JP2003236554A - Apparatus for removing free carbonic acid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a compact and low-cost apparatus with which corrosive free carbonic acid in water is removed. <P>SOLUTION: Before or after treatment of removing the corrosive free carbonic acid from water to be treated by making the water go through a dissolving water tank 40 containing calcium carbonate and making a reaction CaCO<SB>3</SB>+ CO<SB>2</SB>+H<SB>2</SB>O→Ca(HCO<SB>3</SB>)<SB>2</SB>take place, the water to be treated is made to flow through opposing electrodes 20 to which alternating voltage is applied and is subjected to electrolytic treatment. Thereby the reaction is accelerated and pre- and posttreatment such as alkali injection, aeration or the like, which require a large-sized and expensive apparatus is made unnecessary. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a free carbon dioxide removing device for removing corrosive free carbon dioxide in water.

[0002]

2. Description of the Related Art Water supplied from well water or the like has a larger amount of carbon dioxide (most of it remains as CO ₂ and a part of molecular weight is higher than that of river water such as rainwater). Carbonated H ₂
In the form of CO ₃ , a small portion of the dissociated H ⁺ , HCO
_{3 ^-} in the form of) it is included. Of these, the remaining carbon dioxide excluding the amount of carbon dioxide (dependent free carbonic acid) necessary to keep the hydrogen carbonate dissolved in water becomes erodible free carbonic acid that corrodes metals, etc. It is a cause of corrosion of water pipes.

Regarding tap water, the target value of the Langeria index is set to "close to -1 or more and as close as possible to 0" in "Notice of establishment of standards for tap water quality" in the notification of the Director of Water Environment Department, Ministry of Health and Welfare, Ministry of Health and Welfare in 1992. Is prescribed. As a method of removing CO ₂ in water to improve the Langerian index, calcium carbonate is added to water to cause a chemical reaction of CaCO ₃ + CO ₂ + H ₂ O → Ca (HCO ₃ ) ₂ (1) formula. Is generally done. Further, since the reaction of the formula (1) is difficult to proceed to the right, it is not enough to pass the raw water through the packed column of calcium carbonate in order to accelerate the reaction, and slaked lime is injected as an aqueous solution of 1000 ppm or more or slaked lime or After making calcium carbonate into a slurry and injecting it, it is necessary to sufficiently react it in a large adjusting tank, and an accompanying treatment such as aeration is also performed. There are "slaked lime injection device" and "slaked lime / carbon dioxide gas injection device" as devices for improving the CO ₂ concentration in water by using these methods.

[0004]

The conventional "slaked lime injection device" and "slaked lime / carbon dioxide gas injection device" are associated with alkali injection, aeration, etc. for promoting the chemical reaction of the formula (1) to the right. Because of the need for treatment, the equipment became expensive and bulky, which was a factor in delaying the water supplier's proper response to the previous notice.

The present invention has been made by paying attention to the problems of such conventional techniques, and provides a small-sized and inexpensive free carbon dioxide removing device which can remove erodible free carbon dioxide in water. It is an object.

[0006]

The gist of the present invention for achieving the above object resides in the inventions of the following items. [1] In a free carbon dioxide removing device for removing corrosive free carbon dioxide in water, a pair of electrodes (20), a voltage applying means (30) for applying an AC voltage between these electrodes, and calcium carbonate or slaked lime in water Etc. (including caustic soda, soda ash, etc.) and a dissolving means (40) for dissolving, and an electric treatment in which an alternating current is applied to the water to be treated by the electrode (20) and the voltage applying means (30), and A device for removing free carbonic acid, characterized by performing a dissolution treatment for dissolving calcium carbonate or slaked lime by a dissolution means (40).

[2] The free carbon dioxide removing device according to [1], wherein the electric treatment and the dissolution treatment are performed while continuously passing water to be treated.

[3] The free carbon dioxide removing device according to [1], wherein the voltage applying means (30) can change the setting of either or both of the applied voltage and the frequency.

