4 Key Factors Affecting Cold Pressed Pellets
Cold Pressed Pellets,binder
Source: internal company
The main equipment of the cold-pressed pellet method is the briquetting machine, which works on the principle of using a pair of pairs of molding rollers to press the powdered raw materials into the corresponding size of the pellet. As shown in Figure 1:
1. The linear speed of the pressure roller
In order to improve the productivity of the ball press, the faster the speed of the two pressure rollers, the better. However, with the extrusion of raw materials between the pressure rollers, the internal air between the loose raw materials will be gradually discharged, when the pressure roller speed is too fast, the surface of the pellet will be too late to discharge the gas between the raw materials and leave cracks, resulting in a reduction in the strength of the pellet or even can not be formed.
All kinds of raw materials due to the different amount of air inside the loose state, the material characteristics are different, so the pressure roll surface requires different linear speed when pressing the ball, different raw materials need to be tested many times to find the most suitable linear speed of ball pressing.
2. Linear pressure between rollers
In order to improve the strength of the pellet, there is a misunderstanding in the production, that the greater the pressure between the two pressure rollers, the higher the strength of the pellet. But in fact, the pressure between the molecules of the material to withstand a limit, when the pressure exceeds this limit, the material molecules will appear between the slip, resulting in the material is crushed, there are a large number of hemispheres, the rate of balling is greatly reduced, but also reduces the strength of the pellet. At present, the domestic ball press generally use hydraulic device to provide counterpressure between the two pressure rollers, and require its pressure adjustable.
3. Balling water content
Ball pressing machine ball pressing in addition to a few raw materials such as limestone, dolomite and other dry powder ball pressing, most of the materials are used wet ball pressing. Moisture changes affect the particle size and quality of the ball, usually too high raw material moisture, the initial ball faster, but easy to cause the ball to bond with each other deformation and not easy to take off the mold, resulting in uneven distribution of the ball size, strength is poor, and at the same time to drying to bring about difficulties; and raw material moisture is too low, it is easy to appear between the two hemispheres to increase the gap between the two hemispheres, resulting in the poor strength of the combination of the powder, the hemisphere is too much, the rate of ball formation is low or even can not be formed into a ball of the phenomenon.
Appropriate moisture content of raw materials is the key to ball formation. In many tests found that different materials have different balling water content. The best balling water content of the physical properties of the material (particle size, hydrophilicity, density, particle void ratio), the composition of the mixture, the production rate of the balling machine and balling conditions.
4. Selection of binder
In the mixing and milling generally add a certain amount of binder to the raw materials, which is mainly to increase the adhesion between the raw materials, adsorption, dispersion. Binder is mainly divided into inorganic binder and organic binder, good performance of organic binder should have the following conditions.
• The molecular structure has multiple polar groups, and it can have a strong chemical adsorption effect with the surface of the concentrate.
• With hydrophilic genes that enhance the hydrophilicity of the mineral surface.
• It has sufficient relative molecular mass and viscosity, and its own chain frame is not easy to break.
• Longer molecular chain and more branched chain.
• Aromatic structure is better than fatty structure.
At the same time should also be based on the requirements of the company's furnace and products combined with the actual local situation of the choice of binder.