CN113566639B - Method and system for controlling circulating water discharge capacity of closed cooling tower - Google Patents
Method and system for controlling circulating water discharge capacity of closed cooling tower Download PDFInfo
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- CN113566639B CN113566639B CN202110747867.3A CN202110747867A CN113566639B CN 113566639 B CN113566639 B CN 113566639B CN 202110747867 A CN202110747867 A CN 202110747867A CN 113566639 B CN113566639 B CN 113566639B
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- XLYOFNOQVPJJNP-UHFFFAOYSA-N water Substances O XLYOFNOQVPJJNP-UHFFFAOYSA-N 0.000 title claims abstract description 244
- 238000001816 cooling Methods 0.000 title claims abstract description 118
- 238000000034 method Methods 0.000 title claims abstract description 38
- 239000007921 spray Substances 0.000 claims abstract description 99
- 238000012544 monitoring process Methods 0.000 claims abstract description 39
- 238000001704 evaporation Methods 0.000 claims abstract description 32
- 230000008020 evaporation Effects 0.000 claims abstract description 32
- 239000010865 sewage Substances 0.000 claims abstract description 30
- 239000000498 cooling water Substances 0.000 claims description 55
- 238000012546 transfer Methods 0.000 claims description 27
- 238000004364 calculation method Methods 0.000 claims description 25
- 238000005259 measurement Methods 0.000 claims description 19
- 238000001514 detection method Methods 0.000 claims description 12
- 238000005507 spraying Methods 0.000 claims description 9
- 230000000704 physical effect Effects 0.000 claims 2
- 230000001276 controlling effect Effects 0.000 abstract description 15
- 230000001105 regulatory effect Effects 0.000 abstract description 10
- 229920006395 saturated elastomer Polymers 0.000 description 7
- 238000004134 energy conservation Methods 0.000 description 4
- 238000012360 testing method Methods 0.000 description 4
- 238000011160 research Methods 0.000 description 3
- 230000001502 supplementing effect Effects 0.000 description 3
- 238000013461 design Methods 0.000 description 2
- 239000003570 air Substances 0.000 description 1
- 230000009286 beneficial effect Effects 0.000 description 1
- 238000007664 blowing Methods 0.000 description 1
- 238000004140 cleaning Methods 0.000 description 1
- 239000012809 cooling fluid Substances 0.000 description 1
- 230000008878 coupling Effects 0.000 description 1
- 238000010168 coupling process Methods 0.000 description 1
- 238000005859 coupling reaction Methods 0.000 description 1
- 230000007547 defect Effects 0.000 description 1
- 238000010586 diagram Methods 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 239000000945 filler Substances 0.000 description 1
- 238000012986 modification Methods 0.000 description 1
- 230000004048 modification Effects 0.000 description 1
- 230000003020 moisturizing effect Effects 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
- 238000002076 thermal analysis method Methods 0.000 description 1
Classifications
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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
Abstract
The invention relates to a closed cooling tower circulating water discharge control method and a system, comprising the following steps: collecting monitoring parameters; according to the monitoring parameters, calculating the mass flow of the tower inlet air, the moisture content of the tower inlet air and the moisture content of the tower outlet air; calculating the spray water evaporation capacity of the closed cooling tower according to the mass flow rate of the tower inlet air, the moisture content of the tower inlet air and the moisture content of the tower outlet air; calculating the circulating water discharge capacity of the closed cooling tower according to the concentration ratio and the spray water evaporation capacity; and controlling the opening of the valve according to the sewage discharge amount of the circulating water. According to the invention, the evaporation capacity of spray water is calculated according to the concentration ratio, the circulating water discharge capacity is calculated, the opening of the discharge valve is regulated according to different tower external meteorological parameters to accurately monitor and regulate the circulating water discharge capacity, the problem that the circulating water discharge capacity is large due to low concentration ratio is avoided, meanwhile, the problem that scaling is easy to occur due to high concentration ratio is avoided, and the purpose of monitoring and regulating the circulating water discharge capacity of the closed cooling tower in real time is realized.
Description
Technical Field
The invention relates to the technical field of cooling towers, in particular to a closed cooling tower circulating water discharge control method and system.
Background
The cooling water is not in direct contact with air during operation of the closed cooling tower, so that the cleaning of cooling water quality is guaranteed, the purpose of efficient operation of the closed cooling tower is realized, the circulating water discharge capacity is changed along with the change of the meteorological parameters outside the tower under the condition of fixed concentration rate, the circulating water discharge capacity is accurately monitored and regulated by adjusting the opening of the discharge valve according to the meteorological parameters outside different towers, the problem that the circulating water discharge capacity is large due to low concentration rate is avoided, and meanwhile the problems that scaling is easy to occur due to high concentration rate are avoided.
