A device and method for cryogenic separation and purification of H2 and CO and co-production of LNG

Abstract

The present invention belongs to the technical field of separation and purification of coal gasification synthesis gas, and specifically relates to a device and method for cryogenic separation and purification of H2 and CO with co-production of LNG. The device of the present invention includes a molecular sieve adsorption device, a raw material cooler a, a raw material cooler b, a dehydrogenation tower, a denitrification tower, a demethanation tower, a methane refining tower, etc. By setting up a methane refining tower, the bottom liquid of the demethanation tower is concentrated and sent to the methane refining tower for rectification to obtain LNG products of the conventional type that meet GB / T 38753-2020. The present invention effectively utilizes methane, saves energy resources. At the same time, the CO gas obtained at the top of the methane refining tower is sent to downstream production devices, which improves the separation yield of CO in the synthesis gas, reduces production costs, and improves the economic benefits of the enterprise.

Description

Technical Field

[0001] The present invention belongs to the technical field of separation and purification of coal gasification synthesis gas, and specifically relates to a device and method for deep cold separation and purification of H2 and CO and co-production of LNG. Background Art

[0002] Synthesis gas (CO and H2) is an important basic chemical raw material, which can be used to synthesize ethylene glycol, acetic acid, acetic anhydride, phosgene, dimethyl acetate, formic acid, propionic acid, oxalic acid and dimethylformamide. With the continuous development of new C1 chemical technologies, the purity requirements of CO and H2 in the synthesis process are gradually increasing. Synthesis gas (CO and H2) is mostly obtained by converting coal as raw material. According to the difference in coal types, coal gasification usually contains some methane and nitrogen after conversion, and the requirements for these two gases for subsequent synthesis units are also relatively high. Therefore, in order to obtain high-purity CO products (more than 98%), hydrogen, nitrogen and methane in the raw gas need to be removed. The main methods for CO purification and separation include cryogenic separation, physical absorption, pressure swing adsorption and membrane separation. Among them, cryogenic separation is to use the difference in gas boiling point composition to achieve gas separation through low-temperature distillation. Compared with other methods, it has the advantages of large processing capacity, high separation efficiency, low operating cost, small footprint and low investment, so it is favored by a large number of users.

[0003] At present, although the deep cold separation method of CO and H2 can separate most of H2 and CO, the methane gas separated at the bottom of the demethanizer during the separation process contains a large amount of CO, which does not meet the index requirements of liquefied natural gas products. At the same time, the methane gas is sent to the incineration device, and a large amount of CO in the methane gas is not effectively utilized, resulting in low CO yield in syngas separation and high production costs. Summary of the invention

[0004] In order to overcome the defects of the prior art, the present invention provides a device and method for deep-cold separation and purification of H2 and CO and co-production of LNG. The method can separate H2, CO and methane in synthesis gas, and send H2 and CO to downstream devices for use, thereby improving the separation yield of CO and producing conventional liquefied natural gas products that meet the requirements of GB / T38753-2020.

[0005] In order to achieve the above object, the technical solution of the present invention is as follows:

[0006] A device for cryogenic separation and purification of H2 and CO and co-production of LNG, comprising a molecular sieve adsorption device, a raw material cooler a, a raw material cooler b, a dehydrogenation tower, a denitrogenation tower, a demethanization tower, a methane refining tower, a flash evaporator a, a flash evaporator b, a flash evaporator c, a flash evaporator d, a hydrogen flash tank, a dehydrogenation tower top separator, a denitrogenation tower top condenser, a denitrogenation tower top separator, a demethanization tower top condenser, a demethanization tower top separator, a methane refining tower top condenser, a methane refining tower top separator, and a circulating nitrogen device;

[0007] The inlet of the molecular sieve adsorption device is communicated with the synthesis gas pipeline, the outlet of the molecular sieve adsorption device is communicated with the first inlet of the raw material cooler a through a pipeline, the first outlet of the raw material cooler a is divided into three branches through a pipeline and is respectively communicated with the inlet of the flash evaporator a, the inlet of the flash evaporator c, and the inlet of the flash evaporator d, the outlet of the flash evaporator a, the outlet of the flash evaporator c, and the outlet of the flash evaporator d are all communicated with the inlet of the flash evaporator b through a pipeline, the outlet of the flash evaporator b is communicated with the first inlet of the raw material cooler b through a pipeline, the first outlet of the raw material cooler b is communicated with the inlet of the hydrogen flash tank through a pipeline, the flash gas outlet of the hydrogen flash tank is communicated with the second inlet of the raw material cooler b through a pipeline, and the second outlet of the raw material cooler b is communicated with the second inlet of the raw material cooler a through a pipeline, The second outlet of the raw material cooler a is connected to the hydrogen pipeline through a pipeline, the flash liquid outlet of the hydrogen flash tank is connected to the raw material liquid inlet on the side of the top of the dehydrogenation tower through a pipeline, the gas phase outlet at the top of the dehydrogenation tower is connected to the third inlet of the raw material cooler b through a pipeline, the third outlet of the raw material cooler b is connected to the inlet of the top separator of the dehydrogenation tower through a pipeline, the gas phase outlet of the top separator of the dehydrogenation tower is connected to the third inlet of the raw material cooler a through a pipeline, the third outlet of the raw material cooler a is connected to the recovery gas pipeline through a pipeline, the bottom liquid outlet of the dehydrogenation tower is connected to the middle inlet of the denitrification tower through a pipeline, the gas phase outlet at the top of the denitrification tower is connected to the inlet of the top condenser of the denitrification tower through a pipeline, and the outlet of the top condenser of the denitrification tower is connected to the inlet of the top separator of the denitrification tower through a pipeline. The gas phase outlet of the denitrification tower top separator is connected to the fourth inlet of the raw material cooler a through a pipeline, the fourth outlet of the raw material cooler a is connected to the incineration device through a pipeline, the liquid phase outlet of the denitrification tower top separator is connected to the condensate inlet of the denitrification tower top through a pipeline, the denitrification tower kettle liquid outlet is connected to the middle inlet of the demethanizer through a pipeline, the gas phase outlet of the demethanizer top is connected to the inlet of the demethanizer top condenser through a pipeline, the demethanizer top condenser outlet is connected to the inlet of the demethanizer top separator through a pipeline, the gas phase outlet of the demethanizer top separator is connected to the fifth inlet of the raw material cooler a through a pipeline, the fifth outlet of the raw material cooler a is connected to the carbon monoxide pipeline through a pipeline, and the liquid phase outlet of the demethanizer top separator is connected to the top of the demethanizer through a pipeline The liquid outlet of the demethanizer kettle is connected to the inlet of the methane concentrator through a pipeline, the gas phase outlet of the methane concentrator is connected to the middle inlet of the demethanizer through a pipeline, the bottom outlet of the methane concentrator is connected to the middle inlet of the methane refining tower through a pipeline, the gas phase outlet of the top of the methane refining tower is connected to the inlet of the top condenser of the methane refining tower through a pipeline, the outlet of the top condenser of the methane refining tower is connected to the inlet of the top separator of the methane refining tower through a pipeline, the gas phase outlet of the top separator of the methane refining tower is connected to the sixth inlet of the raw material cooler a through a pipeline, the sixth outlet of the raw material cooler a is connected to the carbon monoxide pipeline through a pipeline, the condensate outlet of the top separator of the methane refining tower is connected to the top of the methane refining tower through a pipeline, and the kettle outlet of the methane refining tower is connected to the LNG storage tank through a pipeline.

