Four-stage absorption and desorption device for purifying acid gas

Abstract

The utility model discloses a four-stage absorption and desorption device for purifying acid gas. The four-stage absorption and desorption device comprises a methanol absorption tower, a carbon dioxide desorption tower, a hydrogen sulfide desorption tower and a mercaptan desorption tower, a mixed gas inlet is formed in the lower part of the methanol absorption tower; the inlet of the carbon dioxide desorption tower is communicated with the methanol absorption tower kettle, and the upper outlet is communicated with the tail gas treatment system; an inlet of the hydrogen sulfide desorption tower is communicated with a lower outlet of the carbon dioxide desorption tower, and an upper outlet of the hydrogen sulfide desorption tower is communicated with the tail gas treatment system; an upper outlet of the mercaptan desorption tower is communicated with the purification system, and a lower outlet of the mercaptan desorption tower is communicated with a circulating methanol pipeline; and the circulating methanol pipeline is communicated with the methanol inlet after being converged with the fresh methanol pipeline through the multi-stage condenser. The device can effectively recover the residual hydrogen sulfide in the mercaptan and disulfide synthesis device and purify the carbon dioxide at the same time, a device for independently purifying the hydrogen sulfide does not need to be established, and the investment and the occupied area are saved.

Description

TECHNICAL FIELD

[0001] The utility model belongs to the technical field of chemical industry device, concretely relates to a four-stage absorption and analysis device for purifying acid gas. TECHNICAL BACKGROUND

[0002] The production process of dimethyl disulfide includes three sections, i.e., a thiol synthesis section, a disulfide synthesis section and a thiol synthesis section. The latter usually adopts a method of generating thiol and sulfide by reacting methanol with hydrogen sulfide, and a certain amount of synthesis gas is generated in the reaction, including hydrogen sulfide, thiol (and sulfide), methane, carbon oxide, etc. The synthesis gas passes through a condenser, and the non-condensed gas after condensation contains a large amount of hydrogen sulfide. If the non-condensed gas is directly sent back to the reactor for recycling by using a compressor, the thiol and sulfide in the gas will cause serious corrosion to the seal of the compressor after being compressed. Therefore, at the present stage, the non-condensed gas is often directly incinerated or treated in tail gas, which not only wastes cost, but also increases the difficulty of tail gas treatment and environmental burden.

[0003] On the other hand, the reaction gas is mostly prepared by the method of coal chemical industry, and a large amount of carbon dioxide is contained in the acid gas from the low-temperature methanol washing device or the acid water gas stripping device, and the proportion is generally between 70% and 90%. In order to produce organic sulfur chemical products by using the hydrogen sulfide resource, the hydrogen sulfide needs to be purified. CONTENT OF THE UTILITY MODEL

[0004] The utility model aims to provide a four-stage absorption and analysis device for purifying acid gas, which purifies the hydrogen sulfide in the acid mixed gas of raw materials and reaction process, so as to solve the problems in the prior art.

[0005] The utility model is realized through the following technical scheme: a four-stage absorption and analysis device for purifying acid gas, characterized by comprising a methanol absorption tower, a carbon dioxide analysis tower, a hydrogen sulfide analysis tower and a thiol analysis tower. A mixed gas inlet is arranged at the lower part of the methanol absorption tower body, a methanol inlet is arranged at the upper part of the tower body, and the upper part outlet of the tower body is connected with the inlet of a separation tank. A non-condensed gas outlet is arranged at the upper part of the separation tank, and the lower part of the separation tank is connected with the tower kettle of the methanol absorption tower. The inlet of the carbon dioxide analysis tower is connected with the tower kettle of the methanol absorption tower, the upper part outlet is connected with a tail gas treatment system, the inlet of the hydrogen sulfide analysis tower is connected with the lower part outlet of the carbon dioxide analysis tower, the upper part outlet of the hydrogen sulfide analysis tower is connected with the tail gas treatment system, and the lower part outlet is connected with the inlet of the thiol analysis tower. The upper part outlet of the thiol analysis tower is connected with a purification system, the lower part outlet is connected with a circulating methanol pipeline, and the circulating methanol pipeline is connected with the methanol inlet after being converged with a fresh methanol pipeline through a multistage condenser.

[0006] Further, a methanol rich liquid feeding pump and a methanol analysis preheater are arranged on the pipeline connecting the tower kettle of the methanol absorption tower and the carbon dioxide analysis tower.

[0007] The beneficial effects of this invention are: this device can effectively recover residual hydrogen sulfide from mercaptan and disulfide synthesis units, while simultaneously purifying carbon dioxide, eliminating the need for a separate hydrogen sulfide purification unit, thus saving investment and land area. This device can obtain pure hydrogen sulfide at the top of the hydrogen sulfide stripping tower by increasing the pressure. The high-pressure stripping tower also solves the problem of hydrogen sulfide not being able to be delivered to higher-pressure equipment. Attached Figure Description

[0008] Fig. 1 This is a schematic diagram of the overall structure of this utility model;

[0009] Fig. 2 This is a schematic diagram of the working process of the device of this utility model.

