Four-stage absorption and desorption device for purifying acid gas and absorption and desorption method

Abstract

The invention discloses a four-stage absorption and desorption device for purifying acid gas and an absorption and desorption method. The 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. According to the scheme, residual hydrogen sulfide in mercaptan and disulfide synthesis can be effectively recovered at the same time, carbon dioxide is purified at the same time, and investment and occupied land are saved.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical equipment, and in particular 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, namely, the mercaptan synthesis section, the disulfide synthesis section, and the mercaptan synthesis section. The latter usually uses methanol and hydrogen sulfide to react to generate mercaptan sulfide. The reaction will produce a certain amount of synthesis gas, including hydrogen sulfide, mercaptan (and sulfide), methane, carbon oxides, etc. The synthesis gas passes through the condenser, and the non-condensable gas after condensation contains a large amount of hydrogen sulfide. If the non-condensable gas is directly sent back to the reactor for recycling by using a compressor, the mercaptan sulfide in the gas will cause serious corrosion to the compressor seal after compression. Therefore, at this stage, these non-condensable gases are often directly incinerated or treated with tail gas, which not only wastes costs, but also increases the difficulty of tail gas treatment and the environmental burden.

[0003] On the other hand, the reaction gas is mostly prepared by coal chemical industry. Most of the acid gas from low-temperature methanol washing device or acid water gas stripping device contains a large amount of carbon dioxide, and the proportion is generally between 70% and 90%. In order to utilize the hydrogen sulfide resources for the production of organic sulfur chemical products, the hydrogen sulfide needs to be purified. Summary of the invention

[0004] The purpose of the present invention is to provide a four-stage absorption and analysis device for purifying acid gas, which can purify hydrogen sulfide in raw materials and acid mixed gas in the reaction process to solve the problems in the prior art.

[0005] The invention is realized by the following technical scheme: a four-stage absorption and analysis device for purifying acid gas, characterized in that it comprises a methanol absorption tower, a carbon dioxide analysis tower, a hydrogen sulfide analysis tower and a mercaptan 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 outlet of the tower body is connected with the inlet of a separation tank; a non-condensable 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, and the upper outlet is connected with the tail gas treatment system; the inlet of the hydrogen sulfide analysis tower is connected with the lower outlet of the carbon dioxide analysis tower, the upper outlet of the hydrogen sulfide analysis tower is connected with the tail gas treatment system, and the lower outlet is connected with the inlet of the mercaptan analysis tower; the upper outlet of the mercaptan analysis tower is connected with the purification system, and the lower outlet is connected with a circulating methanol pipeline; the circulating methanol pipeline is connected with the methanol inlet after passing through a multi-stage condenser and merging with a fresh methanol pipeline.

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

[0007] The present invention also discloses a four-stage absorption and analysis method for purifying acid gas, which adopts the four-stage absorption and analysis device as described above, and is characterized in that it comprises the following steps: S1: The non-condensable gas containing hydrogen sulfide from the mercaptan section, the non-condensable gas containing hydrogen sulfide from the disulfide section and the raw hydrogen sulfide containing carbon dioxide enter the methanol absorption tower from the mixed gas inlet. Fresh methanol enters the multi-stage condensation and the circulating methanol is combined and cooled, and then enters from the top of the methanol absorption tower, and contacts with the mixed gas in reverse direction to absorb the hydrogen sulfide in the mixed gas. The non-condensable gas that cannot be absorbed is separated by liquid separation in the separation tank, and the gas phase goes to the tail gas treatment system, and the liquid phase returns to the bottom of the methanol absorption tower; S2: The methanol-rich liquid at the bottom of the methanol absorption tower is pressurized by the methanol-rich liquid feeding pump and sent to the methanol desorption preheater for preheating before entering the carbon dioxide desorption tower; S3: After the carbon dioxide analysis tower analyzes, the carbon dioxide at the top of the tower is removed to the tail gas treatment system, and the material at the bottom of the carbon dioxide analysis tower is fed from the middle of the hydrogen sulfide analysis tower; S4: a hydrogen sulfide tail gas treatment system at the top of the hydrogen sulfide analysis tower, where the material at the bottom of the hydrogen sulfide analysis tower is discharged and fed from the middle of the mercaptan analysis tower; S5: After the mercaptan analysis tower analyzes, the recovered mercaptan at the top of the tower is sent to the purification system, the material at the bottom of the mercaptan analysis tower is sent back to the top of the methanol absorption tower for recycling after multi-stage cooling, and the mercaptan sulfide at the top of the tower is sent to the mercaptan purification system after cooling.

