KR20130103201A - Method of desalination and desalination apparatus - Google Patents

Abstract

The present invention relates to a brine desalination method and desalination apparatus. In the desalination method of the present invention, the saline solution is placed in the brine space of the forward osmosis reactor, and the induction solution including the inducing solute is placed in the osmotic induction solution space so that the water of the brine moves to the osmotic induction solution space by osmotic pressure. Performing a forward osmosis process to be included in; Cooling at least one induction solution having undergone the forward osmosis to precipitate at least a portion of the inducing solute; And producing fresh water by performing a reverse osmosis process on the induction solution having a lower concentration. According to the present invention, it is possible to produce fresh water efficiently with low energy as compared to the conventional desalination process.

Description

Desalination method and desalination apparatus {Method of desalination and desalination apparatus}

The present invention relates to a desalination method and desalination apparatus. More specifically, the present invention relates to a desalination process and a desalination apparatus that hybridizes the forward osmosis process, the cooling process, and the reverse osmosis process in order to increase the efficiency of the desalination process.

In order to obtain fresh water from seawater, dissolved or suspended components in seawater must be removed to meet water and drinking water standards. Common processes for desalination of seawater are known as evaporation, membrane separation, electrodialysis, and freezing, and the most widely used techniques are evaporation and membrane separation.

As the evaporation method, multiple stage flash (MSF), multiple effect evaporation (ME), etc. are mainly used and are widely used in the early stages. However, due to the high energy consumption, high corrosion of the high temperature operation, large production area and initial investment cost, it is mainly used for large-scale seawater desalination facilities in the Middle East where energy is abundant, and energy consumption, facility investment cost, and maintenance cost are high.

Membrane separation can be divided into reverse osmosis and forward osmosis.

Reverse osmosis is a method of separating ionic substances and pure water from the reverse osmosis membrane of the components contained in seawater.In order to separate ionic substances and pure water from seawater, a high pressure of more than osmotic pressure is required. It is called osmotic pressure. In general, since the use of a high-pressure pump that consumes most of the power as the seawater supply means as described above, there was a disadvantage in that considerable energy is consumed for desalination of seawater. In addition, the large-scale desalination treatment method as a membrane separation method requires a lot of initial investment costs, there is a problem that requires a great care in pretreatment in order to prevent fouling (fouling) by organic or inorganic.

Recently, the forward osmosis method of separating water from seawater by pure osmosis without using a high pressure pump has been developed. However, in the osmotic method, the osmotic solution containing a higher concentration of the osmotic solute than the seawater is used, so it is difficult to separate the osmotic solute from the osmotic solution diluted by the water moved through the osmotic membrane.

In order to solve the problems of the prior art as described above, an object of the present invention is to provide a desalination method capable of efficiently desalination of brine while consuming less energy.

Moreover, an object of this invention is to provide a desalination apparatus.

In order to achieve the above object, the present invention is to place the saline water (saline water) in the brine space of the forward osmosis reactor and the osmotic pressure by placing a draw solution containing a draw solute in the osmotic induction solution space Performing a forward osmosis process by which the brine water moves to the osmotic induction solution space to be included in the induction solution;

Cooling at least one induction solution having undergone the forward osmosis to precipitate at least a portion of the inducing solute; And

It provides a desalination method of the brine comprising the step of performing a reverse osmosis process to produce a fresh water for the concentration solution is lowered.

In addition, the present invention is divided into the osmotic induction solution space and the brine space by the semi-permeable membrane, the forward osmosis reactor including a first inlet connected to the osmotic induction solution space and the second inlet connected to the brine space on one side;

One side is connected to the other side of the forward osmosis reactor, the cooling reactor for cooling the induction solution delivered in the forward osmosis reactor to precipitate at least a portion of the induction solute contained in the induction solution; And

It is divided into an induction solution space and a fresh water space by a reverse osmosis membrane, and one side of the induction solution space is connected to the other side of the cooling reactor to desalination of the induction solution delivered from the cooling reactor by reverse osmosis. It provides a desalination apparatus comprising a reverse osmosis reactor to discharge to the outlet of.

