Formation of Liquid and Solid Products of Liquid Phase Pyrolysis

Formation of Liquid and Solid Products of Liquid Phase Pyrolysis

Schwaiger, N. Feiner*, R. Zahel*, K. Pieber*, A. Witek, V.* Pucher*, P. Ahn*, E. Schroettner⁺, H. Siebenhofer, M.

Graz University of Technology Institute for Chemical Engeneering and Environmental Technology, * BDI-BioEnergy International AG, ⁺Graz University of Technology Institute for Electron Microscopy, Austria

Lignocellulosic feed is expected to contribute significantly to production of liquified and solid combustibles. The aim of this project is the production of high quality biochar and a liquid energy carrier. Therefore the pyrolytic degradation of softwood during liquid phase pyrolysis was investigated. The process was carried out in a semi-batch reaction vessel under isothermal conditions at various temperatures. Process pressure was ambient. For optimum heat transfer pyrolysis was carried out in liquid heat carrier phase which provides high heat conductivity. Liquid phase pyrolysis is an exothermic process which produces 25-28% liquid CHO products, independent of biomass particle size within a range of 630µm and 10mm. The enthalpy of reaction is -864±25 kJ/kg at T=350°C. To gain data on kinetics of formation of liquid products and the solid residue, degradation of soft wood and product formation was recorded.

During pyrolysis the Carbon to Oxygen ratio of the solid phase was tracked. The measurements were made with energy dispersive x-ray spectroscopy, elemental analysis and ATR-IR. Figure 1 shows three distinct phases of product formation in liquid phase pyrolysis at T=350°C and ambient pressure. The feed undergoes rapid change in the C:O ratio in two steps and finally stabilizes at nearly constant ratio but ongoing loss of solids mass.