Numerical study on coal pyrolysis behavior during carbonization in a coke oven

A one-dimensional transient mathematical model is systematically investigated to analyze the thermal evolution of coal during carbonization in an industrial-scale coke oven. The model incorporates the key physical processes governing coking, including heat conduction, moisture evaporation, condensation, and steam migration within the coal charge. Appropriate initial and boundary conditions are specified to ensure the closure of the energy and mass balance formulations. The governing equations are solved using an implicit Crank–Nicolson scheme, and the model is validated against established numerical results from existing literature. This study examines the temperature evolution of three coal types, and the results show that moisture distribution, plastic-layer thickness, and resolidification temperature strongly influence the transient thermal behavior and volatile release patterns. Temperature-dependent expressions for the specific heat are evaluated using both Einstein's model and empirical correlations, while the effective thermal conductivity is assessed by considering interstitial gas conduction, evolving porosity, and radiative transfer across fissures in the semi-coke. The model predicts drying times, coking durations, and total heat-input requirements and quantifies the influence of the furnace-wall temperature, initial moisture content, and dry bulk density, thereby enabling the assessment of the operating conditions that promote energy-efficient carbonization. Overall, the model provides a robust framework for interpreting the coupled thermophysical processes that occur during carbonization and offers practical guidance for optimizing coke-oven operation and charge preparation.