Desalination method and apparatus of the present invention has the effect of reducing the energy consumption compared to the fresh water production compared to the conventional desalination process. In particular, the use of a high pressure pump is not required compared to the reverse osmosis process, which also eliminates the need for a high pressure reverse osmosis membrane.

1 is a schematic diagram showing a desalination method according to an embodiment of the present invention.
2 illustrates a desalination apparatus according to an embodiment of the present invention.
3 is a schematic diagram illustrating a desalination process using a Matlab program according to an embodiment of the present invention.

In the desalination method of the present invention, saline water is placed in the brine space of the forward osmosis reactor, and a draw solution including a draw solute is placed in the osmotic induction solution space to obtain the brine by osmotic pressure. Performing an forward osmosis process in which water moves to the osmotic induction solution space to be included in the induction solution; Cooling at least one induction solution having undergone the forward osmosis to precipitate at least a portion of the inducing solute; And producing fresh water by performing a reverse osmosis process on the induction solution having a lower concentration.

In addition, the desalination apparatus of the present invention is divided into an osmotic induction solution space and a saline space by a semipermeable membrane, and includes a first inlet connected to the osmotic induction solution space and a second inlet connected to the saline space on one side. Reactor;

One side is connected to the other side of the forward osmosis reactor, the cooling reactor for cooling the induction solution delivered in the forward osmosis reactor to precipitate at least a portion of the induction solute contained in the induction solution; And

It is divided into an induction solution space and a fresh water space by a reverse osmosis membrane, and one side of the induction solution space is connected to the other side of the cooling reactor to desalination of the induction solution delivered from the cooling reactor by reverse osmosis. And a reverse osmosis reactor for discharging to the freshwater outlet.

In the present invention, the terms first, second, etc. are used to describe various components, and the terms are used only for the purpose of distinguishing one component from another.

While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention.

Hereinafter, with reference to the drawings will be described in detail the desalination method and desalination apparatus of the present invention.

The desalination process is a process of producing fresh water that can be used as drinking water by removing salt from salt mixed water, that is, saline water.

1 is a schematic diagram showing a desalination method according to an embodiment of the present invention.

Referring to FIG. 1, first, saline water is placed in a saline space of an forward osmosis reactor, and a draw solution including a draw solute is placed in an osmotic induction solution space. The water is moved to the osmotic induction solution space to perform the forward osmosis process to be included in the induction solution (step S10).

In the desalination method of the present invention, the brine to be desalination may be not only general salt or sea water containing salt, but also contaminated water (waste water) that is difficult to use as it is. According to one embodiment of the invention, in particular, it can be used for desalination of seawater.

According to one embodiment of the invention, the induction solution may be an aqueous solution in which the inducing solute is dissolved in water.

The principle of the forward osmosis process is to use the osmotic induction solution containing the solute at a higher concentration than the desalination solution, so that the water in the desalination solution naturally moves toward the osmotic induction solution and then dilutes due to the difference in osmotic pressure. Separating the solute from the osmotic induction solution to obtain fresh water only. Since the forward osmosis process is a process using a difference in osmotic pressure between the saline solution and the osmotic induction solution, it does not require a high-pressure pump to perform the process, and thus has the advantage of low energy.

After performing the forward osmosis process, the brine water penetrates into the osmotic induction solution space so that the brine is more concentrated than the inflow, and the concentrated brine can be used for other purposes by treating or recovering the brine.

Since the induction solution having undergone the forward osmosis process has water permeated in the brine, the concentration is lower than the initial state, and fresh water may be produced by separating the inducing solute and water therefrom.

Selection of the inducing solute is important for an efficient forward osmosis process, and the inducing solute should be able to induce higher osmotic pressure than saline because it has high solubility in water. In particular, the greater the difference in osmotic pressure between saline and induced solutes, the better. Further, according to the desalination method of the present invention, after performing the forward osmosis process, the induced solute is subsequently separated by a cooling process, wherein the induced solute should be easily separated from the diluted induction solution. According to the desalination method of the present invention, the separation of the inducing solute uses the difference in solubility and osmotic pressure of the inducing solute at the temperature in the forward osmosis process and the temperature in the cooling process. Therefore, the greater the osmotic pressure at the temperature of the forward osmosis process step, the better, and the lower the osmotic pressure or solubility at the temperature of the subsequent cooling process is better. In addition, for industrial applicability, it must be easy to obtain, harmless to the human body, and economical.

