Fused salt heat storage system coupled with coal-fired unit

Abstract

The invention provides a fused salt heat storage system coupled with a coal-fired unit, and relates to the field of energy storage systems, high-temperature flue gas and low-temperature flue gas are taken from the two sides of a high-temperature flue and a low-temperature flue of a boiler, the four strands of flue gas enter a flue gas mixer to be mixed, and the mixed flue gas enters a flue gas-fused salt heat exchanger to serve as a heat source for heating fused salt; fused salt in the low-temperature fused salt tank is heated after passing through the flue gas-fused salt heat exchanger and enters the high-temperature fused salt tank. When the unit needs to increase the load, the fused salt steam generation system is started, high-temperature fused salt in the high-temperature fused salt tank is introduced into the fused salt steam generation system, heat is released in the fused salt steam generation system, so that the fused salt steam generation system generates steam, and the steam enters the steam inlet of a load object through the steam outlet to increase the load. According to the scheme, high-temperature flue gas and low-temperature flue gas are taken from the left sides and the right sides of the high-temperature flue and the low-temperature flue of the boiler and mixed into the flue gas mixer to be mixed, and the stability of the flue gas output by the flue gas mixer is guaranteed.

Description

Technical Field

[0001] The present invention relates to the technical field of energy storage systems, and in particular to a molten salt heat storage system coupled with a coal-fired unit. Background Art

[0002] As the proportion of renewable energy installed capacity in the power grid increases, thermal power units need to have sufficient flexibility to adapt to the randomness and volatility of renewable energy output. The flexible operation of thermal power units is mainly supported by energy storage inside and outside the units. Molten salt, as a heat storage medium, has the characteristics of high energy storage efficiency and strong peak-shaving capacity. In recent years, it has gradually been applied to the field of coal-fired thermal power generation. Technicians build a heat storage system based on the characteristics of molten salt, so that the heat storage system can absorb energy when the unit needs to reduce the load, and release energy when the unit needs to increase the load, so as to achieve the function of peak shaving and valley filling. When constructing a heat storage system, the heat source on the molten salt heat storage side can be selected from high-temperature steam, high-temperature flue gas and electricity.

[0003] In the currently widely used boiler flue gas heating molten salt heat storage system, the induced draft fan is used to control the flue gas flow rate, and the molten salt pump is used to control the molten salt flow rate, thereby realizing the basic operation and control of the molten salt heat storage system. However, when the unit changes load, the flue gas temperature at the boiler will fluctuate significantly. The single-loop control method on the flue gas side cannot solve the imbalance of the flue gas temperature on the left and right sides, which leads to the problem of unstable molten salt heating and affects the working performance of the heat storage system. Summary of the invention

[0004] In view of this, an embodiment of the present invention provides a molten salt heat storage system coupled to a coal-fired unit to provide a low-cost molten salt heating solution for the coal-fired unit.

[0005] To achieve the above objectives, the embodiments of the present invention provide the following technical solutions:

[0006] A molten salt heat storage system coupled with a coal-fired unit, comprising:

[0007] Molten salt heat storage system and molten salt steam generation system based on flue gas heating;

[0008] The molten salt heat storage system based on flue gas heating includes a boiler, a flue gas mixer, a flue gas-molten salt heat exchanger, a low-temperature molten salt tank and a high-temperature molten salt tank;

[0009] The first smoke inlet of the smoke mixer is connected to the first side of the high-temperature smoke duct of the boiler, the second smoke inlet of the smoke mixer is connected to the first side of the low-temperature smoke duct of the boiler, the third smoke inlet of the smoke mixer is connected to the second side of the low-temperature smoke duct of the boiler, and the fourth smoke inlet of the smoke mixer is connected to the second side of the high-temperature smoke duct of the boiler;

[0010] The flue gas inlet of the flue gas-molten salt heat exchanger is connected to the gas outlet of the flue gas mixer, and the flue gas outlet of the flue gas-molten salt heat exchanger is connected to the flue gas inlet of the boiler;

[0011] The molten salt inlet of the high-temperature molten salt tank is connected to the molten salt outlet of the flue gas-molten salt heat exchanger and the molten salt inlet of the molten salt steam generation system;

[0012] The molten salt outlet of the high-temperature molten salt tank is connected to the molten salt inlet of the flue gas-molten salt heat exchanger and the molten salt inlet of the low-temperature molten salt tank;

[0013] The molten salt outlet of the low-temperature molten salt tank is connected to the molten salt inlet of the flue gas-molten salt heat exchanger;

[0014] The steam outlet of the molten salt steam generating system is connected to the steam inlet of the load object.

[0015] Optionally, in the molten salt heat storage system coupled with the above-mentioned coal-fired unit,

[0016] The first smoke inlet, the second smoke inlet, the third smoke inlet and the fourth smoke inlet of the smoke mixer are all provided with baffles;

[0017] The flue gas inlet of the flue gas-molten salt heat exchanger is connected to the gas outlet of the flue gas mixer through a high-temperature heat exchange pipeline, and the flue gas outlet of the flue gas-molten salt heat exchanger is connected to the flue gas inlet of the boiler through the high-temperature heat exchange pipeline;

[0018] The molten salt outlet of the low-temperature molten salt tank is connected to the molten salt inlet of the flue gas-molten salt heat exchanger through a low-temperature heat exchange pipeline;

[0019] The molten salt inlet of the high-temperature molten salt tank is connected to the molten salt outlet of the flue gas-molten salt heat exchanger through the low-temperature heat exchange pipeline;

[0020] The molten salt outlet of the high-temperature molten salt tank is connected to the low-temperature heat exchange pipeline between the low-temperature molten salt tank and the flue gas-molten salt heat exchanger through a high-temperature molten salt flow regulating pipeline;

[0021] The molten salt outlet of the high-temperature molten salt tank is connected to the molten salt inlet of the low-temperature molten salt tank through a molten salt steam heating pipeline, and the molten salt steam heating pipeline passes through the molten salt steam generating system.

[0022] Optionally, in the molten salt heat storage system coupled with the above-mentioned coal-fired unit,

[0023] The high-temperature heat exchange pipeline is provided with an induced draft fan;

[0024] The low-temperature heat exchange pipeline is provided with a first molten salt flow regulating valve and a low-temperature molten salt pump;

[0025] The high-temperature molten salt flow regulating pipeline is provided with a first high-temperature molten salt pump;

[0026] The molten salt steam heating pipeline is provided with a second high-temperature molten salt pump and a second molten salt flow regulating valve, and the second high-temperature molten salt pump is provided on the molten salt steam heating pipeline between the high-temperature molten salt pump and the molten salt steam generating system.

[0027] Optionally, in the molten salt heat storage system coupled with the above-mentioned coal-fired unit,

[0028] A low-temperature molten salt recirculation regulating pipeline, one end of which is connected to the low-temperature heat exchange pipeline between the low-temperature molten salt pump and the flue gas-molten salt heat exchanger, and the other end is connected to the molten salt inlet of the low-temperature molten salt tank, and a low-temperature molten salt recirculation regulating valve is provided on the low-temperature molten salt recirculation regulating pipeline;

[0029] A high-temperature molten salt recycling regulating pipeline, one end of which is connected to the molten salt steam heating pipeline between the high-temperature molten salt pump and the molten salt steam generating system, and the other end is connected to the molten salt inlet of the high-temperature molten salt tank.

[0030] Optionally, in the molten salt heat storage system coupled with the above-mentioned coal-fired unit,

[0031] The molten salt steam heating pipeline is provided with a molten salt main regulating valve and a molten salt bypass regulating valve, and the molten salt main regulating valve and the molten salt bypass regulating valve are connected in parallel with each other.

[0032] Optionally, in the above-mentioned molten salt heat storage system coupled with a coal-fired unit, the molten salt steam generation system comprises:

[0033] A deaerator, a preheater, an evaporator and a superheater, wherein the preheater, the evaporator and the superheater are connected in series in sequence;

[0034] The molten salt inlet of the superheater is connected to the molten salt outlet of the high-temperature molten salt tank;

[0035] The molten salt outlet of the preheater is connected to the molten salt inlet of the low-temperature molten salt tank;

[0036] The steam outlet of the superheater serves as the steam outlet of the molten salt steam generating system;

[0037] The water inlet of the preheater is connected to the water outlet of the deaerator.

[0038] Optionally, in the molten salt heat storage system coupled to the above-mentioned coal-fired unit, a water feed pump is provided on the water inlet pipeline between the preheater and the deaerator.

[0039] Optionally, the molten salt heat storage system coupled with the coal-fired unit further includes:

[0040] A water supply recirculation pipeline, one end of which is connected to the water inlet pipeline between the water supply pump and the preheater, and the other end of which is connected to the return water port of the deaerator. A water supply recirculation regulating valve is provided on the water supply recirculation pipeline.

[0041] Optionally, the molten salt heat storage system coupled with the coal-fired unit further includes:

[0042] A main water supply regulating valve and a bypass water supply regulating valve are arranged on the water inlet pipeline, and the main water supply regulating valve and the bypass water supply regulating valve are connected in parallel with each other.

[0043] Optionally, in the molten salt heat storage system coupled with the coal-fired unit, the steam outlet of the molten salt steam generation system is connected to the steam inlet of the load object through a steam output pipeline:

[0044] The steam output pipeline includes a first steam output pipeline connected to the first load steam inlet and a second steam output pipeline connected to the second load steam inlet;

[0045] The first steam output pipeline is provided with a steam main regulating valve;

[0046] The second steam output pipeline is provided with a steam bypass regulating valve.

[0047] Optionally, the molten salt heat storage system coupled with the coal-fired unit further includes: a working mode controller;

[0048] The working mode controller is used to control the working states of various valves and pumps in the molten salt heat storage system of the coupled coal-fired unit based on the working mode of the molten salt heat storage system of the coupled coal-fired unit, and the working mode includes heat storage mode, heat release mode, insulation mode and heating mode.

[0049] Optionally, the molten salt heat storage system coupled with the coal-fired unit further includes: a flue gas damper controller;

[0050] The flue gas damper controller is used to control the second damper at the second flue gas inlet and the third damper at the third flue gas inlet of the flue gas mixer to open when the molten salt heat storage system of the coupled coal-fired unit is in the heat storage mode and started, so that the low-temperature flue gas in the boiler enters the flue gas-molten salt heat exchanger. When preheating is completed, the first damper at the first flue gas inlet and the fourth damper at the fourth flue gas inlet of the flue gas mixer are controlled to open, so that the high-temperature flue gas in the boiler enters the flue gas-molten salt heat exchanger.

[0051] Optionally, in the molten salt heat storage system coupled with the coal-fired unit, when the molten salt heat storage system coupled with the coal-fired unit is in the start-up stage of the heat storage mode, controlling the second baffle at the second flue gas inlet and the third baffle at the third flue gas inlet of the flue gas mixer to open includes:

[0052] Obtaining an opening degree of the second baffle at the second smoke inlet and an opening degree of the third baffle at the third smoke inlet;

[0053] Get the actual load of the unit;

[0054] Based on the first control function, a target opening of the second damper and a target opening of the third damper matching the actual load of the unit are obtained;

[0055] Calculating an opening adjustment instruction of the second baffle based on a target opening of the second baffle and an opening of the second baffle;

[0056] An opening adjustment instruction of the third damper is calculated based on the target opening of the third damper and the opening of the third damper.

[0057] Optionally, in the molten salt heat storage system coupled to the coal-fired unit, obtaining the opening of the second baffle at the second flue gas inlet and the opening of the third baffle at the third flue gas inlet includes:

[0058] Acquire the opening of the second baffle at the second smoke inlet, where the opening of the second baffle is the opening corrected by the smoke temperature difference in the pipeline where the third baffle is located;

[0059] The opening of the second baffle at the third flue gas inlet is obtained, where the opening of the third baffle is the opening corrected by the flue gas temperature difference in the pipeline where the second baffle is located.

[0060] Optionally, in the molten salt heat storage system coupled to the coal-fired unit, after preheating is completed, controlling the first baffle at the first flue gas inlet and the fourth baffle at the fourth flue gas inlet of the flue gas mixer to open includes:

[0061] Acquire the opening of the first baffle at the first smoke inlet and the opening of the fourth baffle at the fourth smoke inlet;

[0062] Get the actual load of the unit;

[0063] Based on the third control function, a target opening of the first damper and a target opening of the fourth damper matching the actual load of the unit are obtained;

[0064] Calculating an opening adjustment instruction of the first baffle based on a target opening of the first baffle and an opening of the first baffle;

[0065] An opening adjustment instruction of the fourth damper is calculated based on the target opening of the fourth damper and the opening of the fourth damper.

[0066] Optionally, in the molten salt heat storage system coupled to the coal-fired unit, obtaining the opening of the first baffle at the first flue gas inlet and the opening of the fourth baffle at the fourth flue gas inlet includes:

[0067] Acquire the opening of the first baffle at the first flue gas inlet, where the opening of the first baffle is the opening corrected by the flue gas temperature difference in the pipeline where the fourth baffle is located;

[0068] The opening degree of the fourth baffle at the fourth flue gas inlet is obtained, where the opening degree of the fourth baffle is the opening degree corrected by the flue gas temperature difference in the pipeline where the first baffle is located.

[0069] Optionally, in the above-mentioned molten salt heat storage system coupled with a coal-fired unit, the working mode controller is also used for:

[0070] When the molten salt heat storage system of the coupled coal-fired unit is in the heat storage mode, the temperature of the molten salt in the high-temperature molten salt tank is detected, and when the molten salt temperature reaches the insulation temperature, the molten salt heat storage system of the coupled coal-fired unit is controlled to enter the insulation mode;

[0071] When the molten salt heat storage system coupled to the coal-fired unit enters the insulation mode, the flue gas damper controller is also used to:

[0072] controlling the opening degrees of the second baffle and the third baffle based on a second control function;

[0073] The opening degrees of the first damper and the fourth damper are controlled based on a fourth control function.

[0074] Optionally, in the molten salt heat storage system coupled to the coal-fired unit, controlling the openings of the second damper and the third damper based on the second control function includes:

[0075] Obtaining an opening degree of the second baffle at the second smoke inlet and an opening degree of the third baffle at the third smoke inlet;

[0076] Get the actual load of the unit;

[0077] Based on the second control function, a target opening of the second damper and a target opening of the third damper matching the actual load of the unit are obtained;

[0078] Calculating an opening adjustment instruction of the second baffle based on a target opening of the second baffle and an opening of the second baffle;

[0079] An opening adjustment instruction of the third damper is calculated based on the target opening of the third damper and the opening of the third damper.

[0080] Optionally, in the molten salt heat storage system coupled to the coal-fired unit, controlling the openings of the first baffle and the fourth baffle based on the fourth control function includes:

[0081] Acquire the opening of the first baffle at the first smoke inlet and the opening of the fourth baffle at the fourth smoke inlet;

[0082] Get the actual load of the unit;

[0083] Based on a fourth control function, a target opening of the first damper and a target opening of the fourth damper matching the actual load of the unit are obtained;

[0084] Calculating an opening adjustment instruction of the first baffle based on a target opening of the first baffle and an opening of the first baffle;

[0085] An opening adjustment instruction of the fourth damper is calculated based on the target opening of the fourth damper and the opening of the fourth damper.

[0086] Optionally, the molten salt heat storage system coupled to the above-mentioned coal-fired unit also includes: an induced draft fan controller, which controls the frequency of the induced draft fan in the high-temperature heat exchange pipeline based on the measured value and design value of the pressure difference in the high-temperature heat exchange pipeline.

