Cold energy utilization and carbon capture system for large LNG (Liquefied Natural Gas) factory in extremely cold area

Abstract

The utility model provides a cold energy utilization and carbon capture system for a large-scale LNG (Liquefied Natural Gas) factory in an extremely cold region, which comprises a natural gas liquefaction unit, a carbon capture unit and a carbon capture unit, the gas turbine power generation unit is connected with the natural gas liquefaction unit and is used for combusting raw material natural gas to generate power and transmitting electric power to the natural gas liquefaction unit; one end of the flue gas capturing and recycling unit is connected with the gas turbine power generation unit, and the flue gas capturing and recycling unit is used for receiving flue gas discharged by the gas turbine and carrying out deep purification and CO2 enrichment and separation on the flue gas; the other end of the cold energy recovery unit is introduced into the natural gas liquefaction unit, penetrates out and returns, and is used for realizing low-temperature liquefaction and recovery of CO2 by utilizing cold energy of the natural gas liquefaction unit; according to the system, cold energy of the extremely cold environment in the arctic region and process pressure difference energy of a large LNG factory are integrated and utilized, meanwhile, CO2 in exhausted smoke of the system is efficiently purified, enriched, captured, liquefied and recycled, the overall energy efficiency of the large LNG factory is remarkably improved, carbon reduction and emission reduction in the polar region are promoted, and the greenhouse effect is relieved.

Description

Technical Field

[0001] The utility model relates to the technical field of liquefied natural gas, and in particular to a cold energy utilization and carbon capture system for a large-scale LNG plant in extremely cold regions. Background Art

[0002] Extremely cold regions, such as the Arctic, are known for their vast expanses and extreme climatic conditions. For example, in Russia's Yamal region, the average annual temperature is -3°C in summer, dropping to -20°C in winter and reaching -52°C in extreme cases. However, this frigid region is a major reservoir of global oil and gas resources, boasting over 20 oil and gas basins and approximately 450 proven oil and gas fields. These reserves account for 2.5% of global conventional oil reserves and a staggering 15.5% of natural gas reserves.

[0003] Figure 3 This is the process system flow chart of the current basic load large-scale LNG plant. Its main technical features are: (1) using large-load gas turbine units to burn self-produced natural gas to generate electricity to meet all the power needs of the system; (2) using mixed refrigerant refrigeration cycle technology to achieve the cooling and liquefaction of natural gas, and the throttling link in the process uses a traditional low-temperature throttle valve; (3) a large amount of BOG evaporation gas is generated during the gas-liquid separation at the end of the natural gas liquefaction stage. By introducing part of the raw natural gas for heat exchange, part of the LNG product can be effectively recovered.

[0004] However, the main shortcomings of this technology in large-scale LNG plants in the Arctic are: (1) the natural gas liquefaction process relies on low-cost traditional throttle valves, which are economical and reliable but inefficient, affecting the energy utilization rate of the system; (2) the flue gas generated by gas turbine power generation is directly discharged, and there is a lack of effective carbon reduction and emission reduction measures; (3) the abundant air cold energy contained in the cold natural environment of the Arctic has not been fully tapped in the LNG production process, resulting in energy waste.

[0005] Therefore, how to provide a cold energy utilization and carbon capture system for large-scale LNG plants in extremely cold regions to improve system efficiency and reduce carbon emissions has become an urgent problem to be solved in the current oil and gas development in the Arctic region. Utility Model Content

[0006] The utility model provides a cold energy utilization and carbon capture system for large-scale LNG plants in extremely cold regions, which integrates the utilization of the cold energy of the extremely cold environment in extremely cold regions and the process pressure difference energy of large-scale LNG plants, and at the same time efficiently purifies, enriches, captures and liquefies the CO2 in the exhaust gas of the recovery system, which can not only significantly improve the overall energy efficiency of large-scale LNG plants, but also help promote carbon reduction and emission reduction in polar regions and mitigate the greenhouse effect.

[0007] The utility model provides a cold energy utilization and carbon capture system for a large LNG plant in extremely cold regions, comprising:

[0008] Natural gas liquefaction unit, used to realize natural gas liquefaction and energy recovery during the process;

[0009] a gas turbine power generation unit connected to the natural gas liquefaction unit, configured to burn the raw natural gas to generate electricity and transmit electricity to the natural gas liquefaction unit;

[0010] The flue gas capture and recovery unit has one end connected to the gas turbine power generation unit, and is used to receive the flue gas emitted by the gas turbine and perform deep purification and CO2 enrichment and separation on the flue gas; the other end of the unit passes into the interior of the natural gas liquefaction unit and passes out and returns, and is used to utilize the cold energy of the natural gas liquefaction unit to achieve low-temperature liquefaction and recovery of CO2.

