Study of the process of charcoal producing by pyrolysis under pressure
The preliminary results of an experimental study of the effect of pressure on the formation of charcoal in the pyrolysis of birch chips are discribed. The experimental investigation was carried out at pressures of 0.1, 0.3, 0.5, 0.7 MPa and at heating rate of the order of 1 °C/min. The initial moisture content of the chips was 14.2 % by weight, and the dimensions -17x8x6 mm. To investigate the effect of pressure on the pyrolysis process, a laboratory bench was designed and constructed. It was found that increasing the pressure from 0.1 to 0.7 MPa increases the yield of charcoal from 25.1 to 32.4 % by weight (relative to the dry weight of the starting material) and the carbon content from 89.1 % by weight at 0.1 MPa to 96.4 % by weight at 0.7 MPa. The calorific value of charcoal decreases from 34.86 MJ/kg at a pressure of 0.1 MPa to 30.23 MJ/kg at a pressure of 0.7 MPa. This is due to release of oxygen-containing components from the porous coal structure, which have higher calorific value than pure carbon. Reduction of charcoal heat combustion with decrease in the amount of oxygen-containing components confirms conclusion that their calorific value exceeds the calorific value of pure carbon.