Fuel gas and steam combined heat storage system based on fused salt and capacity calculation method

Abstract

The embodiment of the invention provides a gas-steam combined heat storage system based on fused salt and a capacity calculation method. The system comprises a gas turbine, a boiler, a gas heat exchanger, a steam heat exchanger, a high-temperature fused salt storage tank and a low-temperature fused salt storage tank. An outlet of the gas turbine is connected with a flue inlet of the boiler; the gas heat exchanger is respectively connected with a gas turbine and a flue between a high-temperature reheater and a high-pressure superheater in the boiler; the steam heat exchanger is respectively connected with the high-pressure superheater and a steam-water pipeline between a high-pressure steam pocket and a low-pressure steam pocket in the boiler; the low-temperature fused salt storage tank is connected with the high-temperature fused salt storage tank through a fused salt conveying pipeline, and the fused salt conveying pipeline is sequentially provided with a steam heat exchanger and a gas heat exchanger in series. The low-temperature fused salt is heated into high-temperature fused salt when sequentially passing through the steam heat exchanger and the gas heat exchanger along the fused salt conveying pipeline. The system realizes reasonable distribution of steam flow and gas flow, remarkably improves the heat exchange efficiency of the heat storage heat exchanger, improves the energy storage density of the fused salt heat storage system under unit mass, and reduces the cost.

Description

Technical Field

[0001] The disclosed embodiments belong to the technical field of gas-steam combined cycle power generation, and specifically relate to a molten salt-based gas-steam combined heat storage system and a capacity calculation method. Background Art

[0002] Gas-steam combined cycle generator sets have fast start-stop speeds, high energy utilization, and high peak load flexibility, making them very suitable for grid peak load dispatching. In recent years, the proportion of combined cycle cogeneration units has been increasing. Since most cogeneration units operate in accordance with the principle of "heat determines electricity", the units are unable to respond promptly and effectively to the loads of the power grid and the heat network at the same time, greatly reducing the economy and flexibility of the unit operation. At the same time, gas-steam combined cycle generator sets are frequently adjusted during actual operation, and the downstream heating safety cannot be guaranteed during shutdown. Standby gas boilers are mostly used for heating. Not only are the costs of multiple starts and stops huge, but the economy of boiler heating is also greatly reduced.

[0003] At present, thermal power units mainly use additional energy storage (heat storage) of a certain scale to assist in improving the deep peak regulation, rapid ramping capability and steam supply guarantee capability of the units. Among them, the widely used technologies include molten salt heat storage technology. For gas-steam combined cycle power generation units, existing research mainly adopts two routes: single steam extraction heating molten salt heat storage or gas extraction heating molten salt heat storage. For the use of steam latent heat to heat molten salt, it is limited by the pinch point temperature difference, and the maximum heating temperature of molten salt is basically between 200-250℃, the heat storage quality is low, and the system cycle efficiency is not high; for gas extraction heating, a large amount of gas is extracted to heat molten salt, which will lead to insufficient heat load of waste heat boiler and affect steam cycle operation.

[0004] In view of the above problems, it is necessary to propose a molten salt-based gas-steam combined heat storage system and capacity calculation method that is reasonably designed and effectively solves the above problems. Summary of the invention

[0005] The embodiments of the present disclosure aim to solve at least one of the technical problems existing in the prior art and provide a molten salt-based gas-steam combined heat storage system and a capacity calculation method.

[0006] One aspect of an embodiment of the present disclosure provides a molten salt-based gas-steam combined heat storage system, including a gas turbine, a boiler, a gas heat exchanger, a steam heat exchanger, a high-temperature molten salt storage tank, and a low-temperature molten salt storage tank;

[0007] The outlet of the gas turbine is connected to the flue inlet of the boiler;

[0008] The flue gas inlet of the gas heat exchanger is connected to the outlet of the gas turbine, and the flue gas outlet of the gas heat exchanger is connected to the flue between the high temperature reheater and the high pressure superheater of the boiler;

