CN113267061B - Cooling tower control system and control method - Google Patents
Cooling tower control system and control method Download PDFInfo
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- CN113267061B CN113267061B CN202110525664.XA CN202110525664A CN113267061B CN 113267061 B CN113267061 B CN 113267061B CN 202110525664 A CN202110525664 A CN 202110525664A CN 113267061 B CN113267061 B CN 113267061B
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28C—HEAT-EXCHANGE APPARATUS, NOT PROVIDED FOR IN ANOTHER SUBCLASS, IN WHICH THE HEAT-EXCHANGE MEDIA COME INTO DIRECT CONTACT WITHOUT CHEMICAL INTERACTION
- F28C1/00—Direct-contact trickle coolers, e.g. cooling towers
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F25/00—Component parts of trickle coolers
- F28F25/10—Component parts of trickle coolers for feeding gas or vapour
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F28—HEAT EXCHANGE IN GENERAL
- F28F—DETAILS OF HEAT-EXCHANGE AND HEAT-TRANSFER APPARATUS, OF GENERAL APPLICATION
- F28F27/00—Control arrangements or safety devices specially adapted for heat-exchange or heat-transfer apparatus
- F28F27/003—Control arrangements or safety devices specially adapted for heat-exchange or heat-transfer apparatus specially adapted for cooling towers
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Abstract
The invention discloses a cooling tower control system and a control method, wherein the control system comprises a control module (8), a water temperature sensor (9), a temperature and humidity sensor (10) and a temperature and humidity forecasting device (11), the control module (8) comprises a water temperature setter (81), a PID (proportion integration differentiation) controller (82) and a cutter (83), and in the control method, an atmosphere wet bulb temperature measurement value and an atmosphere wet bulb temperature forecast value are respectively input into the water temperature setter (81), and a temperature set value ST is output after analysis. The control system provided by the invention has the advantages of simple structure, low cost, stable and reliable control method, high efficiency, energy conservation, wide adaptability and easy realization.
Description
Technical Field
The invention relates to the field of cooling towers, in particular to a cooling tower control system and a control method.
Background
Industrial recirculating cooling water systems are widely used in various industrial sectors for the purpose of cooling the equipment and materials at the end of the process. The temperature of the circulating cooling water is raised after heat exchange with equipment or materials at the tail end of the process, the circulating cooling water flows back to the cooling tower, and flows to the tail end of the process again after evaporation cooling to form circulation. A large amount of electric energy is consumed to drive an overhead fan to suck air in the atmospheric environment in the working process of the cooling tower so as to promote evaporative cooling of cooling water, and the driving force in the process is the difference between the temperature of the cooling water and the temperature of an atmospheric wet bulb.
Theoretically, if the air volume of the tower top fan is infinite, the cooling water can be cooled to the wet bulb temperature of the atmosphere, wherein the wet bulb temperature of the atmosphere is obtained by looking up a table of a dry bulb temperature value and a humidity value. In engineering practice, even if the rotating speed of the tower top fan is adjusted to the highest value to enable the air volume to be at the maximum load, the lowest limit water temperature of cooling water cooled by a cooling tower is about 3-4 ℃ higher than the temperature value of an atmospheric wet bulb.
In order to reduce the operation energy consumption of the tower top fan and the water temperature interval required by the heat exchange at the tail end of the process as much as possible, the rotating speed of the tower top fan needs to be controlled. In the currently known cooling tower control method, the temperature of the outlet water of the cooling tower is generally collected and compared with a given temperature, the deviation of the outlet water and the given temperature is sent to a PID (proportion integration differentiation) controller, and the speed regulation value of a tower top fan is output to complete feedback control. This control method, although simple, fails to take into account the effects of atmospheric wet bulb temperature changes. On one hand, the atmospheric wet bulb temperature is the theoretical lowest limit of the outlet water temperature of the cooling tower, and due to the change of the atmospheric environment, if the given outlet water temperature is equal to or only slightly less than the current atmospheric wet bulb temperature, no matter the rotating speed of a fan at the top of the tower is increased at most, the outlet water temperature of the cooling water cannot reach the given temperature value, and only the power consumption is wasted; on the other hand, the atmospheric wet bulb temperature changes dynamically, if the atmospheric wet bulb temperature rises significantly in a short period of time in the future through weather forecast, the outlet water temperature of cooling water should be reduced as far as possible at present to catch the opportunity to refrigerate as much as possible, so that the circulating water accumulates as much "cold energy" as possible to cope with the adverse effect of the rising event of the atmospheric wet bulb temperature on the operation energy consumption of the process terminal and the cooling tower after the short period of time in the future.
