The characteristics of pelletizing in sand blending are manifested by high clay content, low moisture, and a relatively low addition of coal powder. To achieve better product quality, what aspects should be focused on when implementing this process? Pellet manufacturers will unravel this mystery for you.
1. Moisture
Moisture in the molding sand for pellet production is a key factor determining plasticity and binding force. When moisture is too high, it can lead to deteriorated binding force, reduced fluidity of the sand, and uneven mold density. When moisture is too low, the sand is difficult to mix uniformly, resulting in low strength, high brittleness, poor mold release, and a tendency for sand sticking defects.
2. Clay Content and Mud Content
Sand with high clay content shows increased strength as specific pressure rises, with effective bentonite typically controlled between 7% and 10%. The sum of effective clay and inactive clay in the sand is equivalent to the mud content, which is generally maintained between 12% and 16%. Both excessively high and low mud content can affect various performance indicators of pellet sand blending.
3. Coal Powder
The effective coal powder content is usually controlled below 5.5%. The supplemental amount of coal powder varies depending on the thickness of the pellets, typically ranging between 0.3% and 1.0%.
4. Raw Sand Particle Size
High-density pellets require sand molds with higher density, which exhibit significant expansion during pouring. Therefore, the particle size of the raw sand should not be overly concentrated. The raw sand particles are generally round, and three-sieve or four-sieve sand is commonly selected.