JP3713245B2 - Free carbonic acid removal device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a free carbonic acid removal device for removing erosive free carbonic acid in water.
[0002]
[Prior art]
Compared to the water from the river water such as rain water, the water that uses well water or the like as the water source contains more carbon dioxide (mostly CO ₂ but partly molecular carbonic acid H _2. In the form of CO _{3 and} a very small part (in the form of dissociated H ⁺ , HCO ₃ ⁻ ). Of these, the remaining carbon dioxide, excluding the amount of carbon dioxide (dependent free carbonic acid) required to dissolve the bicarbonate in water, becomes erodible free carbonic acid that corrodes metals, etc. It causes water pipes to corrode.
[0003]
As for tap water, the target value of the Langeria index is set to “-1 or more and close to 0 as much as possible” in the “Notice of Establishing Standards for Water Quality” issued by the Director of the Water Environment Department of the Health and Welfare Bureau of the Ministry of Health and Welfare in 1992 Has been. As a method of improving the Langeria index by removing CO ₂ in water, adding calcium carbonate to water,
CaCO ₃ + CO ₂ + H ₂ O → Ca (HCO ₃ ) ₂ (1) Generally, a chemical reaction of the formula (1) is performed. Also, since the reaction of formula (1) is difficult to proceed in the right direction, in order to promote the reaction, it is not necessary to simply pass the raw water through a packed column of calcium carbonate, and slaked lime can be injected as an aqueous solution of 1000 ppm or more. After slurrying and injecting calcium carbonate, it is necessary to sufficiently react in a large adjustment tank, and an accompanying process such as aeration is also performed. Devices that improve the CO ₂ concentration in water using these methods include “slaked lime injection device” and “slaked lime / carbon dioxide gas injection device”.
[0004]
[Problems to be solved by the invention]
The conventional “slaked lime injection device” and “slaked lime / carbon dioxide gas injection device” require additional processing such as alkali injection and aeration to promote the chemical reaction of the formula (1) in the right direction. It became expensive and large, and this caused delays in the appropriate response of water utilities to the previous notice.
[0005]
The present invention has been made paying attention to such problems of the conventional technology, and aims to provide a small and inexpensive free carbonic acid removing device capable of removing erosive free carbonic acid in water. Yes.
[0006]
[Means for Solving the Problems]
The gist of the present invention for achieving the object lies in the inventions of the following items.
[1] In a free carbonic acid removal device for removing erosive free carbonic acid in water,
A pair of electrodes (20), a voltage applying means (30) for applying an alternating voltage between these electrodes, and a dissolving means for dissolving calcium carbonate or slaked lime (including caustic soda and soda ash etc.) in water (40 )
The water to be treated is subjected to an electrical treatment in which an alternating current is caused to flow by the electrode (20) and the voltage application means (30) and a dissolution treatment to dissolve calcium carbonate or slaked lime by the dissolution means (40). Free carbonic acid removal device.
[0007]
[2] The apparatus for removing free carbonic acid according to [1], wherein the electrical treatment and the dissolution treatment are performed while continuously passing water to be treated.
[0008]
[3] The free carbonic acid removing device according to [1], wherein the voltage applying means (30) is capable of changing the setting of both or one of the applied voltage and frequency.
[0009]
[4] Water discharge measuring means (60) for measuring the Langerial index of water after the electric treatment and the dissolution treatment or a value in place of it,
The voltage application means (30) controls the applied voltage and / or the frequency so that the measured value of the water discharge measuring means (60) becomes a predetermined value [1] or [2 ] The free carbonic acid removal apparatus as described in.
[0010]
[5] Incoming water measuring means (50) for measuring the incoming Langerial index or an alternative value thereof,
The voltage application means (30) controls the applied voltage and / or the frequency based on the measured value of the incoming water measurement means (50) [1], [2], [ 3] or the free carbonic acid removing apparatus according to [4].
[0011]
The present invention operates as follows.
The free carbonic acid removing device performs an electric process for supplying an alternating current to water to be treated and a dissolving process for dissolving calcium carbonate or slaked lime. By performing an electrical treatment that causes an alternating current to flow through water, the chemical reaction of formula (1) is promoted to the right, and carbon dioxide (erodible free carbonic acid) in water can be efficiently removed.
