Backpressure control device of indirect air-cooled condensing steam turbine
By designing an indirect air-condensing steam turbine backpressure control device in the turbine, the single and double backpressure switching is achieved, and the problems of water corrosion and vibration increase of the last-stage blade of the turbine are solved, coal consumption is reduced, and economy and safety are improved.
Patent Information
- Application Number
- CN202420772026.7
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-04-15
- Publication Date
- 2025-03-21
- Estimated Expiration
- 2034-04-15
AI Technical Summary
When the turbine runs at the end stage of the low-pressure cylinder, water corrosion and vibration increase are prone to increased water corrosion and vibration increase. When the ambient temperature is low in winter, the circulating water temperature regulation is restricted by blocked back pressure, resulting in an increase in coal consumption of the unit and a decrease in economic efficiency.
A backpressure control device for indirect air condenser steam turbine is designed, including a low-pressure side condenser, a high-pressure side condenser, a vacuum pump and a control valve. By setting up two sets of control valves, the single and double backpressure switching is realized, and the condenser backpressure is controlled to ensure the economic and safety of the unit.
Through single and double backpressure switching, the overload and water corrosion risk of the end-stage blades of the low-pressure cylinder of the turbine is reduced, the coal consumption of the unit is reduced, and economic and safety is improved.
Smart Images
Figure CN222650043U_ABST
Abstract
Description
Technical Field
[0001] The utility model relates to the field of steam turbine back pressure control, in particular to an indirect air-cooled condensing steam turbine back pressure control device. Background Art
[0002] The blocking back pressure of a steam turbine refers to the back pressure when the steam velocity at the outlet of the last stage blade of the steam turbine is close to the sonic level at that location. The Mach number of the sonic level is about 0.95. It is related to the steam inlet of the steam turbine. Different steam inlet has different blocking back pressure values. When the back pressure of the steam turbine condenser is reduced, the cycle thermal efficiency is increased, and the steam inlet of the steam turbine can be reduced under the same power generation, but there is a limit value, which is the blocking back pressure of the steam turbine. When the back pressure of the steam turbine is lower than the blocking back pressure, the result of reducing the back pressure is that the steam inlet of the steam turbine under the same power generation will increase. The reason is: the additional loss caused by the turbulent expansion of steam in the last stage blade. At the same time, the decrease in the back pressure of the low-pressure condenser is accompanied by a decrease in the exhaust temperature. After the steam in the low-pressure cylinder does work, the superheated steam may be converted into saturated steam or even wet steam, causing water erosion of the last stage blade of the low-pressure cylinder of the steam turbine. The turbulent steam flow formed after the last stage blade may also cause the vibration of the steam turbine to increase, posing a threat to the safe operation of the steam turbine. In order to ensure the safe operation of the last stage blades of the turbine and the economical operation of the unit, the condenser back pressure must be higher than the corresponding load blocking value during daily operation.
[0003] The ambient temperature is low in winter, and the circulating water temperature can be adjusted over a wide range. However, due to the limitation of blocked back pressure, the operating personnel need to close the cooling shutters to increase the circulating water temperature control back pressure value. This operation causes the average back pressure of the unit to increase, the coal consumption of the unit to increase, and the economy to decrease. Utility Model Content
[0004] In order to overcome the deficiencies of the prior art, the purpose of the utility model is to provide an indirect air-cooled condensing steam turbine back pressure control device, which ensures the economy of the unit while also ensuring the safe operation of the last stage blades of the low-pressure cylinder of the turbine.
[0005] To achieve the above purpose, the utility model provides the following solutions:
[0006] An indirect air-cooled condensing steam turbine back pressure control device, comprising: a low-pressure side condenser, a high-pressure side condenser, a second vacuum pump, a first vacuum pump connected to the high-pressure side condenser, a third vacuum pump connected to the low-pressure side condenser, a first control valve connected to the high-pressure side condenser and the second vacuum pump, respectively, and a second control valve connected to the second vacuum pump and the low-pressure side condenser, respectively;
[0007] The low-pressure side condenser and the high-pressure side condenser are used to cool the input high-temperature exhaust steam; the first vacuum pump, the second vacuum pump and the third vacuum pump are all used to extract non-condensable gases in the low-pressure side condenser and the high-pressure side condenser; the first control valve is used to control the conduction between the high-pressure side condenser and the second vacuum pump; the second control valve is used to control the conduction between the second vacuum pump and the low-pressure side condenser; the working states of the first control valve and the second control valve include: normally closed state and normally open state.
