Effects of pitch addition on the properties of environmental-friendly tap-hole clay

摘要

An environmentally friendly tap-hole clay that contains almost no benzo[a]pyrene was developed using resin and pitch as binder. The effects of the pitch addition on the tap-hole clay were investigated through evaluating the physical and chemical properties together with the microstructure, phase compositions and thermal analysis. The plasticity of the tap-hole clay is significantly improved with increasing pitch addition. However, the bulk density of tap-hole clay decreases gradually with increasing pitch content after treatment at different temperatures, while the apparent porosity increases due to the evaporation of pitch components and relatively low solid components. Also, this phenomenon is the main reason for the poor volume stability of tap-hole clay after heat treatment at different temperatures, although mullite formation has negated some of the shrinkage. Mechanical-strength evolution of the tap-hole clay is closely related to the carbonization process of the resin and pitch at high temperatures. Oxidation resistance could be significantly improved with 2 wt % of the pitch, but there is almost no change with much more than 2 wt %. However, the higher pitch content corresponds to better slag resistance. In terms of the comprehensive performance of the tap-hole clay, 4 wt % of the pitch would be better.