US1322089A - Production of zinc oxid. - Google Patents

Description

UNITED 'srnras PATENT OFFICE.

FRANK G. BREYER, ALBERT E. HALL, AND GEORGE R. WALTZ, OF PALMERTON, PENN- SYLVANIA, ASSIGNORS TO THE NEW JERSEY ZINC COMPANY, OF NEW YORK, N. Y.,

A CORPORATION OF NEW JERSEY.

PRODUCTION OF ZINC OXID.

To all whom it may concern:

Be it known that we, FRANK G. BREYER, ALBERT E. HALL, and GEo'non R. WALTZ, residing at Palmerton, Carbon county, Pennsy vania, have invented certain new and useful Improvements in the Production of Zinc Oxid; and We do hereby declare the following to be a full, clear, and exact description of the invention, such as will enable others skilled in the art to which it appertalns to make and use the same.

This invention relates to the production of zinc oxid or leaded zinc oxid by the Wetherill process, and has for its object the provision of certain improvements in this process of producing zinc oxid, or leaded zinc oxid.

Zinc oxid and leaded zinc cipally produced in commercial the so-called Wetherill process. By the expression \Vetherill process, as we have used the same herein, is to be understood the oxid are prinpractlce by furnacing step of the process for producing zinc oxid, or leaded zinc oxid, as a finished commercial product, or as a zinc oxid (or zinc-lead) concentrate, or in any other form, in which a charge of the zinkiferous (or zinkiferous and plumbiferous) material mixed with a reducing agent and spread on an ignited bed of fuel is-subjected to a combustion supporting blast or draft and brought to a sufliciently high temperature to reduce the compounds of zinc and Volatilize the reduced metal (and to reduce and (or) volatilize the compounds of lead when present) Without bringing the charge to a condition where it becomes the blast or draft; the entire charge being supported on a furnace hearth or grate designed to hold it without letting any considerable part drop through, and the workedofl' material being discharged as a clinker or sinter. The furnacing step is inde: pendent of the subsequent treatment of the laden furnace gases and of the collection of the zinc oxid or leaded zinc oxid.

In the commercial production of zinc oxid (including leaded zinc oxid) by means of the VVetherill process, it has heretofore been customary to first charge upon the perforated hearth or grate of the present day type of zinc oxid furnace a layer of buckwheat anthracite coal (which is thereupon ignited by the residual heat of the furnace) Specification of Letters Patent.

impervious to Patented Nov. 18 1919.

Application filed July 12, 1919. Serial No. 310,489.

a forced draft or blast of air to bring this initial layer of coal to Well-developed combustion. Upon this layer, of bed coal is then charged the customa mixture or working charge characteristic of the Vetherill process, that is to say, a mixture of finely-divided reducing coal with the finely-divided zinkiferous (or zinkiferous and plumbiferous) material, such as zinc silicate, called mixed sulfide of zinc and lead, spelter-retort residues, or other reducible zinc-containing (or zinc and lead contain ing) material at the disposal of the operator. The forced air draft is continued, and, when the familiar flames of greenish tint, known as zinc candles, begin to make their a pearance above the upper surface of t e charge, indicating that the reduction and volatilization of the zinc and its oxidation to the form of fume is Well under way, the products of combustion carrying the zinc oxid fume and other volatilized metallic compounds are conveyed through the customary coolingflues, etc, to the bag-room wherein, in 'a cooled condition, they filter through the bags and pass ofl-"into the at mosphere, leaving the fume collected in the interior of the bags, from which it is removed at convenient intervals. The furnace operation is continued until the production of fume therefrom in ap reciable quantity ceases, whereupon the resldual charge, which is, to a large extent, sintered together, is broken up by long handled ra'bbles and pried up and lifted o" scraped out through the furnace doors into a receiving pit, or the like, preparatory to the starting of a new operation. The coal or other carbonaceous material of the charge serves the two fold purpose of furnishing a reducing agent for effecting the reduction of the zinkiferous, or zinkiferous and plumbiferous, material of the charge and of'furnishing, by combustion, the necessary degree of heat to bring these materials to the reducing temperature characteristic of the process.

