JPS5850763B2 - water generator - Google Patents

Description

[Detailed description of the invention] The present invention relates to a water supply device.

Electrodialysis (also referred to as ion exchange membrane) and reverse osmosis have been used for the purpose of concentrating and desalting salts in solutions, and their usefulness has been established in commercial practice.

It is generally known that power consumption costs and membrane replacement costs account for a large portion of the processing cost in processing solutions using the above method.

Furthermore, there is a complementary relationship between power consumption and the membrane area of the device, and if conditions such as solution quality and device capacity are the same, the membrane area of the device tends to increase if power consumption is saved.

SUMMARY OF THE INVENTION Therefore, the present invention aims to reduce power consumption per unit amount of treated water and provide a water generating apparatus that can realize lower treatment costs.

The principle of reverse osmosis is that the solution to be treated containing salt is
kg/cviG or more, the pressure energy exceeding the osmotic pressure of the solution causes mainly only the solvent in the solution to be oozed out through the reverse osmosis membrane, which is collected and made into a dilute solution, and the solvent is permeated. The remaining solution to be treated is made into a concentrated solution.

Currently, commercial reverse osmosis equipment performs this continuously, typically obtaining 70-80% of the liquid to be treated as a dilute solution.

In particular, in the desalination treatment of seawater with a high salt concentration, only 20 to 40% of the seawater to be treated is obtained as fresh water, and the remainder is discarded as concentrated brine in a state containing high pressure energy.

Especially when desalting solutions with high salt concentration, reverse osmosis method has the drawback that not only the energy utilization rate is low, but also the utilization rate of the treated solution that has undergone expensive pretreatment is low. According to the present invention, it is possible to overcome these drawbacks with respect to salt treatment.

On the other hand, in the electrodialysis method, flat membranes of cation exchange membranes and anion exchange membranes are alternately combined in a filter press,
A dialysis tank is used, in which electrodes are installed at both ends of a large number of pairs of membranes that alternately form concentration and dilution chambers, creating an electric field in the vertical direction across the membranes.

The solution to be treated that is supplied to the concentration chamber takes in cations and anions that are dialyzed by the principle of electrodialysis from the adjacent dilution chamber through a cation exchange membrane and an anion exchange membrane to become a concentrated solution. Further, the solution to be treated that is supplied to the dilution chamber becomes a diluted solution and is discharged from the dialysis tank.

In commercial electrodialysis equipment, the solution to be treated that is supplied to the concentration chamber and the dilution chamber forms independent circulation loops, each loop is equipped with a supply line and a drain line, and either batch or continuous operation is performed. is being driven by.

The circulation of the solution in the circulation loop takes place under atmospheric pressure and at a flow rate several times the flow rate of the processing liquid to be obtained.

In electrodialysis equipment used for the purpose of desalting salts in solutions, the salt content of the dilute solution to be obtained is reduced to 500 pp.
In order to maintain the flow rate at a low level of less than m, the above-mentioned liquid circulation amount is generally performed at a flow rate of 10 times or more of the flow rate of the dilute solution to be obtained.

The present invention provides a more economical solution concentration and desalination processing system by recovering the high-pressure energy of the concentrated brine discharged from the reverse osmosis device to replace the above-mentioned circulation power required in the operation of the electrodialysis device. This is what makes it possible.

The "salt in solution" described in the present invention is not limited to simply inorganic salt, but is applicable to general solutes that can be effectively treated in electrodialysis equipment and reverse osmosis equipment.

Furthermore, as a method for recovering the above-mentioned power, for example, a power recovery turbine having an ejector single rotation mechanism having a nozzle mechanism may be used, but is not limited to these. The present invention is applied to a power recovery device that has a mechanism that can transfer liquid energy into low-pressure liquid energy at a relatively large flow rate, and can be adapted to the purpose of the present invention.

Figure 1 shows a flow sheet of a seawater desalination equipment using a conventional two-stage reverse osmosis method, where 1 is a raw seawater receiving tank, 2A is a first-stage reverse osmosis module, 2B is a second-stage reverse osmosis module, and 3A
is a first-stage high-pressure pump, and 3B is a second-stage high-pressure pump.

In this conventional example, 129.3T of pretreated raw seawater was used.
/HR is supplied to the raw seawater receiving tank 1, and the first stage high pressure pump 3
At A, this is pressurized and supplied to two first-stage reverse osmosis modules.

1 feed also includes the concentrated brine from the second stage reverse osmosis module 2B, so the feed rate is 137.5T/HR1 and the salinity is 33,800 ppm.

The first stage reverse osmosis module has two people with a salt removal rate of 95% and a membrane area of 4080 m, and the pressure of the feed liquid is 57 kg/crtiG, so it is used as concentrated brine.
9.3 T/HR is discarded at 56800 ppm, and 58.2 T/HR is supplied as a permeate at 2270 ppm to the second stage high pressure pump 3B.

