KR20060113125A - A system for desalination by producing gas-hydrate or clathrate and method thereof - Google Patents

Abstract

A new desalination system and a new desalination method are provided to efficiently separate components such as salt or contaminants from a slurry column in which a mixture of seawater and gas is formed and recycle the recovered heat value in the gas/water separation process by recovering a heat value generated from the gas-hydrate generation process in a method for desalination of seawater through a gas-hydrate generation process. A system for desalination of seawater comprises: a slurry column(10) having a fractionation apparatus(11) installed therein to fractionate components contained in seawater by stages and a seawater pipe(13) for heat exchange installed on an inner wall thereof, wherein the seawater pipe for heat exchange has a coil structure so that seawater is heated by calorific value of a gas-hydrate, and the gas-hydrate is generated in a lower part of the slurry column and moves to an upper part of the slurry column; a seawater/gas mixer(20) which is installed on a lower portion of the slurry column, and into which seawater and gas flow so as to generate a seawater/gas mixed slurry; a gas saturator(30) for saturating gas into seawater and injecting the saturated gas into the seawater/gas mixer; a heat exchanger(40) for dissociate the gas-hydrate flown in from the slurry column into gas and water; and a gas-water separator(50) for separating the gas and water dissociated by the heat exchanger.

Description

System for Desalination by Producing Gas Hydrate and Desalination Method {A System for Desalination by Producing Gas-Hydrate or Clathrate and Method}

1 is a schematic block diagram showing a system for desalination of seawater by producing gas hydrate according to the present invention.

2 is a schematic perspective view of a fractionation apparatus installed in the slurry column of FIG.

FIG. 3 is a schematic diagram for showing a state where the fractionation apparatus of FIG. 2 is installed inside the slurry column.

4 is a schematic perspective view of a heat exchanger used in the system of FIG.

FIG. 5 is a schematic perspective view of a rotary valve installed on top of the slurry column of FIG.

6 is a schematic cross-sectional view showing the structure of the gas saturation device of FIG.

FIG. 7 is a schematic cross-sectional view showing the structure of the seawater / gas mixing device of FIG.

8 is a view showing a material resin according to an embodiment of the present invention for generating and desalination of gas hydrate of seawater using propane gas.

9 is a view showing a material resin according to an embodiment of the present invention for generating and desalination of gas hydrate of seawater using methane gas.

10 is a view showing a material resin according to an embodiment of the present invention for generating and desalination of gas hydrate of seawater using carbon dioxide gas.

* Brief description of the major symbols in the drawings *

10: slurry column 20: sea water / gas mixing device

30 gas saturator 40 heat exchanger

50: gas / water separator 60: gas collector

11: fractionation apparatus 12: rotary valve

13: pipe for heat exchange

14, 15, 21, 31, 32, 34, 41, 51, 52, 53: pipe

22, 33, 54: valve 16, 17: concentrated seawater

23: gas hydrate generation zone 61: compressor

Field of invention

The present invention relates to a method for desalination of seawater by producing gas hydrates. More specifically, the present invention relates to a method of desalination of seawater by mixing gas with seawater to generate gas hydrates, and then separating the liquid water and the gaseous gas. The present invention also includes a system for producing gas hydrates to desalination of seawater.

Background of the Invention

Since seawater contains various mineral components including salt, it is necessary to go through a desalination process to separate salts in order to use these components or to obtain fresh water as drinking water. Various methods of desalination of seawater have been proposed so far, and desalination facilities are installed and operated.

The oldest desalination methods include distillation using water phase change and reverse osmosis using reverse concentration. Distillation consumes a lot of energy because water requires a larger amount of heat source than other materials for phase change. Therefore, the desalination method by distillation method is economical and it is concentrated in only the Middle East countries where almost no practical use is produced in most countries. Desalination of seawater by reverse osmosis also requires additional treatment because seawater needs to be pretreated and high operating pressure is required. Therefore, this method does not appear to be far superior to the distillation method in economics. In addition to these two methods, a recently developed method is a desalination method through a gas hydrate process. This method mixes gas capable of forming a hydrate with seawater to be desalted to produce a gas hydrate, and then separates gas and water, ultimately desalting seawater and separating concentrated seawater such as salts contained in the seawater. That's how.

