torrefaction process for wood biomass

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Torrefaction Process for Wood Biomass

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• Torrefaction is a thermochemical treatment of biomass at 300 to 600 0F carried out under an inert atmosphere.

• Torrefaction is a mild form of pyrolysis • Torrefaction is the roasting of wood or other biomass to

remove moisture and low energy volatiles, creating a product that has increased energy density, is easy to handle and transport, and is practical to co-fire in existing coal plants.

All the above definitions are regarding “biocoal.”




• As the term “biocoal” suggests – the purpose of this process is to make a product that resembles coal from a biomass such as wood.

• Mass of biocoal is reduced by approximately 30% • Energy content of biocoal is approximately 85% retained • Researchers have found that each combination of

temperature, processing time and wood species will result in a given “biocoal” product, which can be reproduced on a continuous basis.



• The tenacious fibre structure of original biomass is largely destroyed through hemicellulose breakdown.

• Essentially all the moisture present in the raw biomass is removed prior to the volatile matter.

• The atomic H/C and O/C ratios are driven downward.



Benefits of Biocoal • Higher energy density – heating value of wood is increased

to approximately 10,000 BTU/lb. • Elimination of biological activity – biological decomposition

such as rotting is stopped. • Improved grindability – biocoal can be pulverized using the

existing equipment in coal-fired power plants leading to more efficient use of this existing equipment.

• Hydrophobic properties improved.



Benefits of Biocoal - Continued • Converts biomass feedstocks, which generally do not have

uniform qualities, into more uniform materials thus serving as a pre-conditioning process.

• Higher energy density means smaller storage requirements. • Higher energy density means lower transportation costs.



Charcoal and Bio-Char • Heating the biomass material under an inert atmosphere to

a final temperature of 7000 F to 9000 F will produce a charcoal product.

• Removal of approximately 45% of the weight of the raw biomass leaving about 20% to 25% volatile matter.

• Fixed carbon percentage would be 70 to 75%. • Approximately 5% ash. • Heating value of material is approximately 12,000 BTU/lb.



Charcoal and Bio-Char • Heating the biomass material under an inert atmosphere to

a final temperature of 15000 F to 16000 F will removal essentially all of the volatile matter.

• Product will be the fixed carbon material from the raw biomass plus the ash content in the biomass

• Process known as pyrolysis or carbonization and is similar to what is done with coal or coconut shells in making material to then be activated.



Charcoal and Bio-Char • Volatiles can be used as a fuel for the drying of the raw

biomass. • Forest land owners interested in building a biocoal

torrefaction plant for the coal fired power plant market are now realizing they can use the same equipment to also make bio-char.

• Question is now what species of wood at what time and temperature process will produce the best material to make activated carbon

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torrefaction process for wood biomass

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