A high-temperature heat pump coupled amine carbon capture process for natural gas decarbonization

Abstract

The present invention relates to a high-temperature heat pump coupled amine carbon capture process for natural gas decarbonization, which is composed of a natural gas absorption module, a natural gas desorption module, and a high-temperature heat pump heating module. After being compressed and cooled, the natural gas enters the absorption tower to react with the lean amine solution and flows out from the top of the tower. The rich amine solution that has absorbed CO2 flows out from the bottom of the tower, is depressurized and heated, and then 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 for the reboiler of the regeneration tower utilizes the wastewater of the natural gas purification plant as the heat source of the heat pump, and adopts the form of a high-temperature heat pump for energy supply. The carbon capture rate of this process can reach more than 95%. Compared with the existing technology, the present invention utilizes the waste heat near the gas field station, greatly improving the energy utilization rate. The technical means of combining the high-temperature heat pump and the amine decarbonization can effectively reduce the regeneration energy consumption in the amine decarbonization while maintaining a high carbon capture rate.

Description

Technical Field

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

[0002] As global reliance on renewable energy increases, natural gas plays an important role as a clean energy source. However, in the long term, the development of decarbonization technologies is crucial for 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 from fossil fuels to non-fossil fuels. Leveraging oilfield resources to support clean energy substitution can achieve energy conservation, emission reduction, cost reduction, and efficiency improvement during oil and gas exploration and development, and is a key measure to promote the green transformation of the oil and gas industry. Many major oil and gas companies, both domestically and internationally, are already utilizing wind power, photovoltaic power generation, and geothermal energy to power oil and gas production. However, with the introduction of various new energy sources, traditional energy usage scenarios and energy management models for oil and gas exploration and development are unable to meet the needs of the deep integration of oil and gas with new energy. Comprehensive design and detailed research are urgently needed regarding production scheduling, consumption scenarios, energy storage methods, and intelligent operation and management of oil and gas multi-energy synergy.

[0003] Chemical absorption is a mature technology commonly used to remove carbon dioxide (CO2) from natural gas. Its main advantages lie in its high efficiency and selectivity. This method involves passing natural gas through a tower filled with an absorbent, where it separates CO2 from the natural gas through a chemical reaction. Commonly used absorbents include amine solutions, such as monoethanolamine (MEA), diethanolamine (DEA), and methanolamine (MDEA). These amine compounds have high absorption capacities and can effectively remove CO2 from natural gas, making them suitable for applications requiring high-purity natural gas or requiring large CO2 removal volumes. Another advantage of chemical absorption is its operational stability, which allows it to adapt to a wide range of inlet CO2 concentration variations.

[0004] However, chemical absorption also has some drawbacks. First, the absorption process requires a high energy input, primarily for regenerating the absorbent. This is because amine absorbents, after adsorbing CO₂, need to be regenerated by heating to release the CO₂ and restore the absorbent's absorption capacity. This regeneration process consumes a large amount of heat energy, increasing operating costs. Second, amine solutions are prone to corrosion and degradation, leading to increased equipment maintenance and replacement costs. Furthermore, the high equipment investment required for chemical absorption makes it suitable for large-scale treatment facilities and may not be economical for small-scale applications or those with large flow rate fluctuations. Therefore, regeneration energy consumption is a key consideration when using chemical absorption for decarbonization.

[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 method and amine method 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 while ensuring the carbon capture rate of natural gas. A high-temperature heat pump coupled amine carbon capture process for natural gas decarbonization is proposed. Traditional processes reduce regeneration energy consumption by adjusting process parameters in the amine decarbonization process, but this method is not universal. Process parameters need to be readjusted for different feed gases and amine decarbonization process flows. The present invention, however, changes the traditional reboiler energy supply method, utilizing wastewater waste heat and adopting a high-temperature heat pump for energy supply. This heating situation is applicable to all amine decarbonization process flows and is therefore universal.

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

[0008] After compression and cooling, natural gas enters the absorption tower, where it reacts with the lean amine solution and flows out from the top. The rich amine solution, which has absorbed CO2, flows out from the bottom of the tower, is depressurized and heated before entering the regeneration tower for reaction. The lean amine solution flowing out of the bottom of the tower is pressurized and cooled before returning to the absorption tower to complete the cycle. The energy required for the reboiler in the regeneration tower is supplied by a high-temperature heat pump, using wastewater from the natural gas purification plant as a heat source.

[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, it enters the absorption tower T-100 from the bottom of the tower.

[0011] (2) The natural gas passed through 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 absorbs CO2 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, 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.

