Single-tank molten salt heat storage and heating system and control method thereof

Abstract

The present invention discloses a single-tank molten salt heat storage heating system and a control method thereof; the heating system includes a molten salt tank; the interior of the molten salt tank is provided with a heat exchange tube and a group of electric heaters uniformly spaced along the circumference; the electric heater is arranged in a high-temperature zone inside the molten salt tank for heating the molten salt; the heat exchange tube is arranged in a low-temperature zone inside the molten salt tank for exchanging heat with the heated molten salt; the water inlet of the heat exchange tube is connected to the water outlet of a water supply pump through a water inlet pipe, and the water inlet of the water supply pump is connected to the water outlet of a water supply device; a desuperheater is connected at the water outlet of the heat exchange tube for regulating the temperature and pressure of the output steam; the electric heater and the water supply pump are electrically connected to a control module respectively. The heating system of the present invention can be flexibly controlled according to the actual operation of the system, has high stability and good safety, does not require special personnel on duty when in use, and has a compact overall structure, small footprint, and low cost of use.

Description

Technical Field

[0001] The present invention relates to the technical field of molten salt energy storage, and in particular to a single-tank molten salt heat storage and heating system and a control method thereof. Background Art

[0002] Molten salt energy storage is a technology that converts chemical energy into thermal energy, and then into electricity or other medium thermal energy. Its basic principle is to heat molten salt to a high temperature and store thermal energy (taking ternary salt as an example, when the storage temperature is 535°C, 1 ton of molten salt can store about 120kWh of thermal energy). When electricity or other medium thermal energy is needed, the thermal energy is converted into electricity or other medium thermal energy. The core of molten salt energy storage is the high-temperature melting property of salts, which enables energy to be converted and stored at high temperature and high thermal efficiency. It is highly flexible and can respond quickly to energy fluctuations and smoothly maintain system stability. As an advanced high-temperature energy storage technology, molten salt energy storage has the advantages of low cost and zero pollution. In addition to the field of solar thermal power generation, it has broad application prospects in heating, steam supply, and flexible transformation of thermal power units.

[0003] Traditional molten salt heat storage technology mainly adopts a hot and cold dual-tank system (hot molten salt tank and cold molten salt tank) to store heat. When storing heat, the molten salt in the cold molten salt tank is heated, and the heated molten salt is introduced into the hot molten salt tank; when releasing heat, the molten salt in the hot molten salt tank is discharged for heat exchange, and the heated molten salt is returned to the cold molten salt tank. Although the application of dual-tank molten salt heat storage technology is relatively mature, it has disadvantages such as high investment cost, long investment recovery period, large equipment footprint, cumbersome operation and management, slow steam production speed, and difficult maintenance. In view of this, many manufacturers have begun to study single-tank molten salt heat storage technology. However, the control of the single-tank molten salt heat storage system in the existing technology is relatively simple, and it cannot be flexibly controlled according to the actual operation conditions of the system, resulting in high energy costs, and it cannot guarantee the safe and stable operation of the heat storage system under low load. Long-term use is likely to cause damage to related equipment. Summary of the Invention

[0004] In order to overcome the above-mentioned problems existing in the prior art, the present application provides a single-tank molten salt heat storage and heating system. The single-tank molten salt heat storage and heating system of the present application is equipped with an electric heater and a heat exchange tube integrated inside the molten salt tank, and a desuperheater is provided at the water outlet of the heat exchange tube, which can adjust the temperature of the output steam to avoid serious water in the steam and ensure the temperature stability of the output steam; and it can be flexibly controlled according to the actual operation conditions of the system, with high stability and good safety. It does not require special personnel on duty during use, and the labor cost is low; in addition, the overall structure of the heating system of the present application is compact and occupies a small area. It can meet the energy storage needs of most factory areas, has low use costs and is easy to promote. Correspondingly, the present application also provides a control method for the above-mentioned single-tank molten salt heat storage and heating system.

