Characterization of Bio-oil, Bio-char, and Pyro-gas derived from cotton stalk slow pyrolysis - as sustainable energy sources

Abstract

The untapped energy present in this cotton stalk residue is one of the major environmental threats due to its field burning. In this research paper, slow pyrolysis process has been performed on cotton stalk having particle size 0.85 mm at 300°C, 400°C, and 500°C, at 10°C/min heating rate and 1-hour residence time. The process produced bio-oil, bio-char and pyro-gas. Physiochemical properties, GC-MS analysis, stability analysis and miscibility analysis of bio-oil have been carried out to ensure its feasibility as energy source. To ensure suitability of bio-char as soil nutrient and energy sources, its elemental analysis, metal element analysis and microscopic examination have been performed. Pyro-gas is characterized to find its suitability as energy source for heating purpose during pyrolysis process by recirculating. The maximum yield for bio-oil and Pyro-gas is 36.60 wt.% and 25.25 wt.%, respectively at 500°C, while maximum yield for char is 58.54 wt. % at 300°C. Result of physiochemical properties of bio-oil reveals remarkable variation as compare to diesel whereas GC-MS analysis found bio-oil as complex mixture. 0.02349 cst/hr. aging rate of bio-oil shows good stability at room temperature. Physiochemical properties of bio-oil vary with pure diesel causes phase separation of bio-oil and diesel during blending. Bio-oil - diesel Stabilized emulsion has been achieved by addition of 6 wt. % of n-butanol as co-solvent. Characterization and microscopic examination of bio-char favours usage of char as soil nutrient and energy substitute. The Pyro-gas analysis confirms its suitability as energy substitute during entire process, as it contains a substantial amount of carbon dioxide and methane.