Method and device for condensing and pressurizing CO2 product gas

Abstract

The invention relates to the technical field of CO2 liquefaction, in particular to a method and a device for condensing and pressurizing CO2 product gas. The method comprises the following steps: carrying out at least one stage of compression on a raw material CO2 product gas, sequentially carrying out CO2 liquefaction, gas-liquid separation and pressurization on the obtained pressurized CO2 product gas, and carrying out vaporization treatment on the obtained pressurized CO2 liquid phase to obtain a high-pressure CO2 product gas; wherein the pressure P0 of the raw material CO2 product gas is greater than or equal to-0.002 MPa (G); the pressure P of the high-pressure CO2 product gas is greater than or equal to 2MPa (G). The method comprises the following steps: performing at least one-stage compression on a raw material CO2 product gas to a certain pressure, performing CO2 liquefaction by adopting a first cold source medium matched with the liquefaction pressure, and pressurizing to obtain a high-pressure CO2 product gas meeting the requirement; the method also optimizes the heat exchange network, recovers the cold energy of the system, reduces the consumption of circulating water, reduces the operation energy consumption, and improves the CO2 utilization rate.

Description

TECHNICAL FIELD

[0001] The application relates to the technical field of CO2 liquefaction, in particular to a CO2 product gas condensing and pressurizing method and a CO2 product gas condensing and pressurizing device. BACKGROUND

[0002] The recovery and utilization of CO2 has become one of the important measures to implement energy saving and emission reduction and improve production efficiency. In a coal chemical plant, low-temperature methanol washing technology is usually used to remove H2S and CO2 in synthesis gas to provide crude hydrogen gas and fuel gas, and the byproduct CO2 product gas; the low-pressure and normal-temperature CO2 product gas obtained through the process is usually sent to a gasification device after being pressurized through multi-stage compression to serve as coal conveying carrier gas, equipment protection gas or to be used to produce urea, olefins and other chemicals, which has become a way of effective utilization of CO2. The tail gas of the tail gas washing tower of the low-temperature methanol washing unit is about 15℃, and contains saturated water, which is easy to precipitate and cause pipeline corrosion, and the cold energy is discharged and lost in the methanol washing system.

[0003] "Analysis of CO2 compressor operation problems and upgrading", discloses a common CO2 product gas pressurization process in the coal chemical industry. The CO2 product gas with a pressure of 0.02 MPaG and a temperature of 20℃ from the outside is introduced into a primary separator for gas-liquid separation, and then into a primary CO2 compressor for compression. The CO2 at the outlet of the primary compressor is cooled by a water cooler and then introduced into a secondary separator for water separation. After being pressurized by a secondary compressor, the CO2 at the outlet of the compressor is cooled by a two-stage cooler, separated from water, and then introduced into a three-stage compressor for compression. After being cooled and separated, the CO2 is introduced into a four-stage compressor for pressurization to a specified pressure and then sent out.

[0004] CN113769541A discloses a method and device for preparing CO2 product gas produced by low-temperature methanol washing into high-pressure CO2 carrier gas. On the basis of the conventional low-temperature methanol washing process CO2 product gas pressurization process, a water washing tower is added to wash off the methanol in the CO2 product gas to meet the environmental protection index requirements of methanol emission when the CO2 is finally discharged.

[0005] CN115790078A discloses a CO2 liquefaction process and a cold box. The cold box comprises, in sequence, a compression device, a purification device, a drying device, a deep cooling separation device and a CO2 refrigeration cycle system. The CO2 refrigeration cycle system comprises, in sequence, a compressor, a freon refrigerator, a reboiler and a heat exchanger. The cold box is used for liquefying CO2, including the following steps: the raw gas is sequentially passed through the compression device, the purification device, the drying device and the deep cooling separation device to obtain liquid CO2; the unliquefied CO2 is input into the CO2 refrigeration cycle system to provide cold energy for the deep cooling separation device.

[0006] In the above existing process, the low-pressure CO2 product gas needs to be separated by multiple stages, and multiple stages of pressurization. Generally, 4-5 stages of compressors and supporting water coolers are needed to cool the CO2 product gas before it is sent to the downstream unit with high pressure. In this process, the number of equipment is large, the land occupation is large, the energy consumption is relatively high, and the process is not reasonable. SUMMARY

[0007] The purpose of the present application is to overcome the above technical problems, provide a CO2 product gas condensation and pressurization method and a CO2 product gas condensation and pressurization device. The method compresses the raw material CO2 product gas to a certain pressure by at least one stage, then liquefies the CO2 by using a first cold source medium with matching liquefaction pressure, and then pressurizes to obtain high-pressure CO2 product gas meeting the requirements. The method also optimizes the heat exchange network, especially by coupling a second cold source medium (preferably the second cold source medium is the exhaust gas of the low-temperature methanol washing unit), to recover the system cold energy, reduce the consumption of circulating water, reduce the operating energy consumption, and improve the CO2 utilization rate.

[0008] To achieve the above purpose, the first aspect of the present application provides a CO2 product gas condensation and pressurization method, which comprises: compressing raw material CO2 product gas by at least one stage, and then sequentially performing CO2 liquefaction, gas-liquid separation, and pressurization on the obtained pressurized CO2 product gas, and then performing vaporization treatment on the obtained pressurized CO2 liquid phase to obtain high-pressure CO2 product gas.

[0009] Preferably, the method comprises the following steps:

[0010] Preferably, the method comprises the following steps:

[0011] (1) The raw material CO2 product gas is compressed by a first compressor to obtain a first pressurized CO2 product gas, and then the first pressurized CO2 product gas is sequentially subjected to first heat exchange and first vaporization to obtain a first cooled CO2 product gas.

[0012] (2) The first cooled CO2 product gas is compressed by a second compressor to obtain a second pressurized CO2 product gas, and then the second pressurized CO2 product gas is subjected to second vaporization to obtain a second cooled CO2 product gas.

[0013] (3) The second cooled CO2 product gas is compressed by a third compressor to obtain a third pressurized CO2 product gas, and then the third pressurized CO2 product gas is sequentially subjected to second heat exchange and third vaporization to obtain a third cooled CO2 product gas.

[0014] (4) The third cooled CO2 product gas and a first cold source medium are subjected to third heat exchange to obtain a CO2 mixed phase, and then the CO2 mixed phase is subjected to the gas-liquid separation to obtain a low-temperature non-condensable gas and a CO2 liquid phase.

[0015] The low-temperature non-condensable gas is returned and subjected to the first heat exchange; the CO2 liquid phase is subjected to the pressurization to obtain the pressurized CO2 liquid phase, which is subjected to the third vaporization to obtain a third vaporization product, which is divided into two streams and subjected to the first vaporization and the second vaporization respectively to obtain high-pressure CO2 product gas;

[0016] When the pressure P0 of the raw material CO2 product gas is less than the pressure P1 of the first pressurized CO2 product gas, the raw material CO2 product gas is subjected to the first compression; or when the pressure P0 of the raw material CO2 product gas is greater than or equal to the pressure P1 of the first pressurized CO2 product gas, the raw material CO2 product gas is subjected to the second compression; or when the pressure P0 of the raw material CO2 product gas is greater than or equal to the pressure P2 of the second pressurized CO2 product gas, the raw material CO2 product gas is subjected to the third compression.

[0017] The second aspect of the present application provides a device for condensing and pressurizing CO2 product gas, which comprises a compression unit, a liquefaction unit, a gas-liquid separation unit, a CO2 liquid phase pump and a vaporization treatment unit connected in sequence.

[0018] The compression unit is used for subjecting raw material CO2 product gas to at least one stage of compression to obtain pressurized CO2 product gas; the liquefaction unit is used for subjecting the pressurized CO2 product gas to CO2 liquefaction to obtain a CO2 mixed phase, which enters the gas-liquid separation unit and the CO2 liquid phase pump in sequence, and the pressurized CO2 liquid phase enters the vaporization treatment unit for vaporization treatment to obtain high-pressure CO2 product gas.

[0019] Preferably, the device comprises a first compressor, a first heat exchanger, a first vaporizer, a second compressor, a second vaporizer, a third compressor, a second heat exchanger, a third vaporizer, a third heat exchanger, a gas-liquid separation unit and a CO2 liquid phase pump connected in sequence.

[0020] The raw material CO2 product gas enters the first compressor for first compression to obtain first pressurized CO2 product gas, which enters the first heat exchanger and the first vaporizer in sequence to obtain first cooled CO2 product gas, the second compressor is used for subjecting the first cooled CO2 product gas to second compression to obtain second pressurized CO2 product gas, the second vaporizer is used for subjecting the second pressurized CO2 product gas to second vaporization to obtain second cooled CO2 product gas, the third compressor is used for subjecting the second cooled CO2 product gas to third compression to obtain third pressurized CO2 product gas as the pressurized CO2 product gas, the second heat exchanger and the third vaporizer are used for subjecting the third pressurized CO2 product gas to third vaporization to obtain third cooled CO2 product gas, the third heat exchanger is used for subjecting the third cooled CO2 product gas to third heat exchange with the first cooling medium to obtain a CO2 mixed phase, and the gas-liquid separation unit is used for subjecting the CO2 mixed phase to gas-liquid separation to obtain low-temperature non-condensable gas and CO2 liquid phase.

[0021] The tower top of the gas-liquid separation unit is connected with the first heat exchanger, and is used for returning the low-temperature non-condensable gas and performing the first heat exchange.