One desalination method through a gas hydrate process is disclosed in US Pat. No. 6,158,239. This method relates to a method of injecting hydrocarbon gas such as methane gas into contaminated water or seawater to generate gas hydrate, and then separating gas and water to purify contaminated water or desalination of seawater.

Another desalination method through a gas hydrate process is disclosed in US Pat. No. 6,562,234. This method relates to a method of purifying contaminated water and a method of desalination of seawater that can inject gas into contaminated water or seawater to generate gas hydrates, and then separate gas and water to obtain cooling water.

The present inventors have remarkably improved the desalination method through the conventional gas hydrate process as described above to efficiently separate components such as salt or contaminants from the slurry column in which a mixture of sea water and gas is formed, The company has developed a new system that can recover the heat and recover it during gas / liquid separation.

An object of the present invention is to provide a new desalination system and method for efficiently separating components such as salts and contaminants in a slurry column in which a mixture of seawater and gas is formed in a method of desalination of seawater through a gas hydrate process. It is to provide.

Another object of the present invention is to provide a new desalination system and method for recovering heat generated during gas hydrate generation in a method of desalination of seawater through a gas hydrate process and recycling the same during gas / liquid separation. .

The above and other objects of the present invention can be achieved by the present invention described below.

Summary of the Invention

In the desalination system of the present invention, a distillation apparatus 11 for dividing the concentrated seawater in stages is installed therein and a heat exchange seawater pipe 13 having a coil structure is installed on the inner wall so that the seawater is heated by the calorific value of the gas hydrate. Slurry column (10) is a gas hydrate is generated from the bottom to move to the upper (Slurry column) 10, Sea water / gas mixing device for generating a sea water / gas mixture slurry is installed in the bottom of the slurry column to the sea water and gas ( 20), a gas saturation device 30 for saturating gas into seawater and injecting it into the seawater / gas mixing device, and a heat exchanger 40 for decomposition or dissociation of gas hydrate flowing from the slurry column into gas and water. ), And a gas-liquid separation tank 50 for separating gas and water dissociated from the heat exchanger. do.

In the system of the present invention, the seawater is heated by the heat generated during the generation of gas hydrate while the seawater moves into the heat exchange seawater pipe 13, and the heated seawater passes through the heat exchanger 40, and the amount of heat required for dissociation of the gas hydrate. To supply.

In the slurry column 10 of the present invention, a dividing apparatus 11 is installed. The dividing apparatus divides the concentrated seawater stepwise by a plurality of dividing members 111 to 115, and blocks the dividing dividing member 113 in the middle. Characterized in that more than one is installed.

The gas separated in the gas-liquid separation tank 50 is collected by the gas collector 60, and the collected gas is circulated in the system of the present invention to produce gas hydrate.

In the desalination method of the seawater according to the present invention, the seawater passing through the heat exchanger 40 is saturated with gas by the gas saturation device 30, and the gas saturated seawater and the gas separate from the seawater / gas mixing device 20. To form a seawater / gas mixture at the bottom of the slurry column, the seawater / gas mixture is moved to the top, and the concentrated seawater is phased by the sorting device 11, and the fresh water produced at the top of the slurry column is The gas hydrate is supplied to wash the gas hydrate, and the washed gas hydrate flows into the heat exchanger 40 to dissociate into gas and water by the heated sea water, and the dissociated gas and water are separated from the gas-liquid separation tank 50. It consists of steps.

The desalination method of the present invention further includes the step of collecting the gas separated in the gas-liquid separation tank 50 by the gas collector 60 and circulating the collected gas to the system of the present invention to generate gas hydrate. do.

In addition, the step of adjusting the pressure in the sea water / gas mixing device 20 further includes collecting and circulating the gas discharged from the mixing device in the gas collector (60).

