Synthetic tail gas separation device based on liquid nitrogen washing mode

Abstract

The utility model provides a synthetic tail gas separation device based on a liquid nitrogen washing mode. The tail gas separation device comprises a TSA adsorption unit, a liquefaction separation unit, a mixed refrigeration circulation unit, a nitrogen circulation unit and a natural gas storage unit, the input end of the TSA adsorption unit is connected with the liquefaction separation unit; the output end of the liquefaction separation unit is respectively connected with the nitrogen-rich out-of-bound area, the hydrogen-rich out-of-bound area and the natural gas storage unit; the mixed refrigeration cycle unit and the nitrogen cycle unit are connected in parallel with the liquefaction separation unit; one path of the output end of the cold box is connected with the dehydrogenation tower; one path of the output end of the dehydrogenation tower is connected with a hydrogen-rich gas outlet area through a cold box; the other path is connected with the denitrification tower; one path of the output end of the denitrification tower is connected with the nitrogen-rich gas out-of-bound area through the return tank and the cold box in sequence; the other path of the output end of the cold box is connected with a liquid nitrogen cooling device through a liquid nitrogen flash tank and a liquid nitrogen booster pump in sequence; according to the device, a mixed refrigerant and liquid nitrogen are used as refrigerating media, and hydrogen-rich gas, nitrogen-rich gas and liquefied natural gas are obtained by separating synthetic tail gas through rectification.

Description

Technical Field

[0001] The utility model belongs to the technology of purification and separation mainly based on coal chemical synthesis tail gas or coke oven tail gas, and particularly relates to a synthetic tail gas separation device based on liquid nitrogen washing method. Background Technique

[0002] In the production process, the synthetic tail gas or coke oven tail gas contains a large amount of gases such as hydrogen, methane, nitrogen, carbon monoxide, etc. At present, the conventional method is to directly extract part of the hydrogen through PSA (pressure swing adsorption device), and the remaining gas is used as fuel gas or sent to the torch for combustion treatment, with extremely low utilization rate and economy. How to efficiently utilize the gases contained in the synthetic tail gas or coke oven tail gas is a technical problem that needs to be solved urgently by those skilled in the art. Content of the Utility Model

[0003] Aiming at the existing technical problems, the utility model provides a synthetic tail gas separation device and method based on liquid nitrogen washing method; the method for separating synthetic tail gas by the liquid nitrogen washing method of the utility model uses liquid nitrogen as a refrigeration medium, and obtains high-pressure hydrogen-rich gas, nitrogen-rich gas and liquefied natural gas through rectification, which has remarkable economic benefits and conforms to the environmental protection concept of energy conservation, consumption reduction and efficiency increase of modern production enterprises.

[0004] In order to solve the existing technical problems, the utility model adopts the following technical solutions:

[0005] A synthetic tail gas separation device based on liquid nitrogen washing method, characterized in that: the tail gas separation device includes a TSA adsorption unit, a mixed refrigeration cycle unit, a nitrogen circulation unit, a liquefaction separation unit and a natural gas storage unit; the input end of the TSA adsorption unit is connected to the liquefaction separation unit; the output end of the liquefaction separation unit is respectively connected to the nitrogen-rich gas out of the boundary area, the hydrogen-rich gas out of the boundary area and the natural gas storage unit; the mixed refrigeration cycle unit and the nitrogen circulation unit are connected in parallel to the liquefaction separation unit; where:

[0006] The liquefaction separation unit is composed of a cold box, a dehydrogenation tower, a liquid nitrogen flash tank, a liquid nitrogen booster pump, a denitrification tower, a liquid nitrogen cooler and a reflux tank; one output path of the cold box is connected to the dehydrogenation tower; one output path of the dehydrogenation tower is connected to the hydrogen-rich gas out of the boundary area through the cold box; another output path of the dehydrogenation tower is connected to the denitrification tower; one output path of the denitrification tower is connected to the nitrogen-rich gas out of the boundary area through the reflux tank and the cold box in sequence; another output path of the cold box is connected in sequence through the liquid nitrogen flash tank, the liquid nitrogen booster pump and the liquid nitrogen cooling device.

