Thermolytical treatment of dried sewage sludge and other biogenic materials - including upgrading of pyrolysis vapours by a cracking catalyst and examination of heavy metals by X-ray fluorescence

Dried sewage sludge from the city of Oldenburg, lacquered wood and linoleum were pyrolyzed in a nitrogen atmosphere (sewage sludge, 600 degrees C; lacquered wood and linoleum, 500 degrees C) in an atmospheric fluidized bed. Each fraction of solid material (feed, solid products) was investigated with X-ray fluorescence in order to estimate, especially, the loss of heavy metals during pyrolysis. Vapour resulting from the pyrolysis was upgraded by a regenerated cracking catalyst coming from a fluid catalytic cracking unit. The vapour/N-2 mixture fluidized the catalyst. The cracking reactions took place at temperatures around 450 degrees C. The resulting vapour was condensed in three steps. Condensation also occurred in a cyclone (behind the catalytic reactor), a condenser cooled down the remaining vapour and permanent gases to -4 degrees C. The remnants of vapour and the permanent gases were trapped with liquid nitrogen. Hydrogen and methane were the only gases not collected on activated carbon located behind the trap. This adsorbing material was added to estimate how much material passed the cold trap. Samples of this gas and the permanent gases leaving the cold trap at room temperature were collected and analyzed. Elemental analysis and gas chromatography-mass spectrometry allowed a rough orientation for the exact characterization of the oils which had been collected in the cold trap, condensers I and II, and on the activated carbon. The objective of this work is to gather information about the pyrolytic treatment within the whole concept of pyrolyzing waste material-of biogenic origin-and gasifying resulting fractions not prone to use from pyrolysis. Therefore, the whole process is called thermolytical treatment. The upgrading of the pyrolysis vapours yields an oil which can be used as chemical feedstock. (C) 1999 Elsevier Science B.V. All rights reserved.