A PHYSICOCHEMICAL STUDY OF CARBONIZATION PHASES .1. TARS MIGRATION AND COKING PRESSURE

During the coking process, the production of volatile matters, in the plastic phase of the coking charge, leads to the development of dangerous internal pressures if hindrance is encountered in the gas release. By withdrawing and quenching coking coal charges at a given temperature in the course of heating, several phases of carbonization were isolated and submitted to physicochemical analyses: diffuse reflectance infrared spectroscopy (DRIFT), proximate and ultimate analysis, N-methyl-2-pyrrolidinone (NMP) extraction and hydrogen transfer (HT). By these means, two distinct ways of migration of volatile matters through coking material were evidenced. For 'dangerous coals' (inducing excessive coking pressure) the volatile materials migrate mainly from the plastic layer to the cold side of the oven, giving rise to impregnation of the remaining coal. On the contrary, a large part of volatile components of 'safe' coals migrate towards the hot side of the oven through semi-coke and coke. These results are in agreement with our preliminary study on the variations of the permeability of the different phases of carbonization.