JPH0798138B2 - Method for measuring the flow state of Bingham fluid in a stirring tank - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION "Industrial field of application" The present invention measures the flow state of a Bingham fluid stored in a stirring tank and efficiently stirs the fluid according to its characteristics. The present invention relates to a method for measuring the flow state of Bingham fluid in a tank.

"Conventional technology and its problems" High-concentration slurry containing fine particles such as clay mud and paint shows so-called Bingham fluid flow behavior in which flow occurs only when shear stress exceeds a certain yield value.
As a result, when stirring is performed in a stirring tank using a turbine blade, a paddle blade, or the like as the stirring blade, a phenomenon occurs in which the fluid flows near the blade and stands still away from the blade.

In addition, since such a high-concentration slurry is a mixture of solid and liquid, it is generally impossible to observe the internal flow from the outside of the stirring tank because light does not pass therethrough, which is the flow of the slurry. This is an obstacle to quantitatively examining the condition.

This invention has been made in view of the above circumstances, prototype electrode probe utilizing the electrical conductivity method, the boundary between the static region and the flow region of the Bingham fluid in the stirring tank,
An object of the present invention is to provide a method for measuring the flow state of a Bingham fluid in a stirring tank, which can detect the direction of flow in a flow region.

[Means for Solving the Problem] In order to achieve the above object, in the present invention, a tracer injection needle that is a positive electrode and an electrolyte tracer solution is injected into the Bingham fluid stored in a stirring tank, and this tracer injection. A step of charging an electrode probe composed of a negative electrode arranged around the needle, and a step of stirring the Bingham fluid in the stirring tank while injecting an electrolyte tracer solution from a tracer injection needle of the electrode probe; , A step of detecting the movement of the electrolyte tracer solution and determining the flow state of the Bingham fluid based on the potential between the tracer injection needle as the positive electrode and the negative electrode, and stored in the stirring tank. The flow state of the Bingham fluid is measured.

[Operation] According to the present invention, it is possible to detect whether or not the electrolyte tracer solution is moving, based on the potential between the tracer injection needle as the positive electrode forming the electrode probe and the negative electrode. And it can be determined whether the Bingham fluid is stationary or flowing.

[Embodiment] An embodiment of the present invention will be described with reference to FIGS. 1 (A) to 9 (A).

The method for measuring the flow state of the Bingham fluid shown as an example of the present invention uses an electric conductivity method in which a difference in electric conductivity between a high-concentration slurry that is an object to be stirred and an electrolyte tracer solution is detected by an electrode probe. It is a thing.

(1) Structure of Electrode Probe First, the structure of the electrode probe will be described with reference to FIG. 1 (A). This electrode probe is a positive electrode and a tracer injection fine needle M into which a strong electrolyte tracer solution is injected. (Tracer injection needle) and negative electrodes 1 to 8 arranged around the tracer injection fine needle M, wherein the negative electrodes 1 to 8 are around the tracer injection fine needle M. And are arranged at equal intervals (a distance of 8 mm in the present method) from the tracer injection fine needles M so as to form a solid and spherical surface.

The total number of the negative electrodes 1 to 8 is eight, but it is preferable that the number is large in order to perform precise measurement. However, if the number of the negative electrodes 1 to 8 is increased too much, interference between the electrodes 1 to 8 occurs or the interval between the electrodes 1 to 8 narrows,
A phenomenon occurs in which the fluid becomes stationary between the electrodes 1 to 8.

Therefore, in this example, the relationship between the number of negative electrodes and the interval between the negative electrodes suitable for measurement was examined, and the number of eight electrodes was determined.

The specific structure of the tracer injection fine needle M is as follows.
As shown in FIG. (B), an insulating coating M ₁ is provided on the outer side, and a positive electrode M ₂ as an injection tube into which the strong electrolyte tracer solution is injected is arranged so as to project from the insulating coating M ₁ . Further, the specific structure of the negative electrodes 1 to 8 is such that the outer side is provided with insulating coatings 1A to 8A as shown in FIG. 1C, and the electrode portions 1B to 8B are arranged so as to project from the insulating coatings. It is a thing.