[0010] The numbers in the diagram are explained as follows: 1 is the methanol absorption tower, 2 is the carbon dioxide stripping tower, 3 is the hydrogen sulfide stripping tower, 4 is the mercaptan stripping tower, 5 is the separator, 6 is the multi-stage condenser, 7 is the methanol stripping preheater, 8 is the methanol rich liquid feed pump, and 9 is the circulating methanol pipeline.

[0011] 101 is the mixed gas inlet, 102 is the methanol inlet, and 103 is the methanol absorption tower outlet;

[0012] 201 is the first inlet, 202 is the carbon dioxide outlet, and 203 is the first outlet;

[0013] 301 is the second inlet, 302 is the hydrogen sulfide outlet, and 303 is the second outlet;

[0014] 401 is the third inlet, 402 is the mercaptan outlet, and 403 is the third outlet.

[0015] 501 is the inlet of the separator, and 502 is the outlet of the non-condensable gas. Detailed Implementation

[0016] Reference Appendix Figs. 1-2 This utility model provides a four-stage absorption and desorption device for purifying acidic gas. The device is a four-stage absorption and desorption device consisting of one absorption tower and three desorption towers, specifically including a methanol absorption tower 1, a carbon dioxide desorption tower 2, a hydrogen sulfide desorption tower 3, and a mercaptan desorption tower 4 connected by corresponding pipeline systems.

[0017] The methanol absorption tower 1 includes a tower body and a tower bottom. A mixed gas inlet 101 is provided at the lower part of the tower body, a methanol inlet 102 is provided at the upper part of the tower body, and a methanol absorption tower outlet 103 is provided at the top of the tower body. This outlet is connected to the separator inlet 501 on the separator 5 (gas-liquid separator). A non-condensable gas outlet 502 is provided at the upper part of the separator 5 and is connected to the tail gas treatment system. The lower part of the separator 5 is connected to the tower bottom of the methanol absorption tower 1.

[0018] The middle part of the carbon dioxide resolving tower 2 is provided with a first inlet 201, the top part is provided with a carbon dioxide outlet 202, and the bottom part is provided with a first outlet 203; wherein the first inlet 201 is connected with the tower kettle of the methanol absorption tower 1, and the carbon dioxide outlet 202 is connected with the tail gas treatment system;

[0019] The middle part of the hydrogen sulfide resolving tower 3 is provided with a second inlet 301, the top part is provided with a hydrogen sulfide outlet 302, and the bottom part is provided with a second outlet 303; the second inlet 301 is connected with the first outlet 203 of the carbon dioxide resolving tower 2, the upper hydrogen sulfide outlet 302 of the hydrogen sulfide resolving tower 3 is connected with the tail gas treatment system, and the lower second outlet 303 is connected with the third inlet of the mercaptan resolving tower 4;

[0020] The middle part of the mercaptan resolving tower 4 is provided with a third inlet 401, the top part is provided with a mercaptan outlet 402, and the bottom part is provided with a third outlet 403; the mercaptan outlet 402 is connected with the purification system, and the third outlet 403 is connected with the circulating methanol pipeline 9;

[0021] The circulating methanol pipeline is cooled by the multi-stage condenser 6, then is combined with the fresh methanol pipeline, and is connected with the methanol inlet 102.

[0022] Preferably, on the pipeline connecting the tower kettle of the methanol absorption tower and the carbon dioxide resolving tower, a methanol rich liquid feeding pump 8 and a methanol resolving preheater 7 are arranged; the methanol resolving preheater 7 is also matched with the pipeline connecting the carbon dioxide resolving tower and the hydrogen sulfide resolving tower, so as to achieve the heat exchange effect.

[0023] Preferably, the lower parts of the tower bodies of the carbon dioxide resolving tower 2, the hydrogen sulfide resolving tower 3 and the mercaptan resolving tower 4 are respectively provided with reboilers for heating the tower bodies; the upper parts of the tower bodies are respectively provided with coolers connected with an external circulating cooling system.

[0024] Preferably, the mixed gas inlet 101 is connected with a pipeline conveying the following gases: non-condensable gas containing hydrogen sulfide from the mercaptan section, non-condensable gas containing hydrogen sulfide from the disulfide section, and raw hydrogen sulfide containing carbon dioxide.

[0025] The connection between the parts in the scheme is realized by corresponding pipelines, and adjusting valves are arranged on the pipelines, and flow meters and other devices can also be arranged. The arrangement and connection relationship of the above-mentioned devices are all prior art in the field.

