Reactor and process design for slow pyrolysis and torrefaction


Slow pyrolysis and torrefaction (a milder form of pyrolysis) are similar methods of thermochemical biomass conversion whereby the biomass degradation reactions take place in the absence of oxygen at low heating rates.  This results in a significant amount of solid char (in the case of pyrolysis) or torrefied biomass (in the case of torrefaction) when compared to fast pyrolysis and vacuum pyrolysis.  Both char and torrefied biomass exhibit improved combustion and handling characteristics and may be used more effectively as a renewable, solid biofuel than the original biomass.

Thermogravimetric analysis (TGA) and differential scanning calorimetry (DSC) will be used to understand the intrinsic thermochemistry behind the degradation reactions.  The resulting data will be incorporated into a model combining the effects of heat and mass transfer, which will in turn be used for reactor design.  This model will be validated against the operation of a  continuous, slow pyrolysis reactor mini-plant (BTG Biomass Technology Group, The Netherlands) which utilizes a rotating screw (auger) to pass biomass through the reactor.  To understand the operation of the mini-plant, the flow and mixing of material in screw conveyors will also be studied.  The mini-plant and an existing batch reactor will be used to generate product samples for subsequent characterization (heating value, grindability, proximate and ultimate analyses).  A techno-economic analysis will form the basis from which the reactor and process design can be optimized and this will result in an indication of the cost of producing pyrolysis char/torrefied biomass for use as a bulk, solid fuel.

Pine Pellets Torrefied at Different Temperatures
Pine Pellets Torrefied at Different Temperatures

Gebruikte uitrusting

Screw pyrolysis/torrefaction mini-plant


Onderzoeker: Robert Nachenius

Financiering: Multidisciplinair Onderzoeksplatform (MRP)  - Ghent BioEconomy

Projectduur: 01.03.2013 - 28.02.2014