A thermochemical recovery system for Rankine cycle cold source loss

Abstract

A thermochemical recovery system for Rankine cycle cold source loss utilizes low-temperature, low-pressure steam directly as a reactant. The reversible thermochemical reaction of CaO + H2O = Ca(OH)2 generates an exothermic hydration reaction in a low-pressure reaction tank, raising the overall temperature of the reaction system and transferring a certain amount of intermediate-temperature heat to the Rankine cycle. Simultaneously, the heat source from the high-temperature section of the Rankine cycle is used to heat a high-pressure reaction tank for a dehydration reaction, raising the overall temperature and water vapor pressure of the reaction system. The high-temperature steam then exits the high-pressure tank, transferring the high-temperature heat to the Rankine cycle, condensing during the heat transfer process. After cooling, the steam returns to the condenser as liquid water. This system utilizes the chemical heat pump effect of the reversible thermochemical reaction to partially recover Rankine cycle cold source loss, improving the overall thermal efficiency of a condensing steam-fired power generator set, reducing the power consumption of the unit's circulating water system, and improving the unit's overall economic efficiency. The system eliminates the need for external heat sources or heat users and has a wide range of applications.

Description

Technical Field

[0001] The present invention relates to the technical field of Rankine cycles, and in particular to a Rankine cycle cold source loss thermochemical recovery and utilization system. Background Art

[0002] The Rankine cycle is the most widely used steam thermodynamic cycle. Condensing steam-fired power plants utilize this cycle to convert heat into work and generate electricity. In Rankine cycle power generation, after fully performing work in the turbine, steam must be discharged into the condenser, where it is condensed into liquid water using cooling water or ambient air to complete the cycle. This condensation process releases a significant amount of latent heat that is lost to the environment as cooling, accounting for 50%-60% of the total heat absorbed by the unit. Because the condensation heat is transferred to low-grade energy sources, it is difficult to recycle. Currently, heat recovery is typically achieved through low-vacuum backpressure units or modified heat pumps. However, large-scale heat supply requires a stable supply of heat users, significantly limiting the feasibility of cooling recovery. Summary of the Invention

[0003] In order to overcome the above-mentioned shortcomings of the prior art, the purpose of the present invention is to provide a Rankine cycle cold source loss thermochemical recovery and utilization system, which utilizes a gas-solid reversible thermochemical reaction to hydrate part or all of the condensed water vapor in the Rankine cycle at low pressure, dehydrate it at high pressure and increase the temperature and pressure, and recover and utilize the condensation heat.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A Rankine cycle cold source loss thermochemical recovery and utilization system includes a high-pressure reaction tank 1 and a low-pressure reaction tank 2. The high-pressure reaction tank 1 and the low-pressure reaction tank 2 have the same structure. The reaction tank is provided with a heat exchange tube bundle 4. The interior of the reaction tank contains CaO / Ca(OH)2 reaction material 6. The heat exchange tube bundle 4 is immersed in the CaO / Ca(OH)2 reaction material 6. The heat exchange tube bundle 4 of the high-pressure reaction tank 1 is connected to the high-temperature steam pipeline of the Rankine cycle. The high-pressure reaction tank 1 is provided with a reaction steam pipeline 5. The reaction steam pipeline 5 connects the high-pressure reaction tank 1 with the condenser in the Rankine cycle. The low-pressure reaction tank 2 is provided with a low-pressure steam pipeline 3. The low-pressure steam pipeline 3 is connected to the exhaust pipeline of the low-pressure cylinder of the turbine in the Rankine cycle.

[0006] The high-pressure reaction tank 1 and the low-pressure reaction tank 2 can switch between their working modes by switching system valves and pipelines.

[0007] A cooler 7 is provided at the end of the reaction steam pipeline 5 , and the cooler 7 is located before the condenser.

[0008] The high-pressure reaction storage tank 1 and the low-pressure reaction storage tank 2 serve as storage containers for the reaction materials and also as chemical reactors, and the reaction materials do not need to be transported.

[0009] The heat exchange tube bundle 4 is in full contact with the CaO / Ca(OH)2 reaction material 6. The heat exchange tube bundle 4 exchanges heat with the CaO / Ca(OH)2 reaction material 6 through water or steam flowing inside, and is isolated from each other, and performs mass and heat exchange with the Rankine cycle.

