US2049633A - Reclamation of battery plate scrap - Google Patents

Description

Patented Aug. 4, 1936 Y f UNITED STATES PATENT OFFICE RECLAMATION OF BATTERY PLATE SCRAP Alfred M. Thomsen, San Francisco, Calif assignor to Thomsen Chemical Corporation, a corporation of California I No Drawing. Application February 24, 1933,

7 Serial No. 658,447,

4 Claims. '(Cl. 75 -77) This application is a continuation in part of 'continuously or intermittently. It will be 'eviapplication Serial No. 609,765, filed May 6, 1932. dent that the charge is kept in a state of con The development of the storage battery has tinuous agitation bythe motion of the roaster, given rise to a new form'of industrial waste,- and thus every opportunity is given the globules 5 namely, old battery plates. Such battery plates 7 of molten 'metal to sift downwards and join are really a mixture of two different substances; the pool of such molten metal which gradually the metallic grid, which is composed of antiforms at theitalus of the sliding, unmelted' parmonial lead, and the paste, with which the ticles, drawn up to the properangle of slip by the grid is filled. Such paste is composed of a mixmotion of the'roaster.

10 ture of the oxides and sulphates of lead, and Having thus separated the fusible from the 10 it is'entirely free from antimony. Direct blast infusible portion of the charge, the temperature furnace smelting of this kind of a mixture can, is raised to the point at which the sulphur comof course, only result in the recovery of a low pounds are broken down with-the formation of antimony alloy,'for, as the ingredients described lead oxide, andthe operation continued as a W are present in about equal proportions, it follows roasting step until only crude litharge remains 1:;

that the resultant metal will only contain half in .the roaster. of the antimony required to qualify as anti- Manifestly, it is impossible to separate the monial lead. V metallic portion from the non-metallic portion The customary reclamation practice of to-day of battery plates with absolute precision by the is to charge the plates into a oupola, and to smelt procedure thus far described. A small amount 20 them, with coke as fuel, into a low-grade, imof shots, or globules, of antimonial lead will be pure antimonial lead. This operation is attended retained in the pulverulent residue remaining by much loss, and virtually puts this high-grade in the furnace, and this metal will in the roastmaterial in the same class as an undesirable antiing step, as previously described, be converted monial lead ore. In order to purify the resultant. into oxide. The crude litharge will therefore 25 low-grade metal obtained from present day contain a certain small percentage of antimony practices, it must be liquated at least once, if oxide. Should it be desirable torender this pernot twice, drossed, oxidized, and reduced. It centage as small as possible, then the pulverumust then be brought up to market standards lent residue, remaining after'the liquation of all by the addition of the requisite amount of metalthe metal that may be drawn from the furnace, 3O lic antimony,-all of which means considerable is discharged, cooled, and passed through a mill, I

expense. such as a set of rolls, or a rod mill. As the My improved process varies radically from 'paste is very brittle, the effect of the mill these present day practices; to elucidate: will be to reduce it to a powder. And as the 5 If we consider the difference in melting point shots of lead, in spite of their antimony conbetween the metal portion and the paste, we tent, are still somewhat malleable, they will find that the metal fuses at below 350 C., that flattenif not too harshly treated. The ground lead oxide fuses at about 900 C., and lead sulresidue may therefore undergo a further puriphate at over 1100 C. It is therefore evident fication by means of screening,-most of the 4 that if the material be heated to a temperature mechanically admixed antimonial lead being re- 40 intermediate between these extremes, then there tained upon the screen, while the undersize will will be effected a separation between the paste be. almost free from antimony. The further and the metallic portion. Furthermore, as the roasting of this undersize tocrude litharge will specific gravity of the metal is over 11, and the be much facilitated by the fact that it is now specific gravity of the paste somewhere bein the form of a line powder, and the roasting i5 tween 9 (for lead oxide) and 6 (for lead sultime will therefore be much shortened. phate), depending upon the relative quantities The breaking up of sulphates in this roasting of these substances present, it will be evident, is aided by the presence of carbon (such asis also, that the tendency of the lead will be to already present as charcoal from plate separatsettle to the bottom, and for the paste to ors), but additional carbon may be added. The e0 float on top of the melted lead. action of this carbon is to reduce the sulphate To carry out this step I prefer the use of a to s ph de, which in turn then exercises a, re-

revolving roaster, in which the solid oxidized ducing action on lead oxide. Such reduced lead lead compounds may readily be retained while the will soon be re-oxidized to litharge, and the sulmobile fused lead is allowed to flow away, either phur has thus been eliminated. s5

Of course, I may avoid the use of the cupola altogether if I now add sufficient carbon in some form (coke, coal charcoal, etc.), to the charge Within the revolving roaster.- This will reduce sulphate to sulphide which in turn will reduce the oxide with which the sulphide is in contact, and the oxide itself will likewise be reduced thereby. 11 may -,thus obtain most of the lead of the charge-in the form of puresoft lead,'eliminating at once the need for the cupola, the drossing furnace, and the softening kettle.

The type of work described in :the last ,two paragraphs is a modern version of Die Roestre-aktions-Arbite, which, in English -is better given by the term roast-reduction, employed in the claims. For full description, reference is made to any work on metallurgy which devotes space to old fashioned procedures-such -:a;s Hofimans Metallurgy of Lead, where, in the seventh impression, chp. 6, we are given a full exposition of reverberatory furnace practice in lead ores. 1t Will;be:se1f-;evidentithat theaddition of carbon. above referred to, toia ;residual of lead sulphate and oxide :will be entirely .in accordance with {the ;description.. Whenever in the claims the expression ".froastereduction :is used it, means ,that combination ;of oxidation and reduction as described in the e-aboveementioned chapter.

H v n thus described improvement, I claim:

1. A process for separating the fused metallic from the unfused non-metallic constituents .-of battery plate, which comprises first heating the material to be treated to a temperature sufficient to fuse the metallic alloy but insuflicienttomelt tion, said liquation being effected by heating 'the .charge,contained within a revolving roaster, to

a sufficiently high temperature to fuse the metallic ingredient while the non-metallic ingredients remain unfused, and submitting the furnace residue to the operation of grinding and screening .for a more thorough separation, substantially as and in the manner indicated.

3. In the process of reclaiming battery plate scrap, the step of separating the fused metallic fromm'the... non-rinsedv non-metallic ingredient withinaairevolving roaster, removing the, fused metallic ingredient, and eliminating the sulphate-sulphunin :the;residue through the additionnf carbonaceous material by roast-reduction treatment. b V

zihinttherprooess of reclaiming-battery plate scrap, ithestep of removing the major portion of antimony there in ;the form of ,antimonial lead byiusion, fol-lowed hyla further removal of part 1 Qfzthesremaining lantimonial lead by grinding and..-screening, submitting-the residue to roastreduction treatment, andsoftening the lead thus produced to obtain the remaining antimony in theform of ,antimonial litharge.

ALFRED 1M. THOMSEN.