3D molecular model BOS reactor C-H2 smelting reduction furnace CFD CFD-DEM COREX COREX melter gasifier Cr2O3 DEM Discrete Element Method EAF Electric Arc Furnace Eulerian multiphase flow GPR Industry 4.0 LF refining slags Lignite PCA Peirce-smith converting RAFT SKS SPH Shuikoushan process TOU electricity pricing Technology: general issues TiN inclusion adaptive finite differences analysis tool angle of repose apparent activation energy