KR101474361B1 - Method and apparatus for recovery of potassium iodide - Google Patents

Abstract

According to a first aspect of the present invention, there is provided a method of recovering a potassium iodide solution, comprising: cooling a potassium iodide solution to a temperature higher than a cooling point temperature to a room temperature; Filtering the foreign matter of the potassium iodide solution using a separation membrane module; And concentrating the filtered potassium iodide solution filtered through the membrane module using a reverse osmosis membrane; And a method for recovering iodide solution.
The present invention can remove foreign matter contained in the potassium iodide solution by using the pressure-reducing type separation membrane, and the potassium iodide solution from which the foreign substance is removed can be recycled by the reverse osmosis membrane.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for recovering a potassium iodide solution,

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and apparatus for recovering potassium iodide solution, and more particularly, to a method and apparatus for recovering a potassium iodide solution that enables a potassium iodide solution used in manufacturing a polarizing film to be recycled.

Liquid Crystal Display (LCD), which has become a necessity for modern people's life due to rapid development of the flat panel display industry in recent years, has been widely used in the fields of TV monitor, computer monitor, navigation, portable telephone, digital camera, game machine, Automobiles, and aircraft, and the recent development of LED LCD has accelerated the development of this field.

Polarizing films are often used to display optical properties on LCDs. Polarizing films are PVA (Poly Vinyl Alcohol) films on which iodine or dichromic dye is adsorbed, and three-layer structures with TAC (Tri Acetyl Cellulose) It is generally used.

(I2) is adsorbed on the PVA film while the PVA film is passed through a solution adjusted with potassium iodide (KI) and iodine (I2) components in the salt-forming process of the polarizing film manufacturing process, and the boric acid component And then crosslinked.

There is a problem that the potassium iodide (KI) solution is continuously discarded and the whole amount is discarded due to the contamination of the PVA component and the fine particles during the process of manufacturing the polarizing film.

In order to solve the above problems, various methods are used to remove impurities from the potassium iodide solution, and then concentrated and reused. However, the following problems occur.

First, the active carbon or chelate adsorbent generally used for the removal of impurities or impurities is subject to a rapid deterioration of the treatment capacity due to foreign substances in the pulmonary potassium iodide solution, which requires periodic replacement and thus increases management costs.

Second, agglomeration or adsorption methods using gunpowder chemicals require additional steps to remove the chemicals.

Third, when UF / NF membranes are used to remove and concentrate the high molecular weight substances in the potassium iodide solution, the UF separation membrane has low treatment efficiency and the NF membrane requires a lot of power for pressure filtration. Further, there is a problem that the lifetime of the separation membrane is lowered at the time of pressurization. In addition, the UF / NF separator has serious performance problems when preprocessing is not performed properly, and an additional pretreatment facility is required to solve the problems.

Fourth, in the case of the electrodialysis method, the cost of the self-contained facility is high and the electric power cost is increased, so that it is difficult to apply to the large-capacity treatment, and the performance varies depending on the process condition.

Fifth, when the reverse osmosis membrane is used, there is a problem that the ionic material is precipitated according to the temperature condition and the equipment is broken.

As a prior art to the present invention, Korean Patent No. 10-1044463 can be exemplified.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method and apparatus for recovering iodide solution that effectively provides impurities and minimizes membrane contamination and problems during separation membrane and reverse osmosis operation.

Another object of the present invention is to provide a method and an apparatus for recovering iodinated solution capable of removing impurities contained in a potassium iodide solution using a pressure reducing type circulating separation membrane.

Another object of the present invention is to provide a method and apparatus for recovering a iodinated solution, which can concentrate and reuse potassium iodide solution from which foreign substances have been removed by a reverse osmosis membrane.