[4] Water discharge measuring means (60) for measuring the Langerian index of water after the electric treatment and the dissolving treatment or a value in place of this is provided, and the voltage applying means (30) is [1] or [2] characterized in that the applied voltage and / or the frequency are controlled so that the measured value of the water discharge measuring means (60) becomes a predetermined value.
The free carbon dioxide removing device described in 1.

[5] Water entry measuring means (50) for measuring the Langerian index of water entry or a value in place of it is provided, and the voltage applying means (30) is the water entry measuring means (50).
[1], [2], characterized in that either or both of the applied voltage and the frequency are controlled based on the measured value of
The free carbon dioxide removing device according to [3] or [4].

The present invention operates as follows. The free carbonic acid removing device performs an electric treatment in which an alternating current is passed through water to be treated and a dissolution treatment in which calcium carbonate or slaked lime is dissolved. By subjecting water to an electric treatment in which an alternating current is applied, the chemical reaction of formula (1) is promoted to the right, and carbon dioxide dioxide (erodible free carbon dioxide) in water can be efficiently removed.

This is because the cluster of H ₂ O molecules is subjected to an electric treatment, and the cluster of dozens (20th to 30th) is reduced from dozens to several dozens. It is considered that this is due to an increase in the number of H ₂ O molecules involved in the reaction. In addition, by applying an electric treatment, H ₂
It has been known that the angle of the O molecule changes from 108 degrees before the treatment to another angle, and it is considered that this is one of the factors that promote the above chemical reaction. After leaving the free carbonic acid treatment device, the chemical reaction of formula (1) slowly progresses to the left, calcium carbonate precipitates and the film adheres to the pipe wall, etc., and water contacts the pipe wall. Since it is cut off, the anticorrosion effect can be obtained.

The order of the electric treatment and the dissolution treatment does not matter. That is, the melting treatment may be performed after the electric treatment, or the electric treatment may be performed after the melting treatment. Further, these processes may be simultaneously performed at the same location. When the electric treatment is performed after the dissolution treatment, calcium carbonate which does not dissolve in the dissolution treatment and flows out into the water as it is may be dissolved by the reaction of the formula (1) being promoted by the electric treatment performed later. Become. That is, in the case of injecting slurry-like calcium carbonate, an adjusting tank for reacting with raw water has been conventionally required, but this is unnecessary or can be downsized.

As described above, by performing the electric treatment in which an alternating current is applied to water, the dissolution treatment for dissolving calcium carbonate or slaked lime in water is promoted, and a large amount of erodible free carbonic acid is efficiently converted into a hydroxide salt. be able to. as a result,
The process of storing in a water tank for a long time to sufficiently carry out the dissolution reaction of calcium carbonate, the process of preparing and mixing an aqueous solution of calcium carbonate in advance to promote the reaction, the aeration process, etc. As a result, it is possible to reduce the size and cost of the device, because the physical processing is not required.
Further, since the dissolution treatment is promoted by performing the electric treatment, it is possible to perform the electric treatment and the dissolution treatment while continuously passing water to be treated.

In other words, conventionally, the reaction was promoted by making calcium carbonate finer or increasing carbon dioxide, whereas the present invention changes the property of water by electric treatment without using a catalyst ( H ₂ O related to the reaction
By increasing the number of molecules of (1), etc.).

In the configuration in which both or one or both of the voltage applied by the voltage applying means (30) and the frequency can be changed, the Langerian exponent of water after the electric treatment and the dissolution treatment has an appropriate value. Can be adjusted to That is, when the voltage or frequency applied between the electrodes is changed, the degree to which the reaction of the formula (1) is promoted to the right changes. Therefore, by adjusting the applied voltage and the like, the water after treatment can be adjusted. It is possible to adjust the Langerian index of to an appropriate value. In this way, changing the applied voltage or frequency changes the degree to which the reaction of equation (1) is promoted to the right. It is thought to be due to changes depending on.

The value of the Langerian index of water after electrolysis and solubilization or an alternative value (eg,
The calcium hardness and the concentration of carbon dioxide) are measured by the water discharge measuring means (60), and both or one or both of the voltage applied by the voltage applying means (30) and the frequency are feedback-controlled so that the measured value becomes a predetermined value. In this case, the quality of the discharged water can be automatically adjusted to the preferred Langerian index.