Disclosure of Invention
In order to solve the technical problems, the invention provides a cooling tower control system which is simple in structure, low in cost, stable and reliable, wide in adaptability and easy to implement. The technical scheme for solving the problems is as follows: the utility model provides a cooling tower control system for cooling control of cooling water in the cooling tower that industrial circulating cooling water system belongs to, industrial circulating cooling water system includes but not limited to cooling tower (1), working shaft (2), female pipe valve (3), female pipe (4) of supplying water, female pipe (7) of return water and a plurality of branch pipes of being connected with female pipe (4) of supplying water and female pipe (7) of return water respectively, and each branch pipe all is equipped with branch pipe valve (5) and terminal heat exchanger (6) of technology, and affiliated cooling tower (1) includes adjustable speed motor (101), top of the tower fan (102) and tower body (103), thereby adjustable speed motor (101) and top of the tower fan (102) mechanical connection just are used for driving top of the tower fan (102) operation to realize the evaporative cooling of cooling water, thereby female pipe (4) of supplying water are drawn forth and are in proper order with working shaft (2) from tower body (103) bottom, The main pipe valve (3) is connected with one end of the branch pipes and supplies water for all the branch pipes, the return main pipe (7) is connected with the other end of the branch pipes and collects the cooling water of all the branch pipes to the top of the tower body (103), and all the branch pipes are connected in parallel; cooling tower control system includes control module (8), temperature sensor (9), temperature and humidity sensor (10) and humiture forecasting device (11) respectively with control module (8) electric connection, control module (8) still with adjustable speed motor (101) electric connection in order to realize the rotational speed perception and the control of adjustable speed motor (101), wherein:
(a) the control module (8) comprises a water temperature setter (81), a PID controller (82) and a chopper (83), and is used for performing control operation according to input information and outputting a speed regulating instruction to the speed-adjustable motor (101);
(b) the water temperature sensor (9) is used for acquiring the temperature of cooling water in a water supply main pipe (4) close to the cooling tower (1) in real time and outputting the temperature to the control module (8);
(c) the temperature and humidity sensor (10) is used for acquiring a temperature value and a humidity value of the atmosphere near the cooling tower (1) in real time, and simultaneously, synchronously converting according to the temperature value and the humidity value of the atmosphere to obtain an atmospheric wet bulb temperature measurement value and outputting the atmospheric wet bulb temperature measurement value to the control module (8);
(d) the temperature and humidity forecasting device (11) is used for being networked with a weather forecasting mechanism in real time to obtain future atmospheric temperature values and humidity values of the region where the cooling tower (1) is located, and meanwhile, the forecasted atmospheric temperature values and humidity values are converted into atmospheric wet bulb temperature forecast values and output to the control module (8).
Based on the cooling tower control system, a cooling tower control method is provided, and an atmospheric wet bulb temperature measured value obtained by a temperature and humidity sensor (10) and an atmospheric wet bulb temperature predicted value obtained by a temperature and humidity forecasting device (11) are respectively input into a water temperature setter (81), and are analyzed by the water temperature setter (81) to output a temperature set value ST; then the temperature set value ST is compared with the water temperature obtained by the water temperature sensor (9) to obtain the deviation of the temperature set value ST and the water temperature, the comparison result is sent to a PID controller (82), and the motor speed regulation value delta n is output after PID operation1To a chopper (83) and simultaneously to the current rotation speed value n of the adjustable speed motor (101)iSending the speed-variable motor to a cutter (83), and performing cutting calculation according to the following formula2And finally output to a speed-adjustable motor (101) to finish speed adjustment:
in the formula (1), Δ n1And Δ n2And Deltan is the motor speed regulating value operation result output by the PID controller (82) and the chopper (83), NminAnd NmaxThe tower top fans are respectively input into the interceptor (83) in advance according to the design data(102) Minimum and maximum permissible rotational speeds of niThe unit of the current rotating speed value of the speed-adjustable motor (101) is r/min.
