Patent GB-690401-A (GB)
Title: Improvements in the dry dust freeing of coals and similar materials
IPC: B07B4/02
Filed: 1951-02-09
Abstract: 690,401. Pneumatic separating. HARVENGT, F. Feb. 9, 1951 [Feb. 10, 1950], No. 3275/51. Class 117 In a method of freeing dry coals and like materials from dust the major portion of - dust and fine particles is initiallv removed by a gaseous fluid current and the residual coarse particles are subiected to preliminary and final treatments in separate fluid currents to complete the dust removal, the fine particles being separated out from the said major portion of dust and fine particles resultins from the initial removal and being subjected to a dust removal treatment in one or more fluid currents separate and distinct from the preliminary and final treatments of the coarse particles. As shown material is fed from a hopper 1 via a valve 2 into a vertical conduit 3 to fall on adjustably spaced and sloping blades 9 forming an apertured wall of the conduit 3 opening into an expansion chamber 10. The initial removal of the major portion of dust and fine particles is effected by an air current flowing up through the conduit 3 and carrying the said dust and fine particles between the blades 9 into the chamber 10 where the fine particles settle out, the dust being carried on via a conduit 5 and a spiral expansion chamber 25 to a cyclone 6 connected to a main suction fan. The residual coarse particles fall through the conduit 3 to pass the air inlet 4 near the bottom of the conduit. the air current entering at this point effecting the preliminary treatment of the coarse particles. From the base of conduit 3 the coarse particles are delivered via a valve 14 into a second vertical conduit 15, at a point intermediate its height. to meet a second upwardly flowing air current entering the conduit 15 through a bottom inlet 16 and. where desired, through additional inlets 17. The final treatment of the coarse particles is effected in the lower portion of the conduit 15 and the dust free particles are discharged via a valve 18. The fine particles separated out in the expansion chamber 10 are collected in one or more hoouers 11b, 11a in decreasing order of particle size, and each hopper delivers the particles via a valve 12h or 12a to a separate vertical conduit 20b or 20a arranged beside the conduit 15 and having separate valve-controlled air inlets 21b, 21a and discharge openings 23b, 23a. The conduit 3, via the chamber 10, and the conduit 15 join at their upper ends with the conduit 5, the conduits 20b, 20a being connected either with the conduit 15 below the junction with conduits 3 and 5 or directly with conduit 5 above the junction. A flap valve is aranged at the said junction to control the relative amounts of air sucked into the conduits 3 and 15 respectively, and where necessary to boost the air currents in the conduits 15, 20b, 20a, a blower 32 with a selector valve 32b is provided. Any fine particles which settle out in the expansion chamber 25 are delivered via a valve 28 to a conduit 27 having a valve 30 whereby the particles may either be discharged or delivered wholly or partially into the conduit 15 into the zone of final treatment of the grains. In alternative arrangements described, the spiral expansion chamber 25 may be replaced by an expansion chamber in the conduit 15 having an adjustable wall to vary its cross-section or the conduits 3 and 15 may lead to separate cyclone separators via separate conduits each with an expansion chamber. The blade 9 in the wall of conduit 3 may be replaced by a fixed or vibrating sieve to assist in the initial removal of dust and fine particles, and the air intake into conduit 3 may be controlled by a rotary device causing a pulsating flow in the conduit 3. The fine particles collected in the expansion chamber(s) 25 may be delivered for further treatment into one of the conduits 20b, 20a instead of into conduit 15 as above. Specification 690,400 is referred to.