Patent GB-519332-A (GB)
Title: Improvements in the manufacture of compositions of lead and its oxides
IPC: C01G21/02
Filed: 1938-09-20
Abstract: 519,332. Ball mills; centrifugal machines. RICHARDSON CO. Sept. 20,1938, No. 27444. Convention date. June 27. [Classes 23 and 59] [Also in Groups III and XXXVI] A composition of lead and its oxides containing variable percentages of lead, preferable over 50 per cent. and suitable for use in storage batteries is produced by reducing the lead to a uniformly finely divided condition and milling the metal in the presence of a heated oxidizing atmosphere while continuously removing oxidized material, providing a controlled circulatory system for the oxidizing atmosphere in the mill, controlling the temperature in the mill, classifying the oxidized material and returning the coarser materials continuously to the mill for reprocessing. In apparatus for carrying out the process, the finely divided lead is introduced into a mill 34 thence to the classifier 41 from which material of a predetermined fineness is removed whilst material not of that fineness is returned to the mill, thence to the separator 52 all these devices being connected in a closed circuit through which the oxidizing gas is impelled by the fan 49. The mill may be of any type, but is preferably that known as a Hardinge mill running on the hollow trunnions 35 and 36. The finely divided lead together with suitable impact devices are introduced into the mill and concurrent attrition and oxidation occur. The more finely divided product is swept out by the air stream through the duct 40 to the classifier. The coarser materials pass downward through the check valve 43 into a casing 44 and thence to the trunnion 35 via the conduit 45 which also serves to introduce the raw material and impact devices into the mill. The finer portions in the classifier are swept on by the air stream to the separator where the solid material is led off by the conduit 53 and the air is led via conduit 54 to the casing 44 for recirculation. On the suction side of the fan is a bleeder 50 to admit new air to the system while any excess leaves via the conduit 55 to a baghouse where dust is separated. The composition and degree of subdivision of the final product may be controlled by adjusting the temperature of the mill, degree of classification, i.e. the amount of recirculation, and the amount of fresh air admitted to the system. The former may be accomplished by an adjustable source of heat beneath the mill the operation of which is assisted by the thermocouple 38 and dial 39. The amount of classification is adjusted bv means of a valve 60 in the conduit 59 which leads air from the conduit 54 to the classifier thus by-passing the mill to a certain extent which if increased tends to carry more of the pulverized product on into the separator 52. The ducts may be lagged as at 40b and material is prevented from accumulating in the gooseneck 40a by a mechanical scraper or electric vibrator. The raw material is preferably filamentous lead wetted and allowed to dry thus commencing hydration. This drying process may be accomplished in a cylindrical steamjacketted hopper having paddles or agitating devices. Specifications 497,586 and 497,610 are referred to.