US2144942A - Metallurgy of zinc - Google Patents

Description

Jan. 24, 1939. w $EGU|NE JR 2,144,942

IEIAALLL'RGY OF ZINC Filed Jan. 9, 1937 iLl. l

INVENTOR WILLIAM SEGUINE,JE

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ATTORNEYS Patented Jan. 24, 1939 =UNI'IIED STATES PATENT OFFICE METALLURGY 0F zmc William Seguine, Jr., Del Bay Beach, Fla.

Application January 9, 1937, Serial No. 119,719

16 Claim.

This invention relates to the metallurgy of zinc and, more particularly, to the production of metallic zinc from zinciferous ores or concentrates in accordance with the well known equation, ZnO+C=Zn+CO.

The conventional practice for the production of zinc by pyrometallurgy involves indirect heating of the reacting materials by the use of large furnaces, each containing rows or tiers of numerous refractory cylindrical vessels made of clay or silicon carbide into which are placed small charges of a mixture of carbonaceous and oxidized zinciferous materials. These vessels, or

retorts, are connected to individual condensers which are situated outside the furnace walls and are adapted to radiate and conduct heat away from the gases, including zinc vapor, which flows thereinto from the retorts, in order to condense this zinc vapor and collect molten zinc. The reaction between the zinciferous and carbonaceous materials in the retorts is strongly endothermic, and it is necessary when following the present practice to transmit a great deal of heat to these materials by conduction through the refractory retort walls. The most economical known method of accomplishing this is by burning gas or other fuels and leading the gases of combustion around the retorts, but even with the cheapest fuels great economic losses occur through loss of an extremely high proportion of the heat energy, which escapes through the stack, in the exit gases andthrough the walls of the furnace by conduction and radiation.

Numerous inherent limitations makethis common process decidedly burdensome and inefiicient.. It is a process which requires distribution of a multitude of small charges into a large number of retorts and separate recovery of the molten zinc collected in the individual condensers. Consequently, operation of the process involves a great deal of labor and attention. The retorts themselves must be made of carefully selected refractory material in order to enable satisfactory conduction of heat to the charge, yet under the intense heat conditions to which they are subjected they quickly deteriorate, andfrequent replacement is necessary. The expense of replacing retorts is one of the most important items in the present retort practice. As mentioned above, the transfer of heat from the furnace into each retortis so ineificient and such great heat losses occur that the cost'of fuel is another very important element. Furthermore,

in order to secure a satisfactory recovery of zincmetal from the zinciferous material placed into the retorts the physical condition of the charge must be carefully controlled. If the zinciferous material is a roasted ore or concentrate, it must be ground to a size similar to that of ordinary sand. If it consists of finely divided roasted 5 flotation concentrates, this must be sintered in order to render it permeable to gas. Similarly, if the material is zinc oxide or a precipitation residue such as the precipitate derived from the manufacture of hydrosulfite of soda, it must be 10 briquett'ed, agglomerated cr sintered in some manner.

The urgency of the need for an efllcient process capable of replacing the retort process requires no further demonstration. Metallurgists 15 in the past have investigated the possibility of using a blast furnace for this purpose, but so far as I am aware all such investigations have proved unsuccessful. Their object has been to employ a blast of air for reacting mixtures of zinciferous 20 and carbonaceous materials so that combustion of the latter will provide sufficient heat for carrying on the endothermic reduction of the zinciferous material to zinc vapor. An air blast conducted into a blast furnace under these conditions, however, inevitably produces such large quantities of carbon monoxide, nitrogen and carbon dioxide in the exit: gases that it is impossible to secure a yield of molten zinc, and whatever recoveries are secured are in the form of 30 reoxidized zinc, or blue powder.

It has also been suggested that either air or oxygen might be used satisfactorily in a blast furnace treatment of zinciferous materials, but the tremendous differences in the properties of 35 air and oxygen apparently have been overlooked, as well as the practical obstacles incident to the use of oxygen in a blast furnace, which would subject the grate or tuyere or other parts at the entry point of the gas to such intense heat that materials possessing adequate strength and reprovided eco- Still another object is to provide processes which enable more intimate contact of the reacting materials.