[0009] The gas heat exchanger is used to extract part of the outlet flue gas of the gas turbine, wherein the extracted flue gas enters the gas heat exchanger to release heat;

[0010] The steam inlet of the steam heat exchanger is connected to the outlet of the high-pressure superheater, and the steam outlet of the steam heat exchanger is connected to the steam-water pipeline between the high-pressure steam drum and the low-pressure steam drum in the boiler;

[0011] The steam heat exchanger is used to extract part of the outlet steam of the high-pressure superheater, wherein the extracted steam enters the steam heat exchanger to release heat;

[0012] The outlet of the low-temperature molten salt storage tank is connected to the inlet of the high-temperature molten salt storage tank through a molten salt delivery pipeline, and the steam heat exchanger and the gas heat exchanger are sequentially arranged in series on the molten salt delivery pipeline;

[0013] The low-temperature molten salt is heated to high-temperature molten salt when passing through the steam heat exchanger and the gas heat exchanger in sequence along the molten salt delivery pipeline.

[0014] Optionally, a smoke extraction valve is also included;

[0015] The first end of the flue gas valve is connected to the gas turbine, and the second end of the flue gas valve is connected to the flue gas inlet of the gas heat exchanger.

[0016] Optionally, a flue gas temperature sensor is also included;

[0017] The flue gas temperature sensor is arranged between the gas turbine and the flue gas valve.

[0018] Optionally, a smoke exhaust valve is also included;

[0019] The first end of the exhaust gas valve is connected to the gas heat exchanger, and the second end of the exhaust gas valve is connected to the steam-water pipeline between the high-pressure steam drum and the low-pressure steam drum.

[0020] Optionally, a steam extraction valve is also included;

[0021] The first end of the steam extraction valve is connected to the high-pressure superheater, and the second end of the steam extraction valve is connected to the steam inlet of the steam heat exchanger.

[0022] Optionally, a flow sensor is also included;

[0023] The flow sensor is arranged between the steam extraction valve and the high-pressure superheater.

[0024] Optionally, it also includes a pressure sensor and a temperature sensor connected in sequence; wherein,

[0025] The pressure sensor and the temperature sensor are arranged between the steam extraction valve and the steam heat exchanger.

[0026] Optionally, it also includes a steam exhaust valve; wherein,

[0027] The first end of the steam exhaust valve is connected to the steam outlet of the steam heat exchanger, and the second end of the steam exhaust valve is connected to the steam-water pipeline between the high-pressure steam drum and the low-pressure steam drum.

[0028] Another aspect of the embodiment of the present disclosure provides a method for calculating the capacity of a gas-steam combined heat storage system based on molten salt, using the system described above, wherein the calculation method includes:

[0029] The extraction steam pressure, extraction steam temperature, extraction steam flow rate and extraction flue gas temperature are obtained respectively, and the temperature difference value at the lower end of the steam heat exchanger, the temperature difference value at the pinch point of the steam heat exchanger, the temperature difference value at the lower end of the gas heat exchanger, the temperature value of the high-temperature molten salt storage tank and the temperature value of the low-temperature molten salt storage tank are set;

[0030] According to the steam extraction pressure, the steam extraction temperature, the steam extraction flow rate, the smoke gas temperature, the temperature difference at the lower end of the steam heat exchanger, the pinch point temperature difference of the steam heat exchanger, the temperature difference at the lower end of the gas heat exchanger, the high-temperature molten salt storage tank temperature value and the low-temperature molten salt storage tank temperature value, the smoke extractor flow rate and the heat storage power are calculated respectively.

