KR101330131B1 - composite desalination device - Google Patents

Abstract

The present invention increases the energy efficiency of the decontamination desalination apparatus by recovering the pressure energy applied to the membrane filtration unit and supplying it to the thermal energy of the evaporation and concentrating unit, and improves the desalination performance by the sequential process of the membrane method and the evaporation method. The present invention relates to a complex desalination desalination apparatus, comprising: a raw water supply unit for supplying pressurized raw water; A membrane filtration unit for separating the raw water supplied from the raw water supply unit into the filtered filtered water and the non-permeable primary concentrated water through the separation membrane; An HST having a turbine which is rotated using the primary concentrated water discharged from the membrane filtration unit; And an evaporation condenser for evaporating the first condensate passing through the HST to separate the condensed condensate and the concentrated second condensate, wherein the vapor outlet of the evaporation concentrator is connected to the vapor compressor of the HST. In the turbine, the rotational force of the turbine is transmitted to the steam compressor to pressurize the steam discharged from the steam outlet to adiabatic compression characterized in that it is supplied to the steam inlet of the evaporative condensation unit.

Description

Composite desalination device

The present invention relates to a complex freshwater decontamination apparatus, and more particularly, by recovering the pressure energy applied to the membrane filtration unit and supplying it to the thermal energy of the evaporation and concentrating unit to increase the energy efficiency of the decontamination desalination system, The present invention relates to a complex desalination system capable of improving desalination performance by a sequential process of evaporation.

Currently known seawater desalination methods are generally known as evaporation, membrane, electrochemical, and the like. The evaporation method uses the principle of evaporating seawater to evaporate the solvent water and retaining the solute. The separation membrane method removes the ionic substances dissolved in water and removes the ionic substances dissolved in water. The material is filtered and the electrochemical method is to alternately arrange the anion membrane and the cationic membrane, and then apply DC voltage to the electrodes located at both ends of the anion membrane and the cationic membrane to remove the cations and anions to obtain pure fresh water.

Desalination can be selected or combined with the optimal technology considering the area (demand) characteristics (economics) according to the fresh water capacity and salt conditions (concentration, composition, impurity type, etc.) in the water. The desalination characteristics of each technique are very important among the freshwater capacity and salinity conditions, which are the basic consideration items for the combination.

For example, ED (Electro Dialysis) and RO (Reverse Osmosis) are suitable for brackish water of less than about 3,500 ppm with low salt concentrations. In particular, although RO is less economical, 35,000 ppm of seawater desalination can be applied, and the average recovery rate (production fresh water / water input) is about 30%, and brine is less than 55,000 ppm. . Therefore, the method using most membranes is suitable for low concentration seawater desalination.

In addition, the evaporation method is advantageous for large-scale desalination and high concentration range, and the recovery rate is up to 90%. Concentrated brine ranges from 100,000 to 200,000 ppm, or 10-20 wt.%.

However, the higher the concentration range, the lower the economic feasibility due to the salt corrosion of the apparatus, the boiling point rising of the solution (BPR), and the boiling point increases and the vapor pressure decreases as the concentration of the solute increases.

Therefore, most of the freshwater is operated within 15wt.%. That is, when the target product is fresh water, only fresh water is taken out, and the brine concentrated in salt is discharged to the sea again. However, in this case, salt shock is generated by supplying a large amount of salt to the sea ecosystem, so if additional fresh minerals are produced from the brine remaining from the concentrated brine, high value-added by-products can be obtained. to be.

However, when operating an undischarged seawater desalination and decontamination system that produces salt (mineral) at the same time as desalination and does not release the concentrated seawater back to the sea, the time and cost for subsequent drying must be concentrated to a concentration of 15-25 wt.%. , Space can be saved. In particular, as the concern for environmental pollution of the sea has increased recently, the zero discharge system has begun to be reviewed to solve the environmental problem of ecosystem disturbance when water with a slight salt concentration is introduced into the seawater.

