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CN208619323U - Minimum flow recirculation valve control system of feed pump - Google Patents

Minimum flow recirculation valve control system of feed pump Download PDF

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Publication number
CN208619323U
CN208619323U CN201821075566.0U CN201821075566U CN208619323U CN 208619323 U CN208619323 U CN 208619323U CN 201821075566 U CN201821075566 U CN 201821075566U CN 208619323 U CN208619323 U CN 208619323U
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China
Prior art keywords
feed pump
pump
saturation temperature
inlet pressure
variable speed
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CN201821075566.0U
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Inventor
高林
李卫东
薛建中
侯玉婷
王明坤
郇庆秋
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Xian Thermal Power Research Institute Co Ltd
Huaneng Power International Inc
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Xian Thermal Power Research Institute Co Ltd
Huaneng Power International Inc
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Abstract

A minimum flow recirculation valve control system of a feed pump is used for driving a regulating device of the feed pump to regulate the power of a driving device of the feed pump, and the feed pump with variable rotating speed is driven by a rotating shaft to realize the control of feed flow by changing the rotating speed; the variable-speed feed water pump sucks working media from the upstream, the working media are pumped to a downstream system for use through the variable-speed feed water pump, an inlet pressure signal measured by an inlet pressure sensor is sent to a saturation temperature module for calculating saturation temperature corresponding to inlet pressure according to physical properties of water and steam, the saturation temperature output by the saturation temperature module and an outlet temperature signal output by an outlet temperature sensor are simultaneously sent to a minimum flow protection recirculation controller, the outlet temperature output by the outlet temperature sensor is controlled to be lower than the saturation temperature corresponding to pump inlet pressure output by the saturation temperature module, when the deviation of the outlet temperature and the saturation temperature is lower than a preset value, a minimum flow recirculation valve of the feed water pump is started, and a part of the water working media are sent back to an upstream pipeline of the variable-speed feed water pump from an outlet.

