A thermochemical heat storage system based on hydroxide

Abstract

This invention discloses a hydroxide-based thermochemical thermal storage system, comprising a thermochemical thermal storage device, a high-temperature thermal storage tank, a low-temperature hot water storage tank, a deaerator, a feed water pump, a steam supply pump, and a steam supply header. This system uses green electricity and off-peak electricity to heat the hydroxide-based thermochemical thermal storage material to store heat, releases heat during peak heat demand, and recovers all the steam heat released during the chemical reaction of the thermal storage process through cascaded thermal storage. It has the advantages of simple system, high efficiency, high thermal storage density of the thermal storage material, no risk of solidification, decomposition reaction producing water that is non-toxic, and high safety.

Description

Technical Field

[0001] This invention belongs to the field of thermal storage technology, and particularly relates to a thermochemical thermal storage system based on hydroxides. Background Technology

[0002] The development of renewable energy has received unprecedented attention, but its biggest drawback is the intermittency and volatility of energy supply. Thermal energy storage technology, as one of the main long-term energy storage technologies, has gained increasing attention to address the intermittency and volatility of new energy sources more economically. Currently commonly used thermal energy storage technologies include molten salt thermal energy storage, hot water thermal energy storage, magnesia brick thermal energy storage, and hydride thermochemical thermal energy storage. Molten salt thermal energy storage suffers from high molten salt solidification temperatures, requiring complex preheating and anti-condensation protection systems to prevent pipe blockage. Hot water thermal energy storage results in high saturated steam pressure at higher temperatures, leading to lower storage density and larger tank volumes for the same storage density, resulting in high tank costs. Magnesia brick thermal energy storage experiences large temperature variations during heat release, with low temperatures at the end of the release phase and small heat exchange differences. Hydride thermochemical thermal energy storage releases high-temperature, high-concentration hydrogen gas during storage, posing safety risks. Storage densities are typically low, generally below 500 kJ / kg. Some thermal energy storage technologies are designed for high pressure and temperature, requiring the devices to be designed as high-temperature, high-pressure vessels, resulting in higher manufacturing and management costs. Summary of the Invention

[0003] The purpose of this invention is to address the shortcomings of existing technologies by providing a hydroxide-based thermochemical thermal storage system.

[0004] The objective of this invention is achieved through the following technical solution: a thermochemical thermal storage system based on hydroxides, comprising a thermochemical thermal storage device, a high-temperature thermal storage tank, a low-temperature hot water storage tank, a deaerator, a feed water pump, a steam supply pump, and a steam supply header; the inlet of the thermochemical thermal storage device is connected to the outlet of the feed water pump, and the steam outlet of the thermochemical thermal storage device is connected to the steam supply header; the heat release steam inlet of the thermochemical thermal storage device is connected to the high-temperature steam inlet of the high-temperature thermal storage tank; the thermal storage exhaust steam outlet of the thermochemical thermal storage device is connected to the high-temperature steam inlet of the high-temperature thermal storage tank; the high-temperature steam inlet of the high-temperature thermal storage tank is equipped with a first valve and a third valve; the high-temperature steam outlet of the high-temperature thermal storage tank is equipped with a second valve and a fourth valve; the first and second valves are used to control the opening and closing of the reaction product steam pipeline during the thermal storage stage; the third and fourth valves are used to control the opening and closing of the reaction water evaporation pipeline during the heat release stage; in the thermochemical thermal storage... A bypass pipe is installed between the water inlet and the steam outlet of the device, and a fifth valve is installed on the bypass pipe. The fifth valve is used to control the outlet steam parameters of the thermochemical thermal storage device. A reaction water makeup pipe is installed between the feed water pump and the low-temperature hot water storage tank. A reaction steam makeup pipe is installed on the steam supply header, and the reaction steam makeup pipe is connected to the exothermic steam inlet. A heat exchanger system pipe is also installed on the steam supply header. The high-temperature end of the heat exchanger system pipe is connected to the steam outlet of the thermochemical thermal storage device, and the low-temperature section of the heat exchanger system pipe is connected to the exothermic steam inlet of the thermochemical thermal storage device. A heat exchanger is installed inside the heat exchanger system pipe. The deaerator is connected to the feed water pump. The inlet of the low-temperature hot water storage tank is connected to the high-temperature steam outlet of the high-temperature thermal storage tank, the outlet of the low-temperature hot water storage tank is connected to the inlet of the steam supply pump, and the outlet of the steam supply pump is connected to the high-temperature steam outlet of the high-temperature thermal storage tank.

