Combined system and method of ammonia gas cold energy gas turbine and co2 rankine cycle

Abstract

The application provides a combined system and method of ammonia gas cold energy gas turbine and CO2 Rankine cycle, comprising: an ammonia gas turbine module and a transcritical CO2 Rankine cycle module. The ammonia gas turbine module is provided with a first cooler, an ammonia gas preheater and an air preheater. Ammonia gas and air are mixed and combusted in a combustion chamber to generate flue gas and release heat. The flue gas is heated in a heat extractor and a flue gas low-temperature recuperator after doing work in an ammonia turbine. In the transcritical CO2 Rankine cycle module, the CO2 low-temperature recuperator and the flue gas low-temperature recuperator are connected in parallel, and then connected with a high-temperature recuperator and a heat extractor in sequence. The first-stage waste heat of the flue gas in the heat extractor is used to preheat the CO2 to the first stage. The preheated CO2 gas does work in a CO2 turbine. The high-temperature CO2 gas released is returned to the high-temperature recuperator and the CO2 low-temperature recuperator to be heated. The cold energy of liquid ammonia in the first cooler is used to cool the low-temperature CO2 gas to a temperature below the critical point and circulate in the transcritical CO2 Rankine cycle module.

Description

Technical Field

[0001] This invention belongs to the field of comprehensive energy utilization, and in particular relates to a combined system and method for recovering ammonia cold energy gas turbine and CO2 Rankine cycle. Background Technology

[0002] Ammonia, as a refrigerant, possesses excellent thermodynamic and physical properties and is environmentally friendly, making it a promising carbon-free fuel suitable for propulsion systems in large, long-distance vessels. It also represents a crucial technological direction for carbon emission reduction in the transition from thermal power generation to industrial use. However, due to its relatively high ignition point, it requires thorough preheating before entering the combustion chamber. Furthermore, since ammonia combustion primarily produces water and nitrogen, the latent heat of water vapor in the flue gas is difficult to utilize. Consequently, the thermal efficiency of ammonia gas turbine cycles is only 36%. Therefore, cold energy recovery during liquid ammonia transportation and comprehensive utilization of flue gas energy from gas turbines are key to improving ammonia utilization efficiency.

[0003] CO2 possesses strong chemical stability, excellent thermodynamic properties, and a relatively low critical temperature (30.8℃), making it suitable as a working fluid in the Rankine cycle. Its cycle structure is simple and its thermal efficiency is high, often used for low-temperature heat source recovery or as a bottom cycle component in combined cycles. However, because the critical temperature of CO2 is not significantly different from room temperature, conventional direct heat exchange cooling methods cannot stably cool it below 30℃, thus requiring additional refrigeration equipment or other cooling methods. Furthermore, near the critical point, the density of CO2 changes drastically with temperature, exhibiting dramatic changes in both density and specific heat. This can lead to a transition from a liquid state to a supercritical gas-liquid coexistence, easily causing pinch-pointing in the regenerator and affecting heat exchange efficiency. Currently, the common approach to addressing regenerator pinch-pointing is to use a split-flow recompression arrangement to improve the overall thermal efficiency of the cycle. However, this arrangement adds a recompression compressor, located far from the CO2 critical point, increasing compression power consumption and system complexity. Summary of the Invention

[0004] To address the aforementioned technical problems, this invention provides a combined system and method for recovering ammonia-cooled gas turbine and a CO2 Rankine cycle, aiming to at least partially solve the above-mentioned technical problems. The specific technical solution is as follows:

[0005] As a first aspect of the present invention, a combined system of ammonia gas turbine and CO2 Rankine cycle is provided, including an ammonia gas turbine module and a transcritical CO2 Rankine cycle module.

[0006] The ammonia gas turbine module is equipped with a first cooler for releasing cold energy through liquid ammonia vaporization, an ammonia preheater for heating the vaporized ammonia to its combustible temperature, and a combustion chamber, arranged according to the ammonia flow direction. It also includes an air preheater and a combustion chamber, where ammonia and air mix and burn to produce flue gas and release heat, arranged according to the flue gas flow direction. Finally, it includes an ammonia turbine, a heat exchanger, and a low-temperature flue gas regenerator, arranged according to the flue gas flow direction.

[0007] The transcritical CO2 Rankine cycle module is equipped with a CO2 low-temperature regenerator, a high-temperature regenerator, a heat exchanger, and a CO2 turbine. The CO2 low-temperature regenerator and the flue gas low-temperature regenerator are connected in parallel, and the transcritical CO2 Rankine cycle module shares a heat exchanger with the ammonia gas turbine module.

[0008] According to the CO2 flow direction on the low-temperature side, CO2 is preheated by passing through the CO2 low-temperature regenerator and the flue gas low-temperature regenerator respectively. After the preheated CO2 gas is mixed, it enters the high-temperature regenerator and the heat exchanger in sequence for gradual heating. After preheating, the CO2 gas enters the CO2 turbine to do work and release high-temperature CO2 gas.

[0009] Following the flow direction of CO2 gas on the high-temperature side, the hot-side outlet of the CO2 turbine is sequentially connected to the hot-side inlet of the high-temperature regenerator and the hot-side inlet of the low-temperature CO2 regenerator. The hot-side outlet of the low-temperature CO2 regenerator is connected to the hot-side inlet of the first cooler. Thus, the high-temperature CO2 gas is gradually cooled down through the high-temperature regenerator and the low-temperature CO2 regenerator to obtain low-temperature CO2 gas. The cold energy released by the liquid ammonia is recovered by the first cooler to cool the low-temperature CO2 gas to a temperature below the critical point. The obtained low-temperature liquid CO2 circulates in the transcritical CO2 Rankine cycle module.

[0010] As a second aspect of the present invention, a method for combining an ammonia-recovery gas turbine with a CO2 Rankine cycle is provided, employing the aforementioned ammonia-recovery gas turbine with a CO2 Rankine cycle combined system, wherein the method includes:

[0011] After liquid ammonia is vaporized into ammonia gas and the cold energy of liquid ammonia is recovered, preheated air and ammonia gas are introduced into the combustion chamber to burn and generate flue gas and release heat. The flue gas flows into the ammonia turbine to do work, outputting electrical energy and generating flue gas.