Description

Minimum Flowrate of Feed Pump recycle valve control system
Technical field
The utility model relates to the automation fields in thermal power plant, and in particular to a kind of Minimum Flowrate of Feed Pump is followed again Ring valve control system.
Background technique
Minimum flow valve can guarantee Minimum Flowrate of Feed Pump, when feed pump rate of discharge is less than minimum discharge, minimum stream It measures valve to automatically turn on, a part of water supply is flowed back into oxygen-eliminating device, feed pump is avoided to work in the case where being lower than minimum discharge environment.It is minimum The control planning of flow valve to feed pump safe operation, but conventional control logic design only consider short-term operation start and stop work Condition.With deep and generation of electricity by new energy the high speed development of Industry Structure transition, fired power generating unit faces promotion flexible operation Property with the tight demand of depth peak regulation.When depth peak regulation, unit operating condition deviation declared working condition is more, and water supply pump discharge is inclined Low, minimum discharge protection act demand is frequent.Under new depth peaking operation demand, it is acute usually to there is underload water supply fluctuation It is strong, a series of problems, such as minimum discharge valve serious wear:
(1) the flow measurement uncertainty of Minimum Flowrate of Feed Pump protection is high, fluctuation is big
For feed pump rate of discharge measuring point itself due to working in higher-pressure region, measurement accuracy is not high, with load and gives water flow The reduction of amount, measured deviation is greatly enlarged, and the fluctuation of signal data is also more obvious, but minimum discharge protects control loop at present Correction of the signal measurement without underload under depth peak regulation easily cause the substantially shake of pitch also without necessary filtering And cause in turn to the oscillation of water management, in some instances it may even be possible to since measurement error is in the amplification of underload, cause to threaten the safety pumped.
(2) it commonly uses minimum flow valve control strategy and is not suitable with the operation of depth peak regulation operating condition
Common Minimum Flowrate of Feed Pump relay protective scheme uses most conventional pid control mode, and control target definite value is 230t/ H, it means that pitch opens the big flow that increases to 230t/h and higher than 230t/h flow when feed pump rate of discharge is less than 230 Shi Guan little needs under underload that pump is kept to work under minimum discharge always.It is minimum since the control target of pump is steam water-level The switch of flow valve can have an impact the control of pump, and so as to cause the fluctuation of pump discharge flow, therefore the PID of definite value target is controlled System easily generates the coupled oscillations with water supply system in minimum discharge threshold switch, and since there are certain controls for PID control Overshoot, therefore in control wave process, easily cause pump work in the operating condition for being less than minimum discharge, there have to the safety of pump to be unfavorable It influences.
(3) minimum discharge protects definite value not load speed-variable pump moving law
The minimum discharge protection of feed pump is to avoid pump that small flow cavitation occurs, and threatens the safety of pump, therefore its minimum stream Amount protection definite value be it is relevant to the revolving speed of variable speed pump, with the reduction of revolution speed, which is also decreased.It is existing It is constant that technology Minimum Flowrate of Feed Pump, which protects definite value, usually according to the featured configuration pumped under rated speed, in depth It is more to revolution speed reduction during peaking operation, it theoretically protects definite value that need to also reduce with revolving speed, such as presses the protection definite value control System certainly will cause to recycle long-term open state operation, while causing valve to wash away loss, also result in long-term economical operation Loss.
Summary of the invention
In view of the above problem of the existing technology, the utility model proposes a kind of Minimum Flowrate of Feed Pump recycle valve controls System processed can avoid the switch motion of most of operating condition minimum discharge valve in underrun, and stability is more preferable, energy conservation effect Fruit is obvious.
In order to achieve the above object, the utility model adopts the following technical solution:
A kind of Minimum Flowrate of Feed Pump recycle valve control system, including for driving the regulating device 1 of feed pump, with tune The driving equipment 2 for the feed pump that regulating device 1 connects, the variable speed feed pump being connect by shaft 3 with the driving equipment 2 of feed pump 4, it is mounted on the inlet pressure transducer 5 of 4 inlet of variable speed feed pump, is mounted on the outlet in 4 exit of variable speed feed pump Temperature sensor 6 is used to satisfy according to water and steam Calculation of Physical Properties inlet pressure is corresponding with what inlet pressure transducer 5 connected With the saturation temperature module 7 of temperature, the minimum discharge protection egr controller 8 being connect with outlet temperature sensor 6, saturation temperature It spends module 7 and connects minimum discharge protection egr controller 8, controlled for saturation temperature to be sent into minimum discharge protection recycling Device 8, minimum discharge protection egr controller 8 are used to compare the outlet temperature and saturation temperature of the output of outlet temperature sensor 6 The corresponding saturation temperature of pump inlet pressure that module 7 exports;It further include protecting egr controller 8 with minimum discharge and becoming to turn The Minimum Flowrate of Feed Pump recycle valve 9 of fast 4 export pipeline of feed pump connection, when the outlet temperature that outlet temperature sensor 6 exports When the corresponding saturation temperature deviation of pump inlet pressure that degree and saturation temperature module 7 export is lower than preset value, minimum discharge protection Egr controller 8 opens Minimum Flowrate of Feed Pump recycle valve 9, by a part of device of working medium from the outlet of variable speed feed pump 4 Pipeline sends the upstream line of variable speed feed pump 4 back to.
