JP2008051603A - Streaming potentiometer - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a streaming potentiometer capable of reducing a noise or a drift to a streaming potential signal generated between electrodes by adjusting a flow velocity state inside a sensor head (especially between the electrodes). <P>SOLUTION: In an insulating and corrosion-resistant straight pipe 6 wherein water to be treated flows, a core body 7 made of a similar material is arranged at a fixed interval with the straight pipe 6 inner surface. This streaming potentiometer wherein at least two electrodes 9 are arranged near both ends of the core body 7, in contact with the water to be treated flowing in the straight pipe 6, equipped with a measuring part 13 for measuring a potential difference generated in the water to be treated between each electrode 9, 9, has characteristics wherein the water to be treated flowing in the fixed interval between the straight pipe 6 inner surface and the core body 7 flows in a laminar state with changing flow velocity. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a flow potentiometer for detecting an aggregation state after adding an aggregating agent in an aggregation precipitation process.

  Conventionally, a coagulating sedimentation process has been widely used in a water purification process that uses surface water such as river water and lake water as raw water, or in industrial water and wastewater. This is because aluminum or iron inorganic flocculant or polymer flocculant is added to the raw water, and first, it is rapidly stirred in a relatively short time to generate micro flocs (small lumps) with turbid particles as the core. . This is a process for obtaining clear supernatant water by carrying out slow agitation, enlarging the micro flocs by collision and bonding of the micro flocs, increasing the sedimentation speed, and carrying out the precipitation treatment. Further, the supernatant water is filtered to remove particles that could not be precipitated.

  In the coagulation precipitation treatment, coagulation conditions such as the addition amount of the coagulant, the stirring intensity, the stirring time, the water temperature, and the pH must be appropriate. In particular, after the addition of the flocculant, it is necessary to detect the agglomerated state quickly and accurately. That is, from this detection result, an appropriate amount of flocculant can be added, the amount of flocculant added can be reduced, and clear treated water can be obtained. As described above, the aggregation state detection sensor plays an important role in the aggregation precipitation process.

  The aggregation state detection sensor is roughly divided into the following two methods. One is a method of directly measuring the particle size of optically turbid particles (see, for example, Patent Document 1).

  The other is a method of measuring the charge state of turbid particles in the test water as a so-called flowing current related to the zeta potential. That is, as is well known, turbid particles, for example, colloidal particles such as dust are charged to (−) charge, and a so-called flow current is measured along with the flow. The colloidal particles alone do not agglomerate because the (−) charged particles repel each other. Therefore, a (+) charge coagulant is added for neutralization. Due to this neutralization of the charges, the colloidal particles become nonpolar particles and are attracted to each other and aggregated by intermolecular force. In addition, the flow current value decreases due to the neutralization of the charge. Therefore, by measuring this flowing current, it is possible to detect the turbid aggregate state after the addition of the flocculant.

  This method of measuring the flowing current was devised by Gerdes as a sensor that can be continuously measured online, and when test water flows into the piston type sensor, it is applied to both ends of the cylinder wall that wraps the piston. This is a method for measuring a flowing current between arranged electrodes. This method is widely used in water purification plants overseas because it can detect the flowing current with a simple structure, and has recently been used in several water purification plants in Japan.

In this system, since the potential detection part of the sensor body is driven by a piston, the shaft center of the piston is displaced from the initial position due to dirt on the cylinder tube wall when continuously operated for a long period of time. As a result, the distance between the piston and the cylinder partially changes, and a stable flow potential (current) cannot be measured. For such a problem, a proposal related to a cleaning apparatus has also been made (for example, see Patent Document 2).
Japanese Patent Laid-Open No. 10-202013 JP-A-9-15193

  As described above, the configuration having the piston has a problem that a stable flowing current cannot be measured due to the influence of dirt due to long-term use.

  Accordingly, the present applicant has proposed a flow electrometer that can measure a flowing current without requiring a movable object such as a piston. This flow potentiometer is a sensor head with a cylindrical cylinder that is a core in an insulating straight pipe, electrodes are placed on both ends of the pipe, and a pulsating flow of test water is circulated through the gap between the core and the straight pipe. This is a method for detecting a flowing current by causing the current to flow.

  Since this flow potential meter does not require a movable object such as a conventional piston, the flow potential (current) can be measured stably over a long period of time. However, since this is a new configuration, various improvements have been found, leading to the present invention.

