JPS5936506A - Method for controlling operation of electrodialysis type water producing equipment - Google Patents

Abstract

PURPOSE:To control voltage by operating a titled device at a fixed current value untill the concentration of salt of a desalted water attains a prescribed value, at the time of starting-up an electric power supply, and measuring the electric conductivity of a produced water in the same manner as in an conventional method of operation control, except said start-up. CONSTITUTION:A circuit having a voltage-current controlling switch 6 and a constant current device 10 are installed between a rectifier 2 and an ammeter 4, and the switch 6 is changed to the current controlling side at the time of power supply, and an impressing current value is set to the current in normal operation or the current close to it perform the operation of a fixed current value. The electric conductivity of a produced desalted water falls with the lapse of power supplying time, but when said conductivity attains the electric conductivity in normal operation or the value close to it, the switch 6 is changed to the voltage controlling side to shift the operation to the voltage controlling one. By this operation, an excessive flow of electric current such as in the case of conventional method is prevented because the control at the time of start-up is switched to the constant current control.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the operation of an electrodialysis water generator,
In particular, the present invention relates to a method of controlling the operation of an electrodialysis water generator with a small rectifier capacity.

The electrodialysis fresh water generator has a structure (1) in which an anode is disposed at one end, a cathode is disposed at the other end, and a large number of anion exchange membranes and cation exchange membranes are alternately sandwiched between these electrodes. When a voltage is applied between these two electrodes, cations migrate to the cathode and anions to the anode, resulting in the formation of numerous demineralization chambers and concentration chambers between the two electrodes. Demineralized water is obtained.

Conventionally, in devices that perform excessive desalination processing, it is necessary to ensure that the electrolytic solution entering the dialysis chamber has a predetermined salt concentration at the outlet, and for this reason, it is necessary to have a structure with a long liquid flow path. Generally, a flow path of 10 m or more is required to produce desalinated water at 500 F from seawater.

In such an electrodialysis water production system that performs excessive desalination processing, the most common method for maintaining the purity of desalinated water is to measure the electrical conductivity of the produced desalinated water and control the voltage accordingly. It is being said. FIG. 1 is a flowchart showing a method for controlling the operation of an electrodialysis water generating apparatus that performs such a conventional one-time desalination process. In this electrodialysis water generator, an electrolytic solution 7 is introduced into a dialysis tank 1, electrodialyzed, and demineralized water 8 and concentrated water 9 are taken out. The conductivity of this demineralized water 8 is measured by the conductivity change needle 5, and the electric pressure (2) is thereby controlled. , 2 in the figure is a rectifier 3, and a chemical pressure gauge.

The number indicates the ammeter.

However, since the concentration of desalinated water in the dialysis tank is high when the water generator starts energizing, a large amount of electricity flows compared to the steady state. Electricity flows. For this reason, in conventional fresh water generation equipment, the capacity of the rectifier must be made extremely larger than the unnecessary capacity during steady operation, and as a result, the rectifier is operated at a low load during steady operation.
The drawback was low power efficiency.

However, in conventional water production equipment, if the point where the conductivity of the produced desalinated water is measured is far away from the dialysis tank, the response to the desalination state in the dialysis tank will be slow, leading to the possibility of incorrect operation of the equipment. was there. For example, if the conductivity indicator of the produced desalinated water indicates a high conductivity even though the desalination process is sufficiently progressing in the dialysis tank, a large amount of current may be applied by mistake and the dialysis There was a possibility that problems would occur that would shorten the life of the membrane.

(3) It is an object of the present invention to provide a method for controlling the operation of an electrodialysis water generating apparatus, which eliminates the drawbacks of the above-mentioned conventional techniques, reduces the capacity of the rectifier, and reduces malfunctions.

The present invention operates at a constant current value until the salt concentration of desalinated water reaches a predetermined value or almost a predetermined value at the start of energization. It measures the temperature and controls the voltage.

Hereinafter, the present invention will be explained in more detail with reference to the drawings. Second
The figure is a system diagram showing one embodiment of the method for controlling the operation of an electrodialysis fresh water generating apparatus according to the present invention. The difference from the conventional device shown in FIG.
and a circuit having the constant current device 10 is provided. At the start of energization, the current-current control switch 6 is switched to the current control side, and the applied current value is set to the current value during steady operation or a current value in the vicinity thereof, thereby performing constant current value operation. As the energization time passes, the conductivity of the produced desalinated water decreases, but the conductivity of this desalinated water remains constant (4).When the conductivity of the desalinated water reaches the value during normal operation or a value close to this,
The voltage-current switch 6 is switched to the voltage control side, and the operation is shifted to voltage control as in the conventional method. According to this operating method, since the switch is made to constant current control at the start of energization, an extremely large amount of current does not flow as in the conventional method, and therefore the capacity of the rectifier remains the same as the capacity during steady operation even at startup. This is extremely advantageous for the device. Further, in the method of the present invention, since the rectifier is used under a state close to full load during steady operation, the power efficiency is high and it is economical from an operational point of view. Furthermore, in the method of the present invention, constant current control is performed at startup, and due to the small capacity of the rectifier, the response of the desalination state in the dialysis tank is slow, which prevents erroneous operations such as accidentally flowing a large amount of current. There is no need for potash to shorten the life of the dialysis membrane.

As described above, according to the present invention, the capacity of the rectifier can be reduced, and the electrodialysis water generation apparatus can be operated efficiently both in terms of equipment and operation.

(5)

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing a conventional method for controlling the operation of an electrodialysis water generating apparatus, and FIG. 2 is a system diagram showing an embodiment of the method for controlling the operation of an electrodialysis water generating apparatus according to the present invention. 1... Dialysis tank, 2... Rectifier, 5...
. . . Conductivity scale, 6 . . . Voltage-current control switch, 8 . . . Desalinated water, 10 . Agent Patent Attorney Takeshi Kawakita (6)

Claims (1)

[Claims] (1) A method for controlling the operation of an electrodialysis water generator in which anion exchange membranes and cation exchange membranes are alternately arranged between an anode and a cathode, characterized by performing constant current value operation at the start of energization. Operation control method for electrodialysis water generation equipment. (2. The method for controlling the operation of an electrodialysis water generating apparatus according to claim 1, wherein the constant current value is a current value during steady operation or a current value in the vicinity thereof.