Marine steam turbine drainage system

Abstract

The invention relates to a marine steam turbine drainage system which comprises a main steam pipeline and a machine warming branch, and the main steam pipeline comprises a temperature sensor, a pressure sensor, a drainage distribution valve, an isolating valve and a main steam valve; main steam is divided into two paths through a drainage distribution valve, wherein one path is connected with a steam turbine through an isolating valve, a pressure reducing pore plate and a heating valve; the other path is connected with a main throttle valve; the drain distribution valve is a three-way valve and can be switched to connect the main steam pipeline to the isolating valve or the main steam valve; the warming-up branch comprises a dehumidification device, a pressure reduction pore plate, a warming-up valve and a steam trap; the dehumidification device is connected in series to a pipeline between the isolating valve and the pressure reducing pore plate and is connected with the steam turbine through a steam trap; the decompression pore plate is connected with a turbine through a heating valve. According to the method, high-humidity and low-pressure low-parameter steam in the starting stage can be effectively utilized. And the service life of the steam turbine is prolonged, and the maneuvering performance of the steam turbine is improved.

Description

Technical Field

[0001] The invention relates to the technical field of marine power equipment, in particular to a novel drain system which shortens the warm-up time of a steam turbine by optimizing the utilization of low-parameter steam. Background Art

[0002] Marine steam turbines are key equipment in marine power and electrical systems and are one of the important prime movers on board.

[0003] Marine steam turbines need to be warmed up for a long time when they are started in cold state. That is, dry steam with less flow and higher temperature is introduced into the flow structure of the steam turbine through the main steam valve and regulating valve, so that the temperature of the turbine cylinder and rotor gradually rises. Warming up can effectively release the thermal stress of the steam turbine during cold start and increase the service life of the steam turbine.

[0004] The shipboard steam system supplies steam to the steam turbine. During the process of the system starting from cold state to outputting rated steam parameters, there is a long period of time when the steam output pressure is low and the dryness is low. Although this steam has a certain temperature, it cannot be used for turbine warm-up. If the steam turbine is started (the main steam valve is opened) when the steam parameters have not reached the rated value, wet steam will enter the steam turbine, which is very likely to cause water hammer accidents and damage the turbine bearings and blades.

[0005] Therefore, low-parameter steam is generally returned to the boiler directly after the residual water vapor in the pipeline is purged and reused. The machine can only be started after the steam parameters reach the rated parameters and the steam is dry steam, so that a small amount of steam can enter the turbine for warming up. For example, the schematic diagram of traditional steam pipeline and drainage management ( Figure 1 shown). Figure 1 The pressure sensor 21, temperature sensor 22, steam trap 23, main steam valve 24, and steam turbine 25 are shown in the figure. The pressure sensor and temperature sensor are used to determine whether the steam parameters have reached the rated parameters. If the rated parameters have not been reached, the steam trap is opened to allow low-parameter steam to return to the system. After the steam reaches the parameters, the main steam valve is opened, the steam trap is closed, and the steam turbine starts to warm up.

[0006] Traditional marine steam turbines need to wait until the steam parameters meet the standards before they can be warmed up, resulting in a long start-up time. For example, Patent Publication No.: CN107559077A relates to a marine steam turbine start-up warm-up control system, which monitors steam parameters in real time through pressure sensors and temperature sensors, and controls the timing of the main steam valve opening to prevent wet steam from entering the turbine. The disadvantage is that warm-up relies on high-parameter dry steam, and low-parameter steam cannot be used, resulting in a long warm-up time. Although the existing drain system can separate water, it does not solve the problem of recycling low-parameter steam. For example, Patent Publication No.: JP2019127236A discloses a steam turbine drain device, which uses a multi-stage dehumidification grid to separate water from wet steam and discharges condensed water through a drain valve. It does not involve the technology of pre-warming the machine through low-parameter steam, and does not integrate a pressure reducing orifice to optimize steam dryness. For example, the adaptive pressure reducing valve structure disclosed in patent publication number: US20200049121A1 realizes steam pressure regulation by dynamically adjusting the orifice plate opening, but the valve switching logic is not designed in combination with the warm-up process, and the recycling of low-parameter steam cannot be realized. In addition, the pressure reduction control accuracy is insufficient.

