KR102210190B1 - Cdi type water treatment apparatus and method for controlling the same - Google Patents

Abstract

The water treatment apparatus of the CDI method according to the present invention includes a filter unit for purifying raw water according to the CDI method; And a control unit for controlling the filter unit based on the electrode efficiency of the filter unit, wherein the electrode efficiency is defined as a value obtained by dividing the amount of ion adsorption by the amount of charge based on a predetermined time, and the control unit maintains the electrode efficiency at a predetermined value or a predetermined range. Controls the level of voltage applied to the filter unit, and the control unit increases the level of voltage applied to the filter unit within the limit of maintaining a predetermined value or a predetermined range when the TDS or flow velocity of the raw water supplied to the filter unit increases. I can make it.
In addition, the method of controlling the water treatment device of the CDI method includes the first step of calculating the amount of ion adsorption and the amount of charge based on a predetermined time, and the electrode which is a value obtained by dividing the amount of ion adsorption by the amount of charge based on the amount of ion adsorption and charge calculated in the first step. A second step of calculating the efficiency, and a third step of controlling the magnitude of the voltage applied to the electrode so that the electrode efficiency maintains a predetermined value or a predetermined range based on the electrode efficiency calculated in the second step, In the step, when the TDS or flow rate of the raw water supplied to the filter unit increases, the magnitude of the voltage applied to the electrode may be increased within a limit in which the electrode efficiency maintains a predetermined value or a predetermined range.

Description

CDI type water treatment device and its control method {CDI TYPE WATER TREATMENT APPARATUS AND METHOD FOR CONTROLLING THE SAME}

The present invention relates to a CDI type water treatment apparatus and a control method thereof, and more particularly, to a CDI type water treatment apparatus capable of maintaining excellent water purification performance regardless of raw water conditions, and a control method thereof.

Various water treatment devices for generating purified water by treating raw water like a water purifier are currently being disclosed. However, recently, electric deionization water treatment devices such as EDI (Electro Deionization), CEDI (Continuous Electro Deionization), and CDI (Capacitive Deionization) are in the spotlight. Among them, the CDI type water treatment system is receiving the most attention.

The CDI method refers to a method of removing ions (pollutants) by using the principle that ions are adsorbed and desorbed from the surface of an electrode by electric force. This will be described in more detail with reference to FIGS. 9 and 10. When raw water including ions is passed through the electrodes while power is supplied to the electrode, as shown in FIG. 9, negative ions move to the positive electrode and positive ions move to the negative electrode. That is, adsorption occurs. Ions (pollutants) contained in raw water can be removed by such adsorption. However, if adsorption continues, the electrode can no longer adsorb ions. In this case, as shown in FIG. 10, it is necessary to regenerate the electrode by desorbing ions adsorbed on the electrode. For this, a voltage can be applied with the opposite polarity of the integer.

However, in the CDI type water treatment apparatus, ions (pollutants) are removed from raw water by applying a constant voltage to the electrodes. However, when a constant voltage is applied to the electrode in this way, when the water treatment device is placed under adverse conditions, such as when the raw water contains more ions (pollutants) than usual, it becomes difficult for the water treatment device to remove ions (pollutants) as usual. .

Accordingly, the present invention has been conceived to solve the above problems, and an object of the present invention is to provide a CDI type water treatment apparatus and a control method thereof capable of maintaining excellent water purification performance even when raw water is under adverse conditions.

The water treatment apparatus of the CDI method according to the present invention includes a filter unit for purifying raw water according to the CDI method through an electrode; And a control unit for controlling the filter unit based on the electrode efficiency of the filter unit, wherein the electrode efficiency is defined by Equation 1 below based on a predetermined time, and the control unit allows the electrode efficiency to maintain a predetermined value or a predetermined range. The level of the voltage applied to the filter unit is controlled, and the control unit, when the TDS (total dissolved solids) or flow rate of the raw water supplied to the filter unit is increased, the electrode efficiency is within a limit to maintain a predetermined value or a predetermined range. The magnitude of the voltage applied to the filter unit may be increased.
Equation 1: ion adsorption amount / charge amount
(In Equation 1 above, the amount of ion adsorption is the amount of ions adsorbed on the electrode, and the amount of charge is the amount of charge that flows through the electrode according to the voltage applied to the electrode.)

