US2204651A - Process for refining lead which contains bismuth - Google Patents

Description

Patented June 18, 1940 PATENT orr ea PRO ESS FOR REFINING LEAD WHICH CONTAINS BISMUTH;

Jesse O. Bettcrton and Yurii E. Lebedeff,

.; K Metuchen, N. J., assignors to; American Smeltl i 1 ing and Refining Company, New York, N. Y.,

a ,ccrporation of New Jersey ticularymetal mixture or alloy and introducing alkali, alkaline earth or rare earth metal reagents therein for the purpose of concentrating one or more of the constituents of theoriginal alloy as v dross or crust which floats upon the molten bath and is readily separated therefrom.

However, early attempts to specifically apply the suggestionto the lead refinery for the removal ofbismuth failed and the advent of any successful, commercialprocesshad to await later discoveries, rjri'anyof which the readerwill find discussed or referred to in an article by applicants appearing in Transactions of the American Ina stitut of" Mining and Metallurgical Engineers,

vol. 121,1pages 205 225 (1936).

Following the discoveries aforementioned, their principles weresoon adapted by various refineries treating thousands of tons annually of lead containing bismuth in the amounts ordinarily encountered which, asis well known, usually range in the neighborhood 'of a few hundredths to afewftenths per cent. In this connection it is highly significant to note that, insofar as applicants are aware, all of the refineries referred to employ calcium as a reagent in debismuthizing such lead.

The present invention provides a process for the removal of bismuth from lead which renders the use of calcium unnecessary. This new process is based upon the simultaneous action of magnesium and alkali metal which action was the more incapable of being predicted since none of the alkali metals alone produces any elimination of bismuth and magnesium alone only produces a partial elimination of bismuth in alloys containing a high content thereof.

The process for deb-ismuthizing lead without the aid of calcium which forms the subject of the present invention thus consists essentially in adding to lead which contains bismuth and which has been previously molten, magnesium and alkali metal in suitable quantities and then allowing the metal bath to cool to near its temperature of solidification.

There is thus formed a floating crust containing bismuth, magnesium, alkali metal and lead and which is separated from the bath of metal by any known process.

This floating crust will contain, according to the proportions of magnesium and alkali metal used,

Application December 24, 1938,

Serial N0. 247,660

the desired part of the bismuth contained, and up i to substantially the whole of the bismuth content.

After thistreatmentthe lead ordinarily contains an excessof magnesium and alkali metal from which it can be freed by any known treatment, for example, with chlorine.

For putting the process according to the invention into effect, themagnesium and alkali metal, e. g;, sodium, may be employed in the state of pure metals or of alloys with lead or with other metals," and by adding successively or simultaneously to the bath of impure metal to be treated. If desired, the proportion of magnesium or alkali metal utilized may be diminished and this ,,diminution be ,compensatedby an increase of alkali met'algor magnesium taking care always to provide a simultaneous or successive addition of alkali metal andmagnesium; one may thus in particular confer upon the refining process additional advantages such as, for example, minimum costs of the reagents employed, greater ease in the treatment of drosses, etc.

It may be noted that if the lead from which the bismuth isto be removed contains, besides bismuth other impurities, these may be partly or wholly contained in the dross with the bismuth. However, as there are atpre'sent efiicacious means for the separation of these other current impurities from impure lead, it may be more economical to separate from the lead to be treated the greator part of its other impurities before applying the process of the invention for the removal of hismuth.

The invention isillustrated in'the following non-limiting examples? Example I A lead containing 0.30% of bismuth is treated in the fused state with an' addition of magnesium equal to eight pounds per short ton and an addition of sodium equal to twelve pounds per short ton. After agitation and cooling to the neighborhood of the temperature of solidification, the floating crust is separated. The lead obtained contains only 0.007%, of bismuth.

Example II calcium used, the sole debismuthizing reagents being sodium and magnesium in the first example and lithium and magnesium in the second example. The results are remarkable in view of the fact that no substantial reduction of bismuth could have been made in the lead of the examples either with alkali metal or with magnesium, alone.

What is claimed is: I 1. Process for refining lead which contains. bismuth, consisting in adding to the lead-in the molten state magnesium and alkali metal, cooling the metallic bath to the neighborhood of its solidification point and then separating therefrom the floating crust in which the bismuth has collected, said process being performed in the absence of calcium. I

2. Process for refining lead which contains bismuth without the aid of calcium, consisting in adding simultaneously to the lead in the molten state magnesium and alkali metal, cooling the metallic bath to the neighborhood of its solidification point and then separating therefrom the floating crust in which the bismuth has collected.

3. Process for refining lead which contains bismuth without the aid of calcium, consisting in adding successively in either sequence to the lead in the molten state magnesium and alkali metal,

cooling the metallic bath to the neighborhood of its solidification point and then separating therefrom the floating crust in which the bismuth has collected. I

4. Process for refining lead which contains bismuth without the aid of calcium,-consisting in adding to the lead in the molten state magnesium and alkali metal in the state of alloys with lead, cooling the metallic bath to the neighborhood of its solidification point and then separating therefrom the floating crust in which the bismuth has collected.

5. Process for refining lead which contains bismuth without the aid of calcium, consisting in adding to the lead in the molten state magnesium and alkali metal in the state'of alloys with other metals, cooling the metallic bath; to the neighborhood of its solidification point and then separating therefrom the floating crustin which thebismuth has collected. v r

the other.

7. Process for refining lead which contains bismuth, consisting in bringing to simultaneous action on the lead in molten state magnesium and alkali metal, cooling the metallic bath to the neighborhood of its solidification point and then separating therefrom the floating crust in which the bismuth has collected, said process being performed in the absence of calcium.

.8. Process for debismuthizing lead which comprises mixing magnesium and alkali metal into a molten body of the lead, cooling same to raise a crust having a higher bismuth content than the original lead, and effecting a separation between said crust and the refined lead, said debismuthization being effected without the aid of calcium reagent.

9. Process for refining lead containing bismuth a acterized in that the process is performedwithout the addition of calcium to the lead.

10. Process for refining lead with respectto bismuth as a contaminant which comprises subjecting the lead in molten state to the conjoint action of sodium and magnesium, concentrating the bismuth as a bismuth-lead-sodium-magnesium product at a temperature favoring such concentration, and efiecting a separation between said product and the rest of the lead, said process being carried out in the absence of any ei'fective amount of calcium reagent.

JESSE O.'BE1'1ERTON. YURII E. LEBEDEFF.