Energy-saving urea production system and process based on carbon capture

Abstract

This invention discloses an energy-saving urea preparation system and process based on carbon capture, belonging to the field of chemical technology. The system comprises: a CCUS carbon capture system, a CO2 booster compressor, a liquid ammonia-CO2 cold energy heat exchange system, a CO2 booster pump, and a urea synthesis system connected in sequence; the liquid ammonia-CO2 cold energy heat exchange system is also connected to a liquid ammonia storage and transportation system and an ammonia gas turbine power generation system; the liquid ammonia storage and transportation system is connected to the urea synthesis system. This invention also discloses a urea preparation process implemented using the above system. By optimizing the compression process, coupling cold and heat energy recovery, and coordinating the waste heat power generation of the supporting system, this invention effectively reduces the energy consumption of the entire urea production process, significantly reduces process carbon emissions, and achieves significant energy-saving and carbon-reduction benefits.

Description

Technical Field

[0001] This invention belongs to the field of chemical technology, specifically relating to an energy-saving urea preparation system and process based on carbon capture. Background Technology

[0002] Currently, industrial urea production uses ammonia and carbon dioxide as raw materials, and urea is produced through the synthesis and dehydration reaction of ammonium carbamate under high temperature and high pressure conditions. The mainstream processes include three main categories: carbon dioxide stripping, ammonia stripping, and aqueous solution full recycling. Their core processes and equipment configurations are highly mature, and they all follow the same material and energy conversion pathways.

[0003] The raw material carbon dioxide mainly comes from by-product gas of the ammonia synthesis decarbonization system or low-pressure gaseous CO2 obtained through carbon capture and suppression system (CCUS). Current practice involves using multi-stage centrifugal compressors to progressively pressurize the CO2 to a synthesis pressure of 140–160 bar. This process releases a large amount of heat of compression, which is typically carried away by circulating water cooling, resulting in low energy efficiency and high operating power consumption. Meanwhile, the raw material ammonia is generally stored as a low-temperature, atmospheric-pressure liquid. This stored cold energy is not recovered in the current process and is directly lost, constituting significant energy waste. Regarding power supply, the urea plant's compressors and pumps rely entirely on external power grids, resulting in low utilization rates of green electricity or self-generated energy.

[0004] With the large-scale application of green ammonia, the promotion of CCUS technology, and the increasing demands for energy conservation in the chemical industry, it is expected that by combining the CO2 liquefaction conditions after carbon capture with the use of liquid CO2 pumping pressurization to replace gaseous compression, while simultaneously recovering the cold energy of liquid ammonia for process cooling, and introducing a green ammonia gas turbine to generate its own power, energy consumption and carbon emissions could be significantly reduced. However, current urea production processes lack a system integration solution that integrates these steps, and there is a lack of technical practice for the synergistic coupling of CO2 liquefaction pressurization, liquid ammonia cold energy recovery, and green ammonia power generation.

[0005] Therefore, a urea production system and its process method that couples carbon capture CO2 liquefaction, liquid ammonia cold energy recovery, liquid CO2 centrifugal pump pressurization and green ammonia gas turbine self-generation are provided. It has the outstanding features of low compression energy consumption, full utilization of cold energy in stages, high proportion of green electricity and low overall carbon emission intensity, and has become a technical problem that urgently needs to be solved by those skilled in the art. Summary of the Invention

[0006] The purpose of this invention is to provide an energy-saving urea preparation system based on carbon capture, which solves the problems of large heat loss from CO2 gaseous compression, idle cold energy of liquid ammonia, simple power structure, and insufficient connection between carbon capture and urea production in the existing technology.

[0007] The second objective of this invention is to provide an energy-saving urea preparation process based on carbon capture, implemented using the above-described system.