[0013] (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 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 from 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 replenished with water through the replenishing element MAKEUP-100.

[0015] (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.

[0016] (7) Waste heat is used as the heat source of the heat pump. The waste heat enters 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 is applicable 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. Unlike 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-based carbon capture process for natural gas decarbonization is characterized in that the high-temperature heat pump employed in step (7) supplies energy to the reboiler. After absorbing heat in the evaporator, the refrigerant enters the compressor for heating and pressurization. The high-temperature, 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. Hot water absorbs heat from the refrigerant in the heat exchanger, condenses and releases heat before entering the condenser to heat 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), which has a low ozone decay index and global warming potential (GWP) value, belongs 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 the characteristics of being flexibly placed at the end of the regeneration tower. It is applicable to all amine decarbonization processes and has universality and flexibility.

[0027] 2. Compared with the conventional amine decarbonization method of optimizing process parameters to reduce regeneration energy consumption, the present invention has a simple process, utilizes the performance parameters of high-temperature heat pumps, outputs higher heat energy through the high-temperature heat pump cycle with less electrical energy, and greatly reduces the regeneration energy consumption of amine decarbonization.

[0028] 3. The present invention effectively utilizes waste water, waste heat and waste resources in natural gas purification plants, greatly improving energy utilization and ensuring that the CO2 capture rate of the process can be above 95%, which can effectively improve the CO2 recovery rate and purity. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 A process flow chart for a high-temperature heat pump coupled with 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 will be 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 plan is as follows Figure 1 As shown, the simulation was performed using Aspen HYSYS software. 3 The carbon capture work is carried out with a mass fraction of 35% MDEA + 3.5% PZ solution, and the working fluid R1233zd (E) is used as the refrigerant. The molar composition of the raw gas is: 93.8063% CO2 + 0.3600% C2H6 + 0.0466% C3H8 + 0.0105% i-C4H 10 +0.0108% n-C4H 10 +0.0045% i-C5H 12 +0.0057% n-C5H 12 +0.0510% H2O+0.0466% H2S+5.660% CO2, pressure 2.5MPa, temperature 25℃, flow rate 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 the compressor, air cooler and condenser to reach 40℃ and 2.9MPa, and then enters the absorption tower T-100 from the bottom of the tower.

[0035] (2) The natural gas passed through 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 absorbs CO2 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 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 at a temperature of 112°C flows out from the bottom of the tower.

[0038] (5) The lean amine solution from 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 replenished with water and amine solution through the replenishing element MAKEUP-100.

[0039] (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.

[0040] (7) Utilize the waste heat at 80℃ as the heat source of the heat pump. The waste heat enters 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] Simulation calculations show that the CO2 capture rate of this carbon capture process, which uses a high-temperature heat pump coupled with MDEA+PZ solution, reaches 95%, the CO2 content in the purified gas is as low as 0.29%, and the energy consumption of the system for capturing unit mass of CO2 is approximately 0.2930kW·h.

[0044] This invention proposes for the first time the coupling of a high-temperature heat pump into a chemical absorption decarbonization process. Compared with existing chemical absorption CO2 capture technologies, the process combining a high-temperature heat pump and amine decarbonization significantly improves the CO2 capture rate and significantly reduces system energy consumption. Simulations using Aspen HYSYS, a software widely used in the petrochemical industry, confirm that the present invention can achieve a CO2 capture rate exceeding 95%, and the CO2 content in the purified gas is reduced to below 0.3%, while significantly reducing the system's regeneration energy consumption and total energy consumption. Furthermore, the process described in this invention is highly adaptable to different feed gas temperature, pressure, and composition conditions and can be applied to 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. After reaching high temperature and high pressure, the raw gas enters the absorption tower T-100 from the bottom of the tower; (2) The natural gas passed through 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 in 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 from 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 from 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 replenished with water through the replenishing 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 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 is applicable to different raw gas compositions and is applicable to most types of natural gas.

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

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

4. A high-temperature heat pump coupled amine carbon capture process for natural gas decarbonization according to claim 1, characterized in that The high-temperature heat pump used in step (7) supplies energy to the reboiler. After absorbing heat in the evaporator, the refrigerant 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 then 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, if the working fluid used is R1233zd(E), it has a low ozone attenuation index and greenhouse effect index GWP value, belongs to A1 type refrigerant, and is an environmentally friendly refrigerant.

6. A high-temperature heat pump coupled amine carbon capture process for natural gas decarbonization according to claim 1, characterized in that The principle of the entire process flow proposed in step (7) 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.

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