Thermal power generating unit energy efficient utilization system coupling solar energy and fused salt heat storage

Abstract

The invention provides a thermal power generating unit energy efficient utilization system coupling solar energy and fused salt heat storage, which comprises a boiler, a steam turbine and a regenerative air exhaust system, the boiler is used for generating steam input into the steam turbine, an outlet of the steam turbine is connected with the regenerative air exhaust system, and the thermal power generating unit energy efficient utilization system further comprises a solar fused salt multi-stage heat exchange system; the solar fused salt multi-stage heat exchange system comprises a solar heat collector, a multi-stage heat exchange system and a pumping system. The solar heat collector and the multi-stage heat exchange system form a closed loop through the pumping system; a medium conveyed by the pumping system is fused salt; and at least one stage of heat exchange system is used for reducing the steam extraction amount of a steam turbine in the regenerative air extraction system by preheating condensate water entering the boiler. According to the invention, gradient utilization of solar energy is realized, the steam extraction amount of the steam turbine is reduced, and the time of a starting-grid connection process of a unit is shortened.

Description

Technical Field

[0001] The present invention relates to the field of thermal power generation, and in particular to a thermal power unit energy efficient utilization system coupling solar energy and molten salt heat storage. Background Art

[0002] my country's current resource structure determines that the main source of electricity in my country is thermal power generation. Thermal power generation has the advantages of stability and high efficiency, but with the shortage of coal resources, traditional power generation methods are facing severe tests. It has become an inevitable trend to accelerate the transformation of my country's electricity towards a low-carbon, clean and green direction and use renewable energy such as solar energy and green hydrogen to replace conventional fossil energy for power generation.

[0003] As a clean energy, green hydrogen has the advantages of easy combustion and high combustion efficiency. In recent years, with the continuous development of water electrolysis technology, it has been widely used in the energy and chemical fields. Mixing green hydrogen with traditional fossil fuels such as coal powder can reduce carbon emissions. Mixing green hydrogen into natural gas pipelines for transportation can replace part of the natural gas.

[0004] At the same time, with the large-scale grid-connected power generation of renewable energy, whether the power system can operate safely and stably is an urgent problem to be solved. The ability of thermal power units to achieve deep peak regulation is the key to ensuring the safe and stable operation of the power grid. Due to the strong coupling relationship between the boiler and the steam turbine of the thermal power unit, it is difficult to achieve deep peak regulation by relying on the unit itself. When the unit is cold-started, the internal temperature of the boiler and the steam turbine is low. In order to ensure the normal operation of the unit, the boiler and the steam turbine need to be warmed up respectively. The commonly used method is to ignite and heat up the boiler, raise the main steam temperature to the temperature required for warming up, and then put the steam turbine into use. This method will result in a longer start-up time for the unit, a lower power system operation regulation capability, and weaker unit operation flexibility. Summary of the invention

[0005] In view of the deficiencies in the prior art, the present invention provides an energy efficient utilization system for thermal power units that couples solar energy and molten salt heat storage, which utilizes solar thermal energy collected by solar collectors to heat molten salt, and stores the heated molten salts at different temperatures in corresponding storage tanks. The high-temperature molten salt exchanges heat with the steam from the boiler through a steam-molten salt heat exchanger; the medium-temperature molten salt exchanges heat with the provided air through an air-molten salt heat exchanger; the low-temperature molten salt exchanges heat with the condensed water from the condenser through a water-molten salt heat exchanger; in addition, the solar photovoltaic array electrolyzes water with the generated electricity through photoelectric conversion, and the generated oxygen is sent to the boiler to enable the boiler to perform oxygen-enriched combustion, and the generated hydrogen is sent to the boiler to be mixed with coal powder for combustion to reduce carbon emissions. The system realizes the cascade utilization of solar energy, reduces the steam extraction of the steam turbine, shortens the time of the unit's "start-grid connection" process, greatly improves the unit's operating flexibility, reduces carbon emissions, and has great energy-saving benefits.

[0006] The present invention achieves the above technical objectives through the following technical means.

[0007] A thermal power unit energy efficient utilization system coupled with solar energy and molten salt heat storage, comprising a boiler, a steam turbine and a heat recovery and exhaust system, wherein the boiler is used to generate steam input into the steam turbine, the outlet of the steam turbine is connected to the heat recovery and exhaust system, and condensed water is preheated by reusing steam of different pressures generated by the steam turbine; and also comprising a solar molten salt multi-stage heat exchange system;

[0008] The solar molten salt multi-stage heat exchange system includes a solar collector, a multi-stage heat exchange system and a pumping system; the solar collector forms a closed loop with the multi-stage heat exchange system through the pumping system; the medium transported by the pumping system is molten salt; at least one stage of the heat exchange system is used to reduce the steam extraction amount of the turbine in the heat recovery extraction system by preheating the condensate entering the boiler.

