Process equipment for extracting high-purity carbon dioxide from landfill gas, biogas or chemical tail gas

Abstract

The process equipment for extracting high-purity carbon dioxide from landfill gas, biogas or chemical tail gas includes a pretreatment system, a cryogenic distillation system and a refrigeration system. The pretreatment system includes a raw material compressor, a precooler and a desulfurization tower in sequence; the cryogenic distillation system includes a first distillation tower, a second distillation tower, a carbon dioxide storage tank and a gas-liquid separator; the refrigeration system includes an ammonia compressor, a first reboiler and a second reboiler in parallel, a top condenser and a recooler in sequence, and the first reboiler and the second reboiler are respectively located at the lower part of the first distillation tower and the second distillation tower. The equipment of the present invention optimizes the device and pipelines, and the equipment runs stably with low energy consumption, can extract high-purity carbon dioxide liquid, greatly improves the utilization rate of waste gas, and reduces environmental pollution.

Description

Technical Field

[0001] The invention relates to the technical field of gas rectification and separation equipment, in particular to process equipment for extracting high-purity carbon dioxide from landfill gas, biogas or chemical tail gas. Background Art

[0002] With the continuous improvement of material level and the continuous development of industry, a large amount of landfill gas, biogas and chemical exhaust gas is generated. If not handled properly, it will cause a series of problems such as global warming and threats to human health.

[0003] For example, landfill gas (biogas) is composed of about 60% methane (CH4), 35% carbon dioxide (CO2), 0%-5% nitrogen (N2), less than 1% hydrogen (H2), less than 0.4% oxygen (O2), 0.1%-3% hydrogen sulfide (H2S), and about 1%-4% saturated water vapor (H2O). The current technical solution is generally to extract methane (CH4) gas for use as fuel, and all the remaining gases are discharged into the atmosphere and treated as waste gas, especially the 35% carbon dioxide (CO2) gas. Large amounts of it discharged into the atmosphere will damage the ozone layer and cause a global greenhouse effect, which runs counter to the current global environment where people are committed to reducing CO2 emissions. Summary of the invention

[0004] The present invention aims to solve the problems of the prior art and provides a process equipment for extracting high-purity carbon dioxide from landfill gas, biogas or chemical tail gas. By optimizing the device and pipelines, the equipment operates stably with low energy consumption and can extract high-purity carbon dioxide liquid.

[0005] To achieve the above object, the technical solution adopted by the present invention is as follows:

[0006] The process equipment for extracting high-purity carbon dioxide from landfill gas, biogas or chemical tail gas includes a pretreatment system, a cryogenic distillation system and a refrigeration system. The pretreatment system includes a raw material compressor, a precooler and a desulfurization tower in sequence, and the raw material compressor is a piston compressor. The cryogenic distillation system includes a first distillation tower, a second distillation tower, a carbon dioxide storage tank and a gas-liquid separator. The refrigeration system includes an ammonia compressor, a first reboiler and a second reboiler in parallel, a top condenser and a recooler in sequence, and the first reboiler and the second reboiler are respectively located at the lower part of the first distillation tower and the lower part of the second distillation tower.

[0007] The raw gas is processed by the pretreatment system, compressed, cooled and purified to 2.5MPa and 10℃ by the compressor, precooler and desulfurization tower, and then enters the recooler after gas-liquid separation, and then enters the middle and lower part of the first distillation tower through the V1 valve pipeline for distillation. The gas coming out of the top of the first distillation tower is divided into two paths, one path enters the middle part of the second distillation tower through the V2 valve pipeline to participate in distillation, and the other path enters the top condenser. The part condensed by the top condenser enters the gas-liquid separator. The liquid phase coming out of the gas-liquid separator is divided into two paths, one path refluxes through the V3 valve pipeline into the first distillation tower to participate in distillation, and the other path refluxes through the V4 valve pipeline into the second distillation tower to participate in distillation. What comes out of the second distillation tower is liquid carbon dioxide with a purity of more than 99.995%. The liquid carbon dioxide enters the top condenser, is supercooled to -25℃, and then throttled to 1.8MPa and enters the carbon dioxide storage tank through the V6 valve pipeline for storage.

