Upgrading of Tannery Wastes under Fast and Slow Pyrolysis Conditions

Abstract

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 study the effect of the tanning process. According to the result obtained, the tanned leather produces more nitrogenated compounds and phenols and less ketones and linear hydrocarbons than pure collagen. A very good agreement between the evolution of pyrolytic gases produced in a slow pyrolysis and the weight loss of the solid measured by thermogravimetric analysis has been observed.

Pyrolysis of biocollagenic wastes of vegetable tanning. Optimization and kinetic study

“…Marcilla et al studied the analytical pyrolysis of tanned-leather using a Pyroprobe device, to compare the effects of different organic and inorganic tanning agents [14,15]. Marcilla et al also evaluated the pyrolysis of chromium-tanned wastes and a commercial collagen to study the effect of the tanning process [16].…”

The stabilization of tannery sludge and the character of humic acid-like during low temperature pyrolysis

“…Sludge, a by-product of wastewater treatment, which contains a large number of pathogens, heavy metals, and organic matter, is defined as waste (Marcilla et al, 2012). Until now, several disposal methods of sludge including incineration (Kavouras et al, 2015), anaerobic digestion (Zupancic and Jemec, 2010), landfilling (Celary and Sobik-Szoltysek 2014), and application in agriculture or building materials (Swarnalatha et al, 2006) have been reported, and each has its own advantages and drawbacks.…”

“…Pyrolysis technology, as the best available thermochemical conversion technology, has attracted great attention since it can turn waste into gas, liquid, and solid residue (Marcilla et al, 2012;Thangalazhy-Gopakumar et al 2015). The pyrolytic gas and liquid can be applied in fuel or chemical feedstock after improvement, and the solid residue, char, was used as cheap adsorbents.…”

“…The pyrolytic gas and liquid can be applied in fuel or chemical feedstock after improvement, and the solid residue, char, was used as cheap adsorbents. Generally, the specific surface area and the adsorption ability of chars can be improved by the physical activating methods such as steam, CO 2 , or the chemical activating methods such as ZnCl 2 , H 3 PO 4 , and alkaline hydroxide (Kantarli and Yanik, 2009;Marcilla et al, 2012). Many studies have shown that the contaminants removal capacity of chars were higher than that of the commercial activated carbon (Kantarli and Yanik, 2009;Chen et al, 2014).…”

“…Most research focused on the physical properties such as the pyrolysis kinetics, the specific surface area of the chars (Kantarli and Yanik, 2009;Gil et al, 2012;Marcilla et al, 2012), while others paid more attention to the leaching toxicity of metals (Agrafioti et al, 2013;Sethuraman et al, 2014). Many studies suggested that the inorganic portion like the chromium content or most heavy metal still remained in the chars, and the leaching toxicity of chars was within the secure level (Agrafioti et al, 2013;Chen et al, 2014).…”