In the recovery of essential oils from vapour and nitrogen streams by cooling, an aerosol is formed. The work described is a study of aerosol formation and the subsequent aerosol collection process for the oil geraniol (C10H130). Vapour at concentration up to 0.03 g/g N2 was cooled and up to 35% of it changed into aerosol having a weight-moment mean diameter, Dwm, of up to 5.1 pm. Results showed that particle size increased with decreasing vapour cooling rate; and that particle size and mass concentration increased with initial vapour concentration. Studies of filter collection efficiency were conducted with a geraniol aerosol of Dwm = 1.0 pm. Its particle number concentration was high, at about 5x10 .//cc N2. Filters used were: (1) glass sintered discs of 50 pm and 110 pm maximum pore size; (2) fibrous filters of 0.004-0.13 packing density and 0.07-12.2 cm thickness made of "Bekinox" stainless steel fibres of 4-22 pm diameter. Filtering area was about 3.1 cm2 and superficial velocity up to 110 cm/s. Filter resistance, liquid saturation which resulted from collecting aerosols, and collection efficiency were determined. For disc filters, resistance and efficiency increased with decreasing pore size. Wetted filter resistance was approximately correlated with disc porosity and simplified capillary number N'a (Qu/At). For fibrous filers in stationary filtration condition, resistance data fitted closer with Davies' empirical model, and efficiency data were close to theoretical values based on the Rappel-Kuwabara flow field. In the non-stationary filtration condition (wet) and at packing densities a > 0.02, liquid saturation correlated with capillary number and a proposed dimensionless group (al/df), and filter resistance correlated approximately with N4ap and (al/df). The efficiency of filters of low packing density (a<0.02) was apparently not affected by liquid saturation, but the efficiency of high packing density filters was increased to varying degrees. For a>0.04, collection efficiency data fitted closely with a proposed model which is based on existing filtration theories with modified parameters including liquid saturation, fibre diameter and superficial velocity.
| Identifer | oai:union.ndltd.org:bl.uk/oai:ethos.bl.uk:637911 |
| Date | January 1983 |
| Creators | Liew, Tow Pin |
| Publisher | Swansea University |
| Source Sets | Ethos UK |
| Detected Language | English |
| Type | Electronic Thesis or Dissertation |
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