According to one embodiment of the invention, for example, sodium periodate (NaIO ₄ ), boric acid (boric acid, H ₂ BO ₃ ), potassium chlorate as an inducing solute meeting all of the above conditions (potassium chlorate, KClO ₃ ), potassium permanganate (KMnO ₄ ), ammonium oxalate (NH 4) ₂ C ₂ O ₄ ), barium nitrate (Ba (NO ₃ ) ₂ ), barium sulfide (barium sulfide, BaS), potassium dichromate (potassium dichromate, K ₂ Cr ₂ O ₇ ), sodium iodate (sodium iodate, NaIO ₃ ), and the like. However, the inducing solute in the production method of the present invention is not limited thereto, and may be used as long as the material satisfies the conditions of the inducing solute required by the present invention in addition to the above-described materials.

The forward osmosis process is performed using an induction solution containing an inducing solute that satisfies the above conditions and having an osmotic pressure higher than that of saline flowing into the forward osmosis process. When the seawater is desalted with the brine, the concentration may be appropriately adjusted according to the type of the solute derived, but in order to obtain a large osmotic pressure difference with the brine, it is preferable to set the concentration close to the saturation concentration of the induction solution.

According to one embodiment of the present invention, sodium periodate, boronic acid, potassium chlorate or potassium permanganate may be used as the inducing solute. For sodium periodate, boronic acid, potassium chlorate and potassium permanganate, osmotic pressures at 0 ° C and 30 ° C are shown in Table 1 below.

Induced solute 0 ℃ 30 ℃ density
(Unit: g / g) Osmotic pressure
(Atm) density
(Unit: g / g) Osmotic pressure
(Atm) Sodium periodate 0.0183 3.835 0.304 70.712 Boronic acid 0.0252 18.280 0.0808 65.049 Potassium chlorate 0.033 12.082 0.139 56.482 Potassium permanganate 0.0283 8.033 0.126 39.696

In addition, according to an embodiment of the present invention, the temperature of the forward osmosis process may be variously selected depending on the type of the inducing solute and the environment in which the process is performed. That is, in the forward osmosis process, since the water of the saline is permeated into the induction solution by using the osmotic pressure difference between the saline solution and the induction solution, the brine, the inflow amount, the concentration of the induction solution, the kind of the inducing solute, and the forward osmosis process. The forward osmosis process may be performed by setting a temperature at which a larger osmotic pressure difference may be generated according to the environment to be performed. For example, the forward osmosis process may be performed at a temperature of about 0 to about 30 ° C., but the temperature may be set differently according to the detailed conditions of the forward osmosis process, but the present invention is not limited thereto.

Referring to FIG. 1, the induction solution having performed the forward osmosis process performs a cooling process (step S20).

The cooling process is a process of separating the water and the inducing solute by depositing the inducing solute from the induction solution by the difference in solubility according to the temperature of the inducing solute in the process of lowering the temperature of the induction solution.

In this case, at least some to most of the induced solute may be precipitated according to the type of the induced solute and the cooling temperature. The precipitated inducing solute can be reused by returning it to be included as an induction solution introduced into the forward osmosis step (S10).

The cooling process is performed at a lower temperature than the forward osmosis process for precipitation due to the difference in solubility depending on the temperature of the inducing solute. That is, the cooling process may be performed by setting a temperature at which a greater solubility difference may be generated according to the type of the inducing solute. For example, the cooling process may be carried out at a temperature of about -20 to about 10 ℃, but the temperature can be set differently according to the detailed conditions, such as the conditions of the preceding forward osmosis process, the type of solute so limited to this It doesn't happen.

As the cooling process is performed, the concentration of the inducing solution is lowered by the precipitated inducing solute by precipitating at least part or most of the inducing solute.

Next, the reverse osmosis (Reverse Osmosis) process is performed for the solution having a lower concentration (step S30).