[0011] According to the cold energy utilization and carbon capture system for large-scale LNG plants in extremely cold regions provided by the present invention, the natural gas liquefaction unit includes:

[0012] A natural gas liquefaction main device, the inlet of which is connected to an external raw natural gas pipeline and is used to cool and liquefy the raw natural gas into high-pressure LNG;

[0013] a cryogenic expander, the inlet of which is connected to the outlet of the natural gas liquefaction main device through a high-pressure LNG pipeline, and is used to reduce the pressure of the high-pressure LNG to low-pressure LNG;

[0014] A gas-liquid separator, the inlet of which is connected to the outlet of the cryogenic expander through a low-pressure LNG pipeline, and the gas-liquid separator is used for separating low-pressure LNG to obtain LNG products and BOG boil-off gas.

[0015] According to the cold energy utilization and carbon capture system for large-scale LNG plants in extremely cold regions provided by the present invention, the natural gas liquefaction unit further includes:

[0016] A low-temperature heat exchanger, one inlet of which is connected to the upper outlet of the gas-liquid separator through a BOG evaporation gas pipeline, and one outlet of which is connected to an external BOG system through a BOG pipeline.

[0017] According to the cold energy utilization and carbon capture system for large-scale LNG plants in extremely cold regions provided by the present invention, the natural gas liquefaction unit further includes:

[0018] An LNG storage tank is connected to the bottom outlet of the gas-liquid separator through an LNG product pipeline and is used to store the LNG product separated by the gas-liquid separator.

[0019] According to the cold energy utilization and carbon capture system for large-scale LNG plants in extremely cold regions provided by the present invention, the gas turbine power generation unit includes:

[0020] A gas turbine generator set, wherein the inlet of the gas turbine generator set is connected to an external raw natural gas pipeline through a fuel gas pipeline, is used to burn the raw natural gas to generate electricity, and is used to provide the generated electricity to the natural gas liquefaction main device; the outlet of the gas turbine generator set is connected to the flue gas capture and recovery unit through a combustion engine exhaust pipeline.

[0021] According to the cold energy utilization and carbon capture system for large-scale LNG plants in extremely cold regions provided by the present invention, the flue gas capture and recovery unit includes:

[0022] An air cooler, the inlet of which is connected to the outlet of the gas turbine generator set through the engine exhaust pipe, and is used to cool the exhaust flue gas using the cold energy of the extremely cold environment;

[0023] A cyclone separator, the inlet of which is connected to the outlet of the air cooler through a flue gas cooling gas pipeline, for performing cyclone separation on the cooled flue gas and discharging the generated condensate through a cyclone drainage pipeline connected to its bottom outlet; the upper outlet of the cyclone separator is connected to another inlet of the low-temperature heat exchanger through a pipeline, for cooling and liquefying the CO2 gas;

[0024] A CO2 storage tank, the inlet of which is connected to the other outlet of the low-temperature heat exchanger through a pipeline, is used to store the liquefied CO2.

[0025] According to the cold energy utilization and carbon capture system for large-scale LNG plants in extremely cold regions provided by the utility model, a purification and enrichment device is further provided between the CO2 storage tank and the cyclone separator. One end of the purification and enrichment device is connected to the upper outlet of the cyclone separator through a pipeline, and the other end of the purification and enrichment device is connected to the other inlet of the low-temperature heat exchanger through a pipeline, so as to cool and liquefy the purified and enriched CO2 gas.

[0026] According to the cold energy utilization and carbon capture system for large-scale LNG plants in extremely cold regions provided by the utility model, a booster is further provided between the purification and enrichment device and the cyclone separator, the inlet end of the booster is connected to the upper outlet of the cyclone separator through a flue gas separation gas pipeline, and the outlet end of the booster is connected to the purification and enrichment device through a high-pressure flue gas pipeline.

