A hybrid cooling system to enable adhesion-free heat recovery from centrifugal granulated slag particles

Abstract

It remains a long-standing challenge to recover high-temperature heat from blast furnace slag. Centrifugal granulation assisted thermal energy recovery (CGATER), although being proposed for tens of years, has gained renewed interests for its potential to enable green and sustainable slag treatment. Yet, the CGATER technology is still not sufficiently mature to be applied in iron and steel industry. One key hurdle towards its industrialization is the easy adhesion of granulated slag particles, which deteriorates heat removal from slag particles. To address this issue, a new method that combines both water and air cooling to eliminate particles adhesion in the course of heat recovery was proposed. As a proof of principle, a hybrid cooling system was built and the behavior of the hot, sticky slag particles inside the system was studied experimentally. Encouragingly, this hybrid cooling system was observed with superb anti-adhesion performance. Such attractive trait of the new system is enabled by the fast slag particles cooling by water and timely slag particles transportation by air. Further, the operational factors including initial slag temperature, air flowrate and rotating speed of granulator were also considered. The optimal rotating speed of granulator was 1800 rpm in the present operating conditions. The maximum heat recovery efficiency of 52% and vitreous content of ~ 98% were achieved when the initial slag temperature was 1500 ℃. This work provides a new attempt to resolve the cumbersome slag adhesion issue and advances the state of the art in the realm of CGATER technology.