US2342368A - Zinc metallurgy - Google Patents

Zinc metallurgy Download PDF

Info

Publication number
US2342368A
US2342368A US394009A US39400941A US2342368A US 2342368 A US2342368 A US 2342368A US 394009 A US394009 A US 394009A US 39400941 A US39400941 A US 39400941A US 2342368 A US2342368 A US 2342368A
Authority
US
United States
Prior art keywords
zinc
zinc oxide
charge
carbon
reduction
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US394009A
Inventor
Queneau Augustin Leon Jean
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Individual
Original Assignee
Individual
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Individual filed Critical Individual
Priority to US394009A priority Critical patent/US2342368A/en
Application granted granted Critical
Publication of US2342368A publication Critical patent/US2342368A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • CCHEMISTRY; METALLURGY
    • C22METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22BPRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B19/00Obtaining zinc or zinc oxide
    • C22B19/04Obtaining zinc by distilling

Definitions

  • oxidic zinc material,I together with carboniferous reducing agent is showered through an environment which ⁇ is heated to temperatures above the reduction and volatilization temperatures of zinc, the reduction taking place in the freely falling charge while the particles are in suspension in the environment.
  • the carbon must be present in suillcient excess to contact efficiently with the zinc oxide particles during their fall, so that reduction and volatilization of the zinc will proceed before the charge reaches the bottom of the reactant environment.
  • the cause of the unsatisfactorily shortened life of the 'silicon carbide "flash columns employed in flash reducing operations as practiced prior to the present invention now is found to be due to the presence of materials associated with zinc oxide, which even though present in sulcicntly small amounts so as to enable the zinc oxide .being employed to be classed as substantially pure zinc oxide, nevertheless, under the conditions existing in the ash column where the entire charge is being made up of continuously y swirling particles being continuously introduced j into the flash column, which particles ⁇ intimately engage the hot silicon carbide surfaces of the column and come into wiping contact therej with, such materials under these ideal conditions for reaction attack both the silicon carbide of the column and the binder employed to bond the silicon carbide during the manufacture of the column, lthe-resulting reactions causing a markedly quick disintegration and deterioration of the column.
  • Such materials are found to be.
  • certain slag-forming materials normally present with zinc oxide produced from zinc ores or concentrates, among which materials may be mentioned, importantly. lime, magnesia, iron bide bricks which oxides, lead, cadmium, silver and alkalies, which under the conditions.. maintained in the retort,-
  • .Zinc ores occur in nature mixed with gangue materials and usually carry too low a percentage ,ofzinc to allow for economicaltreatment for reduction to metal or chemical compounds.
  • the crude ores therefore, are processed so as to; yield high grade concentrates; in the case of .sulphide ore, of 60 per cent zinc or better. ,'Even these high grade zinc concentrates contain substantial amounts of contaminating chemical elements or compounds, such as sulphur, iron, silica, lime,
  • the sulphur may be eliminated by suitable oxidizing treatment, such as roasting;
  • suitable oxidizing treatment such as roasting
  • there are concentrated further the zinc contents of roasted zinc concentrates by the further elimination ofthe remaining vimpurities by a suitable pyro-metallurgical treatment described herein'.
  • the roasted zinc concentrates containing as main impurities iron and/or manganese oxides, lead sulphate, and small amounts of cadmium and precious metals, in accordance with the present invention are mixed with a suitable proportion of carbonaceous material, such as coke 6r anthracite coal, or other carbonaceous material high in fixed carbon, and the resulting mixture is fed into an inclined rotary kiln of the general type used inthe well-known Waelz process for producing zinc oxide.
  • carbonaceous material such as coke 6r anthracite coal, or other carbonaceous material high in fixed carbon
  • the heat gradient required for .the operation is maintained principally by the combination of the fuel addition to the zinc ore charge and, in addition, if required, by a burner supplying additional heat through the burning of powdered coal, fuel oil, or other suitable fuel, the selection of the fuel supply for the burner being largely a question of convenience and costs.
  • the vapors of the reduced zinc are burned, zinc oxide is re-formed. But now this zinc oxide is liberated almost completely freed from gangue impurities, except a small amount thereof that is carried as ne dust by the gas stream sweeping through the kiln to its exit.
  • the resulting zinc oxide usually contains some lead, cadmium, and silver, since lead is reduced with the zinc and volatilizes as leadA retaining the precious metals in a complex ironcopper matte which is an active absorber of gold and silver. If copper is absent in the zinc calcines, an addition of copper-bearing material to the charge may be found to be advantageous.
  • the initially puried zinc oxide is collected in any suitable way, as in textile bags, or in -a Cottrell precipitator.
  • This zinc oxide contains substantially all of the zinc content of the roasted ore charge with its lead and cadmium contents. It also includes a small amount of fine particles of gangue, of carbon, and also a comparatively large volume of sulphur dioxide and other gases s occluded and adsorbed on the zinc oxide particles, so that further treatment of the zinc oxide is required for the elimination of the lead. cadmium, silver, and the occluded gases.
  • the crude zinc oxide is mixed thoroughly with a halide compound, preferably sodium chloride.
  • a halide compound preferably sodium chloride.
  • the resulting mixture is fed onto the bed of a blast sintering machine, such as a Dwight-Lloyd machine, with the salt presentV in the charge in slight excess of the stoichiometric requirements of the lead, cadmium, and silver.
