JPS6082186A - Desalting method of high silica-containing water - Google Patents

Abstract

PURPOSE:To obtain permeated water at a high yield by treating raw water contg. >=40mg/l silica with a reverse osmosis membrane device having a specific silica removing rate and a rate of removing bivalent ion of a strong electrolyte then subjecting the water to an ion exchange resin treatment. CONSTITUTION:Raw water 6 contg. >=40mg/l silica is supplied under pressure to a reverse osmosis membrane device 1 mounted with a reverse osmosis membrane having performance of <=50% removing rate of silica and at least >=80% removing rate of bivalent ion of a strong electrolyte by a high pressure pump 7. Non- permeated water 8 in which salts and colloidal material ars thickened and permeated water 9 from which the colloidal material is removed and in which the salts are decreased are obtd. The water 9 is then admitted into a K column 2 where the residual cation is subjected to an ion exchange and acidic soft water 10 is obtd. The soft water is treated in a deoxidizing column 3. The treated water is admitted into an A column 4 where the residual anion is subjected to an ion exchange and pure water 12 is obtd.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for desalinating water containing high 7 lye containing silica at an ao of 111 g/1 or more using a reverse osmosis membrane device and an ion exchange device. The purpose is to obtain permeated water in a high yield without precipitating silica in the non-permeated water of the osmotic membrane device.

1. In the electronics industry that manufactures S[ and Super 1,81, etc., colloidal substances and ion h are used to clean the products.
It requires so-called ultra-pure water that has reduced the amount of l, down to ppb order. When producing such ultrapure water, reverse osmosis membrane devices are often used in recent years. In other words, raw water that has undergone appropriate pretreatment such as turbidity removal treatment such as coagulation sedimentation filtration and activated carbon filtration is de-jetized using a reverse osmosis membrane device.
9. Next, salts, impurities, etc. remaining in the demineralized water are generally treated with a pure water production device, a precision filtration device e'l', a polisher, etc.

The reverse osmosis membrane device supplies raw water to the reverse osmosis membrane under pressure higher than the osmotic pressure of dissolved salts, and the reverse osmosis membrane blocks most of the salts to obtain permeated water with reduced salts as treated water.・Salts During this treatment, the colloidal substances contained in the raw water can also be blocked by the reverse osmosis membrane, which is convenient for the production of ultrapure water. . Since reverse osmosis membrane equipment processes raw water through the operations described above, the higher the concentration ratio of the raw water, the more permeated water can be obtained from a constant supply of raw water. be advantageous to

However, if the nuclear concentration magnification is increased too much, silica with relatively low solubility will precipitate on the membrane surface of the concentration system, especially the reverse osmosis membrane, lowering its performance. For example, if the raw water has a total 7 Lika content of about 20+ ng/I or less, it will not be much of a problem.

If the content exceeds 4 (l mg/l), the solubility of silica becomes an obstacle and the recovery rate of permeated water has to be lowered, resulting in extremely uneconomical results.To explain this point in more detail: In desalination using a combination of a reverse osmosis membrane device and an ion exchange device in I'm here.

Conventionally, this reverse osmosis membrane device has a warping force rejection rate of 80.
The removal rate of monovalent ions of strong electrolytes such as chlorine ions, sodium ions, and ions is 90% or more, and the rejection rate of divalent ions of strong electrolytes such as sulfate ions and calcium ions is 95% or more. A reverse osmosis membrane with high performance was used.

On the other hand, the solubility of solica is 120+y/at room temperature and neutral temperature.
For example, the silica concentration is 4 o ny7r
When raw water is treated with the above-mentioned conventional reverse osmosis membrane with a permeate recovery rate of 75%, the average silica concentration on the non-permeate side is 40XO, 128mg according to the formula 8X100/25.
/j, and silica will precipitate in the non-permeable water.

Therefore, when the silica concentration of raw water is 40 mg/or more, the permeate recovery rate has to be set to 75 mg or less, which is extremely uneconomical.

The solubility value of 12o + ng/+ is a theoretical value. Considering the influence of local concentration on the membrane surface of the reverse osmosis membrane, the average silica concentration in non-permeated water is loo.
It is necessary to operate in such a way that the silica concentration in the raw water does not exceed 4 mg/l.
In the case of 0 mg/l, the permeated water recovery rate had to be kept within 68%, and if the raw water silica concentration was 40 mg/1 or more, the recovery rate had to be further reduced.

The above-mentioned point is the biggest drawback in desalination using the conventional reverse osmosis membrane device and ion exchange device combination K.
Since the ion exchange device is installed after the reverse osmosis membrane device, the reverse osmosis membrane device 6 in the front stage allows more 7 liqium of raw water to permeate than before, and the silica that has permeated is removed with the ion exchange device in the latter stage. By doing so, it is possible to reduce the concentration of 7-liquid water in the non-permeable water system, and it is possible to prevent silica from precipitating in the non-permeable water system even if the permeate recovery rate is increased.

In this way, the load on the subsequent ion exchange device is reduced to 1-
Is it larger? Considering the whole thing, it is more economical.

