A steam generation system for a solar thermal power station and an operating method thereof

Abstract

The present invention relates to a steam generating system for a solar thermal power station and an operating method thereof. The steam generating system provides water as a working medium through a water supply unit. The steam generating system includes a preheater, a venturi nozzle, an evaporator, a steam drum and a starting unit. The present invention utilizes the kinetic energy of the feed water and combines the principle of the venturi nozzle. On the one hand, the accelerated mixing function of the venturi nozzle is used to promote the circulation of the steam-water medium between the evaporator and the steam drum. It is a structure between natural circulation and forced circulation. On the other hand, when the feed water temperature is lower than the freezing point of the molten salt, the feed water can also be mixed with the steam and water in the steam drum downcomer through the venturi nozzle, and finally the feed water temperature entering the evaporator is increased. The present invention saves the investment in the forced circulation pump, improves the reliability of the system operation, and saves factory electricity.

Description

Technical Field

[0001] The present invention relates to the technical field of solar thermal power generation, and in particular to a steam generation system for a solar thermal power station and an operating method thereof. Background Art

[0002] Solar energy can be utilized in a variety of ways, including wind power, tidal power, photovoltaic power generation, and concentrated solar power generation. Solar thermal power generation is categorized into trough, tower, butterfly, and linear Fresnel types, depending on the structure of the concentrating mirror and collector.

[0003] If solar thermal technology is to stand out among many power generation technologies and ultimately achieve a significant breakthrough in cost, at least two problems need to be solved: one is the reliability of the equipment, and the other is to optimize the system structure and reduce equipment investment through process improvements.

[0004] Whether based on trough, tower, butterfly, or linear Fresnel technology, the current power generation scheme employed by CSP plants utilizes steam to propel turbine generators to generate electricity. This steam generation requires a steam generation system. For subcritical and supercritical units, steam generation systems employ a forced circulation scheme, as traditional natural circulation schemes struggle to achieve efficient steam generation. This scheme requires a forced circulation pump as the power source for the steam-water circulation between the drum and evaporator. However, the use of forced circulation pumps presents two problems: First, compared to conventional water pumps, forced circulation pumps operate at higher temperatures and pressures, resulting in higher costs and impacting the CSP industry's urgent need to reduce costs. Second, because forced circulation pumps are moving parts, they significantly increase the system's operational failure rate and operational risks compared to natural circulation schemes. The operational performance of steam generation systems in the first batch of CSP demonstration projects demonstrates the severity of this problem.

[0005] In addition, due to the particularity of the molten salt heat exchanger, when the water working medium temperature in the molten salt heat exchanger is lower than the freezing point of the molten salt working medium, the molten salt will solidify and cause a production stoppage accident. Therefore, it is particularly important to increase the water working medium temperature at the inlet of the molten salt heat exchanger. The current solution is generally to add a set of heat exchangers in front of the molten salt heat exchanger to increase the feed water temperature. However, this solution may still cause the feed water temperature to be lower than the freezing point of the molten salt working medium during the startup and low-load operation stages of the steam turbine power generation system.

[0006] Therefore, a reliable solution is needed to properly solve the problem that natural circulation cannot meet the steam generation demand, avoid the cost increase and failure rate increase brought by the use of forced circulation pumps, and at the same time ensure that the water working medium temperature at the inlet of the molten salt heat exchanger is higher than the freezing point of the molten salt working medium. Summary of the Invention

[0007] The object of the present invention is to provide a steam generation system for a solar thermal power station and an operating method thereof, which utilizes the kinetic energy of the water working medium in the Venturi nozzle and changes the internal pipe diameter of the Venturi nozzle to increase the circulation rate of the pipeline between the steam drum and the evaporator. At the same time, the Venturi nozzle is further utilized to mix the water working medium in the steam drum to the evaporator pipeline and the water supply pipeline, so that the temperature of the water working medium entering the evaporator is finally higher than the freezing point of the heat storage medium, thereby eliminating the forced circulation pump used in the traditional design, saving equipment costs and ensuring the operational reliability of the steam generation system.