[0008] Preferably, the circulating water pipeline is connected to the outer walls of the low-pressure side condenser and the high-pressure side condenser in sequence;
[0009] The circulating water pipeline is used to provide a cooling water source for the low-pressure side condenser and the high-pressure side condenser through a circulating water pump.
[0010] Preferably, the high-pressure side condenser and the low-pressure side condenser are both double-shell, double-back-pressure, single-flow and regenerative condensers.
[0011] Preferably, the high-pressure side condenser and the low-pressure side condenser are respectively connected to the low-pressure cylinder;
[0012] The low-pressure cylinder is used to provide the high-temperature exhaust steam to the high-pressure side condenser and the low-pressure side condenser.
[0013] Preferably, a central controller; the central controller is respectively connected to the high-pressure side condenser, the low-pressure side condenser, the first control valve, the second control valve and the circulating water pipe;
[0014] The central controller is used to collect operation data; the operation data includes: ambient temperature data, wind speed data, start and stop data of the circulating water pump, and back pressure data of the high-pressure side condenser and the low-pressure side condenser.
[0015] Preferably, the central controller has a built-in touch screen; the touch screen is used to display the operating data and collect control commands from staff on the switches of the first control valve and the second control valve.
[0016] According to the specific embodiments provided by the utility model, the utility model discloses the following technical effects:
[0017] The utility model provides an indirect air-cooled condensing steam turbine back pressure control device, belonging to the field of steam turbine back pressure control; comprising: a low-pressure side condenser, a high-pressure side condenser, a second vacuum pump, a first vacuum pump connected to the high-pressure side condenser, a third vacuum pump connected to the low-pressure side condenser, a first control valve connected to the high-pressure side condenser and the second vacuum pump respectively, and a second control valve connected to the second vacuum pump and the low-pressure side condenser respectively; the first control valve is used to control the conduction between the high-pressure side condenser and the second vacuum pump; the second control valve is used to control the conduction between the second vacuum pump and the low-pressure side condenser; the working states of the first control valve and the second control valve include: a normally closed state and a normally open state. The utility model ensures the economic efficiency of the unit and also ensures the safe operation of the last stage blades of the low-pressure cylinder of the steam turbine by setting two groups of control valves. BRIEF DESCRIPTION OF THE DRAWINGS
[0018] In order to more clearly illustrate the embodiments of the utility model or the technical solutions in the prior art, the drawings required for use in the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the utility model. For ordinary technicians in this field, other drawings can be obtained based on these drawings without paying creative labor.
[0019] Figure 1 A structural diagram of a gas condensation system provided in an embodiment of the utility model;
[0020] Figure 2 A diagram showing the effect of switching between single and double back pressures provided by an embodiment of the utility model;
[0021] Figure 3 A comparison diagram before and after the optimization operation provided in an embodiment of the utility model.
[0022] Description of reference numerals:
[0023] 1- low-pressure side condenser, 2- high-pressure side condenser, 3- third vacuum pump, 4- first vacuum pump, 5- second vacuum pump, 6- second control valve, 7- first control valve. DETAILED DESCRIPTION
[0024] The following will be combined with the drawings in the embodiments of the utility model to clearly and completely describe the technical solutions in the embodiments of the utility model. Obviously, the described embodiments are only part of the embodiments of the utility model, not all of the embodiments. Based on the embodiments in the utility model, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the utility model.
[0025] The utility model aims to provide a back pressure control device for an indirect air-cooled condensing steam turbine, which ensures the economic efficiency of the unit and also ensures the safe operation of the last stage blades of the low-pressure cylinder of the steam turbine.
[0026] In order to make the above-mentioned purposes, features and advantages of the present invention more obvious and easy to understand, the present invention is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.