[0022] The CO2 liquid phase pump is connected with the bottom of the gas-liquid separation unit and the third vaporizer, and the third vaporizer is connected with the first vaporizer and the second vaporizer, and is used for performing the third vaporization on the pressurized CO2 liquid phase, and obtaining the third vaporization product, which is divided into a partial third vaporization product and a remaining third vaporization product, and is returned and used for performing the first vaporization and the second vaporization respectively, so as to obtain the high-pressure CO2 product gas.

[0023] Compared with the prior art, the present application has the following advantages:

[0024] (1) The technical scheme provided by the present application adopts at least one stage of compression on the low-pressure raw material CO2 product gas, pressurizes the raw material CO2 product gas to a certain pressure, performs CO2 liquefaction on the raw material CO2 product gas by using a first cold source medium matched with the liquefaction pressure, and then pressurizes the CO2 liquid phase by using a CO2 liquid phase pump, so as to obtain the high-pressure CO2 product gas meeting the needs, especially the equipment protection gas, the urea raw material gas and the conveying carrier gas. Meanwhile, the method also optimizes the heat exchange network, especially by coupling the second cold source medium (i.e. the discharge tail gas of the low-temperature methanol washing unit), recovers the system cold energy, reduces the consumption of circulating water, reduces the operation energy consumption, and improves the CO2 utilization rate.

[0025] (2) The technical scheme provided by the present application involves the compressors (e.g. the first compressor, the second compressor and the third compressor), the outlet pressure of which is relatively low, and the operation is more stable and reliable, and the failure rate is small. After the CO2 is liquefied, the volume is small, the pressurization efficiency is high, and the energy consumption is lower.

[0026] (3) The technical scheme provided by the present application can supply the second cold source medium by the ice machine unit matched with the low-temperature methanol washing unit, or optimize the cold energy of the low-temperature methanol washing unit, so as to realize more reasonable utilization of the cold energy of the low-temperature methanol washing unit. For example, the tail gas of the low-temperature methanol washing unit and the CO2 product gas are used for heat exchange to recover the system cold energy, the CO2 product gas is pre-cooled, and then the first cold source medium is used for condensation, so as to improve the temperature of the low-temperature methanol washing discharge tail gas, avoid the temperature reduction in the tail gas discharge process, avoid the condensation of water vapor, and finally avoid the pipeline corrosion.

[0027] (4) The technical scheme provided by the present application can also flexibly adjust the heat exchange load of the first vaporizer, the second vaporizer and the third vaporizer in combination with the temperature requirement of the high-pressure CO2 product gas outside the boundary.

[0028] (5) The technical scheme provided by the present application selects the gas-liquid separation unit from the gas-liquid separator internally provided with a filler layer, so as to improve the purity and flow of the high-pressure CO2 product gas. BRIEF DESCRIPTION OF DRAWINGS

[0029] Figure 1 is a schematic diagram of the device structure for condensing and pressurizing CO2 product gas provided by the present application;

[0030] Figure 2 is a schematic diagram of the device structure provided by Comparative Example 1.

[0031] Explanation of Reference Signs

[0032] V1, first separator; V2, second separator; V3, third separator; K1, first compressor; K2, second compressor; K3, third compressor; Q1, first heat exchanger; Q2, second heat exchanger; Q3, third heat exchanger; T1, first vaporizer; T2, second vaporizer; T3, third vaporizer; S, gas-liquid separator; P, CO2 liquid-phase pump; 01, packing layer;

[0033] 1, raw material CO2 product gas; 2, first separated CO2 product gas; 3, first pressurized CO2 product gas; 4, first heat-exchanged CO2 product gas; 5, first cooled CO2 product gas; 6, second separated CO2 product gas; 7, second pressurized CO2 product gas; 8, second cooled CO2 product gas; 9, third separated CO2 product gas; 10, third pressurized CO2 product gas; 11, second heat-exchanged CO2 product gas; 12, third cooled CO2 product gas; 13, CO2 mixed phase; 14, first cold source medium; 15, heat-exchanged first cold source medium; 16, CO2 liquid phase; 17, pressurized CO2 liquid phase; 18, low-temperature incondensable gas; 19, third vaporized product; 19-i, part of the third vaporized product; 19-ii, remaining part of the third vaporized product; 20, incondensable gas; 20-i, part of the incondensable gas; 20-ii, remaining part of the incondensable gas; 21, high-pressure CO2 product gas; 21-i, first vaporized product; 21-ii, second vaporized product; 22, second cold source medium; 23, heat-exchanged second cold source medium.

[0034] D001, one-stage separation tank; D002, two-stage separation tank; D003, three-stage separation tank; D004, four-stage separation tank; K001, one-stage compressor; K002, two-stage compressor; K003, three-stage compressor; K004, four-stage compressor; E001, one-stage cooler; E002, two-stage cooler; E003, three-stage cooler. DETAILED DESCRIPTION

[0035] The endpoints of the ranges and any values ​​disclosed herein are not limited to the precise ranges or values, and these ranges or values ​​should be understood to include values ​​close to these ranges or values. For numerical ranges, the endpoints of each range, the endpoints of each range and individual point values, and the individual point values ​​can be combined with each other to obtain one or more new numerical ranges, which should be considered to be specifically disclosed herein.

[0036] In the present invention, unless otherwise specified, the terms "first," "second," and "third" do not indicate a sequential order, nor do they limit the materials or steps involved. They are used only to distinguish or indicate that they are not the same material or step. For example, the terms "first," "second," and "third" in "first vaporization," "second vaporization," and "third vaporization" are used only to indicate that they are not the same vaporization; similarly, the terms "first cooled CO2 product gas," "second cooled CO2 product gas," and "third cooled CO2 product gas" are used only to indicate that they are not the same cooled CO2 product gas.

[0037] In the present invention, unless otherwise specified, the "top" of a container refers to the position 0-10% from the top of the container; the "upper" of a container refers to the position 10-40% from the top of the container; the "middle" of a container refers to the position 40-60% from the top of the container; the "lower" of a container refers to the position 60-90% from the top of the container; and the "bottom" of a container refers to the position 90-100% from the top of the container.

[0038] A first aspect of the present invention provides a method for condensing and pressurizing CO2 product gas, the method comprising: compressing the raw CO2 product gas at least one stage, sequentially performing CO2 liquefaction, gas-liquid separation, and pressurization on the obtained pressurized CO2 product gas, and vaporizing the obtained pressurized CO2 liquid phase to obtain high-pressure CO2 product gas;

[0039] Wherein, the pressure of the raw CO2 product gas P0≥-0.002MPa(G); the pressure of the high-pressure CO2 product gas P≥2MPa(G).

[0040] In the present invention, unless otherwise specified, the pressure of the raw CO2 product gas is less than the pressure of the pressurized CO2 product gas and less than the pressure of the high-pressure CO2 product gas.

[0041] In some embodiments of the present invention, preferably, the method comprises the following steps:

[0042] (1) subjecting the raw CO2 product gas to a first compression, and sequentially subjecting the obtained first pressurized CO2 product gas to a first heat exchange and a first vaporization to obtain a first cooled CO2 product gas;

[0043] (2) the first cooled CO2 product gas is subjected to second compression to obtain a second pressurized CO2 product gas, and the second pressurized CO2 product gas is subjected to second vaporization to obtain a second cooled CO2 product gas;

[0044] (3) the second cooled CO2 product gas is subjected to third compression to obtain a third pressurized CO2 product gas, and the third pressurized CO2 product gas is subjected to second heat exchange and third vaporization in sequence to obtain a third cooled CO2 product gas;

[0045] (4) the third cooled CO2 product gas is subjected to third heat exchange with a first cold source medium to obtain a CO2 mixed phase, and the CO2 mixed phase is subjected to the gas-liquid separation to obtain low-temperature non-condensable gas and a CO2 liquid phase;

[0046] wherein the low-temperature non-condensable gas is returned to the first heat exchange, and the CO2 liquid phase is subjected to the pressurization to obtain a pressurized CO2 liquid phase, and the pressurized CO2 liquid phase is subjected to the third vaporization to obtain a third vaporization product, and the third vaporization product is divided into two streams and subjected to the first vaporization and the second vaporization, respectively, to obtain a high-pressure CO2 product gas;

[0047] wherein when the pressure P0 of the raw material CO2 product gas is less than the pressure P1 of the first pressurized CO2 product gas, the raw material CO2 product gas is subjected to the first compression; or when the pressure P0 of the raw material CO2 product gas is greater than or equal to the pressure P1 of the first pressurized CO2 product gas, the raw material CO2 product gas is subjected to the second compression; or when the pressure P0 of the raw material CO2 product gas is greater than or equal to the pressure P2 of the second pressurized CO2 product gas, the raw material CO2 product gas is subjected to the third compression.

[0048] The inventor of the present application has found that in the low-temperature methanol washing process, the CO2 product gas subjected to low-pressure flash evaporation and then reheated is generally sent out at a pressure of about 0.02 MPa (G), and the critical pressure of CO2 is relatively low, being 7.2 MPa (G) and the critical temperature being 30℃. When the CO2 product gas is used as a conveying carrier gas for pulverized coal gasification, the CO2 pressure is required to be above 8 MPa (G); when the CO2 product gas is used as a raw material gas for a urea device, the CO2 raw material is required to be above 14 MPa (G); the high-pressure CO2 product gas under these working conditions all reaches a supercritical state, and the CO2 under the supercritical state is in a homogeneous phase, and the density is very large (200-800 kg / m 3 ), the efficiency of the work of the compressor is reduced, and the power consumption of the compressor is high. According to the use experience of the CO2 compressor of the urea device, the failure rate of the compressor is also relatively high.

