Thermal Energy Storage/Waste Heat Recovery Applications in the Cement Industry

Abstract

The cement industry is the most energy-intensive industry in the United States in terms of energy cost as a percentage of the product according to a 1973 report by the Cost of Living Council. Martin Marietta Aerospace, Denver Division, and the Portland Cement Association have studied the potential benefits of using waste heat recovery methods and thermal energy storage systems in the cement manufacturing process. This work was performed under DOE Contract No. EC-77-C-01-50S4. The study has been completed and illustrates very attractive cost benefits realized from waste heat recovery/thermal storage systems. This paper will identify and quantify the sources of rejected energy in the cement manufacturing process, establish uses of this energy, exhibit various energy storage concepts, and present a methodology for selection of most promising energy storage systems. Two storage systems show the best promise - rock beds and draw salt storage. Thermal performance and detailed economic analyses have been performed on these systems and will be presented. Through use of thermal energy storage in conjunction with waste heat electric power generation units, an estimated 2.4 x 1013 BTU per year, or an equivalent of 4.0 x 10 barrels of oil per year, can be conserved. Attractive rates of return on investment of the proposed systems are an incentive for utilization and further development.