CN112004588A

CN112004588A - Method and equipment for recycling tail gas of low-temperature methanol washing unit and multiple sets of Claus units

Info

Publication number: CN112004588A
Application number: CN201880092510.2A
Authority: CN
Inventors: 夏玛·阿努帕; 石瑞福·亚历山大; 朱恩斯特·埃克哈德; 费舍尔·马蒂亚斯
Original assignee: LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Current assignee: LAir Liquide SA pour lEtude et lExploitation des Procedes Georges Claude
Priority date: 2018-04-26
Filing date: 2018-04-26
Publication date: 2020-11-27
Also published as: WO2019205055A1

Abstract

A method and apparatus for the combined recycling of tail gas from a low temperature methanol wash unit and multiple trains of claus units, wherein two or more sets of claus units (21) operating in parallel are used to treat acid gases from the low temperature methanol wash unit (20) for recovery of elemental sulphur; the tail gas of two or more sets of Claus units (21) is completely circularly conveyed back to a reabsorption tower of the low-temperature methanol washing unit (20) after being hydrogenated and chilled, wherein the two or more sets of Claus units (21) which are operated in parallel respectively comprise respective Claus combustors (4) and two-stage or multi-stage Claus catalytic reactors (5) connected with the same.

Description

Method and equipment for recycling tail gas of low-temperature methanol washing unit and multiple sets of Claus units

Technical Field

The invention relates to a method and equipment for purifying and recovering coal gas, natural gas and other carbonyl gas, in particular to a method and equipment for recycling tail gas of a low-temperature methanol washing unit integrated Claus unit.

Background

Most gasification systems for the production of synthesis gas, particularly those relying on coal as the primary fuel, have major problems including high volume percentages of carbon monoxide and carbon dioxide, and sulfur compounds (e.g., H)₂S and COS) and even nitrides. All of this reduces the heating value of the syngas (thermal value), creating complex pollution control problems and reducing the efficiency of the combined cycle plant. Thus, in recent years, various types of research have focused on reducing the amount of sulfur and other non-fuel components in the syngas feed.

The low-temperature methanol washing process is a purification process developed and applied in the last 50 th century, and particularly has an excellent purification effect on synthesis gas prepared by taking coal and heavy oil as raw materials. At present, low-temperature methanol washing is widely applied to the gas purification process for producing synthetic ammonia, synthetic methanol and the like, and the process comprises the following steps: acid gas removal, commonly referred to as CO, using cold methanol as solvent₂And H₂And S, gradually separating the methanol and the acid gas through pressure reduction, gas stripping and heating to achieve the purposes of separation and recovery. Typically, the Claus (Claus) process is used in conjunction with the treatment of hydrogen sulfide gas for recovery as sulfur.

The Claus sulphur recovery process has been the most mature sour gas containing sulphur, especially H, in the world today over more than 100 years of development₂And S treatment process. Conventional claus plants comprise a hot section and a catalytic section. ClausThe hot part of the plant consists essentially of a Claus furnace in which the feed gas contains H₂Part of S is burnt into SO under the condition of supplying air₂. Associated with the Claus hot section is a catalytic section, the catalytic section of the Claus plant consisting of a plurality, typically two or three, catalytic Claus stages. That is, a claus plant comprises, in addition to a hot claus stage, two or three catalytic claus stages (i.e. two or three claus reactors), usually denoted as a two-stage or three-stage claus plant. SO formed during combustion in the catalytic Claus section₂And H₂S is subjected to a Claus reaction to generate sulfur. But the sulfur recovery rate of the conventional Claus process of two-stage catalytic conversion is limited by chemical reaction balance to be 90-95%, the sulfur recovery rate of the conventional Claus process of three-stage conversion can only reach 95-98%, and the tail gas still contains 1-3% of elemental sulfur and sulfur-containing compounds (SO) by volume fraction₂、H ₂S, COS). With the increasing enhancement of environmental awareness and the improvement of environmental standards, the emission of sulfides in the tail gas of the conventional claus process cannot meet the requirements of the current environmental standards.

Oxygen Claus of Lurgi

The technology improves the high efficiency combustion capability of existing claus and tail gas plants by adding air and oxygen. This patented burner increases the operational flexibility of the plant to accommodate feed gases of different sulfur contents by automatically switching from air to oxygen operation.

The gases coming out of the claus reactor, which also contain small amounts of sulphur compounds, are fed to a post-combustion unit for re-combustion of the gases, which is associated with the recovery of sulphur, in order to ensure that the sulphur components remaining in trace amounts in these gases are converted to SO before they enter the atmosphere₂. SO after burning of device tail gas₂Large discharge amount, high concentration and great environmental pollution. Various forms of sulfur and sulfide in the conventional Claus tail gas are treated byReduction to H by perhydrogenation₂S, then absorbing, and discharging after burning, the total sulfur yield of the method can reach more than 99.8 percent, and SO in burning tail gas₂The content is less than 300 ppm. The process has the advantages of complex flow, more equipment, large construction investment, high operating cost and high energy consumption.