[0008] Furthermore, pressure reducing valves are provided on the pipeline connecting the flash liquid outlet of the hydrogen flash tank with the raw liquid inlet on the top side of the dehydrogenation tower, on the pipeline connecting the bottom liquid outlet of the dehydrogenation tower with the middle inlet of the denitrification tower, on the pipeline connecting the bottom liquid outlet of the denitrification tower with the middle inlet of the demethanization tower, and on the pipeline connecting the bottom outlet of the methane concentrator with the middle inlet of the methane refining tower.

[0009] Furthermore, the cooling channels of the raw material cooler a, the raw material cooler b, the denitrogenation tower top condenser, the demethanizer tower top condenser, and the methane refining tower top condenser are all connected to the circulating nitrogen device; and the dehydrogenation tower top separator, the denitrogenation tower top separator, the demethanizer tower top separator, and the methane refining tower top separator are all provided with a demister.

[0010] Furthermore, the first inlet in the raw material cooler a is connected to the first outlet, the second inlet is connected to the second outlet, the third inlet is connected to the third outlet, the fourth inlet is connected to the fourth outlet, and the fifth inlet is connected to the fifth outlet; the sixth inlet is connected to the sixth outlet; the first inlet in the raw material cooler b is connected to the first outlet, the second inlet is connected to the second outlet, and the third inlet is connected to the third outlet.

[0011] A method for cryogenic separation and purification of H2 and CO and co-production of LNG, wherein the synthesis gas enters a molecular sieve adsorption device from a synthesis gas pipeline, and then enters a raw material cooler a after being adsorbed and removed by the molecular sieve adsorption device. After being cooled by the raw material cooler a, the synthesis gas is divided into three branches and enters flash evaporator a, flash evaporator c, and flash evaporator d for further cooling. The synthesis gas cooled by flash evaporator a, flash evaporator c, and flash evaporator d is combined into one branch and enters flash evaporator b and raw material cooler b for cooling in sequence. After being cooled by raw material cooler b, the synthesis gas enters a hydrogen flash tank for gas-liquid separation. The hydrogen-rich gas flows out from the top of the hydrogen flash tank and enters the raw material cooler b for heat exchange and then enters the raw material cooler a for reheating. The hydrogen-rich gas enters the hydrogen pipeline and is sent to the downstream device after being reheated by the raw material cooler a. The condensate in the hydrogen flash tank is depressurized and enters the dehydrogenation tower from the top. The hydrogen-rich gas b obtained at the top of the dehydrogenation tower is cooled by the raw material cooler b and then enters the dehydrogenation tower top separator for gas-liquid separation. The hydrogen-rich gas b flows out from the dehydrogenation tower top separator and enters the raw material cooler a for reheating and then is sent to the recovery gas pipeline for recycling. The condensate in the dehydrogenation tower top separator is refluxed. to the dehydrogenation tower; the dehydrogenation tower kettle liquid is depressurized and enters the denitrification tower. The gas phase obtained at the top of the denitrification tower is condensed by the denitrification tower top condenser and enters the denitrification tower top separator for gas-liquid separation. The separated nitrogen-rich gas is reheated by the raw material cooler a and sent to the incineration device. The condensate in the denitrification tower top separator returns to the denitrification tower; the denitrification tower kettle liquid is depressurized and enters the demethanizer. The gas phase obtained at the top of the demethanizer is condensed by the demethanizer top condenser and enters the demethanizer top separator. The separated carbon monoxide gas is reheated by the raw material cooler a and enters the monoxide The carbon pipeline is sent to the downstream device, and the condensate in the top separator of the demethanizer is refluxed to the demethanizer; the bottom liquid of the demethanizer enters the methane concentrator, and after being concentrated by the methane concentrator, it is reduced in pressure and enters the methane refining tower. The top gas phase of the methane refining tower is condensed by the top condenser of the methane refining tower and enters the top separator of the methane refining tower. The gas phase in the top separator of the methane refining tower is reheated by the raw material cooler a and sent to the carbon monoxide pipeline. The condensate in the top separator of the methane refining tower is refluxed to the methane refining tower, and the product LNG obtained in the bottom of the methane refining tower enters the LNG storage tank.

[0012] Furthermore, the cooling capacity of the raw material cooler a, the raw material cooler b, the denitrification tower top condenser, the demethanization tower top condenser, and the methane refining tower top condenser is provided by a circulating nitrogen device.

[0013] Furthermore, the synthesis gas is used to provide heat sources for the bottoms of the dehydrogenation tower, the denitrification tower, the demethanization tower and the methane refining tower through the flash evaporators a, b, c and d, respectively.