[0012]
This is because a cluster of H ₂ O molecules is reduced from a dozen (20 to 30-position) aggregates to a dozen to several aggregates by performing an electrical treatment. This is thought to be due to the increase in the number of H ₂ O molecules involved. Moreover, it has been found that the angle of the H ₂ O molecule changes from 108 degrees before the treatment to another angle by applying the electrical treatment, and this is considered to be a factor for promoting the chemical reaction. After leaving the free carbonic acid treatment device, the chemical reaction of formula (1) proceeds slowly to the left, calcium carbonate is deposited and the film adheres to the tube wall, etc., and the water contacts the tube wall. The anticorrosive effect can be obtained.
[0013]
The order of electrical treatment and dissolution treatment is not limited. That is, the dissolution treatment may be performed after the electrical treatment, or the electrical treatment may be performed after the dissolution treatment. Furthermore, you may comprise so that these processes may be performed simultaneously in the same location. In the case where the electric treatment is performed after the dissolution treatment, the calcium carbonate which has not been dissolved in the dissolution treatment and has flowed into the water as it is is dissolved by the reaction of formula (1) being promoted by the electric treatment applied later. Become. In other words, when calcium carbonate in the form of a slurry is injected, an adjustment tank for reacting with raw water has been conventionally required, but this is unnecessary or can be reduced in size.
[0014]
In this way, by performing an electrical treatment that causes an alternating current to flow in water, a dissolution treatment for dissolving calcium carbonate or slaked lime in water is promoted, and a large amount of erodible free carbonic acid can be efficiently converted into a hydroxide salt. . As a result, conventional processes such as a process of storing in a water tank for a long time to sufficiently dissolve calcium carbonate and the like, a process of preparing and mixing an aqueous solution of calcium carbonate in advance to promote the reaction, and an aeration process are performed. Therefore, the accompanying process is no longer necessary, and the apparatus can be reduced in size and price. Moreover, since the dissolution treatment is promoted by applying the electrical treatment, the electrical treatment and the dissolution treatment can be performed while continuously passing the water to be treated.
[0015]
That is, in the past, attempts have been made to promote the reaction by making calcium carbonate finer or increasing carbon dioxide, but the present invention changes the properties of water by electroprocessing without using a catalyst (related to the reaction). The reaction of the formula (1) is promoted by increasing the number of H ₂ O molecules.
[0016]
In the case where the voltage applied by the voltage application means (30) and / or the frequency can be set and changed, the Langeria index of water after the electrical treatment and the dissolution treatment is set to an appropriate value. Can be adjusted. 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. Can be adjusted to an appropriate value. Thus, changing the applied voltage and frequency changes the degree to which the reaction of formula (1) is promoted in the right direction because the number of water molecules constituting the cluster and the angle of the molecules are the applied voltage and frequency. This is thought to be due to changes depending on the situation.
[0017]
After the electrical treatment and the dissolution treatment, the Langerian index of water or a value (for example, calcium hardness or carbon dioxide concentration) is measured by the water discharge measuring means (60), and the measured value becomes a predetermined value. As described above, when the voltage application means (30) performs feedback control of the applied voltage and / or the frequency, the water quality of the discharged water can be automatically adjusted to a preferred Langeria index.
[0018]
Furthermore, the Langerian index of the incoming water before the electrical treatment or the dissolution treatment or a value instead of this is measured by the incoming water measuring means (50), and the applied voltage and frequency of the voltage applying means (30) are measured based on the measured value. In the case where both or one of them is feedforward controlled, it is possible to discharge water having a preferable Langeria index from the beginning. For example, when measuring the calcium hardness of water as an alternative to the Langeria index, the hardness of the well water is almost dependent on the calcium hardness, so the water discharge measuring means (60) and the incoming water measuring means (50) A meter can be used.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 shows a schematic configuration of a free carbonic acid removing device 10 according to an embodiment of the present invention. The free carbonic acid removing device 10 includes a pump 12, two electrodes 20 arranged opposite to each other in a water channel, a voltage applying means 30 for applying an AC voltage to the electrodes 20, and a dissolving means for storing granular calcium carbonate. The dissolved water tank 40, the incoming water measuring means 50, and the discharged water measuring means 60 are provided. Thick line arrows in the figure indicate paths through which water to be treated flows.
[0020]
The pump 12 takes in raw water such as well water from a water intake port (not shown) and sends out the taken water so that the water taken out is discharged from a water discharge port (not shown) between the two electrodes 20 and the dissolved water tank 40. To fulfill. The voltage applying means 30 applies an alternating voltage between the two electrodes 20. The voltage application unit 30 includes a control circuit 31, a transmission circuit 32, and a drive circuit 33. The transmission circuit 32 generates an alternating current signal, and the control circuit 31 controls the frequency and voltage of the alternating current 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.
