What are the factors that affect the mixing speed and mixing degree of laboratory hopper mixers

The laboratory hopper mixer is directly connected to the spindle by a vertical motor through a cycloidal needle wheel reducer, and there are two large and lower screw belts
on the spindle.

After starting the mixer, the rotating screw belt will lift or throw the material in the mixing chamber along the wall in a bottom-up circumferential movement, when the material reaches the center position or the highest point, it will move downward by its own weight, so that the material diffuses, convection, shear, dislocation and mixing in the tapered mixing chamber, forcing the space of the material to be irregular compound movement
.

Small footprint, simple structure, easy maintenance, can be equipped with hot and cold sandwich and liquid spray device
.

It is a mechanical equipment
that uses mechanical force and gravity to uniformly mix two or more materials.

In the mixing process, the contact surface area of the material can also be increased to promote chemical reactions; It is also possible to accelerate physical changes
.

In the laboratory hopper mixer, a variety of solid materials are often accompanied by segregation phenomenon, segregation is the opposite of the particle mixing, hindering good mixing, but also can make the mixture material that has been mixed re-layered, reduce the degree of
mixing.

Therefore, there are many factors that affect the mixing speed and mixing degree in the actual mixing operation, which makes the mixing process more complicated, and it is difficult to use separate factors to investigate one by
one.

In general, it is divided into material factors, equipment factors and operational factors
.

(1) The shape and size of the equipment type mixer, the internal inserts (baffles, forced agitation, etc.
), the material and surface conditions affect the mixing effect, and the appropriate mixer
should be selected according to the nature of the material.

(2) The filling amount of materials under operating conditions, the charging method, the mixing ratio, the rotation speed of the mixer and the mixing time affect the mixing effect
.

When the filling volume of the laboratory hopper mixer accounts for about 30% of the container volume, the mixing effect is good
.

When the speed of the rotating mixer is too low, the particles slide down the surface of the material layer, such as the separation phenomenon is easy to occur when the physical property difference of the particles of each component is large; When the speed is too high, the rat is subjected to the action of centrifugal force and rotates with the bowl without any mixing effect
.

Suitable speed - generally take 0.
7 to 0.
9 times
the critical speed.

When the density difference and particle size difference between the components are large, the material with small density or large particle size is installed first, and the material with large density or small particle size is installed, and the mixing time should be appropriate
.

(3) The particle size distribution, particle morphology and surface state, particle density and stacking density, water content, fluidity (recuperation angle, internal friction coefficient, etc.
), adhesion, cohesion, etc.
of the material will affect the mixing process
.

In particular, when there are significant differences in particle size, particle form, density, etc.
between the various components, it is easy to isolate during or after mixing and lose uniform mixing
.

In general, small particle size, large density particles are easy to flow down in the gap of large particles and affect uniform mixing, but when the particle size is less than 30μm, the size of the particle density will not become a factor leading to separation; When the powder with a particle size of less than 5μm is mixed with the particles of larger particle size, the powder adheres to the surface of the large particle and becomes a coating state, and no separation occurs and a homozygous mixture is formed; When the mixture contains a small amount of moisture, it can effectively prevent segregation
.

In general, the effect of particle size^ large, the effect of density is more pronounced
in fluidization operations than particle size.