[0008] To achieve the above objectives, the technical solution adopted by the present invention is as follows: The first aspect of this invention discloses an energy-saving urea preparation system based on carbon capture, comprising: The system includes a CCUS carbon capture system, a CO2 booster compressor, a liquid ammonia-CO2 cold energy heat exchange system, a CO2 booster pump, a urea synthesis system, a liquid ammonia storage and transportation system, and an ammonia gas turbine power generation system; among which, The CO2 outlet of the CCUS carbon capture system is connected via pipeline to the inlet of the CO2 booster compressor. The outlet of the CO2 booster compressor is connected via pipeline to the CO2 inlet of the liquid ammonia-CO2 cold energy heat exchange system. The CO2 outlet of the liquid ammonia-CO2 cold energy heat exchange system is connected via pipeline to the inlet of the CO2 booster pump. The outlet of the CO2 booster pump is connected via pipeline to the CO2 inlet of the urea synthesis system. The liquid ammonia outlet of the liquid ammonia storage and transportation system is connected to the liquid ammonia inlet of the liquid ammonia-CO2 cold energy heat exchange system and the liquid ammonia inlet of the urea synthesis system via pipelines. The ammonia outlet of the liquid ammonia-CO2 cold energy heat exchange system is connected to the ammonia inlet of the ammonia gas turbine power generation system via a pipeline.

[0009] In some embodiments of the present invention, the power output terminal of the ammonia gas turbine power generation system is connected to the power input terminal of the urea synthesis system via a green power transmission line, for supplying green power to the urea synthesis system.

[0010] In some embodiments of the present invention, a waste heat recovery system is also included. The heat source inlet of the waste heat recovery system is connected to the exhaust gas outlet of the ammonia gas turbine power generation system, and its steam outlet is connected to the heating medium inlet of the urea synthesis system. The system is used to recover the waste heat of the high-temperature exhaust gas of the ammonia gas turbine and produce low-pressure steam as a byproduct for heating the urea synthesis system process.

[0011] In some embodiments of the present invention, a high-pressure liquid ammonia pump is installed on the pipeline between the liquid ammonia storage and transportation system and the urea synthesis system to pressurize the liquid ammonia to the pressure required for urea synthesis and then send it into the urea synthesis system.

[0012] In some embodiments of the present invention, an ammonia reheating heat exchanger is installed on the pipeline between the liquid ammonia-CO2 cold energy heat exchange system and the ammonia gas generator system. The ammonia reheating heat exchanger uses circulating water to reheat the vaporized ammonia gas, thereby increasing the temperature of the ammonia gas entering the ammonia gas generator.

[0013] A second aspect of this invention discloses an energy-saving urea preparation method based on carbon capture, which is implemented using the above-described system and includes the following steps: The CO2 captured by the CCUS carbon capture system is pressurized by the CO2 booster compressor and then sent to the liquid ammonia-CO2 cold energy heat exchange system to exchange heat with the liquid ammonia from the liquid ammonia storage and transportation system, thereby cooling the CO2 and at the same time vaporizing the liquid ammonia into ammonia gas. After heat exchange, the CO2 is pressurized to the synthesis pressure by a CO2 booster pump and then sent into the urea synthesis system. Another portion of the liquid ammonia from the liquid ammonia storage and transportation system is sent to the urea synthesis system, where it reacts with pressurized CO2 to synthesize urea. The ammonia gas obtained from gasification is fed into an ammonia gas turbine power generation system for combustion and power generation; the electricity generated by the ammonia gas turbine power generation system is used by the urea synthesis system.

[0014] In some embodiments of the present invention, the method further includes: recovering the waste heat of the high-temperature exhaust gas from the ammonia gas turbine power generation system to produce low-pressure steam as a byproduct for process heating of the urea synthesis system.

[0015] In some embodiments of the present invention, another portion of the liquid ammonia is pressurized to the synthesis pressure by a high-pressure liquid ammonia pump before being sent into the urea synthesis system.

[0016] In some embodiments of the present invention, the ammonia gas obtained from gasification is reheated by circulating water before being sent to the ammonia gas turbine power generation system.