Although increased sulfur recovery through reprocessing of the claus off-gas can increase the production of valuable material sulfur, the costs of further cleaning and desulfurizing the claus off-gas far outweigh the benefits of sulfur production increase. Especially when the gas conditions of coal gasification or natural gas vary widely, this results in the sulfur component content in the upstream feed gas deviating far from the original design value of the system. The change of the sulfur component in the feed gas can cause the problems of insufficient cold supply of an ammonia cooler at the top of the hydrogen sulfide concentration tower, increase of methanol circulation amount, insufficient supply of nitrogen for gas stripping and the like. Therefore, in the subsequent production process, the sulfur recovery rate of the sulfur recovery and tail gas treatment device is low, and the discharged tail gas cannot reach the national environmental protection standard.

Disclosure of the invention

The technical problem to be solved by the invention is to make the claus sulfur recovery system have a flexible operation range to adapt to feed gases with different sulfur contents, and at the same time, make the operation of the sulfur recovery system have higher stability and have less influence on the upstream and downstream devices of the claus plant. If a set of Claus units with larger treatment capacity is arranged, when the sulfur content in the feed gas is smaller, the low-load operation cost is overhigh; the invention provides two or more sets of Claus units connected in parallel, one set of Claus units can be independently operated or two or more sets of Claus units (Claus train) can be simultaneously operated according to the sulfur content in the feed gas, when H in the feed gas₂When the S content or the flow of the inlet gas to be treated fluctuates greatly, two or more sets of Claus units (Claus train) connected in parallel can be operated simultaneously, and each unit is provided with a Claus burner and a Claus catalytic reactor. The arrangement enables the sulfur recovery system to have a larger flexible operation range, reduces the operation cost for long-term use, and increases the running stability of the upstream and downstream devices.

On the other hand, if one set of claus units fails, such an arrangement can avoid the shutdown of the entire integrated plant, resulting in a loss of productivity, caused by the failure or maintenance of a single claus unit. Although capital costs may increase during the initial stages of investment, the system benefits over conventional equipment in long term operation.

The invention aims to solve the other technical problem of reducing the cost of acid gas treatment in the synthesis gas, which is different from the traditional tail gas treatment (such as incineration or emission to the atmosphere), and the invention provides the tail gas circulation combination method of the low-temperature methanol washing unit integrated Claus unit, which recycles part of the treated tail gas to the low-pressure section reabsorption tower of the upstream low-temperature methanol washing unit, so that the method can save a large amount of operation cost of a sulfur recovery system, save an amine liquid absorption device and a regeneration device arranged in the tail gas treatment unit, reduce the energy consumption for compression, and achieve the sulfur recovery rate of 100 percent (99.8 to 99.9 percent), thereby being beneficial to meeting the waste gas emission standard of a gasification synthesis gas plant.

In accordance with one subject matter of the present invention, a method is disclosed for the combined use of a low temperature methanol wash unit and two or more sets of claus unit tail gas recycle, comprising: providing a low temperature methanol washing unit for removing undesired components from a raw synthesis gas containing acid gases, comprising an absorption tower for absorbing acid gases, a flash tower and a thermal regeneration tower and associated ancillary equipment; downstream of the low temperature methanol wash unit, providing a claus unit for sulfur recovery comprising a claus burner and a two-stage or multi-stage claus catalytic reactor connected in series; providing a claus tail gas treatment unit comprising a hydrogenation column and a quench column for catalytic reduction of a claus tail gas formed by the claus unit, optionally comprising a compression device; introducing the crude synthesis gas containing acid gas into a low-temperature methanol washing unit, separating the acid gas from the methanol by using cold methanol as a solvent in an absorption tower, sending the acid gas to a Claus unit through a flash tower and a thermal regeneration tower, burning the acid gas by a Claus burner, and then introducing the acid gas into a Claus catalytic reactor for Claus reaction, recovering sulfur element in a simple substance form, and sending the purified synthesis gas to the downstream for further purification or synthesis; hydrogenating and cooling the Claus tail gas after the Claus reaction in a Claus tail gas treatment unit, optionally compressing, partially or completely returning to the bottom of a reabsorption tower of a low-temperature methanol washing unit, desulfurizing with acid gas, and recycling to the Claus unit; the device comprises a sulfur recovery device, a sulfur recovery system, a tail gas treatment unit, a first Claus unit, a second Claus unit, a first Claus burner and a second Claus catalytic reactor, wherein the first Claus burner and the second Claus burner are sequentially connected, the first Claus unit and the second Claus unit are sequentially connected, the second Claus burner and the first Claus catalytic reactor are sequentially connected, the first Claus burner and the second Claus burner are sequentially connected, the second Claus burner and the second Claus.

