JPH06269640A - Membrane treatment apparatus - Google Patents

Abstract

PURPOSE:To provide a membrane treatment apparatus by which filtered water with stable quality can be obtained surely with no need of a large size installation to remove air. CONSTITUTION:A circulation pump 2 is installed in the raw water side of a membrane module to form a closed loop circulation line. A vertical type air separator 8 whose cross-section surface area is widened is installed in a pipeline 7 between the membrane module 1 and either suction side or discharge side of the circulation pump 2 and an air releasing valve 9 is installed in the upper end part of the separator. The flow rate of the liquid in the inside of the separator 8 is set preferably to be 0.5m/sec or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a membrane treatment apparatus in which a closed loop circulation line is formed on the raw water side of a membrane module.

[0002]

2. Description of the Related Art In a film processing apparatus of the above type, if air is mixed in the circulation line, the following problems will occur. Due to the air remaining in the circulation line,
Even if raw water is supplied, the air contracts, so the pressure to be filtered cannot be directly applied to the membrane, and stable filtration cannot be performed. If air remains in the membrane module, the effective area of the membrane will be small because the air cannot be filtered.
Membrane blockage is encouraged. There is a high possibility that the circulation pump installed in the circulation line may cause cavitation, resulting in a decrease in discharge amount, a decrease in discharge pressure, pump failure, and the like. When backwashing with high pressure air from the permeate side, or when backwashing with pressurized water, if there is an air pool in the membrane module, the air will contract during pressurization and air or backwashing pressurized water will flow to the raw water side. Because of the leakage, the backwash effect is reduced.

Therefore, conventionally, as shown in FIG. 4, an open type tank 3 is installed in a circulation line composed of a membrane module 1 and a circulation pump 2 to remove air from the circulation line. However, the film processing apparatus of FIG. 4 has the following problems. A large-capacity tank 3 is required to prevent the suction of air bubbles. Since the open line tank 3 is included in the circulation line, the method of closing the valve 4 and applying a constant pressure to the membrane module 1 by the circulation pump 2 (constant pressure filtration method) was adopted.
However, this method cannot secure a stable amount of filtered water because the amount of filtered water decreases as the membrane is blocked. Since the energy loss in the valve 4 is large, when trying to cross-flow filter by circulating the liquid,
Economic loss is large.

[0004]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems of the prior art and provides a membrane treatment apparatus which does not require a large facility for removing air and which can secure a stable filtered water amount. It was completed for the purpose.

[0005]

SUMMARY OF THE INVENTION The present invention, which has been made to solve the above-mentioned problems, is a membrane treatment apparatus in which a closed loop circulation line is formed on the raw water side of a membrane module, or the suction side of a membrane module and a circulation pump A vertical type air separator having a cross-sectional area larger than that of the pipeline is provided in the pipeline between the discharge side and an air vent valve at the upper end of the pipeline.

[0006]

The present invention will be described below in more detail with reference to the illustrated embodiments. 1 and 2, 1 is a membrane module, 2 is a circulation pump for circulating raw water on the raw water side, 5 is a raw water tank, and 6 is a supply pump for supplying raw water from the raw water tank 5 to a circulation line. An air separator 8 is provided in the middle of the conduit 7 between the membrane module 1 and the suction side of the circulation pump 2.

The air separator 8 has a vertical cylindrical shape as shown in an enlarged view in FIG. 2, and has a cross sectional area much larger than that of the duct 7. For this reason, the flow velocity of the circulating liquid flowing in from the conduit 7 rapidly decreases inside the air separator 8, and the air bubbles in the circulating liquid separate and float. For this purpose, the flow velocity in the air separator 8 is 0.5 m / sec or less, more preferably 0.1-
The cross-sectional area of the air separator 8 is determined to be 0.2 m / sec, which is 0.16 m / sec in the embodiment. The shape of the air separator 8 is preferably vertically longer than twice the diameter in order to ensure air separation, and in the embodiment in which the circulating liquid volume is 50 liters per minute,
The diameter is 80 mm and the height is 300 mm.

An air vent valve 9 is provided at the upper end of the air separator 8. In the embodiment, a float vent is adopted, and when the amount of air reaches a certain amount, the float 10 is pushed down to open the valve, and the air is discharged to the outside. In addition, it is preferable that the ceiling surface of the air separator 8 is provided with a slope so that air can easily collect in the air vent valve 9.

[0009]

The film processing apparatus of the present invention thus constructed is
The raw water is circulated to the raw water side of the membrane module 1 by the circulation pump 2, and the raw water tank 5 is fed by the supply pump 6.
The membrane module 1 performs filtration while supplying raw water to the circulation line. At this time, the air contained in the circulating liquid is separated and floated inside a vertical air separator 8 having a cross-sectional area larger than that of the duct 7, and is released into the atmosphere from an air vent valve 9 at the upper end. It Therefore, the filtration can be continuously progressed while the circulation line is kept pressurized by the supply pump 6, and stable filtration is possible without the above-mentioned troubles caused by air. Further, when the membrane module 1 is blocked, it is necessary to perform backwashing using high pressure air or pressurized water, but at this time, the air mixed in the raw water side can also be quickly removed by the air separator 8.

As described above, according to the present invention, stable filtration is possible. However, when the air separator 8 is not installed, the discharge amount of the circulation pump 2 is insufficient, the mechanical seal of the circulation pump 2 fails, and the permeation flux is increased. , And early blockage of the membrane occurred. Although the circulation pump 2 is provided at the position shown in FIG. 1 in the above-described embodiment, the same effect can be obtained by providing the circulation pump 2 at the position shown in FIG.

[0011]

As described above, the membrane treatment apparatus of the present invention is a vertical type in which the cross-sectional area of the conduit between the membrane module and the suction side or the discharge side of the circulation pump is larger than that of the conduit. Since an air separator is installed and an air vent valve is installed at the upper end of the air separator, it does not require large equipment for removing air as in the past, and it provides stable filtration and excellent backwashing. There is an advantage that the effect can be obtained. Further, since the air can be removed and the raw water can be supplied at the same time, the permeation flux can be always kept constant. Therefore, the present invention is a film processing apparatus that solves the conventional problems and has a great contribution to the industrial development.

[Brief description of drawings]

FIG. 1 is a piping system diagram showing an embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a main part of the embodiment.

FIG. 3 is a piping system diagram showing another embodiment.

FIG. 4 is a piping system diagram showing a conventional example.

[Explanation of symbols]

 1 Membrane Module 2 Circulation Pump 7 Pipeline 8 Air Separator 9 Air Vent Valve

Claims (2)

[Claims] 1. In a membrane treatment apparatus in which a closed loop circulation line is formed on the raw water side of a membrane module, the cross-sectional area of the pipeline between the membrane module and the suction side or discharge side of the circulation pump is larger than that of the pipeline. A membrane processing apparatus comprising an enlarged vertical air separator and an air vent valve at the upper end thereof. 2. The membrane processing apparatus according to claim 1, wherein the flow velocity in the air separator is 0.5 m / sec or less.