[0017] In some embodiments of the present invention, the CO2 pressurized to the synthesis pressure by the CO2 booster pump is first reheated to 100-200°C using a process heat source before being sent to the urea synthesis system.

[0018] The heat source of the process in this invention refers to the heat generated within the system itself. It includes (1) waste heat from the tail gas of the ammonia gas turbine: the heat from the tail gas of the ammonia gas turbine is recovered through the waste heat recovery system, and low-pressure steam or hot water is produced as a by-product for CO2 reheating; (2) heat from the urea synthesis reaction: the urea synthesis reaction is a strongly exothermic reaction, and part of the reaction heat can be recovered through a heat exchanger for CO2 reheating.

[0019] In one embodiment, CO2 from a CO2 booster pump enters a heat exchanger connected to a waste heat recovery system, where it is heated to 100-200°C using low-pressure steam produced as a byproduct of the waste heat from the ammonia gas turbine exhaust.

[0020] In another embodiment, CO2 is heated to 100-200°C by absorbing the heat of reaction through a heat exchanger connected to the urea synthesis reactor before entering the urea synthesis system.

[0021] The CO2 raw material of this invention mainly comes from the by-product of the decarbonization system of the ammonia synthesis unit, or exists in gaseous form after being captured by CCUS.

[0022] Compared with the prior art, the present invention has the following beneficial effects: This invention features a scientifically designed and ingeniously conceived technical solution. By optimizing the compression process, coupling cold and heat energy recovery, and coordinating the three core components of waste heat power generation, it effectively reduces energy consumption throughout the urea production process, significantly reduces carbon emissions, and yields remarkable energy-saving and carbon-reducing benefits. This invention is widely applicable to various scenarios, including new large-scale synthetic urea plants, energy-saving and low-carbon retrofitting of existing urea production facilities, and urea production supporting the green ammonia industry. It has strong industrial adaptability and broad market application prospects and promotional value.

[0023] In the carbon dioxide compression process, traditional methods require directly compressing atmospheric CO2 to 150 barA. Taking a 1760-ton-per-day urea plant as a reference, the required shaft power is approximately 6500 kW. This new process first pressurizes the CO2 to 17 barA to liquefy it, then further pressurizes it to 150 barA via a liquid pump. The total shaft power for both parts is 4290 kW. Compared to the previous method, compression power consumption is reduced by approximately 34%, corresponding to annual electricity savings of over 17 million kWh. The core principle behind this energy-saving advantage is that replacing the traditional high-pressure gas compression process with a highly efficient liquid pressurization method completely avoids the technical defects of high efficiency loss and low energy utilization in the traditional high-pressure gas compression process, significantly improving the energy utilization efficiency of the carbon dioxide pressurization process.

[0024] In terms of coupled cold and heat energy utilization, this invention fully recovers and utilizes the cold energy released during the low-temperature liquid ammonia vaporization process, directly applying it to the carbon dioxide liquefaction process, completely replacing the external refrigeration unit required by traditional processes. For urea production units of the same scale, the energy consumption of the entire refrigeration system required by traditional processes is completely eliminated, reducing the energy consumption of this process to zero. This coupled cold and heat energy recovery mode requires no additional equipment investment, has a simple structure, and is highly adaptable. It also eliminates the supporting costs of refrigerant replenishment and equipment maintenance required by traditional refrigeration processes, forming a dual technological advantage in cost reduction and efficiency improvement, as well as energy conservation and consumption reduction.