[0087] Optionally, the molten salt heat storage system coupled with the coal-fired unit further includes:

[0088] An electric heating device is arranged in the low-temperature molten salt tank.

[0089] Optionally, the molten salt heat storage system coupled with the coal-fired unit further includes: a molten salt temperature controller

[0090] The molten salt temperature controller is used to: when it is detected that the low-temperature molten salt pump corresponding to the low-temperature molten salt tank is at minimum power, control the flow in the low-temperature heat exchange pipeline through the molten salt flow regulating valve until the opening of the molten salt flow regulating valve reaches the maximum.

[0091] Optionally, in the above-mentioned molten salt heat storage system coupled with a coal-fired unit, the molten salt temperature controller is also used for:

[0092] When it is detected that the opening of the molten salt flow regulating valve reaches the maximum, the flow in the low-temperature heat exchange pipeline is controlled by the low-temperature molten salt pump until the low-temperature molten salt pump corresponding to the low-temperature molten salt tank reaches the minimum power.

[0093] Optionally, in the molten salt heat storage system coupled with the above-mentioned coal-fired unit, the molten salt temperature controller includes:

[0094] a molten salt temperature main controller, a first molten salt temperature sub-controller and a second molten salt temperature sub-controller;

[0095] The molten salt temperature main controller is used to generate a molten salt flow rate setting value in the low-temperature heat exchange pipeline based on the deviation between the molten salt temperature setting value and the measured value in the low-temperature heat exchange pipeline when the molten salt heat storage system coupled to the coal-fired unit is in the insulation mode;

[0096] The first molten salt temperature sub-controller is used to: when it is detected that the opening of the molten salt flow regulating valve reaches the maximum, based on the deviation between the molten salt flow setting value and the measured value of the molten salt in the low-temperature heat exchange pipeline, calculate the target output power of the low-temperature molten salt pump, and adjust the output power of the low-temperature molten salt pump based on the target output power and the measured output power of the low-temperature molten salt pump until it is detected that the low-temperature molten salt pump reaches the minimum power;

[0097] The second molten salt temperature sub-controller is used for: when it is detected that the low-temperature molten salt pump corresponding to the low-temperature molten salt tank is at minimum power, based on the deviation between the molten salt flow rate set value and the measured value of the molten salt in the low-temperature heat exchange pipeline, calculating the target opening of the molten salt flow rate regulating valve, and adjusting the opening of the molten salt flow rate regulating valve based on the target opening and the measured opening of the molten salt flow rate regulating valve, until it is detected that the opening of the molten salt flow rate regulating valve reaches the maximum, controlling the molten salt flow rate regulating valve to enter a manual adjustment state.

[0098] Optionally, in the molten salt heat storage system coupled to the above-mentioned coal-fired unit, the measured output power of the low-temperature molten salt pump is the output power corrected by the molten salt temperature at the molten salt inlet of the flue gas-molten salt heat exchanger;

[0099] The measured opening of the molten salt flow regulating valve is the opening corrected by the molten salt temperature at the molten salt inlet of the flue gas-molten salt heat exchanger.

[0100] Optionally, the molten salt heat storage system coupled with the coal-fired unit further includes:

[0101] Direct energy balance controller;

[0102] The direct energy balance controller is used to generate and output a molten salt flow instruction based on the deviation between the energy demand signal and the energy supply signal of the molten salt steam generation system, and the molten salt flow instruction is used to characterize the target molten salt flow of the low-temperature heat exchange pipeline.

[0103] Optionally, the molten salt heat storage system coupled with the coal-fired unit further includes: a molten salt main flow controller;

[0104] When the molten salt heat storage system coupled to the coal-fired unit is in the heat release mode, the molten salt main flow controller is used to: generate a molten salt pump frequency adjustment instruction based on the target molten salt flow and the measured molten salt flow of the low-temperature heat exchange pipeline, and control the power of the second high-temperature molten salt pump based on the molten salt pump frequency adjustment instruction.

[0105] Optionally, in the molten salt heat storage system coupled with the coal-fired unit, after the molten salt pump frequency adjustment instruction is generated, the molten salt main flow controller is further used to:

[0106] The molten salt pump frequency adjustment instruction is corrected based on the differential result of the energy demand signal.

[0107] Optionally, the molten salt heat storage system coupled with the coal-fired unit further includes: a molten salt bypass flow controller;

[0108] When the molten salt heat storage system of the coupled coal-fired unit is in the heating mode, the molten salt bypass flow controller is used to: obtain the target molten salt flow, calculate the target opening of the molten salt bypass regulating valve based on the target molten salt flow and the measured molten salt flow in the low-temperature molten salt recycling pipeline, and adjust the opening of the molten salt bypass regulating valve based on the target opening of the molten salt bypass regulating valve.

[0109] Optionally, in the above-mentioned molten salt heat storage system coupled with a coal-fired unit, the direct energy balance controller is also used for:

[0110] An energy demand signal is calculated based on the steam pressure at the steam inlet of the load, the measured value of the steam pressure at the superheater outlet, and the set value of the steam pressure at the superheater outlet;

[0111] The energy supply signal is calculated based on the energy demand signal, the energy supply signal, the heat storage coefficient of the molten salt heat release system and the drum pressure.

[0112] Optionally, the molten salt heat storage system coupled with the coal-fired unit further includes:

[0113] A steam flow controller is used to obtain the steam temperature output by the superheater, correct the steam temperature based on a sixth function, and obtain a steam flow setting value that matches the corrected steam temperature; and control the flow rate of the output steam of the superheater based on the steam flow setting value.

[0114] Optionally, in the molten salt heat storage system coupled with the above-mentioned coal-fired unit, the steam flow controller includes: a superheated steam main flow controller;

[0115] The superheated steam main flow controller is used to calculate the opening adjustment instruction of the steam main flow regulating valve based on the difference between the steam flow setting value and the actual steam flow value, and the opening adjustment instruction is used to adjust the opening of the steam main flow regulating valve.

[0116] Optionally, in the molten salt heat storage system coupled with the above-mentioned coal-fired unit, the steam flow controller further includes:

[0117] The pressure calculation unit is used to obtain a superheated steam pressure setting value and an actual superheated steam pressure value; calculate the difference between the superheated steam pressure setting value and the actual superheated steam pressure value, and record it as a main steam pressure difference; use a seventh function to correct the main steam pressure difference; and correct the opening adjustment instruction based on the corrected main steam pressure difference.

[0118] Optionally, in the molten salt heat storage system coupled with the above-mentioned coal-fired unit, the steam flow controller further includes:

[0119] The superheated steam bypass flow controller is used to calculate the opening adjustment instruction of the steam bypass regulating valve based on the difference between the superheated steam flow set value and the actual measured value of the superheated steam flow in the steam bypass pipeline, and adjust the opening of the steam bypass regulating valve based on the opening adjustment instruction.

[0120] Optionally, in the molten salt heat storage system coupled with the coal-fired unit, the steam flow controller further comprises: a first switch;

[0121] The first switch is used for: when the superheated steam flow in the steam output pipeline increases from 0 to the first steam flow, controlling the superheated steam bypass flow controller to start, controlling the superheated steam main flow controller to stop; when the superheated steam flow in the steam output pipeline increases to the first steam flow and continues to increase, controlling the superheated steam main flow controller to start, controlling the superheated steam bypass flow controller to stop, and keeping the superheated steam main flow controller in the open state; when the superheated steam flow in the steam output pipeline decreases to the second steam flow, the superheated steam bypass flow controller is stopped; when the superheated steam flow in the steam output pipeline decreases to the second steam flow and needs to continue to decrease, controlling the superheated steam bypass flow controller to start, and controlling the superheated steam main flow controller to stop;

[0122] Wherein, the first steam flow rate is greater than the second steam flow rate.

[0123] Optionally, the molten salt heat storage system coupled with the coal-fired unit further includes: an evaporator liquid level main controller and an evaporator liquid level sub-controller;

[0124] The evaporator liquid level main controller is used to obtain a feed water flow setting value by weighted summing the evaporator liquid level setting value, the liquid level actual value and the superheated steam flow actual value, and calculate the feed water flow adjustment instruction based on the feed water flow setting value and the feed water flow actual value in the feed water pipeline;

[0125] The evaporator liquid level sub-controller is used to adjust the water supply amount of the evaporator based on the water supply flow adjustment instruction.

[0126] Optionally, in the above-mentioned molten salt heat storage system coupled with a coal-fired unit, the evaporator liquid level sub-controller includes: a first evaporator liquid level sub-controller, a second evaporator liquid level sub-controller and a third evaporator liquid level sub-controller;

[0127] The first evaporator liquid level sub-controller is used for:

[0128] The first evaporator liquid level sub-controller is used to: adjust the opening of the feedwater bypass regulating valve based on the feedwater flow rate regulating instruction;

[0129] The second evaporator liquid level sub-controller is used to: adjust the opening of the water supply main line regulating valve based on the water supply flow rate adjustment instruction;

[0130] The third evaporator liquid level sub-controller is used to adjust the output power of the feed water pump at the water outlet of the deaerator based on the feed water flow adjustment instruction.

[0131] Optionally, the molten salt heat storage system coupled with the coal-fired unit further includes: a second switch;

[0132] The second switch is used to: when it is monitored that the feed water pump of the deaerator is running at the minimum power, control the first evaporator liquid level sub-controller to start, when it is monitored that the opening of the feed water bypass regulating valve reaches the first opening, if the feed water flow needs to continue to increase, control the second evaporator liquid level sub-controller to start, when it is monitored that the opening of the feed water main regulating valve reaches the second opening, if the feed water flow needs to continue to increase, control the third evaporator liquid level sub-controller to start;

[0133] Optionally, the molten salt heat storage system coupled with the coal-fired unit further includes: a third switch;

[0134] The third switch is used to: when it is detected that the molten salt steam generation system cuts off the heating mode or detects that the opening of the water supply bypass regulating valve reaches the maximum, turn off the first evaporator liquid level sub-controller; when it is detected that the power of the water supply pump reaches the minimum value, the opening of the water supply main regulating valve reaches the minimum value and the molten salt steam generation system switches into the heating mode, control the first evaporator liquid level sub-controller to start;

[0135] When it is detected that the molten salt steam generation system cuts off the heating mode or detects that the opening of the water supply main line regulating valve reaches the maximum, the second evaporator liquid level sub-controller is turned off; when it is detected that the power of the water supply pump reaches the minimum value, the opening of the water supply bypass regulating valve reaches the maximum value and the molten salt steam generation system cuts into the heating mode, the second evaporator liquid level sub-controller is controlled to start;

[0136] When it is detected that the molten salt steam generation system cuts off the heating mode or detects that the water supply pump power reaches the minimum value, the third evaporator liquid level sub-controller is turned off. When it is detected that the opening of the water supply main line regulating valve reaches the maximum, the opening of the water supply bypass regulating valve reaches the maximum value and the molten salt steam generation system enters the heat release mode, the third evaporator liquid level sub-controller is controlled to start. After obtaining the adjustment instruction output by the evaporator liquid level main controller, the first evaporator liquid level sub-controller, the second evaporator liquid level sub-controller or the third evaporator liquid level sub-controller in the startup state controls their respective control objects based on the control instruction.

[0137] Optionally, the molten salt heat storage system coupled with the coal-fired unit further includes: a recirculation regulating valve controller;

[0138] The recirculation regulating valve controller is used to: when it is detected that the outlet flow rate of the target pump increases to its corresponding first target value, when the outlet flow rate of the target pump continues to increase, control the opening of the circulation regulating valve corresponding to the target pump to decrease as the outlet flow rate of the target pump increases, until the opening is reduced to 0; when it is detected that the outlet flow rate of the target pump decreases to its corresponding second target value, when the outlet flow rate of the target pump continues to decrease, control the opening of the circulation regulating valve corresponding to the target pump to increase as the outlet flow rate of the target pump decreases, until the opening increases to a maximum opening;

[0139] The target pump is a low-temperature molten salt pump, a second high-temperature molten salt pump or a water feed pump;

[0140] The first target value is smaller than the second target value.

[0141] Optionally, in the molten salt heat storage system coupled to the coal-fired unit, controlling the opening of the circulation regulating valve corresponding to the target pump to decrease as the outlet flow of the target pump increases includes:

[0142] Based on the eighth control function, controlling the opening of the circulation regulating valve corresponding to the target pump to decrease as the outlet flow rate of the target pump increases;

[0143] Controlling the opening of a circulation regulating valve corresponding to a target pump to increase as the outlet flow rate of the target pump decreases, comprising:

[0144] Based on the ninth control function, the opening degree of the circulation regulating valve corresponding to the target pump is controlled to increase as the outlet flow rate of the target pump decreases;

[0145] The eighth control function and the ninth control function are respectively used to express the mapping relationship between the outlet flow rate of the target pump and the opening degree of the circulation regulating valve corresponding to the target pump.

[0146] Based on the above technical solution, the molten salt heat storage system of the above-mentioned coupled coal-fired unit provided in the embodiment of the present invention, in order to suppress the temperature fluctuation on the heat source side, taking into account the flue gas heat balance on the left and right sides of the boiler, both high-temperature flue gas and low-temperature flue gas are taken on the left and right sides of the high-temperature flue and the low-temperature flue of the boiler. The four flue gases enter the flue gas mixer after passing through their corresponding flue gas pipes, and the mixed flue gas enters the flue gas-molten salt heat exchanger as a heat source for heating the molten salt. The molten salt in the low-temperature molten salt tank is heated after passing through the flue gas-molten salt heat exchanger, and the heated molten salt enters the high-temperature molten salt tank. When the unit needs to increase the load, the molten salt steam generation system is started, and the high-temperature molten salt in the high-temperature molten salt tank flows back to the low-temperature molten salt tank after passing through the molten salt steam generation system, and the high-temperature molten salt releases heat in the molten salt steam generation system, so that the molten salt steam generation system generates a large amount of steam, and these steams enter the steam inlet of the load object through the steam outlet of the molten salt steam generation system, thereby increasing the load of the unit. This solution takes high-temperature flue gas and low-temperature flue gas from both sides of the high-temperature flue and low-temperature flue of the boiler and mixes them into the flue gas mixer to ensure the stability of the flue gas output by the flue gas mixer. At the same time, this solution uses flue gas heat as an energy source and uses high-temperature flue gas to heat the molten salt, realizing the recovery and reuse of waste heat in the boiler and reducing energy consumption costs. BRIEF DESCRIPTION OF THE DRAWINGS

[0147] 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. Obviously, the drawings described below are only embodiments of the present invention. For ordinary technicians in this field, other drawings can be obtained based on the provided drawings without paying creative work.