[0012] According to the flow direction of the flue gas, the primary waste heat of the flue gas is used for primary cooling in the heat exchanger. After primary cooling, the secondary waste heat of the flue gas is used for secondary cooling in the air preheater and ammonia preheater respectively. After secondary cooling, the tertiary waste heat of the flue gas is used for tertiary cooling in the flue gas low-temperature regenerator to obtain low-temperature flue gas.

[0013] According to the flow direction of CO2 on the low-temperature side, the low-temperature liquid CO2 flows into the flue gas low-temperature regenerator and the CO2 low-temperature regenerator for three-stage heating. After heating, the CO2 gas merges and flows into the high-temperature regenerator for two-stage heating, and then enters the heat exchanger for one-stage heating. The CO2 gas, heated step by step, flows into the CO2 turbine to do work, output electrical energy and release high-temperature CO2 gas.

[0014] Following the flow direction of CO2 gas on the high-temperature side, the high-temperature CO2 gas flows back to the high-temperature regenerator for primary reheating. The CO2 gas after primary reheating flows back to the low-temperature CO2 regenerator for secondary reheating of low-temperature liquid CO2. The temperature of the high-temperature CO2 gas is gradually reduced to obtain low-temperature CO2 gas. After the low-temperature CO2 gas is cooled to below the critical point by the cold energy recovered by the first cooler, the obtained low-temperature liquid CO2 circulates in the transcritical CO2 Rankine cycle module.

[0015] Based on the above technical solution, the present invention provides a combined system and method for recovering ammonia-cooled gas turbine and CO2 Rankine cycle, which includes at least one of the following beneficial effects:

[0016] (1) According to an embodiment of the present invention, by setting a first cooler in the flow direction of ammonia to recover the cold energy of ammonia, the low-temperature CO2 gas returning in the CO2 Rankine cycle can be cooled to a liquid state. The flue gas generated by the combustion of preheated ammonia and air in the combustion chamber enters the ammonia turbine to expand and do work, outputting electrical energy and flue gas. The heat exchanger is used as the coupling point between the ammonia gas turbine module and the transcritical CO2 Rankine cycle module to exchange heat between the flue gas and CO2 in the two modules respectively. In the flow direction of the flue gas, the primary waste heat of the flue gas in the heat exchanger can be used to raise the temperature of the low-temperature CO2 gas in the CO2 Rankine cycle module in the first stage, and the secondary waste heat of the residual flue gas can be used to preheat the air and ammonia respectively, improving the combustion efficiency when the two are combined and reducing the NOx generated during the combustion of ammonia; the tertiary waste heat of the residual flue gas flows into the flue gas low-temperature regenerator, which can release heat to the liquid CO2 entering the flue gas low-temperature regenerator, and vaporize the liquid CO2 into CO2 gas. Thus, after the flue gas outputs electrical energy from the gas turbine, it undergoes three stages of heat exchange, releasing heat step by step, comprehensively utilizing the energy from various parts of the ammonia gas turbine module. After three stages of heat exchange, the flue gas temperature is ultimately reduced to near the dew point, efficiently converting the energy contained in the flue gas and improving the net cycle efficiency.

[0017] (2) According to an embodiment of the present invention, in the CO2 flow direction on the low-temperature side, a flue gas low-temperature regenerator and a CO2 low-temperature regenerator are connected in parallel and then sequentially connected to a high-temperature regenerator and a heat exchanger to achieve a step-by-step heating of the CO2 on the low-temperature side. The primary waste heat of the flue gas in the heat exchanger is used to further heat the CO2 gas in the high-temperature regenerator (i.e., primary heating). The heated CO2 gas enters the CO2 turbine, expands, does work, and releases high-temperature CO2 gas. In the high-temperature CO2 gas flow direction, by sequentially connecting the CO2 turbine, the high-temperature regenerator, and the CO2 low-temperature regenerator, the high-temperature CO2 gas is used to preheat the low-temperature CO2 gas, while the high-temperature CO2 gas is gradually cooled to obtain low-temperature CO2 gas. By using the three-stage waste heat from the gradual cooling of flue gas as energy to match the vaporization of liquid CO2 in the low-temperature flue gas regenerator, the liquid CO2 is heated, avoiding the power consumption generated by the re-compressor. At the same time, the three-stage waste heat of the flue gas is introduced during the diversion of low-temperature liquid CO2, so that the temperature gradient on both sides near the low-temperature regenerator is matched, solving the problem of pinch points easily generated at both ends of the regenerator.

[0018] (3) According to an embodiment of the present invention, the obtained low-temperature CO2 gas is transported to the first cooler and cooled by liquid ammonia to obtain liquid CO2. The liquid CO2 can be recycled as the working fluid of the transcritical CO2 Rankine cycle module, thereby achieving the purpose of zero carbon emissions and no pollution to the environment. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of the framework of the combined system of ammonia-recovering cold energy gas turbine and CO2 Rankine cycle according to an embodiment of the present invention;

[0020] Figure 2 This is a schematic diagram of the framework of a combined system of ammonia-recovering cold energy gas turbine and CO2 Rankine cycle in another embodiment of the present invention.

[0021] [Explanation of Labels in the Attached Image]

[0022] 1-Air compressor, 2-Air preheater, 3-Liquid ammonia pump, 4-First cooler, 5-Ammonia preheater, 6-Combustion chamber, 7-Ammonia turbine, 8-Heat exchanger, 9-CO2 pump, 10-Flue gas low-temperature regenerator, 11-CO2 low-temperature regenerator, 12-High-temperature regenerator, 13-CO2 turbine, 14-Ammonia compressor, 15-Condenser, 16-Throttle valve, 17-Second cooler, 18-Heat exchanger. Detailed Implementation

[0023] To make the objectives, technical solutions, and advantages of the present invention clearer, the present invention will be further described in detail below with reference to specific embodiments and accompanying drawings.

[0024] Ammonia, as a refrigerant, possesses excellent thermodynamic and physical properties and is environmentally friendly. When used as a fuel, it has a high hydrogen content and can be liquefied at -33°C or 0.9 MPa at room temperature. Combustion produces no carbon emissions, and its energy density is three times that of hydrogen, making it easy to store and transport. It is a potential clean fuel for power generation, following hydrogen. Furthermore, ammonia is easy to produce, has low cost, and high purity, and it does not corrode metal components, making it a green energy source. However, ammonia has a relatively high ignition point (700–780°C) and is not easily combustible. It requires sufficient preheating before entering the combustion chamber, such as through catalytic cracking to promote stable combustion. Therefore, how to comprehensively utilize the cold energy of ammonia and the energy required to heat it to combustion temperature is a major challenge in improving ammonia utilization efficiency.