Further, the value of the Langeria index of the incoming water before the electric treatment or the dissolution treatment or the value of the alternative is measured by the incoming water measuring means (50), and the voltage applied by the voltage applying means (30) is based on the measured value. And / or frequency feed-forward control,
It is possible to discharge water having a preferable Langerian index from the beginning. For example, when measuring the calcium hardness of water as an alternative to the Langerian index, since the hardness of well water depends almost entirely on the calcium hardness, the hardness of the water discharge measuring means (60) and the water inflow measuring means (50) is A meter can be used.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 shows a schematic configuration of a free carbon dioxide removing device 10 according to an embodiment of the present invention.
The free carbon dioxide removing device 10 is a pump 12, two electrodes 20 arranged to face each other in a water channel, a voltage applying means 30 for applying an AC voltage to the electrode 20, and a dissolving means for accommodating granular calcium carbonate. It has a dissolution water tank 40, a water inflow measuring means 50, and a water discharge measuring means 60. The bold arrows in the figure indicate the paths through which the water to be treated flows.

The pump 12 takes in raw water such as well water through an intake port (not shown) and discharges the taken-in water from an outlet port (not shown) between the two electrodes 20 and the dissolving water tank 40. It serves the function of sending to. The voltage applying means 30 applies an AC voltage between the two electrodes 20. The voltage applying means 30 is
The control circuit 31, the transmission circuit 32, and the drive circuit 33 are provided. The transmission circuit 32 generates an AC signal, and the control circuit 31 controls the frequency and voltage of the AC signal generated by the transmission circuit 32. The drive circuit 33 amplifies the AC signal generated by the transmission circuit 32 and applies it to the electrode 20.

The dissolution water tank 40 is a water tank for performing a dissolution treatment in which calcium carbonate or slaked lime is dissolved in water which has been electroprocessed by passing between the electrodes 20, and is a granular calcium carbonate. Is stored or slaked lime is added. The dissolution water tank 40 has a water inlet 41 in the lower part and a water outlet 42 in the upper part. Further, the dissolving water tank 40 can be replenished with calcium carbonate or slaked lime by opening an upper lid (not shown). As the calcium carbonate, for example, oyster shells, ako shellfish shells, which are usually treated as waste, may be used. Further, instead of slaked lime, caustic soda or soda ash may be used.

The incoming water measuring means 50 measures the Langerian index of incoming water (raw water) before being subjected to electrical treatment or dissolution treatment, or a value in place of this. The water discharge measuring means 60 measures the Langerian index of water after electrical treatment and dissolution treatment, or a value in place of it. For example, when measuring the calcium hardness instead of the Langerian index, the hardness of well water or the like usually depends on the calcium hardness, so that a hardness meter is used as the water inflow measuring means 50 and the water discharge measuring means 60. be able to. The concentration of carbon dioxide in water may be used instead of the Langerian index. When the concentration of carbon dioxide in water is extremely high (for example, free carbonic acid of 10 ppm or more), it is considered necessary to improve the Langeria index, and when using a groundwater source, the concentration can be as high as about 30 ppm. Since this is reached, the AC voltage and frequency are adjusted according to this concentration.

The control circuit 31 of the voltage applying means 30 has a function of feed-forward controlling the voltage and frequency applied to the electrode 20 based on the measured value of the water entering measuring means 50.
The electrode 2 so that the measured value of the water discharge measuring means 60 becomes a predetermined value
It has a function of feedback controlling the voltage and frequency applied to 0. The voltage applying means 30 includes two electrodes 2
The voltage applied between 0 is 0.5 volt to 1 in effective voltage.
In the range of 0.0 volt, the frequency is 30Hz to 10k
It can be controlled between Hz.

