Reinventing Cement Manufacturing through Engineering Innovation: Toward Sustainable and Circular Energy Systems

The cement industry is an energy-intensive sector in rotary kiln combustion where coal is the primary fuel. There has been an extreme global coal price increase up to 200% and intensifying decarbonization pressures, hence this necessitated a transition to sustainable alternative fuels. This study investigated the optimization of carbon rubber, waste tire pyrolysis product, as an alternative fuel. The aim is to evaluate synergistic performance when blended with coal and biomass in the rotary kiln system. The research was aimed to promote a circular economy by valorizing industrial rubber waste into high value thermal energy. This research applied the Design of Experiment (DoE) approach, wirh a mixture design and ANOVA analysis as well, employed to evaluate the effects of varying fuel compositions on kiln operational performance. The actual plant trials were obtained under the normal conditions, encompassed fuel consumption, energy performance, and clinker quality. Upon examination, the results indicate that increasing the carbon rubber fraction improved the Thermal Substitution Rate (TSR) by 12%, reduced Specific Thermal Energy Consumption (STEC) by 14%, and achieved to 17% fuel cost savings without compromising kiln feed rate. The optimal composition was identified at 78% of coal, 18% of biomass, and 4% of carbon rubber respectively. The clinker analysis was found to confirm that calcination degree, free lime content, and Lime Saturation Factor (LSF) remained in the standard limits. Hence, it can be drawn that carbon rubber can be effectively integrated as a sustainable alternative fuel in cement kilns.