US2061251A - Process for separating metals - Google Patents

Description

NOV. 17, 1936. pERKlNS 2,061,251

PROCESS FOR SEPARATING METALS Filed July 25, 1954 2 Sheets-Sheet 1 IIIIII 1' llil 1mg: 3

INVENTOR BY Zmqm 17% K ATTORNEY Nov. 17, 1936. M. F. PERKINS PROCESS FOR SEPARATING METALS Filed July 25, 1934 2 Sheets-Sheet 2 INVENTOR Jg/z/1ZZeF/ rhkz ATTORNEY Patented Nov. 1?, 1936 PATENT OFFICE PROCESS FOR SEPARATING METAL Melville F. Perkins, Woodbridge, N. J., assignor to American Smelting and Refining Company, New York, N. Y., a corporation of New Jersey Application July 25, 1934, Serial No. 736,896

13 Claims.

This invention relates to the separation and/or purification of substances by liquation and distillation.

Among other features, the invention provides 5 a process for continuously effecting the removal of a lower boiling component as a substantially pure vapor from a bath of material containing a higher boiling component by constantly maintaining the total content of the higher boiling component of the bath ata low value throughout the process. The invention also provides for concentrating the higher boiling component while simultaneously removing the lower boiling component vapor. The novel manner in which the low content of the higher boiling component of the bath is maintained is also a feature of the invention.

For example, in treating spelter, the invention contemplates continuously and simultaneously distilling and liquating the spelter in such manner that zinc is continuously distilled from a bath'whose lead content is maintained at a low value by continuous liquation, the process being readily accomplished in an appropriate furnace having two chambers or compartments connected with suitable passageways for effecting intercirculation of metal between the chambers.

The present application is a continuation in part of the co-pending application of Melville F. Perkins, Serial No. 627,589, filed August 5, 1932.

Although the novel features which are believed to be characteristic of this invention will be particularly pointed out in theflclaims appended hereto, the invention itself, as to its objects and advantages, and the manner in which it may be carried out may be better understood by referring to the following description taken in connection with the accompanying drawings forming a part thereof, in which Fig. l is a cross section of a furnace embodying the principles of the invention.

Fig. 2 is a plan view in section of the same furnace on the line 2-2 of Fig. 1.

In the drawings accompanying and forming 45 part of this specification, certain specific disclosures of the invention are made for purposes of explanation, but it will be understood that the details may be modified in various respects without departure from the broad aspects of the invention.

Referring more particularly to the drawings, a furnace is shown having walls I 0, H, 12 and I3, roof l4 and hearth 15, the latter resting on base material I6. Insulation His provided to cover 55" the roof and walls.

A common wall l8 extending .from the roof I 4 to the hearth I5 divides the-interior of the furnace into two chambers or compartments l9 and 20, which are connected by ports or passageways 2! and 22 extending through wall l8. Fire 5 tubes 23 of suitable refractory material extend through walls 12 and I3 and chamber 20. Passageway 24 connects flue 26 with chamber I9 through port 25. Chamber I9 is provided with a charging port 21 and tap hole 28, while cham- 10 bers l9 and 20 are provided with exits 29 and 30 respectively. A safety trap 3! is provided in the lower portion of flue 26 by dam 32. Suitable doors not shown are provided for cleaning compartments I9 and 20.

In operation, the invention may be practiced as follows:

The furnace is charged with the material to be treated and the furnace heated to the proper temperature. For the recovery of zinc from 20 lead, typical substances which may form the charge are raw spelter, galvanizers dross, zinc dross, leady zinc, salvage materials of a similar nature, and the like. It is generally preferable to introduce the charge into the liquation compartment through charging port 21, although special cases may warrant direct charging to the distillation chamber. Again, the charge may be introduced either in the liquid or solid state, depending ,upon circumstances.

After melting the charge in the furnace, the respective baths of the liquation and distillation compartments are brought to their appropriate temperatures. The temperature in the liquation compartment is maintained at a value slightly above the melting point of the bath, while in the distillation compartment a sufiicient temperature is maintained to insure rapid boiling of zinc. It has been found, generally, that a temperature range of from 430 C. to 500 C. is appropriate 40 for the liquation compartment, while operation of the distillation compartment at temperatures slightly above 900 C. gives excellent results, when a Working with normal materials at normal atmospheric pressure.

