JPS59147691A - Seawater desalination apparatus - Google Patents

Abstract

PURPOSE:To improve the quality and stability of the produced water in the salt-to-fresh water distallation by using a two stage reverse osmosis membrane apparatus consisting of a preceding and a succeeding stage, by dividing the succeeding stage reverse osmosis membrane apparatus into two parts, and adjusting the electric conductivity of the transmitted water in one of the two parts. CONSTITUTION:The seawater F1 is sent into a preceding stage reverse osmosis membrane apparatus 2 through a pretreatment apparatus 1, and the transmitted water T1 is stored in a pit 3. The concentrated water is sent to a turbine-driven pump 4. The water F21 fed from the pit 3 is sent to the first succeeding stage reverse osmosis membrane apparatus 6 by the pump 4, and the transmitted water T21 is sent to a succeeding stage pit 8. The water F22 fed from the pit 3 is sent to the second succeeding stage reverse osmosis membrane apparatus 7 by a motor-driven pump 5, and the transmitted water T22 is sent to the pit 8. The electric conductivity of the produced water in the pit 8 is detected by an electric conductivity control meter 9, and the motor-driven pump 5 is started when the detected value becomes higher than the set value. The motor 5 is stopped when the detected value becomes lower than the set value, and a part of the transmitted water T1 in the pit 3 is sent to the pit 8 through a pipe 10 by overflowing to keep the electric conductivity of the produced water constant.

Description

[Detailed description of the invention] The present invention relates to a seawater desalination device.

This type of equipment is broadly divided into reverse osmosis membrane type and evaporation type.The former has an energy advantage over the latter, so it is possible to use cellulose acetate membranes, aromatic polyamide membranes, etc. With the development of high-strength reverse osmosis membranes, they now occupy the majority of actual equipment.

In a known reverse osmosis membrane type seawater desalination device, for example, as shown in the system diagram in Figure 1, the total dissolved solid content (hereinafter T
985-9
95% TDS? Removed as permeate TDSL, 75
~525 ppm of freshwater T can be obtained, with
Since the residual pressure of the concentrated water R is 52 to 57 Kz/ffl, in order to recover the high pressure energy of this concentrated water R, the motor M is
The power of the motor M of the seawater supply pump P is reduced by guiding the seawater to a recovery turbine 13 coaxially connected to the seawater supply pump P.

However, in irrigation desalination equipment such as
For example, for a product with a production capacity of 300 T/D, the required power of motor M is as follows: 80 V to 140 kW
Since the culm size is only reduced, the energy saving is not so great considering the increase in equipment cost and space due to the installation of the recovery turbine B.

In addition, in such seawater desalination equipment, the outlet TDS of permeate fluctuates widely due to load fluctuations and disturbances caused by pre-treatments such as H adjustment, sterilization, and turbidity removal. If the purpose of salt water is general drinking water, its TDS should be about 500 pprn or less, but in the case of process water for food, medicine, etc., for example, 501)
1) A high persuasion rate of less than m is required9.

The present invention has been proposed in view of the above circumstances, and an object of the present invention is to provide a seawater desalination apparatus that saves energy, improves the quality of produced water, and improves the stability of the finished product.

To this end, the present invention desalinates seawater using a two-stage reverse osmosis membrane device consisting of a first stage and a second stage, which are separated into the second stage reverse osmosis membrane system set 1 and the second reverse osmosis membrane system and installed in parallel. and a permeated water pit for storing permeated water of both said rear stage reverse osmosis membrane devices, a conductivity control meter provided in said permeated water bit, and a permeated water pit installed in the upstream pipe line of said first rear stage reverse osmosis membrane device. A turbine and a drive pump driven by the concentrated water of the first-stage reverse osmosis membrane device are installed in the upstream pipe line of the second second-stage reverse osmosis membrane device, and the start and stop are controlled by the conductivity controller. The invention is characterized by comprising a motor-driven pump.

An embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a system diagram thereof.

In Fig. 2, 1 is a pre-treatment device that introduces the raw material seawater F1, 2 is a pre-stage reverse osmosis membrane device that introduces the sea whose pressure is increased through a pump (not shown) from the pre-treatment device 1, and 3 is a pre-stage reverse osmosis membrane device. The front-stage permeated water pit, 1, which stores the permeated water T1 of the membrane device 2, is driven by the concentrated water R1 of the front-stage reverse osmosis membrane device 2, pressurizes a part of the front-stage permeated water T1 as the rear-stage feed water F21, and supplies it to the second stage. A turbine and a drive pump 5 supply the second stage reverse osmosis membrane device 6 to the second stage reverse osmosis membrane device 7. Pump, 8 is the first rear stage reverse osmosis membrane device 6
and a second rear stage reverse osmosis membrane device 6 that stores permeated water T21 and T22 of the second rear stage reverse osmosis membrane device 7. They are connected in parallel with the rear stage reverse osmosis membrane device 7, and form the rear stage desalination threads.

9 detects the electrical conductivity of the permeated water in the rear stage permeated water pit 8, and thereby controls the motor of the motor-driven pump 5 on and off. is stopped, an overflow one-way bypass pipe line that introduces the permeated water in the first stage permeated water pit 3 to the second stage permeated water pit 8, 11 is the concentrated water R21 and B of the second stage reverse osmosis membrane devices 6 and 7. 2? This is a feedback conduit that feeds back a part of > to the preprocessing device 1.

