Steam generation system capable of improving system circulation efficiency and prolonging service life of evaporator through heat pump

Abstract

The invention discloses a steam generation system capable of improving system circulation efficiency and prolonging the service life of an evaporator through a heat pump. A salt discharge port of the evaporator is connected with a salt inlet of a high-temperature heat radiator through a fourth salt conveying pipe, and a salt discharge port of the high-temperature heat radiator is connected with a middle salt inlet of the evaporator through a fifth salt conveying pipe; a salt discharging opening of the preheater is connected with a salt inlet of the low-temperature fused salt heat absorber through a sixth salt conveying pipe, and the low-temperature fused salt heat absorber, the high-temperature heat radiator, the compressor and the throttling valve are used for heating discharged salt of the evaporator after the temperature level of heat of low-temperature fused salt discharged by the preheater is increased through a heat exchange medium and returning the discharged salt to the evaporator again. The heat transfer temperature difference of the evaporator can be increased, the heat transfer area of the evaporator is reduced, the pipe length of the evaporator is shortened, the equipment investment is reduced, the pressure drop in the pipe is reduced, the steam-water circulation efficiency is improved, the service life of equipment is prolonged, the heat absorption reliability of an evaporation section in a loop is effectively improved, and the safety of a natural circulation loop is improved.

Description

Technical Field

[0001] The invention belongs to the field of solar thermal power generation systems, and in particular relates to a steam generation system which improves system circulation efficiency and prolongs the life of an evaporator through a heat pump. Background Art

[0002] At present, conventional renewable energy power generation technologies such as hydropower, photovoltaic power generation, and wind power generation all have problems with seasonality, intermittency, and stability. Combining solar thermal power generation with the above renewable energy power generation can achieve continuous and stable power generation, is adjustable, easy to connect to the grid, and has little environmental impact throughout its life cycle. Solar thermal power has the advantages of no need for reactive power compensation and high power quality.

[0003] Solar thermal power generation is a high-tech technology that relies on various concentrators to gather the sun's radiation energy, transmits the energy to the steam generation system through a heat carrier (thermal oil or molten salt, etc.), and uses the high-temperature steam generated by the steam generation system to drive the steam turbine (or gas turbine) to convert work into electrical energy. If solar thermal technology is to stand out among many power generation technologies and ultimately achieve a significant breakthrough in cost, there are at least two problems that need to be solved. One is the reliability of the equipment, and the other is to optimize the system structure and reduce equipment investment through process improvements.

[0004] The upstream (heat source) of the steam generation system is the molten salt from the high-temperature molten salt tank of the heat storage system. The high-temperature molten salt (550°C) passes through the superheater (and the reheater in parallel with the superheater), evaporator, and feed water preheater of this system in turn. The final temperature of the molten salt heat exchange is about 300°C, and finally returns to the low-temperature molten salt tank of the heat storage system (the low-temperature molten salt is sent to the solar collector system for heating and then returns to the high-temperature molten salt tank. The above process forms a complete heat release, heat absorption, and heat storage cycle of the molten salt medium); the feed water comes from the high-pressure heater of the heat recovery system, and is heated to a final temperature of 252°C before being sent to this system. The high-pressure feed water is first heated to a temperature close to the saturated water temperature in the feed water preheater, and then sent to the steam drum and steam generator to produce steam. The dry steam after steam-water separation is sent to the superheater to be superheated to 540°C, and then sent to the high-pressure cylinder of the steam turbine. The steam after steam work (about 320°C) is then sent to the steam generation system reheater through the cold re-steam pipeline, and after heat exchange with the high-temperature molten salt to 540°C, it returns to the low-pressure cylinder of the steam turbine to generate electricity.

[0005] The steam generation system is an important subsystem of solar thermal power generation, and the evaporator is the core equipment of the steam generation system. Based on the requirement that the preheater does not vaporize, the molten salt temperature at the evaporator outlet is only 340°C, while the evaporation temperature on the water side is about 337°C. The heat transfer end difference is small, resulting in a large required heat transfer area and equipment cost for the evaporator. In addition, since the steam and water are arranged in the tube side, the density difference between steam and water is small under high pressure, and there is a risk of circulation stagnation and circulation backflow. If the required evaporator heat exchange area is large, the heat exchange tube is long, resulting in a higher pressure drop in the tube, which aggravates this risk and damages the service life of the equipment. Therefore, it is necessary to design a steam generation system to reduce the equipment specifications of the evaporator and increase the circulation rate, thereby eliminating the risk of thermal fatigue.

