Molten salt pump outlet pipeline system adopting two-stage closed type check valve and method

Abstract

The invention belongs to the field of tower type photo-thermal power station pipeline systems, and provides a fused salt pump outlet pipeline system adopting a two-stage closed type check valve and a method. The system comprises an upper tower fused salt pipeline system and a heat pump pipeline system, the upper tower fused salt pipeline system comprises a cold salt storage tank, a cold salt pump, an inlet buffer tank, a heat collector and an outlet buffer tank; the heat pump pipeline system comprises a hot salt storage tank, a hot salt pump, a steam generator and a cold salt storage tank; the upper tower fused salt pipeline system and the heat pump pipeline system share one cold salt storage tank; a first two-stage closed check valve is arranged on a pipeline between the cold salt pump and the heat collector; and a second two-stage closed check valve is arranged on the pipeline between the hot salt pump and the steam generator.

Description

Technical Field

[0001] The present invention belongs to the field of tower-type solar thermal power station pipeline systems, and in particular relates to a molten salt pump outlet pipeline system and method using a two-stage closed check valve. Background Art

[0002] The statements in this section merely provide background information related to the present invention and do not necessarily constitute prior art.

[0003] In the molten salt pump outlet pipeline system, due to the high head of the cold salt pump and the hot salt pump, the molten salt medium has a large inertia, and the height difference of the upper tower molten salt pipeline system is large. If the pump is suddenly stopped when the two systems are running, the flow state of the molten salt medium in the pipeline will change sharply, and the salt hammer phenomenon will occur. When the salt hammer phenomenon occurs, it will cause the pipeline to vibrate violently. When the pressure is too high, it will increase the possibility of pipe burst and increase the risk of equipment damage. When the salt hammer phenomenon occurs, the impact force is large. Applying design optimization solutions to reduce the salt hammer force of the two systems has an important impact on ensuring the safe and stable operation of the system.

[0004] Under normal circumstances, at the outlet of the cold salt pump of the upper tower molten salt pipeline system of a tower-type CSP power station, there is no check valve or an ordinary swing check valve is installed, while the outlet of the hot salt pump of the heat pump system is equipped with an ordinary swing check valve. However, not installing a check valve or installing an ordinary swing check valve will cause the following problems:

[0005] (1) The solution of not installing a check valve in the molten salt pipeline system of the upper tower: When the system suddenly stops the pump, the molten salt will flow back to the cold salt pump because the shut-off valve is closed for a long time. If the pump has a small moment of inertia, the pump impeller may overspeed and reverse under the impact of the molten salt. During the overspeed reversal process, the impeller will bear the impact force of the molten salt, which may cause the impeller or other parts to loosen or be damaged in severe cases;

[0006] (2) Installing ordinary swing check valves at the outlets of cold salt pumps and hot salt pumps: When the system stops pumping suddenly, the check valve will also close quickly. At the moment of closing, due to the inlet pressure difference and the reverse flow of large flow, a strong vertical impact force will be instantly generated. The impact load reaches the maximum after the check valve is quickly closed, and the recoil force will act entirely on the check valve. In severe cases, it may cause the check valve to rupture. Summary of the invention

[0007] In order to solve the technical problems existing in the above-mentioned background technology, the present invention provides a molten salt pump outlet pipeline system and method using a two-stage closed check valve, which can effectively reduce the salt hammer force, reduce the civil foundation and structural load, reduce the project cost, and improve the safety and stability of the operation of the solar thermal power station, which has important economic value and safety benefits to the solar thermal power station.

[0008] In order to achieve the above object, the present invention adopts the following technical solution:

[0009] A first aspect of the present invention provides a molten salt pump outlet piping system using a two-stage closing check valve.

[0010] A molten salt pump outlet pipeline system using a two-stage closed check valve comprises: an upper tower molten salt pipeline system and a heat pump pipeline system; the upper tower molten salt pipeline system comprises a cold salt storage tank, a cold salt pump, an inlet buffer tank, a heat collector and an outlet buffer tank; the heat pump pipeline system comprises a hot salt storage tank, a hot salt pump, a steam generator and a cold salt storage tank; the upper tower molten salt pipeline system and the heat pump pipeline system share a cold salt storage tank; a first two-stage closed check valve is arranged on the pipeline between the cold salt pump and the heat collector; a second two-stage closed check valve is arranged on the pipeline between the hot salt pump and the steam generator.

[0011] As an embodiment, the first two-stage closed check valve and the second two-stage closed check valve have the same structure.