Heat may be supplied to the distillation compartment by means of submerged fire tubes constructed of carborundum, graphite, or similar material which are fired internally with an airfuel mixture employing the principles of surface combustion. If desired the fire tubes may be anchored for increased mechanical strength. Other heating means may be employed, but those in which the heat is supplied below the free surface of the bath are preferable.

A portion or all of the hot gaseous products of combustion from the fire tubes 23 may be conducted through passageway 24 and into the liquation compartment through port 25 to complete the heat balance in that compartment of the furnace. Combustion gases not used for this purpose are vented through flue 26.

To provide intercirculation and exchange between the' liquation and distillation compartments, suitable ports 2| and 22 are provided in the dividing wall l8. The rate of circulation may be controlled by the number, size and location of these connecting ports, thus eliminating any necessity for employing a pumping scheme or other method of forced circulation. The rate of flow may be, of course, controlled by any suitable mechanism, such for example, by a spindle valve (not shown) located preferably in the upper port.

By reason of the novel furnace design and the method of operation already described, the bath in the distillation compartment has, at all times, actually and relatively, a low lead content. Hence, in operation, zinc vapor substantially free from lead is volatilized and removed from the compartment through exit 30, whence it may be condensed to form high grade zinc metal, burned to produce zinc oxide, or otherwise utilized. v

Unlike ordinary distillation practices in which the ratio of lead to zinc in the bath must necessarily increase as volatilization of the zinc progresses, the present invention continuously maintains a low ratio of lead to zinc inthe bath undergoing distillation. The maintenance of this low lead value is made possible by the intercirculation and exchange effected between the distillation and liquation compartments. As a result of this circulation, the lead left behind in the distillation compartment following the volatilization of the zinc is circulated into the liquation compartment which, as before stated, is substantially cooler than the distillation compartment. At this lower temperature, the lead is less soluble in the zinc, and, hence, separates out as a liquid which collects at the bottom of the compartment because of its higher specific gravity.

As the zinc content in the furnace is decreased by volatilization and the lead collected in the bottom of the liquation chamber, additional charges of material may be added to the system without interrupting the continuous operation of the furnace. As before stated, the charge may be liquid or solid and may be charged to either compartment, although it will normally be introduced into the liquation compartment. As lead accumulates in the liquation compartment, it

may be removed at convenient intervals through tap hole 28.

.In order to more clearly illustrate the advantages'of the present invention and its mode of operation, the following specific example is set forth:

Zinc containing from 6% to 10% lead with a trace of iron was charged to the furnace. The liquation compartment was maintained at from 450 C. to 500 C., while the distillation compartment was operated slightly in excess of 900 C., at which temperature volatilization of the zinc proceeded rapidly. Samples of the metal taken from the distillation compartment and the upper stratum of the liquation chamber analyzed 3.06% lead, and 3.00% lead, respectively. At the same time, a sample taken from the bottom of the liquation chamber analyzed 98.3% lead, while the volatilized zinc emerging from the distillation compartment analyzed less than 0.003% lead.

As previously stated, it is possible'by the present invention to distill continuously zinc vapor from a bath of low lead content and the above Analysis of the distilled Analysis of melt and condensed zinc in the retort Lead, by weight Less than 0. 001 3 Lead, 51 weight Nab- H OM00! 0000 arch-mo This table clearly illustrates the well known fact that as the percentage of lead in a bath from which zinc is being volatilized is increased, the percentage of lead in the vapor and condensate is also increased. By means heretofore described, the present invention, at all times, insures a low lead content in the bath from which the zinc is distilled and thus makes possible the continuous evolution of substantially pure zinc vapor.

The invention has for an important adaptation the treatment of salvage material such as diecastings or scrap containing predominately zinc together with smaller amounts of other metals, such, forexample, as aluminum, tin, copper and lead, together with other minor When operating upon such materials, the zinc is boiled off, as described above, and the lead and tin are liquated out. The remaining constituents of the metal, such as the aluminum and copper, and other minor impurities gradually accumulate in the bath, and are periodically removed by tapping the bath from the furnace.

Various heating means and media may, of course, be employed for both the liquation and distillation chambers. For example, in furnace design, burners have been installed in the liquation chamber for melting material charged in the solid state.

Again, while the invention has been described with reference to the separation of lead and zinc,

' it will be appreciated that the method and apparatus of the invention may be used to advantage in effecting a large number of separations wherein the appearance of a new phase is produced by change of thermodynamic environment. Thus, for example, zinc and selenium may be sepa rated; also, zinc and bismuth, and zinc and thallium; and also, sodium and magnesium.

