JP4240351B2 - Evaporation concentration device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an evaporating and concentrating apparatus for evaporating and concentrating a liquid. More specifically, the heat energy of condensed water is used to preheat raw water using a heat exchanger, thereby reducing the energy required for operating the apparatus. It is related with the evaporative concentration apparatus which can be made.
[0002]
[Prior art]
As a method for supplying and discharging raw water and condensed water in a conventionally known evaporative concentration apparatus, a method of controlling the liquid level in the apparatus (JP-A-9-57001, JP-A-10-118402, etc.), or raw water A method for measuring and adjusting the flow rate on the supply side (Japanese Patent No. 1117733) is known.
The problem with these prior arts is that either the supply amount of raw water or the discharge amount of condensed water is controlled, so that the balance of heat energy transfer in the heat exchanger provided to preheat the raw water with condensed water is lost. That is.
For this reason, the supply temperature of the raw water varies, and the evaporation concentration process under reduced pressure causes a problem of bumping in the apparatus when the supply temperature is high, and the evaporation amount decreases when the supply temperature is low. There arises a problem of using extra energy such as heating by a heater. When bumping occurs, contamination of condensed water due to mist and foaming occurs, and it is necessary to shift to an operation for temporarily stopping or avoiding the apparatus. In any case, since a stable device operation cannot be obtained, extra operating energy is used.
[0003]
For example, in the flow rate control method using the liquid level control in the evaporative concentration device, the flow rate of the supplied raw water is not adjusted, and the supply is stopped when the raw water in the device reaches a certain amount. Variations in supply temperature. Also, in the method of measuring the supply amount on the raw water supply side and controlling the flow rate, foreign substances such as scales adhere to the piping and heat exchanger in the evaporation concentrator due to long-term operation, and heat transfer efficiency decreases, As the concentration process proceeds, the amount of evaporation per unit time decreases, so the amount of condensed water obtained also decreases.
Therefore, just adjusting the supply amount of raw water with a flow meter cannot cope with a change in flow rate over time such as a decrease in the amount of condensed water, so that the flow rate balance between raw water and condensed water is lost. Similarly, in the case of vacuum evaporation treatment, the degree of vacuum in the device decreases due to leakage from each equipment mounting part and pipe joint, etc., and the raw water does not boil at the initial treatment temperature, the amount of condensed water decreases, suddenly, A situation may occur in which the condensed water discharged is less than or equal to the amount of condensed water obtained at the initial stage of the evaporative concentration apparatus.
In a heat exchanger that preheats raw water with condensed water, if the flow rate of condensed water drops and the flow rate balance with raw water is disrupted, as is clear from the following (Equation 1), when the flow rate G2 of condensed water decreases, It can be seen that (t2-t1) decreases if the flow rate G1 of the raw water does not change. That is, the temperature t2 when the raw water is discharged from the heat exchanger is lowered, and the raw water must be transferred to the treatment tank at a low temperature and heated with extra energy using a heater.
Q = G1C1 (t2-t1) = G2C2 (t1'-t2 ') (Formula 1)
Q: heat transfer amount per unit time in heat exchanger G1; flow rate of raw water G2; flow rate of condensed water C1: specific heat of raw water C2; specific heat of condensed water
t1; Temperature before raw water flows into the heat exchanger
t2: Temperature when raw water is discharged from the heat exchanger
t1 '; temperature before the condensed water flows into the heat exchanger
t2 ′; temperature at which condensed water is discharged from the heat exchanger [0004]
[Problems to be solved by the invention]
The present invention measures the flow rate of the condensed water in the evaporative concentrator and adjusts the supply amount of the raw water so that the flow rate balance in the heat exchanger is not lost, and the evaporation does not consume extra energy. An object is to provide a concentrator.
[0005]
[Means for Solving the Problems]
That is, the present invention provides a means for measuring the discharge amount of the condensed water to be discharged and the raw water in the evaporative concentration apparatus having a heat exchanger for preheating the raw water to be concentrated with the condensed water discharged from the raw water. Means for measuring supply amount, means for adjusting the discharge amount and supply amount, and control means for controlling these means so that the discharge amount of the condensed water and the supply amount of raw water are the same. The present invention relates to an evaporative concentration apparatus characterized in that
[0006]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, explanation will be made based on a schematic flow diagram of an evaporative concentration apparatus showing an embodiment of the present invention. 1 is a processing tank 5 for storing raw water 1, a vacuum pump 16 for decompressing the inside of the apparatus, a heater 7 for heating raw water 1, and a heat exchanger for preheating raw water 1 with condensed water 14. 4. Condensation with a condensate pump 12 capable of adjusting the flow rate by rotational speed control for extracting the condensed water 14 from under reduced pressure, an upper limit level meter 18 for measuring the flow rate of the condensed water 14, and a lower limit level meter 19 A water tank 11, a flow meter 3 and a flow rate adjustment valve 2 for measuring and adjusting the flow rate of the raw water 1, a flow meter 13 for measuring the discharge amount of the condensed water pump 12, and a control unit 22 for controlling these devices are provided. Vapor compression type concentrator.
