration reaction in the line 47. Taking into account the amount of elemental sulfur 64 that is generated and the like, it is supplied to the reactor 16 during the absorption step.

In other words, the gas in line 59 (= 45) that has been SO ₂ recovered and removed in the SO ₂ reduction and sulfur recovery process contains a small amount of unreacted SO ₂ , H ₂ O, COS and gaseous sulfur. Valve 46
The gas is introduced into the reactor 16 through which the absorption step is performed to cause an absorption reaction, thereby achieving both balance in the system and gas purification.

On the other hand, from the viewpoint of heat balance, as can be seen from Fig. 3, the mixed gas at the outlet of the two regeneration reactors at the start of regeneration has the lowest temperature during the regeneration cycle, but it is still around 550 ° C, and on average. The temperature is kept higher than the predetermined temperature (for example, 300 ° C.) required for the SO ₂ reduction reaction, which is advantageous in terms of heat balance in the regeneration system during gas switching.

If the flow rate of the high-temperature reducing gas in line 1 is reduced under low load or low-sulfur coal is used, formula (3),
The amount of FeS in the absorbent produced by the absorption reaction of the equation (4) becomes smaller than usual, the heat of the regeneration reaction decreases, and it becomes gradually difficult to obtain the heat balance of the regeneration system. When it becomes difficult to obtain the heat balance due to the load being below a predetermined value (for example, 50% or less), it is possible to adopt a method in which the Claus reaction system is partially bypassed. At this time, a single sulfur-producing reaction occurs only in the SO ₂ reduction reaction system, and the sulfur content is 50 to 70%.
%, And the residual H ₂ S and sulfur vapor in the reaction system outlet gas are combusted at the inlet or inside the regeneration reactor, and thus contribute to the supplementary heat in the regeneration system. It should be noted that only the SO ₂ reduction reaction system (without Claus reaction system) is sufficient as an S recovery system. At this time, residual H ₂ S and sulfur paper slightly increase in the gas, and O ₂ gas is consumed and burned, so the amount of air required for regeneration increases by about 10% compared to the case with the Claus reaction system. However, it does not cause a big problem in the system.

On the other hand, in order to switch the reactor 18 that has completed the cooling process to the reduction process, the flow path switching valves 13, 24, 37 are closed and 12, 35 are opened, and a part of the dedusting gasified gas in line 1 To ventilate. At the start of the reduction step, in order to treat the trace amount of SO ₂ gas remaining in the reactor 18 with the SO ₂ reduction and sulfur recovery device 53, a short time flow is performed before opening the flow path switching valve 26. After confirming that the SO ₂ gas has been exhausted by opening the flow switching valve 43, open the flow switching valve 26 and close 43 to the reactor.
The outlet gas of 18 is introduced into the middle of the reactor 17 which has entered the absorption step. The reason why the gas after the reduction reaction is not directly mixed with the purified gas 42 via the flow path switching valve 33 is as follows.

That is, when regeneration is insufficient due to a temperature decrease inside the reactor 18 due to operation management error in the regeneration process, or when sulfate is accumulated in the absorbent 20 due to a performance deterioration phenomenon over time, the sulfate is reduced. Reaction with H ₂ and CO in the gas occurs as shown in formulas (16) to (22), and sulfur compounds such as SO ₂ and H ₂ S are generated.

FeSO ₄ ＋ 2 / 3H ₂ → 1 / 3Fe ₃ O ₄ ＋ SO ₂ ＋ 2 / 3H ₂ O …… (16) Fe ₂ (SO ₄ ) ₃ ＋ 10 / 3H ₂ → 2 / 3Fe ₃ O ₄ ＋ 3SO ₂ ＋ 10 / 3H ₂ O ......
(17) Fe ₂ (SO ₄ ) ₃ ＋ 10H ₂ → 2FeS + SO ₂ ＋ 10H ₂ O …… (18) FeSO ₄ ＋ 2 / 3CO → 1 / 3Fe ₃ O ₄ ＋ SO ₂ ＋ 2 / 3CO ₂ …… (19) Fe ₂ (SO ₄ ) ₃ + 10 / 3CO → 2 / 3Fe ₃ O ₄ ＋ 3SO ₂ ＋ 10 / 3CO ₂ ……
(20) Fe ₂ (SO ₄ ) ₃ ＋ 10CO → 2FeS + SO ₂ ＋ 2H ₂ O …… (21) SO ₂ ＋ 3H ₂ O → H ₂ S ＋ 2H ₂ O …… (22) A considerable part of this sulfur compound is generated in the reduction process. It is absorbed and removed, but part of it is contained in the gas after the reduction treatment, and the concentration of its sulfur compounds may be too high to be ignored depending on the amount of sulfate accumulated in the absorbent 20. This is because it is not preferable to mix the latter gas with the purified gas in the line 42 at the outlet of the absorption process.

When moving to the reduction step, the temperature of the absorbent in the reactor is higher than the temperature of the high-temperature reducing gas by about 50 to 300 ° C. due to an accumulation phenomenon, but this is due to the reduction performance of ordinary absorbents. Does not adversely affect, but rather, when a part of the absorbent is not sufficiently regenerated at the time of life and sulfate is generated, the higher the temperature of the absorbent is, the higher the temperature of the absorbent is, so that the decomposition of the sulfate is caused by the above-mentioned reduction. It can be said that it is preferable because it is promoted according to the equations (16) to (23).

