Thermal power plant waste heat recovery system coupled with thermochemical heat storage and operation method of thermal power plant waste heat recovery system

Abstract

The invention discloses a thermal power plant waste heat recovery system coupled with thermochemical heat storage and an operation method of the thermal power plant waste heat recovery system. The system comprises a thermal power plant unit and a calcium chloride thermochemical energy storage unit. The calcium chloride thermochemical energy storage unit comprises a hydrated calcium chloride decomposition bed, a dryer, a second heat exchanger, a third heat exchanger and a fourth heat exchanger; the outlet of the dryer is connected with the inlet of the calcium chloride hydrate decomposition bed after passing through the second heat exchanger, the third heat exchanger and the fourth heat exchanger. The thermal power plant unit is connected with the calcium chloride thermochemical energy storage unit through heat exchangers, a first heat exchanger in the thermal power plant unit is connected with a third heat exchanger in the calcium chloride thermochemical energy storage unit through hot water circulation, and a flue gas outlet of a boiler in the thermal power plant unit is connected with a fourth heat exchanger in the calcium chloride thermochemical energy storage unit; the system provides a new mode for recycling and long-term stable storage of waste heat of flue gas of a thermal power plant unit and a working medium at an outlet of a low-pressure cylinder, and the heat efficiency of the system can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of low-temperature waste heat utilization and energy storage, and in particular to a waste heat recovery system for a thermal power plant coupled with thermochemical heat storage and an operation method thereof. Background Art

[0002] With the continuous development of industrialization, the thermal energy utilization rate of various high-energy-consuming industrial processes has received more and more attention. In these processes, a large amount of waste heat is discharged in a low-grade form, resulting in energy waste and environmental thermal pollution. Boiler waste heat is an important component of industrial waste heat, which mainly comes from boiler exhaust and cooling systems. However, since boiler waste heat is mostly low-temperature waste heat, direct recovery and utilization faces technical bottlenecks such as low thermal energy quality and low transmission efficiency. In recent years, thermochemical energy storage technology has gradually attracted attention due to its high energy density, flexible heat storage / release capacity and good thermal energy quality regulation characteristics. Thermochemical energy storage uses the endothermic and exothermic characteristics of reversible chemical reactions to convert low-grade thermal energy into chemical energy storage and release it when needed. Compared with traditional sensible heat storage and latent heat storage, thermochemical energy storage has significant advantages such as high energy density, no storage heat loss and flexible temperature matching. Combining thermochemical energy storage with boiler waste heat system can not only effectively improve the utilization rate of waste heat, but also realize the spatial and temporal regulation of thermal energy. However, there is no technical solution combining thermochemical energy storage with boiler waste heat system in the prior art. Summary of the invention

[0003] In order to solve the above problems existing in the prior art, the purpose of the present invention is to provide a waste heat recovery system for a thermal power plant coupled with thermochemical heat storage and an operation method thereof, which can improve the cycle efficiency of the entire system.

[0004] In order to achieve the above object, the present invention adopts the following technical solution:

[0005] A waste heat recovery system for a thermal power plant coupled with thermochemical heat storage, comprising a thermal power plant unit 1 and a calcium chloride thermochemical energy storage unit 2;

[0006] The thermal power plant unit 1 comprises a boiler 1-1, a steam turbine high-pressure cylinder 1-2, a steam turbine low-pressure cylinder 1-3, a first heat exchanger 1-4, a condenser 1-5 and a working fluid pump 1-6;

[0007] The boiler 1-1 is connected to the inlet of the high-pressure cylinder 1-2 of the steam turbine, the outlet of the high-pressure cylinder 1-2 of the steam turbine is connected to the inlet of the low-pressure cylinder 1-3 of the steam turbine, the outlet of the low-pressure cylinder 1-3 of the steam turbine is connected to the inlet of the condenser 1-5 through the first heat exchanger 1-4, the outlet of the condenser 1-5 is connected to the inlet of the working fluid pump 1-6, and the outlet of the working fluid pump 1-6 is connected to the boiler 1-1;

[0008] The calcium chloride thermochemical energy storage unit 2 comprises a calcium chloride hydrate decomposition bed 2-1, a dryer 2-2, a second heat exchanger 2-3, a third heat exchanger 2-4 and a fourth heat exchanger 2-5;

[0009] The outlet of the calcium chloride hydrate decomposition bed 2-1 is connected to the inlet of the dryer 2-2, and the outlet of the dryer 2-2 is connected to the inlet of the calcium chloride hydrate decomposition bed 2-1 after passing through the second heat exchanger 2-3, the third heat exchanger 2-4 and the fourth heat exchanger 2-5.

