A process for separating acid gas

Abstract

The present application provides an acid gas separation process, which comprises the following steps: separating the acid gas to be treated into gas and liquid, wherein the liquid is sent to a sewage buffer tank, and the gas is sent to a booster compressor; the liquid produced after boosting is sent to the sewage buffer tank, and the boosted gas is sent to a deliquidation device; the removed liquid is sent to the sewage buffer tank, and the gas is sent to a primary electric heater for heating, and then sent to a hollow fiber membrane group for separation, H 2 S output to H 2 S booster compressor boosts pressure, mixed with H 2 S'CO 2 After being separated by hollow fiber membrane group again, H 2 S output to H 2 S booster compressor boost, CO 2 Output to CO 2 In booster compressor; in H 2 S booster compressor boosts H 2 When S reaches a supercritical state, it is sent to the formation for storage; 2 In CO 2 After the pressure is increased and adjusted in the booster compressor, it is sent to the formation for sealing or transported to the oil recovery well for oil recovery.

Description

Technical Field

[0001] The present application provides an acid gas separation process, and particularly relates to an acid gas separation process based on a membrane method. Background Art

[0002] Many natural gas reservoirs often contain non-hydrocarbon components such as H2S and CO2. The natural gas produced from such natural gas reservoirs is acidic natural gas, which contains a large amount of sulfides (especially hydrogen sulfide).

[0003] Acidic natural gas cannot be used directly. Various countries and pipeline companies have strict restrictions on the H2S content in natural gas. These acidic components must be removed before entering the pipeline and being used. The byproduct of the desulfurization process is acid gas. Acid gas refers to toxic acidic gas with a total molar content of H2S and CO2 greater than 90%. It is also a suffocating and irritating gas that is extremely harmful to human survival and the environment. Therefore, acid gas treatment has become a standard process that must be possessed by the natural gas purification industry. The main methods of acid gas treatment are: sulfur recovery, venting and combustion, and acid gas reinjection process.

[0004] The investment and operation costs of sulfur recovery equipment are very high. First of all, it requires sufficient acid gas and sulfur production scale (sulfur production is greater than 10t / d). At the same time, its production process is also subject to the sulfur market. While natural gas is being produced, acid gas and sulfur will be continuously produced. If the sulfur produced cannot find a market due to market constraints, it will be accumulated in large quantities. Treatment and landfill will also increase additional costs and cause secondary pollution.

[0005] In the past, small amounts of acid gas were mostly flared, but now national laws and regulations, the public's environmental awareness, and the sense of social responsibility of the intellectual and industrial communities have a huge impact on the emission of acid gas. As environmental protection requirements become increasingly stringent, many national laws have restricted the flaring of large amounts of acid gas. Strict limits and high carbon taxes have also forced many natural gas producers to replace their traditional acid gas treatment systems with acid gas reinjection to seal CO2-rich acid gas. As a result, the demand for large-scale acid gas reinjection has emerged. At the same time, using the reinjected acid gas to increase formation pressure and increase production while reducing emissions is also a hot topic.

[0006] In terms of CO2 flooding demonstration projects, many practical projects have been established or planned abroad: (1) Canada's Weyburn Oilfield began to use carbon dioxide miscible flooding to improve oil recovery in 2000. It is predicted that carbon dioxide miscible flooding will increase the oil recovery rate of the Weyburn Oilfield from 30% of water flooding to 46%, an increase of 16 percentage points. This means that in the next 20-30 years, the production of crude oil will increase by 130 million barrels (while the cumulative production of the Weyburn Oilfield in the past 46 years of development is 360 million barrels), and 30 million tons of carbon dioxide will be permanently stored underground. (2) The United States: The United States' laboratory and field test research on carbon dioxide miscible flooding began in the late 1940s and early 1950s. Since the 1970s, due to the discovery of a large number of high-purity carbon dioxide gas reservoirs in the West, carbon dioxide flooding has begun to receive attention, especially the successful laying of the carbon dioxide gas pipeline through West Texas in the 1980s, which has enabled the rapid development of carbon dioxide flooding projects. Oilfield development in the United States pays more attention to the use of carbon dioxide flooding to improve oil recovery. (3) Norway: In 1996, the Norwegian National Petroleum Corporation implemented a CCS project in the Sleipner gas field in the North Sea. The project injected carbon dioxide into the Utsira regional saline layer, which is located 1,000 meters below the seabed. The layer is 200-300 meters thick, 500 km long, 50 km wide, and covers an area of ​​approximately 26,000 km. 2 The total available storage space is estimated to be 660 million m 3 , capable of storing 600 billion tons of carbon dioxide. Since September 1996, 1 ​​million tons of carbon dioxide have been injected each year, making it the world's first industrial-scale and largest saline aquifer carbon dioxide storage project.