[0027] According to the cold energy utilization and carbon capture system for large-scale LNG plants in extremely cold regions provided by the present invention, the purification and enrichment device includes:

[0028] an adsorption purifier, the inlet of which is connected to the outlet of the supercharger through the high-pressure flue gas pipeline, for purifying the flue gas;

[0029] A CO2 membrane enrichment separator, the inlet of which is connected to the outlet of the adsorption purifier via a flue gas purification pipeline, for enriching and separating the purified flue gas; one outlet of the CO2 membrane enrichment separator is connected to the waste gas pipeline, for discharging the separated waste gas, and the other outlet of the CO2 membrane enrichment separator is connected to the low-temperature heat exchanger via a high-pressure CO2 pipeline, for passing the separated high-purity CO2 gas into the interior of the low-temperature heat exchanger for liquefaction through heat exchange and cooling.

[0030] According to the cold energy utilization and carbon capture system for large-scale LNG plants in extremely cold regions provided by the utility model, it also includes a CO2 expander, the inlet of the CO2 expander is connected to the low-temperature heat exchanger through a high-pressure CO2 liquid pipeline, and the outlet of the CO2 expander is connected to the inlet of the CO2 storage tank through a low-pressure CO2 liquid pipeline. The CO2 expander is used to expand and reduce the pressure of the cooled and liquefied high-pressure CO2 liquid into a low-pressure CO2 liquid and transport it into the CO2 storage tank for storage.

[0031] The utility model provides a cold energy utilization and carbon capture system for large-scale LNG plants in extremely cold regions. The utility model realizes efficient energy utilization and environmentally friendly production processes by integrating three units: natural gas liquefaction, gas turbine power generation and flue gas capture and recovery. During the natural gas liquefaction process, the system can recover a large amount of cold energy, which is often wasted in traditional processes, but is effectively utilized in this system, thereby improving the overall energy efficiency and the economic feasibility of the project; the gas turbine power generation unit uses part of the raw natural gas as fuel to generate electricity and transmit electricity to the natural gas liquefaction unit, reducing dependence on external electricity; the flue gas capture and recovery unit processes the flue gas emitted by the gas turbine, removes harmful substances and enriches and separates CO2, and can utilize the cold energy generated in the natural gas liquefaction process to realize low-temperature liquefaction of CO2, which not only saves additional refrigeration costs but also improves the CO2 recovery rate. The system can significantly reduce greenhouse gas emissions and realize the reuse of resources and energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] In order to more clearly illustrate the technical solutions in the present invention or the prior art, a brief introduction will be given below to 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 any creative work.

[0033] Figure 1 This is a module diagram of a cold energy utilization and carbon capture system for a large LNG plant in extremely cold regions proposed by the utility model;

[0034] Figure 2 This is a flow chart of a cold energy utilization and carbon capture system for a large LNG plant in extremely cold regions proposed by the utility model;

[0035] Figure 3 This is a process system flow chart of a large-scale base load LNG plant in the prior art.

[0036] Reference numerals:

[0037] M1, natural gas liquefaction unit; M2, gas turbine power generation unit; M3, flue gas capture and recovery unit;

[0038] 1. Natural gas liquefaction main unit; 2. Cryogenic expander; 3. Gas-liquid separator; 4. LNG storage tank; 5. Cryogenic heat exchanger; 6. Gas turbine generator set; 7. Air cooler; 8. Cyclone separator; 9. Booster; 10. Adsorption purifier; 11. CO2 membrane enrichment generator; 12. CO2 expander; 13. CO2 storage tank;

[0039] P1, raw natural gas pipeline; P2, high-pressure LNG pipeline; P3, low-pressure LNG pipeline; P4, LNG product pipeline; P5, BOG evaporated gas pipeline; P6, BOG pipeline; P7, fuel gas pipeline;

[0040] Y1, gas turbine exhaust pipeline; Y2, flue gas cooling pipeline; Y3, swirl drainage pipeline; Y4, flue gas separation pipeline; Y5, high-pressure flue gas pipeline; Y6, flue gas purification pipeline; Y7, waste gas pipeline; Y8, high-pressure CO2 pipeline; Y9, high-pressure CO2 liquid pipeline; Y10, low-pressure CO2 liquid pipeline. DETAILED DESCRIPTION

[0041] To make the purpose, technical solutions, and advantages of the present invention more clear, the following will be combined with the accompanying drawings to clearly and completely describe the technical solutions of the present invention. Obviously, the embodiments described are only some of the embodiments of the present invention, not all of them. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without making creative efforts are within the scope of protection of the present invention.

[0042] The following combination Figure 1-Figure 3 The utility model describes a cold energy utilization and carbon capture system for a large LNG plant in an extremely cold region.

