JPS59154113A - Ultrafiltering method - Google Patents

Abstract

PURPOSE:To obtain a concentrated liquid and a transmitted liquid having stabilized quality by detecting the inlet pressure of the membrane in a circulation-type ultrafiltering apparatus, and controlling the supply rate of the original liquid in accordance with the fluctuation of the pressure to maintain the pressure exerted to the membrane at an adequate value. CONSTITUTION:In transmitting and concentrating a liquid from an original liquid tank 2 by an ultrafilter membrane 5 through a pump 2, an inlet pressure of the membrane 5 is detected by a pressure sensor 4. And the supply rate of the original liquid is regulated by controlling the number of revolutions of the pump 2 to keep constant the set pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION In circulating ultrafiltration, the present invention stably circulates, condenses, and permeates the stock solution under a set appropriate pressure within the permissible pressure unique to the filtration membrane, thereby preventing destruction of the filtration membrane. At the same time, the present invention relates to a method for obtaining a concentrated liquid and a permeated liquid of stable quality.

Circulating ultrafiltration is a method in which a concentrated solution and a permeated solution are obtained by circulating a stock solution through an ultrafiltration membrane, but as concentration progresses, the viscosity of the stock solution increases significantly. Although it varies depending on the type of stock solution, an increase in viscosity of 3 to 5 times is observed. As the viscosity of the stock solution increases, the resistance during passage through the filtration membrane increases, and the pressure inside the filtration membrane increases rapidly, destroying the filtration membrane.

In order to prevent this destruction of the filtration membrane, it is necessary to adjust the amount of stock solution supplied to the filtration membrane.

In the conventional circulating ultrap filter method, as shown in Fig. 1, a relief valve or a flow rate adjustment valve (7) is installed in the circulation pipe (3) of the filtration membrane (5), and the pressure is detected by a pressure sensor (4). The relief valve or flow rate adjustment valve (7) is adjusted manually or automatically according to the pressure applied to the stock solution tank (
In this method, the amount of stock solution returned to step 1) and supplied to the filtration membrane (5) is controlled.

This method wastes a lot of power, and depending on the type of stock solution, it may promote foaming and reduce filtration efficiency.

In addition, depending on the structure of the IJ IJ valve and the flow rate adjustment valve (7), it is difficult to control the flow rate, and the temperature of the stock solution may change due to the rise in temperature and destroy the filtration membrane (5), making it impossible to achieve stable filtration. The process was not performed.

The present invention solves these drawbacks and provides a method that can obtain a concentrated liquid and a permeated liquid of stable quality without destroying the filtration membrane, and at the same time save power.

An example of the method of the present invention will be explained in detail with reference to FIG.

In order to always perform stable filtration at an appropriate pressure without destroying the filtration membrane, the pressure is detected by the pressure sensor (4), and the rotation speed of the pump (2) is controlled to maintain the set pressure at all times. Enshrine the undiluted solution supply.

In this case, the pump (2) is preferably of a positive displacement type.

An example of a method for controlling the pump (2) based on pressure changes detected by the pressure sensor (4) is to convert pressure changes into voltage or low flow changes using a pressure potentiometer, and then control the pump using an inverter or speed controller. The rotation speed of the pump (2) is controlled by changing the rotation speed of the drive motor (2) or by changing the transmission gear ratio using the pilot motor.

The concentrated liquid and permeated liquid obtained by the method of the present invention have good and stable quality without any change in quality due to thermal changes.

In addition, there is no reduction in filtration efficiency due to foaming, and there is no unnecessary return flow from the primary side of the filtration membrane to the stock solution tank, allowing stable circulating p-filtration with the minimum necessary power.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a conventional circulating type ultra-particle filtration apparatus, and FIG. 2 is a schematic diagram of an apparatus for explaining the circulating type constant pressure ultra-particle filtration method of the present invention. (1) Stock solution tank, (2) Pump, (3) Circulation system, (4) Pressure sensor, (5) Filtration membrane,
(6) Return piping, (7) IJ! J-F valve or flow rate adjustment valve, (8) Relief piping.

Claims (1)

[Claims] The pressure applied to the filtration membrane is always maintained at the appropriate pressure by detecting the filtration membrane inlet pressure of the circulating ultrafiltration device, following its fluctuations, and automatically controlling the pump rotation speed to control the supply amount to the filtration membrane. An ultrapolar filtration method that is characterized by obtaining concentrated liquid and permeated liquid of stable quality while maintaining the same quality.