[0007] Therefore, it is necessary to design a new marine steam turbine drain system to achieve efficient warm-up by integrating multi-stage valves and parameter feedback control. Summary of the invention

[0008] The present invention proposes a novel marine steam turbine drain system, which can effectively utilize low-parameter steam with high humidity and low pressure during the startup phase, shorten the turbine warm-up time, increase the turbine service life, and improve the turbine maneuverability.

[0009] To achieve the above object, the technical solution of the present invention is: a marine steam turbine drain system, comprising: a main steam pipeline, a warm-up branch,

[0010] The main steam pipeline includes a temperature sensor, a pressure sensor, a drain distribution valve, a block valve, and a main steam valve; the main steam is divided into two paths through the drain distribution valve: one path is connected to the steam turbine through the block valve, the pressure reducing orifice plate, and the warm-up valve; the other path is connected to the main steam valve; the drain distribution valve is a three-way valve, which can switch to connect the main steam pipeline to the block valve or the main steam valve;

[0011] The warm-up branch includes a dehumidification device, a pressure reducing orifice plate, a warm-up valve, and a steam trap; the dehumidification device is connected in series to the pipeline between the isolation valve and the pressure reducing orifice plate, and is connected to the steam turbine through the steam trap; the pressure reducing orifice plate is connected to the steam turbine through the warm-up valve.

[0012] Furthermore, the warm-up valve is a three-state valve, connecting the downstream of the pressure reducing orifice plate to the exhaust cylinder, the flow structure or the closed pipeline.

[0013] Furthermore, the dehumidification device is built with a multi-layer corrugated dehumidification grid, the inlet is connected to the isolation valve, and the outlet is divided into two routes: one route is through the steam trap to the discharge cylinder, and the other route is through the pressure reducing orifice plate to the warm-up valve.

[0014] Furthermore, the aperture of the pressure reducing orifice is designed according to the rated parameters of the steam turbine, so that the steam dryness is increased to a supercritical state after the steam pressure is reduced.

[0015] Furthermore, the valve stem position of the warm-up valve is controlled by feedback signals from a downstream temperature sensor and a pressure sensor.

[0016] Furthermore, a ground sealing surface is used between the valve stem and the housing of the drain distribution valve to ensure no steam leakage.

[0017] Furthermore, during the cold start phase of the steam turbine, the drain distribution valve directs the steam to the warm-up branch, while the warm-up valve switches the reduced-pressure steam to the cylinder discharge or flow structure to achieve staged preheating.

[0018] A control method based on a marine steam turbine drain system comprises the following steps:

[0019] (1) Detect the temperature and pressure of the main steam pipeline;

[0020] (2) When the steam is wet steam, open the drain distribution valve to the warm-up branch and adjust the steam parameters through the dehumidification device and the pressure reducing orifice plate;

[0021] (3) When the steam reaches dry steam conditions after decompression, switch the warm-up valve to the flow structure for pre-warming.

[0022] Furthermore, after the turbine reaches the preheating threshold, the warm-up branch is closed and the drain distribution valve is switched to the main steam valve to achieve rapid startup.

[0023] Furthermore, after the system operates normally, the two isolation valves are closed to block the leakage of the drain branch.

[0024] The beneficial effects of the present invention are:

[0025] The present invention proposes a novel marine steam turbine drain system, which can effectively utilize the low-parameter steam with high humidity and low pressure during the startup phase by adopting a drain distribution valve, a dehumidification device, a steam trap, a pressure reducing orifice plate and a warm-up valve. The warm-up time of the steam turbine is shortened, the service life of the steam turbine is increased, and the maneuverability of the steam turbine is improved. Among them, the dryness of the low-parameter steam is increased to a usable level through the combination of a three-way valve and a pressure reducing orifice plate; a valve control strategy based on sensor feedback is adopted to achieve leakage-free switching; and staged preheating reduces the thermal stress of the steam turbine by 50% and prolongs its service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1It is a schematic diagram of traditional steam pipeline and drain pipeline;

[0027] Figure 2 It is the overall structural diagram of the marine steam turbine drain system of the present invention;

[0028] Figure 3 It is a schematic diagram of the structure of the steam trap distribution valve;

[0029] Figure 4 There are two working states of the steam trap distribution valve;

[0030] Figure 5 It is a schematic diagram of the warm-up valve structure;

[0031] Figure 6 It is the principle of switching between three working states of the warm-up valve;

[0032] Figure 7 It is the internal grille layout of the dehumidifier. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] like Figure 2 As shown, a novel marine steam turbine drain system proposed in an embodiment of the present invention is composed of temperature sensors 1, 2 1, 7, pressure sensors 1, 2 2, 8, a drain distribution valve 3, isolation valves 1, 2 4, 12, a dehumidification device 5, a pressure reducing orifice 6, a drain valve 9, a main steam valve 10, a warm-up valve 11, etc.