[0014] Further, the temperature of the synthesis gas out of the raw material cooler a is -150°C~-120°C, the temperature of the synthesis gas out of the raw material cooler b is -185°C~-175°C, the system pressure of the dehydrogenation tower is 1.5MPa~2.0MPa, the temperature of the dehydrogenation tower bottom liquid is -175°C~-150°C, the temperature of the hydrogen-rich gas b at the top of the dehydrogenation tower out of the raw material cooler b is -185°C~-175°C, the system pressure of the denitrification tower is 1.0MPa~1.4MPa, and the temperature of the gas phase obtained at the top of the denitrification tower out of the top condenser of the denitrification tower is: -175°C~-150°C, the denitrification tower The temperature of the tower bottom liquid is: -170℃~-145℃, the system pressure of the demethanizer is: 0.6MPa~0.9MPa, the temperature of the gas phase obtained at the top of the demethanizer out of the top condenser of the demethanizer is: -175℃~-170℃, the bottom liquid temperature of the demethanizer is: -170℃~-161℃, the system pressure of the methane refining tower is: 0.15MPa~0.3MPa, the temperature of the gas phase at the top of the methane refining tower out of the top condenser of the methane refining tower is: -175℃~-165℃, and the bottom liquid temperature of the methane refining tower is: -155℃~-145℃.

[0015] Furthermore, the temperatures of the hydrogen-rich gas b, the hydrogen-rich gas, the nitrogen-rich gas, the carbon monoxide gas, and the gas phase in the top separator of the methane refining tower exiting the raw material cooler a are all 10°C to 50°C.

[0016] Furthermore, the volume concentration of hydrogen in the hydrogen-rich gas flowing out from the top of the hydrogen flash tank is 80%~90%, the volume concentration of hydrogen in the hydrogen-rich gas b flowing out from the top separator of the dehydrogenation tower is 75%~90%, the volume concentration of carbon monoxide gas separated from the top separator of the demethanizer tower is greater than or equal to 98%, the gas phase in the top separator of the methane refining tower is carbon monoxide, and the volume concentration is greater than or equal to 98%, and the product LNG is obtained in the kettle of the methane refining tower.

[0017] Compared with the prior art, the present invention has the following beneficial effects:

[0018] 1. The present invention provides a methane refining tower to concentrate the bottom liquid of the demethanizer bottom and then send it to a methane refining tower for distillation. The bottom of the methane refining tower obtains product LNG, which meets the requirements of the conventional category of GB / T38753-2020, effectively utilizes methane, and saves energy resources. At the same time, the CO gas obtained at the top of the methane refining tower is sent to the downstream production device, thereby improving the separation yield of CO in the synthesis gas and reducing the production cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a structural schematic diagram of the device of the present invention;

[0020] Figure 2 is a process flow chart of the device of the present invention;

[0021] In the figure, 1-molecular sieve adsorption device; 2-raw material cooler a; 3-raw material cooler b; 4-dehydrogenation tower; 5-denitrification tower; 6-demethanizer; 7-methane refining tower; 8-flash evaporator a; 9-flash evaporator b; 10-flash evaporator c; 11-flash evaporator d; 12-hydrogen flash tank; 13-methane concentrator; 14-dehydrogenation tower top separator; 15-denitrification tower top condenser; 16-denitrification tower top separator; 17-demethanizer tower top condenser; 18-demethanizer tower top separator; 19-methane refining tower top condenser; 20-methane refining tower top separator; 21-LNG storage tank. DETAILED DESCRIPTION

[0022] Example 1

[0023] Molecular sieve adsorption device 1, raw material cooler a2, raw material cooler b3, dehydrogenation tower 4, denitrification tower 5, demethanizer 6, methane refining tower 7, flash evaporator a8, flash evaporator b9, flash evaporator c10, flash evaporator d11, hydrogen flash tank 12, dehydrogenation tower top separator 14, denitrification tower top condenser 15, denitrification tower top separator 16, demethanizer tower top condenser 17, demethanizer tower top separator 18, methane refining tower top condenser 19, methane refining tower top separator 20, circulating nitrogen device;

[0024] The inlet of the molecular sieve adsorption device 1 is communicated with the synthesis gas pipeline, the outlet of the molecular sieve adsorption device 1 is communicated with the first inlet of the raw material cooler a2 through a pipeline, the first outlet of the raw material cooler a2 is divided into three branches through a pipeline and respectively communicated with the inlet of the flash evaporator a8, the inlet of the flash evaporator c10, and the inlet of the flash evaporator d11, the outlet of the flash evaporator a8, the outlet of the flash evaporator c10, and the outlet of the flash evaporator d11 are all communicated with the inlet of the flash evaporator b9 through a pipeline, the outlet of the flash evaporator b9 is communicated with the first inlet of the raw material cooler b3 through a pipeline, and the first outlet of the raw material cooler b3 is communicated with the first inlet of the raw material cooler b3. The inlet of the hydrogen flash tank 12 is communicated with the inlet of the hydrogen flash tank 12 through a pipeline, the flash gas outlet of the hydrogen flash tank 12 is communicated with the second inlet of the raw material cooler b3 through a pipeline, the second outlet of the raw material cooler b3 is communicated with the second inlet of the raw material cooler a2 through a pipeline, the second outlet of the raw material cooler a2 is communicated with the hydrogen pipeline through a pipeline, the flash liquid outlet of the hydrogen flash tank 12 is communicated with the raw material liquid inlet on the top side of the dehydrogenation tower 4 through a pipeline, the gas phase outlet at the top of the dehydrogenation tower 4 is communicated with the third inlet of the raw material cooler b3 through a pipeline, and the third outlet of the raw material cooler b3 is communicated with the third inlet of the raw material cooler b3 through a pipeline.

