JPS6019003A - Operation of membrane module - Google Patents

Abstract

PURPOSE:To make it possible to effectively restore the permeation capacity of a membrane module, by flowing saturated or overheated steam through the membrane module by temporarily interrupting the operation of the membrane module. CONSTITUTION:The reduction in the amount of a permeation liquid can be detected by a flow meter 52 and, when this reduction in the amount of the permeation liquid is detected, valves 22, 31, 51 are closed while valves 41, 61, 71, 82 are opened to allow the steam of a boiler source B to flow through a membrane module 1. Steam passes through the membrane module 1 according to a route shown by arows a1, a2 and accompanies the contamination substance removed from the membrane surface to reach a heat exchanger 8 where condensed and cooled by inderect heat exchange due to cooling water to be discharged along with the contamination substance. This flow of steam is succeeded for a definite time to sufficiently remove the contamination substance and, thereafter, the valves 41, 61, 71, 82 are closed while the valves 22, 31, 51 are opened to return the membrane module 1 to steady operation.

Description

[Detailed description of the invention] The present invention relates to a method of operating a membrane module.

In membrane separation methods such as ultrapolar permeability and reverse osmosis methods, it is said that when a membrane module is used for a long time, the membrane surface of the membrane module becomes contaminated and the performance (permeated water amount or desalination rate) of the membrane module decreases. There's a problem. For this reason, it is known that after operating the membrane module for a predetermined period of time, the operation of the membrane module is interrupted and the membrane module is cleaned by flowing a cleaning liquid. However, in the conventional cleaning method, it is necessary to select a cleaning liquid depending on the change in the properties of contaminants in the processing stock solution, which is troublesome.

Furthermore, when considering the chemical influence of the cleaning liquid on membranes, pipes, etc., it is extremely difficult to select the optimum cleaning liquid.

Conventionally, it has been known to use water vapor for the purpose of sterilizing membrane modules, but the present inventor discovered that this water vapor is effective for desorption and removal of a wide range of pollutants from membrane modules, and furthermore, It has been found that there is no effect on the membrane, and that there is virtually no effect on the membrane by limiting the flow time of water vapor.

The method for operating a membrane module according to the present invention is a method invented based on the above-mentioned knowledge, and during operation of the membrane module, the operation of the membrane module is temporarily interrupted and the membrane module is saturated or superheated by flowing steam. This method is characterized by washing.

The temperature of the steam used in the present invention is 100 to 120
°C is appropriate. Water vapor can be flowed from the raw solution side (or outlet side) of the membrane module to the raw solution outlet side (or side) at normal pressure, or the water vapor can be flowed from the raw solution side of the membrane module so that it passes through the membrane. It is also possible to flow from the (or outlet side) toward the permeation chamber side. In this case, the flow rate of water vapor through the membrane is suitably in the range of 0.001 to 0.1 m/sec. In this case, since the pressure of water vapor increases depending on the resistance to passage through the membrane, it is necessary to provide a safety valve or the like to protect the membrane module and piping. The duration of water vapor flow is determined depending on the nature and amount of the pollutant.
In order to protect the membrane, it is desirable to set the time to 0.5 to 5 hours.

The present invention will be explained below with reference to the drawings.

The drawing shows a liquid separation system for use in the present invention.

In the figure, reference numeral 1 indicates a reverse osmosis membrane module or an ultra membrane module, and any of the hollow fiber type, spiral type, and tubular type can be used, and the membrane material is a heat-resistant membrane such as polysulfone. 2 is a stock solution supply pipe, 21 is a stock solution pressure pump, and 22 is a valve. 3 is the concentrate extraction pipe;
31 is a valve. A steam supply pipe 4 communicates the boiler B with the concentrate outlet via a valve 41 and a flow meter 42. 5 is a permeate extraction pipe, 51 is a valve, and 52 is a flow meter.

6 is a shunt for the raw solution pipe 2, 61 is a valve, 7 is a shunt for the permeate pipe, 71 is a valve, 8 is a heat exchanger, 8
1 is a cooling water passage of the heat exchanger, and 82 is a valve.

In the above system, during normal operation, the valve 41
, 61, 71.82 are closed and the valve 22° 31.51 is opened, the stock solution is pumped to the membrane module 1 by the pump 21, and the stock solution concentrated by solvent separation, that is, the concentrate, is sent from the concentrate pipe 3. The separation solvent, ie, the permeate, is taken out from the permeate take-out pipe 5. As described above, as this operation progresses, the performance of the membrane module 1 decreases due to contamination of the membrane surface, and the amount of permeate decreases.

This reduction in the amount of permeated liquid is detected by the flowmeter 52, and when this reduction in the amount of permeated liquid is detected, the valve 22° 31.51 is closed and the valves 41, 61, 71.82 are opened and the membrane module 1 is Steam from boiler source B is made to flow within the boiler. Water vapor is indicated by arrow a1. It passes through the membrane module 1 along route a2, reaches the heat exchanger 8 along with the contaminants removed from the membrane surface, is condensed and cooled by indirect heat exchange with cooling water, and is drained together with the contaminants.

After continuing the flow of this steam for a certain period of time and sufficiently removing contaminants, the valves 41, 61.71.

82 is closed and the valves 22, 31.51 are opened to return the membrane module 1 to normal operation.

The present invention is effective regardless of the type of membrane contaminants, including organic substances such as hydrocarbons, esters, ketones, alcohols, amines, and fatty acids, inorganic elements and compounds such as nitrogen, sulfur, and halogens, and organic substances such as proteins. It can be widely applied to pollutants whose main components are

Examples of the present invention will be described below in comparison with comparative examples.

Example In an ultrapure water line using a hollow fiber complete reverse osmosis separation membrane module, the amount of permeated water was at the initial value (approximately 40017
m, Hr), saturated water vapor (100″C11 atm) was passed through the membrane at a rate of 0, Ol m
/ S e Q for 1 hour.

Comparative Example 1 Instead of flowing saturated steam as in the example, a mixed solution of methanol and hydrochloric acid (60% methanol) was filled into a membrane module and allowed to stand for 3 hours.

Comparative Example 2 Instead of filling and leaving the mixed liquid in Comparative Example 1, the mixed liquid was circulated for 3 hours (repeatedly returning the liquid on the concentrate outlet side of the module to the stock solution side).

Comparative Example 3 The same procedure as Comparative Example 1 was carried out except that a mixed solution of hydrogen peroxide and ammonia (hydrogen peroxide 1.5%) was used as the mixed solution.

Comparative Example 4 The same procedure as Comparative Example 2 was carried out except that a mixed solution of hydrogen peroxide and ammonia (hydrogen peroxide 1.5%) was used as the mixed solution.

After cleaning according to the above Examples and Comparative Examples, the amount of water permeated through the membrane module (ultrapure water line) was measured and found to be as follows.

As is clear from this measurement result, according to the present invention, the permeation performance of the membrane module can be effectively restored. Also, since the cleaning agent is saturated or heated steam and is compatible with a wide range of contaminants, there is no need for the traditional problems of selecting a cleaning solution.

[Brief explanation of the drawing]

The drawing is an explanatory diagram showing a liquid separation system used in the present invention.

Claims (1)

[Claims] (1) A method for operating a membrane module, which comprises temporarily interrupting operation of the membrane module during operation of the membrane module, and cleaning the membrane module by flowing saturated or superheated steam.