KR102203652B1 - Air gap membrane distillation apparatus and controlling method thereof - Google Patents

Abstract

The present invention, with a raw water tank; A membrane distillation module for separating steam from the raw water supplied from the raw water tank and condensing it in an air gap provided therein; A production water tank for storing production water produced from the membrane distillation module; And a vacuum pump connected to the air gap portion of the membrane distillation module and applying a vacuum pressure to the air gap portion, and a control method thereof.

Description

TECHNICAL FIELD [0001] Air gap membrane distillation apparatus and controlling method thereof

The present invention relates to an air gap type membrane distillation water treatment apparatus for producing filtered water by condensing vapor in an air gap between raw water and cooling water, and a control method thereof.

The membrane distillation process is a water treatment process in which pollutants are removed from raw water by using a porous separator having a hydrophobic surface. In this membrane distillation process, high-temperature raw water and low-temperature cooling water are located on both sides of the separator, and at this time, a phase change occurs on the surface of the raw water side separator due to the difference in vapor pressure caused by the temperature difference between the raw water and the cooling water. The pure vapor from which contaminants have been removed is permeated through the fine pores of the separator and condensed by the cooling water.

Since the separation membrane used in the membrane distillation process has high hydrophobicity, raw water and cooling water do not permeate into the micropores of the separation membrane due to high surface tension.

Membrane distillation methods used in the membrane distillation process include Direct Contact Membrane Distillation (DCMD), Air Gap Membrane Distillation; AGMD), Sweep Gas Membrane Distillation (SGMD), and Vacuum Membrane Distillation (VMD).

Among these methods, the air gap-type membrane distillation method is a method of obtaining filtered water by condensing steam inside the gap by placing an air gap between the raw water and the cooling water, thereby increasing thermal efficiency compared to other methods, and has a simple device configuration. . However, due to the air gap, the difference in vapor pressure, which is the driving force, is reduced, and thus the filtration flux is low. Since such a low filtration flux causes an increase in facility cost and site area, there is a demand for technology development capable of improving filtration flux.

Japanese Laid-Open Patent Publication No. 1997-024249 (1997.01.28)

The present invention has been devised in view of the above, and provides an air gap membrane distillation water treatment device and a control method thereof having a configuration capable of improving filtration flux compared to the existing technology in a water treatment device using the air gap membrane distillation method. Making it a technical task.

According to an embodiment of the present invention, a raw water tank; A membrane distillation module for separating steam from the raw water supplied from the raw water tank and condensing it in an air gap provided therein; A production water tank for storing production water produced from the membrane distillation module; And a vacuum pump connected to the air gap of the membrane distillation module and applying a vacuum pressure to the air gap.

In addition, the membrane distillation module, provided on one side of the air gap, a low-temperature portion to which the low-temperature raw water supplied from the raw water tank is supplied; A high-temperature portion for heating the raw water discharged from the low-temperature portion and introducing it, and generating a vapor pressure difference due to a temperature difference with the low-temperature portion; And a separation membrane provided between the high temperature portion and the air gap portion, and separating and permeating only the vapor separated from the raw water of the high temperature portion.

In addition, the air gap type membrane distillation water treatment apparatus includes: a raw water supply passage connecting the raw water tank and a low temperature portion of the membrane distillation module to supply raw water to the membrane distillation module; A connection passage connecting the low temperature part and the high temperature part so that raw water from the low temperature part of the membrane distillation module is supplied to the high temperature part; And a raw water circulation passage for circulating the raw water discharged from the high temperature portion to the raw water tank.

In addition, the air gap type membrane distillation water treatment apparatus, the cooler is installed in the raw water supply flow path, cooling the raw water from the raw water tank; And a heater installed in the connection passage and heating raw water from the low temperature portion of the membrane distillation module.

In addition, a raw water circulation pump may be installed in at least one of the raw water supply passage and the raw water circulation passage.

In addition, the air gap type membrane distillation water treatment apparatus may further include a chemical cleaning unit for chemically cleaning the separation membrane by supplying a chemical cleaning solution to the raw water supply passage by receiving a part of the product water from the production water tank. .

