Process and device for recovering CO2 in acid gas

Abstract

The invention belongs to the technical field of natural gas separation treatment, and relates to a process and a device for recovering CO2 in acid gas. The process comprises the following steps: absorbing H2S in acid gas by an alkaline aqueous solution of an iron ion catalyst to obtain desulfurized acid gas; liquefying the desulfurized acid gas to obtain liquid CO2 and non-condensable gas from which H2S and CO2 are removed; and non-condensable gas is recovered to a natural gas system. The device comprises a complexing iron and sulfur recovery process unit, a CO2 purification and capture process unit and a non-condensable gas recovery process unit which are connected in sequence. The problem of capturing CO2 in the exhaust gas of the natural gas purification plant is solved by adopting a combined process mode, and compared with a complex iron single-tower self-circulation process, the complex iron sulfur recovery process has the advantages that regenerated air is not doped, and a high-concentration carbon source can be provided; the non-condensable gas pressurization recovery process can reduce the emission of methane in the conventional sulfur recovery process.

Description

Technical Field

[0001] The invention belongs to the technical field of natural gas separation and processing, and particularly relates to a process and device for recovering CO2 from acid gas. Background Art

[0002] Sour natural gas contains a certain amount of H2S and CO2, which need to be removed from the raw gas in the natural gas purification plant to meet the quality index requirements of commercial natural gas. The resulting acid gas contains a high concentration of CO2. At present, after sulfur is recovered from the acid gas of the natural gas purification plant, the SO2 in the tail gas meets the standard and is directly discharged. CO2 recovery is not carried out, but it is discharged into the atmosphere together.

[0003] The sulfur recovery process of natural gas purification plants currently mainly adopts three processes according to different latent sulfur contents: one is the complex iron single tower self-circulation process when the latent sulfur content is less than or equal to 10t / d; the second is the direct oxidation + alkali washing tail gas treatment process when the latent sulfur content is greater than 10t / d but the hydrogen sulfide content is less than or equal to 15%; the third is the Claus hydrogenation tail gas treatment process when the hydrogen sulfide content in the acid gas is greater than 15%. Regardless of the sulfur recovery process, air will be supplemented as an oxidizing medium, resulting in a decrease in the CO2 concentration in the sulfur recovery tail gas.

[0004] The tail gas at the sulfur recovery outlet contains sulfur components such as O2 and N2, causing the CO2 content to drop to 70% or even lower. There are three main methods for capturing medium-concentration CO2: one is the amine liquid absorption-regeneration method (referred to as the "amine method"), which is suitable for situations where the CO2 content in the mixed gas is low. It has high removal efficiency, simple operation, and strong economic adaptability. It is widely used in the domestic and foreign petroleum and petrochemical fields, but its regeneration heat load is relatively high; the second is the pressure swing adsorption method, which is a new type of cost-effective separation method and is widely used in flue gas capture, but the energy consumption required for the regeneration of its adsorption medium is large; the third is low-temperature separation, which uses the principle that various gases have different condensation phase characteristics to achieve gas separation, but it has high energy consumption and high cost, and is not widely used in the industrial sector.

[0005] From the above, it can be seen that the recovery of CO2 from the acid gas of the natural gas purification plant first needs to solve the problem of minimizing the reduction of CO2 concentration in the tail gas and the addition of other impurity gases during the sulfur recovery stage, so as to provide a good quality carbon source for the next step of CO2 capture. The next step is to develop economical CO2 capture technology and non-condensable gas treatment technology, and finally adopt a combined process to solve the CO2 capture in the exhaust gas of the natural gas purification plant. Summary of the invention

[0006] In view of the above problems, the technical solution adopted by the present invention is as follows: a process for recovering CO2 from acid gas, the process comprising the following steps:

[0007] The alkaline aqueous solution containing iron ion catalyst absorbs H2S in the acid gas to obtain desulfurized gas;

[0008] The desulfurized gas is liquefied to obtain liquid CO2 and non-condensable gas after H2S and CO2 are removed;

[0009] Non-condensable gas is recycled to the natural gas system.