[0148] Figure 1 A schematic structural diagram of a molten salt heat storage system based on flue gas heating in a molten salt heat storage system coupled to a coal-fired unit provided in an embodiment of the present application;

[0149] Figure 2 A schematic diagram of the structure of a molten salt steam generation system in a molten salt heat storage system coupled to a coal-fired unit provided in an embodiment of the present application;

[0150] Figure 3 A control logic diagram of a smoke damper controller provided in an embodiment of the present application;

[0151] Figure 4 A schematic diagram of the structure and control logic of the molten salt temperature controller provided in an embodiment of the present application;

[0152] Figure 5 A control logic diagram of a molten salt steam generation system provided in an embodiment of the present application;

[0153] Figure 6 A schematic diagram of bypass control conditions of a steam generation system provided in an embodiment of the present application;

[0154] Figure 7 A schematic diagram of the structure and control logic of a steam flow controller provided in an embodiment of the present application;

[0155] Figure 8 A schematic diagram of the structure and control logic of the evaporator liquid level controller provided in an embodiment of the present application;

[0156] Fig. 9 A control logic diagram of a target pump provided in an embodiment of the present application;

[0157] Fig.10 This is a relationship curve diagram of the flow rate of the target pump and the opening degree of the corresponding recirculation valve disclosed in the embodiment of the present application. DETAILED DESCRIPTION

[0158] The following will be combined with the drawings in the embodiments of the present invention to clearly and completely describe the technical solutions in the embodiments of the present invention. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0159] See also Figure 1 and Figure 2 , the molten salt heat storage system coupled with the coal-fired unit disclosed in the embodiment of the present application may include: a molten salt heat storage system based on flue gas heating and a molten salt steam generation system;

[0160] The molten salt heat storage system based on flue gas heating includes a boiler 1, a flue gas mixer 2, a flue gas-molten salt heat exchanger 3, a low-temperature molten salt tank 4 and a high-temperature molten salt tank 5;

[0161] Regarding boiler 1, the flue in boiler 1, as a channel for flue gas flow, can be mainly divided into low-temperature flue and high-temperature flue according to the different flue gas temperatures. The high-temperature flue is located near the combustion area of ​​boiler 1 and is used to discharge high-temperature flue gas generated from the combustion chamber. These flue gases carry a large amount of heat energy. Usually, heating surfaces such as superheaters or reheaters are set in the high-temperature flue to effectively absorb and utilize this heat energy to heat the feed water into steam or further increase the temperature and pressure of the steam. When the flue gas leaves the high-temperature area and enters the low-temperature area, it enters the low-temperature flue. In the low-temperature flue, the flue gas temperature is relatively low, but it still has a certain amount of heat energy. Therefore, heating surfaces such as economizers or air preheaters are usually set in the low-temperature flue to further recover and utilize the waste heat in the flue gas and improve the thermal efficiency of boiler 1.

[0162] The first flue gas inlet of the flue gas mixer 2 is connected to the first side of the high-temperature flue of the boiler 1, the second flue gas inlet of the flue gas mixer 2 is connected to the first side of the low-temperature flue of the boiler 1, the third flue gas inlet of the flue gas mixer 2 is connected to the second side of the low-temperature flue of the boiler 1, and the fourth flue gas inlet of the flue gas mixer 2 is connected to the second side of the high-temperature flue of the boiler 1; the first side and the second side refer to the left and right sides of the flue of the boiler 1, and the flue gas entering through the four flue gas inlets of the flue gas mixer 2 is fully mixed in the flue gas mixer 2, and then enters the flue gas-molten salt heat exchanger 3 through the flue gas inlet of the flue gas-molten salt heat exchanger 3.

[0163] The flue gas inlet of the flue gas-molten salt heat exchanger 3 is connected to the gas outlet of the flue gas mixer 2, and the flue gas outlet of the flue gas-molten salt heat exchanger 3 is connected to the flue gas inlet of the boiler 1; the flue gas-molten salt heat exchanger 3 is a place for heat exchange between flue gas and molten salt, and the heat in the flue gas in the flue gas-molten salt heat exchanger 3 will be absorbed by the molten salt.

[0164] The molten salt inlet of the high-temperature molten salt tank 5 is connected to the molten salt outlet of the flue gas-molten salt heat exchanger 3 and the molten salt inlet of the molten salt steam generating system. The flue gas after heat exchange in the heat exchanger flows out from the molten salt outlet of the flue gas-molten salt heat exchanger 3 and returns to the flue of the boiler 1.

[0165] The molten salt outlet of the high-temperature molten salt tank 5 is connected to the molten salt inlet of the flue gas-molten salt heat exchanger 3 and the molten salt inlet of the low-temperature molten salt tank 4. At this time, the high-temperature molten salt in the high-temperature molten salt tank 5 can enter the flue gas-molten salt heat exchanger 3 for reheating, or return to the low-temperature molten salt tank 4. In this solution, the molten salt outlet of the high-temperature molten salt tank 5 may include a first molten salt outlet and a second molten salt outlet, the first molten salt outlet is connected to the molten salt inlet of the flue gas-molten salt heat exchanger 3, and the second molten salt outlet is connected to the molten salt inlet of the low-temperature molten salt tank 4;

[0166] The molten salt outlet of the low-temperature molten salt tank 4 is connected to the molten salt inlet of the flue gas-molten salt heat exchanger 3. At this time, the molten salt in the low-temperature molten salt tank 4 can enter the flue gas-molten salt heat exchanger 3 to perform heat exchange with the high-temperature flue gas in the flue gas-molten salt heat exchanger 3;

[0167] The steam outlet of the molten salt steam generating system is connected to the steam inlet of the load object, and the high-temperature steam generated by the molten salt steam generating system enters the load through the steam inlet of the load object to increase the load.

[0168] When the unit is under load change, the flue gas temperature at boiler 1 will fluctuate significantly. If a single flue gas is used to heat the molten salt in the molten salt tank, it will affect the temperature of the molten salt in the molten salt tank. In order to suppress the temperature fluctuation on the heat source side and take into account the flue gas heat balance on the left and right sides of boiler 1, both high-temperature flue gas and low-temperature flue gas are taken on the left and right sides of the high-temperature flue and low-temperature flue of boiler 1. The four flue gases enter the flue gas mixer 2 after passing through their respective corresponding flue gas pipes. The mixed flue gas enters the flue gas-molten salt heat exchanger 3 as the heat source for heating the molten salt. The molten salt in the low-temperature molten salt tank 4 is heated after passing through the flue gas-molten salt heat exchanger 3, and the heated molten salt enters the high-temperature molten salt tank 5. When the unit needs to increase its load, the molten salt steam generation system is started, and the high-temperature molten salt in the high-temperature molten salt tank 5 flows back to the low-temperature molten salt tank 4 after passing through the molten salt steam generation system, and the high-temperature molten salt releases heat in the molten salt steam generation system, so that the molten salt steam generation system generates a large amount of steam, and the steam enters the steam inlet of the load object through the steam outlet of the molten salt steam generation system, thereby increasing the unit load. This unit load increase scheme uses flue gas heat as an energy source and uses high-temperature flue gas to heat the molten salt, thereby realizing the recovery and reuse of waste heat in the boiler 1 and reducing energy consumption costs.

[0169] For further information, see Figure 1 and Figure 2In this embodiment, the first smoke inlet, the second smoke inlet, the third smoke inlet and the fourth smoke inlet of the smoke mixer 2 are all provided with baffles. Specifically, the first smoke inlet of the smoke mixer 2 is connected to the first side of the high-temperature flue of the boiler 1, and a first baffle 01 is provided on the pipeline between the first smoke inlet of the smoke mixer 2 and the first side of the high-temperature flue. The second smoke inlet of the smoke mixer 2 is connected to the first side of the low-temperature flue of the boiler 1, and a second baffle 02 is provided on the pipeline between the second smoke inlet of the smoke mixer 2 and the first side of the low-temperature flue. The third flue gas inlet of the mixer 2 is connected to the second side of the low-temperature flue of the boiler 1, and a third baffle 03 is arranged on the pipeline between the third flue gas inlet of the flue gas mixer 2 and the second side of the low-temperature flue. The fourth flue gas inlet of the flue gas mixer 2 is connected to the second side of the high-temperature flue of the boiler 1, and a fourth baffle 04 is arranged on the pipeline between the fourth flue gas inlet of the flue gas mixer 2 and the second side of the high-temperature flue. By adjusting the opening of the first baffle 01, the second baffle 02, the third baffle 03 and the fourth baffle 04, the amount of flue gas entering each smoke inlet of the smoke mixer 2 can be adjusted.

[0170] The flue gas inlet of the flue gas-molten salt heat exchanger 3 is connected to the gas outlet of the flue gas mixer 2 through the high-temperature heat exchange pipeline L1, so that the flue gas output by the flue gas mixer 2 enters the flue gas-molten salt heat exchanger 3, and the flue gas outlet of the flue gas-molten salt heat exchanger 3 is connected to the flue gas inlet of the boiler 1 through the high-temperature heat exchange pipeline L1, so that the flue gas after releasing heat flows back into the flue gas-molten salt heat exchanger 3 in the boiler 1 for heating;

[0171] The molten salt outlet of the low-temperature molten salt tank 4 is connected to the molten salt inlet of the flue gas-molten salt heat exchanger 3 through the low-temperature heat exchange pipeline L2, so that the low-temperature molten salt in the low-temperature molten salt tank 4 enters the flue gas-molten salt heat exchanger 3 for heating;

[0172] The molten salt inlet of the high-temperature molten salt tank 5 is connected to the molten salt outlet of the flue gas-molten salt heat exchanger 3 through the low-temperature heat exchange pipeline L2 to collect and store the high-temperature molten salt;

[0173] The molten salt outlet of the high-temperature molten salt tank 5 is connected through the high-temperature molten salt flow regulating pipeline L3 and the low-temperature heat exchange pipeline L2 between the low-temperature molten salt tank 4 and the flue gas-molten salt heat exchanger 3, so that the high-temperature molten salt in the high-temperature molten salt tank 5 is heated again by the flue gas-molten salt heat exchanger 3 to keep the molten salt in the high-temperature molten salt tank 5 warm;

[0174] The molten salt outlet of the high-temperature molten salt tank 5 is connected to the molten salt inlet of the low-temperature molten salt tank 4 through a molten salt steam heating pipeline L4. The molten salt steam heating pipeline L4 passes through the molten salt steam generating system, so that the high-temperature molten salt releases heat in the molten salt steam generating system, so that the molten salt steam generating system generates a large amount of steam and flows the lava after heat release back into the low-temperature molten salt tank 4.

[0175] For further information, see Figure 1 and Figure 2 The high-temperature heat exchange pipeline L1 is provided with an induced draft fan 6 or other flow regulating equipment, and the low-temperature flue gas after releasing heat in the flue gas-molten salt heat exchanger 3 can be introduced into the boiler 1 for reuse through the induced draft fan 6 or other flow regulating equipment. In this embodiment, the induced draft fan 6 can be arranged on the high-temperature heat exchange pipeline L1 between the boiler 1 and the flue gas outlet of the flue gas-molten salt heat exchanger 3.

[0176] The low-temperature heat exchange pipeline L2 is provided with a first molten salt flow regulating valve K1 and a low-temperature molten salt pump B2, wherein the first molten salt flow regulating valve K1 and the low-temperature molten salt pump can be arranged on the low-temperature heat exchange pipeline L2 between the low-temperature molten salt tank 4 and the molten salt inlet of the flue gas-molten salt heat exchanger 3, and the first molten salt flow regulating valve K1 is arranged close to the molten salt inlet of the flue gas-molten salt heat exchanger 3, and the low-temperature molten salt pump is arranged close to the low-temperature molten salt tank 4, and the molten salt flow in the low-temperature heat exchange pipeline L2 can be adjusted by the first molten salt flow regulating valve K1 and the low-temperature molten salt pump.

[0177] The high-temperature molten salt flow regulating pipeline L3 is provided with a first high-temperature molten salt pump B1, one end of the high-temperature molten salt flow regulating pipeline L3 is connected to the molten salt outlet of the high-temperature molten salt tank 5, and the other end of the high-temperature molten salt flow regulating pipeline L3 is connected to the low-temperature heat exchange pipeline L2 between the first molten salt flow regulating valve K1 and the low-temperature molten salt pump;

[0178] The molten salt steam heating pipeline L4 is provided with a second high-temperature molten salt pump B3 and a second molten salt flow regulating valve K2. The second high-temperature molten salt pump is arranged on the molten salt steam heating pipeline L4 between the high-temperature molten salt pump and the molten salt steam generating system. The second molten salt flow regulating valve K2K2 is arranged on the molten salt steam heating pipeline L4 between the flue gas outlet of the molten salt steam generating system and the low-temperature molten salt tank 4. The flue gas flow in the molten salt steam heating pipeline L4 is adjusted by the second high-temperature molten salt pump B3 and the second molten salt flow regulating valve K2K2.

[0179] For further information, see Figure 1 and Figure 2, the above scheme also includes: a low-temperature molten salt recycling regulating pipeline L6 and a high-temperature molten salt recycling regulating pipeline L7;

[0180] One end of the low-temperature molten salt recycling regulating pipeline L6 is connected to the low-temperature heat exchange pipeline L2 between the low-temperature molten salt pump and the flue gas-molten salt heat exchanger 3, and the other end of the low-temperature molten salt recycling regulating pipeline L6 is connected to the molten salt inlet of the low-temperature molten salt tank 4. A low-temperature molten salt recycling regulating valve K3 is provided on the low-temperature molten salt recycling regulating pipeline L6. The low-temperature molten salt drawn out of the low-temperature molten salt tank 4 can be recycled into the low-temperature molten salt tank 4 through the low-temperature molten salt recycling regulating pipeline L6, and the molten salt flow in the low-temperature molten salt recycling regulating pipeline L6 can be adjusted through the low-temperature molten salt recycling regulating valve K3;

[0181] One end of the high-temperature molten salt recycling regulating pipeline L7 is connected to the molten salt steam heating pipeline L4 between the high-temperature molten salt pump and the molten salt steam generating system, and the other end is connected to the molten salt inlet of the high-temperature molten salt tank 5. The high-temperature molten salt drawn out of the high-temperature molten salt tank 5 can be recycled into the high-temperature molten salt tank 5 through the high-temperature molten salt recycling regulating pipeline L7, and the molten salt flow in the high-temperature molten salt recycling regulating pipeline L7 can be adjusted through the high-temperature molten salt recycling regulating valve K4.

[0182] For further information, see Figure 1 and Figure 2 In this embodiment, a molten salt main regulating valve K5 and a molten salt bypass regulating valve K6 are provided on the molten salt steam heating pipeline L4, and the molten salt main regulating valve K5 and the molten salt bypass regulating valve K6 are connected in parallel with each other. The molten salt main regulating valve K5 and the molten salt bypass regulating valve K6 cooperate with the second high-temperature molten salt pump to more accurately adjust the flue gas flow in the molten salt steam heating pipeline L4.

[0183] In this embodiment, the molten salt steam generation system includes: a deaerator 11, a preheater 12, an evaporator 13 and a superheater 14, wherein the preheater, the evaporator and the superheater are connected in series in sequence;

[0184] The molten salt inlet of the superheater is connected to the molten salt outlet of the high-temperature molten salt tank 5;

[0185] The molten salt outlet of the preheater is connected to the molten salt inlet of the low-temperature molten salt tank 4;

[0186] The steam outlet of the superheater serves as the steam outlet of the molten salt steam generating system;

[0187] The water inlet of the preheater is connected to the water outlet of the deaerator.

[0188] The high-temperature molten salt in the high-temperature molten salt tank 5 enters the superheater and then enters the evaporator, and then enters the preheater, and flows out through the molten salt outlet of the preheater. The low-temperature molten salt flowing out of the molten salt outlet of the preheater returns to the low-temperature molten salt tank 4; the water flowing out of the water outlet of the deaerator enters the preheater through the water inlet of the preheater, and enters the evaporator after being preheated by the preheater, and then the evaporator converts the entering water into steam, and the steam enters the superheater. After being processed by the superheater, the steam flows out from the steam outlet of the superheater to enter the steam inlet of the load object.

