Molten salt steam generation system and control method thereof

Abstract

The invention discloses a fused salt steam generation system and a control method thereof. A high-temperature molten salt tank, a salt feeding pump, a molten salt channel of a second-stage superheater, a molten salt channel of a first-stage superheater, a molten salt channel of an evaporator, a molten salt channel of a preheater and a low-temperature molten salt tank of the system are communicated in sequence; the water supply end, the water supply pump, a steam-water channel of the preheater, the steam pocket, the pressure regulating valve, a steam-water channel of the first-stage superheater, the water spraying and temperature reducing device, a steam-water channel of the second-stage superheater and the steam removal end are sequentially communicated, and a descending pipe and an ascending pipe of the steam pocket are communicated with a steam-water channel of the evaporator. The control method aims at the system. The method has the advantages that the steam pocket pressure is actively adjusted during load rising, the liquid working medium is flashed, a load instruction can be quickly responded, steam is stably generated according to the instruction and merged into the steam turbine, and the stability and safety of the steam turbine are improved; the steam pocket of the evaporation system is used as steam storage equipment, so that an independent steam storage pocket is prevented from being arranged in the evaporation system, the cost is reduced, and the control logic is simplified.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of molten salt energy storage and molten salt coupled coal-fired power generation, and particularly relates to a molten salt steam generation system and a control method thereof. BACKGROUND

[0002] In a molten salt heat storage coupled coal-fired power unit peak shaving and frequency modulation system, the steam generated by the molten salt steam generation system needs to be quickly and stably incorporated into the steam turbine thermal system to respond to the load demand. However, the existing technology generally has problems such as steam generation rate lag and insufficient dynamic response performance, and the main reason is that the steam generation process of most molten salt steam generation systems simply relies on indirect adjustment of the feed water flow and the molten salt flow, and due to the limitation of equipment and working fluid thermal inertia, this passive control is difficult to meet the stringent requirements of modern power systems for fast frequency modulation and flexible operation. Especially under the background of high proportion of renewable energy grid connection, the power grid puts forward higher standards for the load regulation rate and accuracy of coal-fired power units, and the existing molten salt steam generation system lacks an active and rapid evaporation capacity adjustment mechanism, and the change of the saturation steam pressure in the steam drum has significant inertia, resulting in delay and fluctuation of steam output during variable load process, which seriously restricts the peak shaving and frequency modulation capability of the unit. In addition, when the molten salt steam generation system is running under variable conditions, the steam parameters often overshoot or oscillate due to large thermal inertia and strong control coupling, further affecting the safety and economy of the unit operation. In view of this technical bottleneck, it is urgent to develop a new method that can realize the rapid response and accurate control of the molten salt steam generation system during the steam generation process, in order to improve the flexible regulation performance of the unit in the new power system. SUMMARY

[0003] The purpose of the present application is to provide a molten salt steam generation system and a control method thereof, and the core innovation point is to control the feed water flow and the molten salt flow in cooperation with the steam drum pressure control to build a steam drum energy storage regulation system.

[0004] The application sets a pressure regulating valve after the steam drum to control the steam drum pressure while controlling the molten salt flow and the water flow of the molten salt steam generation system. When the molten salt steam generation system is in a small load stable operation or load reduction, the pressure in the steam drum is raised in advance to store energy. When the molten salt steam generation system receives a unit instruction to increase load to bear part of the unit load, the molten salt flow and the water flow are increased, and the opening degree of the pressure regulating valve is increased to reduce the steam drum pressure, so that the saturation temperature is reduced, and the internal water of the steam drum is rapidly vaporized. Compared with simply controlling the molten salt flow and the water flow, the saturation water in the steam drum is flashed and rapidly vaporized after the steam drum pressure is reduced, and the response speed is obviously faster than the heat transfer-evaporation response speed after the salt and water are adjusted. The steam production is accurately controlled through the opening degree of the pressure regulating valve to meet the unit demand, and the large steam production fluctuation is avoided to cause the steam turbine inlet flow fluctuation and affect the safe operation of the steam turbine.

