Variable working medium thermodynamic cycle construction method for coupling chemical reaction

Abstract

The invention discloses a variable working medium thermodynamic cycle construction method for coupling chemical reaction, which belongs to the technical field of thermodynamic cycle, and introduces controllable reversible chemical reaction into cycle, so that the chemical composition of a working medium is periodically and actively changed at different stages, and a dynamic conversion system for coupling heat energy, chemical energy and work is constructed. An adaptive reversible reaction system is screened, a heat absorption process and a heat release process are integrated, a chemical reaction process is utilized to replace a compression and expansion acting process in original circulation, an electrochemical reactor can be adopted to replace a traditional mechanical compression / expansion part, a static system without a moving part is constructed, and a target substance purification function can be integrated. Optimal matching of working media in all stages of circulation is achieved, the energy conversion efficiency is greatly improved, the multifunctional characteristic of energy and material collaborative conversion is expanded, the system structure is simplified, the system is matched with multiple scenes such as solar thermal power generation, industrial waste heat recovery, CCUS and strategic resource extraction, and the remarkable economic and environment-friendly value is achieved.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of heat cycle, in particular to a variable working medium heat cycle coupled with chemical reaction construction method. BACKGROUND

[0002] Traditional heat cycles represented by Rankine cycle and Brayton cycle are the core foundation of energy power systems. The core principle is to rely on a single and fixed chemical composition working medium to realize the conversion of heat energy to mechanical energy or electrical energy through physical state changes such as compression, heating, expansion and cooling.

[0003] However, this single cycle working medium mode has inherent limitations. The theoretical efficiency has bottlenecks. The cycle efficiency is not only restricted by Carnot theorem, but also depends on the thermophysical properties of the working medium itself, such as specific heat capacity, critical parameters, etc. In many actual application scenarios such as low-temperature heat sources, the efficiency improvement faces significant difficulties. The matching of working medium and heat process is not good, and the single working medium is difficult to maintain optimal performance in the whole heat process of the cycle. High temperature section requires working medium to have good stability, low temperature condensation section has moderate requirement for saturation pressure of working medium, and single working medium is usually difficult to meet these different requirements. The system function is relatively single, and the core function of traditional cycle is limited to "heat-work" or "heat-electricity" conversion. However, in actual application scenarios, there are often multiple requirements such as CO2 capture, lithium resource extraction and fuel preparation, which cannot be met by traditional cycles. The manufacturing difficulty of core components is high. The high-performance rotating machinery such as turbine and compressor has very high requirements for design and manufacturing precision, which leads to high cost, and the challenge is more prominent in small-scale, distributed and other application scenarios.

[0004] Although there are attempts to improve temperature matching by using non-azeotropic mixed working medium, such methods still do not fundamentally solve the above-mentioned inherent problems because the structure of working medium molecules does not change. SUMMARY

[0005] The purpose of the present application is to provide a variable working medium heat cycle coupled with chemical reaction construction method to solve the above problems.

[0006] The present application provides a variable working medium heat cycle coupled with chemical reaction construction method, which comprises the following core steps: Step 1, according to the heat source conditions and product requirements of the target application, select a suitable reversible chemical reaction system as working pair, which can occur controllable forward and reverse reactions under different temperature and pressure conditions. Step 2, the reversible chemical reaction of the working pair is integrated with the thermodynamic process, the chemical composition of the working pair is changed periodically and purposefully in different stages of the cycle, and a cycle system coupling heat, chemical energy and work is constructed; Step 3, the cycle system contains endothermic process, exothermic process, forward chemical reaction process and reverse chemical reaction process, and realizes the recycling and regeneration of the chemical composition of the working pair and energy conversion; Step 4, by selecting a specific reversible chemical reaction system, the cycle completes energy conversion or realizes the separation and purification of target substances.

