Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Reexamination Certificate
1999-10-20
2002-01-01
Drodge, Joseph W. (Department: 1723)
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
C210S321690, C210S637000, C210S652000, C210S669000
Reexamination Certificate
active
06334955
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a fresh water generator and a fresh water generating method for desalinating a target liquid containing residual chlorine by feeding the same to a fresh water generating cartridge having a reverse osmosis membrane.
2. Description of the Prior Art
When desalinating a target liquid (hereinafter referred to as raw water) such as service water or industrial water containing residual chlorine, a fresh water generator having a fresh water generating cartridge including a reverse osmosis membrane (RO membrane) separates the raw water into permeated water and concentrated water. In order to obtain permeated water in a necessary and sufficient flow rate in a fresh water generator having a limited scale, a permeated water storage tank is provided on the fresh water generator for storing unused permeated water therein or a pressure pump is provided on the fresh water generator for increasing the permeate flow rate per unit membrane area.
FIG. 8
is a block diagram showing an exemplary conventional fresh water generator having a pressure pump
100
.
The fresh water generator shown in
FIG. 8
employs the pressure pump
100
and a fresh water generating cartridge
4
for desalination. The fresh water generating cartridge
4
includes a reverse osmosis membrane. The reverse osmosis membrane is reduced in durability when exposed to chlorine for a long time, and hence an active carbon cartridge
2
is employed for pretreatment in order to remove residual chlorine contained in raw water.
The raw water is fed to the active carbon cartridge
2
through a raw water feed pipe
1
. The pressure pump
100
feeds the water permeating the active carbon cartridge
2
as pretreated water to the fresh water generating cartridge
4
through a pretreated water feed pipe
3
. The fresh water generating cartridge
4
having the reverse osmosis membrane separates the pretreated water into permeated water and concentrated water. The separated permeated water is taken out from the fresh water generating cartridge
4
as treated water through a permeated water outlet pipe
5
. On the other hand, the concentrated water is discharged from the fresh water generating cartridge
4
through a concentrated water discharge pipe
7
. The concentrated water discharge pipe
7
is provided with a pressure regulating valve
6
, for suppressing the concentrate flow rate. Thus, permeation through the membrane is prompted in the fresh water generating cartridge
4
.
However, the aforementioned fresh water generator requires a driver (not shown) such as a motor or an engine for driving the pressure pump
100
and a controller (not shown) for controlling the driver. Thus, the fresh water generating cost as well as the price of the fresh water generator increase. Further, noise generated in the pressure pump
100
and the driver results in a problem.
When the pretreated water is fed to the fresh water generating cartridge
4
without employing the pressure pump
100
, a sufficient linear velocity cannot be obtained on the surface of the reverse osmosis membrane of the fresh water generating cartridge
4
and hence contaminants such as impurities adhere to the membrane surface. When such a fresh water generator is continuously operated for a long time, the performance of the reverse osmosis membrane of the fresh water generating cartridge
4
is reduced to disadvantageously deteriorate the quality of the obtained permeated water and reduce the permeate flow rate over time.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a fresh water generator and a fresh water generating method which can be reliably operated at a low cost over a long time with no problem of noise.
The inventor has made various experiments and deep study for desalinating a target liquid without employing a pressure pump while suppressing propagation of bacteria, to find out that it is possible to desalinate a target liquid having a pressure of not more than 2 kgf/cm
2
by feeding the same to a fresh water generating cartridge having a reverse osmosis membrane without employing a pressure pump when employing a reverse osmosis membrane having a rejection of at least 95% for an NaCl aqueous solution of 0.05% in concentration and a permeate flow rate of at least 0.1 m
3
/m
2
·day·kgf/cm
2
.
The inventor has found out that a practical permeate flow rate can be obtained over a long time by providing a flushing device on a fresh water generator. The inventor has proposed the present invention on the basis of such recognition.
A fresh water generator according to an aspect of the present invention comprises a freshwater generating cartridge, including a reverse osmosis membrane, for desalinating a target liquid, a feed system feeding the target liquid having a prescribed pressure to the fresh water generating cartridge without through a step-up device stepping up the pressure of the target liquid and a flushing device flushing the reverse osmosis membrane of the fresh water generating cartridge.
The term “flushing” indicates an operation of washing the surface of a separation membrane with a water stream.
In this fresh water generator, the target liquid having a prescribed pressure is fed to the fresh water generating cartridge having the reverse osmosis membrane by the feed system and desalinated. The flushing device flushes the reverse osmosis membrane of the fresh water generating cartridge so that impurities remaining on the surface of the reverse osmosis membrane of the fresh water generating cartridge can be discharged from the fresh water generating cartridge.
In the fresh water generator, the target liquid having a prescribed pressure is fed to the fresh water generating cartridge in a non-powered manner without through a pressure pump serving as a step-up device, whereby neither a driver for driving the pressure pump nor a controller for controlling the driver is necessary. Thus, the fresh water generating cost is reduced while increase of the price of the fresh water generator is suppressed. Further, no problem of noise is caused by any pressure pump or driver. In addition, the fresh water generator requiring no pressure pump, no driver and no controller is miniaturized and no electric charge is required.
The prescribed pressure may be at least 0.3 kgf/cm
2
and not more than 3 kgf/cm
2
. In this case, desalination can be performed without employing a pressure pump.
The flushing device may periodically perform a flushing operation. Thus, impurities remaining on the surface of the reverse osmosis membrane of the fresh water generating cartridge can be periodically discharged from the fresh water generating cartridge.
The flushing device may perform the flushing operation when fresh water generation work with the fresh water generating cartridge is started. Thus, impurities such as fungi generated and deposited in the fresh water generating cartridge during stoppage of fresh water generation work can be discharged from the fresh water generating cartridge.
The flushing device may perform the flushing operation during fresh water generation work with the fresh water generating cartridge. Thus, impurities remaining on the surface of the reverse osmosis membrane of the fresh water generating cartridge during fresh water generation work can be discharged from the fresh water generating cartridge. In this case, flushing may be periodically or non-periodically performed during fresh water generation work.
The flushing device may perform the flushing operation simultaneously with stoppage of fresh water generation work with the fresh water generating cartridge. Thus, impurities remaining on the surface of the reverse osmosis membrane of the fresh water generating cartridge during fresh water generation work can be discharged from the fresh water generating cartridge.
The flushing device may perform the flushing operation during stoppage of fresh water generation work with the fresh water generating cartridge. Thus, impurities such as fungi generated and deposi
Kawada Ichirou
Kawashima Toshiyuki
Akin Gump Strauss Hauer & Feld L.L.P.
Drodge Joseph W.
Nitto Denko Corporation
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