The spheroidal mechanism of iron concentrates--the role of liquids and solids (1)
(1) Wetting phenomenon
When the liquid and the solid come into contact, there are two phenomena of wetting and non-wetting. If water can wet the glass, mercury will be spherical on the glass and will not wet the glass. If the water droplets are on the surface of the paraffin, the water is in the shape of a bead, and the paraffin is not wetted. These phenomena can be explained by the relationship between adhesion and cohesion.
As shown in Figure 1, there is an adhesion layer at the contact between the liquid and the wall, the thickness of which corresponds to the radius of action of the molecule, the liquid molecules in the adhesion layer, the force is asymmetric, if the interaction between the liquid molecules and the wall molecules - - The adhesion is greater than the interaction force between liquid molecules - cohesion, the generator wall is wetted by the liquid, as shown in Figure 1 (a). Conversely, if the cohesive force of the liquid molecules is greater than the adhesion to the walls of the device, the non-wetting phenomenon shown in Fig. 1(b) occurs.
The water droplets are placed on the solid surface at the liquid-solid phase contact, and the angle between the liquid surface and the solid surface is called the contact angle θ.
If θ = 0, the liquid can completely wet the solid, called ideal wetting. If θ = π, the liquid does not wet the solid at all, which is called ideal non-wetting.
Iron ore is the contact angle of water is less than π / 2, it may be wet with water, and thus can concentrate powder by the action of water to ball type. [next]
(2) Capillary phenomenon
A tube with a very small diameter is called a capillary. If a capillary tube is inserted into the basin, the liquid level in the tube rises, as shown in Figure 3. The height at which the liquid level rises in the tube can be obtained by the following formula.
Where a———the surface tension coefficient;
θ———contact angle;
d———capillary diameter;
Ï———liquid density;
g———Gravity acceleration.
It can be seen from the formula (1) that the smaller the diameter d of the capillary, the higher the liquid level in the tube rises. When the diameter of the capillary is constant, the larger the surface tension coefficient of the liquid is, the smaller the density is, and the smaller the contact angle is, the higher the liquid level rises in the tube.
If two sheets of paper are inserted into the water in parallel, when the two sheets approach a certain distance, a capillary is formed between the two sheets, and the surface tension of the curved water surface pulls the two sheets together. Based on the same principle, if there is a drop of water between the two mineral powder particles, the mineral powder particles are hydrophilic. When the two particles approach a certain distance, a capillary is formed between them, and two curved liquid levels appear, and the surface tension of the liquid pulls the two particles together. This is the role of capillary phenomena in the formation of iron concentrates (Figure 4).
Strip Spreader,Compost Spreader Bcs,Trans Spread Fertilizer,4 Wheeler Fertilizer Spreader
Gongzhuling Huaxi Agricultural Machinery Manufacturing Co.LTD , https://www.tractionsprayer.com