[0031] Optionally, the smoke extractor flow rate and heat storage power are calculated by the following formulas:

[0032] t s1 -Δt win =t w1

[0033] t(P w )-Δt min =t s2

[0034] q w (h(t(P w ),P w )-h(t w1 ,P w ))=q s (h(t s2 )-h(t s1 ))

[0035] q w (h(t w3 ,P w )-h(t(P w ),P w ))=q s (h(t s3)-h(t s2 ))

[0036] t gout =t s3 +Δt g

[0037] Q=(t s4 -t s1 )q s

[0038] in,

[0039] P w represents the extraction steam pressure, t w3 represents the steam extraction temperature, q w represents the steam extraction flow rate, t gin represents the exhaust gas temperature, Δt win Indicates the temperature difference at the lower end of the steam heat exchanger, Δt min represents the pinch point temperature difference of the steam heat exchanger, Δt g represents the temperature difference at the lower end of the gas heat exchanger, t s1 represents the temperature value of the high temperature molten salt storage tank and t s4 Indicates the temperature value of the low-temperature molten salt storage tank;

[0040] q g represents the exhaust gas flow rate, Q represents the heat storage power, t w1 represents the outlet temperature of the water side of the steam heat exchanger, t s2 represents the flue gas temperature at the pinch point of the steam heat exchanger, q s represents the molten salt flow rate, t s3 represents the salt temperature at the salt side outlet of the steam heat exchanger and t gout Indicates the flue gas temperature at the outlet of the gas heat exchanger 23;

[0041] The thermodynamic specific enthalpy of steam is represented by the function h(t, p), and the saturation temperature is represented by the function t(p). The thermodynamic specific enthalpy and temperature of flue gas are represented by the functions h(t) and t(h), respectively.

[0042] The gas-steam combined heat storage system and capacity calculation method based on molten salt in the disclosed embodiment, by adding a molten salt heat storage system, when the power grid requires the unit to be deeply peaked, part of the gas turbine outlet flue gas and high-pressure superheater outlet steam are extracted through the gas heat exchanger and the steam heat exchanger respectively, the boiler inlet flue gas and high-pressure superheater outlet steam are reduced, and the boiler heat load and steam turbine work capacity are reduced simultaneously, so that the combined cycle unit can achieve a deep peaking effect. At the same time, the extracted flue gas and steam enter the steam heat exchanger and the gas heat exchanger to release heat, and the low-temperature molten salt is heated to high-temperature molten salt and then stored in the high-temperature molten salt storage tank, and the heat is released in the high-load stage of the unit for heating or power generation. The system not only improves the flexible operation capability of the gas-steam combined cycle power generation system, but also solves the problem that the pinch point temperature difference under the single steam heating mode limits the molten salt from reaching a very high temperature, realizes the reasonable distribution of steam flow and gas flow, significantly improves the heat exchange efficiency of the heat storage heat exchanger, and improves the energy storage density per unit mass of the molten salt heat storage system, reduces the system investment, and has broad application prospects in the combined cycle. BRIEF DESCRIPTION OF THE DRAWINGS

[0043] Figure 1 This is a schematic structural diagram of a gas-steam combined heat storage system based on molten salt according to an embodiment of the present disclosure. DETAILED DESCRIPTION

[0044] In order to enable those skilled in the art to better understand the technical solutions of the embodiments of the present disclosure, the embodiments of the present disclosure are further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0045] like Figure 1 As shown, one aspect of an embodiment of the present disclosure provides a molten salt-based gas-steam combined heat storage system, which includes a gas-steam combined cycle power generation system and a molten salt heat storage system.

[0046] Among them, the gas-steam combined cycle power generation system specifically includes a compressor 1, a combustion chamber 2, a gas turbine 3, a boiler 4, a high-pressure cylinder 5, a medium-pressure cylinder 6, a low-pressure cylinder 7, a condenser 8, a condensate pump 9, a medium-pressure feed water pump 10, a high-pressure feed water pump 11, a low-pressure economizer 12, a low-pressure superheater 13, a low-temperature reheater 14, a high-temperature reheater 15, a high-pressure superheater 16, a high-pressure steam drum 17, a medium-pressure steam drum 18, and a low-pressure steam drum 19.

