Multi-stage electric heat pump-salt battery cascade heat storage steam supply device and steam supply method

Abstract

The present application relates to a kind of multi-stage electric heat pump-salt cascade heat storage steam supply device and steam supply method, including thermal power unit, molten salt heat storage device and multi-stage electric heat pump;The thermal power unit connects the molten salt heat storage device, provides the steam for the molten salt heat storage device with heat storage;The molten salt heat storage device connects the multi-stage electric heat pump, and the heated desalted water introduced from the multi-stage electric heat pump is formed into superheated steam.It has beneficial effects, compared with prior art, it can maximize the recovery of thermal power unit waste heat, increase the external steam supply capacity of thermal power unit, achieve the effect of medium, high pressure and large flow steam supply under the condition of energy saving.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of industrial steam supply, and particularly relates to a multi-stage electric heat pump-molten salt cascade heat storage steam supply device and a steam supply method. BACKGROUND

[0002] At present, domestic thermal power generating units have the function of providing industrial steam for the region or industrial park where the thermal power plant is located. In the supply of external industrial steam, it is crucial to ensure continuous supply of high parameters, but at present, due to the need for flexible peak regulation of thermal power generating units, the requirement for load is decreasing, but under low load, the steam extraction pressure cannot be guaranteed. The molten salt energy storage system that has been actually applied has the function of guaranteeing the peak regulation and frequency modulation of thermal power generating units under the load instruction of the power plant, but the existing molten salt heat storage system cannot guarantee the realization of medium and high pressure and large flow steam supply alone under the condition of saving energy.

[0003] Therefore, there is an urgent need for a steam supply device and a steam supply method that can realize medium and high pressure and large flow steam supply under the condition of saving energy. SUMMARY

[0004] (I) Technical problems to be solved

[0005] In view of the above-mentioned defects and deficiencies of the prior art, the present application provides a multi-stage electric heat pump-molten salt cascade heat storage steam supply device and a steam supply method, which solves the technical problem that the prior art cannot realize medium and high pressure and large flow steam supply under the condition of saving energy.

[0006] (II) Technical solutions

[0007] In order to achieve the above-mentioned purposes, the main technical solutions adopted by the present application include:

[0008] In a first aspect, the present application provides a multi-stage electric heat pump-molten salt cascade heat storage steam supply device, comprising a thermal power generating unit, a molten salt heat storage device and a multi-stage electric heat pump; the thermal power generating unit is connected to the molten salt heat storage device and provides steam for heat storage for the molten salt heat storage device; the molten salt heat storage device is connected to the multi-stage electric heat pump, and converts the desalted water heated multiple times introduced from the multi-stage electric heat pump into superheated steam.

[0009] Optionally, the molten salt heat storage and release device comprises a molten salt heat storage device and a molten salt heat release device; the molten salt heat storage device comprises a molten salt cold tank, a first molten salt heat exchanger, a second molten salt heat exchanger and a molten salt hot tank; the molten salt cold tank is connected to the first molten salt heat exchanger through a first transmission pipeline and connected to the second molten salt heat exchanger through a second transmission pipeline; the first molten salt heat exchanger and the second molten salt heat exchanger are both heat-exchanged by steam from the thermal power generating unit and both connected to the molten salt hot tank through pipelines; the molten salt heat release device comprises a heat absorption end, a molten salt drum, a molten salt superheater and a molten salt evaporator; the heat absorption end is used for receiving heat desalted water from a multi-stage electric heat pump and connected to the molten salt drum through a first loop; the molten salt drum is connected to the molten salt superheater through a third transmission pipeline; the molten salt superheater is connected to the molten salt evaporator through a fourth transmission pipeline; the molten salt evaporator is connected to the molten salt drum through a second loop; the molten salt hot tank is connected to the molten salt superheater through a fifth transmission pipeline; and the molten salt evaporator is connected to the molten salt cold tank through a sixth transmission pipeline.

[0010] Optionally, the multi-stage electric heat pump comprises a heat exchanger, a first-stage heating mechanism, a second-stage heating mechanism and a third-stage heating mechanism; the heat exchanger is connected to a desalted water inlet pipe; desalted water introduced through the desalted water inlet pipe is sequentially input to the heat absorption end after passing through the heat exchanger, the first-stage heating mechanism, the second-stage heating mechanism and the third-stage heating mechanism.

[0011] Optionally, the heat exchanger is connected to a first-stage condenser in the first-stage heating mechanism through a first desalted water outlet pipe; the first-stage condenser is connected to a second-stage condenser in the second-stage heating mechanism through a second desalted water outlet pipe; the second-stage condenser is connected to a third-stage condenser in the third-stage heating mechanism through a third desalted water outlet pipe; and the third-stage condenser is connected to the heat absorption end through a pipeline.

[0012] Optionally, the heat exchanger is connected to a first-stage evaporator in the first-stage heating mechanism, a second-stage evaporator in the second-stage heating mechanism and a third-stage evaporator in the third-stage heating mechanism through a circulating water pipeline respectively.

[0013] Optionally, the thermal power generating unit comprises a boiler, a high-pressure cylinder of a steam turbine, a medium-pressure cylinder of a steam turbine and a low-pressure cylinder of a steam turbine; the boiler is connected to the high-pressure cylinder of the steam turbine, the medium-pressure cylinder of the steam turbine, the first molten salt heat exchanger and the second molten salt heat exchanger through pipelines; the medium-pressure cylinder of the steam turbine is connected to the low-pressure cylinder of the steam turbine through a pipeline; and the high-pressure cylinder of the steam turbine is connected to the boiler through a steam return pipeline.