The present invention is based on the above-mentioned knowledge. By using a reverse osmosis membrane device equipped with a reverse osmosis membrane that has a lower rejection rate of glue force than conventional ones, it is possible to eliminate silica from being deposited on the non-permeated water side. The purpose is to obtain permeated water at a high yield. Raw water containing 40 μ/1 or more of silica. The rejection rate of 7 silica is less than 50%. At least the rejection rate of divalent ions of the strong electrolyte is so. Desalination of water containing high 7 Lika, which is characterized in that it is treated with a reverse osmosis membrane device equipped with a reverse osmosis membrane with a performance of % or more, and then treated with an ion exchange device that uses a cation exchange resin and an anion exchange resin. [1], relates to VC.

The present invention will be explained in detail below.

In the present invention, a reverse osmosis membrane with a silica rejection rate of 50 cm or less is used as the reverse osmosis membrane installed in the reverse osmosis membrane device.As mentioned above, the reason for this is that as much as possible of the silica in the raw water is permeated to the permeated water side and This is to reduce the silica concentration on the permeate side. For example, in a reverse osmosis membrane with a 1f rejection rate of 70% or more, the silica concentration on the non-permeated water side becomes too high, making it difficult to achieve the object of the present invention.

However, if a reverse osmosis membrane with a silica rejection rate that is too low is used, the f'i load of the subsequent ion exchange device will become large.Therefore, it is desirable to use a reverse osmosis membrane with a rejection rate of at least 20 factors or higher.

On the other hand, it is desirable to remove salts other than Norica as much as possible using a reverse osmosis membrane device.It is preferable that the reverse osmosis membrane used in the present invention has at least a strong electrolyte with a rejection rate of 80 or higher. By using a reverse osmosis membrane that has a strong electrolyte divalent ion rejection rate of 80% or more, calcium ions/l magnesium ions are difficult to desorb during regeneration in the subsequent ion exchange.・The concentration of sulfate ions in permeated water can be reduced. ・The load on the subsequent ion exchange device can be reduced.

It is advantageous to use a reverse osmosis membrane that can remove monovalent ions of strong electrolytes such as sodium ions and chloride ions as much as possible. It is desirable to use those with 4.

In addition, in the present invention, a reverse osmosis membrane and a cap having a silica rejection rate of 50% and a 4j1 division rate of at least 80% of divalent ion of the strong electrolyte, for example, raw water with a silica concentration of 40IIIg/L. The permeation pressure is 20 kg
/(1?l'・When permeation treatment is carried out at a temperature of 25℃・Refers to a reverse osmosis membrane in which the silica concentration of permeated water is 2 omg/ or more・For example, when raw water with a sulfuric acid ion concentration of 50111 g/l is permeated at a permeation pressure of 20 kg/c+M , when -C permeation treatment is carried out at a temperature of 25”・The sulfate ion concentration of the permeated water is 10mg/
Refers to a reverse osmosis membrane with a silica rejection rate of 50% or less used in the present invention, such as 0 or more, and a reverse osmosis membrane with the performance of at least 80% or more of strong electrolyte divalent ion rejection rate. The membrane is Nitto Denko's NT Roof 250/N.
i, '1L-1550r N'l'1L-1530+
N'll'R-1510 (all product names), Sumitomo Chemical Sollosox 5o-5000 (product name), Desalination Co., Ltd. 0-5, G-10 (product name), Filmtic Co., Ltd. 1i 'T-4o (product name) etc.

Next, in the present invention, an ion exchange device is installed after the reverse osmosis membrane device, but the ion exchange device may be a strong acid cation exchange resin alone or a combination of a weak acid cation exchange resin and a strong acid thio/exchange resin. A two-bed type or two-bed type using a column I packed with a layered bed and a column A packed with a strong basic anion exchange resin alone or a multilayer bed of a weak basic anion exchange resin and a strong basic anion exchange resin. Use conventional pure water production equipment such as column type pure water production equipment or mixed bed type water production equipment that uses a strong acidic thio/exchange resin and a strong anion exchange resin in the same column. Good.

Next, an actual M11 aspect of the present invention will be explained based on the drawings.

Drawing 1 shows a flow diagram that is an example of an embodiment of the present invention, and is located in Shikoku. 1 is a reverse osmosis membrane device, 2 is a strong acid 11: a tower filled with cation exchange resin, 3 is a decarboxylation tower, and 4 is a strong acid Tower A/5, in which the basic anion exchange resin is passed through f1, is a monobet polisher filled with a strong acidic cation exchange resin and a strong basic anion exchange resin.