[0010] The thermal power plant unit 1 and the calcium chloride thermochemical energy storage unit 2 are connected via a heat exchanger, wherein the first heat exchanger 1-4 and the third heat exchanger 2-4 are connected via a hot water circulation, and the flue gas outlet of the boiler 1-1 is connected to the fourth heat exchanger 2-5 of the calcium chloride thermochemical energy storage unit 2.

[0011] Furthermore, the circulating working medium in the calcium chloride thermochemical energy storage unit 2 is air.

[0012] Furthermore, in the thermal power plant unit 1, a first heat exchanger 1-4 is arranged to recover low-temperature waste heat of the working fluid at the outlet of the low-pressure cylinder 1-3 of the steam turbine.

[0013] Furthermore, in the calcium chloride thermochemical energy storage unit 2, the calcium chloride hydrate decomposition bed 2-1 is a solid particle fixed bed containing calcium chloride hydrate particles, and the charging temperature range is 90-150°C.

[0014] Furthermore, in the calcium chloride thermochemical energy storage unit 2, the second heat exchanger 2-3 is connected to the water supply and return pipes of the heating network.

[0015] Furthermore, in the calcium chloride thermochemical energy storage unit 2, the working medium flow rate of the unit is controlled to control the working medium temperature at the inlet of the calcium chloride hydrate decomposition bed 2-1 to 120-150°C, and the packing density of the calcium chloride hydrate particles is controlled to control the working medium temperature at the outlet of the calcium chloride hydrate decomposition bed 2-1 to 90-100°C.

[0016] Further, in the calcium chloride thermochemical energy storage unit 2, the flue gas temperature of the boiler 1-1 passing through the fourth heat exchanger 2-5 is 150-200°C.

[0017] Furthermore, in the calcium chloride thermochemical energy storage unit 2, the return water flow rate of the heating network is controlled to control the water supply temperature of the heating network to be 30°C-80°C.

[0018] The operation method of the waste heat recovery system of a thermal power plant coupled with thermochemical heat storage, the operation method of the thermal power plant unit 1 is:

[0019] The working fluid enters the boiler 1-1, is heated to a high temperature and high pressure state, and then flows out, and at the same time, a high temperature flue gas with a temperature of 150-200°C is generated. The flue gas enters the calcium chloride thermochemical energy storage unit 2 for waste heat recovery. The high temperature and high pressure working fluid enters the turbine high pressure cylinder 1-2 and the turbine low pressure cylinder 1-3 in turn to expand and do work, and then flows into the first heat exchanger 1-4 for waste heat recovery and then flows out, and after being cooled by the condenser 1-5, enters the working fluid pump 1-6, and then is pumped by the working fluid pump 1-6 and returned to the boiler 1-1 for circulation.

[0020] The operation method of the calcium chloride thermochemical energy storage unit 2 is:

[0021] The working fluid enters the third heat exchanger 2-4 to recover the waste heat in the first heat exchanger 1-4 for preheating, then enters the fourth heat exchanger 2-5 to exchange heat with the high-temperature flue gas flowing out of the thermal power plant unit 1 and is heated to 120-150°C before flowing out, enters the calcium chloride hydrate decomposition bed 2-1 to heat the calcium chloride hydrate solid particles to decompose them into water vapor and calcium chloride particles, and converts the thermal energy of the working fluid into chemical energy in the calcium chloride particles, and then the generated water vapor is mixed with the working fluid and flows out into the dryer 2-2 for drying, and the outflowing dry working fluid flows into the second heat exchanger 2-3 to provide heat for the heating network water supply, then flows out, and enters the third heat exchanger 2-4 for circulation.