In such a device, the seawater that has been treated by the pretreatment device 1 is pressurized to about 1000 y / 7 by a pump (not shown) and is supplied to the upstream reverse osmosis membrane device 2, where it is converted into translucent water T] and concentrated. The permeated water T1 is divided into water R1 and the like, and the permeated water T1 is temporarily stored in the pre-stage permeated water bit 3.

On the other hand, concentrated water R1 is about 55Kg/cr? Since the water is introduced into the turbine of the turbine-driven pump 4 with a pressure of about 30 K7/ff1 (the working pressure of the rear-stage reverse osmosis membrane device) The pressure is raised to about -^- of that of the first stage reverse osmosis membrane device) and supplied to the first second stage reverse osmosis membrane device 6, where the second stage permeated water T21 and the second stage concentrated water R21
On the other hand, the feed water F22 from the first-stage permeated water pit 3 is also pressurized to about 30 K9/crl by the motor-driven pump 5 and is supplied to the second second-stage reverse osmosis membrane device 7. The water is separated into second-stage permeated water T22 and second-stage concentrated water R22.

The second-stage permeated water T21 and T22 are stored in the second-stage permeated water pit 8 and used as produced water.

At this point, the electrical conductivity control unit 9 detects the electrical conductivity of the produced water in the downstream permeated water pipe 1-8, and when it exceeds the set value, starts the operation of the motor-driven pump 5 and adjusts the set value. When the following conditions occur, the operation of the motor-driven pump is stopped. By directly introducing/mixing into the downstream permeated water pit S, the electrical conductivity of the produced water in the downstream permeated water pit is kept constant.

This is because the predetermined water quality cannot be obtained using only the first stage reverse osmosis membrane device 2, and when the entire amount is desalted in two stages using the first and second stage reverse osmosis membrane devices 6 and 7, the water quality often exceeds the predetermined level. Therefore, by detecting the electrical conductivity proportional to TDS and desalinating a part of the first-stage permeated water T1 in two stages using the second second-stage reverse osmosis membrane device as needed, the specified amount of water can be desalted with the minimum amount of power. This is to enshrine the quality of the water.

With this, the required power can be balanced when the flow ratio between the turbine-driven pump 11 and the motor-driven pump 5 is between 7:3 and 5:5.

The second-stage concentrated water R21 and R22 are either combined and discharged to the outside, or some of them are connected to the feedback pipe 11.
It is then fed back to the preprocessing device 1.

This is because raw seawater usually has a p I-I of around 8, so the p
It is desirable to operate this device with adjustment to H'(i=6), and for that purpose, all sulfuric acid # is used to adjust pHJ111, but concentrated water R21 and R22 have low TDS,
This is because the consumption of sulfuric acid and the like can be reduced by utilizing the fact that the pH is around 55 and feeding it back to the pretreatment device 1 (1) to mix it into the raw material seawater.

In short, according to the present invention, in the desalination of seawater using a two-stage reverse osmosis membrane device consisting of a front stage and a rear stage,
a permeated water pit which divides the latter stage reverse osmosis membrane device into a first and second reverse osmosis membrane device and installs them in parallel and stores permeated water from both of the rear stage reverse osmosis membrane devices; and the permeated water pit. a turbine-driven pump installed in the upstream pipe line of the first reverse osmosis membrane device and driven by the concentrated water of the first reverse osmosis membrane device; A high-performance and economical The present invention is industrially extremely useful since it is used in seawater desalination equipment.

[Brief explanation of the drawing]

FIG. 1 is a system diagram showing a known seawater desalination device, and FIG. 2 is a system diagram showing an embodiment of the present invention. ... Front stage permeated water bit, 4... Turbine driven pump, 5... Motor 1 driven pump, 6... First rear stage reverse osmosis membrane device, 7
...Second rear stage reverse osmosis membrane device, 8..Rear stage permeated water pit, 9..Conductivity control meter, 10..Bypass pipe line, 11..
・Feed pack pipe, Fl...Another Mj5 water, F2...Previous stage permeated water, Fzl,
,]v22...Late stage supply water, T1...First stage permeated water, T2
1. T22...Late stage permeated water, R1...First stage concentrated water, R2
1, R22...Late Stage Concentrated Water, Agent Patent Attorney Masaru Tsukamoto Written Procedural Amendment 1955 7 Tsubo F Month xρ Commissioner of the Japan Patent Office 1, Indication of Case 1988 Patent Application No. 2 ] 079 No. 2 Invention 0 Name Seawater Desalination Plant 3, Person making the amendment Relationship to the incident Location: 2-Marunouchi, Kanashiro Maru-ku, Tokyo Tel: 6-2-4 Amending by proxy. -462-

Claims (1)

[Claims] In a device that desalinates seawater using a two-stage reverse osmosis membrane device consisting of a first stage and a second stage, the second stage reverse osmosis membrane device is divided into a first and second reverse osmosis membrane device and installed in parallel, a permeated water pit for storing permeated water of the reverse osmosis membrane device; a conductivity control meter provided in the permeated water pit; A turbine 1-driven pump driven by concentrated water of the membrane device, and a motor-driven pump incorporated in the upstream pipe line of the second downstream reverse osmosis membrane device and whose start and stop are controlled by the conductivity controller. A seawater desalination device characterized by: