CN111238165A - Carbon dioxide rectification device and rectification method based on tail gas cold energy utilization - Google Patents
Carbon dioxide rectification device and rectification method based on tail gas cold energy utilization Download PDFInfo
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- CN111238165A CN111238165A CN202010166960.0A CN202010166960A CN111238165A CN 111238165 A CN111238165 A CN 111238165A CN 202010166960 A CN202010166960 A CN 202010166960A CN 111238165 A CN111238165 A CN 111238165A
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- CURLTUGMZLYLDI-UHFFFAOYSA-N Carbon dioxide Chemical compound O=C=O CURLTUGMZLYLDI-UHFFFAOYSA-N 0.000 title claims abstract description 90
- 229910002092 carbon dioxide Inorganic materials 0.000 title claims abstract description 46
- 239000001569 carbon dioxide Substances 0.000 title claims abstract description 45
- 238000000034 method Methods 0.000 title claims abstract description 22
- 239000007788 liquid Substances 0.000 claims abstract description 86
- 239000002994 raw material Substances 0.000 claims abstract description 63
- 238000009833 condensation Methods 0.000 claims abstract description 20
- 230000005494 condensation Effects 0.000 claims abstract description 20
- 239000007789 gas Substances 0.000 claims description 230
- 239000007791 liquid phase Substances 0.000 claims description 26
- 239000012071 phase Substances 0.000 claims description 23
- 239000000112 cooling gas Substances 0.000 claims description 12
- 238000001816 cooling Methods 0.000 claims description 9
- 238000000926 separation method Methods 0.000 claims description 7
- 238000005265 energy consumption Methods 0.000 abstract description 8
- 239000000463 material Substances 0.000 abstract description 4
- 238000004821 distillation Methods 0.000 abstract description 2
- 230000008569 process Effects 0.000 description 8
- UHOVQNZJYSORNB-UHFFFAOYSA-N Benzene Chemical compound C1=CC=CC=C1 UHOVQNZJYSORNB-UHFFFAOYSA-N 0.000 description 6
- OKKJLVBELUTLKV-UHFFFAOYSA-N Methanol Chemical compound OC OKKJLVBELUTLKV-UHFFFAOYSA-N 0.000 description 6
- JJWKPURADFRFRB-UHFFFAOYSA-N carbonyl sulfide Chemical compound O=C=S JJWKPURADFRFRB-UHFFFAOYSA-N 0.000 description 4
- 238000000746 purification Methods 0.000 description 4
- CDBYLPFSWZWCQE-UHFFFAOYSA-L Sodium Carbonate Chemical compound [Na+].[Na+].[O-]C([O-])=O CDBYLPFSWZWCQE-UHFFFAOYSA-L 0.000 description 3
- 230000007547 defect Effects 0.000 description 3
- 238000012546 transfer Methods 0.000 description 3
- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 description 3
- RWSOTUBLDIXVET-UHFFFAOYSA-N Dihydrogen sulfide Chemical compound S RWSOTUBLDIXVET-UHFFFAOYSA-N 0.000 description 2
- 238000009825 accumulation Methods 0.000 description 2
- 230000001174 ascending effect Effects 0.000 description 2
- 238000007710 freezing Methods 0.000 description 2
- 230000008014 freezing Effects 0.000 description 2
- 229910000037 hydrogen sulfide Inorganic materials 0.000 description 2
- 230000009467 reduction Effects 0.000 description 2
- OKTJSMMVPCPJKN-UHFFFAOYSA-N Carbon Chemical compound [C] OKTJSMMVPCPJKN-UHFFFAOYSA-N 0.000 description 1
- WSFSSNUMVMOOMR-UHFFFAOYSA-N Formaldehyde Chemical compound O=C WSFSSNUMVMOOMR-UHFFFAOYSA-N 0.000 description 1
- XSQUKJJJFZCRTK-UHFFFAOYSA-N Urea Chemical compound NC(N)=O XSQUKJJJFZCRTK-UHFFFAOYSA-N 0.000 description 1
- 238000013475 authorization Methods 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 239000004202 carbamide Substances 0.000 description 1
- 229910052799 carbon Inorganic materials 0.000 description 1
- 230000006837 decompression Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 238000009776 industrial production Methods 0.000 description 1
- 239000002440 industrial waste Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 239000003507 refrigerant Substances 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 229910000029 sodium carbonate Inorganic materials 0.000 description 1
- 235000017550 sodium carbonate Nutrition 0.000 description 1
- 238000003860 storage Methods 0.000 description 1
- 238000012360 testing method Methods 0.000 description 1
- 239000002912 waste gas Substances 0.000 description 1
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F25—REFRIGERATION OR COOLING; COMBINED HEATING AND REFRIGERATION SYSTEMS; HEAT PUMP SYSTEMS; MANUFACTURE OR STORAGE OF ICE; LIQUEFACTION SOLIDIFICATION OF GASES
- F25J—LIQUEFACTION, SOLIDIFICATION OR SEPARATION OF GASES OR GASEOUS OR LIQUEFIED GASEOUS MIXTURES BY PRESSURE AND COLD TREATMENT OR BY BRINGING THEM INTO THE SUPERCRITICAL STATE
- F25J3/00—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification
- F25J3/02—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream
- F25J3/0228—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream
- F25J3/0266—Processes or apparatus for separating the constituents of gaseous or liquefied gaseous mixtures involving the use of liquefaction or solidification by rectification, i.e. by continuous interchange of heat and material between a vapour stream and a liquid stream characterised by the separated product stream separation of carbon dioxide
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02C—CAPTURE, STORAGE, SEQUESTRATION OR DISPOSAL OF GREENHOUSE GASES [GHG]
- Y02C20/00—Capture or disposal of greenhouse gases
- Y02C20/40—Capture or disposal of greenhouse gases of CO2
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- Engineering & Computer Science (AREA)
- Chemical & Material Sciences (AREA)
- Chemical Kinetics & Catalysis (AREA)
- Physics & Mathematics (AREA)
- Mechanical Engineering (AREA)
- Thermal Sciences (AREA)
- General Engineering & Computer Science (AREA)
- Separation By Low-Temperature Treatments (AREA)
Abstract
The invention discloses a carbon dioxide rectifying device and a rectifying method based on tail gas cold energy utilization, and belongs to the technical field of carbon dioxide distillation.A raw material gas enters a first rectifying tower after passing through a raw material gas compressor to remove components heavier than carbon dioxide, and the rest components come out from the top of the tower; the tail gas separated by the second gas-liquid separator exchanges heat with the low condensation point gas discharged from the top of the first rectifying tower through the second condenser to provide cold energy, the temperature of the tail gas after heat exchange is reduced to-40 to-48 ℃, the tail gas then cools the raw material gas through the gas inlet heat exchanger, and the temperature of the raw material gas is reduced to 20 to 24 ℃. The cold energy cools the system material twice, reduces energy consumption, and simultaneously cools the raw material gas, so that more raw material gas enters the raw material gas compressor, and the system yield is increased.
Description
Technical Field
The invention belongs to the technical field of carbon dioxide distillation, and particularly relates to a carbon dioxide rectifying device and a rectifying method based on tail gas cold energy utilization.
Background
Liquid carbon dioxide is a refrigerant, can be used for preserving food, can also be used for artificial rainfall, is an industrial raw material, and can be used for preparing soda ash, urea and soda water.
At present, the industrial production of carbon dioxide mainly utilizes industrial carbon-containing waste gas (CO)2Content > 80%) of CO in industrial waste gas2In addition, it may contain a large amount of N having a very low freezing point2、O2、H2CO, etc. In the process of rectifying and purifying carbon dioxide, raw gas is separated by a low-temperature rectifying system, and the gas with very low condensation point can not be condensed into liquid all the time and is finally directly discharged after the pressure is reduced to the normal pressure from the top of a rectifying tower.
Authorization notice number: CN104654739A discloses a device and a method for preparing food-grade liquid carbon dioxide by using double-tower rectification purification, and specifically discloses: the device comprises an inlet of a gas inlet buffer tank and an inlet of a feed gas three-stage compressor, wherein an outlet of the feed gas four-stage compressor is connected with a feed gas inlet at the middle lower part of a first rectifying tower through a first reboiler, a liquid phase outlet at the bottom of the first rectifying tower is connected with a collector, a gas phase outlet at the top of the first rectifying tower is connected with a gas phase inlet of a tower top condenser, a liquid phase outlet of the tower top condenser is connected with a liquid phase inlet at the upper part of the first rectifying tower, a first tee joint is arranged on a pipeline between the liquid phase outlet of the tower top condenser and the liquid phase inlet at the upper part of the first rectifying tower, and a third end of the first tee joint is connected with a; a liquid phase outlet at the bottom of the second rectifying tower is connected with a liquid inlet of the first heat exchanger through a pipeline, and a liquid outlet of the first heat exchanger is connected with a carbon dioxide storage tank; has the advantages of simple process flow, simple and convenient operation, stable operation and low energy consumption.