[0005] Furthermore, the thermochemical thermal storage device is a container capable of withstanding high temperatures; the thermochemical thermal storage device is provided with an external insulation layer, and the interior consists of thermochemical thermal storage material, an electric heater, and a steam generator.

[0006] Furthermore, the thermochemical heat storage material is a hydroxide heat storage material.

[0007] Furthermore, the hydroxide heat storage material is Ca(OH)2, Sr(OH)2, Mg(OH)2 or Ba(OH)2.

[0008] Furthermore, the electric heater is a resistance heater used to heat the thermochemical heat storage material.

[0009] Furthermore, the steam generator is a built-in heat exchange tube, the interior of which contains water and steam media.

[0010] Furthermore, the high-temperature heat storage tank contains high-temperature heat storage materials and a tubular heat exchanger.

[0011] Furthermore, the high-temperature thermal storage material is a visible thermal storage material and a phase change thermal storage material.

[0012] Furthermore, the heat storage medium of the low-temperature hot water storage tank is water.

[0013] The beneficial effects of this invention are as follows: This invention provides a hydroxide-based thermochemical thermal storage system with high thermal storage density, exceeding 1000 kJ / kg, which is more than twice that of commonly used molten salt thermal storage. The thermochemical thermal storage equipment operates at low pressure, resulting in low equipment shell cost. Simultaneously, the system is simple, the thermal storage material has no risk of solidification, and the decomposition reaction produces non-toxic water, ensuring high safety. Waste heat is recovered in stages during thermal storage, with no heat loss from emissions. Furthermore, the high thermal storage density means that for the same amount of stored heat, the surface area is smaller than that of molten salt, water, and other thermal storage materials, resulting in minimal heat dissipation loss. Attached Figure Description

[0014] Figure 1 This is a structural diagram of a hydroxide-based thermochemical thermal storage system;

[0015] In the diagram, 1-Thermochemical thermal storage device; 2-High-temperature thermal storage tank; 3-Low-temperature hot water storage tank; 4-Steam pump; 5-Deaerator; 6-Feed water pump; 7-Electric heater; 8-Steam generator; 9-Heat exchanger; 10-First valve; 11-Second valve; 12-Third valve; 13-Fourth valve; 14-Fifth valve; 15-Steam supply header; 16-Bypass pipeline; 17-Heat exchanger system pipeline; 18-Reaction water makeup pipeline; 19-Reaction steam makeup pipeline; 20-Water inlet; 21-Steam outlet; 22-Exothermic steam inlet; 23-Temperature thermal storage exhaust port; 24-High-temperature steam inlet; 25-High-temperature steam outlet. Detailed Implementation

[0016] To make the objectives, technical solutions, and advantages of this invention clearer, the invention will be further described in detail with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and not all embodiments. All other embodiments obtained by those skilled in the art based on the embodiments of this invention without inventive effort are within the scope of protection of this invention.

