Patent GB-669091-A (GB)
Title: Improvements relating to the extraction of a component from a composite fluid
IPC: B01D11/04
Filed: 1948-09-27
Abstract: <PICT:0669091/III/1> In a process for the extraction of undesirable components such as sulphur and its compounds and cyanides, e.g. hydrocyanic acid, from composite fluids, particularly petroleum oils in which the composite fluid is passed through a main extraction zone wherein the undesirable materials are extracted from it by absorption in an extracting medium and the extracting medium containing the extracted substance is then passed from the main extracting zone for conversion of the extracted substance into a form amenable for separation by washing from the extracting medium, the conversion and washing steps are carried out concurrently and in the same zone.  The composite fluid is passed from a feed pipe 11 up an extractor tower 10 down which flows an extracting medium which extracts the unwanted components, the purified fluid leaving by conduit 30.  The extracting medium containing the extracted substance is then passed via pipes 16, 18 to a converter 19 wherein the extracted substance is converted, e.g. by the action of air or oxygen supplied through pipe 22, into a form amenable for separation from the extracting medium and concurrently with this conversion process and in the same vessel 19 the converted substance is washed from the extracting medium by a washing liquid supplied through pipes 27 and 18.  The mixture from the converter 19 is led to a separator 12 or settling tank, from which the purified extracting medium is passed by means of pump 13 and pipe 15 back to the tower 10 and the washing liquid is returned to the vessel 19 by pump 26 until the content therein of extracted substance renders its re-use no more profitable, whereupon it is discharged through pipe 27.  In the extraction of sulphur compounds in combination with hydrocarbon radicals from a hydrocarbon solution as found in petroleum refinery practice, the extracting medium may be an aqueous phase such as caustic solution with or without the benefit of promoters or sulutizers.  The fat p  liquor obtained is fed from the bottom of tower 10 into converter 19, where it is mixed with air or steam to convert the extracted sulphurous impurities into different sulphur compounds; mercaptans e.g. being oxidized to disulphides which are washed from the caustic solution by hydrocarbon solution, e.g. that being purified fed from pipe 11 through valve and pipe 21 to pipe 18, or other hydrocarbon solvent from pipe 20, or that separated out in separator 12 to which the mixture from the converter 19 is fed. The caustic solution settled in separator 12 is fed back to tower 10.  The contents of the converter 19 are thoroughly agitated by mechanical agitators 23 or by the introduction of the conversion medium such as air under pressure.  In the extraction of H2S, the extracting medium may be soda ash, the sulphide-laden soda ash being passed from the line 17 to a heater prior to treatment in the converter 19 with air, in the presence may be of a catalyst, to produce elemental sulphur which is dissolved by hydrocarbon oil such as benzol used as the washing medium.  The removal of hydrocyanic acid may be effected by an aqueous caustic soda solution.  The fat liquid from the tower extractor 10 is treated with air or carbonic acid to convert the hydrocyanic acid absorbed thereby and the conversion product washed with a solvent such as an aliphatic hydrocarbon or gasoline.