(2) Overall Structure An outline of the stirring tank in which the above electrode probe is used for measurement will be described with reference to FIG. 2 (A).

In FIG. 2 (A), reference numeral 10 is a cylindrical flat-bottom type stirrer tank without an obstruction plate having an inner diameter of 20 cm. In this stirring tank 10, six flat blades having a diameter of 1/2 of the inner diameter of the tank are provided. Turbine blades 11 are arranged.

The six flat blade turbine blades 11 are arranged at the center position of the tank 10 and at a position half the depth of the tank 10,
The drive is performed by the motor 12.

In addition, the electrode probe described in (1) is arranged in the measurement area shown by the hatching in the stirring tank 10.

This electrode probe is provided with a conduit 13 connected to the positive electrode M ₂ which is an injection tube, a micro metering pump 14 for supplying a strong electrolyte tracer solution through this conduit 13, and the potentials of the negative electrodes 1 to 8 respectively. A measuring circuit 15 (to be described later) for measuring is provided respectively.

Further, the positive electrode M ₂ as the injection tube of the electrode probe has 15
V voltage (constant) is applied.

In addition, using the electrode probe, in the measurement region in the stirring tank 10 shown by hatching in the figure, the radial direction of the stirring tank 10 and the liquid depth direction are measured at intervals of 5 mm (described later). . As the stirring blades used in the stirring tank 10, in addition to the turbine blade 11 shown in the schematic view of FIG. 2 (A) and the perspective view of FIG. 2 (B), the stirring blade of FIG. The paddle wings 16 shown in perspective view are used.

(3) Measurement Principle [3-] Regarding the determination standard K, a strong electrolyte tracer solution adjusted to have the same rheological characteristics as the high-concentration slurry from the tracer injecting fine needle M is used at a constant rate by the micro-quantitative pump 14. After the injection, the potentials of the negative electrodes 1 to 8 were instantaneously and simultaneously held and measured after a fixed time after a relatively short time.

Then, using the value measured at this time, that is, the potential Ei of the electrode, a value K, which is a reference for determining whether the high-concentration slurry is stationary or flowing, was calculated by the following equation.

K = (Ei−E _min ) / (E _o −E _min ), where “Ei” is each potential of the negative electrodes 1 to 8 (where i is
Is 1 to 8). Since a constant voltage is applied to the positive electrode M ₂ of the electrode probe, the potentials of the positive electrodes M ₂ and the negative electrodes 1 to 8 are consequently detected by detecting the potentials of the negative electrodes 1 to 8. Will be detected.

Further, "Emin" represents the negative electrode 1 to 8 (where i is the minimum potential among the potentials indicated by, and "O" represents the potential of the strong electrolyte tracer solution itself.

[3-] Discrimination of Boundary Position between Stationary Region and Flowing Region From the criterion K obtained in this way,
Whether to determine whether the high-concentration slurry is stationary or flowing will be described with reference to FIGS. 3 (A), 3 (B) and FIG.

The numbers 1 to 8 shown in these figures are numbers conveniently attached to the eight electrodes, and the shaded portions represent the strong electrolyte tracer solution.

FIG. 3 (A) shows an example of the flow of the strong electrolyte tracer solution in the static region. In this case, the strong electrolyte tracer solution supplied from the tracer injection fine needle M is injected by the tracer. The high-concentration slurry is diffused almost evenly around the fine needle M. Further, FIG. 3 (B) shows an example of the flow state of the strong electrolyte tracer solution in the flow region. In this case, the strong electrolyte tracer solution supplied from the tracer injection fine needle M is It moves following the flow of high-concentration slurry.

[3−] Change in K value of each electrode in each region As shown in FIG. 4, the horizontal axis represents each electrode number (i = 1 to 8),
Taking K on the vertical axis and examining the change in the value of K in each of the stationary state and the flowing state, the value of K is relative in the stationary state (the state shown in FIG. 3A) as shown by the thin line. It is understood that the value of K is relatively large in the flow state (the state shown in FIG. 3B) as shown by the thick line, while it is minute and has little variation.

