JPS6210366B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a measuring device for powder and granular materials. The apparatus of the present invention is particularly useful as a measuring apparatus for measuring alumina, and is suitably used as a measuring apparatus used for quantitatively supplying alumina to an electrolytic cell in aluminum electrolytic smelting.

As is well known, aluminum is produced by electrolytically reducing alumina in an electrolytic bath mainly composed of cryolite. Alumina dissolved in the electrolytic bath is consumed by electrolytic reactions, so alumina is regularly replenished.

In this case, if the amount of alumina supplied is too large, the electrolytic bath will become saturated, and a portion of the supplied alumina will accumulate at the bottom of the electrolytic bath, resulting in the formation of so-called sludge. The formation of this sludge results in an increase in voltage loss at the cathode and a decrease in current efficiency due to agitation of the aluminum metal on the cathode of the electrolytic cell. On the other hand, if the amount of alumina supplied is too low, the anodic effect will occur frequently, resulting in loss of power, increased amount of work, loss of fluoride, etc.

As described above, the frequent occurrence of sludge formation or anode effect is unfavorable in terms of electrolyzer operation. Therefore, in order to operate the electrolytic cell stably, it is necessary to accurately supply the required amount of alumina. Generally, a large number of aluminum electrolytic cells are arranged and operated in a factory, and therefore, the measuring device installed in each electrolytic cell is required to be inexpensive, easy to maintain and inspect, and highly accurate.

Figures 1 and 2 are schematic diagrams of a metering device conventionally used for supplying alumina.
The figure is a front sectional view, and FIG. 2 is a sectional view taken along the line AA' in FIG. 1.

The measuring device includes a measuring container 2 with a known internal volume, a fluidizing mechanism (such as an air slide) 5 for introducing and filling alumina into the measuring container 2 from a storage tank hopper 1, and a fluidizing mechanism for discharging alumina from the measuring container 2. 6, and an exhaust path 4 for extracting gas (such as air) that flows into the measuring container 2 together with alumina during alumina filling. To supply alumina, first open the solenoid valve 11 installed in the middle of the compressed gas piping that connects the fluidization mechanism 5 for filling and the compressed gas source 10, and fluidize the alumina on the fluidized bed 8. and introduced into the measuring container 2 via the filling path 7. After sufficient time has passed for the measuring container 2 to be filled with alumina, the solenoid valve 11 is closed, and then the solenoid valve 12 is opened to send compressed gas to the fluidization mechanism 6 to fluidize the alumina on the fluidized bed 9. The alumina is discharged from the discharge route 3. After the discharge is completed, the solenoid valve 12 is closed again and the system waits until the next supply of alumina.

Although it is possible to supply a substantially constant amount of alumina to the electrolytic cell through such an operation, this metering device has the following problems.

That is, during alumina filling, alumina from the storage tank hopper 1 is introduced into the weighing container 2 in a fluidized state by the fluidization mechanism 5, while the gas that flows into the weighing container 2 together with the alumina is exhausted to the outside of the container through the exhaust path 4. As the filling amount of alumina increases, the powder level of fluidized alumina also rises, and alumina eventually enters the exhaust path 4.

The amount of alumina that enters the exhaust route 4 varies depending on the particle size of the alumina, the apparent specific gravity of the alumina in a fluidized state, the pressure of the compressed gas, etc. However, the amount of alumina that enters the exhaust route 4 is determined by the amount of alumina other than the required amount entering the electrolytic tank. This is not preferable for the operation of the electrolytic cell.

The present inventors have conducted various studies to prevent alumina from entering the exhaust path 4, improve the accuracy of the metering device, and operate the electrolytic cell stably. The present invention was achieved by discovering that it is possible to effectively prevent alumina from entering the exhaust path by using a specific valve mechanism in the exhaust port portion.

