Preliminary Studies on Moving Bed Torrefaction System for Biomass

• Main Authors: Cheng-Yu Hsu, 許政裕
• Other Authors: 李允中
• Format: Others
• Language: zh-TW
• Published: 2012
• Online Access: http://ndltd.ncl.edu.tw/handle/80023879226272541303

碩士 === 國立臺灣大學 === 生物產業機電工程學研究所 === 100 === Wood is a high potential alternative to petrochemical fuels due to the mass production by growing plants. The pyrolysis of wood, which involves various conditions produces corresponding rich carbon content residues, char or gas and liquid products. Different from gas and liquid fuels, biochar, a stable solid created by pyrolysis of biomass, is easier for storage and transportation. In our study, therefore, we focused on the torrefaction process that leads to a final dry solid product. We used COMSOL Multiphysics 4.2a to simulate the heat and mass transfer of a cubed biomass, Cryptomeria japonica, with 20 mm edge length during torrefaction process. Then, we validated the simulation results by comparing to torrefaction experiments. Simulation result showed that the concentration of hemicellulose, cellulose, and lignin were decreased from the center towards the surface of biomass, meanwhile, the concentration of biochar was increased. Experimental data also indicated the same tendency of the concentration of hemicellulose, cellulose. It is hard to measure the concentration of lignin since some lignin-like products are undissolved during the separation of lignin by using strong acid solvents. However, we measured the total weight of products from torrefaction and lignin, and the measured data were agreed with the simulated results. During 30 min torrefaction process at 250°C, 270°C, and 290°C, the average error between simulation and experiment were 9.0%, 9.0, and 4..1%, respectively. Also, the yield of biochar are 39.19%, 36.13%, and 34.15%, respectively. According to previous results, we designed a torrefaction reactor for biochar production, and this reactor can obtain the energy from combustion of the wood itself for energy conservation and environmental protection. Besides, the performance of the reactor can be well operated in the temperature range for torrefaction, which is validated by using RTD (Resistance Temperature Detectors). However, improvements are needed for solid material flow and exhaustion in operation of this reactor.