FIG. 2 shows a water tube 22 for voltage application to which an electrode 20 is attached. Two electrodes 20 formed of a stainless material or the like are arranged opposite to each other inside the voltage application water pipe 22. An electrode connecting portion 23 for connecting a power supply lead wire from the drive circuit 33 is formed near the center of the electrodes 20. Water tube for voltage application 22
Joints 24 for connecting to another water pipe 29 are formed at both ends of the. In the free carbon dioxide removing device 10, between an intake port (not shown) for taking in raw water and the inlet side of the pump 12, between the outlet side of the pump 12 and one end of the voltage application water pipe 22, and between the voltage application water pipe 22. A water pipe is connected between the other end and a water inlet 41 of the dissolution water tank 40, and a water outlet 42 of the dissolution water tank 40 and a discharge port (not shown).

The Langerian index (saturation index ... SI) is S
I = pH-pHs ... (2) Formula is represented. In equation (2), pH is the actual pH of water and pHs is the saturated pH. pHs is the pH of water when the rightward and leftward progress of the chemical reaction shown in equation (1) is in equilibrium.
Is. If SI> = 0, the water is not corrosive,
If SI <0, it is corrosive. pHs = pHs =
(9.3 + A + B)-(C + D) ... (3) Formula can be calculated | required. In equation (3), A is the evaporation residue coefficient, B is the temperature coefficient, C is the calcium hardness coefficient, and D is the alkalinity. Each coefficient of A, B, C and D can be obtained from the analysis value of the target water and the conversion table shown in FIG.

As an alternative to the Langerian index, calcium hardness may be used, or a value based on both calcium hardness and water temperature may be used. This is because, as shown in FIG. 3, the value of the evaporation residue coefficient A has a small variation range and does not significantly affect the Langerian index obtained by the equation (3). Also, in the case of well water, the water temperature is stable, so the measurement of the water temperature may be omitted. Furthermore, the water source of well water and tap water is usually in the inland area, and therefore the hardness of the water as the water source does not need to consider sodium and depends almost on the calcium hardness, so instead of calcium hardness, use a hardness meter. You may use the measured hardness. In addition, the carbon dioxide concentration in water may be used instead of the Langerian index. That is, when the carbon dioxide concentration is equal to or higher than a predetermined value, it is determined that erosive free carbonic acid is present and the AC voltage or frequency is controlled. There is also a method of using pH, but since pH moves in the acidic direction depending on the carbon dioxide concentration and moves in the alkaline direction depending on the calcium (or sodium) concentration, use pH only when either one is stable raw water. Good. However, the location of the water purification plant is near the sea, and surface water (river) and groundwater source (well water) are used as water sources.
When and are blended or the blend ratio is changed as necessary, it is desirable to find as many parameters as possible, preferably the Langerian index.

Next, the operation will be described. Free carbon dioxide removal device 1
For 0, the raw water is taken in from the water intake by the pump 12.
The taken-in water passes between the electrodes 20 arranged opposite to each other in the voltage application water pipe 22, and then passes through the dissolving water tank 40 from the water inlet 41 to the water outlet 42 to remove the free carbon dioxide removing device 1
It flows out from the discharge port of 0. The water intake measuring means 50 measures the calcium hardness as the Langeria index of the raw water taken in from the water intake or as an alternative thereto. The control circuit 31 of the voltage applying means 30 feedforward-controls the AC voltage and the frequency applied between the electrodes 20, based on the measured value of the water inflow measuring means 50. The control circuit 31 is data indicating the correspondence relationship between the applied voltage and / or frequency that should be set so that the Langerian index at the discharge port becomes the target value and the measured value of the water immersion measuring means 50, and is obtained in advance by an experiment. I remember. The control circuit 31 refers to the above data on the basis of the measured value of the water inflow measuring means 50 to obtain appropriate applied voltage and frequency values and performs feedforward control.

Further, the value of the Langerian index of water discharged from the water outlet 42 of the dissolution water tank 40 or a substitute value thereof is measured by the water discharge measuring means 60, and the control circuit 31 makes this measured value a predetermined target value. Thus, the voltage and frequency of the AC signal applied between the two electrodes 20 are feedback-controlled. Here, the target value of the Langerian index is −
It is set to a predetermined value between 1 and +0.8.

