The pyrolysis of biomass briquettes: Effect of pyrolysis temperature and phosphorus additives on the quality and combustion of bio-char briquettes

Abstract

The influences of pyrolysis temperature and phosphorus additives on physico-chemical quality and combustion property of bio-char briquettes were investigated in this research. Bio-char briquettes were obtained from directly pyrolysis of maize straw briquettes. Pyrolysis temperature were from room temperature to 250–650°C with a heating rate 10°C/min. Combustion tests were performed in a thermal-gravimetric analyzer. Results showed that with the increased pyrolysis temperature, volume density decreased initially and subsequently turned flat. While durability rating and mass yield sustained to decline. The optimal pyrolysis temperature was estimated to be 550°C, gave the higher heating value 21.05MJ/kg, energy-mass co-benefit (EMCI) 8.14. The volumetric energy densities were mainly in the range of 10–14GJ/m3. Combustion feature of bio-char acquired at 250°C was significantly different. Both the index S and Di at the first stage were obviously higher; the S was improved by addition of Ca(H2PO4)2 at a suitable pyrolysis temperature. The E generally showed increasing trend with enhanced pyrolysis temperature. In the same pyrolysis temperature, the sequence of E from high to low is: EMS, EMS-CPM and EMS-ADP. The performance of NH4H2PO4 on combustion characteristics was worst.