Dry-type vacuum-pumping system for power plant

Abstract

The utility model discloses a dry-type vacuum-pumping system of a power plant, which relates to the technical field of vacuum steam extraction systems and comprises a front cooler, a dry-type screw vacuum pump, a condensate water tank and a controller, the front cooler is connected with an extraction opening of a condenser through a mixed gas inlet pipeline, the mixed gas inlet pipeline is communicated with a shell pass inlet of the front cooler, and the dry-type screw vacuum pump is connected with the condensate water tank. A shell pass gas outlet of the front cooler is connected with the gas inlet end of the dry type screw vacuum pump through an exhaust pipeline, a shell pass liquid outlet of the front cooler is located below the front cooler, and the shell pass liquid outlet of the front cooler is communicated with a liquid inlet of the condensate water tank through a liquid inlet pipeline. A liquid outlet of the condensate pipe is connected with a liquid outlet pipeline, and the dry-type screw vacuum pump is electrically connected with the controller. By adopting the matching mode of the front cooler and the dry type screw vacuum pump, the energy consumption can be effectively reduced, and the working efficiency is high.

Description

Technical Field

[0001] The utility model relates to the technical field of vacuum extraction systems, in particular to a dry vacuum extraction system for power plants. Background Art

[0002] The exhaust steam discharged from the low-pressure cylinder of the steam turbine in the power plant enters the condenser (the exhaust steam in the air-cooled power plant is discharged into the air-cooled island). However, due to the negative pressure operation of the condenser system, dry air inevitably enters the system. If there is no subsequent vacuum extraction system, the pressure in the condenser system will become higher and higher, reducing the power generation efficiency of the steam turbine. Therefore, a vacuum extraction system is needed to timely discharge the air entering the system.

[0003] At present, the vacuum extraction system has gone through four forms: traditional water jet ejectors, steam jet ejectors, liquid ring vacuum pumps, and Roots liquid ring units.

[0004] Among them, the disadvantages of the water jet ejector system include: high energy consumption and low efficiency. Using the Venturi effect, its efficiency is relatively low; the single-stage water jet compression ratio is low, and the vacuum degree is not high; it cannot recover steam condensate, and due to the circulating water quality problem, it may pollute the water and cannot achieve the recovery of steam condensate.

[0005] The disadvantages of the steam jet ejector system include: high energy consumption and waste of steam; due to the limited compression ratio, 2 stages are required to reach a reasonable vacuum degree for the steam turbine; the system is complex and there are potential safety hazards, and the steam jet ejector is at a high temperature (above 100°C); it is difficult to recover steam condensate.

[0006] Due to the principle, the water jet ejector system and the steam jet ejector system have relatively low efficiency (the efficiency is about 10%-20%, the initial investment is low, and the operating cost is high), and they have been basically phased out (only used on small-power steam turbines).

[0007] The disadvantages of the liquid ring mechanical vacuum pump system include: high energy consumption and low efficiency. The liquid ring pump needs to agitate water by the impeller to form a water ring, which wastes limited energy. Its efficiency is generally below 50%; the liquid ring pump system is complex, and it generally uses a separator and a heat exchanger to form a closed system; it cannot recover condensate. The liquid ring pump generally uses overflow, and its condensate cannot be directly used due to pollution.

[0008] The disadvantages of the Roots liquid ring unit system include: the system is complex. Since the Roots pump cannot directly evacuate, it needs to be started gradually, and the control is complex; the compression ratio and pressure difference of the Roots pump are limited. Generally, the compression ratio of the Roots pump is relatively low, and at the same time, the pressure difference of the compressor is 3-5 kPa. It is easily affected by the ultimate vacuum and steam extraction volume of the main pump, the liquid ring pump. Therefore, its vacuum system is prone to losing balance; the outlet temperature of the Roots pump is relatively high, and there may be a situation of high-temperature seizure.

[0009] In existing power plants, water ring vacuum pump systems are mostly used to extract steam. However, due to the inherent factors of the water ring pump, it also leads to higher energy consumption.

[0010] Therefore, there is an urgent need in the art for a new dry vacuum pumping system for power plants to solve the above problems. Utility Model Content

[0011] The purpose of the utility model is to provide a dry vacuum pumping system for a power plant to solve the problems existing in the above-mentioned prior art, effectively reduce the energy consumption of the system, and improve the working efficiency.

[0012] To achieve the above purpose, the utility model provides the following solutions:

[0013] The utility model discloses a dry vacuum pumping system for a power plant, comprising a front cooler, a dry screw vacuum pump, a condensate tank and a controller, wherein the front cooler is connected to the air extraction port of a condenser through a mixed gas intake pipeline, the mixed gas intake pipeline is communicated with the shell side inlet of the front cooler, the shell side gas outlet of the front cooler is connected to the air intake end of the dry screw vacuum pump through an exhaust pipeline, the shell side liquid outlet of the front cooler is located below the front cooler, the shell side liquid outlet of the front cooler is communicated with the liquid inlet of the condensate tank through a liquid intake pipeline, the liquid outlet of the condensate tank is connected with a liquid outlet pipeline, and the dry screw vacuum pump is electrically connected to the controller.