The above patent has a drawback in that the low freezing point gas becomes an ultra-low temperature gas after being decompressed in the above process, and the cold energy is not fully utilized.
Disclosure of Invention
The invention aims to: the carbon dioxide rectifying device and the rectifying method based on tail gas cold energy utilization are provided to solve the defect that in the existing process of preparing food-grade liquid carbon dioxide by double-tower rectification and purification, cold energy is not fully utilized, and energy consumption and high yield are low.
The technical scheme adopted by the invention is as follows:
the carbon dioxide rectifying device based on tail gas cold energy utilization comprises a gas inlet heat exchanger, wherein an outlet of the gas inlet heat exchanger is connected with an inlet of a raw gas compressor through a pipeline, an outlet of the raw gas compressor is connected with a raw gas inlet at the middle lower part of a first rectifying tower, a gas-phase outlet at the top of the first rectifying tower is connected with a gas-phase inlet of a first condenser, a gas-liquid mixed phase outlet of the first condenser is connected with a gas inlet of a first gas-liquid separator through a pipeline, a liquid-phase outlet of the first gas-liquid separator is connected with a liquid-phase inlet at the upper part of the first rectifying tower, a gas-phase outlet of the first gas-liquid separator is connected with a gas-phase inlet of a second condenser, a gas-liquid mixed phase outlet of a second cooling condenser is connected with a gas inlet of a second gas-liquid separator through a pipeline; the gas phase outlet of the second gas-liquid separator is connected with the cooling gas inlet of the second condenser through a pipeline, the cooling gas outlet of the second condenser is connected with the cooling gas inlet of the gas inlet heat exchanger, and the gas inlet heat exchanger is further provided with a cooling gas outlet.
In the technical scheme of the application, a raw gas enters a raw gas compressor after being subjected to heat exchange by a gas inlet heat exchanger to become compressed gas, the compressed gas enters a raw gas inlet at the middle lower part of a first rectifying tower through a pipeline, a first reboiler is arranged in the first rectifying tower, condensed liquid and ascending gas transfer heat and mass transfer heat, the condensed liquid finally falls into a first tower kettle, the first reboiler in the first tower kettle heats the liquid, a part of the liquid is changed into gas and then flows upwards, a part of the liquid flows out, gas discharged from the top of the first rectifying tower enters a first gas-liquid separator after passing through a first condenser, liquid discharged from a liquid phase port of the first gas-liquid separator enters a liquid phase inlet at the upper part of the first rectifying tower, gas discharged from the first gas-liquid separator and gas with a low condensation point discharged from the top of a second rectifying tower enter a second gas-liquid separator after passing through a second condenser, and separated liquid enters a liquid phase inlet at the upper part of the second, the working principle of a second reboiler in the second rectifying tower is the same as that of a first reboiler in the first rectifying tower; and the tail gas separated by the second gas-liquid separator exchanges heat with the low condensation point gas discharged from the top of the first rectifying tower through the second condenser to provide cold energy, the temperature of the tail gas after heat exchange is reduced to-40 to-48 ℃, the tail gas is cooled for the raw material gas through the gas inlet heat exchanger, the temperature of the raw material gas is reduced to 20 to 24 ℃, and then the tail gas is discharged. The cold energy of the discharged tail gas is cooled for the system material twice, the cold energy is fully and scientifically utilized, the energy consumption of the system is reduced, and meanwhile, the temperature of the raw material gas is reduced, so that more raw material gas enters the carbon dioxide compressor, the system yield is increased, and the defects of insufficient utilization of the cold energy and low energy consumption and high yield in the existing process of preparing food-grade liquid carbon dioxide by using double-tower rectification and purification are overcome.
In the technical scheme of this application, be provided with the governing valve on the tail gas pipeline that comes out from second vapour and liquid separator, the purpose is control system pressure, and tail gas has become and has just reduced pressure automatically because of the pipe diameter when getting into the second condenser in addition.
Preferably, the bottom of the first rectifying tower is provided with a liquid phase outlet connected with the first collector. The first collector is convenient for collecting components heavier than carbon dioxide, such as water, carbonyl sulfide, benzene, methanol, hydrogen sulfide and the like, which come out from the bottom of the first rectifying tower.
