JPS5851217B2 - Slurry concentration measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a method for automatically and continuously measuring the concentration of slurry containing solid suspensions that are relatively easy to settle, such as mixer wash wastewater in a ready-mixed concrete plant or mixer car wash wastewater. This invention relates to a slurry concentration measuring device for the purpose of.

In ready-mixed concrete production plants, secondary cement product plants, etc., wastewater is used to clean concrete mixers, concrete mixer trucks, formwork, etc., and wastewater generated during the recovery of aggregate from waste concrete, etc.
There are many places where large amounts of wastewater and slurry containing cement and fine sand are generated.

If such wastewater or slurry is discharged outside the factory, it will cause pollution due to water pollution, so it is required that it be used as concrete mixing water within the factory and not be discharged outside the factory. For this purpose, an automatic slurry concentration measuring device is required that can accurately and continuously measure the solid content in these wastewaters.

However, since this type of slurry contains unhydrated cement, it is likely that solids will form inside the containers and pipes in which it is deposited, and the sedimentation rate of the slurry is relatively fast, so if it is left untreated, Conventionally, it has been considered extremely difficult to continuously automatically measure @1 degree of this type of slurry because cement and sand settle and accumulate at the bottom of the device, making continuous operation difficult.

In general, there are two methods for measuring the concentration of slurry, which is made up of fine solids turbid in a liquid. A method of measuring the concentration of the slurry by utilizing changes in specific gravity is conventionally known.

However, when ultrasonic measurement is used to measure the concentration of slurry generated from a ready-mixed concrete manufacturing plant, cement tends to stick to the surfaces of the ultrasonic transmitter and receiver, causing serious errors. The relationship between ultrasound attenuation and slurry concentration is typically highly non-linear, so the solids content required for this type of measurement is stable over a wide range of 0-15%. It has been considered extremely difficult to carry out accurate measurements.

In addition, the ultrasonic method often causes serious errors due to air bubbles contained in the slurry due to the AE agent normally contained in this type of wastewater, which is extremely problematic in practice.

Measurement methods that take advantage of the fact that the specific gravity of slurry changes due to changes in slurry concentration include methods that collect slurry in a container with a fixed volume and measure its weight, and methods that take advantage of the fact that the specific gravity of slurry changes due to changes in slurry concentration. There are known methods that utilize the fact that buoyancy changes with changes in slurry concentration, and measurement methods that take advantage of the fact that the pressure at a constant level of slurry changes with changes in slurry concentration.

Among these methods, the method of measuring the weight by collecting the sample in a container causes an extremely large error due to cement etc. adhering to the container and changing the dead weight of the container, making it difficult to carry out safe continuous measurement over a long period of time. It is practically difficult to use for this purpose.

Next, the measurement method that uses the buoyant force acting on the float still causes large errors due to cement adhering to the surface of the float, and it can be said that this method is also almost impossible to use for the above purpose.

In addition, there is also a measurement method that utilizes the fact that the liquid pressure in slurry at a certain depth changes depending on the concentration of the slurry. In this case, the change in liquid pressure caused by the change in concentration is about 3% of the slurry concentration, which is reused as mixing water in ready-mixed concrete manufacturing plants and secondary cement product plants. This method only changes the ±0.2% required for measuring the concentration of slurry used in mixing water in a ready-mixed concrete plant.
In order to measure with an accuracy of 1,000 mm, it is necessary to measure the hydraulic pressure with an accuracy of 1 minute per 1,000 mm of water column, that is, an accuracy of 1/1000.This is more than 1/1,000 even if we look only at the pressure detection device. This requires measurement accuracy of
It must be said that this is not possible as an industrial measurement method.

In addition, the slurry is based on the fact that the liquid pressure at a certain measurement depth changes due to changes in slurry concentration due to changes in air temperature, liquid temperature, flow rate changes in the slurry to be measured, and other factors. It is impossible to adopt the concentration measurement method as a method for measuring the concentration of slurry used in mixing water for freshly mixed compost.

