Granulation of teawaste and limestone using sodium-based lignosulfonate and DEM simulation of powder mixing

Abstract

Co-granulation of teawaste with limestone was investigated using sodium-based lignosulfonate as a binder. A quality by design (QbD) approach was employed to formulate models for predicting the granule mean size, granule strength, limestone and binder uniformity from the process, and formulation variables. The results showed that teawaste volume fraction and liquid to solid ratio had a greater effect than other variables on granule mean size. Increasing teawaste in a binary mixture had a negative effect on granule mean size but positive effect on granule tensile strength. Limestone and binder uniformity could be increased by using higher impeller speed. DEM simulation showed that the impeller speed had a significant effect on the mixing quality and light particle fraction could significantly affect the fluctuation of the mixing index at the equilibrium stage. X-ray micro-computer tomography was applied as a technique to see the internal structure of the granules produced.