[0010] Furthermore, the absorption tower contains Fe 3+ The alkaline aqueous solution of the catalyst absorbs H2S in the acid gas to obtain sulfur and Fe 2+ absorbent solution; sulfur and Fe 2+ The absorbent solution is transported to the regeneration tower through the rich liquid delivery pump, and undergoes oxidation reaction with the O2 in the air blown into the regeneration tower to make Fe 2+ Regeneration to Fe 3+ , Fe 3+ The absorbent solution is transported to the absorption tower through the lean liquid reflux pump.

[0011] Furthermore, the acid gas is separated from the sulfuric acid gas separator and enters the absorption tower after being pressurized by the ejector; Fe 3+ The absorbent solution is transported to the absorption tower through the lean liquid reflux pump and the lean liquid flow control module, and mixed with the acid gas in the absorption tower.

[0012] Furthermore, the desulfurized gas is pressurized, cooled and dehydrated to obtain dry desulfurized gas; the dry desulfurized gas is liquefied after cold exchange to obtain liquid CO2; the liquefied liquid CO2 is separated from the hydrocarbon gas in the liquid CO2 through the combined action of a distillation tower and a reboiler to obtain purified liquid CO2.

[0013] Furthermore, the purified liquid CO2 is supercooled, and the supercooled liquid CO2 is stored.

[0014] Furthermore, the dry desulfurized gas is liquefied after cold exchange to obtain liquid CO2, wherein:

[0015] The liquefaction pressure is 2.0~2.5MPa, the cooling temperature in the cold exchange is -30~-20℃, and the cold source in the cold exchange is provided by propane refrigeration;

[0016] Liquefaction to obtain liquid CO2 satisfies:

[0017] CO2 content ≥95%, N2 content ≤4%, O2 content ≤10ppm, H2S content ≤20ppm and sulfur ≤30ppm.

[0018] Furthermore, the non-condensable gas is output from the top of the distillation tower for cold recovery, and then returned to the raw natural gas system after pressurization, air cooling and separation.

[0019] Furthermore, the non-condensable gas is output from the top of the distillation tower for cold recovery and then pressurized to a natural gas system pressure of 4.5 to 5.6 MPa.

[0020] In addition, the present invention also provides a CO2 recovery device in acid gas, which comprises a complex iron-sulfur recovery process unit, a CO2 purification and capture process unit and a non-condensable gas recovery process unit connected in sequence; wherein,

[0021] The complex iron-sulfur recovery process unit is used to absorb H2S in the acid gas with an alkaline aqueous solution of an iron ion catalyst to obtain desulfurized gas;

[0022] The CO2 purification and capture process unit is used to obtain liquid CO2 after liquefaction of desulfurized gas and non-condensable gas after removal of H2S and CO2;

[0023] The non-condensable gas recovery process unit is used to recover non-condensable gas to the raw natural gas system.

[0024] Furthermore, the complex iron-sulfur recovery process unit includes a sulfuric acid gas separator, an absorption tower, an ejector, an acid gas separator and a regeneration tower; wherein,

[0025] The inlet of the sulfuric acid gas separator is connected to the desulfurization and decarbonization device, the top outlet of the sulfuric acid gas separator is connected to the inlet of the ejector, the outlet of the ejector is connected to the first inlet of the bottom of the absorption tower, and the ejector is used to control the acid gas ejection pressure; the first outlet at the top of the absorption tower is connected to the inlet of the acid gas separator, the first outlet of the acid gas separator is connected to the CO2 purification and capture process unit, the second outlet at the bottom of the absorption tower and the second outlet of the acid gas separator are both connected to the first inlet of the regeneration tower through the rich liquid delivery pump; the second inlet of the regeneration tower is connected to the blower, the blower is used to blow the regeneration air into the regeneration tower, and the first outlet of the regeneration tower is used to discharge the regeneration air that does not participate in the reaction in the regeneration tower.

