Improvement of Fuel Properties of Corn Stalk by Torrefaction

Agricultural residues are one of the important biomass sources. Its high moisture content, low calorific value, large volume and low bulk density make it difficult to use biomass directly as fuel. In this study, it was aimed to improve the solid fuel properties of agricultural wastes, which have a significant potential and a certain shape in our country, by torrefied them in their current shapes. In the presented study, corn stalk, which is a problem for the producer to evaluate and dispose of at the end of the season, was used as agricultural waste. Corn stalk is a waste biomass that is very difficult to transport and store due to its low density. For this purpose, 2 cm long corn stalks were torrefied for different residence times at three process temperatures, 220°C, 260°C and 300°C, in a pyrex glass reactor placed in a circular-section vertical refractory chamber containing resistance wires. Torrefaction process was carried out in two different environments: stagnant air and inert gas (nitrogen).

It has been determined that a coal-like appearance occurs as the processing temperature increases in the samples subjected to torrefaction. In order to obtain a solid product from corn stalk with properties similar to coal, it was determined that a short residence time at 300°C in an inert environment and a long residence time at low temperatures (260-220°C) in a stagnant air environment were suitable. As a result of the torrefaction process performed at different temperatures, O/C and H/C ratios were found to be in the range of 0.45-0.67 and 0.85-1.58, respectively. These values indicate that a peat-like solid fuel with a high lignin content is obtained as a result of torrefaction of corn stalk in both environments. In addition, it was determined that the higher heating value of the solid products obtained as a result of the torrefaction process was higher than the raw sample.