While certain novel features of the invention 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, and that it is intended and desired toembrace within the scope of the invention such modifications and changes as may be necessary to adapt it to varying conditions and uses.

What is claimed is:

l. The process for separating metals which impurities.

comprises forming a molten'bath thereof, subjecting a portion of such bath to a temperature sufficient to effect volatilization of one of the metals, simultaneously maintaining the remaining portion of the bath at a temperature suitable for the liquation of the other metal and effecting intercirculation and exchange between the respective portions of the bath while conducting said volatilizing and liquating operations.

2. In separating metals which exhibit a single liquid phase at one temperature but which present an additional phase at a lower temperature, the improvement which consists in effecting intercirculation and exchange between two baths of such metals while maintaining said baths at such different temperatures that distillation of the lower boiling metal is effected in one bath and the other metal is removed from the system by liquation in the other of said baths.

3. The process for separating metals which comprises simultaneously subjecting different portions of a bath of the metals to distillation and liquation while effecting circulation and exchange between said portions.

4. The process for obtaining substantially pure zinc vapor from zinc contaminated with lead.

which comprises subjecting such metal to a temperature slightly in excess of 900 C. thereby volatilizing zinc while continuously effecting intercirculation between such metal and a body of similar metal maintained at a temperature of from 430 to 500 C., thereby maintaining the lead content of the metal at the higher temperature at a low value.

5. The process for treating a metal containing zinc and lead which comprises charging such metal to a furnace having liquation and distillation compartments,.establishing intercirculation and exchange of metal between said compartments, and operating the furnace in a manner calculated to maintain the metal in the liquation and distillation compartments at temperatures of from 430 to 500 C. and slightly in excess of 900 C., respectively.

6. The method of treating zinc containing lead which comprises establishing a molten bath thereof, subjecting a portion of such bath to temperatures sufiicient to effect volatilization of zinc, simultaneously maintaining the remaining portion of the bath at a temperature suitable for the liquation of lead from zinc and effecting intercirculation and exchange between the respective portions of the bath during said volatilizing and liquating operations.

7. The process for separating zinc from lead which comprises simultaneously subjecting different portions of a bath of these metals to distillation and liquation while effecting circulation and exchange between said portions.

8. The process for treating zinc contaminated with lead which comprises subjecting a first portion of a molten bath thereof to distillation while subjecting a second portion of said bath to liquation and simultaneously effecting intercirculation and exchange of metal between said first and second portions.

9. The process for refining spelter which comprises applying suificient heat below the free surface of a bath thereof to distill the zinc and maintaining the lead content of the bath at a constantly low value as the distillation progresses.

10. In the production of high grade zinc by distillation from zinc contaminated with lead, the improvement which consists in maintaining circulation between the metal undergoing distillation and a similar bath of metal. maintained at a temperature suitable for liquation of lead from zinc thereby constantly maintaining the lead content of the metal undergoing distillation at a low value.

11. The process for producing high grade zinc from zinc contaminated with lead which consists in heating a bath of such metal below the free surface thereof to a temperature suiiicient to effect removal of zinc as vapor and simultaneously effecting intercirculation of metal between said bath and a similar bath of metal maintained at a temperature favoring the liquation of lead from zinc.

12. The process for treating salvage material such as die-castings or scrap containing predominately zinc together with smaller amounts of aluminum, tin, copper and lead and other minor impurities which comprises forming a molten bath thereof, subjecting a portion of such bath to a temperature sufficient to effect boiling of the zinc, simultaneously maintaining the remaining portion of the bath at a temperature suitable for liquation of the lead and tin, the aluminum and copper remaining in the bath, and effecting intercirculation and exchange between the respective portions of the bath.

13. The process for treating salvage material such as die-castings or scrap containing predominately zinc together with smaller amounts of aluminum, tin, copper, and lead and other minor impurities which comprises forming a molten bath thereof, subjecting a portion of such bath to a temperature sufficient to effect boiling of the zinc, simultaneously maintaining the remaining portion of the bath at a temperature suitable for liquation of the lead and tin, effecting intercirculation and exchange between the respective portions of the bath, allowing the remaining metals to accumulate in the bath and periodically removing accumulated portions of the bath to remove the contaminating metals contained therein.

MELVIILE F. PERKINS.

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