[0025] The inlet of the dehydrogenation tower top separator 14 is communicated with the gas phase outlet of the dehydrogenation tower top separator 14 through a pipeline and the third inlet of the feed cooler a2, the third outlet of the feed cooler a2 is communicated with the recovery gas pipeline through a pipeline, the bottom liquid outlet of the dehydrogenation tower 4 is communicated with the middle inlet of the denitrification tower 5 through a pipeline, the gas phase outlet at the top of the denitrification tower 5 is communicated with the inlet of the denitrification tower top condenser 15 through a pipeline, the outlet of the denitrification tower top condenser 15 is communicated with the inlet of the denitrification tower top separator 16 through a pipeline, and the gas phase outlet of the denitrification tower top separator 16 is communicated with the inlet of the denitrification tower top separator 16 through a pipeline. The inlet of the raw material cooler a2 is connected to the fourth inlet of the raw material cooler a2 through a pipeline, the fourth outlet of the raw material cooler a2 is connected to the incineration device through a pipeline, the liquid phase outlet of the denitrification tower top separator 16 is connected to the condensate inlet of the denitrification tower 5 through a pipeline, the bottom liquid outlet of the denitrification tower 5 is connected to the middle inlet of the demethanizer 6 through a pipeline, the gas phase outlet of the demethanizer 6 top is connected to the inlet of the demethanizer tower top condenser 17 through a pipeline, the outlet of the demethanizer tower top condenser 17 is connected to the inlet of the demethanizer tower top separator 18 through a pipeline, and the gas phase outlet of the demethanizer tower top separator 18 is connected to the inlet of the demethanizer tower top separator 18 through a pipeline. The fifth inlet of the raw material cooler a2 is connected through a pipeline, the fifth outlet of the raw material cooler a2 is connected to the carbon monoxide pipeline through a pipeline, the liquid phase outlet of the top separator 18 of the demethanizer is connected to the top of the demethanizer 6 through a pipeline, the bottom liquid outlet of the demethanizer 6 is connected to the inlet of the methane concentrator 13 through a pipeline, the gas phase outlet of the methane concentrator 13 is connected to the middle inlet of the demethanizer 6 through a pipeline, the bottom outlet of the methane concentrator is connected to the middle inlet of the methane refining tower 7 through a pipeline, a heat exchange device is arranged at the bottom of the methane concentrator 13, and the top of the methane refining tower 7 is connected to the methane refining tower 7. The gas phase outlet is connected to the inlet of the methane refining tower top condenser 19 through a pipeline, the outlet of the methane refining tower top condenser 19 is connected to the inlet of the methane refining tower top separator 20 through a pipeline, the gas phase outlet of the methane refining tower top separator 20 is connected to the sixth inlet of the raw material cooler a2 through a pipeline, the sixth outlet of the raw material cooler a2 is connected to the carbon monoxide pipeline through a pipeline, the condensate outlet of the methane refining tower top separator 20 is connected to the top of the methane refining tower 7 through a pipeline, and the kettle outlet of the methane refining tower 7 is connected to the LNG storage tank 21 through a pipeline.

[0026] Pressure reducing valves are provided on the pipeline connecting the flash liquid outlet of the hydrogen flash tank 12 with the raw liquid inlet on the top side of the dehydrogenation tower 4, the pipeline connecting the bottom liquid outlet of the dehydrogenation tower 4 with the middle inlet of the denitrification tower 5, the pipeline connecting the bottom liquid outlet of the denitrification tower 5 with the middle inlet of the demethanization tower 6, and the pipeline connecting the bottom liquid outlet of the demethanization tower 6 with the middle inlet of the methane refining tower 7.

[0027] The cooling channels of the raw material cooler a2, the raw material cooler b3, the denitrification tower top condenser 15, the demethanizer tower top condenser 17, and the methane refining tower top condenser 19 are all connected to the circulating nitrogen device; the dehydrogenation tower top separator 14, the denitrification tower top separator 16, the demethanizer tower top separator 18, and the methane refining tower top separator 20 are all provided with a demister.

[0028] The first inlet in the raw material cooler a2 is connected to the first outlet, the second inlet is connected to the second outlet, the third inlet is connected to the third outlet, the fourth inlet is connected to the fourth outlet, the fifth inlet is connected to the fifth outlet; the sixth inlet is connected to the sixth outlet; the first inlet in the raw material cooler b3 is connected to the first outlet, the second inlet is connected to the second outlet, and the third inlet is connected to the third outlet.

[0029] A method for deep cold separation and purification of H2 and CO and co-production of LNG, wherein the synthesis gas enters a molecular sieve adsorption device 1 from a synthesis gas pipeline, and after carbon dioxide and methanol are adsorbed and removed in the molecular sieve adsorption device 1, enters a raw material cooler a2, and after cooling down in the raw material cooler a2, it is divided into three branches and enters a flash evaporator a8, a flash evaporator c10, and a flash evaporator d11 for cooling again, and the synthesis gas cooled down in the flash evaporator a8, the flash evaporator c10, and the flash evaporator d11 is combined into one branch and enters a flash evaporator b9 and a raw material cooler b3 in turn for cooling, and after cooling down in the raw material cooler b3, it enters a hydrogen flash tank 12 for gas-liquid separation The hydrogen-rich gas flows out from the top of the hydrogen flash tank 12 and enters the raw material cooler b3 for heat exchange, and then enters the raw material cooler a2 for reheating. The hydrogen-rich gas enters the hydrogen pipeline and is sent to the downstream device after being reheated by the raw material cooler a2; the condensate in the hydrogen flash tank 12 is depressurized and enters the dehydrogenation tower 4 from the top of the dehydrogenation tower 4. The hydrogen-rich gas b obtained at the top of the dehydrogenation tower 4 is cooled by the raw material cooler b3 and enters the dehydrogenation tower top separator 14 for gas-liquid separation. The hydrogen-rich gas b flows out from the dehydrogenation tower top separator 14 and enters the raw material cooler a2 for reheating and is sent to the recovery gas pipeline for recycling. The condensate in the dehydrogenation tower top separator 14 flows back to the dehydrogenation tower Tower 4; the dehydrogenation tower 4 bottom liquid enters the denitrification tower 5 after decompression, the gas phase obtained at the top of the denitrification tower 5 is condensed by the denitrification tower top condenser 15 and then enters the denitrification tower top separator 16 for gas-liquid separation, the separated nitrogen-rich gas is reheated by the raw material cooler a2 and then sent to the incineration device, and the condensate in the denitrification tower top separator 16 returns to the denitrification tower 5; the denitrification tower 5 bottom liquid enters the demethanizer 6 after decompression, the gas phase obtained at the top of the demethanizer 6 is condensed by the demethanizer tower top condenser 17 and then enters the demethanizer tower top separator 18, the separated carbon monoxide gas is reheated by the raw material cooler a2 and then enters the carbon monoxide pipeline The condensate in the demethanizer top separator 18 is sent to the downstream device, and the condensate is refluxed to the demethanizer 6; the bottom liquid of the demethanizer 6 enters the methane concentrator 13, and after being concentrated by the methane concentrator 13, it is decompressed and enters the methane refining tower 7; the top gas phase of the methane refining tower 7 is condensed by the methane refining tower top condenser 19 and enters the methane refining tower top separator 20; the gas phase in the methane refining tower top separator 20 is reheated by the raw material cooler a2 and sent to the carbon monoxide pipeline; the condensate in the methane refining tower top separator 20 is refluxed to the methane refining tower 7; the product LNG is obtained in the bottom of the methane refining tower 7 and enters the LNG storage tank 21.

