High-temperature heat pump coupling amine method carbon capture process for natural gas decarburization

Abstract

The invention relates to a high-temperature heat pump coupling amine method carbon capture process for natural gas decarburization. A natural gas absorption module, a natural gas desorption module and a high-temperature heat pump heat supply module are included. Natural gas enters the absorption tower after being compressed and cooled, reacts with the lean amine solution and flows out of the tower top, the rich amine solution absorbing CO2 flows out of the tower bottom, is depressurized and heated and then enters the regeneration tower to react, and the lean amine solution flowing out of the tower bottom is pressurized and cooled and then enters the absorption tower again to complete circulation. Waste water of a natural gas purification plant is used as a heat source of a heat pump for energy required by a reboiler of the regeneration tower, the situation of a high-temperature heat pump is adopted for energy supply, and the carbon capture energy of the process can reach 95% or above; compared with the prior art, the waste heat near the gas field station yard is utilized, the energy utilization rate is greatly improved, and the regeneration energy consumption in amine decarburization can be effectively reduced while the high carbon capture rate is kept by combining the high-temperature heat pump and the amine decarburization technical means.

Description

Technical Field

[0001] The invention belongs to the technical field of chemical separation, and designs a natural gas carbon capture process using an alcohol amine method, which is a carbon capture process combining a high-temperature heat pump with amine decarbonization. Background Art

[0002] As the world's reliance on renewable energy increases, natural gas plays an important role as a clean energy source. However, in the long run, the development of its decarbonization technology is a key link in achieving comprehensive decarbonization and transitioning to a cleaner and more sustainable energy system. Reducing the carbon footprint of natural gas use through technological innovation will help accelerate the transition of the energy structure from fossil fuels to non-fossil fuels. Using oilfield resources to support clean energy substitution can achieve energy conservation and emission reduction and cost reduction and efficiency improvement in the process of oil and gas exploration and development, and is an important measure to promote the green transformation of the oil and gas industry. Many large oil and gas companies at home and abroad are already using wind power, photovoltaic power generation, and geothermal energy to supply oil and gas production. However, after the introduction of a variety of new energy sources, the traditional energy use scenarios and energy management and control modes of oil and gas exploration and development are difficult to meet the needs of deep integration of oil and gas and new energy. It is urgent to carry out comprehensive design and detailed research on production scheduling, consumption scenarios, energy storage methods, oil and gas-multi-energy collaborative intelligent operation and control of oil and gas and new energy.

[0003] Chemical absorption is a method commonly used to remove carbon dioxide (CO 2 ) is a mature technology, and its main advantages are high efficiency and selectivity. This method passes natural gas into a tower filled with absorbent and uses chemical reactions to convert CO 2 Separated from natural gas. Commonly used absorbents include amine solutions, such as monoethanolamine (MEA), diethanolamine (DEA) and methanolamine (MDEA). These amine compounds have high absorption capacity and can effectively absorb CO 2 Removed from natural gas, suitable for high purity natural gas or CO 2 Another advantage of the chemical absorption method is that it has good operational stability and can adapt to a wider range of inlet CO 2 Concentration changes.

[0004] However, chemical absorption also has some disadvantages. First, the absorption process requires a high energy input, mainly for regenerating the absorbent. This is because amine absorbents absorb CO 2 After that, it needs to be regenerated by heating to release CO 2And restore the absorbent to its absorption capacity. This regeneration process consumes a lot of heat energy, increasing operating costs. Secondly, amine solutions are prone to corrosion and degradation, resulting in increased maintenance and replacement costs for equipment. In addition, the chemical absorption method has a high equipment investment and is suitable for large-scale treatment facilities. It may not be economical for small-scale applications or applications with large flow fluctuations. Therefore, when using the chemical absorption method for decarbonization, it is necessary to focus on the regeneration energy consumption.