[0008] In order to solve the above problems, the present invention provides a steam generation system for a solar thermal power station, wherein the steam generation system provides water working medium through a water supply unit, wherein the water supply unit includes a water supply source and a water supply pipeline; the steam generation system includes a preheater, an evaporator, a steam drum and a starting unit, wherein the preheater and the evaporator are heat exchangers for exchanging heat between the heat storage medium and the water working medium; the starting unit includes a starting circulation pump inlet switch valve, a starting circulation pump and a starting heater, and the steam generation system also includes a Venturi nozzle, wherein the Venturi nozzle includes a nozzle inlet, a nozzle mixing inlet and a nozzle outlet:

[0009] The water supply source is connected to the water inlet of the water inlet pipe of the preheater and the water inlet of the water supply bypass pipe respectively through the water supply pipe, and a water supply regulating valve is provided on the water inlet pipe of the preheater; the water outlet of the water supply bypass pipe is connected to the nozzle inlet, and a water supply bypass regulating valve is provided on the water supply bypass pipe;

[0010] The preheater is connected to the nozzle inlet or the water supply pipe of the steam drum through its water outlet pipe;

[0011] The nozzle outlet is connected to the riser of the steam drum through the evaporator; the downcomer of the steam drum is connected to the nozzle mixing inlet and the starting unit respectively, and the starting unit is connected to the preheater through the water inlet pipe of the preheater.

[0012] Preferably, the starting unit is connected to the downcomer of the steam drum and the water inlet of the water inlet pipe of the preheater respectively through a starting circulation pipe;

[0013] The starting circulation pump inlet switch valve, the starting circulation pump and the starting heater are connected in series and are sequentially arranged on the starting circulation pipe according to the flow direction of the water working medium.

[0014] Preferably, the Venturi nozzle is a device that utilizes the Bernoulli effect to achieve accelerated mixing of fluids.

[0015] The present invention further provides a method for operating a steam generation system for a solar thermal power station as described in the above embodiment, comprising:

[0016] When the steam generation system is started in a cold state, the water supply bypass regulating valve is closed, the water supply regulating valve and the starting circulation pump inlet switch valve are opened, and the water supply unit supplies water to the preheater, evaporator and steam drum; when the water working medium level in the steam drum reaches the starting liquid level, the water supply unit stops supplying water, the starting circulation pump and the starting heater are turned on, and the water working medium in the steam generation system starts to circulate and heat until the water working medium temperature in the steam generation system is higher than the freezing point of the heat storage medium, and the startup of the steam generation system is completed.

[0017] Preferably, after the steam generation system is started up, the startup circulation pump inlet switch valve is closed, the startup circulation pump and the startup heater are closed, the steam generation system operates normally, and the water supply unit continues to supply water.

[0018] Preferably, when the steam generating system operates normally, the operating method includes:

[0019] If the temperature of the water medium in the water supply pipe is lower than the freezing point of the heat storage medium, the water supply regulating valve is closed and the water supply bypass regulating valve is opened. At this time, the water medium in the water supply pipe entering the venturi nozzle from the nozzle inlet through the water supply bypass pipe and the water medium in the steam drum entering the venturi nozzle from the nozzle mixing inlet through the downcomer are mixed in the venturi nozzle and then enter the evaporator from the nozzle outlet.

[0020] Preferably, the temperature of the water working medium after being mixed by the Venturi nozzle and flowing out from the nozzle outlet is higher than the freezing point of the heat storage medium.

[0021] Preferably, the water outlet pipe of the preheater is connected to the nozzle inlet. When the steam generation system operates normally, the operation method includes:

[0022] If the temperature of the water medium in the water supply pipe is higher than the freezing point of the heat storage medium, the water supply regulating valve is opened and the water supply bypass regulating valve is closed. At this time, the water medium in the water supply pipe heated by the preheater enters the venturi nozzle from the nozzle inlet, and the water medium in the steam drum enters the venturi nozzle from the nozzle mixing inlet through the downcomer, are mixed in the venturi nozzle, and at the same time, the circulation of the steam-water medium between the evaporator and the steam drum is promoted.