[0014] Optionally, the boiler is connected to the high-pressure cylinder of the steam turbine through a first steam pipeline, and a first steam branch pipeline is branched from the first steam pipeline and connected to the first molten salt heat exchanger; the boiler is connected to the intermediate-pressure cylinder of the steam turbine through a second steam pipeline, and a second steam branch pipeline is branched from the second steam pipeline and connected to the second molten salt heat exchanger.

[0015] Optionally, the first molten salt heat exchanger is connected to the boiler through a first heat exchange return pipeline; and the second molten salt heat exchanger is connected to the low-pressure cylinder of the steam turbine through a second heat exchange return pipeline.

[0016] In a second aspect, the present application provides a multi-stage electric heat pump-molten salt step heat storage steam supply method, and the method comprises the following steps:

[0017] S1, a thermal power unit provides steam to make a molten salt heat storage device store heat;

[0018] S2, a desalted water is introduced into the molten salt heat storage device after being continuously heated by the multi-stage electric heat pump;

[0019] S3, the molten salt heat storage device heats the desalted water introduced after being heated by the multi-stage electric heat pump, and the heated desalted water is subjected to vapor-liquid separation to form steam, and the steam is heated to a required temperature and supplied to an industrial steam user.

[0020] Optionally, in the S2 step, the temperature of the desalted water after being continuously heated by the multi-stage electric heat pump is 60-65℃, and the pressure is 1.6-2.6Mpa.

[0021] (Three) beneficial effects

[0022] The multi-stage electric heat pump-molten salt step heat storage steam supply device and the steam supply method of the present application have the following beneficial effects: the multi-stage electric heat pump is used to heat a desalted water, and the temperature of the heated desalted water can reach 60-65℃, and then the desalted water is introduced into a molten salt heat storage device to be heated and subjected to vapor-liquid separation to form high-temperature steam, and the temperature of the output steam can reach 200-380℃, so as to meet the requirements of medium and high pressure and large flow steam supply. In addition, the waste heat of the circulating water of the unit is absorbed in the multi-stage electric heat pump, and all the heat is derived from the cold source loss of the thermal power unit, so the energy-saving effect is remarkable. According to the back pressure of 4-5Kpa in winter, the circulating water temperature is 35℃, the input electric power of the multi-stage heat pump is 1760kW, the total heat capacity is 10.5MW, and the COP is above 5, so the energy efficiency ratio is high. Compared with the prior art, the present application can maximize the recovery of waste heat of the thermal power unit, increase the external steam supply capacity of the thermal power unit, and achieve the effect of medium and high pressure and large flow steam supply under the condition of energy saving. BRIEF DESCRIPTION OF DRAWINGS

[0023] Figure 1This is a schematic diagram of the overall structure of Example 1 of the multi-stage electric heat pump-molten salt cascade heat storage steam supply device and steam supply method of the present invention;

[0024] Figure 2 for Figure 1 Enlarged schematic diagram of a multi-stage electric heat pump.

[0025] [Description of Reference Numerals]

[0026] 1: Molten salt cold tank;

[0027] 2: First molten salt heat exchanger;

[0028] 3: Second molten salt heat exchanger;

[0029] 4: Molten salt hot tank;

[0030] 5: First transmission pipeline;

[0031] 6: Second transmission pipeline;

[0032] 7: heat absorbing end;

[0033] 8: Molten salt drum;

[0034] 9: Molten salt superheater;

[0035] 10: Molten salt evaporator;

[0036] 11: First circuit;

[0037] 12: The third transmission pipeline;

[0038] 13: fourth transmission pipeline;

[0039] 14: Second circuit;

[0040] 15: fifth transmission pipeline;

[0041] 16: sixth transmission pipeline;

[0042] 17: heat exchanger;

[0043] 18: First stage heating mechanism;

[0044] 181: first stage condenser;

[0045] 182: first stage evaporator;

[0046] 19: Second stage heating mechanism;

[0047] 191: second stage condenser;

[0048] 192: Second stage evaporator

[0049] 20: third-level heating mechanism;

[0050] 201: third stage condenser;

[0051] 202: third stage evaporator;

[0052] 21: first desalted water outlet pipe;

[0053] 22: second desalted water outlet pipe;

[0054] 23: third desalted water outlet pipe;

[0055] 24: circulating water pipeline;

[0056] 25: boiler;

[0057] 251: first steam pipeline;

[0058] 2512: first heat exchange return pipe;

[0059] 252: second steam pipeline;

[0060] 2521: second steam branch pipe;

[0061] 2522: second steam return pipe;

[0062] 253: third steam pipeline;

[0063] 26: high-pressure cylinder of steam turbine;

[0064] 261: steam return pipe;

[0065] 27: medium-pressure cylinder of steam turbine;

[0066] 28: low-pressure cylinder of steam turbine;

[0067] 29: external discharge pipeline;

[0068] 30: desalted water inlet pipe;

[0069] 31: pipeline pump;

[0070] 32: photovoltaic power station;

[0071] 33: auxiliary power;

[0072] A: thermal power unit;

[0073] B: multi-stage electric heat pump;

[0074] C: molten salt heat storage device;

[0075] D: molten salt heat release device. DETAILED DESCRIPTION

[0076] For better explaining the present application, in order to facilitate understanding, the following specific embodiments, combined with the drawings, are described in detail.

