JPS58186490A - Method for removing dissolved oxygen from sea water or brine in desalting process by reverse osmosis method - Google Patents

Abstract

PURPOSE:To remove dissolved oxygen efficiently and to improve durability of a film module, by introducing sea water or brine into a deaeration column having a negative pressure space, and generating cavitation in the sea water or brine. CONSTITUTION:Sea water or brine 1 is pumped 2 through a feed pipe 3 and fine holes 5 into a deaeration column 4 maintained under negative pressure by the residual pressure of condensed water. Cavitation is generated in the sea water when the water passes through the hole 5 by which a large amt. of fine bubbles is generated in the treated water 1 and dissolved oxygen is removed. The treated water 1' deaerated in the column 4 is pressurized through a connecting pipe 6 by a high pressure pump 7 and is supplied into a reverse osmosis treatment tank 8, where the water is separated to the concd. water of the high residual pressure and the permeated water of the atmospheric pressure by the film module provided in the tank 8. The concd. water is injected to an ejector 10 connected to the column 4 and is then discharged through a discharge pipe 11.

Description

Detailed Description of the Invention The present invention efficiently separates and removes dissolved oxygen in seawater or brine by utilizing the high residual pressure of concentrated water generated when seawater or brine is desalinated by reverse osmosis. Regarding the method.

The reverse osmosis desalination process, which is attracting attention as an economical and efficient water supply process compared to existing methods, applies pressure greater than osmotic pressure to the salt water side, and converts the fresh water in the salt water into fresh water through a membrane module. It is designed to separate fresh water from salt water by permeation. Various types of membrane modules, which are the central part of this reverse osmosis process, have been put into practical use, such as spiral type and hollow fiber deaf. Measures against dissolved oxygen are required. In other words, if the membrane module is exposed to salt water containing dissolved oxygen for a long period of time, the dissolved oxygen will reduce the desalination performance of the exchange module. It is necessary to extend the

Conventionally, prior to desalination treatment of saltwater such as seawater or brine,
In order to remove dissolved oxygen in salt water, it is common to add a reducing agent such as sodium bisulfite or hydrazi 7 to perform chemical treatment. Usually around 8 ppm of dissolved oxygen is dissolved in seawater or brine, but to reduce and remove this oxygen it is necessary to add about 60 ppm of sodium bisulfite, and the reaction between oxygen and sodium bisulfite is It takes about 30 minutes. □ When this reduction treatment step is added to the reverse osmosis desalination process,
In addition to the problem of how to obtain chemicals and the price, the reduction reaction time is relatively long, so a large reaction tank is required in a large-capacity water supply plant, which significantly increases the cost of the entire process. There is.

In addition, in various equipment industries or photographic industries, etc., in advance,
A method of removing dissolved oxygen from the paper by vacuum degassing or heating has been adopted (for example, % Japanese Patent Application Laid-Open No. 55-15661, Japanese Patent Application Laid-open No. 55-94605).

However, these methods have the disadvantage that a vacuum pump and a heater must be installed separately, which increases equipment costs.

The present invention focuses on the energy of concentrated water that has a high residual pressure in the reverse osmosis desalination process, and operates an ejector that uses concentrated water as a fluid body to introduce seawater or brine into a degassing tower. A negative pressure space is formed to remove dissolved oxygen from seawater or brine.

That is, the present invention provides seawater or brine in advance in a reverse osmosis desalination process in which seawater or brine is pressurized to a predetermined pressure and supplied to a reverse osmosis treatment tank and separated into permeated water and concentrated water having a high residual pressure. At the same time, the separated nine-chain condensed water is communicated to the deaeration tower and injected from the nine ejector to create a negative pressure space in the deaeration tower, and this is converted into seawater or cancer water. This is a method for removing dissolved oxygen in which cavitation is generated and dissolved oxygen is separated and removed.

Further, the present invention is a method for removing dissolved oxygen, in which a reducing agent such as bisulfite, hydrazine, etc. is further added to seawater or brine from which dissolved oxygen has been removed as described above.

The drawings show an example of the method of desalinating seawater or brine while removing dissolved chlorine according to the present invention.

1 Fi, seawater or brine is introduced by the pump 2 through the water supply pipe 5 into the degassing tower 4 through the pores 5 . During degassing, the residual pressure of the concentrated water (described later) is maintained at a negative pressure inside the degassing tower, and a cavity is generated when it passes through the pores 5, causing it to leak into seawater or water. Many fine bubbles are generated,
Dissolved oxygen is removed. The seawater or gun water 1' degassed in the degassing tower 4 passes through the connecting pipe 6 and reaches the high-pressure pump 7, where it is pressurized to a predetermined pressure by the skeleton/gua and supplied to the reverse osmosis treatment tank 8. be done. A membrane module made of spiral type, hollow fiber, etc. is installed inside the scissors processing cypress 8 to separate the supplied seawater or gun water into permeated water at normal pressure and concentrated water with high residual pressure. The permeated water is taken out to the outside through the intake pipe 9, and the concentrated water is injected into the ejector 10 connected to the degassing tower 4, and then discharged through the discharge pipe 11. By operating the ejector using concentrated water as the driving fluid, the inside of the degassing tower 4 is brought to a negative pressure, cavitation is generated in the seawater or brine, and dissolved oxygen is removed.

