DME production with self-condensing transcritical co2 alam cycle combined system, method

Abstract

The application provides a dimethyl ether production and self-condensation transcritical CO2 Al-ram cycle combined system and method, wherein in the Al-Ram cycle module, the working medium liquid CO2 passes through the critical point from liquid state to gas state through a heat exchanger or a low-temperature regenerator, CO2 gas is mixed with oxygen to form an oxygen aid after being heated by the regenerator and is introduced into a combustion chamber, products containing CO2 and water vapor generated by combustion of fuel in the combustion chamber enter a gas turbine to do work and generate electricity, the gas after doing work is heated by the regenerator, liquid water and CO2 gas are separated by a first gas-liquid separator, the separated CO2 gas is condensed to liquid state by a condenser, and at least part of the liquid CO2 is recycled. Liquid dimethyl ether is transported to the condenser, dimethyl ether is gasified and pressurized while CO2 is liquefied, and the pressurized dimethyl ether gas is transported to the combustion chamber for combustion; the dimethyl ether preparation module is provided with a dimethyl ether absorption unit, and the heat exchange between the purge gas and the liquid CO2 in the heat exchanger is used to adjust the specific heat matching of the two ends of the regenerator.

Description

Technical Field

[0001] The present invention belongs to the field of transcritical carbon dioxide (CO2) Allam cycle, and in particular relates to a combined system and method for dimethyl ether production and self-condensing transcritical CO2 Allam cycle. Background Art

[0002] With limited oil and natural gas reserves and coal dominating available energy sources, the conversion and efficient, clean utilization of coal are gaining increasing attention. Dimethyl ether (DME) boasts excellent compressibility, ease of transportation, high energy density, and is a green energy source. Upon complete combustion, it produces only CO2 and water, making it an ideal product for coal chemical industry. Technically, DME can be converted from coal to methanol through catalytic methanol synthesis and dehydration at 3.5-5.0 MPa and 230-250°C, achieving a one-step conversion.

[0003] Fuels commonly used in the Allam cycle include methane, natural gas, and hydrogen. These gases need to be compressed before entering the combustion chamber, but gas is not easily compressed, resulting in significant compression work losses. To maximize Allam cycle efficiency and facilitate the capture of CO2 in a liquid state and the separation of the combustion product, water, the portion of CO2 that is recycled must be cooled to a liquid state before passing from the gas turbine outlet to the next cycle inlet. Cooling the 7.31 MPa CO2 to below 31°C requires an additional forced cooling system, which consumes a significant amount of work. Furthermore, in the one-step catalytic synthesis of dimethyl ether (DME), only a portion of the heat-rich purge gas from DME production is recovered and re-entered into the slurry bed reactor for the reaction, while the remaining portion is difficult to utilize. Related technologies have proposed methods for feeding the purge gas into a gas turbine to generate power, but the pressure and temperature are low, placing high demands on the gas turbine design and making the turbine too large for practical application. Summary of the Invention

[0004] In response to the above technical problems, the present invention provides a system and method for combining dimethyl ether production with a self-condensing transcritical CO2 Alam cycle, in order to at least partially solve the above technical problems. The specific technical solutions are as follows:

[0005] As a first aspect of the present invention, a combined system for dimethyl ether production and self-condensing transcritical CO2 Allam cycle is provided, comprising: an Allam cycle module and a dimethyl ether production module;

[0006] The Alam cycle module includes a CO2 pump, a heat exchanger, a regenerator, a combustion chamber, a gas turbine, a first gas-liquid separator, a condenser, and pipelines for connecting these components to form a CO2 circulation loop;

[0007] The working fluid liquid CO2 is pumped by a CO2 pump, passes through a heat exchanger or a low-temperature regenerator, crosses the critical point from the liquid state, and is heated by the regenerator. The heated CO2 gas is introduced into the combustion chamber to mix with oxygen to form an oxygen-enriched agent of 95% CO2 and 5% O2. The products containing CO2 and water vapor generated by the combustion of the fuel in the combustion chamber enter the gas turbine to generate power. The gas after the power generation recovers heat through the regenerator, and the liquid water and CO2 gas are separated through the first gas-liquid separator. The separated CO2 gas is condensed to a liquid state through a condenser, and at least part of the liquid CO2 returns to the CO2 pump for another cycle.

[0008] The Alam cycle module also includes a fuel feed path, in which liquid dimethyl ether fuel is delivered to a condenser, where it exchanges heat with the separated CO2 gas, liquefying the CO2 while simultaneously vaporizing and pressurizing the dimethyl ether. The pressurized dimethyl ether gas is then delivered to the combustion chamber for combustion.

[0009] The dimethyl ether production module is equipped with a dimethyl ether absorption unit. The outlet of the dimethyl ether absorption unit is connected to the heat exchanger. The relaxation gas is used to exchange heat with the liquid CO2 in the heat exchanger to adjust the specific heat matching at both ends of the heat recovery.

[0010] As a second aspect of the present invention, a method for combining dimethyl ether production with a self-condensing transcritical CO2 Alam cycle is provided, comprising:

[0011] In the self-condensing transcritical CO2 Allam cycle, the working fluid liquid CO2 is transported by a CO2 pump to a heat exchanger or a low-temperature regenerator for conversion from liquid to gas, and is heated in the regenerator. The heated CO2 gas is introduced into the combustion chamber and forms an oxygen enhancer with the oxygen entering the combustion chamber. The gasified fuel enters the combustion chamber and burns to produce products containing CO2 gas and water vapor, of which CO2 gas accounts for 95% and oxygen accounts for 5%.

