Patent GB-466731-A (GB)
Title: Improvements in or relating to deasphalting and dewaxing of hydrocarbon oils
IPC: C10G21/00
Filed: 1936-02-20
Abstract: In a process for separating asphalt and wax from hydrocarbon oils in separate stages with a liquefied normally gaseous solvent, a solution of the oil in solvent passes through the asphalt and wax-removal stages while maintaining in each stage a pressure greater than the equilibrium pressure by means of an added gas or vapour whose vapour pressure is higher than that of the solvent at the same temperature. Liquefied solvents specified are propane, n- or iso-butane or mixtures of these.  The added gas or vapour which under the conditions employed is substantially insoluble in the liquid mixture consists of a hydrocarbon lighter than that used as solvent.  A hydrocarbon oil containing asphalt and wax passes to a mixer 9 from a tank 10 together with 4 to 5 parts of liquefied propane from a tank 1.  The oil before admission to the mixer passes through a heater <PICT:0466731/III/1> 13 and is mixed with brine water or other immiscible liquid from a tank 14 to render the oil easy-flowing.  The mixture passes from the mixer 9, at about 80 DEG  F., with additional solvent added through a pipe 19 if necessary, to an accumulator 20a having a gas dome and pressure relief valve 22.  Ethane contained in a pressure gas tank 26 at 200 lbs. pressure is added through a pipe 25.  The mixture containing precipitated asphalt is forced under the pressure into a centrifuge 31 where pressure is slightly lower than in the accumulator.  The discharge lines of the centrifuge are connected by a pressureequalizing manifold 59.  Asphalt and brine are discharged through a pipe 42 into a receiver 43 from which they pass to a still 48.  Solvent vapours are condensed and pass through a pipe 51 to the tank 1.  Asphalt is withdrawn through a line 55, and the brine through a line 52 to the tank 14. The asphalt-free oil solution passes from the centrifuge through a pipe 56 into a receiver 57, from which it passes with additional solvent if necessary from a line 85 and under additional pressure from the ethane tank 26 to two groups of indirect heat exchangers 91, 93, where final temperature used is between - 20 and 0 DEG  F. Cooling is effected by brine circulated from a refrigeration plant 114.  By indirect cooling (instead of auto - refrigeration), the solvent does not boil and crystal-formation proceeds unhindered. The chilled mixture containing precipitated wax passes to an accumulator 95 having a gas dome connected to the ethane tank 26, and then to a dewaxing centrifuge 100, the discharge lines of which are provided with a pressure-equalizing manifold 101. Wax-free oil and solvent are discharged through a line 125 to a receiver 126 and then through the first group of chillers and to a still 132 maintained under pressure.  Solvent vapours pass through coolers 138 and gas separator 140 whereby liquefied solvent is separated from the ethane and returned to the storage tanks.  The dewaxed oil is withdrawn through a pipe 142.  The wax and some solvent is discharged from the centrifuge through a pipe 144 to a receiver 145, and then passes to a still 155 maintained under pressure.  Solvent vapours join those from the still 132.  Wax is withdrawn through a line 160.  Specification 389,113 is referred to.