[0026] Furthermore, the complex iron-sulfur recovery process unit also includes a lean liquid tank, a lean liquid flow control module, a plate-frame filter and a sulfur foam tank; wherein the first inlet of the lean liquid tank is connected to the second outlet of the regeneration tower, the second inlet of the lean liquid tank is used to inject a NaOH solution for controlling the complex iron solution, and the third inlet of the lean liquid tank is used to inject a catalyst for controlling the replenishment of the complex iron solution; the inlet of the sulfur foam tank is connected to the third outlet of the regeneration tower, and the outlet of the sulfur foam tank is connected to the inlet of the plate-frame filter via a sulfur foam pump; the first outlet of the plate-frame filter is used to output sulfur, and the second outlet of the plate-frame filter is connected to the fourth inlet of the lean liquid tank; the outlet of the lean liquid tank is connected to the second inlet at the top of the absorption tower via a lean liquid reflux pump;

[0027] A lean liquid flow control module is also provided on the pipeline connecting the lean liquid reflux pump and the second inlet at the top of the absorption tower. The lean liquid flow control module is used to control the Fe 3+ The flow rate of absorbent regeneration solution entering the absorption tower.

[0028] Furthermore, the CO2 purification and capture process unit includes a pressurization system, an air cooling system, a separation system, a dehydration system, a cold exchange system, a distillation tower and a reboiler; wherein,

[0029] The first inlet of the boosting system is connected to the first outlet of the acid gas separator, the second inlet of the boosting system is connected to the first outlet of the dehydration system, the first outlet of the boosting system is connected to the inlet of the air cooling system, and the second outlet of the boosting system is connected to the second inlet of the dehydration system; the outlet of the air cooling system is connected to the inlet of the separation system, the outlet of the separation system is connected to the first inlet of the dehydration system, the second outlet of the dehydration system is connected to the inlet of the reboiler, the first outlet of the reboiler is connected to the first inlet of the cold exchange system, the first outlet of the reboiler is connected to the second inlet of the cold exchange system, the first outlet of the cold exchange system is connected to the inlet of the distillation tower, the second outlet of the cold exchange system is connected to the CO2 storage tank, the top outlet of the distillation tower is connected to the third inlet of the cold exchange system, the third outlet of the cold exchange system is connected to the non-condensable gas recovery process unit, and the second outlet of the cold exchange system is used to transport the non-condensable gas output from the top of the distillation tower to the non-condensable gas recovery process unit.

[0030] Furthermore, the cold exchange system includes a CO2 cold box and a propane refrigeration system, and the CO2 cold box and the propane refrigeration system are connected in a closed loop.

[0031] Furthermore, the non-condensable gas recovery process unit includes a non-condensable gas compression device, a non-condensable gas air cooling device and a non-condensable gas outlet separation device connected in sequence; wherein,

[0032] The non-condensable gas outlet separation device is used to transport the compressed, air-cooled and separated non-condensable gas to the natural gas system.

[0033] The present invention proposes a CO2 recovery process in acid gas, which adopts a combined process to solve the problem of capturing CO2 in the exhaust gas of a natural gas purification plant. First, the corrosive gas H2S in the acid gas is removed by a complex iron-sulfur recovery process, and then liquid CO2 is produced by a low-temperature process of pressurization, drying, and propane refrigeration. The remaining non-condensable gas containing alkanes is pressurized and recovered and then transported to the raw gas system, thereby achieving "zero" emissions of CO2 and alkanes in the entire natural gas purification plant. Compared with the complex iron single-tower self-circulation process, the complex iron-sulfur recovery process does not have the addition of regenerated air and can provide a high-concentration carbon source; the non-condensable gas pressurization recovery process can reduce the methane emissions of conventional sulfur recovery processes.

[0034] Other features and advantages of the present invention will be described in the following description, and part of them will become obvious from the description, or be understood by practicing the present invention. The purpose and other advantages of the present invention can be realized and obtained through the description and the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the following briefly introduces the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are some embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative work.

