CN213630384U - Automatic control system for smoke temperature and water temperature in low-temperature economizer of thermal power generating unit - Google Patents
Automatic control system for smoke temperature and water temperature in low-temperature economizer of thermal power generating unit Download PDFInfo
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- CN213630384U CN213630384U CN202022712521.3U CN202022712521U CN213630384U CN 213630384 U CN213630384 U CN 213630384U CN 202022712521 U CN202022712521 U CN 202022712521U CN 213630384 U CN213630384 U CN 213630384U
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Abstract
An automatic control system for smoke temperature and water temperature in a low-temperature economizer of a thermal power generating unit comprises a water quantity regulating valve of the low-temperature economizer arranged at the outlet of a No. 7 low-pressure heater and a PID (proportion integration differentiation) controller connected with the water quantity regulating valve; a water intake regulating valve at a low water inlet arranged at the inlet of the No. 8 low-pressure heater and a PID controller connected with the water intake regulating valve; the boosting circulating pump is arranged at the tail end of the low-temperature economizer system, and the PID controller is connected with the boosting circulating pump and controls the smoke temperature in the low-temperature economizer through the water quantity regulating valve of the low-temperature economizer; the circulating pump that steps up and the low inlet water intaking governing valve that adds jointly control the temperature in the low temperature economizer, and after the circulating pump that steps up and the low inlet water intaking governing valve that adds drop into simultaneously automatically, the system can be according to current running state, and automatic judgement which regulation circuit plays, and the two can not influence each other, has saved a large amount of work for operating personnel, also provides further guarantee for power plant's economy, safe operation simultaneously.
Description
Technical Field
The utility model relates to a thermal power station automatic control technical field, concretely relates to smoke temperature and temperature automatic control system in thermal power unit low temperature economizer.
Background
In recent years, the installed capacity of thermal power generating units in China is continuously and rapidly increased, and the installed capacity in service and under construction is in the forefront of the world. At present, a thermal power plant consumes 50% of the total coal output in China, and the exhaust heat loss of the thermal power plant is the largest one of various heat losses of a boiler, generally 5% -8%, and accounts for about 80% or higher of the total heat loss of the boiler. The main factor influencing the heat loss of the exhaust smoke is the exhaust smoke temperature of the boiler, and generally, the heat loss of the exhaust smoke is increased by 0.6 to 1.0 percent when the exhaust smoke temperature is increased by 10 ℃. The exhaust gas temperature of a boiler in an active thermal power generating unit in China is generally maintained at about 125-150 ℃, and the high exhaust gas temperature is a common phenomenon. In addition, the rise of the exhaust gas temperature increases the amount of the exhaust gas, and influences the working environments of a draught fan, a dust remover and desulfurization equipment, so that the reasonable reduction of the exhaust gas temperature of the boiler plays a crucial role in improving the safety and the economy of a unit. Meanwhile, with the increase of the smoke discharge loss, the corresponding coal consumption is also increased. Therefore, reducing the temperature of the exhaust gas has important practical significance for saving fuel and reducing pollution.
In practice, the boiler technology with the aim of reducing the exhaust gas temperature is improved more, but due to the practical conditions that most of power plant tail flue spaces are too small, the requirements for abrasion resistance and corrosion resistance are high, the pressure head allowance of a draught fan is not large, and the like, a plurality of schemes are difficult to realize. At present, in order to reduce the exhaust gas temperature, reduce the exhaust gas loss and improve the operation economy of a power plant, most thermal power generating units in China adopt a scheme that a low-temperature economizer device is additionally arranged on a flue.
The specific scheme is as follows: the low-temperature coal economizer is arranged in a horizontal flue at the inlet of the electric dust collector, 4 low-temperature coal economizers are arranged in each unit, and H-shaped finned tubes are adopted, and double-tube-ring, in-line and countercurrent arrangement is adopted. The working principle is that the condensed water absorbs the heat of the exhaust smoke in the low-temperature economizer, the temperature of the exhaust smoke is reduced, the condensed water is heated, and the condensed water with the raised temperature returns to the low-pressure heater system, so that the overall thermal efficiency of the unit is improved.
The unit after the low-temperature economizer of the boiler is reformed reduces the exhaust gas temperature of the boiler and the exhaust gas loss. According to the thermodynamic principle, the condensed water of the steam turbine absorbs the heat of the flue gas at the tail of the boiler, the temperature of the condensed water of the steam turbine is increased, the water supply temperature of the boiler is further increased, and the overall coal consumption of the unit is reduced. The waste heat of the flue gas of the boiler is utilized to heat the condensed water, the temperature of the condensed water is improved, namely, the redundant heat is added into a steam extraction system of the steam turbine, the effective steam quantity entering the steam turbine is increased, and the equivalent enthalpy drop of the unit is improved. Therefore, after the low-temperature economizer is additionally arranged, the heat consumption rate of the steam turbine is reduced. After the condenser is used as an analysis main body, the temperature of condensed water is increased compared with the temperature before installation after the low-temperature economizer is additionally installed, the steam extraction quantity of a low-pressure heater of a steam turbine is reduced, the redundant exhaust flow of a low-pressure cylinder is increased, and the vacuum of the condenser is further reduced.