In addition, the vacuum pump may be connected to a product water discharge passage connecting between the air gap of the membrane distillation module and the product water tank.

In addition, the air gap type membrane distillation water treatment apparatus may include a plurality of temperature sensors for sensing a temperature of the front and rear ends of the membrane distillation module; And a control unit controlling the vacuum pressure of the vacuum pump so that the filtration flux of the membrane distillation module is kept constant based on the sensing value of the temperature sensor.

In addition, the control unit may calculate a vacuum pressure for maintaining the filtration flux at a preset operation setting value using the permeation constant of the separation membrane calculated through the sensing value of the temperature sensor.

In addition, the control unit may be configured to operate the chemical cleaning mode when the vacuum pressure reaches a preset limit value.

On the other hand, according to another embodiment of the present invention, the step of setting an operation setting value of the filtration flux of the membrane distillation module; Calculating a vacuum pressure for generating the filtration flux at the operation set value, and operating the vacuum pump so that the vacuum pressure is applied to the air gap; Measuring the temperature at the front and rear ends of the membrane distillation module; And controlling the operation of the vacuum pump so that the filtration flux maintains an operation set value using the measured temperature at the front and rear ends of the membrane distillation module. There is provided a control method of an air gap type membrane distillation water treatment apparatus comprising a.

In addition, controlling the operation of the vacuum pump may include calculating a current filtration flux by using the measured temperature at the front and rear ends of the membrane distillation module; Calculating an error rate between the calculated value of the filtration flux and an operation set value; Calculating a permeation constant of the separation membrane when the error rate reaches a set threshold value; Recalculating the vacuum pressure for maintaining the operating set point of the filtration flux using the calculated permeation constant; And adjusting the vacuum pressure of the vacuum pump so that the recalculated vacuum pressure is applied to the air gap.

In addition, the control method of the air gap type membrane distillation water treatment apparatus includes: checking whether the recalculated vacuum pressure reaches a preset limit value; And stopping the operation of the vacuum pump and operating a chemical cleaning mode according to the confirmation result.

According to an embodiment of the present invention, by installing a vacuum pump for applying a vacuum pressure to the air gap portion of the membrane distillation module, there is an effect of improving the filtration flux of the membrane distillation module.

In addition, there is an advantage that constant flow rate operation is possible even if membrane contamination occurs by adjusting the vacuum pressure so that the filtration flux can be kept constant at the initially set operation setting value.

In addition, when the vacuum pressure limit value of the vacuum pump is reached, the operation is stopped and the separation membrane is chemically cleaned, thereby extending the life of the separation membrane and producing filtered water of stable water quality.

1 is a view schematically showing the configuration of an air gap type membrane distillation water treatment apparatus according to an embodiment of the present invention.
Figure 2 is a block diagram of the air gap type membrane distillation water treatment apparatus shown in Figure 1;
3 is a flow chart showing a control method of the air gap type membrane distillation water treatment apparatus according to an embodiment of the present invention.

Since the present invention can apply various transformations and have various embodiments, specific embodiments are illustrated in the drawings and will be described in detail in the detailed description. However, this is not intended to limit the present invention to a specific embodiment, it is to be understood to include all conversions, equivalents, and substitutes included in the spirit and scope of the present invention. In describing the present invention, when it is determined that a detailed description of a related known technology may obscure the subject matter of the present invention, a detailed description thereof will be omitted.

Terms such as first and second may be used to describe various components, but the components should not be limited by the terms. These terms are used only for the purpose of distinguishing one component from another component.

The terms used in the present application are used only to describe specific embodiments, and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates otherwise. In the present application, terms such as "comprises" or "have" are intended to designate the presence of features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, but one or more other features. It is to be understood that the presence or addition of elements or numbers, steps, actions, components, parts, or combinations thereof, does not preclude in advance.

Hereinafter, an embodiment of an air gap type membrane distillation water treatment apparatus and a control method thereof according to the present invention will be described in detail with reference to the accompanying drawings. In the description with reference to the accompanying drawings, the same or corresponding components are the same. Reference numerals are assigned and redundant descriptions thereof will be omitted.