As described above, according to the present invention, dissolved oxygen in seawater or brine can be easily removed without installing special equipment separately in the conventional reverse osmosis desalination process, and the durability of the membrane module can be improved. can improve sex.

In addition, if the above process alone is insufficient to remove dissolved oxygen, for example, if the salt concentration is low and the pressurization of seawater or brine supplied to the reverse osmosis treatment tank is weak, the residual pressure of the concentrated water may be low and the removal of dissolved oxygen may be insufficient. In order to prevent insufficient air pollution from the cavities generated in the gas column, a predetermined amount of bisulfite is added to the reverse osmosis before supplying it to the salt cylinder. It can be further separated and removed. In this case, since most of the dissolved oxygen has been removed in advance, the amount of reducing agent to be added can be small, the processing time can be shortened, and the capacity of the reaction tank can also be small.

Example 1 Dissolved oxygen a 1 ppm, total salinity (TDS) 3
40CIOppm.

18 m"/D t" II of seawater at a temperature of 25°C was collected and filtered to remove suspended solids, and then degassed in a degassing tower with a diameter of 150 cm and a height of 2.6 m that maintained a degree of vacuum of 707 orrK. Dissolved oxygen decreased to α5 ppm. When this degassed water was pressurized to 56 Kg/cd・G using a high-pressure pump and supplied to a reverse osmosis treatment tank equipped with a spiral membrane module, the permeated water and residual pressure of &2 m'/D were obtained. 5
9.8 m"/D of concentrated water of 4 h/d@G was obtained. When this concentrated water was injected from the ejector connected to the deaeration tower, the inside of the deaeration tower was constantly maintained at 70 Torr. Can be a friend.

Example 2 Dissolved oxygen & lppm, total salt concentration (TDS) 5500
Ppm, brine 18 m"/D at a temperature of 25°C was subjected to coagulation filtration to remove suspended solids, and the degree of vacuum was 100'l'o.
When deaeration was performed using a degassing tower with a diameter of 150 m and a height of 2.6 m maintained at rrlc, dissolved oxygen was reduced to 0.7 ppm. Add 25 ppm of sodium bisulfite to this brine and let it react for 50 minutes until the remaining oxygen reaches CL4.
This degassed water, which has been reduced to 7ppm, is pumped to 5ppm using a high-pressure pump.
When 12.5 was pressurized to 47 cd-G and supplied to a reverse osmosis treatment tank equipped with a spiral membrane module, 12.
Permeated water of 6 m"/D and concentrated water of 5.4 m"/D of residual pressure 35 cm/CIi・G were obtained. When this concentrated water was injected into the injection pipe connected to the deaeration tower through an orifice, the inside of the deaeration tower could be maintained at a constant pressure of 100 Torr KM.

[Brief explanation of drawings]

The drawings are explanatory diagrams showing an example of the implementation procedure of the method of the present invention. 1.1'... Seawater (brine) 2... Pump 3... Water supply pipe 4... ...... Deaeration tower 6 ...... Connection pipe 7 ...... High pressure pump 8 ...
・・・・・・Reverse osmosis treatment tank 9・・・・・・・・・・・・
Water intake pipe 10... Ejector 11...
・・・・・・・・・Discharge pipe

Claims (2)

[Claims] (1) In the reverse osmosis desalination process, in which seawater or brine is pressurized to a predetermined pressure and supplied to a reverse osmosis treatment tank and separated into permeated water and concentrated water with high residual pressure, seawater or brine is desalinated in advance. Along with introducing it into the air tower, shrimp! The separated concentrated water is communicated with the degassing tower and injected into the tank to create a negative pressure space in the degassing tower, thereby creating cavities in the seawater or brine and removing dissolved oxygen. A method for removing dissolved oxygen in seawater or brine in a reverse osmosis treatment tank process, which comprises separating and removing dissolved oxygen. (2) In the reverse osmosis desalination process in which seawater or brine is pressurized to a predetermined pressure and supplied to a reverse osmosis treatment tank and separated into permeated water and concentrated water with high residual pressure, Reverse osmosis desorption involves creating a voltage space in the degassing tower, creating cavities in seawater or brine, separating and removing dissolved oxygen, and then adding a reducing agent for reduction treatment. Method for removing dissolved oxygen in seawater or brine in salt processing.