In the cooling tower control method, the temperature set value ST analyzed and output by the water temperature setter (81) is calculated according to the following formula:
in the formula (2), ST is a temperature set value output by the water temperature setter (81); t is tiAnd tfRespectively obtaining a current atmospheric wet bulb temperature measured value obtained by a temperature and humidity sensor (10) and an atmospheric wet bulb temperature forecast value obtained by a temperature and humidity forecast device (11) after h hours, wherein h is between 0.5 and 5; t isminAnd TmaxRespectively determining the lower limit value and the upper limit value of the optimal temperature of cooling water in the water supply main pipe (4) according to the process requirements of a circulating cooling water system; a and b are a first temperature difference value and a second temperature difference value, respectively, wherein a is between 2 and 4 ℃ and b is between 3 and 5 ℃.
The invention has the beneficial effects that:
1. the control system provided by the invention only comprises the control module, the water temperature sensor, the temperature and humidity sensor and the temperature and humidity forecasting device, and the control module can be realized by slightly improving the existing controller, so that the control system has the advantages of simple structure and low cost.
2. The control method of the invention fully considers the influence of the atmospheric wet bulb temperature and the change condition thereof in a short period of time in the future on the refrigerating capacity of the cooling tower, and simultaneously considers the requirements of the tail end of the process and the operation energy saving requirement of the tower top fan: if the current atmospheric wet bulb temperature is higher, the current atmospheric wet bulb temperature minus a smaller temperature difference value is still higher than the upper limit value of the optimal temperature of the cooling water in the water supply main pipe (4), at this moment, the cooling tower cannot actually supply the upper limit value of the optimal temperature of the cooling water in the water supply main pipe (4), and the current atmospheric wet bulb temperature minus a smaller temperature difference value is taken as a given temperature value of the cooling water in the control system. If the current atmospheric wet bulb temperature minus a small temperature difference value is lower than the upper limit value of the optimal temperature of the cooling water in the water supply main pipe (4), whether the atmospheric wet bulb temperature can be obviously increased in a short period of time in the future or not should be considered: if the temperature does not rise remarkably, the upper limit value of the optimal temperature of the cooling water in the water supply main pipe (4) is used as a given temperature value of the cooling water in the control system, so that the process requirement is met, and the rotating speed of a tower top fan is as low as possible to save the operation energy consumption; otherwise, the given temperature value of the cooling water in the control system is compared with the result obtained by subtracting a certain smaller temperature difference from the optimal temperature upper limit value of the cooling water in the water supply main pipe (4) and the current atmospheric wet bulb temperature, and the larger value of the two is taken, so that the process requirement is met, the tower top fan is enabled to develop enough horsepower to promote the cooling of the circulating cooling water as far as possible, and the 'cold energy' is accumulated to solve the problems of difficult cooling and higher cooling energy consumption caused by the obvious rise of the future atmospheric wet bulb temperature, so that the efficient and stable operation of the circulating cooling water system is ensured.
3. In the control method, the interceptor is additionally arranged on the basis of the PID controller, and the motor speed regulation value output by the PID controller and the current rotating speed value of the motor are simultaneously input into the interceptor to ensure that the motor speed regulation value finally output to the actuating mechanism is between the lowest allowable rotating speed value and the highest allowable rotating speed value of the speed-adjustable motor, so that control errors can be avoided, and the rotating speed of the speed-adjustable motor is always equal to or greater than the minimum allowable rotating speed value to meet the lowest refrigeration requirement of the cooling tower and is less than or equal to the highest allowable rotating speed value.
Drawings
Fig. 1 is a schematic structural diagram of an industrial circulating cooling water system and a control system for controlling the cooling tower of the cooling water system in an embodiment of the invention, wherein 1 is a cooling tower 1, 2 is a water supply pump, 3 is a main pipe valve, 4 is a water supply main pipe, 5 is a branch pipe valve, 6 is a process end heat exchanger, 7 is a return water main pipe, 8 is a control module, 9 is a water temperature sensor, 10 is a temperature and humidity sensor, and 11 is a temperature and humidity forecasting device; wherein 101 in the cooling tower (1) is a speed regulating motor, 102 is a tower top fan, and 103 is a tower body.
