Conversão termoquímica de capim-elefante em reator rotativo

Abstract

In recent years, renewable energy has received increased importance due to increased anthropogenic emissions of greenhouse gases to the atmosphere. Biomass is a promising renewable resource for the production of energy. Pyrolysis is one of the most promising thermal conversion technologies, creating value-added products, especially from other sources of renewable energy. In the present study addressed the thermal conversion (pyrolysis) of elephant grass (Pennisetum purpureum S.) in a rotating reactor in order to determine the best operating conditions (temperature and speed) for the production of hydrogen. The elephant grass was subjected to various characterization tests by elemental analysis (CHNS) and immediate, analysis chemical (lignin, cellulose, hemicellulose and extractives) higher heating value, particle size analysis, metal analysis and non-metals and thermal gravimetric analysis. The pyrolysis tests were conducted to a final temperature of 700 °C with application of 30 minute isothermal, heating rate 10 ° C/min, N2 inert atmosphere with a flow rate of 1 L/min. The fuel gas produced in the pyrolysis process was collected at 500, 600 and 700 ° C. The tests were conducted with the reactor operating without rotation, and rotation speeds of 2 and 4 rpm. Results of chemical analysis and metals and nonmetals, show that the elephant grass has a higher concentration of lignin in relation to other perennial grasses (Switch grass/Miscanthus) as well as a high concentration of potassium (K) in its composition. The increase of the rotational speed reduced fuel gas yield fron 34.6% (0 rpm) to 19.2% (4 rpm), and increased the yield of bio-oil 37.2% (0 rpm) to 53,0% (4 rpm). The yield of biochar was not significantly influenced by the rotational speed (approximately 27% in all conditions). The presence of high amounts of potassium (K) and nitrogen (N) biochar enable its use as a source of nutrients for the soil, as well as their basic character (high pH) indicate their use to adjust the pH of acidic soils. The highest concentration of hydrogen (65% v/v) was observed in experiments without rotation of the reactor at a temperature of 700 °C. The maximum calorific value (15.128 MJ.Nm-3) was observed at a temperature of 600 °C for all investigated speed.