[0036] Figure 1 It is an overall schematic diagram of a CO2 recovery process in acid gas;

[0037] Figure 2 It is a schematic diagram of the complex iron-sulfur recovery process unit and the complex iron-sulfur recovery process in the first embodiment of the present invention;

[0038] Figure 3 A schematic diagram of a CO2 purification and capture process unit and a CO2 purification and capture process in a second embodiment of the present invention;

[0039] Figure 4 It is a schematic diagram of a non-condensable gas recovery process unit and a non-condensable gas recovery process in the third embodiment of the present invention. DETAILED DESCRIPTION

[0040] In order to make the purpose, technical solution and advantages of the embodiments of the present invention clearer, the technical solution in the embodiments of the present invention will be clearly and completely described below. Obviously, the described embodiments are part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0041] like Figure 1 As shown, the present invention adopts a combined acid gas CO2 recovery process of "complex iron-sulfur recovery process, CO2 purification and capture process and non-condensable gas recovery process", wherein the complex iron-sulfur recovery process is to absorb hydrogen sulfide in the gas with an alkaline aqueous solution of an iron ion catalyst, and adopt a double-tower process of "absorption tower and regeneration tower"; the mixed solution that absorbs hydrogen sulfide is heated in L-Fe n+ (L represents an iron ion chelating agent)) is catalyzed and regenerated by oxidation with air to produce sulfur as a by-product. The regenerated mixed solution is recycled.

[0042] The principle of iron ion sulfur recovery is as follows:

[0043] Absorption reaction: H2S(g)+2L~Fe 3+ →2H + +S↓+2L~Fe 2+ ;

[0044] Regeneration reaction: 2L~Fe 2++H2O+1 / 2O2(air)→2OH － +2L~Fe 3+ ;

[0045] Overall reaction equation: H2S+1 / 2O2→H2O+S↓.

[0046] As a first embodiment of the present invention, a complex iron-sulfur recovery process and a device thereof are as follows Figure 2 As shown, the complex iron-sulfur recovery process unit includes a sulfuric acid gas separator, an ejector, an absorption tower, an acid gas separator and a regeneration tower; wherein, the inlet of the sulfuric acid gas separator is connected to the desulfurization and decarbonization device, the top outlet of the sulfuric acid gas separator is connected to the ejector inlet, the ejector outlet is connected to the first inlet at the bottom of the absorption tower, the ejector is used to control the acid gas ejection pressure, and pressurizes the low-pressure acid gas separated from the sulfuric acid gas separator into the absorption tower; the first outlet at the top of the absorption tower is connected to the inlet of the acid gas separator, the first outlet of the acid gas separator is connected to the CO2 purification and capture process unit, the second outlet at the bottom of the absorption tower and the second outlet of the acid gas separator are both connected to the first inlet of the regeneration tower via a rich liquid delivery pump; the second inlet of the regeneration tower is connected to a blower, the blower is used to blow the regeneration air into the regeneration tower, and the first outlet of the regeneration tower is used to discharge the regeneration air that does not participate in the reaction in the regeneration tower. At the same time, the second inlet of the regeneration tower is also connected to a pipeline. Since a large amount of gas phase is carried away during the regeneration reaction, desalted water needs to be injected for water replenishment. On the other hand, the regeneration air in the regeneration tower is compressed and the temperature is around 95°C, so the water injection port is set in the regeneration air pipeline to reduce the temperature of the regeneration air entering the regeneration tower.