[0005] The application is achieved by the following technical solutions: A molten salt steam generation system, comprising a high-temperature molten salt tank and a water supply end, the high-temperature molten salt tank, a molten salt pump, a molten salt passage of a secondary superheater, a molten salt passage of a primary superheater, a molten salt passage of an evaporator, a molten salt passage of a preheater, and a low-temperature molten salt tank are sequentially connected; the water supply end, a water pump, a steam-water passage of the preheater, a steam drum, a pressure regulating valve, a steam-water passage of the primary superheater, a water spray desuperheating device, a steam-water passage of the secondary superheater, and a steam outlet end are sequentially connected, a downcomer of the steam drum is connected with the steam-water passage of the evaporator, and the steam-water passage of the evaporator is connected with an upcomer of the steam drum.

[0006] A control method of a molten salt steam generation system, aiming at the molten salt steam generation system; a molten salt side process is that high-temperature salt flows out of the high-temperature molten salt tank, passes through the molten salt pump, and then sequentially flows through the secondary superheater, the primary superheater, the evaporator, and the preheater to exchange heat with the steam-water working medium, and then flows into the low-temperature molten salt tank after transferring heat to the steam-water working medium; A steam-water side process is that water at the water supply end flows into the preheater through the water pump, is heated in the preheater, and then flows into the steam drum, and then flows into the evaporator through the downcomer to generate a phase change, and then flows back into the steam drum through the upcomer to mix with saturated water, the steam-water mixture is separated by a steam-water separator in the steam drum, the saturated water and the water from the preheater are mixed and then flow into the evaporator through the downcomer again, the saturated steam flows into the primary superheater through the pressure regulating valve, flows into the secondary superheater through the desuperheating device, is heated again by the high-temperature molten salt, and then becomes rated superheated steam to flow into the steam outlet end.

[0007] Further, in a steady-state operation or load reduction condition of the system, the opening degree of the pressure regulating valve is controlled to be reduced to increase the steam drum pressure; when the system receives an instruction to increase load to rapidly produce steam, the opening degree of the pressure regulating valve at the outlet of the steam drum is adjusted to reduce the pressure in the steam drum, and the stored heat energy in the steam drum is released by using the flashing effect caused by the pressure reduction process.

[0008] Further, after the drum pressure is raised, the steam temperature at the outlet of the first superheater is higher than the rated temperature at the inlet of the second superheater, and the superheated steam is sprayed and cooled by the water spraying and cooling device to the rated temperature at the inlet of the second superheater after passing through the first superheater; after the drum pressure is reduced, the outlet steam temperature is reduced due to the expansion effect caused by the pressure reduction in the drum, at this time, the water spraying and cooling flow rate after the first superheater is reduced to ensure that the outlet steam temperature of the first superheater meets the standard.

[0009] Further, in the load dynamic adjustment process, the control system realizes optimal response through multi-parameter collaborative control: first, the target steam production and response time are set based on the unit demand, then the key operating variables of the molten salt flow, the feedwater flow, the pressure regulating valve opening and the water spraying and cooling flow of the four modules are synchronously adjusted by using the PID feedback control algorithm based on real-time monitoring of system parameters, the multi-parameter collaborative strategy continuously corrects the operating parameters through the closed-loop feedback mechanism to ensure that the system reaches the target steam production within the specified response time, and meanwhile, each parameter is maintained within the safety range.

[0010] Further, the control system first outputs the steam production set value to each module, calculates the feedforward value from the steam production set value, and calculates the feedback value from the set value and the measured value of each control parameter after addition and subtraction, and the feedback value and the feedforward value are added to obtain the control instruction of each parameter.

