CN107246807B - Efficient adjustable vacuum control method and system for power plant - Google Patents
Efficient adjustable vacuum control method and system for power plant Download PDFInfo
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- CN107246807B CN107246807B CN201710484629.1A CN201710484629A CN107246807B CN 107246807 B CN107246807 B CN 107246807B CN 201710484629 A CN201710484629 A CN 201710484629A CN 107246807 B CN107246807 B CN 107246807B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28B—STEAM OR VAPOUR CONDENSERS
- F28B9/00—Auxiliary systems, arrangements, or devices
- F28B9/10—Auxiliary systems, arrangements, or devices for extracting, cooling, and removing non-condensable gases
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
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Abstract
The invention relates to a high-efficiency adjustable vacuum control method and a system for a power plant, wherein the method comprises the following steps: and acquiring, calculating and analyzing the vacuum influence parameters, and obtaining a real-time condenser vacuum response value through necessary correction. And the control unit sends the vacuum response value as an adjusting instruction to the high-efficiency vacuum pump set executing mechanism, adjusts the input and output power of the high-efficiency vacuum pump set and obtains the input of the minimum power of the vacuum pump set and the vacuum response value of the set. The front ends of the positive displacement main pump and the water ring pump are both provided with gas coolers for cooling the pumped gas so as to improve the efficiency of the pump set. The capacity of the vacuum pump set is selected according to the steam discharge corresponding standard of the unit, so that non-condensable gas of the unit under different working conditions can be continuously pumped out, and stable adjustment of the whole pumping flow of the pump set is realized by changing the input frequency of a main pump.
Description
Technical Field
The invention relates to the field of vacuum maintenance and energy conservation of condensers of power plants, in particular to a high-efficiency adjustable vacuum control method and system for a power plant.
Background
The steam turbine condenser is an important component of a thermal power plant, plays a role of a cold source in the thermodynamic cycle of a condensing unit, the exhaust steam of the steam turbine is condensed in the condenser and forms vacuum in the condenser, and the steam is condensed into water and then is continuously sent to a boiler system to complete the thermodynamic cycle. The vacuum degree of the unit is one of important indexes which influence the economy and the safety of the unit. Under the condition that the steam inlet temperature is not changed, the heat efficiency of the unit is increased by about 3.5% when the steam exhaust temperature of the steam turbine is reduced by 10 ℃; within the range of the set safe back pressure, the power of the turbine changes by about +/-1% -2% when the back pressure changes by +/-1 kPa, which is considerable in a power plant. If the vacuum degree of the unit is too low, the effective enthalpy drop of steam in the unit is reduced, the cycle heat efficiency is reduced, and faults such as the steam exhaust temperature rise of a steam turbine, the deformation of an exhaust cylinder and the vibration caused by the change of the center of a bearing can be caused. In practice, the reduction of the vacuum degree of the condenser causes other hazards, such as the increase of the oxygen content in the condensed water, and iron oxide generated by corrosion of the condensed water system equipment and pipelines enters the boiler, so that the equipment and pipelines such as water walls, superheaters and the like are corroded.
In recent years, with the improvement of energy conservation and emission reduction requirements of power plants, equipment with smaller power is used under the condition of ensuring the functions of the equipment, so that the consumption of auxiliary power can be reduced. The originally designed high-capacity vacuum pump of the power plant mainly takes air in a condenser into consideration in the starting stage of a unit, and the vacuum establishing time is shortened. Because the condenser vacuum is mainly formed by the exhaust steam condensation of the steam turbine, the leakage rate of the condenser is very low when the unit normally operates, and the air pumping quantity of the required vacuum pump is far less than that of the vacuum establishing stage, so that a low-power vacuum maintaining system can be used in the unit operating stage.
In recent years, some power plants try to modify a vacuum system, and most of selected vacuum pump sets are calculated according to the steam extraction mass flow of a running stage of a calculation unit or designed according to the rated working condition in a vacuum mode. In the actual operation process of the unit, the unit is restricted by environmental and equipment factors, the unit is difficult to keep the designed rated vacuum operation, and the optimal vacuum of the unit is difficult to achieve through a vacuum pumping system. And along with the change of unit vacuum, the vacuum pump suction flow also changes greatly, is difficult to maintain the design operating mode.