[0025] In terms of energy supply, this invention adds an ammonia-fired turbine waste heat power generation system, which can recover and utilize surplus waste heat from the production system to generate electricity. The generated electricity can be directly supplied to the urea production unit for its own use, effectively reducing the unit's dependence on external power grids and achieving system energy self-sufficiency and efficiency improvement. Simultaneously, this invention uses captured and recovered carbon dioxide and green ammonia as raw materials, eliminating the introduction of fossil carbon sources throughout the entire production process, achieving low-carbon production from the source. Combined with the aforementioned energy-saving optimization of the compression process and waste heat and cold energy coupling recovery technologies, the overall carbon emission level of this invention is significantly reduced compared to traditional urea production units, comprehensively achieving the technical goals of energy saving, carbon reduction, and efficiency improvement. Attached Figure Description

[0026] Appendix Figure 1 This is a schematic diagram of the system of the present invention. Detailed Implementation

[0027] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail below with reference to the accompanying drawings. Obviously, the described embodiments are merely some embodiments of this invention, and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without creative effort are within the scope of protection of this invention.

[0028] Example 1 As attached Figure 1 As shown, this embodiment discloses an energy-saving urea preparation system based on carbon capture, which includes: The system includes a CCUS carbon capture system, a CO2 booster compressor, a liquid ammonia-CO2 cold energy heat exchange system, a CO2 booster pump, a urea synthesis system, a liquid ammonia storage and transportation system, and an ammonia gas turbine power generation system; among which, The CO2 outlet of the CCUS carbon capture system is connected via pipeline to the inlet of the CO2 booster compressor. The outlet of the CO2 booster compressor is connected via pipeline to the CO2 inlet of the liquid ammonia-CO2 cold energy heat exchange system. The CO2 outlet of the liquid ammonia-CO2 cold energy heat exchange system is connected via pipeline to the inlet of the CO2 booster pump. The outlet of the CO2 booster pump is connected via pipeline to the CO2 inlet of the urea synthesis system. The liquid ammonia outlet of the liquid ammonia storage and transportation system is connected to the liquid ammonia inlet of the liquid ammonia-CO2 cold energy heat exchange system and the liquid ammonia inlet of the urea synthesis system via pipelines. The ammonia outlet of the liquid ammonia-CO2 cold energy heat exchange system is connected to the ammonia inlet of the ammonia gas turbine power generation system via a pipeline.

[0029] The system of this invention effectively reduces energy consumption throughout the urea production process, significantly reduces carbon emissions, and has remarkable energy-saving and carbon-reducing benefits.

[0030] Example 2 As attached Figure 1 As shown, this embodiment discloses an energy-saving urea preparation system based on carbon capture, which includes: The system includes a CCUS carbon capture system, a CO2 booster compressor, a liquid ammonia-CO2 cold energy heat exchange system, a CO2 booster pump, a urea synthesis system, a liquid ammonia storage and transportation system, and an ammonia gas turbine power generation system; among which, The CO2 outlet of the CCUS carbon capture system is connected via pipeline to the inlet of the CO2 booster compressor. The outlet of the CO2 booster compressor is connected via pipeline to the CO2 inlet of the liquid ammonia-CO2 cold energy heat exchange system. The CO2 outlet of the liquid ammonia-CO2 cold energy heat exchange system is connected via pipeline to the inlet of the CO2 booster pump. The outlet of the CO2 booster pump is connected via pipeline to the CO2 inlet of the urea synthesis system. The liquid ammonia outlet of the liquid ammonia storage and transportation system is connected to the liquid ammonia inlet of the liquid ammonia-CO2 cold energy heat exchange system and the liquid ammonia inlet of the urea synthesis system via pipelines. The ammonia outlet of the liquid ammonia-CO2 cold energy heat exchange system is connected to the ammonia inlet of the ammonia gas turbine power generation system via a pipeline.

[0031] The power output of the ammonia gas turbine power generation system is connected to the power input of the urea synthesis system via a green power transmission line, which is used to supply green power to the urea synthesis system.

[0032] This embodiment 2 presents a more preferred technical solution based on embodiment 1. Specifically, it defines that the power output terminal of the ammonia gas turbine power generation system is connected to the power input terminal of the urea synthesis system via a green power transmission line, for supplying green power to the urea synthesis system. Directly supplying the green power generated by the ammonia gas turbine power generation system to the urea synthesis system achieves efficient coupling between on-site consumption of clean energy and chemical production, significantly reducing carbon emissions and dependence on external power grids throughout the entire process.