Preferably, the second rectifying column is connected to the subcooler through a pipe. And the liquid carbon dioxide coming out of the second rectifying tower is cooled by a cooler to form collectable liquid carbon dioxide.
More preferably, a second collector is arranged at one side of the subcooler, and the subcooler is connected with the second collector through a pipeline. The collected carbon dioxide by the second collector meets the national standard GB 10621-2006 food-grade carbon dioxide industry standard.
A rectification method of a carbon dioxide rectification device based on tail gas cold energy utilization comprises the following steps:
(1) raw material gas enters a raw material gas compressor after passing through a gas inlet heat exchanger, the raw material gas is changed into 2.3-2.5 MPa compressed gas by the raw material gas compressor, then double-rectification separation is carried out, high-purity liquid carbon dioxide is obtained from the bottom of a second rectifying tower, gas with a low condensation point and a temperature of-15 to-20 ℃ is discharged from the top of the second rectifying tower, gas discharged from a first gas-liquid separator and gas with a low condensation point and discharged from the top of the second rectifying tower enter a second gas-liquid separator after passing through a second condenser, the temperature of tail gas discharged from the second gas-liquid separator is reduced to-63 to-68 ℃ after pressure reduction, and the separated liquid enters a liquid phase inlet at the upper part of the second rectifying tower;
(2) and tail gas discharged after separation by the second gas-liquid separator exchanges heat with low condensation point gas discharged from the top of the first rectifying tower through the second condenser to provide cold energy, the temperature of the tail gas after heat exchange is reduced to-40 to-48 ℃, the tail gas then cools the raw material gas through the gas inlet heat exchanger, and the temperature of the raw material gas is reduced to 20-24 ℃.
Preferably, the pressure at the inlet of the raw material gas compressor in the step (1) is 18-22 KPa, and the temperature is 10-35 ℃.
Preferably, the pressure at the inlet to the feed gas compressor in step (1) is 20KPa and the temperature is 23 ℃.
More preferably, in the step (1), the raw gas is changed into the compressed gas of 2.45MPa by the raw gas compressor, and the gas with the low condensation point and the temperature of-68 ℃ is discharged from the top of the second rectifying tower.
More preferably, the temperature of the tail gas after heat exchange in the step (2) is reduced to-45 ℃, and then the tail gas is used for cooling the raw material gas through the gas inlet heat exchanger, so that the temperature of the raw material gas is reduced to 23 ℃.
In summary, due to the adoption of the technical scheme, the invention has the beneficial effects that:
1. according to the invention, the cold energy of the discharged tail gas is used for cooling the system materials twice, namely the tail gas separated by the second gas-liquid separator is used for exchanging heat with the low condensation point gas discharged from the top of the first rectifying tower through the second condenser to provide cold energy, the temperature of the tail gas after heat exchange is reduced to-40 to-48 ℃, the tail gas is used for cooling the raw material gas through the gas inlet heat exchanger, the temperature of the raw material gas is reduced to 20-24 ℃, the cooling capacity of the system is reduced, and energy is saved and the consumption is reduced;
2. the cold energy of the system is fully utilized, the energy consumption of the system is reduced, and the investment cost is reduced;
3. the temperature of the raw material gas is reduced, so that more raw material gas enters a raw material gas compressor, and the system yield is increased;
4. the raw material gas compressor can process 583m of raw material gas at 20KPa per hour3The final yield of the raw material gas can be increased by 0.167 tons per hour, the yield is improved by 2.4 percent, the daily accumulation and the monthly accumulation are realized, the increased yield is immeasurable, the time is money, and the efficiency is the technical effect of life;
5. the prepared liquid carbon dioxide meets the industrial standard of food-grade carbon dioxide of national standard GB 10621-2006.
Drawings
FIG. 1 is a schematic structural diagram of a carbon dioxide rectification device and a rectification method based on tail gas cold energy utilization.
The labels in the figure are: 1-a gas inlet heat exchanger, 2-a raw gas compressor, 3-a first rectifying tower, 4-a first reboiler, 5-a first condenser, 6-a first gas-liquid separator, 7-a first collector, 8-a second rectifying tower, 9-a second reboiler, 10-a second condenser, 11-a second gas-liquid separator, 12-a subcooler, 13-a second collector and 14-a regulating valve.
Detailed Description
In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.