According to a first aspect of the present invention, there is provided a method for purifying a potassium iodide solution, comprising: cooling a potassium iodide solution to a temperature at which a potassium iodide solution does not freeze, thereby precipitating a boric acid component; Filtering the impurities of the potassium iodide solution and the precipitated boric acid component using a membrane module; And concentrating the filtered potassium iodide solution filtered through the membrane module using a reverse osmosis membrane; And a method for recovering iodide solution.

The temperature of the potassium iodide solution supplied to the reverse osmosis membrane may be from room temperature to 85 ° C.

According to a second aspect of the present invention, there is provided an apparatus for recovering a potassium iodide solution, comprising: a first storage tank for storing the potassium iodide solution; A cooling unit for cooling the potassium iodide solution stored in the first storage tank; A filtration unit for filtering the foreign substances and the polymer substances contained in the cooled potassium iodide solution; And a concentrating unit for concentrating the potassium iodide solution filtered by the filtration unit using a reverse osmosis membrane; And an iodide solution recovery device.

The filtration unit may include a filtration tank in which a space is formed to store the potassium iodide solution supplied from the first storage tank and a depressurization type submerged membrane module disposed in the filtration tank.

The concentrating unit may include a reverse osmosis membrane vessel for containing a potassium iodide solution inward, a reverse osmosis membrane disposed inside the reverse osmosis membrane vessel, and a pressurizing pump for pressurizing the potassium iodide solution supplied to the reverse osmosis membrane vessel, The reverse osmosis membrane may be of a spiral wound type. The reverse osmosis membrane has a salt removal rate of 99.0% or more, thermal durability against hot water of 90 ° C, durability against acidic and alkali materials, operation pressure of 50kg / , And continuous operation at a temperature of 50 to 60 DEG C can be possible.

A heating unit for heating the potassium iodide solution supplied to the reverse osmosis membrane vessel is provided, and the heating unit includes a condensing tank for storing the potassium iodide solution that has passed through the filtering unit, a condensing tank having one end connected to the condensing tank, A collecting line connected to the concentrating unit, a heat exchanger disposed in the collecting line, And a steam supply line for supplying steam to the heat exchanger to heat the potassium iodide solution flowing through the recovery line.

A second filtration tank for storing the potassium iodide solution concentrated in the concentrating section; a second cooling section for cooling the second filtration tank; and a second separation membrane module mounted in the second filtration tank And a second filter unit.

The present invention can provide a method and apparatus for iodized solution recovery that effectively provides impurities contained in a pulsed iodination solution and minimizes film contamination and problems during reverse osmosis operation.

In addition, the present invention can remove foreign matters contained in the potassium iodide solution by using the pressure-sensitive cyclic separation membrane.

In addition, the present invention can concentrate and recycle the waste potassium iodide solution from which the foreign substance is removed by the reverse osmosis membrane.

1 is a flow chart showing a configuration of a potassium iodide solution recovery method according to the present invention.
2 is a configuration diagram showing a configuration of a potassium iodide solution recovery apparatus according to an embodiment of the present invention.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 is a flow chart showing a configuration of a method for recovering a iodinated solution according to the present invention. 2 is a block diagram showing a configuration of an iodinated solution recovery apparatus according to an embodiment of the present invention.

Referring to FIG. 1, a method for recovering a iodine solution according to the present invention includes preparing a solution (S110), cooling (S120), filtering (S130), and concentrating (S140).

2, the apparatus 100 for recovering potassium iodide according to an exemplary embodiment of the present invention includes a first storage tank 110, a cooling unit 120, a filtration unit 130, a heating unit 140, An enrichment unit 150, and a second filtration unit 160.

In step S110, the potassium iodide (KI) solution used as the main raw material in the polarizing film production process is mixed with the polyvinyl alcohol (potassium iodide) in the potassium iodide solution during the process of the dyeing, stretching, (KI) solution in which the concentration of foreign substances such as iodine, boric acid, etc. is increased and the concentration of potassium iodide (KI) is lowered.

The prepared potassium iodide solution is stored in the first storage tank 110 and can be supplied to the filtration unit 130 described later. The supply of the pulmonary iodide solution can be carried out by a feed pump not shown.

