Patent GB-632328-A (GB)
Title: Process for removing asphaltic or resinous material from mineral oil
IPC: C10G73/06
Filed: 1947-05-12
Abstract: <PICT:0632328/III/1> Asphaltic or resinous material is removed from mineral oil by extracting with a liquefied normally gaseous hydrocarbon, separating a resultant raffinate phase essentially comprising resinous material from a liquid extract solution comprising normally gaseous hydrocarbon, dissolved mineral oil and a minor amount of extracted resinous material, precipitating a heavier mineral oil fraction containing the extracted resinous material from the liquid extract solution, subjecting the heavier mineral oil fraction to further contact with the liquefied normally gaseous hydrocarbon, withdrawing the remainder of the liquid extract solution, heating and separating it into a phase of substantially pure normally gaseous hydrocarbon and into a mineral oil phase substantially free from resinous material in a settling zone maintained at a temperature and pressure at least as high as the critical temperature and pressure of the normally gaseous hydrocarbon present, effecting an indirect transfer of heat from the separated phase of normally gaseous hydrocarbon at a pressure at least as high as its critical pressure to the liquid remainder upon withdrawal of the latter from the precipitation step, and recovering the mineral oil phase substantially free of resinous material.  The liquified normally gaseous hydrocarbon may be mixtures of ethane, propane and butane, ethane and propane, propane and butane, or propane or butane alone; unsaturated olefins such as ethylene, propylene and butylenes or mixtures thereof, and mixtures of saturated and unsaturated hydrocarbons are also specified.  Apparatus which may be used is shown in Fig. 1, in which a reduced crude charging stock is introduced through line 1, pump 3 and heat-exchanger 70 into tower 8 where it is contacted with liquid propane to effect a separation of resinous material; a temperature of about 10 DEG  to 150 DEG  C. and a pressure of about 20 to 50 atmospheres absolute may be used.  The propane-oil mixture is passed through line 72 and heat-exchanger 74 to the top of tower 8 above blind tray 88, in which it separates into two phases.  The lower phase, containing substantially all the resinous material is returned through line 77 to the lower part of the column, where it contacts the propane-oil mixture rising through the column at a lower temperature and thus causes the separation of additional resinous material.  The upper phase consisting of a propane-oil mixture is passed by line 9 through heat-exchangers 67 and 90 in which the temperature is raised above the critical temperature of propane, into settler 15 which is maintained above the critical temperature and pressure of propane and in which pure propane is separated from the oil.  The oil, containing a little propane, is passed by line 16 into flash tower 18 wherein propane is flashed from the oil by reduction in pressure, and then by line 21 to stripper 23, from which the resin-free or deasphalted oil is withdrawn through line 84.  The resinous material separated in treating tower 8 is removed by line 48, heated to about 200-260 DEG C. in furnace 51 and passed into chamber 54 wherein propane is separated by vaporization. Substantially all of the remaining propane is removed by distillation in chamber 59 and the resinous material is withdrawn by line 32.  The pure propane separated from settler 15 is withdrawn by line 65, passed through heat-exchangers 67 and 70 in indirect heat-exchange with the propane-oil mixture and the incoming resinous oil respectively, and then directed into high pressure receiver 96.  The propane from stripper 23 and chamber 59, after washing in tower 28, and that from tower 18, is directed to low-pressure receiver 36, from which, mixed with propane from high-pressure receiver 96, it may be recirculated to tower 8.  In a modification, (Fig. 2, not shown), tower 8 is not separated into upper and lower parts, but a portion of the oil separated in settler 15 is recirculated to the top of the tower where it causes separation of the propane-oil mixture into two phases, the lower of which flows down the tower in a manner analogous to that of the system shown in Fig. 1.