[0006] In addition, it can be seen from the figure that in the original conventional steam generation system, under high load conditions, if the preheater molten salt discharge temperature is reduced, there is a heat transfer pinch point at the evaporator position. Based on this, the preheater discharge temperature is as high as 297°C, while the melting crystallization temperature of the high-temperature molten salt in the current market is 238°C, indicating that the recycling efficiency of the molten salt needs to be improved. Under low load conditions, due to the heat transfer pinch point at the evaporator position, a higher molten salt flow rate needs to be maintained to ensure the molten salt temperature at the evaporator position. However, since the system pressure is reduced at this time, in order to ensure that the preheater position does not gasify, the molten salt can only be bypassed, which reduces the system circulation efficiency. It can be seen from the table below that the bypass molten salt flow rate at this time is about 200-400t / h, and the molten salt temperature is as high as 285-340°C, which has a high recovery value. Summary of the invention

[0007] (1) Technical problems to be solved: The required heat transfer area and equipment cost of the evaporator in the prior art are relatively large. In addition, since the steam and water are arranged in the tube side, the density difference between the steam and water is small under high pressure, and there is a risk of circulation stagnation and circulation backflow. If the required evaporator heat exchange area is large, the heat exchange tube is long, resulting in a higher pressure drop in the tube, which further aggravates this risk and damages the service life of the equipment. In addition, the high-temperature molten salt of the preheater cannot be fully utilized, and the circulation heat exchange efficiency still needs to be improved. In view of the above-mentioned defects, the present invention provides a steam generation system that improves the system circulation efficiency and extends the life of the evaporator through a heat pump. It can not only reduce equipment specifications, but also increase the circulation rate and service life of the evaporator. At the same time, it can fully utilize the 297°C high-temperature molten salt of the preheater to improve the system circulation efficiency.

[0008] (2) The technical solution adopted by the present invention is as follows:

[0009] A steam generating system for improving system circulation efficiency and extending the life of an evaporator by means of a heat pump, comprising a preheater, an evaporator, a superheater, a reheater, a steam drum and a heat pump system, wherein the heat pump system comprises a compressor, a throttle valve, a low-temperature molten salt heat absorber and a high-temperature heat emitter, wherein the water inlet of the preheater is connected to a water supply pipeline, the drain outlet of the preheater is connected to the water inlet of the steam drum through a pipeline one, the downcomer of the steam drum is connected to the water inlet of the evaporator through a pipeline three, the drain outlet of the evaporator is connected to the riser of the steam drum through a pipeline four, the steam outlet of the steam drum is connected to the steam inlet of the superheater through a pipeline five, the salt inlet of the superheater and the salt inlet of the reheater are both connected to the salt inlet pipeline, the salt discharge outlet of the superheater is connected to the salt inlet of the evaporator through a salt delivery pipe one, the salt discharge outlet of the reheater is connected to the salt inlet of the evaporator through a salt delivery pipe The second is connected to the salt inlet of the evaporator, the salt discharge port of the evaporator is connected to the salt inlet of the preheater through a salt delivery pipe three, the salt discharge port of the evaporator is connected to the salt inlet of the high-temperature radiator through a salt delivery pipe four, the salt discharge port of the high-temperature radiator is connected to the middle salt inlet of the evaporator through a salt delivery pipe five, the salt discharge port of the preheater is connected to the salt inlet of the low-temperature molten salt heat absorber through a salt delivery pipe six, the salt discharge port of the low-temperature molten salt heat absorber is connected to the salt discharge pipeline, a heat exchange medium circulation pipeline is arranged between the low-temperature molten salt heat absorber and the high-temperature radiator, a compressor and a throttle valve are arranged on the heat exchange medium circulation pipeline, the low-temperature molten salt heat absorber, the high-temperature radiator, the compressor and the throttle valve are used to heat the low-temperature molten salt discharged from the preheater by raising the temperature through the heat exchange medium, and then heat the discharged salt of the evaporator and return it to the evaporator.