[0077] The multi-stage electric heat pump-salt cascade heat storage steam supply device and the steam supply method of the embodiment of the present application solve the technical problem that the prior art cannot realize medium and high pressure and large flow steam supply under the condition of energy saving. The device comprises a thermal power unit, a molten salt heat storage device and a multi-stage electric heat pump. The thermal power unit is connected to the molten salt heat storage device to provide steam for heat storage of the molten salt heat storage device. The molten salt heat storage device is connected to the multi-stage electric heat pump to form superheated steam from heated desalted water introduced from the multi-stage electric heat pump. The present application uses the multi-stage electric heat pump to perform primary heating on a single desalted water, maximally recovers waste heat of the thermal power unit, and heats the desalted water heated by the multi-stage electric heat pump by the molten salt heat storage device to a required temperature of industrial steam supply, generally 200-380℃. The device can increase the external steam supply capacity of the thermal power unit, and realizes medium and high pressure and large flow steam supply under the condition of energy saving.

[0078] In order to better understand the above technical solutions, the following will describe the exemplary embodiments of the present application in more detail with reference to the drawings. Although the exemplary embodiments of the present application are shown in the drawings, it should be understood that the present application can be implemented in various forms and should not be limited by the embodiments described herein. On the contrary, these embodiments are provided to enable a clearer, more thorough understanding of the present application and to fully convey the scope of the present application to those skilled in the art.

[0079] Embodiment 1:

[0080] With reference to Figure 1 The multi-stage electric heat pump-salt cascade heat storage steam supply device of the present application comprises a thermal power unit A, a molten salt heat storage device and a multi-stage electric heat pump B. The thermal power unit A is connected to the molten salt heat storage device, and the thermal power unit A provides steam for heat storage of the molten salt heat storage device. The steam generated by the thermal power unit A is used to store heat for the molten salt heat storage device, avoiding the problem of energy waste caused by directly using electricity to store heat for the molten salt heat storage device. The multi-stage electric heat pump is connected to the molten salt heat storage device, and the multi-stage electric heat pump introduces desalted water heated by the multi-stage heating to the molten salt heat storage device and finally forms the required superheated steam. That is, the multi-stage electric heat pump is used to heat the desalted water to a higher temperature, for example, 60-65℃, and then the desalted water is input into the molten salt heat storage device to form the required superheated steam. Since the desalted water input into the molten salt heat storage device is heated by the multi-stage heating, the temperature of the desalted water is high, which can greatly improve the efficiency of forming superheated steam by the desalted water in the molten salt heat storage device and save energy. The multi-stage electric heat pump can absorb waste heat of circulating water of the thermal power unit, and all the heat can come from the cold source loss of the unit to achieve energy saving.

[0081] Further, for the preferred embodiment 1, the molten salt heat storage device comprises a molten salt heat storage device C and a molten salt heat release device D. The molten salt heat storage device C comprises a molten salt cold tank 1, a first molten salt heat exchanger 2, a second molten salt heat exchanger 3 and a molten salt hot tank 4. The molten salt cold tank 1 is used to store ternary salt. The first molten salt outlet of the molten salt cold tank 1 is connected to the first molten salt heat exchanger 2 through a first transmission pipeline 5, and ternary salt can be made to flow from the molten salt cold tank 1 into the first molten salt heat exchanger 2 through the first transmission pipeline 5 by using a molten salt pump. The second molten salt outlet of the molten salt cold tank 1 is connected to the second molten salt heat exchanger 3 through a second transmission pipeline 6, and ternary salt can be made to flow from the molten salt cold tank 1 into the second molten salt heat exchanger 3 through the second transmission pipeline 6 by using a molten salt pump. The first molten salt heat exchanger 2 and the second molten salt heat exchanger 3 are both heat-exchanged with steam from the thermal power generating unit A, and the first molten salt heat exchanger 2 and the second molten salt heat exchanger 3 are both connected to the molten salt hot tank 4 through pipelines. That is, after ternary salt entering the first molten salt heat exchanger 2 and the second molten salt heat exchanger 3 absorbs heat from steam and is heated to about 360°C, the ternary salt enters the molten salt hot tank 4 and is used for subsequent molten salt-steam heat exchange for the molten salt superheater 9.

[0082] The molten salt heat release device D comprises a heat absorption end 7, a molten salt drum 8, a molten salt superheater 9 and a molten salt evaporator 10. The heat absorption end 7 is used to receive desalted water which has been heated through multiple stages from the multi-stage electric heat pump B. The heat absorption end 7 is connected to the molten salt drum 8 through a first loop 11, so that desalted water entering the heat absorption end 7 forms steam after passing through the molten salt drum 8. The molten salt drum 8 is connected to the molten salt superheater 9 through a third transmission pipeline 12, so that steam formed after passing through the molten salt drum 8 enters the molten salt superheater 9 through the third transmission pipeline 12, and after molten salt-steam heat exchange, forms heated steam which is supplied to users through an external discharge pipeline 29. The molten salt hot tank 4 is connected to the molten salt superheater 9 through a fifth transmission pipeline 15, so that ternary salt from the molten salt hot tank 4 participates in molten salt-steam heat exchange in the molten salt superheater 9. The molten salt superheater 9 is connected to the molten salt evaporator 10 through a fourth transmission pipeline 13, so that ternary salt which has been subjected to molten salt-steam heat exchange in the molten salt superheater 9 enters the molten salt evaporator 10. The molten salt evaporator 10 is connected to the molten salt drum 8 through a second loop 14, and is used to provide heat for the molten salt drum 8. The molten salt evaporator 10 is connected to the molten salt cold tank 1 through a sixth transmission pipeline 16, so that ternary salt which has been subjected to heat exchange in the molten salt evaporator 10 returns to the molten salt cold tank 1.

