A power generation system with decoupling of boiler regulation process based on high-temperature molten salt energy storage

Abstract

The present invention discloses a power generation system with decoupling of the boiler regulation process based on high-temperature molten salt energy storage; comprising: a boiler, a water vapor coal-fired power generation system, a molten salt storage tank group and a sCO2 circulation system arranged outside the boiler; a molten salt heat exchanger is arranged in the boiler, and the inlet and outlet of the molten salt heat exchanger are connected to the molten salt working medium inlet and outlet of the molten salt storage tank group; the molten salt heat storage tank system comprises: a working group and a standby group in which both the carbon dioxide working medium pipeline and the molten salt working medium pipeline are connected in parallel, and both the working group and the standby group are provided with a carbon dioxide working medium inlet and outlet and a molten salt working medium inlet and outlet, and the standby group carbon dioxide working medium outlet merges with the working group carbon dioxide working medium outlet and is connected to the turbine inlet in the sCO2 circulation system as the carbon dioxide working medium outlet of the molten salt heat storage tank system. The present invention combines the S-CO2 cycle with high-temperature molten salt energy storage, and the molten salt energy storage can decouple the boiler regulation process and break through the existing variable load rate bottleneck.

Description

Technical Field

[0001] The present invention belongs to the technical field of steam superheating, and in particular relates to a power generation system with decoupling of a machine and boiler regulation process based on high-temperature molten salt energy storage. Background Art

[0002] At present, the load regulation speed of coal-fired thermal power generation is only 1.5% of rated load / minute, which is far from meeting the high flexibility requirements.

[0003] The regulation capacity of coal-fired power generation is constrained by the inertia of each key link, which can be roughly divided into the inertia on the boiler side and the inertia on the circulation side. Among them, the inertia delay on the boiler side is the main reason for the slow response speed of the unit.

[0004] Molten salt energy storage uses nitrates and other materials as heat transfer media and has been widely used in solar thermal power generation systems. The outlet steam temperature of thermal power plant boilers is between 540 and 620°C, and high-temperature molten salt heat storage technology can match this temperature parameter. At the same time, high-temperature molten salt improves energy quality and provides conditions for the efficient use of stored thermal energy.

[0005] The S-CO2 cycle has received extensive attention in recent years and is considered a new generation of heat-to-work conversion technology that can replace the steam Rankine cycle. Compared with the steam Rankine cycle, the S-CO2 cycle has the following advantages: (1) CO2 has stable chemical properties and weak reaction with metal materials at high temperatures, which lays the foundation for further improving the main steam parameters. (2) The cycle has good heat recovery effect and a narrow heat absorption temperature range. When the main steam temperature exceeds 550°C, the S-CO2 cycle efficiency is higher than that of the steam Rankine cycle. (3) The entire S-CO2 cycle system operates at high pressure, the system is compact, and has higher flexibility.

[0006] If the boiler regulation process can be decoupled and a fast heat source response can be achieved, the load change rate of the unit will be greatly improved. To this end, we introduced high-temperature molten salt energy storage and supercritical carbon dioxide (S-CO2) circulation to explore the realization of highly flexible and efficient coal-fired power generation technology.

[0007] Therefore, the present invention discloses a power generation system with decoupled boiler regulation process based on high-temperature molten salt energy storage. The S-CO2 cycle is combined with the high-temperature molten salt energy storage to bear part of the power generation load of the steam cycle coal-fired unit, which can effectively improve the power generation efficiency of the system. At the same time, the molten salt energy storage can decouple the boiler regulation process and break through the existing bottleneck of variable load rate. Summary of the invention

[0008] In view of the problems existing in the background technology, the present invention provides a power generation system with decoupling of the boiler and machine regulation process based on high-temperature molten salt energy storage, characterized in that it comprises: a boiler, a steam coal-fired power generation system, a molten salt storage tank group and a sCO2 circulation system arranged outside the boiler; wherein the molten salt heat exchanger is arranged in the boiler, and the inlet and outlet of the molten salt heat exchanger are connected to the inlet and outlet of the molten salt working medium of the molten salt storage tank group; the low-temperature reheater and the low-temperature superheater are arranged in the tail flue;

[0009] The molten salt heat storage tank system comprises: a working group and a standby group in which a carbon dioxide working medium pipeline and a molten salt working medium pipeline are connected in parallel, the working group and the standby group each comprise at least one molten salt storage tank, the working group and the standby group are both provided with a carbon dioxide working medium inlet and outlet and a molten salt working medium inlet and outlet, the carbon dioxide working medium outlet of the standby group passes through an outlet valve of the standby group, merges with the carbon dioxide working medium outlet of the working group and is connected to the turbine inlet in the sCO2 circulation system as the carbon dioxide working medium outlet of the molten salt heat storage tank system; the cold side outlet of the high temperature regenerator in the sCO2 circulation system is divided into two parallel paths, one path is connected to the carbon dioxide working medium inlet of the working group, and the other path passes through the outlet valve of the standby group. The inlet valve of the standby group is connected to the carbon dioxide working fluid inlet of the standby group; the molten salt working fluid outlet of the molten salt heat exchanger is divided into two routes, one route is connected to the molten salt working fluid inlet of the working group through the active group heat inlet valve, and the other route is connected to the molten salt working fluid inlet of the standby group through the standby group heat inlet valve; after the molten salt working fluid outlet of the working group and the molten salt working fluid outlet of the standby group are merged, they are connected to the molten salt working fluid inlet of the molten salt heat exchanger, wherein the active group heat inlet valve is arranged at the inlet of the molten salt working fluid pipeline of the working group to control the total flow of the molten salt storage tank in the group; the standby group heat inlet valve is arranged at the inlet of the molten salt working fluid pipeline of the standby group to control the total flow of the molten salt storage tank in the group.