[0007] Further, a liquid nitrogen washing part is arranged at the top of the dehydrogenation tower, and a reboiler is arranged at the bottom of the dehydrogenation tower; the liquid nitrogen washing part is an internal cold box or a liquid nitrogen distributor.

[0008] Furthermore, a liquid nitrogen cooling section is provided at the top of the denitrification tower, and a reboiler is provided at the bottom of the tower.

[0009] Furthermore, the cold box adopts a plate-fin cold box.

[0010] Furthermore, the mixed refrigeration cycle unit is composed of a refrigerant compressor, an inter-stage cooler of the refrigerant compressor, an outlet cooler of the refrigerant compressor, an inter-stage separator of the refrigerant compressor, and an outlet separator of the refrigerant compressor.

[0011] Furthermore, the nitrogen circulation unit is composed of a nitrogen compressor, a first-stage cooler of the nitrogen compressor, a second-stage cooler of the nitrogen compressor, and a third-stage cooler of the nitrogen compressor.

[0012] Furthermore, the TSA adsorption unit is composed of a solid adsorbent composite bed; the solid adsorbent composite bed uses a solid adsorbent or an alkaline liquid absorbent.

[0013] Furthermore, the natural gas storage unit consists of a BOG compressor and a natural gas storage tank.

[0014] Beneficial Effects

[0015] Compared with the traditional technical solution, the beneficial effects brought by the present utility model are as follows:

[0016] 1. The present utility model uses liquid nitrogen as a cold source and absorbent to separate the synthesis tail gas to produce high-pressure hydrogen-rich gas, nitrogen-rich gas, and liquefied natural gas with economic value, creating economic benefits for enterprises.

[0017] 2. The liquefaction of the methane-rich gas dried by TSA in the present utility model realizes the separation of the synthesis tail gas by adopting a mixed refrigeration, nitrogen refrigeration, and low-temperature rectification dehydrogenation and denitrification process; the present utility model has high heat transfer efficiency, good heat exchange effect in the cryogenic section, and is relatively easy to control.

[0018] 3. In the present utility model, the nitrogen circulation unit uses nitrogen pressurization and throttling refrigeration to provide a cryogenic temperature field for the low-temperature rectification of the liquefaction separation unit, and the technology is mature and reliable.

[0019] 4. In the present utility model, the liquefaction separation unit adopts a low-temperature rectification dehydrogenation and denitrification method, and the equipment selection and parameter design are carried out in combination with the entire process requirements. The process flow of the present utility model is smooth, the operation is stable, the control is simple, and the cost is saved, as shown in the following table:

[0020] Main material balance of the present utility model

[0021] Description of the Drawings

[0022] Figure 1 is a schematic structural diagram of a device for separating synthesis tail gas based on a liquid nitrogen washing method of the present utility model.

[0023] Figure 2 This is the process flow diagram of a device for separating synthetic tail gas based on the liquid nitrogen washing method of the present utility model. Specific embodiments

[0024] The following will be described in detail with reference to the attached Figure 1 and the attached Figure 2 to explain the present utility model as follows:

[0025] As Figure 1 shown, the present utility model provides a device for separating synthetic tail gas based on the liquid nitrogen washing method. The separation tail gas device includes: a TSA adsorption unit 101, a mixed refrigeration cycle unit 201, a nitrogen circulation unit 301, a liquefaction separation unit 401, and a natural gas storage unit 501; the TSA adsorption unit is composed of a solid adsorbent composite bed; the mixed refrigeration cycle unit is composed of a refrigerant compressor, an inter-stage cooler of the refrigerant compressor, an outlet cooler of the refrigerant compressor, an inter-stage separator of the refrigerant compressor, and an outlet separator of the refrigerant compressor; the nitrogen circulation unit is composed of a nitrogen compressor, a first-stage cooler of the nitrogen compressor, a second-stage cooler of the nitrogen compressor, and a third-stage cooler of the nitrogen compressor; the liquefaction separation unit 401 is composed of a cold box, a dehydrogenation tower, a liquid nitrogen flash tank, a liquid nitrogen booster pump, a denitrification tower, a liquid nitrogen cooler, and a reflux tank; the natural gas storage unit 501 is composed of a BOG compressor and a natural gas storage tank; the input end of the adsorption bed is connected to the synthetic tail gas unit; its output end is connected to the liquefaction separation unit; the mixed refrigeration cycle unit and the nitrogen circulation unit are respectively connected in parallel to the input end of the liquefaction separation unit; the output end of the liquefaction separation unit is connected to the natural gas storage unit; where:

