Patent GB-418939-A (GB)
Title: An improved method for the separation of mixtures of liquid and solid constituents
IPC: C10G73/02
Filed: 1933-11-30
Abstract: A mixture of liquids and solids is fed against one side of a filtration membrane under the influence of differential filtration pressures, that on the liquids exceeding that on the solids by an amount greater than the gravitational <PICT:0418939/III/1> <PICT:0418939/III/2> <PICT:0418939/III/3> <PICT:0418939/III/4> pressure; the filtrate is then withdrawn from the other side of the membrane.  The process may be applied to the separation of wax and asphalt from mineral oils, or to the removal of solid materials from vegetable, animal and marine oils.  The cell 2, Fig. 1, has a membrane 3, and a pipe 1 for the supply of a liquid mixture containing solids possessing high magnetic properties.  An electromagnet 6 exerts an attractive force on the solids while the liquid passes through the membrane to the discharge pipe 5.  In the cell 14, Fig. 2, the suspended particles in the liquid carry electric charges, and the sides of the cell are maintained at different potentials by the connections 17, 17<a>.  The force with which the solids reach the membrane 13 is therefore diminished without the passage of the liquid being impeded.  Where the liquid has a greater density than the solid, the mixture is led inside a centrifugal drum with the filter membrane on the cylindrical wall.  Where the solid has a greater density than the liquid, the mixture is supplied to the space outside the drum and the liquid passes inwards through the membrane to discharge outlets.  A modification for the filtration of wax from a heavy lubricating oil prepared by adding a diluent and chilling is shown in Fig. 5.  The wall 43 of the drum is the filtration membrane and a second membrane 43<b> is provided at the top, the two membranes being connected by a solid part 43<a>.  The mixture is supplied through the central feed pipe 41 and passes beneath the spreading plate 48<a>.  The filtrate flows through the membrane 43 and then upwards over the wall 42<b> to the chamber 44 while the wax moves up to the part 43<a> and the membrane 43<b> where it is washed by liquid supplied by the pipe 41<a>; the washed wax is drawn off by the skimming pipe 101.  In the further modification shown in Fig. 6, the axis of the filtering drum 53 is horizontal and the mixture is fed in through the annular space between the wall of the hollow shaft 58 and the pipe 51<a>.  The partition 53<a> divides the drum into two parts and the wax, which is separated in the first part, is washed in the second by liquid supplied through the pipe 51<a> and arms 51<b>.  The filtrates from the two parts of the drum may be discharged together or separately, and a stationary or rotary screw 201 may be used to discharge the wax.  The operations are performed at a temperature low enough to keep the wax solid.  The diluents used preferably increase the difference in gravity between the oil and wax and consist of the halogenated hydrocarbons, especially the halogenated derivatives of acetylene, ethylene, propylene and butylene.  Aromatic hydrocarbons, naphtha, petroleum ether, or liquefied hydrocarbon gases may be used alone in conjunction with alcohols, ketones and esters may be added.  For example, lubricating oil containing wax, slop distillate or residues are mixed with propylene or ethylene dichloride and carbon tetrachloride or toluol and after chilling to 0 to 5 DEG  F. are filtered in apparatus shown in Fig. 5.  These diluents may be mixed with or replaced by aryl, ethyl or isopropyl alcohol, butyl or amyl acetate or formate, ethyl carbonate, acetic or formic acid, acetone, methyl, ethyl ketone or hydrogenated cyclic hydrocarbons.  The process may be applied to purifying waxes such as petrolatum or amorphous paraffin wax.