Industrial Case-study: Re-emulsification of expired highly viscous emulsion product
Advancing the chemical engineering fundamentals
Interfacial & Colloidal Phenomena - III (T2-6c)
Keywords: Re-emulsification, Viscous emulsion, Mixing, Centrifugation, Stability
Lim Tau Yee*, Ng Wai Kiong, Choi Won Jae, and Murugapillai Venugopal
Institute of Chemical and Engineering Sciences, Agency for Science, Technology and Research (A*STAR)
1, Pesek Road, Jurong Island, Singapore 627833
Tel: (65) 6796 3867 and Fax: (65) 6316 6183
Email: lim_tau_yee@ices.a-star.edu.sg*, ng_wai_kiong@ices.a-star.edu.sg,
choi_won_jae@ices.a-star.edu.sg, Murugapillai_Venugopal@ices.a-star.edu.sg
Abstract
A continuous industrial-scale static mixing process is used to emulsify a highly viscous feed into oil-in-water emulsion product. Unfortunately, during prolonged storage, some product could not be utilized before the shelf-life expired and separated into two immiscible phases (expired emulsion) leading to economic losses. In open literature, there were few technical reports on re-emulsification of expired highly viscous emulsion, which was normally treated as know-how in industries. The aim of this work is to conduct a technical feasibility study to minimize the loss of emulsion product by developing a small-scale process to re-emulsify this leftover product. An attempt is made to apply a batch dynamic mixing process at laboratory-scale to achieve similar product specifications as that of the original product produced by large-scale static mixing. Surfactant and bio analysis were carried out to evaluate the need to replace the separated aqueous phase containing surfactants and stabilizers. It was found that arising from the growth of micro-organisms in the expired emulsion, only negligible quantities of surfactants and stabilizers remained in the aqueous phase. Therefore, all re-emulsification work was carried out using additional surfactants, de-ionized water and the recovered oil phase. The original and re-emulsified products were characterized using optical microscopy (droplet shape and size), laser diffraction (droplet size distribution)1, viscometer (dynamic viscosity), Karl Fisher titration (water content) and centrifuge (relative stability against centrifugation)2,3. In order to mimic large-scale continuous static mixing, special considerations in terms of the number of the mixing stages and residence time distribution need to be accounted for in the batch process.
Our results revealed that it was technically feasible to recover phase separated emulsion product using a small batch dynamic mixing process. While the droplet size distribution of recovered product was slightly smaller as compared with the original product, there was a small improvement in viscosity of the recovered product. Measurements also showed that the original and the re-emulsified emulsions contained approximately same water contents. After centrifugation at 6,000 rpm for 15 minutes, it appeared that the recovered product and the original had similar relative stability against centrifugation force and could imply roughly similar shelf life. It is hoped that this work could serve as a reference industrial case-study in exploring the recovery of expired highly viscous emulsion product during prolonged storage using a small-scale batch process.
References:
1. Roland, I., Peil, G., Delattre, L., and Evrard, B., Systematic characterization of oil-in-water emulsions for formulation design, Int. J. Pharm., 263 (2003), 85-94.
2. Sobisch, T., and Lerche, D., Rapid emulsifier selection and evaluation of emulsion stability by analytical centrifugation, Chemistry Preprint Archive, 5 (2004), 7-18.
3. Sobisch, T., Lerche, D., and Küchler, S., Stability analyzer LUMiFuge 116 for rapid evaluation of emulsion stability and demulsifier selection, Chemistry Preprint Archive, 6 (2002), 5-11.
Presented Thursday 20, 11:40 to 12:00, in session Interfacial & Colloidal Phenomena - III (T2-6c).
