(135b) Process Design Data for Liquid Phase Pyrolysis of Biogenic Feedstock

Pyrolytic conversion of biogenic feedstock has become a high priority task due to declining crude oil reserves.

This project focuses on pyrolytic conversion of CHO-feedstock such as fir chips under liquid phase operation conditions. From liquid phase pyrolysis improved convective heat transfer is expected, enabling fast pyrolysis conditions at ambient pressure. Investigations may be classified as isothermal. Operation temperature is limited to a range of less than 650 K.

The process data were determined in a lab scale reactor in the semi-batch mode. The rate of degradation for nearly monodisperse feed was recorded. The feed quantity was limited to an amount which caused a maximum deviation of the reactor temperature of less than 2 K each feed cycle. The effect of temperature on product distribution was investigated.

The gaseous, liquid and solid products were characterized by GC-MS, NMR-spectroscopy and elemental analysis.

Subject of this project is the determination of design parameters for industrial scale plant design, including reaction mechanisms, thermodynamics and kinetics. The obtained technical expertise is used as basis knowledge to transfer the process from lab scale to technical scale.

Figure 1 shows the formation of liquid products based on dry feed and different reaction temperature. The ratio of water formed during pyrolytic degradation increases with increasing temperature, passing a maximum, while formation of CHO-products linearly correlates with the operation temperature. Carbon transfer from feed to gaseous and liquid product phase also correlates linearly with the temperature.

According to Figure 2 formation of liquid products seemingly undergoes a shift in the reaction mechanism.

Following interpretation of process thermodynamics liquid phase pyrolysis of biogenic wood based feedstock is a moderately exothermic process.

Figure 1: Formation of liquid CHO-products and reaction water based on dry feed.

Figure 2: Kinetic Data for the formation of liquid products based on dry feed.