Effects of heating rate and water leaching of perennial energy crops on pyrolysis characteristics and kinetics

Abstract

Aiming to investigate the suitability of perennial crops for heat and power applications, three energy crops produced under the Greek climatic conditions were pyrolyzed by non-isothermal thermogravimetry over the temperature range of 25–850 °C. The effects of heating rate and water washing of the fuels on thermal decomposition characteristics, reactivity and kinetics were examined. The thermochemical reactivity of the biomass materials was determined by their volatile and ash contents, as well as the distribution of organic and inorganic constituents among plant parts. Switchgrass leaves exhibited the highest pyrolysis rate, while cardoon leaves the lowest. An increase of the heating rate delayed thermal decomposition processes and increased degradation rates. Raw fuel washing enhanced reaction rates of switchgrass and giant reed, whereas it influenced the sensitivity of cardoon in nitrogen, by shifting the peak temperature to higher values. A first-order parallel reactions model fitted the experimental results accurately. A higher heating rate, or a lower content of K, P, S and Cl in ashes increased the kinetic parameters corresponding to hemicellulose and cellulose decomposition.