Heat strengthening of double-field coupling demulsification of industrial waste oil emulsion

Abstract

Demulsification of highly aqueous waste oil is difficult to complete by a single process efficiently. The dewatering-type hydro-cyclone is used as the unit body and includes the high-voltage electrode to realize demulsification and dewatering ability of the coupling of high-voltage electric and swirling centrifugal fields in waste oil emulsion efficiently. This study considers the influence of heating temperature on demulsification in coupled field. Thus, a heat-strengthening double-field demulsification process is proposed. Specifically, the effect of heat strengthening on demulsification, dewatering, and separation of double-field coupled by numerical simulation and experimental methods was investigated. The temperatures of heat-strengthening were 60 °C, 65 °C, 70 °C, and 75 °C. The results show that the separation efficiency predicted by numerical simulation are in good agreement with the experimental results. And the heat-strengthening can effectively enhance the separation effect of two fields and improve the efficiency of the oil-water separation of industrial waste oil. When the heating temperature is raised from 60 to 65 °C, and from 65 to 70 °C, the separation efficiency increases by approximately 4.1% and 6.7%, respectively. List of symbols D Nominal diameter, mm D i Inlet diameter, mm D o Overflow orifice diameter, mm D u Underflow orifice diameter, mm d The initial separation between two dipoles, m d j Droplet diameter, mm E 0 Amplitude effective value of electric field, kV·m −1 E i i = 1, 2, 3, electric field strength along the axis, kV·m −1 E j j = 1, 2, 3, electric field strength along the axis, kV·m −1 E S Separation efficiency, % F e Body force, N ƒ x , ƒ y , ƒ z Electric field body force along x, y, and z direction , N g Gravitational acceleration, 9.8 m·s −2 L o Insertion length of overflow pipe, mm L u Length of underflow straight pipe, mm n Integer 0, 1, 2 … N Number of drops p Pressure, Pa Q in Inlet flow rate, m 3 ·h −1 Q o Flow rate of overflow orifice, m 3 ·h −1 Q u Flow rate of underflow orifice, m 3 ·h −1 r 1, r 2 Radius of droplets, mm R Droplet size, mm T Maxwell stress tensor T ij Element of Maxwell stress tensor t Residence time, s t 1 Coalescence time of two drops, s v dr,k Drift velocity of phase k, m·s −1 v k Velocity of phase k, m·s −1 v m Velocity of the mixture phase, m·s −1 V xyz Volume of cell, m 3 α Large cone angle, ° α k Volume fraction of phase k, % α in Volume fraction of inlet orifice α o Volume fraction of overflow orifice