[0047] The complex iron-sulfur recovery process unit also includes a lean liquid tank, a plate-frame filter and a sulfur foam tank; wherein the first inlet of the lean liquid tank is connected to the second outlet of the regeneration tower, the second inlet of the lean liquid tank is used to inject a NaOH solution for controlling the complex iron solution, and the third inlet of the lean liquid tank is used to inject a catalyst for controlling the replenishment of the complex iron solution; the inlet of the sulfur foam tank is connected to the third outlet of the regeneration tower, and the outlet of the sulfur foam tank is connected to the inlet of the plate-frame filter via a sulfur foam pump; the first outlet of the plate-frame filter is used to output sulfur, and the second outlet of the plate-frame filter is connected to the fourth inlet of the lean liquid tank; the outlet of the lean liquid tank is connected to the second inlet at the top of the absorption tower via a lean liquid reflux pump, and a lean liquid flow control (FC) module is also provided on the pipeline connecting the lean liquid reflux pump and the second inlet at the top of the absorption tower, and the lean liquid flow control module is used to control the Fe in the lean liquid tank. 3+ The flow rate of absorbent regeneration solution entering the absorber, Fe 3+ The absorbent regeneration solution is fully mixed with the acid gas, and the desulfurization effect is better.

[0048] In the embodiment of the present invention, the regeneration tower can be a floating regeneration tower, and the sulfur foam is discharged from the third outlet of the regeneration tower at the top of the regeneration tower, which solves the problem of sulfur deposition and sulfur blockage caused by sulfur discharge at the bottom of the conventional regeneration tower. The regeneration tower can also be a flat-bottomed regeneration tower, which has a simple equipment structure and reduces the height of the equipment.

[0049] The complex iron-sulfur recovery process specifically includes the following steps: the sulfuric acid gas from the desulfurization and decarbonization device enters the sulfuric acid separator, removes the free liquid entrained upstream, and the generated condensate is discharged into the sewage treatment device. The gas phase enters the absorption tower after being pressurized by the ejector from the top outlet of the sulfuric acid separator. In the absorption tower, the H2S in the sulfuric acid gas contacts the complex iron solution, and the H2S is absorbed by the solution and oxidized to elemental sulfur by the trivalent iron ions in the solution. The acid gas after H2S removal leaves from the first outlet at the top of the absorption tower and then enters the acid gas separator. After the acid gas after H2S removal removes the entrained complex iron solution in the acid gas separator, it is sent to the downstream CO2 purification and capture process unit through the first outlet of the acid gas separator. The sulfur-containing reaction solution flows out from the second outlet at the bottom of the absorption tower, enters the rich liquid delivery pump together with the free liquid through the second outlet of the acid gas separator, and then enters the regeneration tower through the first inlet of the regeneration tower to regenerate the iron ion catalyst. Air is blown into the second inlet of the regeneration tower by a Roots blower and evenly distributed in the tower through an air distributor. 2+ Oxidized to Fe 3+ The remaining waste air is directly discharged into the atmosphere from the first outlet on the top of the regeneration tower. 3+ The solution enters the lean liquid tank through the second outlet of the regeneration tower, and then is pressurized by the lean liquid reflux pump. After that, it is circulated back to the regenerated Fe in the absorption tower through the lean liquid flow control module. 3+ The solution flow enters the absorption tower together with the acid gas for full mixing. At the same time, the NaOH solution for controlling the complex iron solution and the supplementary catalyst are respectively injected into the lean liquid tank. The sulfur foam flows from the third outlet of the regeneration tower in the upper middle part of the regeneration tower to the sulfur foam tank, and then is transported to the plate and frame filter through the sulfur foam pump to produce crude sulfur with a water content of less than about 20%, which is then entrusted to a professional company for treatment as solid waste. The filtrate discharged from the plate and frame filter is returned to the lean liquid tank, and then returned to the absorption tower for recycling.

