Estimation of Thermal Stress at an Early Step of Coking Process

A new method, based on the incremental theory, is proposed to predict thermal stress in the coke layer during carbonization. In this method, the deformation of the coke layer and the effect of the pressure caused in the plastic layer are considered. As a result of estimations of thermal stress variations with time at a constant heating rate, the tensile stress has a maximum value at each of the heated surfaces and the resolidification surface at the early step of carbonization, clarifying the time when microfissures are formed. The effects of heating rate and load on lump coke size are measured and it is found that the lump coke size decreases with increases of the heating rate and the load. The cause is clarified analytically that microfissures are producted easily with increases of heating rate and load and that they grow into macrofissures due to the tensile stress within the coke layer.