[0007] Preferably, the specific implementation of step 2 includes: a) Forward chemical reaction: input electric energy by using an electrolytic cell device to increase the electrochemical potential of the working pair reactant A, and obtain a working pair with high chemical potential; b) Endothermic and chemical reaction: the working pair with high chemical potential absorbs heat from a high-temperature heat source in an endothermic reactor, part of the heat is used for physical heating of the working pair, and the other part of the heat drives the endothermic chemical reaction to generate high-temperature and high-pressure chemical products B and C; c) Reverse chemical reaction: using a primary cell device, the working pair with high chemical potential, i.e. products B and C, directly generates electric energy through electrochemical reaction to realize synchronous pressure and temperature drop; d) Exothermic and reverse chemical reaction: the working pair releases heat to a low-temperature heat sink in an exothermic reactor, and occurs reverse chemical reaction under suitable temperature and pressure conditions to regenerate the initial reactant A and release reaction heat, completing the cycle of the working pair from A to B / C and back to A.

[0008] Preferably, the reversible chemical reaction system in step 1 includes but is not limited to any one of the following: methanol cracking / synthesis reaction, methane steam reforming reaction, electrochemical reaction, and reaction for separation of specific substances.

[0009] Preferably, the forward reaction of the working pair in step 1 is an endothermic reaction and can occur in the high-temperature region of the cycle, and the reverse reaction of the working pair is an exothermic reaction and can occur spontaneously in the low-temperature region of the cycle.

[0010] Preferably, the specific implementation of the substance purification and separation in step 4 is that the working pair selectively absorbs target substances in the endothermic and chemical reaction stage of step b), and releases a high-purity target substance stream in the exothermic and reverse chemical reaction stage of step d), realizing heat-driven separation and purification of target substances.

[0011] Therefore, the application adopts the above-mentioned construction method of the variable working medium thermodynamic cycle coupled with chemical reactions to realize a breakthrough in energy conversion efficiency by coupling reversible chemical reactions with thermodynamic and electrochemical processes. The periodic active change of the chemical composition of the working medium enables the matching of dynamic working medium with optimal performance at each stage of the cycle, solving the problem of single working medium adaptation throughout the process. In the high-temperature heat absorption link, thermal energy is simultaneously converted into sensible heat and chemical energy of the working medium, reducing irreversible loss and achieving a theoretical efficiency far exceeding that of traditional cycles, effectively breaking through the bottleneck of low-temperature heat source efficiency improvement. The traditional single-function limitation of heat-to-work / electricity conversion in traditional cycles is completely broken, and a comprehensive energy and material conversion platform is constructed. The same system can simultaneously output energy and high-value chemicals such as hydrogen, or complete tasks such as CO2 capture, strategic metal extraction, and wastewater recovery, expanding the application boundaries of thermodynamic cycles in energy, chemical industry, environmental protection, and other fields. The system uses an electrochemical reaction device to replace traditional high-precision rotating machinery, constructing a static thermoelectrochemical system without moving parts. This significantly reduces equipment manufacturing difficulty, maintenance cost, and operating noise, adapts to distributed energy and special working conditions, and solves the cost and technical problems of traditional cycles in miniaturization and distributed applications. According to the heat source conditions and product demand, the reversible reaction system can be flexibly selected to derive customized cycle schemes. It can accurately adapt to multiple scenarios such as solar thermal power generation, industrial waste heat recovery, and CCUS, breaking the limitation of narrow adaptation range of traditional cycles. The static structure without moving parts reduces the risk of mechanical failure, and combined with a multi-stable state control strategy, it ensures stable and efficient operation under different working conditions. The system simultaneously realizes pollutant removal and resource recovery, meets the needs of low-carbon environmental protection and resource recycling, and has significant economic and social value.

[0012] The technical solutions of the application will be further described in detail below with the aid of the accompanying drawings and examples. BRIEF DESCRIPTION OF DRAWINGS

[0013] Figure 1 A process flow chart of the construction method of the variable working medium thermodynamic cycle coupled with chemical reactions of the application; Figure 2 A structure diagram of the system for realizing organic integration of reversible chemical reactions and thermodynamic processes of working pairs of the application; Figure 3 A coordinate system diagram of the system for realizing organic integration of reversible chemical reactions and thermodynamic processes of working pairs of the application.

[0014] Reference signs: 1, heat absorption reactor; 2, primary cell device; 3, heat release reactor; 4, electrolytic cell device. DETAILED DESCRIPTION

[0015] In order to better understand the above technical solutions, the above technical solutions will be described in detail below in combination with specific embodiments. Obviously, the described embodiments are only some of the embodiments of the present application, not all. Based on the embodiments in the present application, all other embodiments obtained by a person of ordinary skill in the art without creative labor fall within the scope of protection of the present application.