As thus ordinarily practised, the abovedescribed furnace operation is attended with certain defects interfering with its full efficiency. Prominent among these defects is the inevitable tendency to the formation of blow-holes or craters at various regions of the charge. \Vorking or rabbling of the and by means of roasted zinc blends, roasted socharge to break up these blow-holes involves cons derable labor, and, in addition, the formation of blow-holes causes waste of fuel and inefficiency in the recovery of values. A further defect of the above-described furnace operation is that the forced draft tends to project into the free 5 ace above the charge more or less dust, an this dusting is further a gravated by the rabbling operan tions. T 1s dust contaminates the fume and damages its color and marketability. These and many of the other defects of the above described furnace operation as heretofore generally practised are overcome to a very remarkable extent by modifying the heretofore customary practice in accordance with the improvements described in the application for Letters Patent of the United States of Frank G. Bre er, James A. Singmaster and Albert E. l-l all, Serial No. 270,179, filed January 8, 1919. These im rovements consist in supplying either or 0th the bed fuel and the working charge to the furnace hearth in the form of briquets. The improved results attendant upon this modification in the prior customary practice are described in detail in the aforementioned application.

We have discovered that a further decided improvement in the efficiency of the aforementioned furnace operation can be secured by, appropriately modifying the relative proportions of fuel, includin reducin agent, in the working charge an bed fue in accordance with the principles hereinafter explained. Thus, briefly, we have discovered that when the reater proportion of the total fuel of the dharge is placed in the form of bri nets in the bed fuel, rather than in the wor ing charge as has heretofore been customary, a very complete work ing-ofl of the volatilizable metal values in effected. The relatively deep bed of fuel briquets when in full combustion imparts to the superposed working charge a highly reducing atmosphere and a sufficiently high and very uniform temperature whereby 90% or more of the volatilizable metals may be recovered from the metalliferous material of the charge, as compared with recoveries of about 7 0% under the heretofore customary furnace practice with unbriqueted charges and recoveries of from 80 to 85% with briqueted charges asdescribed in the aforepientioned Breyer-Singmaster-Hall applica- The residual charge from the hereinbefore described furnace operation (with unbriqueted charges) consists of a more or less slntered masscontaining the ash of the con- Sumed fuel, unconsumed fuel and the worked-off metalliferous (zinkiferous or zinluiferous and plumbiferous) material. These various materials are more or less 65 mixed together and their mixed condition seriously prejudices subsequent treatment of the residue and the separation and recovery therefrom of such valuable materials as it usually contains. When this heretofore customary practice is modified by supplying the usual working charge mixture to the furnace hearth in the form of briquets, the worked-off charge is still a mixture of ash, unconsumed fuel and worked-off metalliferone material. By placing the greater proportion of the total fuel of the charge in the bed fuel in the form of briquets, and by supplying the working charge, with its oorresporidingly reduced content of fuel and reducing agent, in the form of briquets, we very materially reduce the amount of combustible materlal associated with the metalliferous material of the working charge and thereby enable the working charge briquets to retain for the most part their original form and shape, whereby the worked-off ore or metalliferous briquets may be readily separated from the clinkered residue of the bed fuel briquets. At the same time, the amount of ash associated with the worked-off ore briquets is of such small amount that these worked-off briquets can be subsequently treated for the recovery of further metallic values without serious difficulty.

In the customary commercial practice of the lVetherill process, the total carbonaceous material in the entire charge, including the bed fuel and the working charge mixture, is several times greater than the theoretical amount required to reduce the compounds of the volatilizable metals in the charge. It has heretofore been thegeneral practice to place the greater proportion of the total carbonaceous material of the entire charge in the working charge mixture. For example, when operating with the well known Franklin furnace zinc oxid ores, it is customary to place from about fifteen (15) to twentyiive (25) per cent. ofv the total carbonaceous material of the entire charge in the bed fuel, while the remaining eighty-five (85) to seventy-five (-75) per cent. of the total carbonaceous material is mixed with the ore to form the working charge. In general terms, the layer of bed fuel is approximately one inch in depth or thickness, while the working charge mixture is spread over the ignited bed fuel in a layer from about five (5) to seven (7) inches in depth or thickness.