[0005] The technical solution of this application is:

[0006] A single-tank molten salt heat storage and heating system comprises a molten salt tank; a salt injection port is provided on the top of the molten salt tank, and a salt discharge port is provided on the bottom; a heat exchange tube and a group of electric heaters are provided inside the molten salt tank; the electric heater is used to heat the molten salt; the heat exchange tube is used to exchange heat with the heated molten salt, and heat the water in the heat exchange tube to generate steam; the water inlet of the heat exchange tube is connected to the water outlet of the water feed pump through a water inlet pipe, and the water inlet of the water feed pump is connected to the water outlet of a water supply device; the water supply device is used to provide pure water; a desuperheater is connected to the water outlet of the heat exchange tube; the water spray port of the desuperheater is connected to the water outlet of the water feed pipe The channel is connected to the water outlet of the water supply pump; a group of A thermocouples are provided inside the molten salt tank for real-time monitoring of the temperature of the molten salt in the molten salt tank; the inlet and outlet of the desuperheater are respectively provided with B thermocouples and C thermocouples for real-time monitoring of the temperature of the steam in the desuperheater; the outlet of the desuperheater is also provided with a pressure sensor for real-time monitoring of the outlet pressure of the desuperheater; the water outlet of the desuperheater is provided with a desuperheating water regulating valve; the outlet of the desuperheater is provided with a steam regulating valve; the A thermocouple, B thermocouple, C thermocouple, pressure sensor, electric heater, water supply pump, desuperheating water regulating valve and steam regulating valve are respectively electrically connected to the control module.

[0007] The single-tank molten salt heat storage and heating system of the present application is equipped with an electric heater and a heat exchange tube integrated in the molten salt tank, and a desuperheater is provided at the water outlet of the heat exchange tube, which can adjust the temperature of the output steam to avoid serious water content in the steam, ensure the temperature stability of the output steam, and achieve good heating effect; and by setting monitoring units such as thermocouples and pressure sensors, it can be flexibly controlled according to the actual operation conditions of the system, with high operation stability and good safety. It does not require special personnel on duty during use, reducing labor costs; in addition, the overall structure of the heating system of the present application is compact and occupies a small area, which can meet the energy storage needs of most factory areas. It can heat and store the molten salt in the molten salt tank during off-peak hours, and use high-temperature molten salt to exchange heat with the heat exchange tube during peak hours to heat the water in the heat exchange tube into steam and transport it to users, thereby realizing long-term energy storage and heat release, low cost of use, and easy promotion.

[0008] As an optimization, in the aforementioned single-tank molten salt thermal storage heating system, the water supply device includes a raw water tank, a pure water tank, and a water purifier located between the raw and pure water tanks. The water purifier comprises multiple filters, a high-pressure pump, and a reverse osmosis unit, purifying the water in the raw water tank to output pure water. The water inlet of the water pump is connected to the outlet of the pure water tank via an outlet pipe. The water supply device utilizes multi-stage filtration and reverse osmosis to treat the feed water, which is easy to implement and has excellent treatment effects. The treated water quality meets the GB / T1576-2018 standard, thereby ensuring safe and stable operation of the evaporator. The water purifier is equipped with a water quality detector. Furthermore, the water supply device can be equipped with a timer to control the water supply device to start purification during off-peak hours. Furthermore, the pure water tank is equipped with a liquid level switch to control the liquid level in the pure water tank, ensuring that the pure water in the pure water tank neither overflows nor drains, and that there is always water, thereby ensuring the safety and stability of the heating process. Furthermore, the liquid level switch may be a float type liquid level switch, which controls the liquid level by the correspondence between the height of the float and the switch.

[0009] As an optimization, in the aforementioned single-tank molten salt heat storage and heating system, two ultrasonic liquid level gauges electrically connected to the control module are provided on the top of the molten salt tank to monitor the liquid level of the molten salt in the molten salt tank in real time to ensure the safety of the operation of the heating system; and two liquid level gauges are provided to ensure measurement accuracy.

[0010] As an optimization, in the aforementioned single-tank molten salt heat storage and heating system, an exhaust pipe is installed above the salt injection port, communicating with the interior of the molten salt tank. This allows for the molten salt to expand during heating, balancing internal and external pressures and further ensuring safe evaporator operation. Furthermore, positioning the exhaust pipe above the salt injection port reduces space requirements.

[0011] As an optimization, in the aforementioned single-tank molten salt heat storage and heating system, a safety valve is installed at the water inlet of the heat exchange tube and the water inlet of the desuperheater. When the pressure exceeds the safety valve setting value, the safety valve automatically trips, providing high reliability.

[0012] As an optimization, in the aforementioned single-tank molten salt heat storage and heating system, the water outlet of the feedwater pump is connected to a bypass line, the other end of which is connected to the pure water tank; a bypass valve is provided on the bypass line. Thus, when the feedwater pump is adjusted to the minimum safe operating flow rate, but still exceeds the pure water flow rate required by the molten salt tank, the bypass valve can be opened to allow some water to return to the pure water tank, thereby reducing the feedwater flow rate. This ensures that the pure water flow rate input to the molten salt tank is less than the minimum safe operating flow rate of the feedwater pump while also protecting the feedwater pump from damage.