Fig. 2 is a flow chart of a cooling tower control method according to an embodiment of the present invention, where 9 is a water temperature sensor, 10 is a temperature and humidity sensor, 11 is a temperature and humidity forecasting device, 101 is a speed adjustable motor in the cooling tower, and 81, 82, and 83 are a water temperature setter, a PID controller, and a chopper in a control module, respectively.
Detailed Description
The invention is further described below with reference to the figures and examples.
As shown in fig. 1 and 2, a cooling tower control system is used for cooling control of cooling water in a cooling tower of an industrial circulating cooling water system, the industrial circulating cooling water system includes, but is not limited to, a cooling tower (1), a water supply pump (2), a main pipe valve (3), a water supply main pipe (4), a water return main pipe (7) and a plurality of branch pipes connected with the water supply main pipe (4) and the water return main pipe (7) respectively, each branch pipe is provided with a branch pipe valve (5) and a process end heat exchanger (6), the cooling tower (1) comprises a speed-adjustable motor (101), a tower top fan (102) and a tower body (103), the speed-adjustable motor (101) is mechanically connected with the tower top fan (102) and is used for driving the tower top fan (102) to operate so as to realize evaporative cooling of the cooling water, the water supply main pipe (4) is led out from the bottom of the tower body (103) and is sequentially connected with the water supply pump (2), The main pipe valve (3) is connected with one end of the branch pipes and supplies water for all the branch pipes, the return main pipe (7) is connected with the other end of the branch pipes and collects the cooling water of all the branch pipes to the top of the tower body (103), and all the branch pipes are connected in parallel; cooling tower control system includes control module (8), temperature sensor (9), temperature and humidity sensor (10) and humiture forecasting device (11) respectively with control module (8) electric connection, control module (8) still with adjustable speed motor (101) electric connection in order to realize the rotational speed perception and the control of adjustable speed motor (101), wherein:
(a) the control module (8) comprises a water temperature setter (81), a PID controller (82) and a chopper (83), and is used for performing control operation according to input information and outputting a speed regulating instruction to the speed-adjustable motor (101);
(b) the water temperature sensor (9) is used for acquiring the temperature of cooling water in a water supply main pipe (4) close to the cooling tower (1) in real time and outputting the temperature to the control module (8);
(c) the temperature and humidity sensor (10) is used for acquiring a temperature value and a humidity value of the atmosphere near the cooling tower (1) in real time, and simultaneously, synchronously converting according to the temperature value and the humidity value of the atmosphere to obtain an atmospheric wet bulb temperature measurement value and outputting the atmospheric wet bulb temperature measurement value to the control module (8);
(d) the temperature and humidity forecasting device (11) is used for being networked with a weather forecasting mechanism in real time to obtain future atmospheric temperature values and humidity values of the region where the cooling tower (1) is located, and meanwhile, the forecasted atmospheric temperature values and humidity values are converted into atmospheric wet bulb temperature forecast values and output to the control module (8).
As shown in fig. 2, in the cooling tower control method based on the cooling tower control system, the measured value of the atmospheric wet bulb temperature obtained by the temperature and humidity sensor (10) and the predicted value of the atmospheric wet bulb temperature obtained by the temperature and humidity forecasting device (11) are respectively input into the water temperature setter (81), and the set temperature value ST is output after being analyzed by the water temperature setter (81); then the temperature set value ST is compared with the water temperature obtained by the water temperature sensor (9) to obtain the deviation of the temperature set value ST and the water temperature, the comparison result is sent to a PID controller (82), and the motor speed regulation value delta n is output after PID operation1To a chopper (83) and simultaneously to the current rotation speed value n of the adjustable speed motor (101)iSending the speed-variable motor to a cutter (83), and performing cutting calculation according to the following formula2And finally output to a speed-adjustable motor (101) to finish speed adjustment:
in the formula (1), Δ n1And Δ n2And Deltan is the motor speed regulating value operation result output by the PID controller (82) and the chopper (83), NminAnd NmaxRespectively, a minimum allowable rotation speed and a maximum allowable rotation speed, n, of a tower top fan (102) inputted to a chopper (83) in advance based on design dataiThe unit of the current rotating speed value of the speed-adjustable motor (101) is r/min.