We have discovered that a very considerable proportion of the carbonaceous or other combustible material can be withdrawn from the working charge and placed in the bed fuel when the bed fuel is a plied to the fur- 1 V nace hearth in the form 0 riquets. Thus, for example, when operating with Franklin furnace zinc oxid ores, we have obtained excellent results by placing from about enty-fivc (75) to eighty-five per cent.

of the total carbonaceous material of the entire charge in the bed fuel and supplying this bed fuel'to the furnace hearth in the form of briquets. The remaining twentyfive (25) to fifteen (15) per cent. of the total carbonaceous material is then admixed with the ore to form the working charge. The working charge is also preferably briqueted and spread on the ignited bed fuel briquets.

In carrying out the invention, the briqueted bed fuel is charged on to the furnace hearth in any appropriate manner, ignited and brought to full combustion by passing a combustion-supporting gas, such as air, into the bed fuel briquets. The working charge is then spread on to the ignited bed of fuel briquets, and the resulting efiluent 1s withdrawn from the furnace and approprlately treated for the removal and collection of the metallic compounds contained thereln. In working with Franklin furnace zinc oxid ores, we have secured very satlsfactory results by charging the briquetedbed fuel in a layer of approximately five (5) to SIX (6) inches in depth or thickness, and spreadlng on to the ignited layer of these bed fuel briquets a layer of working charge briquets or approximately four (4) to five (5) inches in depth or thickness When the compounds of the volatilizable metals of the working charge have been worked-off to the desired extent, the residual charge may be withdrawn or discharged from the furnace in any suitable manner. This residual charge consists of a relatively thin layer of clinker on which rests the worked-oil ore briquets. During the process the bed fuel briquets undergo substantially complete combustion, and are discharged as a clinkered ash. On the other hand, the physical form of the briquetcd working charge is not materially altered and for the most part the worked-off ore briquets retain their original shape with only incipient fusion.

The bed fuel briquets may be prepared by compressing finely divided coal, together with a suitable binder, such, for example, as the concentrated waste sulfite liquor of the sulfite paper pulp industry. Various forms and grades of carbonaceous material are available for the bed fuel briquets. Thus, for example, anthracite coal below the No. 3 buckwheat size, such as No. 4 buckwheat, colliery washings, dirt coal, dust coal, as Well as coke breeze, may be utilized in the production of the bed fuel briquets.

The bed fuel .briquets are of such size and shape as to materially reduce the resistance to the combustion supporting gas, and nevertheless to supply such a substantially uniform sub-stratum for the support of the superposed working charge as to give free access therethrough and \practically equal distribution thereto of the combustion supporting gas. To, this end, the bed fuel brlquets, as well as the working charge briquets, should be of substantially uniform size, and preferably of such shape that they roll or tumble easily over one another. Thus, we have found the so-called pillow block, eggette, rounded pillow block, overstuffed pillow, and similar shapes well suited to the purpose of the invention.

Whilev the working charge consisting of a mixture of the zinkiferous, or zinkiferous and plumbiferous, material and an appropriate reducing agent may be supplied to the ignited layer of bed fuel briquets' in an unbriqueted form, we prefer to briquet the Working charge because of the many attendant advantages. Furthermore, we wish it to be understood that the metalliferous (zinkiferous, or zinkiferous and plumbiferous) material may be briqueted alone, without'briqueting the reducing agent, or the reducing agent may be briqueted alone without brlqueting the metalliferous material, or the reducing agent and the metalliferous material may be separately briqueted. However, our preferred practice is to briquet a mixture of the metalliferous material and the reducing agent.