[0043] like Figure 1 As shown, this embodiment provides a cold energy utilization and carbon capture system for a large-scale LNG plant in an extremely cold region, comprising: a natural gas liquefaction unit M1, a gas turbine power generation unit M2 and a flue gas capture and recovery unit M3.

[0044] Among them, the natural gas liquefaction unit M1 is used to realize natural gas liquefaction and energy recovery in the process; the gas turbine power generation unit M2 is connected to the natural gas liquefaction unit M1, and is used to burn raw natural gas to generate electricity and transmit electricity to the natural gas liquefaction unit M1; one end of the flue gas capture and recovery unit M3 is connected to the gas turbine power generation unit M2, and is used to receive the flue gas discharged by the gas turbine, and to deeply purify the flue gas and enrich and separate CO2; its other end is passed into the interior of the natural gas liquefaction unit M1 and passes out and returns, and is used to use the cold energy of the natural gas liquefaction unit M1 to realize low-temperature liquefaction and recovery of CO2.

[0045] With such an arrangement, the utility model realizes efficient energy utilization and an environmentally friendly production process by integrating the three units of natural gas liquefaction, gas turbine power generation and flue gas capture and recovery. During the natural gas liquefaction process, the system can recover a large amount of cold energy, which is often wasted in traditional processes, but is effectively utilized in this system, thereby improving the overall energy efficiency and the economic efficiency of the project; the gas turbine power generation unit M2 uses part of the raw natural gas as fuel to generate electricity and transmit electricity to the natural gas liquefaction unit M1, reducing dependence on external electricity; the flue gas capture and recovery unit M3 processes the flue gas emitted by the gas turbine, removes harmful substances and enriches and separates CO2, and can use the cold energy generated in the natural gas liquefaction process to realize the low-temperature liquefaction of CO2, which not only saves additional refrigeration costs but also improves the recovery rate of CO2. The system can significantly reduce greenhouse gas emissions and realize the reuse of resources and energy.

[0046] In this embodiment, the natural gas liquefaction unit M1 includes: a natural gas liquefaction main device 1, a cryogenic expander 2, and a gas-liquid separator 3. The inlet of the natural gas liquefaction main device 1 is connected to an external raw natural gas pipeline P1, and is used to cool and liquefy the raw natural gas into high-pressure LNG. The inlet of the cryogenic expander 2 is connected to the outlet of the natural gas liquefaction main device 1 through a high-pressure LNG pipeline P2, and is used to reduce the pressure of the high-pressure LNG to low-pressure LNG. The inlet of the gas-liquid separator 3 is connected to the outlet of the cryogenic expander 2 through a low-pressure LNG pipeline P3. The gas-liquid separator 3 is used to separate the low-pressure LNG into LNG product and BOG boil-off gas.

[0047] Such a setting realizes efficient liquefaction, pressure regulation and gas-liquid separation of natural gas. By adopting the low-temperature expander 2 to replace the traditional throttle valve, while achieving the expansion and pressure reduction of high-pressure low-temperature LNG to low-pressure LNG, it can also utilize the pressure difference between the two logistics to drive the expander to rotate and generate electricity, realizing the conversion of mechanical energy into electrical energy. This part of electrical energy can be directly used for other electrical equipment in the system, realizing efficient recovery and utilization of electricity.

[0048] The operating principle of the aforementioned gas-liquid separator 3 is as follows: after low-pressure LNG enters the separator, the pressure drops, causing some of the LNG to evaporate, forming BOG (Boil-Off Gas). The separator then physically separates the liquid LNG from the gaseous BOG. ​​It should be noted that the separator 3 is conventional equipment in the prior art, and its structure and operating principles are not the focus of this article and will not be discussed in detail.

[0049] Furthermore, the natural gas liquefaction unit M1 further includes: a low-temperature heat exchanger 5, one inlet of the low-temperature heat exchanger 5 is connected to the upper outlet of the gas-liquid separator 3 through the BOG evaporation gas pipeline P5, and one outlet of the low-temperature heat exchanger 5 is connected to the external BOG system through the BOG pipeline P6.

[0050] Preferably, the natural gas liquefaction unit M1 further includes: an LNG storage tank 4 , which is connected to the bottom outlet of the gas-liquid separator 3 through an LNG product pipeline P4 and is used to store the LNG product separated by the gas-liquid separator 3 .