  An object of the present invention is to provide a flow electrometer that can reduce noise and drift to a flow potential signal generated between electrodes by adjusting the flow velocity state inside the sensor head (particularly between the electrodes). is there.

  In the flow potential meter according to the present invention, a core is arranged in a straight pipe through which water to be treated flows, and an outer peripheral surface thereof forms a flow path having a constant interval with the inner peripheral surface of the straight pipe. A flow electrometer equipped with a measuring part for measuring a potential difference generated in the water to be treated between these electrodes by arranging electrodes so as to be in contact with the water to be treated flowing in this flow path at or near both ends of the path, There is provided a means for flowing the water to be treated flowing through the flow path at a predetermined interval between the inner surface of the straight pipe and the core body in a laminar flow state so that the flow rate thereof changes.

  In the present invention, the straight pipe is provided with a valve capable of adjusting the flow rate of the water to be treated flowing through the straight pipe, and the bypass pipe that bypasses the inflow side and the outflow side of the straight pipe including the valve. The roads may be connected.

  Moreover, in this invention, you may arrange | position the rectifier which rectifies | straightens the flow of the to-be-processed water in this straight pipe pipe to a laminar flow state in the to-be-processed water inflow side of a straight pipe.

  Further, in the present invention, among the electrodes arranged in the straight pipe, the upstream side electrode has a laminar flow state of the water to be treated from the start end of the flow path constituted by the straight pipe and the core. The downstream electrode may be disposed on the downstream side by a distance that settles down, and the downstream electrode may be disposed at a predetermined distance from the upstream electrode.

  In the present invention, the distance from the start end to the end end of the flow path constituted by the straight pipe and the core is set to be twice or more the distance required for normal flow potential measurement. With respect to the direction of the treated water flow, electrodes are installed at the upstream, intermediate, and downstream distances required for normal flow potential measurement, and the measurement unit includes an upstream electrode, an intermediate electrode, and an intermediate electrode. The structure which measures each potential difference which arises in to-be-processed water between downstream electrodes may be sufficient.

  Moreover, in this invention, the means to flow so that the flow rate of to-be-processed water may change shall change the flow rate of to-be-processed water to the pulse shape which repeats with a predetermined period.

  Moreover, in the present invention, the means for flowing the flow rate of the water to be treated is controlled so that the flow rate of the water to be treated is a triangular wave that rises and falls at a constant rate and at a constant rate. But you can.

  Further, in the present invention, the means for flowing the flow rate of the water to be treated is controlled so that the flow rate of the water to be treated is a square wave having a predetermined period and a constant flow rate change for a certain period. But you can.

  According to the present invention, the water to be treated that flows in the flow path between the inner surface of the straight pipe and the core material flows in a laminar flow state so that its flow rate changes, thereby generating a flow potential generated between the electrodes. Noise and drift to the signal can be reduced.

  Hereinafter, an embodiment of a flow potential meter according to the present invention will be described in detail with reference to the drawings.

  FIG. 1 conceptually shows the overall configuration of the flow electrometer. In FIG. 1, reference numeral 1 denotes a sensor head, and water to be treated (also water to be tested) is supplied by a pump 2. The treated water that circulates in the sensor head 1 is drained through the flow meter 5. The sensor head 1 measures the flow potential (current) of the water to be treated. In addition, the flow meter 5 measures the flow rate of the water to be treated flowing through the sensor head 1 and monitors the flow state.

  Reference numeral 3 denotes a control circuit which inputs measurement values from the sensor head 1 and the flow meter 5 and outputs a control command to the pump 2. 4 is a computer for monitoring control (a personal computer is used in the figure), and is connected to the control circuit 3. The measured flow potential value is input from the control circuit 3 to detect the aggregation state of the water to be treated. To do.

  Next, the internal configuration of the sensor head 1 will be described with reference to FIG.