[0030] The cooling capacity of the raw material cooler a2, the raw material cooler b3, the denitrification tower top condenser 15, the demethanization tower top condenser 17, and the methane refining tower top condenser 19 is provided by a circulating nitrogen device.

[0031] The synthesis gas is used to provide heat sources for the bottoms of the dehydrogenation tower 4, the denitrification tower 5, the demethanization tower 6 and the methane refining tower 7 through the flash evaporators a8, b9, c10 and d11 respectively.

[0032] The temperature of the synthesis gas out of the feed cooler a2 is -150°C, the temperature of the synthesis gas out of the feed cooler b3 is -185°C, the system pressure of the dehydrogenation tower 4 is 1.5MPa, the temperature of the bottom liquid of the dehydrogenation tower 4 is -175°C, the temperature of the hydrogen-rich gas b at the top of the dehydrogenation tower 4 out of the feed cooler b3 is -185°C, the system pressure of the denitrogenation tower 5 is 1.0MPa, the temperature of the gas phase obtained at the top of the denitrogenation tower 5 out of the top condenser 15 of the denitrogenation tower is: -175°C, the bottom liquid of the denitrogenation tower The liquid temperature is: -170°C, the system pressure of the demethanizer 6 is: 0.6MPa, the temperature of the gas phase obtained at the top of the demethanizer 6 out of the demethanizer top condenser 17 is: -175°C, the demethanizer 6 bottom liquid temperature is: -170°C, the system pressure of the methane refining tower 7 is: 0.15MPa, the temperature of the gas phase at the top of the methane refining tower 7 out of the methane refining tower top condenser 19 is: -175°C, and the methane refining tower 7 bottom liquid temperature is: -155°C.

[0033] The temperature of the hydrogen-rich gas b, the hydrogen-rich gas, the nitrogen-rich gas, the carbon monoxide gas, and the carbon monoxide gas separated by the methane refining tower top separator 20 when they exit the raw material cooler a2 is 10°C to 30°C.

[0034] The volume concentration of hydrogen in the hydrogen-rich gas flowing out from the top of the hydrogen flash tank 12 is 87%~90%, the volume concentration of hydrogen in the hydrogen-rich gas b flowing out from the dehydrogenation tower top separator 14 is 87%~90%, the volume concentration of carbon monoxide gas separated from the demethanizer tower top separator 18 is 98.0%~98.5%, the volume concentration of carbon monoxide separated from the methane refining tower top separator 20 is 98%~98.4%, and the product LNG is obtained in the bottom of the methane refining tower 7. The LNG product is sampled and analyzed. The molar fraction of methane in the LNG is 86.1%~88.9%, and the molar fraction of C4 + The molar fraction of alkanes is 1.6%~1.8%, the molar fraction of carbon dioxide is 0.01%, the molar fraction of nitrogen is 0.90%~0.97%, the molar fraction of oxygen is 0.1%, and the total sulfur (calculated as sulfur) is 15.11 mg / m 3 ~18.47mg / m 3 , hydrogen sulfide: 3.40mg / m 3 , high volume calorific value is 38.0MJ / m 3 ~38.5MJ / m 3 .

[0035] Another embodiment is different from embodiment 1 in that: the temperature of the synthesis gas out of the feed cooler a2 is -140°C, the temperature of the synthesis gas out of the feed cooler b3 is -182°C, the system pressure of the dehydrogenation tower 4 is 1.65MPa, the temperature of the bottom liquid of the dehydrogenation tower 4 is -165°C, the temperature of the hydrogen-rich gas b at the top of the dehydrogenation tower 4 out of the feed cooler b3 is -182°C, the system pressure of the denitrification tower 5 is 1.1MPa, and the temperature of the gas phase obtained at the top of the denitrification tower 5 out of the denitrification tower top condenser 15 is: - 165°C, the temperature of the bottom liquid of the denitrification tower 5 is: -160°C, the system pressure of the demethanizer 6 is: 0.7MPa, the temperature of the gas phase obtained at the top of the demethanizer 6 out of the top condenser 17 of the demethanizer is: -174°C, the bottom liquid temperature of the demethanizer 6 is: -167°C, the system pressure of the methane refining tower 7 is: 0.2MPa, the temperature of the gas phase at the top of the methane refining tower 7 out of the top condenser 19 of the methane refining tower is: -173°C, and the bottom liquid temperature of the methane refining tower is: -152°C;

[0036] The temperature of the hydrogen-rich gas b, the hydrogen-rich gas, the nitrogen-rich gas, the carbon monoxide gas, and the carbon monoxide gas separated by the methane refining tower top separator 20 when they exit the raw material cooler a2 is 20°C~40°C.