[0005] Based on the research of other invention patents, this invention uses high-temperature heat pump technology for the first time to study the energy reduction of regeneration energy consumption in the chemical absorption and amine decarbonization process. Summary of the invention

[0006] The purpose of the present invention is to reduce the regeneration energy consumption in the amine decarbonization process, and it is necessary to ensure the carbon capture rate of natural gas, and a high-temperature heat pump coupled amine carbon capture process for natural gas decarbonization is proposed. The traditional process is to reduce the regeneration energy consumption by adjusting the process parameters in the amine decarbonization process, but this method is not universal. For different raw gas and amine decarbonization process, the process parameters need to be readjusted. The present invention changes the traditional energy supply method of the reboiler, utilizes the waste heat of wastewater, and adopts a high-temperature heat pump to supply energy. This heating situation is applicable to all amine decarbonization process flows and is universal.

[0007] Combination Figure 1 The process flow chart shown in the figure, the purpose of the present invention can be achieved by the following technical solutions:

[0008] After being compressed and cooled, the natural gas enters the absorption tower, reacts with the lean amine solution, and flows out from the top of the tower, absorbing CO 2 The rich amine solution flows out from the bottom of the tower, and after being reduced in pressure and heated up, it enters the regeneration tower for reaction. The lean amine solution flowing out from the bottom of the tower is pressurized and cooled, and then enters the absorption tower again to complete the cycle. The energy required by the reboiler of the regeneration tower uses the wastewater from the natural gas purification plant as the heat source of the heat pump, and adopts the high-temperature heat pump method for energy supply.

[0009] This process specifically includes the following steps:

[0010] (1) The raw gas is pressurized and cooled by compressors K-100 and K-101, air coolers, and condensers, and then enters separators V-100 and V-101 for separation. After reaching high temperature and high pressure, the raw gas enters the absorption tower T-100 from the bottom of the tower.

[0011] (2) The natural gas from step (1) enters the absorption tower T-100 and reacts with the lean amine solution from the top of the tower. The purified natural gas flows out from the top of the tower and absorbs CO 2 The rich amine solution flows out from the bottom of the tower.

[0012] (3) The rich amine solution passing through step (2) first enters the throttle valve VLV-100 for throttling and pressure reduction, and then enters the separator V-102 for gas-liquid separation. The liquid rich amine solution enters the lean-rich liquid heat exchanger E-102 for heating.

[0013] (4) The rich amine solution from step (3) enters the regeneration tower T-101 from the top of the tower to react, and the high CO content is desorbed. 2 The gas flows out from the top of the tower, and the remaining lean amine solution flows out from the bottom of the tower.

[0014] (5) The lean amine solution obtained in step (4) enters the lean-rich liquid heat exchanger E-102 for cooling. The cooled lean amine solution enters the pump P-100 for pressure reduction and is then supplemented with water through the supplementary element MAKEUP-100.

[0015] (6) The lean amine solution from step (5) enters the condenser E-103 for cooling and reducing the pressure, and then enters the absorption tower T-100 through the circulation element RCY-1 for reaction, completing the entire circulation process.

[0016] (7) Waste heat is used as the heat source of the heat pump. The waste heat enters from the evaporator C-100 to heat the refrigerant. The refrigerant that has absorbed the heat enters the compressor K-102 for heating and pressurization.

[0017] (8) The refrigerant passing through step (7) enters the heat exchanger E-105 to condense and release heat, then enters the throttle valve VLV-101 to throttle and reduce the pressure, and then enters the evaporator for the next cycle.

[0018] (9) The hot water absorbs heat through the heat exchanger E-105 and then enters the condenser E-104 for condensation and heat release. The released heat is used to heat the reboiler of the regeneration tower T-101. The condensed water enters the heat exchanger E-105 again for the next cycle.

[0019] Among them, the high-temperature heat pump coupled amine carbon capture process for natural gas decarbonization is characterized in that the proposed process can be applied to different raw gas compositions and is applicable to most types of natural gas.