[0047] Specifically, the compressor 1 is connected to the combustion chamber 2, the gas turbine 3, and the boiler 4 in sequence. The outlet of the high-pressure superheater 16 is connected to the inlet of the high-pressure cylinder 5, the outlet of the high-pressure cylinder 5 is connected to the outlet of the low-temperature reheater 14 and then enters the high-temperature reheater 15 together, the outlet of the high-temperature reheater 15 is connected to the inlet of the medium-pressure cylinder 6, the outlet of the medium-pressure cylinder 6 is connected to the inlet of the low-pressure cylinder 7, the low-pressure superheater 13 is connected to the inlet of the low-pressure cylinder 7, the outlet of the low-pressure cylinder 7 is connected to the inlet of the condenser 8, the outlet of the condenser 8 is connected to the inlet of the condensate pump 9, the outlet of the condensate pump 9 is connected to the inlet of the low-pressure economizer 12, and the low-pressure economizer 1 2 outlet is connected to the inlet of low-pressure drum 19, the steam outlet of low-pressure drum 19 is connected to the inlet of low-pressure superheater 13, the feedwater outlet of low-pressure drum 19 is connected to the inlet of medium-pressure feedwater pump 10 and the inlet of high-pressure feedwater pump 11 respectively, the outlet of medium-pressure feedwater pump 10 is connected to the inlet of medium-pressure drum 18, the steam outlet of medium-pressure drum 18 is connected to the inlet of low-temperature reheater 14, the outlet of high-pressure feedwater pump 11 is connected to the inlet of high-pressure drum 17, and the steam outlet of high-pressure drum 17 is connected to the inlet of high-pressure superheater 16.

[0048] The molten salt heat storage system mainly includes a gas heat exchanger 23 , a steam heat exchanger 22 , a high-temperature molten salt storage tank 21 and a low-temperature molten salt storage tank 20 .

[0049] The outlet of the gas turbine 3 is connected to the flue inlet of the boiler 4 .

[0050] The flue gas inlet of the gas heat exchanger 23 is connected to the outlet of the gas turbine 3 , and the flue gas outlet of the gas heat exchanger 23 is connected to the flue between the high-temperature reheater 15 and the high-pressure superheater 16 in the boiler 4 .

[0051] The gas heat exchanger 23 is used to extract part of the outlet flue gas of the gas turbine 3, wherein the extracted flue gas enters the gas heat exchanger 23 to release heat.

[0052] The steam inlet of the steam heat exchanger 22 is connected to the outlet of the high-pressure superheater 16 , and the steam outlet of the steam heat exchanger 22 is connected to the steam-water pipeline between the high-pressure steam drum 17 and the low-pressure steam drum 19 in the boiler 4 .

[0053] The steam heat exchanger 22 is used to extract part of the outlet steam of the high-pressure superheater 16, wherein the extracted steam enters the steam heat exchanger 22 to release heat.

[0054] The outlet of the low-temperature molten salt storage tank 20 is connected to the inlet of the high-temperature molten salt storage tank 21 through a molten salt delivery pipeline, and a steam heat exchanger 22 and a gas heat exchanger 23 are sequentially arranged in series on the molten salt delivery pipeline.

[0055] The low-temperature molten salt is heated to high-temperature molten salt when passing through the steam heat exchanger 22 and the gas heat exchanger 23 in sequence along the molten salt delivery pipeline.

[0056] Specifically, when the power grid requires deep peak regulation of the unit, the gas heat exchanger 23 is connected to the gas turbine 3 and the boiler 4 respectively, and the steam heat exchanger 22 is connected to the steam-water pipeline between the high-pressure superheater 16 and the high-pressure drum 17 and the low-pressure drum 19 of the boiler 4 respectively. Through the gas heat exchanger 23 and the steam heat exchanger 22, part of the flue gas at the outlet of the gas turbine 3 and the steam at the outlet of the high-pressure superheater 16 are extracted respectively, the flue gas at the inlet of the boiler 4 and the steam at the outlet of the high-pressure superheater 16 are reduced, and the heat load of the boiler 4 and the working capacity of the steam turbine are reduced simultaneously, so that the combined cycle unit can achieve a deep peak regulation effect. At the same time, the extracted flue gas and steam enter the steam heat exchanger 22 and the gas heat exchanger 23 to release heat, so that the low-temperature molten salt and the low-temperature molten salt flowing through the steam heat exchanger 22 and the gas heat exchanger 23 are heated to high-temperature molten salt and stored in the high-temperature molten salt storage tank 21, and release heat in the high-load stage of the unit for heating or power generation.