As mentioned above, the first method to solve the problem is
As shown in the figure, a reference cylinder 52 containing no slurry is provided in parallel with the slurry concentration measuring cylinder 51, and the upper ends of the slurry to be measured and the reference liquid are held in the same plane by means such as overflow, The liquid pressure at each same depth is measured by a method such as measuring the exhaust pressure of a pressure transmission pipe, and the liquid pressure is calculated based on the change in slurry concentration at a given depth by removing the effects of changes in liquid temperature and air temperature. A known method is to measure the slurry concentration by detecting only changes in pressure using a differential pressure gauge or the like.

However, even with this method, when the purpose is to measure low concentrations such as slurry used as mixing water in raw compost, it is extremely difficult to maintain a constant flow rate of slurry concentration in the measuring tube. Q
As shown above, the depth of the slurry overflow shown by is ±1.
Since it is practically impossible to keep the temperature constant within a certain range, this method also cannot fully satisfy the purpose of the present invention.

Next, we improved the method shown in Figure 1 by connecting the overflow surface of the reference tube to the overflow surface of the measurement tube, so that even if the slurry supply amount fluctuates to some extent, the liquid level of the reference tube and slurry The inventor has separately proposed a method for achieving the object of the present invention by improving the overflow surface so that it changes in conjunction with the measuring depth so that the measured depth remains substantially the same (see patent application No. 1 filed at the same time). )issue)
However, this is as shown in FIGS. 3 and 2.

Note that FIG. 8 is a sectional view taken along [[-■] of FIG.

However, in this method, it is often necessary to use a type of water such as industrial water that inevitably contains some contaminants as the reference liquid indicated by the arrow 50, and in such cases, As shown in Figure 2, a water outlet 10' is provided at the bottom of the reference tube, and care must be taken to prevent sediment from accumulating at the bottom of the reference tube. The amount of water flowing into the tank must be maintained at a certain level per minute. Therefore, if a relatively small slurry concentration adjustment tank is used and continuous operation is required, the arrow in Figure 3 is used. A problem arises in that the consumption of water used for the measurements indicated by 50 is high and this affects the operation of the plant.

Although this problem can be alleviated to a considerable extent by using fresh water as the water supplied to the reference tube and by eliminating the water outlet 10' at the lower end, this device cannot be used outdoors in the winter. Accidents occur when the water remaining in the reference cylinder freezes when the operation is stopped, and this problem can sometimes be solved by installing a solenoid valve or the like to drain the water when the operation is stopped. However, actually using such a device in a cold region is not a desirable method as it is likely to cause trouble.

As explained in detail above, the present invention includes conventional methods and methods separately proposed by the inventors (patent application (1) filed at the same time).
This solution solves many of the problems inherent in the slurry, almost eliminates the need for water as a reference liquid for measurement, and eliminates the influence of large fluctuations in the supply amount of the slurry to be measured. It is possible to continuously and automatically measure the concentration of slurry containing cement and fine sand, which is reused as mixing water in ready-mixed concrete in very small quantities, with an accuracy of about 0.2% at a concentration of around 3%, and the maintenance and management of the equipment is easy. The present invention makes it possible to provide a slurry concentration measuring device that is easy and inexpensive.

The main parts of the slurry concentration measuring device according to the present invention are shown in FIGS. 5 and 4.

Figure 5 shows v-■ of the slurry concentration measuring device shown in Figure 4.
It is a directional cross-sectional view.

In the sectional view shown in FIG. 4, the slurry to be measured is supplied into the measuring tube 39 through the inlet 2 as indicated by the arrow 1.

In this case, an overflow edge 9 is provided at the upper end of the supply port, and a discharge port 5 is provided at the bottom end of the overflow edge 9, so that a portion of the slurry supplied by arrow 1 is disposed as shown by arrow 10. Discharged through outlet 5, the other portion forms an overflow surface indicated by 13 and overflows into slurry overflow device 38 and is discharged out of the device as indicated by arrow 7.

