Pulsed Power for Process Optimization - Selected Applications and Technologies

Within the last two decades, several pulsed power applications on different fields of technology have been investigated and developed in order to enhance and optimize established industrial processes, and to enable new ways of material processing. The talk will give an overview on selected applications and technologies.
The crushing of concrete and minerals by means of electrodynamic fragmentation has been established as an industrial process for efficient recycling of materials like gravel from concrete, or metals from waste incineration plants.
The pulsed electric field treatment of biological tissue enables an energy-efficient extraction of substances from plant cells on an industrial scale. Already in the first decade of this century, the pulsed electric field (PEF) treatment of potatoes for manufacturing potato chips has been introduced to the industry and replaces the conventional heat treatment of potatoes in spring time in order to extract sugars to prevent the sliced potatoes from blackening during frying and to avoid the formation of carcinogenic substances. Due to the additonal advantages of a fat-reduced production of the potato chips and longer blade service life in the slicing machines, the PEF treatment devices are operated around the clock all over the year at six days a week. ... mehrA related application is the extraction of sugar from sugar beets in the course of the sugar production. Experiments on site in a sugar factory showed, that the PEF treatment of sugar beets enables in combination with modified processing steps, the so called alcaline extraction, savings of fossil fuels in the order of 20% of the current consumption. Moreover, due to an alcaline environment the corrosion of tubes is significantly reduced compared to the conventional processing method. The PEF treatment of crushed grapes in the course of the production of red and white wine enables savings in time. Moreover, due to an enhanced extraction process the grape juice becomes richer, fostering the quality of the wine produced from it. From a measurement of the complex electric impedance of the grape mash a disintegration index can be derived, which is useful for process control.
For the mentioned applications Marx generators equipped with spark gap switches have been employed. The generators and the switches have been adapted for the specific applications.
Water-based cathodic dip coating for coating vehicle bodies can spoil due to colonisation by bacteria. In a recently completed research project, it was shown that PEF treatment of the paint to reduce bacterial growth is possible without depositing paint on the electrodes. Thereby, a pulse generator equipped with IGBT switches in bridge configuration is employed for generating bipolar pulses in order to keep the pH-value at the electrodes well below the limit for the release of the pigments from the paint.
The application of a pulsed electron beam to a metallic surface allows for melting a thin layer of the surface. The subsequent cooling process hardens die surface while preserving the original properties in the bulk of the material. For driving the device at a voltage level of 120 kV a 149-stage pulse generator equipped with IGBT switches has been set up. lt is capable of stepped arbitrary waveform generation. The drivers for the IGBTs feature capacitively coupled gate boosting, enabling a significant reduction in the turn-on and turn-off times of the IGBTs. The gate-boosted operation of IGBTs and MOSFETs allows for a fast operation under hard-switching conditions at significantly reduced switching losses. This technology is under continuous development. Recently, the turn-on of a GaN HEMT in less than a nanosecond has been demonstrated.
In the talk, the advantages of the application of pulsed power technology on selected industrial processes and the related advancements in pulsed power technology itself will be presented.