A kind of Minimum Flowrate of Feed Pump recycle valve control system, using 4 pressure at inlet of variable speed feed pump Based on the measurement of outlet temperature signal, from the minimum discharge protection philosophy of variable speed feed pump 4, turn by comparing becoming The deviation size of fast 4 outlet temperature of feed pump and the corresponding saturation temperature of inlet pressure realizes the control of minimum discharge valve opening; Mature conventional PID controller can be used in minimum discharge protection egr controller 8, and proportion of utilization, integral and the differential action begin Guarantee that 4 outlet temperature of variable speed feed pump and the deviation of the corresponding saturation temperature of inlet pressure are less than certain protective margin and control eventually Error processed.
A kind of Minimum Flowrate of Feed Pump recycle valve control system is not provided with the limitation of minimum discharge absolute value, benefit With 4 working principle of variable speed feed pump, by comparing 4 outlet temperature of variable speed feed pump saturation temperature corresponding with inlet pressure Deviation size can avoid variable speed feed pump 4 from doing work or be mixed into cavitation caused by elevated-temperature seal water simultaneously under the conditions of variable speed Risk, and 4 rotation speed change of variable speed feed pump is adapted to automatically, without opening min.flow quantityregcirculating valve too early when reducing load 9, to be the damage of the service life of water supply system stability and min.flow quantityregcirculating valve 9 generation when substantially alleviating unit depth peak regulation Evil.
The control method of a kind of Minimum Flowrate of Feed Pump recycle valve control system, for driving the tune of feed pump Regulating device 1 adjusts the power of the driving equipment 2 of feed pump, drives variable speed feed pump 4 by shaft 3, real by changing revolving speed The control of existing feedwater flow;Variable speed feed pump 4 sucks working medium from upstream, send working medium to down-stream system through variable speed feed pump 4 It uses, the inlet pressure signals that inlet pressure transducer 5 measures are sent into saturation temperature module 7, for according to water and steam The saturation temperature of the corresponding saturation temperature of Calculation of Physical Properties inlet pressure, the saturation temperature module 7 output is sensed together with outlet temperature The outlet temperature signal that device 6 exports is sent into minimum discharge protection egr controller 8 simultaneously, controls outlet temperature sensor 6 The outlet temperature of output is lower than the corresponding saturation temperature of pump inlet pressure that saturation temperature module 7 exports, when the two deviation is lower than When preset value, minimum discharge protects egr controller 8 to open Minimum Flowrate of Feed Pump recycle valve 9, by a part of device of working medium Send the upstream line of variable speed feed pump 4 back to from the outlet conduit of variable speed feed pump 4, feedwater flow reduces, and unit can be automatic It opens big regulating device 1 and then improves the revolving speed of variable speed feed pump 4 and the flow of pumping, the work of such variable speed feed pump 4 Flow increases, and efficiency increases, and operating point is further away from cavitation risk, so that adaptive rotation speed change realizes the protection of pump, and Avoid economic loss caused by unnecessary bypass flow.
Compared with the prior art, the utility model has following advantage:
1. the protection of Minimum Flowrate of Feed Pump from the basic principle of pump cavitation, does not use declared working condition minimum discharge fixed Value carries out protection control, directlys adopt carbonated drink parameter, ensures that the working flow of pump is in level of security from source, compared to current For the flow rate set value protection of mainstream, it is more suitable for the fired power generating unit new situations of current depth peaking operation, it can be in underrun When avoid the switch motion of most of operating condition minimum discharge valve, stability is more preferable, and energy-saving effect is obvious.
2. pump net positive suction head needed for the design phase to calculate, and related main stream approach cavitation analytical calculation all only with pump The pressure and temp parameter of entrance is related, but the most first occurred position of cavitation is revolved generally in the workspace of impeller of pump in the impeller of pump During turning, due to mechanical movement, local depression can be formed in the suction surface of impeller, while can also cause the liter of fluid working substance Temperature, this is easy to make on the spot, and lower than the corresponding saturation temperature of local depression, these are all easy that local temperature is made to be higher than local pressure temperature The corresponding saturation temperature of power in turn results in cavitation damage to flash.And according to above-mentioned analysis it is found that local depression is high There are certain deviations for temperature and pump intake parameter, need to use biggish safety allowance according to suction parameter judgement.The utility model It is used for as protection benchmark because of outlet temperature since the enthalpy liter due to of pump improves using inlet pressure measuring point and outlet temperature measuring point It protects more safer than suction parameter;On the other hand when flow and revolving speed reduce, adaptive change correspondingly occurs for protective condition, In comparison, the prior art carries out judging generally to only have the corresponding net positive suction head of declared working condition for protecting using suction parameter Shield, but often lack the data of variable working condition in underload low discharge operating condition, so as to cause min.flow quantityregcirculating valve in load down It opens too early in the process, not only causes unnecessary recycling economic loss, but also switching process severe jamming unit is to water control System, brings a series of hidden danger of safety and life of valve.
3. for the feed pump using hydraulic seal, low discharge and slow-speed of revolution operating condition be easy to cause sealing water be mixed into Water is further exacerbated by the risk of cavitation, and this kind of temperature rise at this time can further be reflected by the raising of feed pump outlet temperature, from And it compensates the minimum discharge therefore generated and protects risk.Therefore, the system of the utility model still may be used for hydraulic seal feed pump Effectively play a role, and conventional cavitation judges that structure cannot be then applicable in method.
Detailed description of the invention
Fig. 1 is the utility model Minimum Flowrate of Feed Pump recirculation control system figure.