[0083] Further, preferably for the embodiment 1, the multi-stage electric heat pump is preferably a three-stage electric heat pump with three-stage heating, i.e. including the heat exchanger 17, the first-stage heating mechanism 18, the second-stage heating mechanism 19 and the third-stage heating mechanism 20. The first-stage heating mechanism 18, the second-stage heating mechanism 19 and the third-stage heating mechanism 20 are identical in structure, each including a condenser and an evaporator, with one side of the condenser and the evaporator connected by a pipeline and the other side connected by a compressor. The condenser and the evaporator in the first-stage heating mechanism 18 are respectively referred to as the first-stage condenser 181 and the first-stage evaporator 182. The condenser and the evaporator in the second-stage heating mechanism 19 are respectively referred to as the second-stage condenser 191 and the second-stage evaporator 192. The third-stage heating mechanism 20 is respectively referred to as the third-stage condenser 201 and the third-stage evaporator 202. The heat exchanger 17 is connected to the desalted water inlet pipe 30. The desalted water introduced through the desalted water inlet pipe 30 is sequentially passed through the heat exchanger 17, the first-stage heating mechanism 18, the second-stage heating mechanism 19 and the third-stage heating mechanism 20 and then input to the heat absorption end 7, i.e. the desalted water is heated by three stages to form hot water at a temperature of, for example, 60-65°C. More specifically, referring to Figure 1 The heat exchanger 17 is connected to the first-stage condenser 181 through the first desalted water outlet pipe 21, and the desalted water is heated by the first-stage condenser 181 to complete the first-stage heating. The first-stage condenser 181 is connected to the second-stage condenser 191 through the second desalted water outlet pipe 22, and the desalted water is heated by the second-stage condenser 191 to complete the second-stage heating. The second-stage condenser 191 is connected to the third-stage condenser 201 through the third desalted water outlet pipe 23, and the desalted water is heated by the third-stage condenser 201 to complete the third-stage heating. The process of heating the desalted water by the condenser is as follows: the condenser is a shell-and-tube heat exchanger, the desalted water enters the shell side of the condenser and absorbs the heat of the medium in the tube side of the condenser, and the heat of the medium in the tube side is derived from the heat absorption in the evaporator. One evaporator and one condenser form one heat pump unit, and the medium in the tube of the condenser is refrigerant.

[0084] The third-stage condenser 201 is connected to the heat absorption end 7 through a pipeline, and the desalted water heated by three stages is input to the heat absorption end 7 for forming high-temperature steam. The temperature of the desalted water after multi-stage heating is greatly increased, so that it can more efficiently form steam after entering the subsequent molten salt heat release device D, and the utilization of the heat of the molten salt can be more sufficient and efficient.

[0085] In addition, the heat exchanger 17 is connected to the first-stage evaporator 182, the second-stage evaporator 192 and the third-stage evaporator 202 through the circulating water pipeline 24, as shown in Figure 1As shown, the first-stage evaporator 182, the second-stage evaporator 192 and the third-stage evaporator 202 are connected in parallel. The heat source used by the heat exchanger 17 is low-grade waste heat in circulating water of a thermal power unit. The circulating water enters the multi-stage electric heat pump at an inlet water temperature of 35°C and exits at an outlet water temperature of 20°C, so that the low-grade waste heat in the circulating water of the thermal power unit can be recovered, energy can be fully utilized, and energy saving and emission reduction can be facilitated.

[0086] Further, preferably for the embodiment 1, the thermal power unit comprises a boiler 25, a high-pressure cylinder 26 of a steam turbine, a medium-pressure cylinder 27 of the steam turbine and a low-pressure cylinder 28 of the steam turbine.

[0087] The first steam outlet of the boiler 25 is connected to the high-pressure cylinder 26 of the steam turbine through a first steam pipeline 251 to provide steam for the high-pressure cylinder 26 of the steam turbine. The high-pressure cylinder 26 of the steam turbine is further connected with a steam return pipeline 261, one end of the steam return pipeline 261 is connected with a steam outlet of the high-pressure cylinder 26 of the steam turbine, and the other end is connected with a steam inlet of the boiler 25. The first steam pipeline 251 branches off a first steam branch pipeline 2511 connected to the first molten salt heat exchanger 2 to provide high-temperature steam for the first molten salt heat exchanger 2. A valve can be provided on the first steam branch pipeline 2511 to adjust the amount of input steam. The second steam outlet of the boiler 25 is connected to the medium-pressure cylinder 27 of the steam turbine through a second steam pipeline 252 to provide steam for the medium-pressure cylinder 27 of the steam turbine. The second steam pipeline 252 branches off a second steam branch pipeline 2521 connected to the second molten salt heat exchanger 3 to use steam to heat the second molten salt heat exchanger 3. A valve can also be provided on the second steam branch pipeline 2521 to adjust the amount of input steam. The medium-pressure cylinder 27 of the steam turbine is connected to the low-pressure cylinder 28 of the steam turbine through a third steam pipeline 253 to provide steam for the low-pressure cylinder 28 of the steam turbine.