[0049] Therefore, the application considers optimizing the inter-stage condensing system of the compressor on the basis of the traditional CO2 pressurization scheme. The traditional CO2 compressor needs to be configured with a low-pressure cylinder and a high-pressure cylinder. The application only uses a low-pressure cylinder (i.e., a third compressor) to pressurize to about 2 MPa (G); the last-stage compressor is optimized to be a CO2 liquid-phase pump; an inter-stage self-heat exchange assembly, i.e., a first heat exchanger, a first vaporizer, a second vaporizer, a second heat exchanger, a third vaporizer and a third heat exchanger, is additionally arranged between the first compressor and the third compressor, so as to reduce the inlet and outlet temperatures of the circulating water cooler, according to the temperature requirement of the external CO2 product gas, without the need of external supply of circulating water or reduction of the circulating water amount, so as to reduce the temperature at the inlet of the second compressor and the third compressor, and the volume of the gaseous CO2 is reduced, and the power consumption of the compressor is reduced. The outlet water cooler of the first compressor, the second compressor and the third compressor is cancelled, and the first vaporizer, the second vaporizer, the third vaporizer and the third heat exchanger are additionally arranged, so that the gaseous CO2 is deeply cooled to a liquid phase by the first cold source medium, pressurized to a specified pressure by the CO2 liquid-phase pump, and sent out after being heated by the vaporizer.

[0050] In the application, the number of compressions depends on the pressure of the raw CO2 product gas without special circumstances. Preferably, the number n of compressions is selected from 1, 2 and 3. That is, the raw CO2 product gas is subjected to one-stage compression, or the raw CO2 product gas is subjected to two-stage compression, or the raw CO2 product gas is subjected to three-stage compression.

[0051] In the first specific embodiment of the application, when the pressure P0 of the raw CO2 product gas is less than the pressure P1 of the first pressurized CO2 product gas, the raw CO2 product gas is subjected to three-stage compression (i.e., first compression, second compression and third compression are sequentially performed).

[0052] In the second specific embodiment of the application, when the pressure P0 of the raw CO2 product gas is greater than or equal to the pressure P1 of the first pressurized CO2 product gas, the raw CO2 product gas is subjected to two-stage compression (i.e., second compression and third compression are sequentially performed).

[0053] In the third specific embodiment of the application, when the pressure P0 of the raw CO2 product gas is greater than or equal to the pressure P2 of the second pressurized CO2 product gas, the raw CO2 product gas is subjected to one-stage compression (i.e., third compression).

[0054] In some embodiments of the application, preferably, the pressure P0 of the raw CO2 product gas is -0.002 MPa (G) to 9 MPa (G); and the pressure P of the high-pressure CO2 product gas is greater than or equal to 7.2 MPa (G).

[0055] In some embodiments of the present application, preferably, in step (1), the CO2 content of the raw CO2 product gas is ≥40 mol%, preferably ≥60 mol%, more preferably ≥90 mol%.

[0056] In the present application, the raw CO2 product gas contains water, combustible gas, etc. in addition to CO2. Further preferably, the water content of the raw CO2 product gas is ≤1%; the combustible gas content is 0.4-60 mol%, and the combustible gas is selected from at least one of H2, CO, CH4 and CH3OH.

[0057] In some embodiments of the present application, preferably, the temperature T0 of the raw CO2 product gas is -10 to 100℃, preferably -10 to 40℃.

[0058] In the present application, the source of the raw CO2 product gas has a wide range of choices as long as the above-mentioned limitations are met. Preferably, the raw CO2 product gas is selected from the low-temperature methanol washing process of a pulverized coal gasification device, the low-temperature methanol washing process of a coal slurry gasification device, or the MDEA decarburization process, or the flue gas or tail gas rich in CO2 gas from other process devices.

[0059] In the present application, the first compression aims to increase the pressure of the raw CO2 product gas. Preferably, the pressure P1 of the first pressurized CO2 product gas is ≤10 MPa(G), preferably 0.1-2.5 MPa(G); the temperature T1 is ≤180℃, preferably 90-160℃.

[0060] In the present application, by default, the pressure drop of the material before and after heat exchange is 0 MPa(G), i.e., the pressure of the first pressurized CO2 product gas is equal to that of the first heat-exchanged CO2 product gas; the pressure drop of the material before and after vaporization is not 0 MPa(G), i.e., the pressure of the first cooled CO2 product gas is lower than that of the first pressurized CO2 product gas.

[0061] In some embodiments of the present application, preferably, the temperature T1' of the first cooled CO2 product gas is ≤80℃, preferably 10-70℃.

[0062] In the present application, since the raw CO2 product gas may entrain a small amount of methanol. Preferably, before the first compression, the raw CO2 product gas is subjected to a first separation to obtain a first separated CO2 product gas.

[0063] In the present application, the second compression aims to further increase the pressure of the first cooled CO2 product gas. Preferably, in step (2), the pressure of the second pressurized CO2 product gas P2≤ 11.5 MPa (G), preferably 0.6-4 MPa (G); the temperature T2≤ 180 ℃, preferably 90-160 ℃.

[0064] In some embodiments of the present application, preferably, the temperature of the second cooled CO2 product gas (8) T2'≤ 80 ℃, preferably 10-70 ℃. In the present application, the pressure of the second cooled CO2 product gas is equal to the pressure of the second pressurized CO2 product gas unless otherwise specified.

[0065] In some embodiments of the present application, preferably, the first cooled CO2 product gas is subjected to a second separation to obtain a second separated CO2 product gas before the second compression.

[0066] In the present application, the third compression aims to further increase the pressure of the second cooled CO2 product gas. Preferably, in step (3), the pressure of the third pressurized CO2 product gas P3≤ 13 MPa (G), preferably 1.8-6.5 MPa (G); the temperature T3≤ 180 ℃, preferably 90-160 ℃.

[0067] In some embodiments of the present application, preferably, the temperature of the third cooled CO2 product gas T3'≤ 80 ℃, preferably -25 to 70 ℃.

[0068] In the present application, the pressure of the third cooled CO2 product gas is equal to the pressure of the third pressurized CO2 product gas unless otherwise specified.

[0069] In the present application, the second heat exchange aims to reduce the temperature of the third pressurized CO2 product gas. Preferably, the third pressurized CO2 product gas and a second cold source medium are subjected to the second heat exchange to obtain a second heat-exchanged CO2 product gas and a heat-exchanged second cold source medium.

[0070] In some embodiments of the present application, further preferably, the temperature of the second heat-exchanged CO2 product gas T3" is 10-60 ℃.

[0071] In the present application, further preferably, the temperature of the second cold source medium is 10-25 ℃. In the present application, the type of the second cold source medium has a wide selection range. Preferably, the second cold source medium includes, but is not limited to, tail gas from a low-temperature methanol washing unit.

[0072] In some embodiments of the present application, preferably, the second cooled CO2 product gas is subjected to a third separation to obtain a third separated CO2 product gas before the third compression is performed.

[0073] In the present application, the third heat exchange is intended to liquefy the third cooled CO2 product gas to obtain a CO2 mixed phase. Preferably, in step (3), the temperature T4 of the CO2 mixed phase is ≥-60℃, preferably -45 to 25℃. In the present application, the pressure of the CO2 mixed phase is equivalent to the pressure of the third pressurized CO2 product gas.

[0074] In the present application, the energy required for liquefying the third cooled CO2 product gas is provided by the first cold source medium. Preferably, the energy required for liquefying the third cooled CO2 product gas ≤ the energy released by the first cold source medium wherein ΔT is the temperature difference between the CO2 mixed phase and the third cooled CO2 product gas, ℃; is the flow rate of the third cooled CO2 product gas, Nm 3 / h; and ΔT' is the temperature difference of the first cold source medium before and after the third heat exchange, ℃; is the flow rate of the first cold source medium, Nm 3 / h.

[0075] In some embodiments of the present application, preferably, the temperature of the first cold source medium is -65 to 40℃, preferably -55 to -35℃; further preferably, the first cold source medium is selected from liquid phase propylene and / or liquid ammonia and the like which can supply the above-mentioned similar temperature level refrigerant.

[0076] In the present application, without special circumstances, the temperature and pressure of the low-temperature non-condensable gas are equivalent to the temperature and pressure of the CO2 liquid phase, respectively.

[0077] In the present application, the first heat exchange is intended to reduce the temperature of the first pressurized CO2 product gas. Preferably, the low-temperature non-condensable gas and the first pressurized CO2 product gas are subjected to the first heat exchange to obtain a non-condensable gas and a first heat-exchanged CO2 product gas.

[0078] In some embodiments of the present application, preferably, the pressure P' of the non-condensable gas is ≤13 MPa (G), preferably 1.8-6.5 MPa (G); and the temperature T' is 40-120℃, preferably 40-90℃.

[0079] In some embodiments of the present application, further preferably, the non-condensable gas is divided into two streams, part of the non-condensable gas is discharged as fuel gas, and the remaining part of the non-condensable gas is returned and subjected to the third compression.