[0013] As an optimization, in the aforementioned single-tank molten salt heat storage and heating system, a flow meter is installed on the water outlet pipe to monitor the flow of pure water in the pipe in real time. When the detected flow rate is less than the set value, it indicates that the molten salt energy storage has been utilized, and the water supply pump needs to be controlled to stop.

[0014] As an optimization, in the aforementioned single-tank molten salt thermal storage and heating system, each electric heater is equipped with two D thermocouples. When the molten salt temperature at the center of the heater tube exceeds a set temperature, the heater automatically stops heating, preventing burnout and ensuring its service life.

[0015] The present application also provides a control method for the single-tank molten salt heat storage and heating system of the present application, which is as follows: during the off-peak period, the control module controls the electric heater to start, heats the molten salt in the molten salt tank, and at the same time, the A thermocouple monitors the temperature of the molten salt in the molten salt tank in real time. If the detected molten salt temperature exceeds the set value, the electric heater is controlled to be powered off; during the peak period, the control module controls the water supply pump to start, and the pure water in the water supply device is pumped into the heat exchange tube; the heated molten salt exchanges heat with the heat exchange tube in the low temperature zone, and heats the pure water in the heat exchange tube to generate steam, and the steam enters the desuperheater from the water outlet of the heat exchange tube for temperature and pressure regulation, and is then delivered to the user; the temperature and pressure regulation process is as follows: the B thermocouple and the C thermocouple monitor the temperature of the steam entering the desuperheater in real time, and the pressure sensor monitors the outlet pressure of the desuperheater in real time; if the B thermocouple detects When the temperature of the steam flowing out of the water outlet of the heat exchange tube is not higher than the set temperature, the attemperating water regulating valve is closed; when the B thermocouple detects that the steam flowing out of the water outlet of the heat exchange tube exceeds the set temperature, the attemperating water regulating valve is opened, and cooling water is sprayed into the desuperheater to evaporate it into water vapor and mix with the superheated steam inside. During this process, if the C thermocouple detects that the steam temperature at the desuperheater outlet is higher than the set temperature, the flow rate of the attemperating water regulating valve is increased until the C thermocouple detects that the steam temperature at the desuperheater outlet is lower than the set temperature, then the attemperating water regulating valve is closed and the water spraying is stopped; at the same time, when the B thermocouple detects that the steam flowing out of the water outlet of the heat exchange tube is lower than the set temperature or the pressure sensor detects that the outlet pressure is higher than the set value, the flow rate of the feed water pump is reduced; when the pressure sensor detects that the outlet pressure is lower than the set value, the opening of the steam regulating valve is reduced.

[0016] Compared with the existing technology, the control method of the single-tank molten salt heat storage and heating system of the present application controls the electric heater to heat the molten salt in the molten salt tank to store energy during the off-peak period, and uses the high-temperature molten salt to exchange heat with the heat exchange tube during the peak period, and heats the water in the heat exchange tube into steam and transports it to the user, thereby realizing long-term energy storage and heat release; at the same time, during the heat exchange process, the temperature and pressure of the output steam are detected by thermocouples and pressure sensors, and the water feed pump and regulating valve are frequency-controlled to avoid serious water contamination in the steam, thereby ensuring the temperature stability of the output steam, good heating effect, high system operation stability and good safety. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 This is a schematic diagram of the structure of the single-tank molten salt heat storage and heating system of the present application;

[0018] Figure 2 This is a schematic diagram of the structure of the single-tank molten salt heat storage and heating system of the present application;

[0019] Figure 3 It is a structural diagram of a single-tank molten salt heat storage and heating system in an embodiment of the present application;

[0020] Figure 4 Schematic diagram of the structure of the water supply device in the embodiment of the present application;

[0021] Figure 5 It is a structural principle diagram of the water supply device in the embodiment of the present application;

[0022] Figure 6 This is a control principle diagram of the single-tank molten salt heat storage and heating system of this application.

