Carbonization pressure influence on fixed carbon yield

Abstract

Biocarbon, or charcoal, is receiving increased attention as an increasingly important reductant in metallurgical industries, and has as well many others uses, e.g. as high quality fuel or as activated carbon. Traditional charcoal production processes are very inefficient, giving charcoal with low fixed carbon yields. A number of parameters influence the yield, including feedstock properties and carbonization process conditions. The importance of temperature is rather well known. However, the influence of pressure is more debated, and many parameters may influence the carbonization process simultaneously, making it hard to establish the real influence of pressure. In this work, based on thermodynamics and kinetics evaluations, and through comparison with experiments at atmospheric and pressurised conditions, the influence of pressure is presented and evaluated, as a function of temperature and choice of carrier gas, as well as feedstock properties. Possibilities for atmospheric carbonization systems to approach the performance of pressurised systems are discussed. Comparison with wet pressurised carbonization systems is made. Finally, recommendations for improved carbonization process conditions are given.