[0012] The product enters the gas turbine to generate electricity. The gas after the work is recycled through the regenerator to recover heat to completely liquefy the water vapor in the combustion products. The first gas-liquid separator is used to separate the liquid water and CO2 gas. The separated CO2 gas exchanges heat with the condenser to liquefy into liquid CO2, at least part of which is transported by the CO2 pump for another cycle.

[0013] After the liquid dimethyl ether exchanges heat with the CO2 gas in the condenser, the liquid dimethyl ether is vaporized into dimethyl ether fuel. The vaporized dimethyl ether is transported to the combustion chamber as fuel for combustion;

[0014] During the dimethyl ether production process, the purge gas generated by dimethyl ether absorption treatment is used to preheat the liquid CO2 entering the heat exchanger and convert it into CO2 gas, while adjusting the specific heat matching at both ends of the heat recovery. The pure dimethyl ether produced is used as a refrigerant in the condenser to exchange heat with the CO2 gas, and as fuel to enter the combustion chamber for combustion.

[0015] Based on the above technical solution, the combined system and method for dimethyl ether production and self-condensing transcritical CO2 Alam cycle provided by the present invention have at least one of the following beneficial effects:

[0016] (1) According to an embodiment of the present invention, a dimethyl ether absorption unit is connected to a heat exchanger, and the off-gas generated by the dimethyl ether unit during the absorption of dimethyl ether is used as heat for the heat exchanger. Then, a portion of the liquid working medium CO2 is transported to the heat exchanger via a CO2 pump, and the waste heat of the off-gas is used to convert the liquid CO2 across the critical point into CO2 gas. The other portion absorbs the residual heat of the reflux CO2 in the low-temperature regenerator and is heated to become gas. The CO2 gas is further heated in the high-temperature regenerator and then introduced into the combustion chamber to form a combustion aid with the oxygen entering the combustion chamber. When the fuel gas enters the combustion chamber, it can catalyze the combustion of the fuel to produce high-temperature gas containing CO2 gas and water vapor. The high-temperature gas enters the gas turbine and expands to produce work and output electrical energy, which can be used for energy consumption in the dimethyl ether production path. The gas after work enters the regenerator for heat recovery. The heat recovery can liquefy the water vapor in the high-temperature gas into liquid water while increasing the temperature of the CO2 gas entering the regenerator. The first gas-liquid separator then separates the liquid water and CO2 gas. The separated CO2 gas is condensed in a condenser and liquefied into liquid CO2. At least a portion of this liquid CO2 can be recirculated within the Allam cycle via a CO2 pump. The Allam cycle also includes a fuel feed path. Liquid dimethyl ether is fed to the condenser, where it exchanges heat with the CO2 gas in the condenser, vaporizing the liquid dimethyl ether into dimethyl ether gas fuel. This dimethyl ether gas fuel then enters the combustion chamber and burns under the catalytic action of an oxygen enhancer.

[0017] (2) According to an embodiment of the present invention, liquid dimethyl ether and gaseous CO2 exchange heat with each other in the condenser of the Allam cycle, raising the temperature of dimethyl ether from its boiling point of -29°C at normal pressure to about 30°C, completing the gasification and pressurization of the dimethyl ether fuel before entering the combustion chamber of the Allam cycle. The boiling point of dimethyl ether at normal pressure matches the liquefaction temperature of CO2. The loss is minimal, and the CO2 gas is fully cooled by the cold energy of the dimethyl ether fuel, converting the CO2 gas into liquid CO2. In other words, the CO2 gas fully utilizes the cold energy of the dimethyl ether fuel to achieve the conversion of CO2 gas into liquid CO2 before entering the CO2 pump, reducing the cost of CO2 gas operation and saving the power consumption of pressurizing and heating the common gaseous fuel before entering the combustion chamber, ensuring the efficiency of the entire cycle.

[0018] (3) According to an embodiment of the present invention, a condenser is provided at the inlet end of the CO2 pump to cool the CO2 to a liquid state, and then the CO2 gas generated by combustion can be directly separated and stored, thereby avoiding the capture of the CO2 gas by compressing it to a liquid state, saving compression power consumption and reducing the CO2 storage space, thereby reducing the high cost of carbon capture and achieving higher working efficiency in the transcritical Allam cycle.

[0019] (4) According to an embodiment of the present invention, the off-gas from the process of coal gasification to produce dimethyl ether is used for heat exchange in a heat exchanger, thereby achieving the goal of using a lower-quality heat source to regulate the pinch point problem on both sides of the regenerator caused by the specific heat properties of CO2. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 This is a schematic diagram of a framework of a combined system for dimethyl ether production and self-condensing transcritical CO2 Alam cycle in an embodiment of the present invention;

[0021] Figure 2 This is a schematic diagram of the framework of a combined system for dimethyl ether production and self-condensing transcritical CO2 Alam cycle in another embodiment of the present invention.

[0022] [Description of Reference Numerals]

[0023] 1-CO2 storage unit, 2-liquid CO2 pump, 3-CO2 pump, 4-fuel pump, 5-condenser, 6-first gas-liquid separator, 7-combustion chamber, 8-compressor, 9-air separation unit, 10-gas turbine, 11-high-temperature regenerator, 12-low-temperature regenerator, 13-heat exchanger, 14-gasification unit, 15-purification unit, 16-catalytic reactor, 17-second gas-liquid separator, 18-CO2 separation unit, 19-dimethyl ether separation unit, 20-distillation cooling unit, 21-absorbent regeneration unit, 22-dimethyl ether absorption unit;

[0024] A-oxygen, B-dimethyl ether, C-liquid CO2, D-impurities, E-purge gas, F-CO2. DETAILED DESCRIPTION

[0025] In order to make the objectives, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with specific embodiments and with reference to the accompanying drawings.

