In this study, the extraction process of essential oil of rosemary plant was considered by steam distillation method. The objective of this work was process optimization and determination of mass transfer coefficient. For vast study on this process an extraction unit comprising a distillation column was constructed then the effect of five factors were examined on extraction yield as follows: Steam flow rate on extraction yield, the number of stages of separation colum, the height of packed bed of plant, the insulation of column; and both distillation time and steam flow rate on quantity of component of essential oil of rosemary.
An each of the experiments was conducted up to 100 minutes. With sampling after 5, 15, 30, 60 and minutes. All the experiments were performed for three steam flow rates of 4,7 and 9 liters per minutes.
It was found that:
The oil yield was increased with decrease of steam flow rate and maximum yield was obtained for steam flow rate of four lit/min. The experiments displayed that with decrease of packed bed height the yield of extraction was increased. In these experiments three packed beds of 100,150 and 200 g were considered. The maximum yied was obtained for 100g. The insulation increased the extraction yield 14 % in comparison with ordinary column. The best result for the yield of essential oil extraction was obtained in the case of multi-stage column. Also columns with one, two and three stages and steam flow rates of four and seven lit/min were examined. It was found that the maximum yield was obtained for three stages was for three stages cokumn with steam flow rate of four lit/min the yield was 1.36%.
The samples were collected for three experiments with steam flow rates of 4, 7 and 9 lit/min and single packed bed with 100g of plant and analyzed with GC and GC-MASS chromatography. It was considered that the effect of distillation time and steam flow rate for a-pinene, 1,8-cineole and camphor resulted in the maximum percentage of extraction in essential oil of rosemary.