[0025] CO2 possesses strong chemical stability, a critical temperature of 30.8℃, and is easily produced under suitable conditions. The organic Rankine cycle is a transcritical closed-loop cycle with a simple structure and high thermal efficiency. Its heat extraction temperature requirements are not high, making it commonly used for low-temperature heat source recovery or as a bottom cycle component in combined cycles. In related technologies, CO2 is used as the working fluid in a Rankine cycle. The CO2 is compressed and boosted by a pump, heat is extracted through an evaporator, and the CO2 expands and performs work on the turbine. It is then cooled below the CO2 critical temperature and returned to the CO2 pump, completing the closed loop. Based on this basic cycle, a regenerator is placed between the CO2 pump and the turbine to improve system efficiency. However, refrigeration technology is still required before the CO2 enters the CO2 pump to lower the working fluid temperature below the critical temperature. Furthermore, since the CO2 critical temperature is not significantly different from room temperature, conventional direct heat exchange cooling methods, such as air cooling and water cooling, are used. However, these methods cannot efficiently and stably cool the working fluid CO2 below 30℃, necessitating the introduction of additional refrigeration equipment or other cooling methods.

[0026] Furthermore, near the critical point, CO2 exhibits a gas-liquid coexistence phenomenon as its density changes from liquid to supercritical with temperature variations, resulting in drastic changes in density and specific heat. Current transcritical CO2 Rankine cycles and simple regenerative arrangements in closed supercritical Brayton cycles suffer from the same regenerator pinch problem, thus affecting heat exchange efficiency. To address this issue, closed supercritical Brayton cycles propose a split-flow recompression arrangement. This arrangement separates the regenerator into a high-temperature regenerator and a low-temperature regenerator without creating a pinch point. The working fluid from the low-temperature regenerator outlet enters the recompressor and then merges between the high-temperature and low-temperature regenerators, improving the overall thermal efficiency of the cycle. However, this split-flow recompression arrangement adds a recompressor, and the recompressor location is far from the CO2 critical point, increasing compression power consumption and system complexity.

[0027] In view of this, the present invention provides a combined system and method for recovering ammonia cooling energy from a gas turbine and a CO2 Rankine cycle. Based on the principles of comprehensive energy utilization and temperature gradient matching, and grounded in the comprehensive utilization of flue gas energy in an ammonia gas turbine unit, the effective utilization of liquid ammonia cooling energy, and the coupled utilization of energy in a Rankine cycle using CO2 as the working fluid, the invention proposes integrating the transcritical CO2 cooling section with the liquid ammonia cooling section. In contrast, the ammonia gas turbine flue gas is effectively cooled in three stages and reheated by diversion. Compared with the previous combined power generation technology of organic Rankine cycle and gas turbine cycle, the cycle of this invention has the characteristics of high cycle efficiency, simple cycle structure, no carbon emissions, and no environmental pollution emissions under ideal conditions.

[0028] Specifically, the first aspect of the present invention provides a combined system of an ammonia gas turbine and a CO2 Rankine cycle, comprising an ammonia gas turbine module and a transcritical CO2 Rankine cycle module. In the ammonia gas turbine module, a first cooler (cool1, C1), an ammonia preheater (PH-AM), and a combustion chamber (C) are arranged according to the ammonia flow direction; an air preheater (PH-A) and a combustion chamber are arranged according to the air flow direction; and an ammonia turbine (T-AM), a heat exchanger (H), a parallel ammonia preheater and air preheater, and a low-temperature regenerator for flue gas (LTR-F) are arranged according to the flue gas flow direction. The transcritical CO2 Rankine cycle module is configured according to the CO2 flow direction on the low-temperature side. The flue gas low-temperature regenerator and the CO2 low-temperature regenerator (LTR-C) are connected in parallel, and then sequentially connected to the high-temperature regenerator and the heat exchanger. Following the CO2 gas flow direction on the high-temperature side, the heat exchanger, the CO2 turbine (TC), and the hot-side inlet of the high-temperature regenerator and the CO2 low-temperature regenerator are sequentially connected. The hot-side outlet of the CO2 low-temperature regenerator is connected to the hot-side inlet of the first cooler. The obtained low-temperature liquid CO2 circulates within the transcritical CO2 Rankine cycle module. The transcritical CO2 Rankine cycle module shares a heat exchanger and a flue gas low-temperature regenerator with the ammonia gas turbine module.

[0029] Figure 1 This is a schematic diagram of the combined system of an ammonia-recovery cold energy gas turbine and a CO2 Rankine cycle according to an embodiment of the present invention. The following is in conjunction with... Figure 1 The ammonia gas turbine module and the transcritical CO2 Rankine cycle module in this invention are described in detail. It should be noted that... Figure 1 The solid lines represent the flow direction of ammonia, air, and flue gas, while the dashed lines represent the flow direction of CO2.

[0030] Specifically, such as Figure 1 As shown, the ammonia gas turbine module, arranged according to the ammonia flow direction, includes a first cooler 4, an ammonia preheater 5, and a combustion chamber 6. The first cooler 4 is used for the vaporization of liquid ammonia to release cold energy, and the ammonia preheater 5 is used to heat the vaporized ammonia to its combustible temperature. Arranged according to the air flow direction, it includes an air preheater 2 and a combustion chamber 6. The air preheater 2 heats the air, and the combustion chamber 6 is used for the mixing and combustion of preheated ammonia and air, generating flue gas and releasing heat. Arranged according to the flue gas flow direction, it also includes an ammonia turbine 7, a heat exchanger 8, and a flue gas cryogenic regenerator 10.

[0031] The transcritical CO2 Rankine cycle module is equipped with a CO2 low-temperature regenerator 11, a high-temperature regenerator 12, a heat exchanger 8, and a CO2 turbine 13. The CO2 low-temperature regenerator 11 and the flue gas low-temperature regenerator 10 are connected in parallel, and the transcritical CO2 Rankine cycle module and the ammonia gas turbine module share a heat exchanger 8.