The stability of the operation parameters of the low-temperature economizer has a close relationship with the change of external load and the change of internal factors of the low-temperature economizer. The low-temperature economizer can affect the stability and the safety of operation as long as any one of the factors is changed, so a series of control and adjustment must be carried out on the low-temperature economizer, the parameters of the low-temperature economizer are adapted to the change of the external or the internal cause, and the safe and economic operation can be realized. At present, after most of thermal power generating units in China are transformed by a low-temperature economizer, a control system is operated in a manual mode and cannot be put into automatic operation, and the phenomenon is caused by the lack of a control strategy meeting the requirements. The operation of operators is greatly burdened, and the danger and the uncertainty of the whole system are increased. Therefore, measures are urgently needed to be taken to optimize and modify a related control system of the thermal power generating unit after the low-temperature economizer is modified.
Disclosure of Invention
For overcoming the problem that above-mentioned prior art exists, the utility model aims to provide a smoke temperature and temperature automatic control system in thermal power unit low temperature economizer can satisfy thermal power unit low temperature economizer and reform transform the back, and automatic operation all can be realized to its smoke temperature and water temperature control circuit, provides further guarantee for power plant's economy, safe operation.
The utility model discloses by following technical scheme implement:
an automatic control system for smoke temperature and water temperature in a low-temperature economizer of a thermal power generating unit comprises condensed water 1, a condensed water pump 2 of a condensed water pressurizing device, a shaft seal heater 3 of a condensed water heating device, a No. 8 low-pressure heater 4 and a No. 7 low-pressure heater 5 of the condensed water heating device, a low-temperature economizer water quantity regulating valve 6 arranged at the outlet of the No. 7 low-pressure heater 5, a first PID controller 14 connected with the low-temperature economizer water quantity regulating valve, a No. 6 low-pressure heater 26 of the condensed water heating device of a deaerator, a low water inlet water taking regulating valve 7 arranged at the inlet of the No. 8 low-pressure heater 4, a second PID controller 15 connected with the low-temperature economizer water quantity regulating valve, a boosting circulating pump 13 arranged at the tail end of the low-temperature economizer system, a third PID controller 16 connected with the boosting circulating pump, a low-temperature economizer A outlet smoke temperature measuring point 8 arranged at the outlet of the low-temperature economizer, and a low-temperature economizer B outlet, a low-temperature economizer C outlet flue gas temperature measuring point 10 arranged at the outlet of the low-temperature economizer C, a low-temperature economizer D outlet flue gas temperature measuring point 11 arranged at the outlet of the low-temperature economizer D, and a low-temperature economizer inlet water temperature measuring point 12 arranged at the outlet of the low water feeding inlet water taking and adjusting valve 7.
The input signal of the first PID controller 14 includes three paths, the first path is the outlet smoke temperature that needs to be controlled and adjusted, and the control object selects the minimum value of the outlet smoke temperature through the small selection controller 17; the second path is a control set value of the outlet smoke temperature, and is realized through a set value 22 of the outlet smoke temperature of the low-temperature economizer, the set value is realized by manually setting by an operator, the outlet smoke temperature is subjected to the large-selection controller 18, the maximum value of the smoke temperature is selected, the maximum value of the smoke temperature output by the large-selection controller 18 is superposed on the set value 22 of the outlet smoke temperature of the low-temperature economizer through an adder 19, and an input signal finally entering the PID controller 14 is formed; the third path is a differential loop of the unit load instruction 21, which is realized by the first differential controller 20 and finally enters a feed-forward part of the first PID controller 14; the first PID controller 14 includes a proportional P, integral I control action.
The input signal of the second PID controller 15 comprises three paths, wherein the first path is a low-temperature economizer inlet water temperature measuring point 12 and is used as a control object of the second PID controller; the second way is a set value 23 of the water temperature at the inlet of the low-temperature economizer, and the set value is manually set by an operator; the third path is a differential loop of the unit load instruction 21, which is realized by a differential controller 24, and finally enters a feedforward part of the PID controller 15, and the PID controller 15 comprises control functions of proportion P and integral I.
The input signal of the third PID controller 16 comprises three paths, wherein the first path is a low-temperature economizer inlet water temperature measuring point 12 and is used as a control object of the controller; the second way is a set value 23 of the water temperature at the inlet of the low-temperature economizer, and the set value is manually set by an operator; the third path is a differential loop of the unit load instruction 21, which is realized by the second differential controller 25, and finally enters a feed-forward part of the PID controller 16, and the PID controller 16 comprises control functions of proportion P and integral I.
Three measuring points are respectively arranged on the low-temperature economizer A outlet flue gas temperature measuring point 8), the low-temperature economizer B outlet flue gas temperature measuring point 9, the low-temperature economizer C outlet flue gas temperature measuring point 10 and the low-temperature economizer D outlet flue gas temperature measuring point 11, and two measuring points are respectively arranged on the low-temperature economizer inlet water temperature measuring point 12.