[0051] In this embodiment, the gas turbine power generation unit M2 includes: a gas turbine generator set 6, the inlet of the gas turbine generator set 6 is connected to the external raw natural gas pipeline P1 through the fuel gas pipeline P7, and is used to burn the raw natural gas to generate electricity and to provide the generated electricity to the natural gas liquefaction main device 1; the outlet of the gas turbine generator set 6 is connected to the flue gas capture and recovery unit M3 through the gas turbine exhaust pipeline Y1.

[0052] With this arrangement, the gas turbine generator set 6 provides the necessary power support for the entire LNG plant, reducing dependence on external electricity. Through the flue gas capture and recovery unit M3, the emission of harmful substances in the flue gas, especially CO2, can be significantly reduced, thereby improving economic benefits and meeting increasingly stringent environmental protection standards.

[0053] In this embodiment, the flue gas capture and recovery unit M3 includes: an air cooler 7, a cyclone separator 8 and a CO2 storage tank 13; wherein, the inlet of the air cooler 7 is connected to the outlet of the gas turbine generator set 6 through the engine exhaust pipe Y1, and is used to use the cold energy of the extremely cold environment to cool the discharged flue gas; the inlet of the cyclone separator 8 is connected to the outlet of the air cooler 7 through the flue gas cooling gas pipe Y2, and is used to perform cyclone separation on the cooled flue gas and discharge the generated condensate through the cyclone discharge pipe Y3 connected to its bottom outlet; the upper outlet of the cyclone separator 8 is connected to the other inlet of the low-temperature heat exchanger 5 through a pipeline, and is used to cool and liquefy the CO2 gas; the inlet of the CO2 storage tank 13 is connected to the other outlet of the low-temperature heat exchanger 5 through a pipeline, and is used to store the liquefied CO2.

[0054] With such an arrangement, when the flue gas passes through the air cooler 7, it exchanges heat with the extremely cold air outside, thereby utilizing the cold energy of the extremely cold environment to cool the discharged flue gas. As a result, in an extremely cold environment, the air cooler 7 can efficiently utilize natural cold energy without the need for additional cooling equipment, thus saving energy. Moreover, through the preliminary cooling of the air cooler 7, the water vapor and other volatile substances in the flue gas will condense into liquid. Through the treatment of the cyclone separator 8, the condensate and other impurities in the flue gas can be effectively removed, which is beneficial to the subsequent centralized treatment of CO2. Afterwards, the flue gas treated by the cyclone separator 8 enters the low-temperature heat exchanger 5, and through heat exchange with the BOG evaporated gas, the CO2 gas is cooled and liquefied, thereby improving the recovery rate and purity of CO2.

[0055] Furthermore, a purification and enrichment device is provided between the CO2 storage tank 13 and the cyclone separator 8. One end of the purification and enrichment device is connected to the upper outlet of the cyclone separator 8 through a pipeline, and the other end of the purification and collection device is connected to another inlet of the low-temperature heat exchanger 5 through a pipeline, so as to cool and liquefy the purified and enriched CO2 gas.

[0056] In this way, the flue gas treated by the cyclone separator 8 enters the purification and enrichment device, and other components in the flue gas, such as N2, O2, SO x and NO x , thereby enriching CO2 gas, which can significantly increase the concentration of CO2, reduce energy consumption in the subsequent liquefaction process, and improve the recovery rate and purity of CO2.

[0057] Preferably, a booster 9 is provided between the purification and enrichment device and the cyclone separator 8. The inlet end of the booster 9 is connected to the upper outlet of the cyclone separator 8 through the flue gas separation gas pipeline Y4, and the outlet end of the booster 9 is connected to the purification and enrichment device through the high-pressure flue gas pipeline Y5.

[0058] With such an arrangement, after the flue gas treated by the cyclone separator 8 enters the booster 9, the pressure of the flue gas is increased by compression. The booster 9 can ensure that the flue gas has sufficient pressure when entering the purification and enrichment device, thereby improving the CO2 capture efficiency and enrichment effect, and ensuring that the flue gas has sufficient power during the entire treatment process.