According to other optional aspects:

in some preferred embodiments, the duty of each of the two or more sets of claus units in parallel is designed to be operable individually to treat all of the acid gas from the upstream low temperature methanol wash unit. During operation of an upstream syngas generation plant, if one set of claus units is suddenly stopped (tripped), the other or more sets of claus units in parallel will be raised to operate at full capacity, without affecting the operation of the syngas generation plant, improving the stability and reliability of the plant and product. Although the capital investment cost of two or more parallel claus unit configurations is significantly higher than that of a single train, it is expected that the increase in product supply and stability of the syngas plant may be a benefit of the plant over long term operation due to conventional equipment, thereby reducing the overall cost of the syngas plant.

In some embodiments, each set of claus units may be simultaneously operated at a non-full load to treat all of the acid gases from the upstream low temperature methanol wash unit.

In some embodiments, each set of claus units may be individually operated at non-full, or excess capacity to treat all of the acid gases from the upstream low temperature methanol wash unit. During operation of an upstream syngas generation plant, if the amount of gas to be processed decreases or one set of claus units suddenly stops (trips), another set or sets of claus units in parallel can be operated separately, which can be raised to operate at full capacity.

In some preferred embodiments, the claus tail gas treatment does not comprise an amine liquor absorption treatment step and a regeneration treatment step. Two or more sets of Claus devices operating in parallel use a set of tail gas treatment system together, and the treated tail gas is recycled to the low-temperature methanol washing unit, so that the fixed asset investment is reduced by 25% compared with the use of respective Claus tail gas circulation systems.

In some embodiments, the claus tail gas after the claus reaction is subjected to hydrogenation and cooling treatment in a claus tail gas treatment unit, and then a part of the claus tail gas is compressed and sent back to the raw synthesis gas feed inlet of the low-temperature methanol washing unit to enter the absorption tower.

In some embodiments, the claus unit may be a conventional claus process or an oxygen-rich claus process. For oxygen-enriched claus processes, air or oxygen-enriched air of different oxygen concentration can be used as adjusted according to the sulphur content in the feed gas.

In some embodiments, the multi-stage claus catalytic reactor is a three-stage claus catalytic reactor.

In some embodiments, elemental sulfur is recovered in the claus unit as elemental sulfur in a liquid or solid state.

In some embodiments, the raw acid gas-containing syngas comprises at least one sulfur-containing component, including but not limited to H₂S，COS。

In some embodiments, the claus tail gas from two or more claus units in parallel is mixed and heated to the desired feed temperature to the hydrogenation column before entering the hydrogenation column of the claus tail gas treatment unit.

In some embodiments, a hydrogen-rich gas is introduced into the hydrogenation column as the reducing agent.

In some embodiments, the reducing agent introduced in the hydrogenation column may be selected from the group consisting of CO/H containing from a claus burner₂Or crude hydrogen from a low temperature methanol wash unit, or a hydrogen rich gas from an external gas source.

In some embodiments, the claus tail gas after the claus reaction is optionally fed to a tail gas incinerator and discharged after incineration. Especially when the Claus tail gas treatment unit fails or the tail gas treated by the Claus tail gas treatment unit cannot be recycled to the low-temperature methanol washing unit, the Claus tail gas can be optionally incinerated, so that the emission of sulfur can be reduced.

In some embodiments, the undesired components from the gas mixture comprise carbon dioxide, hydrogen sulfide, hydrogen cyanide, carbonyl sulfide, mercaptans, and ammonia.

According to another aspect of the present invention, there is also disclosed a device for recycling tail gas from a low temperature methanol wash unit in combination with two or more sets of claus units, comprising: a low temperature methanol wash unit for removing undesired components from the raw syngas containing acid gases, comprising an absorber column for absorbing acid gases, a flash column and a thermal regenerator column and associated ancillary equipment; a Claus unit for recovering elemental sulfur, located downstream of the low temperature methanol wash unit, connected thereto via a pipeline, comprising a Claus burner and a two-stage or multi-stage Claus catalytic reactor connected in series; a claus tail gas treatment unit connected by a pipeline to a tail gas outlet of the claus unit, comprising a hydrogenation column and a quench column for catalytic reduction of a claus tail gas formed by the claus unit, optionally comprising a compression device; part or all of the claus tail gas after hydrogenation and cooling treatment by the claus tail gas treatment unit is conveyed back to a pipeline at the bottom of a flash tower of the low-temperature methanol washing unit, and a gas compression device is optionally arranged on the pipeline; the system comprises at least two sets of Claus units for sulfur recovery, wherein the Claus units at least comprise a Claus combustor and a two-stage or multi-stage Claus catalytic reactor which are sequentially connected, the two sets or the plurality of sets of Claus units are arranged in parallel, and the tail gas outlet downstream of all the Claus units is connected with one Claus tail gas treatment unit through a pipeline.