[0026] The working process of the four-stage absorption and resolving device for purifying sour gas described in the scheme is as follows:

[0027] S1: The hydrogen sulfide-containing non-condensable gas from the mercaptan section, the hydrogen sulfide-containing non-condensable gas from the disulfide section and the raw hydrogen sulfide containing carbon dioxide enter the methanol absorption tower from the mixed gas inlet, the fresh methanol enters the multi-stage condenser and the circulating methanol after being mixed and cooled, enters the top of the methanol absorption tower, and is in contact with the mixed gas in the reverse direction, absorbs the hydrogen sulfide in the mixed gas, and the non-condensable gas that cannot be absorbed is separated in the separation tank, and then the gas phase is sent to the tail gas treatment system, and the liquid phase is returned to the tower bottom of the methanol absorption tower;

[0028] S2: The methanol-rich liquid at the bottom of the methanol absorption tower is pressurized by the methanol-rich liquid feeding pump, preheated by the methanol desorption preheater, and then enters the carbon dioxide desorption tower;

[0029] S3: After desorption in the carbon dioxide desorption tower, the carbon dioxide at the top is sent to the tail gas treatment system, and the material at the bottom of the carbon dioxide desorption tower is fed from the middle of the hydrogen sulfide desorption tower;

[0030] S4: The hydrogen sulfide at the top of the hydrogen sulfide desorption tower is sent to the tail gas treatment system, and the material at the bottom of the hydrogen sulfide desorption tower is discharged and fed from the middle of the mercaptan (or sulfide, the same below) desorption tower;

[0031] S5: After desorption in the mercaptan desorption tower, the recovered mercaptan at the top is sent to the purification system, the material at the bottom of the mercaptan desorption tower is sent back to the top of the methanol absorption tower after multi-stage cooling for recycling, and the mercaptan and sulfide at the top are cooled and sent to the mercaptan purification system.

[0032] Among them, the hydrogen sulfide desorbed from the hydrogen sulfide desorption tower is returned to the hydrogen sulfide buffer tank before the hydrogen sulfide buffer tank of the mercaptan synthesis device. The mercaptan desorbed from the mercaptan desorption tower is returned to the mercaptan purification device of the mercaptan device.

[0033] Among them, the temperature of the methanol absorption tower is -5~0℃, and the pressure is 0.2~0.35MPaG; the temperature of the carbon dioxide desorption tower is 0~200℃, and the pressure is 3.5~5MPaG; the temperature of the hydrogen sulfide desorption tower is 20~180℃, and the pressure is 2~3MPaG; the temperature of the mercaptan desorption tower is 50~120℃, and the pressure is 0.5~1MPaG.

[0034] Preferably, in the present scheme, the desorption tower is the existing structure, such as a packed tower and a plate tower, and the packed tower is bulk packing or structured packing.

[0035] Preferably, in the device, each desorption tower is provided with a gas phase outlet at the top, a pressure gauge at the upper and lower parts of the rectifying tower, a plurality of thermometers distributed at each part of the high-pressure rectifying tower, a plurality of material inlets at the middle of the rectifying tower, a liquid level meter at the tower bottom, a reboiler outlet pipeline connection port, a reboiler inlet pipeline connection port, a tower bottom material discharge outlet and a reflux liquid inlet.

[0036] Preferably, the overhead temperature controller of the distillation column is linked to the condenser coolant feed control valve to control the condenser outlet temperature, the bottom temperature controller is linked to the reboiler steam feed control valve to control the column bottom temperature, and the column sump level controller is linked to the column sump to buffer tank reflux line control valve to control the column sump level.

Claims

1. A four-stage absorption and desorption apparatus for purifying acidic gases, characterized in that: This includes methanol absorption towers, carbon dioxide stripping towers, hydrogen sulfide stripping towers, and mercaptan stripping towers; The methanol absorption tower has a mixed gas inlet at the bottom and a methanol inlet at the top. The outlet at the top of the tower is connected to the inlet of the separator. The separator has a non-condensable gas outlet at the top and is connected to the bottom of the methanol absorption tower at the bottom. The inlet of the carbon dioxide stripping tower is connected to the bottom of the methanol absorption tower, and the upper outlet is connected to the tail gas treatment system. The inlet of the hydrogen sulfide stripping tower is connected to the lower outlet of the carbon dioxide stripping tower, the upper outlet of the hydrogen sulfide stripping tower is connected to the tail gas treatment system, and the lower outlet is connected to the inlet of the mercaptan stripping tower. The upper outlet of the mercaptan stripping tower is connected to the purification system, and the lower outlet is connected to the circulating methanol pipeline. The circulating methanol pipeline merges with the fresh methanol pipeline through a multi-stage condenser and is then connected to the methanol inlet.

2. The four-stage absorption and desorption apparatus for purifying acidic gas according to claim 1, characterized in that: A methanol rich liquid feed pump and a methanol desorption preheater are installed on the pipeline connecting the bottom of the methanol absorption tower and the carbon dioxide desorption tower.

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