Pyrolysis coupled pulse oxygen incineration for disposal of hazardous chromium impregnated fine particulate solid waste generated from leather industry

This paper focuses on characterization and pyrolysis coupled pulse oxygen incineration (PyPOI) of hazardous chromium (Cr3+) impregnated microfined solid particulate matter (MSPM) generated from leather industry. The PyPOI process yielded gaseous products, 47.46%; condensate oil, 34.20%; and remnant ash 18.34%. The energy profile of MSPM under PyPOI process was studied and compared with pyrolysis process. The energy released under varied mass loading of MSPM through PyPOI process was 4140 kJ, 9468 kJ, 12,816 kJ and 13,968 kJ for 0.5 kg, 1.0 kg, 1.5 kg and 2.0 kg respectively. The constituents of pyrolytic gases were CO, CO2, CxHy, O2, SO2, NOx and H2. The MSPM, remnant ash and distillate were characterized using TGA, FT-IR and SEM/EDX. The TGA of remnant ash of MSPM confirmed that about 80% of the material was thermally stable up to 800 °C. Maximum weight loss of MSPM was achieved under PyPOI process using pulse oxygen supplied at the rate of 1.75 g/min inside the reactor vessel in the temperature range from 600 °C to 800 °C. The SEM images proved that unburnt carbon slabs were obtained under pyrolysis while crumbled carbon flakes were obtained under PyPOI process. FT-IR of condensate oil confirmed the presence of aromatic nitrogen compounds. The hexavalent chromium (Cr6+) content of remnant ash under PyPOI process was 0.028 ± 0.006 mg/kg which was well within the limit of disposal (4 mg/kg).