According to other optional aspects, the apparatus further comprises:

in some preferred embodiments, the duty of each of the two or more sets of claus units in parallel is designed to be operable individually to treat all of the acid gas from the upstream low temperature methanol wash unit. The duty of each set of claus units is designed to be individually operable to treat at its full capacity all of the acid gases from the upstream low temperature methanol wash unit. In some embodiments, each set of claus units may be simultaneously operated at a non-full load to treat all of the acid gases from the upstream low temperature methanol wash unit. In some embodiments, each set of claus units may be individually operated at non-full, or excess capacity to treat all of the acid gases from the upstream low temperature methanol wash unit.

In some preferred embodiments, the claus tail gas treatment unit does not comprise an amine liquid absorption unit and a regeneration unit.

In some preferred embodiments, the method further comprises a pipeline for conveying part of the claus tail gas after hydrogenation and cooling treatment in the claus tail gas treatment unit back to the raw synthesis gas feed inlet of the low temperature methanol washing unit, the pipeline comprising a gas compression unit.

In some embodiments, the claus unit may be a conventional claus unit or an oxygen-rich claus unit. The parameters and catalysts of the claus process and the operating schemes can be considered to be well known to the person skilled in the art.

In some embodiments, the claus catalytic reactor comprises means for recovering elemental sulphur in elemental form, in liquid or solid form.

In some embodiments, the acid gas-containing syngas comprises at least one sulfur-containing component, including but not limited to H₂S，COS。

In some embodiments, the conduit connecting the claus tail gas outlet to the hydrogenation column after two or more sets of claus units in parallel comprises a heating means for heating the mixed claus tail gas to the desired feed temperature to the hydrogenation column.

In some embodiments, the hydrogenation column also contains a conduit for an introduced hydrogen-rich gas of the reducing agent.

In some embodiments, further optionally comprising CO/H-containing from the claus burner₂The gaseous by-product of (a) or crude hydrogen from a low-temperature methanol washing unit or hydrogen-rich gas from an external gas source is used as a reducing agent to be fed into a pipeline of the hydrogenation tower. The parameters such as the content of hydrogen in the reducing agent can be adjusted according to the sulfur concentration in the feed gas, and the related contents can be considered as common knowledge in the field.

In some embodiments, a tail gas incinerator is included, optionally for incinerating claus tail gas from a claus unit. In particular, the method is used for dealing with the condition that the Claus tail gas treatment device fails or the treated tail gas can not be recycled to the low-temperature methanol washing unit.

In the invention, two or more sets of Claus units capable of running in parallel are arranged, and when H is in the air inlet₂When the S content or the flow of the inlet gas material to be processed has large fluctuation, one or more sets of two or more sets of Claus units (Claus train) connected in parallel can be operated in an adjustable mode, so that the problem that the whole integrated device is shut down and the productivity loss is caused due to the loss caused by the fault or maintenance of any one Claus unit connected in parallel is avoided as much as possible. Although capital costs may increase during the initial stages of investment, the system benefits over conventional equipment in long term operation. According to the invention, after two or more sets of Claus units are connected in parallel, Claus tail gas from all the Claus units enters one Claus tail gas treatment unit, and the treated tail gas is recycled to the low-temperature methanol washing unit, so that an amine liquid absorption device and a regeneration device arranged in the tail gas treatment unit can be omitted, the operation cost of a large amount of sulfur recovery systems can be saved, and the sulfur recovery rate can reach 100%.

Brief description of the drawings

The drawings in the present disclosure are only for illustration of the invention for understanding and explaining the spirit of the invention, but not for limiting the invention in any way. The figures are generally schematic and are not drawn to scale for the sake of clarity. The same or corresponding technical features share the same reference numerals throughout the drawings.

FIG. 1 is a schematic flow diagram of a conventional sulfur recovery system.

Fig. 2(a) is a schematic flow diagram of the claus unit of fig. 1.

Fig. 2(b) is a schematic flow diagram of two sets of claus units in parallel in one embodiment of the present invention.

FIG. 3(a) is a schematic flow diagram of the off-gas treatment unit of FIG. 1.

Fig. 3(b) is a schematic flow diagram of an off-gas treatment unit in an embodiment of the invention.

FIG. 4 is a flow diagram of one embodiment of the present invention.

1-low-temperature methanol washing absorption tower, 2-flash evaporation section, 3-thermal regeneration tower, 4-Claus burner, 5-Claus catalytic reactor, 7-hydrogenation tower, 8-chilling tower, 9-amine absorption tower, 10-regeneration tower, 11-incinerator, 20-low-temperature methanol washing unit, 21-Claus unit, 22-traditional tail gas treatment unit, and 23-Claus tail gas treatment unit in the invention.

Best mode for carrying out the invention

Syngas (Syngas/synthesis gas) generally refers to a fuel gas (sometimes containing some carbon dioxide) in which carbon monoxide is mixed with hydrogen, typically the product of a gasification reaction, and in this disclosure, Syngas includes any raw Syngas produced by gasification of a carbon-rich feedstock (e.g., refinery, waste residues, or petroleum coke).