1 is a diagram schematically showing the configuration of an air gap type membrane distillation water treatment apparatus according to an embodiment of the present invention, and FIG. 2 is a block diagram of the air gap type membrane distillation water treatment apparatus shown in FIG. 1.

1 and 2, the air gap type membrane distillation water treatment apparatus according to the present embodiment includes a raw water tank 10, a membrane distillation module 20, a production water tank 30, and a vacuum pump 40.

The raw water tank 10 functions to receive raw water to be treated, and is configured to receive raw water from the outside.

The membrane distillation module 20 separates steam from the raw water supplied from the raw water tank 10 and condenses it in the air gap 24 provided therein. The membrane distillation module 20 may be connected to the raw water tank 10 by the raw water supply passage 1. A cooler 50 for cooling the raw water from the raw water tank 10 to a set temperature may be provided on the raw water supply passage 1. As the cooler 50, it is possible to apply various types of coolers such as a heat exchanger and a tubular cooler.

The membrane distillation module 20 includes a low temperature section 21, a high temperature section 22, and a separation membrane 23.

The low temperature part 21 is provided on one side of the air gap part 24, and low temperature raw water is supplied through the raw water supply passage 1. The raw water supply flow path 1 connects the raw water tank 10 and the low temperature part 21 of the membrane distillation module 20 so that raw water is supplied to the membrane distillation module 20.

The high temperature part 22 is fed by heating the raw water discharged from the low temperature part 22, and generates a vapor pressure difference due to the temperature difference with the low temperature part 22. A connection flow path 2 is provided between the low temperature part 21 and the high temperature part 22 of the membrane distillation module 20, and the raw water from the low temperature part 21 is supplied to the high temperature part 22 through the connection flow path 2 do.

A heater 70 for heating the raw water from the low temperature part 21 may be provided on the connection flow path 2. Like the cooler 60, the heater 70 may also have various forms such as a heat exchanger and a tubular heater, and waste heat, solar heat, or the like may be used as an energy source.

The separation membrane 23 is a porous membrane having a hydrophobic surface, and is provided between the high temperature portion 22 and the air gap portion 24. The separation membrane 23 separates and permeates only the vapor separated from raw water. Due to the difference in vapor pressure generated by the temperature difference between the high temperature part 22 and the low temperature part 21, a phase change occurs on the surface of the separator 23, so that only pure vapor passes through the micropores of the separator 23, and the air gap 24 ) And condensate.

The raw water circulation flow path 3 is connected between the high temperature part 22 of the membrane distillation module 20 and the raw water tank 10, and the raw water discharged from the high temperature part 22 through the raw water circulation flow path 3 is the raw water tank 10 ) Can be cycled. At least one of the raw water supply passage 1 and the raw water circulation passage 3 may be provided with a circulation pump 50 for generating a driving force for raw water circulation, and in this embodiment, the circulation pump 50 is the raw water supply passage ( 1) is an example of the installed configuration.

The product water tank 30 functions to store the product water produced from the membrane distillation module 20, and an air gap to receive condensed product water from the air gap 24 of the membrane distillation module 20 It is connected with (24). Between the product water tank 30 and the air gap 24 may be connected by a product water discharge passage 4.

The vacuum pump 40 is connected to the air gap 24 of the membrane distillation module 20 and applies a vacuum pressure to the air gap 24. The vacuum pump 40 may be connected to the product water discharge passage 4 connecting between the air gap 24 and the product water tank 30, and in this embodiment, branched on the product water discharge passage 4 The configuration provided on the flow path is illustrated. The vapor pressure difference of the membrane distillation module 20 can be increased by the vacuum pressure applied to the air gap 24 by the vacuum pump 40, thereby improving the filtration flux.

The raw water supply flow path 1 may be connected to a chemical cleaning unit 80 that receives a part of the production water tank 30 and supplies a chemical cleaning solution to the raw water supply flow path 1, through which the membrane distillation module 20 When the separation membrane 23 is contaminated, chemical cleaning may be performed thereon.