The reducing agent of the working charge may be of any suitable kind, and While we now prefer to employ carbonaceous material as the reducing agent, it will be understood by those skilled in the art that reducing agents other than carbonaceous materials are available for the purposes of the invention. One of the advantages of employing a briqueted reducing agent in any of the forms hereinbefore described. is that it permits the use of carbonaceous materials of cheaper grades and finer mesh, such as anthracite coal of finer mesh than No. 3 buckwheat, colliery washings, dust coal, coke breeze and the like.

The bed fuel briquets and the working charge briquets may be prepared in any appropriate manner. lVe have found the procedure described in the aforementioned application of Frank G. Breyer, James A. Singmaster and Albert E. Hall, Serial No. 270,179, for preparing similar fuel and working charge briquets well adapted for the purposes of our present invention. This procedure involves generally the steps of mixin the material to be briqueted with a suitab e binder, such as concentrated waste sulfite liquor of 30 Baum, molding the mixture into briquets of the desired size and shape, and drying or baking the briquets at a temperature of approximately 200 Ch, so as to impart to them the desirable amount of resistance to crumbling and breaking so that they may be freely subjected to the rough handling incident to storing them, conveying them to the furnace, and lncident to charging them into the furnace either by hand or otherwise. In the case of the briqueted metalliferous material, it is also desirable that the briquets possess such resistance to crumbling and breaking as to substantially maintain their form during the entire furnacing operation, so that they are for the greater part discharged from the furnace in substantially their original physical form.

\Vhen practising the Wetherill process in accordance with the rinciples of our present invention, the residual charge consists of a more or less clinkered coal ash, resulting from the combustion of the bed fuel briquets, and a residue, resulting from the working-oil of the metalliferous charge. When, as in the preferred embodiment of the invention, the metalliferous material of the working charge is supplied to the furnace hearth in the form of briquets, this residue contains the worked-oil ore briquets in substantially their original physical form. Some of the working charge briquets will almost inevitably become roken or crushed in the preliminary handling and furnacing operation, but these briquets for the greater part retain their original physi cal form. After the furnacing operation, these briquets are remarkably hard and almost coke-like in their physical characteristics, and are readily separated from the clinkered coal ash of the bed fuel briquets.

This ca ability of readily separating the worked-o mctalliferous or ore briquets from the ash of the fuel briquets is of especial advantage when the worked-off ore hriquets are to be subjected to further treatment for the recovery of valuable metals not volatilizable by the Wetherill process. As a result of practising the Wetherill process in accordance with our present invention, this advantage is greatly augmented by the fact that the worked-0E metallifcrous briquets contain at most only a relatively small amount of ash. Where the working charge briquets consist of a mixture of metalliferous material and carbonaceous reducing agent, the worked-ofi briquets will contain, in addition to the worked-0d metalliferous material, the ash from the consumed carbonaceous reducing agent as well as the unconsumed portion of the reducing agent. The ash is composed principally of silica and alumina, and is generally objectionable in any subsequent treatment of the worked-oil metalliferous briquets. Thus, for example, in those instances in which the worked-off metalliferous bri. nets are smelted in a blast turnaoe for t e production of spiegeleisen a .certain amount of fluxing agents is necessary for slagging 05 the ash present in the worked-oft metalliferous briquets, and when this amount of ash is relatively large an objectionably large amount of fluxing agent is required, with the resultant production of an objectionably large amount of slag. By the practice of our present invention the main bulk, for example, around eight -five (85) per cent, of the ash of the tota carbonaceous material of the charge is in the clinker resultin from the combustion of the bed fuel briquets, and the worked-off metalliferous briquetsare consequently contaminated with only a relatively small amount of ash. On account of this relatively slight ash contamination of the worked-off metalliferous briquets, as well as on account of their physical roperties, these briquets are peculiarly we adapted for subsequent treatment in blast furnaces. In addition to retaining their original form, these briquets are, moreover, of a porous character, due to the removal of the volatilizable metals therefrom, and this porous property of the Worked-off briquets is also of advantage in their subsequent treatment.

