US2109144A - Process of treating metal - Google Patents

Description

Feb. 22, 1938.

J. O. BETTERTON ET AL PROCESS OF TREATING METAL original Filed Aug. 17, 1933 INVENTORS Jesse 05d/Wlan BYE/iz' 1i Medef] MOM/MS Patented Feb. 22, i938 OFFICE PROCESS F TREATING METAL .lesse 0. Betterton and Y tuchen, N. J., assignors and Refining Company a. Lenssen. M- to erican Smelting New York, N. Y., a oorporation or New Jersey Application August 17, 1933, Serial No. 685,586

newed August 28, 1937 Cla.

This invention relates to an improved process of treating metals to eect the removal therefrom of contaminating metal values.

The invention provides a process for treating 5 molten metal at low temperatures by which contaminating metals are readily and effectively removed without the formation of excessively large amounts of complex slags or dresses.

Among other features, the invention contemplates the establishment and maintenance of a liquid' two phase equilibrium system comprising the molten metal undergoing treatment and a slag which is uid at the operating temperatures employed and also non-reactive with respect both to the metal treated and reagents, if any, used.

It is, of course, well known that as a general rule the degree of solubility of one metal in another varies with the temperature and that fact is commonly taken into consideration in practising ordinary liquidation separations. Again, it is common practise to remove impurites from metals by incorporating suitable reagents therein which will selectively react with the impurities and permit their accumulation and removal .as

drosses. However, these processes or combinations thereof as generally practised usually have some'inherent disadvantages among which may be mentioned the formation of large or excessive quantities of dross, the diculties encountered in treating the dross arising from both the large quantity thereof and its physical and chemical composition, the excessive oxidation of the metal and the loss of eiciency due either to the chemi cal conversion of relatively large amounts of the metal treated to undesired compounds or its mechanical entrapment in the impurity being removed.

The foregoing and other disadvantages are overcome and new and useful results obtained 40 by employing a two phase equilibrium system, in

accordance with the present invention' In geng eral, the improved process may be practised by l covering a molten oath oi the metal to be reiined with a suitable slag, that is, one which is chemically inert with reference both to the metal being rened and the contaminants being removed therefrom and which is and remains duid at the operating temperature employed. By agitating the bath, equilibrium is established and maintained between the different phases of the system. 1n ease the equilibrium value for a particular separation is not sufciently low, suitable reagents may be employed to lower such. value as will be hereinafter described.

The drawing accompanying the specication is a flow sheet illustrating the process ci the invention.

In order to more fully illustrate the many novel features and advantages of the invention several specic examples of the process as applied to 5 decopperizing lead are given, although it is to be understood that the invention is not limited thereby as it may be utilized in conducting other refining operations, such as, for example, the desilverization of lead.

Example 1 In this instance impure blast furnace lead was meltedV down in a cast iron kettle, the dross skimmed and. the bath sampled. The total weight of the bath was 188.5 lbs. and was shown by analysis to contain 0.90% copper, 0.31% arsenic, 1.83% antimony, and 392 oz./ton dor. At a temperature of 850 F., a slag comprising 0.44 lb. of zinc chloride and 0.15 lb. oi sodium chloride wasadded to the surface of the bath and allowed to melt. The bath was then agitated by an ordinary mixing machine beginning at a temperature of 725 F. and continued until the temperature had fallen to 600 F. At this stage a preheated hand operated press was placed in the kettle and the metallic mushy liquate intermixed with the chloride slag was skimmed into the press. The bath was pressed clean at 595 F. and the pressed dross weighing only 6.25 ibs. was found to analyze 25.3% copper. .an analysis oi the final bath which weighed' i822 lbs. showed 0.06% copper, 0.08% arsenic, 1.61% antimony and 392.0 ca /ton of dor.

it will l noted that in Example 1 the copper content was reduced to 0.06%, which figure represents the approximate equilibrium value ior that system. in order, then, to lower that value and further decrease the copper content in acn cordance with the invention, the 182.2 lbs. of lead were treated as follows: the bath wasv reheated to 660 F; and 0.22 lb. of zinc chloride and 0.08 lb. of sodium chloride added and allowed to melt at 640 F. At this stage, 0.360 lb. of zinc dust were incorporated in the bath, after which the mushy drow was pressed as in Example l. The pressed dross weighed 0.9 lb. and analyzed 6.7% copper while the bath weighed 181.7 lbs. and contained 0.03% copper, 0.08% arsenic, 1.67% antimony and 386.5 oz./ton oi dor. l

Example 3 In this instance, a bath of copper-bearing lead weighing 153.7 lbs. after melting down and shim-n copper.

Example 4 One hundred, forty-four and eighth-tenths lbs. of lead were melted in a small cast iron kettle and 1.1 lbs. of dross formed during the melting down operation were skimmed at a temperature of 660y F. By analysis, the bath was found to contain 0.115% copper. Powdered sulfur to the f amount of 0.175 lb. was added to the bath at a temperature of 630 F. and thoroughly incorporated therein. 'Ihis operation was performed in 22 minutes, at which time the dross weighing 17.5 lbs. or 12.08% by weight of the original lead treated was removed from the bath Aat a temperature of 660 F. The molten lead bath was then sampled and found to contain 0.06% copper. At this stage, a slag comprising 1.3 lbs. of zinc chloride and 0.3 lb. of sodium chloride was added to the surface of the bath and allowed to completely melt at 650 F. 'I'he 17.5 lbs. of mushy dross were returned to the bath, the contents of the kettle mixed by hand for a few minutes and the slag skimmed from the bath. The gross weight of the slag was only 3.5 lbs. or a net weight of 1.9 lbs., equivalent to 1.31% by weight of the lead originally treated. The bath analyzed 0.06% copper.