Further, the temperature set value ST analyzed and outputted by the water temperature setter (81) as described above is calculated by the following equation:
in the formula (2), ST is a temperature set value output by the water temperature setter (81); t is tiAnd tfRespectively obtaining a current atmospheric wet bulb temperature measured value obtained by a temperature and humidity sensor (10) and an atmospheric wet bulb temperature forecast value obtained by a temperature and humidity forecast device (11) after h hours, wherein h is between 0.5 and 5; t isminAnd TmaxRespectively determining the lower limit value and the upper limit value of the optimal temperature of cooling water in the water supply main pipe (4) according to the process requirements of a circulating cooling water system; a and b are a first temperature difference value and a second temperature difference value, respectively, wherein a is between 2 and 4 ℃ and b is between 3 and 5 ℃.
Examples
A cooling tower is used by a certain chemical plant to provide refrigeration for a circulating cooling water system, 5 branch pipes which are connected in parallel are arranged in a water supply main pipe and a water return main pipe of circulating cooling water, each branch pipe is provided with a branch pipe valve and a heat exchanger, the circulating cooling water system and a cooling tower control system can be seen in an attached drawing 1, and the working principle of the control system can be seen in an attached drawing 2. The control system and the control method thereof in the embodiment are mainly realized by performing embedded development based on an Arm chip and a related integrated circuit.
In the embodiment, the process requirement of the circulating cooling water system is to determine the lower limit value T of the optimal temperature of cooling water in the water supply main pipe (4) close to the cooling tower (1)min30 ℃, upper limit value T of optimum temperaturemax35 ℃. According to the design data, NminAnd NmaxRespectively, the lowest allowable rotation speed N of the tower top fan (102) inputted into the cutoff device (83) in advance according to the design datamin50r/min, maximum allowable speed Nmax＝300r/min。
The temperature difference between day and night is big and the weather is complicated changeable in this chemical plant place. The current rotating speed value n of the speed-adjustable motor (101) at a certain moment before sunrise in early morning of a certain dayi150r/min, the current atmospheric wet bulb temperature measurement t obtained by the temperature and humidity sensor (10)iThe water temperature sensor (9) collects the close signals at 28 DEG CThe temperature of cooling water in a water supply main pipe (4) of a cooling tower (1) fluctuates at about 34 ℃, a temperature and humidity forecasting device (11) is networked to know that the temperature will rise rapidly after 1 hour in the future from a meteorological department, and the atmospheric humidity will rise rapidly after 4 hours in the future when heavy rain happens, and specifically, an atmospheric wet bulb temperature forecast value t after 4 hours is obtainedfAt 36 ℃. Taking the first temperature difference value a as 3 ℃ and the second temperature difference value b as 4 ℃, obviously t is presenti-a＝28-3＝25℃≤TmaxAnd t isi+b＝28+4＝32℃<tfTherefore, the water temperature setter calculates the set temperature value ST of the control system as max (T)min，ti-a) max (30, 25) 30 ℃ and output. Comparing the set temperature ST of 30 deg.C with the water temperature obtained by the water temperature sensor to obtain the deviation between the two, sending the comparison result to the PID controller, and outputting the motor speed regulation value delta n after PID operation1160r/min to a cut-off device, and simultaneously, the current rotating speed value n of the speed-adjustable motor (101) is adjustedi150r/min is sent to the chopper.
Due to delta n1+ni＝160+150＝310r/min>NmaxTherefore, truncation calculation is required. Calculating to obtain a speed regulating value delta n of the adjustable speed motor (101)2＝Nmax-Δn1300 and 160 are 140r/min, and finally output to the speed-adjustable motor (101) to finish the speed adjustment, and at the moment, the speed of the tower top fan (102) is adjusted to the maximum allowable speed of 300 r/min.
As can be seen from the above, if the atmospheric wet bulb temperature is not forecasted, the rotating speed of the speed-adjustable motor (101) at the current moment is kept in a lower rotating speed interval of about 150r/min for operation. In this case, although the process requirement can be met, after 4 hours, the atmospheric wet bulb temperature is sharply increased to 36 ℃ and is higher than the upper limit value of the optimal temperature of the cooling water in the water supply main pipe (4) close to the cooling tower (1), and at that time, the temperature of the cooling water in the water supply main pipe (4) close to the cooling tower (1) cannot be adjusted to be lower than 36 ℃ no matter the rotating speed of the tower top fan (102) is adjusted to be at most high level, and the heat exchange requirement at the tail end of the process cannot be met.