[0080] In some embodiments of the present application, more preferably, the molar flow ratio of the portion of non-condensable gas and the remaining portion of non-condensable gas is 0-10:10-0, preferably 1-3:3-1. In the present application, the above-mentioned molar ratio depends on the other components in the raw CO2 product gas in addition to CO2, and the higher the other components, the higher the proportion of non-condensable gas exhaust.

[0081] In a preferred embodiment of the present application, preferably, when the combustible gas content in the non-condensable gas is ≥25 mol%, the non-condensable gas is all exhausted; when the combustible gas content in the non-condensable gas is ≤5 mol%, the non-condensable gas is all returned to the third compression; otherwise, the non-condensable gas is divided into two streams and simultaneously exhausted and thirdly compressed.

[0082] In a first specific embodiment of the present application, the low-temperature non-condensable gas and the first pressurized CO2 product gas are subjected to the first heat exchange, and the combustible gas content in the obtained non-condensable gas is ≥25 mol%, and the non-condensable gas is all exhausted as fuel gas.

[0083] In a second specific embodiment of the present application, the low-temperature non-condensable gas and the first pressurized CO2 product gas are subjected to the first heat exchange, and the combustible gas content in the obtained non-condensable gas is ≤5 mol%, and the non-condensable gas is all returned and subjected to the third compression.

[0084] In a third specific embodiment of the present application, the low-temperature non-condensable gas and the first pressurized CO2 product gas are subjected to the first heat exchange, and the combustible gas content in the obtained non-condensable gas is greater than 5 mol% and less than 25 mol%, and the non-condensable gas is divided into two streams, part of the non-condensable gas is exhausted as fuel gas, and the remaining portion of the non-condensable gas is returned and subjected to the third compression; wherein the molar flow ratio of the portion of non-condensable gas and the remaining portion of non-condensable gas is 1-3:3-1.

[0085] In some embodiments of the present application, preferably, the temperature T1” of the first heat-exchanged CO2 product gas is ≤150℃, preferably 50-130℃.

[0086] In the present application, the third vaporization converts the pressurized CO2 liquid phase into vaporization on the one hand, and the third pressurized CO2 product gas is cooled on the other hand. Preferably, the temperature T4” of the third vaporization product is -20 to 70℃, preferably 10-50℃.

[0087] In some embodiments of the present application, preferably, the first heat-exchanged CO2 product gas and part of the third vaporization product are subjected to the first vaporization to obtain the first cooled CO2 product gas and the first vaporization product.

[0088] In some embodiments of the present application, preferably, the second pressurized CO2 product gas and the remaining third vaporization product are subjected to the second vaporization to obtain a second cooled CO2 product gas and a second vaporization product.

[0089] In some embodiments of the present application, preferably, the third pressurized CO2 product gas is subjected to the second heat exchange with the tail gas from the rectisol unit and the third vaporization with the CO2 liquid phase in sequence to obtain a third cooled CO2 product gas and a third vaporization product.

[0090] In some embodiments of the present application, further preferably, the molar flow ratio of the partial third vaporization product to the remaining third vaporization product is 1-5:5-1, preferably 1-2:2-1. In the present application, the above-mentioned molar flow ratio distribution depends on the CO2 content in the raw gas, the cooling temperature of the first cold source medium and the utilization of the cooling capacity of the second cold source medium (i.e. the tail gas of the rectisol unit).

[0091] In some embodiments of the present application, further preferably, the first vaporization product and the second vaporization product are mixed to obtain the high-pressure CO2 product gas.

[0092] In some embodiments of the present application, preferably, the high-pressure CO2 product gas is used for equipment protection gas, urea raw gas, CO2 gas for oil field flooding and conveying carrier gas; further preferably, when the high-pressure CO2 product gas is used for equipment protection gas or conveying carrier gas, the pressure P of the high-pressure CO2 product gas is ≥8 MPa (G); when the high-pressure CO2 product gas is used for urea raw gas, the pressure P of the high-pressure CO2 product gas is ≥14 MPa (G).

[0093] In some embodiments of the present application, further preferably, the high-pressure CO2 product gas is subjected to desulfurization and deoiling and hydrocarbon removal drying in sequence to obtain an industrial-grade CO2 product gas or a food-grade CO2 product gas.

[0094] In some embodiments of the present application, further preferably, the first pressurized CO2 product gas, or the second pressurized CO2 product gas, or the third pressurized CO2 product gas is subjected to desulfurization and deoiling and hydrocarbon removal drying in sequence, and the CO2 mixed phase is subjected to rectification to obtain an industrial-grade CO2 product gas or a food-grade CO2 product gas.

[0095] In the present application, the industrial-grade CO2 product gas or the food-grade CO2 product gas is of higher quality without special circumstances.

[0096] The second aspect of the present application provides a device for condensing and pressurizing CO2 product gas, which comprises a compression unit, a liquefaction unit, a gas-liquid separation unit, a CO2 liquid phase pump and a vaporization treatment unit connected in sequence.

[0097] Among them, the compression unit is used to compress the raw CO2 product gas at least one stage to obtain pressurized CO2 product gas; the liquefaction unit is used to liquefy the pressurized CO2 product gas into CO2, and the obtained CO2 mixed phase enters the gas-liquid separation unit and the CO2 liquid phase pump in sequence, and the obtained pressurized CO2 liquid phase enters the vaporization treatment unit for vaporization treatment to obtain high-pressure CO2 product gas.

[0098] According to the present invention, preferably, the structural diagram of the device is as follows Figure 1 As shown by Figure 1 It can be seen that the device includes a first compressor K1, a first heat exchanger Q1, a first vaporizer T1, a second compressor K2, a second vaporizer T2, a third compressor K3, a second heat exchanger Q2, a third vaporizer T3, a third heat exchanger Q3, a gas-liquid separation unit and a CO2 liquid phase pump P connected in sequence;

[0099] Among them, the raw CO2 product gas 1 enters the first compressor K1 for the first compression, and the obtained first pressurized CO2 product gas 3 enters the first heat exchanger Q1 and the first vaporizer T1 in sequence. The obtained first cooled CO2 product gas 5 enters the second compressor K2 for the second compression, the obtained second pressurized CO2 product gas 7 enters the second vaporizer T2, and the obtained second cooled CO2 product gas 8 enters the third compressor K3 for the third compression. The obtained third pressurized CO2 product gas 10 enters the second heat exchanger Q2 and the third vaporizer T3 as the pressurized CO2 product gas in sequence. The obtained third cooled CO2 product gas 12 undergoes the third heat exchange with the first cold source medium 14 in the third heat exchanger Q3. The obtained CO2 mixed phase 13 enters the gas-liquid separation unit for gas-liquid separation to obtain low-temperature non-condensable gas 18 and CO2 liquid phase 16;

[0100] The top of the gas-liquid separation unit is connected to the first heat exchanger Q1, which is used to return the low-temperature non-condensable gas 18 and perform the first heat exchange;

[0101] Among them, the CO2 liquid phase pump P is connected to the bottom of the gas-liquid separation unit and the third vaporizer T3, and the third vaporizer T3 is connected to the first vaporizer T1 and the second vaporizer T2, and is used to pressurize the CO2 liquid phase 16 and perform the third vaporization. The obtained third vaporization product 19 is divided into a partial third vaporization product 19-i and the remaining third vaporization product 19-ii, which are returned and subjected to the first vaporization and the second vaporization respectively to obtain a high-pressure CO2 product gas 21.

[0102] According to the present invention, Figure 1As shown, preferably, the first heat exchanger Q1 is further connected with the third compressor K2, for dividing the non-condensed gas 20 obtained by the first heat exchange into two parts, part of the non-condensed gas 20-i is discharged as fuel gas, and the remaining part of the non-condensed gas 20-ii is returned and subjected to the third compression.

[0103] According to the present application, as shown in Figure 1 As shown, preferably, the device further comprises a first separator V1, for performing first separation on the raw material CO2 product gas 1 before the first compression, to obtain a first separated CO2 product gas 2.

[0104] According to the present application, as shown in Figure 1 As shown, preferably, the device further comprises a second separator V2 arranged between the first vaporizer T1 and the second compressor K2, for performing second separation on the first cooled CO2 product gas 5 before the second compression, to obtain a second separated CO2 product gas 6.

[0105] According to the present application, as shown in Figure 1 As shown, preferably, the device further comprises a third separator V3 arranged between the second vaporizer T2 and the third compressor K3, for performing third separation on the second cooled CO2 product gas 8 before the third compression, to obtain a third separated CO2 product gas 9.

[0106] According to the present application, as shown in Figure 1 As shown, preferably, the gas-liquid separation unit is selected from a gas-liquid separator S internally provided with a packing layer 01.

[0107] In one embodiment of the present application, preferably, the device further comprises a desulfurization and deoiling device and a dehydrocarbon drier connected in sequence, wherein the desulfurization and deoiling device and the dehydrocarbon drier are arranged on a pipeline connecting the first vaporizer and the second vaporizer, for sequentially performing desulfurization and deoiling and dehydrocarbon drying on the high-pressure CO2 product gas, to obtain an industrial-grade CO2 product gas or a food-grade CO2 product gas.

[0108] In another embodiment of the present application, preferably, the device further comprises a desulfurization and deoiling device and a dehydrocarbon drier connected in sequence, wherein the desulfurization and deoiling device and the dehydrocarbon drier are arranged at the outlet of the first compressor, the second compressor or the third compressor, and the gas-liquid separation unit is selected from a rectification tower, for sequentially performing desulfurization and deoiling and dehydrocarbon drying on the first pressurized CO2 product gas, the second pressurized CO2 product gas and the third pressurized CO2 product gas, and performing rectification on the CO2 liquid phase, to obtain an industrial-grade CO2 product gas or a food-grade CO2 product gas.