In the present invention, the method of evaporating and concentrating is not limited to the vapor compression method, and the condensed water is discharged at a higher liquid temperature than the raw water, and the raw water is preheated with the condensed water, or the condensed water is cooled with the raw water. Other possible evaporation concentrators may be used.
[0007]
The method for measuring the flow rate of the condensed water 14 may be a flow meter capable of outputting a signal, such as an electromagnetic flow meter or a vortex flow meter. In the case of FIG. 1, the time during which the condensed water 14 rises or falls between the upper limit level meter 18 and the lower limit level meter 19 provided in the condensed water tank 11 is measured. The controller 22 calculates the flow rate. As long as the level meter used at this time can sense the liquid level, its method and means are not limited.
The operation at the start of operation does not perform the extraction of the condensed water 14 by the condensed water pump 12 until the upper limit level meter 18 detects the condensed water accumulated in the condensed water tank 11, and starts the extraction after the detection. If the maximum condensate discharge amount of the apparatus is F (L / min), the condensate water 14 starts to be extracted from the condensate tank 11 at a flow rate of F + α (L / min). At this time, the value of α is 0 <α <F. If the volume between the upper limit level meter 18 and the lower limit level meter 19 is W (L), it can be pulled out to the lower limit level 19 in a time of W / α (min). When the lower limit level meter 19 detects the amount of extraction after detection as F-α (L / min), the time for filling the volume W (L) requires W / α (min). By measuring the time until the actual upper limit level meter 18 and lower limit level meter 19 detect these W / α (min), the actual emission amount can be calculated from the following equation.
V1 = (F + α) −W / T1 (Formula 2)
V2 = (F−α) + W / T2 (Formula 3)
[0008]
(Equation 2) is a calculation formula used when the volume W (L) is extracted from the condensed water tank 11, and (Equation 3) is a calculation formula used when the volume W (L) is satisfied. V1 and V2 (L / min) Is the discharge amount obtained from the actual device, T1 (min) is the actual time required to extract the volume W (L), and T2 (min) is the actual time required when the volume W (L) is satisfied Is the time. Therefore, the calculated V1 and V (L / min) are compared, the larger value is set as V0 (L / min), and the value calculated by subtracting F (L / min) from V0 (L / min) is newly added. Set the α to operate.
If the supply amount of the raw water 1 is automatically adjusted using the flow rate adjustment valve 2 and the opening of the flow regulating valve 2 based on the calculated numerical value, the raw water 1 can be supplied while continuously controlling the flow rate. The flow rate balance between the supplied raw water 1 and the discharged condensed water 14 can be maintained with an accuracy of ± α.
α can be made close to 0 while monitoring the discharge amounts V1 and V2 obtained from the actual apparatus, thereby improving the accuracy of the flow rate balance. Therefore, by adjusting the flow rate of the raw water 1 so as to be the flow rate calculated by (Equation 2) and (Equation 3), the temperature drop of the raw water 1 discharged from the heat exchanger 4 can be prevented.
[0009]
The heat exchanger 4 that exchanges heat between the raw water 1 and the condensed water 14 may be a plate type, a multi-pipe type, a serpentine type, or the like, as long as it is a means for efficiently exchanging heat between the raw water 1 and the condensed water 14. In addition, a throttle valve, a needle valve, a pump capable of controlling the number of revolutions, etc. are used as a method for adjusting the flow rate of the raw water or the condensed water, and preferably it can be automatically adjusted according to the flow rate of the condensed water 14 calculated by the controller 22. A mechanism is preferably provided.
As described above, the evaporative concentration apparatus of the present invention can automatically control the flow rate of the raw water 1 by the control unit 22 even if the flow rate of the condensed water 14 is changed, so that the flow rate balance in the heat exchanger 4 is balanced. The raw water 1 can be preheated without collapsing, and the apparatus can be stably operated without increasing the amount of energy consumed by the apparatus for heating the raw water 1.
[0010]
【Example】
Hereinafter, an embodiment of the present invention will be described based on a schematic flow of the evaporative concentration apparatus shown in FIG. 1, but the present invention is not limited to this. .
The evaporative concentration apparatus in FIG. 1 is an evaporative concentration apparatus using a vapor compression type. In this example, the rinse waste water drained from the degreasing and cleaning device for processed parts was used as raw water. The flow rate of the raw water 1 is adjusted by detecting a signal obtained from the flow meter 3 with the control unit 22 and adjusting the opening degree of the flow rate adjusting valve 2.