[0007] Since the 1960s, Daqing, Shengli, Renqiu, Jiangsu, Zhongyuan and other oil fields in my country have successively carried out carbon dioxide flooding experiments. Due to the lack of natural carbon dioxide resources in my country and the lack of large carbon dioxide gas reservoirs, the technology in this area started late. However, with the discovery of small carbon dioxide gas reservoirs, the application of carbon dioxide flooding began to enter the mines and achieved relatively obvious results, especially for oil reservoirs with poor water flooding effects and closed small fault block oil reservoirs, carbon dioxide flooding can achieve very good results. Summary of the invention

[0008] The present invention provides a separation process of acid gas, which comprises the following steps:

[0009] 1) The acid gas to be treated is separated into gas and liquid, the liquid is sent to the sewage buffer tank, and the gas is sent to the first-stage booster compressor;

[0010] 2) pressurizing the gas sent to the first-stage booster compressor, wherein the liquid produced after the pressurization is sent to the sewage buffer tank, and the pressurized gas is sent to the dehydration device;

[0011] 3) deliquoring the gas sent to the deliquoring device, wherein the deliquored gas is sent to the sewage buffer tank and the gas is sent to a primary electric heater for heating; for example, the gas may be heated to a temperature of 40 to 60° C.;

[0012] 4) The heated gas is sent to the first-stage hollow fiber membrane group for separation, wherein H2S is output from the high-pressure side to the H2S booster compressor for boosting, and CO2 mixed with H2S (a small amount) is output from the permeation side to the second-stage booster compressor;

[0013] 5) The CO2 mixed with a small amount of H2S that is pressurized in the secondary booster compressor is sent to the secondary heater for heating; for example, it can be heated to a temperature of 40 to 60°C;

[0014] 6) The heated CO2 mixed with a small amount of H2S is sent to the secondary hollow fiber membrane group for separation, wherein the H2S is output from the high pressure side to the H2S booster compressor for boosting, for example, the H2S output from the high pressure side is combined with the H2S output from the high pressure side of the primary hollow fiber membrane group and sent to the H2S booster compressor, and the CO2 is output from the permeate side to the CO2 booster compressor;

[0015] 7) When the H2S pressurized in the H2S booster compressor reaches a supercritical state, it is sent to a formation for sealing; the formation is preferably a formation that no longer produces gas; for example, when the H2S reaches a supercritical state, it is transported to a treatment well through a pipeline, and then injected into a formation that no longer produces gas through a wellbore for sealing.

[0016] 8) After the CO2 is pressurized and the pressure is adjusted in the CO2 booster compressor, it is sent to the formation for storage, or transported to the oil recovery well for oil recovery.

[0017] In a specific embodiment, the fibers in the hollow fiber membrane group are at least one of amino polyimide, amino cellulose acetate and amino polysulfone.

[0018] In a specific embodiment, the hollow fiber membrane group is composed of a pressure-resistant metal shell and hollow fiber membranes filling the pressure-resistant metal shell, wherein an air inlet is provided on the shell, and air outlets are provided on both sides of the cavity.

[0019] In a specific embodiment, in step 1), the acid gas is subjected to gas-liquid separation by a gas-liquid separator.

[0020] In a specific embodiment, the deliquation device in step 2) is a molecular sieve deliquation device.

[0021] In a specific embodiment, the pressure increased by the primary booster compressor and the pressure increased by the secondary compressor are independently 1 to 2 MPa.

[0022] In a specific embodiment, the pressure increased by the H 2 S booster compressor and the pressure increased by the CO 2 booster compressor are independently 10 to 30 MPa.

[0023] In a specific embodiment, in step 7), H2S is pressurized by the H2S booster compressor and then sent to a flow meter, and then sent to a pressure regulating device for pressure regulation to make the H2S reach a supercritical state.