[0059] like Figure 2As shown, in some specific embodiments, the purification and enrichment device includes: an adsorption purifier 10 and a CO2 membrane enrichment separator 11. The inlet of the adsorption purifier 10 is connected to the outlet of the booster 9 through the high-pressure flue gas pipeline Y5, which is used to purify the flue gas; the inlet of the CO2 membrane enrichment separator 11 is connected to the outlet of the adsorption purifier 10 through the flue gas purification pipeline Y6, which is used to enrich and separate the purified flue gas; one outlet of the CO2 membrane enrichment separator 11 is connected to the exhaust gas pipeline Y7, which is used to discharge the separated exhaust gas, and the other outlet of the CO2 membrane enrichment separator 11 is connected to the low-temperature heat exchanger 5 through the high-pressure CO2 pipeline Y8, which is used to pass the separated high-purity CO2 gas into the interior of the low-temperature heat exchanger 5 for cooling and liquefaction through heat exchange.

[0060] In this embodiment, a CO2 expander 12 is also included. The inlet of the CO2 expander 12 is connected to the low-temperature heat exchanger 5 through the high-pressure CO2 liquid pipeline Y9, and the outlet of the CO2 expander 12 is connected to the inlet of the CO2 storage tank 13 through the low-pressure CO2 liquid pipeline Y10. The CO2 expander 12 is used to expand and reduce the pressure of the cooled and liquefied high-pressure CO2 liquid into a low-pressure CO2 liquid and transport it into the CO2 storage tank 13 for storage.

[0061] With such an arrangement, when the liquefied high-pressure CO2 liquid passes through the CO2 expander 12, the pressure difference between the two logistics can be used to drive the CO2 expander to generate electricity, thereby converting mechanical energy into electrical energy. This not only helps to improve the overall energy efficiency of the system, but also can reduce energy consumption and operating costs by recycling electrical energy for use by other equipment in the system.

[0062] The beneficial effects of the utility model are:

[0063] (1) Efficiently utilize the extremely cold environment in extremely cold areas, fully cool the system exhaust through air coolers, and maximize the utilization of natural cooling energy.

[0064] (2) A low-temperature expander is used to replace the traditional throttle valve. While expanding and reducing the high-pressure low-temperature LNG to low-pressure LNG, the pressure difference between the two streams can be used to drive the expander to rotate and generate electricity, thereby converting mechanical energy into electrical energy. This part of the electrical energy can be directly used for other electrical equipment in the system, realizing efficient recovery and utilization of electricity.

[0065] (3) The system integrates adsorption purification and CO2 membrane enrichment and separation technology to deeply purify and enrich the CO2 in the exhaust gas of the capture system. At the same time, the BOG evaporation gas cooling energy is used for heat exchange through the low-temperature heat exchanger 5 to realize the liquefaction, recovery and utilization of CO2, which not only achieves economic benefits but also promotes carbon emission reduction.

[0066] (4) The system is divided into three units and adopts a modular design to support global procurement and manufacturing, effectively shorten the construction period, significantly reduce the workload on the polar site, and achieve efficient optimization of project investment costs.

[0067] In a specific embodiment, a basic load large-scale LNG plant with an LNG production scale of 5 million tons / year is taken as an example to illustrate a cold energy utilization and carbon capture system for a large-scale LNG plant in extremely cold regions provided by the present invention, and its process implementation steps include a natural gas liquefaction process, a gas turbine power generation process and a flue gas capture and recovery process.

[0068] The process flow of natural gas liquefaction is as follows:

[0069] The external raw natural gas is introduced into the natural gas liquefaction main device 1 at a temperature of 25.0°C, a pressure of 85.0 bar, and a flow rate of 580.0 kg / h, where it is cooled and liquefied into high-pressure LNG at a temperature of -156.9°C and a pressure of 74.0 bar. It is expanded and reduced in pressure by the low-temperature expander 2 to become low-pressure LNG at a temperature of -159.7°C and a pressure of 1.3 bar. It then enters the gas-liquid separator 3 for gas-liquid separation. The separated LNG product is introduced into the LNG storage tank 4 for storage at a temperature of -159.7°C, a pressure of 1.3 bar, and a flow rate of 570.7 kg / h. The separated BOG evaporated gas enters the low-temperature heat exchanger 5 at a temperature of -159.7°C, a pressure of 1.3 bar, and a flow rate of 9.4 kg / h for heat exchange with the high-purity CO2 of the flue gas capture and recovery unit M3 before being passed to the external BOG system.

[0070] The process flow of gas turbine power generation is as follows:

[0071] The gas turbine generator set 6 introduces a stream of fuel gas from external raw natural gas for combustion and power generation. The generated electricity is supplied to the natural gas liquefaction main device 1 of the natural gas liquefaction unit M1. The gas turbine exhaust temperature is 550°C. After the unit's supporting waste heat boiler recovers part of the heat, the outlet exhaust temperature is 235°C and is passed to the flue gas capture and recovery unit M3. The molar concentration of CO2 in the system exhaust is 15%, and NO X The content is less than 15ppm.