On the other hand, even if the amount of processing gas to be refined and the content of sulfur compounds change due to changes in the load of the gasification furnace, changes in coal type, etc., it is strongly required in practice to stabilize the absorption performance and regeneration performance. It

For example, when the flow rate of the high-temperature reducing gas 1 containing a sulfur compound such as H ₂ S, COS decreases, or when low-sulfur coal is used, the amount of FeS in the absorbent produced by the absorption reaction is usually This reduces the load on the regeneration process. Therefore, when the regeneration reaction is performed at the same circulating gas flow rate as the normal load, the reaction is completed in a short time, and the heat of the regeneration reaction decreases with the passage of time in the regeneration process. Therefore, the internal temperature of the reactor and the outlet gas temperature during the regeneration process are relatively lower than those under normal load, so supplementary heat is required to maintain stable regeneration operation.

As a method for supplementing this heat, it is conceivable to supply the gasification gas in line 1 containing a combustible gas such as CO or H ₂ from outside the system and utilize the combustion heat by the combustion reaction between the gas and oxygen. However, such use of the gasified gas consumes CO, H _{2 and the} like to be used on the downstream side of the gas purification, and it is preferable to avoid it as much as possible from the viewpoint of increasing the economical efficiency of the gas purification system. .

Therefore, in order to maintain stable continuous operation even under a low load, it is possible to deal with the problem by reducing the recycle gas circulation amount and extending the regeneration reaction time. The regeneration gas circulation line at low load is the same as that at normal load described above, but the following measures are taken to protect the blower 60. That is, in general, when the suction gas amount of the blower decreases, the cooling becomes insufficient and the temperature rises excessively. Therefore, it is preferable that the suction gas amount of the blower be constant. Therefore, as the regeneration gas circulation flow rate decreases, a part of the gas in the line 59 after the sulfur recovery and removal is returned to the front of the final sulfur condenser 56 via the line 62 via the flow path switching valve 61, and the blower 60 Then, make sure to secure almost the same amount of gas as under normal load.

If the heat in the regeneration reaction system cannot be supplemented simply by adjusting the amount of the recycle gas, a high-temperature reducing gas is further supplied to the reactor inlet line 41 during the regeneration process via the flow path switching valve 63. It is possible to supplement the heat by utilizing the combustion heat from the combustion reaction of H ₂ and CO combustible gas.

Note that, although FIG. 1 shows an example of a flow in which the absorption and regeneration operations are carried out in a countercurrent (backflow) in the reactor, the operations may be carried out in parallel.

〔The invention's effect〕

According to the method of the present invention, at least four reactors packed with an absorbent are used, and two regeneration reactors are installed among them, and a regeneration operation is performed in a part of series operation, whereby the absorbent derived from the heat of regeneration reaction is absorbed. The abnormal heat storage in the regeneration reactor is mitigated, the life of the absorbent is protected, the fluctuation of the concentration of SO ₂ gas produced in the regeneration reactor is suppressed, and regeneration is performed without introducing O ₂ gas into the subsequent S recovery system. Since it can be sufficiently carried out, the absorbent can continuously and stably absorb and remove the sulfur compound.

[Brief description of drawings]

FIG. 1 is a diagram showing a flow for explaining an embodiment of the method of the present invention, FIG. 2 is a diagram showing a time schedule of an absorption regeneration cycle when the present invention is carried out, and FIG. 3 is a regenerator outlet gas. It is a figure which shows an example of the time change of temperature.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Toru Seto 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. Hiroshima Research Laboratory (72) Kaoru Mitsuoka 4 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture 6-22 22 Mitsubishi Heavy Industries, Ltd. Hiroshima Research Institute (72) Inventor Kenji Inoue 4-6-22 Kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries Ltd. Hiroshima Research Institute (56) Reference JP-A-61-245819 (JP, A) Special table Sho 62-502815 (JP, A)

Claims (1)

[Claims] 1. A method for absorbing and removing a sulfur compound such as hydrogen sulfide and carbonyl sulfide contained in a high-temperature reducing gas with an absorbent, wherein at least four reactors filled with the absorbent are used to remove the sulfur compound. Absorption step of absorbing and removing with an absorbent, regeneration step of regenerating the absorbent with an oxygen-containing gas, cooling step after completion of the regeneration step, reducing gas of the regenerated absorbent with a high-temperature reducing gas before and after the absorbing agent It consists of four steps of reduction process to reduce to the same concentration, and performs partial parallel regeneration with the reactor which starts the next regeneration process before the regeneration in the reactor in the regeneration process is completed. Along with this, the outlet gas of the reactor in the cooling step after the regeneration is introduced into the reactor in the regeneration step and used as a part of the regeneration gas, and in the regeneration step, the high temperature gas from the regeneration reactor outlet is continuously supplied. Heat Absorbing perform yield method for purifying a high-temperature reducing gas which is characterized in that to stabilize the performance of the playback.