Effect of Pyrolysis Temperature and Residence Time on Bio-char Obtained from Pyrolysis of Shredded Cotton Stalk

Bio-char is carbon-rich product generated from biomass through batch type slow pyrolysis. In this study, the effects of pyrolysis temperature and residence time on the yield and properties of bio-chars obtained from shredded cotton stalks were investigated. Safely said that the quality of bio-char of shredded cotton stalk obtained at 500°C temperature and 240 min is best out of the all experimental levels of variables of temperature and residence time. At this temperature and residence time, the quality of bio-char in terms higher heating value (8101.3cal /g or 33.89 MJ/kg), nitrogen (1.56%), Carbon (79.30%), and C/N ratio (50.83) respectively. The quality of bio-char for various applications is discussed along with different quality parameters. The bio-char could be used for the production of activated carbon, in fuel applications, and water purification processes. Average bulk density of whole cotton stalk and shredded cotton stalk was found as 29.90 kg/m3 and 147.02 kg/m3 respectively. Thus density was increased by 3.91 times. The value of pH, EC and CEC of shredded cotton stalk biomass was found as 5.59, 0.03 dS/m and 38.84 cmol/kg respectively. Minimum and maximum values pH, EC and CEC of its bio-char was found as 5.85 to9.86, 0.04 to 0.10 dS/m and 38.02 to 24.39 cmol/kg at 200°C and 60 min and; 500°C and 240 min temperature and residence time respectively. Moisture content, ash content, volatile matter and fixed carbon of shredded cotton stalk biomass were found as, 12.5, 5.27, 80.22, and 14.51 (%, d.b) respectively. The minimum and maximum value of bio-char in terms of ash content, volatile matter and fixed carbon of bio-char were found as 5.5 to 15.56, 48.02 to 79.48 and 15.02 to 36.40 (%, d.b) respectively. Calorific value of cotton stalk biomass was found as 3685.3 cal /g. The minimum and maximum higher heating value of its bio-char was found as 4622.0 cal/ g and 8101.3 cal/g at 200°C and 60 min and; 500˚C and 240 min temperature and residence time.