[0027] Figure 1 is the structure diagram of the condensing system, such as Figure 1 As shown, the utility model provides an indirect air-cooled condensing steam turbine back pressure control device, comprising: a low-pressure side condenser, a high-pressure side condenser, a second vacuum pump, a first vacuum pump connected to the high-pressure side condenser, a third vacuum pump connected to the low-pressure side condenser, a first control valve connected to the high-pressure side condenser and the second vacuum pump respectively, and a second control valve connected to the second vacuum pump and the low-pressure side condenser respectively;
[0028] The low-pressure side condenser and the high-pressure side condenser are used to cool the input high-temperature exhaust steam; the first vacuum pump, the second vacuum pump and the third vacuum pump are all used to extract non-condensable gases in the low-pressure side condenser and the high-pressure side condenser; the first control valve is used to control the conduction between the high-pressure side condenser and the second vacuum pump; the second control valve is used to control the conduction between the second vacuum pump and the low-pressure side condenser; the working states of the first control valve and the second control valve include: normally closed state and normally open state.
[0029] Further, the circulating water pipeline is connected to the outer walls of the low-pressure side condenser and the high-pressure side condenser in sequence;
[0030] The circulating water pipeline is used to provide a cooling water source for the low-pressure side condenser and the high-pressure side condenser through a circulating water pump.
[0031] Specifically, the high-pressure side condenser and the low-pressure side condenser are both double-shell, double-back-pressure, single-flow and regenerative condensers.
[0032] Further, the high-pressure side condenser and the low-pressure side condenser are respectively connected to the low-pressure cylinder;
[0033] The low-pressure cylinder is used to provide the high-temperature exhaust steam to the high-pressure side condenser and the low-pressure side condenser.
[0034] Optionally, a central controller; the central controller is respectively connected to the high-pressure side condenser, the low-pressure side condenser, the first control valve, the second control valve and the circulating water pipe;
[0035] The central controller is used to collect operation data; the operation data includes: ambient temperature data, wind speed data, start / stop data of the circulating water pump, and back pressure data of the high-pressure side condenser and the low-pressure side condenser.
[0036] Optionally, the central controller is embedded with a touch screen; the touch screen is used to display the operation data and collect control commands from the staff for the opening and closing of the first control valve and the second control valve.
[0037] Specifically, the exhaust comes from a steam turbine of the type of high-efficiency ultra-supercritical, once-through reheat, four-cylinder four-exhaust, single-shaft, double-back pressure and indirect air-cooled reaction condensing type
[0038] Furthermore, the exhaust of the low-pressure cylinder enters the low- and high-pressure condensers respectively. The circulating water passes through the low- and high-pressure condensers in series, enters from the low-back pressure condenser, and the outlet water enters the high-back pressure condenser. After heat exchange, it is transported to the indirect air-cooling tower for cooling by the indirect air-cooling circulating water pump. The difference in the inlet water temperature of the circulating water in the two condensers generates the high- and low-pressure condenser chambers.
[0039] Even further, the main functions of the condenser are: one is to establish and maintain a high vacuum at the exhaust port of the steam turbine, and the other is that the water condensed from the exhaust of the steam turbine serves as boiler feed water to form a complete cycle. The condenser maintains a high vacuum by exchanging heat with the circulating water. The functions of the vacuum pump are: during the startup of the unit, the vacuum pump is used to evacuate the air and drain water in the steam, water pipelines and each heater, and establish a certain vacuum on the steam side of the condenser to accelerate the startup speed and avoid steam-water impact. During normal operation, the vacuum pump timely extracts the non-condensable gas leaking into the condenser and the vacuum system to maintain the vacuum of the condenser.
[0040] Further, the exhaust of the steam turbine enters the corresponding condenser, and through surface heat exchange in the condenser, the heat is transferred to the tube bundle, and the tube bundle transfers the heat to the circulating water pipeline. The exhaust of the steam turbine condenses into water. The volume of the gas is larger than that of the condensed water, and the volume becomes smaller after condensation, and the reduced part forms a vacuum.