[0072] The process flow of flue gas capture and recovery is as follows:

[0073] The exhaust gas from the flue gas capture and recovery unit M3 has a temperature of 235°C, a pressure of 1.2 bar, and a flow rate of 27.9 kg / h. It first enters the air cooler 7 and is fully cooled by the cold energy of the extremely cold environment in the extremely cold area. It then enters the cyclone separator 8 for cyclone separation. The condensate produced is discharged through its bottom outlet. The separated flue gas enters the booster 9 through its upper outlet for compression and pressure increase to 20.0 bar. The high-pressure flue gas enters the adsorption purifier 10 for deep purification. The H2O content is less than 50 ppm. Then it enters the CO2 membrane enrichment separator 11 for enrichment and separation. The main components of the separated waste gas are nitrogen, O2 and a small amount of CO2, which are directly discharged. The separated high-purity CO2 gas with a purity of 99.98% is passed into the low-temperature heat exchanger 5 of the natural gas liquefaction unit M1, and is cooled to a liquefied temperature of -40°C and a pressure of 19.5 bar. After passing through the low-temperature heat exchanger 5 and returning to the CO2 expander 12, it is expanded and depressurized to become a low-pressure CO2 liquid with a pressure of 1.3 bar, and is introduced into the CO2 storage tank 13 for storage.

[0074] In this embodiment, taking a basic load large-scale LNG plant with an LNG production scale of 5 million tons / year as an example, the polar air cooling energy that can be utilized is 15,067 kW / year, the pressure difference power generation of the recovery system is 15,660 kW / year, and the amount of CO2 that can be recycled is 53,024 tons / year, realizing an economic benefit of approximately RMB 5.54 million / year.

[0075] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it. 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 replacements for some of the technical features therein. However, these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the various embodiments of the present invention.

Claims

1. A cold energy utilization and carbon capture system for a large LNG plant in extremely cold regions, characterized by: include: Natural gas liquefaction unit (M1), used to realize natural gas liquefaction and energy recovery during the process; a gas turbine power generation unit (M2), connected to the natural gas liquefaction unit (M1), for burning raw natural gas to generate electricity and transmitting electricity to the natural gas liquefaction unit (M1); A flue gas capture and recovery unit (M3), one end of which is connected to the gas turbine power generation unit (M2), for receiving flue gas emitted by the gas turbine and performing deep purification and CO2 enrichment and separation on the flue gas; The other end thereof passes into the interior of the natural gas liquefaction unit (M1) and passes out and returns, and is used to utilize the cold energy of the natural gas liquefaction unit (M1) to realize low-temperature liquefaction and recovery of CO2.

2. The cold energy utilization and carbon capture system for a large-scale LNG plant in extremely cold regions according to claim 1 is characterized in that: The natural gas liquefaction unit (M1) includes: A natural gas liquefaction main device (1), the inlet of the natural gas liquefaction main device (1) is connected to an external raw natural gas pipeline (P1), and is used to cool and liquefy the raw natural gas into high-pressure LNG; a low-temperature expander (2), the inlet of the low-temperature expander (2) being connected to the outlet of the natural gas liquefaction main device (1) via a high-pressure LNG pipeline (P2), and being used for reducing the pressure of the high-pressure LNG to low-pressure LNG; A gas-liquid separator (3), the inlet of the gas-liquid separator (3) is connected to the outlet of the low-temperature expander (2) through a low-pressure LNG pipeline (P3), and the gas-liquid separator (3) is used for separating low-pressure LNG to obtain LNG products and BOG boil-off gas.

3. The cold energy utilization and carbon capture system for a large-scale LNG plant in extremely cold regions according to claim 2 is characterized in that: The natural gas liquefaction unit (M1) further comprises: A low-temperature heat exchanger (5), wherein an inlet of the low-temperature heat exchanger (5) is connected to the upper outlet of the gas-liquid separator (3) through a BOG evaporation gas pipeline (P5), and an outlet of the low-temperature heat exchanger (5) is connected to an external BOG system through a BOG pipeline (P6).

4. The cold energy utilization and carbon capture system for a large-scale LNG plant in extremely cold regions according to claim 2 is characterized in that: The natural gas liquefaction unit (M1) further comprises: An LNG storage tank (4) is connected to the bottom outlet of the gas-liquid separator (3) through an LNG product pipeline (P4) and is used to store the LNG product separated by the gas-liquid separator (3).