[0189] In this embodiment, a water supply pump B4 is provided on the water inlet pipeline L5 between the preheater and the deaerator, and the flow rate in the water inlet pipeline L5 can be adjusted by the water supply pump.

[0190] In this embodiment, the molten salt heat storage system coupled with the coal-fired unit further includes:

[0191] A water supply recirculation pipeline L8, one end of which is connected to the water inlet pipeline L5 between the water supply pump and the preheater, and the other end of which is connected to the water return port of the deaerator, and a water supply recirculation regulating valve K7 is provided on the water supply recirculation pipeline L8. The flow rate in the water supply pipeline can be accurately adjusted by the water supply pump and the water supply recirculation regulating valve K7.

[0192] In this embodiment, the molten salt heat storage system coupled with the coal-fired unit further includes:

[0193] The main water supply regulating valve K8 and the water supply bypass regulating valve K9 are arranged on the water inlet pipeline L5, and the main water supply regulating valve K8 and the water supply bypass regulating valve K9 are connected in parallel with each other. The main water supply regulating valve K8, the water supply bypass regulating valve K9, the water supply pump and the water supply recirculation regulating valve K7 can achieve more precise regulation of the flow in the water supply pipeline.

[0194] In this embodiment, the steam outlet of the molten salt steam generation system in the molten salt heat storage system coupled with the coal-fired unit is connected to the steam inlet of the load object through the steam output pipeline L9:

[0195] The steam output pipeline includes a first steam output pipeline L91 connected to the first load steam inlet and a second steam output pipeline L92 connected to the second load steam inlet;

[0196] The first steam output pipeline is provided with a steam main regulating valve K10, and the steam main regulating valve K10 is used to regulate the steam flow in the first steam output pipeline;

[0197] The second steam output pipeline is provided with a steam bypass regulating valve K11, and the steam bypass regulating valve K11 is used to regulate the steam flow in the second steam output pipeline.

[0198] It can be seen from the above scheme that the present application provides a flue gas loop structure of a molten salt heat storage system coupled to a coal-fired unit. The working mode of the molten salt heat storage system coupled to the coal-fired unit needs to be controlled by a controller. Specifically, the molten salt heat storage system coupled to the coal-fired unit in the present application may include a working mode controller, which is used to control the working state of each valve and pump in the molten salt heat storage system of the coupled coal-fired unit based on the working mode of the molten salt heat storage system of the coupled coal-fired unit. The working mode includes a heat storage mode, a heat release mode, a heat preservation mode and a heating mode. More specifically, the heat storage mode and the heat preservation mode refer to the heat storage mode and the heat preservation mode of a molten salt heat storage system based on flue gas heating. The molten salt heat storage system based on flue gas heating is composed of a boiler 1, a low-temperature molten salt tank 4, a high-temperature molten salt tank 5, a flue gas-molten salt heat exchanger 3, a flue gas mixer 2 and related pipelines. The exothermic mode and the tracing mode refer to the exothermic mode and the tracing mode of the molten salt steam generation system. The molten salt heat storage system based on flue gas heating and the working mode of the molten salt steam generation system are controlled independently of each other. In the heat storage mode, the coal-fired unit heats the molten salt through the flue gas energy source and stores the heat in the high-temperature molten salt tank 5. In the exothermic mode, the high-temperature molten salt in the high-temperature molten salt tank 5 enters the molten salt steam generation system through the molten salt pump, and the molten salt steam generation system is assisted to generate a large amount of steam, which can be applied to the load end to achieve the unit's thermal and electrical decoupling or rapid load increase and peak power generation. The insulation mode is mainly to maintain the temperature of the molten salt in the molten salt heat storage system to prevent heat loss. In the insulation mode, the system can reintroduce the high-temperature molten salt in the high-temperature molten salt tank 5 into the flue gas-molten salt heat exchanger 3 through the high-temperature molten salt flow regulating pipeline L3, so that the high-temperature molten salt in the high-temperature molten salt tank 5 is kept at a higher temperature. In the tracing mode, there is a lower flow in the flue gas pipeline, the molten salt pipeline, the water supply pipeline and the steam pipeline to maintain the fluidity of the molten salt.

[0199] On the molten salt heat storage side (molten salt heat storage system based on flue gas heating), the disclosed technology also does not take into account the accuracy limitation of the on-site flue gas flow rate, and only provides a simple single-loop control method, which cannot adapt to the molten salt heat storage control when the unit changes operating conditions over a wide range. In response to this, the present application also discloses a specific control scheme for a molten salt heat storage system based on flue gas heating, and the specific content can be seen in the following introduction.

[0200] When the working mode controller controls the molten salt heat storage system of the coupled coal-fired unit to enter the heat storage mode, the working mode controller can first control the molten salt heat storage system of the coupled coal-fired unit to enter the heat storage mode startup phase. In the startup phase, the second baffle 02 at the second flue gas inlet of the flue gas mixer 2 and the third baffle 03 at the third flue gas inlet can be controlled to open through the baffle controller line. At this time, the low-temperature flue gas on the left and right sides of the boiler 1 is first drawn out, so that the low-temperature flue gas in the boiler 1 enters the flue gas-molten salt heat exchanger 3 to preheat the relevant flue gas side pipes and the flue gas mixer 2 and the flue gas-molten salt heat exchanger 3. When the preheating is completed, the first baffle 01 at the first flue gas inlet of the flue gas mixer 2 and the fourth baffle 04 at the fourth flue gas inlet are controlled to open, so that the high-temperature flue gas in the boiler 1 enters the flue gas-molten salt heat exchanger 3. After the system runs stably, each pipeline is controlled to be put into automatic operation mode to control the flow in each pipeline based on the custom design rules.

[0201] When the temperature of the molten salt in the high-temperature molten salt tank 5 reaches a certain temperature, the system exits the heat storage mode. After the heat storage mode is exited, the temperature of the molten salt in the high-temperature molten salt tank 5 will slowly decrease. When it drops to a certain critical temperature, the system needs to enter the heat preservation mode. At this time, the molten salt in the high-temperature molten salt tank 5 enters the flue gas-molten salt heat exchanger 3 again through the first high-temperature molten salt pump, absorbs the heat in the flue gas for heating, thereby achieving the purpose of heating. After heating, the molten salt enters the high-temperature molten salt tank 5 again to keep the temperature in the high-temperature molten salt tank 5 within a certain temperature range.

[0202] When the unit system needs to increase the load, it is necessary to control the molten salt heat storage system of the coupled coal-fired unit to provide steam for the load, which can be the steam turbine of the unit. At this time, it is necessary to control the molten salt heat storage system of the coupled coal-fired unit to enter the heat release mode. In the heat release mode, the high-temperature molten salt in the high-temperature molten salt tank 5 enters the molten salt steam generation system (enters the superheater, evaporator and preheater in sequence) after the second high-temperature molten salt pump, the molten salt bypass regulating valve K6 / molten salt main line regulating valve K5, and finally enters the low-temperature molten salt tank 4. Correspondingly, the water in the deaerator enters the preheater after the feed water pump, the feed water main line regulating valve K8 / feed water bypass regulating valve K9, and enters the evaporator to generate saturated steam after the water temperature rises, and then is heated by the superheater to generate superheated steam that meets the work requirements of the load (steam turbine) and is sent to the load. In order to put the molten salt heat storage system of the coupled coal-fired unit into use as soon as possible when the unit is loaded, the system needs to be in hot standby state before the molten salt heat storage system of the coupled coal-fired unit is put into use, that is, there is a small flow in the pipeline (flue gas pipeline, molten salt pipeline, water supply pipeline and steam pipeline). At this time, the molten salt heat storage system of the coupled coal-fired unit operates in the heating mode, and the working fluid in the molten salt pipeline and the steam-water pipeline needs to be controlled by the bypass regulating valve. The steam generated by the molten salt heating water supply enters the second load, which can be a four-stage pumping.

[0203] In the heat storage process, the most important controlled parameter is the molten salt temperature at the molten salt outlet of the flue gas-molten salt heat exchanger 3. Its influencing factors include the mixed flue gas temperature in the flue gas mixer 2, the mixed flue gas flow in the high-temperature heat exchange pipeline L1, the low-temperature molten salt flow in the low-temperature heat exchange pipeline L2, the low-temperature molten salt temperature, etc. In order to accurately control the molten salt temperature at the molten salt outlet of the flue gas-molten salt heat exchanger 3, the present invention proposes a control method of "coarse adjustment of flue gas and fine adjustment of molten salt". On the flue gas side, the controlled variables include the mixed flue gas temperature and the mixed flue gas flow, and the control quantity is the opening of the four flue gas dampers (the first to fourth dampers 04). Considering that the accuracy of flue gas flow detection is not high and frequent actions will affect the service life of the damper, an open-loop control method is adopted for coarse adjustment on the flue gas side. In this embodiment, the working status of the first to fourth baffles 04 is controlled by a flue gas damper controller, which is used to control the second baffle 02 at the second flue gas inlet and the third baffle 03 at the third flue gas inlet of the flue gas mixer 2 to open when the molten salt heat storage system of the coupled coal-fired unit is in the start-up stage of the heat storage mode, so that the low-temperature flue gas in the boiler 1 enters the flue gas-molten salt heat exchanger 3. When the preheating in the heat storage mode is completed, the first baffle 01 at the first flue gas inlet and the fourth baffle 04 at the fourth flue gas inlet of the flue gas mixer 2 are controlled to open, so that the low-temperature flue gas in the boiler 1 enters the flue gas-molten salt heat exchanger 3.

[0204] In order to realize the opening control of the first baffle 01, the second baffle 02, the third baffle 03 and the fourth baffle 04, the present application also discloses a specific control logic of the baffles. Figure 3As shown, first, the flue gas damper controller obtains the actual load of the unit and the operating mode of the molten salt system (heat storage mode and insulation mode), and selects the first control function f1(x) or the second control function f2(x) based on the operating mode of the molten salt system to control the opening of the second damper 02 and the third damper 03, and selects the third control function f3(x) or the fourth control function f4(x) based on the operating mode of the molten salt system to control the opening of the first damper 01 and the fourth damper 04. For example, when the operating mode of the molten salt system is the heat storage mode or the heat release mode, the first control function f1(x) and the third control function f3(x) are selected; when the operating mode of the molten salt system is the insulation mode or the heating mode, the second control function f2(x) and the fourth control function f4(x) are selected, and then the target opening of the second damper 02, the target opening of the third damper 03, and the target opening of the first damper 01 that match the actual load of the unit are calculated based on the selected control function. and the target opening of the fourth baffle 04, then obtain the opening of the first baffle 01, the opening of the second baffle 02, the opening of the third baffle 03 and the opening of the fourth baffle 04, and then calculate the opening adjustment instruction of the second baffle 02 based on the target opening of the second baffle 02 and the opening of the second baffle 02, calculate the opening adjustment instruction of the third baffle 03 based on the target opening of the third baffle 03 and the opening of the third baffle 03, calculate the opening adjustment instruction of the first baffle 01 based on the target opening of the first baffle 01 and the opening of the first baffle 01; calculate the opening adjustment instruction of the fourth baffle 04 based on the target opening of the fourth baffle 04 and the opening of the fourth baffle 04, and adjust the openings of the first baffle 01, the second baffle 02, the third baffle 03 and the fourth baffle 04 based on the opening adjustment instructions corresponding to the first baffle 01, the second baffle 02, the third baffle 03 and the fourth baffle 04.

[0205] For example, taking the heat storage mode as an example, when the molten salt heat storage system coupled with the coal-fired unit is in the start-up stage of the heat storage mode, the second baffle 02 at the second flue gas inlet and the third baffle 03 at the third flue gas inlet of the flue gas mixer 2 are controlled to open, including:

[0206] Obtain the opening of the second baffle 02 at the second flue gas inlet and the opening of the third baffle 03 at the third flue gas inlet; obtain the actual load of the unit; obtain the target opening of the second baffle 02 and the target opening of the third baffle 03 that match the actual load of the unit based on the first control function; calculate the opening adjustment instruction of the second baffle 02 based on the target opening of the second baffle 02 and the opening of the second baffle 02; calculate the opening adjustment instruction of the third baffle 03 based on the target opening of the third baffle 03 and the opening of the third baffle 03.

[0207] When the molten salt heat storage system coupled to the coal-fired unit is in the heat storage mode and preheating is completed, the first baffle 01 at the first flue gas inlet and the fourth baffle 04 at the fourth flue gas inlet of the flue gas mixer 2 are controlled to open, including:

[0208] Obtain the opening of the first baffle 01 at the first flue gas inlet and the opening of the fourth baffle 04 at the fourth flue gas inlet; obtain the actual load of the unit; obtain the target opening of the first baffle 01 and the target opening of the fourth baffle 04 that match the actual load of the unit based on the third control function; calculate the opening adjustment instruction of the first baffle 01 based on the target opening of the first baffle 01 and the opening of the first baffle 01; calculate the opening adjustment instruction of the fourth baffle 04 based on the target opening of the fourth baffle 04 and the opening of the fourth baffle 04.

[0209] Furthermore, in this embodiment, considering that the biased burning of boiler 1 will cause inconsistent flue gas temperatures in the left and right flues, in order to weaken its influence on the mixed flue gas control, the opening of the left low-temperature flue gas damper (second damper 02) needs to perform a feedforward correction of the opening of the second damper 02 according to the right low-temperature flue gas temperature. Correspondingly, the opening of the right low-temperature flue gas damper (third damper 03) also needs to perform a feedforward correction of the opening of the third damper 03 according to the left low-temperature flue gas temperature. The opening of the left high-temperature flue gas damper (first damper 01) needs to perform a feedforward correction of the opening of the first damper 01 according to the right high-temperature flue gas temperature. Correspondingly, the opening of the right high-temperature flue gas damper (fourth damper 04) also needs to perform a feedforward correction of the opening of the fourth damper 04 according to the left high-temperature flue gas temperature. That is, the openings of the first damper 01, the second damper 02, the third damper 03, and the fourth damper 04 obtained in the above text include:

[0210] Obtaining the opening of the second baffle 02 at the second flue gas inlet, where the opening of the second baffle 02 is the opening corrected by the flue gas temperature difference in the pipeline where the third baffle 03 is located;

[0211] The opening degree of the third baffle 03 at the third flue gas inlet is obtained, where the opening degree of the third baffle 03 is the opening degree corrected by the flue gas temperature difference in the pipeline where the second baffle 02 is located.

[0212] Obtaining the opening of the first baffle 01 at the first flue gas inlet, where the opening of the first baffle 01 is the opening corrected by the flue gas temperature difference in the pipeline where the fourth baffle 04 is located;

[0213] The opening degree of the fourth baffle 04 at the fourth flue gas inlet is obtained, where the opening degree of the fourth baffle 04 is the opening degree corrected by the flue gas temperature difference in the pipeline where the first baffle 01 is located.

[0214] See also Figure 3 As shown, the parameters acquired by the flue gas damper controller may also include the molten salt system operation mode (heat storage mode, heat release mode, insulation mode and heating mode), and the flue gas damper controller is also used to adjust the target coefficients in the first control function, the second control function, the third control function and the fourth control function based on the molten salt system operation mode, so as to adjust the opening of the first damper 01, the second damper 02, the third damper 03 and the fourth damper 04 based on different molten salt system operation modes.