[0020] Furthermore, the high-temperature heat pump coupled amine carbon capture process for natural gas decarbonization is characterized in that the mixed amine solution used in step (2) is MDEA+PZ solution. Different from the decarbonization with a single alcohol amine solution, the decarbonization with PZ activated MDEA solution can effectively improve the carbon capture rate.

[0021] Furthermore, the high-temperature heat pump coupled amine carbon capture process for natural gas decarbonization is characterized in that the waste heat resource utilized in step (7) is wastewater from the gas field station, and the waste resources are recycled, thereby improving energy utilization and enhancing environmental protection.

[0022] Furthermore, the high-temperature heat pump coupled amine carbon capture process for natural gas decarbonization is characterized in that the high-temperature heat pump used in step (7) supplies energy to the reboiler, the refrigerant absorbs heat in the evaporator and then enters the compressor for heating and pressurization, the high-temperature and high-pressure refrigerant enters the heat exchanger for condensation and heat release, then enters the throttle valve for throttling and pressure reduction, and then enters the evaporator to complete the cycle. The hot water meets the refrigerant in the heat exchanger and absorbs heat, and then enters the condenser for condensation and heat release to supply heat to the regeneration tower, completing the entire process.

[0023] Furthermore, the high-temperature heat pump coupled amine carbon capture process for natural gas decarbonization is characterized in that R1233zd(E) is used as a refrigerant in step (7), and has a low ozone attenuation index and a greenhouse effect index GWP value, belonging to the A1 type refrigerant, and is an environmentally friendly refrigerant.

[0024] Furthermore, the high-temperature heat pump coupled amine carbon capture process for natural gas decarbonization is characterized by the entire process flow proposed in step (7), the principle of which is to use the refrigerant of the high-temperature heat pump cycle for energy supply, and to obtain the performance parameters of the high-temperature heat pump cycle by dividing the output heat energy by the input electrical energy, thereby reducing the regeneration energy consumption of the regeneration system.

[0025] The beneficial effects of the present invention are :

[0026] 1. The present invention uses a high-temperature heat pump to reduce regeneration energy consumption, solves the problem of optimizing the conventional natural gas decarbonization process, and has targeted characteristics. The high-temperature heat pump can be flexibly placed at the end of the regeneration tower, and is applicable to the amine decarbonization process, with universality and flexibility.

[0027] 2. Compared with the conventional method of optimizing process parameters for decarbonization by amine method to reduce regeneration energy consumption, the process of the present invention is simple, and the performance parameters of high-temperature heat pump are utilized to output higher heat energy through the high-temperature heat pump cycle with less electric energy, thereby greatly reducing the regeneration energy consumption of decarbonization by amine method.

[0028] 3. The present invention effectively utilizes waste water, waste heat and waste resources in the natural gas purification plant, greatly improves energy utilization, and ensures the CO 2 The capture rate can be above 95%, which can effectively improve CO 2 Recovery and purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A process flow chart of a high-temperature heat pump coupled amine carbon capture process for natural gas decarbonization

[0030] Among them, K-compressor; AC-air cooler; V-separator; E-heat exchanger; T-100 absorption tower; T-101 analysis tower; VLV-valve; P-pump; C-evaporator; MAKEUP-make-up; RCY-circulation. DETAILED DESCRIPTION

[0031] The present invention is described in detail below with reference to the accompanying drawings and specific embodiments.

[0032] Example 1

[0033] A high temperature heat pump coupled amine carbon capture process for natural gas decarbonization, the implementation scheme is as follows Figure 1 As shown, Aspen HYSYS software was used for simulation. 3 The mass fraction of 35% MDEA + 3.5% PZ solution is used for carbon capture, and the working fluid R1233zd (E) is used as the refrigerant. The molar composition of the raw gas is: 93.8063% CO 2 +0.3600%C 2 H 6 +0.0466%C 3 H 8 +0.0105%iC 4 H 10 +0.0108%nC 4 H 10 +0.0045%iC 5 H 12 +0.0057%nC 5 H 12 +0.0510%H 2 O+0.0466%H 2 S+5.660%CO 2 , pressure is 2.5MPa, temperature is 25℃, flow rate is 1000m 3 / h. The specific steps of a high-temperature heat pump coupled amine carbon capture process for natural gas decarbonization are as follows:

[0034] (1) The raw gas is pressurized and cooled by a compressor, air cooler, and condenser to reach 40°C and 2.9MPa, and then enters the absorption tower T-100 from the bottom of the tower.