In order to solve the problems, the prior art proposes a technical scheme of a mixed-flow closed cooling tower checking and calculating method: according to meteorological conditions and cooling requirements, coil specifications are selected, a coil structure comprises a transverse tube center distance, a longitudinal tube center distance, the number of layers of each flow tube, a heat exchange tube inclination design and the like, a filler structure form and size are designed, fan air quantity and spray water quantity are designed, thermal analysis is carried out according to an energy conservation and heat transfer basic formula and a heat exchange tube heat transfer and mass transfer experience formula, a wet area mass transfer process is considered, a coil heat transfer coefficient and a mass transfer coefficient are calculated, and parameters such as a closed cooling tower cooling fluid outlet tower temperature, a spray water average temperature, an outlet tower air temperature, a moisture content, a spray water evaporation quantity, a water supplementing quantity and the like are obtained.
The scheme only adopts a basic heat exchange formula to calculate and thermally analyze the closed cooling tower, and the accuracy of the calculated tower air temperature, moisture content and enthalpy value is not verified. Moreover, only the evaporation capacity and the water supplementing quantity parameters of the spray water are calculated, and the monitoring and the adjustment of the discharge capacity of the spray water aiming at the meteorological parameters outside the tower are not involved.
Disclosure of Invention
The invention aims to solve the technical problem of providing a closed cooling tower circulating water discharge control method and system aiming at the defects in the prior art.
The technical scheme adopted for solving the technical problems is as follows: a method for controlling the sewage discharge amount of circulating water of a closed cooling tower is constructed, which comprises the following steps:
collecting monitoring parameters;
according to the monitoring parameters, calculating the mass flow of the tower inlet air, the moisture content of the tower inlet air and the moisture content of the tower outlet air;
calculating the spray water evaporation capacity of the closed cooling tower according to the mass flow rate of the tower inlet air, the moisture content of the tower inlet air and the moisture content of the tower outlet air;
calculating the circulating water discharge capacity of the closed cooling tower according to the concentration ratio and the spray water evaporation capacity;
and controlling the opening of the valve according to the sewage discharge amount of the circulating water.
In the closed cooling tower circulating water discharge control method of the present invention, the calculating the mass flow of the tower inlet air, the moisture content of the tower inlet air and the moisture content of the tower outlet air according to the monitoring parameters includes:
calculating a closed water-cooling heat and mass transfer model according to the monitoring parameters;
calculating the mass flow rate of the tower inlet air and the moisture content of the tower inlet air according to the monitoring parameters;
and calculating the moisture content of the tower outlet air according to the closed water-cooling heat and mass transfer model.
In the closed cooling tower circulating water discharge amount control method of the invention, the monitoring parameters comprise: parameters, cooling water parameters of the closed cooling tower and spray water parameters of the closed cooling tower;
the parameters include: air dry bulb temperature, air wet bulb temperature, air flow rate and atmospheric pressure;
the cooling parameters include: the inlet water temperature and the cooling water flow rate of the cooling water;
the spray water parameters include: spray water flow rate and spray water outlet temperature.
In the closed cooling tower circulating water discharge control method, the parameters are detected and collected by a detection device arranged at a preset distance from the closed cooling tower;
the detection device includes: an anemometer for collecting air flow rate, a dry bulb temperature sensor for collecting air dry bulb temperature, a wet bulb temperature sensor for collecting wet bulb temperature and a barometer for collecting atmospheric pressure.
In the closed cooling tower circulating water discharge control method, the cooling water parameters are collected through a DCS control system.
In the closed cooling tower circulating water discharge control method, the spraying parameters are collected through a spraying detection device arranged on a water inlet pipeline of a spraying device of the closed cooling tower;
the spray detection device includes: a water temperature sensor and a flowmeter which are arranged on a water inlet pipeline of the spraying device;
the water temperature sensor is used for collecting the inlet water temperature of the cooling water, and the flowmeter is used for collecting the flow of the cooling water.
In the closed cooling tower circulating water discharge control method of the invention, the closed water cooling heat and mass transfer model comprises: a glass-plar model or a mecol model.
In the closed cooling tower circulating water discharge amount control method of the invention, the method further comprises the following steps:
detecting the flow of the sewage pipes in real time after the opening of the valve is controlled according to the sewage quantity of the circulating water, and obtaining a sewage pipe flow measurement value;
and adjusting the opening of the valve based on the circulating water discharge amount and the discharge pipe flow amount measurement.
In the closed cooling tower circulating water discharge amount control method of the present invention, the adjusting the opening of the valve based on the circulating water discharge amount and the discharge pipe flow amount measurement includes:
comparing the circulating water discharge amount with the discharge pipe flow amount measurement;
judging whether the circulating water discharge amount is equal to the discharge pipe flow amount measurement value;
if yes, stopping adjusting the opening of the valve;
if not, readjusting the opening of the valve until the circulating water discharge amount is equal to the discharge pipe flow amount measurement value.