[0012] As an implementation mode, the initial states of the first two-stage closed check valve and the second two-stage closed check valve are both in a maximum opening state.

[0013] As an implementation mode, the first stage is entered when the first two-stage closed check valve and the second two-stage closed check valve begin to close.

[0014] As an implementation mode, the first stage of the first two-stage closed check valve and the second two-stage closed check valve causes the corresponding closed check valve to be closed to a set opening, and the remaining opening of the corresponding closed check valve is completely closed in the second stage.

[0015] As an implementation method, the closing time determination process of the first stage and the second stage of the first two-stage closed check valve is as follows:

[0016] By changing the first and second stage closing time of the first two-stage closed check valve, the pressure and salt hammer force of the upper tower cold salt pipeline system under different closing time combinations are obtained;

[0017] The time combination with the minimum system pressure and salt hammer force is taken as the closing time of the first stage and the second stage of the first two-stage closed check valve.

[0018] As an implementation method, the closing time determination process of the first stage and the second stage of the second two-stage closed check valve is as follows:

[0019] By changing the closing time of the first and second stages of the second two-stage closed check valve, the pressure and salt hammer force of the heat pump pipeline system under different closing time combinations are obtained;

[0020] The time combination with the minimum system pressure and salt hammer force is taken as the closing time of the first stage and the second stage of the second two-stage closed check valve.

[0021] As an implementation mode, the closing time of the first stage of the first two-stage closed check valve and the second two-stage closed check valve is 2-7s and the corresponding closed check valve is closed by 70%-80%.

[0022] As an implementation manner, the closing time of the second stage of the first two-stage closed check valve and the second two-stage closed check valve is 10-30 seconds and the corresponding closed check valves are closed by a remaining 20%-30%.

[0023] A second aspect of the present invention provides a control method for a molten salt pump outlet pipeline system using a two-stage closing check valve.

[0024] A control method for a molten salt pump outlet pipeline system using a two-stage closed check valve, comprising:

[0025] By changing the closing time of the first and second stages of the corresponding two-stage closed check valve, the pressure and salt hammer force of the molten salt pump outlet pipeline system under different closing time combinations are obtained.

[0026] Take the time combination with the minimum system pressure and salt hammer force as the closing time of the first stage and the second stage of the corresponding two-stage closed check valve;

[0027] Check whether the cold salt pump or hot salt pump stops working;

[0028] If the cold salt pump or the hot salt pump stops working, the corresponding two-stage closed check valve is controlled to perform corresponding actions according to the closing time of the first stage and the second stage of the two-stage closed check valve corresponding to the stopped pump.

[0029] The beneficial effects of the present invention are:

[0030] The present invention arranges a first two-stage closed check valve on the pipeline between the cold salt pump and the collector, and arranges a second two-stage closed check valve on the pipeline between the hot salt pump and the steam generator. The first stage of the two-stage closed check valve is used to close the valve to a small opening in a very short time, thereby cutting off most of the molten salt fluid and effectively controlling the reverse flow of the molten salt medium and the reversal rate of the molten salt pump. The second stage valve begins to close slowly until it is fully closed, thereby solving the problem of large salt hammer force in the outlet pipeline system of the molten salt pump, reducing the risk of pipeline vibration, avoiding damage to equipment such as pump bodies and valves, and improving the safety and stability of the operation of the solar thermal power station. The present invention can be promoted and applied in tower solar thermal power station projects.

[0031] Advantages of additional aspects of the present invention will be given in part in the following description, and in part will become obvious from the following description, or will be learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0032] The accompanying drawings in the specification, which constitute a part of the present invention, are used to provide a further understanding of the present invention. The exemplary embodiments of the present invention and their descriptions are used to explain the present invention and do not constitute improper limitations on the present invention.

[0033] Figure 1 Schematic diagram of the structure of a molten salt pump outlet pipeline system using a two-stage closed check valve according to an embodiment of the present invention;

[0034] Figure 2 It is a schematic diagram of the working process of the two-stage closing check valve according to an embodiment of the present invention.

[0035] Among them, 1. cold salt storage tank, 2. cold salt pump, 3. check valve, 4. shut-off valve, 5. inlet buffer tank, 6. collector, 7. outlet buffer tank, 8. hot salt storage tank, 9. hot salt pump, 10. steam generator. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with the accompanying drawings and embodiments.