Here, after completion of the polarizing film production process, the potassium iodide solution can be stored in a predetermined tank and discarded. However, during the polarizing film production process, an auxiliary filtration process for filtering foreign substances is performed using a filtration means such as a microfilter can do.

The step of cooling (S120) is a step of cooling the prepared potassium iodide solution to a predetermined temperature before feeding to the filtering step (S130) described later. When the pulmonary iodide solution is cooled, the boric acid contained in the pulmonary potassium iodide solution precipitates. When boric acid is precipitated in the pulverized potassium iodide solution, it is possible to remove the precipitated particles through the depressurized membrane filtration process, to improve the efficiency of the subsequent process (especially the concentration step) Can be saved. In addition, wear and tear of equipment used in the process can be minimized. In addition, the precipitation of boric acid can be minimized in the step of filtration in the filtration unit described later, so that contamination and trouble of the membrane can be minimized.

For performing the cooling step (S120), the cooling unit (120) may be disposed in the storage tank (110). The cooling section 120 cools the waste potassium iodide solution in the storage tank to a predetermined cooling temperature. Here, the cooling temperature may be variously set to a temperature immediately before the freezing of the potassium iodide solution at room temperature or below, if boric acid is easily precipitated.

The filtering step (S130) is a step of removing foreign matters from the potassium iodide solution in which boric acid is precipitated.

The filtering step S 130 may be performed by the filtering unit 130.

The filtration unit 130 may include a filtration tank 131 for providing a rectangular space therein and a separation membrane module 132 disposed inside the filtration tank.

Here, the filtration tank 131 is accommodated in the inside thereof with a solution of potassium iodide, and the inside of the filtration tank 131 is configured to minimize unutilized space. The filtration tank 131 is preferably configured to be able to use the square tank as a chemical cleaning tank as well, without having to immerse in a separate cleaning tank in order to clean the contaminated separation membrane according to long-term operation. Since the chemical cleaning tank is used once in several months in a general submerged membrane separation process, if the filtration tank is used as a chemical cleaning tank, the cost and installation space can be reduced.

A depressurization type submerged membrane is disposed as a membrane module 132 inside the filtration tank. Here, the number of the arrangement of the pressure-reducing submerged membrane can be variously set according to the user's need. As the pressure-sensitive submerged membrane used in the present invention, the membrane module unit disclosed in the registered patent application 10-0666669 filed by the present applicant can be used. Also, a membrane module used in the separation membrane module disclosed in Japanese Patent Application Laid-Open No. 2010-0000662 may be applied.

Such a membrane module can minimize the wear and tear of the pump by effectively removing the precipitated boric acid particles and the impurities generated after the reaction and minimizes the precipitation of boric acid even in the reverse osmosis process, .

The decompression type submerged separation membrane is separated by using a decompression pressure generated when the suction pump 133 operates.

For membrane cleaning, the filtration unit 130 may include components capable of performing a back wash process.

After the filtering step (S130) is performed, a concentration step (S140) is performed.

The step of concentrating (S140) is a step of concentrating the potassium borohydride solution from which boric acid precipitates, foreign substances and polymer substances have been removed. The concentration step (S140) is performed by pressurizing and supplying a potassium iodide solution to a reverse osmosis membrane (RO).

The concentration step S140 may be performed by the concentration unit 150. [

The enrichment unit 150 includes a pressurizing pump 152, a reverse osmosis membrane vessel 154, and a reverse osmosis (RO)

The pressurizing pump 152 applies a predetermined pressure to the filtered potassium iodide solution to be supplied to the reverse osmosis membrane vessel 154 to be described later.

The reverse osmosis membrane vessel 154 provides a space for the disposition of the reverse osmosis membrane 156, which will be described later. The reverse osmosis membrane vessel 154 may be configured in various forms depending on the concentration of the potassium iodide solution.