[0009] Furthermore, the multi-stage heat exchange system is a two-stage heat exchange system, wherein a first-stage heat exchange system is used to preheat condensed water, and another-stage heat exchange system is used to preheat air entering the boiler.

[0010] Furthermore, the multi-stage heat exchange system is a three-stage heat exchange system, the third-stage heat exchange system is used to preheat the condensate entering the boiler, the second-stage heat exchange system is used to heat the air entering the boiler, and the first-stage heat exchange system is used to heat the steam at the boiler outlet. The pumping system enables the solar collector to form a closed loop with the first-stage heat exchange system, the second-stage heat exchange system and the third-stage heat exchange system.

[0011] Furthermore, the three-stage heat exchange system includes a water-molten salt heat exchanger, an air-molten salt heat exchanger, a steam-molten salt heat exchanger, a first heat storage device, a second heat storage device, and a third heat storage device; the solar collector is connected to the first heat storage device through a pumping system; the first heat storage device is connected to the steam-molten salt heat exchanger through a pumping system, and is used to heat the steam at the boiler outlet; the steam-molten salt heat exchanger outlet is connected to the second heat storage device, and the second heat storage device is connected to the air-molten salt heat exchanger through a pumping system, and is used to heat the air entering the boiler; the air-molten salt heat exchanger outlet is connected to the third heat storage device, and the third heat storage device is connected to the water-molten salt heat exchanger through a pumping system, and is used to preheat the condensate entering the boiler.

[0012] Furthermore, the first heat storage device stores molten salt flowing out of the solar collector; the second heat storage device stores molten salt flowing out of the outlet of the steam-molten salt heat exchanger; the third heat storage device stores molten salt flowing out of the outlet of the air-molten salt heat exchanger; the temperature of the molten salt stored in the first heat storage device is greater than the temperature of the molten salt stored in the second heat storage device, and the temperature of the molten salt stored in the third heat storage device is greater than the temperature of the molten salt stored in the third heat storage device.

[0013] Furthermore, it also includes a water electrolysis device and a solar photovoltaic array, wherein the solar photovoltaic array uses solar energy to generate electrical energy; the water electrolysis device uses the electrical energy generated by the solar photovoltaic array to generate hydrogen and oxygen through electrolysis.

[0014] Furthermore, the generated oxygen is input into the boiler for oxygen-enriched combustion in the boiler; and the generated hydrogen is input into the boiler for mixing with pulverized coal for combustion.

[0015] The beneficial effects of the present invention are:

[0016] 1. The energy efficient utilization system of thermal power units coupled with solar energy and molten salt heat storage described in the present invention preheats the condensed water entering the boiler through the first-stage heat exchange system in the multi-stage heat exchange system, thereby reducing the steam extraction of the turbine in the heat recovery extraction system. In the prior art, the condensed water passes through the low-pressure heater and the high-pressure heater in sequence, wherein the heat exchange of the low-pressure heater and the high-pressure heater generally comes from steam of different pressures at various stages in the steam turbine, which consumes a lot of steam in the steam turbine and increases the steam extraction. The present invention utilizes solar thermal energy to heat the molten salt and utilizes one of the first-stage heat exchange systems to heat the condensed water, thereby reducing the amount of heating of the boiler feed water by the high-pressure heater, thereby reducing the steam extraction of the steam turbine.

[0017] 2. The energy efficient utilization system of thermal power units coupled with solar energy and molten salt heat storage described in the present invention is provided with a three-stage heat exchange system. The third-stage heat exchange system is used to preheat the condensed water entering the boiler and reduce the steam extraction of the steam turbine; the second-stage heat exchange system uses solar thermal energy to heat the air entering the furnace, rapidly increases the temperature of the air entering the furnace, and makes the fuel fully burn when the boiler is ignited, reduces the amount of fuel, and allows the boiler to quickly enter the warm-up state; the first-stage heat exchange system uses solar thermal energy to heat the steam at the boiler outlet, so that the temperature of the steam further rises before entering the steam turbine, allowing the steam turbine to quickly enter the warm-up state.

