The grain mix to be granulated with different grain shape & surface is moved in such a way that the most effective bonds required for good ball formation can arise. This movement is achieved by using suitable apparatus and special tools, e.g. drum & disc pelletizers/granulators.
When a loose mass is dumped on a plain surface, a pyramid with a specific angle of repose is formed which results from the frictional resistance of the pile. Dry grains form a flat angle of repose while irregularly shaped & wet grains with a major friction form a steeper one. In the position of rest the pile forms a static angle of repose.
When the fiction is overcome at a steeper slope, the pile surface undergoes a rolling movement until the static angle of repose is again reached and the pile is once more in apposition of rest. The rolling movement can be maintained if it is possible to keep the grains moving so that the angle of repose is below the dynamic one. This can be achieved if the grains are placed on an adequately inclined support moving in the opposite direction to the gravity of the mass i.e. moving diagonally upwards.
In this way the support continuously moves material upwards due to the frictional resistance between support & the material. When the angle of the inclined support becomes steeper, the grains are compelled to reverse and roll downwards over the material surface. On rolling down the wet grains tend to pick up other particle and start forming the balls. It this downward movement can continue in the presence of new, fresh particles, the diameter of the agglomerates increases and green nodules of desired size are finally formed.