[0010] A further technical solution is that the evaporator includes an outer shell, the interior of the outer shell is divided into a molten salt zone and a water separation zone by a tube sheet, the water separation zone is divided into a water inlet zone and a drainage zone by a partition, a water inlet is provided on the outer shell at a position corresponding to the water inlet zone, a drainage outlet is provided on the outer shell at a position corresponding to the drainage zone, heat exchange tubes are evenly distributed in the molten salt zone, both ends of the heat exchange tubes pass through the tube sheet to respectively connect the water inlet zone and the drainage zone, a salt inlet is provided at one end of the outer shell at a position corresponding to the molten salt zone, and a salt discharge outlet is provided at the other end, and an intermediate salt inlet is provided on the outer shell at a position corresponding to the molten salt zone, and the temperature of the molten salt entering from the intermediate salt inlet is adapted to the temperature of the molten salt in the molten salt zone near the intermediate salt inlet.

[0011] A further technical solution is that a valve one is provided on the salt delivery pipe one, a valve two is provided on the salt delivery pipe two, a valve four is provided on the salt delivery pipe four, and a water supply valve is provided on the water supply pipe.

[0012] A further technical solution is that a pipeline pump and a check valve are connected to the salt delivery pipe five.

[0013] A further technical solution is that a bypass pipeline is provided between the salt inlet of the preheater and the salt discharge outlet of the preheater, and a bypass regulating valve is provided on the bypass pipeline.

[0014] (3) Due to the adoption of the above technical solution, the beneficial effects of the present invention are:

[0015] 1. The salt discharge port of the evaporator is connected to the salt inlet of the high-temperature radiator through a salt delivery pipe 4, the salt discharge port of the high-temperature radiator is connected to the middle salt inlet of the evaporator through a salt delivery pipe 5, the salt discharge port of the preheater is connected to the salt inlet of the low-temperature molten salt heat absorber through a salt delivery pipe 6, the salt discharge port of the low-temperature molten salt heat absorber is connected to the salt discharge pipeline, a heat exchange medium circulation pipeline is arranged between the low-temperature molten salt heat absorber and the high-temperature radiator, a compressor and a throttle valve are arranged on the heat exchange medium circulation pipeline, the low-temperature molten salt heat absorber, the high-temperature radiator, the compressor and the throttle valve are used to heat the heat of the low-temperature molten salt discharged from the preheater through the heat exchange medium to heat the discharged salt of the evaporator and return it to the evaporator, so as to improve the heat transfer temperature difference of the evaporator, reduce the heat transfer area of ​​the evaporator, shorten the tube length of the evaporator, reduce equipment investment, reduce the pressure drop in the tube, improve the efficiency of the steam-water cycle, improve the service life of the equipment, effectively improve the heat absorption reliability of the evaporation section in the loop, and increase the safety of the natural circulation loop.

[0016] 2. By adding a heat pump system, the heat in the molten salt discharged from the preheater can be recovered and fully utilized in the evaporator, which can improve the utilization efficiency of the molten salt heat. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] Figure 1 It is a schematic diagram of the overall structure of the present invention;

[0018] Figure 2 It is a structural schematic diagram of a steam generating system in the prior art;

[0019] Figure 3 It is a diagram of the working temperatures of the hot and cold sides in the existing process flow.

[0020] Figure 4 It is a structural schematic diagram of the evaporator of the present invention. DETAILED DESCRIPTION

[0021] In order to make the purpose, technical solutions and advantages of the present invention more clearly understood, the present invention is further described in detail below in conjunction with the accompanying drawings and embodiments.