[0057] The gas-steam combined heat storage system based on molten salt in the disclosed embodiment not only improves the flexible operation capability of the gas-steam combined cycle power generation system, but also solves the problem that the pinch temperature difference under the single steam heating mode limits the molten salt from reaching a very high temperature, realizes the reasonable distribution of steam flow and gas flow, significantly improves the heat transfer efficiency of the heat storage heat exchanger, improves the energy storage density per unit mass of the molten salt heat storage system, reduces the system investment, and has broad application prospects in the combined cycle.

[0058] For example, Figure 1 As shown, the molten salt-based gas-steam combined heat storage system further includes a flue gas valve 27 . A first end of the flue gas valve 27 is connected to the gas turbine 3 , and a second end of the flue gas valve 27 is connected to a flue gas inlet of the gas heat exchanger 23 .

[0059] In this embodiment, the opening of the flue gas valve 27 can control part of the flue gas of the gas heat exchanger 23 to enter the gas heat exchanger 23 for heat exchange. In the normal mode of the unit operation, when the unit does not need deep peak regulation, the flue gas valve 27 is closed, and the gas heat exchanger 23 does not extract the flue gas at the outlet of the gas turbine 3; when the power grid requires the unit to perform deep peak regulation, the flue gas valve 27 is opened, and part of the flue gas at the outlet of the gas turbine 3 is extracted through the gas heat exchanger 23 to reduce the flue gas at the inlet of the boiler 4.

[0060] For example, Figure 1 As shown, the molten salt-based gas-steam combined heat storage system further includes a flue gas temperature sensor 31 , which is disposed between the gas turbine 3 and the flue gas valve 27 .

[0061] In this embodiment, the flue gas temperature sensor 31 can monitor the temperature of the flue gas entering the gas heat exchanger 23 .

[0062] For example, Figure 1As shown, the molten salt-based gas-steam combined heat storage system further includes an exhaust gas valve 26. A first end of the exhaust gas valve 26 is connected to the gas heat exchanger 23, and a second end of the exhaust gas valve 23 is connected to the steam-water pipeline between the high-pressure steam drum 17 and the low-pressure steam drum 19.

[0063] In this embodiment, by opening the exhaust gas valve 26, the flue gas after heat exchange in the flue gas heat exchanger 23 can be discharged to the steam-water pipeline between the high-pressure steam drum 17 and the low-pressure steam drum 19 for recycling.

[0064] For example, Figure 1 As shown, the molten salt-based gas-steam combined heat storage system further includes a steam extraction valve 24. A first end of the steam extraction valve 24 is connected to the high-pressure superheater 16, and a second end of the steam extraction valve 24 is connected to the steam inlet of the steam heat exchanger 22.

[0065] In this embodiment, the steam extraction valve 24 is opened to control the outlet steam of the high-pressure superheater 16 to enter the steam heat exchanger 22 for heat exchange.

[0066] For example, Figure 1 As shown, the molten salt-based gas-steam combined heat storage system further includes a flow sensor 30 , which is disposed between the steam extraction valve 24 and the high-pressure superheater 16 .

[0067] In this embodiment, the steam flow rate entering the steam heat exchanger 22 can be monitored by the flow sensor 30 .

[0068] For example, Figure 1 As shown, the molten salt-based gas-steam combined heat storage system further includes a pressure sensor 28 , wherein the pressure sensor 28 is disposed between the steam extraction valve 24 and the steam heat exchanger 22 .

[0069] In this embodiment, the pressure sensor 28 can be provided to monitor the pressure of the steam entering the steam heat exchanger 22 .

[0070] Exemplarily, the molten salt-based gas-steam combined heat storage system further includes a temperature sensor 29 ; wherein the temperature sensor 29 is disposed between the pressure sensor 28 and the steam heat exchanger 22 .