The invention also provides a closed cooling tower circulating water discharge control system, which comprises:
the acquisition unit is used for acquiring the monitoring parameters;
the first calculation unit is used for calculating the mass flow of the tower inlet air, the moisture content of the tower inlet air and the moisture content of the tower outlet air according to the monitoring parameters;
the second calculation unit is used for calculating the spray water evaporation capacity of the closed cooling tower according to the mass flow rate of the tower inlet air, the moisture content of the tower inlet air and the moisture content of the tower outlet air;
the third calculation unit is used for calculating the circulating water discharge capacity of the closed cooling tower according to the concentration ratio and the spray water evaporation capacity;
and the control unit is used for controlling the opening of the valve according to the circulating water discharge amount.
The closed cooling tower circulating water discharge control method and system have the following beneficial effects: comprising the following steps: collecting monitoring parameters; according to the monitoring parameters, calculating the mass flow of the tower inlet air, the moisture content of the tower inlet air and the moisture content of the tower outlet air; calculating the spray water evaporation capacity of the closed cooling tower according to the mass flow rate of the tower inlet air, the moisture content of the tower inlet air and the moisture content of the tower outlet air; calculating the circulating water discharge capacity of the closed cooling tower according to the concentration ratio and the spray water evaporation capacity; and controlling the opening of the valve according to the sewage discharge amount of the circulating water. According to the invention, the evaporation capacity of spray water is calculated according to the concentration ratio, the circulating water discharge capacity is calculated, the opening of the discharge valve is regulated according to different tower external meteorological parameters to accurately monitor and regulate the circulating water discharge capacity, the problem that the circulating water discharge capacity is large due to low concentration ratio is avoided, meanwhile, the problem that scaling is easy to occur due to high concentration ratio is avoided, and the purpose of monitoring and regulating the circulating water discharge capacity of the closed cooling tower in real time is realized.
Drawings
The invention will be further described with reference to the accompanying drawings and examples, in which:
FIG. 1 is a schematic flow chart of an embodiment of a method for controlling the discharge amount of circulating water of a closed cooling tower according to an embodiment of the present invention;
FIG. 2 is a schematic flow chart of a second embodiment of a method for controlling the discharge amount of circulating water in a closed cooling tower according to the embodiment of the present invention;
fig. 3 is a schematic block diagram of a closed cooling tower circulating water discharge control system according to an embodiment of the present invention.
Detailed Description
For a clearer understanding of technical features, objects and effects of the present invention, a detailed description of embodiments of the present invention will be made with reference to the accompanying drawings.
Referring to fig. 1, a schematic flow chart of an embodiment of a method for controlling the discharge amount of circulating water in a closed cooling tower according to the present invention is shown.
The closed cooling tower circulating water discharge control method is based on tower outlet air parameter calculation.
Specifically, as shown in fig. 1, the method for controlling the circulating water discharge capacity of the closed cooling tower comprises the following steps:
and S101, collecting monitoring parameters.
In an embodiment of the present invention, the monitoring parameters include: parameters, cooling water parameters of the closed cooling tower and spray water parameters of the closed cooling tower.
Wherein the parameters include: air dry bulb temperature, air wet bulb temperature, air flow rate, and atmospheric pressure. The cooling parameters include: the inlet water temperature and the cooling water flow rate of the cooling water. The spray water parameters include: spray water flow rate and spray water outlet temperature.
Optionally, in the embodiment of the present invention, the parameter is detected and collected by a detection device disposed at a preset distance from the closed cooling tower. Generally, the preset distance may be set to 1000m to 2000m.
The detection device comprises: an anemometer for collecting air flow rate, a dry bulb temperature sensor for collecting air dry bulb temperature, a wet bulb temperature sensor for collecting wet bulb temperature and a barometer for collecting atmospheric pressure.
Specifically, in the open area at the position 1000 m-2000 m away from the closed cooling tower, an anemometer, a temperature sensor, a humidity sensor and a barometer are arranged at the position vertical to the wind direction, so that the air dry bulb temperature, the air wet bulb temperature, the air flow rate and the atmospheric pressure of the air around the closed cooling tower can be measured in real time.
Optionally, the cooling water parameters are collected by a DCS control system.
Optionally, the spray parameters are collected by a spray detection device disposed on a spray device water inlet pipe of the closed cooling tower.
Wherein, spray detection device includes: a water temperature sensor and a flowmeter which are arranged on a water inlet pipeline of the spraying device. The water temperature sensor is used for collecting the inlet water temperature of the cooling water, and the flowmeter is used for collecting the flow of the cooling water.
In the step, after the temperature sensor, the humidity sensor, the water temperature sensor, the flowmeter, the barometer and the anemometer enter a stable state, the test time exceeds one hour to be an effective test working condition, and at least three effective test working conditions exist. Wherein, the following requirements are satisfied as effective test conditions: the change of circulating water flow is less than 3%, the temperature difference of water entering and exiting the tower is less than 5%, the difference between the measured value of dry bulb temperature and the average value is not more than 2 ℃, and the difference between the measured value of wet bulb temperature and the average value is not more than 0.5 ℃.
