US2462783A - Apparatus for refining zinciferous lead - Google Patents

Description

Feb. 22, w49., w. w. sHRoPsHIRE @PPARTUS FOR REFINING ZINCIFEROS LEAD Original Filed Dec. 22, 1'943 ATTORN EYS Patented Feb. 22, 1949 2,462.183 APPARATUS Foa adi-:mme .zmcIFEaoUs William Wallace Shropshire, Chicago, Ill.,vassign or to International Smelting and Rening Company, a corporation vof Montana original application December ze, 19413, serial No.

1946, Serial No. 666,432

. l This invention relates to apparatus suitable for refining of zinciferous lead, and has for its object the provision of certain improvements in apparatus suitable for refining zinciferous lead with chlorine. This application is' a division of my copending application Serial No. 515,231, ,illed December 22, 1943, now Patent No. 2,411,940.

In desilverizing argentiferous lead by the Parkes process, the desilverized lead contains upwards to 0.55% zinc. This zinc must be removed to render the lead salable. While several methods are known and practiced for dezincing such zinciferous lead, the present invention is primarily concerned with the process in which the zinc is removed by the preferential action of chlorine on zinc when the chlorine is brought into contact with a mixture of lead and zinc in the molten state. As is well known in the art, chlorine reacts preferentially with zinc as long as any zinc is present in the molten metal, in accordance with the following reaction:

If and when the zinc has been practically all removed and chlorine remains in contact with the dezinced lead, the following reaction will take place:

While this reaction and the resultant formation of lead chloride is not desirable, in practice it is permitted to take place in order to completely dezinc the lead at a satisfactory rate, and consequently some lead chloride is produced with and at the same time as the nal zinc chloride is produced. This formation of lead chloride gives rise to lead losses of considerable magnitude, and further contaminates the otherwise pure zinc chloride product, so that the contaminated product must be purified before it can be sold as zinc chloride.

The processes and apparatus heretofore commonly used for dezinclng zinciferous lead produce a zinc chloride slag or product contaminated with lead chloride. Furthermore, no entirely satisfactory method is available for separating or removing the slag of mixed zinc and lead chlorides from the surface of the molten refined lead except by laborious skimming or ladling. This method of handling the slag is costly, and taken with the cost of the subsequent purlcation of the slag, so increases the cost of the dezincing treatment as to frequently render it of doubtful economy.

The present invention aims to overcome the Divided and this appllcatlonvMay 1,

foregoing objectionable and costly features in the heretofore commonly practiced methods of dezincing zinclferous lead by the action of chlorine. I have discovered that it is possible to vrefine the zinciferous lead with chlorine, purify the resulting zinc chloride slag, and separate the puriiied zinc chloride from the refined lead in substantially one operation. Based on this discovery, the present 'invention provides improved apparatus suitable for use in refining zinciferous lead by the action of chlorine. In accordance with the invention, apparatus is provided so that chlorine may be introduced at spaced intervals along the length of an elongated bath of molten zinciferous lead of progressively decreasing zinc content and thereby there is formed on the surface of the molten metal a molten slag of mixed zinc and lead chlorides of progressively decreasing lead chloride content in the direction of `the progressively increasing zinc content of the g5 tent, and so that zinc chloride (preferably substantially free from lead chloride) may be withdrawn from the bath approximate its other end. The apparatus is arranged so that the operation may be carried out in a continuous manner by continuously supplying molten zinciferous lead to that end of the elongated bath of maximum zinc content, continuously withdrawing molten lead (preferably substantially zinc-free) from the other end of the bath, and continuously withdrawing molten zinc chloride (preferably substantially free of lead chloride) from the bath approximate the supply of zinciferous lead thereto and at a levelabove the level of the bath.

The apparatus of the invention is particularly adapted for dezincing zinciferous lead with chlorine, but is also adapted for various other treatments of molten metals. Generally speaking, the apparatus comprises a container having a. novel arrangement ofpartitions and ballles inducing and permitting countercurrent movement of a bath of molten metal and an overlying layer of molten slag, with means for supplying and withdrawing metal from the molten metal bath and for withdrawing slag from the overlying layer thereof.

The invention will be better understood from the following description taken in conjunction with the accompanying drawings in which,

Fig. 1 is a top plan of the apparatus vof the.i

invention,

Fig. 2 isa longitudinal sectional elevation on the section line 2-2 of Fig. 1, and

Fig. 3 is a transverse sectional elevation on Ythe section line 3--3 of Fig. 1.

As illustrated in the drawings, the apparatus comprises a rectangular container or tank 5 open at-the top, but covered, in operation. with a suitable hood 6 (Fig. 3). The container is divided into two compartments 'I and 8 by a centrally positioned longitudinal partition 9. The height of the partition 9 corresponds substantially with the depth of the container 5. One end of the partition ts snugly against the adjacent end of the container and the other end of the partition is provided with two openings I and II at dierent levels. The opening I0 is at or near the bottom of the container. While the opening II is near the top of the container, and the two openings thus permit communication between the two compartments 1 and 8 near the bottom and top thereof, respectively. The two communicating compartments I and 8 form an elongated treatment zone having an effective length about twice the length of the container.