[0023] The markings in the attached figure are: 1-molten salt tank, 101-salt injection port, 102-salt discharge port, 103-upper cover plate; 2-heat exchange tube; 3-electric heater, 301-D thermocouple; 4-A thermocouple; 5-diversion fence; 6-water pump; 7-water supply device, 701-raw water tank, 702-pure water tank, 703-water purifier, 7031-quartz sand filter, 7032-activated carbon filter, 7033-scale inhibition and dosing system, 7034-precision filter, 7035-first-stage high-pressure pump, 7036-first-stage reverse osmosis unit, 7037 -Secondary high-pressure pump, 7038-Secondary reverse osmosis unit, 704-Raw water pump, 705-Water quality detector, 706-Liquid level switch; 8-Desuperheater, 801-Thermocouple B, 802-Thermocouple C, 803-Pressure sensor, 804-Desuperheating water regulating valve, 805-Steam regulating valve; 9-Liquid level gauge; 10-Exhaust pipe; 11-Center tube sheet; 12-Lifting ring; 13-Insulation layer; 14-Safety valve; 15-Support rod; 16-Bypass valve; 17-Flow meter; 18-Control module; 19-Heat-using equipment; 20-Drain valve. DETAILED DESCRIPTION

[0024] The present application is further described below with reference to the accompanying drawings and embodiments, but they are not intended to limit the present application.

[0025] In order to overcome the problems of the molten salt heat storage system in the prior art, such as large equipment footprint, high investment cost, slow steam production speed, difficult maintenance and the risk of solidification and freezing, the present application provides a single-tank molten salt heat storage and heating system, which integrates salt storage, electric heating and heat exchange, and can be flexibly controlled according to the actual operation conditions of the system. It has high stability and good safety. It does not require special personnel on duty during use, and the labor cost is low. In addition, the overall structure is simple and compact, and the investment is small. It is suitable for small-scale retail steam supply, heating, hot water supply, clean electricity consumption and other fields.

[0026] See also Figure 1 and Figure 2 , a single tank molten salt heat storage and heating system, comprising a molten salt tank 1; a salt injection port 101 is provided on the top of the molten salt tank 1, and a salt discharge port 102 is provided on the bottom (to facilitate the discharge of molten salt when the heating system is shut down or under maintenance); a heat exchange tube 2 and a group of electric heaters 3 are provided inside the molten salt tank 1; the electric heater 3 is used to heat the molten salt; the heat exchange tube 2 is used to exchange heat with the heated molten salt, and heat the water in the heat exchange tube 2 to generate steam; the water inlet of the heat exchange tube 2 is connected through the water inlet pipe The heat exchange tube 2 is connected to the water outlet of the water pump 6 (a drain valve 20 is provided on the water inlet pipe for draining water when the heating system is under maintenance or shut down), and the water inlet of the water pump 6 is connected to the water outlet of the water supply device 7; the water supply device 7 is used to provide pure water; the water outlet of the heat exchange tube 2 is connected to the desuperheater 8; the water outlet of the desuperheater 8 is connected to the water outlet of the water pump 6 through the water supply pipe; a group of A thermocouples 4 are provided inside the molten salt tank 1 for real-time monitoring of the temperature of the molten salt in the molten salt tank 1 The inlet and outlet of the desuperheater 8 are respectively provided with a B thermocouple 801 and a C thermocouple 802 for real-time monitoring of the temperature of the steam in the desuperheater 8; the outlet of the desuperheater 8 is also provided with a pressure sensor 803 for real-time monitoring of the outlet pressure of the desuperheater 8; the water outlet of the desuperheater 8 is provided with a desuperheating water regulating valve 804; the outlet of the desuperheater 8 is provided with a steam regulating valve 805, the outlet of the steam regulating valve 805 is connected to the heat-using device 19; when the B thermocouple 801 detects that the steam coming out of the heat exchange tube 2 When the steam flowing out of the water outlet exceeds the set temperature, the cooling water regulating valve 804 opens and sprays cooling water into the desuperheater 8, causing it to evaporate into water vapor and mix with the superheated steam inside until the steam temperature detected by the C thermocouple 805 meets the set temperature, and the water spraying is stopped; the electric heater 3, A thermocouple 4, water feed pump 6, B thermocouple 801, C thermocouple 802, pressure sensor 803, cooling water regulating valve 804 and steam regulating valve 805 are respectively electrically connected to the control module 18.

[0027] The heating medium of the heating system of the present application is pure water, and the product is steam. Trace impurities in the water are allowed to deposit on the inner wall of the heat exchange tube 2; the life of the heat exchange tube 2 can be determined by calculating the amount of deposition.