And step S102, calculating mass flow of the tower inlet air, moisture content of the tower inlet air and moisture content of the tower outlet air according to the monitoring parameters.
In some embodiments, calculating the mass flow rate of the in-column air, the moisture content of the in-column air, and the moisture content of the out-column air based on the monitored parameters comprises: calculating a closed water-cooling heat and mass transfer model according to the monitoring parameters; according to the monitoring parameters, calculating the mass flow rate of the tower inlet air and the moisture content of the tower inlet air; and calculating the moisture content of the tower air according to the closed water-cooling heat and mass transfer model.
Alternatively, the closed water-cooling heat and mass transfer model may employ: a glass-plar model or a mecol model. Specifically, when the heat and mass transfer model is built by taking cooling water as a research object, the heat change of the cooling water along the flowing direction of the coil is taken as a reference; when the spray water is taken as a research object to establish a heat and mass transfer model, taking the heat change of the spray water along the horizontal and vertical directions of the tower as a reference; when the air is used as the research object to build the heat and mass transfer model, the coupling heat and mass exchange of air and spray water and cooling water is used as the reference.
In some embodiments, calculating the mass flow of the inlet tower air based on the monitored parameters includes: calculating the air flow rate of the inlet tower according to the air flow rate and the sectional area of the inlet of the cooling tower; and calculating the mass flow rate of the tower inlet air according to the tower inlet air flow rate and the air density. The mass flow of the air entering the tower is calculated according to the following formula:
G a ＝Q a r a /3600 (1)。
wherein: q (Q) a For the flow rate of air entering the tower (m) 3 /h)；r a Is of air density (kg/m) 3 )；G a Is the mass flow of the air entering the tower, (kg/s). The calculation formula of the tower inlet air flow is as follows:
Q a ＝v*S (2)。
wherein: v is the air flow rate (m/s); s is the cross-sectional area (m) of the inlet of the cooling tower 2 )。
Calculating the moisture content of the inlet air according to the monitoring parameters comprises: calculating relative humidity according to the air dry bulb temperature and the air wet bulb temperature; calculating saturated steam pressure corresponding to the air dry bulb temperature according to the air dry bulb temperature; and calculating the moisture content of the air entering the tower according to the saturated steam pressure, the atmospheric pressure and the relative humidity corresponding to the air dry bulb temperature. Wherein, the calculation formula of the moisture content of the tower inlet air is as follows:
wherein: x is x T For the moisture content of the inlet air, (kg/kg (DA)); p is p T "is the saturated steam pressure corresponding to the dry bulb temperature of the air entering the tower, kPa; p is the atmospheric pressure of air, kPa; phi is the relative humidity.
The relative humidity is calculated as:
wherein: p' Ta Saturated steam atmospheric pressure corresponding to the wet bulb temperature of the air entering the tower is kPa; p' T Saturated steam atmospheric pressure corresponding to the temperature of the dry ball of the air entering the tower is kPa; t (T) a The temperature of the dry ball of the air entering the tower is set at DEG C; t (T) as The temperature is the wet bulb temperature of the air entering the tower and is at the temperature of DEG C; p is atmospheric pressure kPa; .
Specifically, the closed water-cooling heat and mass transfer model comprises:
(1) Mass conservation equation for the micro-element of the heat and mass exchange module:
G f +G a +G p ＝G f +G a (1+dd a )+G p (1-dG p ) (6)。
wherein: g f Kg/h is the mass flow of the cooling water (wherein the mass flow of the cooling water is calculated by the flow of the cooling water and the density of the cooling water); g a Kg/h for mass flow of air entering the tower; d, d a For the moisture content of the off-column air, kg/kg; g p Kg/h is the mass flow of the spray water (wherein the mass flow of the spray water is calculated by the flow of the spray water and the density of the spray water); dd a For variation of moisture content of the air leaving the towerConverting to kg/kg; dG (dG) p Kg/h for the change of the spray water mass flow.
(2) Energy conservation equation for the heat and mass exchange module microelements:
wherein: c (C) pf kJ/(kg. Deg.C) for specific heat capacity of cooling water; t (T) f The temperature of the inlet water of the cooling water is at DEG C; h da Is the enthalpy value of air, kJ/kg; c (C) pp kJ/(kg. Deg.C) for specific heat capacity of spray water; t (T) p The temperature of the inlet water of the spray water is DEG C; dT (dT) f Is the variation of the cooling water temperature, and is at the temperature of DEG C; dH (dH) da kJ/kg is the variation of the enthalpy value of the air; dT (dT) p The temperature of the spray water is the variation quantity of the spray water temperature.
Wherein the enthalpy value H of dry air per unit mass da The expression is:
H da ＝C pa T a +d a (C pv T a +H z0 ) (8)。
wherein: c (C) pa The specific heat capacity of the air temperature, kJ/(kg. DEG C); t (T) a Air temperature, DEG C; c (C) pv kJ/(kg. DEG C.) is the specific heat capacity of water vapor; h z0 Is the enthalpy value of water vapor, kJ/kg.