The membrane distillation module 20 may be provided with a temperature sensor 90 for sensing the temperature of the front and rear ends, that is, the temperature of the low temperature part 21 and the high temperature part 22. The temperature sensor 90 includes first and second sensors 91 and 92 respectively installed at the inlet and outlet portions of the low temperature portion 21, and third and fourth sensors 93 respectively installed at the inlet and outlet portions of the high temperature portion 22. 94) may be included. According to this, the average value of the sensing values of the first and second sensors 91 and 92 is calculated as the temperature of the low-temperature part 21, and the average value of the sensing values of the third and fourth sensors 93 and 94 is calculated in the high-temperature part. It is calculated as the temperature of (22).

Meanwhile, the above-described configurations of the circulation pump 50, the vacuum pump 40, the cooler 60, and the heater 70 are controlled by the controller 100 (see FIG. 2). The controller 100 controls the overall operation of each device according to a preset setting.

The controller 100 is connected to the temperature sensor 90 so as to receive the sensing value of the temperature sensor 90, and the filtration flux of the membrane distillation module 20 is constant based on the sensing value of the temperature sensor 90. The vacuum pressure of the vacuum pump 40 is controlled to be maintained. A method of controlling the vacuum pressure of the vacuum pump 40 will be described in detail later.

Unlike the conventional reverse osmosis method, the membrane distillation method has a disadvantage that it is difficult to operate a constant flow rate when membrane contamination occurs. In the case of reverse osmosis, when membrane contamination occurs, the production of filtered water can be easily maintained by adjusting the operating pressure. However, the membrane distillation method has a very large heat capacity and specific heat of water, so the production amount is quickly adjusted through the temperature adjustment of the raw water and operated at a constant flow rate. It is difficult.

According to this embodiment, constant flow rate operation is possible by controlling the vacuum pressure of the vacuum pump 40 so that the filtration flux of the membrane distillation module 20 is kept constant.

When describing the operating state of the air gap type membrane distillation water treatment apparatus having the above configuration, the raw water from the raw water tank 1 is supplied to the membrane distillation module 20 according to the driving of the raw water circulation pump 50, at this time The temperature of the raw water is adjusted by the cooler 60 to a preset temperature (for example, 20°C). The raw water introduced into the low temperature section 21 of the membrane distillation module 20 is heated to a preset temperature (for example, 80° C.) by the heater 70 before flowing into the high temperature section 22, and is brought to the high temperature section 22. Will be introduced.

By the cooler 60 and the heater 70, the front and rear ends of the membrane distillation module 20, that is, between the low-temperature part 21 and the high-temperature part 22, exhibit a constant temperature difference, resulting in a difference in vapor pressure, and thus the air gap ( The steam is moved to 24), and the steam in the air gap part 24 is condensed by heat exchange with low-temperature raw water passing through the low-temperature part 21 and is stored in the product water tank 30.

At this time, the filtration flux is improved by the vacuum pressure of the vacuum pump 40 connected to the air gap 24 of the membrane distillation module 20, and the vacuum pump ( By controlling the vacuum pressure of 40), constant flow rate operation is possible even if membrane contamination occurs as the operation time increases.

The raw water discharged from the membrane distillation module 20 is recovered back to the raw water tank 10 through the circulation passage 3, so that the raw water circulation process as described above is continued.

3 is a flow chart showing a control method of the air gap type membrane distillation water treatment apparatus according to an embodiment of the present invention, and hereinafter, a control method of the water treatment apparatus will be described in more detail with reference to this.

First, the control unit 100 sets the operation set value of the filtration flux set by the user (S10), and calculates the vacuum pressure for generating the filtration flux at the operation set value (S20).

The formula for the filtration flux can be expressed by the following [Equation 1].

(J: filtration flux, B _m : permeation constant of the membrane, p _f : vapor pressure generated at the front end of the membrane distillation module, p _b : vapor pressure generated at the rear end of the membrane distillation module, p _v = vacuum pressure)

In addition, the vapor pressures (p _f , p _b ) generated at the front and rear ends of the membrane distillation module 20 may be calculated through the following [Equation 2] using a sensing value measured by the temperature sensor 90.