[0088] The first molten salt heat exchanger 2 is connected to the steam inlet of the boiler 25 through a first heat exchange return pipeline 2512 to form a heat exchange loop, so that the steam after releasing heat in the first molten salt heat exchanger 2 can still return to the reheater of the boiler 25, without affecting the reheated steam temperature and the reheater wall temperature of the boiler 25. The first heat exchange return pipeline 2512 can be directly connected with the steam return pipeline 261. The second molten salt heat exchanger 3 is connected to the low-pressure cylinder 28 of the steam turbine through a second steam return pipeline 2522, for example, the second steam return pipeline 2522 can be directly connected to the third steam pipeline 253. The steam extracted from the boiler 25 through the second steam branch pipeline 2521 enters the second molten salt heat exchanger 3 to release heat, and then returns to the low-pressure cylinder 28 of the steam turbine through the second steam return pipeline 2522 to do work, so that the energy can be maximally utilized. At the same time, the extracted steam returns to the low-pressure cylinder 28 of the steam turbine to continue to do work, without affecting the steam balance of the original boiler-steam turbine, and ensuring that the heat absorption and release processes of the molten salt heat storage and release device do not affect the stable operation of the unit.

[0089] Embodiment 2:

[0090] Reference Figure 1The embodiment provides a multi-stage electric heat pump-fused salt step heat storage steam supply method, and the method steps are as follows:

[0091] S1, a thermal power unit A provides steam to make a fused salt heat storage device store heat; that is, the steam on the side of the thermal power unit A: one steam is extracted from main steam, enters a first fused salt heat exchanger 2 in the fused salt heat storage device through a first steam branch 2511, and the steam after heat exchange is combined with the steam at the outlet of a high-pressure cylinder 26 of a steam turbine. One steam is further extracted from heat, enters a second fused salt heat exchanger 3 in the fused salt heat storage device through a second steam branch 2521, and the steam after heat exchange continues to enter a low-pressure cylinder 28 of the steam turbine to do work.

[0092] S2, one desalted water is introduced into the fused salt heat storage device after being continuously heated at multiple stages by a multi-stage electric heat pump B. Further to the step S2: the temperature of the desalted water after being continuously heated at multiple stages is 60-65 DEG C; and the pressure is 1.6-2.6 MPa.

[0093] The working fluid of the multi-stage electric heat pump B, i.e., desalted water, is described as follows: the desalted water from the water treatment system of a power plant is introduced into the multi-stage electric heat pump B, heated to hot water at, for example, 60-65°C, and introduced into the inlet of the molten salt heat storage device. The pressure of the desalted water at the inlet of the molten salt heat storage device can be designed according to the actual demand of industrial steam supply pressure, for example, the steam supply pressure can be designed as 1.6 MPa for the demand of medium-pressure industrial steam, and as 2.0 MPa or higher for the demand of high-pressure industrial steam. A pipeline pump 31 can be arranged on the pipeline leading to the heat absorption end 7 of the multi-stage electric heat pump B. That is, the inlet of the pipeline pump 31 is in communication with the outlet of the third condenser 201, and the outlet of the pipeline pump 31 is in communication with the heat absorption end 7. The desalted water can be pressurized to 2.2-2.6 MPa by the pipeline pump 31, and then introduced into the heat absorption end 7, i.e., the molten salt preheater, for heat absorption. The desalted water vapor-liquid two-phase flow after heat absorption is introduced into the molten salt drum 8, and the steam and the liquid are separated in the molten salt drum 8. The steam is heated to the required temperature in the molten salt superheater 9, and the temperature of the molten salt, i.e., ternary salt, is designed as 360°C. The molten salt superheater 9 can heat 2.6 MPa / 320°C steam for industrial steam users. The liquid in the molten salt drum 8 is introduced into the molten salt evaporator 10, and the steam after heat absorption and flash evaporation is returned to the molten salt drum 8. Specifically, the heat absorption end 7 is a tube-in-shell heat exchanger. The shell side of the tube-in-shell heat exchanger is the desalted water input from the multi-stage electric heat pump B, and the tube side of the tube-in-shell heat exchanger is steam, which is sourced from the molten salt drum 8. The molten salt drum 8 is a vapor-liquid separator. The steam side of the molten salt drum 8 is connected to the molten salt superheater 9 through a third transmission pipeline 12, and is also connected to the tube side of the heat absorption end 7 for preheating steam. The liquid side of the molten salt drum 8 is connected to the molten salt evaporator 10 for heat absorption and flash evaporation of the separated liquid desalted water to form steam, which is re-input into the steam side of the molten salt drum 8 and mixed with the steam in the steam side. The mixed steam continues to enter the molten salt superheater 9 through the third transmission pipeline 12, and enters the tube side of the heat absorption end 7. The steam in the heat absorption end 7 is re-input into the molten salt drum 8 for vapor-liquid separation. The separated steam in the steam side of the molten salt drum 8 is mixed with the flash evaporated steam from the molten salt evaporator 10 and then output to the molten salt superheater 9 and the tube side of the heat absorption end 7. The separated liquid is re-input into the molten salt evaporator 10 for flash evaporation to form flash evaporated steam. The specific operation process is as follows: initially, the desalted water input from the multi-stage electric heat pump B is first introduced into the heat absorption end 7, but there is no steam in the tube side of the heat absorption end 7 at this time, and the preheating function is not started. The desalted water is introduced into the molten salt drum 8 for vapor-liquid separation. A small amount of steam is first introduced into the molten salt superheater 9 and the tube side of the heat absorption end 7, which is called the starting period.After the desalted water passes through the molten salt drum 8 for vapor-liquid separation, the desalted water separated on the liquid side enters the molten salt evaporator 10, where it absorbs heat and flashes to form high-temperature flash steam. This flash steam enters the steam side of the molten salt drum 8 and mixes with the steam separated from the molten salt drum 8. The temperature of the mixed steam gradually increases as the cycle proceeds. The mixed steam is transported to the molten salt superheater 9 on one side and to the tube side of the heat absorption end 7 on the other side, providing heat exchange heat for the heat absorption end 7. At this time, the temperature of the tube side of the heat absorption end 7 gradually increases, and the heat absorption end 7 starts and enters normal operation. As the heat absorption end 7 operates normally, the steam ratio in the desalted water vapor-liquid two-phase flow after heat exchange at the heat absorption end 7 increases. This vapor-liquid two-phase flow then enters the molten salt drum 8 for vapor-liquid separation. The separated steam mixes with the flash steam from the molten salt evaporator 10 and heats up. It is then transported to the molten salt superheater 9 on one side and supplied to the tube side of the heat absorption end 7 on the other side. This cycle repeats, which is called a cycle period.