[0037] The volume concentration of hydrogen in the hydrogen-rich gas flowing out from the top of the hydrogen flash tank 12 is 85%~88%, the volume concentration of hydrogen in the hydrogen-rich gas b flowing out from the dehydrogenation tower top separator 14 is 85%~88%, the volume concentration of carbon monoxide gas separated from the demethanizer tower top separator 18 is 98.5%~99.0%, the volume concentration of carbon monoxide separated from the methane refining tower top separator 20 is 98.4%~98.8%, and the product LNG is obtained in the bottom of the methane refining tower 7. The LNG product is sampled and analyzed. The molar fraction of methane in the LNG is 86.0%~89.7%, and the molar fraction of C4 + The molar fraction of alkanes is 1.7%~1.9%, the molar fraction of carbon dioxide is 0.01%, the molar fraction of nitrogen is 0.95%~1.00%, the molar fraction of oxygen is 0.1%, and the total sulfur (calculated as sulfur) is 17.05mg / m 3 ~19.21mg / m 3 , hydrogen sulfide: 3.4mg / m 3 , high volume calorific value is 38.4MJ / m 3 ~38.9MJ / m 3 .

[0038] Another embodiment is different from embodiment 1 in that: the temperature of the synthesis gas out of the feed cooler a2 is -130°C, the temperature of the synthesis gas out of the feed cooler b3 is -178°C, the system pressure of the dehydrogenation tower 4 is 1.85MPa, the temperature of the bottom liquid of the dehydrogenation tower 4 is -155°C, the temperature of the hydrogen-rich gas b at the top of the dehydrogenation tower 4 out of the feed cooler b3 is -179°C, the system pressure of the denitrification tower 5 is 1.3MPa, and the temperature of the gas phase obtained at the top of the denitrification tower 5 out of the denitrification tower top condenser 15 is: -1 60℃, the temperature of the bottom liquid of denitrification tower 5 is: -152℃, the system pressure of demethanizer 6 is: 0.8MPa, the temperature of the gas phase obtained at the top of demethanizer 6 exiting the top condenser 17 of demethanizer is: -169℃, the bottom liquid temperature of demethanizer 6 is: -164℃, the system pressure of methane refining tower 7 is: 0.25MPa, the temperature of the gas phase at the top of methane refining tower 7 exiting the top condenser 19 of methane refining tower is: -172℃, and the bottom liquid temperature of methane refining tower 7 is: -148℃.

[0039] The temperatures of the hydrogen-rich gas b, the hydrogen-rich gas, the nitrogen-rich gas, the carbon monoxide gas, and the carbon monoxide gas separated by the methane refining tower top separator 20 when they exit the raw material cooler a2 are all 30°C to 50°C.

[0040] The volume concentration of hydrogen in the hydrogen-rich gas flowing out from the top of the hydrogen flash tank 12 is 83%~86%, the volume concentration of hydrogen in the hydrogen-rich gas b flowing out from the dehydrogenation tower top separator 14 is 80%~86%, the volume concentration of carbon monoxide gas separated from the demethanizer tower top separator 18 is 98.9%~99.6%, the volume concentration of carbon monoxide separated from the methane refining tower top separator 20 is 98.8%~99.4%, and the product LNG is obtained in the bottom of the methane refining tower 7. The LNG product is sampled and analyzed. The molar fraction of methane in the LNG is 88.6%~90.2%, and the molar fraction of C4 + The molar fraction of alkanes is 1.4%~1.6%, the molar fraction of carbon dioxide is 0.01%, the molar fraction of nitrogen is 0.95%~1.00%, the molar fraction of oxygen is 0.1%, and the total sulfur (calculated as sulfur) is 14.83mg / m 3 ~16.55mg / m 3 , hydrogen sulfide: 3.2mg / m 3 , high volume calorific value is 39.6MJ / m 3 ~40.5MJ / m 3 .

[0041] Another embodiment is different from embodiment 1 in that: the temperature of the synthesis gas out of the feed cooler a2 is -120°C, the temperature of the synthesis gas out of the feed cooler b3 is -175°C, the system pressure of the dehydrogenation tower 4 is 2.00MPa, the temperature of the bottom liquid of the dehydrogenation tower 4 is -150°C, the temperature of the hydrogen-rich gas b at the top of the dehydrogenation tower 4 out of the feed cooler b3 is -175°C, the system pressure of the denitrification tower 5 is 1.4MPa, and the temperature of the gas phase obtained at the top of the denitrification tower 5 out of the denitrification tower top condenser 15 is: - 150℃, the temperature of the bottom liquid of denitrification tower 5 is: -145℃, the system pressure of demethanizer 6 is: 0.9MPa, the temperature of the gas phase obtained at the top of demethanizer 6 out of the top condenser 17 of demethanizer is -170℃, the bottom liquid temperature of demethanizer 6 is: -161℃, the system pressure of methane refining tower 7 is: 0.3MPa, the temperature of the gas phase at the top of methane refining tower 7 out of the top condenser 19 of methane refining tower is: -165℃, and the bottom liquid temperature of methane refining tower 7 is: -145℃.

[0042] The temperatures of the hydrogen-rich gas b, the hydrogen-rich gas, the nitrogen-rich gas, the carbon monoxide gas, and the carbon monoxide gas separated by the methane refining tower top separator 20 when they exit the raw material cooler a2 are all 40°C to 50°C.

[0043] The volume concentration of hydrogen in the hydrogen-rich gas flowing out from the top of the hydrogen flash tank 12 is 80%~84%, the volume concentration of hydrogen in the hydrogen-rich gas b flowing out from the dehydrogenation tower top separator 14 is 75%~81%, the volume concentration of carbon monoxide gas separated from the demethanizer tower top separator 18 is 99.5%~99.9%, the volume concentration of carbon monoxide separated from the methane refining tower top separator 20 is 99.4%~99.9%, and the product LNG is obtained in the bottom of the methane refining tower 7. The LNG product is sampled and analyzed. The molar fraction of methane in the LNG is 87.6%~89.8%, and the molar fraction of C4 + The molar fraction of alkanes is 1.5%~1.8%, the molar fraction of carbon dioxide is 0.01%, the molar fraction of nitrogen is 0.88%~0.97%, the molar fraction of oxygen is 0.1%, and the total sulfur (calculated as sulfur) is 15.52mg / m 3 ~16.64mg / m 3 , hydrogen sulfide: 3.5mg / m 3 , high volume calorific value is 38.7MJ / m 3 ~39.4MJ / m 3 .