[0028] The heating system of the present application can use low-valley electricity to heat the molten salt in the molten salt tank 1 during off-peak hours, and use the heat in the molten salt tank 1 to heat the water in the heat exchange tube 2 during peak hours to generate steam for delivery to users. For example, it can be supplied to enterprises that require high-temperature steam in production processes such as chemical and papermaking, or to small generators for power generation. The setting of the desuperheater 8 can ensure the temperature stability of the output steam. In actual operation, the operating temperature of the output steam of the heating system can be set to slightly superheated (pressure 1.0MPa, temperature 190°C) to avoid serious water contamination in the steam and ensure steam quality.

[0029] Example:

[0030] In this embodiment, six evenly spaced electric heaters 3 are provided inside the molten salt tank 1; each electric heater 3 is provided with two D thermocouples 301 for real-time monitoring of the molten salt temperature at the center of the electric heater tube. Eight evenly spaced A thermocouples 4 are provided inside the molten salt tank 1 for real-time monitoring of the molten salt temperature in various areas within the molten salt tank 1.

[0031] In this embodiment, the thermocouples A, B, C, and D are K-type thermocouples.

[0032] See also Figure 3 In this embodiment, the electric heater 3 surrounds the outside of the heat exchange tube 2, and a guide fence 5 is provided between the heat exchange tube 2 and the electric heater 3 (in order to clearly show the heat exchange tube 2, the guide fence 5 is transparent); the guide fence 5 is opened at the top and bottom, surrounds the outside of the heat exchange tube 2, and divides the internal space of the molten salt tank 1 into a high temperature zone and a low temperature zone; the space inside the guide fence 5 is the low temperature zone, and the space between the molten salt tank 1 and the guide fence 5 is the high temperature zone; the electric heater 3 is located in the high temperature zone, and the The heat exchange tubes 2 are located in the low-temperature zone. When the molten salt releases heat, the molten salt in the diversion fence 5 exchanges heat with the heat exchange tubes 2, heating the water in the heat exchange tubes 2 into steam. At this time, the molten salt temperature drops and its density increases, flowing toward the bottom of the molten salt tank 1. The molten salt in the high-temperature zone, due to its relatively high temperature and low density, flows toward the top of the molten salt tank 1. After the high-temperature molten salt accumulates at the top of the molten salt tank 1, it enters the diversion fence 5 through the opening above the diversion fence 5, thus forming a natural flow loop, allowing the molten salt to circulate naturally within the molten salt tank 1. The diversion fence 5 is square in shape.

[0033] See also Figure 4 and Figure 5The water supply device 7 includes a raw water tank 701, a pure water tank 702, and a water purifier 703 arranged between the raw water tank 701 and the pure water tank 702; the water purifier 703 includes a quartz sand filter 7031, an activated carbon filter 7032, a scale inhibition and dosing system 7033, a precision filter 7034, a first-level high-pressure pump 7035, a first-level reverse osmosis unit 7036, a second-level high-pressure pump 7037 and a second-level reverse osmosis unit 7038, which are used to purify the water in the raw water tank 701 to output pure water; a raw water pump 704 is provided between the raw water tank 701 and the quartz sand filter 7031; the water inlet of the water supply pump 6 is connected to the water outlet of the pure water tank 702 through an outlet pipe. The water supply device 7 uses the principle of multi-stage filtration and reverse osmosis to treat the water supply, which is easy to implement and has a good treatment effect, so that the water quality after treatment can meet the GB / T1576-2018 standard, thereby ensuring the safety and stability of the evaporator operation. The water purifier 703 is provided with a water quality detector 705 for detecting the water purified by the purifier 703. Furthermore, a flow meter 17 is provided on the outlet pipe for real-time monitoring of the flow of pure water in the pipe; when the detected flow is less than the set value, it means that the molten salt energy storage has been utilized, and it is necessary to control the water supply pump to stop working. Furthermore, a time-controlled switch is also provided in the water supply device 7 for controlling the water supply device 7 to start purification during the off-peak period. Furthermore, the pure water tank 702 is equipped with a float-type liquid level switch 706. The corresponding relationship between the height of the float and the switch controls the liquid level in the pure water tank 702. This ensures that the pure water in the pure water tank 702 neither overflows nor drains, and always has water, thereby ensuring the safety and stability of the heating process. The water inlet of the raw water tank 701 is connected to natural water, and the raw water tank 701 is also equipped with a float-type liquid level switch for controlling the liquid level.