[0050] Specifically, as a second embodiment of the present invention, the CO2 purification and capture process unit is as follows: Figure 3As shown, it includes a boosting system, an air cooling system, a separation system, a dehydration system, a cold exchange system, a distillation tower and a reboiler; wherein, the first inlet of the boosting system is connected to the first outlet of the acid gas separator, the second inlet of the boosting system is connected to the first outlet of the dehydration system, the first outlet of the boosting system is connected to the inlet of the air cooling system, and the second outlet of the boosting system is connected to the second inlet of the dehydration system; the outlet of the air cooling system is connected to the inlet of the separation system, the outlet of the separation system is connected to the first inlet of the dehydration system, the second outlet of the dehydration system is connected to the inlet of the reboiler, the first outlet of the reboiler is connected to the first inlet of the cold exchange system, the first outlet of the reboiler is connected to the second inlet of the cold exchange system, the first outlet of the cold exchange system is connected to the inlet of the distillation tower, the second outlet of the cold exchange system is connected to the CO2 storage tank, the top outlet of the distillation tower is connected to the third inlet of the cold exchange system, the third outlet of the cold exchange system is connected to the non-condensable gas recovery process unit, and the second outlet of the cold exchange system is used to transport the non-condensable gas output from the top of the distillation tower to the non-condensable gas recovery process unit.

[0051] The boosting system can be a desulfurized gas booster fan, and the desulfurized gas booster fan uses a screw compressor; the air cooling system can be a desulfurized gas air cooler, the separation system can be a desulfurized gas separator, the dehydration system can be a molecular sieve dehydration system, and the cold exchange system includes a CO2 cold box and a propane refrigeration system, and the CO2 cold box and the propane refrigeration system are closed-loop connected.

[0052] The CO2 purification and capture process includes the following steps: the desulfurized gas separated from the first outlet of the acid gas separator enters the screw compressor for pressurization, and the pressure is increased to 2.5MPa. The pressurized gas is cooled again by the desulfurized gas air cooler and the liquid water precipitated during the cooling process is separated, and then enters the molecular sieve dehydration system to control the water dew point to -30°C. The molecular sieve regeneration uses the high-temperature wet gas at the outlet of the acid gas compressor, enters the series electric heater to heat it to 220°C, and enters the regeneration tower for desorption. The high-temperature wet gas returns to the inlet of the acid gas compressor after throttling, cooling, and separation.

[0053] The heat source of the reboiler is the dry acid gas with a temperature of 50°C and a pressure of 2.5MPa after pressurization and dehydration. First, the dry acid gas enters the reboiler as the heat source for CO2 purification. The temperature of the dry acid gas is reduced to 4°C and then enters the CO2 cold box for liquefaction. The dry acid gas enters the CO2 cold box and exchanges cold with the low-temperature propane from the propane refrigeration device. After the temperature of the dry acid gas is reduced to -30°C, the dry acid gas is liquefied and enters the distillation tower. Through the combined effects of the stripping section, the distillation section and the reboiling at the bottom of the tower, the hydrocarbon gas in the liquid CO2 is separated from the tower. The temperature of the liquefied and purified liquid CO2 is -17°C. The liquefied and purified liquid CO2 meets the standards of CNPC for reinjection and oil recovery, namely: CO2 content ≥95%, N2 content ≤4%, O2 content ≤10ppm, H2S content ≤20ppm, sulfur ≤30ppm. At the same time, in order to prevent the volatilization of the liquid, the liquid CO2 enters the cold box for supercooling, and the supercooled liquid CO2 enters the storage tank for storage. The non-condensable gas components at the top of the distillation tower are mainly methane and a small amount of CO2. After the cold is recovered by the cold box, it is transported to the downstream non-condensable gas recovery process unit.

[0054] Specifically, as a third embodiment of the present invention, the non-condensable gas recovery process unit is as follows: Figure 4 As shown, it includes a non-condensable gas compression device, a non-condensable gas air cooling device and a non-condensable gas outlet separation device connected in sequence. As the third embodiment of the present invention, the non-condensable gas compression device can be a non-condensable gas compressor, and the non-condensable gas compressor can be a reciprocating compressor; the non-condensable gas air cooling device can be a non-condensable gas air cooler, and the non-condensable gas outlet separation device can be a non-condensable gas outlet separator.

[0055] The non-condensable gas recovery process includes the following steps: the non-condensable gas coming out of the distillation tower is recovered through a cold box, then pressurized to the raw natural gas system pressure (the raw natural gas system pressure is 4.5-5.6MPa) through a reciprocating compressor, and then returned to the raw natural gas system after air cooling and separation, thereby realizing the closed circulation and "zero" emission of alkane gases.

