Numerical Simulation of Heat Transfer Characteristics of Petroleum Hydrocarbon-Contaminated Soil During Ex-Situ Indirect Thermal Desorption

Indirect thermal desorption process of petroleum hydrocarbon contaminated soil is very complex and difficult to be analyzed by engineering full-scale numerical simulation considering multi-phase flow and interphase heat as well as mass transfer. Therefore, it is urgent to develop a simple and rapid calculation method to guide technology development and engineering applications. In this paper, the method of equivalent specific heat approximation was proposed to simplify the mass transfer process on the material side to the heat transfer process under variable specific heat conditions, and the numerical simulation of engineering scale indirect thermal desorption equipment was studied by coupling the diffusion flame combustion model, weighted-sum-of-gray-gases model, and discrete ordinates model. The heating process of soil in thermal desorption chamber was simulated, and the influence of soil residence time and designed feed rate on process parameters was obtained. The research results showed that soil residence time should be extended appropriately under the condition of less than 1.75 hours and designed feed rate be limited within 4 t/h to ensure reasonable soil discharge temperature that was directly related to the removal efficiency of petroleum hydrocarbons in contaminated soil. Meanwhile, the modification scheme of power distribution of combustion system was further studied to improve the heating uniformity of tubes.