According to the working method of the automatic control system for the smoke temperature and the water temperature in the low-temperature economizer of the thermal power generating unit, when the thermal power generating unit normally operates, a main water supply loop is pressurized and heated by condensed water 1 from a hot well sequentially through a condensed water pump 2 and a shaft seal heater 3, and is continuously heated by a No. 8 low-pressure heater 4 and a No. 7 low-pressure heater 5, the heated condensed water enters a low-temperature economizer water quantity regulating valve 6 for regulation, and finally enters a deaerator after being heated by a No. 6 low-pressure heater 26; the water entering the low-temperature economizer system for cooling the smoke temperature is respectively taken from the inlet of a No. 8 low-pressure heater 4, and the temperature of the water is lower than the smoke temperature and the temperature of the outlet water in the low-temperature economizer; the temperature of the outlet of the No. 7 low-pressure heater 5 is higher than that of the inlet of the No. 8 low-pressure heater 4, and the requirement of a unit on the smoke temperature is met by jointly adjusting the water quantity adjusting valve 6 of the low-temperature economizer, the water taking adjusting valve 7 of the low feeding inlet and the boosting circulating pump 13; the water after cooling the smoke temperature is circulated by a low-temperature economizer system, then is converged into a main water supply system before a No. 6 low-pressure heater 26, and then enters a deaerator.
The common adjusting method of the water quantity adjusting valve 6, the low water inlet water taking adjusting valve 7 and the boosting circulating pump 13 of the low-temperature economizer comprises the following steps: the water quantity regulating valve 6 of the low-temperature economizer regulates the smoke temperature at the outlet of the low-temperature economizer, and the water inlet water taking regulating valve 7 of the low feeding port and the boosting circulating pump 13 jointly regulate the water temperature at the inlet of the economizer;
the outlet smoke temperature of each low-temperature economizer is controlled by a water quantity regulating valve 6 of the low-temperature economizer, a plurality of smoke measuring points are uniformly distributed at the outlets of the four low-temperature economizers, and the plurality of measuring points are subjected to median processing; considering the problem that the flue gas runs at low temperature for a long time and causes low-temperature corrosion to the pipe wall, the four screened outlet flue gas temperature measuring points pass through the small selection controller 17 to obtain a minimum flue gas temperature value as a controlled object of the first PID controller 14, the control set value of the outlet flue gas temperature is a low-temperature economizer outlet flue gas temperature set value 22, and the set value is manually set by an operator; the first PID controller 14 adjusts the functions including proportion P and integral I, when the minimum value of the smoke temperature at the outlet of the low-temperature economizer rises, positive deviation occurs between the actual minimum value of the smoke temperature of the low-temperature economizer and a set value 22 signal of the smoke temperature at the outlet of the low-temperature economizer, so that the proportion P and integral I functions of the PID controller 14 start to act, an instruction for closing the action of the water quantity regulating valve 6 of the low-temperature economizer is sent, and the smoke temperature is reduced by reducing the water temperature; similarly, when the minimum value of the smoke temperature at the outlet of the low-temperature economizer is reduced, a negative deviation occurs between the actual minimum value of the smoke temperature of the low-temperature economizer and the set value 22 signal of the smoke temperature at the outlet of the low-temperature economizer, so that the proportional P action and the integral I action of the PID controller 14 start to act, an instruction for opening the water quantity regulating valve 6 of the low-temperature economizer is sent, and the smoke temperature is increased by increasing the water temperature;
in order to prevent the maximum value of the outlet smoke temperature from being higher, the four screened outlet smoke temperature measuring points pass through a large selection controller 18 to obtain a maximum smoke temperature value, and when the maximum smoke temperature value of the low-temperature economizer is higher than the set value of the outlet smoke temperature of the low-temperature economizer by 223-6 ℃ under abnormal working conditions, downward small-amplitude correction processing is carried out on the set value 22 of the outlet smoke temperature of the low-temperature economizer through an adder 19 to form a final set value of the outlet smoke temperature control of the low-temperature economizer to enter adjustment;
considering the change working condition of the unit load instruction 21, the instruction of the water quantity regulating valve 6 of the low-temperature economizer is acted in advance through the action of the differential controller 20; when the unit load instruction 21 rises, the flue gas volume and the flue gas temperature rise, and at the moment, the differential controller 20 directly gives an instruction for closing the water regulating valve 6 of the low-temperature economizer to maintain the temperature stability; when the unit load instruction 21 is reduced, the flue gas volume and the flue gas temperature are both reduced, and then the differential controller 20 directly gives an instruction for opening the water regulating valve 6 of the low-temperature economizer to maintain the temperature stability;
finally, considering that the water quantity regulating valve 6 of the low-temperature economizer is a main regulating valve for feeding water into the deaerator, the whole unit has enough water feeding flow, a minimum flow protection link is designed, and when the actual water feeding flow is lower than a preset water feeding flow value, the water quantity regulating valve 6 of the low-temperature economizer is forbidden to be continuously closed;