[0056] Although the present invention has been described in detail with reference to the aforementioned embodiments, those skilled in the art should understand that they can still modify the technical solutions described in the aforementioned embodiments, or make equivalent substitutions for some of the technical features therein; and these modifications or substitutions do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A process for recovering CO2 from acid gas, characterized in that: The process comprises the following steps: The alkaline aqueous solution containing iron ion catalyst absorbs H2S in the acid gas to obtain desulfurized gas; The desulfurized gas is liquefied to obtain liquid CO2 and non-condensable gas after H2S and CO2 are removed; Non-condensable gas is recycled to the natural gas system.

2. A process for recovering CO2 from acid gas according to claim 1, characterized in that: In the absorption tower, Fe 3+ The alkaline aqueous solution of the catalyst absorbs H2S in the acid gas to obtain sulfur and Fe 2+ absorbent solution; sulfur and Fe 2+ The absorbent solution is transported to the regeneration tower through the rich liquid delivery pump, and undergoes oxidation reaction with the O2 in the air blown into the regeneration tower to make Fe 2+ Regeneration to Fe 3+ , Fe 3+ The absorbent solution is transported to the absorption tower through the lean liquid reflux pump.

3. A process for recovering CO2 from acid gas according to claim 2, characterized in that: The acid gas is separated from the sulfuric acid gas separator and enters the absorption tower after being pressurized by the ejector; Fe 3+ The absorbent solution is transported to the absorption tower through the lean liquid reflux pump and the lean liquid flow control module, and mixed with the acid gas in the absorption tower.

4. A process for recovering CO2 from acid gas according to claim 1, characterized in that: The desulfurized gas is pressurized, cooled and dehydrated to obtain dry desulfurized gas; the dry desulfurized gas is liquefied after cold exchange to obtain liquid CO2; the liquefied liquid CO2 is separated from the hydrocarbon gas in the liquid CO2 by the combined action of a distillation tower and a reboiler to obtain purified liquid CO2.

5. A process for recovering CO2 from acid gas according to claim 4, characterized in that: The purified liquid CO2 is supercooled and the supercooled liquid CO2 is stored.

6. A process for recovering CO2 from acid gas according to claim 4 or 5, characterized in that: The dry desulfurized gas is liquefied to obtain liquid CO2 after cold exchange, where: The liquefaction pressure is 2.0~2.5MPa, the cooling temperature in the cold exchange is -30~-20℃, and the cold source in the cold exchange is provided by propane refrigeration; Liquefaction to obtain liquid CO2 satisfies: CO2 content ≥95%, N2 content ≤4%, O2 content ≤10ppm, H2S content ≤20ppm and sulfur ≤30ppm.

7. A process for recovering CO2 from acid gas according to claim 1, characterized in that: The non-condensable gas is output from the top of the distillation tower for cold recovery, and then returns to the raw natural gas system after pressurization, air cooling and separation.

8. A process for recovering CO2 from acid gas according to claim 7, characterized in that: The non-condensable gas is output from the top of the distillation tower for cold recovery and then pressurized to the natural gas system pressure of 4.5 to 5.6 MPa.

9. A CO2 recovery device in acid gas, characterized in that: The device comprises a complex iron-sulfur recovery process unit, a CO2 purification and capture process unit and a non-condensable gas recovery process unit connected in sequence; wherein, The complex iron-sulfur recovery process unit is used to absorb H2S in the acid gas with an alkaline aqueous solution of an iron ion catalyst to obtain desulfurized gas; The CO2 purification and capture process unit is used to obtain liquid CO2 after liquefaction of desulfurized gas and non-condensable gas after removal of H2S and CO2; The non-condensable gas recovery process unit is used to recover non-condensable gas to the raw natural gas system.