[0016] The terms used in the embodiments of the present application are only for the purpose of describing specific embodiments, and are not intended to limit the present application. The singular forms "a", "said" and "the" used in the embodiments of the present application and the appended claims are also intended to include the plural forms, unless the context clearly indicates otherwise. "Multiple" generally includes at least two.

[0017] It should also be noted that the term "comprise", "include" or any other variant thereof is intended to cover non-exclusive inclusion, so that the product or device including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such product or device. Without more limitation, the element defined by the sentence "comprises a" does not exclude the presence of another identical element in the product or device comprising the element.

[0018] The present application provides a method for constructing a variable working medium thermodynamic cycle coupled with chemical reactions, comprising the following core steps: Step 1, according to the heat source conditions and product requirements of the target application, select a suitable reversible chemical reaction system as the working pair, which can occur controllable forward and reverse reactions under different temperature and pressure conditions; Step 2, integrate the reversible chemical reaction of the working pair with the thermodynamic process, so that the chemical composition of the working pair actively changes periodically at different stages of the cycle, and construct a cycle system coupled with heat, chemical energy and work; Step 3, the cycle system includes heat absorption process, heat release process, forward chemical reaction process and reverse chemical reaction process, to realize the cycle regeneration of working chemical composition and energy conversion; Step 4, by selecting a specific reversible chemical reaction system, the cycle completes energy conversion or realizes the separation and purification of target substances.

[0019] The specific embodiment of step 2 includes: a) Forward chemical reaction: input electric energy by using electrolytic cell device 4 to increase the electrochemical potential of working reactant A, and obtain working reactant A with high chemical potential; b) heat absorption and chemical reaction: the high-chemical-potential working substance absorbs heat from a high-temperature heat source in the heat absorption reactor 1, part of the heat is used to physically heat the working substance, and the other part of the heat drives the heat absorption chemical reaction to generate high-temperature and high-pressure chemical products B and C; c) reverse chemical reaction: the high-chemical-potential working substance, i.e. the products B and C, directly generates electric energy through electrochemical reaction by using the original battery device 2, so as to realize synchronous reduction of pressure and temperature; d) heat release and reverse chemical reaction: the working substance releases heat to a low-temperature heat sink in the heat release reactor 3, and under the conditions of suitable temperature and pressure, the reverse chemical reaction occurs to regenerate the initial reactant A and release reaction heat, thereby completing the cycle of the working substance from A to B / C and back to A.

[0020] The reversible chemical reaction system in step 1 includes but is not limited to any one of the following: methanol cracking / synthesis reaction, methane steam reforming, electrochemical reaction, and reaction for separation of specific substances.

[0021] The forward reaction of the working substance pair in step 1 is an endothermic reaction and can occur in the high-temperature region of the cycle; the reverse reaction of the working substance pair is an exothermic reaction and can spontaneously occur in the low-temperature region of the cycle.

[0022] The specific embodiment of the substance purification and separation in step 4 is that in the heat absorption and chemical reaction stage of step b), the working substance selectively absorbs the target substance; in the heat release and reverse chemical reaction stage of step d), the high-purity target substance stream is released, thereby realizing heat-driven separation and purification of the target substance. If the target substance is CO2, the working substance selectively absorbs CO2 in the flue gas in the heat absorption reaction stage, and releases a high-purity CO2 stream in the reverse reaction stage, thereby realizing heat-driven carbon capture.

[0023] The core mechanism of the present application is based on the deep coupling and synergy of reversible chemical reaction, thermodynamic process and electrochemical process, which essentially breaks through the technical paradigm of traditional thermodynamic cycle relying on single fixed working substance physical state change, and realizes multi-dimensional optimization of energy conversion efficiency, system function and structural complexity.

[0024] The core limitation of the traditional cycle is that a single working substance cannot simultaneously match the optimal thermophysical properties of the whole cycle (high-temperature heating, low-temperature condensation, etc.), while the present application utilizes the temperature and pressure dependence of reversible chemical reaction to make the working substance undergo periodic and controllable chemical composition change in the cycle. In the high-temperature region, the product working substance with excellent high-temperature stability is generated through heat absorption and positive reaction, and in the low-temperature region, the initial working substance with suitable condensation characteristics is regenerated through heat release and reverse reaction, so that the working substance can match the customized optimal working substance in each key stage of the cycle, thereby improving the matching degree of the working substance and the thermodynamic process from the root and minimizing the irreversible loss in the heat and mass transfer process, laying a foundation for efficiency breakthrough.