Specific embodiment
The utility model is described in further details with reference to the accompanying drawings and detailed description.
The utility model technical principle is as follows:
The minimum discharge of centrifugal pump is generally measured and is provided by pumping factory, generally by more than the permission cavitation that is indicated with waterpower height difference Amount is used as design standard, and to avoid pump to work under cavitation operating condition as far as possible in design, and designing has minimum discharge to follow again Loop system makes pump can be avoided cavitation damage to increase the flow by pump when process system flow is lower than certain level Generation.
According to the principle of centrifugal pump it is found that when pump is run under small flow, the most economical operating condition of operating condition deviation is more, under efficiency Drop is obvious, and the input work of pump is more converted into the thermal energy of working medium and non-kinetic, at this time easily because the impeller of pump moves and acts on Temperature rise is generated in working medium, and local temperature is caused to be higher than when the corresponding saturation temperature of ground pressure, makes working medium that flash distillation and cavitation occur, Cause the destruction of pump.When fluid temperature reaches, and system available NPSH is made to be equal to the necessary net positive suction head of pump, this temperature The protection temperature of cavitation does not occur as, pump need to be kept above the flow of temperature operation, this is to determine to pump minimum Continuous Heat The conventional method of flow.
However, current high-power fired power generating unit is all made of the change of steam turbine or variable-frequency motor driving because energy-saving effect is significant Revolving speed feed pump.It is remote small due to speed-variable pump as the reduction available NPSH and Minimum protection flowrate of revolving speed all decline therewith In the corresponding protection definite value of rated speed, but at present, most high-power fired power generating units generally use preceding method according to specified The minimum discharge numerical value that parameter determines carries out protection control, this directly results in min.flow quantityregcirculating valve under underload and opens too early It opens, not only causes unnecessary economic loss, but also the unlatching of min.flow quantityregcirculating valve will have a direct impact on to the steady of water management It is qualitative, it be easy to cause and frequently switches on and vibrate.Under depth peak regulation background, the above problem may cause depth peak regulation during it is steady Qualitative question in turn results in non-blowing-out danger.
The utility model proposes a kind of Minimum Flowrate of Feed Pump recycle valve control system composition it is as shown in Figure 1.For It drives the regulating device 1 of feed pump to adjust the power of the driving equipment 2 of feed pump, drives variable speed feed pump 4 logical by shaft 3 It crosses and changes the control that revolving speed realizes feedwater flow.Variable speed feed pump 4 sucks working medium from upstream, and is installing at pump intake There is inlet pressure transducer 5, send working medium to use to down-stream system through variable speed feed pump 4, wherein going out to be equipped with close to pump discharge Outlet temperature sensor 6.The inlet pressure signals that inlet pressure transducer 5 measures are sent into saturation temperature module 7, are used for basis The corresponding saturation temperature of water and steam Calculation of Physical Properties inlet pressure, the saturation temperature of the saturation temperature module 7 output is together with out The outlet temperature signal that mouth temperature sensor 6 exports is sent into minimum discharge protection egr controller 8 simultaneously, and control outlet is warm It spends the outlet temperature that sensor 6 exports and is lower than the corresponding saturation temperature of pump inlet pressure that saturation temperature module 7 exports, work as the two Deviation is lower than certain value (such as 0), and minimum discharge protects egr controller 8 to open Minimum Flowrate of Feed Pump recycle valve 9, by one Part device of working medium sends the upstream line of variable speed feed pump 4 back to from the outlet conduit of variable speed feed pump 4, and feedwater flow reduces, Unit can hold big regulating device 1 automatically and then improve the revolving speed of variable speed feed pump 4 and the flow of pumping, such variable speed water supply The working flow of pump 4 increases, and efficiency increases, and operating point is further away from cavitation risk, so that adaptive rotation speed change realizes pump Protection, and avoid economic loss caused by unnecessary bypass flow.
Embodiment:
As shown in Figure 1, feedwater flow needed for unit is greatly decreased when unit depth peaking operation, regulating device 1 is automatic The power for reducing the driving equipment 2 of feed pump is adjusted, and then reduces the revolving speed of variable speed feed pump 4 by shaft 3, is made to water flow It measures to be greatly decreased.At this point, since the operating point of variable speed feed pump 4 deviates significantly from optimal declared working condition, effect Rate is greatly reduced, and more mechanical outputs are converted directly into the interior energy of water supply, the feed temperature for exporting variable speed feed pump 4 It increases, meanwhile, high temperature water-supply pump seal water is mixed into, and makes further to be promoted to temperature, so that pump be made to face potential cavitation Risk.At this point, the temperature signal that the outlet temperature sensor 6 for being mounted on the outlet of variable speed feed pump 4 measures is admitted to minimum stream Amount protection egr controller 8, the corresponding saturation temperature of inlet pressure for calculating with saturation temperature module 7 carry out deviation control System opens Minimum Flowrate of Feed Pump recycle valve 9 if the two deviation is less than given definite value (such as 0), makes variable speed feed pump 4 A part of flow of outlet sends the upstream of pump intake back to, and feedwater flow reduces, and unit can hold big regulating device 1 automatically and then improve To maintain required final feedwater flow, the working flow pumped in this way increases for the revolving speed of variable speed feed pump 4 and the flow of pumping, Efficiency increases, and operating point is further away from cavitation risk, so that adaptive rotation speed change realizes the protection of pump.

