Selection Principle of Powder Mixing Equipment (1)

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Source: internal company

The choice of mixing equipment is actually varies from different materials in different working conditions. Similar materials for different purposes, the choice of equipment is also different. We carry on the comb according to own practice experience. I hope it helps you.

1. Mixing conditions

No.	Condition description		Materials	Evaluation
1	Dry Powder Mixing	Specific gravity varies little.	Dry mixing of mortar	Mixing difficulty is low
		The specific gravity of materials varies greatly	Slaked lime and straw powder	Mixing difficulty is high
		The proportions of mixed components varies little	Limestone with different granularity.	Mixing difficulty is low
		The specific gravity of materials varies greatly.	Coal and bituminous powder.	Mixing difficulty is high
2	Mixing of dry powder and liquid	A lot of dry powder and a little liquid	Metallurgical dust removal and binder	Mixing difficulty is high
2	Mixing of dry powder and liquid	Dry powder with lots of liquid	Flour and water	Mixing difficulty is high
3	Mixing of viscous materials		Converter sludge and iron scale, dust removal,Red mud,Phosphogypsum and other mixed materials	It varies according to mixing requirements
4	Hot mixing		Pulverized coal and liquid asphalt Diatomite and lard
5	Sludge mixture		Urban sludge and waste, Urban sludge and carbon source
6	Mixing of high abrasion materials		Iron ore and Bentonite clay. Sintering raw material mixing. Chromium ore powder, manganese ore powder and binder mixture. Chromium iron mixed with nickel iron.	The difficulty lies in the great wear of the material and the high requirement of the material.

In fact, the choice of mixing equipment varies from different working conditions. The above listed are only some typical working conditions and many are actually encountered in production.

2. Factors influencing solid mixing

As solid material mixing does not have the property of self-diffusion, external force must be used to force the material to flow. There are many factors affecting the mixing, mainly including particle size and distribution, apparent density, surface properties, electrostatic charge, moisture content, fluidity, cohesion and so on. In the initial stage of mixing, the mixing degree increases rapidly, and then flattens out in the later stage. If the particle size difference is too large, the mixing process will be unstable. This is because large particles are easy to separate and small particles are easy to deposit in the lower part of the device. If the density of powder particles differs too much, the mixing degree will be irregular at the beginning of mixing, but will decrease at a certain mixing degree. If the material has a certain electrostatic charge, at the initial mixing stage, the mixing degree rises with poor regularity, and then rises slowly to a certain extent.

3. Mixing process mechanism

3.1 Diffusion mixing. The material moves randomly in a small range, so long as the segregation does not occur at the same time, the diffusion mixing can finally make the mixing of solids highly uniform. Typical equipment and cylinder mixer, general mixing time is longer, used for mixing between powder is possible, more suitable for mixing between very worn powder.

3.2 Convective mixing. The material is moving randomly on a large scale and may form a circulation and mix simultaneously. Convective mixing has the difference between weak convection and strong convection. Generally speaking, equipment with low mixing velocity such as twin-shaft mixer is a relatively typical weak convective mixing, while the high-intensity mixer belongs to strong convective mixing.

3.3 Shear mixing. The mixing produced by the relative movement of particles within a material, typical of equipment such as a wheel mill. Virtually all devices have three mixing mechanisms at once, but there is always one mechanism mainly on charge.

Be continued.