[0215] In this scheme, when the molten salt heat storage system of the coupled coal-fired unit is in the heat storage mode, the working mode controller is also used to: when the molten salt heat storage system of the coupled coal-fired unit is in the heat storage mode, detect the molten salt temperature in the high-temperature molten salt tank 5; when the molten salt temperature in the high-temperature molten salt tank 5 reaches the insulation temperature, control the molten salt heat storage system of the coupled coal-fired unit to enter the insulation mode; when the molten salt heat storage system of the coupled coal-fired unit enters the insulation mode, the flue gas damper controller controls the opening of the second damper 02 and the third damper 03 based on the second control function, and controls the opening of the first damper 01 and the fourth damper 04 based on the fourth control function. At this time, the opening of the second baffle 02 and the third baffle 03 is controlled based on the second control function, including: obtaining the opening of the second baffle 02 at the second flue gas inlet and the opening of the third baffle 03 at the third flue gas inlet; obtaining the actual load of the unit; obtaining the target opening of the second baffle 02 and the target opening of the third baffle 03 that match the actual load of the unit based on the second control function; calculating the opening adjustment instruction of the second baffle 02 based on the target opening of the second baffle 02 and the opening of the second baffle 02; calculating the opening adjustment instruction of the third baffle 03 based on the target opening of the third baffle 03 and the opening of the third baffle 03. Controlling the opening of the first baffle 01 and the fourth baffle 04 based on the fourth control function includes: obtaining the opening of the first baffle 01 at the first flue gas inlet and the opening of the fourth baffle 04 at the fourth flue gas inlet; obtaining the actual load of the unit; obtaining the target opening of the first baffle 01 and the target opening of the fourth baffle 04 that match the actual load of the unit based on the fourth control function; calculating the opening adjustment instruction of the first baffle 01 based on the target opening of the first baffle 01 and the opening of the first baffle 01; calculating the opening adjustment instruction of the fourth baffle 04 based on the target opening of the fourth baffle 04 and the opening of the fourth baffle 04.

[0216] In this embodiment, the differential pressure between the flue gas pressure at the outlet of the induced draft fan 6 and the furnace pressure of the boiler 1 can also be controlled by controlling the power of the induced draft fan 6, so as to provide a certain pressure head for the high-temperature heat exchange pipeline L1. Specifically, the above scheme can also include an induced draft fan 6 controller, which is used to control the frequency of the induced draft fan 6 in the high-temperature heat exchange pipeline L1 according to the measured value and the design value of the pressure difference in the high-temperature heat exchange pipeline L1.

[0217] In this embodiment, on the molten salt side, the low-temperature molten salt temperature and the low-temperature molten salt flow rate in the low-temperature heat exchange pipeline L2 will affect the molten salt temperature at the molten salt outlet of the flue gas-heat exchanger. In order to ensure that the low-temperature molten salt temperature and the low-temperature molten salt flow rate are not too low or too small, the molten salt heat storage system coupled to the coal-fired unit also includes an electric heating device arranged in the low-temperature molten salt tank 4, and the low-temperature molten salt in the low-temperature molten salt tank 4 is heated by the electric heating device to ensure that the temperature of the molten salt in the low-temperature molten salt tank 4 is not lower than its freezing point.

[0218] In this embodiment, the flue gas heated molten salt heat storage system controls the flow of each pipeline in the system based on the flow demand. In this embodiment, the molten salt flow in the low-temperature heat exchange pipeline L2 can be adjusted based on the low-temperature molten salt pump and the molten salt flow regulating valve. Specifically, the molten salt heat storage system coupled with the coal-fired unit may also include a molten salt temperature controller, which is used to: when it is detected that the low-temperature molten salt pump corresponding to the low-temperature molten salt tank 4 is at minimum power, the flow in the low-temperature heat exchange pipeline L2 is controlled by the molten salt flow regulating valve until the opening of the molten salt flow regulating valve reaches the maximum. When it is detected that the opening of the molten salt flow regulating valve reaches the maximum, the flow in the low-temperature heat exchange pipeline L2 is controlled by the low-temperature molten salt pump until the low-temperature molten salt pump corresponding to the low-temperature molten salt tank 4 reaches the minimum power. That is, when it is necessary to adjust the molten salt flow in the low-temperature heat exchange pipeline L2, it is judged whether the low-temperature molten salt pump is at the minimum power. When it is at the minimum power, the molten salt flow regulating valve is adjusted so that the molten salt flow in the low-temperature heat exchange pipeline L2 reaches the target flow. When it is detected that the opening of the molten salt flow regulating valve reaches the maximum, when it is necessary to continue to increase the molten salt flow in the low-temperature heat exchange pipeline L2, the low-temperature molten salt pump is adjusted so that the molten salt flow in the low-temperature heat exchange pipeline L2 reaches the target flow. When the low-temperature molten salt pump is not at the minimum power (the opening of the molten salt flow regulating valve reaches the maximum), the low-temperature molten salt pump is adjusted so that the molten salt flow in the low-temperature heat exchange pipeline L2 reaches the target flow. When the power of the low-temperature molten salt pump reaches the minimum power, if it is still necessary to reduce the molten salt flow in the low-temperature heat exchange pipeline L2, the molten salt flow regulating valve is adjusted so that the molten salt flow in the low-temperature heat exchange pipeline L2 reaches the target flow.

[0219] See also Figure 4 , the molten salt temperature controller may include a molten salt temperature main controller, a first molten salt temperature sub-controller and a second molten salt temperature sub-controller;

[0220] The molten salt temperature main controller is used to generate a molten salt flow rate setting value in the low-temperature heat exchange pipeline L2 based on the deviation between the molten salt temperature setting value in the low-temperature heat exchange pipeline L2 and the measured value (the molten salt temperature at the molten salt outlet of the flue gas-molten salt heat exchanger 3);

[0221] The first molten salt temperature sub-controller is used to: when it is detected that the opening of the molten salt flow control valve reaches the maximum, control the low-temperature molten salt pump to enter the automatic adjustment state, in the automatic state, based on the deviation between the molten salt flow set value and the measured value of the molten salt in the low-temperature heat exchange pipeline L2, calculate the target output power of the low-temperature molten salt pump, and adjust the output power of the low-temperature molten salt pump based on the target output power and the measured output power of the low-temperature molten salt pump, until it is detected that the low-temperature molten salt pump reaches the minimum power, control the low-temperature molten salt pump to enter the manual adjustment state;

[0222] The second molten salt temperature sub-controller is used for: when it is detected that the low-temperature molten salt pump corresponding to the low-temperature molten salt tank 4 is at minimum power, controlling the molten salt flow regulating valve to enter an automatic control state, in which, based on the deviation between the molten salt flow set value and the measured value of the molten salt in the low-temperature heat exchange pipeline L2, the target opening of the molten salt flow regulating valve is calculated, and the opening of the molten salt flow regulating valve is adjusted based on the target opening and the measured opening of the molten salt flow regulating valve, until it is detected that the opening of the molten salt flow regulating valve reaches the maximum, then controlling the molten salt flow regulating valve to enter a manual adjustment state.

[0223] In the present embodiment, controlling the low-temperature molten salt pump to enter the automatic adjustment state refers to starting the first molten salt temperature sub-controller, and using the first molten salt temperature sub-controller to adjust the output power of the low-temperature molten salt pump. Controlling the low-temperature molten salt pump to enter the manual adjustment state refers to shutting down the first molten salt temperature sub-controller, and the low-temperature molten salt pump remains in the current state and does not change. Further consideration is given that only when the molten salt heat storage system coupled to the coal-fired unit is cut into the heat storage mode, a large flow rate is required in the low-temperature heat exchange pipeline L2, and the low-temperature molten salt pump needs to be started. In other modes (such as the insulation mode), there is no need to start the low-temperature molten salt pump. Therefore, in the present embodiment, the molten salt heat storage system coupled to the coal-fired unit is also cut off / cut into the heat storage mode as a stop and start condition for the first molten salt temperature sub-controller. For details, see Figure 4, the first molten salt temperature sub-controller can be controlled to stop and start in the following manner: when it is detected that the low-temperature molten salt pump reaches the minimum power or the molten salt heat storage system coupled to the coal-fired unit cuts off the heat storage mode, the first molten salt temperature sub-controller is turned off; when the opening of the molten salt flow regulating valve reaches the maximum and the molten salt heat storage system coupled to the coal-fired unit enters the heat storage mode, the first molten salt temperature sub-controller is started; after the first molten salt temperature sub-controller is started, the target output power of the low-temperature molten salt pump is calculated based on the deviation between the set value and the measured value of the molten salt flow rate of the molten salt in the low-temperature heat exchange pipeline L2; and the output power of the low-temperature molten salt pump is adjusted based on the target output power and the measured output power of the low-temperature molten salt pump.

[0224] Similarly, controlling the molten salt flow regulating valve to enter the automatic adjustment state refers to starting the second molten salt temperature sub-controller, and using the second molten salt temperature sub-controller to adjust the opening of the molten salt flow regulating valve. Controlling the molten salt flow regulating valve to enter the manual adjustment state refers to closing the second molten salt temperature sub-controller, and the molten salt flow regulating valve remains in the current state and does not change. Further consideration is that when the molten salt heat storage system coupled to the coal-fired unit enters the heat storage mode, if the power of the low-temperature molten salt pump is adjusted to the maximum, it still cannot meet the flow requirements of the low-temperature heat exchange pipeline L2. At this time, it is necessary to adjust the molten salt flow regulating valve to further increase the flow of the low-temperature heat exchange pipeline L2. When the molten salt heat storage system coupled to the coal-fired unit switches from the heat storage mode to other modes (insulation mode), the flow in the low-temperature heat exchange pipeline L2 is large. It is necessary to first adjust the low-temperature molten salt pump to reduce the flow in the warm heat exchange pipeline L2. When the power of the low-temperature molten salt pump reaches the minimum, the flow of the low-temperature heat exchange pipeline L2 is adjusted by the molten salt flow regulating valve. Therefore, refer to Figure 4 In this embodiment, the cut-in / cut-out condition of the heat storage mode of the molten salt heat storage system coupled to the coal-fired unit is also used as the stop and start judgment condition of the second molten salt temperature sub-controller. For details, see Figure 4, the second molten salt temperature sub-controller can be controlled to stop and start in the following manner: when it is detected that the low-temperature molten salt pump reaches the maximum power and the molten salt heat storage system coupled to the coal-fired unit is cut into the heat storage mode, the second molten salt temperature sub-controller is started, that is, the second molten salt temperature sub-controller is controlled only when the molten salt heat storage system coupled to the coal-fired unit is in the heat storage mode and the low-temperature molten salt pump reaches the maximum power, and the molten salt temperature sub-controller is turned off when the opening of the molten salt flow control valve reaches the maximum or the molten salt heat storage system coupled to the coal-fired unit cuts off the heat storage mode. After the second molten salt temperature sub-controller is started, the target opening of the molten salt flow control valve is calculated based on the deviation between the set value and the measured value of the molten salt flow in the low-temperature heat exchange pipeline L2, and the opening of the molten salt flow control valve is adjusted based on the target opening and the measured opening of the molten salt flow control valve.

[0225] In this embodiment, the measured output power of the low-temperature molten salt pump used in "adjusting the output power of the low-temperature molten salt pump based on the target output power and the measured output power of the low-temperature molten salt pump" and "adjusting the opening of the molten salt flow control valve based on the target opening and the measured opening of the molten salt flow control valve" is the output power corrected by the molten salt temperature at the molten salt inlet of the flue gas-molten salt heat exchanger 3, and the measured opening of the molten salt flow control valve is the opening corrected by the molten salt temperature at the molten salt inlet of the flue gas-molten salt heat exchanger 3. By correcting the low-temperature molten salt pump frequency instruction and the molten salt flow control valve opening instruction by the molten salt temperature at the molten salt inlet of the flue gas-molten salt heat exchanger 3, the disturbance effect of the molten salt temperature at the molten salt inlet of the flue gas-molten salt heat exchanger 3 on the outlet molten salt temperature can be suppressed.

[0226] In the molten salt heat storage system coupled with the coal-fired unit, the control of the molten salt heat release side (molten salt steam generation system) is also particularly important. As an additional steam source for the steam turbine, the molten salt steam generation system shoulders the heavy task of improving the variable load rate of the coal-fired unit. The existing technology for the molten salt steam generation system mostly adopts a single level of control of molten salt or feed water, and cannot be applied to different operating modes. It is necessary to study the control method of the molten salt steam generation system when it is operating in all directions and under all working conditions. In order to ensure the stable operation of the molten salt steam generation system, the existing technology discloses a molten salt steam generation system and a control method suitable for full-load operation of a solar thermal power station. The system decouples the heat exchange process in the superheater, evaporator and preheater, and controls the molten salt flow through the superheater, evaporator and preheater by adjusting the valve opening when the load changes, thereby reducing the solidification risk of the molten salt. However, the existing technology only regulates the molten salt flow, and lacks attention to the feed water flow and steam flow, which may cause an imbalance between the feed water and steam, affecting the safe operation of the unit. In addition, the existing technology only controls the molten salt flow rate in the molten salt heat release mode, and lacks hot standby conditions and control methods thereof.

[0227] Considering the hot standby condition, the molten salt steam generation system and control method of the existing technology coupling coal-fired units set two different "feedwater flow-regulating valve opening" functions, which act on the main feedwater line and bypass respectively, to adapt to the requirements of the heat release and heating modes for the feedwater flow, and then control the evaporator liquid level. However, due to the different characteristics of the main and bypass valves, the two functions need to be obtained through precise on-site debugging, and as the equipment ages, the valve flow characteristics will change, and the corresponding functions need to be repeatedly debugged to obtain. On the other hand, using a feedwater pump to control the pipeline differential pressure may cause large throttling losses, which is not conducive to the economy of the system operation.

[0228] Therefore, the present application also discloses a control strategy for a molten salt steam generation system, and the specific control strategy can be seen in the following content.

[0229] In the molten salt steam generation system, the molten salt steam power represents the load support capacity of the molten salt system in the heat release mode. It is a variable that needs to be focused on in the molten salt system. Its set value is given by the load command decomposition loop of the boiler 1-turbine-molten salt heat storage coordinated control system. However, there is no actual measurement point for the molten salt steam power and it cannot be used directly for control. Considering that under certain temperature conditions, the steam flow rate is positively correlated with the power, the molten salt superheated steam flow rate can be used to characterize the steam power. The steam pressure can characterize the heat release state of the molten salt, and the evaporator liquid level can represent the balance characteristics between the molten salt energy supply and the steam-water energy demand, both of which require precise control during the operation of the system.

[0230] During the operation of the molten salt steam generation system, the coupling phenomenon between superheated steam pressure and steam flow is obvious, and it is difficult to control them separately. They can be considered as a whole, and the direct energy balance control of the molten salt steam generation system can be designed by constructing the steam energy demand signal and the steam supply energy signal. Indicates. Among them, It represents the pressure of the steam generated by the molten salt when it enters the load (such as a steam turbine) (i.e., the steam pressure at the steam inlet of the load). Also called vapor pressure, It represents the measured value of the steam pressure at the steam outlet of the molten salt steam generating system (the steam outlet of the superheater), also known as Measured value of superheated steam pressure, represents the steam pressure setting value at the steam outlet (steam outlet of the superheater) of the molten salt steam generation system, The fifth control function of the available unit load command The energy supply signal of the molten salt side is Indicated by. Where C represents the heat storage coefficient of the molten salt heat release system, which is a pre-calibrated value. Indicates the drum pressure of the molten salt steam generation system. In static state, the drum pressure remains unchanged, the drum pressure setting value is equal to the actual drum pressure value, and the energy supply signal is equal to the energy demand signal.