[0010] The molten salt heat exchanger is arranged in the semi-radiation zone of the boiler and the convection zone in the horizontal flue, and the platen superheater, high-temperature superheater and high-temperature reheater are arranged side by side with the molten salt heat exchanger; the platen superheater, high-temperature superheater, high-temperature reheater, low-temperature superheater and low-temperature reheater are arranged in sequence along the flue gas flow order.

[0011] When there is more than one molten salt storage tank in the working group and the standby group, the total number of molten salt storage tanks in each group is controlled according to the flow rate during design, and the connection method of the carbon dioxide working fluid and molten salt working fluid pipelines between the molten salt storage tanks is series connection, parallel connection, or a combination of series and parallel connection.

[0012] The sCO2 circulation system includes: a turbine, a high-temperature regenerator, a low-temperature regenerator, a second compressor, a first compressor and a cooler; wherein the turbine outlet is connected to the hot side inlet of the high-temperature regenerator, the hot side outlet of the high-temperature regenerator is connected to the hot side inlet of the low-temperature regenerator, the hot side outlet of the low-temperature regenerator is respectively connected to the hot side inlet of the cooler and the second compressor, the hot side outlet of the cooler is connected to the inlet of the first compressor, the outlet of the first compressor is connected to the cold side inlet of the low-temperature regenerator, and the cold side outlet of the low-temperature regenerator is connected to the cold side inlet of the high-temperature regenerator after merging with the outlet of the second compressor.

[0013] The steam coal-fired power generation system comprises: a water-cooled wall, a pressure pump, a steam drum, a platen superheater, a high-temperature superheater, a high-temperature reheater, a low-temperature superheater, a low-temperature reheater, an economizer, a high-pressure steam turbine, a medium-pressure steam turbine, a low-pressure steam turbine, a condenser, a condensate pump, a drain device, seven coolers, a deaerator, a circulating water pump, a feed water pump and a small steam turbine; wherein the first outlet below the steam drum is connected to the lower part of the water-cooled wall through the pressure pump, and the upper part of the water-cooled wall arranged in the boiler furnace is connected to the first inlet on the upper left of the steam drum to form a loop; the second outlet on the upper part of the steam drum is connected to the inlet below the low-temperature superheater, and the second inlet on the right side of the steam drum is connected to the outlet of the economizer arranged in the flue at the tail of the furnace;

[0014] The outlet of the low-temperature superheater is connected to the inlet of the platen superheater, the outlet of the platen superheater is connected to the inlet of the high-temperature superheater, the outlet of the high-temperature superheater is connected to the inlet of the high-pressure steam turbine, the first air extraction port of the high-pressure steam turbine is respectively connected to the inlet of the low-temperature reheater and the steam inlet of the second cooler, the second air extraction port of the high-pressure steam turbine is connected to the steam inlet of the first cooler, the outlet of the high-temperature reheater, the steam inlet of the medium-pressure steam turbine, the steam outlet, the steam inlet of the low-pressure steam turbine, the steam outlet and the condenser are sequentially connected;

[0015] The first air extraction port of the medium-pressure steam turbine is connected to the steam inlet of the third cooler, the second air extraction port of the medium-pressure steam turbine is respectively connected to the steam inlets of the small steam turbine and the deaerator, the first air extraction port, the second air extraction port, the third air extraction port and the fourth air extraction port of the low-pressure steam turbine are respectively connected to the steam inlets of the fourth cooler, the fifth cooler, the sixth cooler and the seventh cooler, and the outlet of the condenser is sequentially connected to the condensate pump, the drain device, the condensate side of the seventh cooler, the condensate side of the sixth cooler, the condensate side of the fifth cooler, the condensate side of the fourth cooler, the condensate inlet of the deaerator, the circulating water pump, the feed water pump, the third cooler, the second cooler, the first cooler and the economizer;

[0016] The power output shaft of the small steam turbine is connected to the power input shaft of the feed water pump; the drain port of the first cooler, the drain port of the second cooler and the drain port of the third cooler merge and enter the water inlet of the deaerator; the drain port of the fourth cooler merges with the drain port of the fifth cooler, the drain port of the sixth cooler, the drain port of the seventh cooler and the drain port of the drain device and is finally connected to the condensate outlet of the condenser.

[0017] The S-CO2 circulation side of the working group in the molten salt heat storage tank drives the sCO2 circulation system to work;

[0018] During stable operation, the inlet valve and outlet valve of the standby group and the heat inlet valve of the standby group that controls the molten salt flow are closed, and the heat inlet valve of the active group is opened. The molten salt carries heat only into the molten salt tank of the working group. There is no time difference between the energy storage and release processes of the molten salt storage tank group. The molten salt acts as a heat transfer intermediate medium to transfer the flue gas heat to the CO2 working fluid.