[0109] Some specific embodiments provided by the present application, as shown in Figure 1As shown, the raw material CO2 product gas 1 enters the first separator V1 for first separation, the obtained first separated CO2 product gas 2 enters the first compressor K1 for first compression, the obtained first pressurized CO2 product gas 3 is subjected to first heat exchange with the low-temperature non-condensable gas 18 from the gas-liquid separator S in the first heat exchanger Q1, the obtained non-condensable gas 20 and the obtained first heat-exchanged CO2 product gas 4 enter the first vaporizer T1 for first vaporization with part of the third vaporization product 19-i, the obtained first vaporization product 21-i, and the obtained first cooled CO2 product gas 5 enters the second separator V2 for second separation, the obtained second separated CO2 product gas 6 enters the second compressor K2 for second compression, the obtained second pressurized CO2 product gas 7 enters the second vaporizer T2 for second vaporization with the remaining part of the third vaporization product 19-ii, the obtained second vaporization product 21-ii, and the obtained second cooled CO2 product gas 8 enters the third separator V3 for third separation, the obtained third separated CO2 product gas 9 enters the third compressor K3 for third compression, the obtained third pressurized CO2 product gas 10 is subjected to second heat exchange with the second cold source medium 22 in the second heat exchanger Q2, the obtained second heat-exchanged CO2 product gas 11 is subjected to third vaporization with the pressurized CO2 liquid phase 17 in the third vaporizer T3, the obtained third vaporization product 19 is divided into two parts, i.e., part of the third vaporization product 19-i and the remaining part of the third vaporization product 19-ii are used in the first vaporizer T1 and the second vaporizer T2 respectively, and the obtained third cooled CO2 product gas 12 enters the third heat exchanger Q3 for third heat exchange with the first cold source medium 14, the obtained heat-exchanged first cold source medium 15, and the obtained CO2 mixed phase 13 enters the gas-liquid separator S provided with a filler layer 01 for gas-liquid separation, the obtained low-temperature non-condensable gas 18 is used in the first heat exchanger Q1, and the obtained CO2 liquid phase 16 enters the CO2 liquid phase pump P for pressurization, the obtained pressurized CO2 liquid phase 17 is used in the third vaporizer T3;

[0110] In the above method, the non-condensable gas 20 is divided into part of the non-condensable gas 20-i and the remaining part of the non-condensable gas 20-ii, which are discharged and subjected to third compression respectively, and the first vaporization product 21-i and the second vaporization product 21-ii are mixed to obtain the high-pressure CO2 product gas 21.

[0111] According to a particularly preferred embodiment of the present application, a method for condensing and pressurizing a CO2 product gas, the method comprises the following steps:

[0112] (1) sequentially subjecting a raw material CO2 product gas to first separation and first compression, and sequentially subjecting the obtained first pressurized CO2 product gas to first heat exchange and first vaporization to obtain a first cooled CO2 product gas;

[0113] (2) the first cooled CO2 product gas is sequentially subjected to second separation and second compression, the obtained second pressurized CO2 product gas is subjected to second vaporization, and a second cooled CO2 product gas is obtained;

[0114] (3) the second cooled CO2 product gas is sequentially subjected to third separation and third compression, the obtained third pressurized CO2 product gas with a pressure of 1.8-6.5 MPa (G) is sequentially subjected to second heat exchange and third vaporization, and a third cooled CO2 product gas is obtained;

[0115] (4) the third cooled CO2 product gas and a first cold source medium are subjected to third heat exchange, and the obtained CO2 mixed phase is subjected to gas-liquid separation, and a low-temperature non-condensable gas and a CO2 liquid phase are obtained;

[0116] wherein the low-temperature non-condensable gas is returned and subjected to the first heat exchange, and a non-condensable gas is obtained; the CO2 liquid phase is subjected to pressurization, and a pressurized CO2 liquid phase is obtained and subjected to the third vaporization, and the obtained third vaporization product is divided into a partial third vaporization product and a remaining third vaporization product, which are subjected to the first vaporization and the second vaporization, respectively, and a high-pressure CO2 product gas is obtained;

[0117] wherein the pressure P0 of the raw material CO2 product gas is -0.002 MPa (G) to 9.0 MPa (G), and the temperature T0 is -10 to 100℃; the pressure P of the high-pressure CO2 product gas is ≥7.2 MPa (G), and the temperature T is ≤160℃;

[0118] wherein the CO2 content in the raw material CO2 product gas is ≥40 mol%; the moisture content is ≤1%, the combustible gas content is 0.4-60 mol%, and the combustible gas is selected from at least one of H2, CO, CH4 and CH3OH;

[0119] wherein the non-condensable gas is divided into two streams, a partial non-condensable gas is discharged as fuel gas, and the remaining non-condensable gas is returned and subjected to the third compression; when the combustible gas content in the non-condensable gas is ≥25 mol%, the non-condensable gas is entirely discharged; when the combustible gas content in the non-condensable gas is ≤5 mol%, the non-condensable gas is entirely returned to the third compression; otherwise, the non-condensable gas is divided into two streams and simultaneously subjected to discharge and third compression;

[0120] wherein the high-pressure CO2 product gas is used as equipment protection gas, urea raw material gas, CO2 gas for oil field oil displacement, and conveying carrier gas.

[0121] The application will be described in detail below through examples.

[0122] Example 1

[0123] The device for condensing and pressurizing the CO2 product gas is as shown in Figure 1As shown, the device comprises: a first separator V1, a first compressor K1, a first heat exchanger Q1, a first vaporizer T1, a second separator V2, a second compressor K2, a second vaporizer T2, a third separator V3, a third compressor K3, a second heat exchanger Q2, a third vaporizer T3, a third heat exchanger Q3, a gas-liquid separator S and a CO2 liquid phase pump P connected in sequence;

[0124] The gas-liquid separator S is internally provided with a packing layer 01, and the top of the gas-liquid separator S is connected to the first heat exchanger Q1; the CO2 liquid phase pump P is connected to the bottom of the gas-liquid separator S and the third vaporizer T3, and the third vaporizer T3 is connected to the first vaporizer T1 and the second vaporizer T2; the first heat exchanger Q1 is also connected to the second compressor K2.

[0125] The method for condensing and pressurizing the CO2 product gas is carried out in the above device, and the method comprises:

[0126] (1) The raw material CO2 product gas 1 (0.03 MPa (G) of pressure P0, 20℃ of temperature T0, 99.3 mol% of CO2 content, 0.5 ppmv of moisture content, and 0.65 mol% of combustible gas content) is subjected to first separation, and the first separated CO2 product gas 2 is subjected to first compression to obtain a first pressurized CO2 product gas 3 (0.3 MPa (G) of pressure P1, 123.7℃ of temperature T1);

[0127] The first pressurized CO2 product gas 3 and the low-temperature incondensable gas 18 are subjected to first heat exchange to obtain a first heat-exchanged CO2 product gas 4 (123.5℃ of temperature T1”) and an incondensable gas 20 (1.91 MPa (G) of pressure P’, 60℃ of temperature T’, and 25.6 mol% of combustible gas content); the incondensable gas 20 is completely discharged as combustible gas;

[0128] The first heat-exchanged CO2 product gas 4 and part of the third vaporization product 19-i are subjected to first vaporization to obtain a first vaporization product 21-i and a first cooled CO2 product gas 5 (0.27 MPa (G) of pressure P1’, 37.8℃ of temperature T1’);

[0129] (2) The first cooled CO2 product gas 5 is subjected to second separation to obtain a second separated CO2 product gas 6, which is subjected to second compression to obtain a second pressurized CO2 product gas 7 (0.8 MPa (G) of pressure P2, 110.9℃ of temperature T2) and the remaining part of the third vaporization product 19-ii, which is subjected to second vaporization to obtain a second vaporization product 21-ii and a second cooled CO2 product gas 8 (0.77 MPa (G) of pressure P2’, 39℃ of temperature T2’);

[0130] (3) the third cooling CO2 product gas 12 is subjected to third heat exchange with the first heat medium 14 (propylene, temperature -40°C) to obtain a CO2 mixed phase 13 (temperature T4 -30°C), which is subjected to gas-liquid separation to obtain the low-temperature non-condensable gas 18 returned to the first heat exchange and the CO2 liquid phase 16 subjected to pressurization to obtain the pressurized CO2 liquid phase 17 (pressure P4 9.52 MPa(G), temperature T4' -25°C) returned to the third vaporization;

[0131] (4) the third cooling CO2 product gas 12 and the first heat medium 14 (propylene, temperature -40°C) are subjected to third heat exchange to obtain a CO2 mixed phase 13 (temperature T4 -30°C), which is subjected to gas-liquid separation to obtain the low-temperature non-condensable gas 18 returned to the first heat exchange and the CO2 liquid phase 16 subjected to pressurization to obtain the pressurized CO2 liquid phase 17 (pressure P4 9.52 MPa(G), temperature T4' -25°C) returned to the third vaporization;

[0132] wherein the molar flow ratio of the partial third vaporization product 19-i and the remaining partial third vaporization product 19-ii is 1:1; the first vaporization product 21-i and the second vaporization product 22-ii are mixed to obtain the high-pressure CO2 product gas 21 (pressure P 9.5 MPa(G), temperature T 60°C) as the equipment protection gas.

