Fractionation of flash pyrolysis condensates by staged condensation

Abstract The utilization of condensates from flash pyrolysis is challenging due to several unwanted properties. The condensates consist of a mixture of many high value compounds, but each of them is only contained in a low concentration. As additional challenge instantaneous phase separation into an aqueous and a sludgy heavy organic phase takes place, if agricultural residues like barley straw are used as raw material for pyrolysis. A separation by means of distillation is not possible as the compounds undergo polymerization reactions when exposed to higher temperature. A different approach for separation based on boiling temperature is staged condensation of original vapors. Ablative flash pyrolysis is performed in a laboratory. The pyrolysis vapors are condensed in either two or three stages, each composed of a double-effect cooler followed by an electrostatic precipitator. The higher boiling fractions are low in water and acid and show a high heating value. This makes it applicable as sulfur-free bunker fuel and replacement of heavy fuel oil. It can also serve as fuel for gasification plants for the production of either combined heat and power or 2nd generation biofuels. Depending on condensation configuration the first fractions can also be utilized for the production of rigid polyurethane foams or phenolic resins. The last fraction obtained at the lowest cooling temperature mainly consists of water and acids. The production of pure acetic acid seems economically feasible and utilization in agricultural biogas plants is also possible. This is proved by batch fermentation experiments in the biological laboratories.