In the present invention, raw water 6 containing a warping force of 40 mg/1 or more, which has been treated with an appropriate pre-treatment device (not shown) such as coagulation sedimentation or filtration, is treated with a silica removal rate of 50% or less than a high-pressure Bonschiff vζ. The non-permeated water 8 in which salts and colloidal substances are concentrated is supplied under pressure to a reverse osmosis membrane device 1 equipped with a reverse osmosis membrane having a performance with a rejection rate of at least 80 factors for divalent ions of a strong electrolyte. - The permeated water 9 from which colloidal substances have been removed and salts have been reduced is a4. Next, the permeated water 9 flows into the column 2, and the remaining cations are ion-exchanged, and acidic soft water 10 is obtained.The acidic soft water] 0
is treated in a decarboxylation tower 3 to perform decarboxylation. Next, the acidic soft water 10 flows into the A column 4 using the decarboxylation pump 11, and the remaining anions are ion-exchanged to obtain pure water 12. The pure water is further treated with Monobetbolin-1'-5, and the remaining anions are ion-exchanged. Pure water of high purity is obtained, and if necessary, ultrapure water is produced by performing precision semi-filtration or ultraviolet sterilization (not shown).

As explained above, the present invention uses silica when treating water containing high adhesive strength of +o+ng/(or more) with a reverse osmosis membrane device and an ion exchange device.As a reverse osmosis membrane used in a reverse osmosis membrane device. Since we use a product with an exclusion rate of less than 50 coefficients and at least an exclusion rate of 80% or more for divalent ions of strong electrolytes, more than 50% of the 7 force in the raw water can be transmitted to the permeated Narcissus.・Therefore, the concentration of force on the non-permeated water side can be significantly lowered than that of the conventional method, and as a result, the permeated water recovery rate can be reduced compared to the conventional method. There's nothing to do.

In addition, in the present invention, since the entire amount of raw water is treated by the reverse osmosis membrane device 4, the colloidal substances present in the raw water can be completely removed by the reverse osmosis membrane device. It is advantageous as a desalination equipment for the electronic T industry that manufactures. Furthermore, even though a reverse osmosis membrane with a low Lika removal rate is used, 1) The if-stage reverse osmosis membrane device can reduce salts in raw water, reducing the load on the subsequent ion exchange device. be able to.

The present invention will be explained in detail below.

Example-1 Well water with total dissolved solids 853 ■/l / 54 ■/+ (15S + Oz) was filtered and the filtered water was adjusted to pH 6-
OVζ adjustment 1, silica rejection rate 25, strong electrolyte 2
A reverse osmosis membrane device equipped with Desalination's G-5, a reverse osmosis membrane with a valent ion rejection rate of 92 cm, an operating pressure of 20 kg/jJ, a permeated water recovery rate of 74 cm, and a water temperature of 25 degrees. 1, which was permeabilized with C, and then the permeated water was treated with the strongly acidic goo-on exchange resin Amberlite (registered trademark) in the H form. IRA
When the water was passed through a two-bed S-tower type pure water production apparatus using A-410, permeated water and ion-exchanged water of the water quality shown in Table 1 were obtained.

On the other hand, for comparison, similar filtered water was operated in a reverse osmosis membrane device equipped with a conventionally used reverse osmosis membrane with a silica rejection rate of 75% and a strong electrolyte divalent ion rejection rate of 95%. Pressure: 30 kg/cJ, permeated water recovery rate: 74% p When permeation treatment was performed at a water temperature of 20"C, silica precipitated on the non-permeated water side, the pressure loss increased, the amount of permeated water decreased, and the desalination rate decreased. did.

Table 1 Example-2 Total dissolved solids 188mg/I, silica 6omg/I
(asSi02) industrial water is filtered and the filtered water is p
Adjusted to l+6.5・Silica removal rate 30%・High electric power W (
The reverse osmosis membrane device is equipped with Nitto Denko's NTR-7250, a reverse osmosis membrane with a high quality divalent ion removal rate of 95%.Operating pressure: 20 kg/anchor.Permeated water recovery rate: 664.
・Permeation treatment was carried out at a water temperature of 25°C. Next, the permeated water was treated with H-type strongly acidic cation exchange resin Amberlite (registered trademark).
Strongly basic anion exchange resin Amberlite (registered trademark) A-410 in IR-1zoB O, 1, and O1l types
When water was passed through a two-bed, three-column pure water production equipment using
Permeated water and ion-exchanged water with the quality shown in the table were obtained.

On the other hand, for comparison, similar filtered water was used in a reverse osmosis membrane device equipped with a reverse osmosis membrane that has a silica rejection rate of 75% and a strong electrolyte divalent ion rejection rate of 95%. Operating pressure 30kg/all, permeate recovery rate 66%
・When permeation treatment was carried out at a water temperature of 20°C, ・Glue force was deposited on the non-permeated water side. ・Pressure loss increased and permeate water drainage decreased. Along with 3. ・Demineralization rate decreased. 5 Table 2.

[Brief explanation of drawings]

The drawing is an explanatory diagram of a flow that is an example of an embodiment of the present invention. . 110. Reverse osmosis membrane device 2. ,,to tower 118. Decarboxylation tower 4...A tower 000. Monobenotoporinya - 600, raw water 000.
Non-permeable water 9... Permeated water

Claims (1)

[Claims] / Raw water containing 40 mg/1 or more of Silica is
Treated with a reverse osmosis membrane device equipped with a reverse osmosis membrane that has a rejection rate of at least 80% or more for strong electrolytes such as divalent oxides.Then, cation exchange resin and anion Treated with an ion exchange device using exchange resin