[0037] It should be noted that the following detailed descriptions are all illustrative and intended to provide further explanation of the present invention. Unless otherwise specified, all technical and scientific terms used herein have the same meanings as those commonly understood by those skilled in the art to which the present invention belongs.

[0038] It should be noted that the terms used herein are only for describing specific embodiments and are not intended to limit exemplary embodiments according to the present invention. As used herein, unless the context clearly indicates otherwise, the singular form is also intended to include the plural form. In addition, it should be understood that when the terms "comprising" and / or "including" are used in this specification, it indicates the presence of features, steps, operations, devices, components and / or combinations thereof.

[0039] Terminology explanation:

[0040] The molten salt pump outlet pipeline system refers to the upper tower molten salt pipeline system and the heat pump outlet pipeline system, both of which are important components of the central storage and heat exchange island in the tower-type solar thermal power station.

[0041] The upper tower molten salt pipeline system is composed of cold salt pump, inlet buffer tank, collector, outlet buffer tank and other equipment. Its main working process is as follows: the low-temperature molten salt medium in the cold salt storage tank is pressurized by the cold salt pump at a height of about -2 meters, and enters the collector at a height of about 185m of the heat collecting island through the check valve (if any) and the shut-off valve for heating, and then generates high-temperature molten salt and enters the outlet buffer tank.

[0042] Heat pump pipeline system: It is composed of hot salt pump, steam generator and other equipment. Its main working process is as follows: the high-temperature molten salt medium in the hot salt storage tank is pressurized by the hot salt pump, enters the steam generator through the check valve and shut-off valve to heat water, and is discharged back to the cold salt storage tank after releasing heat.

[0043] Figure 1 Schematic diagram of the structure of the molten salt pump outlet pipeline system using a two-stage closed check valve according to an embodiment of the present invention. Figure 1 As shown, a molten salt pump outlet pipeline system using a two-stage closed check valve in an embodiment of the present invention includes: an upper tower molten salt pipeline system and a heat pump pipeline system; the upper tower molten salt pipeline system includes a cold salt storage tank, a cold salt pump, an inlet buffer tank, a collector and an outlet buffer tank; the heat pump pipeline system includes a hot salt storage tank, a hot salt pump, a steam generator and a cold salt storage tank; the upper tower molten salt pipeline system and the heat pump pipeline system share a cold salt storage tank; a first two-stage closed check valve is arranged on the pipeline between the cold salt pump and the collector; a second two-stage closed check valve is arranged on the pipeline between the hot salt pump and the steam generator.

[0044] In an embodiment of the present invention, the first two-stage closed check valve and the second two-stage closed check valve have the same structure.

[0045] The first two-stage closed check valve and the second two-stage closed check valve both include a rotating shaft and a first weight and a second weight disposed at both ends of the rotating shaft.

[0046] It should be noted here that the first two-stage closed check valve and the second two-stage closed check valve may be equipped with an actuator or without an actuator. When equipped with an actuator, the start and stop of the pump are interlocked with the valve; if not equipped with an actuator, the first two-stage closed check valve and the second two-stage closed check valve automatically start to close due to the impact force of the reverse flow of the medium.

[0047] Among them, when the start and stop of the cold salt pump and the hot salt pump are interlocked with the corresponding check valve, when the pump stops working, the corresponding check valve will start to act.

[0048] In the specific implementation process, the initial states of the first two-stage closed check valve and the second two-stage closed check valve are both in the maximum opening state. The first stage of closing the check valve opening is achieved by setting a block on the weight: In the molten salt pump outlet pipeline system, in order to increase the closing time of the check valve, a weight-type two-stage closed molten salt check valve is used. The main principle is that when the check valve is closed, a reverse torque is applied by the weight to reduce the angular acceleration of the valve disc to achieve a slow closing function.

[0049] When the first two-stage closed check valve and the second two-stage closed check valve begin to close, the first stage is entered. The first stage of the first two-stage closed check valve and the second two-stage closed check valve causes the corresponding closed check valve to be closed to the set opening, and the remaining opening of the corresponding closed check valve is completely closed in the second stage.

[0050] Among them, the closing time determination process of the first stage and the second stage of the first two-stage closed check valve is:

[0051] By changing the first and second stage closing time of the first two-stage closed check valve, the pressure and salt hammer force of the upper tower cold salt pipeline system under different closing time combinations are obtained;

[0052] The time combination with the minimum system pressure and salt hammer force is taken as the closing time of the first stage and the second stage of the first two-stage closed check valve.