The compartment 1 of the container has a transverse bailie I2 near the end opposite the openings I0 and II of the partition 9. The baille I2 depends from the top of the container to within a short distance of the bottom, thereby providing a space beneath the baille for the ow of molten metal. The compartment 8 has, at the same end, a similar transverse and depending baille I3, although the baille I3 is' somewhat nearer the end of the container than is the baille I2.

An external (slag-discharge) well I4 is provided adjacent the compartment 'I and slightly further from the end of the container than the baille I2. Communication between the compartment 1 and the Well I4 is provided by two openings I5 and I6` at different levels inthe side wall of the container (Fig. 3). a discharge outlet I1 at about the same level as the upper opening I6.

, The baffle I2 forms, in effect, a charging well I8 communicating (beneath the baille I2) with the compartment 'I. Molten metal is supplied to the charging well I8 from a delivery pipe I9. The baille I3 forms, in eect. a discharging well 20 at the same end of the container, in communication (beneath the bame I3) with the compartment 8. The discharge well 20 has an outlet 2| at approximately the same level as the lower edge of the opening II, and slightly lower than the upper opening I6 into the slag-discharge well I4. An outlet 22 communicating with the bottom of the compartment 8 is provided for emptying the container.

Pipes 23 having valves 24 depend from a header 25 into the compartments I and 8 at spaced intervals in the length thereof. These pipes serve to supply chlorine to the molten lead, and it will be noted that a substantial distance separates the (slag-discharge) well I4 and the nearest chlorine delivery pipe 23.

In employing the apparatus illustrated in the *drawingsl for dezincing lead with chlorine, a molten zinciferous lead is delivered from the pipe I9 to the charging well I8 communicating with the compartment 'I. The molten metal may be derived fromk any suitable source, such as a furnace, kettle or the like, and may be supplied to the delivery pipe I9 in any appropriate mantainer to the level controlled by the overow pipe 2I,.is conducted back to a molten metal reservoir.

Chlorine gas is introduced into the molten metal bath through the pipes 23, the rate of chlorine delivery of each pipe being capable of individual adjustment through the valves 24.

With molten metal owing or circulating through.

the container, chlorine in controlled amount is allowed to pass through the pipes 23 into the moving elongated stream or bath of molten metal. The'chlorine reacts with the zinc and some lead to form a molten slag of mixed zinc and lead chlorides which rises to the surface and oats on the molten metal. Baftle I3 traps the molten slag on the metal discharge end of the container, and in order to leave the container the slag must rise to the level of the opening I8 of the slag-dischargewell I4. Thus, as slag is continuously formed and builds up to a level slightly higher than the opening I 6, a continuous ilow of slag is maintained from compartment 8, through opening II (the lower edge of which is approximately coincident with the molten metal level), into compartment 7, and thence to the slag-discharge well I4. The ilow of the molten slag is countercurrent to the ow of the molten metal upon which it iioats.

By appropriate control of the rateof impure metal delivery (through pipe I9), or of the chlorine delivery rate. or both, the metal becomes progressively lower in zinc content in the direction of its ow until it reaches the metal discharge well 28 as dezinced metal. In the final stages of dezincing, that is towards the end of the compartment 8 adjacent the metal discharge well 20, some lead chloride will be formed, and, mixed with zinc chloride, will ow towards the slag discharge well I4. In the course of its'ilow, and more particularly towards the end of the compartment 'I adjacent the charging well I8 where the zinc content of the molten metal is highest, the lead chloride reacts with zinc to form zinc chloride and lead, in accordance with the following reaction:

Thus, the lead chloride content of the molten slag decreasesin the direction of its .ow. -until approximate the slag discharge well I4 the slag into the molten metal for some distance from the well in the direction of the molten metal flow. The relatively high zinc content of the molten metal in the vicinity of the slag discharge well insures the removal of lead chloride from the slag before it flows into the slag discharge well. From the slag discharge well I4 to the metal discharge well 20, the lead chloride content of the iloating slag progressively increases.

The zinc chloride slag, substantially free of lead chloride, flows by gravity from the compartment 1, through the opening I6 into the slag discharge well I4. The relatively quiescent condition of. the molten metal and slag in this well permits any metal entrained in the slag to settle out, and to return to the compartment 'l through the lower opening I5. at a higher level than the metal overflow pipe 2 I', only slag can be discharged through the opening I6. The molten and puried zinc chloride (slag) flows by gravity through the outlet Il into any suitable container. It may be barreled for shipment without further treatment, or it may be discharged into water, dissolved and recovered as zinc chloride solution.