  In FIG. 2, 6 is a straight pipe through which the water to be treated flows, and is made of an insulating and corrosion-resistant material, and forms an outline of the sensor head 1. A core 7 made of the same material is concentrically disposed on the shaft core in the insulating and corrosion-resistant straight pipe 6. The core body 7 is disposed such that the outer peripheral surface thereof is spaced from the inner peripheral surface of the straight pipe 6. The core body 7 is fixed by a core holding jig 8 disposed inside caps 12 provided at both ends of the straight pipe 6. The holding jig 8 has a plurality of liquid circulation holes. The cap 12 was screwed into the pipe, and an O-ring was inserted inside the cap 12 to prevent liquid leakage. A hose nipple 10 can be attached to the cap 12 and a hose 11 through which water to be treated (measuring liquid) can be circulated. Therefore, the water to be treated that flows into the cap 12 from the hose 11 passes through the liquid flow hole of the holding jig 8 and is formed between the inner peripheral surface of the straight pipe 6 and the outer peripheral surface of the core body 7. It passes through the channel of the interval, and is drained to the hose 11 through the holding jig 8 and the cap 12 on the opposite side.

  Furthermore, the electrode 9 is arrange | positioned in the straight pipe 6 near the both ends of the core body 7, respectively. The electrode 9 is formed in a ring shape and is placed in contact with the water to be treated flowing in the straight pipe 6. These electrodes 9 are connected to a measuring unit 13 that measures a potential difference generated in water to be treated between these electrodes.

  Here, the material of the straight pipe 6 and the core 7 installed therein may be any insulating and corrosion-resistant material. For example, polyvinyl chloride, Teflon (registered trademark), delrin (polyacetal resin), or the like is used. It is done. As the electrode 9, stainless steel (SUS304) was used. The gap between the outer peripheral surface of the core body 7 and the inner peripheral surface of the straight pipe 6 was 0.2 ± 0.05 mm. However, this gap can be freely adjusted by changing the diameter of the core body 7 or the pipe 6. In this example, the straight pipe 6 has a diameter of about 30 mm and a length of about 45 mm.

  To this sensor head 1, water to be treated is sent in a pulsating manner by a diaphragm pump 2, and the gap between the core body 7 and the pipe wall of the straight pipe 6 is circulated, and is generated at the electrodes 9 at both ends of the core body 7. The electromotive force was amplified to obtain a flowing current.

  Thus, since the flowing current can be detected by the sensor head 1 having a simple structure, a stable output can be obtained over a longer period of time than before.

  However, in order to realize a fine flocculant injection according to the aggregation state in the water purification plant, it is important to improve the sensitivity of the sensor for capturing the aggregation state and its change.

Here, when a fluid is passed through two parallel flat plates having a small interval, the voltage (flow potential correlating to the aggregation state) V generated at both ends of the flow path (parallel flat plate) is expressed by the following equation. .

Where ε: dielectric constant, L: channel length, σ: conductivity, u ₀ : maximum liquid flow velocity, E: magnitude of electric field, a: channel width, Φo: potential of parallel plate It is.

  The sensor head 1 can be considered to be approximately equivalent by considering a cylindrical structure in which two parallel flat plates are rolled and connected.

  In the above equation (1), the permittivity and conductivity depend on the treated water, and the influence on the streaming potential equation can be corrected by using a sensor for measuring each. Further, the structural elements relating to the structure of the sensor head 1, a: the width of the flow path, L: the length of the sensor head, and Φo: the potential of the sensor head may be considered to be substantially constant if the material, shape and dimensions are determined. it can. For this reason, the equation (1) can be considered as simplified as the following equation (2).

V = C × u ₀ (2)
Here, C is a constant (considered to be constant depending on the correction of dielectric constant and conductivity, the material of the sensor head, shape and size), and u ₀ is the maximum flow velocity of the liquid. Therefore, the flow potential V is considered to be proportional to the maximum flow velocity u _{0 of the} liquid.

  However, in practice, the flow velocity is limited in the following points.

a: The flow state is laminar.

b: Large polarization does not occur on the electrode surface.

  Regarding a, the flow current is difficult to detect in the vicinity of the electrode in the turbulent flow due to the measurement principle of the streaming potential, so it must be in a laminar flow state. Regarding b, at a steady flow rate, polarization occurs between the metal surface in contact with the fluid due to the difference between the potential of the metal itself and the potential of the fluid. That is, as is well known, each substance has its own potential. There is a capacitive component (C) between the water and the metal, and when the water is stationary or the water flow is constant, the capacitive component causes polarization and the voltage becomes unstable. When the potential between the electrodes 9 and 9 is measured in this state, the polarization state changes due to changes in the flow state and fluid composition, resulting in noise and drift in the signal detected between the electrodes. .