At the beginning of operation of this device, as is clear from the figure, the slurry supplied to the measuring tube 39 is connected to the measuring tube 39 at the lower end 36 by the partition plate 25 which exists inside the device and forms the reference tube 16. The reference cylinder 16 where it communicates is filled.

In this case, 11 in FIG. 4 indicates the measuring tube 39 and the reference tube 1.
It shows the depth of communication with 6.

Note that the upper end of the reference tube 16 is sufficiently higher than the overflow edge of the upper end of the measurement tube 39, and has a structure that surrounds the reference tube 16 on all sides.
The liquid level of the slurry formed at the upper end of the slurry 6 does not form an overflow surface, but forms a free liquid level 15.

Therefore, at the beginning of the operation of this device, since the slurry existing in the measurement cylinder 39 and the slurry existing inside the reference cylinder 16 are almost the same slurry, the free surface 15 formed at the upper end of the measurement cylinder is located at approximately the same position as the overflow surface 13 of the measuring cylinder 39.

However, as time passes after the start of operation, there is almost no flow in the slurry inside the reference cylinder 16, so the solid matter in the slurry inside the reference cylinder 16 gradually settles, and after the start of operation, the solids in the slurry inside the reference cylinder 16 gradually settle. After a few minutes to more than 10 minutes have elapsed, only the reference liquid containing no solids will exist inside the reference cylinder 16.

Therefore, in such a situation, the hydraulic pressure in the measuring tube 39 in the communicating section 11 and the hydraulic pressure in the communicating section 11 of the reference tube 16 will be equal, so that the difference in specific gravity between the two liquids will cause the pressure in the measuring tube 39 in the communicating section 11 to be equal to that in the communicating section 11. There is a liquid depth difference, C, between the height of the liquid column existing above, that is, the overflow height B of the slurry to be measured, and the depth A of the free liquid surface of the reference liquid from the communication part 11. This difference in liquid level height C is the specific gravity of the standard solution, ρw1, measurement depth B, and the difference △ρ between the specific gravity of the slurry to be measured and the standard solution is expressed by the following relational expression. holds true, and C is directly proportional to the difference in specific gravity between the two liquids, resulting in a linear relationship.

Therefore, in the measuring apparatus shown in FIGS. 5 and 4, the concentration of the slurry to be measured is measured by measuring the height difference C between the overflow surface of the slurry and the free liquid level of the reference liquid. be able to.

Any method can be used to measure C1 in FIG. 4, that is, the difference in liquid level between the overflow surface of the slurry to be measured and the free surface 15 of the standard solution.
The figure shows a pressure transmission pipe 20 inserted slightly deeper than the overflow edge 9 of the slurry to be measured, and a pressure transmission pipe 19 inserted into the reference liquid to the same depth as 20.
When the gas indicated by 4 is bubbled through the fluid resistances 17 and 18, the respective exhaust pressures are introduced into the differential pressure gauge 23 through the impulse pipes 21 and 22, and the difference C between the liquid levels of both liquids is calculated.
This is an example of a case in which .

In the slurry concentration measuring device according to the present invention, arrow 1
When the supplied amount of slurry to be measured, which is indicated by Fluctuations in the base slurry overflow surface 13 will immediately receive pressure transmission from this communication and the free surface of the reference liquid shown at 15 will also fluctuate accordingly, so that they do not cause significant errors.

In this case, near the lower end of the reference cylinder 16, that is, the communication part 11
If the free surface 15 of the reference liquid rises in the vicinity, some slurry may flow into the reference cylinder 16, but this will immediately settle to form the reference liquid, so it is not practical. An acceptable response of the measuring device can be obtained.

Note that there is an inlet 2 for introducing the slurry 1 to be measured into the measuring tube 39.
As for the position of , it is best to introduce it from the middle of the measuring tube 39 as shown in FIG.
0, but the flow rate is regulated by the differential pressure determined by the fluid resistance at the discharge port 5 and the depth of the overflow surface of the slurry, so the fluid resistance at the discharge port 5 By appropriately determining , the flow of slurry existing near the communication portion 11 is hardly affected by fluctuations in the amount of slurry introduced.
The effects of variations in the free surface of the reference liquid 15 caused by changes in slurry concentration and changes in slurry flow rate do not significantly affect the results of the measurements.