[0024] In one specific embodiment, in step 8), CO2 is pressurized by the CO2 booster compressor and then sent to a flow meter, and then sent to a pressure regulating device for pressure regulation. The flow meter can be used to measure CO2, which helps to accurately separate the amount of CO2 for subsequent use or oil recovery and storage.

[0025] In a specific embodiment, the acid gas to be treated comes from the MDEA regeneration tower, and the liquid sent to the sewage buffer tank is sent back to the MDEA regeneration tower. The liquid in the sewage buffer tank can be pumped into the MDEA regeneration tower by a pump, wherein the liquid is mainly water. In this way, on the one hand, the water balance of the system can be maintained and the water replenishment of the system can be reduced, and on the other hand, zero emission of H2S and CO2 can be achieved.

[0026] In a specific embodiment, the crude oil extracted from the oil recovery well by the oil pump is sent to the three-phase separator through the pipeline, and the separated high-CO2 output gas is pressurized to 10MPa to 30MPa by the CO2 reinjection compressor and injected into the oil recovery well for oil recovery. After the crude oil enters the separator on the ground, since the CO2 is separated from the crude oil and the pressure drops, the separated CO2 needs to be circulated and pressurized before it can be reinjected. After the CO2 is injected into the underground oil recovery and sealed, the CO2 reaches a supercritical state and mixes with the crude oil. In the process of oil production, it is inevitable that a small amount of CO2 (about 30%) will return to the ground with the crude oil.

[0027] Beneficial effects of the present invention:

[0028] 1) The membrane separation mixed gas technology using the amino fiber membrane of the present invention is a physical separation technology, which has the advantages of energy saving, low investment, easy installation, easy movement, simple operation, no need to add other components, and no pollution.

[0029] 2) Driven by environmental pressure and economic benefits, the acid gas is separated by the modified fiber membrane of the present invention to obtain CO2 and H2S output gas, of which CO2 is used for oil recovery and H2S is geologically sealed by reinjection technology, thereby realizing an effective way to maximize resource utilization.

[0030] 3) The process of the present invention can achieve zero emission of H2S and CO2. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of the process for separating H2S and CO2 using a dual-stage hollow fiber membrane module is shown. DETAILED DESCRIPTION

[0032] The present invention will be further described below in conjunction with examples, but the examples of the present invention are only exemplary descriptions, and the implementation methods do not constitute limitations of the present invention under any circumstances.

[0033] Unless otherwise specified, the materials used in the present invention are all commercially available.

[0034] Example 1

[0035] The selective permeability coefficients of aminoacetate cellulose, aminopolydimethylsiloxane, aminopolyimide, aminopolycarbonate and aminopolysulfone were determined by isobaric method according to ISO 15105-2:2003. The results are shown in Table 1.

[0036] Table 1 Selective permeability coefficients of five types of films at 30°C (cm3(STP)·cm·cm -2 ·s -1 ·Pa -1 )

[0037] polymer <![CDATA[H2S Permeability Coefficient]]> <![CDATA[CO2 Permeability Coefficient]]> Separation factor Cellulose Glycol Acetate <![CDATA[5.74×10 -14 ]]> <![CDATA[4.726×10 -11 ]]> 8.23 Amodimethicone <![CDATA[6.02×10 -11 ]]> <![CDATA[2.03×10 -10 ]]> 3.37 Amino polyimide <![CDATA[4.75×10 -14 ]]> <![CDATA[8.27×10 -13 ]]> 17.41 Amino polycarbonate <![CDATA[4.26×10 -14 ]]> <![CDATA[2.31×10 -13 ]]> 5.43 Amino polysulfone <![CDATA[5.61×10 -14 ]]> <![CDATA[4.201×10 -13 ]]> 7.49

[0038] Example 2

[0039] Hollow fiber membrane module

[0040] The amino polyimide hollow fiber bundle with an outer diameter of 500 to 600 pum, an inner diameter of 200 to 300 pum, and a length of 3 to 6 meters is filled into a high-pressure metal shell (the pressure resistance can be determined according to the requirements and the existing process), one end of the fiber bundle is sealed, and the other end is bonded together with a composite epoxy resin adhesive to form a hollow fiber membrane module consisting of a shell and a hollow fiber bundle. Among them, an air inlet is provided on the shell, and air outlets are provided on both sides of the cavity.

[0041] Example 3

[0042] Flat membrane module

[0043] There is a film on each side of the support plate, and the front side (material passing side) of the film is opposite to the front side of the adjacent film on the adjacent support plate, forming a material passing cavity.