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

Detailed Description of the Invention

The present invention relates to a method and system for desalination of seawater by mixing gas with seawater to produce gas hydrates and then separating the liquid water and the gaseous gas.

1 is a schematic block diagram showing a system for desalination of seawater by producing gas hydrate according to the present invention.

The desalination process of seawater according to the invention is carried out in a slurry column 10 installed vertically as shown in FIG. Capacity such as diameter or height of the slurry column can be determined according to the treatment capacity of the seawater, which can be easily carried out by those skilled in the art.

First, the seawater to be treated is saturated with a gas by the gas saturation device 30, and then supplied to the seawater / gas mixing device 20 installed under the slurry column. The seawater flowing into the gas saturation device may maintain the appropriate temperature as the seawater passing through the heat exchanger 40. The gas entering the gas saturator is used in the system of the present invention to circulate the collected gas. The gas flowing into the gas saturator is supplied to the gas collector 60 by the compressor 61 through the pipes 31 and 32 and regulated by the valve 33. 6 is a schematic cross-sectional view showing the structure of the gas saturation device.

The gas saturated seawater generated by the gas saturation device 30 and a separate gas are introduced into the seawater / gas mixing device 20 and mixed. The seawater / gas mixing device 20 may be partially introduced into the fresh water containing a small amount of salt treated in the system of the present invention through the pipe 51. In addition, a valve 22 may be installed to adjust the pressure in the seawater / gas mixing device 20, and the gas discharged through the valve is collected and reused through the pipe 21 to the gas collector 60. The seawater / gas mixing device may be preferably a venturi mixer, an eductor, an ejector, a static mixer, or the like, which mixes gas and liquid into a slurry state. At the top of this mixing device, a gas hydrate slurry is produced. The region 23 in which the gas hydrate slurry is produced is shown schematically in FIG. In this region 23, seawater and gas begin to form gas hydrates, forming a turbulent flow with strong mixing. 7 is a schematic cross-sectional view showing the structure of the seawater / gas mixing device.

Gas used to generate gas hydrate in the present invention may be a gas such as carbon dioxide, including hydrocarbon gas such as methane, propane and the like. Gases for forming gas hydrates or clathrates can be readily carried out by those skilled in the art.

Gases used to generate gas hydrates are known to be gaseous under at least 100 types of atmospheric conditions, and are known to have different crystal structures depending on the type of gas. In addition, depending on the type of gas, the temperature and pressure conditions under which the gas hydrate is formed vary, and thus, both the forming material and the energy balance are different. CH ₄ , C ₂ H ₆ , C ₃ H ₈ , C ₄ H ₁₀ , O ₂ , H ₂ , N ₂ , CO ₂ , H ₂ S, Cl ₂ , CH ₃ Cl, C ₃ H ₆ , CH ₃ CCl ₂ There are various kinds of gas hydrate formers such as F, CH ₃ CClF ₂ , CH ₃ CHF ₂ , CHClF ₂ , CH ₂ ClF, SF ₆ , CF ₄ , LNG and the like. Among these forming gases, if there are no environmental problems, no toxicity, no flammability, are safe at atmospheric conditions, inexpensive, the operating temperature and pressure are appropriate, and finally there is no problem in the selection of the material in contact with the gas. desirable. Most gases, however, did not meet one or two of these selection criteria.

In addition, the crystal structure of the gas hydrate is different depending on the type of the gas forming agent. When the diameter of the former gas molecule is small, a gas hydrate of structure-I is formed, and a larger gas hydrate is formed of structure-II, structure-H, or the like as the molecule becomes larger. CO ₂ , H ₂ S, CH _4, etc. are in structure-I form, R141b (Dichloromonofluoroethane, CCl ₂ FCH ₃ ) is in structure-II form, and propane forms a structure-II form hydrate. Therefore, depending on the structure and size of the hydrate is formed, the method of washing, the separation method from the concentrated salt water, etc. are all different. Gas hydrates that are too small are quite difficult to clean and separate from seawater and have a relatively high salt concentration of pure water obtained. The best gas hydrate size for subsequent work is 250-400 μm.