[0041] Specifically, assume that the temperature of the circulating water is T1 before entering. The first condenser passed through is called the low-pressure side condenser, and the temperature of the circulating water at this time is T2. The condenser passed through later is called the high-pressure side condenser, and the temperature of the circulating water at this time is T3. Since the circulating water is a heat absorption process, T1 < T2 < T3. For the exhaust in the condenser, it is a cooling process, and the lower the temperature, the better the cooling effect. Because T1 < T2, the exhaust in the low-pressure side condenser has a better cooling effect than that in the high-pressure side condenser. Therefore, the vacuum in the low-pressure side condenser is higher than that in the high-pressure side condenser, and the corresponding back pressure (back pressure = vacuum value + local atmospheric pressure value) is smaller for the low-pressure side condenser and higher for the high-pressure side condenser.
[0042] More specifically, double back pressure operation means that the exhaust steam of the steam turbine enters the corresponding condenser, the circulating water passes through the condenser in turn for cooling, the vacuum pumps extract the non-condensable gas inside each (the first control valve is closed or the second control valve is closed), and the high and low pressure condensers are not connected. Single back pressure operation means that the exhaust steam of the steam turbine enters the condenser, the circulating water passes through the condenser in turn for cooling, and the vacuum pumps simultaneously extract the non-condensable gas inside the high and low pressure condensers (the first control valve and the second control valve are both open).
[0043] Furthermore, during normal operation of the steam turbine, the operating back pressure of the high and low pressure condensers cannot be lower than the blocking back pressure value of the corresponding load. During the adjustment of the intercooling system, the closer the operating back pressure is to the blocking back pressure value, the better the economy. This embodiment provides the blocking back pressure values under various load conditions as shown in Table 1:
[0044] Table 1
[0045] Steam flow 1200 1300 1400 1500 1600 1700 Blocking backpressure 4.6 4.65 4.75 4.8 4.9 5 Steam flow 1800 1900 2000 2100 2200 2300 Blocking backpressure 5.1 5.2 5.25 5.35 5.45 5.55 Steam flow 2400 2500 2600 2700 2800 2900 Blocking backpressure 5.65 5.75 5.85 5.9 5.95 6.1
[0046] Optionally, when the condenser back pressure is lower than the blocking back pressure value, the operator opens the control valve to connect the condensers on both sides, and the back pressures of the two condensers of the turbine tend to be consistent, and finally reach a balanced state, changing to single back pressure operation. The intercooling circulating water pump is started and stopped according to the on-site ambient temperature, wind speed and unit load, and the working state of the control valve is regulated by referring to the blocking back pressure value and combining the change trends of the above three parameters. A vacuum pump is stopped to switch to single back pressure operation mode or a vacuum pump is started to switch to double back pressure operation mode.
[0047] refer to Figure 2 The pipelines connected to the gas inlet ends of the first vacuum pump, the second vacuum pump and the third vacuum pump are provided with check valves, butterfly valves and throttle valves in sequence; the check valve is used to prevent the medium from flowing back and the pump from reversing; the butterfly valve is used to cut off the gas pipeline and throttle; the throttle valve is used to change the throttling section to control the gas flow; the gas outlet ends of the first vacuum pump, the second vacuum pump and the third vacuum pump are all connected to the separator; the separator is used to separate the received non-condensable gas, discharge the separated gas into the atmosphere and cool the working fluid in the vacuum pump.
[0048] refer to Figure 3, the condenser single and double back pressure switching not only meets the purpose of deeply reducing the back pressure, but also avoids the low-pressure cylinder turbine from operating under the blocking back pressure, ensuring the unit's economy while also ensuring the safe operation of the turbine's low-pressure cylinder's last-stage blades. After the optimization of the condenser single and double back pressure switching operation, the utility model has achieved good energy-saving and consumption-reducing effects while ensuring the safe operation of the unit equipment. When the condenser back pressure is lower than the blocking value, it switches to single back pressure operation, and the average back pressure of a single unit drops by 0.5 kPa. According to the unit performance test coal consumption impact value, when the back pressure is below 8.5 kPa, each 1 kPa of back pressure affects the coal consumption by 0.751 g / kWh. According to the winter working conditions, the daily electricity consumption is 40,000 MWh and the measure is used for 6 hours a day. The double-machine power generation is 1.5 billion kWh, and the annual standard coal saving is 563.25 tons. Calculated at the standard coal price of 740 yuan / ton, the fuel cost is saved by about 4.16805 million yuan. In terms of carbon emissions, based on the calculation of 2.6 tons of carbon emissions per ton of standard coal, carbon emissions were reduced by about 1,464.45 tons. The power saving benefits of single-double back pressure switching combined with vacuum pump optimization: by shutting down one vacuum pump during single back pressure operation, the two units save about 155,430 kWh of plant electricity each year. Based on the on-grid electricity price of 0.3 yuan / kWh, the five-month winter operation period saves about 466,920 yuan in plant electricity costs.