Example 1
Referring to fig. 1, the carbon dioxide rectification device based on tail gas cold energy utilization comprises an inlet gas heat exchanger 1, an outlet of the gas inlet heat exchanger 1 is connected with an inlet of a raw gas compressor 2 through a pipeline, an outlet of the raw gas compressor 2 is connected with a raw gas inlet at the middle lower part of a first rectifying tower 3, a gas-phase outlet at the top of the first rectifying tower 3 is connected with a gas-phase inlet of a first condenser 5, a gas-liquid mixed phase outlet of the first condenser 5 is connected with a gas inlet of a first gas-liquid separator 6 through a pipeline, a liquid-phase outlet of the first gas-liquid separator 6 is connected with a liquid-phase inlet at the upper part of the first rectifying tower 3, a gas-phase outlet of the first gas-liquid separator 6 is connected with a gas-phase inlet of a second condenser 10, a gas-liquid mixed phase outlet of a second condenser is connected with a gas inlet of a second gas-liquid separator 11 through a pipeline, and a liquid-phase outlet; the gas phase outlet of the second gas-liquid separator 11 is connected with the cooling gas inlet of the second condenser 10 through a pipeline, the cooling gas outlet of the second condenser 10 is connected with the cooling gas inlet of the gas inlet heat exchanger 1, and the gas inlet heat exchanger 1 is further provided with a cooling gas outlet.
In the technical scheme of the application, a raw gas enters a raw gas compressor 2 after being subjected to heat exchange by an air inlet heat exchanger 1 to become a compressed gas, the compressed gas enters a raw gas inlet at the middle lower part of a first rectifying tower 3 through a pipeline, a first reboiler 4 is arranged in the first rectifying tower 3, condensed liquid and ascending gas transfer heat, the condensed liquid finally falls into a first tower kettle, the first reboiler 4 in the first tower kettle heats the liquid, a part of the liquid is changed into gas and then flows upwards, a part of the liquid flows out, gas discharged from the top of the first rectifying tower 3 enters a first gas-liquid separator 6 through a first condenser 5, liquid discharged from a liquid phase port of the first gas-liquid separator 6 enters a liquid phase inlet at the upper part of the first rectifying tower 3, gas discharged from the first gas-liquid separator 6 and gas discharged from the top of a second rectifying tower 8 at a low condensation point enter a second condenser 10 and then enter a second gas-liquid separator 11, the separated liquid enters a liquid phase inlet at the upper part of a second rectifying tower 8, and a second reboiler 9 in the second rectifying tower 8 has the same working principle with the first reboiler 4 in the first rectifying tower 3; the tail gas separated by the second gas-liquid separator 11 exchanges heat with the low condensation point gas discharged from the top of the first rectifying tower 3 through the second condenser 10 to provide cold energy, the temperature of the tail gas after heat exchange is reduced to-40 to-48 ℃, the tail gas is cooled for the raw material gas through the gas inlet heat exchanger 1, the temperature of the raw material gas is reduced to 20 to 24 ℃, and then the tail gas is discharged. The cold energy of the discharged tail gas is cooled for the system material twice, the cold energy is fully and scientifically utilized, the energy consumption of the system is reduced, and meanwhile, the temperature of the raw material gas is reduced, so that more raw material gas enters the carbon dioxide compressor, the system yield is increased, and the defects of insufficient utilization of the cold energy and low energy consumption and high yield in the existing process of preparing food-grade liquid carbon dioxide by using double-tower rectification and purification are overcome.
In the technical scheme of this application, be provided with governing valve 14 on the tail gas pipeline that comes out from second vapour and liquid separator 11, the purpose is control system pressure, and tail gas has become just automatic decompression because of the pipe diameter when getting into second condenser 10 in addition.
Example 2
Referring to fig. 1, in addition to embodiment 1, the bottom of the first rectifying tower 3 is provided with a liquid phase outlet connected with a first collector 7.
The first collector 7 is convenient for collecting components heavier than carbon dioxide, such as water, carbonyl sulfide, benzene, methanol, hydrogen sulfide, etc., which come out from the bottom of the first rectifying tower 3.
Example 3
Referring to fig. 1, in example 1, a second rectifying column 8 is connected to a subcooler 12 through a pipe.
The liquid carbon dioxide coming out of the second rectifying tower 8 is cooled by a cooler 12 to form collectable liquid carbon dioxide.