Among other objects which will become apparent as the description of the invention proceeds are to enable substantial reductions in the quantity of fuel required to carry out the invention as compared with retort practice and to avoid the expense incident to heavy consumption of refractory materials.

In its broader aspects, my invention contemplates the reduction of zinciferous materials in contact with a large excess of carbonaceous material, supplying the endothermic heat necessary for the reduction reaction by burning carbon in direct contact with the zinciferous material, controlling the character of the gases leaving the combustion and reduction zone by appropriate control over the temperatures of reaction and the nature of gases introduced to efiect combustion and condensing the zinc vapor in the exit gases to either molten zinc or zinc dust in a condensation chamber.

I have found that liquid zinc may be produced by a process of this character only when appropriate control is maintained over the character of the gas employed to efiect combustion of the carbonaceous material and reduction of the zinciferous material. In the practice of the invention, I preferably employ a gas which consists substantially entirely of oxygen. It will be made apparent hereinafter, however, that air enriched with oxygen is a suitable combustion gas under some conditions, provided that the content of gases other than oxygen does not exceed 50%, and is not so great as to interfere with recovery of. liquid zinc in the condensation cham-' ber.

While the improved process is not limited to any particular apparatus, I prefer to carry it out by the use of apparatus which I have devised for the purpose, which includes a rotary furnace or kiln comprising refractory walls and two communicating chambers, one for the reduction and combustion reactions and the other for the condensation of zinc vapor. In one embodiment of the invention, I place into the reaction chamber of such a furnace a charge consisting of zinciferous material, such as ore or concentrates, and an amount of carbonaceous material which is at least three times the molecular equivalent of the zinciferous material. Although this type of charge may be reacted merely by burning the carbon with oxygen introduced thereinto, it is preferable to preheat the charge to a high temperature before the reaction is commenced, in order to enable savings of fuel and, as will be explained below, more eflicient recovery of zinc. The reaction chamber is preferably provided with lifters along its inside walls so that during rotation of the furnace, or kiln, the mixture of zinciferous and carbonaceous materials is picked up by the lifters and showered through the gases within the furnace. After the charge has been preheated to a suitable temperature, it is necessary only to introduce a gas consisting principally of oxygen, such as so-called oxygenated air, into the entry end of the reaction chamber, whereupon this gas causes combustion of the carbon with generation of a great deal of heat and formation of. carbon monoxide. At temperatures which may be maintained by the heat of combustion of the carbon, the carbon monoxide resulting from combustion reduces the zinciferous material and forms zinc vapor and carbon dioxide, the latter being immediately reduced to carbon monoxide by the action of the unburned hot carbon in the reaction chamber. The mixture of zinc vapor and carbon monoxide thus formed, including only an insignificant quantity of carbon dioxide, flows into the condensation chamber, and in the latter, which is maintained 1 at a temperature below the dew point for the prevailing concentration of zinc vapor and at a temperature above the melting point of zinc, a constantly increasing pool of liquid zinc is collected. The residual gases are passed out of the condensation chamber, and the carbon monoxide content thereof may be utilized for related purposes, for example, as fuel for an engine driving a compressor which manufactures oxygen for the process, or for preheating succeeding charges in the reaction chamber.

.An important advantage of my invention is that the materials in the reaction chamber are constantly showered through the entering gases so that there is intimate contact between these materials and the gases, with resulting efficiency in the reactions that take place, and substantially complete extraction of zinc from the zinciferous material. materials of almost any physical form to be reduced without requiring preliminary agglomeration, briquetting or sintering operations. In contrast to the retort process, materials having particles so finely divided that over 50% will pass through a 65 mesh screen may be treated satisfactorily.

Another important advantage is that it permits the use of oxygen for combustion, which may be introduced into the heart of the reaction chamber where intense temperatures may be produced without in any way damaging the apparatus, since the excess heat is constantly dissipated through the endothermic reduction of the zinoiferous material before it is able to harm the furnace. I

Still another advantage of the improved process is that the point at which the entire 'zinciferous content of a charge has been exhausted through the combustion of carbon in contact therewith may easily -be determined by pyrometric observation, since the inhibiting influence of the reduction reaction is at that time ended and the temperature of the furnace thenincreases greatly because of the unused heat generated by combustion of the carbon.