[0022] Compared with the prior art, the present invention has the following advantages:

[0023] (1) The use of thermochemical energy storage system coupled with thermal power plant system can improve the cycle efficiency of the entire system;

[0024] (2) By selecting hydrated calcium chloride as the reactant, the energy storage temperature is matched with the boiler flue gas temperature, thereby improving the waste heat utilization efficiency;

[0025] (3) Multiple heat exchangers are set up in the system to utilize waste heat resources in a cascade manner, thereby improving the utilization rate of thermal energy. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1 It is a schematic diagram of a waste heat recovery system for a thermal power plant coupled with thermochemical heat storage according to the present invention. DETAILED DESCRIPTION

[0027] The present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods. It should be understood that the preferred implementation examples described herein are only used to illustrate and explain the present invention, and are not used to limit the present invention.

[0028] like Figure 1 As shown, the present invention provides a waste heat recovery system for a thermal power plant coupled with thermochemical heat storage, comprising a thermal power plant unit 1 and a calcium chloride thermochemical energy storage unit 2;

[0029] The thermal power plant unit 1 comprises a boiler 1-1, a steam turbine high-pressure cylinder 1-2, a steam turbine low-pressure cylinder 1-3, a first heat exchanger 1-4, a condenser 1-5 and a working fluid pump 1-6;

[0030] The boiler 1-1 is connected to the inlet of the high-pressure cylinder 1-2 of the steam turbine, the outlet of the high-pressure cylinder 1-2 of the steam turbine is connected to the inlet of the low-pressure cylinder 1-3 of the steam turbine, the outlet of the low-pressure cylinder 1-3 of the steam turbine is connected to the inlet of the condenser 1-5 through the first heat exchanger 1-4, the outlet of the condenser 1-5 is connected to the inlet of the working fluid pump 1-6, and the outlet of the working fluid pump 1-6 is connected to the boiler 1-1;

[0031] The calcium chloride thermochemical energy storage unit 2 comprises a calcium chloride hydrate decomposition bed 2-1, a dryer 2-2, a second heat exchanger 2-3, a third heat exchanger 2-4 and a fourth heat exchanger 2-5;

[0032] The outlet of the calcium chloride hydrate decomposition bed 2-1 is connected to the inlet of the dryer 2-2, and the outlet of the dryer 2-2 is connected to the inlet of the calcium chloride hydrate decomposition bed 2-1 after passing through the second heat exchanger 2-3, the third heat exchanger 2-4 and the fourth heat exchanger 2-5.

[0033] The thermal power plant unit 1 and the calcium chloride thermochemical energy storage unit 2 are connected via a heat exchanger, wherein the first heat exchanger 1-4 and the third heat exchanger 2-4 are connected via a hot water circulation, and the flue gas outlet of the boiler 1-1 is connected to the fourth heat exchanger 2-5 of the calcium chloride thermochemical energy storage unit 2.

[0034] Furthermore, the circulating working fluid in the calcium chloride thermochemical energy storage unit 2 is air, so as to reduce the water vapor partial pressure during the decomposition of hydrated calcium chloride and accelerate the reaction rate of the decomposition reaction.

[0035] Furthermore, in the thermal power plant unit 1, a first heat exchanger 1-4 is arranged to recover low-temperature waste heat of the working fluid at the outlet of the low-pressure cylinder 1-3 of the steam turbine to improve system efficiency.

[0036] Furthermore, in the calcium chloride thermochemical energy storage unit 2, the calcium chloride hydrate decomposition bed 2-1 is a solid particle fixed bed containing calcium chloride hydrate particles, and the charging temperature range is 90-150°C to match the hydrolysis temperature range of calcium chloride hydrate.

[0037] Furthermore, in the calcium chloride thermochemical energy storage unit 2 , the second heat exchanger 2 - 3 is connected to the water supply and return pipes of the heat network to recover the waste heat resources in the thermal power plant unit 1 .