The reverse osmosis membrane (156) concentrates the potassium iodide solution to increase the concentration of the filtered potassium iodide solution.

The reverse osmosis membrane 156 may be disposed at least one inside the reverse osmosis membrane vessel 154. At this time, the arrangement number of the reverse osmosis membrane 156 can be variously set according to the user's need.

Here, the reverse osmosis membrane 156 is of the spiral wound type, and preferably has a diameter of 2 to 8 inches and a length of 40 inches. The reverse osmosis membrane preferably has a salt removal rate of 99.0% or more, thermal durability against hot water at 90 ° C, and acidity and durability against an alkali substance. Further, it is preferable that the operation pressure of the reverse osmosis membrane is 50 kg / cm < 2 > and that continuous operation is possible at a temperature of 50 to 60 DEG C.

Therefore, the pressure state of the waste solution by the pressurizing pump 152 is preferably equal to or lower than the operating pressure of the reverse osmosis membrane.

During the process of the concentration unit 150, the generated wastewater is discharged to the outside and discarded. In addition, it is preferable that the reverse osmosis membrane 156 can be cleaned so that the concentration state in the concentrating part 150 can be maintained constant. Herein, the cleaning of the reverse osmosis membrane 156 may be performed by injecting washing chemicals or the like.

On the other hand, the heating unit 140 may be disposed so that the temperature of the potassium iodide solution can be set to a predetermined value or more by the filtering unit 130 so that the concentration step (S140) can be easily performed.

The heating unit 140 heats the potassium iodide solution from room temperature to 85 캜 and supplies it to the concentrating unit. As a result, the permeability of the concentrated portion using the reverse osmosis membrane is greatly improved to improve the economical efficiency, and at the same time, the membrane can be used less and the productivity can be improved.

Further, there is an advantage that a stable reverse osmotic pressure process can be carried out because no additional precipitation of boric acid occurs during the concentration process of the concentrated portion.

Further, the concentrated potassium iodide solution may be re-cooled through a cooling process of flowing a coolant through the heating portion, and the precipitated boric acid may be transferred to a second filtration portion to be described later to obtain a more pure potassium iodide solution.

The heating unit 140 includes a concentration tank 135, a recovery line 136, a heat exchanger 142, and a steam supply line 141.

A collection tank 135 for storing a concentrated potassium iodide solution after passing through the filtration unit is disposed between the filtration unit and the condensation unit, and a recovery line 136 through which the recovered potassium iodide solution flows, .

The heat exchanger is formed in the recovery line, and the recovery line is formed to pass through the heat recovery line. The steam supply line is formed to penetrate the heat exchanger, and the steam is supplied to the heat exchanger to heat the potassium iodide solution passing through the recovery line.

The heated potassium iodide solution passing through the heat exchanger is supplied to the filtration unit again through the concentration tank.

If the temperature of the potassium iodide solution supplied to the filtration part is increased above a predetermined level, the precipitation of the remaining boric acid in the solution is reduced without precipitating in the previous step, so that the degree of contamination of the reverse osmosis membrane is decreased and the permeability is improved, . In addition, the number of arrangement of the reverse osmosis membrane can be reduced, and the installation cost of the entire apparatus can be reduced. Concentration of ionic substances in raw water is very important for RO concentration. The higher the concentration of the ionic substance, the higher the osmotic pressure. The higher the osmotic pressure, the higher the pressure of the pump for operating the RO membrane, and since there is a limit concentration that can be concentrated by the RO membrane due to the osmotic pressure, In order to maximize the necessary concentration of potassium iodide, the concentration of dissolved boric acid adversely affects the concentration of potassium iodide. Removal of boric acid in the waste solution by pretreatment filtration using a precooled and pressure-reduced membrane takes less osmotic pressure, and consequently, potassium iodide can be concentrated to a higher concentration, thereby increasing the yield of the final product.

The concentrated potassium iodide solution in the concentration unit 150 may be transferred to the second filtration unit 160.

