Microwave treatment of crude oil emulsions: Effects of water content

•2.45 GHz microwaves were employed to heat water emulsions in native crude oils.•Volume fractions of water in emulsion ranged from 0.04 to 0.77.•Heating rates of emulsions were measured at 20–45 °C.•Separation of free water was triggered by exothermic processes in emulsions.•Optimal, energy saving, volume fractions of water were 0.18 and 0.56.

The main objective of this work was to investigate the effect of water content in crude oil emulsions upon the microwave demulsification process. The microwave heating properties were examined for samples of neat water, neat oil and W/O emulsions with volume fractions of water ϕ ranging from 0.04 to 0.77. The observed changes in initial heating rates correlated with structural transformations in the disperse phase of as-prepared emulsions. In course of heating emulsions with ϕ<0.40, a characteristic succession of endothermic and exothermic processes was observed, the latter process triggering the phase separation of free water. The optimal conditions for microwave irradiation were determined by calculating the amount of microwave energy required for the onset of phase separation. In the studied emulsions, minimum energy consumption was observed at volume fractions of water ϕ≈0.18 and ϕ≈0.56.

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