[0019] When load reduction is required, adjust the valve opening, open the standby group heat inlet valve that controls the molten salt flow, and reduce the opening of the active group heat inlet valve; allow part of the high-temperature molten salt to carry heat into the molten salt storage tank in the standby group, while the flow of high-temperature molten salt flowing into the working group molten salt tank is reduced; on the S-CO2 circulation side, the power generation on the S-CO2 circulation side is reduced because the standby group inlet valve and the standby group outlet valve that control the CO2 working fluid maintain a low flow rate or even close the valve; at the same time, gradually reduce the pulverized coal input for burner combustion to achieve the load reduction target of the entire unit.

[0020] When the load needs to be increased, there are two operating conditions according to the temperature of the molten salt tanks in the working group and the standby group. In both operating conditions, the S-CO2 circulation side uses heat storage to achieve a rapid increase in load; at the same time, the pulverized coal input is gradually increased with the combustion of the burner to achieve a rapid load increase of the unit;

[0021] Among them, when the temperature of the molten salt tank in the working group is higher than that in the standby group, the inlet valve and the outlet valve of the standby group are opened, and the valve opening is increased. At the same time, the standby group heat inlet valve that controls the molten salt flow is closed, and the active group heat inlet valve is kept open and the valve opening is adjusted, so that the CO2 working fluid only absorbs the heat stored in the molten salt tank in the standby group;

[0022] When the temperature of the molten salt tank in the working group is lower than that in the standby group, the standby group heat inlet valve that controls the molten salt flow is opened and maintained at a large opening, the active group heat inlet valve is closed, and the standby group inlet valve and the standby group outlet valve are kept closed; allowing CO2 to continue to absorb the heat stored in the molten salt tank in the standby group.

[0023] The beneficial effects of the present invention are:

[0024] 1. Combining the S-CO2 cycle with high-temperature molten salt energy storage to bear part of the power generation load of the steam cycle coal-fired unit can effectively improve the power generation efficiency of the system. At the same time, molten salt energy storage can decouple the boiler regulation process and break through the existing load change rate bottleneck.

[0025] 2. After a systematic study of supercritical carbon dioxide (sCO2) coal-fired power generation, S-CO2 coal-fired power generation has been proven to be highly efficient, with a power generation efficiency of 51% under rated load, which is 3 to 4 percentage points higher than the existing steam units, and has better flexibility.

[0026] 3. One boiler drives both the steam turbine and the CO2 turbine at the same time, and cooperates with the molten salt heat storage system to achieve decoupling of the boiler and machine regulation process; by changing the load of the CO2 unit, the total load is adjusted; high flexibility of coal-fired thermal power generation is achieved, and the load regulation speed is greater than 6% of the rated load / minute.

[0027] 4. This patent takes a subcritical parameter unit as an example, but in practice it can also be applied to a supercritical unit. BRIEF DESCRIPTION OF THE DRAWINGS

[0028] Figure 1 A schematic top view of a boiler heating surface in an embodiment of a power generation system with decoupling of a machine-furnace regulation process based on high-temperature molten salt energy storage according to the present invention;

[0029] Figure 2 This is a schematic diagram of the layout test of the coupled molten salt energy storage system, sCO2 circulation system and boiler in an embodiment of the present invention;

[0030] Figure 3 This is a schematic structural diagram of a steam coal-fired power generation system according to an embodiment of the present invention;

[0031] Figure 4 It is a schematic diagram of a flow chart of a variable load regulation strategy based on decoupling of the boiler regulation process during stable operation in an embodiment of the present invention;

[0032] Figure 5 It is a schematic diagram of the flow of load reduction in the variable load regulation strategy based on decoupling of the boiler regulation process in an embodiment of the present invention;

[0033] Figure 6 It is a schematic diagram of the process flow when the load is increased in the variable load regulation strategy based on the decoupling of the machine and boiler regulation process in an embodiment of the present invention.

[0034] Among them, 100-steam coal-fired power generation unit, 102-water-cooled wall, 103-pressure pump, 104-steam drum, 105-platen superheater, 106-high-temperature superheater, 107-high-temperature reheater, 108-low-temperature superheater, 109-low-temperature reheater, 110-economizer, 111-high-pressure steam turbine, 112-medium-pressure steam turbine, 113-low-pressure steam turbine, 114-condenser, 115-condensate pump, 116-drain device, 125-circulating water pump, 126-feedwater pump, 127-small steam turbine, 200-sCO2 circulation System, 228-turbine, 229-high temperature regenerator, 230-low temperature regenerator, 231-second compressor, 232-first compressor, 233-cooler, 300-molten salt heat storage tank system, 301-molten salt heat exchanger, 334-standby first supplementary molten salt storage tank, 335-standby group main molten salt storage tank, 336-working first supplementary molten salt storage tank, 337-working group main molten salt storage tank, 338-standby group inlet valve, 339-standby group outlet valve, 340-standby group heat inlet valve, 341-active group heat inlet valve, 400-boiler. DETAILED DESCRIPTION

[0035] The present invention is further described in detail below in conjunction with the accompanying drawings.