In another embodiment of the invention, I place within the reaction chamber a charge consisting only of carbonaceous material and bring this material to the reaction temperature before The invention thus enables zinciferous introducing the zinciferous material into the chamber. With the furnace so conditioned for operation, a stream of oxygen-bearing gas is conducted into the entry end of the reaction chamber simultaneously with the introduction of zinciferous material in quantities regulated in accordance with the quantity of oxygen being introduced.

in the exit gases and thus more easily avoid the formation of zinc oxide in the condensation chamber.

In still another. embodiment, the invention may be carried out by introducing regulated quantities of zinciferous material, carbonaceous material and oxygen-bearing gas into the reaction chamber as the reaction proceeds.

In the drawing appended hereto I have shown illustrative forms of apparatus suitable for carrying out the invention.

Figure 1 is a longitudinal cross section of a rotary furnace or kiln adapted for use in the embodiment employing a charge of combined zinciferous and carbonaceous material.

Figure 2 is a vertical section on the line 2--2 of Figure 1.

Figure 3 shows a modification adapted for the introduction of zinciferous material simultaneously with the oxidizing gas and indicates a suitable manner for utilizing residual gases leaving the condensation chamber.

A furnace suitable for the production of liquid zinc is illustrated in Figures 1 and 2. The furnace I0 is preferably a cylindrical, steel-jacketed kiln, provided with refractory inside walls. Its interior is divided by a refractory partition I6, forming a reaction chamber I 2. and a condensation chamber I4 which communicates with the reaction chamber through an opening I8 in the partition, each of these chambers communicating at their end portions, respectively, with openings 22 and 20 formed in standards 60 and 58, respectively.

The apparatus is provided with means for tumbling and intimately contacting the materials in the reaction chamber, which in the illustrated embodiment comprises means for rotating the furnace and means for lifting the solid materials in the chamber I2 and showering them through the gases in this chamber. Annular runners 5|] and 52 surrounding the furnace and restrials in the bottom of the chamber, carrying them= to a point adjacent the top of the chamber and dropping them through the gases in the central part thereof. The ends of the chambers I2 and I4 are rotatively related to and substantially sealed against projections of the standards 60 and 58 in which the openings 22 and 28 are formed. In operation, the lifters 28 continually mix the materials in chamber I2 and keep them in intimate contact, thus ensuring satisfactory reaction even though the materials be extremely finely divided.

In order to permit charging and discharging of solid materials, the reaction chamber is provided with a port that is normally closed by a door 26. A wallof the condensation chamber I4 is formedwith an outlet 30, normally closed, permitting the recovery of zinc products from time to time as they accumulate. Both chambers also communicate with gas conducting means, which are preferably extended into the'standard's 60 and 58 andin'communication with the openings 22 and 20. Thus I preferably provide a concentric feed device leading into the reaction chamber, including a burner Ii-connected with a conduit 46 for preheating the react'ion chamber and a tuyre 42 connected with aconduit 44 for conducting oxygen-bearing gas into the reaction chamber after the preheating operation, while an appropriate conduit 62 is provided for conducting residual gases from the condensation chamber. It is, of course, unnecessary to use a concentric feed device of the kind illustrated, since any suitable burner may beinserted into the opening. 22 in order to preheat the charge and then withdrawn and substituted by a tuyere for oxygen-bearing gas.

The apparatus preferably includes means, such as the jets 32 connected with the header 34 and the pipe 36, for applying a cooling medium to the outside of the condensation chamber so as to maintain desired temperature conditions therein.

In Figure 3 is illustrated a form of apparatus that is speciallyadapted for the practice of embodiments of the invention in which zinciferous material, or such material and carbonaceous material, is fed into the rection chamber I2 as the reaction proceeds. The standard I 68 is similar to member 68 of Figure 1, but is provided with an opening I82 accommodating a feeding means, such as the chute I64, for introducing solid material into the chamber I2. If desired, the discharge end of the chute I64 may be valved in order to enable better control over the rate of flow of the materials passing therethrough.

Figure 3 also illustrates a preferred manner of utilizing the residual carbon monoxide gas which leaves the condensation chamber, such gas being conducted through a conduit I88 to an engine and compressor, indicated generally at I10, where it is used as a fuel 'for the engine, to drive the compressor and produce oxygen. Oxygen so produced is introduced into the reaction chamber, for example, through conduits I12 and 44, to support the combustion of carbon therein.