At the starting stage of a unit or some test requirements, the vacuum value of the unit is required to be changed frequently to adapt to operation requirements, a vacuum breaker valve or a vacuum main pipe manual drain valve commonly used by a power plant at present breaks vacuum regulation backpressure, and the operation safety of the unit is greatly influenced due to the large action stroke of a valve position of the vacuum breaker valve and the difficulty in control of the manual valve.
In view of the above, the present inventors have made active research and innovation to create a method and a system for controlling vacuum in a power plant, which are highly efficient and adjustable, and thus have industrial utility value.
Disclosure of Invention
In order to solve the technical problems, the invention aims to provide a high-efficiency adjustable vacuum control system for a power plant, which has the advantages of simple structure, energy conservation and strong universality.
In order to achieve the purpose, the high-efficiency adjustable vacuum control method for the power plant is characterized in that steam extraction and extraction ports on a condenser are respectively connected with a main steam extraction device, the main steam extraction device comprises a positive displacement vacuum pump which is communicated with the steam extraction ports on the condenser through a main steam extraction pipeline, and the positive displacement vacuum pump is connected with a final stage water circulation vacuum pump in series; the positive displacement vacuum pump is electrically connected with the variable frequency motor, the positive displacement vacuum pump is driven by the variable frequency motor, and the variable frequency motor is connected with the controller; the vacuum control method of the condenser comprises the following steps:
collecting parameters affecting condenser vacuum, the parameters comprising: inlet water temperature t of condenser cooling water w1 The sum D of the steam condensing amount of the steam turbine and the steam amount entering the condenser c And cooling water flow D of condenser W ；
Calculating a real-time condenser vacuum reaching value, comparing the condenser vacuum reaching value with a current condenser real-time vacuum value, outputting a control instruction of a variable frequency motor by a controller according to the condenser vacuum reaching value, and adjusting the input and output power of a positive displacement vacuum pump by the variable frequency motor, wherein the real-time condenser vacuum reaching value calculation formula is as follows:
t s ＝Δt+δ t +t w1
in the formula: p 0 kPa is the calculated vacuum response value;
P s calculating the pressure, kPa, for the condenser;
t s is the saturated steam temperature, deg.C, corresponding to the condenser pressure;
delta t is the temperature rise of cooling water in a condenser at DEG C;
t w1 the water inlet temperature of the cooling water of the condenser is DEG C;
D c the steam condensing amount of the steam turbine is the sum of the steam amount entering the condenser in kg/s;
D w cooling water flow, kg/s;
k is the total heat transfer coefficient of the cooling water, and the design fixed value is adopted, namely kW/(m) 2 ·℃)；
A c For the cooling area of the condenser, a design constant value, m 2 ；
δ t Is the heat transfer end difference in the condenser, and is DEG C.
Further, the adjusting method of the variable frequency motor comprises the following steps: and comparing the obtained vacuum answer value with the current unit vacuum value, using the difference value of the two as a variable input instruction, sending the variable input instruction to a variable frequency motor of the positive displacement vacuum pump to adjust the rotating speed of the positive displacement vacuum pump, if the current vacuum level of the unit is lower than the calculated vacuum answer value, increasing the rotating speed of the positive displacement vacuum pump, and if the current vacuum level of the unit is higher than the calculated vacuum answer value, reducing the rotating speed of the positive displacement vacuum pump until the current vacuum level of the unit and the calculated vacuum answer value are consistent.