[0036] like Figure 1 to Figure 3 The embodiment of the present invention shown includes: a boiler 400, a steam coal-fired power generation system 100, a sCO2 circulation system 200 arranged outside the boiler 400, and a molten salt storage tank group 300; wherein, a molten salt heat exchanger 301 is provided in the semi-radiation zone of the boiler 400 and the convection zone in the horizontal flue, and the inlet and outlet of the molten salt heat exchanger 301 are connected to the molten salt working medium inlet and outlet of the molten salt storage tank group 300; a screen superheater 105, a high-temperature superheater 106 and a high-temperature reheater 107 are arranged side by side with the molten salt heat exchanger 301, a low-temperature superheater 108 and a low-temperature reheater 109 are arranged in the tail flue, and the screen superheater 105, the high-temperature superheater 106, the high-temperature reheater 107, the low-temperature reheater 109 and the low-temperature superheater 108 are arranged in sequence along the flue gas flow order.

[0037] In this embodiment, the molten salt heat exchanger 301 can also be arranged in the furnace of the boiler 400 to absorb heat together with the water-cooled wall, thereby realizing a more complete molten salt heat storage and heat absorption process from the furnace.

[0038] In this embodiment, the sCO2 circulation system 200 and the molten salt storage tank group 300 are arranged outside the boiler to form an integrated boiler-machine arrangement.

[0039] The molten salt heat storage tank system 300 includes: a working group and a standby group in which a carbon dioxide working medium pipeline and a molten salt working medium pipeline are connected in parallel, the working group and the standby group each include at least one molten salt storage tank, and the working group and the standby group are both provided with a carbon dioxide working medium inlet and outlet and a molten salt working medium inlet and outlet. The carbon dioxide working medium outlet of the standby group passes through the standby group outlet valve 339, merges with the carbon dioxide working medium outlet of the working group, and is connected to the turbine 228 in the sCO2 circulation system 200 as the carbon dioxide working medium outlet of the molten salt heat storage tank system 300; the cold side outlet of the high-temperature regenerator 229 in the sCO2 circulation system 200 is divided into two parallel paths, one of which is connected to the carbon dioxide working medium inlet of the working group, and the other is connected through the standby group outlet valve 339. The standby group inlet valve 338 is connected to the carbon dioxide working fluid inlet of the standby group; the molten salt working fluid outlet of the molten salt heat exchanger 301 is divided into two paths, one path is connected to the molten salt working fluid inlet of the working group through the active group heat inlet valve 341, and the other path is connected to the molten salt working fluid inlet of the standby group through the standby group heat inlet valve 340; after the molten salt working fluid outlet of the working group and the molten salt working fluid outlet of the standby group are merged, they are connected to the molten salt working fluid inlet of the molten salt heat exchanger 301, wherein the active group heat inlet valve 341 is arranged at the inlet of the molten salt working fluid pipeline of the working group to control the total flow of the molten salt storage tank in the group; the standby group heat inlet valve 340 is arranged at the inlet of the molten salt working fluid pipeline of the standby group to control the total flow of the molten salt storage tank in the group.

[0040] When there is more than one molten salt storage tank in the working group and the standby group, the total number of molten salt storage tanks in each group is controlled according to the flow rate during design, and the connection mode of the carbon dioxide working fluid and molten salt working fluid pipelines between the molten salt storage tanks can be series or parallel or a combination of series and parallel according to the needs; Figure 1 and Figure 2 In the embodiment shown, both the working group and the standby group include two molten salt storage tanks, and both are connected in series. It is easy to understand that parallel connection is also an optional method.

[0041] Therefore, specifically in this embodiment, the working group includes: a working group main molten salt storage tank 337 and a working first supplementary molten salt storage tank 336, both of which are connected in series with the carbon dioxide working fluid and molten salt working fluid pipelines; the standby group includes: a standby first supplementary molten salt storage tank 334 and a standby group main molten salt storage tank 335, both of which are connected in series with the carbon dioxide working fluid and molten salt working fluid pipelines.

[0042] like Figure 2The sCO2 circulation system 200 shown includes: a turbine 228, a high-temperature regenerator 229, a low-temperature regenerator 230, a second compressor 231, a first compressor 232 and a cooler 233; wherein, the outlet of the turbine 228 is connected to the hot side inlet of the high-temperature regenerator 229, the hot side outlet of the high-temperature regenerator 229 is connected to the hot side inlet of the low-temperature regenerator 230, the hot side outlet of the low-temperature regenerator 230 is respectively connected to the hot side inlet of the cooler 233 and the second compressor 231, the hot side outlet of the cooler 233 is connected to the inlet of the first compressor 232, the outlet of the first compressor 232 is connected to the cold side inlet of the low-temperature regenerator 230, the cold side outlet of the low-temperature regenerator 230 is connected to the cold side inlet of the high-temperature regenerator 229 after merging with the outlet of the second compressor 231; cooling water is introduced into the cold side of the cooler 233.

[0043] like Figure 3 The steam coal-fired power generation system 100 shown in the figure includes: a water-cooled wall 102, a pressure pump 103, a steam drum 104, a platen superheater 105, a high-temperature superheater 106, a high-temperature reheater 107, a low-temperature superheater 108, a low-temperature reheater 109, an economizer 110, a high-pressure steam turbine 111, a medium-pressure steam turbine 112, a low-pressure steam turbine 113, a condenser 114, a condensate pump 115, a drain device 116, seven coolers (No. 1 to No. 7 coolers), a deaerator 120, a circulating water pump 125, and a feed Water pump 126 and small steam turbine 127; wherein, the first outlet below the steam drum 104 is connected to the lower part of the water-cooled wall 102 through the pressure pump 103, and the upper part of the water-cooled wall 102 arranged in the furnace of the boiler 400 is connected to the first inlet on the upper left of the steam drum 104 to form a loop; the second outlet on the upper part of the steam drum 104 is connected to the inlet below the low-temperature superheater 108, and the second inlet on the right side of the steam drum 104 is connected to the outlet of the economizer 110 arranged in the flue at the rear of the furnace; the pressure pump 103 makes the forced circulation effect better.