[0032] Following the flow direction of low-temperature CO2, the flue gas low-temperature regenerator 10 and the CO2 low-temperature regenerator 11 are connected in parallel, and then connected in sequence with the high-temperature regenerator 12 and the heat exchanger 8 to gradually raise the temperature of the low-temperature CO2. The transcritical CO2 Rankine cycle module and the ammonia gas turbine module share a heat exchanger 8. The low-temperature CO2 is preheated by utilizing the primary waste heat of the flue gas in the heat exchanger 8. The preheated CO2 gas enters the CO2 turbine 13 to do work and release high-temperature CO2 gas. Following the flow direction of CO2 gas on the high-temperature side, the outlet of CO2 turbine 13 is sequentially connected to the hot-side inlet of high-temperature regenerator 12 and the hot-side inlet of low-temperature CO2 regenerator 11. The hot-side outlet of low-temperature CO2 regenerator 11 is connected to the hot-side inlet of first cooler 4. Thus, heat exchange is performed between the high-temperature regenerator 12 and the low-temperature CO2 regenerator 11 and the low-temperature CO2, thereby raising the temperature of the low-temperature CO2 while gradually cooling the high-temperature CO2 gas to obtain low-temperature CO2 gas. The first cooler 4 is used to recover the cold energy released by liquid ammonia to cool the low-temperature CO2 gas to a temperature below the critical point. The obtained low-temperature liquid CO2 circulates within the transcritical CO2 Rankine cycle module.

[0033] In embodiments of the present invention, taking advantage of the ease of production and low cost of ammonia, and the fact that pure ammonia does not corrode metal components, a first cooler is installed in the flow direction of the ammonia to recover its cold energy, which is then directly used in the CO2 Rankine cycle to liquefy the returning low-temperature CO2 gas. The preheated ammonia and air are burned in the combustion chamber, and the resulting flue gas enters the ammonia turbine to expand and perform work, outputting electrical energy and generating high-temperature waste heat. A heat exchanger is used as the coupling point between the ammonia gas turbine module and the transcritical CO2 Rankine cycle module, allowing for heat exchange between the flue gas and CO2 gas in both modules. In the flow direction of the flue gas, the primary waste heat from the flue gas in the heat exchanger is used to preheat the low-temperature CO2 gas in the CO2 Rankine cycle module, and the secondary waste heat from the residual flue gas is used to preheat both the air and ammonia, thereby improving the combustion efficiency when the two are combined and reducing NOx production during ammonia combustion. The residual heat from the third stage of flue gas flows into the flue gas cryogenic regenerator, where it releases heat from the liquid CO2 entering the regenerator, vaporizing it into CO2 gas. After the flue gas outputs electrical energy from the ammonia gas turbine, the waste heat is released stage by stage through a three-stage heat exchange system designed to comprehensively utilize the energy from various parts of the ammonia gas turbine module. After the three-stage heat exchange, the flue gas temperature is finally reduced to near the dew point, efficiently converting the energy contained in the flue gas and improving the net cycle efficiency.

[0034] In the low-temperature CO2 flow direction, the flue gas low-temperature regenerator 10 and the CO2 low-temperature regenerator 11 are connected in parallel and then sequentially connected to the high-temperature regenerator 12 and the heat exchanger 8 for staged heating. The primary waste heat of the flue gas in the heat exchanger 8 is used to heat the CO2 gas heated by the high-temperature regenerator 12 in the first stage (i.e., the primary heat exchange of the flue gas). The heated CO2 gas enters the CO2 turbine 13, expands, does work, and releases high-temperature CO2 gas. In the high-temperature CO2 gas flow direction, by sequentially connecting the CO2 turbine 13, the high-temperature regenerator 12, and the CO2 low-temperature regenerator 11, the high-temperature CO2 gas is used to preheat the low-temperature CO2 gas while simultaneously cooling the high-temperature CO2 gas in stages to obtain low-temperature CO2 gas. By using the waste heat from the third stage of flue gas as energy to match the vaporization of liquid CO2 in the flue gas cryogenic regenerator and employing a split-flow regeneration method, both liquid CO2 and the low-temperature CO2 gas are heated. This avoids the power consumption generated by the re-compressor and simultaneously matches the temperature gradient on both sides near the cryogenic regenerator, solving the pinch-point problem that easily occurs at both ends of the regenerator. The obtained low-temperature CO2 gas is then transported to the first cooler 4, where liquid ammonia refrigerant cools and liquefies the CO2 gas to obtain liquid CO2. This liquid CO2 can be recycled as the working fluid in the transcritical CO2 Rankine cycle module, achieving zero carbon emissions and no environmental pollution.

[0035] According to an embodiment of the present invention, continuing as follows Figure 1 As shown, according to the flue gas flow direction, the hot-side outlet of the heat exchanger 8 is connected to the hot-side inlet of the air preheater 2 and the hot-side inlet of the ammonia preheater 5, respectively. This utilizes the secondary waste heat of the residual flue gas in the heat exchanger 8 to preheat the air in the air preheater 2 and the ammonia in the ammonia preheater 5 (i.e., secondary heat exchange of the flue gas), allowing the ammonia to reach its combustible temperature (700-800℃) and preheating the air, thereby improving the combustion efficiency of ammonia in the combustion chamber 6 and reducing NOx generation. By utilizing the secondary waste heat of the flue gas to heat the air and ammonia, the potential utilization of flue gas waste heat is realized. The hot-side outlets of the air preheater 2 and the ammonia preheater 5 are connected to the hot-side inlet of the low-temperature flue gas regenerator 10, so as to recover the tertiary waste heat of the residual flue gas in the air preheater 2 and the ammonia preheater 5 to the low-temperature flue gas regenerator 10 for subsequent energy utilization in the CO2 Rankine cycle (i.e., tertiary heat exchange of the flue gas). The hot-side outlet of the flue gas low-temperature regenerator 10 is connected to the flue. After three stages of heat exchange, the temperature of the flue gas is reduced to near the dew point, which efficiently converts the energy contained in the flue gas and discharges the lower-temperature flue gas into the environment, reducing energy waste and thermal pollution to the environment.

