Optimisation of corn straw biochar treatment with catalytic pyrolysis in intensive agricultural area

The crop biomass treatment is the challenging issue in the intensive agricultural area and the catalyst has the potential to solve this problem. This preliminary study examined the response of the corn straw biochar treatment to the catalytic pyrolysis and applications of catalyst to the sustainable agricultural with cost savings. The surface morphology of corn straw after pyrolysis was compared with the electron microscope scanned images. The pyrolytic characteristics and kinetics of corn straw were studied using a thermogravimetric analyser from ambient temperature to 900 degrees C under a nitrogen atmosphere at heating rates of 10, 20, 30 and 40 degrees C min(-1). The mass loss and the rate of mass loss curves derived from the pyrolysis of corn straw biochar and the biochar with the addition of 5% (wt.%) ammonium dihydrogen phosphate (ADP) catalyst. The pyrolysis process was consisted of three distinct stages, and impact of catalyst on the temperature distribution was distinguished. The catalytic pyrolysis process was mainly categorised by removal of water including free water and combined water, decomposition of hemicellulose, cellulose and lignin; and carbonisation. With the increase of pyrolysis rate, the maximum weight loss temperature shifted to lower temperatures. The kinetic process characteristics of corn straw biochar at three levels of ADP addition and four kinds of temperature were calculated. The activation energies and pre-exponential factors of the pyrolysis process were calculated by the Flynn-Wall-Ozawa method, modified Coats-Redfern model-free method and Kissinger method. The detailed information of kinetic parameters also helped to improve the biomass pyrolysis process. The analysis demonstrated that the ADP had a catalytic effect on the pyrolysis behaviour of biomass and was able to reduce the activation energy of biomass pyrolysis. Therefore, the catalyst can improve the pyrolysis process and have great potential to increase crop residue treatment efficiency, especially in the intensive agricultural area. (C) 2015 Elsevier B.V. All rights reserved.