[0021]
The dissolution water tank 40 is a water tank for performing a dissolution treatment for dissolving calcium carbonate or slaked lime in water that has been subjected to electrical treatment by passing between the electrodes 20, and contains granular calcium carbonate. Slaked lime is added. The dissolution water tank 40 has a water inlet 41 at the lower part and a water outlet 42 at the upper part. The dissolved water tank 40 can be replenished with calcium carbonate and slaked lime by opening an upper lid (not shown). As calcium carbonate, for example, shells of oysters, oysters or shellfish that are usually treated as waste may be used. Caustic soda and soda ash may be used instead of slaked lime.
[0022]
The incoming water measuring means 50 measures the Langeria index of incoming water (raw water) before being subjected to electrical treatment or dissolution treatment or a value instead of this. The water discharge measuring means 60 measures the Langerian index of water after the electric treatment and the dissolution treatment or a value in place of it. For example, when the calcium hardness is measured instead of the Langeria index, since the hardness of well water or the like usually depends almost on the calcium hardness, a hardness meter is used as the incoming water measuring means 50 or the discharged water measuring means 60. be able to. Further, the concentration of carbon dioxide in water may be used instead of the Langeria index. If the carbon dioxide concentration in the water is extremely high (for example, there is free carbon dioxide of 10 ppm or more), it is considered necessary to improve the Langeria index. If a groundwater source is used, the concentration is about 30 ppm. Therefore, the AC voltage and frequency are adjusted by this concentration.
[0023]
The control circuit 31 of the voltage application unit 30 performs a feedforward control of the voltage and frequency applied to the electrode 20 based on the measurement value of the water entry measurement unit 50, and the measurement value of the water discharge measurement unit 60 becomes a predetermined value. Thus, the voltage and frequency applied to the electrode 20 have a function of feedback control. The voltage applying means 30 can control the voltage applied between the two electrodes 20 in the range of 0.5 to 10.0 volts as an effective voltage and the frequency between 30 Hz and 10 kHz. ing.
[0024]
FIG. 2 shows the voltage application water tube 22 to which the electrode 20 is attached. In the tube of the voltage application water tube 22, two electrodes 20 formed of stainless steel or the like are disposed to face each other. Near the center of these electrodes 20, an electrode connection portion 23 for connecting a power supply lead wire from the drive circuit 33 is formed. Joints 24 for connecting to other water pipes 29 are formed at both ends of the voltage application water pipe 22. In the free carbonic acid removal device 10, between the 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 tube 22, the voltage application water tube 22 A water pipe is connected between the other end and the water inlet 41 of the dissolved water tank 40, and between the water outlet 42 of the dissolved water tank 40 and a discharge port (not shown).
[0025]
The Langeria index (saturation index... SI) is expressed by SI = pH-pHs (2). 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 represented by the formula (1) is in an equilibrium state. If SI> = 0, the water is not corrosive, and if SI <0, it is corrosive. pHs can be obtained by pHs = (9.3 + A + B) − (C + D) (3). In equation (3), A is an evaporation residue coefficient, B is a temperature coefficient, C is a calcium hardness coefficient, and D is 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.
[0026]
As an alternative to the Langeria index, calcium hardness may be used, or a value based on two of 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 change width and does not have a great influence on the Langeria index obtained by the equation (3). In the case of well water, since the water temperature is stable, measurement of the water temperature may be omitted. Furthermore, the water source for well water and clean water is usually inland, so the hardness of the water that is the source of water does not need to be considered as sodium, and almost depends on the calcium hardness. The measured hardness may be used. In addition, carbon dioxide concentration in water may be used instead of the Langeria 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 and frequency are controlled. There is also a method using pH, but pH moves in the acidic direction depending on the carbon dioxide concentration, and moves in the alkali direction depending on the calcium (or sodium) concentration. Therefore, only one of them is used when the raw water is stable. Also good. However, if the location of the water treatment plant is close to the sea and the surface water (river) and groundwater (well water) are blended as the water source, or if the blend ratio is changed as necessary, as many parameters as possible, If possible, it is desirable to obtain the Langeria index.
[0027]
Next, the operation will be described.
The free carbonic acid removing device 10 takes in raw water from a water intake through a 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 from the water inlet 41 to the water outlet 42 through the dissolved water tank 40 and is discharged from the free carbonic acid removal device 10. It flows out from the exit. The incoming water measuring means 50 measures the calcium hardness as a Langeria index of raw water taken from the intake port or as an alternative to this. The control circuit 31 of the voltage application means 30 performs feedforward control on the AC voltage and the frequency applied between the electrodes 20 based on the measurement value of the incoming water measurement means 50. The control circuit 31 is data indicating the correspondence relationship between the applied voltage and / or frequency to be set so that the Langelia index at the discharge port becomes the target value and the measured value of the incoming water measuring means 50, and obtained in advance by experiments. Is remembered. The control circuit 31 refers to the previous data based on the measured value of the incoming water measuring means 50 to obtain appropriate applied voltage and frequency values and performs feedforward control.