[0053] In some embodiments, when the first two-stage closed check valve is closed without an actuator, the upper tower cold salt pipeline system can be dynamically simulated by using fluid resistance analysis software, and the pressure and salt hammer force of the upper tower cold salt pipeline system under different closing time combinations can be obtained by changing the first and second stage closing times of the first two-stage closed check valve.

[0054] In other embodiments, when the first two-stage closed check valve is closed with an actuator, the first and second stage closing times of the first two-stage closed check valve are controlled by the actuator to obtain the pressure and salt hammer force of the upper tower cold salt pipeline system under different closing time combinations.

[0055] Among them, the closing time determination process of the first stage and the second stage of the second two-stage closed check valve is:

[0056] By changing the closing time of the first and second stages of the second two-stage closed check valve, the pressure and salt hammer force of the heat pump pipeline system under different closing time combinations are obtained;

[0057] The time combination with the minimum system pressure and salt hammer force is taken as the closing time of the first stage and the second stage of the second two-stage closed check valve.

[0058] In some embodiments, when the second two-stage closing check valve is closed without an actuator, the heat pump pipeline system can be dynamically simulated by using fluid resistance analysis software, and the pressure and salt hammer force of the heat pump pipeline system under different closing time combinations can be obtained by changing the first and second stage closing times of the second two-stage closing check valve.

[0059] In other embodiments, when the second two-stage closed check valve is closed with an actuator, the first and second stage times of closing the second two-stage closed check valve are controlled by the actuator to obtain the pressure and salt hammer force of the upper tower cold salt pipeline system under different closing time combinations.

[0060] Specifically, the closing time of the first two-stage closed check valve and the second two-stage closed check valve in the first stage is 2-7s, and the corresponding closed check valve is closed by 70%-80%. The closing time of the second stage of the first two-stage closed check valve and the second two-stage closed check valve is 10-30s, and the corresponding closed check valve is closed by the remaining 20%-30%.

[0061] For example, the total closing state of the first two-stage closed check valve or the second two-stage closed check valve is as follows: Figure 2 As shown: the initial position is the fully open position of the valve, at which time the first and second weights are in a naturally drooping and unstressed state. When the valve is closed to 20% opening, only the first weight provides reverse torque. When the valve is opened from 20% to fully closed, the first and second weights provide reverse torque at the same time.

[0062] When the first two-stage closed check valve or the second two-stage closed check valve begins to close, the connecting shaft of the valve plate begins to rotate, and the rotating sleeve on the connecting shaft contacts the block of the first heavy hammer. The rotating shaft drives the first heavy hammer to rotate, and the valve closes and enters the first stage. The first heavy hammer provides reverse torque to the valve plate to slow down the closing speed of the valve in the first stage, and the second heavy hammer is not subjected to force at this time.

[0063] When the connecting shaft of the valve plate rotates to 20% opening, the rotating sleeve on the connecting shaft will contact the rotating shaft, and the rotating shaft drives the second weight to rotate, which means that the valve is closed and enters the second stage. The second weight provides reverse torque to the valve plate. Because the valve plate in the second stage is simultaneously subjected to reverse torques of the first weight and the second weight, the closing time of the first two-stage closed check valve or the second two-stage closed check valve is longer than that of the first stage. The opening dividing point between the first stage and the second stage is achieved by setting the position of the rotating shaft.

[0064] In one or more embodiments, a control method for a molten salt pump outlet pipeline system using a two-stage closed check valve includes:

[0065] By changing the closing time of the first and second stages of the corresponding two-stage closed check valve, the pressure and salt hammer force of the molten salt pump outlet pipeline system under different closing time combinations are obtained.

[0066] Take the time combination with the minimum system pressure and salt hammer force as the closing time of the first stage and the second stage of the corresponding two-stage closed check valve;

[0067] Check whether the cold salt pump or hot salt pump stops working;

[0068] If the cold salt pump or the hot salt pump stops working, the corresponding two-stage closed check valve is controlled to perform corresponding actions according to the closing time of the first stage and the second stage of the two-stage closed check valve corresponding to the stopped pump.

[0069] When the check valve is not equipped with an actuator, the two-stage closing check valve is closed to a certain angle at a certain moment from the pump stopping to the initial backflow of the molten salt medium, so as not to cause excessive changes in salt hammer pressure. When the valve starts to close slowly, the reverse flow is small and the pressure acting on the water pump impeller is also small. Although the slow closing time is long, it will not cause the unit to have a large reverse speed.