[0094] S3: The molten salt heat storage and discharge device absorbs heat from the desalted water after multi-stage heating and separates it into steam. This steam is then heated to the required temperature and supplied to industrial steam users. Here, the molten salt working fluid is explained: the ternary salt stored in the molten salt cold tank 1 is pumped into the first molten salt heat exchanger 2 via a molten salt pump, absorbing heat from the main steam in the first steam branch 2511. The heated ternary salt then flows directly into the molten salt hot tank 4. The ternary salt stored in the molten salt cold tank 1 is pumped into the second molten salt heat exchanger 3 via a molten salt pump, absorbing heat from the reheated steam in the second steam branch 2521. The heated ternary salt then flows directly into the molten salt hot tank 4. The 360°C ternary salt stored in the molten salt hot tank 4 enters the molten salt superheater 9 for molten salt-steam heat exchange. After heat exchange, the ternary salt enters the molten salt evaporator 10. After heat exchange in the molten salt evaporator 10, the ternary salt returns to the molten salt cold tank 1, completing its cycle in the molten salt system.

[0095] In addition, the multi-stage electric heat pump B is driven in the following manner:

[0096] Method 1 uses plant power to drive a multi-stage compression heat pump, recovering the unit's exhaust steam and waste heat. In this method, plant power drives the compressors in heat exchanger 17, first-stage heating mechanism 18, second-stage heating mechanism 19, and third-stage heating mechanism 20 via a transformer.

[0097] The second method is to use photovoltaic and plant power to drive, that is, if the thermal power plant has supporting photovoltaic, use photovoltaic power to drive the multi-stage compression heat pump, the focus is on absorbing photovoltaic power as much as possible, and if photovoltaic power cannot be used, it is necessary to use plant power to drive the multi-stage heat pump to recover the waste heat of the unit. In this method, refer to Figure 1As shown, the photovoltaic power station 32 drives the compressors in the heat exchanger 17, the first-stage heating mechanism 18, the second-stage heating mechanism 19 and the third-stage heating mechanism 20 through the transformer. At the same time, the auxiliary power is also connected to the compressors in the heat exchanger 17, the first-stage heating mechanism 18, the second-stage heating mechanism 19 and the third-stage heating mechanism 20 through the transformer. On a sunny day, the electricity generated by the photovoltaic power station 32 is used to drive the multi-stage electric heat pump B, and the surplus electricity is integrated into the auxiliary power 33. On a rainy day or at night, the multi-stage electric heat pump B can be driven by the auxiliary power. Under the national "carbon peak and carbon neutralization" policy, actively developing new energy has become the trend of the times, and each province gradually carries out the construction of thermal power unit flexibility and plant photovoltaic power. Photovoltaic power generation is more economical because of its special timeliness, and can reduce environmental pollution and achieve zero carbon emission.

[0098] Reference Figure 1 Further combing the use process of the present application, the description is only an example of combining the above-mentioned multiple preferred modes to facilitate comprehensive description, but this description is not a limitation of the embodiments of the present application, and the description is as follows:

[0099] The ternary salt stored in the molten salt cold tank 1 is pumped into the first molten salt heat exchanger 2 by the molten salt pump, absorbs the heat from the main steam in the first steam branch 2511, and the heated ternary salt directly enters the molten salt hot tank 4. The ternary salt stored in the molten salt cold tank 1 is pumped into the second molten salt heat exchanger 3 by the molten salt pump, absorbs the heat from the reheated steam in the second steam branch 2521, and the heated ternary salt directly enters the molten salt hot tank 4. The 360℃ ternary salt stored in the molten salt hot tank 4 is subsequently introduced into the molten salt superheater 9 for molten salt-steam heat exchange.

[0100] A 200t / h (according to the actual industrial steam supply demand), 20℃ desalinated water is introduced by the desalinated water pipe 30, such as 330MW unit, the desalinated water pipe pressure is 0.4-0.5Mpa. The desalinated water enters the multi-stage electric heat pump B, and we take three-stage heating as an example, that is, the multi-stage electric heat pump B is a three-stage green electric heat pump. The desalinated water is first heated to 30℃ by the heat exchanger 17, then enters the first-stage condenser 181 and is heated to 45℃, then enters the second-stage condenser 191 and is heated to 55℃, and finally enters the third-stage condenser 201 and is heated to 65℃, and then is pumped into the heat absorption end 7 of the molten salt heat storage device by the pipe pump 31. The inlet desalinated water pressure of the heat absorption end 7 is designed according to the actual demand of the industrial steam supply pressure. For the demand of medium-pressure industrial steam, the steam supply pressure can be designed as 1.6Mpa. For the demand of high-pressure industrial steam, the pressure can be designed as more than 2.0Mpa. In this embodiment, the pressure is taken as an example of being increased to 2.2-2.6Mpa by the pipe pump. The desalinated water enters the heat absorption end 7, that is, the molten salt preheater, absorbs heat, and the vapor-liquid two-phase flow after heat absorption enters the molten salt drum 8, and after vapor-liquid separation in the molten salt drum, the steam enters the molten salt superheater 9 through the third transmission pipeline 12 and is heated to the required temperature by molten salt-steam heat exchange. The molten salt, that is, ternary salt, is designed at 360℃, and 2.6Mpa / 320℃ steam can be supplied to the industrial steam user through the discharge pipeline 29. The ternary salt after heat exchange in the molten salt superheater 9 enters the molten salt evaporator 10 for heat exchange. The liquid side water in the molten salt drum 8 also enters the molten salt evaporator 10, is flashed after heat absorption in the molten salt evaporator 10, and the steam is returned to the molten salt drum 8. The ternary salt after heat exchange in the molten salt evaporator 10 returns to the molten salt cold tank 1, and completes the circulation in the molten salt system.