[0017] like Figure 1As shown, this invention provides a hydroxide-based thermochemical thermal storage system, comprising a thermochemical thermal storage device 1, a high-temperature thermal storage tank 2, a low-temperature hot water storage tank 3, a deaerator 5, a feed water pump 6, a steam supply pump 4, and a steam supply header 15. The inlet 20 of the thermochemical thermal storage device 1 is connected to the outlet of the feed water pump 6, and the steam outlet 21 of the thermochemical thermal storage device 1 is connected to the steam supply header 15; the heat release steam inlet 22 of the thermochemical thermal storage device 1 is connected to the high-temperature steam inlet 24 of the high-temperature thermal storage tank 2; and the thermal storage exhaust steam outlet 23 of the thermochemical thermal storage device 1 is connected to the high-temperature steam inlet 24 of the high-temperature thermal storage tank 2. The high-temperature steam inlet 24 of the high-temperature thermal storage tank 2 is equipped with a first valve 10 and a third valve 12; the high-temperature steam outlet 25 of the high-temperature thermal storage tank 2 is equipped with a second valve 11 and a fourth valve 13; the first valve 10 and the second valve 11 are used to control the opening and closing of the steam pipeline of the reaction product during the thermal storage stage; the third valve 12 and the fourth valve 13 are used to control the opening and closing of the evaporation pipeline of the reaction water during the exothermic stage. The first valve 10 is located between the thermal storage exhaust port 23 and the high-temperature steam inlet 24; the second valve 11 is located between the high-temperature steam outlet 25 and the inlet of the low-temperature hot water storage tank 3; the third valve 12 is located between the exothermic steam inlet 22 and the high-temperature steam inlet 24; the fourth valve 13 is located between the outlet of the steam supply pump 4 and the high-temperature steam outlet 25. A bypass pipe 16 is provided between the water inlet 20 and the steam outlet 21 of the thermochemical thermal storage device 1, and a fifth valve 14 is provided on the bypass pipe 16; the fifth valve 14 is used to control the outlet steam parameters of the thermochemical thermal storage device 1. A reaction water makeup pipe 18 is installed between the water supply pump 6 and the low-temperature hot water storage tank 3 to replenish the reaction water in the low-temperature hot water storage tank 3. A reaction steam makeup pipe 19 is installed on the steam supply header 15, and the reaction steam makeup pipe 19 is connected to the exothermic steam inlet 22 for emergency steam makeup during the exothermic reaction of the thermochemical thermal storage device 1. A heat exchanger system pipe 17 is also installed on the steam supply header 15. The high-temperature end of the heat exchanger system pipe 17 is connected to the steam outlet 21 of the thermochemical thermal storage device 1, and the low-temperature section of the heat exchanger system pipe 17 is connected to the exothermic steam inlet 22 of the thermochemical thermal storage device 1; a heat exchanger 9 is installed inside the heat exchanger system pipe 17. The deaerator 5 is connected to the water supply pump 6; the inlet of the low-temperature hot water storage tank is connected to the high-temperature steam outlet 25 of the high-temperature hot water storage tank 2; the outlet of the low-temperature hot water storage tank 3 is connected to the inlet of the steam supply pump 4; and the outlet of the steam supply pump 4 is connected to the high-temperature steam outlet 25 of the high-temperature hot water storage tank 2.

[0018] The thermochemical heat storage device 1 is a container that can withstand high temperatures; the thermochemical heat storage device 1 is provided with an external insulation layer, and the interior consists of thermochemical heat storage material, an electric heater 7, and a steam generator 8.

[0019] The thermochemical heat storage material is a hydroxide heat storage material. The hydroxide heat storage material is Ca(OH)₂, Sr(OH)₂, Mg(OH)₂, or Ba(OH)₂. The thermochemical heat storage material can also be a material that decomposes into water and other reactants when heated in a reversible reaction.

[0020] The thermochemical heat storage material mainly utilizes the reaction between water (steam) and metal oxides to store and release heat. Its chemical reaction principle is as follows:

[0021] The electric heater 7 is a resistance heater used to heat the thermochemical heat storage material and convert electrical energy into thermochemical energy.

[0022] The steam generator 8 is a built-in heat exchange tube, the interior of which contains water and steam media. The heat exchange tube is a finned heat exchange tube, which is modularly designed and manufactured as an integral part of the thermochemical heat storage material. Its function is to reduce the heat exchange resistance of water and steam in the thermochemical heat storage material and the finned heat exchange tube, thereby enhancing heat exchange.

[0023] The high-temperature thermal storage tank 2 contains high-temperature thermal storage material and a tubular heat exchanger. The function of the high-temperature thermal storage tank 2 is to absorb the high-grade heat from the high-temperature steam emitted during the thermal storage process; the medium inside the tubes is steam. The high-temperature thermal storage material can be a sensible thermal storage material or a phase change thermal storage material. The sensible thermal storage material can be concrete, steel, or sand. The phase change thermal storage material can be molten salt, paraffin wax, sugar alcohol, or polyethylene.

[0024] The heat storage medium of the low-temperature hot water storage tank 3 is water, and steam is directly injected for mixing and heat exchange. The low-temperature hot water storage tank 3 is used to directly inject steam or hot water after heat exchange in the high-temperature heat storage tank 2 into the hot water tank for mixing and heat exchange with water. Its function is to absorb the low-grade heat of the high-temperature steam emitted during the heat storage process.