[0008] Further: the temperature of the methanol absorption tower is -5~0℃, and the pressure is 0.2~0.35MPaG; the temperature of the carbon dioxide analysis tower is 0~200℃, and the pressure is 3.5~5MPaG; the temperature of the hydrogen sulfide analysis tower is 20~180℃, and the pressure is 2~3MPaG; the temperature of the mercaptan analysis tower is 50~120℃, and the pressure is 0.5~1MPaG.

[0009] The advantages of the present invention are: the present scheme can effectively recover the remaining hydrogen sulfide in the mercaptan and disulfide synthesis device, and purify the raw gas containing carbon dioxide at the same time, without building a separate device for purifying hydrogen sulfide, thus saving investment and land.

[0010] This solution can increase the pressure of the hydrogen sulfide analysis tower so that pure hydrogen sulfide can be obtained at the top of the hydrogen sulfide analysis tower. The high-pressure analysis tower also solves the problem that hydrogen sulfide cannot be transported to higher pressure equipment.

[0011] This solution can recycle excess hydrogen sulfide back to the reactor for use as raw material, saving costs.

[0012] In the present scheme, in the synthesis of methyl mercaptan (ether), raw material methanol is selected as the absorption liquid, which is easy to obtain. When the recovered hydrogen sulfide is returned to the reactor, the methanol is brought into the reactor without affecting the reaction. The methanol used as the absorption liquid can be recycled, saving the amount of methanol and saving costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 It is a schematic diagram of the overall structure of the present invention; Figure 2 It is a process flow chart of the present invention.

[0014] Explanation of the serial numbers in the figure: 1 is a methanol absorption tower, 2 is a carbon dioxide analysis tower, 3 is a hydrogen sulfide analysis tower, 4 is a mercaptan analysis tower, 5 is a separation tank, 6 is a multi-stage condenser, 7 is a methanol analysis preheater, 8 is a methanol rich liquid feeding pump, and 9 is a circulating methanol pipeline; 101 is the mixed gas inlet, 102 is the methanol inlet, and 103 is the methanol absorption tower outlet; 201 is a first inlet, 202 is a carbon dioxide outlet, and 203 is a first outlet; 301 is the second inlet, 302 is the hydrogen sulfide outlet, and 303 is the second outlet; 401 is the third inlet, 402 is the mercaptan outlet, and 403 is the third outlet; 501 is the inlet of the separation tank, and 502 is the outlet of the non-condensable gas. DETAILED DESCRIPTION

[0015] Reference Figure 1-2 The present invention provides a four-stage absorption and analysis device for purifying acid gas, which is a four-stage absorption and analysis device composed of an absorption tower and three analysis towers, specifically including a methanol absorption tower 1, a carbon dioxide analysis tower 2, a hydrogen sulfide analysis tower 3, and a mercaptan analysis tower 4 connected by corresponding pipeline systems; The methanol absorption tower 1 includes a tower body and a tower kettle, wherein 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, which is connected to a separation tank inlet 501 on a separation tank 5 (gas-liquid separation tank); a non-condensable gas outlet 502 connected to a tail gas treatment system is provided at the upper part of the separation tank 5, and the lower part of the separation tank 5 is connected to the tower kettle of the methanol absorption tower 1; A first inlet 201 is provided in the middle of the carbon dioxide analysis tower 2, a carbon dioxide outlet 202 is provided at the top, and a first outlet 203 is provided at the bottom; wherein the first inlet 201 is connected to the kettle of the methanol absorption tower 1, and the carbon dioxide outlet 202 is connected to the tail gas treatment system; A second inlet 301 is provided in the middle of the hydrogen sulfide analysis tower 3, a hydrogen sulfide outlet 302 is provided at the top, and a second outlet 303 is provided at the bottom; the second inlet 301 is connected to the first outlet 203 of the carbon dioxide analysis tower 2, the upper hydrogen sulfide outlet 302 of the hydrogen sulfide analysis tower 3 is connected to the tail gas treatment system, and the lower second outlet 303 is connected to the third inlet of the mercaptan analysis tower 4; A third inlet 401 is provided in the middle of the mercaptan analysis tower 4, a mercaptan outlet 402 is provided at the top, and a third outlet 403 is provided at the bottom; the mercaptan outlet 402 is connected to the purification system, and the third outlet 403 is connected to the circulating methanol pipeline 9; The circulating methanol pipeline is cooled by the multi-stage condenser 6 and then merged with the fresh methanol pipeline and connected to the methanol inlet 102 .