In addition, depending on the type of forming agent gas used, the density of the gas hydrate is lower than that of seawater, which has a positive buoyancy and the gas hydrate moves upwards. In each case, the subsequent devices and operations for obtaining pure water are also different. A typical case there is a CH ₄ and CO _2, in the case of CH ₄ rises continuously up to the amount by which the density of the gas hydrates is lower than sea water buoyant, in the case of CO _2, the density of the gas hydrate is higher than sea water gas hydrate is below the sea water Sink.

In the present invention, LNG, LPG, R141b, H ₂ S or CO ₂ is used as the forming gas. The reason these gases are used is because, firstly, LNG and LPG are the most commonly obtained around us, and R141b has the fewest drawbacks except that it has ozone depletion index as the forming gas. ₂ or H ₂ S is because the purpose of removing CO ₂ and H ₂ S at the same time affecting the environment and the purpose of desalination.

Inside the slurry column, a dividing device 11 for classifying the concentrated seawater contained in the seawater is provided in stages, and the seawater pipe 13 for heat exchange having a coil structure is heated so that the seawater is heated by the calorific value of the gas hydrate. Is installed on. Gas hydrate formation is an exothermic reaction that raises the internal temperature of the slurry column. Accordingly, a seawater pipe 13 having a coil structure along the inner wall of the slurry column is provided to exchange heat between the seawater flowing through the slurry and the gas hydrate slurry. That is, the seawater to be treated is introduced into the heat exchange seawater pipe 13 through the pipe 14 and heated, and then flows into the heat exchanger 40 for dissociation of the gas hydrate through the pipe 15.

A fractionation apparatus 11 is installed inside the slurry column to classify the concentrated seawater contained in the seawater step by step. FIG. 2 is a schematic perspective view of the fractionation apparatus installed in the slurry column of FIG. 1, and FIG. 3 is a schematic diagram for showing a state where the fractionation apparatus is installed in the slurry column.

In the sorting apparatus 11 of the present invention, two or more sorting members 111 to 115 are installed at two or more support members 118 and 119 at regular intervals, so that the concentrated seawater is classified step by step. ) Is installed at least one. Each sorting member has a top and bottom penetrating shape and a fan-shaped cone to move gas hydrate. The gas hydrate slurry produced by the seawater / gas mixer 20 is moved upwards to the slurry column by its buoyancy. As the gas hydrate slurry moves upward along the fractionator 11, concentrated seawater is collected downward along the sides of each fractionation member. For example, concentrated seawater collected downward in FIG. 1 along the sorting members 114 and 115 is discharged through the pipe 16. The sorting member 113 is a blocking sorting member that serves to block the concentrated seawater from falling further. Therefore, the concentrated seawater collected downward along the fractionation members 111, 112, 113 is discharged through the pipe 17. If the length of the slurry column is longer, more sorting members should be installed, and blocking sorting members may be further installed at regular intervals.

In the upper part of the slurry column, fresh water produced in the system of the present invention is introduced into the pipe 52 to wash the gas hydrate which is supported upward.

The gas hydrate lifted through the fractionation device 11 is introduced into the heat exchanger 40 through the rotary valve 12. Instead of a rotary valve a slide valve may be applied. 5 is a schematic perspective view of a rotary valve installed on top of a slurry column. This rotary valve is designed to be operated in consideration of the safety of the slurry column, and the overflowed slurry in an emergency is designed to be discharged through the pipe 18.