[0025] The innovation realizes the multi-path collaborative conversion of "thermal energy-chemical energy-mechanical energy / electric energy". In the high-temperature heat absorption stage, the thermal energy provided by the heat source is not only used to increase the temperature of the working medium, but also part of the thermal energy is fixed as the chemical energy of the working medium by driving the endothermic chemical reaction, realizing the multi-level storage and utilization of thermal energy; in the subsequent electrochemical power generation process, the sensible heat and chemical energy of the working medium are released synchronously, which is converted into mechanical work or electric energy. Compared with the traditional cycle which only relies on the mode of sensible heat conversion, the depth and efficiency of energy utilization are greatly improved, especially for low-temperature heat sources. The chemical energy can break through the efficiency bottleneck of direct conversion of low-grade heat energy.

[0026] The core of the system structure simplification mechanism is the electrochemical replacement logic: the compression and expansion processes of the traditional cycle rely on high-precision rotating machinery, which has high design and manufacturing difficulty and cost. However, the present application uses the energy conversion characteristics of electrochemical reaction to input electric energy to improve the electrochemical potential of the working medium through electrolytic cell and other devices, replacing the pressurization function of mechanical compression; through the device such as primary battery, the high-chemical-potential working medium is allowed to undergo electrochemical reaction, directly converting chemical energy into electric energy, replacing the work function of mechanical expansion. This replacement not only eliminates the moving parts in the system, but also integrates energy conversion and working medium state regulation, making the system upgrade from a dynamic mechanical cycle to a static thermoelectrochemical cycle, significantly reducing equipment manufacturing, maintenance cost and operation noise.

[0027] The selective design of the reaction system realizes the collaborative conversion of energy and matter. For specific target substances (such as CO2 and lithium resources), reversible reaction systems with selective adsorption and conversion characteristics are selected, so that the working medium can specifically react (or adsorb) with the target substance in the heat absorption reaction stage, separating and combining it from the mixed system (such as flue gas and salt lake brine); in the low-temperature reverse reaction stage, the target substance is released from the working medium through working condition regulation, forming a high-purity product. This design allows the cycle to complete energy conversion while simultaneously purifying and recycling target substances, making the system upgrade from a simple energy converter to an energy-matter collaborative conversion platform, expanding the application boundary of the thermodynamic cycle.

[0028] The working principle of the present application is based on the logic of reversible chemical reaction cycle as the core, thermodynamic / electrochemical process as the support, and functional requirements as the guide. The specific implementation process is as follows: First, according to the core parameters of the target application scenario, such as the heat source temperature range, heat source type, and target product, a reversible chemical reaction system with excellent thermodynamic performance, controllable reaction kinetics, safety, and economy is selected as the circulating working medium pair. The selection criteria include: the endothermic / exothermic characteristics of the reaction should match the heat source and heat sink temperatures, the high-temperature zone should be able to spontaneously perform endothermic positive reactions, and the low-temperature zone should be able to spontaneously perform exothermic reverse reactions; the reaction rate should be moderate, facilitating cycle control; the chemical stability of the reactants and products should be good, with no toxic and harmful by-products; the pressure and temperature window of the reaction should be compatible with actual engineering application conditions. Typical examples include methanol cracking / synthesis reactions, methane steam reforming, and amine absorption / desorption reaction systems for CO2 capture.

[0029] The specific process of the method for constructing a closed-loop system of a working medium chemical cycle and a thermodynamic cycle is as follows: Electrochemical potential of the working medium is raised under the driving of electric energy: the initial working medium A enters an electrochemical compression device, such as an electrolytic cell, and the electrochemical potential of the working medium is raised by driving the working medium to undergo electrode reactions through input of electric energy into the device. The pressure level is determined according to the reaction characteristics and energy output requirements, so that the working medium has the energy state required for subsequent chemical reactions and creates temperature conditions for subsequent chemical reactions.

