Ablative

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Ablative pyrolysis

In ablative pyrolysis biomass is pressed onto a hot surface (approx. 600 degrees centigrade), see the picture on the right side
Ablative.png
. In the nineties BBC (Canada) demonstrated such an ablative flash pyrolysis technique for the disposal of tires (10-25 kg/hr capacity). Other pioneering work was carried out by NREL where biomass was pressed to a hot surface by centrifugal forces in a vortex reactor. The vortex design concept was abandoned in 1997. In the nineties, Aston University (Birmingham, UK), built and tested a prototype rotating blade reactor for ablative pyrolysis on a small scale of several kg/hr, but further developments seem to have stopped. At present, the German company Pytec seems the only company developing ablative pyrolysis technology further, with a pilot plant of 250 kg/hr in operation near Hamburg and plans for demonstration of a 2 t/hr unit in Mecklenburg-Vorpommern in Germany. Though not abandoned, the latest reporting date from 2007.

In general various limitations for this ablative technology can be expected such as (i) limited heat transfer rates to the hot surface due to the indirect heating principle, based on a relatively small limited temperature difference between hot flue gas (likely around 800 degrees centigrade) and pyrolysis reactor (around 500 degrees centigrade), and a low heat transfer coefficient and (ii) restrictions in feedstock morphology (particle shape, structure and density), the particle size and its free flowing characteristics, because the material needs to be pressed against a hot surface.