That is, an object of the present invention is to improve the measurement accuracy of a powder or granular material measuring device, and this purpose is to provide a measuring container having an exhaust port on the upper surface, and a powder or granular material disposed on the upper surface of the measuring container. In a measuring device for powder and granular material, which includes a filling mechanism for fluidizing the powder with gas and introducing it into the measuring container, and a discharge mechanism provided at the lower part of the measuring container for discharging the powder and granular material from the measuring container. , near the lower side of the exhaust port, a valve body having an apparent specific gravity that can float on the powder in a fluid state and an upper surface shape that can block the exhaust port when pressed against it; This can be easily achieved by a powder/grain material measuring device that is held so as to be able to move up and down.

The present invention will be described in detail below with reference to FIGS. 3 to 5, which show examples of specific embodiments thereof.

3 to 5 are diagrams schematically showing an example of the measuring device for powder or granular material of the present invention, FIG. 3 is a front sectional view thereof, and FIGS. 4 and 5 are B--B in FIG. 3, respectively.
FIG.

The construction and operation of this device are basically the same as the conventional weighing device shown in FIGS. 1-2.

That is, in FIG. 3, the alumina in the storage tank hopper 1 is fluidized on the fluidized bed 8 by the fluidization mechanism 5 and introduced into the measuring container 2 through the filling path 7. The filling path 7, as shown in FIGS. 3-4,
It is preferable that the cylindrical measuring container 2 is connected to the side surface near the upper end so that the alumina is introduced tangentially, so that the alumina rotates along the inner wall of the measuring container 2. Therefore, it is possible to prevent alumina from entering the discharge path 4 from the exhaust port 13 immediately after the start of alumina filling. From the viewpoint of metering accuracy, it is preferable to keep the height Ha of the filling path 7 as small as possible without risk of clogging. In the case of weighing alumina, the height Ha of the filling path 7 is preferably 1 cm or more and 5 cm or less. Also, the section length La of the filling path 7
is preferably at least twice the height Ha and no more than 10 times the height Ha. If the length La is shorter than 2Ha, the effect of narrowing down the height will be lost, leading to deterioration of measurement accuracy;
If it is too long, the flow in the fluidization mechanism 5 will be inhibited, leading to the risk of blockage.

The gas that fluidizes the alumina and flows into the measuring container 2 together with the alumina is discharged from the exhaust port 13 to the outside of the measuring container 2 through the exhaust path 4. Preferably, the exhaust path 4 leads from the upper surface of the metering container 2 into the cover covering the electrolytic cell. The inside of the cover communicates with the suction piping that sucks the gas generated from the electrolytic cell and leads it to the gas processing equipment, so even if the exhaust gas from the metering container is introduced into the cover, no environmental problems will occur. That's because there isn't.

The metering device of the present invention is characterized in that its exhaust port portion is equipped with a specific valve mechanism. The valve mechanism includes a valve body having an apparent specific gravity that allows it to float on the powder in a fluid state and a top surface shape that can close the exhaust port when pressed against it; It basically consists of a mechanism for holding the valve body near the lower side of the exhaust port so as to be able to move up and down. The mechanism for holding the valve element described above is designed to ensure that when the upper surface of the fluidized powder in the measuring container rises and pushes up the valve element, the upper surface of the valve element can block the exhaust port without fail. There is no particular limitation as long as the valve body can be held in a certain position. Therefore, the valve body may be suspended directly from the inner upper surface of the measuring container so that it can move up and down, or a plate with a hole may be installed directly below the exhaust port and the valve body may be placed on top of it. .

The valve mechanism 21 shown in FIGS. 3 and 4 includes a valve body 2
0. A valve seat 23 for stably holding the valve body when the valve body blocks the exhaust port 13, and a valve body holding frame 2 for holding the valve body so as to be able to move up and down near the lower side of the exhaust port.
2. The shape of the valve body 20 is not particularly limited as long as it has a top surface that can close the exhaust port when pressed against it, but it may be spherical so that a mechanism for controlling the rotation of the valve body can be omitted. It is most preferable to The material of the valve body 20 may be any material as long as it has an apparent specific gravity such that the valve body as a whole can float on alumina in a fluid state, and may be a solid body or a hollow body. In order to improve the contact between the valve body 20 and the valve seat 23,
It is desirable that the apparent specific gravity of the valve body be 1/2 or less, preferably 1/5 or less of the apparent specific gravity of alumina in a fluidized state. Specific examples of such a valve body include hollow rubber. Examples include spheres, foamed polyurethane spheres with surface treatment, etc.