In addition, in the control method of the CDI type water treatment apparatus, in the control method of the CDI type water treatment apparatus in which raw water is purified according to the CDI method through a filter unit having an electrode, the amount of ions adsorbed on the electrode based on a predetermined time is ions. A first step of calculating an adsorption amount and an amount of charge that is an amount of the charge supplied to the electrode; A second step of calculating electrode efficiency, which is a value obtained by dividing the amount of ion adsorption by the amount of charge based on the amount of ion adsorption and the amount of charge calculated in the first step; And a third step of controlling the magnitude of the voltage applied to the electrode so that the electrode efficiency maintains a predetermined value or a predetermined range based on the electrode efficiency calculated in the second step, wherein the third step includes the filter When the TDS (total dissolved solids) or flow rate of raw water supplied to the negative is increased, the magnitude of the voltage applied to the electrode may be increased within a limit in which the electrode efficiency maintains a predetermined value or a predetermined range.

Since the CDI type water treatment apparatus and the control method thereof according to the present invention control the filter unit based on the electrode efficiency of the filter unit, even if raw water is in adverse conditions, there is an effect of preventing electrode damage and maintaining excellent water purification performance.

1 is a perspective view showing a filter module including a filter unit according to an embodiment of the present invention
2 is an exploded perspective view showing the filter module of FIG. 1 by exploding
3 is an exploded perspective view showing a filter unit and a terminal unit in the filter module of Fig. 1
4 is a cross-sectional view taken along line AA of the filter module of FIG. 1
5 is a graph showing the ion removal rate according to the TDS of the raw water when the flow rate of raw water supplied to the filter unit is 0.5 LPM and the voltage applied to the electrode of the filter unit is 1.7 V.
6 is a graph showing electrode efficiency according to TDS of raw water when the flow rate of raw water supplied to the filter unit is 0.5 LPM and the voltage applied to the electrode of the filter unit is 1.7 V.
7 is a graph showing the ion removal rate according to the flow rate of the raw water when the concentration of raw water supplied to the filter unit is 100 ppm and the voltage applied to the electrode of the filter unit is 1.7 V.
8 is a graph showing electrode efficiency according to the flow rate of the raw water when the concentration of raw water supplied to the filter unit is 100 ppm and the voltage applied to the electrode of the filter unit is 1.7 V.
9 is a conceptual diagram illustrating the principle that integers are formed in the CDI method
10 is a conceptual diagram illustrating the principle of reproduction in the CDI method

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, the present invention is not limited or limited by the following examples.

A water treatment apparatus according to an embodiment of the present invention relates to a water treatment apparatus of a CDI method, and basically includes a filter unit 110 and a control unit (not shown) that controls the filter unit 110. Hereinafter, the filter module 100 including the filter unit 110 will be described in detail with reference to FIGS. 1 to 4. Here, FIG. 1 is a perspective view showing a filter module including a filter unit according to an embodiment of the present invention, FIG. 2 is an exploded perspective view showing the filter module of FIG. 1, and FIG. 3 is a filter of FIG. It is an exploded perspective view showing the filter part and the terminal part of the module in exploded view, and FIG. 4 is a cross-sectional view taken along line AA of the filter module of FIG. 1.

[Filter module]

The filter module 100 includes a filter unit 110, a filter case unit 130, and a terminal unit 150. First, a look at the filter unit 110. The filter unit 110 serves to purify raw water through the electrodes 111 and 113 in a CDI method. More specifically, the filter unit 110 is formed by alternately stacking the electrodes 111 and 113 and the separator 112, as shown in FIG. 3. At this time, the electrode includes an anode 111 and a cathode 113. That is, the filter unit 110 is formed by stacking the anode 111 and the cathode 113 to face each other through the separator 112.

However, the electrodes 111 and 113 may generally be formed by coating activated carbon on both surfaces of a graphite foil. In this case, the graphite foil may include a body portion to which activated carbon is applied (refer to a portion marked with hatched in FIG. 3) and protruding portions 111a and 113a that protrude from the body portion but are not coated with activated carbon. Here, the protruding portions 111a and 113a form electrode tabs of the electrodes 111 and 113. The filter unit 110 may be operated by supplying power (or voltage or current) to the electrodes 111 and 113 through the electrode tabs 111a and 113a.