(3) Energy conservation equation of cooling water microelements in a pipe:
dQ f ＝-G f C pf dT f ＝K(T f -T p )dA (9)。
wherein: k is the heat transfer coefficient of cooling water and spray water, kJ/(m) 2 ·℃)。
(4) And the mass conservation equation of the spray water outside the pipe and the air infinitesimal body:
dG a ＝m p-a (d p -d a )dA＝G a dd a ＝-dG p (10)。
wherein: the mass of the spray water lost is the moisture content obtained by dry air, m p-a For the mass transfer coefficient of the spray water film to the air, kg/(m) 2 ·s)。
(5) Energy conservation equation of spray water and air infinitesimal outside the pipe:
dQ a ＝h p-a (T p -T a )dA+H v m p-a (d p -d a )dA (11)。
wherein: d, d p The saturated air moisture content corresponding to the spray water temperature is kg/kg;
the difference between the spray water film temperature and the air temperature is:
wherein: h b The enthalpy value of saturated air corresponding to the spray water temperature is kJ/kg;
substituting the formula (12) into the formula (11) and using the Lewis relation Le f ＝h p-a /m p-a ·C pa The following relationship can be found:
wherein: le (Le) f Is the Lewis number of air, h p-a To spray the heat transfer coefficient of the water film to the air, kJ/(m) 2 ·℃)。
Specifically, according to the closed water-cooling heat and mass transfer model, the calculation of the moisture content of the tower air comprises the following steps:
according to the formulas (6) to (13), the acquired monitoring parameters are combined: the air dry bulb temperature, the atmospheric pressure, the air flow rate, the water inlet temperature of the cooling water, the flow rate of the cooling water, the water inlet temperature of the spray water and the flow rate of the spray water can be calculated to obtain the moisture content of the air of the tower. In addition, the embodiment of the invention can also calculate and obtain the mass flow of the spray water, the outlet water temperature of the cooling water, the Lewis number and the enthalpy value of the outlet air.
Wherein, the solution formula of (1) the mass flow of the spray water is as follows:
dG p ＝-G a dd a (14)。
(2) The solving formula of the outlet water temperature of the spray water is as follows:
(3) The solving formula of the outlet water temperature of the cooling water is as follows:
(4) The solution formula of the Lewis number is:
(5) The solution formula of the moisture content of the tower outlet air is as follows:
(6) The solution formula of the enthalpy value of the outlet air is as follows:
it should be noted that, each row of pipes of the closed cooling tower is used as a unit control body, the closed cooling tower pipe bundle comprises N rows of pipes, each row of pipes is used as a unit (iterative calculation unit), each unit is subjected to differential (including but not limited to backward differential, center differential and windward differential) iterative solution, the air outlet parameters (temperature, moisture content), cooling water outlet temperature and spray water temperature calculated by the former unit are used as input conditions of the latter unit, the cooling water flows horizontally, the spray water flows vertically downwards, the air flows reversely, and the physical parameters (air density, specific heat and heat conductivity) of air of each unit are calculated by the temperature value of the former unit.
And step S103, calculating the spray water evaporation capacity of the closed cooling tower according to the mass flow rate of the tower inlet air, the moisture content of the tower inlet air and the moisture content of the tower outlet air.
Specifically, the calculation formula of the spray water evaporation capacity of the closed cooling tower is as follows:
Z s ＝G a (d c -x T )*3600 (20)。
wherein: d, d c For the moisture content of the off-column air, kg/kg; z is Z s The spray water evaporation capacity of the closed cooling tower.
And step S104, calculating the circulating water discharge capacity of the closed cooling tower according to the concentration ratio and the spray water evaporation capacity.
Specifically, the calculation formula of the circulating water discharge capacity of the closed cooling tower is as follows:
wherein: p (P) w The sewage discharge capacity of the circulating water is kg/h; m is the concentration ratio of the circulating water; q (Q) f The air blowing loss of the circulating water is kg/h.
Generally, Q f It may be set to (100 to 200) kg/h as usual.
Furthermore, in the embodiment of the invention, the circulating water supplementing amount can be calculated according to the spray water evaporation amount of the closed cooling tower.
Wherein, the formula of calculation of circulating water moisturizing is:
Q S ＝Z s +Q f (22)。
and step 105, controlling the opening of the valve according to the sewage discharge amount of the circulating water.
Referring to fig. 2, a schematic flow chart of a second embodiment of a method for controlling the discharge amount of circulating water in a closed cooling tower according to the present invention is shown.
As shown in fig. 2, in this embodiment, after step S105, further includes:
and S106, detecting the flow of the sewage pipes in real time after controlling the opening of the valve according to the sewage amount of the circulating water, and obtaining a sewage pipe flow measurement value.