[0025] The heat exchanger 9 can be a shell-and-tube type, plate type, or microchannel heat exchanger. Its function is to open the heat exchanger system pipeline 17 when the temperature of the high-temperature heat storage tank 2 is insufficient to evaporate the water at the outlet of the steam supply pump 4 in the later stage of heat release, so as to heat the reaction water at the outlet of the steam supply pump 4 through the main steam at the outlet of the thermochemical heat storage device 1.

[0026] The deaerator 5 is used to remove dissolved oxygen from the water, prevent corrosion of the steam generator, and ensure safe operation.

[0027] The water pump 6 is used to deliver water to the steam generator for heating, ensuring the outlet steam pressure of the steam generator 8.

[0028] The steam pump 4 delivers the reaction water to the low-temperature hot water storage tank 3 and the high-temperature heat storage tank 2 for heat exchange and evaporation, thus providing reaction water for the thermochemical heat storage device 1.

[0029] In this embodiment, the specific working process of the present invention is as follows: During heat storage, the electric heater 7 inside the thermochemical heat storage device 1 heats the material, and then the high-temperature heat storage material absorbs heat and undergoes a chemical reaction, releasing high-temperature water vapor. The water vapor passes through the high-temperature heat storage tank 2 for heat exchange and storage, and then enters the low-temperature hot water storage tank 3. The residual heat of the released steam is completely stored in stages. At this time, the first valve 10 and the second valve 11 are open, and the third valve 12 and the fourth valve 13 are closed. During heat release, the hot water stored in the low-temperature hot water storage tank 3 is transported to the high-temperature heat storage tank 2 for heat exchange via the steam supply pump 4. After heat exchange, it becomes water vapor and enters the thermochemical heat storage device 1 to react with the high-temperature heat storage material, releasing heat. At this time, the first valve 10 and the second valve 11 are closed, and the third valve 12 and the fourth valve 13 are open. In the later stage of heat release, when the temperature of the high-temperature heat storage tank 2 is insufficient to evaporate the water at the outlet of the steam supply pump 4, the heat exchanger system pipeline 17 is opened, and the main steam at the outlet of the thermochemical heat storage device 1 heats the reaction water at the outlet of the steam supply pump 4. Meanwhile, water from deaerator 5 is pumped by feedwater pump 6 to thermochemical thermal storage device 1 to absorb heat and turn into steam for power generation and heating. The bypass pipeline 16 controls the stability of the outlet steam parameters by adjusting the fifth valve 14. During the startup phase of the new device or when reaction water is lost, reaction water is replenished to the low-temperature hot water storage tank 3 through the reaction water makeup pipeline 18. When the high-temperature thermal storage tank 2 or the low-temperature hot water storage tank 3 fails, the steam supply header 15 connected to thermochemical thermal storage device 1 is used for emergency steam replenishment for the exothermic reaction of thermochemical thermal storage device 1 through the reaction steam makeup pipeline 19.

[0030] The above description is only a preferred 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 within the scope of protection of the present invention.