In this case, the potential of the negative electrode (in this case, the negative electrode in which i is 1 and 5: see FIGS. 4 and 3B) in the flow direction as shown by the thick line is higher than the potentials of the other electrodes. Becomes higher,
Therefore, the value of the criterion K also becomes large.

Even if one of the K obtained here is a certain set criterion value
If there is more than K _c , it is determined that the strong electrolyte tracer solution is flowing together with the high-concentration slurry, and conversely, if all K are K _c or less, the strong electrolyte tracer solution with the high-concentration slurry is determined. The solution was determined to be stationary.

[Three -] stationary, wherein the determination of the criterion value K _c of the flow, either in the present process a high concentration slurry is stationary, in order to determine whether the criterion value K _c is flowing, to flow at a constant rate The electrode probe was inserted into the high-concentration slurry, and the potential difference was measured by changing the slurry speed. The measurement results are summarized in FIG.

FIG. 5 shows the potential difference between the velocity V of the slurry on the horizontal axis and the potential of the measured electrode i (the potential of the third electrode here) on the vertical axis and the minimum value of the potentials of the negative electrodes 1 to 8. (Ei-Emin), respectively.

Then, as can be seen from FIG. 5, it was confirmed that the potential difference remarkably appeared when the flow velocity of the slurry was about 0.15 mm / s or more.

At this time, K calculated from the potential of each electrode is 0.09.
Becomes Although only the third electrode is shown here, it has been confirmed that the potential difference becomes remarkable when the velocity of the slurry is 0.15 mm / s or more in other electrodes, and K at that time becomes 0.09.

Therefore, in this method, the same numerical value of 0.09 is used as the reference value for stationary and flow.
I decided to set it as K _c .

By the above-mentioned method, at a large number of measurement positions in the stirring tank 10, the stationary state of the high-concentration slurry in the stirring tank 10 is determined based on the data of the determination of the stationary state and the flowing state. be able to.

On the other hand, when some of the potentials of the electrodes show values of K _c or more, the flow direction of the high-concentration slurry can also be determined. This will be described later with reference to FIGS. 8 (A) to 8 (C) and FIGS. 9 (A) to 9 (C).

(4) Peripheral devices and various conditions for experiments [4] Block diagram of measuring circuit Next, the measuring circuit 15 shown in the schematic diagram of the stirring tank in FIG.
The block diagram of will be described with reference to FIG.

Hold circuit 20 takes in signals from eight negative electrodes 1 to 8 instantaneously and simultaneously, and controls these signals.
21 is used to sequentially select by the photo isolation relay 22, and A / D conversion is performed by the A / D conversion circuit 23 to display the potentials of the negative electrodes 1 to 8 on the display unit 24.

In the measuring circuit of FIG. 6, the reference numeral 25 indicates a bypass circuit for adjusting the output voltage from the photo isolation relay 22, and the reference numeral 26 always indicates the potential based on the ground. It is a zero adjustment circuit.

[4-] Target Bingham pseudo-fluid (and tracer solution) The Bingham pseudo-fluid as a high-concentration slurry that is an object to be measured will be described.

This Bingham pseudo-fluid is calcium carbonate (density ρ = 14
It is a non-sedimenting slurry that is mixed with water (60 kg / m ³ , an average particle size of 3.12 μm and having a very sharp particle size distribution) and water at a ratio of 50 wt% to form a suspension water.

The flow curve of this fluid is "U-Rheometer manufactured by Iwamoto Seisakusho"
The results are shown in FIG.

In Fig. 7, the horizontal axis is the shear rate [0 to 1500 l / s] and the vertical axis is the shear stress τ [Pa]. The relationship between them is examined. It was confirmed that it had a flow curve. The rheological equation of this fluid is expressed by τ = τ _o + η _o ·, and from this equation, the yield stress (τ _o ) and plastic viscosity (η _o ) of the fluid are expressed as follows. That is, yield stress; τ _o = 1.01 × 10 ² Pa, plastic viscosity: η _o ＝ 4.59 × 10
It has been confirmed to be ^-2 Pa · s.