the water temperature at the inlet of the low-temperature economizer is adjusted by a boosting circulating pump 13 and a low water inlet water taking adjusting valve 7 together, a plurality of measuring points are arranged on a low-temperature economizer inlet water temperature measuring point 12, and the plurality of measuring points are averaged; when the unit operates in a low-load section, the inlet water temperature is low, then the regulation is carried out through the boosting circulating pump 13, the regulation adopts a third PID controller 16 for regulation, the regulation comprises a proportion P function and an integral I function, when the inlet water temperature measuring point 12 of the low-temperature economizer rises, a positive deviation occurs between the actual inlet water temperature of the low-temperature economizer and a set value 23 signal of the inlet water temperature of the low-temperature economizer, so that the proportion P function and the integral I function of the PID controller 16 start to act, and an instruction for turning off the boosting circulating pump 13 to act is sent out to meet the requirement of the water temperature; similarly, when the water temperature measuring point 12 at the inlet of the low-temperature economizer is lowered, a negative difference occurs between the actual water temperature at the inlet of the low-temperature economizer and a signal of a set value 23 of the water temperature at the inlet of the low-temperature economizer, so that the proportional P function and the integral I function of the PID controller 16 start to act, and an instruction for starting the boosting circulating pump 13 to act is sent out to meet the requirement of the water temperature;
meanwhile, when the unit load command 21 changes, the command of the boosting circulating pump 13 is also acted in advance through the action of the differential controller 25 to meet the temperature requirement; when the unit load instruction 21 rises, the smoke volume and the smoke temperature rise, and at this time, the differential controller 25 directly gives an instruction for turning off the boosting circulating pump 13 to meet the temperature requirement; when the unit load instruction 21 is reduced, the smoke volume and the smoke temperature are reduced, and the differential controller 25 directly gives an instruction for starting the boosting circulating pump 13 to meet the temperature requirement;
when the unit runs from a low load to a high load section, the boosting circulating pump 13 is gradually closed along with the rising of water temperature, and after the opening degree of the boosting circulating pump is 5 percent, if the water temperature measuring point 12 at the inlet of the low-temperature economizer is still higher than a set water temperature value 23 at the inlet of the low-temperature economizer, the fact that the boosting circulating pump 13 has no adjusting margin is shown, and the system is automatically switched to the water intake adjusting valve 7 at the low inlet to continuously adjust the water temperature measuring point 12 at the inlet of the low-temperature economizer; the regulation is realized by adopting a second PID controller 15, and comprises a proportional P action and an integral I action;
when the water temperature measuring point 12 at the inlet of the low-temperature economizer rises, a positive deviation occurs between the actual water temperature at the inlet of the low-temperature economizer and a signal of a set value 23 of the water temperature at the inlet of the low-temperature economizer, so that the proportional P action and the integral I action of the PID controller 15 start to act, and an instruction for opening the water intake regulating valve 7 at the low inlet is sent out to meet the requirement of the water temperature; similarly, when the water temperature measuring point 12 at the inlet of the low-temperature economizer is lowered, a negative difference occurs between the actual water temperature at the inlet of the low-temperature economizer and a signal of a set value 23 of the water temperature at the inlet of the low-temperature economizer, so that the proportional P function and the integral I function of the PID controller 15 start to act, and an instruction for closing the water intake regulating valve 7 at the inlet is sent out to meet the requirement of the water temperature;
meanwhile, when the unit load command 21 changes, the low inlet water intake regulating valve 7 command is also actuated in advance through the action of the differential controller 24 to meet the temperature requirement; when the unit load instruction 21 rises, the smoke gas quantity and the smoke gas temperature rise, and at the moment, the differential controller 24 directly gives an instruction of opening the water intake regulating valve 7 at the low water inlet to meet the temperature requirement; when the unit load instruction 21 is reduced, the smoke gas quantity and the smoke gas temperature are reduced, and at the moment, the differential controller 24 directly gives an instruction for closing the water intake regulating valve 7 at the low inlet to meet the temperature requirement;
when the unit is switched from high load to low load operation, the low water inlet water-taking regulating valve 7 is gradually closed, and when the lower limit is closed, if the low-temperature economizer inlet water temperature measuring point 12 is still lower than the low-temperature economizer inlet water temperature set value 23, the low water inlet water-taking regulating valve 7 is indicated to have no regulating margin, and the system is automatically switched to the boosting circulating pump 13 to continue regulating the low-temperature economizer inlet water temperature measuring point 12.
Compared with the prior art, the utility model discloses possess following advantage:
(1) in the operation loop of the low-temperature economizer, control objects of the automatic control gates are determined, and the working intervals of the automatic control gates are reasonably arranged.
(2) For controlling the water temperature at the inlet of the low-temperature economizer, the idea of jointly controlling the boosting circulating pump and the low water inlet water taking regulating valve is provided, two sets of automatic control logics are mutually undisturbed and autonomously switched according to the operating load working condition, after the boosting circulating pump and the low water inlet water taking regulating valve are simultaneously put into automation, the system can automatically judge which regulating loop plays a role according to the current operating state, and the two regulating loops cannot mutually influence.
(3) And (4) intelligently predicting the change of the steam temperature when the load changes by considering the variable load working condition, and intervening in advance.
(4) After the control method can meet the requirement of transforming the low-temperature economizer of the thermal power generating unit, the smoke temperature and water temperature control loop can realize automatic operation. The operation burden of operators can be greatly reduced, and further guarantee is provided for the economical and safe operation of the power plant.