Claims (1)

1. a kind of Minimum Flowrate of Feed Pump recycle valve control system, it is characterised in that: including for driving the adjusting of feed pump Device (1), the driving equipment (2) for the feed pump connecting with regulating device (1), passes through the driving equipment of shaft (3) and feed pump (2) the variable speed feed pump (4) connected, is mounted on the inlet pressure transducer (5) of variable speed feed pump (4) inlet, installs Outlet temperature sensor (6) in variable speed feed pump (4) exit, what is connect with inlet pressure transducer (5) is used for basis The saturation temperature module (7) of the corresponding saturation temperature of water and steam Calculation of Physical Properties inlet pressure, with outlet temperature sensor (6) The minimum discharge of connection protects egr controller (8), and saturation temperature module (7) connects minimum discharge and protects egr controller (8);It further include the water supply being connect with minimum discharge protection egr controller (8) and variable speed feed pump (4) export pipeline It pumps min.flow quantityregcirculating valve (9).
CN201821075566.0U 2018-07-06 2018-07-06 Minimum flow recirculation valve control system of feed pump Active CN208619323U (en)

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Application Number Priority Date Filing Date Title
CN201821075566.0U CN208619323U (en) 2018-07-06 2018-07-06 Minimum flow recirculation valve control system of feed pump

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Application Number Priority Date Filing Date Title
CN201821075566.0U CN208619323U (en) 2018-07-06 2018-07-06 Minimum flow recirculation valve control system of feed pump

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110259703A (en) * 2019-06-22 2019-09-20 大唐郓城发电有限公司 A kind of anti-vaporization guard method of gearshift adjustment water pump
CN111608928A (en) * 2020-05-25 2020-09-01 西安热工研究院有限公司 Energy-saving optimization method for controlling opening and closing of recirculation valve of steam turbine feed pump

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN110259703A (en) * 2019-06-22 2019-09-20 大唐郓城发电有限公司 A kind of anti-vaporization guard method of gearshift adjustment water pump
CN111608928A (en) * 2020-05-25 2020-09-01 西安热工研究院有限公司 Energy-saving optimization method for controlling opening and closing of recirculation valve of steam turbine feed pump

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