[0036] According to an embodiment of the present invention, continuing as follows Figure 1 As shown, an air compressor 1 (CA) is also installed in the airflow direction. The inlet of the air compressor 1 is connected to an external air storage tank, and the outlet of the air compressor 1 is connected to the cold-side inlet of the air preheater 2. Air is introduced through the air compressor 1, compressed, and its temperature is initially increased. After compression, the air enters the air preheater 2 for preheating. The cold-side outlet of the air preheater 2 is connected to the combustion chamber 6 to allow some of the preheated air to be introduced into the combustion chamber 6 as an oxidant to catalyze the combustion of ammonia. The cold-side outlet of the air preheater 2 is also connected to the pipeline between the combustion chamber 6 and the ammonia turbine 7 to mix some of the air with the flue gas before it flows into the ammonia turbine 7, thereby adjusting the temperature of the combustion gas entering the ammonia turbine 7 and improving the net efficiency of the ammonia gas turbine. The remaining small amount of air can also be used as cooling air for the turbine blades to reduce the turbine temperature and prevent turbine failure.

[0037] Ammonia gas has a high latent heat of phase change and is a natural refrigerant, often transported in liquid form. Therefore, a liquid ammonia pump 3 is installed in the direction of ammonia flow. One end of the pump 3 is connected to a liquid ammonia storage tank, and the other end is connected to the inlet of the first cooler 4. The pump 3 is used to transport liquid ammonia from the storage tank to the first cooler 4. After pressurizing the liquid ammonia using the pump 3, it is transported to the first cooler 4 for heat exchange. The vaporization of liquid ammonia at -34℃ releases a large amount of cold energy, which matches the cold energy required below the critical temperature (30.8℃) for converting CO2 gas into liquid CO2 in the transcritical CO2 Rankine cycle, thus achieving CO2 liquefaction while simultaneously converting liquid ammonia into ammonia gas. Furthermore, the first cooler 4 is connected to the ammonia preheater 5, and the heat-exchanged (heated) ammonia is introduced into the ammonia preheater 5 for preheating. The preheated ammonia is then introduced into the combustion chamber 6 and mixed with the air entering the combustion chamber 6. The air acts as an oxidant to catalyze the combustion of ammonia, generating flue gas and releasing heat at the same time.

[0038] According to an embodiment of the present invention, a CO2 pump 9 (PC) is also provided in the transcritical CO2 Rankine cycle module. One end of the CO2 pump 9 is connected to the first cooler 4, and the other end of the CO2 pump 9 is connected to the flue gas low-temperature regenerator 10 and the CO2 low-temperature regenerator 11, respectively, for pressurizing and transporting the externally liquefied liquid CO2 and / or the low-temperature liquid CO2 in the transcritical CO2 Rankine cycle to the flue gas low-temperature regenerator 10 and the CO2 low-temperature regenerator 11 for heat exchange.

[0039] Specifically, according to the flow direction of CO2 on the low-temperature side, one end of CO2 pump 9 is connected to the first cooler 4, and the other end is connected to the flue gas low-temperature regenerator 10 and the CO2 low-temperature regenerator 11 respectively, so as to transport the cooled liquid CO2 to the flue gas low-temperature regenerator 10 and the CO2 low-temperature regenerator 11 for three-stage heating, converting the liquid CO2 into CO2 gas. After the three-stage heating, the CO2 gas merges and enters the high-temperature regenerator 12 for two-stage heating. The CO2 gas after the two-stage heating enters the heat exchanger 8, and uses the first-stage waste heat of the flue gas in the heat exchanger 8 to preheat the low-temperature side CO2 (the CO2 gas after the two-stage heating). The preheated CO2 gas enters the CO2 turbine 13 to expand and do work, outputting electrical energy and releasing high-temperature CO2 gas.

[0040] In the high-temperature CO2 gas flow direction, the CO2 turbine 13 is connected to the hot-side inlet of the high-temperature regenerator 12. The high-temperature CO2 gas enters the high-temperature regenerator 12 for primary regeneration. After primary regeneration, the high-temperature CO2 gas enters the low-temperature CO2 regenerator 11 through the hot-side inlet for secondary regeneration. Through primary and secondary regeneration, the temperature of the high-temperature CO2 gas is gradually reduced to obtain low-temperature CO2 gas. At the same time, energy is supplied to the liquid CO2 after the CO2 pump 9 to vaporize it, thus realizing the energy utilization of CO2 gas. After the low-temperature CO2 gas is cooled in the first cooler 4, liquid CO2 is obtained. The obtained liquid CO2 is transported by the CO2 pump 9 for recirculation in the CO2 Rankine cycle.

[0041] Furthermore, to avoid insufficient CO2 cooling in the transcritical CO2 Rankine cycle module and the first cooler 4, the combined system of the present invention also provides an ammonia refrigeration cycle module, including a throttle valve 16 (TV), a second cooler 17 (cool 2, C2), an ammonia compressor 14 (ammonia compressor, C-AM), and a condenser 15 (condenser, CD).

[0042] In the ammonia flow direction of the ammonia refrigeration cycle module, a closed loop consisting of a throttle valve 16, a second cooler 17, an ammonia compressor 14, and a condenser 15 is established. The ammonia is connected to the cold-side inlet of the throttle valve 16 and the second cooler 17 via a pipeline. The hot-side inlet of the second cooler 17 is connected to the hot-side outlet of the CO2 cryogenic regenerator 11, allowing the low-temperature CO2 gas in the CO2 cryogenic regenerator 11 to exchange heat with the ammonia gas, further reducing the temperature of the CO2 gas. The cold-side outlet of the second cooler 17 is connected to the inlet of the CO2 pump 9, allowing the cooled CO2 gas to be discharged through the outlet of the second cooler 17 and mixed with the liquid CO2 cooled by the first cooler 4. The mixed liquid CO2 then enters the CO2 Rankine cycle module via the CO2 pump 9 for circulation. The ammonia gas, after heat exchange with the second cooler 17, enters the ammonia compressor for heating and pressurization before entering the condenser 15.

[0043] According to an embodiment of the present invention, the cold inlet of the condenser 15 is connected to an external air storage tank to use the outside air as a coolant to liquefy the ammonia in the condenser, while simultaneously discharging excess heat into the air. The liquefied liquid ammonia flows back into the throttle valve 16 for repeated circulation.