Drawings
Fig. 1 is a schematic view of the control system of the present invention.
Description of reference numerals:
1-condensed water; 2-condensate pump; 3-shaft seal heater;
4-No. 8 low pressure heater; 5-No. 7 low pressure heater;
6-water quantity regulating valve of low-temperature economizer; 7-low inlet water intake regulating valve;
8, measuring a smoke temperature point at the outlet of the low-temperature economizer A;
9-measuring point of smoke temperature at outlet of low-temperature economizer B;
10-measuring point for smoke temperature at outlet of low-temperature economizer C;
11-measuring point of smoke temperature at outlet of low-temperature coal economizer D;
12-measuring point for water temperature at inlet of low-temperature economizer;
13-pressure boosting circulation pump; 14-first PID controller; 15-second PID controller; 16-third PID controller;
17-small selection controller; 18-large selection controller; 19-adder; 20-first derivative controller;
21-unit load command; 22-set value of smoke temperature at outlet of low-temperature economizer;
23-set value of water temperature at inlet of low-temperature economizer; 24-differential controller; 25-second derivative controller;
26-No. 6 low pressure heater.
Detailed Description
The present invention will be described in further detail with reference to the accompanying drawings and specific embodiments.
As shown in figure 1, the utility model relates to an automatic control system for smoke temperature and water temperature in a low-temperature economizer of a thermal power generating unit, which comprises condensed water 1 from a hot well, a condensed water pump 2 of a condensed water pressurizing device, a shaft seal heater 3 of the condensed water heating device, a No. 8 low-pressure heater 4 and a No. 7 low-pressure heater 5 of the condensed water heating device, a low-temperature economizer water quantity regulating valve 6 arranged at the outlet of the No. 7 low-pressure heater 5 and a first PID controller 14 connected with the low-temperature economizer water quantity regulating valve, a No. 6 low-pressure heater 26 of the condensed water heating device to a deaerator, a low inlet water intake regulating valve 7 arranged at the inlet of the No. 8 low-pressure heater 4 and a second PID controller 15 connected with the low inlet water intake regulating valve, a boosting circulating pump 13 arranged at the tail end of the low-temperature economizer system and a third PID controller 16 connected with the low-temperature economizer, a smoke temperature measuring point 8, three measuring points are usually arranged, a low-temperature economizer B outlet flue gas temperature measuring point 9 arranged at the outlet of a low-temperature economizer B is usually arranged, three measuring points are usually arranged, a low-temperature economizer C outlet flue gas temperature measuring point 10 arranged at the outlet of a low-temperature economizer C is usually arranged, three measuring points are usually arranged, a low-temperature economizer D outlet flue gas temperature measuring point 11 arranged at the outlet of a low-temperature economizer D is usually arranged, three measuring points are usually arranged, and a low-temperature economizer inlet water temperature measuring point 12 arranged at the outlet of a low water feeding and adjusting valve 7 is usually arranged. The input signal of the first PID controller 14 comprises three paths, the first path is the outlet smoke temperature needing to be controlled and regulated, the control object selects the minimum value of the outlet smoke temperature through the small selection controller 17, the small selection controller 17 is used for selecting the minimum value of the input signal as an output signal, and the control of the minimum value means that the occurrence of low-temperature corrosion in the low-temperature economizer is prevented; the second path is a control set value of the outlet smoke temperature, and is realized through a set value 22 of the outlet smoke temperature of the low-temperature economizer, the realization mode of the set value is that an operator manually sets the set value, the outlet smoke temperature is subjected to a large selection controller 18 to select the maximum value of the smoke temperature, the large selection controller 18 is used for selecting the maximum value of an input signal as an output signal, the output maximum value of the smoke temperature is superposed on the set value 22 of the outlet smoke temperature of the low-temperature economizer through an adder 19, and the significance of the part is to prevent the over-high controlled smoke temperature and form the input signal finally entering the PID controller 14; the third path is a differential loop of the unit load instruction 21, which is realized by the first differential controller 20, and finally enters a feedforward part of the first PID controller 14, and the feedforward is a part of the first PID controller 14, so that the output can be more accurate and faster, and the first PID controller 14 has the control functions of proportion P and integral I. The input signal of the second PID controller 15 comprises three paths, wherein the first path is a low-temperature economizer inlet water temperature measuring point 12 and is used as a control object of the controller; the second way is a set value 23 of the water temperature at the inlet of the low-temperature economizer, and the set value is manually set by an operator; the third path is a differential loop of the unit load instruction 21, which is realized by a differential controller 24, and finally enters a feedforward part of the PID controller 15, and the PID controller 15 comprises control functions of proportion P and integral I. The input signal of the third PID controller 16 comprises three paths, wherein the first path is a low-temperature economizer inlet water temperature measuring point 12 and is used as a control object of the controller; the second way is a set value 23 of the water temperature at the inlet of the low-temperature economizer, and the set value is manually set by an operator; the third path is a differential loop of the unit load instruction 21, which is realized by the second differential controller 25, and finally enters a feed-forward part of the PID controller 16, and the PID controller 16 comprises control functions of proportion P and integral I.