[0133] Example 2

[0134] The device according to Example 1;

[0135] The method is carried out in the above device, and the method comprises:

[0136] (1) the raw material CO2 product gas 1 (pressure P0 0.03 MPa(G), temperature T0 20°C, CO2 content 99.3 mol%, moisture content 0.5 ppmv, combustible gas content 0.65 mol%) is subjected to first separation to obtain the first separation CO2 product gas 2, which is subjected to first compression to obtain the first pressurized CO2 product gas 3 (pressure P1 0.3 MPa(G), temperature T1 123.7°C) ;

[0137] The first pressurized CO2 product gas 3 and the low-temperature non-condensable gas 18 are subjected to first heat exchange to obtain the first heat exchange CO2 product gas 4 (temperature T1" 123.5°C) and the non-condensable gas 20 (pressure P' 1.91 MPa(G), temperature T' 30°C, combustible gas content 25.6 mol%) ; the non-condensable gas 20 is completely discharged as combustible gas;

[0138] The first vaporization of the above-mentioned first heat-exchanged CO2 product gas 4 and part of the third vaporization product 19-i is carried out to obtain the first vaporization product 21-i and the first cooled CO2 product gas 5 (the pressure P1' is 0.27 MPa(G) and the temperature T1' is 39.5°C) ;

[0139] (2) The second separation of the above-mentioned first cooled CO2 product gas 5 is carried out to obtain the second separated CO2 product gas 6, which is subjected to the second compression to obtain the second pressurized CO2 product gas 7 (the pressure P2 is 0.8 MPa(G) and the temperature T2 is 112.9°C) and the remaining part of the third vaporization product 19-ii, which is subjected to the second vaporization to obtain the second vaporization product 21-ii and the second cooled CO2 product gas 8 (the pressure P2' is 0.77 MPa(G) and the temperature T2' is 38.1°C) ;

[0140] (3) The third separation of the above-mentioned second cooled CO2 product gas 8 is carried out to obtain the third separated CO2 product gas 9, which is subjected to the third compression to obtain the third pressurized CO2 product gas 10 (the pressure P3 is 2 MPa(G) and the temperature T3 is 122.9°C), which is subjected to the second heat exchange with the second heat medium 22 (the tail gas from the low-temperature methanol washing unit, the temperature is 16°C) to obtain the second heat-exchanged CO2 product gas 11 (T3" is 30°C), which is subjected to the third vaporization with the pressurized CO2 liquid phase product 17 to obtain the third vaporization product 19 (the temperature T4" is 25°C) and the third cooled CO2 product gas 12 (the pressure P3' is 1.97 MPa(G) and the temperature T3' is -18.6°C) ;

[0141] (4) The third heat exchange of the above-mentioned third cooled CO2 product gas 12 and the first heat medium 14 (propylene, the temperature is -40°C) is carried out to obtain the CO2 mixed phase 13 (the temperature T4 is -30°C), which is subjected to the gas-liquid separation to obtain the low-temperature non-condensable gas 18, which is returned to the above-mentioned first heat exchange, and the CO2 liquid phase 16, which is subjected to the pressurization to obtain the pressurized CO2 liquid phase product gas 17 (the pressure P4 is 14.06 MPa(G) and the temperature T4' is -22.2°C), which is returned to the above-mentioned third vaporization;

[0142] The molar flow ratio of the above-mentioned part of the third vaporization product 19-i and the remaining part of the third vaporization product 19-ii is 1:1; the above-mentioned first vaporization product 21-i and the second vaporization product 22-ii are mixed to obtain the high-pressure CO2 product gas 21 (the pressure P is 14 MPa(G) and the temperature T is 70°C) as the urea raw material gas.

[0143] Example 3

[0144] The device according to Example 1;

[0145] The method is performed in the above-described apparatus, and the method includes:

[0146] (1) The raw material CO2 product gas 1 (pressure P0 is -0.002 MPa (G), temperature T0 is 20°C, CO2 content is 99.3 mol%, moisture content is 0.5 ppmv, and combustible gas content is 0.65 mol%) is subjected to first separation, and the first separated CO2 product gas 2 is subjected to first compression to obtain first pressurized CO2 product gas 3 (pressure P1 is 0.3 MPa (G), and temperature T1 is 147.1°C);

[0147] The above-described first pressurized CO2 product gas 3 and low-temperature incondensable gas 18 are subjected to first heat exchange to obtain first heat-exchanged CO2 product gas 4 (temperature T1" is 146.9°C) and incondensable gas 20 (pressure P' is 1.91 MPa (G), temperature T' is 60°C, and combustible gas content is 25.8 mol%); and the above-described incondensable gas 20 is entirely discharged as combustible gas;

[0148] The above-described first heat-exchanged CO2 product gas 4 and part of the third vaporization product 19-i are subjected to first vaporization to obtain first vaporization product 21-i and first cooled CO2 product gas 5 (pressure P1' is 0.27 MPa (G), and temperature T1' is 34.1°C);

[0149] (2) The above-described first cooled CO2 product gas 5 is subjected to second separation to obtain second separated CO2 product gas 6, which is subjected to second compression to obtain second pressurized CO2 product gas 7 (pressure P2 is 0.8 MPa (G), and temperature T2 is 106.7°C) and the remaining part of the third vaporization product 19-ii, which is subjected to second vaporization to obtain second vaporization product 21-ii and second cooled CO2 product gas 8 (pressure P2' is 0.77 MPa (G), and temperature T2' is 31.5°C);

[0150] (3) The above-described second cooled CO2 product gas 8 is subjected to third separation to obtain third separated CO2 product gas 9, which is subjected to third compression to obtain third pressurized CO2 product gas 10 (pressure P3 is 2 MPa (G), and temperature T3 is 115.3°C), which is subjected to second heat exchange with second cold source medium 22 (boundary from tail gas of a low-temperature methanol washing unit, and temperature is 20°C) to obtain second heat-exchanged CO2 product gas 11 (T3" is 30°C), which is subjected to third vaporization with pressurized CO2 liquid phase 17 to obtain third vaporization product 19 (temperature T4" is 25°C) and third cooled CO2 product gas 12 (pressure P3' is 1.97 MPa (G), and temperature T3' is -18.6°C);

[0151] (4) The third cooled CO2 product gas 12 and the first cooling medium 14 (propylene, temperature -40°C) are subjected to third heat exchange, and the obtained CO2 mixed phase 13 (temperature T4 -30°C) is subjected to gas-liquid separation, and the obtained low-temperature non-condensable gas 18 is returned to the above-mentioned first heat exchange, and the obtained CO2 liquid phase 16 is subjected to pressurization, and the obtained pressurized CO2 liquid phase 17 (pressure P4 14.06 MPa (G), temperature T4' -22.2°C) is returned to the above-mentioned third vaporization;

[0152] The molar flow ratio of the above-mentioned partial third vaporization product 19-i and the remaining partial third vaporization product 19-ii is 1:1; the above-mentioned first vaporization product 21-i and the second vaporization product 22-ii are mixed, and the obtained high-pressure CO2 product gas 21 (pressure P 14 MPa (G), temperature T 79.5°C) is used as the urea raw material gas.

[0153] Example 4

[0154] The device according to Example 1;

[0155] The method is carried out in the above-mentioned device, and the method comprises:

[0156] (1) The raw material CO2 product gas 1 (pressure P0 9 MPa (G), temperature T0 90°C, CO2 content 40 mol%, water content 100 ppmv, combustible gas content 2 mol%) is subjected to first separation, and the obtained first separated CO2 product gas 2 is subjected to first compression, and the obtained first pressurized CO2 product gas 3 (pressure P1 10 MPa (G), temperature T1 102.6°C);

[0157] The above-mentioned first pressurized CO2 product gas 3 and the low-temperature non-condensable gas 18 are subjected to first heat exchange, and the obtained first heat-exchanged CO2 product gas 4 (temperature T1" 25°C) and the non-condensable gas 20 (pressure P' 12.95 MPa (G), temperature T' -5°C, combustible gas content 2.3 mol%) are obtained; the above-mentioned non-condensable gas 20 is completely discharged as combustible gas;

[0158] The above-mentioned first heat-exchanged CO2 product gas 4 and the partial third vaporization product 19-i are subjected to first vaporization, and the obtained first vaporization product 21-i and the obtained first cooled CO2 product gas 5 (pressure P1' 9.97 MPa (G), temperature T1' 62.5°C) are obtained;

[0159] (2) subjecting the first cooled CO2 product gas 5 to a second separation to obtain a second separated CO2 product gas 6, which is subjected to a second compression, and the obtained second pressurized CO2 product gas 7 (pressure P2 is 11.5 MPa(G), temperature T2 is 78.4°C) and the remaining third vaporized product 19-ii are subjected to a second vaporization to obtain a second vaporized product 21-ii and a second cooled CO2 product gas 8 (pressure P2' is 11.47 MPa(G), temperature T2' is 70°C);

