In our previous work of the pyrolysis of cellulose, small steel tubing bomb reactors - heated quickly in a fluidized sand bath - produced charcoals with very high fixed carbon and charcoal yields (around 30 % and 50 % respectively) thereby attaining the theoretical fixed carbon yields. We therefore confirmed many of Violette’s 19th century observations at similar conditions.
Following the successful results, we varied the heat treatment temperatures and initial nitrogen pressures toward a quality charcoal based on the fixed carbon content and yield. The cellulose charcoal showed evidence of a molten phase at heat treatment temperatures over 240 °C and around 2 Mpa. This molten phase charcoal reminds us of coking coal. The influence of increasing initial nitrogen pressure (from 0.1 to 4.79 MPa) showed a marginal increase in fixed carbon yield and fixed carbon content. Increasing the temperature of the sand bath from 240 to 400 °C seemed to have a more pronounced effect on our two quality parameters. The extremely high ash contents of the charcoals compared to the feed (from 0.044 to ~2 wt%) remain a mystery.