10. The CO2 recovery device in acid gas according to claim 9, characterized in that: The complex iron-sulfur recovery process unit includes a sulfuric acid gas separator, an absorption tower, an ejector, an acid gas separator and a regeneration tower; The inlet of the sulfuric acid gas separator is connected to the desulfurization and decarbonization device, the top outlet of the sulfuric acid gas separator is connected to the inlet of the ejector, the outlet of the ejector is connected to the first inlet of the bottom of the absorption tower, and the ejector is used to control the acid gas ejection pressure; the first outlet at the top of the absorption tower is connected to the inlet of the acid gas separator, the first outlet of the acid gas separator is connected to the CO2 purification and capture process unit, the second outlet at the bottom of the absorption tower and the second outlet of the acid gas separator are both connected to the first inlet of the regeneration tower through the rich liquid delivery pump; the second inlet of the regeneration tower is connected to the blower, the blower is used to blow the regeneration air into the regeneration tower, and the first outlet of the regeneration tower is used to discharge the regeneration air that does not participate in the reaction in the regeneration tower.

11. A CO2 recovery device in acid gas according to claim 10, characterized in that: The complex iron-sulfur recovery process unit also includes a lean liquid tank, a lean liquid flow control module, a plate and frame filter and a sulfur foam tank; wherein, The first inlet of the lean liquid tank is connected to the second outlet of the regeneration tower, the second inlet of the lean liquid tank is used to inject NaOH solution for controlling the complex iron solution, and the third inlet of the lean liquid tank is used to inject a catalyst for controlling the replenishment of the complex iron solution; the inlet of the sulfur foam tank is connected to the third outlet of the regeneration tower, and the outlet of the sulfur foam tank is connected to the inlet of the plate and frame filter through a sulfur foam pump; the first outlet of the plate and frame filter is used to output sulfur, and the second outlet of the plate and frame filter is connected to the fourth inlet of the lean liquid tank; the outlet of the lean liquid tank is connected to the second inlet at the top of the absorption tower through a lean liquid reflux pump; A lean liquid flow control module is also provided on the pipeline connecting the lean liquid reflux pump and the second inlet at the top of the absorption tower. The lean liquid flow control module is used to control the Fe 3+ The flow rate of absorbent regeneration solution entering the absorption tower.

12. A CO2 recovery device in acid gas according to claim 10 or 11, characterized in that: The CO2 purification and capture process unit includes a pressurization system, an air cooling system, a separation system, a dehydration system, a cold exchange system, a distillation tower and a reboiler; The first inlet of the boosting system is connected to the first outlet of the acid gas separator, the second inlet of the boosting system is connected to the first outlet of the dehydration system, the first outlet of the boosting system is connected to the inlet of the air cooling system, and the second outlet of the boosting system is connected to the second inlet of the dehydration system; the outlet of the air cooling system is connected to the inlet of the separation system, the outlet of the separation system is connected to the first inlet of the dehydration system, the second outlet of the dehydration system is connected to the inlet of the reboiler, the first outlet of the reboiler is connected to the first inlet of the cold exchange system, the first outlet of the reboiler is connected to the second inlet of the cold exchange system, the first outlet of the cold exchange system is connected to the inlet of the distillation tower, the second outlet of the cold exchange system is connected to the CO2 storage tank, the top outlet of the distillation tower is connected to the third inlet of the cold exchange system, the third outlet of the cold exchange system is connected to the non-condensable gas recovery process unit, and the second outlet of the cold exchange system is used to transport the non-condensable gas output from the top of the distillation tower to the non-condensable gas recovery process unit.

13. A CO2 recovery device in acid gas according to claim 12, characterized in that: The cold exchange system includes a CO2 cold box and a propane refrigeration system, and the CO2 cold box and the propane refrigeration system are connected in a closed loop.

14. A CO2 recovery device in acid gas according to claim 13, characterized in that: The non-condensable gas recovery process unit includes a non-condensable gas compression device, a non-condensable gas air cooling device and a non-condensable gas outlet separation device connected in sequence; wherein, The non-condensable gas outlet separation device is used to transport the compressed, air-cooled and separated non-condensable gas to the natural gas system.

Images