[Four-] setting conditions for measurement Using the experimental apparatus shown in (2) above and the Bingham fluid prepared in [Four-], when the high-concentration slurry was stirred, the high-concentration slurry flowed. It was determined whether or not the robot was standing still. However, the slurry flow rate is set to 0.15 mm / s or higher.

The following settings were made for such measurement.

(1) As the strong electrolyte tracer solution, a solution prepared by dissolving sodium chloride in the Bingham fluid prepared in [4] above was used. At this time, the NaCl concentration of the strong electrolyte tracer solution was 0.15 mol / l.

(2) The strong electrolyte tracer solution was supplied from the tracer injection fine needle M at a rate of 3.6 × 10 ^-2 ml / s. At this time, after the injection of the strong electrolyte tracer solution, the hold circuit 20
Therefore, the time to hold the potential was set to 10 s.

The strong electrolyte tracer solution measures the potentials of the negative electrodes 1 to 8 for various NaCl concentrations and creates a calibration curve for the relationship between these potentials and the NaCl concentration.
The optimum NaCl concentration (0.15 mol / l) was detected from this calibration curve.

Further, in the measurement by the electrode probe, in order to improve the resolution, the electrode probe is slightly rotated in the horizontal plane at the same measurement position point, or the insertion direction is changed in several steps, and the measurement is performed several times.

[4-] Example of measurement results using turbine blade (experimental device shown in FIGS. 2A and 2B) As an example of measurement by the measurement device described in (2) above, a blade is used.
The rotation speed n of 11 was changed to 3.33, 5.00, and 6.67 s ^-1 in three steps, and the radial direction R (from the center of the tank to the tank wall) about the shaded portion (see FIG. 2 (A)) in the device diagram. ), The electric potential is measured by changing the measurement position at intervals of 5 mm in the liquid depth direction Z (from the center position of the tank to the liquid surface), and from this measurement result, it can be determined whether the high-concentration slurry is flowing or stationary. It was judged.

The determination results are shown in FIGS. 8 (A) and 8 (B). In these figures, the black circles indicate the flow region,
The other part is the still area.

From these results, within the range of n in this experiment, the stirring tank 10
It was found that there were a static region and a flow region inside, and it was confirmed that the flow region indicated by a black circle increased as n increased.

In this case, the flow region has a strong tendency to expand in the liquid depth direction Z rather than the radial direction R as the rotational speed of the blade 11 increases. It was also confirmed that it was remarkable.

On the other hand, the flow direction of the slurry in the flow region is
Although the downward flow and the upward flow are measured in the vicinity of the shaft supporting the shaft and in the vicinity of the wall side boundary of the stirring tank 10, respectively, most of them are in the θ direction, that is, the rotation direction of the blade 11, and the fluid in the flow region is the blade. Along with 11, it was also confirmed that a circular flow was occurring.

[4−] Example of measurement result using paddle blade (shown in FIG. 2 (C)) Next, a turbine blade 11 is used by using a six-paddle blade 16 as shown in FIG. 2 (C). The measurement was performed under the same conditions and under the same conditions as the experimental apparatus shown in FIG. 2 (A). An example of the experimental result at this time is shown in FIG.

As can be seen from FIGS. 9 (A) to 9 (C), when the paddle blade 16 is used, the blade rotation speed n is 6.67 as compared with the result when the turbine blade 11 is used. At s ^-1 , the flow region extends to the tank wall, and at the same n paddle blades 16
Is that the flow area near the stirring axis is wider in the liquid depth direction.
It was confirmed that the shape of the flow region differs depending on the blade shape.

[4−] Static and Flow Region Visualization Experiments Above, examples of the results of static and flow region measurement of the high-concentration slurry in the stirring tank 10 using the present measuring device are shown. Inside, a visualization experiment was conducted to observe the state of the static region and the flow region. In this visualization experiment, the high-concentration slurry is stirred in the stirring tank 10, and a tracer in which India ink is mixed is injected into the vicinity of the blade 11, and then the rotation of the blade 11 is stopped.