In the heat exchanger 40, gas hydrates are decomposed or dissociated to separate water and gas particles from each other. 4 is a schematic perspective view showing one embodiment of a heat exchanger used in the desalination system of the present invention. As shown in FIG. 4, the heat exchanger 40 has a conical structure extending from the bottom to the top, and a plurality of holes 44 are formed from the bottom to the top so that the gas hydrate can move. A plurality of holes 45 are formed at regular intervals in the horizontal direction so that the sea water can move. Since the dissociation process of the gas hydrate is an endothermic reaction, heat dissipation is performed by passing the seawater heated in the slurry column. As such, in the present invention, since the heat generated in the slurry generation process is used in the dissociation process of the gas hydrate, it can be said that the system can reduce the energy cost. The vertical hole 44 is designed such that the upper portion 44a has a larger diameter than the lower portion 44b so that the gas hydrate is easily dissociated while moving. On the other hand, the horizontal hole 45 is designed to have a constant diameter because the sea water flows. The heat exchanger used in the present invention is not limited to that shown in FIG. 4, and the gas hydrate is dissociated into water and gas particles as the gas hydrate moves in the vertical direction, and at the same time, if the heat exchange is performed for the endothermic reaction, the heat exchanger has a different structure. Both heat exchangers can be used.

The gas and water dissociated from the heat exchanger are transferred to the gas-liquid separation tank 50 and separated into fresh water and gas. Fresh water is discharged through the pipe 53 and gas is collected by the valve 54 to the gas collector 60.

In the desalination method of the seawater according to the present invention, the seawater passing through the heat exchanger 40 is saturated with gas by the gas saturation device 30, and the gas saturated seawater and the gas separate from the seawater / gas mixing device 20. To form a seawater / gas mixture at the bottom of the slurry column, the seawater / gas mixture is moved to the top, and the concentrated seawater is phased by the sorting device 11, and the fresh water produced at the top of the slurry column is The gas hydrate is supplied to wash the gas hydrate, and the washed gas hydrate flows into the heat exchanger 40 to dissociate into gas and water by the heated sea water, and the dissociated gas and water are separated from the gas-liquid separation tank 50. It consists of steps.

The desalination method of the present invention further includes the step of collecting the gas separated in the gas-liquid separation tank 50 by the gas collector 60 and circulating the collected gas to the system of the present invention to produce gas hydrate. .

In addition, the step of adjusting the pressure in the sea water / gas mixing device 20 further includes collecting and circulating the gas discharged from the mixing device in the gas collector (60).

The desalination method and system of the present invention can of course be applied to desalination of seawater, but can also be applied almost intact to purification of contaminated water.

The invention can be better understood by the following examples, which are intended for the purpose of illustration of the invention and are not intended to limit the scope of protection defined by the appended claims.

Example 1

In Example 1, gas hydrate was produced using propane gas. 8 is a view showing a material resin according to the present embodiment for generating and desalination of gas hydrate of seawater using propane gas. A 3.5 wt% NaCl solution was prepared at 4 ° C. and injected at a rate of 100 kg / hr. Propane gas was initially injected at 15 kg / hr, recycled and used continuously. The gas hydrate mixer was operated at 6 kg / cm ² g and propane gas formed gas hydrates of structure-II and the gas hydrates had a negative buoyancy due to their density higher than that of seawater and settled down. In this case, the gas-forming agent was excessively injected to artificially have positive buoyancy.

Example 2

In Example 2, gas hydrate was produced using methane gas. 9 is a view showing a material resin according to the present embodiment for generating and desalination of gas hydrate of seawater using methane gas. A 3.5 wt% NaCl solution was prepared at 4 ° C. and injected at a rate of 100 kg / hr. Methane gas was initially injected at 12 kg / hr, recycled and used continuously. The gas hydrate mixer was operated at 40 kg / cm ² g and methane gas formed gas hydrates of structure-I and the gas hydrates rose up with positive buoyancy because their density was lower than that of seawater. There was no reason to inject excess gas formers in this case.

Example 3

In Example 3, carbon dioxide was used to produce gas hydrate. FIG. 10 is a view showing a material resin according to an embodiment of the present invention in which gas hydrate of seawater is generated and desalted using carbon dioxide. A 3.5 wt% NaCl solution was prepared at 4 ° C. and injected at a rate of 100 kg / hr. Carbon dioxide gas was initially injected at 33 kg / hr, recycled and used continuously. The gas hydrate manufacturing apparatus was operated at 25 kg / cm ² g, and the carbon dioxide gas formed gas hydrates of structure-I, and the gas hydrates had a negative buoyancy due to their density higher than that of the seawater and settled down. In this case, the gas-forming agent was excessively injected to artificially have positive buoyancy.

