The mixing of light powder and heavy powder is a classic mixing process difficulty, which is due to the following reasons: firstly, during the mixing movement, light powder often floats above the powder due to its light weight, and even floats in the air; The second reason is that there is a tendency for the heavy powder to sink at the bottom of the material barrel during powder mixing due to its large proportion, and the larger the proportion, the more significant the sinking.

1、 Provide examples to ask questions

For example, in seasoning mixing, it is necessary to mix heavier salt particles with lighter powders such as chili powder and scallion powder. The specific gravity of the salt particles is 1.4, while the specific gravity of plant powders such as chili is 0.25. This mixing task is a typical problem of mixing light and heavy powders. It is difficult for ordinary mixers to mix salt and plant powder evenly through experiments, and even if the mixing time is extended, it is still difficult to mix evenly.

2、 Cause analysis

Through the explanation of the liquid state model of the moving powder (see the content of the mixing model in Encyclopedia Topic 18), it can be seen that in the moving mixing container, the powder is mostly suspended above the material due to the fact that the specific gravity of the fine and light chili powder and dried scallion powder is much smaller than that of the powder such as salt and monosodium glutamate, and some of the light and fine powder even floats in space, causing difficulties in mixing. Without mandatory means, even if mixed for a long time, they are still difficult to mix into the main powder.

3、 Solution

1. The mixing equipment selected for the floating light powder should have the ability to press the floating light powder down into the main powder.

Among the current types of mixers, dual motion ® The mixer can effectively solve this problem due to the dual motion ® The rotation of the mixer container and the rotation of the internal blades are carried out in the same direction (with different rotational speeds), so that the container and blades will carry the light powder floating above into the main heavy powder, so that the light powder and heavy powder can be evenly mixed.

2. For heavy powder with excessive specific gravity, it can be solved in two steps

1) For heavy powder with a larger specific gravity (the specific gravity of the heavy powder is less than 4 times that of the main powder), a drum rotating mixer can be used to solve the problem. By using the rotating drum, the heavy powder at the bottom of the drum can be rotated, lifted, and wrapped into the main powder.

2) For heavy powder with a particularly high specific gravity (the specific gravity of the heavy powder is more than 5 times that of the main powder), it is difficult to mix evenly solely using a mixer. The specific gravity and particle size of the heavy powder can be reduced through crushing and grinding, thereby reducing the difficulty of mixing and achieving the goal of uniform mixing.

In response to the problem of salt particles and monosodium glutamate having a high specific gravity and a smooth surface, which can easily sink to the bottom during mixing, the particles can be ground and refined to reduce their specific gravity to 0.8, thereby reducing the sinking trend during mixing and achieving uniform mixing.

It can also be calculated and analyzed through the Metallurgical Mixing Index (see Encyclopedia Topic 19 for details) to point out that the differences in the Metallurgical Mixing Index of heavy powders such as salt and monosodium glutamate are too large, which makes it difficult for uniform mixing. It is pointed out that it is necessary to grind and refine heavy powders such as salt and monosodium glutamate, so that their metallurgical mixing index is close, that is, the equilibrium values of specific gravity and average particle size become smaller and closer to chili powder and dried scallion powder, thereby reducing the difficulty of the mixing process.