On the contrary, in the embodiment, by means of the prediction result of the atmospheric wet bulb temperature, the opportunity of lower atmospheric wet bulb temperature in the early morning is grasped in advance, and the temperature set value ST of the control system is set to be as low as possible, so that the temperature set value ST is as close to the limit refrigerating capacity of the cooling tower in the engineering as possible and is not lower than the optimal temperature lower limit value of the cooling water in the water supply main pipe (4) close to the cooling tower (1), thereby meeting the requirement of the current process and also being as high as possible in horsepower refrigeration, enabling the circulating cooling water to accumulate as much "cold energy" as possible to solve the refrigeration problem that the atmospheric wet bulb temperature is increased sharply after 4 hours, avoiding the inefficient rotation of the tower top fan (102) at an overhigh speed after 4 hours, and having a remarkable energy-saving effect.
The control system provided by the embodiment only comprises a control module, a water temperature sensor, a temperature and humidity sensor and a temperature and humidity forecasting device, and the control module can be realized by slightly improving the existing controller. In the aspect of the control method, the influence of the atmospheric wet bulb temperature and the change condition thereof in a short period of time in the future on the refrigerating capacity of the cooling tower is fully considered, and the requirements of the tail end of the process and the operation energy conservation of the tower top fan are considered: if the current atmospheric wet bulb temperature is higher, the current atmospheric wet bulb temperature minus a smaller temperature difference value is still higher than the upper limit value of the optimal temperature of the cooling water in the water supply main pipe (4), at this moment, the cooling tower cannot actually supply the upper limit value of the optimal temperature of the cooling water in the water supply main pipe (4), and therefore the current atmospheric wet bulb temperature minus a smaller temperature difference value is used as a given temperature value of the cooling water in the control system. If the current atmospheric wet bulb temperature minus a small temperature difference value is lower than the upper limit value of the optimal temperature of the cooling water in the water supply main pipe (4), whether the atmospheric wet bulb temperature can be obviously increased in a short period of time in the future is also considered: if the temperature does not rise remarkably, the upper limit value of the optimal temperature of the cooling water in the water supply main pipe (4) is used as a given temperature value of the cooling water in the control system, so that the process requirement is met, and the rotating speed of a tower top fan is as low as possible to save the operation energy consumption; otherwise, the given temperature value of the cooling water in the control system is compared with the result obtained by subtracting a certain smaller temperature difference from the optimal temperature upper limit value of the cooling water in the water supply main pipe (4) and the current atmospheric wet bulb temperature, and the larger value of the two is taken, so that the process requirement is met, the tower top fan is enabled to develop enough horsepower to promote the cooling of the circulating cooling water as far as possible, and the 'cold energy' is accumulated to solve the problems of difficult cooling and higher cooling energy consumption caused by the obvious rise of the future atmospheric wet bulb temperature, so that the efficient and stable operation of the circulating cooling water system is ensured. In addition, a chopper is additionally arranged on the basis of the PID controller, and the motor speed regulation value output by the PID controller and the current rotating speed value of the motor are simultaneously input into the chopper, so that the motor speed regulation value finally output to the actuating mechanism is ensured to be between the lowest allowable rotating speed value and the highest allowable rotating speed value of the speed-adjustable motor, and control errors are avoided. Therefore, the cooling tower system provided by the embodiment has the advantages of simple structure, low cost, stable and reliable corresponding control method, high efficiency, energy conservation, wide adaptability and easy realization, and is very suitable for adjusting the outlet water temperature of the cooling tower in the areas with complicated and changeable atmospheric weather conditions.