[0011] Further, in the molten salt flow control module, first, the steam production set value is calculated based on the rated power and the load instruction, the steam production set value is calculated to obtain the feedforward value of the molten salt flow to quickly respond to disturbances, and the deviation between the steam production set value and the steam production measured value and the deviation between the drum pressure set value and the drum pressure measured value are added to be used as the input variable of the deviation PID controller, the PID controller calculates the PID adjustment amount by saving the error values of the current and the previous two control periods and combining the preset proportional, integral and differential parameters, and finally, the feedback value of the molten salt flow is calculated after the PID signal is output, and finally, the molten salt flow instruction is obtained by adding the feedback value multiplied by the correction coefficient to the feedforward value. f 1 (x) Further, in the molten salt flow control module, first, the steam production set value is calculated based on the rated power and the load instruction, the steam production set value is calculated to obtain the feedforward value of the molten salt flow to quickly respond to disturbances, and the deviation between the steam production set value and the steam production measured value and the deviation between the drum pressure set value and the drum pressure measured value are added to be used as the input variable of the deviation PID controller, the PID controller calculates the PID adjustment amount by saving the error values of the current and the previous two control periods and combining the preset proportional, integral and differential parameters, and finally, the feedback value of the molten salt flow is calculated after the PID signal is output, and finally, the molten salt flow instruction is obtained by adding the feedback value multiplied by the correction coefficient to the feedforward value. f 2 (x) Further, in the molten salt flow control module, first, the steam production set value is calculated based on the rated power and the load instruction, the steam production set value is calculated to obtain the feedforward value of the molten salt flow to quickly respond to disturbances, and the deviation between the steam production set value and the steam production measured value and the deviation between the drum pressure set value and the drum pressure measured value are added to be used as the input variable of the deviation PID controller, the PID controller calculates the PID adjustment amount by saving the error values of the current and the previous two control periods and combining the preset proportional, integral and differential parameters, and finally, the feedback value of the molten salt flow is calculated after the PID signal is output, and finally, the molten salt flow instruction is obtained by adding the feedback value multiplied by the correction coefficient to the feedforward value.

[0012] Further, in the pressure regulating valve opening control module after the drum, first, the steam production set value is calculated based on the rated power and the load instruction, the steam production set value is calculated to obtain the feedforward value of the valve opening, and the steam production deviation is calculated from the real-time monitored steam production measured value and the steam production set value, and the deviation signal is used as the process variable input of the PID controller, the PID controller calculates the PID adjustment amount signal by saving the error values of the current and the previous two control periods and combining the preset proportional, integral and differential parameters, and finally, the feedback value of the valve opening is calculated after the PID signal is output. f 3 (x) Further, in the pressure regulating valve opening control module after the drum, first, the steam production set value is calculated based on the rated power and the load instruction, the steam production set value is calculated to obtain the feedforward value of the valve opening, and the steam production deviation is calculated from the real-time monitored steam production measured value and the steam production set value, and the deviation signal is used as the process variable input of the PID controller, the PID controller calculates the PID adjustment amount signal by saving the error values of the current and the previous two control periods and combining the preset proportional, integral and differential parameters, and finally, the feedback value of the valve opening is calculated after the PID signal is output. f4 (x) The valve opening feedback value is calculated, and the new valve opening is obtained by adding the feedforward value to the feedback value multiplied by the correction coefficient as the valve opening command output.

[0013] Further, in the feedwater flow control module, first, the steam production set value is calculated based on the system rated power and the load command, and the steam production set value is sent to the PID controller after being multiplied by the correction coefficient. f 5 (x) The feedforward value of the feedwater flow is calculated, and the feedforward control can quickly respond to major disturbances. At the same time, the system sets the intermediate water level in the steam drum as the steam drum water level set value, and the water level deviation is obtained by comparing the current water level measurement value with the set value as the input of the PID controller. The PID adjustment amount signal is calculated through the comprehensive action of the proportional, integral, and differential three links, and then input to the f 6 (x) The feedback value of the feedwater flow is obtained, and the new feedwater flow command output is composed of the feedforward value and the feedback value.

[0014] Further, in the secondary superheater front water spray desuperheating flow control module, first, the steam production set value is calculated based on the system rated power and the load command, and the steam production set value is sent to the PID controller after being multiplied by the correction coefficient. f 7 (x) The feedforward value of the water spray desuperheating flow is calculated, and the temperature deviation is calculated by monitoring the secondary superheater inlet temperature measurement value and the set value in real time as the input of the PID controller. The PID adjustment amount signal is calculated through the comprehensive action of the proportional, integral, and differential three links, and then input to the f 8 (x) The feedback value of the water spray desuperheating flow is obtained, and the new water spray desuperheating flow command output is composed of the feedforward value and the feedback value and the correction coefficient.

[0015] The beneficial effects of the present application are: 1. When the load is increased, the steam drum pressure is actively adjusted, the liquid working medium is flashed, the load command can be quickly responded, the steam is stably generated according to the command and enters the steam turbine, and the stability and safety of the steam turbine are improved.