[0026] The Allam cycle is a semi-closed Brayton cycle that uses CO2 as the working fluid and a mixture of CO2 and O2 as an oxygen enhancer. The heat generated by the combustion of gaseous fuel in the combustion chamber directly heats the working fluid CO2, which then enters the gas turbine to generate power. The CO2 and water produced by the fuel combustion are completely captured at the gas turbine outlet, and the remaining CO2 is cooled and put into the next operation. The Allam cycle has two main features: replacing the compressor in the closed Brayton recompression cycle with a pump and directly burning the fuel to heat the working fluid. This improves the thermodynamic efficiency of the cycle compared to the original closed Brayton cycle. Furthermore, the Allam cycle often uses hydrocarbon fuels as fuel, and after complete combustion, the water in the combustion products is separated, allowing the CO2 produced by the combustion to be drawn out and sealed, while the remaining part continues to participate in the cycle as a working fluid, achieving carbon capture at a low cost. This can be used as an effective way to help achieve carbon peaking and carbon neutrality. However, the fuel commonly used in the Allam cycle is difficult to compress, resulting in a large amount of compression work loss. Furthermore, CO2 cooling requires an additional forced refrigeration system, and the purge gas generated during the dimethyl ether production process cannot be utilized. To address these issues, the present invention provides a combined system and method for dimethyl ether production and a self-condensing transcritical CO2 Allam cycle. Through the structural design of the combined system, the CO2 gas is liquefied using the inherent cooling energy of dimethyl ether, while the waste heat of the purge gas during the dimethyl ether production process is used to resolve the pinch point problem at both ends of the regenerator.

[0027] Specifically, as a first aspect of the present invention, a combined system of dimethyl ether production and self-condensing transcritical CO2 Allam cycle is provided, comprising: an Allam cycle module and a dimethyl ether production module, wherein the Allam cycle module includes a CO2 pump, a heat exchanger, a regenerator, a combustion chamber, a gas turbine, a first gas-liquid separator, a condenser and pipelines for connecting these components to form a CO2 circulation loop; the dimethyl ether production module is provided with a dimethyl ether absorption unit.

[0028] In the Allam cycle module, liquid CO2 is pumped by a CO2 pump. It passes through a heat exchanger or low-temperature regenerator, where it crosses the critical point from the liquid state and is heated in the regenerator. The heated CO2 gas is then introduced into a combustion chamber, where it mixes with oxygen to form an oxygen-enriched mixture of 95% CO2 and 5% O2. The products of fuel combustion in the combustion chamber, consisting of CO2 and water vapor, are then fed into a gas turbine to generate power. The resulting gas is then passed through a regenerator to recover heat. Liquid water and CO2 gas are separated in a first gas-liquid separator. The separated CO2 gas is condensed to a liquid state in a condenser, and at least a portion of the liquid CO2 is returned to the CO2 pump for another cycle. The Allam cycle module also includes a fuel feed path, where liquid dimethyl ether fuel is fed to the condenser, where it exchanges heat with the separated CO2 gas, vaporizing and pressurizing the dimethyl ether while liquefying the CO2. The pressurized dimethyl ether gas is then fed to the combustion chamber for combustion.

[0029] The dimethyl ether production module is equipped with a dimethyl ether absorption unit. The outlet of the dimethyl ether absorption unit is connected to the heat exchanger. The relaxation gas is used to exchange heat with the liquid CO2 in the heat exchanger to adjust the specific heat matching at both ends of the heat recovery.

[0030] In an embodiment of the present invention, a dimethyl ether (DME) absorption unit is connected to a heat exchanger, utilizing the offgas generated during the DME absorption process as heat for the heat exchanger. A portion of the liquid CO2 working fluid is then pumped into the heat exchanger via a CO2 pump. The waste heat from the offgas in the heat exchanger transforms the liquid CO2 beyond its critical point into CO2 gas. The remaining portion absorbs the residual heat of the refluxed CO2 in a low-temperature regenerator, where it is heated to form a gas. This CO2 gas is further heated in a high-temperature regenerator and then introduced into a combustion chamber, where it reacts with oxygen entering the combustion chamber to form a combustion aid. When the fuel gas enters the combustion chamber, it catalyzes fuel combustion, producing high-temperature gas containing CO2 and water vapor. This product enters a gas turbine, expands, and generates work to produce electrical energy, which can be used to power the DME production process. The resulting gas enters the regenerator for reheating, where it liquefies the water vapor in the high-temperature gas into liquid water while simultaneously increasing the temperature of the CO2 gas entering the regenerator. The first gas-liquid separator then separates the liquid water and CO2 gas. The separated CO2 gas is condensed in a condenser and liquefied into liquid CO2. At least a portion of this liquid CO2 can be recirculated within the Allam cycle via a CO2 pump. The Allam cycle also includes a fuel feed path. Liquid dimethyl ether is fed to the condenser, where it exchanges heat with the CO2 gas in the condenser, vaporizing the liquid dimethyl ether into dimethyl ether gas fuel. This dimethyl ether gas fuel then enters the combustion chamber and burns under the catalytic action of an oxygen enhancer.

[0031] Figure 1 This is a schematic diagram of the framework of a combined system for dimethyl ether production and self-condensing transcritical CO2 Alam cycle in an embodiment of the present invention.

[0032] like Figure 1 As shown, the combined system of dimethyl ether production and self-condensing transcritical CO2 Allam cycle includes an Allam cycle module at the top and a dimethyl ether production module at the bottom, wherein the dimethyl ether production module adopts a one-step catalytic synthesis of dimethyl ether.