[0034] In this embodiment, two ultrasonic level gauges 9 are installed on the top of the molten salt tank 1 to monitor the molten salt level in real time, ensuring the safe operation of the heating system. The presence of two level gauges 9 ensures measurement accuracy. Furthermore, ultrasonic level gauges are microprocessor-controlled digital level meters that utilize a non-contact measurement method. The measured medium is virtually unlimited and can be widely used to measure the height of various liquid and solid materials.

[0035] In this embodiment, an exhaust pipe 10 is provided above the salt injection port 101, and the exhaust pipe 10 is connected to the interior of the molten salt tank 1 (a mounting plate is provided at the salt injection port 101, and the exhaust pipe 10 is fixed to the mounting plate; when in use, the mounting plate can be removed for salt injection). As a result, when the volume of the molten salt expands during heating, exhaust can be exhausted through the exhaust pipe 10 to balance the internal and external pressures, further ensuring the operational safety of the evaporator; in addition, connecting the exhaust pipe 10 from the salt injection port 101 can reduce the occupied space. The exhaust pipe 10 needs to be connected to a safe place.

[0036] In this embodiment, a safety valve 14 is provided at the water inlet of the heat exchange tube 2 and the water inlet of the desuperheater 8. When the pressure exceeds the set value of the safety valve 14, the safety valve 14 automatically trips, and the reliability of use is high.

[0037] In this embodiment, the water outlet of the water supply pump 6 is connected to a bypass line, the other end of which is connected to the pure water tank 702; a bypass valve 16 is provided on the bypass line. Thus, when the water supply pump 6 is adjusted to the minimum safe operating flow rate (in this embodiment, the minimum safe operating flow rate is 250 kg / h), if it is still higher than the pure water flow rate required by the molten salt tank 1, the bypass valve 16 can be opened to allow some water to return to the pure water tank 702 to reduce the water supply flow rate, thereby achieving the pure water flow rate input to the molten salt tank 1 less than the minimum safe operating flow rate of the water supply pump 6, and ensuring that the water supply pump 6 will not be damaged.

[0038] In this embodiment, the heat exchange tube 2 is fixed on the central tube plate 11; the central tube plate 11 is detachably connected to the upper cover plate 103 of the molten salt tank 1 (connected by a flange). Therefore, when the heat exchange tube 2 is damaged and needs to be replaced, the central tube plate 11 can be directly lifted upwards and the heat exchange tube 2 can be pulled out from the top without cutting the tank body of the molten salt tank 1, which is very convenient for maintenance. Furthermore, two lifting rings 12 are symmetrically provided on the top of the central tube plate 11. Therefore, during later maintenance, the lifting rope can be installed in the lifting ring 12, and then the central tube plate 11 can be lifted and moved using a crane, which is more convenient to operate. An insulation layer 13 is provided on the outer wall of the molten salt tank 1 to reduce the heat loss of the molten salt tank; the material of the insulation layer 13 is aerogel, and the insulation thickness is 200mm; when arranged indoors, when the molten salt temperature is 410°C, the outer wall temperature is not greater than the ambient temperature plus 10°C.

[0039] In this embodiment, the electric heater 3 is used to heat the molten salt in the tank during the off-peak period; during the peak period, the high-temperature molten salt in the molten salt tank 1 is used to exchange heat with the heat exchange tube 2. The water in the heat exchange tube 2 is heated by the molten salt to generate slightly superheated steam which is transported to the user, completing the molten salt heat release cycle.

[0040] See also Figure 6 The control method of the single-tank molten salt heat storage and heating system of this embodiment is as follows:

[0041] During the off-peak period, the control module 18 controls the electric heater 3 to start and heat the molten salt in the molten salt tank 1. At the same time, the thermocouple A 4 monitors the temperature of the molten salt in the molten salt tank 1 in real time, and the thermocouple D 301 monitors the temperature of the molten salt at the center of the electric heater tube in real time. If it is detected that the molten salt temperature in the molten salt tank 1 exceeds the set value (410°C), or if it is detected that the molten salt temperature at the center of the electric heater tube exceeds the set value (450°C), the electric heater 3 is controlled to be powered off; the water supply device 7 is started, and the raw water pump 704 draws water from the raw water tank 701 and inputs it into the water purifier 703 for purification, and then inputs it into the pure water tank 702 for storage;

[0042] During peak power periods, the control module 18 controls the electric heater 3 to turn off and turns on the water supply pump 6 to pump the pure water in the water supply device 7 into the heat exchange tube 2; the heated molten salt exchanges heat with the heat exchange tube 2 in the low-temperature zone, heating the pure water in the heat exchange tube 2 to generate steam, and the steam enters the desuperheater 8 from the water outlet of the heat exchange tube 2 for temperature and pressure regulation before being delivered to the user.

