Zur Gewinnung von BtL-Kraftstoffen aus frischer Biomasse ist eine energieeffiziente Trocknung erforderlich. Die elektroporationsunterstützte Trocknung ermöglicht durch eine verbesserte Abpressbarkeit der Biomasse eine Einsparung an Verdampfungswärme. Darüber hinaus beschleunigt ein verbessertes Diffusionsverhalten des elektroporierten Materials die Trocknung. Durch eine geringere Verweildauer im Trocknungsofen können die Ofenverluste gesenkt und die Ofengröße reduziert werden.
Test set-ups and devices:
For energy efficient processing of a product stream electroporation chambers with a substantially homogeneous field distribution in the treatment area have been designed. The electroporation chamber for the mobile electroporation device for mash treatment KEA-WEIN has been built for a voltage application symmetric to ground potential. The ground-symmetric operation enables the advantage of less insulation distance and, hence, a more compact design of the device.
For the pulse generation with pulse lengths in the micro- and millisecond range single-stage- and multi-stage pulse generators equipped with storage capacitors are used. Semiconductor switches can be used advantageously for switching smaller pulsed power. They enable pulse repetition rates of up to several Kilohertz. For high power applications switching spark gaps are the more cost effective alternative. Research and development is done in the field of both switching technologies.
For short pulses in the nanosecond range transmission-line pulse generators with semiconductor- and spark gap switches have been developed.
For electroporation of plant cells in industrial scale, for example sugar beets, an average power of up to several 100 kW is required. Together with our co-operation partner SÜDZUCKER KIT/IHM is developing an industrial electroporation device for sugar beets with a synchronous operation of several Marx generators. In order to enable a reliable ling-term operation the generators are equipped with a wear-less over-voltage trigger device. A semiconductor pulse generator generates a trigger pulse, which is added to the charging voltage of the first stage by means of a pulse transformer replacing the charging coil between the first and the second stage and, hence, causes switching of the spark gap. By means of pre-ionisation a low jitter of the switching time can be achieved.
Among measuring pulse parameters (pulse voltage, pulse current etc.) the measurement of process parameters is important for process control. For energy efficient operation of the electroporation devices a device for a continuous on-line measurement of the degree of cell opening is currently being developed. The measurement principle is based on the evaluation of the phase angle of the complex impedance of the process material a one discrete measurement frequency. The cell membranes can be considered as capacitors causing a phase shift between voltage and current when applying an ac-voltage. Pores in the cell membranes and extracted juice act as short-circuit and cause a decrease of the phase angle with increasing degree of cell opening.
Electromagnetic compatibility plays an important role in the design and setup of pulsed-power devices. All devices are designed for trouble-free operation and long lifetime.