[0016] 2. The steam drum of the evaporation system is used as the steam storage device, avoiding setting a separate steam storage drum in the evaporation system, reducing the system cost, and simplifying the control logic.

[0017] 3. The molten salt flow, the feedwater flow, the pressure regulating valve opening (steam drum pressure), and the water spray desuperheating flow of the molten salt steam generating system are simultaneously controlled to ensure the parameter matching of the molten salt steam generating system.

[0018] The foregoing main scheme of the present application and each further selected scheme thereof can be freely combined to form multiple schemes, all of which are the schemes that can be adopted and claimed by the present application; and the present application can also be freely combined between each non-conflicting selection and between and other selections. A person skilled in the art can understand that there are multiple combinations according to the prior art and common knowledge after understanding the schemes of the present application, all of which are the technical schemes claimed by the present application, and are not listed here. BRIEF DESCRIPTION OF DRAWINGS

[0019] Figure 1 is a system schematic diagram of the present application.

[0020] Figure 2 is a molten salt flow control logic schematic diagram of the present application.

[0021] Figure 3 is a back pressure regulating valve opening control logic schematic diagram of the present application.

[0022] Figure 4 is a feedwater flow control logic schematic diagram of the present application.

[0023] Figure 5 is a desuperheating water flow control logic schematic diagram of the present application.

[0024] In the figure: f 1 (x) is a function for calculating a molten salt flow feedforward value according to a steam production set value, f 2 (x) is a function for calculating a molten salt flow feedback value according to a deviation PID signal, f 3 (x) is a function for calculating a valve opening feedforward value according to a steam production set value, f 4 (x) is a function for calculating a valve opening feedback value according to a deviation PID signal, f 5 (x) is a function for calculating a feedwater flow feedforward value according to a steam production set value, f 6 (x) is a function for calculating a feedwater flow feedback value according to a deviation PID, f 7 (x) is a function for calculating a desuperheating water flow feedforward value according to a steam production set value, f 8 (x) is is a function for calculating a desuperheating water flow feedback value according to a deviation PID, and ∑ is a summation. DETAILED DESCRIPTION

[0025] The following non-limiting examples are used to illustrate the present application.

[0026] Example 1 Reference Figure 1As shown, a molten salt steam generation system includes a high-temperature molten salt tank 1, a salt feeding pump 2, a secondary superheater 3, a water spray desuperheating device 4, a primary superheater 5, a pressure regulating valve 6, a steam drum 7, an evaporator 8, a preheater 9, a water feeding pump 10, a low-temperature molten salt tank 11, a downcomer 12, an upcomer 13, a water feeding end and a steam discharging end, forming a complete steam generation loop.

[0027] On the molten salt side, the high-temperature molten salt tank 1, the salt feeding pump 2, the molten salt passage of the secondary superheater 3, the molten salt passage of the primary superheater 5, the molten salt passage of the evaporator 8, the molten salt passage of the preheater 9, and the low-temperature molten salt tank 11 are sequentially communicated. The molten salt flows in sequence along the flow direction on the molten salt side to provide heat for the steam-water working medium.

[0028] On the steam-water side, the water feeding end, the water feeding pump 10, the steam-water passage of the preheater 9, the steam drum 7, the pressure regulating valve 6, the steam-water passage of the primary superheater 5, the water spray desuperheating device 4, the steam-water passage of the secondary superheater 3, and the steam discharging end are sequentially communicated, and the steam drum 7 is provided with the downcomer 12 and the upcomer 13 in communication, the downcomer 12 of the steam drum 7 is in communication with the steam-water passage of the evaporator 8, and the steam-water passage of the evaporator 8 is in communication with the upcomer 13 of the steam drum 7. The water flows in sequence along the flow direction on the steam-water side, absorbs the heat of the molten salt working medium, and gradually changes into steam to finally enter the steam discharging end. Preferably, the water feeding end supplies the deaerator, the steam discharging end supplies the steam turbine, and the water of the water spray desuperheating device 4 is taken from the unit desuperheating water pipeline.