[0008] As a priority, a V8 valve pipeline is provided at the bottom of the first distillation tower, and the V8 valve pipeline is connected to the waste liquid recovery tank. The trace components such as butane and isobutane with high boiling points are discharged from the bottom of the first distillation tower, which can be recycled and reused by storing in the waste liquid recovery tank to avoid being discharged into the atmosphere.

[0009] As a priority, the gas coming out of the top of the second distillation tower first enters the top condenser, and after the cold is recovered, it is then vented through the V7 valve pipeline.

[0010] As a preference, a methane purification system is also included, and the gas phase part coming out of the gas-liquid separator enters the methane purification system through the V5 valve pipeline. The gas phase part is methane-rich gas, and the methane purification system recovers methane.

[0011] As a preference, the methane purification system comprises a third distillation tower, a condenser and a liquid nitrogen storage tank connected thereto are arranged above the third distillation tower, a third reboiler and a nitrogen compressor and a vaporizer connected thereto are arranged below the third distillation tower, and a pipeline is arranged at the bottom of the third distillation tower to connect to a methane storage tank. Methane-rich gas enters the third distillation tower for distillation, and methane liquid enters the methane storage tank for storage through the bottom pipeline.

[0012] Preferably, a pipeline is provided at the top of the third distillation tower to vent the remaining gas.

[0013] Preferably, the first distillation tower, the second distillation tower, the gas-liquid separator, the first reboiler, the second reboiler, the top condenser and the recooler are located in a cold box, and the carbon dioxide storage tank, the ammonia compressor and the waste liquid recovery tank are located outside the cold box. The cold box ensures extremely tight insulation and avoids the problem of easy dissipation of cold due to low temperature in the system.

[0014] Preferably, the third distillation tower, condenser, liquid nitrogen storage tank and third reboiler are located in the same cold box, and the nitrogen compressor, vaporizer and methane storage tank are located outside the cold box.

[0015] As a priority, valves are provided on the pipelines connecting the various devices in the equipment, such as the V9 valve pipeline and the V10 valve pipeline between the ammonia compressor and the first reboiler and the second reboiler in the refrigeration system, the V12 valve pipeline between the first reboiler and the top condenser of the second reboiler, and the V12 valve pipeline between the top condenser and the recooler, and these valves are regulating valves.

[0016] As a priority, process equipment is made of alloy aluminum materials, including pipes, towers, separators and other devices.

[0017] The beneficial effects of the present invention are: 1. Through the optimization of the device and pipelines, a large amount of water and hydrogen sulfide (H2S) are removed from landfill gas, biogas or chemical tail gas during the purification process, and then the CO2 low-temperature liquid is converted into high-purity CO2 liquid at the bottom of the distillation tower through a low-temperature distillation process, which greatly improves the utilization rate of waste gas and reduces environmental pollution.

[0018] 2. High-purity CO2 liquid can be used in the fields of protective gas for electronic manufacturing production lines, steel welding processes, and food-grade CO2 can be used in beverage and beer filling, food freezing and preservation, the use of refrigerant media, and oil field oil production and pressurization.

[0019] 3. The process uses alloy aluminum materials, including pipes, towers, separators, etc., which have low temperature resistance, ensure the stress strength of container equipment, and reduce the total tonnage of the equipment.

[0020] 4. The process equipment uses liquid ammonia as the refrigerant for circulating refrigeration, which has a refrigeration efficiency 15%-20% higher than that of R22 refrigerant, R404A and propane refrigerant, and can reduce the energy consumption of the equipment. BRIEF DESCRIPTION OF THE DRAWINGS

[0021] Figure 1 It is a structural schematic diagram of the present invention.

[0022] Explanation of symbols in the figure: 1. Raw material compressor, 2. Precooler, 3. Desulfurization tower, 4. First distillation tower, 5. Second distillation tower, 6. Recooler, 7. Ammonia compressor, 8. First reboiler, 9. Second reboiler, 10. Top condenser, 11. Carbon dioxide storage tank, 12. Gas-liquid separator, 13. Waste liquid recovery tank, 14. Third distillation tower, 15. Condenser, 16. Liquid nitrogen storage tank, 17. Nitrogen compressor, 18. Third reboiler, 19. Vaporizer, 20. Methane storage tank. DETAILED DESCRIPTION

[0023] The present invention will be further described below through specific implementation modes and accompanying drawings.