To achieve the above objects, the present invention provides an efficient adjustable vacuum control system for a power plant, comprising:
the steam extraction and extraction port on the condenser is respectively connected with a main steam extraction device and a standby steam extraction device, wherein the main steam extraction device comprises a positive displacement vacuum pump which is communicated with the steam extraction port on the condenser through a main steam extraction pipeline, and the positive displacement vacuum pump is connected with a final stage water circulation vacuum pump in series; a first switch valve is arranged on a main steam pipeline between the positive displacement vacuum pump and the condenser; the positive displacement vacuum pump is electrically connected with the variable frequency motor and is driven by the variable frequency motor; be connected with measuring unit on the condenser, measuring unit includes: the system comprises a temperature sensor for measuring the inflow temperature of cooling water of the condenser, a steam pressure sensor for measuring the steam quantity entering the condenser and a flow sensor for measuring the inflow flow of the cooling water of the condenser; the temperature sensor, the steam pressure sensor and the flow sensor are respectively connected with the controller; the variable frequency motor is controlled by the controller;
the measuring unit is used for acquiring the inlet water temperature t of the cooling water of the condenser w1 The sum D of the steam condensing amount of the steam turbine and the steam amount entering the condenser c And cooling water flow D of condenser W ；
The controller is used for calculating a real-time condenser vacuum reaching value, comparing the condenser vacuum reaching value with a current condenser real-time vacuum value, outputting a control instruction of the variable frequency motor by the controller according to the condenser vacuum reaching value, and adjusting the input and output power of the positive displacement vacuum pump by the variable frequency motor, wherein the real-time condenser vacuum reaching value calculation formula is as follows:
t s ＝Δt+δ t +t w1
in the formula: p 0 kPa is the calculated vacuum response value;
P s calculating the pressure, kPa, for the condenser;
t s the saturated steam temperature is equal to the condenser pressure;
delta t is the temperature rise of cooling water in the condenser, DEG C;
t w1 the water inlet temperature of the cooling water of the condenser is DEG C;
D c the steam condensing amount of the steam turbine is the sum of the steam amount entering the condenser, and is kg/s;
D w cooling water flow in kg/s;
k is the total heat transfer coefficient of the cooling water, and a design fixed value is adopted, namely kW/(m) 2 ·℃)；
A c For the cooling area of the condenser, a design constant value, m 2 ；
δ t Is the heat transfer end difference in the condenser, and is DEG C.
The steam condenser is characterized by further comprising a standby steam extraction device, wherein the standby steam extraction device comprises a standby steam extraction pipeline communicated with the steam condenser, and a primary water circulation vacuum pump and a secondary water circulation vacuum pump are connected to the standby steam extraction pipeline in series; and a second switch valve is arranged on a standby steam pipeline between the primary water circulation vacuum pump and the condenser, and the first switch valve and the second switch valve are electric valves, pneumatic valves or manual valves.
Furthermore, the air outlets of the final water circulating vacuum pump and the secondary water circulating vacuum pump are communicated with the air inlets of the steam-water separator, the liquid outlets of the final water circulating vacuum pump and the secondary water circulating vacuum pump are communicated with one end of the heat exchanger, and the other end of the heat exchanger is communicated with the steam-water separator;
furthermore, an overflow port of the steam-water separator is communicated with a wastewater recovery device, and the steam-water separator adopts a vertical structure.
Further, the cooling device comprises a cooling tank with an air inlet and an air outlet, the air inlet is connected with the turbine condenser, and the air outlet is connected with the vacuum pump; and the cooling box is also connected with a cooling water input pipe for inputting cooling water into the cooling box.
Furthermore, the air outlet of the positive displacement vacuum pump is connected with a silencer through a connecting pipeline.
Furthermore, a cooling water inlet of the cooling device is provided with a temperature sensor.
Compared with the prior art, the invention has the following advantages:
1. necessary parameters influencing the vacuum of a condenser of a unit are collected, a required value which can be obtained by the vacuum of the condenser under the influence of a set environmental condition is obtained through calculation and correction, and the vacuum required value is used as a vacuum adjusting target instead of a constant-speed vacuum pump which is generally adopted at present and is used for vacuumizing to the maximum degree under power frequency.
2. And selecting the capacity of a vacuum pump set according to the corresponding standard of the steam discharge amount of the unit, converting a control instruction by using a vacuum response value obtained by calculation and analysis, and adjusting the power input of a displacement pump serving as a main pump in the high-efficiency vacuum pump set to achieve the aim of adjusting the vacuum of the condenser to a target value.
3. The efficient vacuum pump set adopts the positive displacement vacuum pump as a main pump, can well realize continuous response to the instruction of the frequency conversion unit, and ensures good performance and efficiency. A water ring vacuum pump is used as a backing pump, and the highest efficiency is maintained by power frequency operation. The air inlets of the vacuum pumps are all provided with coolers, so that the temperature of sucked gas is reduced, and the working efficiency of the pump set is improved.