The low temperature methanol wash (Rectisol)^TMProcess) is an acid gas purification Process using physical absorption method, developed by Linde (Linde) company and Lurgi (Lurgi) company in germany, and refers to a Process for physical acid gas removal using an organic solvent (typically methanol) at low temperature. The acid gas contained in the raw material gas is removed by physical absorption of a solvent (cold methanol), and the removed acid gas components are carbon dioxide and sulfurHydrogen sulfide, carbonyl sulfide, mercaptans, ammonia, hydrogen cyanide, and almost all other trace components that can be detected; the rich liquid can be regenerated by flashing and stripping. With the wide application of the low-temperature methanol washing process in an industrial device, aiming at different raw materials and gasification methods, Lurgi company and Linde company develop various process flows, and the efficiency of the whole low-temperature methanol washing process is higher and the energy utilization is more sufficient and reasonable by continuously optimizing the original flow and improving equipment. The related technical characteristics are similar or identical and comprise an acid gas absorption tower and a solution regeneration system, including medium-pressure flash evaporation for recovering H₂With CO, CO₂Desorption, N₂Gas stripping, H₂S thermal regeneration with methanol/water separation, etc. In the low temperature methanol wash unit described herein, not all details are described, but should be apparent to those skilled in the art. In a low temperature methanol wash unit, H₂The S gas is sent to a sulfur recovery device after being cooled, condensed and recycled with methanol.

Herein, sulfur recovery is performed using a claus unit. The feedstock to the Claus sulphur recovery unit is derived primarily from the H-containing feed to the low temperature methanol wash unit₂And S acid gas. The main reactions of the conventional claus process include a thermal reaction stage in a combustion furnace and a catalytic reaction stage in a catalyst bed, and since the claus reaction is limited by factors such as thermodynamic and kinetic balances, the sulfur recovery of conventional claus plants is usually only 95-97%, and the SO recovery of the tail gas of the plant after incineration is usually 95-97%₂Large discharge amount, high concentration and great environmental pollution. Oxygen-enriched claus is a variant of the claus process, and the main difference from conventional claus is that the main combustion furnace uses oxygen-enriched air or pure oxygen for air supply to promote more efficient combustion. The main principle is the same as that of the conventional Claus process, and sulfur is produced through the Claus reaction. In a conventional claus plant, a combustion furnace with partial combustion of the inlet air of a waste heat boiler, a claus reactor with auxiliary devices and a desulfurizer are included, which are used in series. The size of these units is based on the H expected in the feed₂S content and feed gas to be treatedAnd (4) flow rate determination. Deviations from the desired production capacity can only fluctuate within narrow limits and, in the event of substantial fluctuations in the H2S content of the feed gas or in the feed gas stream to be treated, two-stage or multi-stage Claus catalysis, usually two-stage or three-stage Claus catalysis, must be used for the treatment. In the first catalytic stage, a special catalyst can be used to mix most of COS and CS₂Conversion to H by hydrolysis₂S, the catalytic section of a claus unit typically comprises two catalytic reactors. In the claus units described herein, not all details, such as catalysts and operating parameters and steps, are described, but should be apparent to those skilled in the art, the claus units include, but are not limited to, conventional claus and oxygen-enriched claus.

The gas withdrawn from the claus catalytic stage is separated from the elemental sulphur in a sulphur condenser. The Claus off-gas of the Claus plant is mixed with a reducing gas and fed to the hydrogenation reactor. Removal of sulfides such as SO₂Is hydrogenated to H₂In addition to S, COS and/or CS also occur in the reactor₂Of virtually all the sulphur compounds contained in the claus off-gas are converted into H₂And S. For hydrogenation and hydrolysis of sulfides to H₂The catalytic process of S and the extraction technique of elemental sulphur can be considered as known in the art.

The present invention will be described in further detail below with reference to the accompanying drawings, but the present invention is not limited to the following embodiments. Figure 4 depicts a preferred non-limiting embodiment of the present invention.

FIG. 1 is a conventional sulfur recovery system comprising: a low temperature methanol wash unit 20 comprising an absorber column 1, a flash section 2 and a thermal regenerator column 3, a claus unit 21 for sulphur recovery and a tail gas treatment unit 22. The raw synthesis gas stream 1' from the upstream gasification synthesis gas plant enters the bottom of an absorption tower 1, and is gradually absorbed by low-temperature methanol entering from the top through multiple sections in the tower to remove CO in the raw synthesis gas₂And H₂And S. Finally, a purified synthesis gas stream of 6 'is taken out of the top of the absorber tower'After being exchanged for recovered cold by a plurality of heat exchangers (not shown in fig. 1), is sent to a downstream purification or synthesis plant (not shown in fig. 1). Absorption of CO by Cold methanol in an absorption column 1₂And H₂S to form a pregnant stream 2 'which is cooled and sent to the low pressure flash section 2 for flash distillation to remove part of the carbon dioxide 5' and dissolved valuable hydrogen and carbon monoxide for recycling. Heating the flash-evaporated stream 3 'in a thermal regeneration tower 3 to above 95 ℃, releasing all the gas absorbed in the methanol to become pure methanol, and sending the cooled regenerated methanol stream 4' back to the absorption tower 1 to continuously absorb CO in the feed gas₂And H₂S, contains H₂The acid gas stream 7' of S is sent to claus unit 21 for sulfur recovery. As shown in FIG. 2(a), the Claus unit may be an oxygen Claus unit