[0022] like Figure 1-Figure 4A steam generating system for improving system cycle efficiency and extending evaporator life by heat pump comprises a preheater 1, an evaporator 2, a superheater 3, a reheater 4, a drum 5 and a heat pump system, wherein the heat pump system comprises a compressor 6, a throttle valve 7, a low-temperature molten salt absorber 8 and a high-temperature radiator 9, wherein the water inlet of the preheater 1 is connected to a water supply pipe 10, the drain outlet of the preheater 1 is connected to the water inlet of the drum 5 through a pipe 11, the downcomer 12 of the drum 5 is connected to the water inlet of the evaporator 2 through a pipe 3 13, the drain outlet of the evaporator 2 is connected to the riser 14 of the drum 5 through a pipe 4 15, the steam outlet of the drum 5 is connected to the steam inlet of the superheater 3 through a pipe 5 16, the salt inlet of the superheater 3 and the salt inlet of the reheater 4 are both connected to a salt inlet pipe 17, the salt outlet of the superheater 3 is connected to the salt inlet of the evaporator 2 through a salt delivery pipe 18, the salt outlet of the reheater 4 is connected to the salt inlet of the evaporator 2 through a salt delivery pipe 19, the salt outlet of the reheater 4 is connected to the salt outlet of the evaporator 2 through a salt delivery pipe 20, and the salt outlet of the reheater 4 is connected to the salt outlet of the evaporator 2 through a salt delivery pipe 11. The salt delivery pipe 2 19 is connected to the salt inlet of the evaporator 2, the salt discharge port of the evaporator 2 is connected to the salt inlet of the preheater 1 through the salt delivery pipe 3 20, the salt discharge port of the evaporator 2 is connected to the salt inlet of the high-temperature radiator 9 through the salt delivery pipe 4 21, the salt discharge port of the high-temperature radiator 9 is connected to the middle salt inlet of the evaporator 2 through the salt delivery pipe 5 22, the salt discharge port of the preheater 1 is connected to the salt inlet of the low-temperature molten salt heat absorber 8 through the salt delivery pipe 6 23, the salt discharge port of the low-temperature molten salt heat absorber 8 is connected to the salt discharge pipeline, a heat exchange medium circulation pipeline 24 is arranged between the low-temperature molten salt heat absorber 8 and the high-temperature radiator 9, and a compressor 6 and a throttle valve 7 are arranged on the heat exchange medium circulation pipeline 24, and the low-temperature molten salt heat absorber 8, the high-temperature radiator 9, the compressor 6 and the throttle valve 7 are used to heat the heat of the low-temperature molten salt discharged from the preheater 1 by raising the temperature through the heat exchange medium, and then heat the discharged salt of the evaporator 2 and return it to the evaporator 2.

[0023] When in use, the feed water comes from the high-pressure heater of the heat recovery system, and is heated to a final temperature of 252°C before being sent to this system. The high-pressure feed water is first heated to a temperature close to the saturated water temperature by the preheater 1, and then sent to the steam drum 5 and the steam generator to produce steam. The dry steam after steam-water separation is sent to the superheater 3 to be superheated to 540°C, and then sent to the high-pressure cylinder of the steam turbine. The steam after steam work (about 320°C) is then sent to the reheater 4 through the cold re-steam pipeline, and after heat exchange with the high-temperature molten salt to 540°C, it is returned to the low-pressure cylinder of the steam turbine to work and generate electricity. The upstream (heat source) of the steam generation system is the molten salt from the high-temperature molten salt tank of the heat storage system. The high-temperature molten salt (550°C) passes through the superheater 3 (and the reheater 4 connected in parallel with the superheater 3), the evaporator 2, and the preheater 1 of the system in sequence. The molten salt discharged from the preheater 1 is sent to the low-temperature molten salt heat absorber 8. After the heat exchange medium (refrigerant) in the heat exchange medium circulation pipeline 24 absorbs heat, the compressor 6 works to increase the temperature, and then exchanges heat with the low-temperature molten salt discharged from the evaporator 2 in the high-temperature heat emitter 9. After the temperature of the molten salt discharged from the evaporator 2 is increased, it returns to the evaporator 2 to work. The final temperature of the molten salt discharged from the preheater 1 is about 300°C. The molten salt discharged from the low-temperature molten salt heat absorber 8 is finally returned to the low-temperature molten salt tank of the heat storage system (the low-temperature molten salt is sent to the heat collection system for heating and then returns to the high-temperature molten salt tank. The above process forms a complete heat release, heat absorption, and heat storage cycle of the molten salt medium); the low-temperature molten salt heat absorber 8 is equivalent to the condenser in the existing heat pump system, and the high-temperature heat emitter 9 is equivalent to the evaporator in the existing heat pump system. The initial setting value (Ys) of the control variable (molten salt temperature) is the molten salt crystallization temperature + 20°C, and the difference (e) between the initial setting value (Ys) and the feedback value (Ym) is less than or equal to ±5°C. The control target is achieved by adjusting the speed of the variable frequency motor of the heat pump compressor 6: the system molten salt outlet temperature is constant and the cycle thermal efficiency is improved.