Claims (1)
1. The cooling tower control method is characterized in that the method is based on a cooling tower control system and is used for cooling control of cooling water in a cooling tower of an industrial circulating cooling water system, the industrial circulating cooling water system comprises a cooling tower (1), a water supply pump (2), a main pipe valve (3), a water supply main pipe (4), a water return main pipe (7) and a plurality of branch pipes which are respectively connected with the water supply main pipe (4) and the water return main pipe (7), each branch pipe is provided with a branch pipe valve (5) and a process tail end heat exchanger (6), the cooling tower (1) comprises a speed-adjustable motor (101), a tower top fan (102) and a tower body (103), the speed-adjustable motor (101) is mechanically connected with the tower top fan (102) and is used for driving the tower top fan (102) to operate so as to achieve evaporative cooling of the cooling water, and the water supply main pipe (4) is led out from the bottom of the tower body (103) and sequentially connected with the water supply pump (2), The main pipe valve (3) is connected with one end of the branch pipes and supplies water for all the branch pipes, the return main pipe (7) is connected with the other end of the branch pipes and collects the cooling water of all the branch pipes to the top of the tower body (103), and all the branch pipes are connected in parallel; cooling tower control system includes control module (8), temperature sensor (9), temperature and humidity sensor (10) and humiture forecasting device (11) respectively with control module (8) electric connection, control module (8) still with adjustable speed motor (101) electric connection in order to realize the rotational speed perception and the control of adjustable speed motor (101), wherein:
(a) the control module (8) comprises a water temperature setter (81), a PID controller (82) and a chopper (83), and is used for performing control operation according to input information and outputting a speed regulating instruction to the speed-adjustable motor (101);
(b) the water temperature sensor (9) is used for acquiring the temperature of cooling water in a water supply main pipe (4) close to the cooling tower (1) in real time and outputting the temperature to the control module (8);
(c) the temperature and humidity sensor (10) is used for acquiring a temperature value and a humidity value of the atmosphere near the cooling tower (1) in real time, and simultaneously, synchronously converting according to the temperature value and the humidity value of the atmosphere to obtain an atmospheric wet bulb temperature measurement value and outputting the atmospheric wet bulb temperature measurement value to the control module (8);
(d) the temperature and humidity forecasting device (11) is used for being networked with a weather forecasting mechanism in real time to obtain future atmospheric temperature values and humidity values of the region where the cooling tower (1) is located, and meanwhile, the forecasted atmospheric temperature values and humidity values are converted into atmospheric wet bulb temperature forecast values and output to the control module (8);
the control method of the cooling tower control system comprises the following steps: respectively inputting an atmospheric wet bulb temperature measurement value obtained by a temperature and humidity sensor (10) and an atmospheric wet bulb temperature forecast value obtained by a temperature and humidity forecast device (11) into a water temperature setter (81), and outputting a temperature set value ST after analysis by the water temperature setter (81); then the temperature set value ST is compared with the water temperature obtained by the water temperature sensor (9) to obtain the deviation of the temperature set value ST and the water temperature, the comparison result is sent to a PID controller (82), and the motor speed regulation value delta n is output after PID operation1To a chopper (83) and simultaneously to the current rotation speed value n of the adjustable speed motor (101)iSending the speed-variable motor to a cutter (83), and performing cutting calculation according to the following formula2And finally output to a speed-adjustable motor (101) to finish speed adjustment:
in the formula (1), Δ n1And Δ n2And Deltan is the motor speed regulating value operation result output by the PID controller (82) and the chopper (83), NminAnd NmaxRespectively, a minimum allowable rotation speed and a maximum allowable rotation speed, n, of a tower top fan (102) inputted to a chopper (83) in advance based on design dataiThe unit of the current rotating speed value of the speed-adjustable motor (101) is r/min;
the temperature set value ST analyzed and output by the water temperature setter (81) is calculated according to the following formula:
in the formula (2), ST is a temperature set value output by the water temperature setter (81); t is tiAnd tfRespectively obtaining a current atmospheric wet bulb temperature measured value obtained by a temperature and humidity sensor (10) and an atmospheric wet bulb temperature forecast value obtained by a temperature and humidity forecast device (11) after h hours, wherein h is between 0.5 and 5; t isminAnd TmaxRespectively determining the lower limit value and the upper limit value of the optimal temperature of cooling water in the water supply main pipe (4) according to the process requirements of a circulating cooling water system; a and b are a first temperature difference value and a second temperature difference value, respectively, wherein a is between 2 and 4 ℃ and b is between 3 and 5 ℃.
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