[0010] Beneficial effects of the present invention:

[0011] The system has two reaction tanks, one high and one low. Low-temperature, low-pressure steam discharged from the Rankine cycle is used directly as a reactant. The CaO+H2O=Ca(OH)2 thermochemical reversible reaction system is used to hydrate CaO in the low-pressure reaction tank, generating Ca(OH)2 through an exothermic hydration reaction. This raises the overall temperature of the reaction system and transfers a certain amount of intermediate-temperature heat to the Rankine cycle. The heat source from the high-temperature section of the Rankine cycle is then used to heat the Ca(OH)2 in the high-pressure reaction tank, causing a dehydration reaction to generate CaO and water vapor. This simultaneously raises the overall temperature and water vapor pressure of the reaction system. The high-temperature water vapor is then discharged from the high-pressure tank, transferring the high-temperature heat to the Rankine cycle and condensing it during the heat transfer process. After cooling, it flows back to the condenser as liquid water. The high- and low-pressure tanks operate simultaneously. When the reactants in the reaction tanks are fully reacted, the operating modes of the high- and low-pressure reaction tanks are switched, with each tank operating in opposite chemical reaction directions, enabling continuous system operation.

[0012] The present invention utilizes the chemical heat pump effect of a reversible thermochemical reaction to convert low-temperature and low-pressure turbine exhaust steam into high-temperature steam with a certain pressure by absorbing a portion of high-temperature thermal energy, transfers the heat back to the Rankine cycle and condenses it, releasing the condensation heat, and returns it to the condenser after cooling in the form of liquid water, ultimately realizing partial recovery of the Rankine cycle cold source loss, improving the overall thermal efficiency of the condensing steam thermal power generating set, reducing the power consumption of the unit's circulating water system, and improving the overall economy of the unit. No external heat source or heat user is required, and the application range is wide. BRIEF DESCRIPTION OF THE DRAWINGS

[0013] Figure 1 Schematic diagram of the system structure of the present invention.

[0014] Among them, 1 is a high-pressure reaction storage tank, 2 is a low-pressure reaction storage tank, 3 is a low-pressure steam pipeline, 4 is a heat exchange tube bundle, 5 is a reaction steam pipeline, 6 is CaO / Ca(OH)2 reaction material, and 7 is a cooler. DETAILED DESCRIPTION

[0015] The present invention will be further described in detail below with reference to the embodiments.

[0016] refer to Figure 1 The Rankine cycle cold source loss thermochemical recovery system of the present invention comprises a high-pressure reaction tank 1, a low-pressure reaction tank 2, a low-pressure steam pipeline 3, a heat exchange tube bundle 4, a reaction steam pipeline 5, a CaO / Ca(OH)2 reaction material 6, and a cooler 7. The lower half of the figure is a schematic diagram of the Rankine cycle steam-water flow of a conventional thermal power generator set. The dotted line in the middle of the figure represents the mass and energy exchange interface between the Rankine cycle cold source loss thermochemical recovery system and the conventional Rankine cycle.

[0017] In the Rankine cycle cold source loss thermochemical recovery system, the high-pressure reaction tank 1 and the low-pressure reaction tank 2 have the same structure. During operation, the high-pressure reaction tank 1 operates at a high water vapor pressure, and the low-pressure reaction tank 2 operates at a low water vapor pressure.

[0018] The high-pressure reaction tank 1 and the low-pressure reaction tank 2 are filled with CaO / Ca(OH)2 reaction material 6, which is Ca(OH)2 and CaO powder or particles. The high-pressure reaction tank 1 and the low-pressure reaction tank 2 serve as both storage containers for the reaction materials and chemical reactors, and the reaction materials do not need to be transported.

[0019] The reaction storage tank has a heat exchange tube bundle 4, which is immersed in the solid CaO / Ca(OH)2 reaction material 6 and is in full contact with the CaO / Ca(OH)2 reaction material 6. The heat exchange tube bundle 4 exchanges heat with the CaO / Ca(OH)2 reaction material 6 through water or steam flowing inside, and is isolated from each other, performing mass and heat exchange with the Rankine cycle.

[0020] The high-pressure reaction tank 1 and the low-pressure reaction tank 2 are provided with heat exchange tube bundles, which exchange heat with the reaction materials through water or steam flowing inside and are isolated from each other. Their function is to achieve mass and energy exchange between the reaction tanks and the Rankine cycle.

