Investigation on pyrolysis and incineration of chrome-tanned solid waste from tanneries for effective treatment and disposal: an experimental study.

Chrome-tanned leather solid wastes (leather finished trimmings (LFT) and chrome shavings (CS)) from tanneries were studied using pyrolysis and incineration. Detailed characterization of CS and LFT indicated higher calorific value of 15.77 MJ/kg and 19.97 MJ/kg respectively, which makes it suitable for thermal treatment. Thermal Gravimetric Analysis (TGA) of CS and LFT recorded a weight loss of 79.82% and 68.22% at 800 °C respectively. Energy-dispersive X-ray spectroscopy and scanning electron microscopy analysis for CS and LFT were also carried out. Pyrolysis of CS and LFT was carried out using a fixed bed-type pyrolysis unit at a temperature of 500 ± 10 °C for a reaction time of 30 min and three different by-products (bio-oil, biochar and pyrolytic gas) were obtained as a result of pyrolysis. From pyrolysis process, higher bio-oil yields of 52 wt.% and 49 wt.% from LFT and CS with calorific value of 28.0 and 27.8 MJ/kg respectively were obtained. The calorific values of the biochar obtained from LFT and CS were found to be 20.5 and 23.0 MJ/kg respectively. Incineration was carried out in the existing incineration facility of 150 kg/h capacity at a temperature of 1200 °C. The results of incineration process showed a higher weight reduction (93.0 wt.%) and higher concentration of gaseous emissions, revealing the need for off-gas treatment. Further, FT-IR spectra of residual ash from the incineration process revealed the occurrence of oxidation of trivalent chromium to its hexavalent form, which could be a potential raw material in the metallurgical/chemical industry for the synthesis of sodium chromate or ferrochrome alloy. Comparative experimental investigations of pyrolysis and incineration revealed that incineration could be a potential treatment and disposal option, in developing countries like India, for chrome-tanned leather solid wastes from tanneries, for producing heat energy and the residue with potential utilization viability in another industry paving a way towards circular economy.

Intermediate pyrolysis of agro-industrial biomasses in bench-scale pyrolyser: Product yields and its characterization.

Pyrolysis of woody biomass, agro-residues and seed was carried out at 500 ± 10 °C in a fixed bed pyrolyser. Bio-oil yield was found varying from 20.5% to 47.5%, whereas the biochar and pyrolysis gas ranged from 27.5% to 40% and 24.5% to 40.5%, respectively. Pyrolysis gas was measured for flame temperature along with CO, CO2, H2, CH4 and other gases composition. HHV of biochar (29.4 MJ/kg) and pyrolitic gas (8.6 MJ/kg) of woody biomass was higher analogous to sub-bituminous coal and steam gasification based producer gas respectively, whereas HHV of bio-oil obtained from seed (25.6 MJ/kg) was significantly more than husks, shells and straws. TGA-DTG studies showed the husks as potential source for the pyrolysis. Bio-oils as a major by-product of intermediate pyrolysis have several applications like substitute of furnace oil, extraction of fine chemicals, whereas biochar as a soil amendment for enhancing soil fertility and gases for thermal application.