JPS61220788A - Method for controlling extremely pure water generator - Google Patents

Abstract

PURPOSE:To perform a resource-saving and energy-saving operation at low cost when the amt. of water to be used at a use point is lower than the specified amt. by detecting the flow rate in a return pipeline from the use point and controlling the number of revolutions of a booster pump to control the flow rate in the return pipeline. CONSTITUTION:The extremely pure water generator consists of a reverse- osmosis membrane 4, ion-exchange resin towers 5 and 6, a UV sterilizer 7, a filter 8, etc. Water is passed by a booster pump 3 arranged at the preceding stage of the reverse-osmosis membrane 4 to produce extremely pure water and a return pipeline for circulating and returning the extremely pure water which is not used at a use point 9 to the suction side of the booster pump 3 is provided. The flow rate in the return pipeline is detected by a flow switch 12, the number of revolutions of the booster pump 3 is controlled by a control panel 10 and the flow rate in the pipeline is controlled. Namely, a resource- saving and energy-saving operation can be performed at comparatively low cost, when the amt. of water to be used at the use point is less than the specified amt.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a method for controlling the operation of an ultrapure water production device that produces ultrapure water from tap water, well water, etc. using a reverse osmosis membrane or the like. be.

[Background of the invention]

A typical flow of a conventional ultrapure water production device is shown in Figure 1. Raw water such as tap water is passed through an activated carbon filter 1 to remove free chlorine, fine particles, etc. contained in the tap water, and then passed through a pre-filter 2. Water is passed through. In the pre-filter 2, in addition to the fine particles in the raw water, fine particles flowing out from the activated carbon filter 1 are removed.

Next, the raw water is pressurized to 10 to 30 kg/cdG by the pressure pump 3 and passed through the reverse osmosis membrane 4, where more than 90% of the ions, particulates, viable bacteria, etc. are removed. .

Approximately 70-80% of organic matter is also removed. Approximately 30 to 70% of the raw water in the reverse osmosis membrane is drained out of the device as a concentrated waste liquid, and the remaining approximately 70 to 30% is sent to a subsequent stage as membrane permeated water.

Polyrasha A5 is a mixture of cation and anion exchange resins, which removes about 99% or more of ions and provides water purity with a specific resistance of about 1 to 10 MΩ·1 or more. Furthermore, ions are removed by Polyrasha 6, which has the same configuration as Polyrasha 5, and the specific resistance value is raised to a water quality level close to theoretically pure water (HIO) of 17 to 18 NΩ. , piping after the reverse osmosis membrane 4,
Sterilize the living bacteria flowing out from Bolitsha A, B, etc. with UV rays.Finally, use the final filter 8 to
Ultrapure water is obtained by filtering out fine particles and dead bacteria. The ultrapure water circulates through the use point 9 and a portion of it is returned to the suction side of the pressure pump 3. Usually, this ultrapure water production equipment.

In order to prevent the growth of living bacteria due to dead water retention, the equipment is operated without stopping and water quality is monitored.

In such ultrapure water production equipment, if the amount of water used at the point of use is less than the specified water amount, the recovery rate at the reverse osmosis membrane 4 (= membrane permeated water amount / (membrane permeated water amount + membrane concentrated wastewater amount)) will be the same as described above. Since it is less than 100%, some of the ultrapure water is drained, which has the drawback of wasting ion exchange resin regeneration costs, raw water costs, and pressure pump power costs.

In addition, as a prior art related to the above technology, Japanese Patent Application Laid-Open No. 57-1
There is No. 174189.

[Purpose of the invention]

An object of the present invention is to provide resource-saving and energy-saving operation when the amount of water used at a point of use is less than a specified amount of water.

[Summary of the invention]

Assuming that the amount of water permeated through the reverse osmosis membrane Q2 is the pressure pump discharge pressure P, then Q,=AXP (A is a constant of proportionality) holds true. On the other hand, the concentrated water amount QI is approximately determined by the water head loss at the concentrated water amount control valve, and is given by QI = 85 (B is the resistance coefficient of the concentrated water amount control valve).

Therefore, when the opening degree of the concentrated water amount control valve is kept constant and the pressurizing pump discharge pressure is changed, as is clear from the above two equations, the amount of change in Q is smaller than in Q.

This shows a tendency to maintain the flow rate, which is essential for preventing membrane surface contamination on the concentrated water side of the membrane.6 The present invention utilizes the fluid performance of this reverse osmosis membrane module to control the rotation speed of the pressure pump, thereby saving resources and energy. Measure your driving.

The amount of water used at the use point is indirectly detected by the increase or decrease in the flow rate of the use point circulation return piping, so the method is to detect the return flow rate and control the rotation speed of the pressurizing pump.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 2 and 3.

In FIG. 2, the flow of the ultrapure water production apparatus is the same as that described in FIG. 1, showing an example of controlling the rotation speed by changing the number of motor poles of a pressurizing pump. A flow switch 12 (
2 contacts, large flow rates Q, 1, and small flow rates QL) are installed. In this embodiment, operation will be explained in two cases where the amount of water used at the point of use is zero and the rated flow rate. Large flow rate Q.

is set to a value slightly below the rated flow rate, and the small flow rate Q4 is set to a value slightly below the return piping minimum flow rate. In the control panel 10, the electrical signal from the flow switch 12 is amplified by a relay, and the number of poles of the pressure pump 3 is changed. An interblock diagram at that time is shown in FIG. Returning from point of use -t Q, is Q.

When the value exceeds 1, the number of poles of the motor is converted to N pole and the motor is operated. If the amount of water used at the use point increases,
Since Q is less than or equal to Q, the number of poles of the motor is converted to M poles, the speed is increased, and the amount of water produced is increased. In this way, the operation of the device is controlled according to the amount of water used at the point of use.In this example, the amount of water used at the point of use is in two stages, but the amount of water used changes continuously. In this case, it is possible to control the amount of return water to be constant using a thyristor inverter, and various control operations can be performed.

〔Effect of the invention〕

The present invention achieves resource-saving and energy-saving operation of an ultrapure water production device at a relatively low cost, and contributes to improving the economic efficiency of the ultrapure water production device. FIG. 3 is an interblock diagram of FIG. 2.

1...Activated carbon filter, 2...Pre-filter-1
3... Pressure pump, 4... Reverse osmosis membrane module, 5
...Polyrasha, 6...Polyrasha, 7...Ultraviolet sterilizer, 8...Final filter, 9...Use point, 10...Control panel, 11...Concentrated water control valve, 12 ...Flow switch.

Tomi 1 Diagram

Claims (1)

[Claims] It consists of a reverse osmosis membrane, an ion exchange resin tower, an ultraviolet sterilizer, a filter, etc. A pressurized pump placed before the reverse osmosis membrane passes water through these to produce ultrapure water, and unused water is stored at the point of use. In an ultrapure water production apparatus having a point of use circulation piping that returns ultrapure water to the suction side of the pressure pump, the flow rate of the point of use return piping is detected, the rotation speed of the pressure pump is controlled, and the return A method for controlling the operation of an ultrapure water production device, the method comprising controlling the flow rate of piping.