[0030] Endothermic reaction and energy storage: the high-pressure working medium enters an endothermic / chemical reactor, which exchanges heat with a high-temperature heat source. Part of the heat absorbed by the working medium is used to raise its temperature and convert it into sensible heat, and the other part is used as a reaction driving force to trigger the positive reaction of the reversible reaction, such as methanol cracking, to generate high-temperature and high-pressure reaction products. This process realizes the simultaneous storage of heat energy into working medium sensible heat and chemical energy, and the chemical composition of the working medium changes from A to mixed products B and C.

[0031] Electrochemical power generation and energy output: the products B and C enter an electrochemical power generation device (such as a fuel cell), and electrochemical reactions (such as the power generation reaction of a hydrogen-oxygen fuel cell) occur under the action of electrode catalysts, directly converting the chemical energy of the working medium into electric energy output, while the chemical potential of the working medium decreases, completing energy release, and the pressure and temperature of the working medium simultaneously decrease to the low-temperature section of the cycle.

[0032] Exothermic reverse reaction and working medium regeneration: the low-temperature and low-pressure working medium enters an exothermic / chemical reverse reactor, which exchanges heat with a low-temperature heat sink, and the working medium releases heat to the heat sink, further lowering the temperature. Under suitable low-temperature and low-pressure conditions, products B and C trigger the reverse reaction of the reversible reaction, regenerating the initial working medium A, and completing the cyclic regeneration of the chemical composition of the working medium. The released reaction heat and the sensible heat of the working medium are taken away by the low-temperature heat sink, and the working medium returns to the initial state, regenerating as the initial working medium A, and then re-entering the electrochemical compression device to form a static cycle closed loop.

[0033] When the system needs to be synchronized to achieve material purification, such as CO2 capture and lithium resource extraction, by screening selective reaction systems, the material separation link is embedded in the above cycle process: Selective adsorption / conversion: In the endothermic reaction stage, working fluid A is in contact with mixed raw materials. By using the selectivity of the reaction system, working fluid A only reacts specifically with the target material or adsorbs it, separating the target material from the mixed raw materials and combining it with the working fluid. The remaining raw materials are discharged from the system.

[0034] Target material release and purification: In the exothermic reverse reaction stage, as the working fluid regeneration reaction proceeds, the target material is released from the working fluid, forming a high-purity target product. After separation by a separator, it is collected, achieving simultaneous completion of material purification and energy conversion.

[0035] To ensure stable and efficient operation of the cycle under different working conditions, the system can be equipped with a multi-parameter control strategy: real-time monitoring of the operating parameters of each reactor and equipment through temperature sensors and pressure sensors; adjusting the heat source input, compressor speed, or electrolytic cell voltage (electrochemical mode) based on monitoring data to control reaction rate and working fluid state; adjusting the heat transfer area or medium flow of the heat exchanger to optimize heat transfer efficiency and ensure the coordinated matching of endothermic and exothermic processes and chemical reactions, ultimately achieving flexible control of energy conversion efficiency and material conversion rate.

[0036] Therefore, the application adopts the above-mentioned construction method of the variable working medium thermodynamic cycle coupled with chemical reaction, and realizes a breakthrough in energy conversion efficiency by coupling reversible chemical reaction with thermodynamics and electrochemical process. The periodic active change of the chemical composition of the working medium matches the dynamic working medium with the optimal performance at each stage of the cycle, solving the problem of single working medium adaptation throughout the process. In the high-temperature heat absorption link, thermal energy is simultaneously converted into sensible heat and chemical energy of the working medium, reducing irreversible loss and achieving a theoretical efficiency far exceeding that of traditional cycles, effectively breaking through the bottleneck of low-temperature heat source efficiency improvement. It completely breaks through the single functional limitation of traditional cycle heat-power / electricity conversion and builds an integrated platform for energy and material conversion. The same system can simultaneously output energy and high-value chemicals such as hydrogen, or complete CO2 capture, strategic metal extraction, wastewater recycling and other tasks, expanding the application boundaries of thermodynamic cycles in energy, chemical industry, environmental protection and other fields. The system uses an electrochemical reaction device to replace traditional high-precision rotating machinery, building a static thermoelectrochemical system without moving parts. It greatly reduces equipment manufacturing difficulty, maintenance cost and operating noise, adapts to distributed energy and special working conditions, and solves the cost and technical problems of traditional cycles in miniaturization and distributed applications. According to the heat source conditions and product demand, the reversible reaction system can be flexibly selected to derive customized cycle solutions. It can accurately adapt to multiple scenarios such as solar thermal power generation, industrial waste heat recovery and CCUS, breaking the limitations of narrow adaptation range of traditional cycles. The static structure without moving parts reduces the risk of mechanical failure, and combined with a multi-stable state control strategy, it ensures stable and efficient operation under different working conditions. The system simultaneously realizes pollutant removal and resource recovery, meets the needs of low-carbon environmental protection and resource recycling, and has significant economic and social value.