The second filtration unit includes a second filtration tank 161, a second separation membrane module 162, and a second cooling unit 163.

The second filtration tank 161 is supplied with the concentrated potassium iodide solution in the filtration section. The second cooling unit 163 may cool the concentrated potassium iodide solution installed in the second filtration tank and stored in the second filtration tank to further crystallize boric acid or other ionic substances. Further, a second separation membrane module 162 is installed in the second filtration tank to remove the precipitated substance, thereby providing a more pure potassium iodide solution.

While the present invention has been described with reference to exemplary embodiments, it is to be understood that the invention is not limited to the disclosed exemplary embodiments, but, on the contrary, is intended to cover various modifications and equivalent arrangements included within the spirit and scope of the appended claims. Accordingly, the true scope of the present invention should be determined by the technical idea of the appended claims.

110: Storage tank 120: Cooling section
130: filtration part 131: filtration tank
132: Membrane module 135: Concentration tank
136: recovery line 140: heating section
150: concentrated portion 160: second filtration portion

Claims (11)

A method for recovering a potassium iodide solution,
Cooling the potassium iodide solution to a temperature at which the potassium iodide solution does not freeze to precipitate the boric acid component;
Heating the potassium iodide solution and filtering the foreign substance of the potassium iodide solution using a separation membrane module; And
Concentrating the filtered potassium iodide solution in the separation membrane module using a reverse osmosis membrane;
Lt; / RTI >
Wherein the precipitation of the boric acid is reduced by heating the potassium iodide solution so that the contamination of the reverse osmosis membrane is reduced and the permeability is improved. The method according to claim 1,
Wherein the temperature of the potassium iodide solution supplied to the reverse osmosis membrane is from room temperature to 85 ° C. The method according to claim 1,
And cooling the concentrated potassium iodide solution to a freezing point temperature. An apparatus for recovering a potassium iodide solution, comprising:
A first storage tank for storing the pulmonary iodide solution;
A cooling unit for cooling the potassium iodide solution stored in the first storage tank;
A filtration unit for filtering the foreign substances and the polymer substances contained in the cooled potassium iodide solution;
A concentrating unit for concentrating the potassium iodide solution filtered by the filtration unit using a reverse osmosis membrane;
A second filtration tank storing the potassium iodide solution concentrated in the concentrating section;
A second cooling unit for cooling the second filtration tank; And
A second filtration unit comprising a second separation membrane module mounted inside the second filtration tank; And an iodide solution recovery device. 5. The method of claim 4,
The filtration unit,
A filtration tank in which a space is formed to store the potassium iodide solution supplied from the first storage tank, and a pressure-reducing submerged membrane module disposed inside the filtration tank. The method according to claim 4 or 5,
The concentrator may include:
A reverse osmosis membrane vessel for containing a pulmonary potassium iodide solution,
A reverse osmosis membrane disposed inside the reverse osmosis membrane vessel,
And a pressurizing pump for pressurizing the potassium iodide solution supplied to the reverse osmosis membrane vessel. The method according to claim 6,
Wherein the reverse osmosis membrane is a spiral wound type. 8. The method of claim 7,
The reverse osmosis membrane has a salt removal rate of 99.0% or more, thermal durability against hot water at 90 ° C, durability against acidic and alkali materials, operation pressure of 50 kg / cm 2, continuous operation at a temperature of 50 to 60 ° C Iodide solution recovery device. The method according to claim 6,
And a heating unit for heating the potassium iodide solution supplied to the reverse osmosis membrane vessel is disposed. 10. The method of claim 9,
The heating unit includes:
A concentrating tank for storing the pulmonary iodide solution that has passed through the filtration unit; a collecting line having one end connected to the concentrating tank and the other end connected to the concentrating unit; and a heat exchanger disposed in the collecting line; And a steam supply line for supplying steam to the heat exchanger to heat the potassium iodide solution flowing through the recovery line.
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