Recovery of waste heat in cement plants for the capture of CO ₂

Large amounts of energy are consumed during the manufacturing of cement especially during the calcination process which also emits large amounts of CO ₂. A large part of the energy used in the making of cement is released as waste heat. A process to capture CO ₂ by integrating the recovery and utilization of waste heat has been designed. Aspen Plus software was used to calculate the amount of waste heat and the efficiency of energy utilization. The data used in this study was based on a dry process cement plant with a 5-stage preheater and a precalciner with a cement output of 1 Mt/y. According to the calculations: 1) the generating capacity of the waste heat recovery system is 4. 9 MW. 2) The overall CO ₂ removal rate was as high as 78. 5%. 3) The efficiency of energy utilization increased after the cement producing process was retrofitted with this integrated design.