[0024] The evaporator 2 includes a shell 25, the inside of the shell 25 is divided into a molten salt area 27 and a water separation area 28 by a tube sheet 26, the water separation area 28 is divided into a water inlet area 30 and a drainage area 31 by a partition 29, a water inlet S3 is arranged on the shell 25 at a position corresponding to the water inlet area 30, a drainage outlet S4 is arranged on the shell 25 at a position corresponding to the drainage area 31, heat exchange tubes 32 are evenly arranged in the molten salt area 27, both ends of the heat exchange tubes 32 pass through the tube sheet 26 to respectively connect the water inlet area 30 and the drainage area 31, a salt inlet S1 is arranged at one end of the shell 25 at a position corresponding to the molten salt area 27, and a salt discharge outlet S2 is arranged at the other end, and an intermediate salt inlet S5 is arranged on the shell 25 at a position corresponding to the molten salt area 27, and the temperature of the molten salt entering from the intermediate salt inlet S5 is adapted to the temperature of the molten salt in the molten salt area 27 near the intermediate salt inlet. Compared with the existing evaporator 2, the evaporator 2 used in the present invention has an additional molten salt inlet, that is, an intermediate salt inlet. The reason for setting a separate intermediate salt inlet is that if two molten salts of different temperatures are mixed through the same inlet, there will be temperature difference loss, which will affect the overall heat transfer driving force. Moreover, the above problem will occur if the intermediate salt inlet is too far or too close to the original salt inlet. As long as the temperature of the molten salt entering from the intermediate salt inlet is compatible with the temperature of the molten salt in the molten salt zone 27 near the intermediate salt inlet, that is, the temperature difference is within the process requirements.

[0025] The salt delivery pipe 18 is provided with a valve 1 33, the salt delivery pipe 2 19 is provided with a valve 2 34, the salt delivery pipe 4 21 is provided with a valve 4 35, and the water supply pipe 10 is provided with a water supply valve 36. According to the actual operation situation, each valve controls the opening and closing of the corresponding pipe.

[0026] The salt delivery pipe 5 22 is connected to a pipeline pump 37 and a check valve 38 .

[0027] A bypass pipe 39 is provided between the salt inlet of preheater 1 and the salt outlet of preheater 1, and a bypass regulating valve 40 is provided on the bypass pipe 39. The outlet temperature of the steam-water side of preheater 11 adopts a single-loop control method. The initial setting value (Ys) of the control variable is the saturation temperature (fixed value) corresponding to the control pressure, and the difference (e) between the initial setting value (Ys) and the feedback value (Ym) is less than or equal to +3°C. The control target is achieved by adjusting the opening of the molten salt bypass regulating valve of preheater 1: preventing boiling at the outlet of the steam-water side of preheater 1 to reduce pipe burst accidents.

[0028] (The heat exchange system in the figure can be used for 100MW steam turbine power generation system and 50MW steam turbine power generation system. The parameters on the molten salt side do not change significantly, and the load is adjusted according to the flow rate. The pressure and flow parameters on the steam side change greatly.

[0029] Example 1 (without heat pump): 100MW unit rated power condition (TMCR), the main technical indicators are as follows:

[0030] On the molten salt side, the high-temperature liquid molten salt inlet -17 has a flow rate of 2240t / h, a temperature of 535℃, and a pressure of 1.6MPaG; the molten salt temperature before the evaporator -18-19 is about 434℃, and the molten salt temperature at the evaporator outlet, i.e. the feed water preheater inlet -20, is 336℃, and the heat exchange system salt discharge temperature (preheater outlet -23) is 295℃, with a pressure of 1.1MPaG and a flow rate of 2240t / h.

[0031] Steam-water side: preheater front-10 main feed water flow rate is about 298t / h, pressure 13.27MPaG, temperature 246℃, superheater outlet-X flow rate is about 295t / h, pressure 13.0MPaG, temperature 528℃. Reheater inlet flow rate is about 267t / h, pressure 2.86MPaG, temperature 321℃, outlet flow rate is about 267t / h, pressure 2.76MPaG, temperature 527℃. Steam turbine power is 100MW.

