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Diatomite filter aid
Diatomite filter aid has good microporous structure, adsorption performance and anti compression performance. It can not only make the filtered liquid obtain a good flow rate ratio, but also filter out fine suspended solids, ensuring the clarity. Diatomite is the remains of ancient single celled diatoms. Its characteristics: light weight, porous, high strength, wear resistance, insulation, thermal insulation, adsorption and filling, etc.
Diatomite is the remains of ancient single celled diatoms. Its characteristics: light weight, porous, high strength, wear resistance, insulation, thermal insulation, adsorption and filling, etc. It has good chemical stability. It is an important industrial material for heat insulation, grinding, filtration, adsorption, anticoagulation, demoulding, filling, carrier, etc. It can be widely used in metallurgy, chemical industry, electric power, agriculture, chemical fertilizer, building materials, thermal insulation products and other industries. It can also be used as industrial functional filler for plastics, rubber, ceramics, paper making, etc.
Category Editing
Diatomite filter aid can be divided into dry products, calcined products and flux calcined products according to different production processes. [1]
① Dried product
The purified, pre dried and crushed silica dry soil raw materials are dried at 600~800 ° C and then crushed. This product has a very fine particle size and is suitable for precision filtration. It is often used in combination with other filter aids. Most of the dried products are light yellow, but also milky white and light gray. [1]
② Calcined product
The purified, dried and crushed diatomite raw materials are fed into the rotary kiln, calcined at 800~1200 ° C, then crushed and graded to obtain calcined products. Compared with dry product, the permeability of calcined product is more than three times higher. Calcined products are mostly light red. [1]
③ Flux calcined product
The purified, dried and crushed diatomite raw material is added with a small amount of sodium carbonate, sodium chloride and other melting aids, calcined at 900~1200 ° C, crushed and graded to obtain the calcined flux. The permeability of flux calcined product is obviously increased, more than 20 times of that of dry product. Flux calcined products are mostly white, and light pink when Fe2O3 content is high or flux dosage is small. [1]
Filtration
The filtering effect of diatomite filter aid is mainly carried out through the following three functions:
Sieving action
This is a kind of surface filtration. When the fluid flows through diatomite, the pore of diatomite is smaller than the particle size of impurity particles, so the impurity particles cannot pass through and are retained. This effect is called screening. In fact, the surface of filter cake can be regarded as a screen surface with equivalent average pore size. When the diameter of solid particles is not less than (or slightly less than) the diameter of diatomite pores, the solid particles will be “screened” out of the suspension, playing the role of surface filtration. [2]
Depth effect
Depth effect is the retention effect of deep filtration. During deep filtration, the separation process only occurs in the “interior” of the medium. Some small impurity particles passing through the surface of the filter cake are blocked by the zigzag microporous channels inside the diatomite and the finer pores inside the filter cake. Such particles are often smaller than the microporous pores of the diatomite. When the particles hit the wall of the channel, it is possible to separate from the liquid flow, but whether it can achieve this, Determined by the balance of inertia force and resistance suffered by particles, this interception and screening action are similar in nature and belong to mechanical action. The ability to filter solid particles is basically related to the relative size and shape of solid particles and pores. [2]
Adsorption
Adsorption is completely different from the above two filtering mechanisms. In fact, this effect can also be considered as electrokinetic attraction, which mainly depends on the surface properties of solid particles and diatomite itself. When the particles with small pores in the diatomite collide with the internal surface of porous diatomite, they are attracted by opposite charges, or the particles attract each other to form chains and adhere to the diatomite, which belongs to adsorption. [2] Adsorption is more complex than the first two. It is generally believed that solid particles smaller than pore diameter are trapped mainly because:
(1) The intermolecular force (also called van der Waals attraction) includes permanent dipole action, induced dipole action and transient dipole action;
(2) The existence of Zeta potential;
(3) Ion exchange process.