[0029] When the system is stably running and the load is reduced, the opening degree of the pressure regulating valve is reduced to increase the back pressure in the steam drum to achieve the purpose of energy storage. When the system has a load increase demand, the opening degree of the pressure regulating valve is adjusted to ensure the rapid response of steam generation. When adjusting the back pressure of the steam drum, the molten salt flow, the water flow, and the water spray desuperheating flow are adjusted synchronously to ensure the output steam parameters. The opening degree of the pressure regulating valve, the molten salt flow, the water flow, and the water spray desuperheating flow are all controlled by the control system.

[0030] Embodiment 2 Reference Figures 1-5 As shown, a control method of a molten salt steam generation system is provided for the molten salt steam generation system of embodiment 1.

[0031] The molten salt side process is as follows: after the high-temperature salt comes out of the high-temperature molten salt tank 1, it flows through the secondary superheater 3, the primary superheater 5, the evaporator 8, the preheater 9, and the low-temperature molten salt tank 11 in sequence after passing through the salt feeding pump 2, exchanges heat with the steam-water working medium, transfers heat to the steam-water working medium, and then flows into the low-temperature molten salt tank 11.

[0032] The steam-water side flow is as follows: the feed water at the feed water end enters the preheater 9 after passing through the feed water pump 10, is heated by the molten salt after passing through the preheater 9, and then enters the steam drum 7, and then enters the evaporator 8 through the downcomer 12 to absorb the heat of the molten salt to generate phase change, and then returns to the steam drum 7 through the riser 13 and mixes with the saturated water, the steam-water mixture is separated by the steam-water separator in the steam drum 7, the saturated water and the feed water from the preheater 9 are mixed and then enter the evaporator 8 through the downcomer 12 again, and the saturated steam enters the first-stage superheater 5, the desuperheating device 4, and then the second-stage superheater 3, is heated again by the high-temperature molten salt, and then becomes the rated superheated steam into the steam end.

[0033] In the steady-state operation or load reduction condition of the system, the opening of the pressure regulating valve 6 is controlled to reduce the opening to increase the pressure of the steam drum, so that the saturation temperature and pressure in the steam drum 7 are maintained at a high level, and the heat storage capacity of the steam drum is significantly enhanced. After the steam drum pressure is increased, the steam temperature at the outlet of the first-stage superheater 5 is higher than the rated temperature at the inlet of the second-stage superheater 3, the superheated steam is sprayed and cooled by the water spraying desuperheating device 4 to the rated temperature at the inlet of the second-stage superheater 3 after passing through the first-stage superheater 5, to prevent the second-stage superheater 3 from overheating and to meet the heat transfer temperature difference of the second-stage superheater, and then enters the second-stage superheater for further superheating.

[0034] When the system receives a load increase instruction and needs to quickly generate steam, the opening of the pressure regulating valve 6 at the outlet of the steam drum 7 is adjusted to reduce the pressure in the steam drum 7, and the heat energy stored in the steam drum is released by using the flashing effect caused by the pressure reduction process. This physical process can generate a large amount of steam in a very short time to meet the demand of rapid load increase of the unit. At the same time, after the steam drum pressure is reduced, the outlet steam temperature will be reduced due to the expansion effect of the steam drum 7 after the pressure drop, at this time, the water spraying desuperheating flow after the first-stage superheater 5 is reduced to ensure that the outlet steam temperature of the first-stage superheater 5 meets the standard.

[0035] The steam drum energy release process adopts a feedforward-feedback compound control strategy, in which the feedforward control provides fast response, and the feedback control uses a PID algorithm to correct the deviation. In the load reduction process, the opening of the pressure regulating valve and other parameters are dynamically adjusted by using a PID algorithm to ensure that the steam generation capacity of the molten salt steam generation system can be smoothly and linearly reduced during the load exit process, and effectively suppress the impact of the steam generation capacity fluctuation of the system on the generator unit.

[0036] During dynamic load adjustment, the control system achieves optimal response through multi-parameter coordinated control. First, the target steam production and response time are set based on unit demand. Then, by real-time monitoring of system parameters (including drum pressure, temperature, and flow rate), a PID feedback control algorithm is used to synchronously adjust key operating variables of four modules: molten salt flow rate, feedwater flow rate, pressure regulating valve opening, and spray desuperheating flow rate. The multi-parameter coordinated strategy continuously corrects operating parameters through a closed-loop feedback mechanism, ensuring the system reaches the target steam production within the specified response time while maintaining all parameters within safe ranges. This control method not only improves the system's response speed but also significantly enhances operational stability and safety, providing an innovative solution for the efficient operation of molten salt steam generation systems under variable load conditions.