The blow-down pipe can be obtained by real-time measurement through a blow-down flowmeter arranged on a blow-down pipeline of the closed cooling tower. The valve for controlling and adjusting the sewage discharge amount of the circulating water can be arranged on the sewage discharge pipeline of the closed cooling tower.
And step S107, adjusting the opening of the valve based on the circulating water discharge amount and the discharge pipe flow amount measurement.
Wherein, adjust the aperture of valve based on circulating water blowdown volume and blow off pipe flow measurement value includes: comparing the circulating water discharge amount with a discharge pipe flow amount measurement; judging whether the circulating water discharge amount is equal to the discharge pipe flow amount measurement value; if yes, stopping adjusting the opening of the valve; if not, the opening of the valve is readjusted until the sewage discharge amount of the circulating water is equal to the sewage discharge pipe flow measurement value.
According to the closed cooling tower circulating water discharge control method, the spray water evaporation capacity is changed based on the change of the weather conditions outside the closed cooling tower, the circulating water discharge is obtained by combining the concentration ratio, the circulating water discharge is accurately monitored and regulated by adjusting the opening of the discharge valve according to different weather parameters outside the tower, the problem that the circulating water discharge is large due to low concentration ratio is avoided, meanwhile, the problem that scaling is easy to occur due to high concentration ratio is avoided, and the purpose of monitoring and regulating the circulating water discharge in real time is achieved.
In one specific application example:
and the working conditions in summer collect meteorological parameters, cooling water parameters and spray water parameters. Meteorological parameters: the dry bulb temperature of the air is 18 ℃, the wet bulb temperature is 15 ℃, the atmospheric pressure is 100.1kPa, and the air quantity is 144000m 3 And/h. Cooling water parameters: the water temperature of the inlet tower is 33 ℃, and the cooling water flow is 100m 3 And/h, the water temperature of the tower outlet is 24 ℃. Spray water parameters: the spray water flow is 230m 3 And/h, the water inlet temperature of the spray water is 21.6 ℃, the water outlet temperature is 23.5 ℃, and the mass flow of the spray water is 3.66kg/s.
According to the calculation of the closed water-cooling heat and mass transfer model, the state parameters of the cooling water, the spray water and the air of the closed cooling tower are solved by adopting a Bopu model. The iterative calculation solves that the outlet water temperature of the cooling water is 24 ℃, the temperature drop is 9 ℃, the enthalpy value of the outlet air is 67.37kJ/kg, the moisture content of the outlet air is 16.38g/kg, and the temperature is 25.52 ℃. Further, the evaporation amount of shower water was calculated to be 1255.74kg/h.
Calculating the circulating water discharge capacity by fixing the concentration ratio, wherein when the concentration ratio is 5, the circulating water discharge capacity depends on the evaporation capacity of spray water, and the calculated circulating water discharge capacity is 313.935kg/h, and under the working condition of summer, the meteorological parameters outside the tower are as follows: when the dry bulb temperature is 18 ℃, the wet bulb temperature is 15 ℃, and the atmospheric pressure is 100.11kPa, the circulating water discharge capacity of the closed cooling tower is 313.935kg/h.
And weather parameters, cooling water parameters and spray water parameters are collected under the working condition in winter. Meteorological parameters: the temperature of the air dry bulb outside the tower is 5 ℃, the temperature of the wet bulb is 4.3 ℃, the atmospheric pressure is 100.1Kpa, and the air quantity is 144000m3/h. Cooling water parameters: the water temperature of the inlet tower is 33 ℃, and the cooling water quantity is 100m 3 And/h, the water temperature of the tower outlet is 24 ℃. Spray water parameters: the spray water flow rate is 230m3/h, the spray water inlet temperature is 13.2 ℃, the spray water outlet temperature is 15.6 ℃, and the calculated spray water mass flow rate is 63.66kg/s.
According to the calculation of the closed water-cooling heat and mass transfer model, the state parameters of the cooling water, the spray water and the air of the closed cooling tower are solved by adopting a Bopu model. The iterative calculation solves that the temperature of the cooling water discharged from the tower is 24 ℃, the temperature drop is 9 ℃, the enthalpy value of the air discharged from the tower is 38.02kJ/kg, the moisture content of the air discharged from the tower is 8.9g/kg, and the temperature is 15.415 ℃. Further, the evaporation amount of shower water was calculated to be 730.08kg/h.
Calculating the circulating water discharge capacity by fixing the concentration ratio, wherein when the concentration ratio is 5, the circulating water discharge capacity depends on the evaporation capacity of spray water, and the calculated circulating water discharge capacity is 182.52kg/h, and under the working condition of winter, the meteorological parameters outside the tower are as follows: the circulating water discharge capacity of the closed cooling tower is 182.52kg/h when the dry bulb temperature is 5 ℃, the wet bulb temperature is 4.3 ℃ and the atmospheric pressure is 100.11 kPa.