The combustion and reduction reaction The usual equation used to indicate the reaction between zinc oxide and carbon, namely-' ZnO+C=Zn+CO, does not accurately portray the reactions that actually take place.

reduction of zinc oxide by carbon involves the following two reactions:

Thermodynamic investigations have established that reaction (1) is rapid at temperatures between 600 and 700 0., while reaction (2) is less rapid at these temperatures but becomes very rapid at temperatures above 1000 C. It has also been determined that if reaction (1) is carried out only in the presence of zinc oxide and carbon monoxide the yield of zinc vapor at one atmosphere of pressure can be greater than 10% of the total gases only at temperatures somewhat above 1000" C., while temperatures of about 1200? C. are necessary to secure a zinc vapor. content of about 30% under'equilibrium conditions. Reac- Thetion (2), however, at 1000 C.'tends to reach an equilibrium condition in which there is only about .6% carbon dioxide in the presence of tent established by the two equations given above.

' For example, if the temperatures in the reaction e V, may be accomplished by combustion of part of chamber should reach only 850 0. there could not be less than 6.2% of carbon dioxide relative to the total volume of carbon monoxide and carbon dioxide in the exit gases, regardless of the quantity of carbon present to convert carbon dioxide to carbon monoxide, since reaction (2) would permit this much'carbon dioxide at 850 C. under equilibrium conditions, and reaction (1) tends to cause a greater quantity to be present. Such a quantity of carbon dioxide, however, would result in the formation of large quantities of zinc oxide or blue powder in the condensation chamber through reversal of the reduction re action as the gases were cooled, interfering greatly with the yield of substantially pure zinc metal.

In the practice of my invention, the presence of substantial quantities of carbon dioxide in the gases leaving the reaction chamber is avoided by maintaining high temperatures and an excess of hot carbon in this chamber. The carbon therefore serves the dual purpose of providing heat for the reduction reaction and of ensuring the absence of substantial quantities of carbon dioxide in the exit gases.

In one embodiment of the invention, as briefly described above, the carbonaceous and zinciferous materials are placed into the reaction chamber together and they are preheated to a temperature of at least 800 C. and preferably to temperatures more closely approximating the desired reduction temperature. ,This preheating may be accomplished by inserting a burner using a gaseous fuel, such as the'carbon monoxide which emanates from the condensation chamber, into the port of the reaction chamber. It is of course obvious that other fuels such as oil, powdered coal and the like might be used for this purpose. After the charge has been brought to the desired preheating temperature, for example, 1000 C., the burner may be removed from the port 22 and replaced by a tuyere for oxygen-bearing gas, or instead of using separate burners and tuyeres, a concentric feed device as described hereinabove may be employed. The gases created during the preheating operation are of course vented through the outlet 62 of the condensation chamber and discharged through a stackor other device provided for the elimination thereof. The point when the charge described generally hereinabove, the reaction chamber is supplied with sufficient carbon to support the reaction for an extended period of time. The temperature of this chamber is raised to about the desired reaction temperature, which the carbon or otherwise, and thereafter regulated streams of oxygen, or oxygenated air, and

' zinciferous material are introduced through the be flowed into the chamberthrough the tuyre 4!, while the zinciferous material isiintroduced through the .chute I64 and the opening 22. As

the zinciferous material enters the chamber l2,

it is intimately mixed with the carbon in this chamber, due to rotation of the kiln and the action of the lifters 28. It is continuously showered through the stream of entering oxygen and continuously reduced to form zinc vapor and, indirectly, carbon monoxide.

In still another embodiment, the reaction may be made substantially continuous by maintaining a quantity of preheated carbon in the reaction chamber and continuously introducing into the entry end thereof amounts of zinciferous and carbonaceous materials and oxygen-bearing gas that are regulated to satisfy the requirements of the process.

The temperature of reaction (1), in any zinc smelting process, must be greater than 860 C. if continuous reduction of the zinciferous material is to be obtained, since the partial pressure of zinc vapor produced at lower temperatures and one atmosphere of pressure is insuflicient to cause continuous venting of the system.