[0033] like Figure 1 As shown, the top Alam cycle module includes a CO2 pump 3, a heat exchanger 13, a regenerator, a combustion chamber 7, a gas turbine 10, a first gas-liquid separator 6, a condenser 5, and pipelines connecting these components to form a CO2 circulation loop. The regenerator includes a low-temperature regenerator 12 and a high-temperature regenerator 11. In terms of the flow direction of the working medium CO2, the low-temperature regenerator 12 is located upstream of the high-temperature regenerator 11 and is connected in parallel with the heat exchanger 13.

[0034] Specifically, according to the flow direction of the liquid CO2 working medium, the outlet of the CO2 pump 3 is connected to the low-temperature regenerator 12 and the high-temperature regenerator 11. The low-temperature regenerator 12 is connected in parallel with the heat exchanger 13. The cold-side outlet of the heat exchanger 13 is connected to the cold-side inlet of the high-temperature regenerator 11. The cold-side outlet of the high-temperature regenerator 11 is connected in sequence to the combustor 7 and the gas turbine 10. The outlet of the gas turbine 10 is connected in sequence to the hot-side inlet of the high-temperature regenerator 11, the hot-side inlet of the low-temperature regenerator 12, the first gas-liquid separator 6, the condenser 5, and the inlet of the CO2 pump 3, forming a CO2 circulation loop. Thus, the liquid CO2 (C) working medium is pumped by the CO2 pump 3, and some of the liquid CO2 (C) is transported to the heat exchanger 13 and the low-temperature regenerator 12 for heating (heat exchange), causing the liquid CO2 (C) to cross the critical point and transform into CO2 gas. After being heated by heat exchanger 13 and low-temperature regenerator 12, the CO2 gas is mixed at the inlet of high-temperature regenerator 11 and then enters high-temperature regenerator 11 for heating. The heated CO2 gas is then passed into combustion chamber 7 and mixed with oxygen A entering combustion chamber 7 to form an oxygen-enriched mixture of 95% CO2 and 5% O2. The mixture then combusts with the fuel entering combustion chamber 7, producing high-temperature gas containing CO2 and water vapor, which enters gas turbine 10 to generate power. The generated gas then recovers heat through high-temperature regenerator 11 and low-temperature regenerator 12, fully liquefying the water vapor in the high-temperature gas into liquid water while simultaneously reducing the temperature of the CO2 in the high-temperature gas. Subsequently, the liquid water and CO2 gas are separated in first gas-liquid separator 6. After the separated CO2 gas is condensed to a liquid state in condenser 5, at least a portion of the liquid CO2 is returned to CO2 pump 3 for further circulation.

[0035] The Allam cycle module also includes: a fuel feed path, which is provided with a fuel pump 4, a condenser 5 and a combustion chamber 7. The fuel is transported to the condenser 5 via the fuel pump 4, and heat is exchanged with the CO2 gas entering the condenser 5, thereby liquefying the CO2 gas into liquid CO2 and simultaneously completing the gasification of the liquid fuel into fuel gas and pressurization. The pressurized fuel is then transported to the combustion chamber 7 for combustion, wherein the fuel can be liquid dimethyl ether. In an embodiment of the present invention, by exchanging heat between the liquid dimethyl ether fuel and the CO2 gas in the condenser of the Allam cycle, the temperature is raised from the boiling point of -29°C at normal pressure to approximately 30°C, thereby completing the gasification and pressurization of the liquid dimethyl ether fuel before it enters the combustion chamber 7 in the Allam cycle. Moreover, the boiling point of the liquid dimethyl ether fuel at normal pressure matches the liquefaction temperature of CO2. The loss is minimal, achieving the goal of fully cooling the CO2 gas using the cold energy of the liquid dimethyl ether fuel, converting the CO2 gas into liquid CO2. Furthermore, the use of liquid CO2 transport reduces energy consumption during CO2 transportation and saves the power consumption of pressurizing and heating the conventional gaseous fuel before it enters the combustion chamber.

[0036] The dimethyl ether production module at the bottom is equipped with a dimethyl ether absorption unit 22, the outlet of which is connected to the hot-side inlet of heat exchanger 13. The purge gas E generated during the dimethyl ether absorption process is used to exchange heat with the liquid CO2 in heat exchanger 13, converting the liquid CO2 into CO2 gas while simultaneously adjusting the specific heats of both ends of the regenerator. In an embodiment of the present invention, the purge gas E released during the coal gasification process to produce dimethyl ether is applied to heat exchanger 13 to exchange heat with the liquid CO2 entering the heat exchanger 13, thereby using a lower-grade heat source to adjust the pinch point problem caused by the specific heat properties of CO2 on both sides of the regenerator.

[0037] According to an embodiment of the present invention, the Allam cycle module is further equipped with an air separation unit 9, which is connected to the inlet of the combustion chamber 7 and is used to separate oxygen A from the air and transport it to the combustion chamber 7. Specifically, according to the direction of air flow, the Allam cycle module is equipped with an air separation unit 9, a compressor 8, and a combustion chamber 7. The air is separated into oxygen A by the air separation unit 9. This oxygen A is compressed by the compressor 8 and then introduced into the combustion chamber 7 to mix with CO2 gas, forming an oxygen-enriched mixture composed of 95% CO2 gas and 5% O2. This allows the heated and pressurized dimethyl ether gas fuel to directly heat the CO2 and O2 in the combustion chamber 7, causing full combustion and producing high-temperature gas containing CO2 gas and water vapor. Furthermore, in an embodiment of the present invention, the O2 (oxygen A) separated from the air by the air separation unit 9 is transported to the combustion chamber 7 to support combustion. The CO2 gas entering the combustion chamber 7 is also used to regulate the O2 concentration in the combustion chamber 7 to ensure safety.

