Charcoal and Bio-Oil Production by Using a Microwave-Assisted Pyrolysis Process

摘要

Bio-energy from biomass can be used as renewable energy to reduce CO_2 emission in some industrial processes. Fast pyrolysis has emerged as the most promising technology to convert organic materials into liquid fuels at a short time but it still faces some technical challenges in improving product yield, its quality and process energy efficiency. Microwave assisted pyrolysis (MAP) of biomass provides distinctive environment to solve these challenges. In this paper, the pyrolysis of Lemon Eucalyptus was investigated using microwave energy as the heat source, and the yield and characteristics of the pyrolysis oils (i.e. elemental analysis, hydrocarbon composition, and potential fuel properties) and gases are presented and discussed. Here, a pilot unit with 150 kg per hour capacity using MAP technique was built in order to evaluate the energy potential of gases (non-condensable gases - NCG) and liquid (condensable gases - CG) of a biomass pyrolysis plant. The pyrolysis process was in continuous mode and in two stages, biomass drying and pyrolysis, with charcoal production, pyrolysis gas and bio-oil. The results showed that about 63% of the raw material was converted to charcoal and 37% to pyrolysis gas and bio-oil. In the pyrolysis gas fraction, 46% corresponds to the nitrogen from the air. There was a 1638 kg of air entering in the system, which was verified by mass balance. This air inlet implies several drawbacks, mainly explosion risks. The bio-oil fraction was analyzed showing that there was a 45% of pyroligneous gas followed by about 33% of water. It can be seen that the lower calorific value of condensable gases can be increased with the removal of water from its composition. The study of energy availability showed an averaged value of 5.60 MWh of thermal energy per ton of charcoal produced in the prototype.