Experimental Research On The Pyrolysis Carbonized Characters Of Cotton Stalks

Biomass is a clean and renewable energy, which plays an important role in solving the energy and environmental problems of recent years. Since the great amount of advantages such as lower pyrolysis temperature, higher yield of energy and directional chemical products etc, the technique of biomass thermal transformation has become a hotspot in this field.In this dissertation, through industry analysis, elemental analysis and component analysis, cotton stalks and their briquettes were studied to identify the research objects’ basic attributes. The pyrolysis behavior was studied in different particle size, different catalyst and different heating rate by thermogravimetric analysis (TG) coupled with differential thermal analysis (DTA) technique and a proper pyrolysis mechanism model was proposed based on Li Chung-Hsiung integral method, which can be described as G(a)=1-(1-α)1/3. It shows that the activation energy(E) and pre-exponential factor(A) can provide more pertinent theoretical model for better use of biomass briquette fuel. The liquid products were detected by TG-GC-MS, which indicates to be good chemical raw materials.The multifunction thermal conversion reactor was designed and the technical parameters and operation parameters were calibrated by experiments. The influence of different atmosphere and pressures on the thermal conversion process of cotton stalks were studied by this reactor, which indicates that the water vapor atmosphere can greatly improve the quality of pyrolysis char while the char yield is decreased. With the improvement of pressure, the yield and fixed carbon content of biomass char increased and the volatile decreased. During the gaseous products under different pyrolysis pressures, the ratio of H2is maximum which reaches to above45%. With the increase of pressure, the volume fraction of H2and CO reduced, and the volume fraction of CO2increased while the volume fraction of CH4varies within a certain range.An orthogonal designed experiment was used to investigate the effects of cotton stalk catalytic pyrolysis conditions on the properties of biological char based on the self-made fixed bed pyrolysis experiment platform. Reaction catalyst, pyrolysis temperature, holding time and carrier gas flow rate were considered as the key factors. The results indicate that with the catalyst of ZnCl2, pyrolysis temperature of400℃, holding time under45min and reaction atmosphere under50ml/min H2O was the best pyrolysis process from the perspective of fuel characteristics. The Fourier transform infrared spectroscopy (FTIR) coupled with scanning electron microcopy (SEM) were applied to inquiry forming mechanism of the biomass char, which indicates that the biomass catalytic pyrolysis char has rich functional group structure and pore structure, which can be the high quality raw materials of more products with fairly high added value and provide more pertinent theoretical support for better use of biomass fuel.