[0035] (2) The natural gas from step (1) enters the absorption tower T-100 and reacts with the lean amine solution from the top of the tower. The purified natural gas flows out from the top of the tower and absorbs CO 2 The rich amine solution flows out from the bottom of the tower.

[0036] (3) The rich amine solution passing through step (2) first enters the throttle valve VLV-100 for throttling and reducing the pressure to 170 kPa, and then enters the separator V-102 for gas-liquid separation. The liquid rich amine solution enters the lean-rich liquid heat exchanger E-102 for heating to 85°C.

[0037] (4) The rich amine solution from step (3) enters the regeneration tower T-101 from the top of the tower to react, and the high CO content is desorbed. 2 The gas flows out from the top of the tower, and the remaining lean amine solution at a temperature of 112°C flows out from the bottom of the tower.

[0038] (5) The lean amine solution obtained in step (4) enters the lean-rich liquid heat exchanger E-102 for cooling. The cooled lean amine solution enters the pump P-100 for pressure reduction, and is then supplemented with water and amine solution through the supplementary element MAKEUP-100.

[0039] (6) The lean amine solution from step (5) enters the condenser E-103 for cooling and reducing the pressure, and then enters the absorption tower T-100 through the circulation element RCY-1 for reaction, completing the entire circulation process.

[0040] (7) Utilize the waste heat at 80℃ as the heat source of the heat pump. The waste heat enters from the evaporator C-100 to heat the working fluid R1233zd(E). After absorbing the heat, the refrigerant enters the compressor K-102 for heating and pressurization.

[0041] (8) The refrigerant passing through step (7) enters the heat exchanger E-105 to condense and release heat, then enters the throttle valve VLV-101 to throttle and reduce the pressure, and then enters the evaporator for the next cycle.

[0042] (9) The hot water absorbs heat through the heat exchanger E-105 and then enters the condenser E-104 for condensation and heat release. The released heat is used to heat the reboiler of the regeneration tower T-101. The condensed water enters the heat exchanger E-105 again for the next cycle.

[0043] Through simulation calculation, it is known that the CO2 of this carbon capture process using a high-temperature heat pump coupled with MDEA+PZ solution is 2 The capture rate is as high as 95%, and the CO in the purified gas 2 The content is as low as 0.29%, and the system captures CO per unit mass 2 The energy consumption is about 0.2930kW·h.

[0044] The present invention proposes for the first time to couple a high temperature heat pump into the chemical absorption decarbonization process. 2Compared with the capture technology, the organic combination of high temperature heat pump and amine decarbonization process described in the present invention makes CO 2 The capture rate of CO2 is significantly improved, and the energy consumption of the system is significantly reduced. The simulation calculation of Aspen HYSYS software widely used in the petrochemical industry confirms that the present invention can achieve CO2 2 The capture rate can reach more than 95%, and the CO in the purified gas 2 The content is reduced to below 0.3%, and the regeneration energy consumption and total energy consumption of the system are greatly reduced. In addition, the process described in the present invention has good adaptability to different temperature, pressure and component conditions of raw gas, and can be used in other amine liquid decarbonization processes.

