Plastic layer permeability estimation using a model of gas pressure in a coke oven

The occurrence of internal gas pressure (IGP) in a coke oven is of considerable interest in cokemaking, because of its relationship to the phenomenon known as oven wall pressure (OWP) or coking pressure. High OWP can lead to a dangerous situation and may be linked to difficulties in pushing a charge. It has long been considered that IGP causes OWP, but there remains some speculation that they are separate phenomena. In this paper, a simplified model of heat transfer and IGP in a coke oven is presented and validated by reference to pilot-scale coke oven experiments. The model can be used to describe the generation of IGP at all stages of the coking process, and results obtained from the pilot-scale coke oven can be scaled up to operational level with the model. The model is used to show that the permeability at the re-solidification end of the plastic layer is a key determinant of the magnitude of the IGP, and ultimately coking pressure. The effect of bulk density on permeability is discussed and the vertical variation of gas pressure in the centre of the oven charge is illustrated. (Original abstract - amended)