Example 4
As shown in fig. 1, in the embodiment 3, a second collector 13 is provided at one side of the supercooler 12, and the supercooler 12 is connected to the second collector 13 through a pipe.
The collected carbon dioxide by the second collector 13 meets the standards of the national standard GB 10621-2006 food grade carbon dioxide industry.
Example 5
Referring to fig. 1, a rectification method of a carbon dioxide rectification device based on tail gas cold energy utilization comprises the following steps:
(1) raw material gas enters a raw material gas compressor 2 after passing through a gas inlet heat exchanger 1, the raw material gas is changed into 2.3MPa compressed gas through the raw material gas compressor 2, then double-rectification separation is carried out, high-purity liquid carbon dioxide is obtained from the bottom of a second rectifying tower 8, gas with a low condensation point and a temperature of minus 20 ℃ is discharged from the top of the second rectifying tower 8, gas discharged from a first gas-liquid separator 6 and gas with a low condensation point and discharged from the top of the second rectifying tower 8 enter a second gas-liquid separator 11 after passing through a second condenser 10, the temperature of tail gas discharged from the second gas-liquid separator 11 is reduced to minus 63 ℃ after pressure reduction, the separated liquid enters a liquid phase inlet at the upper part of the second rectifying tower 8, the pressure of an inlet of the raw material gas compressor 2 is 18KPa, and the temperature is 35 ℃;
(2) the tail gas discharged after separation by the second gas-liquid separator 11 exchanges heat with the gas with a low condensation point discharged from the top of the first rectifying tower 3 through the second condenser 10 to provide cold energy, the temperature of the tail gas after heat exchange is reduced to-40 ℃, the tail gas then reduces the temperature of the raw material gas through the gas inlet heat exchanger 1, and the temperature of the raw material gas is reduced to 20 ℃.
Example 6
As shown in fig. 1, on the basis of example 5, (1) the compressed gas is changed into 2.45MPa by the raw gas compressor 2, the gas with a low condensation point and a temperature of-17 ℃ is discharged from the top of the second rectifying tower 8, the pressure at the inlet of the raw gas compressor 2 is 20KPa, the temperature is 23 ℃, and the temperature of the tail gas discharged from the second gas-liquid separator 11 is reduced to-65 ℃ after being decompressed; (2) the temperature of the tail gas after heat exchange is reduced to-45 ℃, the tail gas is used for cooling the raw material gas through the gas inlet heat exchanger 1, the temperature of the raw material gas is reduced to 23 ℃, and the rest steps are the same as those in the embodiment 5.
Example 7
As shown in fig. 1, on the basis of example 5, (1) the compressed gas is changed into 2.5MPa by the raw gas compressor 2, the gas with low condensation point and temperature of-15 ℃ is discharged from the top of the second rectifying tower 8, the pressure at the inlet of the raw gas compressor 2 is 22KPa, the temperature is 10 ℃, and the temperature of the tail gas discharged from the second gas-liquid separator 11 is reduced to-68 ℃ after being decompressed; (2) the temperature of the tail gas after heat exchange is reduced to-48 ℃, the tail gas is used for cooling the raw material gas through the gas inlet heat exchanger 1, the temperature of the raw material gas is reduced to 24 ℃, and the rest steps are the same as those in the embodiment 5.
Test examples
Taking the example of a double-tower rectification separation process producing 7 tons of liquid carbon dioxide per hour as a raw material gas CO2The purity is 88.3 percent, the purity of N2 is 11.2 percent, and the rest is trace components. The inlet pressure of the raw material gas is 20KPa, the temperature is 30 ℃, the raw material gas is changed into 2.45MPa compressed gas by the raw material gas compressor 2, then the compressed gas is separated by a double rectifying tower, the temperature of the tail gas discharged from the second gas-liquid separator 11 is reduced to minus 68 ℃ after the pressure is reduced, and the gas content of the tail gas is 665Nm3And the second condenser 10 at the top of the second rectifying tower 8 is used for exchanging heat for the tower top gas from the first rectifying tower 3, so that 7.5KW of cold energy can be provided, and the temperature of the tail gas is reduced to-45 ℃ after heat exchange. The tail gas passes through the gas inlet heat exchanger 1 to cool the raw material gas, and finally the raw material gas with the temperature of 30 ℃ can be cooled to 23 ℃. Thus, the raw material gas compressor 2 can process 583m of raw material gas at 20KPa per hour3The final yield of the raw material gas can be increased by 0.167 tons per hour, which is improved by 2.4 percent.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.
