Dimethyl ether production and self-condensation transcritical CO2 Alam cycle combined system and method

Abstract

The invention provides a dimethyl ether production and self-condensation transcritical CO2 Alam cycle combined system and method.In an Alam cycle module, working medium liquid CO2 passes through a heat exchanger or a low-temperature heat regenerator and crosses a critical point from the liquid state, CO2 gas is heated through the heat regenerator and then is introduced into a combustion chamber to be mixed with oxygen to form a pro-oxygen agent, and the pro-oxygen agent is introduced into a combustion chamber to be mixed with oxygen; products containing CO2 and water vapor generated by fuel combustion in the combustion chamber enter the gas turbine to do work for power generation, heat of gas obtained after acting is recycled through the heat regenerator, liquid water and CO2 gas are separated through the first gas-liquid separator, the separated CO2 gas is condensed to be in a liquid state through the condenser, and at least part of the liquid CO2 is circulated again. The liquid dimethyl ether is conveyed to a condenser, gasification and pressurization of the dimethyl ether are achieved while CO2 is liquefied, and the pressurized dimethyl ether gas is conveyed to a combustion chamber to be combusted; the dimethyl ether preparation module is provided with a dimethyl ether absorption unit, and purge gas is used for exchanging heat with liquid CO2 in the heat exchanger so as to adjust the matching of specific heat at the two ends of regenerative heat.

Description

Technical Field

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

[0002] With limited reserves of oil and natural gas and coal dominating available energy sources, people are paying more and more attention to the conversion and efficient and clean use of coal. Dimethyl ether has good compressibility, easy transportation, high energy density and is a green energy source. After full combustion, it only produces CO2 and water, making it one of the ideal products of coal chemical industry. In terms of technical route, dimethyl ether can be oxidized and gasified by coal, and then catalyzed by methanol synthesis and dehydration in an environment of 3.5-5.0MPa and 230-250℃ to achieve one-step conversion of dimethyl ether.

[0003] The fuel commonly used in the Allam cycle is gaseous fuel such as methane, natural gas, and hydrogen. The gas needs to be compressed before entering the combustion chamber, but the gas is not easy to compress, resulting in a large amount of compression work loss. On the one hand, in order to pursue the high efficiency of the Allam cycle and facilitate the capture of CO2 in liquid form and the separation of combustion product water, part of the CO2 involved in the recycle needs to be cooled to a liquid state before it reaches the next cycle inlet from the gas turbine outlet, and cooling the 7.31MPa CO2 to below 31°C requires an additional forced cooling system, which consumes a lot of work. On the other hand, in the one-step catalytic synthesis of dimethyl ether, only a part of the purge gas with a large amount of heat in the preparation of dimethyl ether is recovered and re-enters the slurry bed reactor to participate in the reaction, and the other part of the purge gas is difficult to use. In the related art, a method is proposed to put the purge gas into the gas turbine to do work, but its pressure and temperature are not high, the gas turbine design requirements are relatively large, and the size is too large, which is not easy to realize practical application. Summary of the invention

[0004] In view of the above technical problems, the present invention provides a combined system and method for dimethyl ether production and 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 of 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 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 enhancer of 95% CO2 and 5% O2. The products containing CO2 and water vapor generated by the combustion of fuel in the combustion chamber enter a gas turbine to generate power. The gas after the work is recovered by the regenerator to recover heat, and liquid water and CO2 gas are separated by a first gas-liquid separator. The separated CO2 gas is condensed to a liquid state by a condenser, and at least part of the liquid CO2 is returned 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, and heat is exchanged with the separated CO2 gas, so that dimethyl ether is gasified and pressurized while liquefying CO2, and the pressurized dimethyl ether gas is delivered to a combustion chamber for combustion;

[0009] The dimethyl ether production module is provided with a dimethyl ether absorption unit, the outlet of which is connected to a 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.

[0010] As a second aspect of the present invention, a combined method for dimethyl ether production and 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 to a heat exchanger or a low-temperature regenerator through a CO2 pump for conversion from liquid to gas, and is heated in the regenerator. The heated CO2 gas is introduced into the combustion chamber to form 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% in the oxygen enhancer.