[0035] Among them: the main steam pipeline includes temperature sensor 1, pressure sensor 2, drain distribution valve 3, isolation valve 1 4 and isolation valve 2 12, and main steam valve 10. One steam outlet of the drain distribution valve 3 is connected to the steam turbine through isolation valve 1 4, pressure reducing orifice 6, warm-up valve 11, and isolation valve 2 12. The other steam outlet of the drain distribution valve 3 is connected to the main steam valve 10.

[0036] The drain distribution valve 3 is a three-way valve that can switch to connect the main steam pipeline to the isolation valve 4 or the main steam valve 10.

[0037] The warm-up branch includes a dehumidifier 5, a pressure reducing orifice 6, a warm-up valve 11, and a steam trap 9. The dehumidifier 5 is connected in series to the pipeline between the isolation valve 4 and the pressure reducing orifice 6, and is connected to the steam turbine through the steam trap 9; the pressure reducing orifice 6 is connected to the steam turbine through the warm-up valve 11.

[0038] like Figure 3 As shown, the drain distribution valve 3 is composed of a base plate 3-1, a shell 3-2, a valve stem 3-3 and an actuator 3-4. The valve stem 3-3 placed in the base plate 3-1 and the shell 3-3 is connected to the actuator 3-4.

[0039] The steam distribution valve 3 has two working states: the valve stem 3-3 moves to the top, and the steam inlet is connected to the isolation valve 4 interface; the valve stem 3-3 moves to the bottom, and the steam inlet is connected to the main steam valve 10. It is essentially a three-way valve. There is a grinding surface 3-5 between the valve stem 3-3 and the bottom plate 3-1 and the shell 3-3 to ensure that steam will not leak. Figure 4 Two working states are given in the figure: (a) the valve stem is at the top and (b) the valve stem is at the bottom.

[0040] like Figure 5 As shown, the warm-up valve 11 is composed of a warm-up valve bottom plate 11-1, a sleeve 11-2, a warm-up valve housing 11-3, a sleeve valve stem 11-4 and a warm-up valve actuator 11-5. The upper end of the warm-up valve housing 11-3 is fixedly connected to the warm-up valve bottom plate 11-1, and the sleeve valve stem 11-4 is connected to the warm-up valve actuator 11-5 through the sleeve 11-2.

[0041] The warm-up valve 11 has three working states. When the valve stem moves to the bottom, the downstream interface of the pressure reducing orifice plate 6 is connected to the discharge cylinder; when the valve stem moves to the top, the downstream interface of the pressure reducing orifice plate 6 is connected to the flow. Figure 6 Three working states are given in the figure: (a) valve stem to the bottom, (b) valve stem to the top, and (c) valve stem to the middle.

[0042] like Figure 7 As shown, the dehumidification device 5 is composed of a dehumidification grid 5-1 and a shell 5-2, and has three interfaces, the inlet is from a blocking valve 4, and the outlet leads to a steam trap 9 and a pressure reducing orifice plate 6.

[0043] When working, the marine steam turbine drain system of the present invention controls the drain distribution valve 3 through the readings of the pressure sensor 2 and the temperature sensor 1. In the startup stage, the steam pressure is low, the temperature is low, and the steam is wet steam. At this time, the drain distribution valve 3 connects the steam inlet with the isolation valve 4, and the steam flows to the isolation valve 4. The low-parameter steam enters the dehumidification device 5 through the isolation valve 4, and the entrained water droplets enter the turbine exhaust cylinder through the drain device 9, and enter the condenser through the exhaust cylinder to re-circulate the water vapor, and the low-parameter steam dryness increases. Then the steam passes through the pressure reducing orifice 6, the steam enthalpy value remains unchanged, the pressure drops, and the dryness increases accordingly.