[0038] Furthermore, in the calcium chloride thermochemical energy storage unit 2, the working medium flow rate of the unit is controlled to control the inlet working medium temperature of the calcium chloride hydrate decomposition bed 2-1 to 120-150°C, and the packing density of the calcium chloride hydrate particles is controlled to control the outlet working medium temperature of the calcium chloride hydrate decomposition bed 2-1 to 90-100°C, wherein the outlet temperature is set to 90-100°C to ensure full utilization of thermal energy.

[0039] Further, in the calcium chloride thermochemical energy storage unit 2, the flue gas temperature of the boiler 1-1 passing through the fourth heat exchanger 2-5 is 150-200°C to ensure heat exchange efficiency.

[0040] Furthermore, in the calcium chloride thermochemical energy storage unit 2, by controlling the return water flow of the heating network, the water supply temperature of the heating network is controlled to be 30°C-80°C, so as to fully recover the waste heat resources and match the heating network demand.

[0041] The operating method of the waste heat recovery system of a thermal power plant coupled with thermochemical heat storage according to the present invention, the operating method of the thermal power plant unit 1 is:

[0042] The working fluid enters the boiler 1-1, is heated to a high temperature and high pressure state, and then flows out, and at the same time, a high temperature flue gas with a temperature of 150-200°C is generated. The flue gas enters the calcium chloride thermochemical energy storage unit 2 for waste heat recovery. The high temperature and high pressure working fluid enters the turbine high pressure cylinder 1-2 and the turbine low pressure cylinder 1-3 in turn to expand and do work, and then flows into the first heat exchanger 1-4 for waste heat recovery and then flows out, and after being cooled by the condenser 1-5, enters the working fluid pump 1-6, and then is pumped by the working fluid pump 1-6 and returned to the boiler 1-1 for circulation.

[0043] Furthermore, according to the operating method of a waste heat recovery system of a thermal power plant coupled with thermochemical heat storage according to claim 1, it is characterized in that the operating method of the calcium chloride thermochemical energy storage unit 2 is:

[0044] The working fluid enters the third heat exchanger 2-4 to recover the waste heat in the first heat exchanger 1-4 for preheating, then enters the fourth heat exchanger 2-5 to exchange heat with the high-temperature flue gas flowing out of the thermal power plant unit 1 and is heated to 120°C before flowing out, enters the calcium chloride hydrate decomposition bed 2-1 to heat the calcium chloride hydrate solid particles to decompose them into water vapor and calcium chloride particles, and converts the thermal energy of the working fluid into chemical energy in the calcium chloride particles, and then the generated water vapor is mixed with the working fluid and flows out into the dryer 2-2 for drying, and the outflowing dry working fluid flows into the second heat exchanger 2-3 to provide heat for the heating network water supply, then flows out, and enters the third heat exchanger 2-4 for circulation.

Claims

1. A waste heat recovery system for a thermal power plant coupled with thermochemical heat storage, characterized in that: It comprises a thermal power plant unit (1) and a calcium chloride thermochemical energy storage unit (2); The thermal power plant unit (1) comprises a boiler (1-1), a steam turbine high-pressure cylinder (1-2), a steam turbine low-pressure cylinder (1-3), a first heat exchanger (1-4), a condenser (1-5) and a working fluid pump (1-6); The boiler (1-1) is connected to the inlet of the high-pressure cylinder (1-2) of the steam turbine, the outlet of the high-pressure cylinder (1-2) of the steam turbine is connected to the inlet of the low-pressure cylinder (1-3) of the steam turbine, the outlet of the low-pressure cylinder (1-3) of the steam turbine is connected to the inlet of the condenser (1-5) through the first heat exchanger (1-4), the outlet of the condenser (1-5) is connected to the inlet of the working fluid pump (1-6), and the outlet of the working fluid pump (1-6) is connected to the boiler (1-1); The calcium chloride thermochemical energy storage unit (2) comprises a calcium chloride hydrate decomposition bed (2-1), a dryer (2-2), a second heat exchanger (2-3), a third heat exchanger (2-4) and a fourth heat exchanger (2-5); The outlet of the calcium chloride hydrate decomposition bed (2-1) is connected to the inlet of the dryer (2-2), and the outlet of the dryer (2-2) is connected to the inlet of the calcium chloride hydrate decomposition bed (2-1) after passing through the second heat exchanger (2-3), the third heat exchanger (2-4) and the fourth heat exchanger (2-5); The thermal power plant unit (1) and the calcium chloride thermochemical energy storage unit (2) are connected via a heat exchanger, wherein the first heat exchanger (1-4) and the third heat exchanger (2-4) are connected via a hot water circulation, and the flue gas outlet of the boiler (1-1) is connected to the fourth heat exchanger (2-5) of the calcium chloride thermochemical energy storage unit (2).