[0044] The outlet of the low-temperature superheater 108 is connected to the inlet of the platen superheater 105, the outlet of the platen superheater 105 is connected to the inlet of the high-temperature superheater 106, the outlet of the high-temperature superheater 106 is connected to the inlet of the high-pressure steam turbine 111, the first air extraction port of the high-pressure steam turbine 111 is respectively connected to the inlet of the low-temperature reheater 109 and the steam inlet of the second cooler 118, the second air extraction port of the high-pressure steam turbine 111 is connected to the steam inlet of the first cooler 117, the outlet of the high-temperature reheater 107, the steam inlet and steam outlet of the medium-pressure steam turbine 112, the steam inlet and steam outlet of the low-pressure steam turbine 113 and the condenser 114 are sequentially connected;

[0045] The first air extraction port of the medium-pressure steam turbine 112 is connected to the steam inlet of the third cooler 119, the second air extraction port of the medium-pressure steam turbine 112 is connected to the steam inlet of the small steam turbine 127 and the deaerator 120 respectively, the first air extraction port, the second air extraction port, the third air extraction port and the fourth air extraction port of the low-pressure steam turbine 113 are connected to the steam inlet of the fourth cooler 121, the fifth cooler 122, the sixth cooler 123 and the seventh cooler 124 respectively, and the coolers 127 and 128 are connected to the steam inlet of the small steam turbine 127 and the deaerator 120 respectively. The outlet of the condenser 114 is sequentially connected to the condensate pump 115, the drain device 116, the condensate side of the seventh cooler 124, the condensate side of the sixth cooler 123, the condensate side of the fifth cooler 122, the condensate side of the fourth cooler 121, the condensate inlet of the deaerator 120, the circulating water pump 125, the feed water pump 126, the third cooler 119, the second cooler 118, the first cooler 117 and the economizer 110;

[0046] The power output shaft of the small steam turbine 127 is connected to the power input shaft of the feed water pump 126; the drain outlet of the first cooler 117, the drain outlet of the second cooler 118 and the drain outlet of the third cooler 119 merge and enter the water inlet of the deaerator 120; the drain outlet of the fourth cooler 121 merges with the drain outlet of the fifth cooler 122, the drain outlet of the sixth cooler 123, the drain outlet of the seventh cooler 124 and the drain outlet of the drain device 116 and is finally connected to the condensate outlet of the condenser 114.

[0047] When working, the three systems of the steam coal-fired power generation unit 100, the sCO2 circulation system 200 and the molten salt heat storage tank system 300 work together to achieve the decoupling of the boiler regulation process, greatly improving the variable load rate of the unit. First, the coal burns in the boiler, and the combustion produces high-temperature flue gas carrying heat. Part of the heat carried by the high-temperature flue gas is absorbed by the water-cooled wall to complete the steam cycle (the heat released by the combustion in the furnace is taken away by the flow of water, and then passes through the superheater, reheater, etc. to perform conventional steam turbine power generation), while the other part of the heat enters the molten salt heat storage tank 300 through the molten salt heat exchanger 301;

[0048] After the CO2 working fluid in the sCO2 circulation system 200 absorbs the heat from the molten salt heat storage tank 300, it flows through various equipment in the system in turn, and the heat energy directly performs work through the turbine; and the heat increased or decreased to meet the load regulation requirement is released or stored by the molten salt heat storage tank, and finally the entire regulation process is decoupled and the load change is quickly responded to. The heat absorption process in the furnace of the molten salt heat storage is realized by the molten salt heat exchanger 301 arranged in the semi-radiation zone of the boiler and the convection zone in the horizontal flue; the molten salt after heat release and cooling flows back to the pipeline arranged in the furnace again, absorbs heat again, and circulates back and forth to form a circulation loop; since there is no time difference between the energy storage and energy release processes in the molten salt storage tank, the molten salt acts as a heat transfer intermediate medium, transferring the flue gas heat to the CO2 working fluid, and the CO2 absorbs the heat and then circulates to generate electricity.

[0049] The process of variable load regulation strategy is as follows Figures 4 to 6 As shown, in all stages of the variable load regulation strategy, the S-CO2 circulation side of the working group of the molten salt heat storage tank 300 drives the sCO2 circulation system 200 to work. When the load needs to be reduced or increased, the decoupling of the standby group is used to adjust:

[0050] Stable runtime ( Figure 4 ), at this time, there is no time difference between the energy storage and energy release process of the molten salt storage tank group 300, and the molten salt acts as a heat transfer intermediate medium to transfer the flue gas heat to the CO2 working medium. At this time, in the molten salt working medium pipeline and the carbon dioxide working medium pipeline of the molten salt storage tank group 300, only the molten salt storage tank of the working group has flow; that is, the standby group inlet valve 338 and the standby group outlet valve 339 that control the CO2 working medium and the standby group heat inlet valve 340 that controls the molten salt flow are closed, and the active group heat inlet valve 341 is opened, and the molten salt carries heat only into the molten salt tank of the working group at this time.