[0026] One output path of the cold box is connected to the dehydrogenation tower; one output path of the dehydrogenation tower is connected to the hydrogen-rich gas out of the boundary through the cold box; the other output path is connected to the denitrification tower; one output path of the denitrification tower is sequentially connected to the hydrogen-rich nitrogen out of the boundary through the reflux tank and the cold box;

[0027] The other output path of the cold box is sequentially connected through a liquid nitrogen flash tank, a liquid nitrogen booster pump, and a liquid nitrogen cooling device.

[0028] In the dehydrogenation tower of the present utility model, a liquid nitrogen washing section is provided at the top of the tower, and a reboiler is provided at the bottom of the tower; the liquid nitrogen washing section is an in-built cold box or a liquid nitrogen distributor; in the denitrification tower of the present utility model, a liquid nitrogen cooling section is provided at the top of the tower, and a reboiler is provided at the bottom of the tower; as Figure 2 shown, where:

[0029] The TSA adsorption unit 101 adopts a composite bed of solid adsorbents, and the composite bed can be a solid absorbent or an alkaline liquid absorbent; the dehydrogenation tower condenses the dry gas output from the TSA adsorption unit into gaseous hydrogen and liquid nitrogen-containing methane; one path of the output end of the dehydrogenation tower outputs the gaseous hydrogen-rich gas out of the boundary area; the other path of its output end sends the liquid methane to the denitrification tower;

[0030] The denitrification tower carries out low-temperature rectification separation on the liquid nitrogen-containing methane into gaseous nitrogen and liquid natural gas; one path of the output end of the denitrification tower outputs the gaseous nitrogen-rich gas out of the boundary area; the other path of its output end sends the liquid natural gas to the natural gas storage unit;

[0031] The mixed refrigeration cycle unit 201 refrigerates the natural gas in the liquefaction separation unit by boosting mixed refrigerants of different components; wherein: the mixed refrigeration cycle unit includes mixed refrigerants, a refrigerant compressor, a refrigerant compressor inlet buffer tank, a refrigerant compressor inter-stage separator, a refrigerant compressor outlet separator, a refrigerant compressor inter-stage cooler, a refrigerant compressor outlet cooler and an on-line analysis module;

[0032] The mixed refrigeration cycle unit 201 forms a gaseous refrigerant medium liquid and a liquid refrigerant medium after boosting the mixed refrigerant by the refrigerant compressor. The mixed refrigeration cycle unit respectively sends the gaseous refrigerant medium and the liquid refrigerant medium to the liquefaction separation unit. Wherein: the gaseous refrigerant medium provides two temperature fields of shallow cooling and deep cooling for the liquefaction separation unit to provide cold energy for the natural gas to achieve the purpose of liquefying methane; the liquid refrigerant medium provides a shallow cooling temperature field to exchange heat with the heat medium, absorb heat and gasify until it is heated to normal temperature; the on-line analysis module is used to monitor the mixing ratio of the mixed refrigerants and the refrigerant circulation amount in the mixed refrigeration cycle unit; and regulate the mixing ratio of the mixed refrigerants and the refrigerant circulation amount according to the production process requirements; the mixed refrigeration cycle unit makes full use of the latent heat of vaporization and sensible heat of different components in the refrigerant to complete the refrigeration of the natural gas during the whole heat exchange process.

[0033] The nitrogen circulation unit 301 refrigerates nitrogen and transports it to the liquefaction separation unit for supplementation; the nitrogen circulation unit is composed of a nitrogen compressor and a cooler, wherein:

[0034] The nitrogen circulation unit 301 enters the liquefaction separation unit after boosting and throttling nitrogen by the compressor. Wherein: a part of the nitrogen is used as a low-temperature medium to provide a refrigerant for the dehydrogenation tower, and another part of the nitrogen provides the cold energy for deep cooling liquefaction of the liquefaction separation unit; meanwhile, the nitrogen circulation unit recovers the nitrogen in the liquefaction separation unit to ensure the nitrogen temperature of the deep cooling temperature field of the liquefaction separation unit.

