Creep analysis of lump coke deformation behaviour during coal carbonization

A thermal stress analysis model, which includes the effect of viscoelasticity of the plastic and semicoke layers, dilatation of the plastic layer and the dependence of the thermophysical properties on the extent of the pyrolytic reaction, has been developed to estimate the coal carbonization process within a coke oven chamber. An experimental study was also carried out to measure the coke displacement and to observe the coke deformation behaviour in a laboratory-scale coke oven at various heating rates. The displacement calculated with the thermophysical properties which depend on the extent of the pyrolysis reaction gives better agreement with experimental data than that calculated with the properties which depend on temperature, as the heating rate increases. This result shows that the effect of heating history is an essential factor in the thermophysical characteristics of lump coke. The displacement estimated by the viscoelastic model agrees well with experimental results, compared with that estimated by the elastic model. This means that the viscoelasticity has to be considered for accurate estimation of the coke deformation behaviour. The estimated maximum principal stress within the lump coke under the constraint of the upper wall of the oven is larger than that under the free dilatation condition. This result is in agreement with experimental observation.