Process and apparatus for electrically resolving oil-continuous dispersions

摘要

Dispersions of particles in oil, as the continuous medium, are removed by passing the oil through an inter-electrode space of large length to gap ratio and applying a high voltage direct current, in which the bulk of the dispersed particles are coalesced and separate out in the early stage, and at a later stage particles are deposited on the electrodes by electrophoresis. Preferably the inter-electrode space is defined by a rod electrode centrally mounted in a tube of length to gap ratio 8 to 30:1 and preferably at least 12 to 25:1. A unidirectional voltage of 6 to 30 k.v. per inch of treating space is applied. A suitable apparatus consists of a cylindrical vessel 10 the cross-section of which is occupied by a cellular electrode assembly comprising tubes of circular or hexagonal or other cross-section 16 and mounted between upper and lower zones 13, 14. Each tube contains a rod electrode 17 suspended centrally therein and attached to a frame 19 connected to a high-voltage source of D.C. The oil dispersion may first be treated to remove coarse suspensions in a high turbulence electric treater 40, and then enters a manifold system 29 discharging streams of the oil through the vertical tube electrodes; spreaders 31 may be used. In the lower region, the oil is submitted to some turbulence and the bulk of the dispersed particles are coalesced, and then enters a quiescent zone 24 of higher voltage gradient, where finer particles are deposited on the tube electrode surface by electro-phoresis. Deposited material sinks slowly downwards on the tube surface to the bottom zone 32. In a modification, the level of the collected dispersed material is arranged to submerge the lower ends of the electrode tubes at L-L and forming a seal, by adjusting level control devices 35 controlling the discharge valve 34. The upper zone 13 may be in the form of a header provided with a collector pipe with openings to receive the rising oil discharged from each tube electrode. The lower inlet zone 14 may also have a series of vertical barrier walls against which the dispersion impinges before entering the tube electrodes, and replaces the manifold 29. The process may be applied to petroleum oils containing dispersed particles of water or caustic soda solution.