[0033] Example 3 As attached Figure 1 As shown, this embodiment discloses an energy-saving urea preparation system based on carbon capture, which includes: The system includes a CCUS carbon capture system, a CO2 booster compressor, a liquid ammonia-CO2 cold energy heat exchange system, a CO2 booster pump, a urea synthesis system, a liquid ammonia storage and transportation system, and an ammonia gas turbine power generation system; among which, The CO2 outlet of the CCUS carbon capture system is connected via pipeline to the inlet of the CO2 booster compressor. The outlet of the CO2 booster compressor is connected via pipeline to the CO2 inlet of the liquid ammonia-CO2 cold energy heat exchange system. The CO2 outlet of the liquid ammonia-CO2 cold energy heat exchange system is connected via pipeline to the inlet of the CO2 booster pump. The outlet of the CO2 booster pump is connected via pipeline to the CO2 inlet of the urea synthesis system. The liquid ammonia outlet of the liquid ammonia storage and transportation system is connected to the liquid ammonia inlet of the liquid ammonia-CO2 cold energy heat exchange system and the liquid ammonia inlet of the urea synthesis system via pipelines. The ammonia outlet of the liquid ammonia-CO2 cold energy heat exchange system is connected to the ammonia inlet of the ammonia gas turbine power generation system via a pipeline.

[0034] The power output of the ammonia gas turbine power generation system is connected to the power input of the urea synthesis system via a green power transmission line, which is used to supply green power to the urea synthesis system.

[0035] This embodiment also includes a waste heat recovery system. The heat source inlet of the waste heat recovery system is connected to the exhaust gas outlet of the ammonia gas turbine power generation system, and its steam outlet is connected to the heating medium inlet of the urea synthesis system. It is used to recover the waste heat of the high-temperature exhaust gas of the ammonia gas turbine and produce low-pressure steam as a by-product for the process heating of the urea synthesis system.

[0036] This embodiment 3 presents a more preferred technical solution based on embodiment 2. Specifically, it also includes a waste heat recovery system for recovering the waste heat from the high-temperature exhaust gas of the ammonia gas turbine and producing low-pressure steam as a byproduct, which is then used for heating the urea synthesis system. By recovering the waste heat from the high-temperature exhaust gas of the ammonia gas turbine and producing low-pressure steam as a byproduct for use in the urea synthesis system, energy cascade utilization is achieved, significantly reducing process heating energy consumption and improving overall economic efficiency.

[0037] Example 4 As attached Figure 1 As shown, this embodiment discloses an energy-saving urea preparation system based on carbon capture, which includes: The system includes a CCUS carbon capture system, a CO2 booster compressor, a liquid ammonia-CO2 cold energy heat exchange system, a CO2 booster pump, a urea synthesis system, a liquid ammonia storage and transportation system, and an ammonia gas turbine power generation system; among which, The CO2 outlet of the CCUS carbon capture system is connected via pipeline to the inlet of the CO2 booster compressor. The outlet of the CO2 booster compressor is connected via pipeline to the CO2 inlet of the liquid ammonia-CO2 cold energy heat exchange system. The CO2 outlet of the liquid ammonia-CO2 cold energy heat exchange system is connected via pipeline to the inlet of the CO2 booster pump. The outlet of the CO2 booster pump is connected via pipeline to the CO2 inlet of the urea synthesis system. The liquid ammonia outlet of the liquid ammonia storage and transportation system is connected to the liquid ammonia inlet of the liquid ammonia-CO2 cold energy heat exchange system and the liquid ammonia inlet of the urea synthesis system via pipelines. The ammonia outlet of the liquid ammonia-CO2 cold energy heat exchange system is connected to the ammonia inlet of the ammonia gas turbine power generation system via a pipeline.

[0038] The power output of the ammonia gas turbine power generation system is connected to the power input of the urea synthesis system via a green power transmission line, which is used to supply green power to the urea synthesis system.