[0043] The temperature and pressure regulation process is as follows: The B thermocouple 801 and the C thermocouple 802 monitor the temperature of the steam entering the desuperheater 8 in real time, and the pressure sensor 803 monitors the outlet pressure of the desuperheater 8 in real time; if the B thermocouple 801 detects that the temperature of the steam flowing out of the water outlet of the heat exchange tube 2 is not greater than the set temperature, the desuperheating water regulating valve 804 is closed; when the B thermocouple 801 detects that the steam flowing out of the water outlet of the heat exchange tube 2 exceeds the set temperature, the desuperheating water regulating valve 804 is opened, and cooling water is sprayed into the desuperheater 8 to evaporate it into water vapor and mix with the superheated steam inside. During this process, if the C thermocouple 805 detects that the outlet steam temperature of the desuperheater 8 is higher than the set temperature, the desuperheating water regulating valve 804 is opened. The flow of the warm water regulating valve 804 is controlled until the C thermocouple 805 detects that the steam temperature at the outlet of the desuperheater 8 is lower than the set temperature, the desuperheating water regulating valve 804 is closed (in this embodiment, the set temperature is 190°C) and the water spraying is stopped; at the same time, when the B thermocouple 801 detects that the steam flowing out of the water outlet of the heat exchange tube 2 is lower than the set temperature or the pressure sensor 803 detects that the outlet pressure is higher than the set value (1.0MPa), the flow of the water feed pump 6 is reduced. If the water feed pump 6 drops to the minimum flow of 250kg / h and still receives a signal to reduce the flow, the bypass valve 16 is controlled to open; when the pressure sensor 803 detects that the outlet pressure is lower than the set value, the opening of the steam regulating valve 805 is reduced.

[0044] Of course, the heating system of the present application is not limited to operating according to the above control method. For example, when the thermal energy stored during off-peak hours cannot meet the demand during peak hours, the electric heater 3 can also be turned on during peak hours.

[0045] The above general description of the invention and the description of its specific embodiments involved in this application should not be understood as limiting the technical solutions of the invention. Based on the disclosure of this application, those skilled in the art may, without violating the constituent elements of the invention involved, add, subtract, or combine the disclosed technical features in the above general description and / or specific embodiments (including examples) to form other technical solutions within the scope of protection of this application.

Claims

1. Single tank molten salt heat storage and heating system, characterized by: The invention comprises a molten salt tank (1); a salt injection port (101) is provided on the top of the molten salt tank (1), and a salt discharge port (102) is provided on the bottom; a heat exchange tube (2) and a group of electric heaters (3) are provided inside the molten salt tank (1); the electric heater (3) is used to heat the molten salt; the heat exchange tube (2) is used to exchange heat with the heated molten salt, and heat the water in the heat exchange tube (2) to generate steam; the water inlet of the heat exchange tube (2) is connected to the water outlet of a water supply pump (6) through a water inlet pipe, and the water inlet of the water supply pump (6) is connected to the water outlet of a water supply device (7); the water supply device (7) is used to provide pure water, including a raw water tank (701), a pure water tank (702), and a water purifier (703) arranged between the raw water tank (701) and the pure water tank (702); the water purifier (703) includes multiple filters, a high-pressure pump and a reverse osmosis unit, and is used to purify the water in the raw water tank (701); the water inlet of the water supply pump (6) is connected to the water outlet of the pure water tank (702) through a water outlet pipe; the water outlet of the heat exchange tube (2) is connected to a desuperheater (8); the water outlet of the desuperheater (8) is connected to the water outlet of the water supply pump (6) through a water supply pipe; The water outlet of the water supply pump (6) is connected to a bypass pipeline, and the other end of the bypass pipeline is connected to the pure water tank (702); a bypass valve (16) is provided on the bypass pipeline, and when the water supply pump (6) is adjusted to the minimum safe working flow rate, which is still higher than the pure water flow rate required by the molten salt tank (1), the bypass valve (16) is opened to reduce the water supply flow rate; a group of A thermocouples (4) are provided inside the molten salt tank (1) for real-time monitoring of the temperature of the molten salt in the molten salt tank (1); the inlet and outlet of the desuperheater (8) are respectively provided with B thermocouples (801) and C thermocouples (802) for real-time monitoring of the desuperheater (8) The outlet of the desuperheater (8) is also provided with a pressure sensor (803) for real-time monitoring of the outlet pressure of the desuperheater (8); the water outlet of the desuperheater (8) is provided with a desuperheating water regulating valve (804); the outlet of the desuperheater (8) is provided with a steam regulating valve (805); the electric heater (3), the thermocouple A (4), the feed water pump (6), the thermocouple B (801), the thermocouple C (802), the pressure sensor (803), the desuperheating water regulating valve (804), the steam regulating valve (805) and the bypass valve (16) are respectively electrically connected to the control module (18).