[0016] Preferably, a methanol rich liquid feeding pump 8 and a methanol analysis preheater 7 are provided on the pipeline connecting the methanol absorption tower kettle and the carbon dioxide analysis tower; the methanol analysis preheater 7 also cooperates with the pipeline connecting the carbon dioxide analysis tower and the hydrogen sulfide analysis tower to achieve the effect of heat exchange.

[0017] Preferably, the lower part of each tower body of the carbon dioxide analysis tower 2, the hydrogen sulfide analysis tower 3, and the mercaptan analysis tower 4 is respectively provided with a reboiler for heating the tower body; and the upper part of each tower body is respectively provided with a cooler, which is connected to the external circulation cooling system.

[0018] Preferably, the mixed gas inlet 101 is connected to a pipeline for 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.

[0019] The communication between the various parts in this solution is achieved through corresponding pipelines, and a regulating valve is arranged on the pipeline, and a flow meter and other devices may also be arranged. The arrangement and communication relationship of the above devices are all existing technologies in this field.

[0020] The working process of the four-stage absorption and analysis device for purifying acid gas described in this scheme is as follows: S1: The non-condensable gas containing hydrogen sulfide from the mercaptan section, the non-condensable gas containing hydrogen sulfide from the disulfide section and the raw hydrogen sulfide containing carbon dioxide enter the methanol absorption tower from the mixed gas inlet. Fresh methanol enters the multi-stage condensation and the circulating methanol is combined and cooled (or combined first and then enters the condenser) and enters from the top of the methanol absorption tower to contact with the mixed gas in reverse direction to absorb the hydrogen sulfide in the mixed gas. The non-condensable gas that cannot be absorbed is separated by liquid separation in the separation tank, and the gas phase goes to the tail gas treatment system, and the liquid phase returns to the bottom of the methanol absorption tower; S2: The methanol-rich liquid at the bottom of the methanol absorption tower is pressurized by the methanol-rich liquid feeding pump and sent to the methanol desorption preheater for preheating before entering the carbon dioxide desorption tower; S3: After the carbon dioxide analysis tower analyzes, the carbon dioxide at the top of the tower is removed to the tail gas treatment system, and the material at the bottom of the carbon dioxide analysis tower is fed from the middle of the hydrogen sulfide analysis tower; S4: a hydrogen sulfide tail gas treatment system at the top of the hydrogen sulfide analysis tower, the material at the bottom of the hydrogen sulfide analysis tower is discharged and fed from the middle of the mercaptan (or thioether, the same below) analysis tower; S5: After the mercaptan analysis tower analyzes, the recovered mercaptan at the top of the tower is sent to the purification system, the material at the bottom of the mercaptan analysis tower is sent back to the top of the methanol absorption tower for recycling after multi-stage cooling, and the mercaptan sulfide at the top of the tower is sent to the mercaptan purification system after cooling.

[0021] Preferably: the hydrogen sulfide analyzed by the hydrogen sulfide analysis tower is returned to the hydrogen sulfide buffer tank before the mercaptan synthesis unit. The mercaptan analyzed by the mercaptan analysis tower is returned to the mercaptan purification unit of the mercaptan unit.

[0022] Preferably: the methanol absorption tower temperature is -5~0°C, and the pressure is 0.2~0.35MPaG; the carbon dioxide analysis tower temperature is 0~200°C, and the pressure is 3.5~5MPaG; the hydrogen sulfide analysis tower temperature is 20~180°C, and the pressure is 2~3MPaG; the mercaptan analysis tower temperature is 50~120°C, and the pressure is 0.5~1MPaG.

[0023] Further: the top temperature of the carbon dioxide analysis tower is 0~10℃, and the bottom temperature is 150~200℃; the top temperature of the hydrogen sulfide analysis tower is 20~50℃, and the bottom temperature is 150~180℃; the top temperature of the mercaptan analysis tower is 50~80℃, and the bottom temperature is 100~120℃.

[0024] Preferably, in this solution, the analytical tower is an existing structure, such as a packed tower and a plate tower, and the packed packing is a bulk packing or a structured packing.