In carrying out my invention, I employ temperatures above 1000 C. and preferably from about 1100" C. to 1300 C. or higher in order to insure rapid reduction of the zinciferous material and rapid reduction of the resulting carbon dioxide so that the exit gases consist essentially of zinc vapor and carbon monoxide along with a negligible quantity of carbon dioxide and whatever nitrogen has been introduced with the oxygen.

Condensation In the condensation stage there are two conditions which must be met by any satisfactory process for recovering liquid zinc: The partial pressure of the zinc vapor in the exit gases from the reaction chamber must be sufficient to insure condensation in liquidform above the melting point of zinc, thus avoiding the formation of zinc dust. The composition of the gases must be such that the reoxidation temperature of zinc vapor for such compositions is below the point at which the vapor condenses to liquid zinc, in order that the formation of zinc oxide, or blue powder may be avoided. If the desired product is zinc dust the first condition is of course modified.

I assure the existence of these conditions, first, by conducting the reaction in the presence of carbon at relatively high temperatures, as explained above, second, by employing as an aid to combustion a gas consisting principally of oxygen, and third, by conducting the reaction products to the condensation zone quickly and under such conditions that there is little opportunity for reoxidation of zinc vapor or dissociation of carbon monoxide into carbon dioxide and carbon.

(a) Excess carbon and temperature eflects acting materials at high temperatures even the presence of carbon would not be suflicient to avoid reoxidation of the zinc vapor, because at temperatures below, for example 1000 C., equations (1) and (2) permit the existence of both zinc' oxide and carbon dioxide in substantial amounts. Whether or not reoxidation actually occurs'depends on the relative volumes of carbon dioxide and carbon monoxide in the gases at any given temperature, and reaction temperatures below 1000 C. produce relative volumes that permit reoxidation of the zinc vapors at temperatures above their dew point, hence before they are able to condense to liquid zinc. The reoxidation temperatures for gas compositions produced at temperatures above 1100 C., however, are much below the dew point of the zinc vapor and it is therefore possible to condense a large proportion of the zinc vapor without reoxidation. As the zinc vapor is condensed the relative concentrations of components in the gases are of course varied, but the ratio of volumes of carbon dioxide and carbon monoxide does not vary materially unless there has been dissociation of carbon monoxide or reoxidation of zinc according to the reactions:

The former of these two reactions normally proceeds so slowly at temperatures encountered in the condensation chamber that its effect is not material. The latter proceeds at a faster rate above 550 C., but its rate is determined by the slower reaction, and I avoid its effect by quickly cooling the gases from the reaction temperature (b) Thermal requirements and partial pressures In the foregoing description, the nature of the reactions involved in the reaction chamber and the conditions which must be maintained in the condensation chamber have been set forth with:

' out reference to the thermal requirements of the system and their influence on gas compositions. By consideration of the known specific heats of the substances involved in the process and the heats involved in the reactions that take place,

which reactions may be equated in concise form as follows: a

it is clearly demonstrable that no process of this when air is used to burn the carbon.

In a system including zinc oxide and carbon, if air is used to eifect combustion of the carbon so as to maintain the reaction at the temperature 1200 0., without preheating, the minimum amount of carbon which must be burned for each 81 pounds of oxide isabout 290 pounds, disregarding heat losses occurring through radiation and conduction. At least 385 pounds, or 11 mols of oiwgen, are needed to carry out the combustion of this carbon, resulting in the formation of 24 mols of carbon monoxide for each mol of zinc vapor, and these gases are accompanied by about 46 molsof nitrogen. The partial pressure of zinc in the exit gases at one atmosphere would approximate one over seventy, which is insufiicient to permit condensation of zinc as liquid metal or recovery of the zinc in any form other than as zinc'oxide.

