Demulsification of heavy crude oil-in-water emulsions: A comparative study between microwave and thermal heating Rafael Martínez-Palou ⇑ , Ricardo Cerón-Camacho 1 , Benjamín Chávez 1 , Alba A. Vallejo 1 , Diana Villanueva-Negrete 1 , Jesús Castellanos 1 , James Karamath 1 , Jesús Reyes 1 , Jorge Aburto 1 Dirección de Investigación y Posgrado, Instituto Mexicano del Petróleo, Eje Central Lázaro Cárdenas 152, 07730 México, D.F., Mexico highlights  A comparative study of demulsification by microwave and oil bath heating.  Results were confirmed by steady state fluorescence spectrometry.  The effect of a demulsifier on the oil-in-water (O/W) emulsion stability was studied.  The effect of salt content on the O/W emulsion stability was evaluated. article info Article history: Received 14 January 2013 Received in revised form 20 May 2013 Accepted 29 May 2013 Available online 12 June 2013 Keywords: Demulsification Microwave O/W emulsions Demulsifier Fluorescence spectrometry abstract Oil-in-water (O/W) emulsions are an innovate manner by which otherwise highly viscous heavy and extra-heavy crude oils can be transported from producing sites to transforming sites through pipelines. In spite of the important reduction in viscosity and pressure drops, water must be removed from the crude oil before further process or refining. Hence, the present study discusses the demulsification of an O/W emulsion prepared with Mexican heavy crude oil. A comparative study was carried out between microwave and oil bath heating with regard to water separation time. The effect of a chemical demulsifier and salt content of the O/W emulsion’s aqueous phase was also investigated. Microwave dielectric heat- ing of O/W emulsions showed a greater degree of water separation in less time than conventional oil bath heating. Water separation of O/W emulsions increased with microwave power and salt content of the aqueous phase, and in the presence of a chemical demulsifier. Finally, the fluorescence emission spectra of the initial and treated O/W emulsions were in agreement with the water separation results and pro- vide a quick and effective way to study the demulsification processes. Ó 2013 Elsevier Ltd. All rights reserved. 1. Introduction Currently, most of the recoverable petroleum in Mexico and in many other countries is heavy crude oil with an API gravity equal to or lower than 20°. The complex composition of these crude oils makes them difficult and expensive to produce and transport through pipelines due to their low mobility and flow near ambient temperature. Also, their high asphaltene and paraffin contents pro- mote pipe clogging, pressure drops, and consequently a lower pro- duction rate than lighter crude oils. Various well developed strategies are used to facilitate the transport of heavy crudes, such as dilution with organic solvents, lighter oils, or condensates; heat- ing (and by necessity, thermally isolating) pipelines; and the use of flow improvers and drag reducing additives. Nevertheless, innova- tive approaches such as the formation of oil-in-water (O/W) emul- sions, known as inverse emulsions within the petroleum community, may contribute as an alternative technology to reduce crude oil’s viscosity and increasing flow with only minor opera- tional issues [1]. The formation of O/W emulsions, industrially known as the Ori- mulsion process [2–4], has proved to be a very reliable method be- cause of its low cost and relative ease in industrial implementation. However, this approach, in which crude oil is transported as drops dispersed in a water continuous phase (20–30% w/w), requires emulsion breakage and water separation before further refining. While there have been fewer studies of O/W emulsions as found in the present article, it is worth mentioning that extensive studies exist on the demulsification of water-in-oil (W/O) emulsions, since emulsions of this type commonly form during crude oil production and pipelining [5–7]. The presence of emulsions is a common feature in oil process- ing. Although the formation of emulsions of different types, such 0016-2361/$ - see front matter Ó 2013 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.fuel.2013.05.094 ⇑ Corresponding author. Tel.: +52 55 91757846; fax: +52 55 91558368. E-mail address: rpalou@imp.mx (R. Martínez-Palou). 1 Tel.: +52 55 91757846; fax: +52 55 91558368. Fuel 113 (2013) 407–414 Contents lists available at SciVerse ScienceDirect Fuel journal homepage: www.elsevier.com/locate/fuel