[0231] In order to control the molten salt flow rate on the molten salt steam generation system side (the molten salt flow rate in the molten salt steam heating pipeline L4), the above-mentioned molten salt heat storage system coupled with the coal-fired unit also includes a direct energy balance controller, which is used to: generate and output a molten salt flow rate instruction based on the deviation between the energy demand signal and the energy supply signal, and the molten salt flow rate instruction is used to adjust the molten salt flow rate in the low-temperature heat exchange pipeline L2.

[0232] See also Figure 5 As shown, the input signal of the direct energy balance controller includes: the fifth control function ( )、Steam pressure , measured value of superheated steam pressure , drum pressure And the heat storage coefficient C of the molten salt system, substitute the obtained relevant parameters into , calculate the energy demand signal, and substitute the obtained relevant parameters into , calculate the energy supply signal, calculate the deviation between the energy demand signal and the energy supply signal, generate and output a molten salt flow instruction based on the calculated deviation, and the molten salt bypass regulating valve K6 instruction can be used to ensure the target molten salt flow of the molten salt steam heating pipeline L4.

[0233] like Figure 5 As shown, the molten salt heat storage system coupled to the coal-fired unit also includes a molten salt main flow controller for responding to the instruction of the molten salt bypass regulating valve K6. When the molten salt heat storage system coupled to the coal-fired unit is in the heat release mode, the molten salt main flow controller is started. After the molten salt main flow controller is started, it is used to: generate a molten salt pump frequency adjustment instruction based on the target molten salt flow determined by the molten salt flow instruction and the measured molten salt flow of the molten salt steam heating pipeline L4, and control the second high-temperature molten salt pump based on the molten salt pump frequency adjustment instruction.

[0234] In this embodiment, in order to make the molten salt steam generating system have a faster response capability when the unit changes load, the differential of the energy demand signal of the molten salt steam generating system can be selected as a dynamic feedforward, and the molten salt pump frequency instruction is corrected based on the dynamic feedforward, that is, the molten salt target flow corresponding to the molten salt pump frequency instruction is corrected. More specifically, the sum of the molten salt target flow corresponding to the molten salt pump frequency instruction and the dynamic feedforward is used as the final molten salt pump frequency instruction.

[0235] like Figure 5 As shown, the molten salt heat storage system coupled with the coal-fired unit also includes a molten salt bypass flow controller for responding to the instruction of the molten salt bypass regulating valve K6. When the molten salt heat storage system coupled with the coal-fired unit is in the heating mode, the system requires a small molten salt flow. At this time, it is only necessary to adjust the molten salt bypass flow controller to start the molten salt bypass flow controller. After starting, the molten salt main flow controller is used to: obtain the target molten salt flow, calculate the target opening of the molten salt bypass regulating valve K6 based on the target molten salt flow and the measured molten salt flow in the low-temperature molten salt recycling pipeline, and adjust the opening of the molten salt bypass regulating valve K6 based on the target opening of the molten salt bypass regulating valve K6.

[0236] Furthermore, in order to prevent the flow rate in the molten salt steam heating pipeline L4 from being too large in the heating mode, when it is detected that the system enters the heating mode, the molten salt main circuit stop valve can be closed. At this time, the molten salt flow rate in the molten salt steam heating pipeline L4 is the molten salt flow rate flowing through the molten salt bypass regulating valve K6. When it is detected that the system enters the heat release mode, the molten salt main circuit stop valve is controlled to open and the molten salt bypass regulating valve K6 is controlled to close. At this time, the molten salt flow rate in the molten salt steam heating pipeline L4 is the molten salt flow rate flowing through the molten salt main circuit stop valve, and the flow rate is controlled by the second high-temperature molten salt pump.

[0237] exist Figure 5In the example shown, the bypass control condition is whether the molten salt heat storage system coupled to the coal-fired unit is in the heating mode or the heat release mode. When in the heating mode, the molten salt bypass flow controller is controlled to start; when in the heat release mode, the molten salt main flow controller is controlled to start.

[0238] In this embodiment, when a pipeline switches between the main route and the bypass, if a single switch signal is selected as the switching condition, it is easy to cause the switching signal to act frequently. Therefore, a certain dead zone needs to be set, such as Figure 6 As shown. On the one hand, when the flow in the pipeline increases from 0 to b, the flow in the pipeline is bypass controlled, and the main flow is 0. If the flow in the pipeline increases further, the main control is started, the flow in the pipeline is main controlled, and the bypass flow is 0. If the flow in the pipeline decreases from the maximum value to a, the flow in the pipeline is main controlled, and the bypass flow is 0. If the flow further decreases, the bypass control is started, the flow in the pipeline is bypass controlled, and the main flow is. Among them, the value of b is greater than the value of a, and the values ​​of a and b corresponding to different pipelines can be different.

[0239] Taking the molten salt steam heating pipeline L4 as an example, the bypass control in the molten salt steam heating pipeline L4 refers to regulating the flow in the molten salt steam heating pipeline L4 through the molten salt bypass regulating valve K6, and the main line control in the molten salt steam heating pipeline L4 refers to regulating the flow in the water supply pipeline through the second high-temperature water pump. When the flow in the molten salt steam heating pipeline L4 increases from 0 to the first flow, the flow in the molten salt steam heating pipeline L4 is regulated by the molten salt bypass regulating valve K6. During this process, the molten salt main line stop valve is in a closed state. When the flow in the molten salt steam heating pipeline L4 decreases from the maximum value to the second flow, the flow in the molten salt steam heating pipeline L4 is regulated by the second high-temperature molten salt pump. During this process, the molten salt bypass regulating valve K6 is in a closed state.

[0240] Taking the water supply pipeline as an example, the bypass control in the water supply pipeline refers to adjusting the flow in the water supply pipeline through the water supply bypass regulating valve K9, and the main line control in the water supply pipeline refers to adjusting the flow in the water supply pipeline through the water supply main line regulating valve K8. When the flow in the water supply pipeline increases from 0 to a first flow, the flow in the water supply pipeline is adjusted by the water supply bypass regulating valve K9, and during this process, the water supply main line regulating valve K8 is in a closed state. When the flow in the water supply pipeline decreases from a maximum value to a second flow, the flow in the water supply pipeline is adjusted by the water supply main line regulating valve K8, and during this process, the water supply bypass regulating valve K9 is in a closed state.

[0241] Taking the steam output pipeline as an example, the bypass control in the steam output pipeline refers to regulating the flow in the steam output pipeline through the steam bypass regulating valve K11, and the main line control in the steam output pipeline refers to regulating the flow in the steam output pipeline through the steam main line regulating valve K10. When the flow in the steam output pipeline increases from 0 to a first flow, the flow in the steam pipeline is regulated by the steam output pipeline regulating valve, and during this process, the steam output pipeline regulating valve is in a closed state. When the flow in the steam output pipeline decreases from a maximum value to a second flow, the flow in the steam output pipeline is regulated by the steam main line regulating valve K10, and during this process, the steam bypass regulating valve K11 is in a closed state.

[0242] Furthermore, considering that the temperature of the superheated steam output by the superheater will fluctuate within a small range when the system is running, a steam flow controller can be used to control the flow of the output steam of the superheater when the superheated steam flow is controlled. In this embodiment, the superheated steam flow setting value is obtained by correcting the superheated steam temperature output by the superheater through the sixth control function f6(x). At this time, the steam flow controller is used to obtain the steam temperature output by the superheater, correct the steam temperature based on the sixth function f6(x), and obtain a steam flow setting value matching the corrected steam temperature; the flow of the output steam of the superheater is controlled based on the steam flow setting value.

[0243] The flow rate of the output steam of the superheater may include main circuit control and bypass control. At this time, the steam flow controller may include a superheated steam main circuit flow controller and a superheated steam bypass flow controller.

[0244] The superheated steam main flow controller is used to implement main flow control. The superheated steam main flow controller is used to: obtain the measured value of the superheated steam main flow, which refers to the steam flow flowing through the steam main flow regulating valve K10, calculate the opening adjustment instruction of the steam main flow regulating valve K10 based on the difference between the steam flow setting value and the measured value of the steam flow, and adjust the opening of the steam main flow regulating valve K10 based on the opening adjustment instruction. Figure 7 In the main circuit control, the superheated steam main circuit flow controller outputs the steam main circuit regulating valve K10 opening instruction according to the deviation between the steam flow setting value and the measured value.

[0245] Furthermore, considering that the frequent changes of the main regulating valve during the frequency and peak regulation of the unit may cause the molten salt energy supply to be unable to accurately track the steam-water energy demand, once the deviation is too large, the pressure stability cannot be achieved by regulating the molten salt flow alone, and it is necessary to use the rapid pressure regulation capability of the regulating valve to compensate, which is the pressure pull-back loop. Inevitably, this will weaken the load regulation capability to a certain extent. Therefore, when the superheated steam main flow controller in this scheme calculates the opening adjustment instruction of the steam main regulating valve K10 based on the difference between the steam flow setting value and the actual measured value of the steam flow, it specifically includes: obtaining the superheated steam pressure setting value and the actual measured value of the superheated steam pressure of the steam output pipeline; calculating the difference between the superheated steam pressure setting value and the actual measured value of the superheated steam pressure, and recording it as the main steam pressure difference; using the seventh function to correct the main steam pressure difference; and correcting the opening adjustment instruction based on the corrected main steam pressure difference. Figure 7 As shown, the deviation between the superheated steam pressure setting value and the measured value is processed by function f7(x), and then superimposed with the opening adjustment instruction to act on the steam main circuit regulating valve K10.

[0246] In contrast to the above-mentioned superheated steam main flow controller, the steam flow controller also includes a superheated steam bypass flow controller, which is used to: calculate the opening adjustment instruction of the steam bypass regulating valve K11 based on the difference between the superheated steam flow set value and the actual measured value of the superheated steam flow in the steam bypass pipeline, and adjust the opening of the steam bypass regulating valve K11 based on the opening adjustment instruction.

[0247] like Figure 7 As shown, Figure 7 The bypass control condition in the description refers to the opening and closing conditions of the superheated steam main flow controller and the superheated steam bypass flow controller. The opening and closing of the superheated steam main flow controller and the superheated steam bypass flow controller can be realized by the first switch in the steam flow controller. The first switch is used to:

[0248] When the superheated steam flow in the steam output pipeline increases from 0 to a first steam flow, the superheated steam bypass flow controller is controlled to start, and the superheated steam main flow controller is controlled to stop; when the superheated steam flow in the steam output pipeline increases to the first steam flow and continues to increase, the superheated steam main flow controller is controlled to start, and the superheated steam bypass flow controller is controlled to stop, and the superheated steam main flow controller remains in an open state; when the superheated steam flow in the steam output pipeline drops to a second steam flow, the superheated steam bypass flow controller is stopped; when the superheated steam flow in the steam output pipeline drops to the second steam flow and needs to continue to drop, the superheated steam bypass flow controller is controlled to start, and the superheated steam main flow controller is stopped.

[0249] The liquid level in the evaporator is controlled by the water supply pipeline. In the technical solution disclosed in this embodiment, the liquid level in the evaporator can be controlled by three impulses in the form of "cascade + feedforward". The system also includes an evaporator liquid level main controller and an evaporator liquid level sub-controller. The evaporator liquid level main controller is used to obtain a feed water flow setting value by weighted summation of the evaporator liquid level setting value, the liquid level actual measurement value and the superheated steam flow actual measurement value, and calculate the feed water flow adjustment instruction based on the feed water flow setting value and the feed water flow actual measurement value in the water supply pipeline;

[0250] The evaporator liquid level sub-controller is used to adjust the water supply of the evaporator based on the water supply flow rate adjustment instruction. Adjusting the water supply of the evaporator means adjusting the flow rate in the water supply pipeline.

[0251] Further, in this embodiment, see Figure 8 , the evaporator liquid level sub-controller comprises: a first evaporator liquid level sub-controller ( Figure 8 Middle evaporator liquid level sub-controller 1), second evaporator liquid level sub-controller ( Figure 8 The liquid level sub-controller 2 of the middle evaporator) and the liquid level sub-controller 3 of the third evaporator ( Figure 8 Evaporator liquid level sub-controller 3);

[0252] The first evaporator liquid level sub-controller is used to: adjust the opening of the feed water bypass regulating valve K9 based on the feed water flow regulating instruction;

[0253] The second evaporator liquid level sub-controller is used to: adjust the opening of the water supply main line regulating valve K8 based on the water supply flow rate adjustment instruction;

[0254] The third evaporator liquid level sub-controller is used to adjust the output power of the feed water pump at the water outlet of the deaerator based on the feed water flow adjustment instruction.

[0255] The system disclosed in the present application may also include a second switcher, and the opening or closing of the first evaporator liquid level sub-controller, the second evaporator liquid level sub-controller and the third evaporator liquid level sub-controller is controlled by the second switcher. The second switcher is used to control the first evaporator liquid level sub-controller to start when it is monitored that the feed water pump of the deaerator is running at the minimum power, and when it is monitored that the opening of the feed water bypass regulating valve K9 reaches the first opening (the maximum opening of the feed water bypass regulating valve K9), if the feed water flow needs to continue to increase, the second evaporator liquid level sub-controller is controlled to start, and when it is monitored that the opening of the feed water main regulating valve K8 reaches the second opening (the maximum opening of the feed water main regulating valve K8), if the feed water flow needs to continue to increase, the third evaporator liquid level sub-controller is controlled to start. This control method can realize the full-condition control of the evaporator liquid level, while reducing the throttling loss of the system and improving the economic efficiency of operation.

[0256] More specifically, the switching on and off of the heating mode and the heat release mode can also be used as the judgment conditions for opening or closing the first evaporator liquid level sub-controller, the second evaporator liquid level sub-controller and the third evaporator liquid level sub-controller. Specifically, at this time, the system can include a third switch, and the third switch is specifically used to: when it is detected that the molten salt steam generation system cuts off the heating mode or detects that the opening of the water supply bypass regulating valve K9 reaches the maximum, the first evaporator liquid level sub-controller is closed, and when it is detected that the power of the water supply pump reaches the minimum value, the opening of the water supply main road regulating valve K8 reaches the minimum value and the molten salt steam generation system cuts into the heating mode, the first evaporator liquid level sub-controller is controlled to start. When it is detected that the molten salt steam generation system cuts off the heating mode or detects that the opening of the water supply main road regulating valve K8 reaches the maximum, the second evaporator liquid level sub-controller is closed, and when it is detected that the power of the water supply pump reaches the minimum value, the opening of the water supply bypass regulating valve K9 reaches the maximum value and the molten salt steam generation system cuts into the heating mode, the second evaporator liquid level sub-controller is controlled to start. When it is detected that the molten salt steam generation system cuts off the heating mode or detects that the water supply pump power reaches the minimum value, the third evaporator liquid level sub-controller is turned off. When it is detected that the opening of the water supply main line regulating valve K8 reaches the maximum, the opening of the water supply bypass regulating valve K9 reaches the maximum and the molten salt steam generation system enters the heat release mode, the third evaporator liquid level sub-controller is controlled to start. After obtaining the adjustment instruction output by the evaporator liquid level main controller, the first evaporator liquid level sub-controller, the second evaporator liquid level sub-controller or the third evaporator liquid level sub-controller in the startup state controls their respective control objects based on the control instruction.