[0038] According to an embodiment of the present invention, one end of the first gas-liquid separator 6 is connected to the low-temperature regenerator 12, and the other end of the first gas-liquid separator 6 is connected to the inlet of the condenser 5. This allows the gas that has performed work to be reheated in the high-temperature regenerator 11 and the low-temperature regenerator 12, completely liquefying the water vapor in the high-temperature gas into liquid water while simultaneously reducing the temperature of the CO2 gas. The liquid water and CO2 gas are then separated by the first gas-liquid separator 6, and the separated CO2 gas is cooled by the condenser 5.

[0039] According to an embodiment of the present invention, the Allam cycle module is further provided with a CO2 storage unit 1. The CO2 storage unit 1 is connected to a pipeline between a CO2 pump 3 and a condenser 5. A liquid CO2 pump 2 is provided on the pipeline to transport some of the liquid CO2 to the CO2 storage unit 1 for storage. In this embodiment of the present invention, by connecting the inlet of the CO2 pump 3 to the condenser 5, the condenser 5 is used to cool and liquefy the CO2 gas into liquid CO2. This allows the direct separation and storage of the CO2 gas generated by combustion, avoiding the need to compress the CO2 gas to capture it in a liquid state, saving compression power and reducing CO2 storage space. This reduces the high cost of carbon capture and makes CO2 more efficient in the transcritical Allam cycle. In addition, carbon capture is fully achieved in the self-condensing Allam cycle, with no carbon or NOx emissions.

[0040] According to an embodiment of the present invention, the dimethyl ether production module at the bottom also includes: a gasification unit 14, a purification unit 15, a catalytic reactor 16, a second gas-liquid separator 17, a CO2 separation unit 18, a dimethyl ether separation unit 19, a dimethyl ether absorption unit 22, an absorbent regeneration unit 21, a distillation cooling unit 20 and pipelines for connecting these components to form a dimethyl ether production path.

[0041] Specifically, the gasification unit 14 is sequentially connected to the purification unit 15, the catalytic reactor 16, the second gas-liquid separator 17, the CO2 separation unit 18, the dimethyl ether separation unit 19, and the distillation cooling unit 20 via pipelines. The second gas-liquid separator 17 is also connected to the dimethyl ether absorption unit 22. Furthermore, one end of the dimethyl ether absorption unit 22 is connected to the heat exchanger 13, and the other end is connected to the CO2 separation unit 18 and one end of the absorbent regeneration unit 21, respectively. The other end of the absorbent regeneration unit 21 is connected to the dimethyl ether separation unit 19, thereby forming a closed loop with pipelines connecting the dimethyl ether absorption unit 22 with the CO2 separation unit 18, the dimethyl ether separation unit 19, the absorbent regeneration unit 21, and the dimethyl ether absorption unit 22. Thus, during the dimethyl ether production process, coal and water vapor are gasified in the gasification unit 14 and then purified by the purification unit 15 to remove impurities D in the synthesis gas, thereby forming a relatively pure synthesis gas, where the impurities D include sulfur and a small amount of CO2 gas. The purified syngas enters the catalytic reactor 16, where it undergoes a catalytic reaction from bottom to top, producing methanol, CO2, dimethyl ether, water, and unreacted syngas. Subsequently, the liquid and gaseous components are separated in the second gas-liquid separator 17. The gaseous component is absorbed by the dimethyl ether absorption unit 22, releasing purge gas E and a mixed gas containing dimethyl ether. The CO2 separation unit 18 separates CO2 (F) from the dimethyl ether-containing mixed gas and liquid components. After separation in the dimethyl ether separation unit 19, a product containing dimethyl ether B is obtained. Part of the dimethyl ether-containing product is regenerated in the absorbent regeneration unit 21, mixed with the gaseous components, and reabsorbed by the dimethyl ether absorption unit 22. Part of the dimethyl ether-containing product is distilled and cooled in the distillation and cooling unit 20 to produce relatively pure dimethyl ether B, which can be used as fuel for the Alam cycle module.

[0042] In an embodiment of the present invention, coal is subjected to a gasification unit 14 and a purification unit 15 to produce synthesis gas, which is then catalytically synthesized in a catalytic reactor 16 in a one-step process to produce a mixture containing dimethyl ether. After gas-liquid separation, the obtained dimethyl ether-containing gas is absorbed by a dimethyl ether absorption unit 22. During the dimethyl ether absorption process, a purge gas E with a large amount of energy is generated (the temperature of the purge gas is about 60°C). In view of the large energy of the purge gas, the present invention proposes connecting the outlet of the dimethyl ether absorption unit 22 to the hot side inlet of the heat exchanger 13, combining the purge gas E with the Alam cycle, and utilizing the heat of the purge gas E to exchange heat with the liquid CO2 entering the heat exchanger 13, converting it from liquid to CO2 gas across the critical point. This achieves the use of a lower-quality heat source to adjust the specific heat matching between the high-temperature regenerator 11 and the low-temperature regenerator 12, thereby solving the pinch point problem caused by the specific heat properties of CO2. In addition, the prepared liquid dimethyl ether can be used as fuel for combustion in the combustion chamber of the Aram cycle, and the cold energy of dimethyl ether can be used as a refrigerant in the condenser to exchange heat with the CO2 gas entering the condenser and liquefy it into liquid CO2.