[0044] Figure 2 This is a schematic diagram of the framework of a combined system of ammonia-recovering cold energy gas turbine and CO2 Rankine cycle in another embodiment of the present invention.

[0045] Figure 2 The structure and Figure 1 The structures are identical, and the functions of each unit are the same. The only difference is that the cold-side inlet of condenser 15 is connected to an external cooling water storage tank, and the hot-side outlet of condenser 15 is connected to the heating module; and the flue is connected to the hot-side outlet of flue gas low-temperature regenerator 10 via heat exchanger 18. The cold-side inlet of heat exchanger 18 is connected to external cooling water, and the hot-side outlet of heat exchanger 18 is connected to the heating unit, where the cooling water can be heating return water. Therefore, the combined cycle system in this invention transforms power generation into combined heat and power (CHP), enabling urban heating. Depending on the temperature of the cooling water (return water), heat extracted from the condenser of the ammonia refrigeration cycle module can be used for radiator heating, and heat extracted from the flue gas discharged from the ammonia gas turbine module can be used for urban underfloor heating, as detailed below:

[0046] By introducing cooling water into the cooler 15 to exchange heat with the ammonia gas inside, the ammonia gas is liquefied into liquid ammonia. Simultaneously, the hot water after heat exchange is discharged through the hot side outlet of the condenser 15 into the heating module for radiator heating. The flue is connected to the flue gas low-temperature regenerator 10 via heat exchanger 18. The flue gas after three stages of heat exchange is introduced into heat exchanger 18 to exchange heat with the external cooling water entering through the cold end of heat exchanger 18, further reducing the waste heat temperature of the flue gas and simultaneously increasing the temperature of the cooling water. The heated cooling water then enters the heating unit for heating, which can be underfloor heating, utilizing the heated cooling water to provide heat. This further realizes the energy utilization of the flue gas. The temperature of the flue gas after three stages of heat exchange is 60-70℃, meeting the temperature requirements for underfloor heating.

[0047] As a second aspect of the present invention, a method for combining an ammonia-recovery cold-energy gas turbine with a CO2 Rankine cycle is also provided, employing the system described in the above embodiments. The following is in conjunction with... Figures 1-2 The method will be explained in detail.

[0048] According to an embodiment of the present invention, the method of combining a gas turbine for recovering ammonia cold energy with a CO2 Rankine cycle includes: after liquid ammonia is vaporized into ammonia gas and the cold energy of liquid ammonia is recovered, preheated air and ammonia gas are introduced into combustion chamber 6 for combustion to generate flue gas and release heat. The flue gas flows into ammonia turbine 7 to do work and output electrical energy and flue gas.

[0049] According to the flow direction of the flue gas, the primary waste heat of the flue gas is used to carry out primary cooling in the heat exchanger 8. After primary cooling, the secondary waste heat of the flue gas is used to carry out secondary cooling in the air preheater 2 and the ammonia preheater 5 respectively. After secondary cooling, the tertiary waste heat of the flue gas is used to carry out tertiary cooling in the flue gas low-temperature regenerator 10 to obtain low-temperature flue gas.

[0050] According to the flow direction of CO2 on the low-temperature side, the low-temperature liquid CO2 flows into the flue gas low-temperature regenerator 10 and the CO2 low-temperature regenerator 11 for three-stage heating. After heating, the CO2 gas merges and flows into the high-temperature regenerator 12 for two-stage heating, and then enters the heat extractor 8 for one-stage heating. The CO2 gas, after being heated step by step, flows into the CO2 turbine 13 to do work, output electrical energy and release high-temperature CO2 gas.

[0051] Following the flow direction of CO2 gas on the high-temperature side, the high-temperature CO2 gas flows back to the high-temperature regenerator 12 for primary reheating. After primary reheating, the CO2 gas flows back to the low-temperature CO2 regenerator 11 for secondary reheating of low-temperature liquid CO2. The temperature of the high-temperature CO2 gas is gradually reduced to obtain low-temperature CO2 gas. After the low-temperature CO2 gas is cooled to below the critical point by the cold energy recovered by the first cooler 4, the obtained low-temperature liquid CO2 circulates in the transcritical CO2 Rankine cycle module.

[0052] According to an embodiment of the present invention, air is delivered to air compressor 1 for compression and pressurization, and the pressurized air is delivered to air preheater 2 for preheating; liquid ammonia is delivered to first cooler 4 for heat exchange using liquid ammonia pump 3, and the preheated ammonia flows into ammonia preheater 5 for further preheating.

[0053] In this embodiment of the invention, outside air is introduced and compressed by an air compressor 1, and then sent to an air preheater 2 for preheating to increase the temperature of the air entering the combustion chamber 6, thereby improving the combustion rate and efficiency of ammonia. Outside liquid ammonia is pumped by a liquid ammonia pump 3 to a first cooler 4 to exchange heat with CO2 gas, vaporizing the liquid ammonia into ammonia gas and liquefying the CO2 gas into liquid CO2. The heat-exchanged ammonia gas is then sent to an ammonia preheater 5 for further preheating, raising its temperature to the ammonia combustion temperature, ensuring sufficient preheating and reducing NOx pollutant generation during ammonia combustion.

[0054] According to an embodiment of the present invention, preheated air is mixed with the flue gas before it enters the ammonia turbine 7 to regulate the combustion gas temperature entering the ammonia turbine 7. Specifically, the preheated air and ammonia are burned in the combustion chamber 6 to produce flue gas, which then enters the ammonia turbine 7 through a pipeline to expand and perform work. Mixing a portion of the air with the flue gas before it enters the ammonia turbine 7 can regulate the combustion gas temperature entering the ammonia turbine 7 and also improve the net efficiency of the ammonia gas turbine. The remaining small amount of air is used as cooling air for the turbine blades to reduce the turbine temperature and prevent malfunctions of the ammonia turbine 7.

[0055] According to an embodiment of the present invention, the primary waste heat of the flue gas is used for primary cooling in the heat exchanger 8, that is, the primary waste heat of the flue gas is used to release heat to CO2 gas in the heat exchanger 8; the secondary waste heat of the flue gas is used for secondary cooling in the air preheater 2 and the ammonia preheater 5, that is, after primary cooling, the secondary waste heat of the flue gas is used to release heat to air and ammonia gas respectively; the tertiary waste heat of the flue gas is used for tertiary cooling in the flue gas low-temperature regenerator 10, that is, after secondary cooling, the tertiary waste heat of the flue gas is used to release heat to liquid CO2 in the flue gas low-temperature regenerator 10.