  From the above, it can be seen that there is a restriction on the flow state of the measurement fluid and the flow velocity associated therewith in order to perform accurate measurement in the apparatus for detecting the flow potential.

  The cause of the problem is likely to occur when the flow state between the electrodes for measuring the streaming potential is other than the laminar flow state, that is, when the Reynolds number is more than a certain value (2000 or more), or when the treated water has a constant flow rate. This is caused by the polarization of the electrode surface. In these cases, the streaming potential cannot be measured accurately, or the error increases even if it can be measured.

  Therefore, in order to achieve a high-sensitivity flow potential meter that is less affected by noise and drift, the maximum flow rate of the water to be treated should be in a range that satisfies the laminar flow state, and measures should be taken so as not to cause large polarization on the electrode surface It will be necessary.

  As shown in FIG. 2, in the flow potential meter of this embodiment, a core 7 made of the same material is concentrically disposed in an insulating and corrosion-resistant straight pipe 6, and the outer peripheral surface of the core 7 A flow path with a constant interval a is formed between the inner peripheral surface of the straight pipe 6 and water to be treated containing colloidal particles flows through the flow path. And the annular electrode 9 is each arrange | positioned in two places of the both ends vicinity of the core 7 so that an inner fluid may be contacted, and each electrode 9 is connected with the electric potential difference measurement part 13 with the electric wire. Therefore, the potential difference measuring unit 13 is configured to measure a potential difference generated between the electrodes 9 when the water to be treated is caused to flow through the flow path.

  The potential difference measured between the electrodes 9 and 9 changes according to the amount of the added flocculant (for example, PAC: polyaluminum chloride) when the water to be treated containing colloidal particles is flowed. That is, the response has a correlation with the aggregation state.

  Here, as described above, a: the flow state is a laminar flow, b: a countermeasure is taken so as not to cause a large polarization between the electrode surface and the specimen (treated water), noise or This is important for stable streaming potential measurement with small drift.

  In order to achieve the laminar flow state of a, the Reynolds number Re = v × d / ν determined from the kinematic viscosity coefficient ν of the subject, the diameter d of the tube through which the subject flows, and the flow velocity v is at most 2000 or less. Need to be. Since the kinematic viscosity coefficient ν of the subject varies depending on the sampling location and season, a certain degree of tendency is grasped from the past water quality test results and test results for a certain period. Then, a numerical value equal to or smaller than the minimum value is adopted. By doing so, the Reynolds number Re is set large, so that even if the kinematic viscosity coefficient of the subject fluctuates, the Reynolds number Re tends to decrease and it is easy to maintain a laminar flow state. The control of the flow rate can be easily realized by controlling the flow rate of the pump 2. That is, as shown in FIG. 1, the flow meter 5 is installed on the downstream side of the sensor head 1 (also on the upstream side), and the flow rate signal is sent to the control circuit 3 so that the flow velocity can maintain the laminar flow state. The pump 2 can be feedback controlled. Even if the pump 2 has an abnormal flow rate (zero flow rate or continuous flow rate that causes turbulent flow, etc.), the control circuit 3 can make a diagnosis and alert the host system and the user. Can be put out.

  In order to prevent the polarization of the electrode surface of b, the polarization state can be prevented by changing the flow rate (flow rate) of the liquid to be treated. How to change will be described later.

  By implementing the above measures, it is possible to detect a streaming potential with less noise and drift.

  Next, the embodiment shown in FIG. 3 will be described. FIG. 3 is a diagram showing the configuration of the sensor head 1 portion and peripheral devices of the flow potential meter. As peripheral devices, there are provided three electric variable valves (hereinafter simply referred to as valves) 21, 22, and 23 and a pipe line 24 that bypasses one part of the sensor head. That is, valves 21 and 22 that can adjust the flow rate of water to be treated flowing through the straight pipe 6 are provided for the straight pipe 6 that constitutes the sensor head 1, and the straight pipe 6 that includes the valves 21 and 22. This is a configuration in which a bypass conduit 24 that bypasses the inflow side and the outflow side is connected. The bypass pipe 24 is provided with a valve 23 that can adjust the bypass flow rate.