[0012] The product enters the gas turbine to generate electricity, and the gas after work is recycled through the regenerator to completely liquefy the water vapor in the combustion product. 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, and the vaporized dimethyl ether is transported to the combustion chamber as fuel for combustion;

[0014] In the process of producing dimethyl ether, the purge gas generated by the absorption treatment of dimethyl ether 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 produced pure dimethyl ether is used as a refrigerant in the condenser to exchange heat with the CO2 gas, and as a fuel to enter the combustion chamber for combustion.

[0015] Based on the above technical solution, the combined system and method of dimethyl ether production and self-condensing transcritical CO2 Alam cycle provided by the present invention include 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 fluid CO2 is transported to the heat exchanger through a CO2 pump, and the residual 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 refluxed CO2 in the low-temperature regenerator and is heated to become gas. The CO2 gas is further heated by 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 to expand and work to 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, and the water vapor in the high-temperature gas can be liquefied into liquid water through heat recovery, while the CO2 gas entering the regenerator is heated. Then, the first gas-liquid separator is used to separate the liquid water and the CO2 gas, and the separated CO2 gas is condensed by the condenser and liquefied into liquid CO2, and at least a part of the liquid CO2 can be circulated again in the Allam cycle through the CO2 pump. The Allam cycle also includes a fuel feed path, and the liquid dimethyl ether is transported to the condenser, and heat is exchanged with the CO2 gas in the condenser to gasify the liquid dimethyl ether into dimethyl ether gas fuel, and the dimethyl ether gas fuel enters the combustion chamber and burns under the catalytic action of the 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 the boiling point of -29°C at normal pressure to about 30°C, completing the gasification and pressurization of dimethyl ether fuel before entering the combustion chamber of the Allam cycle, and the boiling point of dimethyl ether at normal pressure matches the liquefaction temperature of CO2. The loss is small, and the CO2 gas is fully cooled by the cold energy of the dimethyl ether fuel, and the CO2 gas is converted into liquid CO2. In other words, before entering the CO2 pump, the CO2 gas fully utilizes the cold energy of the dimethyl ether fuel to realize the conversion of CO2 gas to liquid CO2, which reduces the cost of CO2 gas operation and saves the power consumption of pressurizing and heating the common gaseous fuel when entering the combustion chamber, ensuring the high efficiency of the overall 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 compressed 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 in the process of producing dimethyl ether by coal gasification is used for heat exchange in a heat exchanger, thereby using a lower-quality heat source to adjust 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 It is a schematic diagram of a framework of a combined system of 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 combustion of gaseous fuel in the combustion chamber generates heat to directly heat the working fluid CO2, which then enters the gas turbine to generate power. The CO2 and water generated by the combustion of the fuel are completely captured at the outlet of the gas turbine, and the remaining CO2 is cooled and put into the next operation. In the Allam cycle, there are two main features: the compressor in the closed Brayton recompression cycle is replaced by a pump, and the fuel is directly burned to heat the working fluid, which improves the thermodynamic efficiency of the cycle relative to the original closed Brayton cycle. On the other hand, the Allam cycle often uses hydrocarbon fuel as fuel, and after complete combustion, the water in the combustion products is separated, so that the CO2 generated by the combustion can be drawn out and sealed, and the other part continues to participate in the cycle as a working fluid, achieving carbon capture at a low cost, which can be used as an effective way to help achieve carbon peak and carbon neutrality. However, the fuel commonly used in the Allam cycle is not easy to compress, resulting in a large amount of compression work loss, and CO2 cooling requires an additional forced refrigeration system and the purge gas generated in the dimethyl ether production process cannot be used. In view of these problems, the present invention provides a combined system and method for dimethyl ether production and self-condensing transcritical CO2 Allam cycle, which uses the cold energy of dimethyl ether itself to realize the liquefaction of CO2 gas through the structural design of the combined system, and uses the waste heat of the purge gas in the dimethyl ether production process to solve 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 comprises 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 Aram cycle module, the working fluid liquid CO2 is pumped by a CO2 pump, which passes through a heat exchanger or a low-temperature regenerator from a liquid state to a critical point, and is heated by the regenerator. The heated CO2 gas is introduced into the combustion chamber to mix with oxygen to form an oxygen enhancer 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 work 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 Aram cycle module also includes a fuel feed path, in which liquid dimethyl ether fuel is transported to the condenser, and heat is exchanged with the separated CO2 gas. While liquefying CO2, dimethyl ether is gasified and pressurized, and the pressurized dimethyl ether gas is transported to the combustion chamber for combustion.