[0037] The control system first outputs the steam production setpoint to each module (including the molten salt flow control module, the valve opening control module of the pressure regulating valve after the steam drum, the feedwater flow control module, and the spray water desuperheating flow control module before the secondary superheater). The feedforward value is calculated from the steam production setpoint. At the same time, the setpoint and measured values ​​of each control parameter are added and subtracted, and the feedback value is calculated by the deviation PID. The feedback value is added to the feedforward value to obtain the control command for each parameter.

[0038] refer to Figure 2 As shown, in the molten salt flow control module, the steam production setpoint is first calculated based on the system rated power and load command. The steam production setpoint is then... f 1 (x) The feedforward value of the molten salt flow rate is calculated to quickly respond to disturbances. Simultaneously, the deviations between the steam production setpoint and the measured steam production, as well as the deviations between the steam drum pressure setpoint and the measured steam drum pressure, are calculated and summed as the input variable for the deviation PID controller. The PID controller calculates the PID adjustment by storing the error values ​​of the current and previous two control cycles and combining them with preset proportional, integral, and derivative parameters. The output PID signal is then processed... f 2 (x) The feedback value of the molten salt flow rate is calculated. Ultimately, the molten salt flow rate command is obtained by adding the feedback value to the feedforward value and multiplying it by a correction factor. If the output change is less than the dead zone setting, the original output value is maintained to avoid minor fluctuations. Simultaneously, upper and lower limits for molten salt flow rate adjustment are set. If the new molten salt flow rate exceeds the safety limit, a limiting process is implemented to prevent exceeding limits from affecting safe operation.

[0039] refer to Figure 3 As shown, in the valve opening control module of the pressure regulating valve after the steam drum, the steam production setpoint is first calculated based on the system rated power and load command. The steam production setpoint is then... f 3 (x)The feedforward value of the valve opening is calculated, and the steam production deviation is calculated by the real-time monitored steam production measured value and the steam production set value. The deviation signal is input as the process variable of the PID controller. The PID controller calculates the PID adjustment signal by saving the error values of the current and previous two control periods and combining the preset proportional, integral, and differential parameters. The PID adjustment signal is input to the f 4 (x) The feedback value of the valve opening is calculated. The new valve opening obtained by adding the feedforward value to the feedback value multiplied by the correction coefficient is used as the valve opening command output. During the calculation, the control system sets the upper and lower limits of the valve opening to protect the system. When the new valve opening is lower than the minimum safety limit, it is automatically limited to the preset minimum value. When it exceeds the upper limit pressure, it is also limited, so as to ensure that the system operates within the safe pressure range.

[0040] Referring to Figure 4 As shown in the figure, in the feedwater flow control module, the steam production set value is first calculated based on the system rated power and the load command. The steam production set value is input to the f 5 (x) The feedforward value of the feedwater flow is calculated. This feedforward control can quickly respond to major disturbances. The system sets the intermediate water level in the steam drum as the steam drum water level set value. The water level deviation obtained by comparing the current water level measured value with the set value is input as the input of the PID controller. The PID adjustment signal is calculated through the comprehensive action of the proportional, integral, and differential three links, and then input to the f 6 (x) The feedback value of the feedwater flow is obtained. The new feedwater flow command output is weighted and synthesized by the feedforward value and the feedback value. To ensure system safety, when the output new feedwater flow command exceeds the safety range, the control system automatically performs the limiting process to prevent the steam drum water level from being out of control.

[0041] Referring to Figure 5 As shown in the figure, in the front water spray desuperheating flow control module of the secondary superheater, the steam production set value is first calculated based on the system rated power and the load command. The steam production set value is input to the f 7 (x) The feedforward value of the water spray desuperheating flow is calculated. The temperature deviation calculated by the real-time monitored secondary superheater inlet temperature measured value and the set value is input as the input of the PID controller. The PID adjustment signal is calculated through the comprehensive action of the proportional, integral, and differential three links, and then input to the f 8 (x) The feedback value of the water spray desuperheating flow is obtained. The new water spray desuperheating flow command output is weighted and synthesized by the feedforward value and the feedback value and the correction coefficient.