[0024] The specific implementation is as follows: Figure 1 As shown, the process equipment for extracting high-purity carbon dioxide from landfill gas, biogas or chemical tail gas includes a pretreatment system, a cryogenic distillation system, a refrigeration system and a methane purification system. The pretreatment system includes a raw material compressor 1, a precooler 2 and a desulfurization tower 3 in sequence. The cryogenic distillation system includes a first distillation tower 4, a second distillation tower 5, a carbon dioxide storage tank 11, a gas-liquid separator 12 and a waste liquid recovery storage tank 13. The refrigeration system includes an ammonia compressor 7, a first reboiler 8 and a second reboiler 9 in parallel, a top condenser 10 and a recooler 6 in sequence, and the first reboiler 8 and the second reboiler 9 are respectively located at the lower part of the first distillation tower 4 and the second distillation tower 5. The methane purification system includes a third distillation tower 14, a condenser 15 and a liquid nitrogen storage tank 16 connected thereto are arranged above the third distillation tower 14, a third reboiler 18 and a nitrogen compressor 17 and a gasifier 19 connected thereto are arranged below the third distillation tower 14, and a pipeline is arranged at the bottom of the third distillation tower 14 to connect the methane storage tank 20.

[0025] Among them, the first distillation tower 4, the second distillation tower 5, the gas-liquid separator 12, the first reboiler 8, the second reboiler 9, the top condenser 10 and the recooler 6 are located in the same cold box, and the third distillation tower 14, the condenser 15, the liquid nitrogen storage tank 16 and the third reboiler 18 are located in the same cold box.

[0026] The working process of the pretreatment system is: the raw gas is compressed, cooled and purified to 2.5MPa and about 10℃ through compressor 1, precooler 2 and desulfurization tower 3, and then the gas and liquid are separated to remove a large amount of water and hydrogen sulfide (H2S).

[0027] The working process of the cryogenic distillation system is as follows: the pretreated gas enters the recooler 6 to be cooled to about -9°C, and then enters the middle and lower part of the first distillation tower 4 through the V1 valve pipeline for distillation. The first distillation tower 4 discharges trace components such as butane and isobutane with high boiling points from the bottom, and enters the waste liquid recovery tank 13 for storage through the V8 valve pipeline. The gas coming out of the top of the first distillation tower 4 is divided into two paths, one of which enters the middle part of the second distillation tower 5 through the V2 valve pipeline to participate in distillation, and the other enters the top condenser 10. The part condensed by the top condenser 10 enters the gas-liquid separator 12, and the gas phase coming out of the gas-liquid separator Part (methane-rich gas) enters the methane purification system through the V5 valve pipeline, and the liquid phase is divided into two paths. One path refluxes through the V3 valve pipeline into the first distillation tower 4 to participate in distillation, and the other path refluxes through the V4 valve pipeline into the second distillation tower 5 to participate in distillation. The gas coming out of the top of the second distillation tower 5 first enters the top condenser 10, and then is discharged through the V7 valve pipeline. What comes out of the second distillation tower 5 is liquid carbon dioxide with a purity of more than 99.995%. The liquid carbon dioxide enters the top condenser 10, is supercooled to -25°C, and then throttled to 1.8MPa and enters the carbon dioxide storage tank 11 for storage through the V6 valve pipeline.

[0028] The working process of the refrigeration system is: the gaseous ammonia passes through the ammonia compressor 7 and enters the cold box and is divided into two paths. One path enters the first reboiler 8 of the first distillation tower 4 through the V9 valve pipeline to provide a heat source for the bottom of the first distillation tower 4, and the other path enters the second reboiler 9 of the second distillation tower 5 through the V10 valve pipeline to provide a heat source for the bottom of the second distillation tower 5. After coming out of the first reboiler 8 and the second reboiler 9, the ammonia gas is condensed into liquid, and enters the top condenser 10 after the pressure is reduced by the V12 valve pipeline. After the liquid ammonia releases the cold energy, it evaporates into gas and is discharged from the top outlet of the top condenser, enters the recooler 6 to recover energy, and then exits the cold box and returns to the ammonia compressor 7, and a refrigeration cycle ends.

