Process simulation and energy integration in the mineral carbonation of blast furnace slag

Large quantities of blast furnace (BF) slag and CO2 are discharged annually from iron and steel industries, along with a large amount of waste heat. The mineral carbonation of BF slag can not only reduce emissions of solid waste but also realize the in-situ fixation of CO2 with low energy consumption if integrated with the waste heat utilization. In this study, based on our previous works, Aspen Plus was employed to simulate and optimize the carbonation process and integrate the process energy. The effects of gehlenite extraction, MgSo(4) carbonation, and aluminum ammonium sulfate crystallization were studied systematically. The simulation results demonstrate that 2.57 kg of BF slag can sequester 1 kg of CO2, requiring 5.34 MJ of energy (3.3 MJ heat and 2.04 MJ electricity), and this energy includes the capture of CO2 from industrial flue gases. Approximately 60 kg net CO2 emission reduction could be achieved for the disposal of one ton of BF slag. In addition, the by-product, aluminum ammonium sulfate, is a high value-added product. Preliminary economic analysis indicates that the profit for the whole process is 1127 CNY per ton of BF slag processed. (C) 2018 The Chemical Industry and Engineering Society of China, and Chemical Industry Press. All rights reserved.