Furthermore, when the flow rate of the slurry introduced into the measuring device shown by the arrow 1 fluctuates, this variation mainly becomes a fluctuation in the flow rate 8 of the overflow formed at the upper end of the measuring tube 39 shown by the arrow 3. However, as mentioned above, within a certain range, this effect can be avoided by communicating the measuring tube and the reference tube.

As shown in detail above, the slurry concentration measuring device according to the present invention shown in FIGS. It is extremely effective for continuously and dynamically measuring the slurry concentration of about 3% solids concentration required when used as There is no need to supply the reference solution that is required in the method shown, which not only saves losses due to dilution of the slurry to be measured and consumption of the reference solution, but also eliminates the need to supply the slurry automatically when the slurry supply is stopped. Since the contents of the device itself are discharged through the discharge port 10, accidents caused by freezing during winter operation can be prevented.

Furthermore, when a bubbling method is used as a device for measuring the difference in liquid level, as in the method shown in Figs. 1, 2, and 3, the insertion depth of the pressure transmission tube can be measured by The fact that it only needs to be installed at an extremely shallow location near the upper end of the liquid level is extremely advantageous in terms of maintenance management, and is useful for maintenance management such as removing slurry that adheres to the inner surface of the pressure transmission pipe or recovery work in the event of a blockage accident. Compared to the slurry concentration meters shown in Figures 1, 2, and 3, it has a much simpler structure and easier maintenance, and its price is also lower. you can get something.

However, in the slurry concentration measuring device according to the present invention shown in FIGS. 4 and 5, it takes some time from the start of supplying the slurry until the slurry finishes settling in the reference tube 16 and a clear reference liquid is formed. is necessary,
For example, if the height of A in FIG. 4 is 500 mm, this will require several minutes to more than ten minutes.

In this case, once the liquid inside the reference tube 16 becomes clear, the response of the measuring device is sufficiently fast and it is possible to use it as a continuous measuring device for adjusting the slurry concentration. Normally, there will be no problem if the time is outside of a few minutes to more than 10 minutes.

However, in very special cases, when there is a need to know the measured value immediately, the water supply indicated by arrow 26 may be forced into the reference tube 16 only at the beginning of operation using the water supply device indicated by 24. If a clear reference liquid is formed by supplying the reference liquid, a measured value can be obtained in about several tens of seconds to one minute, and then the supply of this reference liquid can be stopped.

Alternatively, the settling accelerator may be supplied by the water supply device 24 only at the beginning of operation to rapidly settle the solids inside the reference cylinder 16.

In this case, of course, it is sufficient to supply the sedimentation accelerator for only a few seconds after the start of operation, and the amount of sedimentation accelerator supplied in this case does not actually pose any problem in terms of operating costs or maintenance. Once this is done, there is no need to supply a reference solution or a sedimentation accelerator.

Next, an embodiment of the slurry concentration measuring device according to the present invention having even more advanced performance will be described in detail.

In the slurry concentration measuring device according to the present invention shown in FIGS. 4 and 5, when the amount of slurry flowing into the measured value fluctuates by about ±25% of the set value, the desired performance is sufficiently maintained. Although it is possible to do this, errors may occur due to even wider fluctuations in the amount of slurry inflow.

The cause of this is the measuring tube 3 shown by arrow 3 in Fig. 4.
The amount of slurry that rises and overflows inside the slurry inlet 9 changes depending on the change in the amount of slurry flow.In this case, if a large fluctuation in the flow rate occurs near the slurry inlet 2, A change in the state of the vortex occurs in the vicinity,
This causes a pressure drop inside the measuring cylinder, and even though there is no change in the slurry concentration, this amount is caused by the fluctuation of the slurry overflow surface 13 through the communication part 11, and the reference liquid
This is because it becomes a factor that changes the water level of No. 5.