[0101] The steam after heat release in the first molten salt heat exchanger 2 returns to the boiler 25 reheater through the first heat exchange return pipe 2512, without affecting the reheating steam temperature and reheater wall temperature of the boiler 25. The steam after heat release in the second molten salt heat exchanger 3 returns to the steam turbine low-pressure cylinder 28 to do work through the second heat exchange return pipe 2522, and the energy is used to the maximum extent. At the same time, the extracted steam returns to the steam turbine low-pressure cylinder 28 to continue to do work, without damaging the original boiler-turbine steam balance, and ensuring that the heat absorption and release processes of the molten salt heat storage device do not affect the stable operation of the unit.

[0102] In summary, the present application maximizes the recovery of unit waste heat, increases the external steam supply capacity of the thermal power unit, and solves the problems existing in the prior art, and is beneficial to popularization and application in the field of industrial steam supply technology.

[0103] In the description of the application, it should be understood that the terms "first", "second" are used only for descriptive purposes and are not to be construed as indicating or implying relative importance or an indicated number of technical features. Therefore, the features defined with "first", "second" can explicitly or implicitly include one or more of the features. In the description of the application, the meaning of "a plurality of" is two or more, unless otherwise explicitly specified and limited.

[0104] In the present application, unless otherwise explicitly specified and limited, the term "connection" and other terms should be understood broadly, for example, it can be fixed connection, or detachable connection, or integral; it can be directly connected, or indirectly connected through intermediate medium; it can also be the internal communication of two elements. For those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0105] In the description of the present application, the description of the terms "embodiment" and the like means that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are contained in at least one embodiment or example of the present application. In the present application, the illustrative description of the above terms is not necessarily directed to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine the different embodiments or examples described in the present application and the features of the different embodiments or examples without contradiction.

[0106] Although the embodiments of the present application have been shown and described above, it should be understood that the above embodiments are exemplary and cannot be construed as limiting the present application, and those skilled in the art can modify, modify, replace and modify the above embodiments within the scope of the present application.

Claims

1. A multi-stage electric heat pump-molten salt cascade heat storage steam supply device, characterized by: It includes a thermal power unit (A), a molten salt heat storage and release device, and a multi-stage electric heat pump (B); The thermal power unit (A) is connected to the molten salt heat storage and release device to provide heat storage steam for the molten salt heat storage and release device; The molten salt heat storage and release device is connected to the multi-stage electric heat pump (B) to convert the desalted water introduced from the multi-stage electric heat pump (B) into superheated steam after multiple heating; The molten salt heat storage and release device includes a molten salt heat storage device (C) and a molten salt heat release device (D); The multi-stage electric heat pump (B) is driven by plant power or by a combination of photovoltaic and plant power. The multi-stage electric heat pump (B) comprises a heat exchanger (17), a first-stage heating mechanism (18), a second-stage heating mechanism (19) and a third-stage heating mechanism (20); the heat exchanger (17) is connected to a desalted water inlet pipe (30); the desalted water introduced through the desalted water inlet pipe (30) passes through the heat exchanger (17), the first-stage heating mechanism (18), the second-stage heating mechanism (19) and the third-stage heating mechanism (20) in sequence and is then input into the molten salt heat release device (D); The molten salt heat storage device (C) comprises a molten salt cold tank (1), a first molten salt heat exchanger (2), a second molten salt heat exchanger (3) and a molten salt hot tank (4); the molten salt cold tank (1) is connected to the first molten salt heat exchanger (2) via a first transmission pipeline (5), and is connected to the second molten salt heat exchanger (3) via a second transmission pipeline (6); the first molten salt heat exchanger (2) and the second molten salt heat exchanger (3) both exchange heat with steam from the thermal power unit (A), and are both connected to the molten salt hot tank (4) via pipelines; The molten salt heat release device (D) comprises a heat absorption end (7), a molten salt drum (8), a molten salt superheater (9) and a molten salt evaporator (10); the heat absorption end (7) is used to receive hot desalted water from a multi-stage electric heat pump (B) and is connected to the molten salt drum (8) through a first loop (11); the molten salt drum (8) is connected to the molten salt superheater (9) through a third transmission pipeline (12); the molten salt superheater (9) is connected to the molten salt evaporator (10) through a fourth transmission pipeline (13); the molten salt evaporator (10) is connected to the molten salt drum (8) through a second loop (14); The molten salt hot tank (4) is connected to the molten salt superheater (9) via a fifth transmission pipeline (15); the molten salt evaporator (10) is connected to the molten salt cold tank (1) via a sixth transmission pipeline (16).