[0039] It also includes a waste heat recovery system. The heat source inlet of the waste heat recovery system is connected to the exhaust gas outlet of the ammonia gas turbine power generation system, and its steam outlet is connected to the heating medium inlet of the urea synthesis system. It is used to recover the waste heat of the high-temperature exhaust gas of the ammonia gas turbine and produce low-pressure steam as a by-product for the process heating of the urea synthesis system.

[0040] A high-pressure liquid ammonia pump is installed on the pipeline between the liquid ammonia storage and transportation system and the urea synthesis system. This pump is used to pressurize the liquid ammonia to the pressure required for urea synthesis before sending it into the urea synthesis system.

[0041] This embodiment 4 presents a more preferred technical solution based on embodiment 3. Specifically, a high-pressure liquid ammonia pump is installed on the pipeline between the liquid ammonia storage and transportation system and the urea synthesis system to pressurize the liquid ammonia to the pressure required for urea synthesis before sending it into the urea synthesis system. Precisely pressurizing the liquid ammonia to the required synthesis pressure ensures that the urea synthesis reaction operates efficiently and stably under optimal conditions.

[0042] Example 5 As attached Figure 1 As shown, this embodiment discloses an energy-saving urea preparation system based on carbon capture, which includes: The system includes a CCUS carbon capture system, a CO2 booster compressor, a liquid ammonia-CO2 cold energy heat exchange system, a CO2 booster pump, a urea synthesis system, a liquid ammonia storage and transportation system, and an ammonia gas turbine power generation system; among which, The CO2 outlet of the CCUS carbon capture system is connected via pipeline to the inlet of the CO2 booster compressor. The outlet of the CO2 booster compressor is connected via pipeline to the CO2 inlet of the liquid ammonia-CO2 cold energy heat exchange system. The CO2 outlet of the liquid ammonia-CO2 cold energy heat exchange system is connected via pipeline to the inlet of the CO2 booster pump. The outlet of the CO2 booster pump is connected via pipeline to the CO2 inlet of the urea synthesis system. The liquid ammonia outlet of the liquid ammonia storage and transportation system is connected to the liquid ammonia inlet of the liquid ammonia-CO2 cold energy heat exchange system and the liquid ammonia inlet of the urea synthesis system via pipelines. The ammonia outlet of the liquid ammonia-CO2 cold energy heat exchange system is connected to the ammonia inlet of the ammonia gas turbine power generation system via a pipeline.

[0043] The power output of the ammonia gas turbine power generation system is connected to the power input of the urea synthesis system via a green power transmission line, which is used to supply green power to the urea synthesis system.

[0044] The system in this embodiment also includes a waste heat recovery system. The heat source inlet of the waste heat recovery system is connected to the exhaust gas outlet of the ammonia gas turbine power generation system, and its steam outlet is connected to the heating medium inlet of the urea synthesis system. It is used to recover the waste heat of the high-temperature exhaust gas of the ammonia gas turbine and produce low-pressure steam as a by-product for the process heating of the urea synthesis system.

[0045] A high-pressure liquid ammonia pump is installed on the pipeline between the liquid ammonia storage and transportation system and the urea synthesis system. This pump is used to pressurize the liquid ammonia to the pressure required for urea synthesis before sending it into the urea synthesis system.

[0046] An ammonia reheating heat exchanger is installed on the pipeline between the liquid ammonia-CO2 cold energy heat exchange system and the ammonia gas turbine power generation system. The ammonia reheating heat exchanger uses circulating water to reheat the vaporized ammonia gas, thereby increasing the temperature of the ammonia gas entering the ammonia gas turbine.