The reverse osmosis process requires a high pressure above the osmotic pressure of the induction solution in order to separate the solute and the pure water. The pressure at this time is called reverse osmosis. In general, the reverse osmosis process for the desalination of seawater requires a high pressure of about 50 to 60 atm. Therefore, since a high pressure pump for supplying seawater at the pressure as described above is used, it is about 4 to 8 kWh / m ³ . Considerable energy is required.

However, according to the present invention, since the concentration of the induction solution through the forward osmosis process and the cooling process as described above (ie, the osmotic pressure is lowered), the pressure required for the reverse osmosis process is lowered. According to one embodiment of the invention, in performing the reverse osmosis process, a pressure of about 15 to about 20 atm is required. This makes it possible to operate below the pressure required for a conventional reverse osmosis process and thus significantly lower the energy required.

According to an embodiment of the present invention, when the seawater desalination is performed in a hybrid process in which the forward osmosis process, the cooling process, and the reverse osmosis process are combined as described above, about 1 to about 3 kWh / m to produce fresh water 1 m ³ . Requires ³ energy. This is significantly less than 4 to 8 kWh / m ^{3 of} energy consumed in the conventional seawater desalination process, according to the desalination method of the present invention, it is possible to efficiently produce fresh water with less energy.

In addition, the reverse osmosis process may be performed by setting a temperature at which a greater reverse osmosis pressure may be generated depending on the concentration of the induction solution, the type of the induced solute, and the environment in which the reverse osmosis process is performed. Can be. According to one embodiment of the present invention, the reverse osmosis process may be performed at a temperature of about 0 to about 30 ° C., but the present invention is not limited thereto since the temperature may be set differently according to detailed conditions.

On the other hand, an aspect of the present invention provides a desalination apparatus.

The desalination apparatus of the present invention is divided into an osmotic induction solution space and a saline space by a semipermeable membrane, and includes a first inlet connected to the osmotic induction solution space and a second inlet connected to the brine space on one side. ; One side is connected to the other side of the forward osmosis reactor, the cooling reactor for cooling the induction solution delivered in the forward osmosis reactor to precipitate at least a portion of the induction solute contained in the induction solution; And an induction solution space and a fresh water space by a reverse osmosis membrane, and one side of the induction solution space is connected to the other side of the cooling reactor to desalination of the induction solution delivered from the cooling reactor by reverse osmosis. It includes a reverse osmosis reactor that discharges to the freshwater outlet of the space.

2 illustrates a desalination apparatus according to an embodiment of the present invention.

Referring to FIG. 2, the desalination apparatus of the present invention includes a forward osmosis reactor 100, a cooling reactor 200 connected to the forward osmosis reactor, and a reverse osmosis reactor 300 connected to the cooling reactor 200.

The forward osmosis reactor 100 is divided into an osmotic induction solution space 20 and a saline space 30 by a semi-permeable membrane 10, and includes a first inlet 25 and a saline space connected to the osmotic induction solution space 20 ( 30 includes a second inlet 35 connected to one side.

Induced solution containing the inducing solute is introduced into the osmotic induction solution space 20 through the first inlet 25, and the brine to the desalination of seawater, etc., through the second inlet 35 into the brine space 30. Will be introduced. As the inducing solute, for example, sodium periodate (NaIO ₄ ), boric acid (boric acid, H ₂ BO ₃ ), potassium chlorate (potassium chlorate, KClO ₃ ), potassium permanganate (potassium permanganate, KMnO) ₄ ), ammonium oxalate (NH 4) ₂ C ₂ O ₄ ), barium nitrate (Ba (NO ₃ ) ₂ ), barium sulfide (BaS), potassium dichromate (potassium dichromate, K ₂₎ Cr ₂ O ₇ ) and one or more selected from the group consisting of potassium iodate (sodium iodate, NaIO ₃ ) may be used, but is not limited thereto. Conditions and a more detailed description of the induced solute are as described above in the desalination method.

The forward osmosis process is performed in the forward osmosis reactor 100 using the induction solution including the inducing solute and having an osmotic pressure higher than that of the brine flowing into the forward osmosis process.

According to one embodiment of the present invention, the forward osmosis reactor 100 may perform the process at a temperature of about 0 to about 30 ° C, but may be set differently according to the detailed conditions of the process as described in the desalination method. It is not so limited.