[0051] When load reduction is required ( Figure 5 ); adjust the valve opening, open the standby group heat inlet valve 340 that controls the molten salt flow, and reduce the opening of the active group heat inlet valve 341 (smaller than during stable operation); allow part of the high-temperature molten salt to carry heat into the molten salt storage tank in the standby group, while the flow of high-temperature molten salt flowing into the working group molten salt tank is reduced; on the S-CO2 circulation side, since the standby group inlet valve 338 and the standby group outlet valve 339 that control the CO2 working fluid maintain a low flow rate or even close the valve, the power generation on the S-CO2 circulation side is reduced; at the same time, the pulverized coal input for burner combustion is gradually reduced to achieve the load reduction target of the entire unit.

[0052] Specifically, the valve openings of the standby group inlet valve 338 and the standby group outlet valve 339 are controlled according to the demand for load reduction, so that the CO2 working fluid flow rate and the power generation on the S-CO2 circulation side match the demand; the opening ratio between the active group heat inlet valve 341 and the standby group heat inlet valve 340 is also adjusted according to the demand; at this time, the amount of high-temperature molten salt allocated to the molten salt tank in the standby group (when operating more stably) increases, the high-temperature molten salt flow rate flowing into the working group molten salt tank decreases, and the power generation on the S-CO2 circulation side is reduced, thereby achieving load reduction while completing the heat storage of excess coal; at the same time, as the burner burns, the coal powder input is gradually reduced to match the load reduction instruction of the power grid, and the system achieves the goal of rapid load reduction; since the flue gas directly flows through the molten salt standby group heat storage, the regulation process is decoupled between the S-CO2 cycle and the boiler, and the load change rate of the power generation system is the load change rate of the S-CO2 circulation side.

[0053] When the load needs to be increased ( Figure 6 ), it is divided into two operating conditions according to the temperature of the molten salt tanks in the working group and the standby group. Under both operating conditions, the S-CO2 circulation side uses heat storage to achieve a rapid increase in load; at the same time, the pulverized coal input is gradually increased along with the combustion of the burner to achieve a rapid load increase of the unit.

[0054] Among them, when the temperature of the molten salt tank in the working group is higher than that of the molten salt tank in the standby group, the standby group inlet valve 338 and the standby group outlet valve 339 are opened, and the valve opening is increased. At the same time, the standby group heat inlet valve 340 that controls the molten salt flow is closed, and the active group heat inlet valve 341 is kept open and the valve opening is adjusted, so that the CO2 working fluid only absorbs the heat stored in the molten salt tank in the standby group; when the temperature of the molten salt tank in the working group is lower than that of the molten salt tank in the standby group, the standby group heat inlet valve 340 that controls the molten salt flow is opened and maintained at a large opening, the active group heat inlet valve 341 is closed, and the standby group inlet valve 338 and the standby group outlet valve 339 are kept closed; allowing CO2 to continue to absorb the heat stored in the molten salt tank in the standby group.

[0055] Since the heat storage of the molten salt tank in the working group or the standby group is used when the load is increased, the S-CO2 cycle and the boiler also achieve decoupling of the regulation process, that is, the load change rate of the power generation system is the load change rate of the S-CO2 cycle side. Through the above operation method, the load change rate of the steam coal-fired power generation unit 100 is improved, breaking through the bottleneck of the existing load change rate.

[0056] In the steam coal-fired power generation unit 100 ( Figure 3), water flowing out from the bottom of the drum 104 is pressurized by the drum circulation pressure pump 103, enters the water-cooled wall 102 arranged in the lower header of the boiler to absorb heat, and returns to the drum 104 for storage; the steam flowing out from the top of the drum 104 enters the low-temperature superheater 108, the platen superheater 105, and the high-temperature superheater 106 to absorb heat in sequence, and then enters the high-pressure steam turbine 111 to perform work; the low-temperature reheater 109 enters the high-temperature reheater 107 to absorb heat, and then enters the medium-pressure steam turbine 112 and the low-pressure steam turbine 113 to perform work in sequence, and finally is discharged into the condenser 114 from the exhaust port of the low-pressure steam turbine 113;

[0057] The steam extracted from the first extraction port of the high-pressure steam turbine 111 is divided into two paths, one path enters the second cooler 118 to release heat, and the other path enters the low-temperature reheater 109 to absorb heat. The steam from the second stage extraction port of the high-pressure steam turbine 111 enters the first cooler 117 to release heat.

[0058] The steam from the first stage steam extraction port of the medium pressure steam turbine 112 enters the third cooler 119 to release heat; the steam extracted from the second steam extraction port of the medium pressure steam turbine 112 is divided into two paths, one path enters the steam inlet of the deaerator 120; the other path enters the steam inlet of the small steam turbine 127 to do work and then drives the feed water pump 126 to work.

[0059] The steam from the first-stage extraction port, the second-stage extraction port, the third-stage extraction port and the fourth-stage extraction port of the low-pressure steam turbine 113 enters the fifth cooler 121, the sixth cooler 122, the seventh cooler 123 and the eighth cooler 124 respectively to release heat.