[0035] The natural gas storage unit 501 stores LNG through an atmospheric-pressure LNG storage tank or a pressurized storage tank, where: the flash gas of the natural gas storage unit is pressurized by a BOG compressor and then undergoes denitrification treatment and is sent to a denitrification tower for denitrification treatment; one path of the output end of the denitrification tower outputs the gas-phase nitrogen-rich gas out of the boundary; the other path of its output end sends the liquid-phase natural gas to the natural gas storage unit.

[0036] The main operating parameters in the present utility model

[0037]

[0038]

[0039] The list of main equipment in the present utility model

[0040]

[0041] Although the present utility model has been described above, the present utility model is not limited to the above specific embodiments. The above specific embodiments are merely illustrative and not restrictive. Under the inspiration of the present utility model, those of ordinary skill in the art can also make many variations without departing from the gist of the present utility model, and all of these fall within the protection scope of the present utility model.

Claims

1. A device for separating synthetic tail gas based on liquid nitrogen washing, characterized in that: The tail gas separation device comprises a TSA adsorption unit, a mixed refrigeration cycle unit, a nitrogen circulation unit, a liquefaction separation unit and a natural gas storage unit; the input end of the TSA adsorption unit is connected to the liquefaction separation unit; the output end of the liquefaction separation unit is respectively connected to the nitrogen-rich gas outbound area, the hydrogen-rich gas outbound area and the natural gas storage unit; the mixed refrigeration cycle unit and the nitrogen circulation unit are connected to the liquefaction separation unit in parallel; wherein: The liquefaction separation unit is composed of a cold box, a dehydrogenation tower, a liquid nitrogen flash tank, a liquid nitrogen booster pump, a denitrogenation tower, a liquid nitrogen cooler and a reflux tank; one path of the output end of the cold box is connected to the dehydrogenation tower; one path of the output end of the dehydrogenation tower is connected to the hydrogen-rich gas outlet zone through the cold box; another path is connected to the denitrogenation tower; one path of the output end of the denitrogenation tower is connected to the nitrogen-rich gas outlet zone through the reflux tank and the cold box in sequence; another path of the output end of the cold box is connected through the liquid nitrogen flash tank, the liquid nitrogen booster pump and the liquid nitrogen cooling device in sequence.

2. The device for separating synthetic tail gas by liquid nitrogen washing according to claim 1, characterized in that: The top of the dehydrogenation tower is provided with a liquid nitrogen washing section, and the bottom of the tower is provided with a reboiler; the liquid nitrogen washing section is a built-in cold box or a liquid nitrogen distributor.

3. The device for separating synthetic tail gas by liquid nitrogen washing according to claim 1, characterized in that: The denitrification tower has a liquid nitrogen cooling section at the top and a reboiler at the bottom.

4. The device for separating synthetic tail gas by liquid nitrogen washing according to claim 1, characterized in that: The cold box adopts a plate-fin cold box.

5. The device for separating synthetic tail gas by liquid nitrogen washing according to claim 1, characterized in that: The mixed refrigeration cycle unit is composed of a refrigerant compressor, a refrigerant compressor interstage cooler, a refrigerant compressor outlet cooler, a refrigerant compressor interstage separator and a refrigerant compressor outlet separator.

6. The device for separating synthetic tail gas by liquid nitrogen washing according to claim 1, characterized in that: The nitrogen circulation unit is composed of a nitrogen compressor, a nitrogen compressor primary cooler, a nitrogen compressor secondary cooler and a nitrogen compressor tertiary cooler.

7. A synthetic tail gas separation device based on liquid nitrogen washing according to any one of claims 1 to 6, characterized in that: The TSA adsorption unit is composed of a solid adsorbent composite bed; the solid adsorbent composite bed adopts a solid adsorbent or an alkaline liquid absorbent.

8. The device for separating synthetic tail gas by liquid nitrogen washing according to claim 7, characterized in that: The natural gas storage unit consists of a BOG compressor and a natural gas storage tank.

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