2. The multi-stage electric heat pump-molten salt cascade heat storage steam supply device according to claim 1, characterized in that: The desalted water introduced through the desalted water inlet pipe (30) passes through the heat exchanger (17), the first-stage heating mechanism (18), the second-stage heating mechanism (19) and the third-stage heating mechanism (20) in sequence and is then input to the heat absorption end (7).

3. The multi-stage electric heat pump-molten salt cascade heat storage steam supply device according to claim 2, characterized in that: The heat exchanger (17) is connected to the first-stage condenser (181) in the first-stage heating mechanism (18) through a first desalted water outlet pipe (21); the first-stage condenser (181) is connected to the second-stage condenser (191) in the second-stage heating mechanism (19) through a second desalted water outlet pipe (22); the second-stage condenser (191) is connected to the third-stage condenser (201) in the third-stage heating mechanism (20) through a third desalted water outlet pipe (23); and the third-stage condenser (201) is connected to the heat absorption end (7) through a pipeline.

4. The multi-stage electric heat pump-molten salt cascade heat storage steam supply device according to claim 3, characterized in that: The heat exchanger (17) is connected to the first-stage evaporator (182) in the first-stage heating mechanism (18), the second-stage evaporator (192) in the second-stage heating mechanism (19), and the third-stage evaporator (202) in the third-stage heating mechanism (20) through a circulating water pipeline (24).

5. The multi-stage electric heat pump-molten salt cascade heat storage steam supply device according to claim 1, characterized in that: The thermal power unit includes a boiler (25), a steam turbine high-pressure cylinder (26), a steam turbine intermediate-pressure cylinder (27) and a steam turbine low-pressure cylinder (28); The boiler (25) is connected to the steam turbine high-pressure cylinder (26), the steam turbine intermediate-pressure cylinder (27), the first molten salt heat exchanger (2) and the second molten salt heat exchanger (3) through a pipeline; the steam turbine intermediate-pressure cylinder (27) is connected to the steam turbine low-pressure cylinder (28) through a pipeline; and the steam turbine high-pressure cylinder (26) is connected to the boiler (25) through a steam return pipe (261).

6. The multi-stage electric heat pump-molten salt cascade heat storage steam supply device according to claim 5, characterized in that: The boiler (25) is connected to the high-pressure cylinder (26) of the steam turbine via a first steam pipeline (251), and a first steam branch (2511) is branched off from the first steam pipeline (251) and connected to the first molten salt heat exchanger (2); the boiler (25) is connected to the intermediate-pressure cylinder (27) of the steam turbine via a second steam pipeline (252), and a second steam branch (2521) is branched off from the second steam pipeline (252) and connected to the second molten salt heat exchanger (3).

7. The multi-stage electric heat pump-molten salt cascade heat storage steam supply device according to claim 6, characterized in that: The first molten salt heat exchanger (2) is connected to the boiler (25) via a first heat exchange return pipe (2512); the second molten salt heat exchanger (3) is connected to the steam turbine low-pressure cylinder (28) via a second heat exchange return pipe (2522).

8. A multi-stage electric heat pump-molten salt cascade heat storage steam supply method, characterized in that: The multi-stage electric heat pump-molten salt cascade heat storage steam supply device according to any one of claims 1 to 7 is used, and the method steps are as follows: S1. The thermal power unit (A) provides steam to enable the molten salt heat storage and release device to store heat; The steam from the thermal power unit (A) enters the molten salt heat storage device (C). The steam after heat exchange merges with the outlet steam of the thermal power unit (A). Then, a path of steam is extracted and enters the molten salt heat storage device (C). The steam after heat exchange continues to enter the thermal power unit (A) to perform work. S2, lead the demineralized water through a multi-stage electric heat pump (B) for multi-stage continuous temperature increase and then lead it into the molten salt heat storage and release device; The desalted water enters the heat absorbing end (7) of the molten salt heat releasing device (D) to absorb heat, and the desalted water vapor-liquid two-phase flow after heat absorption enters the molten salt drum (8), and after the vapor and liquid are separated in the molten salt drum (8), the steam enters the molten salt superheater (9) and is heated to the required temperature. The liquid side water in the molten salt drum (8) enters the molten salt evaporator (10), and after absorbing heat and flash evaporation in the molten salt evaporator (10), the steam is returned to the molten salt drum (8); S3. The molten salt heat storage and release device absorbs heat from the desalted water after multi-stage heating and separates the steam and liquid to form steam. The steam is heated to the required temperature and then supplied to industrial steam users. The ternary salt stored in the molten salt cold tank (1) is pumped into the molten salt heat storage device (C) to absorb the steam heat from the thermal power unit (A), and the heated ternary salt directly enters the molten salt heat storage device (C); the ternary salt stored in the molten salt cold tank (1) is pumped into the molten salt heat storage device (C) to absorb the reheated steam heat from the thermal power unit (A), and the heated ternary salt directly enters the molten salt heat storage device (C); the ternary salt stored in the molten salt heat storage device (C) enters the molten salt superheater (9) for molten salt-steam heat exchange, and the ternary salt after heat exchange enters the molten salt evaporator (10), and the ternary salt after heat exchange in the molten salt evaporator (10) returns to the molten salt heat storage device (C), completing the cycle in the molten salt system.

9. The multi-stage electric heat pump-molten salt cascade heat storage and steam supply method according to claim 8, characterized in that: In the step S2, the temperature of the desalted water after multi-stage continuous heating is 60-65°C and the pressure is 1.6-2.6 MPa.

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