[0044] Example 4

[0045] Spiral membrane module

[0046] The rolled membrane element is mainly made of flat membrane, including flat membrane, feed grid, dialysate grid, glue and dialysate collection tube and other components.

[0047] The common spiral membrane elements used for industrial separation also have anti-twist devices at both ends. The main advantages of spiral membrane components are high packing density, easy operation and relatively consistent industry standards. Because in most membrane applications, the membrane is in the form of spiral membrane.

[0048] Example 5

[0049] In such Figure 1 Determination of hollow fiber membrane modules, spiral membrane modules (only Figure 1 The hollow fiber membrane modules in the Figure 1 The pressure drop of the hollow fiber membrane assembly in the membrane module is replaced by a flat membrane assembly): a pressure gauge or pressure transformer is installed at the permeate inlet, permeate outlet and high-pressure outlet of each membrane assembly for measurement.

[0050] The measurement results show that the pressure drop of hollow fiber membrane module is ≤1.5MPa; the pressure drop of spiral membrane module is ≤1.2MPa; the pressure drop of flat membrane module is ≤0.5MPa.

[0051] Determination of separation recovery rates of hollow fiber membrane modules, rolled membrane modules and flat membrane modules: CO2 recovery rate of hollow fiber membrane modules ≥80%; CO2 recovery rate of pressure drop of rolled membrane and flat membrane modules ≥60%.

[0052] Table 2 Comparison of advantages and disadvantages of three types of membrane modules for H2S / CO2 separation at 30℃

[0053] project Hollow fiber membrane module Spiral membrane module Flat membrane module Produces pressure drop high Moderate Low Suitable for high pressure operation Suitable Moderate Moderate Area Small Moderate big Separation recovery rate (separation effect) high Moderate Moderate

[0054] Note: "High pressure" in Table 2 refers to above 10MPa.

[0055] Example 6

[0056] according to Figure 1As shown, firstly, the oil recovery well 20 is recovered, and the crude oil extracted from the oil recovery well 20 by the oil pump 21 is sent to the three-phase separator 22 by the pipeline, and the separated high-CO2 content output gas is pressurized to 10MPa to 30MPa by the CO2 reinjection compressor 23, and then injected into the storage well 19 through the third flowmeter 24 and the pressure regulating device 18, and the separated crude oil is transported out by a tank truck. The associated gas from the oil field is desulfurized and decarbonized in the MDEA regeneration tower 1, and then the acid gas from the MDEA regeneration tower 1 enters the separator 2 for gas-liquid separation. The liquid below the separator 2 is sent to the sewage buffer tank 14, and the gas above is sent to the first-level booster compressor 3 for pressurization. After the pressure is increased to 1Mpa to 2MPa, it is sent to the molecular sieve 4 for molecular sieve dehydration. The water removed by the molecular sieve 4 is combined with the water removed by the first-level booster compressor 3 and sent to the sewage buffer tank 14. The acidic sewage in the sewage buffer tank 14 is sent to the MDEA regeneration tower 1 by the sewage pump 15. On the one hand, it can maintain the water balance of the system and reduce the water replenishment of the system. On the other hand, it can achieve zero emission of H2S and CO2; the dehydrated acid gas is sent to the first-level heater 5 for heating and then sent to the first-level hollow fiber membrane group 6 for membrane separation. After separation, H2S is output from the high-pressure side and sent to the H2S booster compressor 10 for pressurization. After the pressure is increased to 10MPa to 30MPa, it is sent to the first flowmeter 11 at high pressure, and then sent to the first pressure regulating device 12 The pressure is adjusted, and after reaching the supercritical state, it is transported to the first storage well 13 through a pipeline, and then injected into the formation that no longer produces gas for storage through the wellbore; the CO2 accompanied by H2S separated by the first-level hollow fiber membrane group 6 passes through the membrane and is sent to the second-level booster compressor 7 from the permeation side for pressurization, and the pressure is increased to 1MPa to 2MPa and sent to the second-level heater 8 for heating. The heated gas is further sent to the second-level hollow fiber membrane group 9 for membrane separation, and the H2S output from the high-pressure side of the second-level hollow fiber membrane group 9 The gas is combined with the H2S gas output from the high-pressure side of the first-level hollow fiber membrane group 6 and sent to the H2S booster compressor 10, and then enters the first pressure regulating device 12 through the first flowmeter 11 for pressure regulation, transportation, and geological storage; the CO2 permeated from the permeation side of the second-level hollow fiber membrane group 9 is transported by a pipeline to the CO2 booster compressor 16, and after the pressure is increased to 10MPa to 30MPa, the flow rate is measured by the second flowmeter 17 and then sent to the second pressure regulating device 18, and after pressure regulation, it is transported to the second storage well 19.