  With this configuration, when the flow rate of the pump 2 cannot be controlled, or when the flow rate range that can be controlled even if the flow rate of the pump 2 is larger than the required flow rate, the three valves 21 shown in FIG. , 22 and 23 can be adjusted to change the flow rate flowing into the sensor head 1, that is, the flow velocity. For example, when the flow velocity to the sensor head 1 is high, in order to reduce the flow velocity, the opening degree of the valves 21 and 22 provided before and after the sensor head 1 is lowered and the valve 23 installed in the bypass line 24 is opened. By increasing the degree, the flow rate to the sensor head 1, that is, the flow velocity can be reduced.

  As described above, it is possible to control the flow rate wider than in the case of the pump 2 alone. In addition, by setting the opening of the valve 23 to 100% and the opening of the valves 21 and 22 provided before and after the sensor head 1 to 0% (completely closed), the inflow of treated water into the sensor head 1 Can be stopped. In this state, maintenance (cleaning, inspection, parts replacement, etc.) of the sensor head 1 can be easily performed.

  Next, the embodiment shown in FIG. 4 will be described. FIG. 4 is a diagram showing the configuration of the sensor head 1 portion and peripheral devices of the flow potential meter. It is the structure which added the rectifier 14 which stabilizes a flow with respect to the structure of FIG. 3 mentioned above. That is, a rectifier 14 that rectifies the flow of the water to be treated in the straight pipe 6 into a laminar flow state is disposed on the treated water inflow side of the straight pipe 6 constituting the sensor head 1.

  Usually, when a butterfly valve, a bent pipe or the like is on the upstream side, the flow state on the downstream side becomes a swirling flow and is disturbed. When the subject flows into the sensor head 1 in the turbulent flow state, the flow state in the sensor head 1 is similarly disturbed, and it becomes difficult to detect the flow potential. Therefore, the rectifier 14 is arranged on the upstream side of the sensor head 1 in order to make the turbulent flow state a stable laminar flow. As the rectifier 14, a plate having a large number of holes formed in parallel is used. When this rectifier 14 is used, even if it is in a turbulent flow state, after passing through the hole of the rectifier 14, it becomes a state parallel to the flow direction, that is, a state close to a laminar flow. As a point to be noted, it is necessary to consider that pressure loss is generated by the rectifier 14.

  Next, the embodiment shown in FIG. 5 will be described. FIG. 5 is a diagram showing the configuration of the sensor head 1 portion of the flow potential meter. The position of the upstream (right side in the drawing) electrode 9a among the electrodes shown in FIG. 2 is moved to the downstream side (left side in the drawing) by a distance Le from the inflow portion as shown in FIG. In FIG. 5, it seems that only the upstream electrode 9a is moved to the downstream side, but the downstream electrode 9b is also moved to the left side by the same distance Le so that the same inter-electrode distance as in FIG. 2 can be obtained. It is composed.

  The reason for this configuration is as follows. In the sensor head 1, a flow path having a very narrow gap (less than 1 mm) is formed between the inner peripheral surface of the straight pipe 6 and the outer peripheral surface of the core body 7 in order to detect the flow potential. Yes. This channel shape is significantly different from the channel shape (pipe diameter) of the subject flowing into the sensor head 1 from the upstream side pipe. For this reason, the flow velocity gradient in the vicinity of the wall surface in the sensor head 1 is increased, and the flow potential of the subject may be disturbed (decreased). The distance until this flow velocity gradient becomes a laminar flow has been determined theoretically and experimentally. The distance Le is expressed by the following equation (3) from the Reynolds number Re and the tube diameter d.

Le = 0.058 × Re × d (3)
Therefore, by moving the positions of the electrodes 9a and 9b in the sensor head 1 to the downstream side by the distance Le from the inflow portion, the flow velocity gradient in the vicinity of the wall surface in the electrode 9a portion inside the sensor head 1 becomes stable (laminar flow). Become. Thereby, the flow potential in which the flow velocity distribution is stable in the laminar flow state can be detected.

  That is, among the two electrodes 9 a and 9 b arranged in the straight pipe 6 constituting the sensor head 1, the upstream electrode 9 a is started from the flow path constituted by the straight pipe 6 and the core body 7. From the end, it is arranged downstream by a distance Le by which the flow of water to be treated settles in a laminar flow state. The downstream electrode 9b is arranged at a predetermined distance from the upstream electrode 9a. With this configuration, the flow velocity gradient in the vicinity of the wall surface in the electrode 9a portion inside the sensor head 1 is in a stable state (laminar flow), and an accurate flow potential in which the flow velocity distribution is stable in the laminar flow state can be detected.