2 arranged inside the voltage application water pipe 22
The properties of the water change as it passes between the electrodes 20. As a result, the chemical reaction of the formula (1) that occurs during or after passing through the dissolution water tank 40 is promoted to the right, and the erosive free carbonic acid is efficiently and sufficiently removed. This is because dozens of H ₂ O molecular clusters (20
It is due to the increase in the number of H ₂ O molecules involved in the chemical reaction of formula (1) from the aggregate of (˜30th position) to more than 10 and several aggregates. It is also known that the angle of the H ₂ O molecule changes from 108 degrees before the treatment to another angle by passing an alternating current in water, which is one of the reasons for promoting the previous chemical reaction to the right. It is believed that there is.

The degree of promotion of the chemical reaction of the equation (1) to the right changes depending on the applied voltage and frequency. Therefore, by controlling the applied voltage and the frequency based on the measured value of the water discharge measuring means 60, it is possible to discharge the water whose Langerian index is adjusted to the target value. Further, since the degree of reaction can be controlled by the applied voltage and frequency, the amount of calcium carbonate contained in the dissolution water tank 40 may be any amount as long as it is a necessary amount or more. As a result, the dissolution water tank 40
The calcium carbonate can be easily replenished and continuous treatment becomes possible.

For example, some water before being treated by the free carbon dioxide removing device 10 has an evaporation residue of 50 to 300 mg.
/ L, and the evaporation residue coefficient A was 0.1 from FIG. The temperature was between 18 and 21 ° C and the temperature coefficient B was 2.1. Calcium hardness is 56 ~ 69mgC
It was aCO ₃ / l and the calcium hardness coefficient C was 1.4. The alkalinity D was 1.6 and the pH was 7.1. Substituting these into equation (3), pHs = (9.3+
0.1 + 2.1)-(1.4 + 1.6) = 8.5. From equation (2), the Langerian index of this water is SI
= 7.1-8.5 = -1.4. Therefore, since this water had SI of -1 or less, it was corrosive.

When the same water as this is treated by the free carbon dioxide removing device 10, the reaction of the formula (1) efficiently proceeds to the right,
Since the amount of hydrated calcium carbonate increases, the calcium hardness becomes 175 to 220 mg CaCO ₃ / l, the calcium hardness coefficient C becomes 1.9, the alkalinity D becomes 2.3, and SI = 7.1-7. It became 3 = -0.2. In addition,
If SI is -1 or more, anticorrosion effect can be expected. After leaving the free carbon dioxide removing device 10,
The chemical reaction of the formula (1) gradually progresses to the left, and the calcium carbonate film adheres to the tube wall and the like to cut off the contact between water and the tube wall, and an anticorrosion effect can be obtained.

The present invention has been described above based on the embodiments, but the present invention is not limited to the examples illustrated in the embodiments, and various modified modes are possible without departing from the spirit of the present invention. It includes. That is, applied voltage, frequency,
The shape and arrangement of the electrodes and the structure of the melting tank are not limited to those shown in the embodiment.

Further, in the embodiment, the feedforward control based on the measured value of the water inflow measuring means 50 and the feedback control based on the measured value of the water discharge measuring means 60 are used together, but even if only one control is adopted. Good. For example, if it is allowed that the Langerian index of the water discharged at the beginning of the operation deviates from the target value, only the feedback control may be adopted. Alternatively, the Langerian index of the discharged water or the value of a substitute thereof may be measured, and the voltage or frequency applied to the electrode 20 may be manually adjusted based on the measurement result.

Further, only one of the paired electrodes may be used, and the other may be the water pipe 22 itself. Alternatively, the two insulated water tubes 22 themselves may be used as the two electrodes without the electrodes. In other words, if electricity can be applied to water, the shape of the electrode does not matter.

In the present embodiment, a device for removing free carbon dioxide is provided in the intake part of the water purification plant, but the present device may be installed in the intake part of a condominium, for example. Further, it may be attached to the water supply connection part of the water heater or may be built in the water heater. Further, not only for tap water but also for industrial water, this device may be attached to the groundwater intake of a factory or a power plant to prevent corrosion of industrial water pipes and cooling system pipes.

In the embodiment, the free carbon dioxide removing device 10 has the pump 12 built therein. However, the free carbon dioxide removing device 1 is a device for sending raw water to the free carbon dioxide removing device 10, such as a pump.
It may be provided separately from 0.