[0257] In this embodiment, considering the operating characteristics of the molten salt pump and the feed water pump, when the outlet flow rate is too low, the trip protection will be triggered. Therefore, the present invention designs the first molten salt recirculation regulating valve, the second molten salt recirculation regulating valve and the feed water recirculation regulating valve K7, and the corresponding recirculation loop to ensure that the pump body can operate normally when the outlet flow rate of the low-temperature molten salt pump, the second high-temperature molten salt pump and the feed water pump is low. Specifically, the above system may also include a recirculation regulating valve controller; the recirculation regulating valve controller is used to: when it is detected that the outlet flow of the target pump increases to its corresponding first target value, when the outlet flow of the target pump continues to increase, control the opening of the circulation regulating valve corresponding to the target pump to decrease as the outlet flow of the target pump increases, until the opening is reduced to 0; when it is detected that the outlet flow of the target pump decreases to its corresponding second target value, when the outlet flow of the target pump continues to decrease, control the opening of the circulation regulating valve corresponding to the target pump to increase as the outlet flow of the target pump decreases, until the opening increases to the maximum opening; the target pump is a low-temperature molten salt pump, a second high-temperature molten salt pump or a water feed pump; the first target value is less than the second target value. Specifically, based on the eighth control function f8(x), the opening of the circulation regulating valve corresponding to the target pump can be controlled to decrease as the outlet flow rate of the target pump increases. Based on the ninth control function f9(x), the opening of the circulation regulating valve corresponding to the target pump can be controlled to increase as the outlet flow rate of the target pump decreases. The eighth control function and the ninth control function are respectively used to express the mapping relationship between the outlet flow rate of the target pump and the opening of the circulation regulating valve corresponding to the target pump.

[0258] See also Fig. 9 , taking the target pump as a low-temperature molten salt pump as an example, its minimum flow control logic is as follows Fig. 9 The control curve is shown as Fig.10 As shown. When the measured value of the outlet flow of the low-temperature molten salt pump increases from 0, after the outlet flow of the low-temperature molten salt pump reaches the first target value a, when it is detected that the outlet flow of the low-temperature molten salt pump continues to increase, the opening of the circulation regulating valve corresponding to the low-temperature molten salt pump is controlled to decrease as the outlet flow of the low-temperature molten salt pump increases, until the opening is reduced to 0. Among them, when the measured value of the outlet flow of the low-temperature molten salt pump increases from 0 to the first target value a, the opening of the circulation regulating valve corresponding to the low-temperature molten salt pump remains unchanged at the maximum opening. As shown Fig. 9 and Fig.10As shown, the opening of the circulation regulating valve corresponding to the low-temperature molten salt pump is controlled to decrease as the outlet flow of the low-temperature molten salt pump increases. Specifically, it can be: based on the eighth control function, the opening of the circulation regulating valve corresponding to the target pump is controlled to decrease as the outlet flow of the target pump increases until the opening is reduced to 0. When the outlet flow of the low-temperature molten salt pump is large, the opening of the first molten salt recirculation valve is 0. When the outlet flow of the low-temperature molten salt pump decreases from a flow with a highest position greater than the first target value a to the second target value b (before it is reduced to the second target value b, the first molten salt recirculation valve remains at 0), if it is detected that the outlet flow of the low-temperature molten salt pump continues to decrease, as the outlet flow of the low-temperature molten salt pump decreases, the opening of the first molten salt recirculation valve begins to rise from 0 to 100% with the trend of f9(x). The purpose of the above design is to ensure that when the pump outlet flow changes, the recirculation valve maintains a certain dead zone to avoid frequent action.

[0259] From the above schemes, it can be seen that the molten salt heat storage system coupled with the coal-fired unit provided by the present invention solves the problems existing in the prior art. On the molten salt heat storage side, the molten salt temperature at the outlet of the flue gas-molten salt heat exchanger must always be maintained near the set value to meet the heat demand of the molten salt heat release. However, during the load change of the unit, the variable disturbances on the flue gas side and the molten salt side will directly or indirectly affect the molten salt temperature at the outlet of the heat exchanger. The present invention performs comprehensive control on the flue gas side and the molten salt side systems, and ensures a certain operating economy while meeting the molten salt temperature control target. On the molten salt heat release side, the molten salt steam generation system control method proposed in the present invention can respond quickly when the unit needs to increase the load, while maintaining the stability of the evaporator liquid level, based on the direct energy balance relationship between the molten salt supply energy and the steam-water demand energy. The control system can be applied to the molten salt heat release mode and the heating mode.

[0260] For the convenience of description, the above system is described as being divided into various modules according to their functions. Of course, when implementing the present invention, the functions of each module can be implemented in the same or multiple software and / or hardware.

[0261] Each embodiment in this specification is described in a progressive manner, and the same or similar parts between the embodiments can be referenced to each other, and each embodiment focuses on the differences from other embodiments. The system and system embodiments described above are merely schematic, wherein the units described as separate components may or may not be physically separated, and the components displayed as units may or may not be physical units, that is, they may be located in one place, or they may be distributed on multiple network units. Some or all of the modules may be selected according to actual needs to achieve the purpose of the scheme of this embodiment. A person of ordinary skill in the art may understand and implement it without creative work.

[0262] Professionals may further appreciate that the units and algorithm steps of each example described in conjunction with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of the two. In order to clearly illustrate the interchangeability of hardware and software, the composition and steps of each example have been generally described in the above description according to function. Whether these functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. Professionals and technicians may use different methods to implement the described functions for each specific application, but such implementation should not be considered to be beyond the scope of the present invention.

[0263] The steps of the method or algorithm described in conjunction with the embodiments disclosed herein may be implemented directly using hardware, a software module executed by a processor, or a combination of the two. The software module may be placed in a random access memory (RAM), a memory, a read-only memory (ROM), an electrically programmable ROM, an electrically erasable programmable ROM, a register, a hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.

[0264] It should also be noted that, in this article, relational terms such as first and second, etc. are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, the elements defined by the sentence "comprise a ..." do not exclude the presence of other identical elements in the process, method, article or device including the elements.

[0265] The above description of the disclosed embodiments enables one skilled in the art to implement or use the present invention. Various modifications to these embodiments will be apparent to one skilled in the art, and the general principles defined herein may be implemented in other embodiments without departing from the spirit or scope of the present invention. Therefore, the present invention will not be limited to the embodiments shown herein, but rather to the widest scope consistent with the principles and novel features disclosed herein.

Claims

1. A molten salt heat storage system coupled with a coal-fired unit, characterized in that: include: Molten salt heat storage system and molten salt steam generation system based on flue gas heating; The molten salt heat storage system based on flue gas heating includes a boiler, a flue gas mixer, a flue gas-molten salt heat exchanger, a low-temperature molten salt tank and a high-temperature molten salt tank; The first smoke inlet of the smoke mixer is connected to the first side of the high-temperature smoke duct of the boiler, the second smoke inlet of the smoke mixer is connected to the first side of the low-temperature smoke duct of the boiler, the third smoke inlet of the smoke mixer is connected to the second side of the low-temperature smoke duct of the boiler, and the fourth smoke inlet of the smoke mixer is connected to the second side of the high-temperature smoke duct of the boiler; The flue gas inlet of the flue gas-molten salt heat exchanger is connected to the gas outlet of the flue gas mixer, and the flue gas outlet of the flue gas-molten salt heat exchanger is connected to the flue gas inlet of the boiler; The molten salt inlet of the high-temperature molten salt tank is connected to the molten salt outlet of the flue gas-molten salt heat exchanger and the molten salt inlet of the molten salt steam generation system; The molten salt outlet of the high-temperature molten salt tank is connected to the molten salt inlet of the flue gas-molten salt heat exchanger and the molten salt inlet of the low-temperature molten salt tank; The molten salt outlet of the low-temperature molten salt tank is connected to the molten salt inlet of the flue gas-molten salt heat exchanger; The steam outlet of the molten salt steam generating system is connected to the steam inlet of the load object.

2. The molten salt heat storage system coupled with a coal-fired unit according to claim 1, characterized in that: The first smoke inlet, the second smoke inlet, the third smoke inlet and the fourth smoke inlet of the smoke mixer are all provided with baffles; The flue gas inlet of the flue gas-molten salt heat exchanger is connected to the gas outlet of the flue gas mixer through a high-temperature heat exchange pipeline, and the flue gas outlet of the flue gas-molten salt heat exchanger is connected to the flue gas inlet of the boiler through the high-temperature heat exchange pipeline; The molten salt outlet of the low-temperature molten salt tank is connected to the molten salt inlet of the flue gas-molten salt heat exchanger through a low-temperature heat exchange pipeline; The molten salt inlet of the high-temperature molten salt tank is connected to the molten salt outlet of the flue gas-molten salt heat exchanger through the low-temperature heat exchange pipeline; The molten salt outlet of the high-temperature molten salt tank is connected to the low-temperature heat exchange pipeline between the low-temperature molten salt tank and the flue gas-molten salt heat exchanger through a high-temperature molten salt flow regulating pipeline; The molten salt outlet of the high-temperature molten salt tank is connected to the molten salt inlet of the low-temperature molten salt tank through a molten salt steam heating pipeline, and the molten salt steam heating pipeline passes through the molten salt steam generating system.

3. The molten salt heat storage system coupled with a coal-fired unit according to claim 2, characterized in that: The high-temperature heat exchange pipeline is provided with an induced draft fan; The low-temperature heat exchange pipeline is provided with a first molten salt flow regulating valve and a low-temperature molten salt pump; The high-temperature molten salt flow regulating pipeline is provided with a first high-temperature molten salt pump; The molten salt steam heating pipeline is provided with a second high-temperature molten salt pump and a second molten salt flow regulating valve, and the second high-temperature molten salt pump is provided on the molten salt steam heating pipeline between the high-temperature molten salt pump and the molten salt steam generating system.

4. The molten salt heat storage system coupled with a coal-fired unit according to claim 3, characterized in that: Also includes: A low-temperature molten salt recirculation regulating pipeline, one end of which is connected to the low-temperature heat exchange pipeline between the low-temperature molten salt pump and the flue gas-molten salt heat exchanger, and the other end is connected to the molten salt inlet of the low-temperature molten salt tank, and a low-temperature molten salt recirculation regulating valve is provided on the low-temperature molten salt recirculation regulating pipeline; A high-temperature molten salt recycling regulating pipeline, one end of which is connected to the molten salt steam heating pipeline between the high-temperature molten salt pump and the molten salt steam generating system, and the other end is connected to the molten salt inlet of the high-temperature molten salt tank.

5. The molten salt heat storage system coupled with a coal-fired unit according to claim 4, characterized in that: The molten salt steam heating pipeline is provided with a molten salt main regulating valve and a molten salt bypass regulating valve, and the molten salt main regulating valve and the molten salt bypass regulating valve are connected in parallel with each other.

6. The molten salt heat storage system coupled with a coal-fired unit according to claim 1, characterized in that: The molten salt steam generating system comprises: A deaerator, a preheater, an evaporator and a superheater, wherein the preheater, the evaporator and the superheater are connected in series in sequence; The molten salt inlet of the superheater is connected to the molten salt outlet of the high-temperature molten salt tank; The molten salt outlet of the preheater is connected to the molten salt inlet of the low-temperature molten salt tank; The steam outlet of the superheater serves as the steam outlet of the molten salt steam generating system; The water inlet of the preheater is connected to the water outlet of the deaerator.

7. The molten salt heat storage system coupled with a coal-fired unit according to claim 6, characterized in that: A water feed pump is arranged on the water inlet pipeline between the preheater and the deaerator.

8. The molten salt heat storage system coupled with a coal-fired unit according to claim 7, characterized in that: Also includes: A water supply recirculation pipeline, one end of which is connected to the water inlet pipeline between the water supply pump and the preheater, and the other end of which is connected to the return water port of the deaerator. A water supply recirculation regulating valve is provided on the water supply recirculation pipeline.

9. The molten salt heat storage system coupled with a coal-fired unit according to claim 8, characterized in that: Also includes: A main water supply regulating valve and a bypass water supply regulating valve are arranged on the water inlet pipeline, and the main water supply regulating valve and the bypass water supply regulating valve are connected in parallel with each other.

10. The molten salt heat storage system coupled with a coal-fired unit according to claim 9, characterized in that: The steam outlet of the molten salt steam generating system is connected to the steam inlet of the load object through a steam output pipeline: The steam output pipeline includes a first steam output pipeline connected to the first load steam inlet and a second steam output pipeline connected to the second load steam inlet; The first steam output pipeline is provided with a steam main regulating valve; The second steam output pipeline is provided with a steam bypass regulating valve.

11. The molten salt heat storage system coupled with a coal-fired unit according to claim 1, characterized in that: Also includes: Working mode controller; The working mode controller is used to control the working states of various valves and pumps in the molten salt heat storage system of the coupled coal-fired unit based on the working mode of the molten salt heat storage system of the coupled coal-fired unit, and the working mode includes heat storage mode, heat release mode, insulation mode and heating mode.

12. The molten salt heat storage system coupled with a coal-fired unit according to claim 11, characterized in that: Also includes: Smoke damper controller; The flue gas damper controller is used to control the second damper at the second flue gas inlet and the third damper at the third flue gas inlet of the flue gas mixer to open when the molten salt heat storage system of the coupled coal-fired unit is in the heat storage mode and started, so that the low-temperature flue gas in the boiler enters the flue gas-molten salt heat exchanger. When preheating is completed, the first damper at the first flue gas inlet and the fourth damper at the fourth flue gas inlet of the flue gas mixer are controlled to open, so that the high-temperature flue gas in the boiler enters the flue gas-molten salt heat exchanger.

13. The molten salt heat storage system coupled with a coal-fired unit according to claim 12, characterized in that: When the molten salt heat storage system coupled to the coal-fired unit is in the heat storage mode startup stage, controlling the second damper at the second flue gas inlet and the third damper at the third flue gas inlet of the flue gas mixer to open includes: Obtaining an opening degree of the second baffle at the second smoke inlet and an opening degree of the third baffle at the third smoke inlet; Get the actual load of the unit; Based on the first control function, a target opening of the second damper and a target opening of the third damper matching the actual load of the unit are obtained; Calculating an opening adjustment instruction of the second baffle based on a target opening of the second baffle and an opening of the second baffle; An opening adjustment instruction of the third damper is calculated based on the target opening of the third damper and the opening of the third damper.

14. The molten salt heat storage system coupled with a coal-fired unit according to claim 12, characterized in that: Obtaining the opening of the second baffle at the second smoke inlet and the opening of the third baffle at the third smoke inlet, comprising: Acquire the opening of the second baffle at the second smoke inlet, where the opening of the second baffle is the opening corrected by the smoke temperature difference in the pipeline where the third baffle is located; The opening of the second baffle at the third flue gas inlet is obtained, where the opening of the third baffle is the opening corrected by the flue gas temperature difference in the pipeline where the second baffle is located.

15. The molten salt heat storage system coupled with a coal-fired unit according to claim 12, characterized in that: After preheating is completed, the first damper at the first smoke inlet and the fourth damper at the fourth smoke inlet of the smoke mixer are controlled to open, including: Acquire the opening of the first baffle at the first smoke inlet and the opening of the fourth baffle at the fourth smoke inlet; Get the actual load of the unit; Based on the third control function, a target opening of the first damper and a target opening of the fourth damper matching the actual load of the unit are obtained; Calculating an opening adjustment instruction of the first baffle based on a target opening of the first baffle and an opening of the first baffle; An opening adjustment instruction of the fourth damper is calculated based on the target opening of the fourth damper and the opening of the fourth damper.

