Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Patent
1989-04-03
1990-06-26
Sever, Frank
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
21032165, B01D 1300
Patent
active
049369970
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
This invention relates to a method of flushing a desalination apparatus equipped with a reverse osmotic membrane module and an apparatus therefor.
BACKGROUND ART
As is well known, the construction of a desalination apparatus with a reverse osmotic membrane module is such that, as shown in FIG. 1, the reverse osmotic membrane module U is adapted to separate permeate water (pure water) WP from raw water (seawater) WF that is pressure-fed by a pump PM through a permeable membrane M, concentrated water (concentrated brine) WB being finally discharged from an outlet valve V2. In this kind of desalination apparatus, a gel layer G (FIG. 2) is formed on the permeable membrane M by contaminants, microbes or the like in the water over a long period of operation and thus the membrane performance or permeation performance deteriorates. It has thus been the practice to recover the permeation performance of the permeable membrane M by closing valve V1 at predetermined intervals of time T1 (once a month in the example shown), as shown by a dotted line A in FIG. 3, the gel layer G on the surface of the permeable membrane M then being dissolved and removed with a liquid chemical. Such removal operation is ordinarily performed at a given frequency within the range of from once every half a month to once every two months, depending on the specific operating conditions, such as the quality of raw water, the recovery rate, etc. Such being the case, certain problems are encountered since not only must the system be shut down, but also the cost of the liquid chemical and labour involved are considerable. These problems lead to an overall increase in the cost of the desalination.
DISCLOSURE OF INVENTION
An object of this invention is to provide a method of flushing a desalination apparatus having a reverse osmotic membrane and an apparatus therefor which can serve to reduce the number of times it is necessary to remove a gel layer with a liquid chemical.
The inventors of this invention found, as a result of various studies, that when a large quantity of low-pressure water is fed through a reverse osmotic membrane over a predetermined period of time, the total quantity of raw water flows to the outlet valve such as to increase the flow velocity through the reverse osmotic membrane, whereby the gel layer is removed by the shearing force of the flow of raw water. The present invention was accomplished having taken notice of this principle.
The present invention relates to a desalination method utilizing a reverse osmotic membrane module, by which means permeate water is separated from raw water pressure-fed by a pump through a reverse osmotic membrane, concentrated water being discharged from an outlet valve, wherein when the membrane performance of the reverse osmotic membrane module deteriorates due to a gel layer, the number of revolutions of a pump driving motor is reduced and the opening of the outlet valve is increased, thereby increasing the flow velocity inside the reverse osmotic membrane module so that the gel layer is removed by the raw water.
Further, the present invention relates to a desalination apparatus for separating by a reverse osmotic membrane module permeate water from raw water pressure-fed by a pump through a reverse osmotic membrane, concentrated water being discharged from an outlet valve, comprising a number-of-revolutions control means for controlling the number of revolutions of a pump driving motor, an opening control means for controlling the opening of the outlet valve and an operation device operable to control the number-of-revolutions control means and the opening control means to reduce the number of revolutions of the pump driving motor and increase the opening of the outlet valve when the membrane performance of the reverse osmotic membrane module is lowered.
According to the present invention, by reducing the number of revolutions of the pump and increasing the opening of the outlet valve, the pressure inside the reverse osmotic membrane module is reduced and the flow rat
REFERENCES:
patent: 3922220 (1975-11-01), Middleman et al.
Abe Takayuki
Mashima Etsuyo
Ochiai Ichiro
Taniguchi Shin
Ebara Corporation
Sever Frank
LandOfFree
Method of flushing desalination apparatus equipped with reverse does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method of flushing desalination apparatus equipped with reverse , we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method of flushing desalination apparatus equipped with reverse will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1124292