In particular, MVR (Mechanical Vapor Recompression) is mechanically compressed and reused as its own heating source without condensing the low temperature latent heat generated in the evaporation tube to minimize energy consumption. The simple structure makes it easy to operate and maintains the advantages of the conventional evaporation method with little maintenance cost. In particular, MVR is one of the technologies that are attracting attention in the desalination apparatus because energy consumption of small and medium-sized scale of 5,000 tons or less is only 1/15 ~ 1/25 compared to the conventional evaporation method. For the method of manufacturing salt using such MVR, Korean Patent Application No. 10-2000-0027775 (Seawater desalination and high concentration brine simultaneous production apparatus), and Korean Patent Application No. 10-2008-0076260 ( Method of producing mineral salts containing minerals separated from deep sea water) and Korean Patent Application No. 10-2008-0076259 (Method of preparing mineral water and mineral salts containing minerals separated from deep sea water).

However, the MVR seawater desalination apparatus is limited in capacity and concentration range (recovery rate) due to technical limitations of the MVR, unlike the similar multi-stage flash distillation (MSF) or multi-effect distillation (MED).

More specifically, the original meaning of MVR, that is, to recompress the self-vapour as a heat source (mechanical auto-Vapor (or self-Vapor) Recompression) because it is different from the MSF or MED that uses boiler steam Otherwise, it is greatly affected by the temperature rise of the compressor or the boiling point of the concentrate.

In other words, it is economical to concentrate 3.5wt% (seawater concentration) to 10-12wt.% With a suitable temperature range of 7-8 ° C., which can be achieved through a single-stage compressor or a blower with economical efficiency. Therefore, it can be said that the concentration of up to 20-25wt.% When salt starts to precipitate from seawater is practically impossible by MVR method. Especially, in case of brine (concentrated water) of 20-21%, its boiling point increases to 4-5 ℃, so it is almost impossible to operate with the heat transfer temperature difference of about 3 ℃ minus 7-8 ℃ for MVR. . Therefore, in order to proceed to decontamination, a large amount of water must be evaporated in order to form salt with concentrated water in the MVR. Therefore, it is necessary to consume energy that is large enough to boil sea water to obtain salt. Using 0076260 and Korean Patent Application No. 10-2008-0076259, it is impossible to plant a device for producing fresh water and salt.

Even if an expensive device is designed / manufactured by this temperature difference, there is no practical installation since the corrosion and scaling of the device is severe at high salt concentrations and temperatures. In order to prevent this, when the vacuum evaporation method of about 60 ° C. is introduced, the specific volume of steam due to low pressure evaporation increases greatly, thereby increasing the power of the compressor, and preventing the inflow of external air due to the vacuum operation and controlling device costs against system instability. The back is greatly increased.

The object of the present invention devised to solve the above problems is to increase the energy efficiency of the decontamination desalination apparatus by recovering the pressure energy applied to the membrane filtration unit and supplying it to the thermal energy of the evaporation and concentration unit, and at the same time, An object of the present invention is to provide a complex desalination apparatus capable of improving desalination performance by a sequential process of evaporation.

The present invention for achieving the above object, the raw water supply unit for supplying pressurized raw water; A membrane filtration unit for separating the raw water supplied from the raw water supply unit into the filtered filtered water and the non-permeable primary concentrated water through the separation membrane; A hydraulic steam turbocharger (HST) consisting of a hydraulic turbine rotated by using the primary condensate discharged from the membrane filter unit and a steam compressor connected thereto; And an evaporation condenser for evaporating the primary condensed water passing through the hydraulic turbine to the condensed fresh water and the second condensed water whose salt concentration is further increased, wherein the vapor outlet of the evaporative condenser is the steam compressor of the HST. And the rotational force of the turbine is transmitted to the steam compressor, pressurizes the steam discharged from the steam outlet, and adiabatic compresses the steam discharged from the steam outlet to supply the steam to the vapor inlet of the evaporative concentration unit.

The steam inlet is connected to the steam inlet, it characterized in that the steam is supplied as a heat source for the initial evaporation from the outside.

The heat exchanger for preheating the primary concentrated water may be installed in the secondary concentrated water discharge pipe of the evaporative concentration part or the condensed freshwater discharge pipe of the evaporative concentration part.

In addition, the steam is characterized in that it is supplied only at the start of the decontamination desalination device.

Through the present invention, the pressure energy applied to the membrane filtration unit is recovered and supplied to the heat energy of the evaporation and concentrating unit to increase the energy efficiency of the decontamination desalination system, and the desalination performance by the sequential process of the membrane method and the evaporation method. Can improve.