If the zincpxide and carbon should be preheated to about;800 C. before starting the reaction, continuing the use of air, the amount of car;

147 pounds for 81 pounds of oxide or over 12 mols for each mol of zinc oxide. This requires about 6 mols of oxygen and about 24 mols of nitrogen in the entering gases and about 12 mols of carbon monoxide and 24 mols of nitrogen in the exit gases, per mol of zinc vapor. The resulting partial pressure of zinc, about one over thirty-six, is

still far too low for condensation as liquid zinc,

. tion of several factors which must be eliminated in order successfully to secure liquid zinc through direct combustion. The large volume of nitrogen necessary to be heated when air is used is dispensed with. The carbon needed to heat this nitrogen is saved. The carbon needed to heat the carbon monoxide gas formed by combustion is saved. Thus the process becomes economically feasible instead of utterly impractical. Of even greater importance, however, is the effect of these savings on the concentration of zinc vapors in the gases leaving the reaction chamber and on the size of the furnace required to carry out the process. Partial pressures of zinc vapor suiflcient to insure condensation of a large proportion thereof into liquid zinc are readily obtained by my process because the only substantial constituents of the exit gases, when oxygen is used, are the zinc vapor'and carbon monoxide, while the latter may be kept at a'relatlvely low point by preheating the charge.

With the charge preheated to 800 C. it is necessary, disregarding heat losses, to use only about 55 to pounds of carbon per mol of zinc oxide in order to maintain the reacting materials and the exit gases at 1200" C. This requires the use of about 2 mols of oxygen, produces not over 5 mols of carbon monoxide and not less than 1 mol of zinc vapor; hence the partial pressure of the zinc vapor is at least one over 'six, which is suflicient to iobtain satisfactory. condensation. Without preheating, the carbon requirements are raised to about 71 pounds, or about 6 mols per mol of zinc oxide, but condensation is still pos sible. Preheating the charge to a higher temperature, for example 1000 (3., effects further economies in fuel and enables greater recoveries of liquid zinc.

A, zinc vapor content of about 9% is essential to secure substantial condensation to liquid zinc, and such a content may be produced by the use of gas containing up to 50% of substances other I than oxygen if the charge is preheated in order is about 55 poundsper 81 pounds of zinc oxide,

and the partial pressure of the resulting zinc vapors is somewhat greater than one over six, again more than sufflcient for good recovery of liqu1d zinc.

It will be understood, of course, that the foregoing determinations of thermal requirements are based upon calculations that do not take into consideration heat losses occuring through conduction and radiation. In a substantially closed refractory furnace of the kind corresponding to my invention, however, the heat losses are not so great as to disturb the comparative significance of these determinations.

In the production of zinc dust according to the present invention the temperatures in the condensation chamber are maintained below the melting point of zinc, which may be accomplished by appropriate chilling of the outer walls of this chamber, as by a spray of cooling fluid from the jets 32, or by eliminating heavy insulation on the inside walls of the condensation chamber so that the cooling may be effected more readily.

The practice of my invention permits eflicient recoveries of liquid zinc, which may be periodically tapped from the condensation chamber and cast into suitable molds, or of zinc dust substantially uncontaminated by zinc oxide, by the use of simple, durable apparatus of relatively large capacity and without involving excessive labor and fuel requirements. Production of two tons of liquid zinc per day may be obtained with a single relatively small kiln. The zinc contents of various grades and sizes of zinciferous materials may be extracted and recovered without preliminary conditioning operations such as are now required in retort smelting practice. Moreover, I have provided a process in which the rate of reduction and other operating conditions may be positively controlled.

My improved apparatus provides the first zinc furnace embodying a reaction chamber for accommodating large quantities of zinciferous and carbonaceous materials, means for keepng these materials intimately mixed and for exposing them uniformly to gases in the chamber, and

a condensation chamber that is integrally and axially mounted with respect to the reaction chamber so that losses and contamination of gases and recovered products are avoided. The apparatus is constructed so that oxygen gas may be used without danger of burning out. It possesses other novel features that are described hereinabove.

It will be understood that the improved process may be carried out in various types of apparatus and.that the invention is not restricted to the details mentioned hereinabove except as required by the claims.

I claim:

1. In the metallurgy of zinc, the process comprising flowing gas consisting principally of oxygen into a charge including zinciferous ore or concentrate and at least. three times the molecularly equivalent quantity of carbonaceous material, maintaining the temperature of the reacting materials in the charge at 1000 C. or above by reacting theoxygen with carbonaceous material and simultaneously reducing zinciferous ore or concentrate to'form zinc vapor, flowing the resulting gases into a condensation chamber, and cooling and condensing zinc vapor from said gases in the condensation chamber.

