Swelling of Pellet during Reduction

Abstract

Two different views were brought by previous works for the swelling of pellets during reduction.“The swelling refers intimately to the transformation of mineral phases during reduction” is the one, and“ The growth of whisker-like fibrous materials cause the swelling like cotton candy” is the another.
The present authors carried out series of experiment on the swelling by various kinds of raw material, after the detailed review on the previous works.
Following explanations are possible. 1. A generation of some kind of force is supposed to be possible in the relatively early stage of reduction, which will cut off the bonds between the constituent grains, and break the grains themselves down into minute fragments. 2. The growth of fibrous material is observed in later stage of reduction after the breaking down came to end, and is found to form cotton candy like body. The breaking down and growth of fibrous materials are absolutely independent in the stage of reduction. 3. Swellings can be prevented by taking the diameters of pellets small, even for the raw material with remarkable swelling nature, and for the pellets fired under such conditions that will cause swelling or preserve the nature of swelling, also.