Biomass Pyrolytic Polygeneration of Tobacco Waste: Product Characteristics and Nitrogen Transformation

Conversion of waste to high-value products by pyrolysis is a suitable and harmless disposal technology for the abundant waste generated in the tobacco industry. To determine the optimum operational parameters for biomass pyrolytic polygeneration using tobacco waste as the feedstock, the product characteristics and nitrogen transformation were investigated from 250 to 950 °C. The highest low calorific values of gas and char were 13 MJ/m³ at 750 °C and 15 MJ/kg at 450 °C, respectively. The optimum operating temperature recommended for biomass pyrolytic polygeneration of tobacco waste is 650 °C when the three products (char, oil, and gas) are balanced. The char formation process is divided into three stages: degradation (250–450 °C), reforming (450–650 °C), and condensation (>650 °C). Three types of N-containing structures are formed in chars: pyridinic N, pyrrolic/pyridine N, and quaternary N. Pyridinic N is dominant at low temperatures, whereas quaternary N becomes dominant at high temperatures. N-containing volatiles escape from chars with increasing temperature and are primarily found in oil below 550 °C and in gas above 650 °C. N-containing compounds are the major components (up to 45%) in the organic portion of oil, with pyridines, pyrroles, and piperidines as the dominant forms. In the gas product, NH₃ and HCN are the major N-containing compounds released above 650 °C. This study is expected to be beneficial for the comprehensive utilization of tobacco waste