The calculation of summer working conditions and winter working conditions can be known: when the concentration ratio is 5, the evaporation capacity of spray water is 1255.74kg/h under the working condition of summer, the sewage discharge capacity of circulating water is 313.935kg/h, the evaporation capacity of spray water is 730.08kg/h under the working condition of winter, the sewage discharge capacity of circulating water is 182.52kg/h, and the difference between the evaporation capacity of spray water and the sewage discharge capacity of circulating water is larger under the working condition of summer and winter, so that under the condition of fixed concentration ratio, the sewage discharge capacity is accurately monitored and regulated by regulating the opening of a sewage discharge valve aiming at different tower external meteorological parameters, the problem that the sewage discharge capacity of circulating water is larger due to low concentration ratio is avoided, meanwhile, the problem that scaling is easy to occur due to high concentration ratio is avoided, and the purposes of monitoring and regulating the sewage discharge capacity of a closed cooling tower in real time are realized.
Referring to fig. 3, the invention further provides a closed cooling tower circulating water discharge control system, which can be used for realizing the closed cooling tower circulating water discharge control method disclosed by the embodiment of the invention.
Specifically, as shown in fig. 3, the closed cooling tower circulating water discharge control system includes:
and the acquisition unit is used for acquiring the monitoring parameters.
And the first calculation unit is used for calculating the mass flow of the tower inlet air, the moisture content of the tower inlet air and the moisture content of the tower outlet air according to the monitoring parameters.
And the second calculating unit is used for calculating the spray water evaporation capacity of the closed cooling tower according to the mass flow rate of the tower inlet air, the moisture content of the tower inlet air and the moisture content of the tower outlet air.
And the third calculation unit is used for calculating the circulating water discharge capacity of the closed cooling tower according to the concentration ratio and the spray water evaporation capacity.
And the control unit is used for controlling the opening of the valve according to the sewage discharge amount of the circulating water.
Compared with the traditional closed cooling tower calculation method, the calculation model of the invention establishes a heat and mass exchange model of cooling water, spray water and air, calculates and verifies by combining measured air, cooling water and spray water data to obtain the temperature, enthalpy value, moisture content, spray water evaporation and circulating water discharge of the air discharged from the closed cooling tower, accurately monitors and adjusts the circulating water discharge by adjusting the opening of the discharge valve according to different outside-tower weather parameters, avoids the problem of larger circulating water discharge due to low concentration ratio, simultaneously avoids the problem of easy scaling due to high concentration ratio, and realizes the purpose of monitoring and adjusting the circulating water discharge of the closed cooling tower in real time.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other. For the device disclosed in the embodiment, since it corresponds to the method disclosed in the embodiment, the description is relatively simple, and the relevant points refer to the description of the method section.
Those of skill would further appreciate that the various illustrative elements and algorithm steps described in connection with the embodiments disclosed herein may be implemented as electronic hardware, computer software, or combinations of both, and that the various illustrative elements and steps are described above generally in terms of functionality in order to clearly illustrate the interchangeability of hardware and software. Whether such functionality is implemented as hardware or software depends upon the particular application and design constraints imposed on the solution. Skilled artisans may implement the described functionality in varying ways for each particular application, but such implementation decisions should not be interpreted as causing a departure from the scope of the present invention.
The steps of a method or algorithm described in connection with the embodiments disclosed herein may be embodied directly in hardware, in a software module executed by a processor, or in a combination of the two. The software modules may be disposed in Random Access Memory (RAM), memory, read Only Memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disk, a removable disk, a CD-ROM, or any other form of storage medium known in the art.
The above embodiments are provided to illustrate the technical concept and features of the present invention and are intended to enable those skilled in the art to understand the content of the present invention and implement the same according to the content of the present invention, and not to limit the scope of the present invention. All equivalent changes and modifications made with the scope of the claims should be covered by the claims.
Claims (9)
1. The method for controlling the sewage discharge amount of the circulating water of the closed cooling tower is characterized by comprising the following steps of:
collecting monitoring parameters;
according to the monitoring parameters, calculating the mass flow of the tower inlet air, the moisture content of the tower inlet air and the moisture content of the tower outlet air;
calculating the spray water evaporation capacity of the closed cooling tower according to the mass flow rate of the tower inlet air, the moisture content of the tower inlet air and the moisture content of the tower outlet air;
calculating the circulating water discharge capacity of the closed cooling tower according to the concentration ratio and the spray water evaporation capacity;
controlling the opening of a valve according to the sewage discharge amount of the circulating water;
the monitoring parameters comprise cooling water parameters of the closed cooling tower and spray water parameters of the closed cooling tower;
according to the monitoring parameters, calculating the mass flow of the tower inlet air, the moisture content of the tower inlet air and the moisture content of the tower outlet air comprises the following steps:
calculating a closed water-cooling heat and mass transfer model according to the monitoring parameters;
calculating the mass flow rate of the tower inlet air and the moisture content of the tower inlet air according to the monitoring parameters;
calculating the moisture content of the tower outlet air according to the closed water-cooling heat and mass transfer model;
the closed cooling tower tube bundle comprises N rows of tubes, each row of tubes is an iterative calculation unit, and each row of tubes of the closed cooling tower is used as a unit control body; carrying out differential iterative solution on each unit, wherein the air outlet parameter, the cooling water outlet temperature and the spray water temperature calculated by the previous unit are used as input conditions of the next unit, the cooling water flows horizontally, the spray water flows vertically downwards, the air flows upwards in countercurrent, and the physical property parameter of the air of each unit is calculated by the temperature value of the previous unit;
wherein the air outlet parameter comprises an air outlet temperature and an air outlet moisture content; the physical parameters comprise air density, specific heat and heat conductivity coefficient.