[0057] After separation treatment by this process, the separation efficiency of H2S and CO2 can reach 90% to 98%, so it is particularly suitable for removing H2S and CO2 with high separation rate.

[0058] Example 7

[0059] The other process steps are the same, except that the secondary booster compressor 7 , the secondary heater 8 and the secondary hollow fiber membrane group 9 are not included.

[0060] After separation treatment by this process, the H2S and CO2 separation efficiency can only reach 80% to 85%.

[0061] Although the present application has been described with reference to specific embodiments, it will be appreciated by those skilled in the art that various changes may be made without departing from the true spirit and scope of the present application. In addition, various changes may be made to the subject, spirit and scope of the present application to adapt to specific situations, materials, material combinations and methods. All of these changes are included within the scope of the claims of the present application.

Claims

1. A process for separating acid gas, comprising the following steps: 1) The acid gas to be treated is separated into gas and liquid, the liquid is sent to the sewage buffer tank, and the gas is sent to the first-stage booster compressor; 2) pressurizing the gas sent to the first-stage booster compressor, wherein: The liquid produced after the pressurization is sent to the sewage buffer tank, and the pressurized gas is sent to the deliquification device; 3) deliquoring the gas sent to the deliquoring device, wherein the deliquored gas is sent to the sewage buffer tank and the gas is sent to a primary electric heater for heating; 4) Sending the heated gas to the first-stage hollow fiber membrane group for separation, wherein H2S is output from the high-pressure side to the H2S booster compressor for boosting, and CO2 mixed with H2S is output from the permeate side to the second-stage booster compressor; wherein the hollow fiber membrane group is composed of a pressure-resistant metal shell and hollow fiber membranes filling the pressure-resistant metal shell, wherein the shell is provided with an air inlet and air outlets are provided on both sides of the cavity; the fibers in the hollow fiber membrane group are amino polyimide; 5) The CO2 mixed with a small amount of H2S that is pressurized in the secondary booster compressor is sent to the secondary heater for heating; 6) The heated CO2 mixed with a small amount of H2S is sent to the secondary hollow fiber membrane group for separation, wherein H2S is output from the high-pressure side to the H2S booster compressor for pressurization, and CO2 is output from the permeate side to the CO2 booster compressor; 7) When the H2S boosted in the H2S booster compressor reaches a supercritical state, it is sent to the formation for storage; 8) After the CO2 is pressurized and the pressure is adjusted in the CO2 booster compressor, it is sent to the formation for storage, or transported to the oil recovery well for oil recovery.

2. The process according to claim 1, characterized in that In step 1), the acid gas is separated into gas and liquid by a gas-liquid separator.

3. The process according to claim 1, characterized in that The deliquation device in step 2) is a molecular sieve deliquation device.

4. The process according to claim 1, characterized in that The pressure increased by the primary booster compressor and the pressure increased by the secondary booster compressor are independently 1 to 2 MPa.

5. The process according to claim 1, characterized in that The pressure increased by the H 2 S booster compressor and the pressure increased by the CO 2 booster compressor are independently 10 to 30 MPa.

6. The process according to claim 1, characterized in that In step 7), the H2S is pressurized by the H2S booster compressor and sent to a flow meter, and then sent to a pressure regulating device for pressure regulation to make the H2S reach a supercritical state; and / or In step 8), CO2 is pressurized by the CO2 booster compressor and sent to a flow meter, and then sent to a pressure regulating device for pressure regulation.

7. The process according to claim 1, characterized in that The acid gas to be treated comes from the MDEA regeneration tower, and the liquid sent to the sewage buffer tank is sent back to the MDEA regeneration tower.

8. The process according to any one of claims 1 to 7, characterized in that The crude oil extracted from the oil recovery well by the oil pump is sent to the three-phase separator through the pipeline. The separated high-CO2 output gas is pressurized to 10MPa to 30MPa by the CO2 reinjection compressor and injected into the oil recovery well again for oil recovery.

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