1 is a schematic diagram of a complex freshwater desalination device according to an embodiment of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described with reference to the accompanying drawings. In the following description, well-known functions or constructions are not described in detail since they would unnecessarily obscure the gist of the present invention.

In FIG. 1, reference numeral 100 denotes a complex freshwater desalination device according to an embodiment of the present invention.

The composite freshwater desalination device 100 includes a raw water supply unit for pressurizing and supplying raw water, and a membrane filtration unit 106 for separating raw water supplied from the raw water supply unit into filtered water and non-permeable primary concentrated water through a separation membrane. , HST 126 having a hydraulic turbine 120 rotated using the primary high pressure concentrated water discharged from the membrane filtration unit 106, and the primary concentrated water passing through the hydraulic turbine 120 The evaporation condensation unit 146 is separated by evaporation to condensed fresh water and the secondary concentrated water having a high salt concentration.

The evaporation concentrator 146 recompresses the self-evaporation steam using energy obtained from the HST 126 and is supplied to the self heating heat source.

Reverse membrane osmosis (RO) or MD (Membrane Distillation) may be applied to the separator filtration unit 106. RO is a process that obtains high purity fresh water by removing solutes dissolved in seawater using semi-permeable membrane and osmotic pressure. MD is a desalination technology combining membrane separation method and evaporation method. Pervaporation is performed using permeation and evaporation simultaneously.

Therefore, the raw water supplied to the membrane filtration unit 106 should have a sufficient pressure (60 to 80 bar) to be filtered, which is due to the raw water supply pump 102 installed in the raw water supply unit. A raw water pressure control valve 104 may be installed between the raw water supply pump 102 and the separator filtration unit 106 to adjust the pressure of the raw water.

Filtrate filtered through the membrane filtration unit 106 may be utilized as drinking water. In addition, the high-pressure primary concentrated water that is not permeated by the membrane filtration unit 106 is supplied to the power source of the hydraulic turbine 120 of the HST part 126 while maintaining the pressure provided by the raw water supply pump 102. do.

Accordingly, while the high pressure primary concentrate water passes through the turbine 120, the pressure energy possessed by the primary concentrate water is transferred to the turbine 120, and the primary concentrate water is decompressed to the evaporative concentration unit 146. Will be reached.

In order to control the flow rate of the high pressure primary concentrated water supplied to the turbine 120, a primary concentrated water flow control valve 108 is installed between the turbine 120 and the membrane filter 106. And, on the output side of the turbine 120, a turbine discharge water pressure control valve 122 for adjusting the pressure of the primary concentrated water passing through the turbine 120 is provided. A well-known needle valve may be used as the primary concentrate water flow control valve 108, and a well-known throttle valve may be used as the turbine discharge water pressure control valve 122.

The evaporation concentration unit 146 is disposed past the turbine discharge water pressure control valve 122. As the evaporation concentration unit 146, a known MD (Membrane Distillation) or a known evaporation method such as MSF, MED may be used.

Since the evaporation concentration unit 146 uses an evaporation phenomenon, heat energy should be supplied. In the present invention, as described above, using the electrical or mechanical energy obtained from the turbine 120 of the HST (126) heat energy to the steam compressor 124 connected to the turbine 120 through the connection portion 125 Can supply The connecting portion 125 connects the shaft of the steam compressor 124 to the shaft of the turbine 120 directly by a mechanical method (for example, using the same shaft or power transmission by an electric mechanism such as a gear) or the like. In addition, a method of operating electricity (not shown) by the turbine 120 to produce electricity and rotating the steam compressor 124 through the motor may be used.

The low pressure steam generated in the evaporative condenser 146 is introduced into the vapor compressor 124 of the HST 126, and the vapor compressor 124 pressurizes / heats up the vapor to condense the evaporative concentrator 146. Heat up to the temperature (for example, 60 ~ 100 ℃) required for evaporation of the low-pressure primary concentrated water introduced into. The steam pressurized / heated up in the steam compressor 124 is recycled back to its own heat exchanger remaining in the heating space of the evaporative concentrator 146 to transfer heat to the low pressure primary concentrated water introduced from the turbine 120. Condensation.