[0044] The steam parameters after the pressure reducing orifice are monitored by the pressure sensor 28 and the temperature sensor 27. When the steam temperature is low and is saturated steam or wet steam, the warm-up valve 11 is connected to the downstream of the pressure reducing orifice 6 and the discharge cylinder, and the wet steam enters the discharge cylinder to heat the discharge cylinder. As the system starts, the steam parameters gradually rise. When the steam reaches dry steam through the pressure sensor 28 and the temperature sensor 27, the warm-up valve 11 is connected to the downstream of the pressure reducing orifice 6 and the inlet cylinder, and the steam turbine starts to rotate. The steam turbine uses this low-pressure, high-temperature dry steam for warming up.

[0045] As the steam parameters continue to rise, the steam detected by the pressure sensor 2 and the temperature sensor 1 changes from wet steam to dry steam. At this time, the valve stem of the warm-up valve 11 moves to the middle position, and the drain pipe is closed. The drain distribution valve 3 connects the steam inlet and the main steam valve 10, and the steam turbine is ready for startup. Start the unit, and the main steam valve 10 opens accordingly. Since the steam turbine has been fully preheated, the startup time can be greatly shortened.

[0046] After the unit is operating normally, close isolation valves 1, 2, 4, and 12 to ensure that there is no steam leakage in the drain pipeline.

[0047] The drain distribution valve, warm-up valve, dehumidification device, isolation valve, pressure reducing orifice plate and steam trap are all conventional structures or mature equipment. They are connected with pipelines, and the drain distribution valve and warm-up valve are controlled by the readings of pressure sensors and temperature sensors to realize the drain system.

Claims

1. A marine steam turbine drain system, characterized in that: include: Main steam pipeline, warm-up branch, The main steam pipeline includes a temperature sensor, a pressure sensor, a drain distribution valve, a block valve, and a main steam valve; the main steam is divided into two paths through the drain distribution valve: one path is connected to the steam turbine through the block valve, the pressure reducing orifice plate, and the warm-up valve; the other path is connected to the main steam valve; the drain distribution valve is a three-way valve, which can switch to connect the main steam pipeline to the block valve or the main steam valve; The warm-up branch includes a dehumidification device, a pressure reducing orifice plate, a warm-up valve, and a steam trap; the dehumidification device is connected in series to the pipeline between the isolation valve and the pressure reducing orifice plate, and is connected to the steam turbine through the steam trap; the pressure reducing orifice plate is connected to the steam turbine through the warm-up valve.

2. The marine steam turbine drain system according to claim 1, characterized in that: The warm-up valve is a three-state valve, which connects the downstream of the pressure reducing orifice plate to the discharge cylinder, the flow structure or the closed pipeline.

3. The marine steam turbine drain system according to claim 1, characterized in that: The dehumidification device is built with a multi-layer corrugated dehumidification grid, the inlet is connected to the isolation valve, and the outlet is divided into two routes: one route is through the steam trap to the discharge cylinder, and the other route is through the pressure reducing orifice plate to the warm-up valve.

4. The marine steam turbine drain system according to claim 1, characterized in that: The aperture of the pressure reducing orifice is designed according to the rated parameters of the steam turbine so that the steam dryness is increased to a supercritical state after the steam pressure is reduced.

5. The marine steam turbine drain system according to claim 2, characterized in that: The valve stem position of the warm-up valve is controlled by feedback signals from a downstream temperature sensor and a pressure sensor.

6. The marine steam turbine drain system according to claim 1, characterized in that: A ground sealing surface is used between the valve stem and the housing of the steam trap distribution valve to ensure no steam leakage.

7. The marine steam turbine drain system according to claim 1, characterized in that: During the cold start phase of the steam turbine, the drain distribution valve directs the steam to the warm-up branch, while the warm-up valve switches the reduced-pressure steam to the cylinder discharge or flow structure to achieve staged preheating.

8. A control method for a marine steam turbine drain system according to any one of claims 1 to 7, characterized in that: The following steps are involved: (1) Detect the temperature and pressure of the main steam pipeline; (2) When the steam is wet steam, open the drain distribution valve to the warm-up branch and adjust the steam parameters through the dehumidification device and the pressure reducing orifice plate; (3) When the steam reaches dry steam conditions after decompression, switch the warm-up valve to the flow structure for pre-warming.

9. The method according to claim 8, characterized in that After the turbine reaches the preheating threshold, close the warm-up branch and switch the drain distribution valve to the main steam valve to achieve rapid startup.

10. The method according to claim 8, characterized in that After the system is operating normally, close the two isolation valves to block the leakage of the drain branch.

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