Comprising a Claus burner 4 and two Claus catalytic reactors 5, the acid gas stream 7' coming from the low-temperature methanol washing unit enters the Claus burner 4 first, the acid gas contains H₂Part of S is burnt to SO under the condition of supplying air or oxygen 8₂Then enters a Claus catalytic section, in two or three Claus catalytic reactors 5, with SO formed during combustion₂And H₂S undergoes a claus reaction to produce sulphur 9 ', 9' which is collected in a sulphur condenser (not shown in figures 1 and 2 (a)). As shown in fig. 1 and 3(a), the claus tail gas stream 10 'is sent to a tail gas treatment unit 22 where a reductant 13' is introduced into the hydrogenation column 7 to reduce the various forms of sulfur and sulfides in the claus tail gas to H₂S, cooling the tail gas after hydrogenation reduction by a chilling tower 8, sending the cooled tail gas into an amine absorption tower 9, then reversely contacting with amine liquid in the amine absorption tower 9 from bottom to top, wherein hydrogen sulfide is absorbed to ppm level, discharging a tail gas stream 11' after incineration or directly discharging the tail gas stream into the atmosphere, regenerating the absorption liquid in a regeneration tower 10, and regenerating H₂S may be recycled back to the claus unit.

FIG. 4 is an embodiment of the present invention, including: a low temperature methanol wash unit 20, a claus unit 21 for sulfur recovery and a claus tail gas treatment unit 23, wherein the low temperature methanol wash unit comprises an absorption column 1, a flash column 2 and a thermal regeneration column 3. The raw synthesis gas from the upstream gasification unit has a major component of H₂、CO、CO ₂、H ₂O、N ₂、H ₂S, COS, at a temperature of 40 deg.C and a pressure of 3.0MPa (g), in the low temperature methanol wash unit 20. The raw synthesis gas stream 1' enters the bottom of an absorption tower 1, and is gradually absorbed by low-temperature methanol entering from the top in the tower through multiple sections to remove CO in the raw synthesis gas₂And H₂And S. Finally, the purified synthesis gas stream 6' (total sulfur less than 0.1ppm, CO) at the top of the absorption tower is obtained₂About 3% or so) is sent to a downstream purification or synthesis plant (not shown in fig. 4) after exchanging the recovered cold through a plurality of heat exchangers (not shown in fig. 4). Absorption of CO by Cold methanol in an absorption column 1₂And H₂S, is cooled to form a pregnant stream 2 'which is sent to the low pressure flash section 2 for flash distillation to remove part of the carbon dioxide 5' and dissolved valuable hydrogen and carbon monoxide for recycling. Then, the methanol is heated to above 95 ℃ in the thermal regeneration tower 3, the gas absorbed in the methanol is completely released to become pure methanol, and the cooled and regenerated methanol stream 4' is sent back to the absorption tower 1 to continuously absorb CO in the raw material gas₂And H₂And S. H-containing from low temperature methanol wash unit desorption₂The acid gas stream 7' of S is sent to claus unit 21 for sulfur recovery. Claus unit 21 for sulfur recovery is shown in FIG. 2(b), and in this example, the Claus unit is two oxygen Claus units connected in parallel

Each oxygen claus unit comprises a claus burner and two or more sets of claus catalytic reactors (not shown in detail in fig. 4, see fig. 2(b) for details), sourThe gas stream 7 'is passed through a claus burner in an oxy claus unit for high temperature combustion to produce sulphur, and the claus tail gas 10' after claus catalytic sulphur production is passed to a claus tail gas treatment unit 23. In the hydrogenation tower 7 (not shown in fig. 4, see fig. 3(b)) of the claus tail gas treatment unit 23, crude hydrogen is introduced from the low-temperature methanol washing unit as a reducing agent 13 ', and the claus tail gas 10' is subjected to hydrogenation reduction under the action of the reducing agent to convert all sulfides in the waste gas into H₂And S, the temperature of the hydrogenated tail gas is about 295 ℃, and heat is recovered through a steam generator. Then passing through a chilling tower 8 (not shown in figure 4, see figure 3(b)) connected with a hydrogenator, washing and dehydrating in the chilling tower, and pumping all or part of the treated tail gas 19' by a compressor to make the pressure of the hydrogenated tail gas reach 0.2MPa (g), namely the pressure of a reabsorber and a tail gas washing tower, and then sending out of a boundary zone to a low-temperature methanol washing device. One part of the tail gas is conveyed back to the bottom of a reabsorber of a flash evaporation section 2 of the low-temperature methanol washing unit 20 as a stream 20', the acid gas and the concentrated acid gas enter a thermal regeneration tower to be analyzed, and H in the tail gas is finally discharged₂S≤20mg/Nm ³. Optionally, another portion is sent back to the raw syngas gas inlet of the low temperature methanol wash unit 20 as stream 21 'to enter the absorber column of the low temperature methanol wash unit with the raw syngas stream 1'. In this embodiment, an incinerator 11 is optionally provided, and part or all of the claus tail gas 10 'and/or part or all of the claus tail gas 19' treated by the claus tail gas treatment unit 23 may be combusted in the incinerator 11 and discharged to the atmosphere.