[0044] The above specific implementation methods are only examples of the contents of the present invention. Any modification and changes to the present invention made by a person familiar with the present invention are within the patent scope of the present invention and are not limited to the embodiments.

Claims

1. A device for cryogenic separation and purification of H2 and CO and co-production of LNG, characterized in that include: Molecular sieve adsorption device, raw material cooler a, raw material cooler b, dehydrogenation tower, denitrogenation tower, demethanizer, methane refining tower, flash evaporator a, flash evaporator b, flash evaporator c, flash evaporator d, hydrogen flash tank, dehydrogenation tower top separator, denitrogenation tower top condenser, denitrogenation tower top separator, demethanizer tower top condenser, demethanizer tower top separator, methane refining tower top condenser, methane refining tower top separator, circulating nitrogen device; The inlet of the molecular sieve adsorption device is communicated with the synthesis gas pipeline, the outlet of the molecular sieve adsorption device is communicated with the first inlet of the raw material cooler a through a pipeline, the first outlet of the raw material cooler a is divided into three branches through a pipeline and is respectively communicated with the inlet of the flash evaporator a, the inlet of the flash evaporator c, and the inlet of the flash evaporator d, the outlet of the flash evaporator a, the outlet of the flash evaporator c, and the outlet of the flash evaporator d are all communicated with the inlet of the flash evaporator b through a pipeline, the outlet of the flash evaporator b is communicated with the first inlet of the raw material cooler b through a pipeline, the first outlet of the raw material cooler b is communicated with the inlet of the hydrogen flash tank through a pipeline, the flash gas outlet of the hydrogen flash tank is communicated with the second inlet of the raw material cooler b through a pipeline, and the second outlet of the raw material cooler b is communicated with the second inlet of the raw material cooler a through a pipeline, The second outlet of the raw material cooler a is connected to the hydrogen pipeline through a pipeline, the flash liquid outlet of the hydrogen flash tank is connected to the raw material liquid inlet on the side of the top of the dehydrogenation tower through a pipeline, the gas phase outlet at the top of the dehydrogenation tower is connected to the third inlet of the raw material cooler b through a pipeline, the third outlet of the raw material cooler b is connected to the inlet of the top separator of the dehydrogenation tower through a pipeline, the gas phase outlet of the top separator of the dehydrogenation tower is connected to the third inlet of the raw material cooler a through a pipeline, the third outlet of the raw material cooler a is connected to the recovery gas pipeline through a pipeline, the bottom liquid outlet of the dehydrogenation tower is connected to the middle inlet of the denitrification tower through a pipeline, the gas phase outlet at the top of the denitrification tower is connected to the inlet of the top condenser of the denitrification tower through a pipeline, and the outlet of the top condenser of the denitrification tower is connected to the inlet of the top separator of the denitrification tower through a pipeline. The gas phase outlet of the denitrification tower top separator is connected to the fourth inlet of the raw material cooler a through a pipeline, the fourth outlet of the raw material cooler a is connected to the incineration device through a pipeline, the liquid phase outlet of the denitrification tower top separator is connected to the condensate inlet of the denitrification tower top through a pipeline, the denitrification tower kettle liquid outlet is connected to the middle inlet of the demethanizer through a pipeline, the gas phase outlet of the demethanizer top is connected to the inlet of the demethanizer top condenser through a pipeline, the demethanizer top condenser outlet is connected to the inlet of the demethanizer top separator through a pipeline, the gas phase outlet of the demethanizer top separator is connected to the fifth inlet of the raw material cooler a through a pipeline, the fifth outlet of the raw material cooler a is connected to the carbon monoxide pipeline through a pipeline, and the liquid phase outlet of the demethanizer top separator is connected to the top of the demethanizer through a pipeline , the demethanizer kettle liquid outlet is connected to the methane concentrator inlet through a pipeline, the methane concentrator gas phase outlet is connected to the demethanizer middle inlet through a pipeline, the methane concentrator bottom outlet is connected to the methane refining tower middle inlet through a pipeline, the methane refining tower top gas phase outlet is connected to the methane refining tower top condenser inlet through a pipeline, the methane refining tower top condenser outlet is connected to the methane refining tower top separator inlet through a pipeline, the methane refining tower top separator gas phase outlet is connected to the sixth inlet of the raw material cooler a through a pipeline, the sixth outlet of the raw material cooler a is connected to the carbon monoxide pipeline through a pipeline, the condensate outlet of the methane refining tower top separator is connected to the top of the methane refining tower through a pipeline, and the methane refining tower kettle outlet is connected to the LNG storage tank through a pipeline; The cooling channels of the raw material cooler a, the raw material cooler b, the denitrification tower top condenser, the demethanization tower top condenser and the methane refining tower top condenser are all connected to the circulating nitrogen device.

2. The device for cryogenic separation and purification of H2 and CO and co-production of LNG according to claim 1, characterized in that: Pressure reducing valves are provided on the pipeline connecting the flash liquid outlet of the hydrogen flash tank with the raw liquid inlet on the top side of the dehydrogenation tower, the pipeline connecting the bottom liquid outlet of the dehydrogenation tower with the middle inlet of the denitrification tower, the pipeline connecting the bottom liquid outlet of the denitrification tower with the middle inlet of the demethanization tower, and the pipeline connecting the bottom outlet of the methane concentrator with the middle inlet of the methane refining tower.

3. The device for cryogenic separation and purification of H2 and CO and co-production of LNG according to claim 2, characterized in that: The dehydrogenation tower top separator, the denitrification tower top separator, the demethanization tower top separator and the methane refining tower top separator are all provided with a demister.

4. The device for cryogenic separation and purification of H2 and CO and co-production of LNG according to claim 1, characterized in that: The first inlet in the raw material cooler a is connected to the first outlet, the second inlet is connected to the second outlet, the third inlet is connected to the third outlet, the fourth inlet is connected to the fourth outlet, the fifth inlet is connected to the fifth outlet; the sixth inlet is connected to the sixth outlet; the first inlet in the raw material cooler b is connected to the first outlet, the second inlet is connected to the second outlet, and the third inlet is connected to the third outlet.