Next, the filter case part 130 is looked at. The filter case unit 130 accommodates the filter unit 110 as shown in FIG. 2. More specifically, the filter case unit 130 has an opening 132 formed at an upper portion thereof and the lower case 131 in which the filter unit 110 is accommodated, and an upper portion sealing the opening 132 of the lower case 131 Includes case 136. That is, after inserting the filter unit 110 into the lower case 131 through the opening 132 of the lower case 131, the opening 132 of the lower case 131 is transferred to the upper case 136. Close it. Here, the lower case 131 has an inlet port 133 through which raw water is obtained on the side, and the upper case 136 has an outlet port 137 through which purified water is discharged. At this time, the outlet 137 is formed to correspond to the outlet hole 115 of the filter unit 110.

According to this structure, raw water is purified through the following process. First, the raw water is supplied to the inside of the filter case 130 through the inlet 133. Then, at the pressure according to the supply, raw water is obtained into the filter unit 110 through the side surface of the filter unit 110. Then, the raw water flows between the anode 111 and the cathode 113 inside the filter unit 110 and is purified according to the CDI method. Then, the raw water (ie, purified water) is discharged to the outside of the filter unit 110 through the water outlet hole 115. Then, the raw water is discharged to the outside of the filter case 130 through the outlet 137 (see FIG. 4).

Next, the terminal unit 150 is examined. The terminal unit 150 is electrically connected to the electrode tabs 111a and 113a to transmit power from an external power source (not shown) to the electrodes 111 and 113. More specifically, the terminal unit 150 includes a conductive electrode terminal 151 in contact with the electrode tabs 111a and 113a at one end, as shown in FIGS. 2 and 3. When power is supplied to the other end of the electrode terminal while the electrode tab is in contact with one end of the electrode terminal, power can be supplied to the electrode tab through the electrode terminal.

It is preferable that the electrode terminal 151 is formed of stainless steel. This is the same for the terminal band 152 to be described later. This is because stainless steel is inexpensive and has good electrical conductivity. However, stainless steel has a limitation in that rust may occur due to oxidation according to the flow of electric current. In order to overcome this limitation, it may be considered to form the electrode terminal 151 of titanium (Ti). However, there is a limit in that titanium is oxidized according to the flow of electric current and thus electrical conductivity may be weakened.

Therefore, the electrode terminal 151 is most preferably formed of platinum (Pt). This is the same for the terminal band 152 to be described later. This is because platinum does not cause problems such as oxidizing and rusting or reducing electrical conductivity. However, considering that it is expensive, it may also be considered to form the electrode terminal 151 by coating platinum (Pt) on the surface.

However, the terminal unit 150 may include a conductive terminal band 152 surrounding the electrode tab 111a or 113a together with the electrode terminal 151. At this time, it is preferable that the terminal band 152 wraps the electrode tabs 111a and 113a together with the electrode terminals 151 so that the electrode tabs 111a and 113a are pressed inward.

[Control unit]

When a voltage is applied between the positive electrode 111 and the negative electrode 113, the filter unit 110 removes ions (pollutants) from the raw water according to the CDI method. That is, when a voltage is applied between the positive electrode 111 and the negative electrode 113, ions (pollutants) are adsorbed to the positive electrode 111 or the negative electrode 113 by electrostatic attraction, through which ions (pollutants) are absorbed from raw water. ) Can be removed.

However, when a voltage exceeding a predetermined size is applied to the electrodes 111 and 113, electrons are exchanged between the electrodes and ions, resulting in damage to the electrodes. Here, a reaction in which oxidation-reduction occurs due to the exchange of electrons is called a faradic reaction, and a reaction in which oxidation-reduction does not occur is called a non-faradic reaction. In the case of the CDI filter unit 110, a non-faradic reaction basically occurs during water purification, but a faradic reaction may also occur depending on the magnitude of the voltage applied to the electrode. In consideration of the durability of the electrode, it is preferable that the faradic reaction occurs less.