[0042] The innovation points of the present application are: 1. A method for adjusting the pressure of a steam drum by setting a pressure regulating valve after the steam drum of a molten salt steam generation system, based on the method for improving the pressure of the steam drum to store energy in the steam drum and reducing the pressure of the steam drum to realize rapid and accurate steam production; 2. A control method and a control system for accurately controlling the steam production of the molten salt steam generation system by combining the molten salt flow control, the feed water flow control, the pressure regulating valve opening control (steam drum pressure control), and the water spray desuperheating flow control, including the aforementioned feedforward setting method and PID control setting method.

[0043] The foregoing basic examples and each further selected example of the present application can be freely combined to form a plurality of embodiments, all of which are embodiments that can be used and claimed by the present application. In the present application, each selected example can be arbitrarily combined with any basic example and selected example.

[0044] The above only describes the preferred embodiments of the present application and is not intended to limit the present application. Any modifications, equivalent replacements, and improvements made within the spirit and principles of the present application shall be included in the protection scope of the present application.

Claims

1. A molten salt steam generating system, comprising a high-temperature molten salt tank (1) and a water supply end, characterized in that: The high-temperature molten salt tank (1), the salt feed pump (2), the molten salt channel of the secondary superheater (3), the molten salt channel of the primary superheater (5), the molten salt channel of the evaporator (8), the molten salt channel of the preheater (9), and the low-temperature molten salt tank (11) are connected in sequence; the water supply end, the water feed pump (10), the steam-water channel of the preheater (9), the steam drum (7), the pressure regulating valve (6), the steam-water channel of the primary superheater (5), the water spray de-heating device (4), the steam-water channel of the secondary superheater (3), and the steam outlet end are connected in sequence; the downcomer (12) of the steam drum (7) is connected to the steam-water channel of the evaporator (8), and the steam-water channel of the evaporator (8) is connected to the riser (13) of the steam drum (7); Under steady-state operation or load reduction conditions, the pressure in the steam drum is increased by controlling the opening of the pressure regulating valve (6); when the system receives a load increase command and needs to generate steam quickly, the pressure in the steam drum (7) is reduced by adjusting the opening of the pressure regulating valve (6) at the outlet of the steam drum (7), and the heat energy stored in the steam drum is released by the flash evaporation effect caused by the pressure reduction process.

2. A control method for a molten salt steam generation system, characterized in that, Regarding the molten salt steam generation system of claim 1; the molten salt side process is as follows: after the high temperature salt comes out of the high temperature molten salt tank (1), it flows through the secondary superheater (3), the primary superheater (5), the evaporator (8), and the preheater (9) in sequence after passing through the salt feed pump (2) to exchange heat with the steam and water working medium, and after transferring the heat to the steam and water working medium, it flows into the low temperature molten salt tank (11). The steam-water side process is as follows: the feed water from the feed water end enters the preheater (9) after being heated by the feed water pump (10), enters the steam drum (7) after being heated by the preheater (9), and then enters the evaporator (8) through the downcomer (12) to produce a phase change. After that, it returns to the steam drum (7) through the riser (13) to mix with the saturated water. The steam-water mixture is separated by the steam-water separator in the steam drum (7). The saturated water and the feed water from the preheater (9) are mixed and then circulated back into the evaporator (8) through the downcomer (12). The saturated steam enters the first-stage superheater (5) and the desuperheating device (4) through the pressure regulating valve (6) and then enters the second-stage superheater (3). After being reheated by the high-temperature molten salt, it becomes the rated superheated steam and enters the steam outlet.

3. The control method for the molten salt steam generation system according to claim 2, characterized in that: After the steam drum pressure is increased, the outlet steam temperature of the first-stage superheater (5) is higher than the inlet rated temperature of the second-stage superheater (3). After passing through the first-stage superheater (5), the superheated steam is cooled down to the inlet rated temperature of the second-stage superheater (3) by water spraying and de-cooling device (4).

4. The control method for the molten salt steam generation system according to claim 2, characterized in that: After the pressure in the steam drum decreases, the expansion effect of the pressure drop in the steam drum (7) will cause the outlet steam temperature to decrease. At this time, the flow rate of the water spray de-cooling after the first-stage superheater (5) will decrease, ensuring that the outlet steam temperature of the first-stage superheater (5) meets the standard.