[0014] Preferably, an inlet pneumatic valve is provided on the mixed gas intake pipeline, and the inlet pneumatic valve is electrically connected to the controller.

[0015] Preferably, an inlet valve is provided on the mixed gas intake pipeline.

[0016] Preferably, a pressure transmitter is provided on the exhaust pipeline, and the pressure transmitter is electrically connected to the controller.

[0017] Preferably, a condensate electric-controlled valve is provided on the liquid inlet pipeline, and the condensate electric-controlled valve is electrically connected to the controller.

[0018] Preferably, a drain valve is provided on the liquid outlet pipeline.

[0019] Preferably, the condensed water tank is provided with a vent, and a vacuum valve is provided at the vent.

[0020] Preferably, the condensate tank is provided with a liquid level transmitter, and the liquid level transmitter is electrically connected to the controller.

[0021] Preferably, a temperature transmitter is provided at the air outlet end of the dry screw vacuum pump, and the temperature transmitter is electrically connected to the controller.

[0022] The utility model has achieved the following technical effects compared with the prior art:

[0023] The utility model adopts a system combination with a dry screw vacuum pump and a pre-cooler as the core. The dry screw vacuum pump itself has the advantages of high working efficiency and energy saving. At the same time, the pre-cooler greatly reduces the condensation heat of the steam entering the dry screw vacuum pump, avoiding damage to the dry screw vacuum pump caused by high-temperature steam.

[0024] Furthermore, the pre-cooler and the condensate tank cooperate to be able to recover condensate, meeting the concept of a green device for water conservation required by the country. When treating organic gases in other similar systems, valuable organic solutions can be recovered. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] In order to more clearly illustrate the technical solutions in the embodiments of the present utility model or the prior art, the following will briefly introduce the drawings required for use in the embodiments. Obviously, the drawings described below are only some embodiments of the present utility model. For those of ordinary skill in the art, without creative efforts, other drawings can also be obtained based on these drawings.

[0026] Figure 1 It is a schematic structural diagram of the dry vacuum extraction system for a power plant in an embodiment of the present utility model;

[0027] In the figure: 1 - pre-cooler; 2 - dry screw vacuum pump; 3 - condensate tank; 4 - controller; 5 - inlet valve; 6 - inlet pneumatic valve; 7 - condensate water electric control valve; 8 - vacuum valve; 9 - drain valve; 10 - pressure transmitter; 11 - level transmitter; 100 - dry vacuum extraction system for a power plant; 200 - condenser; 300 - steam turbine; 400 - steam extraction system of water ring pump. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0028] The following will clearly and completely describe the technical solutions in the embodiments of the present utility model with reference to the drawings in the embodiments of the present utility model. Obviously, the described embodiments are only some embodiments of the present utility model, rather than all embodiments. Based on the embodiments of the present utility model, all other embodiments obtained by those of ordinary skill in the art without creative efforts belong to the scope of protection of the present utility model.

[0029] The purpose of the present utility model is to provide a dry vacuum extraction system for a power plant to solve the problems existing in the above-mentioned prior art, which can effectively reduce the energy consumption of the system and improve the working efficiency.

[0030] To make the above-mentioned objects, features, and advantages of the present utility model more obvious and understandable, the present utility model will be further described in detail below with reference to the drawings and specific embodiments.

