Pyrolysis of rapeseed stalk: Influence of temperature on product characteristics and economic costs

In this study, the influence of temperature on the pyrolytic product characteristics and economic costs was investigated and an optimum operational temperature was determined. Because of the relatively high contents of CH4 (21 vol%) and H2 (32 vol%), the low heat value of gas at 750 °C reached 17.64 MJ/m3, while the largest yield of gas was achieved at 950 °C. The obtained oil could be divided into the following three types in accordance with the temperature change: high acidity oil (250 °C-350 °C), phenol-enriched oil (450 °C-650 °C), and heavy oil enriched with fused rings (650 °C-950 °C). The heaviest oil contained fused rings (∼50%), phenols (∼30%), and acids (∼20%), and it showed good stability of ingredients in oil. The largest yield of char was detected below 350 °C. To obtain quality smokeless solid fuel and activated char, the operational temperature should be set to 550 °C and 750 °C, respectively. The results from the economic analysis on biomass pyrolysis using a moving bed reactor suggested that the optimum operation temperature was 650 °C and the maximum profit could reach to 25 million yuan per year.