After that, the blade was gently pulled out upward, a thin transparent plate having an edge-treated edge was inserted, and the inserted transparent plate was vertically divided into two parts, and a photograph was taken from the side.

Referring to the photograph obtained by this photography, it was confirmed that there was a flow region colored with India ink and a non-colored white stationary region, and the flow region was as shown in FIG. 8 (A).
-It was confirmed that it exists in the same range as the experimental results shown in Fig. 8 (C) and Fig. 9 (A) -Fig. 9 (C).

As described in detail above, according to the method for measuring the flow state of the Bingham fluid in the stirring tank shown in the present embodiment, in the high-concentration slurry as the Bingham fluid stored in the stirring tank 10, the positive electrode and the electrolyte A step of introducing an electrode probe composed of a tracer injection fine needle M into which a tracer solution is injected and negative electrodes 1 to 8 arranged around the tracer injection fine needle M, and tracer injection of the electrode probe The process of stirring the high-concentration slurry in the stirring tank 10 while injecting the electrolyte tracer solution from the fine needle M for use, and the potentials of the tracer injection fine needle M of the electrode probe and the negative electrodes 1 to 8 From the step of determining the flow state of the high-concentration slurry, it is detected whether the strong electrolyte tracer solution injected from the tracer injection fine needle M is moving, and It can be determined whether the slurry is stationary or flowing.

Then, based on the judgment results obtained in this way, the type of stirring blade and the rotation speed can be set to the optimum one, and a high-concentration slurry containing fine particles such as clay mud and paint can be adjusted according to its characteristics. The effect of being able to stir efficiently is obtained.

[Advantages of the Invention] As described above, according to the present invention, it is determined whether the Bingham fluid is stationary or flowing, and based on the determination result, the type of stirring blade and the rotation speed are optimized. Can be set to.

As a result, a high-concentration slurry containing fine particles such as clay mud and paint can be efficiently stirred according to its characteristics.

Further, by varying the measurement position by the electrode probe, it is possible to obtain the effect that the distribution of the Bingham fluid flow region can be known and the flow direction of the fluid can also be known. .

[Brief description of drawings]

1 (A) to 9 (C) are views showing an embodiment of the present invention, wherein FIG. 1 (A) is a detailed view of the tip of an electrode probe, and FIG. 1 (B) is tracer injection. Showing a fine needle for the first
FIG. 2C is a diagram showing a negative electrode, FIG. 2A is a schematic diagram of an experimental device, FIGS. 2B and 2C are turbine blades,
FIG. 3 (A) and FIG. 3 (B) are diagrams showing the paddle blades, respectively, and FIG. 3 (A) and FIG. FIG. 5 is a diagram showing a change, FIG. 5 is a diagram showing a minimum slurry velocity at which an electrode can sense, FIG. 6 is a block diagram of a measuring circuit, FIG. 7 is a diagram showing a flow curve of a high-concentration slurry, FIG. 8 ( 8A to 8C are diagrams showing changes in the flow region when the rotational speed is changed using turbine blades, and FIG. 9A to FIG.
FIG. 9 (C) is a diagram showing changes in the flow region when the rotation speed is changed by using a paddle blade. M: Tracer injection fine needle (tracer injection needle), 1-8
…… Negative electrode, 10 …… Stirring tank.

Claims (1)

[Claims] 1. An electrode probe comprising a tracer injection needle, which is a positive electrode and into which an electrolyte tracer solution is injected, into a Bingham fluid stored in a stirring tank, and a negative electrode arranged around the tracer injection needle. And a step of stirring the Bingham fluid in the stirring tank while injecting the electrolyte tracer solution from the tracer injection needle of the electrode probe, and the potential between the tracer injection needle as the positive electrode and the negative electrode. The method of measuring the flow state of the Bingham fluid in the stirring tank, which comprises the step of detecting the movement of the electrolyte tracer solution and determining the flow state of the Bingham fluid based on the above.