As a typical instance of the practice of the invention, we will briefly describe a particular charge and the manner of working the same. The charge was made up of the well known Franklin furnace zine oxid ores and dust coal. Approximately eighty-five (85) per cent. of the total coal of the charge was briqueted with concentrated waste sulfite liquor as the binder, in the manner previously described. The remaining fifteen (15) per cent. of the total coal was mixed with the ore (in the proportion of about ninety (90) parts of ore to ten (10) parts of coal dust) to which was added about three (3) per cent. of concentrated waste sultite liquor as a binder and the mixture was then hriquctcd and the briquets baked, as previously described. The fuel briqucts were first charged onto the perforated hearth of the present day customary type of zinc oxid furnace and ignited by the residual heat of the preceding furnacing operation. A thin layer of fuel hriquets was first chargei'l. and after these had been well ignited, the remainder of the fuel briquets were charged, producing a layer of bed fuel of about six ((3) inches in depth. When this layer of bed fuel had reached full combustion, the hriquotcd working charge was spread thereon. producing a superposed layer of working charge briquets of about fiv (5) inches in depth. During these operations, a blast of air was maintained through the perforated grate, and when active reduction of the zinkiferous material of the charge began, the eiliuent from the furnace was conducted to the oxid drums and thence to the bag-room in the usual manner. The temperature of the charge was maintained at from about 1100 C. to about 1250" 0., and the fume emitting period was of substantially four hours duration.

The residual charge consisted of a more or less clinkered coal vash of about threefourths (g) to one and one-half (12 inches in thickness, resulting from the combustion of the fuel briquets, and worked-off metalliferous or ore briquets retaining for the greater part their original form with only incipient fusion. This residual charge was withdrawn from the furnace by hand and the worked-off ore briquets separated from the remainder of the residual charge for subsequent treatment. 7

The zinc oxid produced was of a very high grade, free from grit or specks and very bright. The recovery of zinc was remarkably high, being about ninety (90) per cent. on the original zinc content of the raw ore.

The relatively deep layer of bed fuel, when in complete combustion, provides a substantially incandescent substratum of carbonaceous material of appreciable depth upon which rests the metalliferous material of the working charge. By appropriately controlling the amount of combustion supporting gas introduced into the bed fuel, complete utilization of the oxygen of such gas can be effected during its passage through the bed fuel and the superposed metalliferous material can be subjected to a strong and effective reducing atmosphere. This reducing atmosphere may be so controlled as to materially reduce the amount of reducing agent in the working charge, and in certain instances may even eliminate the necessity of admixing any reducing agent with the metalliferous material of the working charge.

We claim:

1. In the production of zinc oxid or leaded zinc oxid by the Wetherill process, the step of supplying to the furnace hearth a relatively deep layer of bed fuel in the form of briquets, together with the step of spreading on the ignited layer ofbed fuel briquets a working charge containing zmkiferous material, or zinki'ferous and plumbiferous material, and a reducing agent; substantially as described.

2. In the production of zinc oxid or leaded zinc oxid by the Wetherill process, the step of supplying to the furnace hearth a relatively deep layer of bed. fuel in the form of briquets, togetherwith the step of spreading on the ignited layer of bed fuel briquets a working charge containing zinkiferous material, or zinkiferous and plumbiferous material, and a briqueted reducing agent; substantially as described.

3. In the production of zinc oxid or leaded zinc oxid by the Wetherill process, the step of supplying to the furnace hearth a relatlvely deep layer of bed fuel in the form of briquets, together with the step of spreading on the ignited layer of bed fuelbriquets a workmg charge containing briqueted zinkiferous material, or briqueted zinkiferous and plumbiferous material, and a reducing agent; substantially as described.

4. In the production of zinc oxid or leaded zinc oxid by the Wetherill process, the step of supplying to the furnace hearth a relatively deep layer of bed'fuel in the form of briquets, together with the step of spreading on the ignited layer of bed fuel briquets a working char e composed of a briqueted mixture of zin iferous material, or zinkiferous and plumbiferous material, and a reducing agent; substantially as described.

