A dispersion is a homogenous different molecule mixture. It appears a dispersing or dissolvent phase and soluts dispersed molecules. In the watery dispersions the water constitutes the dispersing phase, whereas the dispersed phase presents several variations:
From small molecules like sodium chloride, to great proteins like albumens.
The dispersions whose dispersed phase has molecules of low molecular mass denominate colloidal dispersions. Supposing that the molecules of the dispersed phase have high molecular masses (more than 10,000 u.m.a.). Or they have a size between 1 and 0.2 microns, denominate colloidal dispersions.
The colloidal dispersions can appear in fluid form (sol) or with gelatinous aspect (gel).
The sol passage to gel always is possible, whereas the inverse step is not it always.
Election of the Mixer for its operation
It is necessary to consider the specific result that is to obtain itself with the mixture. Thus, an agitator who is satisfactory to stimulate the soluble solid dissolution eliminate can not be effective to maintain solid insoluble in a uniform suspension.
In many cases, the agitator can be needed to make two or more synchronize functions:
Good contact between inmiscibles liquids and at the same time, has to stimulate the effective heat transmission to the interior of the material and from him.
The selection of the appropriate mixer will also depend on the means in which it is had to work; or a gas, a liquid or a mass of solid particles; or he is homogenous or heterogenous with respect to the phases; or the phases; or of discharge or low consistency.
The design or project of an agitator demands the specification of the type of apparatus, the dimensions and proportions of the mixer element, the situation of this element within this container for the mixture and the conditions of operation of the agitator. In general, the optimal mixer, like the optimal equipment for other unitary operations, will be the one that obtains the result wished with the economic combination of steady loads and operation.
Actually the scatterer is selected current that assures more effective results and is more attractive from the points of view of its installed cost and its conservation, since the energy consumed in the mixture is frequently only one small part of the necessary one for all the process.
However, the meticulous designer will investigate the energy necessities, particularly in the operations that demand scatterers of great power. The type, or the types, the dimensions and the position of the agitator for the operation are determined first starting off of general the empirical principles. Soon the conditions of operation are specified; these are less easy to generalize and they are deduced by the experience of the engineer or the salesman of the equipment, or by means of tests of models.
Type of Equipment
Although they exist a great variety of mixers and scatterers in the market, these can be divided in applications of low and high effort of cut. In the form, typically propulsive trowels or type, the reduction as large as the particle does not take place, the battle is conducted by the melting and/or dissolution.
The mixer serves to maintain the homogeneity of the composition and the uniformity of the temperature, providing a small increase itself. In a complete case, exists a passage in which the particles physically are reduced in size by the mechanical / hydrodinamic cut with the combination of the rotor/estator accompanied by a small increase of the temperature by the mixed energy
Such equipment, even working with size of particles superior to pellets, provide fast and efficient mixed dispersion.
Equipment of high effort of cut exists of two different ways, type vertical immersion and the mixed one in line.
* The vertical, the rotor/estator this mounted on an immersed platform and in a material tank, depending on the mixer mall pillow to circulate the mixture and to assure homogeneity.
* The case of the mixed one in line, the combination of mixed in a tank recirculating by a pump the mill.
Experiences have demonstrated that this type of equipment, which assures a total dissolution, gives to a greater rapidity and performance than the disintegration with a single vertical mixer, specially for great volumes of production, tanks greater to 25 tons.