[0029] The dimethyl ether production module is provided with a dimethyl ether absorption unit, the outlet of which is connected to a 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.

[0030] In 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 the heat of the heat exchanger. Then, a portion of the liquid working fluid CO2 is transported to the heat exchanger through a CO2 pump, and the residual heat of the off-gas in the heat exchanger 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 by 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 product enters the gas turbine to expand and work to 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, and the water vapor in the high-temperature gas can be liquefied into liquid water through heat recovery while the CO2 gas entering the regenerator is heated. Then, the first gas-liquid separator is used to separate the liquid water and the CO2 gas, and the separated CO2 gas is condensed by the condenser and liquefied into liquid CO2, and at least a part of the liquid CO2 can be circulated again in the Allam cycle through the CO2 pump. The Allam cycle also includes a fuel feed path, and the liquid dimethyl ether is transported to the condenser, and heat is exchanged with the CO2 gas in the condenser to gasify the liquid dimethyl ether into dimethyl ether gas fuel, and the dimethyl ether gas fuel enters the combustion chamber and burns under the catalytic action of the oxygen enhancer.

[0031] Figure 1 It is a schematic diagram of the framework of a combined system of 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 Aram cycle module at the top 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 for connecting these components to form a CO2 circulation loop. The regenerator includes a low-temperature regenerator 12 and a high-temperature regenerator 11. According to 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 working medium liquid CO2, the outlet of the CO2 pump 3 is connected to the low-temperature regenerator 12 and the high-temperature regenerator 11, and 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, and the cold side outlet of the high-temperature regenerator 11 is connected to the combustion chamber 7 and the gas turbine 10 in sequence. The outlet of the gas turbine 10 is connected 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 in sequence, forming a CO2 circulation loop. Thus, the working medium liquid CO2 (C) is pumped by the CO2 pump 3, and part of the liquid CO2 (C) is respectively transported to the heat exchanger 13 and the low-temperature regenerator 12 for heating (heat exchange), so that the liquid CO2 (C) crosses the critical point and is converted 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. The heated CO2 gas is introduced into the combustion chamber 7 and mixed with the oxygen A entering the combustion chamber 7 to form an oxygen enhancer of 95% CO2 and 5% O2, and then burns with the fuel entering the combustion chamber 7 to generate high-temperature gas containing CO2 and water vapor, which enters the gas turbine 10 to generate power. The gas after work recovers heat through the high-temperature regenerator 11 and the low-temperature regenerator 12 to fully liquefy the water vapor in the high-temperature gas into liquid water and reduce the temperature of the CO2 gas in the high-temperature gas. Subsequently, the liquid water and CO2 gas are separated by the first gas-liquid separator 6, and the separated CO2 gas is condensed to liquid by the condenser 5, and at least part of the liquid CO2 returns to the CO2 pump 3 for another cycle.

[0035] The Allam 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 at the same time. The pressurized fuel is transported to the combustion chamber 7 for combustion, wherein the fuel may 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 about 30°C, thereby completing the gasification and pressurization of the liquid dimethyl ether fuel before entering the combustion chamber 7 in the Allam cycle, and the boiling point of the liquid dimethyl ether fuel at normal pressure matches the liquefaction temperature of CO2. The loss is small, and the CO2 gas is fully cooled by the cold energy of the liquid dimethyl ether fuel, and the purpose of converting the CO2 gas into liquid CO2 is achieved. In addition, the use of liquid CO2 transportation reduces the energy consumption during the transportation of CO2 gas, and also saves the power consumption of pressurizing and heating the commonly used gaseous fuel when it enters the combustion chamber.

[0036] 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, and the purge gas E generated during the dimethyl ether absorption process is used to exchange heat with the liquid CO2 in the heat exchanger 13, so as to convert the liquid CO2 into CO2 gas, and at the same time achieve the purpose of adjusting the specific heat matching at both ends of the heat regenerator. In the embodiment of the present invention, the purge gas E released during the process of generating dimethyl ether by coal gasification is applied to the heat exchanger 13, and is used for heat exchange with the liquid CO2 entering the heat exchanger 13, so as to achieve the pinch point problem caused by the specific heat property of CO2 on both sides of the heat regenerator by using a lower-grade heat source.