[0018] 3. The energy efficient utilization system of thermal power units coupled with solar energy and molten salt heat storage described in the present invention uses the electricity obtained by the solar photovoltaic array to electrolyze water, and the generated oxygen is sent to the boiler to make the boiler perform oxygen-enriched combustion, which is more complete. The generated hydrogen is sent to the boiler to be mixed with coal powder for combustion, which reduces the use of coal powder and reduces carbon emissions. The system can shorten the time of the unit's "start-up-grid connection" process, greatly improve the unit's operating flexibility, reduce carbon emissions, and have great energy-saving benefits. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the description of the prior art will be briefly introduced below. The drawings described below are some embodiments of the present invention. For ordinary technicians in this field, it is obvious that other drawings can be obtained based on these drawings without paying any creative work.

[0020] Figure 1 This is a schematic diagram of the energy efficient utilization system of a thermal power unit coupling solar energy and molten salt heat storage according to the present invention.

[0021] In the figure:

[0022] 1- boiler; 2- turbine; 3- condenser; 4- condensate pump; 5- low-pressure heater; 6- deaerator; 7- feed pump; 8- high-pressure heater; 9- water-molten salt heat exchanger; 10- air-molten salt heat exchanger; 11- steam-molten salt heat exchanger; 12- low-temperature heat storage tank; 13- medium-temperature heat storage tank; 14- high-temperature heat storage tank; 15- solar collector; 16- low-temperature molten salt pump; 17- low-temperature molten salt regulating valve; 18- medium-temperature molten salt pump; 19- medium-temperature molten salt regulating valve; 20- high-temperature molten salt pump; 21- high-temperature molten salt regulating valve; 22- low-temperature molten salt control valve; 23- high-temperature molten salt control valve; 24- solar photovoltaic array; 25- water electrolysis device. DETAILED DESCRIPTION

[0023] Embodiments of the present invention are described in detail below, examples of which are shown in the accompanying drawings, wherein the same or similar reference numerals throughout represent the same or similar elements or elements having the same or similar functions. The embodiments described below with reference to the accompanying drawings are exemplary and are intended to be used to explain the present invention, and should not be construed as limiting the present invention.

[0024] In the description of the present invention, it should be understood that the terms "center", "longitudinal", "lateral", "length", "width", "thickness", "upper", "lower", "axial", "radial", "vertical", "horizontal", "inner", "outer" and the like indicate positions or positional relationships based on the positions or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as limiting the present invention. In addition, the terms "first" and "second" are only used for descriptive purposes, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of technical features indicated. Thus, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "multiple" is two or more, unless otherwise clearly and specifically defined.

[0025] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection or an electrical connection; it can be a direct connection, or it can be an indirect connection through an intermediate medium, or it can be the internal communication of two components. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0026] like Figure 1 As shown, the energy efficient utilization system of thermal power units coupled with solar energy and molten salt heat storage of the present invention comprises a boiler 1, a steam turbine 2 and a heat recovery and exhaust system, wherein the boiler 1 is used to generate steam input to the steam turbine 2, and the outlet of the steam turbine 2 is connected to the heat recovery and exhaust system, and condensed water is preheated by reusing steam of different pressures generated by the steam turbine 2; the heat recovery and exhaust system comprises a steam turbine 2, a condenser 3, a condensate pump 4, a low-pressure heater 5, a deaerator 6, a feed water pump 7 and a high-pressure heater 8, and the steam side outlet of the boiler 1 is sequentially connected to the steam turbine 2, the condenser 3, the condensate pump 4, the low-pressure heater 5, the deaerator 6, the feed water pump 7, the high-pressure heater 8 and the inlet of the boiler 1. The circuits of different pressures of the steam turbine 2 are respectively connected to the low-pressure heater 5 and the high-pressure heater 8 for heating the condensed water. In the prior art, a large amount of steam in the steam turbine 2 needs to be consumed to heat the condensed water, resulting in an increase in the amount of steam extraction.

[0027] Therefore, the present invention also includes a solar molten salt multi-stage heat exchange system; the solar molten salt multi-stage heat exchange system includes a solar collector 15, a multi-stage heat exchange system and a pumping system; the solar collector 15 forms a closed loop with the multi-stage heat exchange system through the pumping system; the medium transported by the pumping system is molten salt; the first-stage heat exchange system in the multi-stage heat exchange system preheats the condensed water entering the boiler 1, which can reduce the steam extraction of the turbine in the heat recovery and exhaust system. In particular, the consumption of the high-pressure heater 8, the high-pressure heater 8 is only used at the beginning, and the condensed water can be heated by the first-stage heat exchange system later, so there is no need to consume high-pressure steam.