On the other hand, the faradic reaction can also be expressed in terms of electrode efficiency. For example, an electrode efficiency of 1 (or 100%) means that the faradic reaction is zero. In other words, it means that ions are adsorbed to the electrode by the amount of charge flowing through the electrode. More specifically, the electrode efficiency may be defined by Equation 1 below based on a predetermined time. In Equation 1 below, the amount of ion adsorption is the amount of ions adsorbed on the electrode for a predetermined time, and the amount of charge is the amount of charge flowing through the electrode according to the voltage applied to the electrode for the same time. For reference, by multiplying Equation 1 below by 100, the electrode efficiency can be expressed in %.

[Equation 1] (ion adsorption amount ÷ charge amount)

Here, the amount of ion adsorption can be expressed as {(TDS of raw water supplied to the filter unit-TDS of purified water discharged from the filter unit) × (accumulated flow rate of raw water supplied to the filter unit for a predetermined time)}. In addition, the amount of charge can be expressed as {(current flowing to the filter unit according to the voltage applied to the filter unit) × (prescribed time)}. For reference, TDS is an index representing the concentration of raw water and represents Total Dissolved Solids.

The water treatment apparatus according to the present exemplary embodiment is characterized in that the control unit controls the filter unit 110 based on the electrode efficiency. More specifically, the controller may control the magnitude of the voltage applied to the filter unit 110 so that the electrode efficiency maintains a predetermined value or a predetermined range.

For example, as shown in FIG. 5, when the TDS of raw water supplied to the filter unit 110 increases, the ion removal rate of the filter unit 110 decreases. 5 is a graph showing the ion removal rate according to the TDS of the raw water when the flow rate of raw water supplied to the filter unit is 0.5 LPM (liter per minute) and the voltage applied to the electrode of the filter unit is 1.7 V. However, as illustrated in FIG. 6, when the TDS of raw water supplied to the filter unit 110 increases, the electrode efficiency of the filter unit 110 increases. 6 is a graph showing electrode efficiency according to TDS of the raw water when the flow rate of raw water supplied to the filter unit is 0.5 LPM and the voltage applied to the electrode of the filter unit is 1.7 V. For reference, the ion removal rate may be expressed as "(TDS of raw water supplied to the filter unit-TDS of purified water discharged from the filter unit) / (TDS of raw water supplied to the filter unit)”.

As described above, when the TDS of the raw water supplied to the filter unit 110 increases, that is, when the raw water supplied to the filter unit 110 contains more pollutants, the electrode efficiency of the filter unit 110 will increase (Fig. 6 Reference) and the ion removal rate of the filter unit 110 will be lowered (see FIG. 5), but if the magnitude of the voltage applied to the filter unit 110 is increased correspondingly, the electrode efficiency of the filter unit 110 will be lowered. The ion removal rate of the filter unit 110 will increase.

That is, when the TDS of the raw water supplied to the filter unit 110 increases, the control unit increases the magnitude of the voltage applied to the filter unit 110 so that the electrode efficiency of the filter unit 110 maintains a predetermined value or a predetermined range. In this way, if the magnitude of the voltage applied to the filter unit 110 is increased, more ions will be adsorbed to the anode 111 or the cathode 113 according to an increase in electrostatic attraction, so the filter unit 110 The ion removal rate of will increase again. Of course, on the contrary, when the TDS of the raw water supplied to the filter unit 110 decreases, the magnitude of the voltage applied to the filter unit 110 may be reduced so that the electrode efficiency of the filter unit 110 maintains a predetermined value or a predetermined range. I can.

As described above, the control unit controls the magnitude of the voltage applied to the filter unit 110 according to the electrode efficiency of the filter unit 110, so that even if the TDS of raw water supplied to the filter unit 110 increases, ions of the filter unit 110 It can prevent the removal rate from being lowered.

In addition, since the control unit controls the level of the voltage applied to the filter unit 110 according to the electrode efficiency of the filter unit 110, even if the voltage level is increased to improve the ion removal rate, damage to the electrode may not occur. This will be described in detail below.

As described above, when a voltage exceeding a predetermined size is applied to the electrode, a faradic reaction may occur between the electrode and the ions. However, the faradic reaction may cause electrode damage and reduce electrode life. In the case of a conventional CDI filter unit, it is known that a faradic reaction occurs when a voltage of 1.2 V or more is applied to the filter unit (electrode). However, it is known that electrode damage occurring in the range of 1.2 to 1.7 V reduces the electrode life within a range that does not cause problems in product commercialization. Therefore, it is preferable to increase the voltage level in terms of an increase in the ion removal rate, but it has conventionally been common to apply a voltage to the filter unit (electrode) within a range of 1.7 V or less in consideration of the electrode life.