[0023] Preferably, the water outlet pipe of the preheater is connected to the water supply pipe of the steam drum. When the steam generation system operates normally, the operation method includes:

[0024] If the temperature of the water medium in the water supply pipe is higher than the freezing point of the heat storage medium, the water supply regulating valve is opened and the water supply bypass regulating valve is closed. At this time, the water medium in the water supply pipe enters the steam drum after being heated by the preheater.

[0025] Compared with the prior art, the present invention has the following technical effects:

[0026] The present invention provides a steam generation system for a solar thermal power station. This system utilizes the kinetic energy of the feed water and incorporates the principle of a Venturi nozzle. On the one hand, the accelerated mixing function of the Venturi nozzle is used to promote the circulation of the steam-water medium between the evaporator and the steam drum. This system represents a structure intermediate between natural circulation and forced circulation. On the other hand, when the feed water temperature is lower than the freezing point of the heat storage medium, the Venturi nozzle can be used to mix the feed water with the steam-water in the steam drum downcomer, ultimately increasing the feed water temperature entering the evaporator. This invention saves investment in forced circulation pumps, improves the reliability of system operation, and conserves plant electricity. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] In order to more clearly illustrate the technical solutions of the embodiments of the present invention, the following briefly introduces the drawings required for describing the embodiments. Obviously, the drawings described below are only some embodiments of the present invention. Those skilled in the art can also derive other drawings based on these drawings without inventive efforts. In the drawings:

[0028] Figure 1 A schematic structural diagram of a steam generation system for a solar thermal power station provided in preferred embodiment 1 of the present invention;

[0029] Figure 2 A schematic structural diagram of a steam generation system for a solar thermal power station provided in preferred embodiment 2 of the present invention. DETAILED DESCRIPTION

[0030] The following will be combined Figure 1 and Figure 2 A steam generation system for a solar thermal power station provided by the present invention is described in detail. This embodiment is implemented on the premise of the technical solution of the present invention, and a detailed implementation method and specific operation process are given. However, the protection scope of the present invention is not limited to the following embodiments. Those skilled in the art can modify and polish it without changing the spirit and content of the present invention.

[0031] Please refer to Figure 1 and Figure 2, a steam generation system for a solar thermal power station. The present invention mainly optimizes the structure and function of the water-side system, and does not elaborate on the structure of the salt-side system. In the present invention, the steam generation system provides water as a working medium through a water supply unit 1, and the water supply unit 1 includes a water supply source 101 and a water supply pipeline 102; the steam generation system includes a preheater 6, an evaporator 9, a steam drum 10 and a starting unit 11, and the starting unit 11 includes a starting circulation pump inlet switch valve 1101, a starting circulation pump 1102 and a starting heater 1103. The steam generation system also includes a venturi nozzle 8, and the venturi nozzle 8 includes a nozzle inlet 801, a nozzle mixing inlet 802 and a nozzle outlet 803:

[0032] The water supply source 101 is connected to the water inlet of the water inlet pipe 5 of the preheater 6 and the water inlet of the water supply bypass pipe 4 through the water supply pipe 102. The water inlet pipe 5 of the preheater 6 is provided with a water supply regulating valve 2. The water outlet of the water supply bypass pipe 4 is connected to the nozzle inlet 801. The water supply bypass pipe 4 is provided with a water supply bypass regulating valve 3.

[0033] The preheater 6 is connected to the nozzle inlet 801 or the water supply pipe of the steam drum 10 through its water outlet pipe 7;

[0034] The nozzle outlet 803 is connected to the ascending pipe of the steam drum 10 through the evaporator 9; the descending pipe of the steam drum 10 is respectively connected to the nozzle mixing inlet 802 and the starting unit 11, and the starting unit 11 is connected to the preheater 6 through the water inlet pipe 5 of the preheater 6.

