Development and performance evaluation of a fixed bed pyrolyser for valorization of selected biomass

Abstract

Efficient waste management in the forestry and wood industries is essential for conserving resources, energy, and costs. This study presents the design and fabrication of a fixed-bed pyrolysis system for the production of bio-oil, bio-char, and syngas from Cola nitida sawdust residues. The system comprises a reactor, condenser, heating unit, and discharge unit, all designed in accordance with ASTM standards (ASTM A36, ASTM C182 and ASTM C133) and fabricated at the Technical Support Unit, Faculty of Technology, University of Ibadan. Dried and sieved sawdust fractions of 0.5, 1.5, and 3.0 mm particle size and mass of 200 ±5 g  mass were pyrolyzed at residence time of 30, 45 and 60 minutes respectively with three replicates runs each under controlled conditions to assess the effects of particle size and residence time on product yield and composition. Results showed that smaller particles (0.5 mm) yielded the highest liquid fraction  (45.8%) due to enhanced heat transfer and rapid devolatilization, while larger sizes (1.5 - 3.0 mm) produced less bio-oil but more bio-char,  with 3.0 mm yielding the most bio-char (38.7%) and prolonged residence times promoted secondary cracking, reducing liquid yield. The developed system, with a total fabrication cost of USD 173 (?276,600), effectively volatilized Cola nitida sawdust.