CFD simulations of rotary BOF slag carbonation kiln reactor with cyclone flow

Rotary kiln reactors play an important role in improving the mechanical properties and usability of basic oxygen furnace slag through a carbonation process. The performance of such reactors is critically dependent on the residence time of the CO2 gas used to promote the carbonation reaction. Accordingly, the present study proposes a rotary kiln reactor in which the residence time is increased by arranging the inlet and outlet pipes obliquely to the reactor centerline; thereby producing a cyclone flow structure within the reactor tube. The optimal geometry parameters and rotational speed of the kiln are determined using the robust Taguchi experimental method. The CO2 residence time in the optimized kiln is then evaluated by means of computational fluid dynamics simulations. It is shown that the residence time increases from 63.587 s in a standard (non-cyclone-flow) rotary kiln to 105.815 s in the optimized rotary kiln; corresponding to a performance improvement of 66.4%.