[0035] The preheater 6 and the evaporator 9 are both heat exchangers for exchanging heat between a heat storage medium and a water working medium. The present invention does not impose any specific restrictions on the heat storage medium, and it can be, for example, molten salt, heat transfer oil, molten metal, etc. The following embodiments are all described in detail using molten salt as an example, but are not limited to molten salt working medium and can be set according to actual needs.

[0036] This system actually also includes connecting pipes between various devices and related valves and other accessories on each pipe. The water supply unit 1, preheater 6, evaporator 9, steam drum 10 and starting unit 11 can all adopt related equipment in the existing technology, and the present invention does not impose specific restrictions on this.

[0037] The Venturi nozzle 8 is a device that uses the Bernoulli effect to achieve accelerated mixing of fluids. All devices that use the Bernoulli effect to achieve accelerated mixing of fluids are considered to be the Venturi nozzle 8 described in the present invention. The Venturi nozzle 8 has at least three interfaces, which are connected to other devices or valves through pipes. Specifically, these interfaces include a nozzle inlet 801, a nozzle mixing inlet 802, and a nozzle outlet 803. The nozzle inlet 801 and the nozzle mixing inlet 802 are both inlets. The nozzle inlet 801 and the nozzle mixing inlet 802 are connected in the Venturi nozzle 8 to form a mixing inlet. The mixing inlet is connected to the nozzle outlet 803 at the outlet end of the Venturi nozzle 8.

[0038] This system can be powered by the starting circulation pump 1102 during the cold start preheating stage, that is, the starting circulation pump 1102 serves as the power source when starting the starting cycle, so that the water working medium forms a closed loop through the connecting pipes between the preheater 6, the evaporator 9, and the steam drum 10; the starting heater 1103 provides energy for system preheating, that is, the starting heater 1103 serves as a heater for heating the circulating water working medium. The present invention does not limit the specific type of heater 1103, as long as it can heat the water working medium, such as an electric heater. During the starting preheating stage, the preheater 6 and the evaporator 9 are not passed through the molten salt working medium. When the system is operating normally, the molten salt working medium is passed through the evaporator 9 and the preheater 6 in turn, that is, the evaporator 9 is a first-stage heat exchanger, and the preheater 6 is a second-stage heat exchanger. The preheating of this system ensures that the molten salt working medium entering the system during normal operation will not solidify, and can also reduce the thermal stress and thermal shock of the equipment.

[0039] The preheater 6 is a water-to-molten salt heat exchanger, and its function is to heat the water in the water supply pipe 102. In the present invention, during the startup phase of the steam generation system, the preheater 6 does not heat the water in the water supply pipe 102. Only when the steam generation system is operating normally will the preheater 6 heat the water in the water supply pipe 102.

[0040] The evaporator 9 is also a water working medium-molten salt working medium heat exchanger. The evaporator 9 is arranged corresponding to the steam drum 10, and its function is to evaporate the water working medium in the steam drum 10. In the present invention, during the startup phase of the steam generation system, the evaporator 9 will not evaporate the water working medium in the steam drum 10. Only when the steam generation system is operating normally, the evaporator 9 will evaporate the water working medium in the steam drum 10. The present invention sets the Venturi nozzle 8 in the circulation between the evaporator 9 and the steam drum 10. When the steam generation system is operating normally, the kinetic energy of the water working medium in the Venturi nozzle 8 is used to ultimately enable the evaporator 9 to more effectively complete the evaporation process of the water working medium in the steam drum 10.

[0041] The water source 101 provides the required water working medium for the steam generation system through the water supply pipe 102. The water supply pipe 102 is respectively connected to the water supply regulating valve 2 and the water supply bypass regulating valve 3. When the temperature of the water working medium in the water supply pipe 102 is lower than the freezing point of the molten salt, the water supply regulating valve 2 is closed and the water supply bypass regulating valve 3 is opened. The water working medium in the water supply pipe 102 enters the venturi nozzle 8 from the nozzle inlet 801 through the water supply bypass pipe 4, and the water working medium in the steam drum 10 enters the venturi nozzle 8 from the nozzle mixing inlet 802 through the downcomer, and is mixed and heated in the venturi nozzle 8, so that the evaporator 9 generation system operates stably.

