Tizane Daho

A New Experimental Method to Determine the Evaporation Coefficient of Trichloroethylene (TCE) in an Arid Soil

This paper presents a new method to determine the evaporation coefficient of trichloroethylene using a new experimental device called “activity-meter”. This device and the associated method have been developed in the Laboratory of Mechanical Engineering of the University of Montpellier 2 (France). The influence of diffusion on the vapor pressure of trichloroethylene and the influence of temperature at the liquid–gas interface were first determined. The results show that diffusion phenomena have no influence on the vapor pressure of trichloroethylene beyond 400 s of experimental time and the temperature is almost constant during experiments. Thus, in order to take into account the effects that are only due to the variation of partial pressure of trichloroethylene at the liquid–gas interface, the time interval used is between 400 s and the time required to reach equilibrium. The influence of pressure and temperature on the evaporation coefficient of pure trichloroethylene in an arid soil was then highlighted. The results show that the evaporation coefficient of trichloroethylene decreases with total vapor pressure but increases with temperature. A comparative study on evaporation coefficients conducted on water, heptane, and trichloroethylene shows that our results are in good agreement with results on volatility.

Impact of pre-treatment by torrefaction and carbonization on temperature field, energy efficiency and tar content during the gasification of cotton stalks

The present study focused on the gasification of raw and pre-treated cotton stalks (CS) by torrefaction and carbonization. Temperature fields, mass balance, energy balance, energy efficiency and tar content of the gas were investigated for the gasification of different types of biomass materials (raw, torrefied and carbonized CS). High temperature and thick reduction zone were obtained during the gasification of pre-treated CS comparatively to the gasification of raw CS. Thus, the thermal and catalytic cracking of the tars may be more pronounced for the gasification of pre-treated biomass particularly for the carbonized biomass. Mass and energy balances have shown a reduction of biomass conversion during the gasification of torrefied and carbonized CS. Indeed, the energy efficiency of 58.7, 46.5 and 38.4% were obtained for raw, carbonized and torrefied CS, respectively. The lowest energetic performances were found during the gasification of torrefied CS due probably to the severe degree of the torrefaction. However, the tar content in gas was drastically decreased by the pre-treatment of the CS. Indeed, the tar contents of 4.41, 2.24 and 0.10 g/Nm3 were obtained for the gasification of raw, torrefied and carbonized CS, respectively. Key words: Biomass gasification, pre-treatment, tar content, energy efficiency.