5. In the production of zinc oxid or leaded zinc oxid by the Wetherill process, the step of supplying to the furnace hearth a layer of bed fuel containing the greater part of the total combustible material of the entire charge in the form of briquets, together with the step of spreading on the ignited layer of bed fuel briquets a working charge containin zinkiferous material, or zinkiferous and pfumbiferous material, and a reducing agent; substantially as described.

6. In the roduction of zinc oxid or leaded zinc oxid by the Wetherill process, the step of supplying to the furnace hearth a layer of bed fuel containing the greater part of the total combustible material of the entire charge in the form of briquets, together with the step of spreading on the ignited layer of bed fuel briquets a working charge containing zinkiferous material, or zinkiferous and plunibiferous material, and a briqueted reducing agent; substantially as described.

7. In the production of zinc oxidor leaded zinc oxid by the Wetherill process, the step of supplying to the furnace hearth a layer of bed fuel containing the greater part of the total combustible material of arge containing briqueted zinkiferous material, or briqueted Zinkiferous and plumbiferous material, and a reducing agent; substantially as described.

8. In the production of zinc oxid or leaded zinc oxid by the Wetherill process, the step of supplying to the furnace hearth a layer of bed fuel containing the greater part of the total combustible material of the entire charge in the form of briquets, together with the step of spreading on the ignited layer of bed fuel briquets a workin charge composed of briqueted mixture 0 zinkiferous material, or zinkiferous and plumbiferous material, and a reducing agent; substantially as described.

9. In the production of zinc oxid or leaded zinc oxid by the Wetherill process, the step of supplylng to the furnace hearth a layer of bed fuel containing from about briquets,

7 5% to about 85% of the total combustible material of the entire charge in the form of briquets, togetherwith the stepof spreading on the ignited layer of bed fuel briquets a working charge containing zinkiferous material, or zinkiferous and plumbiferous material, and a reducing agent; substantially as described.

10. In the production of zinc oxid or leaded zinc oxid by the Wetherill process, the step of supplying to the furnace hearth a layer of bed fuel containing from about 75% to about 85% of the total combustible material of the entire charge in the form of together with the step of spreading on the ignited layer of bed fuel briquets a working charge containing zinkiferone material, or zinkiferous and plumbiferous material, and a briqueted reducm g agent; substantiall as described.

11. In the pro notion of zinc oxid or leaded zinc end by the Wetherill process, the step of supplying to the furnace hearth a layer of bed fuel containin from about 75% to about 85% of the tota combustible material of the entire charge in the form of briquets, together with the step of spreading on the ignited layer of bed fuel briquets a working charge containing briqueted zinkiferous material, or briqueted zinkiferone and plumbiferous material, and a reducing agent; substantially as described.

12. In the production of zinc oxid or leaded zinc oxid by the Wetherill process, the step of supplying to the furnace hearth a layer of bed fuel containing from about 75% to about 85% ofv the total combustible material of the entire charge in the form of briquets, together with the step of spreading on the ignited layer of bed fuel br quets a, working charge composed of a briqueted mixture of zinkiferous material, or zinkiferous and plumbifero-us material, and a reducing agent; substantially as described.

13. In the reduction of zinc oxid or leaded 'zinc 0nd by the Wetherill process,

the step of supplying to the furnace hearth a relatively deep layer of bed fuel in the form of briquets, together with the step of spreading on the ignited layer o f bed fuel briquets a working charge containing z1nk1ferous material, or kinkiferous and plumbiferous material; substantiall as described.

14. In th production 0 zinc oxid or leaded zinc oxid by the Wetherill process, thestep of supplying to the furnace hearth a relatively deep layer of bed fuel, together with the step of spreading on the ig2'.=.1ted layer of bed fuel a working charge containin briqueted zinkiferous material, or brlqueted zinkiferous and plumhiferous material; substantial)? as described.

