Abstract
This dissertation discusses some aspects of steam distillation extraction of essential oils from vegetable sources. This has not received much attention in terms of technological advancement as a chemical engineering process despite the fact it has been in existence for many years. More than 90% of the different essential oils that are used as fragrances in general household and personal care products and medicinal formulations are produced by steam distillation extraction. Despite this dominance of the method as a means of essential oils extraction not much information is available for its optimisation. In order to address this lack of attention a study of the steam distillation extraction was carried. First a steam distillation extraction process was designed and commissioned and used for pilot plant distillation. It was then used together with gas chromatography to study steam distillation extraction in order to add more understanding of the process. The steam distillation rig was designed so that it could produce about 2 ml to more than 50 ml of steam per minute. The findings of the study were that proportionally low steam flow rate for a given packed bed mass produced richer (in terms of oil content) condensate and the converse was true. Sample yield curves, which show the mass of oil in each similar sample of condensate volume during the course of each run showed that for a period of time the oil content in a sample is at maximum, before the yield decay period sets in. This maximum was determined mainly by the size of the packed bed and the steam flow rate. For each new and higher steam flow rate, a new but lower maximum oil yield was developed for a fixed bed height. There is a direct relationship between concentration of oil in the vapour phase, CO, and steam residence time, x, in packed bed. This can be expressed as CO, and the proportionality constant depends on the physical characteristics of packed bed. This pattern was similar for either subcutaneous or superficial oil sources. The amount of the oil yield was determined by profiling the major components during the entire extraction period using gas chromatography. Based on the results a systematic method, which involves practical experimentation was developed, and can be used to optimise steam distillation of essential oils.