2.1. Cavitation of charcoal
The study was carried out on charcoal obtained from an industrial
installation located in the Bieszczady Mountains (southeastern Poland).
The production process was performed using deciduous wood. Before
starting dry distillation, feedstock was ground and treated with drying
gases at 160-180 °C. Then, the material was placed in a retort. After
closing the retort, the residual water evaporates, and the thermal
decomposition of the wood begins. It is initiated by hot gases of
250-300 °C, moving from the central part of the retort (annealing zone).
The process is exothermic. The organic mass of wood is charred. The
partially charred wood mass has a reduced volume; hence, it moves down
the retort and enters the annealing zone. Here, at 500-550 °C, the final
form of charcoal is formed (Lewandowski and Milchert, 2011).
The cavitation process was carried out in 10% w/w aqueous charcoal
mixture (particle size of 0-0.5 mm). The suspension was placed in a tank
to which a 2.5 kW cavitation pump was connected. After passing through
the pump, the suspension was returned to the tank (closed circuit). The
micronisation time for 150 dm3 of the suspension was 2
hours, and the temperature increase during the cavitation process was
from 40 °C (initial stage) to 60 °C (final stage).