[0043] According to an embodiment of the present invention, the outlet of the dimethyl ether absorption unit 22 is connected to the inlet of the catalytic reactor 16 and the inlet of the CO2 separation unit 18 through a pipeline, and the outlet of the absorbent regeneration unit 21 is connected to the inlet of the catalytic reactor 16 through a pipeline, so that the synthesis gas that is not completely reacted in the dimethyl ether absorption unit 22 and the synthesis gas analyzed in the absorbent regeneration unit 21 are re-introduced into the catalytic reactor 16 through the inlet of the catalytic reactor 16 for re-catalysis, thereby improving the utilization efficiency of the synthesis gas.

[0044] Furthermore, the present invention improves the position of the heat exchanger through structural design to solve the pinch point problem at both ends of the regenerator. The specific structure is as follows: Figure 2 shown.

[0045] Figure 2 This is a schematic diagram of the framework of a combined system for dimethyl ether production and self-condensing transcritical CO2 Alam cycle in another embodiment of the present invention.

[0046] like Figure 2 As shown, the combined system of dimethyl ether production and self-condensing transcritical CO2 Allam cycle still includes the top Allam cycle module and the bottom dimethyl ether production module. Figure 2 and Figure 1 The same components have the same functions.

[0047] like Figure 2As shown, the top Alam cycle module includes a CO2 pump 3, a heat exchanger 13, a regenerator, a combustion chamber 7, a gas turbine 10, a first gas-liquid separator 6, a condenser 5, and pipelines connecting these components to form a CO2 circulation loop. In terms of the flow direction of the working medium CO2, the heat exchanger 13 is located upstream of the regenerator. The existing high-temperature regenerator 11 and low-temperature regenerator 12 are combined into a single regenerator, which is connected in series with the heat exchanger 13.

[0048] Specifically, the outlet of the CO2 pump 3 is sequentially connected to the heat exchanger 13, the regenerator, the combustion chamber 7, and the gas turbine 10, following the flow direction of the liquid CO2 working medium. The outlet of the gas turbine 10 is sequentially connected to the regenerator, the first gas-liquid separator 6, the condenser 5, and the inlet of the CO2 pump 3, forming a CO2 circulation loop. Thus, the liquid CO2 (C) working medium is pumped by the CO2 pump 3, and all of the liquid CO2 is transported to the heat exchanger 13 for heat exchange, causing the liquid CO2 to cross the critical point and transform into CO2 gas. The CO2 gas, heated in the regenerator, is then introduced into the combustion chamber 7 and mixed with oxygen A to form an oxygen-enhancing agent composed of 95% CO2 and 5% O2. The combustion-enhancing agent combusts with the fuel in the combustion chamber 7, producing high-temperature gas containing CO2 and water vapor, which enters the gas turbine 10 to generate power. The resulting gas then passes through the regenerator to recover heat, fully liquefying the water vapor in the high-temperature gas into liquid water while simultaneously reducing the temperature of the CO2 gas in the high-temperature gas. Liquid water and CO2 gas are separated by the first gas-liquid separator 6, and the separated CO2 gas is condensed into liquid by the condenser 5, and at least part of the liquid CO2 returns to the CO2 pump 3 to be circulated again.

[0049] The Aram cycle module also includes: a fuel feed path, on which a fuel pump 4, a condenser 5 and a combustion chamber 7 are provided. The fuel is transported to the condenser 5 through the fuel pump 4, and heat is exchanged with the CO2 gas entering the condenser 5, so that the CO2 gas is liquefied into liquid CO2, and the liquid fuel is gasified into fuel gas and pressurized. The pressurized fuel is transported to the combustion chamber 7 for combustion, wherein the fuel can be liquid dimethyl ether, that is, liquid dimethyl ether is gasified into dimethyl ether gas fuel.

[0050] The dimethyl ether production module at the bottom is provided with a dimethyl ether absorption unit 22, the outlet of which is connected to the hot side inlet of the heat exchanger 13. The relaxation gas E generated during the dimethyl ether absorption process is used to exchange heat with the liquid CO2 in the heat exchanger 13 to convert the liquid CO2 into CO2 gas, while adjusting the specific heat matching at both ends of the heat recovery.

[0051] In an embodiment of the present invention, the high-temperature regenerator 11 and the low-temperature regenerator 12 are combined into one regenerator, which is arranged downstream of the heat exchanger 13 and connected in series with the heat exchanger. It is also possible to utilize the waste heat of the purge gas in the heat exchanger 13 to heat the liquid CO2, so that it is converted into CO2 gas across the critical point, while avoiding the pinch point problem caused by the large change in the hot melting properties of CO2 near the critical point, and reducing the space of the system.

[0052] According to an embodiment of the present invention, changes in the number and position of the CO2 and the relaxation gas heat exchangers can be regarded as alternative forms of the present invention; an air cooler or other cooling method can be added before the condenser 5, which can be regarded as an alternative form of the present invention. The first gas-liquid separator 6 is arranged on the heat recovery path of the regenerator, which can also be regarded as an alternative form of the present invention. In addition, due to the different specific temperatures of the relaxation gas, changes in the matching position of the heat exchanger and the regenerator can be regarded as an alternative form of the present invention.

[0053] As a second aspect of the present invention, a method for combining dimethyl ether production and self-condensing transcritical CO2 Aram combined cycle is provided, which uses the dimethyl ether production and self-condensing transcritical CO2 Aram combined cycle system in the above embodiment. Figure 1-Figure 2 The framework shown details the combined cycle approach for dimethyl ether production with self-condensing transcritical CO2 Alam.

