Comparative pyrolysis characteristics and kinetics of agricultural food grains by thermogravimetric analysis

Pyrolysis precedes the development of smouldering or flaming fires in storage and processing facilities. Understanding this process and determining the parameters that characterise it is essential for controlling fires. This study analysed the pyrolysis of African food grains that are important for food security but historically have received limited attention. Cowpeas, lentils, millet, soybeans, unshelled peanuts, flax, sunflowers, shelled peanuts, and sesame were subjected to thermogravimetry in a nitrogen atmosphere at heating rates of 5, 10, 20, and 40 degrees C/min from ambient to 600 degrees C. All grains were completely dehydrated at 170 degrees C and started decomposing at about 180 degrees C. The decomposition patterns varied with the relative proportion of hemicellulose, cellulose, protein and, particularly, lipids (oil content). Pyrolysis rates peaked at lower temperatures of about 300 degrees C for non-oil grains but at higher temperatures of 400 degrees C for oil grains. Friedman and Coats-Redfern methods were used to determine activation energies (130-355 kJ/mol), preexponential factors (8.1 x 107-1.0 x 1031 s-1) and the numerical values of the complex, multistep reaction models. Oil grains (or their powder) generally have lower activation energies, are thus more reactive than non-oil grains, and therefore constitute critical consideration for fire safety in processing facilities. The work is important for developing fire engineering solutions for food facilities based on quantitative fire behaviour data.

Automated summary

This study analyzed the pyrolysis process of African food grains and determined the pyrolysis parameters. The study found that oil grains are more reactive than non-oil grains and have implications for fire safety in food processing facilities.