[0037] According to an embodiment of the present invention, the Aram cycle module is further provided 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 air flow direction, the Aram cycle module is provided 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, and the oxygen A is compressed by the compressor 8 and introduced into the combustion chamber 7 to mix with CO2 gas to form an oxygen-enhancing agent with 95% CO2 gas and 5% O2, so that the dimethyl ether gas fuel after temperature and pressure increase directly heats CO2 and O2 in the combustion chamber 7 and fully burns to produce high-temperature gas containing CO2 gas and water vapor. In addition, 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 for combustion support, and the CO2 gas entering the combustion chamber 7 is used to adjust 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, so that the gas after work is reheated by the high-temperature regenerator 11 and the low-temperature regenerator 12 to completely liquefy the water vapor in the high-temperature gas into liquid water, while reducing the temperature of the CO2 gas. Then, the liquid water and the CO2 gas are separated by the separation treatment of 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, and the CO2 storage unit 1 is connected to the pipeline between the CO2 pump 3 and the condenser 5, and a liquid CO2 pump 2 is provided on the pipeline to transport part of the liquid CO2 to the CO2 storage unit 1 for storage. In an embodiment of the present invention, by connecting the inlet of the CO2 pump 3 to the condenser 5, the CO2 gas is cooled and liquefied into liquid CO2 by the condenser 5, and the CO2 gas generated by combustion can be directly separated and stored, avoiding the capture of CO2 gas compressed to liquid, saving compression power consumption and reducing CO2 storage space, thereby reducing the high cost of carbon capture, making CO2 more efficient in the transcritical Allam cycle. In addition, carbon capture is fully realized in the self-condensing Allam cycle, and there is no carbon and NOx emission.

[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 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 rectification cooling unit 20 in sequence through pipelines, wherein the second gas-liquid separator 17 is also connected to the dimethyl ether absorption unit 22. Further, one end of the dimethyl ether absorption unit 22 is connected to the heat exchanger 13, and the other end is respectively connected to the CO2 separation unit 18 and one end of the absorbent regeneration unit 21, and the other end of the absorbent regeneration unit 21 is connected to the dimethyl ether separation unit 19, thereby forming a closed cycle with pipelines connecting the dimethyl ether absorption unit 22 and the CO2 separation unit 18, the dimethyl ether separation unit 19, the absorbent regeneration unit 21 and the dimethyl ether absorption unit 22. Thus, in the process of preparing dimethyl ether, after coal and water vapor are gasified in the gasification unit 14, the impurities D in the synthesis gas are purified by the purification unit 15 to form a relatively pure synthesis gas, wherein the impurities D include sulfur and a small amount of CO2 gas. The purified synthesis gas enters the catalytic reactor 16 and undergoes a catalytic reaction from bottom to top to generate methanol, CO2, dimethyl ether, water and synthesis gas that has not been completely reacted. Subsequently, the liquid component and the gaseous component are separated by the second gas-liquid separator 17, and the gaseous component is absorbed by the dimethyl ether absorption unit 22 and releases the purge gas E and the mixed gas containing dimethyl ether. The CO2 separation unit 18 is used to separate CO2 (F) from the mixed gas and liquid component containing dimethyl ether, and after separation by the dimethyl ether separation unit 19, a product containing dimethyl ether B is obtained. Part of the product containing dimethyl ether is regenerated by the absorbent regeneration unit 21 and mixed with the gaseous component, and the dimethyl ether absorption unit 22 reabsorbs dimethyl ether B. Part of the product containing dimethyl ether B is distilled and cooled by the distillation cooling unit 20 to obtain a relatively pure dimethyl ether B, which can be used as fuel for the Alam cycle module.

[0042] In the embodiment of the present invention, coal is subjected to gasification unit 14 and purification unit 15 to obtain synthesis gas, and the synthesis gas is catalytically synthesized into a mixture containing dimethyl ether in a one-step process in catalytic reactor 16. After gas-liquid separation, the obtained gas containing dimethyl ether is absorbed by dimethyl ether absorption unit 22. During the absorption of dimethyl ether, 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 to connect the outlet of the dimethyl ether absorption unit 22 with the hot side inlet of the heat exchanger 13, combine the purge gas E with the Alam cycle, and use 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, thereby achieving the use of a lower-quality heat source to adjust the specific heat matching on both sides of the high-temperature regenerator 11 and the low-temperature regenerator 12, and solving the pinch point problem caused by the specific heat property 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 to 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 problem of pinch points 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 Alam cycle still includes the Alam cycle module at the top and the dimethyl ether production module at the bottom. Figure 2 and Figure 1 The same components have the same functions.