[0028] In one embodiment of the present invention, the multi-stage heat exchange system is a two-stage heat exchange system, in which the first-stage heat exchange system is used to preheat condensed water, and the other-stage heat exchange system is used to preheat the air entering the boiler 1, which can quickly increase the temperature of the air entering the furnace, so that the fuel can be fully burned when the boiler is ignited, reduce the amount of fuel, and allow the boiler to quickly enter the heating state.

[0029] like Figure 1As shown, in another embodiment of the present invention, the multi-stage heat exchange system is a three-stage heat exchange system, the third-stage heat exchange system is used to preheat the condensate entering the boiler 1, the second-stage heat exchange system is used to heat the air entering the boiler 1, and the first-stage heat exchange system is used to heat the steam at the outlet of the boiler 1. The pumping system is used to form a closed loop between the solar collector 15 and the first-stage heat exchange system, the second-stage heat exchange system and the third-stage heat exchange system.

[0030] The third-stage heat exchange system includes a water-molten salt heat exchanger 9 and a low-temperature heat storage tank 12, the inlet of the low-temperature heat storage tank 12 is connected to the molten salt side outlet of the air-molten salt heat exchanger 10, and the outlet of the low-temperature heat storage tank 12 is connected to the low-temperature molten salt pump 16, the low-temperature molten salt regulating valve 22, the molten salt side inlet of the water-molten salt heat exchanger 9 and the inlet of the solar collector 15. The outlet of the feed water pump 7 is also connected to the low-temperature molten salt control valve 22 and the water side inlet of the water-molten salt heat exchanger 9, and the water side outlet of the water-molten salt heat exchanger 9 is connected to the inlet of the boiler 1.

[0031] The second stage heat exchange system includes an air-molten salt heat exchanger 10 and a medium temperature heat storage tank 13, the inlet of the medium temperature heat storage tank 13 is connected to the molten salt side outlet of the steam-molten salt heat exchanger 11, and the outlet of the medium temperature heat storage tank 13 is connected to a medium temperature molten salt pump 18, a medium temperature molten salt regulating valve 19 and the molten salt side inlet of the air-molten salt heat exchanger 10. The air side inlet of the air-molten salt heat exchanger 10 directly provides air.

[0032] The third-stage heat exchange system includes a steam-molten salt heat exchanger 11 and a high-temperature heat storage tank 14, the inlet of the high-temperature heat storage tank 14 is connected to the outlet of the solar collector 15-1, and the outlet of the high-temperature heat storage tank 14 is connected to a high-temperature molten salt pump 20, a high-temperature molten salt regulating valve 21 and the molten salt side inlet of the steam-molten salt heat exchanger 11. The steam side outlet of the boiler 1 is also connected to the high-temperature molten salt control valve 23 and the flue gas side inlet of the steam-molten salt heat exchanger 11, and the flue gas side outlet of the flue gas-molten salt heat exchanger 11 is connected to the inlet of the steam turbine 2. The molten salt temperature in the high-temperature heat storage tank 14 is greater than the molten salt temperature in the medium-temperature heat storage tank 13 and greater than the molten salt temperature in the low-temperature heat storage tank 12.

[0033] The energy efficient utilization system of thermal power units coupled with solar energy and molten salt heat storage described in the present invention is provided with a three-stage heat exchange system. The third-stage heat exchange system is used to preheat the condensed water entering the boiler and reduce the steam extraction of the steam turbine; the second-stage heat exchange system uses solar thermal energy to heat the air entering the furnace, quickly increases the temperature of the air entering the furnace, so that the fuel is fully burned when the boiler is ignited, reduces the amount of fuel, and allows the boiler to quickly enter a warm-up state; the first-stage heat exchange system uses solar thermal energy to heat the steam at the boiler outlet, so that the temperature of the steam is further increased before entering the steam turbine, allowing the steam turbine to quickly enter a warm-up state.

[0034] The present invention also includes a water electrolysis device 25 and a solar photovoltaic array 24. The solar photovoltaic array 24 generates electricity using solar energy; the water electrolysis device 25 generates hydrogen and oxygen by electrolysis using the electricity generated by the solar photovoltaic array 24. The electricity obtained by the solar photovoltaic array is used to electrolyze water, and the generated oxygen is sent to the boiler to make the boiler perform oxygen-enriched combustion, which is more complete. The generated hydrogen is sent to the boiler and mixed with coal powder for combustion, which reduces the use of coal powder and reduces carbon emissions. The system can shorten the time of the unit's "start-grid connection" process, greatly improve the unit's operating flexibility, reduce carbon emissions, and have great energy-saving benefits.