4. Through adjusting control system output instruction, realize the whole steady regulation of suction flow of pump package to reach condenser vacuum to expected value, satisfy and start shutting down or experimental stage to the special demand in vacuum, avoid operating the unit operation safety risk that vacuum boundary brought.
The foregoing description is only an overview of the technical solutions of the present invention, and in order to make the technical solutions of the present invention more clearly understood and to implement them in accordance with the contents of the description, the following detailed description is given with reference to the preferred embodiments of the present invention and the accompanying drawings.
Drawings
FIG. 1 is a system diagram of an efficient adjustable vacuum control system for a power plant of the present invention.
Detailed Description
The following detailed description of embodiments of the present invention is provided in connection with the accompanying drawings and examples. The following examples are intended to illustrate the invention but are not intended to limit the scope of the invention.
Example 1
As shown in FIG. 1, the present embodiment provides a method for controlling an adjustable vacuum of a power plant, which includes:
the steam extraction and extraction ports on the condenser are respectively connected with a main steam extraction device, the main steam extraction device comprises a positive displacement vacuum pump which is communicated with the steam extraction ports on the condenser through a main steam extraction pipeline, and the positive displacement vacuum pump is connected with a final stage water circulation vacuum pump in series; the positive displacement vacuum pump is electrically connected with the variable frequency motor, the positive displacement vacuum pump is driven by the variable frequency motor, and the variable frequency motor is connected with the controller; the vacuum control method of the condenser comprises the following steps:
collecting parameters affecting condenser vacuum, the parameters including: inlet water temperature t of condenser cooling water w1 The sum D of the steam condensing amount of the steam turbine and the steam amount entering the condenser c And cooling water flow D of condenser W ；
Calculating a real-time condenser vacuum reaching value, comparing the condenser vacuum reaching value with a current condenser real-time vacuum value, outputting a control instruction of a variable frequency motor by a controller according to the condenser vacuum reaching value, and adjusting the input and output power of a positive displacement vacuum pump by the variable frequency motor, wherein the real-time condenser vacuum reaching value calculation formula is as follows:
t s ＝Δt+δ t +t w1
in the formula: p 0 kPa is the calculated vacuum response value;
P s calculating the pressure, kPa, for the condenser;
t s is the saturated steam temperature, deg.C, corresponding to the condenser pressure;
delta t is the temperature rise of cooling water in the condenser, DEG C;
t w1 the water inlet temperature of the cooling water of the condenser is DEG C;
D c the steam condensing amount of the steam turbine is the sum of the steam amount entering the condenser, and is kg/s;
D w cooling water flow in kg/s;
k is the total heat transfer coefficient of the cooling water, and the design fixed value is adopted, namely kW/(m) 2 ·℃)；
A c For the cooling area of the condenser, a design constant value, m 2 ；
δ t Is the heat transfer end difference in the condenser, DEG C.
In this embodiment, the method for adjusting the inverter motor includes: and comparing the obtained vacuum answer value with the current unit vacuum value, using the difference value of the two as a variable input instruction, sending the variable input instruction to a variable frequency motor of the positive displacement vacuum pump to adjust the rotating speed of the positive displacement vacuum pump, if the current vacuum level of the unit is lower than the calculated vacuum answer value, increasing the rotating speed of the positive displacement vacuum pump, and if the current vacuum level of the unit is higher than the calculated vacuum answer value, reducing the rotating speed of the positive displacement vacuum pump until the current vacuum level of the unit and the calculated vacuum answer value are consistent.
In the embodiment, after the unit establishes vacuum, in the normal operation and starting and stopping processes, the existing measurement points of the unit are used for collecting, calculating and analyzing the vacuum influence parameters by establishing an analysis model, and the real-time condenser vacuum response value is obtained through necessary correction. And the control unit sends the adjusting instruction to the high-efficiency vacuum pump set executing mechanism, continuously adjusts the input and output power of the high-efficiency vacuum pump set, obtains the minimum power input of the vacuum pump set and the vacuum pump set, and finally realizes the integral energy-saving operation of the unit. When special requirements are met, the control system can be adjusted to output instructions to adjust the vacuum of the condenser to a preset value, so that the continuous, stable and adjustable operation of the unit vacuum is realized, and the unit operation safety risk brought by operating a vacuum boundary is avoided.