[0032] Example 2 (without heat pump): 100MW unit 75% THA condition, the main technical indicators are as follows:

[0033] On the molten salt side, the high-temperature liquid molten salt inlet -17 has a flow rate of 1659t / h, a temperature of 531℃, and a pressure of 1.6MPaG; the molten salt temperature before the evaporator -18-19 is about 431℃, and the molten salt temperature at the evaporator outlet, i.e. the feed water preheater inlet -20, is 314℃, and the heat exchange system salt discharge temperature (preheater outlet -23) is 275℃, with a pressure of 1.1MPaG and a flow rate of 1659t / h.

[0034] Steam-water side: preheater front-10 main feed water flow rate is about 228t / h, pressure 10.24MPaG, temperature 245℃, superheater outlet-X flow rate is about 226t / h, pressure 9.9MPaG, temperature 528℃, reheater inlet flow rate is about 200t / h, pressure 2.12MPaG, temperature 321℃, outlet flow rate is about 200t / h, pressure 2.02MPaG, temperature 527℃. Steam turbine power is 75MW.

[0035] According to the above data, the crystallization temperature of molten salt binary crystals is about 240°C, and the safe salt discharge temperature is about 260°C. When the molten salt heat storage and exchange system is loaded at 75% or more, there is a temperature difference of about 15 to 35°C, and the molten salt energy is not effectively utilized. The main reason for the obstacle is that the saturation temperature under the water side pressure of the preheater leads to limited heat transfer and incomplete heat extraction. If the heat pump can be increased to extract this part of the heat energy to realize the conversion of heat energy into electrical energy, according to the mainstream heat pump energy efficiency ratio of 1:4.5 on the market, a 100MW solar power station can save about 8% energy, which has a good application prospect.

[0036] The upstream (heat source) of the steam generation system is the molten salt from the high-temperature molten salt tank of the heat storage system. The high-temperature molten salt (550℃) passes through the superheater (and the reheater in parallel with the superheater), evaporator, and feed water preheater of this system in turn. The final temperature of the molten salt heat exchange is about 300℃, and finally returns to the low-temperature molten salt tank of the heat storage system (the low-temperature molten salt is sent to the heat collection system for heating and then returns to the high-temperature molten salt tank. The above process forms a complete heat release, heat absorption, and heat storage cycle of the molten salt medium); the downstream of the steam system is the steam turbine generator set, and the feed water of the steam generation system comes from the high-pressure heater of the steam turbine heat recovery system. The condensate of the steam turbine condenser is boosted by the condensate pump and heated by the low-pressure heater of the heat recovery system, and then sent to the deaerator of the heat recovery system for deoxygenation. The deoxygenated water is boosted by the pump and passes through the high-pressure heaters of the heat recovery system at each level in turn. It is heated to a final temperature of 252℃ and then sent to this system. The high-pressure feed water is first heated to a temperature close to the saturated water temperature by the feed water preheater, and then sent to the steam drum and steam generator to produce steam. The dry steam after steam-water separation is sent to the superheater to be superheated to 540°C, and then sent to the high-pressure cylinder of the steam turbine. The steam (about 320°C) after steam work is then sent to the steam generation system reheater through the cold re-steam pipeline, and after heat exchange with high-temperature molten salt to 540°C, it returns to the low-pressure cylinder of the steam turbine to work and generate electricity. The exhaust steam from the low-pressure cylinder of the steam turbine is cooled by water (or air) to produce condensate. After the condensate is refined, it is boosted by the condensate pump and sent to the low-pressure heater of the steam turbine heat recovery system. The above process forms a complete steam-water working medium cycle of work, heat release, heating, steam production, and work.

[0037] SGS system working fluid heat balance data (maximum VWO, 100% THA, 85% THA, 75% THA, 50% THA, 25%

[0038] THA, 15% THA)

[0039]

[0040]

[0041]

[0042] The above table summarizes the salt discharge temperature of the preheater and the molten salt bypass flow rate of the preheater under different operating conditions of the solar thermal power generation steam generation system, indicating that the heat pump system has great energy-saving potential and application prospects.

[0043] The above are only preferred embodiments of the present invention.

