Upgrading of Tannery Wastes under Fast and Slow Pyrolysis Conditions

The pyrolysis of a chromium-tanned waste (bovine split leather) under inert atmosphere has been carried out in a vertical lab scale reactor. The influence of process conditions, such as temperature, residence time, and heating rate on the pyrolytic product distribution has been studied, in order to optimize the liquid fraction obtained. Flash pyrolysis at three different temperatures (450, 500, and 550 °C) and slow pyrolysis up to 750 °C have been performed. Results indicate that, in the range of low temperatures, the product distribution is slightly dependent on temperature. In general, a reduction of the heating rate or residence time favors the presence of heavy gases (i.e., more than four carbon atoms hydrocarbons). The analysis of the pyrolytic liquid shows a wide spectrum of products (mainly nitrogenated and oxygenated compounds and phenols) which can be useful as a source of chemicals. A comparison between the results reached in the pyrolysis of tanned leather and a commercial collagen allows us to...