[0054] According to an embodiment of the present invention, Figure 2 As shown, a combined cycle method for producing dimethyl ether with self-condensing transcritical CO2 ARAM comprises:

[0055] In the self-condensing transcritical CO2 Allam cycle, the working fluid, liquid CO2, is transported by CO2 pump 3 to heat exchanger 13 for liquid-to-gas conversion. It is then heated in a regenerator. The heated CO2 gas is then introduced into combustion chamber 7 and mixed with oxygen entering the combustion chamber 7 to form an oxygen enhancer. The gasified fuel enters combustion chamber 7 and burns to produce high-temperature gas containing CO2 gas and water vapor, with the oxygen enhancer comprising 95% CO2 gas and 5% oxygen. The high-temperature gas enters the gas turbine to generate power. The generated gas then recovers heat in the regenerator to completely liquefy the water vapor in the combustion products. Liquid water and CO2 gas are separated by a first gas-liquid separator 6. The separated CO2 gas then exchanges heat with condenser 5, liquefying the CO2 gas into liquid CO2. At least a portion of the liquid CO2 is then transported by CO2 pump 3 for further circulation. After liquid dimethyl ether exchanges heat with the CO2 gas in condenser 5, it vaporizes into dimethyl ether fuel, which is then transported to combustion chamber 7 for combustion. During the dimethyl ether production process, the purge gas E generated by the dimethyl ether absorption process is used to preheat the liquid CO2 entering heat exchanger 13, converting it into CO2 gas while also adjusting the heat balance between the two ends of the heat recovery process. The resulting pure dimethyl ether then serves as the refrigerant in condenser 5, exchanging heat with the CO2 gas, and then entering combustion chamber 7 as fuel for combustion.

[0056] According to another embodiment of the present invention, Figure 1 As shown, a combined cycle method for producing dimethyl ether with self-condensing transcritical CO2 ARAM comprises:

[0057] In the self-condensing transcritical CO2 Allam cycle, the liquid CO2 working fluid is partially transported by CO2 pump 3 to heat exchanger 13 for liquid-to-gas conversion. It then passes through the regenerator for both primary and secondary heating. The regenerator comprises a low-temperature regenerator 12 and a high-temperature regenerator 11, with the low-temperature regenerator 12 connected in parallel with the heat exchanger 13 and the high-temperature regenerator 11 connected in series. A portion of the liquid CO2 undergoes heat exchange in heat exchanger 13, while the remaining portion undergoes primary heating in low-temperature regenerator 12. The remaining portion, along with the CO2 that has undergone heat exchange in heat exchanger 13, then enters high-temperature regenerator 11 for secondary heating, where the secondary heating temperature is greater than the primary heating temperature. In other words, the working fluid, liquid CO2 (C), is pumped by the CO2 pump 3, and a portion of the liquid CO2 is transported to the heat exchanger 13 and the low-temperature regenerator 12 for heating (i.e., a primary heating step is performed in the low-temperature regenerator 12), causing the liquid CO2 to cross the critical point and transform into CO2 gas. The CO2 gas heated by the heat exchanger 13 and the low-temperature regenerator 12 is mixed at the inlet of the high-temperature regenerator 11 and then enters the high-temperature regenerator 11 for heating. That is, the mixed CO2 gas enters the high-temperature regenerator 11 for a secondary heating step. The heated CO2 gas is introduced into the combustion chamber 7 to mix with oxygen A to form an oxygen enhancer, which catalyzes the combustion of the fuel in the combustion chamber 7 to produce products containing CO2 and water vapor. The product enters the gas turbine 10 to generate electricity. The gas after work recovers heat through the high-temperature regenerator 11 and the low-temperature regenerator 12 to completely liquefy the water vapor in the product. The first gas-liquid separator 6 is used to separate liquid water and CO2 gas. The separated CO2 gas exchanges heat with the condenser 5 to liquefy the CO2 gas into liquid CO2, at least part of which is transported by the CO2 pump 3 for further circulation.

[0058] After liquid dimethyl ether exchanges heat with the CO2 gas in condenser 5, it vaporizes into dimethyl ether fuel, which is then transported to combustion chamber 7 for combustion. During the dimethyl ether production process, the purge gas E generated by the dimethyl ether absorption process is used to preheat the liquid CO2 entering heat exchanger 13, converting it into CO2 gas while also adjusting the specific heats of the two ends of the heat recovery process. The resulting pure dimethyl ether acts as a refrigerant in condenser 5 to exchange heat with the CO2 gas and is then transported to combustion chamber 7 as fuel for combustion.

[0059] According to an embodiment of the present invention, the partially condensed liquid CO2 is stored. In other words, a liquid CO2 pump 2 is provided on the pipeline connection between the CO2 pump 3 and the condenser 5, and the liquid CO2 pump 2 is used to transport part of the liquid CO2 to the CO2 storage unit 1 for storage.

[0060] The specific embodiments described above further illustrate the objectives, technical solutions and beneficial effects of the present invention in detail. It should be understood that the above are only 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 in the scope of protection of the present invention.