Therefore, water vapor evaporated from the evaporation concentrator 146 is condensed and discharged to the outside in the form of fresh water, and in the concentrated space, secondary concentrated water of high concentration is formed by continuous evaporation of water vapor. The high concentration of the secondary concentrated water thus formed is discharged to the outside for decontamination. The condensed freshwater is combined with the filtrate obtained from the membrane filtration unit 106 and stored in a freshwater storage tank or discharged in connection with an external water pipe network. The lower part of the filtration space and the enrichment space should be isolated so that the condensed water and the secondary concentrated water do not mix with each other.

Since the high concentration secondary concentrated water and the condensed water discharged from the evaporation concentration unit 146 are hot water each having a temperature close to a boiling point, the high concentration secondary concentration water discharge pipe of the evaporation concentration unit 146 or the evaporation concentration unit 146. The condensate discharge pipe of the heat exchanger (147, 148) may be equipped for preheating the low pressure primary concentrated water flowing into the turbine.

In addition, the evaporation concentration unit 146 must maintain a boiling point temperature in order to continuously evaporate the primary concentrated water, but at the first start-up, since the temperature of the evaporation concentration unit 146 is lower than the boiling point temperature, evaporation is possible. It is desirable to supply hot steam from the outside so as to quickly heat up to temperature. The supply amount of steam is controlled by the steam control valve 150 is installed in the steam supply pipe connected to the evaporative concentrator 146.

The recycling pipe and the steam supply pipe may be separately installed on the evaporation concentration unit 146 or may be integrally connected to the evaporation concentration unit 146.

The high concentration secondary concentrated water obtained by the secondary concentration by the membrane filtration unit 106 and the evaporation concentration unit 146 may obtain a salt concentration of 18 to 25 wt. However, when the raw water and the primary concentrated water are pretreated by a chemical for the purpose of preventing various fouling and scaling in the membrane filtration unit 106 or the evaporation concentration unit 146, the precipitated salt is used for industrial rather than edible. .

In particular, in the case of edible salt manufacturing, the concentrated water having a salt concentration of about 18 to 25 wt.% May contain a large amount of Mg component depending on the raw water, thereby having a bitter taste. Therefore, it is preferable to adjust and separate the Mg component to an appropriate amount, and the separation method may use a known selective adsorption separation method.

Then, when the separated concentrated brine is dried again using wind and solar heat, natural salt can be finally obtained. Therefore, since the concentrated water introduced into the salt field starts to precipitate salt, the size of the salt pond (Solar Pond) for producing salt can be greatly reduced. In particular, when using a solar greenhouse to install a greenhouse on the upper side of the salt field, it is possible to maximize the production of fresh water because it can collect fresh water by evaporation during the production of salt.

As described above, although described with reference to a preferred embodiment of the present invention, those skilled in the art various modifications and changes of the present invention without departing from the spirit and scope of the present invention described in the claims below I can understand that you can.

100: combined fresh water decontamination apparatus 102: raw water supply pump
104: raw water pressure control valve 106: membrane filter
108: primary concentrated water flow control valve 120: hydraulic turbine
122: turbine discharge water pressure control valve 124: steam compressor
125: connecting portion 126: HST
146: evaporation concentration section 147, 148: preheat exchanger
150: steam control valve

Claims (4)

Raw water supply unit for supplying the raw water by pressing;
A membrane filtration unit for separating the raw water supplied from the raw water supply unit into the filtered filtered water and the non-permeable primary concentrated water through the separation membrane;
An HST having a turbine which is rotated using the primary concentrated water discharged from the membrane filtration unit; And
It includes an evaporation concentration unit for evaporating the primary concentrated water passing through the HST to separate the condensed condensed water and the concentrated secondary concentrated water,
The steam outlet of the evaporative condenser is connected to the steam compressor of the HST, and in the HST, the rotational force of the turbine is transmitted to the steam compressor to pressurize the steam discharged from the steam outlet to insulate and compress the steam to the vapor inlet of the evaporative condenser. Decontamination desalination device characterized in that the supply.
The decontamination desalination device according to claim 1, wherein the steam inlet is connected to a steam supply unit so that steam is supplied as a heat source for evaporation from the outside.
The decontamination desalination apparatus according to claim 1, wherein a heat exchanger is installed in the secondary concentrated water discharge pipe of the evaporative concentration part or the filtrate discharge pipe of the evaporative concentration part.
The desalination desalination apparatus according to claim 2, wherein the steam is supplied only at the start of the decontamination desalination apparatus.

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