[0070] Among them, the two-stage closed check valve can adjust the closing time of the valve appropriately within a certain range according to the actual needs of the project. For example, the dynamic simulation of the upper tower cold salt pipeline system shows that when the fast-closing check valve is selected, the full closing time is 2s, and the salt hammer force of the longest pipe section of the cold salt pump outlet pipeline system is about 8t; when the two-stage closed check valve is selected, the first stage is fast closed to 20%, the time is set to 2s, and the second stage is slow closed, the time is set to 15s, and the salt hammer force of the longest pipe section of the system is about 2t. It can be seen that the salt hammer force of the system is significantly reduced.

[0071] The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and variations. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included in the protection scope of the present invention.

Claims

1. A molten salt pump outlet pipeline system using a two-stage closed check valve, comprising: An upper tower molten salt pipeline system and a heat pump pipeline system; the upper tower molten salt pipeline system includes a cold salt storage tank, a cold salt pump, an inlet buffer tank, a collector and an outlet buffer tank; the heat pump pipeline system includes a hot salt storage tank, a hot salt pump, a steam generator and a cold salt storage tank; the upper tower molten salt pipeline system and the heat pump pipeline system share a cold salt storage tank; it is characterized in that a first two-stage closed check valve is provided on the pipeline between the cold salt pump and the collector; a second two-stage closed check valve is provided on the pipeline between the hot salt pump and the steam generator.

2. The molten salt pump outlet pipeline system using a two-stage closed check valve according to claim 1 is characterized in that: The first two-stage closed check valve and the second two-stage closed check valve have the same structure.

3. The molten salt pump outlet pipeline system using a two-stage closed check valve according to claim 1 is characterized in that: The initial states of the first two-stage closed check valve and the second two-stage closed check valve are both in the maximum opening state.

4. The molten salt pump outlet pipeline system using a two-stage closed check valve according to claim 1 is characterized in that: The first stage is entered when the first two-stage closed check valve and the second two-stage closed check valve begin to close.

5. The molten salt pump outlet pipeline system using a two-stage closed check valve according to claim 4 is characterized in that: The first stage of the first two-stage closed check valve and the second two-stage closed check valve causes the corresponding closed check valve to be closed to a set opening, and the remaining opening of the corresponding closed check valve is completely closed in the second stage.

6. The molten salt pump outlet pipeline system using a two-stage closed check valve according to claim 5, characterized in that: The process of determining the closing time of the first and second stages of the first two-stage closed check valve is as follows: By changing the first and second stage closing time of the first two-stage closed check valve, the pressure and salt hammer force of the upper tower cold salt pipeline system under different closing time combinations are obtained; The time combination with the minimum system pressure and salt hammer force is taken as the closing time of the first stage and the second stage of the first two-stage closed check valve.

7. The molten salt pump outlet pipeline system using a two-stage closed check valve according to claim 5, characterized in that: The process of determining the closing time of the first and second stages of the second two-stage closed check valve is as follows: By changing the closing time of the first and second stages of the second two-stage closed check valve, the pressure and salt hammer force of the heat pump pipeline system under different closing time combinations are obtained; The time combination with the minimum system pressure and salt hammer force is taken as the closing time of the first stage and the second stage of the second two-stage closed check valve.

8. The molten salt pump outlet pipeline system using a two-stage closed check valve according to claim 1, characterized in that: The closing time of the first stage of the first two-stage closed check valve and the second two-stage closed check valve is 2-7s and the corresponding closed check valve is closed by 70%-80%.

9. The molten salt pump outlet pipeline system using a two-stage closed check valve according to claim 1, characterized in that: The closing time of the second stage of the first two-stage closed check valve and the second two-stage closed check valve is 10-30s and the corresponding closed check valve is closed by 20%-30%.

10. A control method for a molten salt pump outlet pipeline system using a two-stage closed check valve according to any one of claims 1 to 9, characterized in that: include: By changing the closing time of the first and second stages of the corresponding two-stage closed check valve, the pressure and salt hammer force of the molten salt pump outlet pipeline system under different closing time combinations are obtained. Take the time combination with the minimum system pressure and salt hammer force as the closing time of the first stage and the second stage of the corresponding two-stage closed check valve; Check whether the cold salt pump or hot salt pump stops working; If the cold salt pump or the hot salt pump stops working, the corresponding two-stage closed check valve is controlled to perform corresponding actions according to the closing time of the first stage and the second stage of the two-stage closed check valve corresponding to the stopped pump.

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