[0071] In this embodiment, the temperature of the steam entering the steam heat exchanger 2 can be monitored by providing a temperature sensor 29 .

[0072] For example, Figure 1 As shown, the molten salt-based gas-steam combined heat storage system also includes a steam exhaust valve 25; wherein the first end of the steam exhaust valve 25 is connected to the steam outlet of the steam heat exchanger 22, and the second end of the steam exhaust valve 25 is connected to the steam-water pipeline between the high-pressure steam drum 17 and the low-pressure steam drum 19.

[0073] like Figure 1 As shown, the working principle of the gas-steam combined heat storage system based on molten salt in the embodiment of the present disclosure is as follows:

[0074] Normal operating mode: When the power grid does not need deep peak regulation of the unit, the steam extraction valve 24, steam exhaust valve 25, flue gas valve 26, and flue gas valve 27 are closed, and gas and steam are not extracted for energy storage. The compressor 1 compresses the air into the combustion chamber 2 and fully burns with the fuel. The high-temperature gas generated drives the gas turbine 3 to do work, the exhaust gas enters the boiler 4, and the feed water enters the boiler 4 to absorb heat and generate high-temperature and high-pressure steam, and the steam enters the steam turbine to do work.

[0075] Energy storage peak-shaving mode: When the power grid requires deep peak-shaving of the unit, open the steam extraction valve 24, steam exhaust valve 25, flue gas exhaust valve 26, and flue gas extraction valve 27 to extract part of the flue gas at the outlet of the gas turbine 3 and the steam at the outlet of the high-pressure superheater 16, respectively, reduce the flue gas at the inlet of the boiler 4 and the steam at the outlet of the high-pressure superheater 16, and simultaneously reduce the thermal load of the boiler 4 and the working capacity of the steam turbine, so that the combined cycle unit can achieve deep peak-shaving effect. At the same time, the extracted flue gas and steam enter the steam heat exchanger 22 and the gas heat exchanger 23 to release heat, heat the low-temperature molten salt to high-temperature molten salt, and then store it in the high-temperature molten salt storage tank 21, and release heat in the high-load stage of the unit for heating or power generation.

[0076] In this embodiment, the steam after heat exchange in the steam heat exchanger 22 can be discharged into the steam-water pipeline between the high-pressure steam drum 17 and the low-pressure steam drum 19 by opening the steam exhaust valve 25 to be circulated.

[0077] During the energy storage process, the steam flow and flue gas flow need to be adjusted to ensure that the high-temperature molten salt temperature meets the requirements. Therefore, the matching flue gas flow needs to be calculated based on the steam extraction flow; at the same time, the maximum heat storage power needs to be calculated based on the maximum steam extraction flow to determine the maximum heat storage scale. In view of this, another aspect of the embodiment of the present disclosure provides a capacity calculation method for a gas-steam combined heat storage system based on molten salt.

[0078] Among them, a capacity calculation method of a gas-steam combined heat storage system based on molten salt in an embodiment of the present disclosure adopts the system described above. The specific structural features of the gas-steam combined heat storage system based on molten salt have been described in detail above and will not be repeated here.

[0079] The capacity calculation method of the molten salt-based gas-steam combined heat storage system includes:

[0080] The extraction steam pressure is obtained by the pressure sensor 28 , the extraction steam temperature is obtained by the temperature sensor 29 , the extraction steam flow is obtained by the flow sensor 30 , and the extraction flue gas temperature is obtained by the flue gas temperature sensor 31 .

[0081] And set the temperature difference value at the lower end of the steam heat exchanger, the temperature difference value at the pinch point of the steam heat exchanger, the temperature difference value at the lower end of the gas heat exchanger, the temperature value of the high-temperature molten salt storage tank, and the temperature value of the low-temperature molten salt storage tank;

[0082] According to the steam extraction pressure, the steam extraction temperature, the steam extraction flow rate, the smoke gas temperature, the temperature difference at the lower end of the steam heat exchanger, the pinch point temperature difference of the steam heat exchanger, the temperature difference at the lower end of the gas heat exchanger, the high-temperature molten salt storage tank temperature value and the low-temperature molten salt storage tank temperature value, the smoke extractor flow rate and the heat storage power are calculated respectively.