The specific control method and the working principle are as follows: when the unit normally operates, the main water supply loop sequentially pressurizes and heats the unit through a condensate pump 2 and a shaft seal heater 3 through condensate water 1 from a hot well, continuously heats the unit through a No. 8 low-pressure heater 4 and a No. 7 low-pressure heater 5, and the heated condensate water enters a low-temperature economizer water quantity regulating valve 6 for regulation and finally enters a deaerator after being heated through a No. 6 low-pressure heater 26. The water entering the low-temperature economizer system to cool the smoke temperature is respectively taken from the inlet of a No. 8 low-pressure heater 4, and the temperature of the water is lower than the smoke temperature and the outlet water temperature in the low-temperature economizer; the temperature of the outlet of the No. 7 low-pressure heater is higher than that of the inlet of the No. 8 low-pressure heater 4, and the requirement of the unit on the smoke temperature is met by jointly adjusting the water quantity adjusting valve 6 of the low-temperature economizer, the water taking adjusting valve 7 of the low inlet and the boosting circulating pump 13. The water after cooling the smoke temperature is circulated by a low-temperature economizer system, then is converged into a main water supply system before a No. 6 low-pressure heater 26, and then enters a deaerator.
At present, the main reason that automatic control can't drop into in the low temperature economizer system is that can not effectual cooperation is adjusted between each governing door, so the utility model aims at providing a practical effectual control strategy. The common adjusting method of the water quantity adjusting valve 6 of the low-temperature economizer, the water intake adjusting valve 7 of the low water inlet and the boosting circulating pump 13 comprises the following steps: the low-temperature economizer water quantity regulating valve 6 regulates the smoke temperature at the outlet of the low-temperature economizer, and the low-feeding-port water taking regulating valve 7 and the boosting circulating pump 13 jointly regulate the water temperature at the inlet of the economizer.
The water quantity regulating valve 6 of the low-temperature coal economizer is designed to control the outlet smoke temperature of each low-temperature coal economizer. The design is that the smoke temperature at the outlet of the controlled quantity is processed at first, smoke measuring points are uniformly distributed at the outlets of four low-temperature coal economizers, wherein three measuring points are generally distributed at the smoke temperature measuring point 8 at the outlet of the low-temperature coal economizer A, and three median processing is carried out on the three measuring points; the method comprises the following steps that (1) three measuring points are generally arranged at an outlet flue gas temperature measuring point 9 of a low-temperature economizer B, and three median values are processed at the three measuring points; three measuring points are generally arranged at an outlet flue gas temperature measuring point 10 of the low-temperature economizer C, and three median values are taken for the three measuring points; three measuring points are generally arranged at an outlet flue gas temperature measuring point 11 of the low-temperature economizer D, and three median values are obtained for the three measuring points. Considering the problem that the long-term low-temperature operation of flue gas can cause low-temperature corrosion to the pipe wall, the screened 4 outlet flue gas temperature measuring points pass through the small selection controller 17 to obtain a minimum flue gas temperature value as a controlled object of the first PID controller 14, the control set value of the outlet flue gas temperature is a low-temperature economizer outlet flue gas temperature set value 22, and the set value is manually set by an operator; the first PID controller 14 adjusts the functions including proportion P and integral I, when the minimum value of the smoke temperature at the outlet of the low-temperature economizer rises, positive deviation occurs between the actual minimum value of the smoke temperature of the low-temperature economizer and the set value 22 signal of the smoke temperature at the outlet of the low-temperature economizer, so that the proportion P and integral I functions of the PID controller 14 start to act, an instruction for closing the action of the water quantity regulating valve 6 of the low-temperature economizer is sent, and the smoke temperature is reduced by reducing the water temperature. Similarly, when the minimum value of the smoke temperature at the outlet of the low-temperature economizer is reduced, a negative deviation occurs between the actual minimum value of the smoke temperature of the low-temperature economizer and the signal of the set value 22 of the smoke temperature at the outlet of the low-temperature economizer, so that the proportional P action and the integral I action of the PID controller 14 start to act, a command for opening the water quantity regulating valve 6 of the low-temperature economizer is sent, and the smoke temperature is increased by increasing the water temperature.
In addition, considering the problem that the flue gas inside the boiler flows unevenly, which may cause large deviation of the outlet flue gas temperature of each low-temperature economizer, in order to prevent the maximum value of the outlet flue gas temperature from being too high, 4 outlet flue gas temperature measuring points which are screened out are passed through a large-selection controller 18 to obtain the maximum flue gas temperature value, and when the maximum flue gas temperature value of the low-temperature economizer is higher than the set value of the outlet flue gas temperature of the low-temperature economizer by about 225 ℃ under abnormal working conditions, the set value 22 of the outlet flue gas temperature of the low-temperature economizer is corrected downwards by a small amplitude through an adder 19 to form the final set value of the outlet flue gas temperature of the low-temperature economizer to be adjusted.