[0025] Preferably, in the device, each analytical tower is provided with a gas phase discharge port at the top of the tower, pressure gauges are provided at the upper and lower parts of the distillation tower, a plurality of thermometers are provided at various parts of the high-pressure distillation tower body, a plurality of material inlets are provided in the middle part of the distillation tower, a liquid level gauge is provided in the kettle of the distillation tower, a reboiler outlet pipeline connection port, a reboiler inlet pipeline connection port, a material discharge port at the bottom of the tower and a reflux liquid inlet.

[0026] Preferably, in the device, the top thermometer of the distillation tower is interlocked with the coolant feed regulating valve of the top condenser to control the condenser outlet temperature, the bottom thermometer is interlocked with the reboiler steam feed regulating valve to control the bottom temperature, and the bottom liquid level gauge is interlocked with the bottom buffer tank reflux pipeline regulating valve to control the bottom liquid level.

Claims

1. A four-stage absorption and analysis device for purifying acid gas, characterized in that: Including methanol absorption tower, carbon dioxide analysis tower, hydrogen sulfide analysis tower, mercaptan analysis tower; The lower part of the methanol absorption tower is provided with a mixed gas inlet, the upper part of the tower is provided with a methanol inlet, and the upper outlet of the tower is connected with the inlet of the separation tank; the upper part of the separation tank is provided with a non-condensable gas outlet, 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 to the kettle of the methanol absorption tower, and the upper outlet is connected to the tail gas treatment system; The inlet of the hydrogen sulfide analysis tower is connected to the lower outlet of the carbon dioxide analysis tower, the upper outlet of the hydrogen sulfide analysis tower is connected to the tail gas treatment system, and the lower outlet is connected to the inlet of the mercaptan analysis tower; The upper outlet of the mercaptan analysis tower is connected to the purification system, and the lower outlet is connected to the circulating methanol pipeline; The circulating methanol pipeline is connected to the methanol inlet after merging with the fresh methanol pipeline through a multi-stage condenser.

2. A four-stage absorption and analysis device for purifying acid gas according to claim 1, characterized in that: A methanol rich liquid feeding pump and a methanol analysis preheater are provided on the pipeline connecting the methanol absorption tower kettle and the carbon dioxide analysis tower.

3. A four-stage absorption and analysis method for purifying acid gas, using the four-stage absorption and analysis device as claimed in claim 1 or 2, characterized in that: The steps include: S1: The non-condensable gas containing hydrogen sulfide from the mercaptan section, the non-condensable gas containing hydrogen sulfide from the disulfide section and the raw hydrogen sulfide containing carbon dioxide enter the methanol absorption tower from the mixed gas inlet. Fresh methanol enters the multi-stage condensation and the circulating methanol is combined and cooled, and then enters from the top of the methanol absorption tower, and contacts with the mixed gas in reverse direction to absorb the hydrogen sulfide in the mixed gas. The non-condensable gas that cannot be absorbed is separated by liquid separation in the separation tank, and the gas phase goes to the tail gas treatment system, and the liquid phase returns to the bottom of the methanol absorption tower; S2: The methanol-rich liquid at the bottom of the methanol absorption tower is pressurized by the methanol-rich liquid feeding pump and sent to the methanol desorption preheater for preheating before entering the carbon dioxide desorption tower; S3: After the carbon dioxide analysis tower analyzes, the carbon dioxide at the top of the tower is removed to the tail gas treatment system, and the material at the bottom of the carbon dioxide analysis tower is fed from the middle of the hydrogen sulfide analysis tower; S4: a hydrogen sulfide tail gas treatment system at the top of the hydrogen sulfide analysis tower, where the material at the bottom of the hydrogen sulfide analysis tower is discharged and fed from the middle of the mercaptan analysis tower; S5: After the mercaptan analysis tower analyzes, the recovered mercaptan at the top of the tower is sent to the purification system, the material at the bottom of the mercaptan analysis tower is sent back to the top of the methanol absorption tower for recycling after multi-stage cooling, and the mercaptan sulfide at the top of the tower is sent to the mercaptan purification system after cooling.

4. The four-stage absorption and analysis method for purifying acid gas according to claim 3, characterized in that: The temperature of the methanol absorption tower is -5~0℃, and the pressure is 0.2~0.35MPaG; the temperature of the carbon dioxide analysis tower is 0~200℃, and the pressure is 3.5~5MPaG; the temperature of the hydrogen sulfide analysis tower is 20~180℃, and the pressure is 2~3MPaG; The temperature of the mercaptan analysis tower is 50~120℃, and the pressure is 0.5~1MPaG.

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