15. In the pr notion of. zinc oxid or leaded zinc oxid by the Wetherill process,

the step of supplying to, the furnace hearth a relatively deep layer of bed fuel in the form of briquets, together with the ste of spreading on the ignited layer of bed fuel briquets, a Working charge containing briqueted zinkiferous material, or briqueted zinkeriferous and plumlbiferous material; substantially as described. 7

l 16. In the roduction of zinc oxid or leaded zinc oxid by the -Wetherill process, the step of supplying to the furnace hearth a relatively deep layer of bed fuel, together with the step of spreading on the ignited layer of bed fuel a working char e composed of a briqueted mixture of zinki erous material, or zinkiferous and plumbiferous mate- .rial, and a reducing agent; substantially as described.

17. In the production of zinc oxid or leaded zinc oxid by the \Vetherill process, the step of supplying to the furnace hearth a layer of bed fuel containing in excess of 25% of the total combustible material of the entire charge in the form of briquets, together with the step of spreading on the i ited layer of bed fuel briquet a working 0 ar e containing zinkiferous material, or zinkiferous and plumbiferous material, substantially as described.

18. In the production of zinc oxid or leaded zinc oxid by the Wetherill process, the step of supplying to the furnace hearth a layer of bed fuel containing in excess of 25% of the total combustible material of the entire charge in the form of briquets, to gether with the step of spreading on the ignited layer of bed fuel briquets a working char e containing briqueted zinkiferous materia or briqueted zinkiferous and plumbiferous material; substantially as described.

19. In the production of zinc oxid or leaded zinc oxid by the Wetherill process, the step of supplying to the furnace hearth a layer of bed fuel containin from about 7 5% to about 85% of the tota combustible material of the entire charge in the form of briquets, together with the step of spreading on the ignited layer of bed fuel briquets a working charge containing zinkiferous material, or zinkiferous and plumbiferous material; substantially as described.

20. In the production of zinc oxid or leaded zinc oxid by the Wetherill process, the step of supplying to the furnace hearth a layer of bed fue containin from about 75% to about 85% of the tota combustible material of the entire charge in the form of briquets, together with the size of spreading op the ignited layer of bed uel briquets a working charge co taining briqueted zinkiferous m'ateria or riqueted zinkiferous and plumbiferous material; substantially as described.

21. In a process for roducin zinc oxid or leaded zinc oxid invo ving the blowing of emma air into a bed containing combustible mate rial and a mixture of the metal bearing material and a reducing agent under conditions which will leave the Worked-oil charge as a clinker and which will produce a volatile fume, the step of supplying the combustible material in the form of a relatively deep layer of briquets; substantially as described.

22. In a process for prbducin zinc oxid 0r leaded zinc oxid involving t e blowing of air into a bed containin combustible material and a mixture of e metal bearing material and a combustible reducing agent under conditions which will leave the worked-oil charge as a clinker and which will roducet a volatile fume, the step of supp ying the combustible material in the form of a relatively deep layer of briquets.

containi the greater part of the total combustib e material of the entire charge; substantially as described.

In a process for roducin zinc oxid or leaded zinc oxid invo ving the lowing of ail-into a bed containing the metal bearing material and 'a combustible material under conditions which will leave the worked-oil' char as a clinker and which will produce a v0 atile fume, the step of supplying at least part of the combustlble material in the form of a relatively deep layer of briquets; substantially as described.

In testimony whereof we aflix our signatures.

FRANK G. BREYER. ALBERT E. HALL. GEORGE R. WALTZ.

Corrections in Letters Patent No. 1,322,089.

It is hereby certified that in Letters Patent No 1,322,089, granted November 18,

1919, 'upon the application of Frank G. BreyenjAlbert E. Hall, and George R. I

Waltz, of .Palmerton, Pennsylvania, foxan improvement in The Production of Zinc Oxid," errors appear in the printed specification correction as follows: Page 2, line 42, for theword in" read is; P ge 6, line 53, claim 13, for the word ln'nkiferous read zinkifemm; and that the said Letters Patent should be read with these corrections therein that the same may conform to the record of the case in the Patent Ofice.

Signed and sealed this 16th day of December, A.- D.-, 1919.

M- H. COULSTON, Acting Commissioner qfPatmte.

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