Treatment Of Waste-Water/Oil Emulsions Using Microwave Radiation

Abstract

Abstract Venezuelan E & P industry carries out an important amount of waste-generating processes that make necessary to develop more appropriate methods for disposing of their waste. Some of these waste materials are emulsions formed by a mix of residues of crude oil, water, drilling muds and other agents. Microwave methods are able to destabilize water/oil emulsions by two means. First by increasing temperature, which reduces the continuous phase viscosity and breaks the outer film of the drops, thus allowing for coalescence; and second by rearranging the electrical charge distribution of the water molecules while rotating them, and moving ions around the drops. These two actions combined result in the breaking of the emulsion without adding any chemical agent. Aiming to mitigate the environmental hazard that these waste emulsions represent, a base study was carried in order to verify the phenomenon described above. The experimental work consisted on breaking the simplest of the emulsions in terms of content, in order to obtain preliminary data that can help to extend the method to manage actual waste material. The samples consisted in water/oil emulsions (with several W/O compositions) which have commercial lubricant basis as the oil phase. The results of the experimental work are temperature profiles and recovery factors of aqueous phase that describe the performance and efficiency of the method. The sample emulsions underwent a domestic microwave radiating process at several exposure times. Certain factors, such as aromatic components and sodium hydroxide content, emulsion mixing method and total heat exposure time proved to be the factors that more strongly affect the results. By using the microwave radiation exposure, results showed an aqueous phase recovery that ranged from 60 to 80 %, which is a significant outcome that reveals the study of this technique needs to be taken further. Introduction An emulsion is a polyphasic system constituted by two inmiscible liquids where one of them is found as tiny drops suspended within the other. First liquid is known as disperse phase, whereas the other is the continuous phase or dispersing media. Emulsions are unstable systems from the thermodynamic point of view. Nevertheless, its stability can be controlled and/or manipulated from the kinetic point of view, by using an adequate surfactant. Stability of emulsions is determined by the oil's aromatic content. Oils with high aromatic content have higher viscosity, which difficults water separation. This difficult separation can also be due to the bases high content of hydrophilic polar components. Most common kinds of unstability of emulsions are flocculation, coalescence, inversion and sedimentation. Apparition of these phenomena can produce drastic changes over emulsion's properties. If the goal of the treatment consists in breaking an emulsion, several other factors have to be accounted for. Some of these are water-oil ratio and drop diameter distribution. These factors influence significantly in the rheological behavior of emulsions. Petroleum exploration, production and refining industry carries out an important amount of waste-generating processes that no longer can be left untreated before disposal. Due to a new and extensive compendium of environmental laws, it is necessary for the industry to develop more appropriate methods for disposing of their waste. Some of these waste materials are emulsions formed by a mix of residues of crude oil, water, drilling muds and other agents. Among these waste-water/oil emulsions, there are several kinds depending on the composition of oil phase. Lubricant paraffinic oil bases, for example, come from crude oils with high alkane content and have a sharp viscosity-temperature relationship. These bases are also called neutral-solvents because the oil has been refined with solvent and its pH is neutral.