What is torrefaction?
Torrefaction, a mild form of pyrolysis, refers to the heat-treatment of biomass at 250-320°C with little or no oxygen present.
The purpose of torrefaction is to remove moisture and volatile organic compounds (VOCs) from raw biomass, thus converting it to a solid, blackened, hydrophobic (water-resistant) material.
The final product, known as torrefied biomass or biocoal (black or torrefied pellets), typically contains 70% of the mass and 90% of the energy content of the pre-treated material.
What is biomass?
Biomass is perhaps the oldest source of energy in the world.
Biomass energy is derived from recently-living organic matter such as sawmill waste, logging residues, low-grade biomass and agricultural residues.
- Sawmill waste includes bark, off-cuts, planer shavings and sawdust;
- Logging residues is the non-merchantable part of trees remaining after a forest harvest operation, such as top of trees, limbs, branches and needles/leaves;
- Low-grade biomass are trees that are low quality for wood products due to shape, size, species or other traits;
- Agricultural residues comprise sugarcane bagasse, corn stover and palm kernel shells.
Advantages of biomass
- Renewable – Sustainably-managed sources of biomass can provide fuel indefinitely.
- Readily available – A significant amount of biomass fuel is available in most regions of North America.
- Dispatchable – A biomass-fired generation plant can increase or decrease electricity production in response to demand.
Biomass and the carbon cycle
The use of fossil fuels releases carbon from ancient pools that cannot be replenished. Biomass, however, contains carbon extracted from the atmosphere. Through photosynthesis, the carbon contained in the atmosphere in a gaseous form is sequestered in a solid form in plants and trees. The carbon is then released again to the atmosphere through natural decomposition or combustion of the biomass. Therefore, there is no net addition of carbon to the atmosphere when biomass is used as a fuel to produce energy.
What makes biomass renewable?
Biomass must be sourced on a sustainable basis in order to be considered renewable. According to the United Nations Framework Convention on Climate Change (UNFCCC), biomass from forest lands is considered renewable if sustainable management practices are undertaken on these forest lands to ensure that the level of carbon stocks does not systematically decrease over time (carbon stock may temporarily due to harvesting).
Biomass feedstock in Canada is certified by CSA, FSC or SFI
The biomass used by Airex Energy originates from Canada, which has the largest area of third-party-certified forests in the world. According to National Resources Canada, as of the end of 2016, Canada had 168 million hectares of independently certified forest land, representing 37% of all certified forests worldwide. Third-party forest management certification complements Canada’s comprehensive and rigorous forest management laws and regulations. It provides added assurance that a forest company is operating legally, sustainably and in compliance with world-recognized standards for sustainable forest management.
Three forest certification systems are used in Canada, those of the Canadian Standards Association (CSA), the Forest Stewardship Council (FSC) and the Sustainable Forest Initiative (SFI).
Airex Energy’s CarbonFX torrefaction technology allows industrial-scale production of a wide range of value-added biocarbon products.
By keeping precise control of both reactor temperature and residence time, CarbonFX delivers end products with unmatched quality, consistency and homogeneity.
Biocoal (Torrefied pellets)
A drop-in replacement for coal in coal-fired power plants and cement/lime kilns
A soil amendment
Lightly torrefied wood flour
For wood-plastic composites
Highly carbonized biocoke
For metallurgical applications
The CarbonFX Torrefaction Process
The biomass fed into the unit is the size of sawdust. It is pre-dried in an aeraulic loop using residual heat from the combustion gas process. This reduces the moisture content of the biomass from 50% to 25%.
The conditioning chamber has four endless screws and a double wall. The combustion gases circulate in the double wall and heat the biomass through indirect contact. The moisture contained in the biomass is converted into steam and the biomass is conditioned in a saturated steam atmosphere. The biomass is then circulated by the hot flue gases from the combustion chamber to the torrefaction reactors.
Biomass is fed into the top of the reactor and spirals in the reactor following a downward cyclonic path to land at the base of the reactor, at the sustentation ring. The sustentation ring allows the biomass to remain suspended in the reactor, by creating a balance between the centrifugal force of the cyclonic effect, the gravitational force of the bulk material and the pushing effect induced by the sustentation ring. The total residence time in the reactor is very short, about 2 to 3 seconds.
The CarbonFX technology provides significant advantages to biocoal producers
The CarbonFX can process a large variety of feedstock including sawdust, bark, shavings, wood chips, recycled wood, agriculture residues and forestland biomass.
Homogeneous end products
The highly turbulent flow inside the cyclonic bed reactor allows an optimal heat transfer rate and ensures very homogenous end products.
Easy transportation and assembly
Modular design allows components to be shipped to site by either rail, sea or truck in standard containers with final assembly on site.
Low operating cost
The CarbonFX operation is fully automated and highly energy efficient as the residual heat from the thermal process is used to pre-dry the biomass feedstock in an integrated system.
The CarbonFX system is simple to manufacture. It doesn’t require pressure vessels, biomass boilers, drum dryers, thermal oil heat exchangers or waste water treatment system.