In addition, when using the differential pressure of the exhaust pressure of the pressure transmission pipe as shown in Fig. 4 as a device for measuring the difference in liquid level between the overflow surface of the slurry and the free surface of the reference liquid, , the insertion depth D of the pressure transmission pipe inserted into the measuring tube 39 varies according to the top and bottom of the overflow surface, and for this depth D, the specific gravity of the slurry liquid differs from the specific gravity of the reference liquid. Therefore, when measuring the difference in liquid level using the differential pressure method, the variation in the depth D of the slurry overflow surface due to the variation in the slurry flow rate is superimposed as an error. It turns out.

All of these problems can therefore be solved if the amount of slurry flowing into the measurement can be kept approximately constant using a very simple device.

In addition to this, foreign matter is often mixed into the slurry used as mixing water in raw compost, and it is difficult to say that there is no possibility that this will cause a clogging accident at the discharge port 5.

Therefore, since the amount of slurry introduced into the measuring device shown in FIGS. 4 and 5 according to the present invention is kept almost constant, and the device for removing foreign matter is incorporated in a simple structure, the slurry concentration measurement according to the present invention can be carried out. The performance of the device is perfect.

The apparatus shown in FIGS. 6 and 7 is a further improvement of the apparatus shown in FIGS. 4 and 5 from the above-mentioned point of view, and according to this embodiment, the slurry concentration is 1:2.
It is possible to reliably measure the slurry concentration with an accuracy of ±0.2% when the slurry concentration used as mixing water in raw compost is around 3% even if the concentration changes within the range of 5. This eliminates the troubles caused by this method, making it possible to provide an ideal slurry concentration measuring device.

Note that FIG. 7 is a plan view of the slurry concentration measuring device according to the present invention shown in FIG. 6, and FIG. 7 is a longitudinal sectional view.

In the slurry concentration measuring device according to the present invention shown in FIGS. 6 and 7, the slurry having extremely large flow rate fluctuations as shown by arrow 1 is preliminarily removed from the slurry supply device shown by 34-35. It is introduced from the bottom.

The slurry supply device 34 - 35 has an overflow edge at its upper part, and the inside of the slurry supply device 34 - 35 is connected to the slurry introduction part 3 by a wire mesh 33.
4 and a slurry filtration section 35, and the slurry filtration section 35 is structured such that it communicates with the measurement tube 39 through the slurry inlet 2 at a position deeper than the overflow surface 13 of the slurry measurement tube 39.

Therefore, the portion of excess flow rate of the slurry to be measured, indicated by arrow 1, forms an overflow surface 30, indicated by arrow 31, by the upper part of the slurry supply device 34-35, and the overflow device 38, as indicated by the overflow 31, forms an overflow surface 30, indicated by arrow 31. The other seven parts pass through a wire mesh or perforated plate 33 to form a nearly identical overflow surface 30 and a filter part 35.
flows into.

Therefore, the slurry filtered in this way has a substantially constant flow rate determined by D and the flow resistance of the inlet 2 due to the difference in water surface height between the overflow surface 30 of the slurry introduction part and the overflow surface 13 of the measuring tube 39. Only the amount corresponding to the flow rate flows into the measuring tube 39.

Therefore, the amount 3 of the slurry that forms the overflow surface 13 in the measuring tube 39 and is discharged to the overflow device 38 is also approximately constant, and similarly, the overflow surface 13 and the slurry discharge port 5 formed at the bottom become approximately constant. The flow rate of the discharge amount 10 determined by the flow resistance is also approximately constant, and therefore the problem that occurs when there is a wide variation in the slurry supply amount of the slurry concentration measuring device according to the present invention as shown in FIGS. 4 and 5. points can be resolved by this method.

Note that it is usually preferable that the height of the inlet 2 between the filtration part 35 and the measuring tube 39 of the slurry supply device is as shallow as possible at the portion below the overflow edge of the upper end of the measuring tube 39; It may be selected appropriately depending on the manufacturing convenience and other factors.