The sulfur content of coal/petroleum coke is typically in the range of 2 to 5 wt%, whereby the sulfur content in the plant process stream in this example can be about 40 to 100 tons/day for a feed rate of 2000 tons coal/day, gasification typically converts more than 80% of the sulfur in the feed to H₂S or COS, calculated accordingly, the sulfur recovery of the unit in this example was about 0-100 tons/day 0.8 x 0.95, with zero sulfur emissions from the sulfur recovery unit. Because two or more sets of Claus units are arranged and run in parallel, when H is in the air intake₂When the S content or the flow of the inlet air material to be processed has large fluctuation,one or more of two or more sets of Claus units (Claus train) connected in parallel are controllably operated, so that the shutdown of the whole integrated device caused by the loss caused by the fault or maintenance of any one Claus unit connected in parallel can be avoided. And after two or more sets of Claus units connected in parallel, Claus tail gas from all the Claus units enters a Claus tail gas treatment unit, the treated tail gas is recycled to the low-temperature methanol washing unit, an amine liquid absorption device and a regeneration device are not arranged in the tail gas treatment unit, and the operation cost of a large amount of sulfur recovery systems is saved.

The sub-equipment used for carrying out the above-described process is equipment known in the art. For example, the operation of the burner and claus reactor with the conditions and catalysts common to the implementation of the claus process is well known to those skilled in the art, as are the operating conditions and schemes of the hydrogenation column for hydrogenating the claus tail gas. Since these process conditions are not the object of the present invention, as are the structures of the respective sub-units, they need not be described in detail here.

Claims

A method of using a low temperature methanol wash unit in conjunction with tail gas recycle from multiple claus units, comprising:

(a) providing a low-temperature methanol washing unit for removing undesired components from the raw synthesis gas containing acid gas, comprising an absorption tower for absorbing acid gas, a flash tower and a heat regeneration tower and corresponding auxiliary equipment;

(b) downstream of the low temperature methanol wash unit, providing a claus unit for sulfur recovery comprising a claus burner and a two-stage or multi-stage claus catalytic reactor connected in series;

(c) providing a claus tail gas treatment unit comprising a hydrogenation column and a quench column for catalytic reduction of a claus tail gas formed by the claus unit, optionally comprising a compression device;

(d) introducing the crude synthesis gas containing acid gas into a low-temperature methanol washing unit, separating the acid gas from the methanol by using cold methanol as a solvent in an absorption tower, separating the acid gas from the methanol by using a flash tower and a thermal regeneration tower, delivering the acid gas to a Claus unit, combusting the acid gas by two or more sets of Claus combustion furnaces, and then delivering the acid gas to a Claus catalytic reactor for Claus reaction, recovering sulfur element in a simple substance form, and delivering the purified synthesis gas to the downstream for further purification or synthesis;

(e) hydrogenating and cooling the Claus tail gas after the Claus reaction in a Claus tail gas treatment unit, optionally compressing, partially or completely returning to the bottom of a reabsorption tower of a low-temperature methanol washing unit, desulfurizing with acid gas, and recycling to the Claus unit;