[0083] Specifically, the capacity of the heat storage system is obtained by the following formula:

[0084] t s1 -Δt win =t w1

[0085] t(P w )-Δt min =t s2

[0086] q w (h(t(P w ),P w )-h(t w1 ,P w ))=q s (h(t s2 )-h(t s1 ))

[0087] q w (h(t w3 ,P w )-h(t(P w ),P w ))=q s (h(t s3 )-h(t s2 ))

[0088] t gout =t s3 +Δt g

[0089] Q=(t s4 -t s1 )q s

[0090] in,

[0091] P w represents the extraction steam pressure, t w3 represents the steam extraction temperature, qw represents the steam extraction flow rate, t gin represents the exhaust gas temperature, Δt win Indicates the temperature difference at the lower end of the steam heat exchanger, Δt min represents the pinch point temperature difference of the steam heat exchanger, Δt g represents the temperature difference at the lower end of the gas heat exchanger, t s1 represents the temperature value of the high temperature molten salt storage tank and t s4 Indicates the temperature value of the low-temperature molten salt storage tank;

[0092] q g represents the exhaust gas flow rate, Q represents the heat storage power, t w1 represents the outlet temperature of the water side of the steam heat exchanger, t s2 represents the flue gas temperature at the pinch point of the steam heat exchanger, q s represents the molten salt flow rate, t s3 represents the salt temperature at the salt side outlet of the steam heat exchanger and t gout Indicates the flue gas temperature at the outlet of the gas heat exchanger 23;

[0093] The thermodynamic specific enthalpy of steam is represented by the function h(t, p), and the saturation temperature is represented by the function t(p). The thermodynamic specific enthalpy and temperature of flue gas are represented by the functions h(t) and t(h), respectively.

[0094] A capacity calculation method for a gas-steam combined heat storage system based on molten salt in an embodiment of the present disclosure can determine the ratio of steam extraction flow rate and gas flow rate according to the molten salt temperature of high and low temperature molten salt storage tanks and the steam extraction-gas temperature, thereby achieving a reasonable distribution of heat between the two locations.

[0095] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the embodiments of the present disclosure, but the embodiments of the present disclosure are not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the embodiments of the present disclosure, and these modifications and improvements are also considered to be within the protection scope of the embodiments of the present disclosure.

Claims

1. A gas-steam combined heat storage system based on molten salt, characterized in that: Including gas turbines, boilers, gas heat exchangers, steam heat exchangers, high-temperature molten salt storage tanks and low-temperature molten salt storage tanks; The outlet of the gas turbine is connected to the flue inlet of the boiler; The flue gas inlet of the gas heat exchanger is connected to the outlet of the gas turbine, and the flue gas outlet of the gas heat exchanger is connected to the flue between the high temperature reheater and the high pressure superheater of the boiler; The gas heat exchanger is used to extract part of the outlet flue gas of the gas turbine, wherein the extracted flue gas enters the gas heat exchanger to release heat; The steam inlet of the steam heat exchanger is connected to the outlet of the high-pressure superheater, and the steam outlet of the steam heat exchanger is connected to the steam-water pipeline between the high-pressure steam drum and the low-pressure steam drum in the boiler; The steam heat exchanger is used to extract part of the outlet steam of the high-pressure superheater, wherein the extracted steam enters the steam heat exchanger to release heat; The outlet of the low-temperature molten salt storage tank is connected to the inlet of the high-temperature molten salt storage tank through a molten salt delivery pipeline, and the steam heat exchanger and the gas heat exchanger are sequentially arranged in series on the molten salt delivery pipeline; The low-temperature molten salt is heated to high-temperature molten salt when passing through the steam heat exchanger and the gas heat exchanger in sequence along the molten salt delivery pipeline.

2. The system according to claim 1, characterized in that Also includes a smoke extraction valve; The first end of the flue gas valve is connected to the gas turbine, and the second end of the flue gas valve is connected to the flue gas inlet of the gas heat exchanger.