[0037] Finally, it should be noted that: the above examples are only used to illustrate the technical solutions of the present application and not to limit it, although the present application has been described in detail with reference to the preferred embodiments, those skilled in the art should understand that: it can still modify or equivalently replace the technical solutions of the present application, and these modifications or equivalent replacements also cannot make the modified technical solutions deviate from the spirit and scope of the technical solutions of the present application.

Claims

1. A method for constructing a variable working medium thermodynamic cycle coupled with a chemical reaction, characterized in that, The core steps include the following: Step 1: Based on the heat source conditions and product requirements of the target application, select a reversible chemical reaction system as the working fluid pair, wherein the working fluid pair undergoes controllable forward and reverse reactions under different temperature and pressure conditions; Step 2: Organically integrate the reversible chemical reaction and thermodynamic process of the working fluid pair, so that the chemical composition of the working fluid undergoes purposeful and periodic active changes at different stages of the cycle, and construct a cycle system that couples thermal energy, chemical energy, and work. Step 3: The circulating system includes an endothermic process, an exothermic process, a forward chemical reaction process, and a reverse chemical reaction process, realizing the recycling and regeneration of the working fluid's chemical composition and energy conversion; Step 4: By selecting a specific reversible chemical reaction system, the cycle completes energy conversion or achieves the separation and purification of the target substance.

2. The method for constructing a variable working medium thermodynamic cycle coupled with a chemical reaction according to claim 1, characterized in that, The specific implementation of step 2 includes: a) Forward chemical reaction: An electrolytic cell is used to input electrical energy to increase the electrochemical potential of reactant A, resulting in a working fluid with a high chemical potential; b) Endothermic reaction and chemical reaction: The working fluid with high chemical potential absorbs heat from a high-temperature heat source in an endothermic reactor. Part of the heat is used to physically raise the temperature of the working fluid, and the other part of the heat drives an endothermic chemical reaction to generate high-temperature and high-pressure chemical products B and C. c) Reverse chemical reaction: Using a galvanic cell device, the working fluid with high chemical potential, i.e. products B and C, directly generates electrical energy through an electrochemical reaction, thereby achieving a simultaneous decrease in pressure and temperature. d) Exothermic reaction and reverse chemical reaction: The working fluid releases heat to the low-temperature heat sink in the exothermic reactor and undergoes a reverse chemical reaction under suitable temperature and pressure conditions, regenerating the initial reactant A and releasing the heat of reaction, completing the cycle of the working fluid from A to B / C and back to A.

3. The method for constructing a variable working medium thermodynamic cycle coupled with a chemical reaction according to claim 1, characterized in that, The reversible chemical reaction system described in step 1 includes, but is not limited to, any one of methanol cracking / synthesis reaction, methane steam reforming, electrochemical reaction, and reaction for the separation of specific substances.

4. The method for constructing a variable working medium thermodynamic cycle coupled with a chemical reaction according to claim 1, characterized in that, The forward reaction of the working fluid pair in step 1 is an endothermic reaction and occurs in the high-temperature region of the cycle; the reverse reaction of the working fluid pair is an exothermic reaction and occurs spontaneously in the low-temperature region of the cycle.

5. The method for constructing a variable working medium thermodynamic cycle coupled with a chemical reaction according to claim 2, characterized in that, The specific implementation method of the substance purification and separation in step 4 is as follows: in the endothermic and chemical reaction stage of step b), the working fluid selectively absorbs the target substance; in the exothermic and chemical reverse reaction stage of step d), a high-purity target substance stream is released, thereby realizing the thermally driven separation and purification of the target substance.

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