Claims

1. A thermochemical thermal storage system based on hydroxides, characterized in that, The system includes a thermochemical thermal storage device (1), a high-temperature thermal storage tank (2), a low-temperature hot water storage tank (3), a deaerator (5), a feed water pump (6), a steam supply pump (4), and a steam supply header (15); the inlet (20) of the thermochemical thermal storage device (1) is connected to the outlet of the feed water pump (6), and the steam outlet (21) of the thermochemical thermal storage device (1) is connected to the steam supply header (15); the heat release steam inlet (22) of the thermochemical thermal storage device (1) is connected to the high-temperature steam inlet (24) of the high-temperature thermal storage tank (2); and the thermal storage exhaust steam outlet (23) of the thermochemical thermal storage device (1) is connected to the high-temperature thermal storage tank (2). The high-temperature steam inlet (24) of the high-temperature heat storage tank (2) is connected to the high-temperature steam inlet (24); the high-temperature steam inlet (24) of the high-temperature heat storage tank (2) is equipped with a first valve (10) and a third valve (12); the high-temperature steam outlet (25) of the high-temperature heat storage tank (2) is equipped with a second valve (11) and a fourth valve (13); the first valve (10) and the second valve (11) are used to control the opening and closing of the steam pipeline of the reaction product in the heat storage stage; the third valve (12) and the fourth valve (13) are used to control the opening and closing of the evaporation pipeline of the reaction water in the heat release stage; the water inlet (20) and the steam outlet (21) of the thermochemical heat storage device (1) are connected to the high-temperature steam inlet (24); the high-temperature steam inlet (24) of the high-temperature heat storage tank (2) is equipped with a first valve (10) and a third valve (12); the high-temperature steam outlet (25) of the high-temperature heat storage tank (2) is equipped with a second valve (11) and a fourth valve (13); the first valve (10) and the second valve (11) are used to control the opening and closing of the steam pipeline of the reaction product in the heat storage stage; the third valve (12) and the fourth valve (13) are used to control the opening and closing of the steam pipeline of the reaction water in the heat release stage; the water inlet (20) and the steam outlet (21) of the thermochemical heat storage device (1) are connected to the high-temperature steam inlet (24); the high-temperature steam inlet (24) of the high-temperature heat storage tank (2) is equipped with a first valve (10) and a third valve (12); the high-temperature steam outlet (25) of the high-temperature heat storage tank (2) is connected to the high-temperature steam inlet (24); the high-temperature steam outlet (24) of A bypass pipe (16) is provided between the two, and a fifth valve (14) is provided on the bypass pipe (16); the fifth valve (14) is used to control the outlet steam parameters of the thermochemical thermal storage device (1); a reaction water makeup pipe (18) is provided between the feed water pump (6) and the low-temperature hot water storage tank (3); a reaction steam makeup pipe (19) is provided on the steam supply header (15), and the reaction steam makeup pipe (19) is connected to the heat release steam inlet (22); a heat exchanger system pipe (17) is also provided on the steam supply header (15), and the heat exchanger system pipe (17) The high-temperature end is connected to the steam outlet (21) of the thermochemical heat storage device (1), and the low-temperature section of the heat exchanger system pipeline (17) is connected to the heat release steam inlet (22) of the thermochemical heat storage device (1); a heat exchanger (9) is installed in the heat exchanger system pipeline (17); the deaerator (5) is connected to the feed water pump (6); the inlet of the low-temperature hot water storage tank is connected to the high-temperature steam outlet (25) of the high-temperature heat storage tank (2), the outlet of the low-temperature hot water storage tank (3) is connected to the inlet of the steam supply pump (4), and the outlet of the steam supply pump (4) is connected to the high-temperature steam outlet (25) of the high-temperature heat storage tank (2).

2. The hydroxide-based thermochemical thermal storage system according to claim 1, characterized in that, The thermochemical heat storage device (1) is a container that can withstand high temperatures; the thermochemical heat storage device (1) is provided with an insulation layer on the outside and thermochemical heat storage material, electric heater (7) and steam generator (8) on the inside.

3. The hydroxide-based thermochemical thermal storage system according to claim 2, characterized in that, The thermochemical heat storage material is a hydroxide heat storage material.

4. The hydroxide-based thermochemical thermal storage system according to claim 3, characterized in that, The hydroxide thermal storage material is Ca(OH)2, Sr(OH)2, Mg(OH)2 or Ba(OH)2.

5. A hydroxide-based thermochemical thermal storage system according to claim 2, characterized in that, The electric heater (7) is a resistance heater used to heat thermochemical heat storage materials.

6. The thermochemical thermal storage system based on hydroxides according to claim 2, characterized in that, The steam generator (8) is a built-in heat exchange tube, and the interior of the heat exchange tube contains water and steam media.

7. The thermochemical thermal storage system based on hydroxides according to claim 1, characterized in that, The high-temperature heat storage tank (2) contains high-temperature heat storage materials and a tubular heat exchanger.

8. The hydroxide-based thermochemical thermal storage system according to claim 7, characterized in that, The high-temperature thermal storage material is either a visible thermal storage material or a phase change thermal storage material.

9. The thermochemical thermal storage system based on hydroxides according to claim 1, characterized in that, The heat storage medium of the low-temperature hot water storage tank (3) is water.

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