` Example5 One hundred fifty-eight and one-half lbs. of copper-bearing lead were melted in a kettle and the dross formed during the melting operation (1.1 lbs.) removed. By analysis the bath contained 0.12% copper. After adding a slag comprising 0.66 lb. of zinc chloride and 0.25 lb. of sodium chloride, sulfur to the amount of 0.66 lb. was incorporated in the bath at a temperature of 630 F. The slag, weighing 2.3 lbs., was skimmed from the surface of the bath and a sample of the bath takenl which analyzed 0.069% copper. At this stage, a second slag comprising 0.1 lb. of zinc chloride and 0.2 lb. of sodium chloride was added to the surface of the bath. 'I'hereafter, 0.32 lb. of powdered zinc was incorporated in the molten lead and the temperature lowered to a point approaching the freezing point of lead. The molten metal was then tapped from the kettle and found to contain only 0.012% copper and 0.06% zinc.

From the several preceding specific examples it will readily be appreciated that new and improved results are obtained when metals are treated in accordance with the two liquid phase process of the present invention. The ease with which contaminants in metal may be reduced to their solubility limits at the temperature employed without the production of large amounts oi' dross or recourse to any reagents is clearly exemplified by Example l. Examples 2 and 3, among other features, illustrate how the amount of a contaminant may readily be reduced simply by employing a reagent which will lower the equilibrium value. The marked reduction in dross produced by employing the equilibrium system in combination with areagent is amply brought out in Example 4, while Example 5 illustrates the consecutive use of reagents which impart different equilibrium values to a given two phase liquid system. ,f-

It is believed that the improved results obtained by the invention may be in a large part explained on the theory that providing a suitable fluid slag on the molten metal optimum conditions of equilibrium between the bath-and slag with relation to the solubility of the contaminant being removed are at all times maintained. Instead of forming a solid dross upon the surface of the bath, the contaminant is maintained in a liquid state and the metal which ordinarily is enmeshed in the dross is allowed to reenter the bath while at the same time the contaminant being in amounts in excess of the solubility of same in the bath at the temperature employed remains in the liquid slag. Hence, it follows that while a vmixture of zinc chloride and sodiumY chloride has been specifically mentioned by way of illustration, any slag, which is fluid at the temperatures employed and which will not react with the metal or reagents, if any, used, may be utilized. It is, of course, obvious that the slag will also serve the secondary purpose of preventing oxidation of the bath and reagents. Y

It is obvious that in addition to decreasing the amount of dross lformed, the invention facilitates the handling and processing of the slag containing the contaminants removed from the metal both from the standpoints of quantity and physical composition. For example, slags obtained by decopperizing lead may be leached with water to remove the soluble constituents therefrom and the4 residue smelted to produce a concentrated copper matte which is readily processed for the recovery of copper.

While certain novel features of the invention v have been disclosed and are pointed out in the annexed claims, it will be understood that various omissions, substitutions and changes may be made by those skilled in the art without departing from the spirit of the invention.

What is claimed is: A

1. In the process of removing copper from lead by incorporating a decopperizing reagent in the molten lead whereby copper is concentrated asa dross, the improvement which comprises conducting the operation in the presence of a uid slag comprising a mixture of"zinc chloride and sodium chloride thereby concentrating the copper in a combined slag and dross of small weight.

2. A process of reflning copper-containing lead, which comprises forming Aa molten bath of the lead, producing on they said bath a molten slag layer comprising zinc chloride and sodium chloride, the slag layer remaining fluid at the temperature of operation and being substantially inert with respect to the lead in the bath, produc- 1 o temperature of the bath and beingsubstantially 1 inert with respect to the lead in the bath, liqu'ating the bath to produce a dross o; the copper contained in the lead, and agitating the bath and slag to concentrate the dross in the slag, thereby establishing conditions of equilibrium between the bath and slag, the said slag being adapted to retain the dross while returning to the bath the lead which was entrapped in the dross.

4. A process of refining copper-containing lead, which comprises forming a molten bath of the lead, producing on the said bath a molten slag layer comprising zinc chloride and sodium chloride, the slag layer remaining fluid at the ternperature of operation and being substantially inert with respect to the lead in the bath, adding to the bath a reagent for the copper adapted to produce a separation of the copper from the bath as a dross, and agitating the bath and slag toconcentrate the dross in the slag, thereby establishing conditions of equilibrium between the bath and slag, the said slag being adapted to retain the dross while returning to the bath the lead which was entrapped in the dross.

5. The process for rening lead by liquation with production of a minimum amount of dross which comprises forming a molten bath of the lead to be liquated, establishing on the bath a fluid, salt slag which is chemically non-reactive with respect to lead and which will retain its uidity throughout the liquating temperature range, bringing the bath and slag into equilibrium with respect to the impurities to be removed by mixing the bath and slag while simultaneously cooling same thereby concentrating impurities in the slag with minimum production of dross and effecting a separation between the refined lead and the slag.

JESSE O. BETTERTON. YURII E. LEBEDEFF.

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