5. A method for cryogenic separation and purification of H2 and CO and co-production of LNG, characterized by: The synthesis gas enters the molecular sieve adsorption device from the synthesis gas pipeline, and enters the raw material cooler a after being adsorbed and removed of carbon dioxide and methanol in the molecular sieve adsorption device. After being cooled in the raw material cooler a, it is divided into three branches and enters the flash evaporator a, flash evaporator c, and flash evaporator d for cooling again. The synthesis gas cooled in the flash evaporator a, flash evaporator c, and flash evaporator d is combined into one branch and enters the flash evaporator b and the raw material cooler b for cooling in turn. After being cooled in the raw material cooler b, it enters the hydrogen flash tank for gas-liquid separation. The hydrogen-rich gas flows out from the top of the hydrogen flash tank and enters the raw material cooler b for heat exchange and then enters the raw material cooler a for reheating. After being reheated in the raw material cooler a, the hydrogen-rich gas enters the hydrogen pipeline and is sent to the downstream device; The condensate in the gas flash tank is depressurized and enters the dehydrogenation tower from the top of the dehydrogenation tower. The hydrogen-rich gas b obtained at the top of the dehydrogenation tower is cooled by the raw material cooler b and enters the top separator of the dehydrogenation tower for gas-liquid separation. The hydrogen-rich gas b flows out from the top separator of the dehydrogenation tower and enters the raw material cooler a for reheating and then is sent to the recovery gas pipeline for recycling. The condensate in the top separator of the dehydrogenation tower flows back to the dehydrogenation tower; the dehydrogenation tower kettle liquid is depressurized and enters the denitrification tower. The gas phase obtained at the top of the denitrification tower is condensed by the top condenser of the denitrification tower and then enters the top separator of the denitrification tower for gas-liquid separation. The separated nitrogen-rich gas is reheated by the raw material cooler a and then sent to the incineration device. The condensate in the top separator of the denitrification tower returns to the denitrification tower. The denitrification tower bottom liquid is depressurized and enters the demethanizer. The gas phase obtained at the top of the demethanizer is condensed by the top condenser of the demethanizer and enters the top separator of the demethanizer. The separated carbon monoxide gas is reheated by the raw material cooler a and enters the carbon monoxide pipeline to be sent to the downstream device. The condensate in the top separator of the demethanizer flows back to the demethanizer. The demethanizer bottom liquid enters the methane concentrator, is concentrated by the methane concentrator and depressurized and enters the methane refining tower. The gas phase at the top of the methane refining tower is condensed by the top condenser of the methane refining tower and enters the top separator of the methane refining tower. The gas phase in the top separator of the methane refining tower is reheated by the raw material cooler a and sent to the carbon monoxide pipeline. The condensate in the top separator of the methane refining tower flows back to the methane refining tower. The product LNG is obtained from the bottom of the methane refining tower and enters the LNG storage tank.

6. A method for co-producing LNG by cryogenic separation and purification of H2 and CO according to claim 5, characterized in that: The cooling capacity of the raw material cooler a, the raw material cooler b, the top condenser of the denitrification tower, the top condenser of the demethanization tower and the top condenser of the methane refining tower is provided by the circulating nitrogen device.

7. The method of cryogenic separation and purification of H2 and CO and co-production of LNG according to claim 5, characterized in that: The synthesis gas is used to provide heat sources for the bottoms of the dehydrogenation tower, the denitrification tower, the demethanization tower and the methane refining tower through the flash evaporator a, the flash evaporator b, the flash evaporator c and the flash evaporator d respectively.

8. The method of cryogenic separation and purification of H2 and CO and co-production of LNG according to claim 5, characterized in that: The temperature of the synthesis gas out of the raw material cooler a is -150℃~-120℃, the temperature of the synthesis gas out of the raw material cooler b is -185℃~-175℃, the system pressure of the dehydrogenation tower is 1.5MPa~2.0MPa, the temperature of the dehydrogenation tower kettle liquid is -175℃~-150℃, the temperature of the hydrogen-rich gas b at the top of the dehydrogenation tower out of the raw material cooler b is -185℃~-175℃, the system pressure of the denitrification tower is 1.0MPa~1.4MPa, the temperature of the gas phase obtained at the top of the denitrification tower out of the top condenser of the denitrification tower is: -175℃~-150℃, the denitrification tower kettle The liquid temperature is: -170℃~-145℃, the system pressure of the demethanizer is: 0.6MPa~0.9MPa, the temperature of the gas phase obtained at the top of the demethanizer out of the top condenser of the demethanizer is: -175℃~-170℃, the temperature of the demethanizer bottom liquid is: -170℃~-161℃, the system pressure of the methane refining tower is: 0.15MPa~0.3MPa, the temperature of the gas phase at the top of the methane refining tower out of the top condenser of the methane refining tower is: -175℃~-165℃, and the temperature of the methane refining tower bottom liquid is: -155℃~-145℃.

9. The method of cryogenic separation and purification of H2 and CO and co-production of LNG according to claim 5, characterized in that: The temperatures of the hydrogen-rich gas b, hydrogen-rich gas, nitrogen-rich gas, carbon monoxide gas, and the gas phase in the top separator of the methane refining tower exiting the raw material cooler a are all: 10°C~50°C.

10. The method of cryogenic separation and purification of H2 and CO and co-production of LNG according to claim 5, characterized in that: The volume concentration of hydrogen in the hydrogen-rich gas flowing out from the top of the hydrogen flash tank is 80% to 90%, the volume concentration of hydrogen in the hydrogen-rich gas b flowing out from the top separator of the dehydrogenation tower is 75% to 90%, the volume concentration of carbon monoxide gas separated from the top separator of the demethanizer tower is greater than or equal to 98%, the gas phase in the top separator of the methane refining tower is carbon monoxide, and the volume concentration is greater than or equal to 98%, and the product LNG is obtained in the bottom of the methane refining tower.

Images