Torrefaction of Straw from Oats and Maize for Use as a Fuel and Additive to Organic Fertilizers—TGA Analysis, Kinetics as Products for Agricultural Purposes

Abstract

This publication presents research work which contains the optimum parameters of the agri-biomass: maize and oat straws torrefaction process. Parameters which are the most important for the torrefaction process and its products are temperature and residence time. Thermogravimetric analysis was performed as well as the torrefaction process using an electrical furnace on a laboratory scale at a temperature between 250–525 °C. These biomass torrefaction process parameters—residence time and temperature—were necessary to perform the design and construction of semi-pilot scale biomass torrefaction installations with a regimental dryer and a woody and agri-biomass regimental torrefaction reactor to perform a continuous torrefaction process using superheated steam. In the design installation the authors also focused on biochar, a bi-product of biofuel which will be used as an additive for natural bio-fertilizers. Kinetic analysis of torrefaction process using maize and oat straws was performed using NETZSCH Neo Kinetics software. It was found that kinetic analysis methods conducted with multiple heating rate experiments were much more efficient than the use of a single heating rate. The best representations of the experimental data for the straw from maize straw were found for the n-order reaction model. A thermogravimetric analysis, TG-MS analysis and VOC analysis combined with electrical furnace installation were performed on the maize and oat straw torrefaction process. The new approach in the work presented is different from that of current scientific achievements due to the fact that until now researchers have worked on performing processes on oat and maize straws by means of the torrefaction process for the production of a biochar as an additive for natural bio-fertilizers. None of them looked for economically reasonable mass loss ratios. In this work the authors made the assumption that a mass loss in the area of 45–50% is the most reasonable loss for the two mentioned agri-biomass processes. On this basis, a semi-pilot installation could be produced in a further BIOCARBON project step. The kinetic parameters which were calculated will be used to estimate the size of the apparatuses, the biomass dryer, and biomass torrefaction reactor.

Keywords

• torrefaction
• oats
• maize
• straw
• biochar