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> Flash Pyrolysis
> Introduction
> Introduction Pyrolysis offers the possibility of de-coupling (time, place and scale), easy handling of the liquids and a more consistent quality compared to any solid biomass. With fast pyrolysis a clean liquid is produced as an intermediate for a wide variety of applications.
> Chemistry
Pyrolysis characterized
> Technology Fast heating of biomass will prevent char forming reactions. In this mode, 75 wt.% bio-oil and only 15 wt.% char and gas are produced as primary products. Rapid removal of the pyrolysis vapours from the hot reactor enclosure ensures that less than 10 wt.% bio-oil is lost due to cracking reactions. Since no "inert" carrier gas is needed (unlike fluidized bed pyrolysis), the pyrolysis products are undiluted. This undiluted and hence small vapour flow results in downstream equipment of minimum size. Consequently, the capital costs of the complete unit are minimal. In mechanical terms, the reactor technology is remarkably simple and robust. The rotational speed of the cone is only 300 rpm and after more than 1000 hours of operation in the current 250 kg/h pilot plant signs of abrasion or wear are absent Scaling up of the rotating cone reactor is possible by increasing its diameter. For capacities which require a cone diameter larger than 2 meters, stacking of multiply cones on a single axis leads to the lowest investment costs. This conventional approach is also encountered in centrifugal disk separators or rotating disks contactors. With these options all pilot plant capacities between 2 and 100 ton/hr can be served.
Feedstock requirements
> Process description Biomass particles are fed near the bottom of the pyrolysis reactor together with an excess flow of hot heat carrier material such as sand, where it is being pyrolysed. The produced vapours pass through several cyclones (not shown) before entering the condenser, in which the vapours are quenched by re-circulated oil. The pyrolysis reactor is integrated in a circulating sand system composed of a riser, a fluidized bed char combustor, the pyrolysis reactor, and a down-comer. In this concept, char is burned with air to provide the heat required for the pyrolysis process. In this case the plant is self sustaining. Oil is the main product; non-condensable pyrolysis gases are currently flared-off, but application in a gas engine is foreseen. Excess heat can be used for drying the feedstock. For details on the oil properties and its applications see bio oil applications
> Status of the technology A number of organic materials has successfully been processed in the current pilot plant, such as bagasse, palm residues, rice husks, straw, automotive scredder residues, dried sludges, pine wood, olive husks, beech wood, oak wood, switch grass and poplar. The 250 kg/h pilot plant has processed in total 50 tonnes of oil for a number of clients Currently BTG is involved in the engineering of a 50 ton/day fast pyrolysis plant for clean wood residues. This plant will be constructed and commissioned in 2003 On request, it is possible for clients to test their waste materials in the 250 kg/h fast pyrolysis pilot plant. Also bio-oil is available on request.
> Economics For its envisaged 2 t/hr unit BTG calculated a bio-oil production cost of less than 85 €/t (approx. € 5,-/GJ, which is close to the crude oil price) assuming feedstock costs of 25 €/t (BTG, 2000). At these levels, the cost of bio-oil is already competitive with industrial light fuel oil, which costs up to 6.64 €/GJ excluding taxes, in certain European markets (e.g. Norway, Denmark, Greece, Italy and Portugal, Figures 1998). The same holds for bio-oil as a substitute in diesel engines. Diesel prices without tax have increase rapidly in recent months and reached levels of up to 10 €/GJ.
> Reference projects
> Leaflet
> Contact |
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| © BTG Biomass Technology Group BV 2002-2003. Last modified on: 5 august 2004 | ||||||||
Yields of the primary pyrolysis products are temperature dependent. It can
be observed that a maximum oil yield of 79 wt.% is obtained at 500 oC.
For the temperature range studied, the char yield decreases and the
gas yield increases with temperature.
BTG's fast pyrolysis technology is based on the rotating cone reactor. It
is a proven gas-solid contactor which has been developed at the
University of Twente (Chem.Eng. Sci., 5109, (1994)).
A schematic representation of the reactor is presented in the figure on the right
hand side. Biomass particles at room temperature and hot sand
particles are introduced near the bottom of the cone where the solids
are mixed and transported upwards by the rotating action of the cone.
In this type of reactor, rapid heating and a short gas phase
residence time can be realized.