[0042] Two specific embodiments are listed below for detailed description.

[0043] Example 1

[0044] Please refer to Figure 1 , a steam generating system for a solar thermal power station, wherein the steam generating system provides water working medium through a water supply unit 1; the steam generating system includes a preheater 6, a venturi nozzle 8, an evaporator 9, a steam drum 10 and a starting unit 11.

[0045] In this embodiment, the water supply unit 1 includes a water supply source 101 and a water supply pipeline 102. The water supply source 101 provides water as a working medium to the steam generation system via the water supply pipeline 102. The water supply source 101 may also be connected to the water supply pipeline 102 via a regulating valve or a water supply pump, etc., to control the on / off state of the water supply pipeline 102. To facilitate the water supply from the water supply source 101 to the steam generation system, in this embodiment, the water supply source 101 pressurizes the water as a working medium before supplying the water to the steam generation system via the water supply pipeline 102.

[0046] The starting unit 11 includes a starting circulation pump inlet switch valve 1101, a starting circulation pump 1102 and a starting heater 1103 connected in series through a pipeline. In this embodiment, the starting circulation pump inlet switch valve 1101, the starting circulation pump 1102 and the starting heater 1103 are arranged in sequence on the starting circulation pipe 1104 according to the flow direction of the water working medium.

[0047] The venturi nozzle 8 includes a nozzle inlet 801, a nozzle mixing inlet 802 and a nozzle outlet 803:

[0048] The water medium of the water supply source 101 is divided into two water paths after passing through the water supply pipe 102. In this embodiment, the water supply pipe 102 is connected to the nozzle inlet 801 through the two parallel water paths. The two water paths are:

[0049] The first water circuit includes a preheater 6 and a water supply regulating valve 2. The preheater 6 is connected to the water supply pipeline 102 via its water inlet pipe 5, and the water supply regulating valve 2 is arranged on this water inlet pipe 5. The preheater 6 is connected to the nozzle inlet 801 of the venturi nozzle 8 via its water outlet pipe 7. Specifically, the water inlet of the water inlet pipe 5 of the preheater 6 is connected to the outlet of the water supply pipeline 102, and the water outlet of the water inlet pipe 5 of the preheater 6 is connected to the water inlet of the preheater 6. The water inlet of the water outlet pipe 7 of the preheater 6 is connected to the water outlet of the preheater 6, and the water outlet of the water outlet pipe 7 of the preheater 6 is connected to the nozzle inlet 801.

[0050] The second waterway includes a water supply bypass pipe 4 and a water supply bypass regulating valve 3. The water supply bypass regulating valve 3 is arranged on the water supply bypass pipe 4. The water inlet of the water supply bypass pipe 4 is connected to the water outlet of the water supply pipe 102, and the water outlet of the water supply bypass pipe 4 is connected to the nozzle inlet 801 of the Venturi nozzle 8.

[0051] The nozzle outlet 803 of the venturi nozzle 8 is connected to the riser of the steam drum 10 through the evaporator 9; the downcomer of the steam drum 10 is respectively connected to the nozzle mixing inlet 802 of the venturi nozzle 8 and the water inlet of the start-up circulation pipe 1104, and the water outlet of the start-up circulation pipe 1104 is respectively connected to the water inlet of the water inlet pipe 5 of the preheater 6 or / and the water inlet of the water feed bypass pipe 4 or / and the water feed pipe 102. This embodiment does not impose any specific restrictions on where the water outlet of the start-up circulation pipe 1104 is connected. When the steam generating system is started in a cold state, it is sufficient to ensure that the water working medium forms a closed loop in the feed water regulating valve 2, preheater 6, venturi nozzle 8, evaporator 9, steam drum 10, start-up circulation pump inlet switch valve 1101, start-up circulation pump 1102 and start-up heater 1103 in sequence.