Example 2
This embodiment is used for high-efficient adjustable vacuum control system of power plant, includes: the steam extraction and extraction device comprises a condenser 1, wherein an extraction steam and extraction opening on the condenser is respectively connected with a main extraction steam device and a standby extraction steam device, the main extraction steam device comprises a positive displacement vacuum pump 4 communicated with the extraction steam opening on the condenser through a main extraction steam pipeline, and the positive displacement vacuum pump is connected with a final stage water circulation vacuum pump 5 in series; a first switch valve 2 is arranged on a main steam pipeline between the positive displacement vacuum pump and the condenser; the positive displacement vacuum pump is electrically connected with the variable frequency motor and is driven by the variable frequency motor 7; be connected with measuring unit 8 on the condenser, measuring unit includes: the temperature sensor is used for measuring the inlet water temperature of the cooling water of the condenser, the steam pressure sensor is used for measuring the steam quantity entering the condenser, and the flow sensor is used for measuring the inlet water flow of the cooling water of the condenser; the temperature sensor, the steam pressure sensor and the flow sensor are respectively connected with the controller 6; the variable frequency motor is controlled by the controller;
the measuring unit is used for acquiring the inlet water temperature t of the cooling water of the condenser w1 The sum of the steam condensing amount of the steam turbine and the amount of steam entering the condenserD c And cooling water flow D of condenser W ；
The controller is used for calculating a real-time condenser vacuum reaching value, comparing the condenser vacuum reaching value with the current condenser real-time vacuum value, outputting a control instruction of the variable frequency motor according to the condenser vacuum reaching value, and adjusting the input and output power of the positive displacement vacuum pump through the variable frequency motor, wherein the real-time condenser vacuum reaching value calculation formula is as follows:
t s ＝Δt+δ t +t w1
in the formula: p is 0 kPa is the calculated vacuum response value;
P s calculating the pressure, kPa, for the condenser;
t s the saturated steam temperature is equal to the condenser pressure;
delta t is the temperature rise of cooling water in a condenser at DEG C;
t w1 the water inlet temperature of cooling water of a condenser is measured at DEG C;
D c the steam condensing amount of the steam turbine is the sum of the steam amount entering the condenser in kg/s;
D w cooling water flow, kg/s;
k is the total heat transfer coefficient of the cooling water, and the design fixed value is adopted, namely kW/(m) 2 ·℃)；
A c For the cooling area of the condenser, a design constant value, m 2 ；
δ t Is the heat transfer end difference in the condenser, and is DEG C.
Example 3
The embodiment of the high-efficiency adjustable vacuum control system for the power plant further comprises a standby steam extraction device (not shown in the figure) on the basis of the embodiment 2, wherein the standby steam extraction device comprises a standby steam extraction pipeline communicated with the condenser, and a primary water circulation vacuum pump and a secondary water circulation vacuum pump are connected to the standby steam extraction pipeline in series; and a second switch valve is arranged on a standby steam pipeline between the primary water circulation vacuum pump and the condenser, and the first switch valve and the second switch valve are electric valves, pneumatic valves or manual valves.
And a second switch valve is arranged on a standby steam pipeline between the primary water circulation vacuum pump and the condenser, and the first switch valve and the second switch valve are electric valves, pneumatic valves or manual valves.
The inlet ends of the positive displacement vacuum pump, the final stage water circulating vacuum pump, the primary water circulating vacuum pump and the secondary water circulating vacuum pump are all connected with a cooling device 3 in series; the medium output by the condenser firstly passes through the cooling device and then enters the positive displacement vacuum pump, the final stage water circulation vacuum pump, the primary water circulation vacuum pump and the secondary water circulation vacuum pump.
In this embodiment, during normal use, the main extraction device operates, and when the main extraction device fails, the standby extraction device is started.
The inlet ends of the positive displacement vacuum pump, the final stage water circulating vacuum pump, the primary water circulating vacuum pump and the secondary water circulating vacuum pump are connected with a cooling device in series; the medium output by the condenser firstly passes through the cooling device and then enters the positive displacement vacuum pump, the final stage water circulation vacuum pump, the primary water circulation vacuum pump and the secondary water circulation vacuum pump.
