Multi-utilization of chicken litter as a biomass source. Part II. Pyrolysis

To determine optimum conditions for producing activated carbon and carbon black from biomass waste (i.e., chicken litter), studies have been performed on the thermal decomposition changes of chicken litter under a nitrogen atmosphere by evolved gas analysis (EGA) including thermogravimetric mass spectrometry (TG-MS), TG-fourier transform infrared (TG-FTIR), and pyrolysis-GC/MS. Samples were prepared by milling and sieving the as-collected chicken litter to obtain three kinds of samples differing in particle size distribution (sample A, above 140 mesh; sample B, 140-325 mesh; sample C, below 325 mesh). Samples A and C were found to show the two extremes in volatile matter to ash content ratios of 54/25% and 35/54%. Thus, to obtain carbon byproducts at a higher yield, decomposition of sample A in nitrogen was studied in particular, and it was found that the process can be roughly divided in four stages. The activation energy, E, was also obtained by kinetic analysis for each of the stages: ( I) release of absorbed water and ammonia stemming from ammonium salts (25-160 degrees C), E = 100.6 kJ mol(-1); (II) devolatilization of mainly lignin and hemicellulose, with evolution of sulfur compounds such as H2S (160-290 degrees C), E = 52.11 kJ mol(-1); (III) devolatilization of mainly cellulose with evolution of N2O (290-390 degrees C), E = 193.9 kJ mol(-1); and (IV) decomposition of cellulose (390-500 degrees C), E = 242.3 kJ mol(-1). Activated carbon can be obtained after stage IV. Ammonia evolution in the lower-temperature regions was attributed to the release from ammonium salts, whereas that in upper-temperature regions was attributed to the decomposition of organic nitrogen compounds.