[0052] When the steam generation system is started in a cold state, such as when the steam generation system is started for the first time or when it is started after a long period of shutdown, since the steam generation system no longer contains any working medium, water working medium needs to be filled into the steam generation system and heated to above the freezing point of the molten salt working medium (for current tower-type solar thermal power plants, the freezing point of the molten salt working medium is generally considered to be 240°C) before further molten salt circulation can be accepted. Otherwise, there is a risk of molten salt solidification. The startup operation process at this time is as follows:

[0053] First, the water supply unit 1 is turned on, the water supply bypass regulating valve 3 is closed, the water supply regulating valve 2 and the starting circulation pump inlet switch valve 1101 are opened, and the pressurized water working medium flows in the water supply pipe 102, and the water working medium flows into the preheater 6, the venturi nozzle 8, the evaporator 9, the steam drum 10, the starting circulation pump inlet switch valve 1101, the starting circulation pump 1102 and the starting heater 1103 in sequence. When the water working medium level in the steam drum 10 reaches the starting liquid level (when the starting liquid level is reached, the preheater 6 and the evaporator 9 are filled with water working medium. The present invention does not impose specific restrictions on the starting liquid level in the steam drum 10, as long as there is a water level in the steam drum 10), the water supply pipe 102 will no longer provide additional water working medium. The water working medium in the steam generating system starts to circulate and heat by opening the starting circulation pump 1102 and the starting heater 1103 until the water working medium temperature in the steam generating system is higher than the freezing point of the molten salt working medium. At this point, the steam generating system is started.

[0054] When the steam generation system is started up, the start-up circulation pump inlet switch valve 1101 is closed, and the start-up circulation pump 1102 and the start-up heater 1103 no longer work. At this time, the steam generation system operates normally, and the water supply pipe 102 continues to supply water.

[0055] When the steam generation system operates normally, it can be divided into the following two situations:

[0056] 1. If the temperature of the water medium in the water supply pipe 102 is lower than the freezing point of the molten salt medium, the water supply regulating valve 2 is closed and the water supply bypass regulating valve 3 is opened. At this time, the water medium in the water supply pipe 102 enters the venturi nozzle 8 from the nozzle inlet 801 through the water supply bypass pipe 4, and the water medium in the steam drum 10 enters the venturi nozzle 8 from the nozzle mixing inlet 802 through the downcomer. Because the temperature of the water medium in the steam drum 10 is higher than that of the water medium in the water supply pipe 102, and the flow rate of the water medium in this part is larger, the water medium (temperature) in the water supply pipe 102 that enters the venturi nozzle 8 from the nozzle inlet 801 through the water supply bypass pipe 4 is The water working medium (with a lower temperature and a smaller flow rate) is mixed with the water working medium in the steam drum 10 in the venturi nozzle 8 from the nozzle mixing inlet 802 through the downcomer (water working medium with a higher temperature and a larger flow rate), and the mixed water working medium coming out of the nozzle outlet 803 enters the evaporator 9. Since the temperature of the mixed water working medium coming out of the nozzle outlet 803 is higher than the freezing point of the molten salt working medium, the evaporator 9 will not be subjected to thermal shock of the water working medium. At the same time, because in the venturi nozzle 8, the kinetic energy of the mixed water working medium flowing through the venturi nozzle 8 accelerates the circulation rate of the water working medium from the steam drum 10 to the evaporator 9, thereby achieving a larger circulation ratio than the natural circulation.