[0047] This embodiment 5 presents a more preferred technical solution based on embodiment 4. Specifically, an ammonia reheating heat exchanger is installed on the pipeline between the liquid ammonia-CO2 cold energy heat exchange system and the ammonia gas turbine power generation system. The ammonia reheating heat exchanger uses circulating water to reheat the vaporized ammonia gas, thereby increasing the temperature of the ammonia gas entering the ammonia gas turbine. Utilizing circulating water to reheat and increase the ammonia gas temperature enhances both the combustion efficiency and operational stability of the ammonia gas turbine, and also enables the cascade utilization of low-grade heat within the system.

[0048] Example 6 This embodiment discloses an energy-saving urea preparation method based on carbon capture, implemented using the system of Example 5, as detailed below: Flue gas from coal-fired power plants enters the CCUS carbon capture system, where it undergoes absorption, desorption, drying, and purification to obtain high-purity CO2.

[0049] Gaseous CO2 first enters the CO2 booster compressor and is pressurized to 17 barA. The pressurized gaseous CO2 then enters the liquid ammonia-CO2 cold energy heat exchange system, where it exchanges heat with cryogenic liquid ammonia from the liquid ammonia storage and transportation system. It is cooled to -25°C and undergoes a phase change liquefaction at 17 barA to form liquid CO2. During this process, the liquid ammonia absorbs heat and vaporizes, and all the released cold energy is used to cool and liquefy the CO2.

[0050] After heat exchange, the liquid CO2 enters the CO2 booster pump, which is a multi-stage centrifugal pump. The CO2 is pressurized stepwise from 17 barA to 140-160 barA to reach the pressure required for urea synthesis. The high-pressure liquid CO2 at the pump outlet is reheated to 100-200℃ by the process heat source and then sent into the urea synthesis system.

[0051] Another portion of liquid ammonia from the liquid ammonia storage and transportation system is pressurized to the synthesis pressure by a high-pressure liquid ammonia pump and then sent to the urea synthesis system to react with reheated CO2 to synthesize urea. The ammonia gas obtained from gasification is reheated by circulating water and then sent to the ammonia gas turbine power generation system for combustion and power generation; the electricity generated by the ammonia gas turbine power generation system is used by the urea synthesis system.

[0052] The high-temperature exhaust gas generated by the ammonia gas turbine power generation system enters the waste heat recovery system, producing low-pressure steam as a byproduct, which is used for process heating in the urea synthesis system. In this embodiment, before entering the urea synthesis system, CO2 first passes through a heat exchanger connected to the urea synthesis reactor, absorbing the heat of reaction and thus being heated to 100-200°C.

[0053] This invention significantly reduces the energy consumption of the equipment. Taking a 1760t / day urea plant as an example, it requires 55t / h of raw material CO2. Using a CO2 gas pressurization method, a two-cylinder, four-stage centrifugal compressor is selected to pressurize CO2 from atmospheric pressure to 150 barA, requiring a shaft power of approximately 6500kW. If a CO2 liquefaction pressurization method is used, the shaft power required to pressurize the atmospheric pressure CO2 purified from CCUS to a liquefaction pressure of 17 barA is approximately 3900kW, and the liquid CO2 booster pump pressurizes from 17 bar to 150 bar requires a shaft power of 390kW, totaling 4290kW. Compared to the traditional compressor process, this results in energy savings of over 50%, saving over ten million kWh of electricity annually, demonstrating outstanding energy-saving performance.

[0054] The above are merely preferred embodiments of the invention and are not intended to limit the invention in any way. Any simple modifications, equivalent substitutions, and improvements made to the above embodiments based on the technical essence of the invention and within the spirit and principles of the invention shall still fall within the protection scope of the invention.