Claims

1. A high-temperature heat pump coupled amine carbon capture process for natural gas decarbonization, characterized in that: The specific steps of this process can be summarized as follows: (1) The raw gas is pressurized and cooled by compressors K-100 and K-101, air coolers, and condensers, and then enters separators V-100 and V-101 for separation, reaching high temperature and high pressure, and then enters the absorption tower T-100 from the bottom of the tower; (2) The natural gas obtained in step (1) enters the absorption tower T-100 and reacts with the lean amine solution from the top of the tower. The purified natural gas flows out from the top of the tower, and the rich amine solution that has absorbed CO2 flows out from the bottom of the tower. (3) The rich amine solution obtained through step (2) first enters the throttle valve VLV-100 for throttling and pressure reduction, then enters the separator V-102 for gas-liquid separation, and the liquid rich amine solution enters the lean-rich liquid heat exchanger E-102 for heating; (4) The rich amine solution obtained in step (3) enters the regeneration tower T-101 from the top of the tower to react, and the desorbed high CO2-containing gas flows out from the top of the tower, and the remaining lean amine solution flows out from the bottom of the tower; (5) The lean amine solution obtained in step (4) enters the lean-rich liquid heat exchanger E-102 for cooling. The lean amine solution after cooling enters the pump P-100 for pressure reduction, and then is supplemented with water through the supplementary element MAKEUP-100; (6) The lean amine solution from step (5) enters the condenser E-103 for cooling and depressurization, and then enters the absorption tower T-100 through the circulation element RCY-1 for reaction, completing the entire circulation process; (7) Using waste heat as the heat source of the heat pump, the waste heat enters from the evaporator C-100 to heat the refrigerant, and the refrigerant that has absorbed the heat enters the compressor K-102 for heating and pressurization; (8) The refrigerant passing through step (7) enters the heat exchanger E-105 to condense and release heat, then enters the throttle valve VLV-101 to throttle and reduce the pressure, and then enters the evaporator for the next cycle; (9) The hot water absorbs heat through the heat exchanger E-105 and then enters the condenser E-104 for condensation and heat release. The released heat is used to heat the reboiler of the regeneration tower T-101. The condensed water enters the heat exchanger E-105 again for the next cycle. Among them, the high-temperature heat pump coupled amine carbon capture process for natural gas decarbonization is characterized in that the proposed process can be applied to different raw gas compositions and is applicable to most types of natural gas.

2. According to the high temperature heat pump coupled amine carbon capture process for natural gas decarbonization as described in claim 1, it is characterized in that The mixed amine solution used in step (2) is MDEA+PZ solution.

3. According to the high temperature heat pump coupled amine carbon capture process for natural gas decarbonization as described in claim 1, it is characterized in that The waste heat resource used in step (7) is waste water from the gas field station, with a temperature between 50° C. and 80° C., which improves energy utilization.

4. According to the high temperature heat pump coupled amine carbon capture process for natural gas decarbonization as described in claim 1, it is characterized in that The high-temperature heat pump used in step (7) supplies energy to the reboiler. After the refrigerant absorbs heat in the evaporator, it enters the compressor for heating and pressurization. The high-temperature and high-pressure refrigerant enters the heat exchanger for condensation and heat release, then enters the throttle valve for throttling and pressure reduction, and then enters the evaporator to complete the cycle. The hot water meets the refrigerant in the heat exchanger and absorbs heat. It enters the condenser for condensation and heat release to supply heat to the regeneration tower, completing the entire process.

5. A high temperature heat pump coupled amine carbon capture process for natural gas decarbonization according to claim 1, characterized in that The circulating working fluid used in step (7) can be replaced at will according to performance requirements. For example, the working fluid used is R1233zd (E) working fluid, which has low ozone attenuation index and greenhouse effect index GWP values, belongs to A1 type refrigerant, and is an environmentally friendly refrigerant.

6. According to the high temperature heat pump coupled amine carbon capture process for natural gas decarbonization as described in claim 1, it is characterized in that The entire process flow proposed in step (7) is based on the principle of utilizing the refrigerant of the high-temperature heat pump cycle for energy supply, dividing the input electrical energy by the output heat energy to obtain the performance parameters of the high-temperature heat pump cycle, thereby reducing the regeneration energy consumption of the regeneration system.

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