According to the present invention, in a method of desalination of seawater through a gas hydrate process, components such as salt or contaminants can be efficiently separated from a slurry column in which a mixture of seawater and gas is formed, and heat generated during gas hydrate generation The invention has the effect of providing a new desalination system and method which can be recovered and recycled in a gas / liquid separation process.

Simple modifications and variations of the present invention can be readily used by those skilled in the art, and all such variations or modifications can be considered to be included within the scope of the present invention.

Claims (9)

A sorting device 11 for classifying the components contained in the seawater in stages is installed therein and a heat exchange seawater pipe 13 having a coil structure is installed on the inner wall so that the seawater is heated by the calorific value of the gas hydrate, A slurry column 10 in which hydrate is produced and moved upwards; A seawater / gas mixing device 20 installed at a lower portion of the slurry column to generate seawater / gas mixed slurry by introducing seawater and gas; A gas saturation device (30) for saturating gas in seawater and injecting it into the seawater / gas mixing device; A heat exchanger 40 for dissociating the gas hydrate flowing from the slurry column into gas and water; And A gas-liquid separation tank 50 for separating gas and water dissociated from the heat exchanger; Desalination system of seawater, characterized in that consisting of. The desalination system of seawater according to claim 1, further comprising a gas collector (60) for collecting the gas separated from the gas-liquid separation tank (50). According to claim 1, wherein the sorting device 11 is provided with two or more sorting members 111 to 115 at regular intervals on two or more support members 118 and 119, the concentrated seawater is classified step by step, intercepted in the middle Seawater desalination system, characterized in that one or more classification member 113 is installed. 2. The desalination system of seawater according to claim 1, further comprising a rotary valve (12) for opening and closing the movement of the gas hydrate lifted through the sorting device (11). According to claim 1, wherein the heat exchanger 40 has a conical structure that extends from the bottom to the top, a plurality of holes 44 are formed from the bottom to the top to move the gas hydrate, seawater for heat exchange A plurality of holes 45 are formed at regular intervals in the horizontal direction so as to be movable, and the holes 44 in the vertical direction have an upper portion 44a having a larger diameter than the lower portion 44b. . Seawater passing through the heat exchanger 40 is saturated with gas by the gas saturation device 30; A gas separate from the gas saturated sea water is introduced into the sea water / gas mixing device 20 to form a sea water / gas mixture at the bottom of the slurry column; Concentrated seawater is phased by the sorting device (11) while the seawater / gas mixture is moved upwards; Supplying fresh water produced at the top of the slurry column to wash gas hydrate; The washed gas hydrate is introduced into a heat exchanger (40) to dissociate into gas and water by the heated seawater; And Separating the dissociated gas and water in a gas-liquid separation tank (50); Desalination method of seawater, characterized in that consisting of steps. The method of claim 6, further comprising the step of collecting the gas separated in the gas-liquid separation tank 50 by the gas collector 60, the collected gas is circulated in the system of the present invention to produce gas hydrate. Desalination method of sea water, characterized in that. 7. The desalination of seawater according to claim 6, further comprising adjusting the pressure in the seawater / gas mixing device 20 to collect and circulate the gas discharged from the mixing device in the gas collector 60. Way. The method of claim 6, wherein the gas generating the gas hydrate is CH ₄ , C ₂ H ₆ , C ₃ H ₈ , C ₄ H ₁₀ , O ₂ , H ₂ , N ₂ , CO ₂ , H ₂ S, Cl ₂ , CH ₃ Cl, C ₃ H ₆ , CH ₃ CCl ₂ F, CH ₃ CClF ₂ , CH ₃ CHF ₂ , CHClF ₂ , CH ₂ ClF, SF ₆ , CF ₄ , or LNG desalination Way.

Images