2. A waste heat recovery system for a thermal power plant coupled with thermochemical heat storage according to claim 1, characterized in that: The circulating working medium in the calcium chloride thermochemical energy storage unit (2) is air.

3. The waste heat recovery system for a thermal power plant coupled with thermochemical heat storage according to claim 1, characterized in that: In a thermal power plant unit (1), a first heat exchanger (1-4) is arranged to recover low-temperature waste heat of working fluid at the outlet of a low-pressure cylinder (1-3) of a steam turbine.

4. The waste heat recovery system for a thermal power plant coupled with thermochemical heat storage according to claim 1, characterized in that: In the calcium chloride thermochemical energy storage unit (2), the calcium chloride hydrate decomposition bed (2-1) is a solid particle fixed bed containing calcium chloride hydrate particles, and the charging temperature range is 90-150°C.

5. The waste heat recovery system for a thermal power plant coupled with thermochemical heat storage according to claim 1, characterized in that: In the calcium chloride thermochemical energy storage unit (2), the second heat exchanger (2-3) is connected to the water supply and return pipes of the heating network.

6. A waste heat recovery system for a thermal power plant coupled with thermochemical heat storage according to claim 5, characterized in that: In the calcium chloride thermochemical energy storage unit (2), the water supply temperature of the heating network is 30-80°C.

7. The waste heat recovery system for a thermal power plant coupled with thermochemical heat storage according to claim 1, characterized in that: In the calcium chloride thermochemical energy storage unit (2), the inlet working medium temperature of the calcium chloride hydrate decomposition bed (2-1) is 120-150°C, and the outlet working medium temperature is 90-100°C.

8. The waste heat recovery system for a thermal power plant coupled with thermochemical heat storage according to claim 1, characterized in that: In the calcium chloride thermochemical energy storage unit (2), the temperature of the flue gas from the boiler (1-1) passing through the fourth heat exchanger (2-5) is 150-200°C.

9. The method for operating a waste heat recovery system for a thermal power plant coupled with thermochemical heat storage according to any one of claims 1 to 8, characterized in that: The operation method of the thermal power plant unit (1) is: The working fluid enters the boiler (1-1), is heated to a high temperature and high pressure state, and then flows out, and simultaneously generates high temperature flue gas with a temperature of 150-200° C. The flue gas enters the calcium chloride thermochemical energy storage unit (2) for waste heat recovery, and the high temperature and high pressure working fluid enters the high pressure cylinder (1-2) and the low pressure cylinder (1-3) of the steam turbine in turn to expand and perform work, and then flows into the first heat exchanger (1-4) for waste heat recovery and then flows out, and then enters the working fluid pump (1-6) after being cooled by the condenser (1-5), and then returns to the boiler (1-1) for circulation after being pumped by the working fluid pump (1-6); The operation method of the calcium chloride thermochemical energy storage unit (2) is: The working medium enters the third heat exchanger (2-4) to recover the waste heat in the first heat exchanger (1-4) for preheating, then enters the fourth heat exchanger (2-5) to exchange heat with the high-temperature flue gas flowing out of the thermal power plant unit (1) and is heated to 120-150° C. before flowing out, enters the calcium chloride hydrate decomposition bed (2-1) to heat the calcium chloride hydrate solid particles to decompose them into water vapor and calcium chloride particles, and converts the heat energy of the working medium into chemical energy in the calcium chloride particles, then the generated water vapor is mixed with the working medium and flows out into the dryer (2-2) for drying, the flowing dry working medium flows into the second heat exchanger (2-3) to provide heat for the water supply of the heating network, then flows out, and enters the third heat exchanger (2-4) for circulation.

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