Production of charcoal as an alternative reducing agent from agricultural residues using a semi-continuous semi-pilot scale pyrolysis screw reactor

Nowadays there is widespread concern regarding the CO2 emissions derived from fossil fuels due to the contribution of this gas to the greenhouse effect. Many metallurgical processes use fossil carbonaceous materials like e.g. petroleum coke as a reducing agent involving the emission of substantial amounts of carbon dioxide. One interesting alternative is the substitution of the mentioned fossil-based reducing agents with biomass derived charcoal. Typical carbonization processes are operated between 623 and 773 K, but this charcoal does not fulfill the required quality for metallurgical processes. In the present paper a (semi-) continuous carbonization process was developed at high temperatures in order to produce charcoal to be used as a reducing agent. The effect of the temperature, residence time, moisture content and grain size were studied in an auger pyrolysis reactor, and the charcoal quality was tested carrying out reactivity tests, CHN + S as well as calculating the fixed carbon percentage.