Claims

1. An energy-saving urea preparation system based on carbon capture, characterized in that, include: The system includes a CCUS carbon capture system, a CO2 booster compressor, a liquid ammonia-CO2 cold energy heat exchange system, a CO2 booster pump, a urea synthesis system, a liquid ammonia storage and transportation system, and an ammonia gas turbine power generation system; among which, The CO2 outlet of the CCUS carbon capture system is connected via pipeline to the inlet of the CO2 booster compressor. The outlet of the CO2 booster compressor is connected via pipeline to the CO2 inlet of the liquid ammonia-CO2 cold energy heat exchange system. The CO2 outlet of the liquid ammonia-CO2 cold energy heat exchange system is connected via pipeline to the inlet of the CO2 booster pump. The outlet of the CO2 booster pump is connected via pipeline to the CO2 inlet of the urea synthesis system. The liquid ammonia outlet of the liquid ammonia storage and transportation system is connected to the liquid ammonia inlet of the liquid ammonia-CO2 cold energy heat exchange system and the liquid ammonia inlet of the urea synthesis system via pipelines. The ammonia outlet of the liquid ammonia-CO2 cold energy heat exchange system is connected to the ammonia inlet of the ammonia gas turbine power generation system via a pipeline.

2. The energy-saving urea preparation system based on carbon capture according to claim 1, characterized in that, The power output of the ammonia gas turbine power generation system is connected to the power input of the urea synthesis system via a green power transmission line, which is used to supply green power to the urea synthesis system.

3. The energy-saving urea preparation system based on carbon capture according to claim 1, characterized in that, It also includes a waste heat recovery system. The heat source inlet of the waste heat recovery system is connected to the exhaust gas outlet of the ammonia gas turbine power generation system, and its steam outlet is connected to the heating medium inlet of the urea synthesis system. It is used to recover the waste heat of the high-temperature exhaust gas of the ammonia gas turbine and produce low-pressure steam as a by-product for the process heating of the urea synthesis system.

4. The energy-saving urea preparation system based on carbon capture according to claim 1, characterized in that, A high-pressure liquid ammonia pump is installed on the pipeline between the liquid ammonia storage and transportation system and the urea synthesis system. This pump is used to pressurize the liquid ammonia to the pressure required for urea synthesis before sending it into the urea synthesis system.

5. The energy-saving urea preparation system based on carbon capture according to claim 1, characterized in that, An ammonia reheating heat exchanger is installed on the pipeline between the liquid ammonia-CO2 cold energy heat exchange system and the ammonia gas turbine power generation system. The ammonia reheating heat exchanger uses circulating water to reheat the vaporized ammonia gas, thereby increasing the temperature of the ammonia gas entering the ammonia gas turbine.

6. A method for preparing energy-saving urea based on carbon capture, characterized in that, The system implementation using any one of claims 1-5 includes the following steps: The CO2 captured by the CCUS carbon capture system is pressurized by the CO2 booster compressor and then sent to the liquid ammonia-CO2 cold energy heat exchange system to exchange heat with the liquid ammonia from the liquid ammonia storage and transportation system, thereby cooling the CO2 and at the same time vaporizing the liquid ammonia into ammonia gas. After heat exchange, the CO2 is pressurized to the synthesis pressure by a CO2 booster pump and then sent into the urea synthesis system. Another portion of the liquid ammonia from the liquid ammonia storage and transportation system is sent to the urea synthesis system, where it reacts with pressurized CO2 to synthesize urea. The ammonia gas obtained from gasification is fed into an ammonia gas turbine power generation system for combustion and power generation; the electricity generated by the ammonia gas turbine power generation system is used by the urea synthesis system.

7. The method according to claim 6, characterized in that, Also includes: Waste heat from the high-temperature exhaust gas of the ammonia gas turbine power generation system is recovered, and low-pressure steam is produced as a byproduct for process heating in the urea synthesis system.

8. The method according to claim 6, characterized in that, Before being fed into the urea synthesis system, another portion of the liquid ammonia is pressurized to the synthesis pressure by a high-pressure liquid ammonia pump.

9. The method according to claim 6, characterized in that, The ammonia gas obtained from gasification is reheated by circulating water before being sent to the ammonia gas turbine power generation system.

10. The method according to claim 6, characterized in that, The CO2, after being pressurized to the synthesis pressure by the CO2 booster pump, is first reheated to 100-200℃ using a process heat source before being sent to the urea synthesis system.

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