5. The cold energy utilization and carbon capture system for a large-scale LNG plant in extremely cold regions according to claim 3 is characterized in that: The gas turbine power generation unit (M2) comprises: A gas turbine generator set (6), wherein the inlet of the gas turbine generator set (6) is connected to an external raw natural gas pipeline (P1) through a fuel gas pipeline (P7), and is used to burn the raw natural gas to generate electricity, and is used to provide the generated electricity to the natural gas liquefaction main device (1); the outlet of the gas turbine generator set (6) is connected to the flue gas capture and recovery unit (M3) through a combustion engine exhaust pipeline (Y1).

6. The cold energy utilization and carbon capture system for a large-scale LNG plant in extremely cold regions according to claim 5 is characterized in that: The flue gas capture and recovery unit (M3) includes: An air cooler (7), the inlet of the air cooler (7) being connected to the outlet of the gas turbine generator set (6) via a combustion engine exhaust pipe (Y1), and being used to cool the exhaust flue gas using cold energy from an extremely cold environment; A cyclone separator (8), the inlet of which is connected to the outlet of the air cooler (7) via a flue gas cooling gas pipeline (Y2), for performing cyclone separation on the cooled flue gas and discharging the generated condensate via a cyclone discharge pipeline (Y3) connected to its bottom outlet; the upper outlet of the cyclone separator (8) is connected to another inlet of the low-temperature heat exchanger (5) via a pipeline, for cooling and liquefying the CO2 gas; A CO2 storage tank (13) has an inlet connected to another outlet of the low-temperature heat exchanger (5) via a pipeline, and is used to store liquefied CO2.

7. The cold energy utilization and carbon capture system for a large-scale LNG plant in extremely cold regions according to claim 6 is characterized in that: A purification and enrichment device is further provided between the CO2 storage tank (13) and the cyclone separator (8), one end of the purification and enrichment device being connected to the upper outlet of the cyclone separator (8) via a pipeline, and the other end of the purification and enrichment device being connected to the other inlet of the low-temperature heat exchanger (5) via a pipeline, for cooling and liquefying the purified and enriched CO2 gas.

8. The cold energy utilization and carbon capture system for a large-scale LNG plant in extremely cold regions according to claim 7 is characterized in that: A booster (9) is further provided between the purification and enrichment device and the cyclone separator (8); the inlet end of the booster (9) is connected to the upper outlet of the cyclone separator (8) via a flue gas separation gas pipeline (Y4); and the outlet end of the booster (9) is connected to the purification and enrichment device via a high-pressure flue gas pipeline (Y5).

9. The cold energy utilization and carbon capture system for a large-scale LNG plant in extremely cold regions according to claim 8, characterized in that: The purification and enrichment device comprises: an adsorption purifier (10), the inlet of the adsorption purifier (10) being connected to the outlet of the booster (9) via the high-pressure flue gas pipeline (Y5), for purifying the flue gas; A CO2 membrane enrichment separator (11) is provided, wherein the inlet of the CO2 membrane enrichment separator (11) is connected to the outlet of the adsorption purifier (10) via a flue gas purification pipeline (Y6), and is used for enriching and separating the purified flue gas; one outlet of the CO2 membrane enrichment separator (11) is connected to an exhaust gas pipeline (Y7), and is used for discharging the separated exhaust gas; the other outlet of the CO2 membrane enrichment separator (11) is connected to the low-temperature heat exchanger (5) via a high-pressure CO2 pipeline (Y8), and is used for passing the separated high-purity CO2 gas into the interior of the low-temperature heat exchanger (5) for liquefaction through heat exchange and cooling.

10. The cold energy utilization and carbon capture system for a large-scale LNG plant in extremely cold regions according to claim 6, characterized in that: It also includes a CO2 expander (12), the inlet of the CO2 expander (12) is connected to the low-temperature heat exchanger (5) through a high-pressure CO2 liquid pipeline (Y9), and the outlet of the CO2 expander (12) is connected to the inlet of the CO2 storage tank (13) through a low-pressure CO2 liquid pipeline (Y10). The CO2 expander (12) is used to expand and reduce the pressure of the cooled and liquefied high-pressure CO2 liquid into a low-pressure CO2 liquid and transport it into the CO2 storage tank (13) for storage.

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