16. The molten salt heat storage system coupled with a coal-fired unit according to claim 15, characterized in that: Obtaining the opening of the first baffle at the first smoke inlet and the opening of the fourth baffle at the fourth smoke inlet, including: Acquire the opening of the first baffle at the first flue gas inlet, where the opening of the first baffle is the opening corrected by the flue gas temperature difference in the pipeline where the fourth baffle is located; The opening degree of the fourth baffle at the fourth flue gas inlet is obtained, where the opening degree of the fourth baffle is the opening degree corrected by the flue gas temperature difference in the pipeline where the first baffle is located.

17. The molten salt heat storage system coupled with a coal-fired unit according to claim 12, characterized in that: The working mode controller is also used for: When the molten salt heat storage system of the coupled coal-fired unit is in the heat storage mode, the temperature of the molten salt in the high-temperature molten salt tank is detected, and when the molten salt temperature reaches the insulation temperature, the molten salt heat storage system of the coupled coal-fired unit is controlled to enter the insulation mode; When the molten salt heat storage system coupled to the coal-fired unit enters the insulation mode, the flue gas damper controller is also used to: controlling the opening degrees of the second baffle and the third baffle based on a second control function; The opening degrees of the first damper and the fourth damper are controlled based on a fourth control function.

18. The molten salt heat storage system coupled with a coal-fired unit according to claim 17, characterized in that: The controlling the opening degrees of the second baffle and the third baffle based on the second control function includes: Obtaining an opening degree of the second baffle at the second smoke inlet and an opening degree of the third baffle at the third smoke inlet; Get the actual load of the unit; Based on the second control function, a target opening of the second damper and a target opening of the third damper matching the actual load of the unit are obtained; Calculating an opening adjustment instruction of the second baffle based on a target opening of the second baffle and an opening of the second baffle; An opening adjustment instruction of the third damper is calculated based on the target opening of the third damper and the opening of the third damper.

19. The molten salt heat storage system coupled with a coal-fired unit according to claim 17, characterized in that: Controlling the openings of the first baffle and the fourth baffle based on a fourth control function includes: Acquire the opening of the first baffle at the first smoke inlet and the opening of the fourth baffle at the fourth smoke inlet; Get the actual load of the unit; Based on a fourth control function, a target opening of the first damper and a target opening of the fourth damper matching the actual load of the unit are obtained; Calculating an opening adjustment instruction of the first baffle based on a target opening of the first baffle and an opening of the first baffle; An opening adjustment instruction of the fourth damper is calculated based on the target opening of the fourth damper and the opening of the fourth damper.

20. The molten salt heat storage system coupled with a coal-fired unit according to claim 3, characterized in that: Also includes: An induced draft fan controller controls the frequency of the induced draft fan in the high-temperature heat exchange pipeline based on a measured value and a design value of the pressure difference in the high-temperature heat exchange pipeline.

21. The molten salt heat storage system coupled with a coal-fired unit according to claim 1, characterized in that: Also includes: An electric heating device is arranged in the low-temperature molten salt tank.

22. The molten salt heat storage system coupled with a coal-fired unit according to claim 5, characterized in that: Also includes: Molten Salt Temperature Controller The molten salt temperature controller is used to: when it is detected that the low-temperature molten salt pump corresponding to the low-temperature molten salt tank is at minimum power, control the flow in the low-temperature heat exchange pipeline through the molten salt flow regulating valve until the opening of the molten salt flow regulating valve reaches the maximum.

23. The molten salt heat storage system coupled with a coal-fired unit according to claim 22, characterized in that: The molten salt temperature controller is also used for: When it is detected that the opening of the molten salt flow regulating valve reaches the maximum, the flow in the low-temperature heat exchange pipeline is controlled by the low-temperature molten salt pump until the low-temperature molten salt pump corresponding to the low-temperature molten salt tank reaches the minimum power.

24. The molten salt heat storage system coupled with a coal-fired unit according to claim 23, characterized in that: Molten salt temperature controller includes: a molten salt temperature main controller, a first molten salt temperature sub-controller and a second molten salt temperature sub-controller; The molten salt temperature main controller is used to generate a molten salt flow rate setting value in the low-temperature heat exchange pipeline based on the deviation between the molten salt temperature setting value and the measured value in the low-temperature heat exchange pipeline when the molten salt heat storage system coupled to the coal-fired unit is in the insulation mode; The first molten salt temperature sub-controller is used to: when it is detected that the opening of the molten salt flow regulating valve reaches the maximum, based on the deviation between the molten salt flow setting value and the measured value of the molten salt in the low-temperature heat exchange pipeline, calculate the target output power of the low-temperature molten salt pump, and adjust the output power of the low-temperature molten salt pump based on the target output power and the measured output power of the low-temperature molten salt pump until it is detected that the low-temperature molten salt pump reaches the minimum power; The second molten salt temperature sub-controller is used for: when it is detected that the low-temperature molten salt pump corresponding to the low-temperature molten salt tank is at minimum power, based on the deviation between the molten salt flow rate set value and the measured value of the molten salt in the low-temperature heat exchange pipeline, calculating the target opening of the molten salt flow rate regulating valve, and adjusting the opening of the molten salt flow rate regulating valve based on the target opening and the measured opening of the molten salt flow rate regulating valve, until it is detected that the opening of the molten salt flow rate regulating valve reaches the maximum, controlling the molten salt flow rate regulating valve to enter a manual adjustment state.

25. The molten salt heat storage system coupled with a coal-fired unit according to claim 24, characterized in that: The measured output power of the low-temperature molten salt pump is the output power corrected by the molten salt temperature at the molten salt inlet of the flue gas-molten salt heat exchanger; The measured opening of the molten salt flow regulating valve is the opening corrected by the molten salt temperature at the molten salt inlet of the flue gas-molten salt heat exchanger.

26. The molten salt heat storage system coupled with a coal-fired unit according to claim 10, characterized in that: Also included is a direct energy balance controller; The direct energy balance controller is used to generate and output a molten salt flow instruction based on the deviation between the energy demand signal and the energy supply signal of the molten salt steam generation system, and the molten salt flow instruction is used to characterize the target molten salt flow of the low-temperature heat exchange pipeline.

27. The molten salt heat storage system coupled with a coal-fired unit according to claim 26, characterized in that: Also includes: Molten salt main flow controller; When the molten salt heat storage system coupled to the coal-fired unit is in the heat release mode, the molten salt main flow controller is used to: generate a molten salt pump frequency adjustment instruction based on the target molten salt flow and the measured molten salt flow of the low-temperature heat exchange pipeline, and control the power of the second high-temperature molten salt pump based on the molten salt pump frequency adjustment instruction.

28. The molten salt heat storage system coupled with a coal-fired unit according to claim 27, characterized in that: After the molten salt pump frequency adjustment instruction is generated, the method further includes: The molten salt pump frequency adjustment instruction is corrected based on the differential result of the energy demand signal.

29. The molten salt heat storage system coupled with a coal-fired unit according to claim 26, characterized in that: Also includes: Molten salt bypass flow controller; When the molten salt heat storage system of the coupled coal-fired unit is in the heating mode, the molten salt bypass flow controller is used to: obtain the target molten salt flow, calculate the target opening of the molten salt bypass regulating valve based on the target molten salt flow and the measured molten salt flow in the low-temperature molten salt recycling pipeline, and adjust the opening of the molten salt bypass regulating valve based on the target opening of the molten salt bypass regulating valve.

30. The molten salt heat storage system coupled with a coal-fired unit according to claim 29, characterized in that: The direct energy balance controller is also used for: An energy demand signal is calculated based on the steam pressure at the steam inlet of the load, the measured value of the steam pressure at the superheater outlet, and the set value of the steam pressure at the superheater outlet; The energy supply signal is calculated based on the energy demand signal, the energy supply signal, the heat storage coefficient of the molten salt heat release system and the drum pressure.

31. The molten salt heat storage system coupled with a coal-fired unit according to claim 10, characterized in that: Also includes: A steam flow controller is used to obtain the steam temperature output by the superheater, correct the steam temperature based on a sixth function, and obtain a steam flow setting value that matches the corrected steam temperature; and control the flow rate of the output steam of the superheater based on the steam flow setting value.

32. The molten salt heat storage system coupled with a coal-fired unit according to claim 31, characterized in that: Steam flow controller, including: superheated steam main flow controller; The superheated steam main flow controller is used to calculate the opening adjustment instruction of the steam main flow regulating valve based on the difference between the steam flow setting value and the actual steam flow value, and the opening adjustment instruction is used to adjust the opening of the steam main flow regulating valve.

33. The molten salt heat storage system coupled with a coal-fired unit according to claim 32, characterized in that: The steam flow controller also includes: The pressure calculation unit is used to obtain a superheated steam pressure setting value and an actual superheated steam pressure value; calculate the difference between the superheated steam pressure setting value and the actual superheated steam pressure value, and record it as a main steam pressure difference; use a seventh function to correct the main steam pressure difference; and correct the opening adjustment instruction based on the corrected main steam pressure difference.

34. The molten salt heat storage system coupled with a coal-fired unit according to claim 32, characterized in that: The steam flow controller also includes: The superheated steam bypass flow controller is used to calculate the opening adjustment instruction of the steam bypass regulating valve based on the difference between the superheated steam flow set value and the actual measured value of the superheated steam flow in the steam bypass pipeline, and adjust the opening of the steam bypass regulating valve based on the opening adjustment instruction.

35. The molten salt heat storage system coupled with a coal-fired unit according to claim 34, characterized in that: The steam flow controller further includes: a first switch; The first switch is used for: when the superheated steam flow in the steam output pipeline increases from 0 to the first steam flow, controlling the superheated steam bypass flow controller to start, controlling the superheated steam main flow controller to stop; when the superheated steam flow in the steam output pipeline increases to the first steam flow and continues to increase, controlling the superheated steam main flow controller to start, controlling the superheated steam bypass flow controller to stop, and keeping the superheated steam main flow controller in the open state; when the superheated steam flow in the steam output pipeline decreases to the second steam flow, the superheated steam bypass flow controller is stopped; when the superheated steam flow in the steam output pipeline decreases to the second steam flow and needs to continue to decrease, controlling the superheated steam bypass flow controller to start, and controlling the superheated steam main flow controller to stop; Wherein, the first steam flow rate is greater than the second steam flow rate.

36. The molten salt heat storage system coupled with a coal-fired unit according to claim 10, characterized in that: Also includes: Evaporator liquid level main controller and evaporator liquid level sub-controller; The evaporator liquid level main controller is used to obtain a feed water flow setting value by weighted summing the evaporator liquid level setting value, the liquid level actual value and the superheated steam flow actual value, and calculate the feed water flow adjustment instruction based on the feed water flow setting value and the feed water flow actual value in the feed water pipeline; The evaporator liquid level sub-controller is used to adjust the water supply amount of the evaporator based on the water supply flow adjustment instruction.

37. The molten salt heat storage system coupled with a coal-fired unit according to claim 36, characterized in that: The evaporator liquid level sub-controller comprises: a first evaporator liquid level sub-controller, a second evaporator liquid level sub-controller and a third evaporator liquid level sub-controller; The first evaporator liquid level sub-controller is used for: The first evaporator liquid level sub-controller is used to: adjust the opening of the feedwater bypass regulating valve based on the feedwater flow rate regulating instruction; The second evaporator liquid level sub-controller is used to: adjust the opening of the water supply main line regulating valve based on the water supply flow rate adjustment instruction; The third evaporator liquid level sub-controller is used to adjust the output power of the feed water pump at the water outlet of the deaerator based on the feed water flow adjustment instruction.

38. The molten salt heat storage system coupled with a coal-fired unit according to claim 37, characterized in that: Also includes: a second switch; The second switch is used to: when it is monitored that the water supply pump of the deaerator is running at the minimum power, control the first evaporator liquid level sub-controller to start; when it is monitored that the opening of the water supply bypass regulating valve reaches the first opening, if the water supply flow needs to continue to increase, control the second evaporator liquid level sub-controller to start; when it is monitored that the opening of the water supply main regulating valve reaches the second opening, if the water supply flow needs to continue to increase, control the third evaporator liquid level sub-controller to start.

39. The molten salt heat storage system coupled with a coal-fired unit according to claim 37, characterized in that: Also includes: A third switch; The third switch is used to: when it is detected that the molten salt steam generation system cuts off the heating mode or detects that the opening of the water supply bypass regulating valve reaches the maximum, turn off the first evaporator liquid level sub-controller; when it is detected that the power of the water supply pump reaches the minimum value, the opening of the water supply main regulating valve reaches the minimum value and the molten salt steam generation system switches into the heating mode, control the first evaporator liquid level sub-controller to start; When it is detected that the molten salt steam generation system cuts off the heating mode or detects that the opening of the water supply main line regulating valve reaches the maximum, the second evaporator liquid level sub-controller is turned off; when it is detected that the power of the water supply pump reaches the minimum value, the opening of the water supply bypass regulating valve reaches the maximum value and the molten salt steam generation system cuts into the heating mode, the second evaporator liquid level sub-controller is controlled to start; When it is detected that the molten salt steam generation system cuts off the heating mode or detects that the water supply pump power reaches the minimum value, the third evaporator liquid level sub-controller is turned off; when it is detected that the opening of the water supply main circuit regulating valve reaches the maximum, the opening of the water supply bypass regulating valve reaches the maximum value and the molten salt steam generation system is switched into the heat release mode, the third evaporator liquid level sub-controller is controlled to start; After obtaining the adjustment instruction output by the evaporator liquid level main controller, the first evaporator liquid level sub-controller, the second evaporator liquid level sub-controller or the third evaporator liquid level sub-controller in the startup state controls the respective control objects based on the control instruction.

40. The molten salt heat storage system coupled with a coal-fired unit according to claim 10, characterized in that: Also includes: Recirculation regulating valve controller; The recirculation regulating valve controller is used to: when it is detected that the outlet flow rate of the target pump increases to its corresponding first target value, when the outlet flow rate of the target pump continues to increase, control the opening of the circulation regulating valve corresponding to the target pump to decrease as the outlet flow rate of the target pump increases, until the opening is reduced to 0; when it is detected that the outlet flow rate of the target pump decreases to its corresponding second target value, when the outlet flow rate of the target pump continues to decrease, control the opening of the circulation regulating valve corresponding to the target pump to increase as the outlet flow rate of the target pump decreases, until the opening increases to a maximum opening; The target pump is a low-temperature molten salt pump, a second high-temperature molten salt pump or a water feed pump; The first target value is smaller than the second target value.

41. The molten salt heat storage system coupled with a coal-fired unit according to claim 40, characterized in that: Controlling the opening of a circulation regulating valve corresponding to a target pump to decrease as the outlet flow rate of the target pump increases, comprising: Based on the eighth control function, controlling the opening of the circulation regulating valve corresponding to the target pump to decrease as the outlet flow rate of the target pump increases; Controlling the opening of a circulation regulating valve corresponding to a target pump to increase as the outlet flow rate of the target pump decreases, comprising: Based on the ninth control function, the opening degree of the circulation regulating valve corresponding to the target pump is controlled to increase as the outlet flow rate of the target pump decreases; The eighth control function and the ninth control function are respectively used to express the mapping relationship between the outlet flow rate of the target pump and the opening degree of the circulation regulating valve corresponding to the target pump.

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