The new mathematical model to estimate the dilatation behavior and coking pressure of packed bed of coal during carbonization is proposed and the thermal stress analysis is then carricd out by using finite element method.In this model,volume fractions of gas,liquid and solid phase in each calculated finite element volume are determined from coal pyrolysis rate equations including the tar devolatilization.We assume that the dilatation of packed bed is caused by the interaction between the pyrolysis gas and the impermeable plastic layer where the tar released from coal mainly exists.The gas released from coal pushes the impermeable plastic layer and then the dilatation pressure against oven wall arises.In this study,the thermal stress analysis using new model is applied to small test packed bed (#PHI#=13mm,h=70mm).the new model can simulate the decrease in permeability caused by tar release,the increase in permeability caused by tar devolatilization and the appearance of the coking pressure in the plastic layer.The coking pressure is then increased with the heating rate.The proposed model may pressure is then to estimate the dilatation behavior and the coking pressure in packed bed of coal.
展开▼