[0028]
In addition, the Languelia index of the water discharged from the outlet 42 of the dissolving water tank 40 or a value instead of this is measured by the water discharge measuring means 60, and the control circuit 31 is configured so that the measured value becomes a predetermined target value. Feedback control is performed on the voltage and frequency of an AC signal applied between the two electrodes 20. Here, the target value of the Langeria index is set to a predetermined value between −1 and +0.8.
[0029]
When passing between the two electrodes 20 arranged inside the voltage application water tube 22, the nature of the water changes. As a result, the chemical reaction of the formula (1) generated during or after passing through the dissolving water tank 40 is promoted to the right, and the erosive free carbonic acid is efficiently and sufficiently removed. This is because when an alternating current is passed through water, the molecular cluster of H ₂ O decreases from an aggregate of several tens (positions 20 to 30) to an aggregate of several tens to several. This is because the number of H ₂ O molecules involved in the chemical reaction increases. In addition, it is known that by passing an alternating current through water, the angle of H ₂ O molecules changes from 108 degrees before treatment to another angle, which is one factor that promotes the previous chemical reaction to the right. It is believed that there is.
[0030]
The degree of acceleration of the chemical reaction of the formula (1) in the right direction varies depending on the applied voltage and frequency. Therefore, by controlling the applied voltage and frequency based on the measurement value of the water discharge measuring means 60, it is possible to discharge water with the Langelia index adjusted to the target value. In addition, since the degree of reaction can be controlled by the applied voltage and frequency, the amount of calcium carbonate accommodated in the dissolving water tank 40 may be any amount as long as it is more than the necessary amount. As a result, it becomes easy to replenish calcium carbonate to the dissolving water tank 40, and continuous processing becomes possible.
[0031]
For example, some water before being treated by the free carbonic acid removing device 10 has an evaporation residue of 50 to 300 mg / l, and the evaporation residue coefficient A is 0.1 from FIG. The temperature was between 18 and 21 ° C., and the temperature coefficient B was 2.1. The calcium hardness was 56 to 69 mg CaCO ₃ / l, and the calcium hardness coefficient C was 1.4. The alkalinity D was 1.6 and the pH was 7.1. When these are substituted into the equation (3), pHs = (9.3 + 0.1 + 2.1) − (1.4 + 1.6) = 8.5. Further, from the formula (2), the Langeria index of this water is SI = 7.1-8.5 = −1.4. Therefore, this SI was corrosive because SI was -1 or less.
[0032]
When this same water is treated by the free carbonic acid removing device 10, the reaction of the formula (1) efficiently proceeds to the right and the amount of calcium carbonate to be hydrated increases, so that the calcium hardness becomes 175 to 220 mgCaCO ₃ / l. The calcium hardness coefficient C was 1.9, the alkalinity D was 2.3, and SI = 7.1-7.3 = −0.2. In addition, if SI is -1 or more, it is supposed that the anticorrosion effect can be anticipated. After leaving the free carbonic acid removal device 10, the chemical reaction of the formula (1) proceeds slowly to the left, and the calcium carbonate film adheres to the pipe wall and cuts off the contact between water and the pipe wall. The anticorrosive effect can be obtained.
[0033]
The present invention has been described above based on the embodiments. However, the present invention is not limited to those exemplified in the embodiments, and includes various modified embodiments without departing from the gist of the present invention. That is, the applied voltage, frequency, electrode shape and arrangement, dissolution tank structure, and the like are not limited to those shown in the embodiment.
[0034]
In the embodiment, the feedforward control based on the measurement value of the incoming water measurement means 50 and the feedback control based on the measurement value of the water discharge measurement means 60 are used together, but only one of the controls may be employed. For example, only feedback control may be employed as long as the Langeria index of water discharged at the beginning of operation is allowed to deviate from the target value. Further, it is also possible to measure the value of the Langeria index of the discharged water or a substitute for it, and manually adjust the applied voltage or frequency to the electrode 20 based on the measurement result.
[0035]
Furthermore, only one of the paired electrodes may be used, and the other may be the water pipe 22 itself. Alternatively, the two water tubes 22 themselves that are insulated without the electrodes may be used as the two electrodes. In other words, if electricity can be passed through water, the shape of the electrode is not particular.