The apparatus of the invention permits the complete dezincing of zinci'ferous lead and the production and recovery of substantially pure zinc chloride in a single operation. The rate of passage of the molten metal through the container depends upon the zinc content of the metal. While I now prefer to eiect the complete dezincing of the lead with one passage through the container, it is to be understood that the molten metal may be recirculated through one container until completely dezinced, or passed consecutively through two or/ more containers in series. The invention results in higher and more satisfactory metal recovery, reduces labor requirements, and saves wear and tear on unnecessary equipment.

While I have particularly described the apparatus of the invention in connection with the method described and claimed in my aforementoned copending application, the apparatus may be used with advantage in various other treatments of molten metal in an elongated treatment zone, and particularly where countercurrent movement through the elongated zone of molten metal and iioating slag or the like can be advantageously utilized. -The arrangement of partition and bailes provides within the container an eiective treatment zone about twice the actual'length of the container. The openings or ports permitting iiow of molten metal between the wells and compartments are positioned below the normal molten metal level, while the openings or ports through which slag iloating on the surface of the molten metal may ow are positioned at or slightly above the molten metal level.

way, molten metal and slag are effectively separated, and can be separately treated, while moving or iiowing in relatively opposite directions with the advantages incident to the treatment of counter-currently moving reacting bodies or materials.

I claim:

l. An apparatus for treating molten metal comprising a container, a longitudinal partition dividing the container into two adjacent compartments and having approximate one end of the container two openings at diierent levels permitting communication between said two compartments, a molten metal charging well communicating with one of said compartments and a molten metal dis- In this Since the opening I6 is i charging well communicating with the adjacent matesaid charging well and having an opening permitting' communication between the slag discharge well and the compartment in communicathe container two openings at different levels permitting communication between said two compartments, the upper opening in said partition being at approximately aY predetermined level for molten metal in the container and the lower opening being near the bottom of the container, a molten metal charging well communicating with one of said compartments and.

a molten metal discharging well communicating Awith the adjacent compartment, each o! said wells being positioned at the end of the con-f talner opposite the end where the two compartments communicate as aforesaid and the only communication between each Well and its compartment being near the bottom of the compartment, an outlet for said molten metal discharging well at approximately the level of the upper opening in said partition, whereby said outlet establishes the aforesaid predetermined level for the molten metal, a slag-discharge well approximate said molten metal charging well and having two openings at different levels permitting communication between the slagdischarge well and the compartment in communication therewith, the upper opening in the slag-discharge well being at a higher level than said molten metal outlet and the lower opening being beneath. t'ie normal molten metal level in the container, and an outlet for said slagdischarge well at approximately the level of the upper opening in that well.

3. An apparatus for dezincing zinciferous lead comprising a container, a longitudinal partition dividing the container into two adjacent compartmentasaid partition having near one end thereof two ports providing communication between the two compartments (l) at approximately a predetermined level for molten lead in thev container and (2) near thev bottom of the container, a charging well for delivering molten zinciferous lead to one compartment at the end opposite the end where the two compartments communicate and wholly below said predetermined level, a discharging well for withdrawing molten dezinced lead from the other compartment at the same end of the container as said molten metal charging well and wholly below said predetermined level, an outlet for said discharging well at approximately the level of the upper of -said two ports in the partition, whereby said outlet establishes the aforesaid predetermined level for molten lead, a slag-discharge Well positioned near said -molten metal charging well for withdrawing molten slag from the container at a level higher than said predetermined level, and pipes for introducing chlorine into each compartment at spaced intervals along the length thereof except in the vicinity of said slag withdrawing means, said pipes'being arranged to deliver the chlorine at a point well below said predetermined level.

4. An apparatus for dezincing zinciferous lead comprising a container, a longitudinal partition dividing the container into two adjacent compartments and having near one end thereof two .Moana ports at different levels permitting communication between the two compartments, the upper port in said partition being at approximately a predetermined level for molten lead in the container and the lower port being near the bottom of the container, a well communicatingl with one of said compartments for delivering molten zinciferous lead to .that compartment and a second well communicating with the adjacent compartment for collecting molten dezinced lead, each of said wells being positioned at the end ofthe container opposite the end where the two compartments communicate and the only communication between each well and its compartment :being near the bottom of the compartment, said well for collecting molten dezinced lead having an outlet at approximately the level of the upper port in said partition, whereby said outlet establishes the aforesaid predetermined level for molten lead, a slag-discharge well approximate said well for the delivery of molten zinciferous lead and having two ports at different levels permitting communication between the slag-discharge well and the compartment in communication therewith, the upper port in the slag-discharge well beingv at a 15 file of this patent:

UNITED STATES PATENTS v Number Name Date 819,651 Harris May 1, 1906 26 1,838,029 Isles Dec. 22, 1931 1,895,683 ROth et al Jan. 31, 1933 2,148,460 Haney Feb. 28, 1939 FOREIGN PATENTS 25 Numberv i Country Date 450,491 Great Britain July 20, 1936 .along the length thereof but not in the vicinity of said slag-discharge well, said means being 'arranged to deliver the chlorine at a point well below said predetermined level.

WILLIAM WALLACE SHROPSHIRE.

REFERENCES CITED The following references are of record in the

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