[0060] The condensed water discharged from the condenser 114 is pressurized by 115, flows into the drain device 116, and then flows through the seventh cooler 124, the sixth cooler 123, the fifth cooler 122 and the fourth cooler 121 in sequence to absorb heat, and flows into the deaerator 120 for deoxidation; the drain water flowing out of the fourth cooler 121, in sequence, with the drain water of the fifth cooler 122, the drain water of the sixth cooler 123, the drain water of the seventh cooler 124 and the drain water of 116, finally converges into the condensed water outlet of the condenser 114;

[0061] The deoxygenated water flowing out of the deaerator 120 is pressurized by the circulating water pump 125 and the feed water pump 126 in sequence and flows to the third cooler 119, the second cooler 118 and the first cooler 117 in sequence to continue to absorb heat, then flows into the inlet of the economizer 110 for heating, and finally flows into the steam drum 104 for storage. The deoxygenated water flowing out of the first cooler 117 is successively merged with the deoxygenated water flowing out of the second cooler 118 and the third cooler 119, and then enters the water inlet of the deaerator 120.

Claims

1. A power generation system with decoupling of boiler regulation process based on high-temperature molten salt energy storage, characterized in that: include: A boiler (400), a steam coal-fired power generation system (100), a molten salt storage tank group (300), and a sCO2 circulation system (200) arranged outside the boiler (400); wherein a molten salt heat exchanger (301) is arranged in the boiler (400), and the inlet and outlet of the molten salt heat exchanger (301) are connected to the molten salt working medium inlet and outlet of the molten salt heat storage tank system (300); a low-temperature superheater (108) and a low-temperature reheater (109) are arranged in the tail flue; The molten salt heat storage tank system (300) comprises: a working group and a standby group in which a carbon dioxide working medium pipeline and a molten salt working medium pipeline are connected in parallel, the working group and the standby group each comprise at least one molten salt storage tank, the working group and the standby group each are provided with a carbon dioxide working medium inlet and outlet and a molten salt working medium inlet and outlet, the carbon dioxide working medium outlet of the standby group passes through an outlet valve (339) of the standby group, merges with the carbon dioxide working medium outlet of the working group and serves as the carbon dioxide working medium outlet of the molten salt heat storage tank system (300) and is connected to an inlet of a turbine (228) in a sCO2 circulation system (200); the high pressure in the sCO2 circulation system (200) The cold side outlet of the warm regenerator (229) is divided into two parallel paths, one of which is connected to the carbon dioxide working medium inlet of the working group, and the other is connected to the carbon dioxide working medium inlet of the standby group through the standby group inlet valve (338); the molten salt working medium outlet of the molten salt heat exchanger (301) is divided into two paths, one of which is connected to the molten salt working medium inlet of the working group through the active group heat inlet valve (341), and the other is connected to the molten salt working medium inlet of the standby group through the standby group heat inlet valve (340); after the molten salt working medium outlet of the working group and the molten salt working medium outlet of the standby group are merged, they are connected to the molten salt working medium inlet of the molten salt heat exchanger (301); When load reduction is required, the valve opening is adjusted to open the standby group heat inlet valve (340) that controls the molten salt flow, and the opening of the active group heat inlet valve (341) is reduced; so that part of the high-temperature molten salt carries heat into the molten salt storage tank in the standby group, while the high-temperature molten salt flow flowing into the working group molten salt tank is reduced; on the S-CO2 circulation side, since the standby group inlet valve (338) and the standby group outlet valve (339) that control the CO2 working fluid maintain a low flow rate or even close the valve, the power generation on the S-CO2 circulation side is reduced; at the same time, the pulverized coal input for burner combustion is gradually reduced to achieve the load reduction target of the entire unit; When the load needs to be increased, the temperature of the molten salt tanks in the working group and the standby group is divided into two working conditions. In both working conditions, the S-CO2 circulation side uses heat storage to achieve a rapid increase in load; at the same time, the pulverized coal input is gradually increased with the combustion of the burner to achieve a rapid load increase of the unit; among them, when the temperature of the molten salt tank in the working group is higher than that of the molten salt tank in the standby group, the standby group inlet valve (338) and the standby group outlet valve (339) are opened, and the valve opening is increased. At the same time, the standby group heat inlet valve that controls the molten salt flow is closed. (340), keep the active group heat inlet valve (341) open and adjust the valve opening, so that the CO2 working fluid only absorbs the heat stored in the molten salt tank in the standby group; when the temperature of the molten salt tank in the working group is lower than the temperature of the molten salt tank in the standby group, open the standby group heat inlet valve (340) that controls the molten salt flow rate and maintain a large opening, close the active group heat inlet valve (341), and keep the standby group inlet valve (338) and the standby group outlet valve (339) closed; so that CO2 continues to absorb the heat stored in the molten salt tank in the standby group.

2. A power generation system with decoupling of machine and boiler regulation process based on high-temperature molten salt energy storage according to claim 1, characterized in that: The molten salt heat exchanger (301) is arranged in the semi-radiation zone of the boiler (400) and the convection zone in the horizontal flue, and the platen superheater (105), the high-temperature superheater (106) and the high-temperature reheater (107) are arranged side by side with the molten salt heat exchanger (301); the platen superheater (105), the high-temperature superheater (106), the high-temperature reheater (107), the low-temperature reheater (109) and the low-temperature superheater (108) are arranged in sequence along the flow of the flue gas.

3. A power generation system with decoupling of machine and boiler regulation process based on high-temperature molten salt energy storage according to claim 1, characterized in that: When there is more than one molten salt storage tank in the working group and the standby group, the total number of molten salt storage tanks in each group is controlled according to the flow rate during design, and the connection method of the carbon dioxide working fluid and molten salt working fluid pipelines between the molten salt storage tanks is series connection, parallel connection, or a combination of series and parallel connection.