  Next, the embodiment shown in FIG. 6 will be described. FIG. 6 is a diagram showing the configuration of the sensor head 1 portion of the flow potential meter. The length of the sensor head 1 shown in FIG. 2 is doubled, the third electrode 9c is arranged between the electrodes 9a and 9b at both ends, and the potential difference between each electrode 9a and 9c and between 9c and 9b is detected. It is the composition to do. That is, the distance from the start end to the end end of the flow path constituted by the straight pipe 6 and the core body 7 of the sensor head 1 is set to at least twice the distance required for normal streaming potential measurement. With respect to the flow direction of the water to be treated in this flow path, an electrode 9a is installed upstream, an electrode 9c is installed in the middle, and an electrode 9b is installed downstream. The distances between these electrodes 9a and 9c and between 9c and 9b are the distances required for normal streaming potential measurement. And the potential difference which arises in the to-be-processed water between the upstream electrode 9a and the intermediate part electrode 9c, and the intermediate part electrode 9c and the downstream electrode 9b is measured by the measurement part 13, respectively.

  In such a configuration, when the flow of water to be treated is stable in a laminar flow, the potential difference (flow potential) generated between the electrodes 9a and 9c and between 9c and 9b is a stable value. . However, when the flow state is disturbed, the potential difference between the upstream electrodes 9a and 9c is disturbed. As a result, it is possible to detect that the flow state is disturbed and the flow is no longer laminar. In the control circuit 3, the pump 2 shown in FIG. 1, the electric variable valve 21 shown in FIGS. 3 and 4, By adjusting the opening degree of 22 and 23, the state of the flow can be stabilized.

  Next, changing the flow rate of the water to be treated will be described. As described above, in order to prevent polarization on the electrode surface, it is necessary to change the flow rate (flow velocity) of the water to be treated. That is, when the flow rate of the water to be treated in the sensor head 1 is constant, the surface of the electrode 9 is polarized as described above due to the potential difference between the surface of the electrode 9 and the subject. For this reason, the polarization state changes due to slight turbulence of the flow or collision with large particles contained in the water to be treated (analyte), causing noise or drift in the potential difference between the electrodes, which becomes an error factor. Therefore, the flow rate of the water to be treated in the sensor head 1 is changed at a flow rate that satisfies the laminar flow condition. By changing the flow rate in this way, polarization can be reduced, and a stable streaming potential can be measured.

  For example, as shown in FIG. 7, the change in the flow velocity causes a pulsed flow in which the flow velocity always changes. Thereby, the influence of the noise and drift by the said polarization can be reduced. However, the pump 2 is controlled below the flow velocity at which the Reynolds number Re in the sensor head 1 is 2000 or less so that the flow state does not become turbulent. As the pump 2, a normally electromagnetically driven diaphragm pump is used. That is, in order to generate a pulsed flow velocity, the operation of a diaphragm pump that can be obtained at low cost can be used as it is. The pulse period tw of the flow velocity is empirically appropriate in the range of 10 ms to 250 ms in consideration of polarization and pump characteristics.

  In this way, changing the flow velocity in a pulse shape can be easily and inexpensively configured. However, on the other hand, the flow rate change is likely to be rapid, and depending on the characteristics of the pump, a hunting-like flow rate change may be superimposed, which may be a noise factor other than polarization. In other words, the diaphragm pump presses the drive rod against the diaphragm due to its operating principle, but this contact causes extra vibration in addition to the meter due to this contact, and this causes a change in flow rate on hunting. This is because it occurs.

  Therefore, as shown in FIG. 8, it is preferable to change the flow velocity in a triangular wave shape so that the flow velocity changes with constant acceleration. Thereby, hunting of the flow velocity is difficult to occur, and noise reduction can be realized. The change in flow velocity in the triangular wave shape can be realized by the opening degree control of the valves 21 and 22 shown in FIGS. The pulse period tw of the flow velocity is empirically appropriate from about 10 ms to 1 s in consideration of polarization.

Furthermore, as another method, as shown in FIG. 9, the flow rate of the water to be treated may be changed in a square wave shape. Here, the flow potential V is proportional to the flow velocity u ₀ as described in the equations (1) and (2). However, when the flow velocity increases, the flow state changes from laminar flow to turbulent flow, and it becomes difficult to detect the flow potential.

