JPH02126922A - Back washing method of separating membrane - Google Patents

Abstract

PURPOSE:To allow easy back washing of a separating membrane by closing the valve of a discharge pipeline to nearly equalize the pressure between the internal pressure of a supply pipeline and the internal pressure of the discharge pipeline, then opening the valve of a recycle pipe to drop the internal pressure of the supply pipeline. CONSTITUTION:An original liquid is introduced by a supply pump 3 from an original liquid tank 1 into a separating membrane module 2 and the filtrate separated by the module 2 is introduced into a filtrate tank 10. The recycle pipe 5 having a 1st valve 6 is connected to the supply pipeline 4 from the supply pipe 3 to the module 2. An accumulator 7 and a 2nd valve 8 are disposed to the discharge pipeline 9 from the module 2 to the filtrate tank 10. This valve 8 is closed to nearly equalize the internal pressure of the supply pipeline 4 and the internal pressure of the discharge pipeline 9; thereafter, the valve 6 is opened to drop the internal pressure of the supply pipeline 4. The separating membrane is back washed by these simple operations.

Description

[Detailed Description of the Invention] [Field of Industrial Application] The present invention relates to a method for backwashing separation membranes, and more specifically, to a method for backwashing separation membranes in membrane separation devices used for oil/water separation and concentration purification in various chemical manufacturing processes. This relates to a backwashing method.

[Prior art]

In general, methods for removing specific substances from stock solutions using membranes include methods that use potential difference, methods that use concentration difference, and methods that use pressure difference. It is widely taken.

A separation device that utilizes this pressure difference uses a supply pump to force feed the stock solution from the stock solution tank to the primary side of the separation membrane module containing the separation membrane, and the pressure difference with the secondary side causes specific substances to be separated from the micropores of the separation membrane. It is filtered from the secondary side to the secondary side.

By the way, in the above-mentioned separation device, solid particles in the raw solution adhere to the primary side of the separation membrane and reduce the permeation flow rate, so it is necessary to remove this. One method for removing this is a backwashing method. .

This method of backwashing the separation membrane is carried out by reversing the pressure water turbines on the primary and secondary sides of the separation membrane module during boat fishing. To achieve this, for example, a pressure supply means is provided on the secondary side, the supply pump on the downstream side is stopped, and the pressure supply means is used to increase the pressure on the secondary side of the separation membrane. There is.

However, according to such a means, it is necessary to stop the supply pump once, making the operation cumbersome. Under these circumstances, a bypass line is connected to the secondary side of the separation membrane module from the pipe connecting the supply pump and the separation membrane module, and during backwashing, the stock solution sent from the supply pump is passed through this bypass line, and the separation membrane is It has been proposed to supply a stock solution to the secondary side and further increase the pressure on the secondary side of the separation membrane using external pressure (for example, JP-A-63-12
6513).

[Problem to be solved by the invention]

By the way, in the above-mentioned separation device provided with a bypass line, it is necessary to specially provide means for supplying pressure to the secondary side, which poses a problem in that the manufacturing cost of the entire device increases.

[Means to solve the problem]

The present invention has been made in order to solve the above-mentioned problems, and includes a supply pump that guides the stock solution from the stock solution tank to the separation membrane module, and guides the filtrate separated by the separation membrane module to the filtrate tank. In the separation membrane apparatus, a recycle pipe having a first valve is connected to the supply pipe from the supply pump to the separation membrane module, and a pressure accumulator and a second valve are connected to the discharge pipe from the separation membrane module to the filtrate tank. and closing the second valve to substantially equalize the internal pressure of the supply pipe and the internal pressure of the discharge pipe, and then opening the first valve to reduce the internal pressure of the supply pipe. This is a method for backwashing a separated separation membrane.

[For production]

In such a separation device, during normal operation, the first valve provided on the recycling pipe is closed, the second valve provided on the discharge pipe is opened, and the supply pump is operated to transfer the stock solution from the stock solution tank to the separation membrane. Supply to the module. The internal pressure of the supply pipe at this time is about 5 kg/ci. The stock solution supplied into the separation membrane module is filtered from the primary side of the separation membrane to the secondary side to remove specific substances due to the pressure difference. At this time, the internal pressure of the discharge pipe on the secondary side is approximately atmospheric pressure.

