JPS6297605A - Liquid membrane separation treatment method - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Application of the Invention] The present invention relates to a liquid membrane separation treatment method in which a liquid to be treated is passed through a plurality of rotating disk membranes to obtain a permeated liquid.

[Prior art]

There are three types of liquid separation membrane modules used in liquid membrane separation treatment methods: hollow fiber type, tubular type, spiral type, and pressure plate type. These membrane modules for liquid separation all obtain a permeate by causing the liquid to be treated to flow and suppressing concentration polarization on the membrane surface. However, these membrane modules for liquid separation do not have sufficient liquid separation performance when the liquid to be processed becomes a high viscosity liquid of 50 Cp or more, and also have problems in terms of energy.

On the other hand, in a liquid membrane separation method using a rotating disk membrane as a liquid separation membrane module, the rotating disk membrane itself is driven to suppress the concentration pole of the liquid near the membrane and obtain a permeate (permeated water). It has the advantage of being able to perform liquid separation with low energy.

However, after long-term operation, the amount of water permeated through the membrane gradually decreases due to concentration polarization of contaminants on the membrane surface.

For this reason, concentration polarization is suppressed by introducing air bubbles into the gaps between rotating disk membranes or by combining disk electrodes with each other during operation of the rotating disk membrane. Even with this method, if the membrane performance deteriorates or the amount of water permeated through the membrane decreases, the operation is stopped and chemical cleaning is performed.

[Purpose of the invention]

An object of the present invention is to provide a liquid membrane separation method that solves the problems of the prior art and allows stable operation without reducing the total amount of water permeated through the membrane even during long-term operation. be.

[Summary of the invention]

The present invention was developed by focusing on the relationship between the viscosity of the liquid to be treated and the rotation speed of the rotating disk membrane, and detects the viscosity of the liquid to be treated before passing through the rotating disk membrane. By controlling the rotational speed of the rotating disc membrane according to the detected value, the amount of liquid permeating through the membrane is always kept above a certain value.

FIG. 1 is a diagram showing the relationship between the viscosity of the liquid to be treated, the rotational speed of the rotating disk membrane, and the amount of water permeated through the membrane. In FIG. 1, the amount of water permeated through the membrane decreases as the viscosity of the liquid to be treated increases. For each liquid to be treated with each viscosity, the amount of water permeated through the membrane becomes a constant value when the rotational speed of the rotating disc membrane becomes a constant value or more.

Therefore, the present invention detects the viscosity of the liquid to be treated before passing through the rotating disk membrane, and as shown in FIG. By controlling the amount of rotation of the membrane, the amount of water permeating through the membrane can be maintained at a set amount at all times, regardless of the viscosity of the liquid to be treated.

In particular, when the viscosity of the liquid to be treated increases during operation, the amount of water permeating the membrane usually decreases, but as is clear from Figure 1, increasing the amount of rotation of the rotating disc membrane can reduce the amount of water permeating the membrane. It can be prevented.

In addition, when controlling the amount of rotation of the rotating disk membrane as described above,
It is desirable to close the knob on the membrane-permeated water side and close the flow path of the membrane-permeated water to achieve the following state. In such a state, the liquid to be treated does not pass through the membrane, so that when the rotating disk membrane rotates, the contaminants deposited on the membrane surface are easily peeled off. As a result, the layer of contaminants on the membrane surface becomes thinner, and the amount of water permeated through the membrane increases. Furthermore, the viscosity of the liquid to be treated before passing through the rotating disk membrane is detected, and the rotational speed of the rotating disk membrane is controlled according to the detected value, and at the same time, the rotational direction of the rotating disk membrane is changed from normal to reverse. If it is carried out in this condition, the effect of removing contaminants from the membrane surface will increase.

However, if the operating pressure is increased, it becomes difficult to remove contaminants from the membrane surface, so it is desirable to avoid this.

Further, in the present invention, the following operations can be used simultaneously with controlling the rotation speed of the rotating disc membrane. That is,
When a gas introduction pipe is installed in the gap between rotating disk membranes arranged in parallel at a predetermined interval in the axial direction of the membrane permeated water collection pipe, a gas such as air is ejected from this gas introduction pipe, The membrane surface can be cleaned by bubbles generated in the liquid to be treated.