[0160] (3) The second cooled CO2 product gas 8 is subjected to a third separation to obtain a third separated CO2 product gas 9, which is subjected to a third compression. The obtained third pressurized CO2 product gas 10 (pressure P3 is 13 MPa(G), temperature T3 is 83.9°C) is subjected to a second heat exchange with a second cold source medium 22 (the boundary area is the tail gas from the low-temperature methanol washing unit, the temperature is 20°C), and the obtained second heat-exchanged CO2 product gas 11 (T3" is 32°C) is subjected to a third vaporization with the pressurized CO2 liquid phase 17 to obtain a third vaporization product 19 (temperature T4" is 25°C) and a third cooled CO2 product gas 12 (pressure P3' is 12.98 MPa(G), temperature T3' is 8.9°C);

[0161] (4) The third cooled CO2 product gas 12 and the first cold source medium 14 (propylene, temperature is -40 ° C) are subjected to a third heat exchange, the obtained CO2 mixed phase 13 (temperature T4 is -32 ° C) is subjected to gas-liquid separation, the obtained low-temperature non-condensable gas 18 is returned to the above-mentioned first heat exchange, and the obtained CO2 liquid phase 16 is pressurized to obtain the pressurized CO2 liquid phase 17 (pressure P4 is 14.02 MPa (G), temperature T4' is -31.2 ° C) and returned to the above-mentioned third vaporization;

[0162] Among them, the molar flow ratio of the above-mentioned part of the third vaporization product 19-i and the remaining part of the third vaporization product 19-ii is 1:1; the above-mentioned first vaporization product 21-i and the second vaporization product 22-ii are mixed to obtain high-pressure CO2 product gas 21 (pressure P is 14 MPa (G), temperature T is 60°C) as urea raw gas.

[0163] Comparative Example 1

[0164] Devices such as Figure 2 As shown, the device includes: a first-stage liquid separating tank D001, a first-stage compressor K001, a first-stage cooler E001, a second-stage liquid separating tank D002, a second-stage compressor K002, a second-stage cooler E002, a third-stage liquid separating tank D003, a third-stage compressor K003, a third-stage cooler E003, a fourth-stage liquid separating tank D004, and a fourth-stage compressor K004, which are connected in sequence.

[0165] The method is carried out in the above-mentioned device, and the method comprises:

[0166] (1) The raw material CO2 product gas 1 of Example 1 was sequentially subjected to a first-stage separation and a first-stage compression, and the first-stage compressed gas (temperature: 198°C, pressure: 0.67 MPa (G)) was subjected to a first-stage cooling to obtain a first-stage cooled gas at a temperature of 40°C;

[0167] (2) The above first-stage cooled gas was sequentially subjected to a second-stage separation and a second-stage compression, and the second-stage compressed gas (temperature: 169°C, pressure: 2.37 MPa (G)) was subjected to a second-stage cooling to obtain a second-stage cooled gas at a temperature of 43°C;

[0168] (3) The above second-stage cooled gas was sequentially subjected to a third-stage separation and a third-stage compression, and the third-stage compressed gas (temperature: 144.7°C, pressure: 6.23 MPa (G)) was subjected to a third-stage cooling to obtain a third-stage cooled gas at a temperature of 43°C;

[0169] (4) The above third-stage cooled gas was sequentially subjected to a fourth-stage separation and a fourth-stage compression, and the fourth-stage compressed gas (temperature: 96°C, pressure: 9.5 MPa (G)) was sent out of the compression unit as a protective gas.

[0170] Comparative Example 2

[0171] According to the method mentioned in the document “Reformation of CO2 compressor high-pressure cylinder in 520,000 tons / year urea plant”, the raw material CO2 product gas of Example 1 was directly pressurized to obtain a high-pressure CO2 product gas as a urea raw material gas.

[0172] The document “Faults and treatment measures of CO2 compressor equipment in chemical machinery equipment” mentioned that the CO2 compressor of the urea plant of the enterprise had appeared abnormal vibration conditions for many times, resulting in failure to start; the document “CO2 mobile phone operation faults and optimization improvement of urea plant” mentioned that in 2017, the CO2 compressor unit faulted and tripped 32 times, and frequent tripping not only caused an increase in power consumption and material consumption, but also easily caused many secondary problems or faults.

[0173] Table 1

[0174]

[0175]

[0176] Note: The operating cost is according to the electricity price of 0.6 yuan / kwh and the circulating water of 0.2 yuan / t; the raw material CO2 product gas amount is according to 20,000 Nm 3 / h.

[0177] The CO2 recovery rate calculation formula is: CO2 recovery rate = CO2 content in CO2 product gas × CO2 product flow rate ÷ (raw material CO2 content × raw material gas flow rate) × 100%.

[0178] Table 1 continued

[0179]

[0180] Compared with Comparative Example 1-2, Example 1-4 uses the method provided by the application, optimizes the heat exchange network at the outlet of each stage of the original CO2 booster system, realizes the cooling of CO2 at the inlet of each stage of the compressor by designing the heat exchange between process streams, can reduce the power consumption of the compressor, reduce the investment of the compressor, and reduce the amount of circulating water of the water cooler; the high-pressure gas-phase CO2 at the outlet of the third compressor is liquefied by the first cold source medium (propylene or other refrigerants such as ammonia) cryogenic cooler, then pressurized to the specified pressure by the CO2 liquid-phase pump, and then the pressurized CO2 liquid phase is heated and gasified to the specified temperature for delivery; the power consumption and equipment investment required by the booster pump instead of the original third and fourth stage compressors or higher pressure CO2 compressors (or the original high-pressure cylinder) are small, which greatly reduces the system energy consumption; at the same time, the gasification of the liquid-phase CO2 is realized by relying on the self-heat exchange of the system, and the cold energy in the system is recovered.

[0181] At the same time, according to the data in Table 1, under the premise that the CO2 recovery rates of Example 1 and Comparative Example 1 are both 99.92%, the power of Example 1 is reduced by 479kw, the annual operating cost is saved by 2.264 million yuan, and the power saving rate is 10%; under the premise that the CO2 recovery rates of Example 2 and Comparative Example 2 are both 99.92%, the power of Example 2 is reduced by 658kw, the annual operating cost is saved by 3.1744 million yuan, and the power saving rate is 12.8%.

[0182] The above describes the preferred embodiments of the application in detail, but the application is not limited thereto. Within the technical concept of the application, various simple modifications can be made to the technical solutions of the application, including the combination of various technical features in any other suitable manner, and these simple modifications and combinations should also be considered as disclosed by the application and fall within the protection scope of the application.

Claims

1. A method of condensing and pressurizing a CO2 product gas, characterized by, The method comprises: at least one stage of compression of raw material CO2 product gas, the pressurized CO2 product gas obtained is sequentially subjected to CO2 liquefaction, gas-liquid separation and pressurization, the pressurized CO2 liquid phase obtained is subjected to vaporization treatment to obtain high-pressure CO2 product gas; Wherein, the pressure P0 of the raw material CO2 product gas is ≥-0.002 MPa(G); the pressure P of the high-pressure CO2 product gas is ≥2 MPa(G).

2. The method of claim 1, wherein, The pressure of the raw material CO2 product gas < the pressure of the pressurized CO2 product gas < the pressure of the high-pressure CO2 product gas; Preferably, the method comprises the following steps: (1) The raw material CO2 product gas is subjected to first compression, and the first pressurized CO2 product gas obtained is sequentially subjected to first heat exchange and first vaporization to obtain first cooled CO2 product gas; (2) The first cooled CO2 product gas is subjected to second compression, and the second pressurized CO2 product gas obtained is subjected to second vaporization to obtain second cooled CO2 product gas; (3) The second cooled CO2 product gas is subjected to third compression, and the third pressurized CO2 product gas obtained is sequentially subjected to second heat exchange and third vaporization to obtain third cooled CO2 product gas as the pressurized CO2 product gas; (4) The third cooled CO2 product gas and first cold source medium are subjected to third heat exchange, and the CO2 mixed phase obtained is subjected to the gas-liquid separation to obtain low-temperature non-condensable gas and CO2 liquid phase; Wherein, the low-temperature non-condensable gas is returned to the first heat exchange; the CO2 liquid phase is subjected to the pressurization to obtain the pressurized CO2 liquid phase which is subjected to the third vaporization to obtain third vaporization products which are divided into two streams and subjected to the first vaporization and the second vaporization respectively to obtain high-pressure CO2 product gas; Wherein, when the pressure P0 of the raw material CO2 product gas is < the pressure P1 of the first pressurized CO2 product gas, the raw material CO2 product gas is subjected to the first compression; or, when the pressure P0 of the raw material CO2 product gas is ≥ the pressure P1 of the first pressurized CO2 product gas, the raw material CO2 product gas is subjected to the second compression; or, when the pressure P0 of the raw material CO2 product gas is ≥ the pressure P2 of the second pressurized CO2 product gas, the raw material CO2 product gas is subjected to the third compression; Preferably, the number n of stages of compression is selected from 1, 2 and 3; Preferably, the pressure P0 of the raw material CO2 product gas is -0.002 MPa(G) to 9 MPa(G); and the pressure P of the high-pressure CO2 product gas is ≥7.2 MPa(G).

3. The method of claim 2, wherein, In step (1), the CO2 content in the raw material CO2 product gas is ≥40 mol%, preferably ≥60 mol%, and more preferably ≥90 mol%; Preferably, the moisture content in the raw material CO2 product gas is ≤1%, and the combustible gas content is 0.4-60 mol%, the combustible gas being selected from at least one of H2, CO, CH4 and CH3OH; Preferably, the temperature T0 of the raw material CO2 product gas is -10 to 100℃, preferably -10 to 40℃; Preferably, the pressure P1 of the first pressurized CO2 product gas is ≤10 MPa(G), preferably 0.1-2.5 MPa(G); the temperature T1 is ≤180℃, preferably 90-160℃; Preferably, the temperature T1' of the first cooled CO2 product gas is ≤80℃, preferably 10-70℃; Preferably, the raw CO2 product gas is subjected to a first separation before the first compression.