Considering the change condition of the unit load instruction 21, the low-temperature economizer water quantity regulating valve 6 instruction is actuated in advance through the action of the differential controller 20. When the unit load instruction 21 rises, the flue gas volume and the flue gas temperature rise, and at the moment, the differential controller 20 directly gives an instruction for closing the water regulating valve 6 of the low-temperature economizer to maintain the temperature stability; when the unit load command 21 is reduced, the flue gas volume and the flue gas temperature are both reduced, and then the differential controller 20 directly gives a command of opening the water regulating valve 6 of the low-temperature economizer to maintain the temperature stable.
And finally, considering that the water quantity regulating valve 6 of the low-temperature economizer is a main regulating valve for feeding water into the deaerator and the whole unit has enough water feeding flow, a minimum flow protection link is specially designed, and when the actual water feeding flow is lower than a preset water feeding flow value, the regulating valve is forbidden to be continuously closed. Taking a certain 660MW ultra-supercritical unit as an example, according to different loads, the required water supply flow is preset as follows:
| load MW | 0 | 300 | 420 | 600 | 650 | 660 | 700 |
| Flow rate t/h | 500 | 650 | 900 | 1300 | 1400 | 1450 | 1500 |
Other different capacity units may set such functions according to specifications provided by the boiler manufacturer.
The design uses a boosting circulating pump 13 and a low inlet water intake regulating valve 7 to jointly regulate the water temperature at the inlet of the low-temperature economizer. The low-temperature economizer inlet water temperature measuring point 12 is generally provided with two measuring points, and two-time averaging processing is carried out on the two measuring points. When the unit operates in a low-load section, the inlet water temperature is low, then the regulation is carried out through the boosting circulating pump 13, the regulation adopts a third PID controller 16 for regulation, the regulation comprises a proportion P function and an integral I function, when the inlet water temperature measuring point 12 of the low-temperature economizer rises, a positive deviation occurs between the actual inlet water temperature of the low-temperature economizer and a set value 23 signal of the inlet water temperature of the low-temperature economizer, so that the proportion P function and the integral I function of the PID controller 16 start to act, and an instruction for turning off the boosting circulating pump 13 to act is sent out to meet the requirement of the water temperature; similarly, when the low-temperature economizer inlet water temperature measuring point 12 is lowered, a negative difference occurs between the actual inlet water temperature of the low-temperature economizer and the signal of the low-temperature economizer inlet water temperature set value 23, so that the proportional P action and the integral I action of the PID controller 16 start to act, and a command of starting the boosting circulating pump 13 is sent out to meet the requirement of water temperature.
Meanwhile, when the unit load command 21 changes, the command of the booster circulation pump 13 is also actuated in advance by the action of the differential controller 25 to meet the temperature demand. When the unit load instruction 21 rises, the smoke volume and the smoke temperature rise, and at this time, the differential controller 25 directly gives an instruction for turning off the boosting circulating pump 13 to meet the temperature requirement; when the unit load command 21 is reduced, the flue gas volume and the flue gas temperature are both reduced, and at this time, the differential controller 25 directly gives a command of starting the boost circulating pump 13 to meet the temperature requirement.
When the unit is in operation from a low load to a high load section, the boosting circulating pump 13 is gradually closed along with the rising of water temperature, and after the opening degree of 5% is closed, if the water temperature measuring point 12 at the inlet of the low-temperature economizer is still higher than the set value 23 of the water temperature at the inlet of the low-temperature economizer, the fact that the boosting circulating pump 13 has no adjusting margin indicates, and the system is automatically switched to the water intake adjusting valve 7 at the low feeding inlet to continuously adjust the water temperature measuring point 12 at the inlet of the low-temperature economizer. The regulation is carried out by a second PID controller 15, and comprises proportional P action and integral I action.
When the water temperature measuring point 12 at the inlet of the low-temperature economizer rises, a positive deviation occurs between the actual water temperature at the inlet of the low-temperature economizer and a signal of a set value 23 of the water temperature at the inlet of the low-temperature economizer, so that the proportional P action and the integral I action of the PID controller 15 start to act, and an instruction for opening the water intake regulating valve 7 at the low inlet is sent out to meet the requirement of the water temperature; similarly, when the low-temperature economizer inlet water temperature measuring point 12 is lowered, a negative difference occurs between the actual inlet water temperature of the low-temperature economizer and the set value 23 signal of the inlet water temperature of the low-temperature economizer, so that the proportional P function and the integral I function of the PID controller 15 start to act, and an instruction for closing the water inlet water taking regulating valve 7 is sent out to meet the requirement of the water temperature.
Meanwhile, when the unit load command 21 changes, the low inlet water intake regulating valve 7 command is also actuated in advance by the action of the differential controller 24 to meet the temperature demand. When the unit load instruction 21 rises, the smoke gas quantity and the smoke gas temperature rise, and at the moment, the differential controller 24 directly gives an instruction of opening the water intake regulating valve 7 at the low water inlet to meet the temperature requirement; when the unit load instruction 21 is reduced, the smoke volume and the smoke temperature are reduced, and at the moment, the differential controller 24 directly gives an instruction for closing the water intake regulating valve 7 at the low inlet to meet the temperature requirement.