[0036]
In this Embodiment, although the apparatus which removes free carbonic acid was provided in the water intake part of the water purification plant, you may attach this apparatus to the water intake part of an apartment, for example. Further, it may be attached to the water supply connection part of the water heater or built in the water heater. Furthermore, not only water but also industrial water may be used for preventing corrosion of industrial water piping and cooling system piping by attaching this apparatus to groundwater intakes of factories and power plants.
[0037]
In the embodiment, the pump 12 is built in the free carbonic acid removing device 10, but a device such as a pump for feeding raw water to the free carbonic acid removing device 10 may be provided separately from the free carbonic acid removing device 10.
[0038]
In addition, in embodiment, it processed in order of the electrical treatment and the melt | dissolution process with respect to incoming water, However, These may be reverse order. Moreover, you may comprise so that an electrical process and a melt | dissolution process may be performed simultaneously in one place. For example, calcium carbonate is disposed between the electrodes 20.
[0039]
【The invention's effect】
According to the apparatus for removing free carbonic acid according to the present invention, since an electric treatment for supplying an alternating current to water and a dissolution treatment for dissolving calcium carbonate or slaked lime in water are performed, calcium carbonate or the like can be used as compared with a case where no electric treatment is performed. The dissolution reaction is promoted, and the erosive free carbonic acid can be converted to a hydroxide salt quickly and efficiently. As a result, the conventional process of storing water in a water tank for a long time to sufficiently perform the dissolution reaction, the process of preparing and mixing an aqueous solution of calcium carbonate to promote the reaction, and aeration No processing or the like is required, and the apparatus can be reduced in size and price. Moreover, since dissolution treatment is promoted by applying electric treatment, erodible free carbonic acid can be removed while continuously passing water to be treated.
[0040]
If the voltage applied by the voltage application means and / or frequency can be set and changed, adjust the Langerial index of water after electrical treatment and dissolution treatment to an appropriate value. Can do.
[0041]
In the case of measuring the Langerial index of water after electric treatment and dissolution treatment or the value of the water substitute, and feedback-controlling applied voltage and / or frequency so that the value becomes a predetermined value The water quality of the discharged water can be automatically adjusted to a preferred Langeria index.
[0042]
In addition, the Langerian index of the incoming water before electric treatment or dissolution treatment or a value of an alternative to this is measured, and based on this value, feedforward control of applied voltage and / or frequency is preferable. Exponential water can be discharged from the beginning.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a schematic configuration of a free carbonic acid removing apparatus according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view showing a voltage application water tube of the free carbonic acid removal apparatus according to one embodiment of the present invention.
FIG. 3 is an explanatory diagram showing a coefficient conversion table for obtaining a Langeria index.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 10 ... Free carbonic acid removal apparatus 12 ... Pump 20 ... Electrode 22 ... Voltage application water tube 23 ... Electrode connection part 30 ... Voltage application means 31 ... Control circuit 32 ... Transmission circuit 33 ... Drive circuit 40 ... Dissolution water tank 41 ... Water inlet 42 ... Water outlet 50 ... Incoming water measuring means 60 ... Water discharge measuring means

Claims (5)

In a free carbonic acid removal device that removes erosive free carbonic acid in water,
A pair of electrodes, a voltage applying means for applying an alternating voltage between these electrodes, and a dissolving means for dissolving calcium carbonate or slaked lime in water,
An apparatus for removing free carbonic acid, comprising: subjecting water to be treated to an electrical treatment in which an alternating current is passed by the electrode and the voltage applying means; and a dissolving treatment to dissolve calcium carbonate or slaked lime by the dissolving means. The apparatus for removing free carbonic acid according to claim 1, wherein the electric treatment and the dissolution treatment are performed while water to be treated is continuously passed. 2. The apparatus for removing free carbonic acid according to claim 1, wherein the voltage applying means is capable of setting and changing both or one of applied voltage and frequency. Having water discharge measuring means for measuring the Langerial index of water after the electric treatment and the dissolution treatment, or a value of an alternative thereto,
3. The free carbonic acid removing device according to claim 1, wherein the voltage application unit controls both or one of the applied voltage and the frequency so that a measured value of the water discharge measuring unit becomes a predetermined value. 4. . It has an incoming water measuring means that measures the value of the Langerian index of incoming water or an alternative,
5. The free carbonic acid removal according to claim 1, wherein the voltage application unit controls the applied voltage and / or the frequency based on a measurement value of the incoming water measurement unit. apparatus.

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