[0031] As Figure 1 shown, this embodiment provides a dry vacuum pumping system 100 for a power plant, which includes a pre-cooler 1, a dry screw vacuum pump 2, a condensate tank 3, and a controller 4. The pre-cooler 1 is connected to the air extraction port of the condenser 200 (or the air extraction port of the air-cooled island if it is an air-cooled power plant) through a mixed gas inlet pipeline, and the inlet port of the condenser 200 is connected to a steam turbine 300. The pre-cooler 1 has a common heat exchanger structure in the prior art, and its interior includes a shell side and a tube side. The steam and dry air from the condenser 200 flow into the shell side of the pre-cooler 1, while the tube side of the pre-cooler 1 is for condensate to pass through. The condensate is used to exchange heat and cool the mixed gas on the shell side, which can effectively reduce the gas temperature entering the dry screw vacuum pump 2 and can also recover a large amount of condensate in the steam, achieving an excellent water-saving effect. In addition, after the steam enters the pre-cooler 1 and condenses into a liquid, the internal pressure of the pre-cooler 1 will also decrease. Due to its negative pressure effect, it can also actively absorb the mixed gas from the mixed gas inlet pipeline, thus indirectly playing the role of a "pump" to further achieve an energy-saving effect. The specific connection relationship is that the mixed gas inlet pipeline is connected to the shell side inlet at the upper end of the pre-cooler 1, and the shell side gas outlet at the upper end of the pre-cooler 1 is connected to the inlet end of the dry screw vacuum pump 2 through an exhaust pipeline. Here, it should be noted that the dry screw vacuum pump 2 is a prior art technology. It uses the rotation of double screws, making it highly efficient, and its efficiency can reach about 80%. In a 300MW power plant, its operating current is greatly reduced, thus playing an energy-saving role. And the ultimate pressure of the dry screw vacuum pump 2 also far meets the requirements of 3 - 5 kPaA of the condenser 200 in the power plant. In addition, the shell side liquid outlet of the pre-cooler 1 is located below the pre-cooler 1. When the steam in the mixed gas condenses, the condensate accumulates at the bottom of the shell side in the pre-cooler 1 due to its own weight. The shell side liquid outlet of the pre-cooler 1 is connected to the liquid inlet of the condensate tank 3 through a liquid inlet pipeline, and the condensate in the pre-cooler 1 flows into the condensate tank 3 through the liquid inlet pipeline. The liquid outlet of the condensate tank is connected to a liquid outlet pipeline, and the condensate in the condensate tank 3 is discharged through the liquid outlet pipeline, and the discharged condensate can be merged with the condensate in the condenser 200 or collected separately. For the controller 4, the controller 4 is a common background computer, and the background computer is equipped with a DCS system. The dry screw vacuum pump 2 and the controller 4 are electrically connected, and the operation of the dry screw vacuum pump 2 is remotely controlled through the DCS system in the controller 4. The DCS system uses a dynamic load calculation algorithm to dynamically match the power generation (load) of the power plant. The dry screw vacuum pump 2 uses variable frequency control because the existing dry screw vacuum pump 2 comes with a variable frequency motor, which can adjust the air extraction capacity of the dry screw vacuum pump 2, thereby minimizing the operating energy consumption.

[0032] During actual operation, the saturated steam containing a certain amount of dry air in the condenser 200 passes through the precooler 1. The precooler 1 condenses a large amount of water vapor, and the gas after temperature reduction enters the dry screw vacuum pump 2 through the exhaust pipe, thereby discharging the dry air leaking into the system. The steam condensed in the precooler 1 becomes liquid condensate, and the condensate enters the condensate tank 3 through the liquid inlet pipe and is finally discharged to the required equipment through the liquid outlet pipe.

[0033] In this embodiment, an inlet pneumatic valve 6 is provided on the mixed gas inlet pipe. The inlet pneumatic valve 6 is an existing electric control valve, and the inlet pneumatic valve 6 is electrically connected to the controller 4 to control the flow of the mixed gas inlet pipe through the inlet pneumatic valve 6.

[0034] In this embodiment, an inlet valve 5 is provided on the mixed gas inlet pipe. The inlet valve 5 is a manual valve, which is generally in an open state during the operation of the system and is only closed when the entire system is shut down.

[0035] In this embodiment, a pressure transmitter 10 is provided on the exhaust pipe. The pressure transmitter 10 is electrically connected to the controller 4. The pressure transmitter 10 is used to detect the air pressure in the exhaust pipe and transmit the relevant pressure value to the controller 4. The reason for setting the pressure transmitter 10 is that when the inlet pneumatic valve 6 is closed, the air pressure in the exhaust pipe is the same as the atmospheric pressure, and the mixed gas inlet pipe is in a negative pressure state because it is connected to the condenser 200. In the case of a large pressure difference at both ends of the inlet pneumatic valve 6, the inlet pneumatic valve 6 may not be able to open. Therefore, when the inlet pneumatic valve 6 needs to be opened, first start the dry screw vacuum pump 2. The dry screw vacuum pump 2 evacuates the exhaust pipe to reduce its air pressure to be approximately the same as the air pressure at the inlet end of the inlet pneumatic valve 6, and then the controller 4 controls the inlet pneumatic valve 6 to open.

[0036] In this embodiment, a condensate electric control valve 7 is provided on the liquid inlet pipe. The condensate electric control valve 7 is electrically connected to the controller 4, and the controller 4 can control the opening and closing of the condensate electric control valve 7 to control the flow of condensate between the precooler 1 and the condensate tank 3.

[0037] In this embodiment, a drain valve 9 is provided on the liquid outlet pipe to control the flow of condensate in the liquid outlet pipe.