4. The method of claim 2 or 3, wherein, In step (2), the pressure P2 of the second pressurized CO2 product gas is ≤11.5 MPa(G), preferably 0.6-4 MPa(G); the temperature T2 is ≤180℃, preferably 90-160℃; Preferably, the temperature T2' of the second cooled CO2 product gas is ≤80℃, preferably 10-70℃; Preferably, the first cooled CO2 product gas is subjected to a second separation before the second compression.

5. The method of any of claims 2-4, wherein, In step (3), the pressure P3 of the third pressurized CO2 product gas is ≤13 MPa(G), preferably 1.8-6.5 MPa(G); the temperature T3 is ≤180℃, preferably 90-160℃; Preferably, the temperature T3' of the third cooled CO2 product gas is ≤80℃, preferably -25 to 70℃; Preferably, the second heat exchange is performed between the third pressurized CO2 product gas and a second cold source medium, to obtain a second heat-exchanged CO2 product gas and a second heat-exchanged cold source medium; Further preferably, the temperature of the second cold source medium is 10-25℃; Further preferably, the temperature T3" of the second heat-exchanged CO2 product gas is 10-60℃; Preferably, the second cooled CO2 product gas is subjected to a third separation before the third compression.

6. The method of any of claims 2-5, wherein, In step (4), the temperature T4 of the CO2 mixed phase is ≥-60℃, preferably -45 to 25℃; Preferably, the energy Q required for the liquefaction of the third cooled CO2 product gas is ≤ the energy Q' released by the first cold source medium, wherein, wherein, ΔT is the temperature difference of the CO2 mixed phase and the third cooled CO2 product gas, ℃; is the flow rate of the third cooled CO2 product gas, Nm 3 / h; ΔT' is the temperature difference of the first cold source medium before and after the third heat exchange, ℃; is the flow rate of the first cold source medium, Nm 3 / h; Preferably, the temperature of the first cold source medium is -65 to 40℃, preferably -55 to -35℃.

7. The method of any of claims 2-6, wherein, The first heat exchange is performed between the low-temperature non-condensable gas and the first pressurized CO2 product gas, to obtain a non-condensable gas and a first heat-exchanged CO2 product gas; Preferably, the pressure P' of the non-condensable gas is ≤13 MPa(G), preferably 1.8-6.5 MPa(G); the temperature T' is 40-120℃, preferably 60-90℃; Preferably, the non-condensable gas is divided into two streams, part of which is discharged as fuel gas, and the remaining part is returned and subjected to the third compression; Further preferably, the molar flow ratio of the part of the non-condensable gas to the remaining part of the non-condensable gas is 0-10:10-0, preferably 1-3:3-1; More preferably, when the combustible gas content in the non-condensable gas is ≥25 mol%, the non-condensable gas is discharged in its entirety; when the combustible gas content in the non-condensable gas is ≤5 mol%, the non-condensable gas is returned in its entirety to the third compression; otherwise, the non-condensable gas is divided into two streams and subjected to discharge and third compression simultaneously; Preferably, the temperature T1" of the first heat-exchanged CO2 product gas is ≤ 150℃, preferably 50-130℃.

8. The method of claim 7, wherein, The temperature T4" of the third vaporized product is -20-70℃, preferably 10-50℃; Preferably, the first heat-exchanged CO2 product gas and part of the third vaporized product are subjected to the first vaporization to obtain the first cooled CO2 product gas and a first vaporized product; Preferably, the second pressurized CO2 product gas and the remaining part of the third vaporized product are subjected to the second vaporization to obtain a second cooled CO2 product gas and a second vaporized product; Further preferably, the molar flow ratio of the part of the third vaporized product to the remaining part of the third vaporized product is 1-5:5-1, preferably 1-2:2-1; Further preferably, the first vaporized product and the second vaporized product are mixed to obtain the high-pressure CO2 product gas; Further preferably, the temperature T of the high-pressure CO2 product gas is ≤ 160℃, preferably 40-130℃.

9. The method of any of claims 1-8, wherein, The high-pressure CO2 product gas is used as equipment protection gas, urea raw material gas, CO2 gas for oil field oil displacement, and conveying carrier gas; Preferably, when the high-pressure CO2 product gas is used as equipment protection gas, the pressure P of the high-pressure CO2 product gas is ≥ 8 MPa(G); when the high-pressure CO2 product gas is used as urea raw material gas, the pressure P of the high-pressure CO2 product gas is ≥ 14 MPa(G); Further preferably, the high-pressure CO2 product gas is subjected to desulfurization and deoiling, and hydrocarbon drying in sequence to obtain an industrial-grade CO2 product gas or a food-grade CO2 product gas; or, The first pressurized CO2 product gas, or the second pressurized CO2 product gas, or the third pressurized CO2 product gas is subjected to desulfurization and deoiling, and hydrocarbon drying in sequence, and the CO2 mixed phase is subjected to rectification to obtain an industrial-grade CO2 product gas or a food-grade CO2 product gas.

10. An apparatus for condensing and pressurizing a CO2 product gas, characterized by, The device comprises a compression unit, a liquefaction unit, a gas-liquid separation unit, a CO2 liquid phase pump, and a vaporization treatment unit connected in sequence; The compression unit is used to compress the raw material CO2 product gas by at least one stage to obtain a pressurized CO2 product gas; the liquefaction unit is used to liquefy the pressurized CO2 product gas to obtain a CO2 mixed phase which enters the gas-liquid separation unit, the CO2 liquid phase pump in sequence; the pressurized CO2 liquid phase enters the vaporization treatment unit for vaporization treatment to obtain a high-pressure CO2 product gas.

11. The apparatus of claim 10, wherein, The device comprises a first compressor, a first heat exchanger, a first vaporizer, a second compressor, a second vaporizer, a third compressor, a second heat exchanger, a third vaporizer, a third heat exchanger, a gas-liquid separation unit, and a CO2 liquid phase pump connected in sequence; The raw material CO2 product gas enters a first compressor for first compression, and the first pressurized CO2 product gas obtained is sequentially introduced into a first heat exchanger and a first vaporizer, and the first cooled CO2 product gas obtained is introduced into a second compressor for second compression, and the second pressurized CO2 product gas obtained is introduced into a second vaporizer, and the second cooled CO2 product gas obtained is introduced into a third compressor for third compression, and the third pressurized CO2 product gas obtained is taken as the pressurized CO2 product gas and sequentially introduced into a second heat exchanger and a third vaporizer, and the third cooled CO2 product gas obtained is subjected to third heat exchange with the first cold source medium in the third heat exchanger, and the CO2 mixed phase obtained is introduced into a gas-liquid separation unit for gas-liquid separation, and low-temperature non-condensable gas and CO2 liquid phase are obtained; The gas-liquid separation unit is connected to the first heat exchanger at the top, and is used to return the low-temperature non-condensable gas and perform the first heat exchange; The CO2 liquid phase pump is connected to the bottom of the gas-liquid separation unit and the third vaporizer, and the third vaporizer is connected to the first vaporizer and the second vaporizer, and is used to pressurize the CO2 liquid phase, perform the third vaporization, and divide the third vaporization product into a partial third vaporization product and a remaining third vaporization product, which are returned and subjected to the first vaporization and the second vaporization, respectively, to obtain high-pressure CO2 product gas.

12. The apparatus of claim 11, wherein, The first heat exchanger is further connected to the third compressor, and is used to divide the non-condensable gas obtained by the first heat exchange into two streams, a part of which is taken as fuel gas and discharged, and the remaining part is returned and subjected to the third compression; Preferably, the device further comprises a first separator, which is used to separate the raw material CO2 product gas before the first compression, to obtain first separated CO2 product gas; Preferably, the device further comprises a second separator arranged between the first vaporizer and the second compressor, which is used to separate the first cooled CO2 product gas before the second compression, to obtain second separated CO2 product gas; Preferably, the device further comprises a third separator arranged between the second vaporizer and the third compressor, which is used to separate the second cooled CO2 product gas before the third compression, to obtain third separated CO2 product gas; Preferably, the gas-liquid separation unit is selected from a gas-liquid separator with a packing layer arranged inside; Preferably, the device further comprises a desulfurization and deoiling device and a dehydrocarbon dryer connected in sequence, The desulfurization and deoiling device and the dehydrocarbon dryer are arranged on a pipeline connecting the first vaporizer and the second vaporizer, and are used to sequentially perform desulfurization and deoiling and dehydrocarbon drying on the high-pressure CO2 product gas, to obtain industrial-grade CO2 product gas or food-grade CO2 product gas; Alternatively, the desulfurization and deoiling device and the dehydrocarbon dryer are arranged at the outlet of the first compressor, the second compressor or the third compressor, and the gas-liquid separation unit is selected from a rectification column, which is used to sequentially perform desulfurization and deoiling and dehydrocarbon drying on the first pressurized CO2 product gas, the second pressurized CO2 product gas and the third pressurized CO2 product gas, to obtain industrial-grade CO2 product gas or food-grade CO2 product gas.

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