Claims (9)
1. Carbon dioxide rectifier unit based on tail gas cold energy utilization, its characterized in that: the device comprises a gas inlet heat exchanger (1), wherein an outlet of the gas inlet heat exchanger (1) is connected with an inlet of a raw material gas compressor (2) through a pipeline, an outlet of the raw material gas compressor (2) is connected with a raw material gas inlet at the middle lower part of a first rectifying tower (3), a gas-phase outlet at the top of the first rectifying tower (3) is connected with a gas-phase inlet of a first condenser (5), a gas-liquid mixed phase outlet of the first condenser (5) is connected with a gas inlet of a first gas-liquid separator (6) through a pipeline, a liquid-phase outlet of the first gas-liquid separator (6) is connected with a liquid-phase inlet at the upper part of the first rectifying tower (3), a gas-phase outlet of the first gas-liquid separator (6) is connected with a gas-phase inlet of a second condenser (10), a gas-liquid mixed phase outlet of the second cooling condenser is connected with a gas inlet of a second gas-liquid separator (11) through a pipeline, and a liquid-phase outlet; the gas phase outlet of the second gas-liquid separator (11) is connected with the cooling gas inlet of the second condenser (10) through a pipeline, the cooling gas outlet of the second condenser (10) is connected with the cooling gas inlet of the gas inlet heat exchanger (1), and the gas inlet heat exchanger (1) is further provided with a cooling gas outlet.
2. The carbon dioxide rectification device based on tail gas cold energy utilization according to claim 1, characterized in that: the bottom of the first rectifying tower (3) is provided with a liquid phase outlet which is connected with a first collector (7).
3. The carbon dioxide rectification device based on tail gas cold energy utilization according to claim 1, characterized in that: the second rectifying tower (8) is connected with the subcooler (12) through a pipeline.
4. The carbon dioxide rectification device based on tail gas cold energy utilization according to claim 3, characterized in that: one side of the subcooler (12) is provided with a second collector (13), and the subcooler (12) is connected with the second collector (13) through a pipeline.
5. The rectification method of the carbon dioxide rectification device based on tail gas cold energy utilization according to any one of claims 1 to 4, characterized by comprising the following steps:
(1) raw material gas enters a raw material gas compressor (2) after passing through a gas inlet heat exchanger (1), the raw material gas is changed into compressed gas with the pressure of 2.3-2.5 MPa through the raw material gas compressor (2), then the compressed gas is subjected to double rectification separation, high-purity liquid carbon dioxide is obtained from the bottom of a second rectifying tower (8), gas with the low condensation point and the temperature of-15 to-20 ℃ is discharged from the top of the second rectifying tower (8), gas discharged from a first gas-liquid separator (6) and gas with the low condensation point and discharged from the top of the second rectifying tower (8) enter a second gas-liquid separator (11) after passing through a second condenser (10), the temperature of tail gas discharged from the second gas-liquid separator (11) is reduced to-63 to-68 ℃ after being decompressed, and separated liquid enters a liquid phase inlet at the upper part of the second rectifying tower (8);
(2) the tail gas discharged after separation of the second gas-liquid separator (11) exchanges heat with the low condensation point gas discharged from the top of the first rectifying tower (3) through the second condenser (10) to provide cold energy, the temperature of the tail gas after heat exchange is reduced to-40 to-48 ℃, then the tail gas cools the raw material gas through the gas inlet heat exchanger (1), and the temperature of the raw material gas is reduced to 20 to 24 ℃.
6. The rectification method according to claim 5, wherein the pressure at the inlet of the raw material gas compressor in the step (1) is 18-22 KPa, and the temperature is 10-35 ℃.
7. The rectification method according to claim 6, wherein the pressure at the inlet of the feed gas compressor in step (1) is 20KPa and the temperature is 23 ℃.
8. The rectification method according to claim 5, characterized in that the compressed gas of 2.45MPa is obtained by the raw gas compressor (2) in the step (1), and the gas with low condensation point and temperature of-68 ℃ is discharged from the top of the second rectification column (8).
9. The rectification method according to claim 5, characterized in that the temperature of the tail gas after heat exchange in the step (2) is reduced to-45 ℃, and the tail gas is subsequently used for cooling the raw gas through the gas inlet heat exchanger (1), and the temperature of the raw gas is reduced to 23 ℃.
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