Study On The Pyrolytic Characteristics And Kinetics Of Wheat Straw From Guanzhong Plain Of Shaanxi

At present, renewable resources have attractd worldwide attention dut to isssues including energy crisis, environmental pollution and climate change that human is facing.Biomass, as a kind of essential renewable resources, is environmental-friendly, easy-to-access, abundant and renewable, which have the potential to replace petroleum fuels. Thermochemical conversion methods are critical to biomass’s efficient utilization, through which biomass can be converted into activated carbon, transportation fuels, and specialized chemicals. Pyrolysis technology, as one of biomass thermochemical methods, is widely used in bioenergy industry due to its versatile target products.The enormous amount of high-cellulose wheat straw produced annually in the Guanzhong Plain of Shaanxi province, China, is a potential source of biomass feedstock. Furthermore, to the best of our knowledge, investigations on the pyrolysis of Guanzhong wheat straw have rarely been performed, suggesting that the abundant wheat straw has not been utilized fully. The main objective of this study is to investigate the pyrolysis behavior, products and pyrolysis mechanism of Guanzhong wheat straw and its main components using TG-FTIR technology. The work conducted in this work are as follows:(1) Physical and chemical characteristics of Guanzhong wheat straw are analyzed detail, the results show that the straw was characterized by a high amount of volatile matter, C, O, H and low content of ash, which is favorable to biomass fuel performance.Besides, the sample most likely consisted of acids, alkanes, alphatics, and aromatics.(2) The pyrolysis process of Guanzhong wheat straw is studied by using TG-FTIR technology at different heating rates, it has found that the pyrolysis process of the straw can be divided into 4 stages:dehydration, and the pyrolysis processes of hemicellulose, cellulose and lignin. The main pyrolysis products identified by FTIR included H2O, CH4, CO2 and CO as well as aromatics, acids, alcohols, alkanes, phenols, ethers, ketones, and aldehydes. Moreever, the effect of different pyrolysis process parameters on the wheat straw pyrolysis characteristics has been studied.(3) Main components extracted from Guanzhong wheat straw are pyrolyzed using TG-FTIR technology. Results found that the pyrolysis behavior of cellulose, hemicellulose and lignin is remarkable due to their differences in chemical structure. The main pyrolysis zone of hemicellulose and cellulose is 180～390 ℃ and 256～412 ℃ respectively while the pyrolysis of lignin proceed at a wide temperature range. The main products of cellulose pyrolysis included H2O, CO, CO2 and hydrocarbons with C-H bond as well as acids with C=O bonds, aldehydes and ketones. The main products of hemicellulose pyrolysis included CO2, CH4, H2O, CO and acids, aldehydes, alkanes as well as esters. While the mian products of lignin pyrolysis included H2O, CO2, formaldehyde, phenols, methyl alcohol and alkanes.(4) The apparent activation energy determined using Model-free methods of FWO and KAS are approximately 202 kJ/mol. That range was 30 kJ/mol higher than the value 171.12 kJ/mol obtained by the Kissinger method. The apparent activation energy of hemicellulose and cellulose in their main pyrolysis region determined by using C-R method is 49.53 kJ/mol and 49.53 kJ/mol respectively based on the assumption of the pyrolysis reaction order is 1. However, the apparent activation energy of lignin at the temperature range of 45～116 ℃ was 34.48 kJ/mol while at the temperature range of 120～252 ℃, the value was 6.64 kJ/mol.In conclusion, investigation on the pyrolysis kinetics of Guanzhong wheat straw and its components are conducted in order to provide technical basis for biomass gasification, optimization of biomass pyrolysis process parameters, upgradation of pyrolysis equipments, integration of gasification process and production of high-quality biomass fuels, which is significant for enhancing the utilization efficiency of biomass energy, and boosting the regional economy. the prospect of fuels and chemicals produced from Guanzhong wheat straw is promising. Further investigation is needed to improve the utilization efficiency of Guanzhong wheat straw and detailed pyrolysis mechanism of Guanzhong wheat straw is still need to be further investigated.