[0035] It should be understood that although this specification is described according to various embodiments, not every embodiment contains only one independent technical solution. This narrative method of the specification is only for the sake of clarity. Those skilled in the art should regard the specification as a whole. The technical solutions in each embodiment may also be appropriately combined to form other implementation methods that can be understood by those skilled in the art.

[0036] The series of detailed descriptions listed above are only specific descriptions of feasible embodiments of the present invention. They are not intended to limit the scope of protection of the present invention. All equivalent embodiments or changes that do not deviate from the technical spirit of the present invention should be included in the scope of protection of the present invention.

Claims

1. A thermal power unit energy efficient utilization system coupled with solar energy and molten salt heat storage, comprising a boiler (1), a steam turbine (2) and a heat recovery and exhaust system, wherein the boiler (1) is used to generate steam input to the steam turbine (2), the outlet of the steam turbine (2) is connected to the heat recovery and exhaust system, and condensed water is preheated by reusing steam of different pressures generated by the steam turbine (2); characterized in that: It also includes a solar molten salt multi-stage heat exchange system; The solar molten salt multi-stage heat exchange system comprises a solar collector (15), a multi-stage heat exchange system and a pumping system; the solar collector (15) forms a closed loop with the multi-stage heat exchange system through the pumping system; the medium transported by the pumping system is molten salt; the first-stage heat exchange system in the multi-stage heat exchange system is used to reduce the steam extraction amount of the turbine in the heat recovery extraction system by preheating the condensate entering the boiler (1).

2. The energy efficient utilization system of thermal power units coupled with solar energy and molten salt heat storage according to claim 1 is characterized in that: The multi-stage heat exchange system is a two-stage heat exchange system, wherein a first-stage heat exchange system is used to preheat condensed water, and another-stage heat exchange system is used to preheat air entering the boiler (1).

3. The energy efficient utilization system of thermal power units coupled with solar energy and molten salt heat storage according to claim 1 is characterized in that: The multi-stage heat exchange system is a three-stage heat exchange system, wherein the third-stage heat exchange system is used to preheat condensed water entering the boiler (1), the second-stage heat exchange system is used to heat air entering the boiler (1), and the first-stage heat exchange system is used to heat steam at the outlet of the boiler (1). The pumping system enables the solar collector (15) to form a closed loop with the first-stage heat exchange system, the second-stage heat exchange system, and the third-stage heat exchange system.

4. The energy efficient utilization system of thermal power units coupled with solar energy and molten salt heat storage according to claim 3 is characterized in that: The three-stage heat exchange system comprises a water-molten salt heat exchanger (9), an air-molten salt heat exchanger (10), a steam-molten salt heat exchanger (11), a first heat storage device, a second heat storage device, and a third heat storage device; the solar collector (15) is connected to the first heat storage device via a pumping system; the first heat storage device is connected to the steam-molten salt heat exchanger (11) via a pumping system, and is used to heat the steam at the outlet of the boiler (1); the outlet of the steam-molten salt heat exchanger (11) is connected to the second heat storage device, and the second heat storage device is connected to the air-molten salt heat exchanger (10) via a pumping system, and is used to heat the air entering the boiler (1); the outlet of the air-molten salt heat exchanger (10) is connected to the third heat storage device, and the third heat storage device is connected to the water-molten salt heat exchanger (9) via a pumping system, and is used to preheat the condensed water entering the boiler (1).

5. The energy efficient utilization system of thermal power units coupled with solar energy and molten salt heat storage according to claim 4 is characterized in that: The first heat storage device stores molten salt flowing out of the solar collector (15); the second heat storage device stores molten salt flowing out of the outlet of the steam-molten salt heat exchanger (11); the third heat storage device stores molten salt flowing out of the outlet of the air-molten salt heat exchanger (10); the temperature of the molten salt stored in the first heat storage device is greater than the temperature of the molten salt stored in the second heat storage device, and the temperature of the molten salt stored in the third heat storage device is greater than the temperature of the molten salt stored in the third heat storage device.

6. The energy efficient utilization system of thermal power units coupled with solar energy and molten salt heat storage according to claim 1 is characterized in that: It also includes a water electrolysis device (25) and a solar photovoltaic array (24), wherein the solar photovoltaic array (24) generates electrical energy using solar energy; and the water electrolysis device (25) generates hydrogen and oxygen through electrolysis using the electrical energy generated by the solar photovoltaic array (24).

7. The energy efficient utilization system of thermal power units coupled with solar energy and molten salt heat storage according to claim 6 is characterized in that: The generated oxygen is input into the boiler (1) for oxygen-enriched combustion in the boiler; the generated hydrogen is input into the boiler (1) for mixing with coal powder for combustion.

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