Meanwhile, as briefly described above, the faradic reaction can also be expressed as electrode efficiency. For example, an electrode efficiency of 100% indicates that no faradic reaction has occurred. That is, the electrode efficiency of 100% indicates that ions are adsorbed to the electrode as much as the current (charge amount) flowing through the electrode.

However, suppose that when raw water of 100 ppm TDS is supplied to the filter unit at 1 LPM, when a voltage of 1.7 V is applied to the filter unit (electrode), the ion removal rate is 90% and the electrode efficiency is 85%. Here, the electrode efficiency of 85% means that 15% of the current flowing through the electrode did not participate in ion removal, and also that all or part of 15% participated in the faradic reaction. However, it is assumed that 15% of them participate in the faradic reaction in an acceptable range when considering electrode life.

Under such premise, if raw water of 1000 ppm TDS is supplied to the filter unit under the same conditions, the ion removal rate will be less than 90% and the electrode efficiency will be more than 85%. Since the amount of ions that the filter unit can remove at a specific voltage is limited, when raw water containing more ions is supplied to the filter unit, the ion removal rate of the filter unit will decrease. However, if the raw water containing more ions is supplied to the filter unit, the opportunity for the current flowing through the electrode to participate in ion removal increases, so the electrode efficiency of the filter unit (electrode) will increase.

If a voltage higher than 1.7 V is applied to the filter unit, the ion removal rate will increase and the electrode efficiency will decrease. At this time, even if the voltage is increased until the electrode efficiency is lowered to 85%, considering the above, there is no problem in the life of the electrode. This is because if the electrode efficiency is the same in the same filter unit, the degree of damage to the electrode will be similar even if the voltage is different. For example, if the electrode efficiencies are the same in the case where 100 ppm of TDS is supplied and the raw water of 1000 ppm TDS is supplied as in the previous example, the degree of electrode damage will be similar to each other.

As a result, since the control unit controls the magnitude of the voltage applied to the filter unit 110 according to the electrode efficiency of the filter unit 110, even if the voltage level is increased to improve the ion removal rate, damage to the electrode may not occur. . (However, it does not mean that electrode damage does not occur at all, and electrode damage usually occurs to the extent that there is no problem in product commercialization.)

Here, it is most preferable that the control unit determines the level of the voltage so that the electrode efficiency of the filter unit 110 is maintained at 85%. This is because maintaining an efficiency of 85% is experimentally the most balanced between ion removal rate and electrode damage. Alternatively, the controller may determine the level of the voltage to maintain the electrode efficiency of 82 to 88%. If the electrode efficiency is less than 82%, it is not preferable because damage to the electrode may increase, and if the electrode efficiency is more than 88%, the ion removal rate is too low, which is not preferable.

Meanwhile, when the flow rate of raw water supplied to the filter unit 110 increases, the control unit may control the magnitude of the voltage applied to the filter unit 110 so that the electrode efficiency maintains a predetermined value or a predetermined range. For example, as shown in FIG. 7, when the flow rate of raw water supplied to the filter unit 110 increases, the ion removal rate of the filter unit 110 decreases. 7 is a graph showing the ion removal rate according to the flow rate of the raw water when the concentration (TDS) of raw water supplied to the filter unit is 100 ppm and the voltage applied to the electrode of the filter unit is 1.7 V. However, as illustrated in FIG. 8, when the flow rate of raw water supplied to the filter unit 110 increases, the electrode efficiency of the filter unit 110 increases. 8 is a graph showing electrode efficiency according to the flow rate of raw water when the concentration of raw water supplied to the filter unit is 100 ppm and the voltage applied to the electrode of the filter unit is 1.7 V.

