Liquid purification or separation – Processes – Liquid/liquid solvent or colloidal extraction or diffusing...
Reexamination Certificate
1999-10-20
2003-01-21
Fortuna, Ana (Department: 1723)
Liquid purification or separation
Processes
Liquid/liquid solvent or colloidal extraction or diffusing...
C210S636000, C210S134000, C210S257200
Reexamination Certificate
active
06508937
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 fresh water generation work with the fresh water generator is stopped over a long period, bacteria propagate in the fresh water generating cartridge and are mixed into permeated water when fresh water generation work is restarted, to deteriorate the quality of the permeated water.
SUMMARY OF THE INVENTION
An object of the present invention is to provide a fresh water generator which can be reliably operated at a low cost while preventing a permeated liquid from deterioration of quality resulting from propagation of bacteria with no problem of noise.
Another object of the present invention is to provide a fresh water generating method which can be reliably carried out at a low cost while preventing a permeated liquid from deterioration of quality resulting from propagation of bacteria 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 performance of 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 also found out that propagation of bacteria in the fresh water generating cartridge can be suppressed by feeding the target liquid to the fresh water generating cartridge through a pretreater for removing residual chlorine while properly feeding the target liquid to the fresh water generating cartridge while bypassing the pretreater. 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 fresh water generating cartridge, including a reverse osmosis membrane, for desalinating a target liquid, a pretreater provided in the preceding stage to the fresh water generating cartridge for removing residual chlorine contained in the target liquid, a feed system feeding the target liquid having a prescribed pressure to the pretreater without through a step-up device stepping up the pressure of the target liquid, a bypass path provided to bypass the pretreater and an opening/closing device opening and closing the bypass path.
In this fresh water generator, the target liquid having a prescribed pressure is fed to the pretreater so that residual chlorine contained therein is removed. The target liquid obtained from the pretreater is fed to the fresh water generating cartridge having the reverse osmosis membrane, and desalinated. If the target liquid from which the residual chlorine having a bactericidal function is removed remains in the fresh water generating cartridge, bacteria readily propagate therein. Therefore, the opening/closing device opens the bypass path, so that the target liquid containing residual chlorine can be fed to the fresh water generating cartridge. Thus, propagation of bacteria can be suppressed in the fresh water generating cartridge. Consequently, the permeated liquid is prevented from deterioration of quality resulting from propagation of bacteria.
In the fresh water generator, the target liquid having a prescribed pressure is fed to the fresh water generating cartridge through the pretreater 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.
If the time interval for feeding the target liquid containing residual chlorine to the fresh water generating cartridge through the bypass path is longer than 12 hours, the bactericidal effect of residual chlorine contained in the target liquid fed to the fresh water generating cartridge through the bypass path is lost and propagation of bacteria is disadvantageously prompted. If the time interval for feeding the target liquid containing residual chlorine to the fresh water generating cartridge through the bypass path is shorter than 10 minutes, on the other hand, the flow rate of a wastefully discharged target liquid is uneconomically increased. Therefore, the time interval for feeding the target liquid containing residual chlorine to the fresh water generating cartridge through the bypass path is preferably at least 10 minutes and not more than 12 hours.
If the time for feeding the target liquid containing residual chlorine to the fresh water generating cartridge through the bypass path is shorter than 5 seconds, propagation of bacteria in the fresh water generating cartridge cannot be sufficiently suppressed. If the time for feed
Kawada Ichirou
Kawashima Toshiyuki
Akin Gump Strauss Hauer & Feld L.L.P.
Fortuna Ana
Nitto Denko Corporation
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