Partial substitution of coal with palm kernel in cement kilns: effects on cement production and quality

Abstract

The production of Portland cement is a complex process involving several chemical reactions and different materials, complex systems, and high temperatures (up to 1500 °C). Traditional fossil fuels such as coal, petroleum coke and natural gas have been used as primary source of energy for the process, though still abundant, their supply is slowly being depleted, and costs associated with obtaining these fuels are increasing with time. Therefore, alternative fuels such as biomass waste (palm kernel, rice, and coffee husks etc.) or processed waste materials (refuse derived fuel, waste tires, waste plastics, used oil etc.) and other types of waste have gained much interest recently in cement industries as they present a potential substitution option. In order to achieve the aim of this study, chemical and physical properties of both coal and PK have been determined and compared. Results show that the PK has an average calorific value ranging from 18-20 MJ/kg which is significantly acceptable and means that the waste can directly be used as fuel in the cement kiln for clinker production. Coal thermal substitution rate was progressively increased depending on the process conditions with the reference case for each kiln run (2% in August 2021, 3% in September 2021 and 5% in January 2022). Impacts on the product quality and process, benefits in terms of emissions and production cost were evaluated and discussed. Technical challenges encountered during the coal and palm kernel milling process and combustion process have been identified and possible solutions have been recommended.