Claims

1. A steam generating system for improving system cycle efficiency and extending evaporator life by means of a heat pump, characterized in that: The invention comprises a preheater (1), an evaporator (2), a superheater (3), a reheater (4), a steam drum (5) and a heat pump system, wherein the heat pump system comprises a compressor (6), a throttle valve (7), a low-temperature molten salt heat absorber (8) and a high-temperature heat emitter (9), wherein the water inlet of the preheater (1) is connected to a water supply pipe (10), the water outlet of the preheater (1) is connected to the water inlet of the steam drum (5) through a pipe 1 (11), and the downcomer (12) of the steam drum (5) is connected to the water inlet of the evaporator (2) through a pipe 3 ( 13), the drain outlet of the evaporator (2) is connected to the riser (14) of the drum (5) through a pipe four (15), the steam outlet of the drum (5) is connected to the steam inlet of the superheater (3) through a pipe five (16), the salt inlet of the superheater (3) and the salt inlet of the reheater (4) are both connected to the salt inlet pipe (17), the salt outlet of the superheater (3) is connected to the salt inlet of the evaporator (2) through a salt delivery pipe one (18), the salt outlet of the reheater (4) is connected to the salt inlet of the evaporator (2) through a salt delivery pipe two (19), and the salt outlet of the reheater (4) is connected to the evaporator (3) through a salt delivery pipe three (19). The salt inlet of the evaporator (2) is connected to the salt inlet of the preheater (1), the salt outlet of the evaporator (2) is connected to the salt inlet of the preheater (1) through a salt delivery pipe three (20), the salt outlet of the evaporator (2) is connected to the salt inlet of the high-temperature radiator (9) through a salt delivery pipe four (21), the salt outlet of the high-temperature radiator (9) is connected to the middle salt inlet of the evaporator (2) through a salt delivery pipe five (22), the salt outlet of the preheater (1) is connected to the salt inlet of the low-temperature molten salt heat absorber (8) through a salt delivery pipe six (23), and the low-temperature molten salt heat absorber (8) is connected to the salt inlet of the preheater (1) through a salt delivery pipe six (23). ) is connected to a salt discharge pipe, a heat exchange medium circulation pipe (24) is provided between the low-temperature molten salt heat absorber (8) and the high-temperature heat emitter (9), a compressor (6) and a throttle valve (7) are provided on the heat exchange medium circulation pipe (24), and the low-temperature molten salt heat absorber (8), the high-temperature heat emitter (9), the compressor (6) and the throttle valve (7) are used to heat the low-temperature molten salt discharged from the preheater (1) by raising the temperature of the heat through the heat exchange medium, and then heat the discharged salt of the evaporator (2) and return it to the evaporator (2).

2. A steam generation system for improving system cycle efficiency and extending evaporator life by heat pump according to claim 1, characterized in that: The evaporator (2) comprises a shell (25). The inside of the shell (25) is divided into a molten salt area (27) and a water separation area (28) by a tube sheet (26). The inside of the water separation area (28) is divided into a water inlet area (30) and a drainage area (31) by a partition (29). A water inlet is provided at a position corresponding to the water inlet area (30) on the shell (25). A drainage outlet is provided at a position corresponding to the drainage area (31) on the shell (25). The molten salt area (27) is uniformly provided with A heat exchange tube (32) is provided at both ends of the heat exchange tube (32) through the tube sheet (26) to respectively connect the water inlet area (30) and the drainage area (31); a salt inlet is provided at one end of the outer shell (25) at a position corresponding to the molten salt area (27), and a salt discharge port is provided at the other end; an intermediate salt inlet is provided at a position corresponding to the molten salt area (27) on the outer shell (25); the temperature of the molten salt entering from the intermediate salt inlet is adapted to the temperature of the molten salt in the molten salt area (27) adjacent to the intermediate salt inlet.

3. A steam generation system for improving system cycle efficiency and extending evaporator life by heat pump according to claim 1, characterized in that: The salt delivery pipe 1 (18) is provided with a valve 1 (33), the salt delivery pipe 2 (19) is provided with a valve 2 (34), the salt delivery pipe 4 (21) is provided with a valve 4 (35), and the water supply pipe (10) is provided with a water supply valve (36).

4. A steam generation system for improving system cycle efficiency and extending evaporator life by heat pump according to claim 1, characterized in that: The salt delivery pipe 5 (22) is connected to a pipeline pump (37) and a check valve (38).

5. A steam generation system for improving system cycle efficiency and extending evaporator life by heat pump according to claim 1, characterized in that: A bypass pipeline (39) is provided between the salt inlet of the preheater (1) and the salt outlet of the preheater (1), and a bypass regulating valve (40) is provided on the bypass pipeline (39).

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