When performing backwashing in the above device, first close the second valve while the supply pump is in operation, and the internal pressure of the supply pipe, that is, the primary side pressure of the separation membrane, and the internal pressure of the discharge pipe, that is, the secondary side pressure of the separation membrane. The side pressure becomes almost uniform. Thereafter, when the second valve is opened, the pressure on the primary side of the separation membrane decreases, and the filtrate on the secondary side flows back. This backflow removes solid particles and the like adhering to the primary side of the separation membrane.

〔Example〕

Embodiments of the method for backwashing a separation membrane according to the present invention will be described below with reference to the drawings.

The figure is a system diagram of the separation device, where 1 is the stock solution tank;
The stock solution tank 1 and the primary side of a separation membrane module 2 containing a separation membrane are connected through a supply pipe 4 having a supply pump 3 . One end of a recycle pipe 5 is connected to the supply pipe 4a between the supply pump 3 and the separation membrane module 2, and the other end of the recycle pipe 5 is connected to the inlet side supply pipe of the supply pump 3 via a first valve 6. 4b.

One end of a discharge pipe 9 having a pressure accumulator 7 and a second valve 8 is connected to the secondary side of the separation membrane module 2.
The other end communicates with the filtrate tank 10. Reference numeral 12 denotes a conduit that guides the stock solution concentrated in the separation membrane module 2 to the concentration tank 13, and a third valve 14 for adjusting the pressure on the primary side is provided along the way.

In the above configuration, when backwashing the separation membrane from normal operation as described above, (1) With the supply pump 3 in operation, the second valve 8
will be closed.

Then, the pressure inside the discharge pipe 9 and pressure accumulator 7 (pressure on the secondary side)
increases, and the pressure almost balances with the pressure in the supply pipe 4, specifically the pressure in the supply pipe 4a between the supply pump 3 and the separation membrane module 2 (pressure on the negative side).

(2) As described above, when the pressure on the secondary side is almost balanced with the pressure on the primary side, the first valve 6 provided in the recycle pipe 5 is opened.

Then, the pressure inside the supply pipe 4a, that is, on the primary side of the separation membrane module 2, decreases.

At this time, by making the diameter of the recycling pipe 5 larger than the diameter of the supply pipe 4, the pressure in the supply pipe 4a can be rapidly reduced.

In this state, the pressure on the secondary side of the discharge pipe 9, that is, the separation membrane module 2, is higher than the pressure on the primary side, so that the filtrate flows backward across the separation membrane.

When the second valve 8 is closed, the pressure in the pressure accumulator 7 is increased to a level that corresponds to the pressure on the primary side, so this pressure accumulating action maintains sufficient backflow time to clean the separation membrane module 3. As a result, solid particles and the like attached to the primary side of the separation membrane can be removed.

〔Effect of the invention〕

As is clear from the above explanation, according to the method for backwashing a separation membrane according to the present invention, there is no need to provide a special pressure supply means on the secondary side of the separation membrane module 2, and the supply pump 3
There is an advantage that the separation membrane can be backwashed by simply closing the second valve 8 and opening the first valve 6, without having to stop the separation membrane.

[Brief explanation of drawings]

The figure is a system diagram of a separation apparatus for carrying out the method for backwashing a separation membrane according to the present invention. ■...Stock solution tank 2...Separation membrane module 3.
... Supply pump 4 ... Supply pipe 5 ... Recycle pipe 6 ... First valve 7 ... Pressure accumulator 8.
... Second valve 9 ... Discharge pipe 10 ... Filtrate tank 12 ... Conduit 13 ... Concentration tank 14 ... Third valve.

Claims (1)

[Claims] In a separation membrane device in which the stock solution is guided from the stock solution tank to the separation membrane module by a supply pump, and the filtrate separated by the separation membrane module is guided to the filtrate tank, a supply pipe line from the supply pump to the separation membrane module, connecting a recycling pipe having a first valve;
A pressure accumulator and a second valve are disposed in the discharge pipe leading from the separation membrane module to the filtrate tank, and the second valve is closed to substantially equalize the internal pressure of the supply pipe and the discharge pipe. A method for backwashing a separation membrane, characterized in that the first valve is opened to reduce the internal pressure of the supply pipe.