3. The system according to claim 2, characterized in that Also included is a flue gas temperature sensor; The flue gas temperature sensor is arranged between the gas turbine and the flue gas valve.

4. The system according to claim 1, characterized in that Also includes a smoke exhaust valve; The first end of the exhaust gas valve is connected to the gas heat exchanger, and the second end of the exhaust gas valve is connected to the steam-water pipeline between the high-pressure steam drum and the low-pressure steam drum.

5. The system according to claim 1, characterized in that Also included is a steam extraction valve; The first end of the steam extraction valve is connected to the high-pressure superheater, and the second end of the steam extraction valve is connected to the steam inlet of the steam heat exchanger.

6. The system according to claim 5, characterized in that Also included is a flow sensor; The flow sensor is arranged between the steam extraction valve and the high-pressure superheater.

7. The system according to claim 5, characterized in that It also includes a pressure sensor and a temperature sensor connected in sequence; wherein, The pressure sensor and the temperature sensor are arranged between the steam extraction valve and the steam heat exchanger.

8. The system according to claim 7, characterized in that Also includes a steam exhaust valve; wherein, The first end of the steam exhaust valve is connected to the steam outlet of the steam heat exchanger, and the second end of the steam exhaust valve is connected to the steam-water pipeline between the high-pressure steam drum and the low-pressure steam drum.

9. A method for calculating the capacity of a gas-steam combined heat storage system based on molten salt, characterized in that: The system according to any one of claims 1 to 8 is used, wherein the calculation method comprises: The extraction steam pressure, extraction steam temperature, extraction steam flow rate and extraction flue gas temperature are obtained respectively, and the temperature difference value at the lower end of the steam heat exchanger, the temperature difference value at the pinch point of the steam heat exchanger, the temperature difference value at the lower end of the gas heat exchanger, the temperature value of the high-temperature molten salt storage tank and the temperature value of the low-temperature molten salt storage tank are set; According to the steam extraction pressure, the steam extraction temperature, the steam extraction flow rate, the smoke gas temperature, the temperature difference at the lower end of the steam heat exchanger, the pinch point temperature difference of the steam heat exchanger, the temperature difference at the lower end of the gas heat exchanger, the high-temperature molten salt storage tank temperature value and the low-temperature molten salt storage tank temperature value, the smoke extractor flow rate and the heat storage power are calculated respectively.

10. The method according to claim 9, characterized in that The smoke extractor flow rate and heat storage power are calculated by the following formulas: t s1 -Δt win =t w1 t(P w )-Δt min =t s2 q w (h(t(P w ),P w )-h(t w1 ,P w ))=q s (h(t s2 )-h(t s1 )) q w (h(t w3 ,P w )-h(t(P w ),P w ))=q s (h(t s3 )-h(t s2 )) t gout =t s3 +Δt g Q=(t s4 -t s1 )q s in, P w represents the extraction steam pressure, t w3 represents the steam extraction temperature, q w represents the steam extraction flow rate, t gin represents the smoke gas temperature, Δt win Indicates the temperature difference at the lower end of the steam heat exchanger, Δt min represents the pinch point temperature difference of the steam heat exchanger, Δt g represents the temperature difference at the lower end of the gas heat exchanger, t s1 represents the temperature value of the high temperature molten salt storage tank and t s4 Indicates the temperature value of the low-temperature molten salt storage tank; q g represents the exhaust gas flow rate, Q represents the heat storage power, t w1 represents the outlet temperature of the water side of the steam heat exchanger, t s2 represents the flue gas temperature at the pinch point of the steam heat exchanger, q s represents the molten salt flow rate, t s3 represents the salt temperature at the salt side outlet of the steam heat exchanger and t gout Indicates the flue gas temperature at the outlet of the gas heat exchanger 23; The thermodynamic specific enthalpy of steam is represented by the function h(t, p), and the saturation temperature is represented by the function t(p). The thermodynamic specific enthalpy and temperature of flue gas are represented by the functions h(t) and t(h), respectively.

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