Furthermore, the gas outlets of the final stage water circulation vacuum pump and the secondary water circulation vacuum pump are communicated with the gas inlets of the steam-water separator, the liquid outlets of the final stage water circulation vacuum pump and the secondary water circulation vacuum pump are communicated with one end of the heat exchanger, and the other end of the heat exchanger is communicated with the steam-water separator.
The cooling device comprises a cooling box with an air inlet and an air outlet, the air inlet is connected with the steam turbine condenser, and the air outlet is connected with the vacuum pump; and the cooling box is also connected with a cooling water input pipe for inputting cooling water into the cooling box. And a cooling water inlet of the cooling device is provided with a temperature sensor. The cooling device reduces the temperature of the sucked gas and improves the working efficiency of the pump set.
Furthermore, an overflow port of the steam-water separator is communicated with a wastewater recovery device. The cooling device comprises a cooling box with an air inlet and an air outlet, the air inlet is connected with the steam turbine condenser, and the air outlet is connected with the vacuum pump; and the cooling box is also connected with a cooling water input pipe for inputting cooling water into the cooling box. And the air outlet of the positive displacement vacuum pump is connected with a silencer through a connecting pipeline. And a cooling water inlet of the cooling device is provided with a temperature sensor.
The system comprises a measuring unit for collecting and influencing the vacuum of the condenser, a controller for calculating and outputting a command for a vacuum influence parameter, a variable frequency motor for responding to the control command, and a high-efficiency vacuum pump set. And calculating and analyzing the vacuum influence parameters, and obtaining a real-time condenser vacuum corresponding value through necessary correction. And the control unit sends the adjusting instruction to the high-efficiency vacuum pump set executing mechanism to adjust the input and output power of the high-efficiency vacuum pump set and obtain the minimum power input of the vacuum and the vacuum pump set of the unit. The high-efficiency vacuum pump set comprises a water ring vacuum pump serving as a backing pump, a positive displacement high-efficiency vacuum pump serving as a main pump, corresponding valves, a working liquid cooling and separating device and the like, wherein gas coolers are designed at the front ends of the positive displacement pump and the water ring pump, and are used for cooling pumped gas so as to improve the efficiency of the pump set. Selecting the capacity of a vacuum pump set according to a corresponding standard of the steam discharge amount of a unit, and realizing the stable adjustment of the whole suction flow of the pump set by changing the input frequency of a main pump so as to achieve the aim of adjusting the vacuum of a condenser; by using a necessary numerical calculation and correction method, the optimal vacuum operation is maintained by continuously adjusting the unit through the high-efficiency vacuum pump set, and finally, the whole energy-saving operation of the unit is realized.
The invention relates to a high-efficiency adjustable vacuum control method and a high-efficiency adjustable vacuum control system for a power plant. And converting the vacuum target value into an adjusting instruction through a control unit, sending the instruction to an execution mechanism of the high-efficiency vacuum pump set, adjusting the input and output power of the high-efficiency pump set, and finally obtaining the minimum power consumption of the vacuum pump set and the vacuum pump set of the unit. The high-efficiency vacuum pump set comprises a water ring vacuum pump serving as a backing pump, a positive displacement high-efficiency vacuum pump serving as a main pump, corresponding valves, a working liquid cooling and separating device and the like, wherein gas coolers are arranged at inlets of the positive displacement vacuum pump and the water ring pump, and are used for cooling pumped gas so as to improve the efficiency of the pump set. Selecting the capacity of a vacuum pump set according to a corresponding standard of the steam discharge amount of a unit, and realizing the stable adjustment of the whole suction flow of the pump set by changing the input frequency of a main pump so as to achieve the aim of adjusting the vacuum of a condenser; and the unit is continuously adjusted to maintain the optimal vacuum operation through the high-efficiency vacuum pump set by using a necessary numerical calculation and correction method, and finally the overall energy-saving operation of the unit is realized.
The method comprises the steps of collecting necessary parameters influencing the vacuum of a condenser of a unit, and giving an achievable value of the vacuum of the condenser under the influence of a set environmental condition through a calculation and correction method.
The vacuum response value is utilized, certain control parameters are designed, control instructions are converted and output to the frequency conversion unit, the power input of a displacement pump serving as a main pump in the high-efficiency vacuum pump set is adjusted, the power output of the high-efficiency vacuum pump set is finally adjusted, and the purpose of continuously adjusting the vacuum value of the condenser to an expected target value is achieved.