[0038] In this embodiment, the condensate water tank 3 is provided with a vent, and a vacuum valve 8 is provided at the vent. When the vacuum valve 8 is opened, the inside of the condensate water tank 3 will be connected to the external atmospheric pressure. The purpose of setting the vacuum valve 8 is that when the drain valve 9 is opened, since the internal air pressure of the condensate water tank 3 may be relatively small, the internal condensate water of the condensate water tank 3 cannot be discharged through the liquid discharge pipeline. At this time, the vacuum valve 8 needs to be opened. Once the internal air pressure of the condensate water tank 3 is connected to the external air pressure, the internal condensate water can be discharged from the liquid discharge pipeline.

[0039] In this embodiment, a liquid level transmitter 11 is provided on the condensate water tank 3. The liquid level transmitter 11 is electrically connected to the controller 4. The liquid level transmitter 11 is used to detect the liquid level height in the condensate water tank 3 and transmit the detected data to the controller 4. When the liquid level transmitter 11 detects that the liquid level in the condensate water tank 3 is too high, the controller 4 controls the condensate water solenoid valve 7 to close.

[0040] In this embodiment, a temperature transmitter is provided at the outlet end of the dry screw vacuum pump 2. The temperature transmitter is electrically connected to the controller 4. The temperature transmitter is used to detect the temperature at the outlet end of the dry screw vacuum pump 2 and transmit the relevant data to the controller 4. When the temperature transmitter detects that the temperature at the outlet end of the dry screw vacuum pump 2 is too high, it indicates that there may be a problem with a certain device in front of the dry screw vacuum pump 2. The gas at too high a temperature is likely to damage the dry screw vacuum pump 2. Therefore, at this time, the system should be shut down in time and the device with the problem should be repaired.

[0041] This embodiment is an improvement based on the original vacuum extraction steam system. Therefore, the original vacuum extraction steam system is also connected in the condenser 200, as Figure 1 shown, it also includes a water ring pump extraction steam system 400 (of course, it can also be other existing vacuum extraction steam systems). It includes two parallel branches, and each branch is provided with a water ring pump and related valves. It belongs to the existing mature technology, so it will not be elaborated here. And this embodiment is set on this basis. During actual use, when the entire system starts up and operates, turn on the water ring pump extraction steam system 400. After the system runs normally for a short period of time, turn off the water ring pump extraction steam system 400 and turn on the dry vacuum extraction system 100 of the power plant.

[0042] In the present utility model, specific examples are used to elaborate on the principle and implementation manner of the present utility model. The description of the above embodiments is only used to help understand the method and its core idea of the present utility model; at the same time, for those of ordinary skill in the art, according to the idea of the present utility model, there will be changes in the specific implementation manner and application scope. In summary, the content of this specification should not be construed as a limitation to the present utility model.

Claims

1. A dry vacuum pumping system for a power plant, characterized in that: It includes a pre-cooler, a dry screw vacuum pump, a condensate tank and a controller, the pre-cooler is connected to the exhaust port of the condenser through a mixed gas inlet pipeline, the mixed gas inlet pipeline is connected to the shell-side inlet of the pre-cooler, the shell-side gas outlet of the pre-cooler is connected to the intake end of the dry screw vacuum pump through an exhaust pipeline, the shell-side liquid outlet of the pre-cooler is located below the pre-cooler, the shell-side liquid outlet of the pre-cooler is connected to the liquid inlet of the condensate tank through a liquid inlet pipeline, the liquid outlet of the condensate tank is connected to the liquid outlet pipeline, and the dry screw vacuum pump and the controller are electrically connected.

2. The dry vacuum pumping system for a power plant according to claim 1, wherein: An inlet pneumatic valve is arranged on the mixed gas intake pipeline, and the inlet pneumatic valve is electrically connected to the controller.

3. The dry vacuum pumping system for a power plant according to claim 1, wherein: An inlet valve is arranged on the mixed gas intake pipeline.

4. The dry vacuum pumping system for power plants according to claim 1, characterized in that: The exhaust pipeline is provided with a pressure transmitter, and the pressure transmitter is electrically connected to the controller.

5. The dry vacuum pumping system for a power plant according to claim 1, characterized in that: The liquid inlet pipeline is provided with a condensed water electric control valve, and the condensed water electric control valve is electrically connected to the controller.

6. The dry vacuum pumping system for power plants according to claim 1, wherein: A drain valve is arranged on the liquid outlet pipeline.

7. The dry vacuum pumping system for a power plant according to claim 1, wherein: The condensed water tank is provided with a vent, and a vacuum valve is provided at the vent.

8. The dry vacuum pumping system for a power plant according to claim 1, characterized in that: The condensed water tank is provided with a liquid level transmitter, and the liquid level transmitter is electrically connected to the controller.

9. The dry vacuum pumping system for a power plant according to claim 1, characterized in that: A temperature transmitter is provided at the gas outlet end of the dry screw vacuum pump, and the temperature transmitter is electrically connected to the controller.

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