The raw water 1 that has flowed into the heat exchanger 4 is heat-exchanged with the condensed water 14 to rise in temperature, and flows into the treatment tank 6 through the piping. The raw water 1 is supplied to the processing tank 5 by reducing the pressure in the apparatus including the processing tank 5 to 19.99 kPa with the vacuum pump 16 and then opening the flow rate adjusting valve 2 to suck in the apparatus. Therefore, the raw water 1 can be supplied.
[0011]
The raw water 1 entering the processing tank 5 is sent to the heater 7 by the circulation pump 6 and heated, and then flows into the heat exchanger 8 through the piping and returns to the processing tank 5. In this series of circulation steps, the temperature of the raw water 1 is raised to 60 ° C. using the heater 7 when the apparatus is started up. The raw water 1 that has reached 60 ° C. starts to evaporate under a reduced pressure of 19.99 kPa, and the treatment tank 5 is filled with water vapor. The water vapor is separated into water vapor and droplets by the steam separator 9, and only the water vapor passes through the pipe and is sucked into the compressor 10.
The sucked water vapor is compressed by the compressor 10, becomes superheated steam of 65 to 70 ° C., and is sent to the heat exchanger 8. In the steady operation, the raw water 1 is heated by the superheated steam inside the heat exchanger 8, and the operating rate of the heater 7 is reduced.
The superheated steam is condensed inside the heat exchanger 8 and sent as condensed water 14 to the condensed water tank 11 through the steam separator 15. A non-condensable gas and a trace amount of water vapor that cannot be condensed are discharged into the atmosphere by the vacuum pump 16.
[0012]
The temperature of the condensed water 14 collected in the condensed water tank 11 is 60 to 65 ° C., and the condensed water 14 is sent to the heat exchanger 4 by the condensed water pump 12 whose rotational speed is controlled by the inverter, and exchanges heat with the raw water 1. Is done. Although the temperature of the raw | natural water 1 was 25-30 degreeC, it confirmed that the temperature when discharged | emitted from the heat exchanger 4 rose to 55-60 degreeC. The flow rate of the raw water 1 and the condensed water 14 at this time is determined by measuring the time of increase / decrease of the condensed water 14 with the upper limit level meter 18 and the lower limit level meter 19 provided in the condensed water tank 11, and the condensed water is controlled by the control unit 22. The flow rate is calculated, and the flow rate adjusting valve 2 and the condensed water pump 12 are controlled by the control unit 22 so that the flow rates of the raw water 1 and the condensed water 14 become the same.
The heat exchanger 4 can be selected from the condensate flow rate determined from the raw water temperature, condensate temperature, and processing capacity at the time of design. The condensed water 14 having a temperature of 25 to 30 ° C. is discharged out of the apparatus after measuring the discharge amount with the flow meter 13. The flow meter 13 compares the flow rate measured and calculated in the condensed water tank 11 with the presence or absence of malfunction. The concentrated raw water in the processing tank 5 is discharged out of the apparatus by the concentrated water pump 20.
By continuously performing the above-described series of steps, the temperature of the treatment tank 5 flows into the raw water 1 that has been raised, so that stable evaporation and concentration treatment can be performed without any extreme temperature change.
[0013]
【The invention's effect】
According to the present invention, even when the flow rate of the condensed water discharged from the evaporative concentrator changes, the raw water corresponding to the change can be supplied to the evaporative concentrator, and the balance of the flow rate in the heat exchanger is not disturbed. The operation of heating the raw water that has not reached the target temperature is eliminated, and an evaporative concentration apparatus excellent in energy saving can be provided.
[Brief description of the drawings]
FIG. 1 is a schematic flow diagram of an evaporative concentration apparatus showing an embodiment of the present invention.
[Explanation of symbols]
1. Raw water 2. Flow control valve 3. Flow meter 4. Heat exchanger 5. Treatment tank 6. Circulation pump 7. Heater 8. Heat exchanger 9. Gas / water separator 10. Compressor 11. Condensate water tank 12. Condensate pump 13. Flow meter 14. Condensate 15. Steam separator 16. Vacuum pump 18. Upper limit level meter 19. Lower limit level meter 20. Concentrated water pump 21. Concentrated water 22. Control unit

Claims (3)

In an evaporative concentrator equipped with a heat exchanger that preheats the raw water to be concentrated with the condensed water discharged from the raw water, a means for measuring the amount of condensed water discharged and the supply amount when supplying the raw water Means for adjusting the discharge amount and the supply amount, and a control means for controlling these means, and controlling the discharge amount of the condensed water and the supply amount of the raw water to be the same. Evaporative concentration device characterized.   2. The evaporative concentration apparatus according to claim 1, wherein the means for measuring the amount of condensed water discharged measures and calculates the time during which the condensed water increases or decreases in a container having a constant volume.   The evaporative concentration apparatus according to claim 1 or 2, wherein the evaporative concentration apparatus is a vapor compression type concentration apparatus that performs a concentration process under reduced pressure.

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