The valve seat 23 preferably has a shape that matches the shape of the valve body 20 so that the valve body can be stably held when the valve body is pressed against the exhaust port 13, and when the valve body is spherical, It is best to have a conical shape. Valve seat 2
The angle of inclination of the inner surface of No. 3 is set to be at least the repose angle of alumina, especially about 40° or more, so as to prevent the powder particles accumulated on the valve body 20 from being caught between the valve body 20 and the valve seat 23. It is better to The shape of the valve seat is the third
It is not limited to what is shown in the figure,
Further, if the exhaust port itself is configured to have a shape that matches the top surface shape of the valve body, there is no need to provide a valve seat.

The valve body holding frame 22 may be of any type as long as it prevents the valve body 20 from falling and holds the valve body near the bottom of the exhaust port without interfering with the vertical movement of the valve body.
It is not limited to the frame body, but it is particularly preferable that the valve body is located directly below the exhaust port when the valve body is held stationary.

In FIGS. 3 and 4, the valve body holding frame is made of thin metal rods arranged in a cross-shaped structure.

Next, the operating status of this valve mechanism will be explained.

The electromagnetic valve 11 is opened, and the alumina fluidized by the gas is introduced into the measuring container 2 in a state close to a fluid. As the amount of alumina charged increases, the powder level of fluidized alumina in the measuring container 2 rises, and when it reaches the height of the valve body 20, the valve body 20 receives buoyancy from the fluidized alumina. It rises and finally comes into close contact with the valve seat 23 to close the exhaust port 13 of the exhaust path 4 (the valve body is at the position 20'). As a result, alumina is prevented from entering the exhaust path 4, allowing highly accurate measurement. When the exhaust port 13 is blocked, the inflow of gas is blocked, and the introduction of alumina is stopped, separation of alumina and gas progresses within the measuring container 2, and the alumina particles gradually settle inside the measuring container 2. I'm going to go. As a result, the valve body 20 is also slightly lowered and the exhaust port 13 is opened.
There is no need to worry about it getting inside.

In the apparatus of the present invention, filling of the measuring container 2 with alumina is completed by such an operation. After the filling is completed, a certain amount of alumina filled in the measuring container 2 is discharged by a suitable discharge operation.

Although the discharge mechanism is not particularly limited, a discharge operation using a fluidization mechanism will be described below.

After filling the measuring container 2 with alumina, the solenoid valve 11 is closed, the solenoid valve 12 is opened, and the alumina is discharged by the discharge fluidizing mechanism 6. Immediately after the start of alumina discharge, the gas that fluidized the alumina is
The air is exhausted from the exhaust port 13 which is already open.

As the discharge progresses, the alumina powder level decreases, and the valve body 20 similarly descends to the position of the valve body holding frame 22, the exhaust port 13 is fully opened, and the alumina in the measuring container 2 is fluidized for discharge. It will be in a state where there will be no hindrance at all.

It is preferable that the inlet of the discharge path 3 provided at the lower part of the measuring container 2 be provided at a higher position than the fluidized bed 9 of the discharge fluidization mechanism 6 so that a certain amount of alumina remains even after the alumina discharge operation is completed. Further, a baffle plate 14 is provided to prevent a "flushing phenomenon" in which alumina in a fluidized state introduced from the upper part of the measuring container 2 flows out from the discharge path 3 as it is. The distance Hb between the lower end of the baffle plate 14 and the fluidized bed 9 is set to an appropriate distance that does not impede the outflow of alumina, and the effective height Hc of the remaining alumina is
is preferably 3 cm or more, preferably 5 cm or more.