Although cleaning the membrane surface using air bubbles is effective in removing contaminants from the membrane surface, it cannot prevent deterioration in membrane performance due to membrane adsorbents. In this case, a chemical solution such as hypochlorous acid is injected from the gas introduction pipe. After the contaminants deposited on the membrane surface are peeled off by air bubbles, the chemical solution is injected from the gas introduction pipe, thereby reducing the amount of the chemical solution required to remove the membrane adsorbed substances.

[Implementation sequence of the invention]

Example 1 Purified water was obtained from activated sludge using a liquid membrane separation device equipped with a rotating disk membrane. The initial sludge concentration is 0.3%.

The liquid viscosity is 5 cp (20'c), and the amount of water permeated through the membrane is as follows: operating pressure 0.5 m/-1 rotation speed of disc membrane 5 Or, p,
Operating condition of m 7t' 1.5rrl/rr? , d. If operation is continued with the rotational speed of the rotating disk membrane (50r, p, m+) constant, the liquid viscosity will rise to 180cp at a sludge concentration of 2.5%, and the amount of water permeated through the membrane will be 0.3rr?/
r? , d.

Incidentally, in conventional treatment operation examples, after the amount of water permeated through the membrane decreases,
The membrane surface was cleaned, etc.

In this implementation series, the viscosity of the liquid to be treated is continuously detected,
When the viscosity of the liquid to be treated is 180 cp and the rotation speed of the rotating disc membrane is 250 r, p, m, the amount of water permeating through the membrane? 1-2nl/n? , d.

All starch saccharification was carried out in a model reactor equipped with a rotating disc membrane. Initial starch concentration 300? /l.

The liquid viscosity was 100 cp (20°C). Glucoamylase was added to this liquid by 0.5 glucoamylase based on the amount of starch, and the entire saccharification reaction was carried out. As the hexasaccharification reaction progressed, the viscosity of Atsushi decreased to 5 to 1 Ocp.

Incidentally, in the conventional processing operation sequence, the rotation speed of the rotating disk membrane is set to 2.
0 Or, p, and m remain constant.

In this actual train, the viscosity of the liquid to be treated is continuously detected,
The rotational speed f 50 r of the rotating disc membrane depends on the decrease in the viscosity of the liquid.
, p, and m, but there was no change in the amount of water permeated through the membrane. Therefore, in this embodiment, the power cost for rotating the rotating disk membrane can be reduced without reducing the amount of water permeated through the membrane.

〔Effect of the invention〕

As described above, according to the present invention, the viscosity of the liquid to be treated before passing through the rotating disk membrane is detected, and the rotational speed of the rotating disk membrane is controlled according to the detected value, so that the membrane can be coated for a long period of time. Performance can be maintained, a predetermined amount of membrane-permeated water can be obtained at all times, and the power cost for rotating the rotating disc membrane can be reduced.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the relationship between the viscosity of the liquid to be treated, the rotational speed of the rotating disk membrane, and the amount of water permeated through the membrane.

Claims (4)

[Claims] (1) Processing the liquid to be treated through multiple rotating disk membranes,
In the membrane separation treatment method for a liquid to obtain a permeate, the viscosity of the liquid to be treated before passing through the rotating disk membrane is detected, and the rotation speed of the rotating disk membrane is controlled according to the detected value. Characteristic liquid membrane separation treatment method. (2) The control operation of the rotation speed of the rotating disk membrane is performed with the flow path on the permeate side closed.
The membrane separation treatment method for liquids described in Section 1. (3) When controlling the rotational speed of the rotating disk membrane, air bubbles are generated in the gaps between the plurality of rotating disk membranes, and the surface of the rotating disk membrane is cleaned with the air bubbles. A method for membrane separation treatment of a liquid according to scope 1. (4) When controlling the rotational speed of the rotating disk membranes, a chemical solution capable of decomposing substances adhering to the membranes is injected into the gaps between the plurality of rotating disk membranes. 1
4. A liquid membrane separation treatment method according to items 1 to 3.