Publication Date: 2009-Sep-09
The IP.com Prior Art Database
In order to use torrefaction in a commercial process, a reactor vessel of the necessary design must be devised. This reactor, likely to be a vertical, cylindrical vessel, but vessels of other shapes might be usable, is a vessel operating at 5 to 20 bar (preferably 10 to 15 bar) being feed via a pressurized feeding device with discharge via a pressurized discharge device. In the reactor interior are a series of multiple trays, permeable trays, with the bottom of the tray capable of rotating (another option would be to have the tray remain stationary but have a opening in a section of the tray and have the biomass fall through the open area) to allow the biomass to fall through the tray. The tray is divided in sections where the biomass collects. The bottom of the vessel may be equipped with a discharge that does not vibrate (but could also be equipped with a vibratory discharge) with a hollow transition portion between a hollow right circular cylindrical main body and a rectangular discharge. The hollow transition may have a substantially circular cross-section open top and a substantially rectangular cross-section open bottom and opposite non-vertical gradually tapering sides, alternatively the hollow transition portion may provide one-dimensional convergence and side relief.
Inventor: Bertil Stromberg
Torrefaction is the thermal treatment of wood, usually in an inert atmosphere, at relatively low temperatures of 225 to 300°C with the aim to produce a fuel with increased energy density relative to the mass, by the decomposition of reactive hemicellulose content of the wood. Wood is made up of fractions: hemicellulose, cellulose and lignin. The aim of torrefaction is to remove from the wood moisture and low weight organic volatile components and to depolymerize the long polysaccharide chains of the hemicellulose portion of the wood to produce a hydrophobic solid product with an increased energy density (on a mass basis) and greatly improved grindability. Because of the change in the chemical structure of the wood after torrefaction, it is suitable for use in coal fired facilities (torrefied wood or biomass has the characteristics that resemble those of low rank coals) or can be compacted into high grade pellets replacing standard wood pellets.
This process is a low temperature, low oxygen pyrolysis process where the easy to remove compounds having the lowest heat and energy values are removed. In this process approximately 30% of the mass is burned off while loosing only 10% of the energy value, that is to say the remaining solid mass (approximately 70% of the original material mass) contains 90% of the heat value originally present. Torrefaction occurs in a pressurized reactor and a temperature of 300°C where there is direct contact of the raw material/biomass (lignocelluosic material), which has been previously dried to remove approximately 95% of the moisture initially present in the biomass, with hot gas (relatively oxygen free gas). Heating of the dried biomass in the torrefaction reactor removes the remaining water from the biomass.
Description of the Invention:
In order to use torrefaction in a commercial process, a reactor vessel of the necessary design must be devised. This reactor, (see attached figure), likely to be a vertical,...