[0057] 2. If the temperature of the water medium in the water supply pipe 102 is higher than the freezing point of the molten salt medium, the water supply regulating valve 2 is opened and the water supply bypass regulating valve 3 is closed. At this time, the water medium in the water supply pipe 102 enters the preheater 6 and is heated by the preheater 6. Then, it flows into the venturi nozzle 8 through the nozzle inlet 801 of the venturi nozzle 8. In the venturi nozzle 8, the water medium in the steam drum 10 enters the venturi nozzle 8 through the downcomer from the nozzle mixing inlet 802. That is, the water working medium in the water supply pipe 102 entering the venturi nozzle 8 from the nozzle inlet 801 after being heated by the preheater 6, and the water working medium in the steam drum 10 entering the venturi nozzle 8 from the nozzle mixing inlet 802 through the downcomer are mixed in the venturi nozzle 8. Therefore, the kinetic energy of the water working medium flowing through the venturi nozzle 8 accelerates the circulation rate of the water working medium from the steam drum 10 to the evaporator 9, thereby achieving a larger circulation ratio compared to natural circulation.

[0058] Example 2

[0059] The difference between the steam generation system provided in this embodiment and the steam generation system provided in Example 1 is that the preheater 6 in Example 1 is connected to the nozzle inlet 801 of the venturi nozzle 8 through its outlet pipe 7, while the preheater 6 in this embodiment is connected to the water supply pipe of the steam drum 10 through its outlet pipe 7. Figure 2 .

[0060] In this embodiment, when the steam generating system is started in a cold state, the startup operation process is as follows:

[0061] First, the water supply unit 1 is turned on, the water supply bypass regulating valve 3 is closed, the water supply regulating valve 2 and the starting circulation pump inlet switch valve 1101 are opened, and the pressurized water working medium flows in the water supply pipe 102. The water working medium flows into the preheater 6, the steam drum 10, the venturi nozzle 8, the evaporator 9, the steam drum 10, the starting circulation pump inlet switch valve 1101, the starting circulation pump 1102 and the starting heater 1103 in sequence. When the water working medium level in the steam drum 10 reaches the starting liquid level (when the starting liquid level is reached, the preheater 6 and the evaporator 9 are filled with water working medium. The present invention does not impose specific restrictions on the starting liquid level in the steam drum 10, as long as there is a water level in the steam drum 10), the water supply pipe 102 will no longer provide additional water working medium. The water working medium in the steam generating system starts to circulate and heat by opening the starting circulation pump 1102 and the starting heater 1103 until the water working medium temperature in the steam generating system is higher than the freezing point of the molten salt working medium. At this point, the startup of the steam generating system is completed.

[0062] When the steam generation system is started up, the start-up circulation pump inlet switch valve 1101 is closed, and the start-up circulation pump 1102 and the start-up heater 1103 no longer work. At this time, the steam generation system operates normally, and the water supply pipe 102 continues to supply water.

[0063] When the steam generation system operates normally, it can be divided into the following two situations:

[0064] 1. If the water medium temperature in the water supply pipe 102 is lower than the freezing point of the molten salt medium, the operation process at this time is consistent with that of Example 1. Therefore, the Venturi nozzle 8 at this time can be used as a steam-water mixing heating device when the water supply temperature is lower than the freezing point of the molten salt medium.

[0065] 2. If the temperature of the water medium in the water supply pipe 102 is higher than the freezing point of the molten salt medium, open the water supply regulating valve 2 and close the water supply bypass regulating valve 3. At this time, the water medium in the water supply pipe 102 enters the steam drum 10 after being heated by the preheater 6. Since the water medium in the preheater 6 does not directly enter the Venturi nozzle 8 at this time, the Venturi nozzle 8 cannot accelerate the steam-water circulation rate between the steam drum 10 and the evaporator 9.

