Separation and recovery of waste heat from millimeter-sized blast furnace slag in cyclone separators

Abstract

Achieving green and energy-efficient heat separation and mitigating thermal pollution from slag with the temperature exceeding 1500 °C and the global annual production of 857 million tons, remains a formidable challenge for the iron and steel industry. To address this issue, this work introduces an innovative approach by leveraging the distinct characteristics of high-speed particle self-rotation and revolution driven by the cyclone separator for slag heat separation. In contrast to the traditional air blast method, the average heat separation coefficient is increased by up to 25.1 %, along with a 30.0 % reduction in energy consumption. This enhancement can be attributed to the cyclone-induced high-speed particle self-rotation behavior, reaching up to 14,459 rpm. The heat separation efficiency of the cyclone separator for blast furnace slag reaches 94.6 %. Moreover, this approach has been applied in a 60 t/h commercial slag disposal project, achieving high-value slag with 100 % glassy content and generating 25,952 kg/h superheated steam. As a result, 706.3 kg CO₂ emissions are reduced, surpassing the state-of-the-art centrifugal granulation technology (31.2 kg CO₂ emissions) per ten tonnes slag processed. Benefiting from the utilization of cyclone separator, an annual reduction of 420,712 GJ in waste thermal emissions has been achieved. This work paves a novel pathway for the green and energy-efficient separation and recovery of heat from the high-temperature slag for the iron and steel industry.