[0021] The high-pressure reaction tank 1 and the low-pressure reaction tank 2 operate simultaneously. The heat exchange tube bundle 4 of the high-pressure reaction tank 1 is connected to the high-temperature steam pipeline of the Rankine cycle. The reaction steam pipeline 5 of the high-pressure reaction tank 1 connects the material space of the high-pressure reaction tank with the condenser in the Rankine cycle. The low-pressure steam pipeline 3 of the low-pressure reaction tank 2 is connected to the exhaust pipeline of the low-pressure cylinder of the steam turbine in the Rankine cycle. The reaction steam pipeline 5 connects the material space of the reaction tank with the condenser of the Rankine cycle, transfers the heat of the high-temperature water vapor generated by the dehydration reaction to the Rankine cycle, and condenses into liquid water at a pressure higher than the condenser pressure. The high-pressure reaction tank 1 absorbs heat at high temperature, and a Ca(OH)2 dehydration reaction occurs to generate CaO and high-temperature water vapor. The low-pressure reaction tank 2 absorbs the low-temperature, low-pressure turbine exhaust steam, and a CaO hydration reaction occurs, releasing heat. When the reaction materials in the high- and low-pressure reaction tanks are completely reacted, the working modes of the high- and low-pressure reaction tanks are switched by switching the system valves and pipelines, and the chemical reactions are carried out in opposite directions to achieve continuous operation of the system.

[0022] The cooler is characterized in that the cooler 7 is located at the end of the reaction steam pipeline 5, further reduces the temperature of the condensed liquid water, discharges it into the Rankine cycle condenser, and discharges the heat into the environment.

[0023] The specific working process of the present invention is:

[0024] The low-temperature, low-pressure steam discharged from the Rankine cycle is discharged into the low-pressure reaction tank 2 through the low-pressure steam pipe 3. The CaO+H2O=Ca(OH)2 thermochemical reversible reaction system is used to undergo an exothermic hydration reaction with CaO in the low-pressure reaction tank 2 to generate Ca(OH)2, thereby increasing the overall temperature of the reaction system. Heat is exchanged with a portion of the low-temperature working fluid of the Rankine cycle through the heat exchange tube bundle 4. At the same time, the steam from the high-temperature section of the Rankine cycle is used to heat the Ca(OH)2 in the high-pressure reaction tank 1 through the heat exchange tube bundle 4 of the high-pressure reaction tank 1 for a dehydration reaction to generate CaO and water vapor, thereby increasing the overall temperature and water vapor pressure of the reaction system. The high-temperature water vapor is discharged from the high-pressure reaction tank 1, transferring the high-temperature heat to the Rankine cycle, and completing the condensation process during the heat transfer process. After being fully cooled by the cooler 7, it flows back to the condenser in the form of liquid water. The high-pressure reaction tank 1 and the low-pressure reaction tank 2 operate simultaneously. When the reaction materials in the reaction tanks are completely reacted, the operation modes of the high-pressure and low-pressure reaction tanks are switched, and each operates in opposite chemical reaction directions to achieve continuous operation of the system.

[0025] The specific implementation methods 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 implementation method 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 Rankine cycle cold source loss thermochemical recovery system, characterized in that: The invention comprises a high-pressure reaction storage tank (1) and a low-pressure reaction storage tank (2), wherein the high-pressure reaction storage tank (1) and the low-pressure reaction storage tank (2) have the same structure, a heat exchange tube bundle (4) is provided on the reaction storage tank, the interior of the reaction storage tank is CaO / Ca(OH)2 reaction material (6), the heat exchange tube bundle (4) is immersed in the CaO / Ca(OH)2 reaction material (6), the heat exchange tube bundle (4) of the high-pressure reaction storage tank (1) is connected to the high-temperature steam pipeline of the Rankine cycle, the high-pressure reaction storage tank (1) is provided with a reaction steam pipeline (5), the reaction steam pipeline (5) connects the high-pressure reaction storage tank (1) with the condenser in the Rankine cycle, and the low-pressure steam pipeline (3) is provided on the low-pressure reaction storage tank (2), and the low-pressure steam pipeline (3) is connected to the exhaust pipeline of the low-pressure cylinder of the steam turbine in the Rankine cycle; The high-pressure reaction storage tank (1) and the low-pressure reaction storage tank (2) serve as storage containers for the reaction materials and also as chemical reactors, and the reaction materials do not need to be transported; The heat exchange tube bundle (4) is in full contact with the CaO / Ca(OH)2 reaction material (6), and the heat exchange tube bundle (4) exchanges heat with the CaO / Ca(OH)2 reaction material (6) through water or steam flowing inside, and is isolated from each other, and performs mass and heat exchange with the Rankine cycle.

2. The Rankine cycle cold source loss thermochemical recovery system according to claim 1, characterized in that: The high-pressure reaction storage tank (1) and the low-pressure reaction storage tank (2) are switched between working modes by switching system valves and pipelines.

3. The thermochemical recovery system for Rankine cycle cold source loss according to claim 1, characterized in that: A cooler (7) is provided at the end of the reaction steam pipeline (5), and the cooler (7) is located before the condenser.

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