  Therefore, the maximum flow velocity that can maintain the laminar flow state as shown in FIG. 9 is ensured for a certain period, and the flow of the flow is made into a square wave that periodically changes the flow velocity at intervals where the polarization of the electrode surface is not large and the influence of noise drift is small. Control. In this case, the pulse period tw of the flow velocity is empirically appropriate from about 10 ms to 1 s in consideration of polarization.

  By doing so, it is possible to maintain a maximum steady flow velocity time in which the streaming potential can be increased and the polarization state does not occur, and it is possible to increase the number of streaming potential measurements and reduce the influence of noise. .

It is a system configuration | structure figure which shows the whole structure of the flow potential meter by this invention. It is a figure explaining the internal structure of the sensor head in one Embodiment same as the above. An embodiment of the present invention in which a bypass path is provided in a sensor head will be described. An embodiment of the present invention in which a rectifier is added to a sensor head will be described. It is a figure explaining embodiment which changed the electrode position in the sensor head of this invention. It is a figure explaining embodiment which increased the number of electrodes in the sensor head of this invention. It is a characteristic view explaining the case where the to-be-processed water in the sensor head of this invention is changed into the flow rate in a pulse form. It is a characteristic view explaining the case where the to-be-processed water in the sensor head of this invention is changed into a triangular wave-like flow velocity. It is a characteristic view explaining the case where the to-be-processed water in the sensor head of this invention is changed into flow velocity in square wave shape.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sensor head 2 Pump 6 Straight pipe 7 Core body 9 Electrode 13 Potential difference measurement part 14 Rectifier 21, 22, 23 Valve 24 Bypass path

Claims (8)

The core body is arranged in the straight pipe where the water to be treated flows, so that the outer peripheral surface forms a channel with a certain distance from the inner peripheral surface of the straight pipe, and this core is located at or near both ends of the channel. Each of the electrodes is disposed so as to be in contact with the water to be treated flowing through the flow path, and is a flow electrometer equipped with a measuring unit that measures a potential difference generated in the water to be treated between these electrodes
A flow electrometer comprising: means for flowing the water to be treated flowing through the flow passage at a predetermined interval between the inner surface of the straight pipe and the core in a laminar flow state so that the flow velocity thereof changes. .   A straight pipe is provided with a valve capable of adjusting the flow rate of water to be treated flowing through the straight pipe, and a bypass pipe that bypasses the inflow side and the outflow side of the straight pipe including the valve is connected. The flow potential meter according to claim 1.   The flow potential according to claim 1 or 2, wherein a rectifier that rectifies the flow of the water to be treated in the straight pipe pipe into a laminar flow state is disposed on the treated water inflow side of the straight pipe. Total.   Out of the electrodes arranged in the straight pipe, the upstream electrode is arranged downstream from the start end of the flow path composed of the straight pipe and the core by the distance at which the water to be treated settles in a laminar flow state. 4. The flow electrometer according to claim 1, wherein the downstream electrode is disposed at a predetermined distance from the upstream electrode. 5.   The distance from the start end to the end end of the flow path composed of the straight pipe and the core is set to at least twice the distance required for normal flow potential measurement, and the flow direction of the treated water in this flow path Electrodes are installed at the upstream, intermediate, and downstream sides of the distance required for normal streaming potential measurement, and the measurement unit is located between the upstream electrode, the intermediate electrode, and the intermediate electrode and the downstream electrode. The flow potential meter according to any one of claims 1 to 4, wherein a potential difference generated in the water to be treated is measured.   The fluid electrometer according to any one of claims 1 to 5, wherein the means for causing the flow rate of the water to be treated to change changes the flow rate of the water to be treated in a pulse shape that repeats at a predetermined cycle. .   The means for causing the flow rate of the water to be treated to change is controlled so that the flow rate of the water to be treated is a triangular wave that rises and falls at a constant rate and at a constant rate. The flow potential meter according to any one of claims 1 to 5.   The means for flowing so that the flow rate of the water to be treated changes is controlled so that the flow rate of the water to be treated has a predetermined period and a square wave shape in which the flow rate change is constant for a certain period. The flow potential meter according to any one of claims 1 to 5.

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