Demulsification of water/crude oil emulsions using functionalised PolyHIPEs in an electrostatic field

Abstract

In petroleum manufacturing, during the crude oil extraction process, water-in-crude oil emulsions with high stability are obtained which are stabilised due to the presence of indigenous surface-active materials within crude oil. The removal of water from crude oil is critical in producing saleable product. It should be conducted at source with the aim to overcome the cost of pumping and the problems associated with the corrosion in pipes during transportation. Many separation technologies exist, e.g. gravity separators, coalescence separators, centrifugal separators, stripping columns and vacuum distillation systems, but most of these cannot remove tightly emulsified or dissolved water in addition to their high cost. Thus, chemical treatments are often required to separate water from these emulsions. Recently, sulphonated hydrophilic micro-porous polymers (named PolyHIPE Polymers) were used as an active membrane layer in a cross-flow microfiltration process to separate water from water-in-crude oil emulsions. However, this did not sufficiently separate water from w/o emulsions under steady state conditions. Therefore, an alternative method for using polyHIPE to achieve the same results has been developed in this project. This thesis focuses on the removal of water and surface-active components from high stability water-in–crude oil emulsions by using a novel combination of a highly porous polymeric material sorbent with an electrostatic separation field to further enhance the efficiency of the separation process. The results are compared to a conventional separation processes. Several micro-porous polyHIPEs (PHPs) with varying functionality have been produced and characterised. These PHP polymers were then utilised in water separation trials from emulsions of water-in-crude oil with high stability. A continuous demulsification process has been developed and tested on a model seawater-in-crude oil emulsion by utilising different PHPs in presence of an electric field. In order to use the optimum samples of the PHPs in the demulsification process, the PHP samples were characterized in terms of morphology, surface area, water uptake, pore size distribution, EDX, and FTIR analyses. Different flow rates of emulsions and various electric field strengths (applied voltages) were employed in this separation process to evaluate their effect on the separation efficiency. Furthermore, the spent PHP samples were reused in the demulsification process to evaluate the potential for sorbent recovery and the change in separation efficiency after reuse. This study succeeded in achieving its main objective namely the production of environmentally sustainable demulsifiers on a laboratory scale. A silane PHP ecofriendly demulsifier was synthesized with a relatively high surface area of 98 m2/g, high water adsorption as well as its ability to remove surface-active species from crude oil that cause emulsification of crude oil such as Mg, Na, Cl and Ca. Another goal was to study the demulsification mechanism by utilising various types of sorbents including standard sulphonated PHP, in situ sulphonated PHP, bindzil PHP and silane PHP to identify the best performance. This required the development of a continuous demulsification process to work at a high electric field strength without breakdown (ranging from 1-5 kV over a few centimetres) and different emulsion inlet flow rates (from 100 to 1500 ml/min). It was found that the best separation efficiency was 89% by using the silane PHP demulsifier at a flow rate of 100 ml/min and an applied voltage of 5 kV. This is comparable to the best results achieved by other methods including chemical demulsification. When reusing the spent silane PHP in the demulsification process under similar parameters, the separation efficiency was reduced to 71%. The final aim, to eliminate the need for larger demulsification equipment by developing a novel approach for the separation of emulsions under the combined impacts of demulsifier and electric technique, was therefore successfully achieved.