2. The closed cooling tower circulating water discharge amount control method according to claim 1, wherein the monitoring parameters include: parameters;
the parameters include: air dry bulb temperature, air wet bulb temperature, air flow rate and atmospheric pressure;
the cooling parameters include: the inlet water temperature and the cooling water flow rate of the cooling water;
the spray water parameters include: spray water flow rate and spray water outlet temperature.
3. The method for controlling the circulating water discharge amount of the closed cooling tower according to claim 2, wherein the parameter is detected and collected by a detection device arranged at a preset distance from the closed cooling tower;
the detection device includes: an anemometer for collecting air flow rate, a dry bulb temperature sensor for collecting air dry bulb temperature, a wet bulb temperature sensor for collecting wet bulb temperature and a barometer for collecting atmospheric pressure.
4. The closed cooling tower circulating water discharge amount control method according to claim 2, wherein the cooling water parameters are collected by a DCS control system.
5. The method for controlling the sewage discharge amount of the circulating water of the closed cooling tower according to claim 2, wherein the spraying parameters are collected by a spraying detection device arranged on a water inlet pipeline of a spraying device of the closed cooling tower;
the spray detection device includes: a water temperature sensor and a flowmeter which are arranged on a water inlet pipeline of the spraying device;
the water temperature sensor is used for collecting the inlet water temperature of the cooling water, and the flowmeter is used for collecting the flow of the cooling water.
6. The closed cooling tower circulating water discharge amount control method according to claim 1, wherein the closed water cooling heat and mass transfer model comprises: a glass-plar model or a mecol model.
7. The closed cooling tower circulating water discharge amount control method according to claim 1, characterized in that the method further comprises:
detecting the flow of the sewage pipes in real time after the opening of the valve is controlled according to the sewage quantity of the circulating water, and obtaining a sewage pipe flow measurement value;
and adjusting the opening of the valve based on the circulating water discharge amount and the discharge pipe flow amount measurement.
8. The closed cooling tower circulating water discharge amount control method according to claim 7, wherein the adjusting the opening of the valve based on the circulating water discharge amount and the discharge pipe flow amount measurement value includes:
comparing the circulating water discharge amount with the discharge pipe flow amount measurement;
judging whether the circulating water discharge amount is equal to the discharge pipe flow amount measurement value;
if yes, stopping adjusting the opening of the valve;
if not, readjusting the opening of the valve until the circulating water discharge amount is equal to the discharge pipe flow amount measurement value.
9. A closed cooling tower circulating water discharge control system, comprising:
the acquisition unit is used for acquiring the monitoring parameters; the monitoring parameters comprise cooling water parameters of the closed cooling tower and spray water parameters of the closed cooling tower;
the first calculation unit is used for calculating the mass flow of the tower inlet air, the moisture content of the tower inlet air and the moisture content of the tower outlet air according to the monitoring parameters;
the second calculation unit is used for calculating the spray water evaporation capacity of the closed cooling tower according to the mass flow rate of the tower inlet air, the moisture content of the tower inlet air and the moisture content of the tower outlet air;
the third calculation unit is used for calculating the circulating water discharge capacity of the closed cooling tower according to the concentration ratio and the spray water evaporation capacity;
the control unit is used for controlling the opening of the valve according to the circulating water discharge amount;
the first computing unit is further configured to:
calculating a closed water-cooling heat and mass transfer model according to the monitoring parameters;
calculating the mass flow rate of the tower inlet air and the moisture content of the tower inlet air according to the monitoring parameters;
calculating the moisture content of the tower outlet air according to the closed water-cooling heat and mass transfer model;
the closed cooling tower tube bundle comprises N rows of tubes, each row of tubes is an iterative calculation unit, and each row of tubes of the closed cooling tower is used as a unit control body; carrying out differential iterative solution on each unit, wherein the air outlet parameter, the cooling water outlet temperature and the spray water temperature calculated by the previous unit are used as input conditions of the next unit, the cooling water flows horizontally, the spray water flows vertically downwards, the air flows upwards in countercurrent, and the physical property parameter of the air of each unit is calculated by the temperature value of the previous unit;
wherein the air outlet parameter comprises an air outlet temperature and an air outlet moisture content; the physical parameters comprise air density, specific heat and heat conductivity coefficient.
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