(p: vapor pressure at the front and rear end of the membrane distillation module, T: temperature at the front and rear end of the membrane distillation module)

The control unit 100 calculates the vapor pressure (p _f , p _b ) generated at the front and rear ends of the membrane distillation module 20 through [Equation 2] using the sensing value of the temperature sensor 90, and the filtration flux ( Since J) and the permeation constant (B _m ) of the separator are known values, the vacuum pressure (p _v ) for generating the filtration flux at the operating set point can be calculated using [Equation 1].

The controller 100 operates the vacuum pump 40 so that the calculated vacuum pressure p _v is applied to the air gap 24 (S30). Of course, the circulation pump 50, the cooler 60, and the heater 70 are also operated to operate the water treatment device.

During operation of the water treatment device, the temperature at the front and rear ends of the membrane distillation module 20 is measured through the temperature sensor 90. This may be measured periodically at a predetermined time period (S40).

The control unit 50 controls the operation of the vacuum pump 40 so that the filtration flux maintains an operation set value using the measured temperature at the front and rear ends of the membrane distillation module 20 (S50),

When the operation control of the vacuum pump 40 is described in detail, first, the current filtration flux J is calculated using [Equation 1] and [Equation 2] using a temperature measurement value (51).

Next, the error rate between the calculated value of the filtration flux J and the operation set value is calculated, and it is checked whether the error rate has reached the set threshold value (S52). If the error rate does not reach the set threshold, the current vacuum pressure is maintained.

However, when the error rate reaches a set threshold value, the transmission constant (B _m ) is calculated using [Equation 1] based on the calculated current filtration flux (J) (S53).

And, applying the calculated permeation constant (B _m ) to [Equation 1] to recalculate the vacuum pressure (p _v ) for maintaining the operating set point of the filtration flux (J) (S55), and the recalculated vacuum pressure The vacuum pressure of the vacuum pump 40 is adjusted so that (p _v ) is applied to the air gap 24 (S57).

As the operation time of the water treatment apparatus increases, when contamination occurs in the separation membrane 23 of the membrane distillation module 20, the permeation constant B _m of the separation membrane 23 decreases. According to the present embodiment, the permeation constant (B _m ) of the separation membrane 23 is recalculated according to membrane contamination, and the vacuum pressure (p _v ) capable of maintaining the operating set value of the filtration flux J is recalculated based on this. By applying, constant flow rate operation was made possible.

When continuous membrane contamination occurs, the vacuum pressure (p _v ) is continuously lowered, and thus the vacuum pump 40 reaches its maximum performance. After the vacuum pump reaches its maximum performance, the more membrane contamination occurs, the lower the filtration flux (J) may occur.

In order to solve this problem, a process of checking whether the recalculated vacuum pressure (p _v ) has reached a preset limit value (S56) may be additionally performed, and according to the confirmation result, the control unit 100 may perform a vacuum pump ( It is possible to operate the chemical cleaning mode in which the operation of 40) is stopped and the chemical cleaning unit 80 is operated. Specifically, if the recalculated vacuum pressure (p _v ) does not reach a preset limit value, the vacuum pump 40 is controlled so that the recalculated vacuum pressure (p _v ) is applied, and the recalculated vacuum pressure ( When p _v ) reaches a preset limit value, the operation of the vacuum pump 40 is stopped and the chemical cleaning mode is operated.

On the other hand, the control unit 100 may be set to perform a production water cleaning mode using production water based on a predetermined period (2 to 5 days) apart from the chemical cleaning as described above for efficient control of membrane contamination.

Although the above has been described with reference to specific embodiments of the present invention, those of ordinary skill in the relevant technical field may vary the present invention within the scope not departing from the spirit and scope of the present invention described in the following claims. You will understand that it can be modified and changed.