The efficient vacuum pump set uses the positive displacement vacuum pump as a main pump, can well realize continuous response to the instruction of the frequency conversion unit, and ensures good performance and efficiency. A water ring vacuum pump is used as a backing pump, and the highest efficiency is maintained by power frequency operation. The coolers are designed in front of the positive displacement vacuum pump and the water ring vacuum pump, so that the temperature of sucked gas is reduced, and the working efficiency of the pump set is improved.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, it should be noted that, for those skilled in the art, many modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (9)
1. A high-efficiency adjustable vacuum control method for a power plant is characterized in that a steam extraction and extraction opening on a condenser is respectively connected with a main steam extraction device, the main steam extraction device comprises a positive displacement vacuum pump which is communicated with the steam extraction opening on the condenser through a main steam extraction pipeline, and the positive displacement vacuum pump is connected with a final stage water circulation vacuum pump in series; the positive displacement vacuum pump is electrically connected with the variable frequency motor, the positive displacement vacuum pump is driven by the variable frequency motor, and the variable frequency motor is connected with the controller; the vacuum control method of the condenser comprises the following steps:
collecting parameters affecting condenser vacuum, the parameters including: inlet water temperature t of condenser cooling water w1 The sum D of the steam condensing amount of the steam turbine and the steam amount entering the condenser c And cooling water flow D of condenser w ；
Calculating a real-time condenser vacuum reaching value, comparing the condenser vacuum reaching value with a current condenser real-time vacuum value, outputting a control instruction of a variable frequency motor by a controller according to the condenser vacuum reaching value, and adjusting the input and output power of a positive displacement vacuum pump by the variable frequency motor, wherein the real-time condenser vacuum reaching value calculation formula is as follows:
t s ＝Δt+δ t +t w1
in the formula: p 0 kPa is the calculated vacuum response value;
P s calculating the pressure, kPa, for the condenser;
delta t is the temperature rise of cooling water in the condenser, DEG C;
t w1 the water inlet temperature of the cooling water of the condenser is DEG C;
D c the sum of the steam condensing amount of the steam turbine and the steam amount entering a condenser is kg/s;
D w cooling water flow, kg/s;
k is the total heat transfer coefficient of the cooling water, and a design fixed value is adopted, namely kW/(m) 2 ·℃)；
A c For the cooling area of the condenser, a design constant value, m 2 ；
2. A high efficiency adjustable vacuum control method for a power plant according to claim 1, characterized in that the adjustment method of the variable frequency motor comprises: and comparing the obtained vacuum answer value with the current unit vacuum value, using the difference value of the two as a variable input instruction, sending the variable input instruction to a variable frequency motor of the positive displacement vacuum pump to adjust the rotating speed of the positive displacement vacuum pump, if the current vacuum level of the unit is lower than the calculated vacuum answer value, increasing the rotating speed of the positive displacement vacuum pump, and if the current vacuum level of the unit is higher than the calculated vacuum answer value, reducing the rotating speed of the positive displacement vacuum pump until the current vacuum level of the unit and the calculated vacuum answer value are consistent.