[0047] like Figure 2As shown, the Aram cycle module at the top 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 for connecting these components to form a CO2 circulation loop. According to the flow direction of the working medium CO2, the heat exchanger 13 is located upstream of the regenerator, wherein the original high-temperature regenerator 11 and the low-temperature regenerator 12 are combined into one regenerator and connected in series with the heat exchanger 13.

[0048] Specifically, according to the flow direction of the working medium liquid CO2, the outlet of the CO2 pump 3 is connected to the heat exchanger 13, the regenerator, the combustion chamber 7 and the gas turbine 10 in sequence. The outlet of the gas turbine 10 is connected to the regenerator, the first gas-liquid separator 6, the condenser 5 and the inlet of the CO2 pump 3 in sequence to form a CO2 circulation loop. Thus, the working medium liquid CO2 (C) is pumped by the CO2 pump 3, and all the liquid CO2 is transported to the heat exchanger 13 for heat exchange, so that the liquid CO2 crosses the critical point and is converted into CO2 gas. Then, the CO2 gas heated by the regenerator is introduced into the combustion chamber 7 and mixed with oxygen A to form an oxygen-supporting agent of 95% CO2 and 5% O2. The combustion-supporting agent burns with the fuel in the combustion chamber 7 to produce a high-temperature gas containing CO2 and water vapor, which enters the gas turbine 10 to generate power, and the gas after work recovers heat through the regenerator to fully liquefy the water vapor in the high-temperature gas into liquid water, while 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 for another cycle.

[0049] The Alam cycle module also includes: a fuel feed path, on which a fuel pump 4, a condenser 5 and a combustion chamber 7 are arranged. 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 at the same time. 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 discharge gas in the heat exchanger 13 to heat the liquid CO2 so that it crosses the critical point and is converted into CO2 gas. At the same time, the pinch point problem caused by the large change in the hot melting properties of CO2 near the critical point is avoided, and the space of the system is reduced.

[0052] According to the embodiments of the present invention, the change in the number and position of the CO2 and the relaxation gas heat exchangers can be regarded as an alternative form of the present invention; an air cooler cold source 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, the change 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 combined cycle method for dimethyl ether production and self-condensing transcritical CO2 Alam is provided, which adopts the combined cycle system for dimethyl ether production and self-condensing transcritical CO2 Alam 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, comprising:

[0055] In the self-condensing transcritical CO2 Aram cycle, the working medium liquid CO2 is transported to the heat exchanger 13 through the CO2 pump 3 for conversion from liquid to gas, and is heated through the regenerator. The heated CO2 gas is introduced into the combustion chamber 7 and mixed with the oxygen entering the combustion chamber 7 to form an oxygen enhancer. The gasified fuel enters the combustion chamber 7 and burns to produce high-temperature gas containing CO2 gas and water vapor, wherein CO2 gas accounts for 95% and oxygen accounts for 5% in the oxygen enhancer; the high-temperature gas enters the gas turbine to generate power, and the gas after work recovers heat through the regenerator to completely liquefy the water vapor in the combustion product. The first gas-liquid separator 6 is used to separate liquid water and CO2 gas, and the separated CO2 gas exchanges heat with the condenser 5 to liquefy the CO2 gas into liquid CO2, wherein at least part of the liquid CO2 is transported by the CO2 pump 3 for another cycle. After the liquid dimethyl ether exchanges heat with the CO2 gas in the condenser 5, the liquid dimethyl ether is vaporized into dimethyl ether fuel, and the vaporized dimethyl ether fuel is transported to the combustion chamber 7 for combustion. In the dimethyl ether production process, the purge gas E generated by the dimethyl ether absorption treatment is used to preheat the liquid CO2 entering the heat exchanger 13 to convert it into CO2 gas while adjusting the specific heat matching at both ends of the heat recovery. The produced pure dimethyl ether is used as the refrigerant in the condenser 5 to exchange heat with the CO2 gas, and as fuel to enter the combustion chamber 7 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, comprising:

