Preparation of CaO-containing carbon pellet from recycling of carbide slag: Effects of temperature and H3PO4

CaO-containing carbon pellets (CCCP) was prepared by mixing carbide slag (Ca(OH)2) and powdered char to produce CaC2, achieving the recycling of carbide slag during CaC2 production process. The thermal strength of CCCP was the focus of most attention when employing arc furnaces as reactors for CaC2 production in industry. To improve the thermal strength of CCCP, H3PO4 was used as a binder in this study. The results indicated that Ca3(PO4)2 reacted by H3PO4 and Ca(OH)2 could help refine the average particle sizes of CaO, resulted in a relatively uniform pore diameter distribution of CCCP with low porosity, therefore improving the thermal strength of CCCP. When H3PO4 content was more than 8 wt%, some over-sintering and melting structure for CaO particles appear, and thus resulting in the decrease in thermal strength of CCCP. The experimental results show that CCCP with 3% H3PO4 has the best thermal strength at 1100 °C. The non-isothermal shrinkage kinetics of CCCP indicated that the addition of 3% H3PO4 reduced the apparent activation energy of sintering reactions and accelerated the sintering of CaO particles in CCCP. Furthermore, the addition of H3PO4 has a positive effect on the formation of CaO sintered necks, enhancing the strength of CCCP.