Kamel Halouani

Depollution of atmospheric emissions of wood pyrolysis furnaces

The wood carbonization in Tunisia consists essentially of traditional activity using charcoaling stacks and pits characterized by high atmospheric pollution and poor energy conversion. Indeed, 70% of the initial mass of anhydrous wood are found in the vapor as aerosols, polluting and toxic gases and complex condensable organic compounds that can cause a substantial pollution of air, ground and water. Several processes of treatment and energy valorization of such effluents were proposed, but the incineration remains at present the most promising technique of depollution. The results show that the incineration, at about 1000°C, of wood carbonization smokes allows the destruction of 99% of the mass of pollutants except CO2 and the reduction of polluting gas emission. The possible valorization of the smoke’s energy in the exit of the incinerator enhances the thermal efficiency of the process.

A PARAMETRIC STUDY OF RADIATIVE HEAT TRANSFER IN AN INDUSTRIAL COMBUSTOR OF WOOD CARBONIZATION FUMES

ABSTRACT Radiative heat transfer is investigated numerically for an industrial combustor of wood carbonization fumes. The combustor has a complex geometry. The finite–volume method (FVM) is applied to study radiative heat transfer in conjunction with the weighted sum of gray gases (WSGG) model of Kim and Song as a non-gray-gas model. The blocked-off-region procedure is applied to treat the geometric irregularities. The reliability of this model, for a complex geometry filled with a semitransparent medium and a regular geometry containing water vapor, is analyzed by comparing its predictions with the exact solution and the Monte Carlo technique associated with the statistical narrow band (SNB) model. Good agreement with benchmarks is found. The extension of this model to a mixture of CO2, H2O, particles, and soot particles (confined in a complex geometry) is made. The effects of soot volume fraction, partial pressure ratio, particle concentration, and thermal nonequilibrium on the inner wall radiative heat flux of the combustor are presented.

Numerical modeling of combined partial oxidation and gasification zones in a downdraft gasifier fueled by almond shell

A two dimensional model is developed for the partial oxidation and reduction zones of a downdraft gasifier. The model is based on the conservation laws of mass, energy and momentum coupled to the chemical kinetics. The predicted results are compared with experimental data obtained from a pilot scale downdraft gasifier fueled by almond shell and a reasonable agreement is found The model is used to investigate the distribution of the temperatures and gases concentrations inside the partial oxidation and reduction zones. Effect of the main operating parameters on gases species yield could be investigated using the elaborated model.