2. The single-tank molten salt heat storage and heating system according to claim 1 is characterized in that: The pure water tank (702) is provided with a liquid level switch (706) for controlling the liquid level in the pure water tank (702).

3. The single-tank molten salt heat storage and heating system according to claim 1 is characterized in that: Two ultrasonic level meters (9) electrically connected to the control module (18) are provided on the top of the molten salt tank (1) for real-time monitoring of the liquid level of the molten salt in the molten salt tank (1).

4. The single-tank molten salt heat storage and heating system according to claim 3 is characterized in that: An exhaust pipe (10) is provided above the salt injection port (101), and the exhaust pipe (10) is connected to the interior of the molten salt tank (1).

5. The single-tank molten salt heat storage and heating system according to claim 4 is characterized in that: A safety valve (14) is provided at the water inlet of the heat exchange tube (2) and the water inlet of the desuperheater (8), respectively.

6. The single-tank molten salt heat storage and heating system according to claim 1 is characterized in that: The water outlet pipe is provided with a flow meter (17) for real-time monitoring of the flow of pure water in the pipe.

7. The single-tank molten salt heat storage and heating system according to claim 1 is characterized in that: Two D thermocouples (301) are respectively provided on each electric heater (3).

8. The control method of the single-tank molten salt heat storage and heating system according to claim 1, characterized in that: During the off-peak period, the control module (18) controls the electric heater (3) to start and heat the molten salt in the molten salt tank (1). At the same time, the thermocouple A (4) monitors the temperature of the molten salt in the molten salt tank (1) in real time. If the detected molten salt temperature exceeds the set value, the electric heater (3) is controlled to be powered off. During peak power periods, the control module (18) controls the water supply pump (6) to start, and pumps pure water in the water supply device (7) into the heat exchange tube (2); the heated molten salt exchanges heat with the heat exchange tube (2) in the low-temperature region, and heats the pure water in the heat exchange tube (2) to generate steam; the steam enters the desuperheater (8) from the water outlet of the heat exchange tube (2), is subjected to temperature and pressure regulation, and is then delivered to the user; The temperature and pressure regulation process is as follows: The B thermocouple (801) and the C thermocouple (802) monitor the temperature of the steam entering the desuperheater (8) in real time, and the pressure sensor (803) monitors the outlet pressure of the desuperheater (8) in real time; if the B thermocouple (801) detects that the temperature of the steam flowing out of the outlet of the heat exchange tube (2) is not greater than the set temperature, the desuperheating water regulating valve (804) is closed; when the B thermocouple (801) detects that the steam flowing out of the outlet of the heat exchange tube (2) exceeds the set temperature, the desuperheating water regulating valve (804) is opened, and cooling water is sprayed into the desuperheater (8) to evaporate it into water vapor and mix it with the superheated steam inside. During this process, if the C thermocouple (802) detects that the outlet steam temperature of the desuperheater (8) is high, the desuperheating water regulating valve (804) is opened. At the set temperature, the flow of the cooling water regulating valve (804) is increased until the C thermocouple (802) detects that the outlet steam temperature of the cooler (8) is lower than the set temperature, and the cooling water regulating valve (804) is closed; at the same time, when the B thermocouple (801) detects that the steam flowing out of the outlet of the heat exchange tube (2) is lower than the set temperature or the pressure sensor (803) detects that the outlet pressure is higher than the set value, the flow of the feed water pump (6) is reduced. If the feed water pump (6) drops to the minimum safe working flow and still receives a signal to reduce the flow, the bypass valve (16) is controlled to open, so that part of the water returns to the pure water tank (702); when the pressure sensor (803) detects that the outlet pressure is lower than the set value, the opening of the steam regulating valve (805) is reduced.

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