Claims

1. A combined system for dimethyl ether production and self-condensing transcritical CO2 Aram cycle, characterized in that: The system includes an Aram cycle module and a dimethyl ether production module; The Alam cycle module includes a CO2 pump, a heat exchanger, a regenerator, a combustion chamber, a gas turbine, a first gas-liquid separator, a condenser, and pipelines for connecting these components to form a CO2 circulation loop; The working fluid liquid CO2 is pumped by a CO2 pump, passes through a heat exchanger or a low-temperature regenerator, crosses a critical point from a liquid state, and is heated by the regenerator. The heated CO2 gas is introduced into a combustion chamber to mix with oxygen to form an oxygen-enriched agent of 95% CO2 and 5% O2. The products containing CO2 and water vapor generated by the combustion of fuel in the combustion chamber enter the gas turbine to generate power. The gas after the power generation recovers heat through the regenerator, and liquid water and CO2 gas are separated through the first gas-liquid separator. The separated CO2 gas is condensed to a liquid state through a condenser, and at least part of the liquid CO2 returns to the CO2 pump for another cycle. The Alam cycle module also includes a fuel feed path, wherein liquid dimethyl ether fuel is delivered to the condenser, exchanges heat with the separated CO2 gas, and simultaneously vaporizes and pressurizes dimethyl ether while liquefying the CO2. The pressurized dimethyl ether gas is then delivered to the combustion chamber for combustion. The dimethyl ether production module is provided with a dimethyl ether absorption unit, the outlet of the dimethyl ether absorption unit is connected to the heat exchanger, and the purge gas is used to exchange heat with the liquid CO2 in the heat exchanger to adjust the specific heat matching at both ends of the heat recovery.

2. The system according to claim 1, wherein: According to the flow direction of the working medium CO2, the heat exchanger is located upstream of the regenerator.

3. The system according to claim 2, characterized in that The regenerator includes a low-temperature regenerator and a high-temperature regenerator. According to the flow direction of the working medium CO2, the low-temperature regenerator is located upstream of the high-temperature regenerator and is connected in parallel with the heat exchanger.

4. The system according to claim 1, wherein: The Aram cycle module is further provided with an air separation unit, which is connected to the inlet of the combustion chamber and is used to separate oxygen from the air and transport it into the combustion chamber.

5. The system according to claim 3, wherein: One end of the first gas-liquid separator is connected to the hot side outlet of the low-temperature regenerator, and the other end is connected to the inlet of the condenser.

6. The system according to claim 5, characterized in that The Aram cycle module is further provided with a CO2 storage unit, which is connected to the pipeline between the CO2 pump and the condenser to store part of the liquid CO2.

7. The system according to claim 1 or 6, characterized in that The dimethyl ether production module includes: a gasification unit, a purification unit, a catalytic reactor, a second gas-liquid separator, a dimethyl ether absorption unit, a CO2 separation unit, a dimethyl ether separation unit, an absorbent regeneration unit, a distillation cooling unit, and pipelines for connecting these components to form a dimethyl ether production path; wherein, after coal and water vapor are gasified in the gasification unit, they are purified by the purification unit to form synthesis gas, the synthesis gas enters the catalytic reactor for catalytic reaction to generate methanol, CO2, dimethyl ether, water, and unreacted synthesis gas, the liquid component and the gaseous component are separated by the second gas-liquid separator, the gaseous component is absorbed by the dimethyl ether absorption unit and releases purge gas and a mixed gas containing dimethyl ether; The CO2 separation unit is used to separate CO2 from the mixed gas containing dimethyl ether and the liquid component. After separation by the dimethyl ether separation unit, a product containing dimethyl ether is obtained. Part of the dimethyl ether-containing product is regenerated by the absorbent regeneration unit and mixed with the gaseous component, and dimethyl ether is reabsorbed by the dimethyl ether absorption unit. Part of the dimethyl ether-containing product is distilled and cooled by the distillation and cooling unit to obtain dimethyl ether. The dimethyl ether is used as fuel for the Alam cycle module.

8. The system according to claim 7, characterized in that The outlet of the dimethyl ether absorption unit is connected to the inlet of the catalytic reactor and the inlet of the CO2 separation unit through pipelines, and the outlet of the absorbent regeneration unit is connected to the inlet of the catalytic reactor through pipelines.

9. A combined process for dimethyl ether production and self-condensing transcritical CO2 Alam cycle, using the system according to any one of claims 1 to 8, characterized in that: The method comprises: In the self-condensing transcritical CO2 Allam cycle, the working medium liquid CO2 is transported by a CO2 pump to a heat exchanger or a low-temperature regenerator for conversion from liquid to gaseous state, and is heated in the regenerator. The heated CO2 gas is introduced into the combustion chamber and forms an oxygen enhancer with the oxygen entering the combustion chamber. The gasified fuel enters the combustion chamber and burns to produce products containing CO2 gas and water vapor, wherein the oxygen enhancer accounts for 95% CO2 gas and 5% oxygen. The product enters the gas turbine to generate electricity, and the gas after the work is recycled through the regenerator to recover heat to completely liquefy the water vapor in the combustion product. The first gas-liquid separator is used to separate liquid water and CO2 gas. The separated CO2 gas exchanges heat with the condenser to liquefy into liquid CO2, at least part of which is transported by the CO2 pump for further circulation. After the liquid dimethyl ether exchanges heat with the CO2 gas in the condenser, the liquid dimethyl ether is vaporized into dimethyl ether fuel, and the vaporized dimethyl ether fuel is transported to the combustion chamber for combustion; During the dimethyl ether production process, the purge gas generated by the dimethyl ether absorption treatment is used to preheat the liquid CO2 entering the heat exchanger to convert it into CO2 gas, while adjusting the specific heat matching at both ends of the heat recovery. The pure dimethyl ether produced is used as a refrigerant in the condenser to exchange heat with the CO2 gas, and as fuel to enter the combustion chamber for combustion.

10. The method according to claim 9, characterized in that The regenerator includes a low-temperature regenerator and a high-temperature regenerator. The low-temperature regenerator is connected in parallel with the heat exchanger. Part of the working fluid liquid CO2 is heat exchanged in the heat exchanger, and the other part is heated in the low-temperature regenerator, and then heated in the high-temperature regenerator together with the heat-exchanged CO2. The secondary heating temperature is greater than the primary heating temperature.

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