The amount of remaining alumina in the lower part of the measuring container 2 or the effective height Hc of the remaining alumina changes depending on the particle size of the alumina, the pressure of the compressed gas for fluidization, etc., and this becomes a factor that deteriorates the measurement accuracy. Therefore, in order to prevent this deterioration of measurement accuracy as much as possible, it is effective to narrow down the cross-sectional area of the weighing container 2, but if the degree of narrowing is too large, it will lead to a decrease in the discharge speed of alumina, so the measurement accuracy and discharge It is best to select an appropriate cross-sectional area, taking into account both speed and speed.

However, even when the cross-sectional area of the weighing container 2 is reduced, the height Hd of the weighing container 2 becomes too high in order to obtain the required measured value, that is, the required volume of the weighing container 2. This may be undesirable due to space limitations, or may cause problems such as difficulty in completely fluidizing the alumina as a whole when discharging the alumina. In such a case, the height Hd may be adjusted by making the upper cross-sectional area _S1 of the measuring container 2 suitably wider than the lower cross-sectional area _S2 . Note that the connecting portion between the upper and lower portions of the measuring container 2 is preferably narrowed with an appropriate slope so as not to create a dead space.

In terms of measurement accuracy, it is preferable to select the amount of alumina to be measured per time in the range of 1 to 30 kg with this device.

After completing the discharge of alumina, close the solenoid valve 12,
Wait until the next weighing.

As described in detail above, according to the measuring device of the present invention, it is possible to accurately weigh the powder and granular material without the powder and granular material entering the exhaust path from the exhaust port.

Further, by supplying alumina to the aluminum electrolytic cell using the apparatus of the present invention, it becomes possible to always supply a predetermined amount of alumina to the electrolytic cell, and the aluminum electrolytic cell can be stably operated.

Although the above explanation was mainly about a measuring device used to supply alumina to an aluminum electrolytic cell, the measuring device of the present invention can be modified by making appropriate design changes depending on the type of powder and the object to be supplied. It is clear that the device can also be used as a metering device for powders other than alumina.

[Brief explanation of the drawing]

1 and 2 are diagrams schematically showing a conventional weighing device for powder and granular materials, with FIG. 1 being a front sectional view and FIG. 2 being a sectional view taken along the line AA' in FIG. 1. 3 to 5 are diagrams schematically showing an example of the measuring device for powder or granular material of the present invention, FIG. 3 is a front sectional view, and FIGS. 4 and 5 are B-B in FIG. 3, respectively. FIG. In the figure, 1: Storage hopper, 2: Measuring container, 3: Discharge route, 4: Exhaust route, 5, 6: Fluidization mechanism, 13: Exhaust port, 14: Baffle plate, 20: Valve body, 21: Valve. Mechanism, 22: Valve body holding frame, 23: Valve seat.

Claims (1)

[Scope of Claims] 1. A measuring container having an exhaust port on the upper surface, a filling mechanism provided at the upper part of the measuring container for fluidizing powder and granular material with gas and introducing the fluidized material into the measuring container, and In a powder measuring device comprising a discharge mechanism provided at the bottom of the measuring container for discharging the powder and granular material from the measuring container, the powder and granular material in a fluid state is placed near the lower side of the exhaust port. A valve body having an apparent specific gravity that allows it to float and an upper surface shape that can close the exhaust port when pressed against the exhaust port, the powder being held so as to be able to move up and down. Granule weighing device. 2. The measuring device for powder or granular material according to claim 1, wherein the filling mechanism is an air slide. 3. A measuring device for powder or granular material according to claim 1 or 2, characterized in that the discharge mechanism is a fluidization mechanism. 4. A measuring device for powder or granular material according to any one of claims 1 to 3, wherein the valve body has a spherical upper surface shape. 5. In the granular material measuring device according to any one of claims 1 to 4, the valve body is held by a valve body holding frame provided near the lower side of the exhaust port. A device characterized by: 6. The measuring device for powder or granular material according to any one of claims 1 to 5, wherein the measuring container is a cylindrical body. 7. The measuring device for powder and granular material according to claim 6, characterized in that the filling mechanism is provided so that the powder and granular material is introduced into the inner surface of the cylindrical body of the measuring container from a tangential direction. device to do.