(216f) Modelling and Optimisation of Essential Oil Fractionation and Rectification Processes

Essential oils are extracts of plants which constitute of various volatile aromatic compounds. The primary markets for these oils are the flavour, fragrance and pharmaceutical industries. Before use, the essential oils are enriched in certain aromatic compounds, although in some cases, a single aromatic compound must be completely isolated.

The separation of essential oils is usually performed in batch columns. The columns used for this purpose in industry today can be up to 40-50 feet in height and large reflux ratios are required to attain the desired separation leading to long operation times. Recently, however, spinning band distillation columns have immerged as a promising alternative to the more traditional batch distillation columns. Spinning band distillation creates intimate contact between vapour and liquid using a helix rotating at high speeds inside the distillation column. The main advantages of such operation include high efficiency and low hold-up.

So far, little or no work has been undertaken on the modelling and optimisation of neither traditional essential oil fractionation and rectification processes, nor the newer spinning band columns. In this work, various operating policies for the rectification of essential oils using traditional batch distillation columns are explored using rigorous distillation models as opposed to short-cut methods put forward by other authors (e.g. Iribarren et al., 2004). This paper also considers, to the best of our knowledge, the first work on modelling of spinning band distillation columns for the separation of a large number of compounds.

Case studies from different industries are used to demonstrate the applicability of the dynamic models as well as the optimal operating policies and to compare the operation of the two different alternatives, batch distillation and spinning band columns. The first case study considers the rectification of orange oil and peppermint oil, the two largest produced essential oils, whilst the second case study focuses on the fractionation of Eucalyptus oil to isolate Citrinellal. Spinning band distillation is found to be a promising alternative to traditional batch distillation for certain conditions.

References Iribarren, O.A., Salomone, H.E., Zamar, S.D., Operation planning in the rectification of essential oils, Journal of Food Engineering, 69 (2005) 207-215.