All other numbers shown in Figures 6 and 7 are number 4.
This is common to FIG. 5 and FIG. 5, and the functions and effects thereof are completely the same, so a description thereof will be omitted.

Note that in FIGS. 6 and 7, the means for measuring differential pressure is omitted.

Next, details of embodiments according to the present invention will be described.

In the slurry concentration measuring device according to the present invention as shown in FIG. 6, the depth B is 500 m71 and the depth D is 3.
00mm and the minimum slurry supply rate is 20t/min, the value of depth C in Figure 6 is as shown in Figure 4. Measure the differential pressure between the supply and exhaust pressure of the pressure transmission pipe with a differential pressure gauge. Measurement of C was carried out by this method.

The characteristic curve obtained as a result is shown in FIG.
It was proved that even if the slurry fluctuates within a range of 50 t, it can be considered to be substantially the same, and that continuous measurement for an extremely long period of time is possible even when foreign matter is contained in the slurry due to the presence of the wire mesh 33.

This device has the great advantage of being able to perform measurements only by supplying slurry, and does not require the supply of a reference solution or any other equipment or utilities, and the structure of the device is extremely simple. As described in detail above, it is convenient to maintain and eliminates freezing accidents during outdoor operation in winter, and has been proven to be an extremely suitable device for measuring slurry concentration in ready-mixed concrete. .

Based on the basic principles of the present invention, various modifications can be made to the embodiments of the present invention, such as using the inner cylinder of a double cylinder as a reference cylinder,
It is also possible to use the intermediate portion between the inner cylinder and the outer cylinder as a measuring cylinder.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal sectional view of a conventional slurry concentration meter, Fig. 2 is a longitudinal sectional view of the actual case of concurrent patent application (1), Fig. 3 is a sectional view taken along the line ■-■ of the same, and Fig. 4 is a longitudinal sectional view of a conventional slurry concentration meter. FIG. 5 is a vertical sectional view of an embodiment of the present invention, FIG. 5 is a sectional view taken along line v-v of the same as above, FIG.
The figure is a differential pressure gauge-slurry concentration characteristic diagram. 2... Slurry inlet, 5... Outlet, 9... Overflow edge, 13... Overflow surface, 1
6, 52...Reference cylinder, 19,20...
Pressure transmission pipe, 23... Differential pressure gauge, 24...
・Water supply device, 25... Partition plate, 34...
・Slurry introduction section, 35...Slurry filtration section,
38...00. Slurry overflow device, 39, 51...
...-MIJ fixed cylinder.

Claims (1)

[Scope of Claims] 1. A measuring cylinder having an overflow edge at the upper end, a discharge port and a slurry inlet at the lower end, and communicating with the measuring cylinder at the bottom at a predetermined depth,
1. A slurry concentration measuring device comprising a reference cylinder having a free liquid level formed at the top thereof. 2. A measuring tube having an overflow edge at the upper end, a discharge port and a slurry inlet at the lower end, and communicating with the measuring tube at the bottom at a predetermined depth,
In a slurry concentration measuring device having a reference cylinder with a free liquid level formed at the top thereof, an outlet located at an intermediate depth of the slurry overflow device having an overflow surface higher than an overflow port of the measuring cylinder; A slurry concentration measuring device characterized in that a measuring tube is connected to a slurry inlet. 3. The slurry concentration measuring device according to claim 2, wherein the slurry overflow device is divided into two by a wire mesh or a perforated plate on the slurry inlet side and the slurry outlet side. 4. A measuring tube having an overflow edge at the upper end, a discharge port and a slurry inlet at the lower end, and communicating with the measuring tube at the bottom at a predetermined depth,
A slurry concentration measuring device having a reference cylinder in which a free liquid level is formed at the upper part, characterized in that a device for supplying a reference liquid that does not contain a suspension or a sedimentation accelerator is added to the reference cylinder. Slurry concentration measuring device.