When the unit is switched from high load to low load operation, the low water inlet water-taking regulating valve 7 is gradually closed, and when the lower limit is closed, if the low-temperature economizer inlet water temperature measuring point 12 is still lower than the low-temperature economizer inlet water temperature set value 23, the low water inlet water-taking regulating valve 7 is indicated to have no regulating margin, and the system is automatically switched to the boosting circulating pump 13 to continue regulating the low-temperature economizer inlet water temperature measuring point 12.
Claims (5)
1. The utility model provides a smoke temperature and temperature automatic control system in thermal power generating unit low temperature economizer which characterized in that: comprises condensed water (1), a condensed water pump (2) of a condensed water pressurizing device, a shaft seal heater (3) of the condensed water heating device, a No. 8 low-pressure heater (4) and a No. 7 low-pressure heater (5) of the condensed water heating device, a low-temperature economizer water quantity regulating valve (6) arranged at the outlet of the No. 7 low-pressure heater (5), a first PID controller (14) connected with the low-temperature economizer water quantity regulating valve, a No. 6 low-pressure heater (26) of the condensed water heating device to a deaerator, a low water inlet water taking regulating valve (7) arranged at the inlet of the No. 8 low-pressure heater (4), a second PID controller (15) connected with the low water inlet water taking regulating valve, a boosting circulating pump (13) arranged at the tail end of a low-temperature economizer system, a third PID controller (16) connected with the boosting circulating pump, and a low-temperature economizer A outlet flue gas temperature measuring point (, a smoke temperature measuring point (9) at the outlet of the low-temperature economizer B, a smoke temperature measuring point (10) at the outlet of the low-temperature economizer C, a smoke temperature measuring point (11) at the outlet of the low-temperature economizer D and a water temperature measuring point (12) at the inlet of the low-temperature economizer, wherein the smoke temperature measuring point is arranged at the outlet of the low-temperature economizer B, the smoke temperature measuring point (11) is arranged at the outlet of the low-temperature economizer D, and the water temperature measuring point (12) at the inlet of the low-temperature.
2. The automatic control system for the smoke temperature and the water temperature in the thermal power generating unit low-temperature economizer according to claim 1 is characterized in that: the input signal of the first PID controller (14) comprises three paths, the first path is the outlet smoke temperature needing to be controlled and regulated, and the control object selects the minimum value of the outlet smoke temperature through the small selection controller (17); the second path is a control set value of the outlet smoke temperature, and is realized through a set value (22) of the outlet smoke temperature of the low-temperature economizer, the set value is realized by manually setting by an operator, the outlet smoke temperature is subjected to a large selection controller (18), the maximum value of the smoke temperature is selected, the maximum value of the smoke temperature output by the large selection controller (18) is superposed on the set value (22) of the outlet smoke temperature of the low-temperature economizer through an adder (19), and an input signal finally entering a PID controller (14) is formed; the third path is a differential loop of the unit load instruction (21), is realized by a first differential controller (20), and finally enters a feed-forward part of a first PID controller (14); the first PID controller (14) includes proportional (P), integral (I) control actions.
3. The automatic control system for the smoke temperature and the water temperature in the thermal power generating unit low-temperature economizer according to claim 1 is characterized in that: the input signal of the second PID controller (15) comprises three paths, wherein the first path is a low-temperature economizer inlet water temperature measuring point (12) and is used as a control object of the second PID controller; the second path is a set value (23) of the water temperature at the inlet of the low-temperature economizer, and the set value is manually set by an operator; the third path is a differential loop of the unit load instruction (21) and is realized by a differential controller (24), and finally enters a feedforward part of a PID controller (15), and the PID controller (15) comprises proportional (P) and integral (I) control functions.
4. The automatic control system for the smoke temperature and the water temperature in the thermal power generating unit low-temperature economizer according to claim 1 is characterized in that: the input signal of the third PID controller (16) comprises three paths, wherein the first path is a low-temperature economizer inlet water temperature measuring point (12) and is used as a control object of the controller; the second path is a set value (23) of the water temperature at the inlet of the low-temperature economizer, and the set value is manually set by an operator; the third path is a differential loop of the unit load instruction (21), is realized by a second differential controller (25), and finally enters a feedforward part of a PID controller (16), and the PID controller (16) comprises proportional (P) and integral (I) control functions.
5. The automatic control system for the smoke temperature and the water temperature in the thermal power generating unit low-temperature economizer according to claim 1 is characterized in that: three measuring points are uniformly arranged on a low-temperature economizer A outlet flue gas temperature measuring point (8), a low-temperature economizer B outlet flue gas temperature measuring point (9), a low-temperature economizer C outlet flue gas temperature measuring point (10) and a low-temperature economizer D outlet flue gas temperature measuring point (11), and two measuring points are arranged on a low-temperature economizer inlet water temperature measuring point (12).
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| CN202022712521.3U CN213630384U (en) | 2020-11-22 | 2020-11-22 | Automatic control system for smoke temperature and water temperature in low-temperature economizer of thermal power generating unit |
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| CN202022712521.3U CN213630384U (en) | 2020-11-22 | 2020-11-22 | Automatic control system for smoke temperature and water temperature in low-temperature economizer of thermal power generating unit |
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