2. In the metallurgy. of zinc, the process comprisingpreheating a charge including zinciferous ore or concentrate and at least three times 1000 C. or above by reacting the oxygen in said 3. Process as claimed in claim 2, in which re sidual gases from the condensation chamber are combusted to effect preheating of succeeding charges.

4. Process as claimed in claim 2, in which the reacting substances are maintained at a temperature between 1100 and 1300 C.

5. Process as claimed in claim 2, in which the gas flowed into the charge is substantially all oxygen.

6. In the metallurgy of zinc, the process comprising preheating a charge including zinciferous ore or concentrate and at least three times the molecularly equivalent quantity of carbonaceous material to a temperature of at least 800 C., tumbling the materials of the charge, flowing gas consisting principally of oxygen into the tumbling materials and thereby intimately contacting them with the gas, maintaining the temperature of the reacting materials in the charge at 1000 C. or above by reacting the oxygen in said gas with the carbonaceous material while reducing zinciferous ore or concentrate to form zinc vapor, flowing the resulting gases into a condensation chamber, and cooling and condensing zinc vapor in the condensation chamber.

Process as claimed in claim ,6, in which the zinciferous material is so finely divided that at least 50% thereof will pass through a 65 mesh screen.

8. In the metallurgy of zinc, the process comprising flowing gas consisting principally of oxy-.- gen into a reaction chamber containing zinciferous ore or concentrate and at least three times the molecularly equivalent quantity of carbonaceous material, tumbling and lifting the materials of the charge and showering them through the entering stream of gas, maintaining the temperature of materials in the charge at 1000 C., or above by reacting the oxygen in said gas with'the carbonaceous material and simultaneously reducing zinciferous ore or concentrate to form zinc vapor, flowing resulting gases into a condensation chamber, and coooling and 0on densing zinc vapor from said gases in the condensation chamber.

9. In the metallurgy of zinc, the process comprising flowing gas consisting principally of oxygen into a charge including zinciferous ore or concentrate and at least three times the molecularly equivalent quantity of carbonaceous gnaterial, maintaining the temperature of reacting materials in the charge at 1000 C. or above by reacting the oxygen with the carbonaceous material and simultaneously reducing zinciferous ore or concentrate to form zinc vapor, flowing the resulting gases into a condensation chamber, and coooling the gases to a temperature above the melting point of zinc and below the dew point of the zinc vapor in the condensation chamber, thereby producing liquid zinc substantially uncontaminated by zinc dust or zinc oxide.

10. Process as claimed in claim 9 in which the charge is preheated to a temperature of at least 800 C. before commencing the flow of O genbearing gas.

11. Process as claimed in claim 9, in which the gases are cooled to a temperature between 450 C. and 700 C. in the condensation chamber.

12. Process as claimed in claim 9, in which the residual gases leaving the condensation chamber are employed as a fuel to generate oxygen for the reaction.

13. In the metallurgy of zinc, the process comprising preheating a body of carbonaceous material in a reaction chamber to a temperature above 800 C., flowing a stream of gas consisting principally of oxygen into the chamber and simultaneously introducing zinciferous ore or concentrate into the chamber in an amount correlated with the amount of oxygen so that the zinciferous material is continuously reduced to form zinc vapor and carbonaceous material is continuously combusted to maintain the temperature of the reacting substances above 1000 C. substantially according to the equation,

flowing the resulting gases into a proximate condensation chamber, and cooling and condensing zinc vapor from said gases in the condensation chamber.

14. Process as claimed in claim 13 in which the reacting materials are maintained at a temperature of at least 1200 C.

15. Process as claimed in claim 13 in which said stream of gas is substantially all oxygen.

16. In the metallurgy of zinc, the steps comprising preheating a body of carbonaceous material in a reaction chamber to a temperature above 800 C., flowing a stream of gas consisting principally of oxygen into the chamber and simultaneously introducing zinciferous ore or concentrate into the chamber, tumbling carbonaceous and zinciferous materials together and intimately contacting them with the stream of gas by showering them through said stream, correlating the amount of oxygen flowed into the chamber with the amount of zinciferous material introduced in order to maintain the temperature of the reacting substances above 1000 C. while continuously reducing the zinciferous material to zinc vapor, substantially according to the equation WILLIAM SEGUINE, JR.

chamber.

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