As such, when the flow rate of the raw water supplied to the filter unit 110 increases, the electrode efficiency of the filter unit 110 will increase (see Fig. 8) and the ion removal rate of the filter unit 110 will decrease (see Fig. 7). In response to this, if the magnitude of the voltage applied to the filter unit 110 is increased, the electrode efficiency of the filter unit 110 will decrease and the ion removal rate of the filter unit 110 will increase. That is, when the flow rate of the raw water supplied to the filter unit 110 increases, the control unit may increase the magnitude of the voltage applied to the filter unit 110 so that the electrode efficiency maintains a predetermined value or a predetermined range. If the magnitude of the voltage applied to the unit 110 is increased, more ions will be adsorbed to the anode 111 or the cathode 113 according to the increase in electrostatic attraction, so the ion removal rate of the filter unit 110 will increase again. .

Control by the control unit can be described in more detail as follows. First, the controller may calculate the amount of ion adsorption and the amount of charge based on a predetermined time (first step). At this time, the predetermined time may be appropriately determined. For example, when a voltage is applied to the electrode of the filter unit 110, the amount of ion adsorption and the amount of charge may be calculated every minute. Here, the amount of ion adsorption and the amount of charge can be calculated according to the above equation. To this end, a TDS sensor for detecting TDS of raw water may be installed at the front end of the filter unit 110. Other sensors can be appropriately installed as needed.

Next, the controller can calculate the efficiency of the electrode based on the amount of ion adsorption and the amount of charge calculated as above (second step). That is, the control unit can calculate the electrode efficiency by dividing the amount of ion adsorption calculated as above by the amount of charge. Next, the controller may control the magnitude of the voltage applied to the electrode of the filter unit 110 based on the electrode efficiency calculated as described above (step 3). In this case, the control unit may control the magnitude of the voltage applied to the electrode so that the electrode efficiency maintains a predetermined value or a predetermined range. More specifically, when the TDS of the raw water supplied to the filter unit 110 increases or the flow rate of the raw water supplied to the filter unit 110 increases, the control unit increases the magnitude of the voltage applied to the electrode of the filter unit 110 I can make it.

100: filter module 110: filter unit
111: positive electrode 111a: positive electrode tab
112: separator 113: negative electrode
113a: negative electrode tab 115: water outlet hole
130: filter case portion 131: lower case
133: inlet 136: upper case
137: outlet 150: terminal
151: electrode terminal 152: terminal band

Claims (10)

A filter unit for purifying raw water according to a CDI method through an electrode; And
And a control unit for controlling the filter unit based on the electrode efficiency of the filter unit,
The electrode efficiency is defined by Equation 1 below based on a predetermined time,
The control unit controls the magnitude of the voltage applied to the filter unit so that the electrode efficiency maintains a predetermined value or a predetermined range,
When the TDS (total dissolved solids) or flow rate of the raw water supplied to the filter unit is increased, the control unit is a CDI that increases the magnitude of the voltage applied to the filter unit within a limit in which the electrode efficiency maintains a predetermined value or a predetermined range. Type water treatment device.
Equation 1: ion adsorption amount / charge amount
(In Equation 1 above, the amount of ion adsorption is the amount of ions adsorbed on the electrode, and the amount of charge is the amount of charge that flows through the electrode according to the voltage applied to the electrode.) delete delete delete delete The method according to claim 1,
The control unit controls a voltage applied to the filter unit to maintain the electrode efficiency of 82% to 88%. In the control method of the CDI type water treatment apparatus for purifying raw water according to the CDI method through a filter unit having an electrode,
A first step of calculating an amount of ion adsorption, which is an amount of ions adsorbed on the electrode, and an amount of charge, which is an amount of charge supplied to the electrode, based on a predetermined time;
A second step of calculating electrode efficiency, which is a value obtained by dividing the amount of ion adsorption by the amount of charge based on the amount of ion adsorption and the amount of charge calculated in the first step; And
A third step of controlling the magnitude of the voltage applied to the electrode so that the electrode efficiency maintains a predetermined value or a predetermined range based on the electrode efficiency calculated in the second step,
In the third step, when the TDS (total dissolved solids) or flow rate of the raw water supplied to the filter unit is increased, the electrode efficiency increases the level of the voltage applied to the electrode within a limit to maintain a predetermined value or a predetermined range. Method of controlling the water treatment device of the type. The method of claim 7,
The third step is a control method of a water treatment apparatus of a CDI method, characterized in that the level of the voltage applied to the electrode is controlled to maintain the electrode efficiency of 82% to 88%. delete delete

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