[0029] The working process of the methane purification system is: the methane-rich gas coming out of the gas-liquid separator 12 enters the third distillation tower 14 through the V5 valve pipeline for distillation, cooperates with the condenser 15 and liquid nitrogen storage tank 16 above, the third reboiler 18 below, and the nitrogen compressor 17 and vaporizer 19 connected to the third reboiler 18 outside the cold box, and the methane liquid enters the methane storage tank 20 for storage through the bottom pipeline, and the participating part is discharged through the top pipeline of the third distillation tower 14.

[0030] In addition, in an embodiment of the present invention, a valve is provided on the pipeline connecting various devices in the process equipment, and the valve may be a regulating valve.

[0031] The above description is only a specific embodiment of the present invention, but the structural features of the present invention are not limited thereto. The present invention can be used on similar products. Any changes or modifications made by any technician in the field of the present invention are covered by the patent scope of the present invention.

Claims

1. Process equipment for extracting high-purity carbon dioxide from landfill gas, biogas or chemical tail gas, including a pretreatment system, a cryogenic distillation system and a refrigeration system, characterized in that: The pretreatment system comprises a raw material compressor (1), a precooler (2) and a desulfurization tower (3) in sequence; the low-temperature distillation system comprises a first distillation tower (4), a second distillation tower (5), a carbon dioxide storage tank (11) and a gas-liquid separator (12); the refrigeration system comprises an ammonia compressor (7), a first reboiler (8) and a second reboiler (9) connected in parallel, a top condenser (10) and a recooler (6) in sequence, wherein the first reboiler (8) and the second reboiler (9) are respectively located at the lower part of the first distillation tower (4) and the second distillation tower (5); the raw material gas is treated by the pretreatment system and then enters the recooler (6), and then enters the first distillation tower (4) through the V1 valve pipeline, and the gas coming out of the top of the first distillation tower (4) is divided into two paths, one of which enters through the V2 valve pipeline The second distillation tower (5) has one path entering the top condenser (10), and then entering the gas-liquid separator (12) after passing through the top condenser (10). The liquid phase part coming out of the gas-liquid separator (12) is divided into two paths, one path entering the first distillation tower (4) through the V3 valve pipeline, and the other path entering the second distillation tower (5) through the V4 valve pipeline. The high-purity liquid carbon dioxide coming out of the second distillation tower (5) first enters the top condenser (10), and then enters the carbon dioxide storage tank (11) through the V6 valve pipeline; and also includes a methane purification system, and the gas phase coming out of the gas-liquid separator (12) enters the methane purification system through the V5 valve pipeline; the gas coming out of the top of the second distillation tower (5) first enters the top condenser (10), and then is discharged through the V7 valve pipeline; The methane purification system comprises a third distillation tower (14), wherein a condenser (15) and a liquid nitrogen storage tank (16) connected thereto are arranged above the third distillation tower (14), a third reboiler (18) and a nitrogen compressor (17) and a vaporizer (19) connected thereto are arranged below the third distillation tower (14), and a pipeline connected to a methane storage tank (20) is arranged at the bottom of the third distillation tower (14).

2. 根据权利要求1所述的垃圾填埋气、沼气或化工尾气提取高纯二氧化碳 The process equipment is characterized by: A V8 valve pipeline is provided at the bottom of the first distillation tower (4), and the V8 valve pipeline is connected to the waste liquid recovery storage tank (13).

3. 根据权利要求2所述的垃圾填埋气、沼气或化工尾气提取高纯二氧化碳 The process equipment is characterized by: A pipeline is provided at the top of the third distillation tower (14) for venting.

4. 根据权利要求2所述的垃圾填埋气、沼气或化工尾气提取高纯二氧化碳 The process equipment is characterized by: The first distillation tower (4), the second distillation tower (5), the gas-liquid separator (12), the first reboiler (8), the second reboiler (9), the top condenser (10) and the recooler (6) are located in a cold box.

5. 根据权利要求3所述的垃圾填埋气、沼气或化工尾气提取高纯二氧化碳 The process equipment is characterized by: The third distillation tower (14), the condenser (15), the liquid nitrogen storage tank (16) and the third reboiler (18) are located in a cold box.

6. 根据权利要求1-5任一项所述的垃圾填埋气、沼气或化工尾气提取高纯 Carbon dioxide process equipment, characterized in that: Valves are provided on the pipelines connecting the various devices in the equipment, and the valves are regulating valves.

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