GB490767A - Improved process and apparatus for treating oil - Google Patents

Abstract

<PICT:0490767/III/1> <PICT:0490767/III/2> Hydrocarbon oil containing not more than 3 per cent of water is dehydrated and purified, e.g. from acids and salts, by dispersing therein other water without combining much of the original and added water, subjecting to the action of an electric field to coalesce the greater part of the 2 kinds of water droplets, and separating the coalesced water masses from the oil. Suitably the added water is 10-50 per cent of the oil, it is dispersed in droplets of larger average size than the original water droplets, its dispersion is effected by successive relatively light mixings, the last mixing taking place as the mixture enters the electric p field, the mixture is at 100-190 DEG F. while in the electric field, the separation is effected by gravity settlement, and the separated hydrocarbon is refined by heating to remove lighter fractions, the vapours of which are used to preheat the water to be added. Crude oils containing large percentages of emulsified water may be treated by first subjecting to a preliminary dehydration. In an example, crude oil is pumped from the well through a pipe 65 to a known centrifugal, electrical, chemical, gravitational, or other dehydrator 66; the oil is forced to a tank 70 and thence by a pipe 72 through heat exchangers 23, 33 so as to enter a pipe 75 at 125-150 DEG F.; cooling water in about 20 per cent by volume of the oil is withdrawn from one or more condensers 24, 34, 44, 54, at about 120 DEG F., as by a pipe 39 and flows through a steam heater 79 so as to be delivered at 160 DEG F., by a pipe 76 to the oil in pipe 75; the mixture is passed by a pipe 78 through a centrifugal or other mixing pump 95 and/or a weighted-valve emulsifier 85 to a pipe 86, from which it is discharged with further mixing into an electric treater 87 through the annular space between resiliently pressed-together top and bottom cylindrical pipes 105. The oil flows from the treater through a pipe 200 to a tank 202, is pumped through a pipe 204, heat exchangers 43, 53, and a pipe 61 to a series of fractioning stills 21, 31, 41, 51, the residue flowing by a pipe 208 to a cracker 210. The vapours from the stills 21-51 flow through dephlegmating towers 22-52, heat exchangers 23-53 and so preheat the oil from the tanks 70 and 202, and condensers 24-54. The electric treater 87 comprises a tank earthed by a wire 118 and carrying insulators 119, 124 from which are suspended live electrodes 120, 121, 128 and 129; each electrode is formed of inner and outer rings, e.g. 132, 133, connected by rods or pipes 134, provided with pins 136 carrying concentric rings 137. The electrodes are connected with the high tension terminals of transformers 160, 161 each developing 12,000 volts, the other terminals of which are earthed by a wire 162, so that the potential across the spaces 126, 127 will be 24,000 volts but that between the tank or the distributer 105 and any of the electrodes will be only 12,000 volts thereby reducing the risk of short-circuiting. The water separating out flows away through a pipe 177 and a valve 182 automatically controlled by linked and pivoted arms 184, 183, 181 and a float 179, which sinks in oil but floats in water, so as to maintain the oil-water level 170 sufficiently below the electrode 121 as to prevent short-circuiting. To prevent the settling water carrying down particles of oil, water is sprayed upwards through a multi-orificed head 190; this water is preferably slightly hotter than that settled in the tank, and is conveniently that from the pipe 76, being delivered to the pipe 197 through a valve 199. The tank 87 is preferably under pressure, e.g. of 20 lb., controlled by the oil-outlet valve 201, the pressure in the pipe 75 being about 50 lb. U.S.A. Specifications 1,838,921 and 1,838,927 are referred to.