3. An efficient adjustable vacuum control system for a power plant, comprising:
the steam extraction and extraction port on the condenser is respectively connected with a main steam extraction device and a standby steam extraction device, wherein the main steam extraction device comprises a positive displacement vacuum pump which is communicated with the steam extraction port on the condenser through a main steam extraction pipeline, and the positive displacement vacuum pump is connected with a final stage water circulation vacuum pump in series; a first switch valve is arranged on a main steam pipeline between the positive displacement vacuum pump and the condenser; the positive displacement vacuum pump is electrically connected with the variable frequency motor and is driven by the variable frequency motor; be connected with measuring unit on the condenser, measuring unit includes: the system comprises a temperature sensor for measuring the inflow temperature of cooling water of the condenser, a steam pressure sensor for measuring the steam quantity entering the condenser and a flow sensor for measuring the inflow flow of the cooling water of the condenser; the temperature sensor, the steam pressure sensor and the flow sensor are respectively connected with the controller; the variable frequency motor is controlled by the controller;
the measuring unit is used for acquiring the inlet water temperature t of the cooling water of the condenser w1 The steam condensing amount of the steam turbine and the sum D of the steam amount entering the condenser c And cooling water flow D of condenser w ；
The controller is used for calculating a real-time condenser vacuum reaching value, comparing the condenser vacuum reaching value with a current condenser real-time vacuum value, outputting a control instruction of the variable frequency motor by the controller according to the condenser vacuum reaching value, and adjusting the input and output power of the positive displacement vacuum pump by the variable frequency motor, wherein the real-time condenser vacuum reaching value calculation formula is as follows:
t s ＝Δt+δ t +t w1
in the formula: p 0 kPa is the calculated vacuum response value;
P s calculating the pressure, kPa, for the condenser;
delta t is the temperature rise of cooling water in a condenser at DEG C;
t w1 the water inlet temperature of the cooling water of the condenser is DEG C;
D c the sum of the steam condensing amount of the steam turbine and the steam amount entering a condenser is kg/s;
D w cooling water flow in kg/s;
k is the total heat transfer coefficient of the cooling water, and the design fixed value is adopted, namely kW/(m) 2 ·℃)；
A c For the cooling area of the condenser, a design constant value m is adopted 2 ；
δ t Is the heat transfer end difference in the condenser, DEG C.
4. The high efficiency adjustable vacuum control system for a power plant of claim 3, further comprising a backup extraction device, wherein the backup extraction device comprises a backup extraction pipeline in communication with the condenser, and a primary water circulation vacuum pump and a secondary water circulation vacuum pump are connected in series to the backup extraction pipeline; and a second switch valve is arranged on a standby steam pipeline between the primary water circulation vacuum pump and the condenser, and the first switch valve and the second switch valve are electric valves, pneumatic valves or manual valves.
5. The high-efficiency adjustable vacuum control system for a power plant of claim 4, wherein the gas outlets of the final stage water circulation vacuum pump and the secondary stage water circulation vacuum pump are both communicated with the gas inlet of the steam-water separator, the liquid outlets of the final stage water circulation vacuum pump and the secondary stage water circulation vacuum pump are communicated with one end of the heat exchanger, and the other end of the heat exchanger is communicated with the steam-water separator.
6. The high-efficiency adjustable vacuum control system for a power plant of claim 5, wherein an overflow port of the steam-water separator is communicated with a wastewater recovery device, and the steam-water separator adopts a vertical structure.
7. A high efficiency adjustable vacuum control system for a power plant as claimed in claim 6, characterized in that the inlet ends of the positive displacement vacuum pump, the final stage water circulation vacuum pump, the primary water circulation vacuum pump and the secondary water circulation vacuum pump are connected in series with a cooling device, the cooling device comprises a cooling tank with an air inlet and an air outlet, the air inlet is connected with the condenser, the air outlet of the cooling device is connected with the vacuum pump connected in series with the cooling device; and the cooling box is also connected with a cooling water input pipe for inputting cooling water into the cooling box.
8. The high efficiency adjustable vacuum control system for a power plant of claim 7, wherein a silencer is connected to an outlet of the positive displacement vacuum pump via a connecting line.
9. The high efficiency adjustable vacuum control system for a power plant of claim 8, wherein a temperature sensor is installed on a cooling water inlet of the cooling device.
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| CN109813137A (en) * | 2019-03-13 | 2019-05-28 | 西安热工研究院有限公司 | A kind of vacuum pump system that can be contributed according to suction air capacity adjustment |
| CN110108134B (en) * | 2019-05-28 | 2020-02-07 | 国电南京电力试验研究有限公司 | Method for evaluating influence of pumping capacity of condenser vacuum pumping equipment on vacuum value |
| CN110285687B (en) * | 2019-06-26 | 2020-11-06 | 双良节能***股份有限公司 | Air cooling control system based on artificial intelligence technology and control method thereof |
| CN110986617B (en) * | 2019-12-11 | 2021-04-02 | 中国船舶重工集团公司第七一九研究所 | Condenser control method |
| JP2023545869A (en) * | 2020-08-28 | 2023-10-31 | エドワーズ テクノロジーズ バキューム エンジニアリング （チンタオ） カンパニー リミテッド | Control of hydraulic fluid flow to liquid ring pump |
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