In addition, in the embodiment, the water treatment is performed in the order of the electric treatment and the dissolution treatment, but they may be performed in the reverse order. Further, the electric treatment and the dissolution treatment may be simultaneously performed at one place. For example, electrode 2
For example, calcium carbonate is placed between zero.

[0039]

EFFECT OF THE INVENTION According to the apparatus for removing free carbon dioxide according to the present invention, the electric treatment in which an alternating current is applied to water and the dissolution treatment to dissolve calcium carbonate or slaked lime in water are performed, so that the electric treatment is not performed. As a result, the dissolution reaction of calcium carbonate or the like is promoted, and the erodible free carbonic acid can be efficiently and promptly converted into a hydroxide salt. As a result, it was provided in the past,
The process of storing water in a water tank for a long time to sufficiently carry out the dissolution reaction, the process of preliminarily preparing and mixing an aqueous solution of calcium carbonate in order to promote the reaction, the aeration process, etc. are not necessary. It is possible to achieve downsizing and cost reduction. Further, since the dissolution treatment is promoted by performing the electric treatment, it is possible to remove the erosive free carbonic acid while continuously passing the water to be treated.

In the configuration in which both or one of the applied voltage and the frequency by the voltage applying means can be changed, the Langerian exponent of water after being subjected to the electric treatment and the dissolution treatment has an appropriate value. Can be adjusted.

After the electric treatment and the dissolution treatment, the Langerian index of water or the value of the substitute is measured, and the applied voltage and / or the frequency are feedback-controlled so that the value becomes a predetermined value. In this case, the quality of the discharged water can be automatically adjusted to a preferable Langerian index.

Further, in the case where the Langerian index of the incoming water before the electric treatment or the dissolution treatment or the value of the substitute is measured, and the feed voltage and / or the applied voltage is feedforward-controlled based on the value. It is possible to discharge water having a preferable Langerian index from the beginning.

[Brief description of drawings]

FIG. 1 is an explanatory diagram showing a schematic configuration of a free carbon dioxide removing device according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a voltage application water pipe of a free carbon dioxide removing device according to an embodiment of the present invention.

FIG. 3 is an explanatory diagram showing a coefficient conversion table for obtaining a Langerian index.

[Explanation of symbols]

10 ... Free carbon dioxide removing device 12 ... Pump 20 ... Electrode 22 ... Water tube for voltage application 23 ... Electrode connection part 30 ... Voltage applying means 31 ... Control circuit 32 ... Oscillation circuit 33 ... Drive circuit 40 ... Dissolution water tank 41 ... Water inlet 42 ... Outlet 50 ... Water entry measuring means 60 ... Water discharge measuring means

Claims (5)

[Claims] 1. A free carbon dioxide removing device for removing corrosive free carbon dioxide in water, a pair of electrodes, a voltage applying means for applying an AC voltage between these electrodes, and a dissolving means for dissolving calcium carbonate or slaked lime in water. Means for removing free carbonic acid, characterized in that the water to be treated is subjected to an electric treatment in which an alternating current is caused to flow by the electrode and the voltage applying means and a dissolution treatment for dissolving calcium carbonate or slaked lime by the dissolving means. apparatus. 2. The free carbon dioxide removing device according to claim 1, wherein the electrical treatment and the dissolution treatment are performed while continuously passing water to be treated. 3. The free carbon dioxide removing device according to claim 1, wherein the voltage applying means is capable of changing the setting of both or one of the applied voltage and the frequency. 4. A water discharge measuring means for measuring the Langerian index of water after the electric treatment and the dissolution treatment or a value in place of the Langereria index, and the voltage applying means has a measured value of the water discharge measuring means. The free carbon dioxide removing device according to claim 1 or 2, wherein both or either of the applied voltage and the frequency are controlled so that is a predetermined value. 5. A water entry measuring means for measuring the Langerian index of water entry or an alternative value thereof, wherein the voltage applying means is based on a measurement value of the water entry measuring means and / or applied voltage and / or frequency. The free carbon dioxide removing device according to claim 1, wherein one of the two is controlled.