Patent GB-783644-A (GB)
Title: Granular solids withdrawal method and apparatus
IPC: B01J8/00
Filed: 1955-06-17
Abstract: <PICT:0783644/III/1> <PICT:0783644/III/2> <PICT:0783644/III/3> <PICT:0783644/III/4> A process in which a liquid (e.g. mineral oil) is treated (e.g. decolorized or converted by contacting it with granular solids (e.g. fuller's earth) within a confined contacting zone, and in which a slurry stream of liquid and granular solids is withdrawn from the contacting zone in liquid type flow and passed through a confined elongated passage to an adjustable flow obstruction, and in which the composition of the stream is unsuitable for dependable control of the granular solids withdrawal rate by the adjustable flow obstruction, includes the improvement which comprises: withdrawing liquid from the slurry stream in an amount sufficient to cause the stream to assume the state of a wet mass of granular solids capable of dependable flow control by the flow obstruction, and using the latter to achieve the desired rate of solids flow in the contacting zone.  The treatment plant of Fig. 2 (not shown), differs from that shown in Fig. 1 of Specification 711,487 in that the apparatus for controlled withdrawal of solids interposed between the oil-treater and the solidswasher, and again between the solidswasher and the solids-drier, is replaced by the apparatus described below, and in that a regenerator is shown interposed in a return line for solids from the drier to the treater. In Fig. 3, liquid-solids mixture issuing from the collector of the treater or from the foot of the washer (neither shown) emerges at 21 into a screw-conveyer 20 having a perforate portion 69 surrounded by a casing 70 to which vacuum may be applied at 22 for withdrawal of liquid and to which backwash liquid may be supplied at 71 for cleaning the part 69.  Sufficient liquid is withdrawn to convert the mixture into no more than a wet mass of granular solids whose rate of removal through an outlet 27 may be effectively controlled by control of the rate of rotation of the screw 68.  The latter control is exercised by a device (not shown) connected to the motor 75 and governed in turn by a device which observes the level of the top of the bed in the treater, the solids removal rate being automatically adjusted to maintain the bed-height constant.  Pressure may be maintained in the treater by admission of an inert gas at 78.  In Fig. 4 (not shown) the perforated portion 69 and chamber 70 are located at the lower end of the pipe 21, and the conveyer 20 lies below it at a small inclination to the horizontal.  In Fig. 5 liquid drains by gravity through an accumulation 83 of granular solids and through a conical screen 82, the solids being removed at a controlled rate by screw conveyer 20.  In Fig. 6 the underside of the screw conveyer casings consists of a screen 69 through which liquid drains into a receptacle 85.  In Fig. 7 a flat screen 89 and a solid-support member 90 partition-off a liquid-receiving chamber 91 in a conduit 86 between flexible couplings 87 (connected to inlet 21) and 88 (connected to outlet 27).  The conduit 86 is vibrated at a rate designed to ensure the desired solids flow rate.  In Figs. 4 and 5 a bucket wheel, a scoop or a moving compartment belt may be used instead of a screw conveyer.  In Fig. 8 (not shown), the pipe 21 is vertical throughout, and below a chamber 70 located around a perforate portion of the pipe a valve, instead of a screw conveyer, is provided in the pipe.  The valve may be replaced by a plate having a variety of differently-sized orifices capable of being positioned within the pipe.  In all cases two solids-controlling devices are arranged in parallel so that one may be used when the other is choked.