JPS6125629A - Powdery body mixer - Google Patents

Abstract

PURPOSE:To obtain a powdery body mixer of improved mixing characteristic by attaching an ultrasonic wave generating element to a part of a container made of metal of high electric conductivity, putting filler of highly conductive metal together with the powdery body 2 in the container 1, and rotating the container itself. CONSTITUTION:An ultrasonic wave generaing element 8 is attached to a part of a container 1 made of metal of high conductivity. At the same time, the filler 7 of metal of high conductivity is put in the container 1 together with the powdery body 2, and the container 1 is rotated. Ultrasonic wave of about 1MHz is generated from the ultrasonic wave generating element 8 through a power source 9. The metallic filler 7 is copper balls of high conductivity and the capacity is about 10cm<3>. The powdery body 2 is filled in the container 1 from charging ports 4 and 5. SiO2, Fe2O3 etc. of average grain diameter 5mu are used as the powdery body 2. By using the material of high conductivity, the accumulation of static electricity is prevented, and by addition of metallic filler and utilization of ultrasonic wave, the mixing effect is improved remarkably.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a device for mixing powder, and particularly to a powder mixer suitable for improving the mixing properties of fine particles.

Powder mixers are used in industries that handle powder, such as chemical plants. A typical mixer is the rotary mixer. This is a device in which the container itself rotates, and the structure is relatively simple, so it is widely used. FIG. 1 shows a schematic diagram of a rotary mixer. In Figure 1, 1 is a container;
2 is a powder, 3 is a rotating shaft, 4.5 is an inlet, and 6 is an outlet.

In a rotary mixer, the powder rises along the inner wall as the container rotates. The powder that has reached the top of the container is mixed while flowing down along the inclined surface.

Now, during the mixing process, the particles come into contact with each other and also with the container. Static electricity with different signs is generated due to contact with objects of the same type and contact with objects of different types. Therefore, different types of static electricity are generated among the powder in the container. The number of static electricity generated is proportional to the frequency of contact between particles. As static electricity builds up, aggregation occurs between particles. Agglomerated particles form blocks, and the adhesion of these blocks is strong, so that the particles are not dispersed even during the mixing process. Therefore, from a microscopic perspective, the powder concentration becomes non-uniform and the mixing characteristics deteriorate. This tendency is remarkable when the particle size of the powder is small. This is because the surface area per unit packed bed of particles increases in inverse proportion to the particle size, so the amount of static electricity increases and particle aggregation becomes noticeable.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate the drawbacks of the prior art described above and to provide a powder mixer with improved mixing characteristics.

The feature of the present invention is that an ultrasonic generating element is attached to a part of a highly conductive metal container in a powder mixer, and a conductive metal filling is placed inside the container along with the powder, and the container itself is rotated. be.

Another feature of the invention is that the ratio of the volume of the conductive metal filler to the volume of the powder is manipulated in the range 0.1 to 0.3.

Hereinafter, the present invention will be explained in detail based on the drawings.

FIG. 2 is a schematic diagram of a powder mixer showing an embodiment of the present invention. In Figure 2, 1 to 6 are the same as in Figure 1, and 7
8 is a metal filling, 8 is an ultrasonic generating element, 9 is a power source, and 10 is a ground. The container 1 had a capacity of 3 tons and was made of steel. The area ratio of the ultrasonic generating element 8 to the container is approximately 0.
．． It is 1. Approximately IM from the ultrasonic element 8 via the power supply 9
H2 ultrasound is generated. The metal filling in the container is a highly conductive steel ball with a capacity of about 10 cIR1. A holder 10 is attached to the container 1.

Silicon dioxide (8 μm) each has an average particle size of 5μ as a powder.
i0. ), and iron dioxide (Fe, O, ) were used. After weighing 5000+1" of these powders, fill the containers IK from the inlet 4 and the inlet 5, respectively. Rotate the container 1 at a speed of 2 Orpm, mix for a certain period of time, and then sample from any location. The concentration of the components was measured.The mixing ratio of the powder was expressed by M in the following formula.

Here, σ: Variance at any time σ,: variance before mixing σ,: dispersion in a completely mixed state M is 0 in an unmixed state and 1 in a completely mixed state.

Experiments were conducted by varying the volume of the metallic filler. FIG. 3 shows the results of determining the degree of mixing M under conditions of a mixing time of 30 minutes.

The vertical axis of the figure represents the ratio of the capacity of the metal packing to the capacity of the powder. In addition, the vertical axis indicates the mixing degree (Mo) when using the conventional powder mixer, and the capacity of the metal filling when using the powder mixer of the present invention (without oscillating ultrasonic waves). Sexuality improves. This is because the added metal filler promotes mixing of the fried powder. On the other hand, when the metal filling becomes 0.3 or more, the degree of mixing decreases. The reason for this is thought to be as follows. As the capacity of the metal filling increases, the chances of contact between the powder and the metal filling increase, and the amount of static electricity generated increases. Since the filling material and the container have good conductivity, the generated static electricity leaks through the space and is reduced, but it is not completely eliminated. Therefore, the agglomeration effect of the particles due to electrostatic pressure exceeds the mixing promotion effect due to the metal filler. In addition, once aggregated particles form a block, and even if static electricity is removed, this block will not collapse.

Next, when ultrasonic waves are oscillated, the degree of mixing is about 10 times greater than when no ultrasonic waves are used.

This is because particle blocks formed by static electricity are destroyed by ultrasonic energy.

When the addition ratio of the filler to the powder is set to 0.1 to 0.3, the degree of mixing is improved by about 50 times compared to the conventional example.

As mentioned above, in the present invention, a material with good conductivity is used.
The accumulation of static electricity can be further prevented, and the mixing effect can be significantly improved by adding metal fillers and using ultrasonic waves.

Nuclear reactor fuel pellets are made from uranium dioxide (UO,) powder adjusted to a predetermined concentration. The concentration can be adjusted by mixing UO and powders of different concentrations.Since the average diameter of 6UO3 powder is about 5μ, the same results as in FIG. 3 can be obtained in this case as well.

Furthermore, the same results as in the case of copper can be obtained when iron, aluminum, or stainless steel is used as the material for the container and the metal filling.

According to the present invention, the degree of mixing is improved by about 50 times compared to the conventional example, so that the concentration of the powder can be made uniform. Moreover, the mixing time can be shortened.

[Brief Description of the Drawings] Fig. 1 is a schematic diagram of a conventional rotary mixer, Fig. 2 is a schematic diagram of an embodiment of the present invention, and Fig. 3 is a schematic diagram of a conventional rotary mixer. FIG. 2 is an experimental data diagram showing the relationship between the metal filler volume ratio and the mixing degree in an experiment in which powders were mixed at a ratio of l=1. 1... Container, 2... Powder, 7... Metal filling, 8
...Superphone arithmetic 10

Claims (1)

[Claims] 1. A powder mixer characterized by attaching an ultrasonic generating element to a part of a conductive metal container, placing a conductive metal filling together with the powder in the container, and rotating the container itself. .