The influence of oil extractability and metal part geometry in degreasing processes using supercritical carbon dioxide

Analytical scale degreasing was performed using model systems of various oils and metal parts of different geometries. All oils are commonly used in mechanical industry. Their extractability in supercritical carbon dioxide was studied by extraction from an inert support. It was found that all oils investigated could be extracted with supercritical carbon dioxide but the extraction process was slow in some cases. One of the oils, UNIQ DP 101, was chosen as a model substance to record extraction profiles for metal parts, in which holes of different dimensions had been drilled. This was done in order to investigate the influence of matrix geometry on the degreasing process. The degreasing process was significantly affected by hole diameter and depth, as well as the position of the holes relative to the flow profile. Bulk oil was, as expected, more easily recovered from wide and shallow holes. Repeated pressure reductions were shown to dramatically decrease the time needed for an efficient extraction. Addition of methanol as modifier did not increase extraction efficiency for the model oil.