the Claus units for sulfur recovery are at least two sets, and respectively comprise a Claus combustor and a two-stage or multi-stage Claus catalytic reactor which are sequentially connected, the two or more sets of Claus units are arranged in parallel, and the tail gas outlet downstream of all the Claus units is connected with one set of Claus tail gas treatment unit through a pipeline.
The method of claim 1 wherein the duty of each of the two or more sets of claus units in parallel is designed to be independently operable to treat all of the acid gas from the upstream low temperature methanol wash unit.
The method of claim 2, wherein each set of claus units can be operated simultaneously at a non-full load to treat all of the acid gases from an upstream low temperature methanol wash unit.
The method of claim 2, wherein each set of claus units can be operated individually at non-full, full or super-full capacity to treat all of the acid gas from an upstream low temperature methanol wash unit.
The method of claim 1, wherein the claus tail gas treatment does not comprise an amine liquor absorption treatment step and a regeneration treatment step.
The method according to claim 1, wherein after the claus tail gas after the claus reaction is hydrogenated and cooled by the claus tail gas treatment unit, part of the claus tail gas is compressed and sent back to the raw synthesis gas feed inlet of the low temperature methanol washing unit to the absorption tower.
The method of claim 1, wherein the claus unit can be a conventional claus process or an oxygen-rich claus process.
The method of claim 1, wherein the multi-stage claus catalytic reactor is a three-stage claus catalytic reactor.
The process of claim 1 wherein elemental sulfur is recovered in the claus unit as elemental sulfur in a liquid or solid state.
The method of claim 1, wherein the raw syngas containing acid gas comprises at least one sulfur-containing component including but not limited to H₂S，COS。
The process of claim 1 wherein the claus tail gas from two or more claus units in parallel is mixed and heated to the desired feed temperature to the hydrogenation column before entering the hydrogenation column of the claus tail gas treatment unit.
The process according to claim 1, wherein a hydrogen-rich gas is introduced into the hydrogenation column as the reducing agent.
The process of claim 12, wherein the reducing agent introduced in the hydrogenation column is selected from the group consisting of CO/H-containing from a claus burner₂Or crude hydrogen from a low temperature methanol wash unit, or a hydrogen rich gas from an external gas source.
The process of claim 1, wherein the claus tail gas after the claus reaction is optionally fed to a tail gas incinerator and incinerated for emission.
The method of any one of claims 1-14, wherein the undesired component from the gas mixture comprises carbon dioxide, hydrogen sulfide, hydrogen cyanide, carbonyl sulfide, mercaptans, and ammonia.
A device for recycling a tail gas from a low temperature methanol wash unit in combination with a plurality of sets of claus units, comprising:

(a) a low temperature methanol washing unit for removing undesired components from the raw synthesis gas containing acid gas, comprising an absorption column for absorbing acid gas, a flash column and a thermal regeneration column and corresponding ancillary equipment;

(b) a Claus unit for recovering elemental sulfur, located downstream of the low temperature methanol wash unit, connected thereto via a pipeline, comprising a Claus burner and a two-stage or multi-stage Claus catalytic reactor connected in series;

(c) a claus tail gas treatment unit connected by a pipeline to a tail gas outlet of the claus unit, comprising a hydrogenation column and a quench column for catalytic reduction of a claus tail gas formed by the claus unit, optionally comprising a compression device;

(d) conveying part or all of the Claus tail gas subjected to hydrogenation and cooling treatment by the Claus tail gas treatment unit back to a pipeline at the bottom of a reabsorption tower of the low-temperature methanol washing unit, wherein the pipeline optionally comprises a gas compression device;

the system comprises at least two sets of Claus units for sulfur recovery, wherein the Claus units at least comprise a Claus combustor and a two-stage or multi-stage Claus catalytic reactor which are sequentially connected, the two sets or the plurality of sets of Claus units are arranged in parallel, and the tail gas outlet downstream of all the Claus units is connected with one Claus tail gas treatment unit through a pipeline.
The plant defined in claim 16 wherein the duty of each of the two or more sets of claus units in parallel is designed to be individually operable to treat all of the acid gas from the upstream cryogenic methanol wash unit.
The apparatus of claim 16, wherein the claus tail gas treatment unit does not comprise an amine liquid absorption unit and a regeneration unit.
The apparatus according to claim 16, further comprising a conduit for returning a portion of the claus tail gas after hydrogenation and cooling in the claus tail gas treating unit to the raw synthesis gas feed inlet of the low temperature methanol scrubbing unit, the conduit comprising a gas compression device.
The apparatus of claim 16, wherein the claus unit can be a conventional claus unit or an oxygen-rich claus unit.
The apparatus of claim 16, wherein the multi-stage claus catalytic reactor is a three-stage claus catalytic reactor.
The apparatus of claim 16, wherein the claus catalytic reactor comprises means for recovering elemental sulphur in the form of elemental sulphur in liquid or solid form.
The plant of claim 16 wherein the acid gas containing syngas contains at least one sulfur containing component including but not limited to H₂S，COS。
The apparatus of claim 16, wherein the conduit connecting the claus tail gas outlet to the hydrogenation column after two or more sets of claus units in parallel comprises a heating means for heating the mixed claus tail gas to the desired feed temperature to the hydrogenation column.
The apparatus of claim 16, wherein the hydrogenation column further comprises a conduit for introducing a hydrogen-rich gas as a reducing agent.
The apparatus of claim 25, further optionally comprising CO/H-containing gas from a claus burner₂The gaseous by-product of (a) or crude hydrogen from a low-temperature methanol washing unit or hydrogen-rich gas from an external gas source is used as a reducing agent to be fed into a pipeline of the hydrogenation tower.
The apparatus of claim 16, further comprising a tail gas incinerator, optionally for incinerating claus tail gas from a claus unit.
The apparatus of any one of claims 16-27, wherein the undesired component from the gas mixture comprises carbon dioxide, hydrogen sulfide, hydrogen cyanide, carbonyl sulfide, mercaptans, and ammonia.