10: raw water tank 20: membrane distillation module
21: low temperature part 22: high temperature part
23: separator 24: air gap
30: production water tank 40: vacuum pump
50: circulation pump 60: cooler
70: heater 80: chemical cleaning unit
90: temperature sensor 100: control unit

Claims (13)

Raw water tank;
A membrane distillation module for separating steam from the raw water supplied from the raw water tank and condensing it in an air gap provided therein;
A production water tank for storing production water produced from the membrane distillation module;
A vacuum pump connected to the air gap of the membrane distillation module and applying a vacuum pressure to the air gap;
A plurality of temperature sensors for sensing the temperature at the front and rear ends of the membrane distillation module; And
Including; a control unit for controlling the vacuum pressure of the vacuum pump so that the filtration flux of the membrane distillation module is kept constant based on the sensing value of the temperature sensor,
The control unit calculates a vacuum pressure for maintaining the filtration flux at a preset operation setting value using the permeation constant of the separation membrane calculated through the sensing value of the temperature sensor.
The method of claim 1, wherein the membrane distillation module,
A low temperature part provided on one side of the air gap and supplied with low temperature raw water supplied from the raw water tank;
A high-temperature portion for heating the raw water discharged from the low-temperature portion and introducing it, and generating a vapor pressure difference due to a temperature difference with the low-temperature portion; And
And a separation membrane provided between the high temperature portion and the air gap portion and configured to separate and permeate only the vapor separated from the raw water of the high temperature portion.
The method of claim 2,
A raw water supply passage connecting the raw water tank and a low temperature portion of the membrane distillation module to supply raw water to the membrane distillation module;
A connection passage connecting the low temperature part and the high temperature part so that raw water from the low temperature part of the membrane distillation module is supplied to the high temperature part; And
An air gap type membrane distillation water treatment apparatus further comprising a; raw water circulation passage for circulating the raw water discharged from the high temperature portion to the raw water tank.
The method of claim 3,
A cooler installed in the raw water supply passage and cooling raw water from the raw water tank; And
An air gap type membrane distillation water treatment apparatus further comprising a; a heater installed in the connection passage and heating the raw water discharged from the low temperature portion of the membrane distillation module.
The method of claim 3,
An air gap type membrane distillation water treatment apparatus, wherein a raw water circulation pump is installed in at least one of the raw water supply passage and the raw water circulation passage.
The method of claim 3,
And a chemical cleaning unit for chemically cleaning the separation membrane by supplying a chemical cleaning solution to the raw water supply passage by receiving a part of the product water from the production water tank.
The method of claim 1,
The vacuum pump is an air gap type membrane distillation water treatment device, characterized in that connected to a product water discharge passage connecting between the air gap portion of the membrane distillation module and the production water tank.
delete delete The method of claim 1, wherein the control unit,
Air gap type membrane distillation water treatment apparatus, characterized in that configured to operate a chemical cleaning mode when the vacuum pressure reaches a preset limit value.
In the control method of the air gap type membrane distillation water treatment apparatus according to claim 1,
Setting an operation setting value of the filtration flux of the membrane distillation module;
Calculating a vacuum pressure for generating a filtration flux at the operation setting value, and operating the vacuum pump so that the vacuum pressure is applied to the air gap;
Measuring the temperature at the front and rear ends of the membrane distillation module; And
Controlling the operation of the vacuum pump so that the filtration flux maintains an operation set value using the measured temperature at the front and rear ends of the membrane distillation module; Control method of an air gap type membrane distillation water treatment apparatus comprising a.
The method of claim 11, wherein controlling the operation of the vacuum pump,
Calculating a current filtration flux using the measured temperature at the front and rear ends of the membrane distillation module;
Calculating an error rate between the calculated value of the filtration flux and an operation set value;
Calculating a permeation constant of the separator when the error rate reaches a set threshold value;
Recalculating the vacuum pressure for maintaining the operating set point of the filtration flux using the calculated permeation constant; And
And adjusting the vacuum pressure of the vacuum pump so that the recalculated vacuum pressure is applied to the air gap. 2. A method of controlling an air gap type membrane distillation water treatment apparatus comprising:
The method of claim 12,
Checking whether the recalculated vacuum pressure reaches a preset limit value; And
According to the confirmation result, stopping the operation of the vacuum pump and operating a chemical cleaning mode; the control method of the air gap type membrane distillation water treatment apparatus further comprising.

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