In the desalination apparatus of the present invention, the forward osmosis reactor 100 may further include a brine outlet 130 that is connected to the other side of the brine space 30 to discharge concentrated brine after performing the forward osmosis process. .

Induction solution diluted from the original concentration by performing the forward osmosis process in the forward osmosis reactor 100 is transferred to the cooling reactor 200 connected to the forward osmosis reactor 100 to perform the cooling process in the cooling reactor 200.

One side of the cooling reactor 200 is connected to the other side of the forward osmosis reactor 100 to receive an induction solution for performing the forward osmosis reaction, the delivered induction solution is cooled in the forward osmosis reactor 100 At least a portion of the inducing solute contained in the induction solution is precipitated.

The cooling process is a process of separating the water and the inducing solute by depositing the inducing solute from the induction solution by the difference in solubility according to the temperature of the inducing solute in the process of lowering the temperature of the induction solution. In this case, at least some to most of the induced solute may be precipitated according to the type of the induced solute and the cooling temperature.

According to one embodiment of the present invention, the cooling reactor 200 further comprises a first circulation pipe 110 for delivering the induced solute precipitated by the cooling process to the first inlet 25 of the forward osmosis reactor 100. It may include. The precipitated inducing solute is transferred to the first inlet 25 through the first circulation pipe 110, and thus may be reused as an induction solution introduced into the forward osmosis reactor 100. Therefore, the induction solution is circulated to further increase the efficiency of the desalination process.

According to one embodiment of the invention, the cooling reactor 200 is It may operate at a temperature of about -20 to about 10 ℃, but the temperature can be set differently according to the detailed conditions, such as the conditions of the preceding forward osmosis reactor 100, the type of solute is not limited thereto.

As the cooling process is performed, the concentration of the inducing solution is lowered by the precipitated inducing solute by precipitating at least part or most of the inducing solute.

The lower concentration of the induced solution is delivered to the reverse osmosis reactor (300).

The reverse osmosis reactor 300 is divided into the induction solution space 50 and the fresh water space 60 by the reverse osmosis membrane 40, and one side of the induction solution space 50 is the other side of the cooling reactor 200. The connected solution delivered from the cooling reactor 200 may be desalted by reverse osmosis, and fresh water may be produced by discharging fresh water through a fresh water discharge port 70 installed at the other side of the fresh water space 60.

In general, the reverse osmosis process for the desalination of seawater requires a high pressure of about 50 to 60 atm. However, according to the present invention, the concentration of the induction solution through the two-stage reaction of the forward osmosis reactor 100 and the cooling reactor 200, as described above, so the pressure required for the reverse osmosis process is lowered. According to one embodiment of the invention, in carrying out the reverse osmosis process, the reverse osmosis reactor 300 requires a pressure of about 15 to about 20 atm. This makes it possible to operate below the pressure required for a conventional reverse osmosis process and thus significantly lower the energy required. Although not shown in the drawings, the reverse osmosis reactor 300 may further include a high pressure pump for supplying the induced solution to the reverse osmosis reactor 300 at an appropriate reverse osmosis pressure.

According to one embodiment of the present invention, the reverse osmosis reactor 300 may perform the reverse osmosis process at a temperature of about 0 to about 30 ℃, but differently set the temperature according to the detailed conditions as described in the desalination method The present invention is not limited thereto.

The reverse osmosis reactor 300 is connected to the other side of the induction solution space 50 so as to perform desalination and circulate the remaining induction solution to the first inlet 25 of the forward osmosis reactor 100 (120). ) May be further included. According to an embodiment of the present invention, the second circulation pipe 120 may be connected to the first circulation pipe 110 of the cooling reactor 200 and lead to the first inlet 25. According to another embodiment of the present invention, the second circulation pipe 120 may be directly connected to the first inlet 25 of the forward osmosis reactor 100.

According to one embodiment of the present invention, when performing the seawater desalination with the desalination apparatus combined with the forward osmosis reactor 100, the cooling reactor 200 and the reverse osmosis reactor 300, to produce fresh water 1m ³ It requires about 1 to about 3 kWh of energy.

Hereinafter, the present invention will be described in more detail with reference to examples according to the present invention. It is to be understood, however, that these embodiments are merely illustrative of the invention and are not intended to limit the scope of the invention.