5. The control method for the molten salt steam generation system according to claim 2, characterized in that: During the dynamic load adjustment process, the control system achieves optimal response through multi-parameter collaborative control: First, the target steam production and response time are set based on the unit demand. Then, by monitoring system parameters in real time, the key operating variables of four modules—molten salt flow, feedwater flow, pressure regulating valve opening, and spray desuperheating flow—are simultaneously adjusted using a PID feedback control algorithm. The multi-parameter collaborative strategy continuously corrects the operating parameters through a closed-loop feedback mechanism to ensure that the system reaches the target steam production within the specified response time, while maintaining each parameter within a safe range.

6. The control method for the molten salt steam generation system according to claim 5, characterized in that: The control system first outputs the steam production setpoint to each module, calculates the feedforward value from the steam production setpoint, and then calculates the feedback value by adding and subtracting the setpoint and measured value of each control parameter using the deviation PID. The feedback value is added to the feedforward value to obtain the control command for each parameter.

7. The control method for the molten salt steam generation system according to claim 6, characterized in that: In the molten salt flow control module, the steam production setpoint is first calculated based on the system's rated power and load command. The steam production setpoint is then... f 1 (x) The feedforward value of the molten salt flow rate is calculated to quickly respond to disturbances. Simultaneously, the deviations between the steam production setpoint and the measured steam production, as well as the deviations between the steam drum pressure setpoint and the measured steam drum pressure, are calculated and summed as the input variable for the deviation PID controller. The PID controller calculates the PID adjustment by storing the error values ​​of the current and previous two control cycles and combining them with preset proportional, integral, and derivative parameters. The output PID signal is then processed... f 2 (x) The feedback value of the molten salt flow rate is calculated. Finally, the molten salt flow rate command is obtained by adding the feedback value to the feedforward value and multiplying it by the correction factor.

8. The control method for the molten salt steam generation system according to claim 6, characterized in that: In the valve opening control module of the pressure regulating valve after the steam drum, the steam production setpoint is first calculated based on the system rated power and load command. The steam production setpoint is then... f 3 (x) The feedforward value for generating the valve opening is calculated, and the steam production deviation is calculated by comparing the real-time monitored steam production measurement value with the steam production setpoint. This deviation signal serves as the process variable input to the PID controller. The PID controller calculates the PID adjustment signal by saving the error values ​​from the current and previous two control cycles and combining them with preset proportional, integral, and derivative parameters. This signal is then processed... f 4 (x) The valve opening feedback value adjustment is calculated, and the new valve opening is obtained by adding the feedforward value to the feedback value and multiplying it by the correction coefficient, which is then used as the valve opening command output.

9. The control method for the molten salt steam generation system according to claim 6, characterized in that: In the water supply flow control module, the steam production setpoint is first calculated based on the system rated power and load command. The steam production setpoint is then... f 5 (x) The feedforward value for generating the feedwater flow rate is calculated. This feedforward control can quickly respond to major disturbances. Simultaneously, the system sets the intermediate water level in the steam drum as the setpoint. By comparing the current measured water level with the setpoint, the water level deviation is obtained and used as the input to the PID controller. The PID control signal is calculated through the combined action of proportional, integral, and derivative components, and then input to the feedwater system. f 6 (x) The feedback value of the water supply flow rate is obtained, and the final output of the new water supply flow rate command is a weighted synthesis of the feedforward value and the feedback value.

10. The control method for the molten salt steam generation system according to claim 6, characterized in that: In the preheater superheater spray desuperheating flow control module, the steam production setpoint is first calculated based on the system rated power and load command. The steam production setpoint is then... f 7 (x) The feedforward value for generating the spray cooling flow rate is calculated, and the temperature deviation is calculated by comparing the real-time monitored inlet temperature of the secondary superheater with the setpoint. This deviation is used as the input to the PID controller. The PID control signal is calculated through the combined action of proportional, integral, and derivative components and then input to the controller. f 8 (x) The feedback value of the water spray cooling flow rate is obtained, and the final output of the new water spray cooling flow rate command is a weighted synthesis of the feedforward value, the feedback value, and the correction coefficient.

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