[0049] The beneficial effects of the utility model are as follows:
[0050] (1) During the single-double back pressure switching process, the back pressure of the condenser on the low-pressure side increases, while the back pressure of the condenser on the high-pressure side decreases, and finally reaches a corresponding equilibrium state, which will not affect the safe operation. The operation is simple and applicable to all double back pressure condenser units.
[0051] (2) The utility model avoids the operation of the steam turbine below the blocked back pressure by converting the double back pressure to the single back pressure operation, and significantly reduces the occurrence of overload and water erosion of the last stage blades of the low-pressure cylinder of the steam turbine.
[0052] The various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.
[0053] This article uses specific examples to illustrate the principles and implementation methods of the utility model. The above examples are only used to help understand the method and core ideas of the utility model. At the same time, for those skilled in the art, according to the ideas of the utility model, there will be changes in the specific implementation methods and application scope. In summary, the content of this specification should not be understood as limiting the utility model.
Claims
1. An indirect air-cooled condensing steam turbine back pressure control device, characterized in that: include: A low-pressure side condenser, a high-pressure side condenser, a second vacuum pump, a first vacuum pump connected to the high-pressure side condenser, a third vacuum pump connected to the low-pressure side condenser, a first control valve connected to the high-pressure side condenser and the second vacuum pump, respectively, and a second control valve connected to the second vacuum pump and the low-pressure side condenser, respectively; The low-pressure side condenser and the high-pressure side condenser are used to cool the input high-temperature exhaust steam; the first vacuum pump, the second vacuum pump and the third vacuum pump are all used to extract the non-condensable gas in the low-pressure side condenser and the high-pressure side condenser; the first control valve is used to control the conduction between the high-pressure side condenser and the second vacuum pump; The second control valve is used to control the conduction between the second vacuum pump and the low-pressure side condenser; The working states of the first control valve and the second control valve include: a normally closed state and a normally open state.
2. The indirect air-cooled condensing steam turbine back pressure control device according to claim 1, characterized in that: Also includes: The circulating water pipeline is connected to the outer walls of the low-pressure side condenser and the high-pressure side condenser in sequence; The circulating water pipeline is used to provide a cooling water source for the low-pressure side condenser and the high-pressure side condenser through a circulating water pump.
3. The back pressure control device for an indirect air-cooled condensing steam turbine according to claim 1, characterized in that: The high-pressure side condenser and the low-pressure side condenser are both double-shell, double-back-pressure, single-flow and regenerative condensers.
4. The back pressure control device for an indirect air-cooled condensing steam turbine according to claim 1, characterized in that: Also includes: The high-pressure side condenser and the low-pressure side condenser are respectively connected to the low-pressure cylinder; The low-pressure cylinder is used to provide the high-temperature exhaust steam to the high-pressure side condenser and the low-pressure side condenser.
5. The indirect air-cooled condensing steam turbine back pressure control device according to claim 2, characterized in that: Also includes: A central controller; the central controller is respectively connected to the high-pressure side condenser, the low-pressure side condenser, the first control valve, the second control valve and the circulating water pipe; The central controller is used to collect operation data; the operation data includes: ambient temperature data, wind speed data, start and stop data of the circulating water pump, and back pressure data of the high-pressure side condenser and the low-pressure side condenser.
6. The back pressure control device for an indirect air-cooled condensing steam turbine according to claim 5, characterized in that: The central controller is embedded with a touch screen; the touch screen is used to display the operating data and collect control commands from the staff on the switches of the first control valve and the second control valve.