Claims

1. A steam generation system for a solar thermal power station, wherein the steam generation system provides water as a working medium through a water supply unit, wherein the water supply unit includes a water supply source and a water supply pipeline; the steam generation system includes a preheater, an evaporator, a steam drum, and a starting unit, wherein the preheater and the evaporator are heat exchangers for exchanging heat between a heat storage medium and the water as a working medium; the starting unit includes a starting circulation pump inlet switch valve, a starting circulation pump, and a starting heater, characterized in that: The steam generating system further comprises a venturi nozzle, wherein the venturi nozzle comprises a nozzle inlet, a nozzle mixing inlet and a nozzle outlet. The water supply source is connected to the water inlet of the water inlet pipe of the preheater and the water inlet of the water supply bypass pipe respectively through the water supply pipe, and a water supply regulating valve is provided on the water inlet pipe of the preheater; the water outlet of the water supply bypass pipe is connected to the nozzle inlet, and a water supply bypass regulating valve is provided on the water supply bypass pipe; The preheater is connected to the nozzle inlet or the water supply pipe of the steam drum through its water outlet pipe; The nozzle outlet is connected to the ascending pipe of the steam drum through the evaporator; the descending pipe of the steam drum is connected to the nozzle mixing inlet and the starting unit respectively, and the starting unit is connected to the preheater through the water inlet pipe of the preheater; The Venturi nozzle is a device that utilizes the Bernoulli effect to achieve accelerated mixing of fluids.

2. A steam generation system for a solar thermal power station according to claim 1, characterized in that: The starting unit is connected to the downcomer of the steam drum and the water inlet of the water inlet pipe of the preheater respectively through a starting circulation pipe; The starting circulation pump inlet switch valve, the starting circulation pump and the starting heater are connected in series and are sequentially arranged on the starting circulation pipe according to the flow direction of the water working medium.

3. The method for operating a steam generation system for a solar thermal power station according to any one of claims 1 to 2, characterized in that: include: When the steam generation system is started in a cold state, the water supply bypass regulating valve is closed, the water supply regulating valve and the starting circulation pump inlet switch valve are opened, and the water supply unit supplies water to the preheater, evaporator and steam drum; when the water working medium level in the steam drum reaches the starting liquid level, the water supply unit stops supplying water, the starting circulation pump and the starting heater are turned on, and the water working medium in the steam generation system starts to circulate and heat until the water working medium temperature in the steam generation system is higher than the freezing point of the heat storage medium, and the startup of the steam generation system is completed.

4. The method for operating a steam generation system for a solar thermal power station according to claim 3, wherein: When the steam generation system is started up, the startup circulation pump inlet switch valve is closed, the startup circulation pump and the startup heater are turned off, the steam generation system operates normally, and the water supply unit continues to supply water.

5. The method for operating a steam generation system for a solar thermal power station according to claim 4, characterized in that: When the steam generation system operates normally, the operating method includes: If the temperature of the water medium in the water supply pipe is lower than the freezing point of the heat storage medium, the water supply regulating valve is closed and the water supply bypass regulating valve is opened. At this time, the water medium in the water supply pipe entering the venturi nozzle from the nozzle inlet through the water supply bypass pipe and the water medium in the steam drum entering the venturi nozzle from the nozzle mixing inlet through the downcomer are mixed in the venturi nozzle and then enter the evaporator from the nozzle outlet.

6. The method for operating a steam generation system for a solar thermal power station according to claim 4, wherein: The temperature of the water working medium after being mixed by the Venturi nozzle and flowing out from the nozzle outlet is higher than the freezing point of the heat storage medium.

7. The method for operating a steam generation system for a solar thermal power station according to claim 4, wherein: The water outlet pipe of the preheater is connected to the nozzle inlet. When the steam generation system operates normally, the operating method includes: If the temperature of the water medium in the water supply pipe is higher than the freezing point of the heat storage medium, the water supply regulating valve is opened and the water supply bypass regulating valve is closed. At this time, the water medium in the water supply pipe heated by the preheater and entering the venturi nozzle from the nozzle inlet, and the water medium in the steam drum entering the venturi nozzle from the nozzle mixing inlet through the downcomer are mixed in the venturi nozzle.

8. The method for operating a steam generation system for a solar thermal power station according to claim 4, wherein: The water outlet pipe of the preheater is connected to the water supply pipe of the steam drum. When the steam generation system operates normally, the operation method includes: If the temperature of the water medium in the water supply pipe is higher than the freezing point of the heat storage medium, the water supply regulating valve is opened and the water supply bypass regulating valve is closed. At this time, the water medium in the water supply pipe enters the steam drum after being heated by the preheater.

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