[0056] According to an embodiment of the present invention, liquid CO2, after being pressurized by CO2 pump 9, flows into the flue gas low-temperature regenerator 10 and the CO2 low-temperature regenerator 11 in two streams. The third-stage waste heat of the flue gas is introduced to ensure that the heat sources at both ends of the regenerators meet the heat matching requirements, thus avoiding the pinch-point problem at both ends of the regenerators. Through the gradual release of energy from the flue gas via the third-stage heat release, the temperature of the CO2 after CO2 pump 9 is reduced to 40-60°C, lowering the flue gas temperature to near the dew point. This effectively reduces the flue gas emission temperature, decreases thermal pollution to the environment, and improves the net cycle efficiency.

[0057] According to an embodiment of the present invention, liquid CO2 is introduced into a flue gas low-temperature regenerator 10, a CO2 low-temperature regenerator 11, a high-temperature regenerator 12, and a heat exchanger 8 for heat exchange. The obtained high-temperature CO2 gas enters a CO2 turbine 13 for expansion and work, and the generated high-temperature CO2 gas continues to flow back to the high-temperature regenerator 12 and the CO2 low-temperature regenerator 11, using the heat of the high-temperature CO2 gas to preheat the low-temperature CO2, thus recycling the energy of CO2. Then, the low-temperature CO2 gas is liquefied into liquid CO2 using a first cooler 4 and circulated in a CO2 Rankine cycle, achieving zero CO2 emissions. In addition, by using a CO2 Rankine cycle module, the temperature of the CO2 gas can be reduced, and then cooled by the first cooler 4 to a level that allows the CO2 gas to be liquefied into liquid CO2, thereby reducing the energy required for cooling and liquefying into liquid CO2 using liquid ammonia phase change (first cooler) and reducing the power consumption of the ammonia refrigeration cycle module.

[0058] According to an embodiment of the present invention, one end of the second cooler 17 in the ammonia refrigeration cycle module is connected to the ammonia storage tank, and the other end is connected to the CO2 low-temperature regenerator 11. Ammonia is introduced into the ammonia refrigeration cycle module, and the ammonia exchanges heat with the low-temperature CO2 gas in the second cooler 17. The low-temperature CO2 gas is cooled into liquid CO2 while the ammonia is heated. The cooled liquid CO2 flows back to the CO2 pump 9 for circulation. The preheated ammonia enters the condenser 15 for liquefaction, thereby solving the problem of insufficient CO2 cooling in the transcritical CO2 Rankine cycle module and the first cooler 4.

[0059] According to an embodiment of the present invention, air is introduced into the condenser 15 to liquefy the ammonia gas in the condenser 15. The liquefied liquid ammonia circulates in the ammonia refrigeration cycle module through the throttle valve 16, and the heated air exhausts heat to the outside.

[0060] According to an embodiment of the present invention, air is replaced with cooling water, that is, cooling water is introduced into the condenser, and the ammonia gas in the condenser is liquefied by the cooling water. The liquefied liquid ammonia circulates in the ammonia gas refrigeration cycle module. At the same time, the cooling water is heated and the heated cooling water is used for heating the radiators. The cooling water can be the return water for the radiators.

[0061] According to an embodiment of the present invention, the flue gas discharged from the system is directly introduced into the heat exchanger 18, and heat exchange is performed between the external cooling water and the flue gas in the heat exchanger 18. The heated cooling water is used for underfloor heating, and the flue gas after heat exchange is discharged from the heat exchanger 18. In an embodiment of the present invention, a heat exchanger 18 (residual heat regenerator) is added at the outlet end of the flue gas low-temperature regenerator 10, wherein the external cooling water can be underfloor heating return water, which can be used for urban underfloor heating.

[0062] According to embodiments of the present invention, when the cooling energy from the liquid ammonia phase change is insufficient to meet the cooling requirements of CO2, other refrigerants or other refrigeration methods can be used for cooling, such as absorption refrigeration, magnetic refrigeration, and acoustic refrigeration. The number and location of the first coolers can be flexibly varied.

[0063] The specific embodiments described above further illustrate the purpose, technical solution, and beneficial effects of the present invention. It should be understood that the above descriptions are merely specific embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the protection scope of the present invention.

Claims

1. A combined system of ammonia gas cold energy gas turbine and CO2 Rankine cycle for recycling, characterized in that, The system comprises an ammonia gas turbine module and a transcritical CO2 Rankine cycle module; The ammonia gas turbine module is provided with a first cooler for vaporizing liquid ammonia to release cold energy, an ammonia preheater for heating the vaporized ammonia to a combustible temperature of ammonia, and a combustion chamber in the ammonia flow direction; and is provided with an air preheater and a combustion chamber in the air flow direction, wherein the ammonia and the air are mixed and combusted in the combustion chamber to generate flue gas and release heat; and is provided with an ammonia turbine, a heat extractor, and a flue gas low-temperature recuperator in the flue gas flow direction; The transcritical CO2 Rankine cycle module is provided with a CO2 low-temperature recuperator, a high-temperature recuperator, a heat extractor, and a CO2 turbine, wherein the CO2 low-temperature recuperator and the flue gas low-temperature recuperator are connected in parallel, and the transcritical CO2 Rankine cycle module shares one heat extractor with the ammonia gas turbine module, In the CO2 flow direction of the low-temperature side, the CO2 is preheated by the CO2 low-temperature recuperator and the flue gas low-temperature recuperator, respectively, and the preheated CO2 gas is mixed and sequentially enters the high-temperature recuperator and the heat extractor for step-by-step temperature rising, and the preheated CO2 gas enters the CO2 turbine to do work and release high-temperature CO2 gas; In the CO2 gas flow direction of the high-temperature side, the hot side outlet of the CO2 turbine is sequentially connected with the hot side inlet of the high-temperature recuperator and the hot side inlet of the CO2 low-temperature recuperator, and the hot side outlet of the CO2 low-temperature recuperator is connected with the hot side inlet of the first cooler, so that the high-temperature side CO2 gas is step-by-step cooled to obtain low-temperature CO2 gas by the high-temperature recuperator and the CO2 low-temperature recuperator, and the low-temperature CO2 gas is cooled to a temperature below the critical point by the first cooler recovering the cold energy released by the liquid ammonia, and the obtained low-temperature liquid CO2 circulates in the transcritical CO2 Rankine cycle module.

