J1119e: Products from Thermochemical Biomass Processing….


The basis of a fuel or chemical production system is that the feedstock is converted to a useful primary energy product and either used as such, or further converted, upgraded or refined in subsequent processes to give a higher quality and higher value secondary product as shown in Figure.

When organic materials are heated in the absence of air, they degrade to a gas, a liquid, and a solid as summarised in Figure. It is possible to influence the proportions of the main products by controlling the main reaction parameters of temperature, rate of heating, and vapour residence time. For example fast or flash pyrolysis is used to maximise either the gas or liquid products, depending on temperature as summarised below:

  • Slow pyrolysis at low temperatures of around 400°C and long reaction times (which can range from 15 minutes to days in traditional beehive kilns) maximises charcoal yields at about 30% wt.
  • Flash pyrolysis at temperatures of typically 500°C; at very high heating rates and short vapour residence times of typically less than 1 second or 500 ms; maximises liquid yields at up to 85% wt (wet basis) or up to 70% dry basis.
  • Similar flash pyrolysis at relatively high temperatures of above 700°C; at very high heating rates and similarly short residence times maximises gas yields at up to 80% wt. with minimum liquid and char production.
  • “Conventional” pyrolysis at moderate temperatures of less than about 500°C and low heating rates (with vapour residence times of 0.5 to 5 minutes) gives approximately equal proportions of gas liquid and solid products

 

Source: A. Bridgwater. Thermal biomass conversion and utilization – Biomass information system. European Commission – Agro-Industrial Research Division. 1996

Regards:
Dr. Jorge Luis Mírez Tarrillo – PERU
Facebook http://www.facebook.com/jorgemirezperu 
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E-mail: jmirez@uni.edu.pe




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