This is pressurized to 42 kg/c4G by the second stage high pressure pump 3B and then supplied to the second stage reverse osmosis module 2B.

The second stage reverse osmosis module 2B is a module having a salt removal rate of 95% and a membrane area of 2050 m, and is recovered to the raw seawater receiving tank 1 as concentrated brine at 8.2 T/HR and 14260 ppm.

The permeate in the second stage reverse osmosis module 2B is the fresh water treated with this device, and is 413 ppm fresh water 50T/HR.
was obtained.

FIG. 2 shows a flow sheet of a seawater desalination device, that is, a fresh water production device, using the reverse osmosis method and the desalination system combined with an electrodialysis device according to the present invention, where 10 is a concentrated brine discharge tank (concentrated liquid discharge tank), and 11 is a A high pressure pump, 12 a reverse osmosis module, and 13 a circulation ejector that circulates concentrated brine using the high pressure brine from the reverse osmosis module 12 as a driving force.
114 is an electrodialysis tank, 15 is a freshwater circulation pump, and 16 is a freshwater circulation tank.

In this embodiment of the present invention, 125 T of pretreated seawater was used.
/HR is received, 57kg/cr with high pressure pump 11
AG is pressurized and supplied to the reverse osmosis module 12.

This reverse osmosis module 12 has a salt removal rate of 95% and a membrane area of 4
It is a module with ororrt, and from this 75
High pressure brine of 56800 ppm of T/HR is supplied to the circulation ejector 13, and using this as a driving force, the circulation ejector 13 produces concentrated brine 5805 of 547T/HR.
Since 0 ppm is sucked from the concentrated brine discharge tank 10, 622 T/HR of concentrated brine is supplied to the concentration chamber of the electrodialysis tank 14, forming a circulation loop with the concentrated brine discharge tank 10.

Permeate water from reverse osmosis module 12 is 2300 ppm
and is supplied to the freshwater circulation tank 16 at 50T/Hp.

Since this freshwater circulation tank 16 forms a circulation loop with the dilution chamber of the electrodialysis tank 14, the salt concentration in the freshwater circulation tank 16 is 560 pprn.

The electrodialysis tank 14 has a membrane pair of 1370 m'', is operated at a current density of 42 AMP/m2, and has a flow rate of 622 m2.
T/) (R1 The fresh water circulated by the fresh water circulation pump 15 with a head of 1 kg/c77 fG is desalted in the dilution chamber of the electrodialysis tank 14 and discharged as 413 ppm.

Of this amount, 5°T/HR is taken out from the circulation loop, so this is the processing capacity of this device.

The concentrated brine supplied to the concentration chamber of the electrodialysis tank 14 by the circulation ejector 13 takes in the dialyzed salt from the dilution chamber, becomes 58,050 ppm, and all enters the concentrated brine discharge tank 10, and the upper part overflows and is concentrated. The brine is discharged from the brine discharge tank 10 at a flow rate of 75 T/HR.

In other words, the conventional first stage reverse osmosis module 2 (FIG. 1)
Reverse osmosis module 12 of people and the present invention (2nd ☆ “Figure)”
Although the concentration of the outlet brine is the same in the reverse osmosis module 12, it is further concentrated in the electrodialysis cell 14, resulting in a higher concentration of brine exiting the system, indicating improved utilization of the treated solution. .

The table below shows a comparison between the conventional example and the embodiment of the present invention.

As described above, according to the present invention described in the embodiments, there is no significant difference in equipment cost or membrane replacement cost compared to the conventional two-stage reverse osmosis equipment, while reducing power consumption. Can be implemented.

[Brief explanation of drawings]

FIG. 1 is a flow sheet showing a conventional example, and FIG. 2 is a flow sheet showing an embodiment of the present invention. 10... Concentrated brine discharge tank, 11...
・High pressure pump, 12...Reverse osmosis module, 1
3...Circulation ejector-14...Electrodialysis tank, 15...Fresh water circulation pump, 16...
・Fresh water circulation tank.

Claims (1)

[Claims] 1 a reverse osmosis module that concentrates solutes in a solution;
an electrodialysis tank for further concentrating the concentrated solution from the reverse osmosis module; a concentrated solution discharge tank for storing the concentrated solution from the electrodialysis tank and discharging a part of it; and the reverse osmosis module and the electrodialysis tank. a circulation ejector that is provided in the middle of the concentrated solution transfer path between the two and is configured to suck and circulate the concentrated solution in the concentrated solution discharge tank to the electrodialysis tank;
A water production device characterized in that the pressure energy of the concentrated solution from the reverse osmosis module is used as the driving force for the circulation ejector.