[0057] In the self-condensing transcritical CO2 Aram cycle, the working medium liquid CO2 is partially transported to the heat exchanger 13 through the CO2 pump 3 for liquid-to-gas conversion, and is heated through the regenerator, including primary heating and secondary heating, wherein the regenerator includes a low-temperature regenerator 12 and a high-temperature regenerator 11, the low-temperature regenerator 12 is connected in parallel with the heat exchanger 13, and the low-temperature regenerator 12 is connected in series with the high-temperature regenerator 11. A part of the working medium liquid CO2 is heat exchanged in the heat exchanger 13, and the other part is heated in the first stage through the low-temperature regenerator 12, and then enters the high-temperature regenerator 11 together with the CO2 after heat exchange in the heat exchanger 13 for secondary heating, wherein 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 part of the liquid CO2 is respectively transported to the heat exchanger 13 and the low-temperature regenerator 12 for heating (i.e., the first-stage heating is performed in the low-temperature regenerator 12), so that the liquid CO2 crosses the critical point and is converted 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 secondary heating. 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, and 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 the liquid water and CO2 gas, and the separated CO2 gas is heat-exchanged 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 circulation again.

[0058] After the liquid dimethyl ether exchanges heat with the CO2 gas in the condenser 5, the liquid dimethyl ether is vaporized into dimethyl ether fuel, and the vaporized dimethyl ether fuel is transported to the combustion chamber 7 for combustion. In the dimethyl ether production process, the purge gas E generated by the dimethyl ether absorption treatment is used to preheat the liquid CO2 entering the heat exchanger 13 to convert it into CO2 gas while adjusting the heat matching at both ends of the heat recovery. The obtained pure dimethyl ether is used as the refrigerant in the condenser 5 to exchange heat with the CO2 gas, and as fuel to enter the combustion chamber 7 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 description is only a specific embodiment of the present invention and is 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 of dimethyl ether production and self-condensing transcritical CO2 Alam 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 enhancer of 95% CO2 and 5% O2. The products containing CO2 and water vapor generated by the combustion of fuel in the combustion chamber enter a gas turbine to generate power. The gas after the work is recovered by the regenerator, and liquid water and CO2 gas are separated by the first gas-liquid separator. The separated CO2 gas is condensed to a liquid state by a condenser, and at least part of the liquid CO2 is returned 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, and heat is exchanged with the separated CO2 gas, and dimethyl ether is gasified and pressurized while liquefying CO2, and the pressurized dimethyl ether gas is 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, characterized in that 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, characterized in that 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, characterized in that 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 Alam cycle module is also 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, and the synthesis gas enters the catalytic reactor for catalytic reaction to generate methanol, CO2, dimethyl ether, water and synthesis gas that has not been completely reacted, and the liquid component and the gaseous component are separated by the second gas-liquid separator, and 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 product containing dimethyl ether 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 product containing dimethyl ether 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 a pipeline, and the outlet of the absorbent regeneration unit is connected to the inlet of the catalytic reactor through a pipeline.

9. A combined method for dimethyl ether production and self-condensing transcritical CO2 Alam cycle, using the system described in any one of claims 1 to 8, characterized in that: The method comprises: In the self-condensing transcritical CO2 Allam cycle, the working fluid liquid CO2 is transported to a heat exchanger or a low-temperature regenerator through a CO2 pump for conversion from liquid to gas, and is heated in the regenerator. The heated CO2 gas is introduced into the combustion chamber to form 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 CO2 gas accounts for 95% of the oxygen enhancer and the oxygen accounts for 5%. The product enters the gas turbine to generate electricity, and the gas after the work is recovered by the regenerator to completely liquefy the water vapor in the combustion product, and the first gas-liquid separator is used to separate the liquid water and CO2 gas, and the separated CO2 gas is heat-exchanged with the condenser to liquefy into liquid CO2, wherein at least part of the liquid CO2 is transported by the CO2 pump for another cycle; After the liquid dimethyl ether exchanges heat with the CO2 gas in the condenser, the liquid dimethyl ether is gasified into dimethyl ether fuel, and the gasified dimethyl ether fuel is transported to the combustion chamber for combustion; In the process of producing dimethyl ether, the purge gas generated by the absorption treatment of dimethyl ether 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 produced pure dimethyl ether is used as a refrigerant in the condenser to exchange heat with the CO2 gas, and as a 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, and the low-temperature regenerator is connected in parallel with the heat exchanger, wherein a portion of the working fluid liquid CO2 is heat exchanged in the heat exchanger, and the other portion is subjected to primary heating through the low-temperature regenerator, and then subjected to secondary heating through the high-temperature regenerator together with the CO2 after heat exchange, wherein the secondary heating temperature is greater than the primary heating temperature.

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