< Example >

Example  One

3 is a schematic diagram simulating a desalination process of seawater according to an embodiment of the present invention using a Matlab program.

The forward osmosis process and the reverse osmosis process were operated at 30 ° C., the cooling process at 0 ° C., and an induction solution containing 0.0183 g / g of sodium periodate (NaIO ₄ ) as an inducing solute. More detailed process conditions are shown in Table 2 below.

As a result, energy consumption for the production of fresh water was found at about 1m ³ 1.768kWh.

Flow rate
(Unit: m ³ / s) Osmotic pressure
(Atm) Temperature
(Unit: ℃) Forward osmosis stage Induction of induction solution 0.0957 71.711 30 In case of seawater inflow 0.0231 28.04 30 On induction solution outflow 0.0957 61.081 30 Cooling step Induction solution
On inflow 0.0170 61.081 30 On induction solution outflow 0.0165 3.8354 0 Reverse osmosis stage Induction solution
On inflow 0.0165 17.785
(Pump pressure) 30

10: semipermeable membrane
20: osmotic induction solution space
25: first inlet
30: brine space
35: second inlet
40: reverse osmosis membrane
50: induction solution space
60: freshwater space
70: freshwater outlet
100: forward osmosis reactor
110: first circulation pipe
120: second circulation pipe
130: brine outlet
200: cooling reactor
300: reverse osmosis reactor

Claims (9)

Saline water is placed in the brine space of the forward osmosis reactor, and a draw solution containing draw solute is placed in the osmotic induction solution space so that the water of the saline is osmotic induced solution by osmotic pressure. Performing a forward osmosis process to move to a space to be included in the induction solution;
Cooling at least one induction solution having undergone the forward osmosis to precipitate at least a portion of the inducing solute; And
The desalination method of the brine comprising the step of producing fresh water by performing a reverse osmosis process to the concentration of the induction solution.
The method of claim 1, wherein the brine is sea water (sea water).
The method of claim 1, wherein the inducing solute is sodium periodate (NaIO ₄ ), boric acid (boric acid, H ₂ BO ₃ ), potassium chlorate (KClO ₃ ), potassium permanganate (potassium permanganate, KMnO ₄ ), ammonium oxalate (NH 4) ₂ C ₂ O ₄ ), barium nitrate (Ba (NO ₃ ) ₂ ), barium sulfide (BaS), potassium dichromate (potassium dichromate, K) ₂ Cr ₂ O ₇ ) and potassium iodate (sodium iodate, NaIO ₃ ) The desalination method of saline containing one or more selected from the group consisting of.
The method of claim 1, wherein the induced solute precipitated by the cooling process further comprises the step of returning to be included in the induction solution of the forward osmosis step.
The method according to claim 1, Reverse osmosis process is a desalination method of brine is carried out at a pressure of 15 to 20 atm.
A forward osmosis reactor divided into an osmotic induction solution space and a saline space by a semi-permeable membrane, the forward osmosis reactor including a first inlet connected to the osmotic induction solution space and a second inlet connected to the brine space;
One side is connected to the other side of the forward osmosis reactor, the cooling reactor for cooling the induction solution delivered in the forward osmosis reactor to precipitate at least a portion of the induction solute contained in the induction solution; And
It is divided into an induction solution space and a fresh water space by a reverse osmosis membrane, and one side of the induction solution space is connected to the other side of the cooling reactor to desalination of the induction solution delivered from the cooling reactor by reverse osmosis. Desalination apparatus comprising a reverse osmosis reactor for discharging to the fresh water outlet.
7. The desalination apparatus according to claim 6, further comprising a first circulation pipe for transferring the precipitated inducing solute in the cooling reactor to the first inlet of the forward osmosis reactor.
The desalination of claim 6, further comprising a second circulation pipe connected to the other side of the induction solution space of the reverse osmosis reactor to perform desalination and circulate the remaining induction solution to the first inlet of the forward osmosis reactor. Device.
The desalination apparatus according to claim 6, further comprising a freshwater outlet connected to the other side of the brine space of the forward osmosis reactor to discharge concentrated brine.

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