4. A power generation system with decoupling of machine and boiler regulation process based on high-temperature molten salt energy storage according to claim 1, characterized in that: The sCO2 circulation system (200) comprises: a turbine (228), a high-temperature regenerator (229), a low-temperature regenerator (230), a second compressor (231), a first compressor (232) and a cooler (233); wherein the outlet of the turbine (228) is connected to the hot side inlet of the high-temperature regenerator (229), the hot side outlet of the high-temperature regenerator (229) is connected to the hot side inlet of the low-temperature regenerator (230), the hot side outlet of the low-temperature regenerator (230) is respectively connected to the hot side inlet of the cooler (233) and the second compressor (231), the hot side outlet of the cooler (233) is connected to the inlet of the first compressor (232), the outlet of the first compressor (232) is connected to the cold side inlet of the low-temperature regenerator (230), and the cold side outlet of the low-temperature regenerator (230) is connected to the cold side inlet of the high-temperature regenerator (229) after merging with the outlet of the second compressor (231).

5. A power generation system with decoupling of machine and boiler regulation process based on high-temperature molten salt energy storage according to any one of claims 1, 2, 3 or 4, characterized in that: The steam coal-fired power generation system (100) comprises: a water-cooled wall (102), a pressure pump (103), a steam drum (104), a platen superheater (105), a high-temperature superheater (106), a high-temperature reheater (107), a low-temperature superheater (108), a low-temperature reheater (109), an economizer (110), a high-pressure steam turbine (111), a medium-pressure steam turbine (112), a low-pressure steam turbine (113), a condenser (114), a condensate pump (115), a drain device (116), seven coolers, a deaerator (120), a circulating A water pump (125), a feed water pump (126) and a small steam turbine (127); wherein a first outlet below the drum (104) is connected to the lower part of the water-cooled wall (102) through a pressure pump (103), and the upper part of the water-cooled wall (102) arranged in the furnace of the boiler (400) is connected to a first inlet on the upper left of the drum (104) to form a loop; a second outlet on the upper part of the drum (104) is connected to an inlet below the low-temperature superheater (108), and a second inlet on the right side of the drum (104) is connected to an outlet of an economizer (110) arranged in the flue at the rear of the furnace; The outlet of the low-temperature superheater (108) is connected to the inlet of the platen superheater (105), the outlet of the platen superheater (105) is connected to the inlet of the high-temperature superheater (106), the outlet of the high-temperature superheater (106) is connected to the inlet of the high-pressure steam turbine (111), the first air extraction port of the high-pressure steam turbine (111) is respectively connected to the inlet of the low-temperature reheater (109) and the steam inlet of the second cooler (118), the second air extraction port of the high-pressure steam turbine (111) is connected to the steam inlet of the first cooler (117), the outlet of the high-temperature reheater (107), the steam inlet and steam outlet of the medium-pressure steam turbine (112), the steam inlet and steam outlet of the low-pressure steam turbine (113) and the condenser (114) are sequentially connected; The first air extraction port of the medium-pressure steam turbine (112) is connected to the steam inlet of the third cooler (119), the second air extraction port of the medium-pressure steam turbine (112) is respectively connected to the steam inlets of the small steam turbine (127) and the deaerator (120), the first air extraction port, the second air extraction port, the third air extraction port and the fourth air extraction port of the low-pressure steam turbine (113) are respectively connected to the steam inlets of the fourth cooler (121), the fifth cooler (122), the sixth cooler (123) and the seventh cooler (124), and the condenser (113) is connected to the steam inlet of the fourth cooler (121), the fifth cooler (122), the sixth cooler (123) and the seventh cooler (124). The outlet of the deaerator (14) is sequentially connected to the condensate pump (115), the drain device (116), the condensate side of the seventh cooler (124), the condensate side of the sixth cooler (123), the condensate side of the fifth cooler (122), the condensate side of the fourth cooler (121), the condensate inlet of the deaerator (120), the circulating water pump (125), the feed water pump (126), the third cooler (119), the second cooler (118), the first cooler (117) and the economizer (110); The power output shaft of the small steam turbine (127) is connected to the power input shaft of the feed water pump (126); the drain port of the first cooler (117), the drain port of the second cooler (118) and the drain port of the third cooler (119) merge and enter the water inlet of the deaerator (120); the drain port of the fourth cooler (121) merges with the drain port of the fifth cooler (122), the drain port of the sixth cooler (123), the drain port of the seventh cooler (124) and the drain port of the drain device (116) and is finally connected to the condensate outlet of the condenser (114).

6. A power generation system with decoupling of machine and boiler regulation process based on high-temperature molten salt energy storage according to any one of claims 1, 2, 3 or 4, characterized in that: The S-CO2 circulation side of the working group in the molten salt heat storage tank system (300) drives the sCO2 circulation system (200) to do work; During stable operation, the standby group inlet valve (338), the standby group outlet valve (339) and the standby group heat inlet valve (340) for controlling the molten salt flow are closed, and the active group heat inlet valve (341) is opened. The molten salt carries heat only into the molten salt tank of the working group. There is no time difference between the energy storage and release processes of the molten salt heat storage tank system (300). The molten salt acts as a heat transfer intermediate medium to transfer the flue gas heat to the CO2 working fluid.

Images