2. The system of claim 1, wherein, The hot side outlet of the heat extractor is connected with the hot side inlet of the ammonia preheater and the hot side inlet of the air preheater, respectively, The hot side outlets of the air preheater and the ammonia preheater are connected with the hot side inlet of the flue gas low-temperature recuperator, and the hot side outlet of the flue gas low-temperature recuperator is connected with a flue.

3. The system of claim 2, wherein, An air compressor is further provided in the air flow direction, and the outlet of the air compressor is connected with the cold side inlet of the air preheater; The cold side outlet of the air preheater is connected with the combustion chamber, and the cold side outlet of the air preheater is also connected with a pipeline between the combustion chamber and the ammonia turbine; A liquid ammonia pump is further provided in the ammonia flow direction, one end of the liquid ammonia pump is connected with a liquid ammonia storage tank, and the other end is connected with the inlet of the first cooler, and the liquid ammonia pump is used to pressurize and deliver the liquid ammonia in the liquid ammonia storage tank to the first cooler.

4. The system of claim 3, wherein, The transcritical CO2 Rankine cycle module is further provided with a CO2 pump, one end of the CO2 pump being connected with the first cooler, and the other end being connected with the flue gas low-temperature regenerator and the CO2 low-temperature regenerator respectively, for pressurizing and conveying the liquefied liquid CO2 from outside and / or the low-temperature liquid CO2 in the transcritical CO2 Rankine cycle to the flue gas low-temperature regenerator and the CO2 low-temperature regenerator respectively.

5. The system of any one of claims 1-4, wherein, The system further comprises an ammonia refrigeration cycle module, which is provided with a closed loop composed of a throttling valve, a second cooler, an ammonia compressor and a condenser in the ammonia flow direction of the ammonia refrigeration cycle module; wherein an outside ammonia storage tank is connected with the cold side inlet of the second cooler, the hot side inlet of the second cooler is further connected with the hot side outlet of the CO2 low-temperature regenerator, and the cold side outlet of the second cooler is connected with the inlet of the CO2 pump.

6. The system of any one of claim 5, wherein, the cold side inlet of the condenser is connected with an outside air storage tank; or the cold side inlet of the condenser is connected with an outside cooling water storage tank, and the hot side outlet of the condenser is connected with a heating module; and the flue gas duct is connected with the hot side outlet of the flue gas low-temperature regenerator through a heat exchanger, the cold side inlet of the heat exchanger is connected with outside cooling water, and the hot side outlet of the heat exchanger is connected with a heating unit.

7. A method for recovering cold energy of ammonia gas combined with CO2 Rankine cycle, using the system according to any one of claims 1-6, characterized in that, The method comprises: After the liquid ammonia is vaporized into ammonia gas and the cold energy of the liquid ammonia is recovered, the preheated air and ammonia gas are introduced into a combustion chamber for combustion to generate flue gas and release heat, the flue gas flows into an ammonia turbine to do work and output electric energy and flue gas; According to the flow direction of the flue gas, the first-stage waste heat of the flue gas is used to perform first-stage cooling in a heat extractor, the second-stage waste heat of the flue gas is used to perform second-stage cooling in an air preheater and an ammonia preheater respectively after the first-stage cooling, and the third-stage waste heat of the flue gas is used to perform third-stage cooling in a flue gas low-temperature regenerator after the second-stage cooling, to obtain low-temperature flue gas; According to the flow direction of the low-temperature side CO2, the low-temperature liquid CO2 flows into the flue gas low-temperature regenerator and the CO2 low-temperature regenerator respectively to perform third-stage heating, the heated CO2 gas is combined and then flows into a high-temperature regenerator to perform second-stage heating and into the heat extractor to perform first-stage heating, and the gradually heated CO2 gas flows into a CO2 turbine to do work, output electric energy and release high-temperature CO2 gas; According to the flow direction of the high-temperature side CO2 gas, the high-temperature CO2 gas flows back to the high-temperature regenerator to perform first-stage heat recovery on the CO2 gas, the first-stage heat recovered CO2 gas flows back to the CO2 low-temperature regenerator to perform second-stage heat recovery on the low-temperature liquid CO2, the temperature of the high-temperature side CO2 gas is gradually reduced to obtain low-temperature CO2 gas, and the low-temperature liquid CO2 obtained after the low-temperature CO2 gas is cooled by the cold energy recovered by the first cooler to a temperature below the critical point circulates in the transcritical CO2 Rankine cycle module.

8. The method of claim 7, wherein, The air is delivered into the air preheater by an air compressor and the liquid ammonia is delivered into the first cooler by a liquid ammonia pump for heat exchange. The preheated ammonia gas flows into the ammonia gas preheater for preheating. The preheated air is mixed with the flue gas before the flue gas enters the ammonia gas turbine to adjust the temperature of the flue gas entering the ammonia gas turbine.

9. The method of claim 7, wherein, One end of the second cooler in the ammonia gas refrigeration cycle module is connected with an ammonia gas storage tank and the other end is connected with a CO2 low temperature regenerator. The ammonia gas is delivered into the ammonia gas refrigeration cycle module and exchanges heat with the low temperature CO2 gas in the second cooler. The low temperature CO2 gas is cooled into liquid CO2 while the ammonia gas is heated. The cooled liquid CO2 gas flows back to the CO2 pump for recycling.

10. The method of claim 8, wherein, Air is delivered into the condenser to liquefy the ammonia gas in the condenser. The liquefied liquid ammonia circulates in the ammonia gas refrigeration cycle module. The heated air is discharged for heat dissipation. Or Cooling water is delivered into the condenser to liquefy the ammonia gas in the condenser. The liquefied liquid ammonia circulates in the ammonia gas refrigeration cycle module. The cooling water is heated at the same time. The heated cooling water is used for radiator heating. And The flue gas discharged from the system is directly delivered into a heat exchanger to exchange heat with the flue gas in the heat exchanger by using external cooling water. The heated cooling water is used for floor heating. The flue gas after heat exchange is discharged from the heat exchanger.

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