  • the charge is sintered,
  • This sintering removes al1 of the contaminating metals, lead, cadmium, and silver, as chlorides and/or sulphates, together with the Whole of any sulphur present. These contaminants are carried /away from the sinter bed by the gases sweeping at high velocity through the bed. The resulting gases pass through a suitable Cottrell precipitator in which the metal compounds are collected. i
  • the sintering operation is carried on in such a way as to produce a light porous sintered product, this being obtained by adding to the charge of the sintering machine a strict minimum amount of xed carbon, such as coke or anthracite coal, for minimizingI the maximum temperature reached in the bed of the sinteringmachine.
  • xed carbon such as coke or anthracite coal
  • the resulting sintered product consists of substantially pure zinc oxide which is highly suitable for further metallurgical treatment for the production of high grade zinc metal by flash or suspensionv reduction or in a vertical continuous retort, or other procedure.
  • the residual gangue matter in the rotary kiln charge is discharged at its lower end, together -with any excess of carbon that may be present.
  • the resulting complex ironcopper matte carrying the precious metals may be separated readily from the otherwise valueless slag by crushing and treatment by the usual oredressing methods,'such as tabling, but preferably by flotation.
  • tions amounting to from about 15 parts by weight to about 20 parts by weight.
  • the mixture then is passed through a steam jacketed pug mill from which the thoroughly lneorporated mixture is extruded in the form of a hollow cylindersix inches in diameter with one and one-half inch central perforation, and cut into twelve-inch lengths orbriquettes.
  • 'I'hese briquettes are piled on a platform car and run into a tunnel furnace, heated indirectly, in which there is maintained a maximum temperature of from about 600 C. to 800 C., the briquettes being brought slowly to full temperature until al1 volatile ymatter has been expelled and the briquettes are coked.
  • the particles of this product consist principally of puritled zinc oxide completely permeated with xed carbon deposited during the distillation and coking of the briquettes. There is provided thereby completely intimate contact between the reducing material and the zinc oxide. 'I'his contact, it is to be emphasized, is not the haphazard Vcontact between nite and separate particles of zinc oxide and carbon, as has been employed in reduction processes prior hereto, but, on the contrary, it is an actual finite zinc oxide-'carbon contact existing within each concrete particle of zinc oxide, thus providing optimum conditions for the rapid reduction of the zinc oxide when these pulverized zinc oxide-coke briquettes are brought up to the required zones of temperature for reduction.
  • pulverized briquettematerial is passed into a preheater consisting of a rotary kiln which is ilred externally and in which a temperature of from about '100 C. to about 800 C. is maintained.
  • the purified sintered zinc oxide prepared'as'above "together with coke, low-ash anthracite coal, or other carbonaceous material lowin mineral matter, and in the proportion of about 100 partsby weight of the zinc oxide sinter to from about-20 vto 25 parts byweight of the low-ash vcarbonaceous reducing material, are' mixedtogethenthoroughly while water-free hot tar is introduced into the mixture.
  • This collected zinc dust and blue powder mud- (zinc dust, zinc oxide, and blue powder) is returned to the pug mill for afurther treatment with the following charge of purified sintered zinc oxide, while the washed carbon monoxide issuing from the zinc condenser is utilized to provide a controlled non-oxidizing atmosphere in both the coking briquette furnace and the preheating rotary kiln for the charge of pulverized briquettes of zinc oxide-carbon.
  • the carbon monoxide after its passage through both furnaces, is burned to supply additional heat units in both furnaces.
  • an incandescent column of coke In the flash reduction furnace, there may be provided an incandescent column of coke, although the presence thereof is not obligatory by any means. But where such coke column is provided, its temperature is at the high heat level required (1200 C.1300 C.), which is maintained by indirect heating, as when adjacent to the flash reduction furnace wall, by electrical resistance,
  • the sized coke (all through a Z-inch ring and plus 3A inch) is fed to the coke column at a continuous rate through a gastight seal 'and there is withdrawn at an equal rate and continuously an equal amount from the foot of the .column also through a gas-tight seal, and quenched.
  • the coke also may be supplied to the reduction furnace in the form of briquettes.
  • the present invention provides means for maintaining carbon in intimate contact with the zinc oxideof the charge; and it has been pointed out above that the reduction of the zinc oxide, proceeds in accordance with the two reactions:
  • producer reaction ⁇ g furnace is brought to a temperature of 800 C.' 900 C. before introduction to the flash reduction metal.
  • the coke fines also carry the residues from the zinc charge of the suspension zinc reduction furnace. These nes pass to the rotary kiln and are mixed with the incoming charge of crude zinc ore calcines and coke.
  • the admission of a regulated amount of air at the base of the incandescent coke column serves the further purpose in helping to scavenge and evacuate therefrom any zinc vapor that might have a tendency to concentrate at the bottom of the furnace within the,coke column. This function is in addition to its assistingl in maintaining the temperature of the coke column at the level desired.
  • the clean residual gases which consist principally of carbon monoxide, pass through a preheater, a portion thereof passing thence to' the preheating furnace in which the' finely com' minuted charge of the suspension zinc reduction furnace.
  • This roasted concentrate was' charged into the rotary kiln and the zinc oxide produced by the kiln in a procedure similarto the well knownl Waelz process.
  • This oxidlc material thenis sintered in the presence of salt, as described above, prior to the mixing with tar in the pug mill.
  • the sintered product analyzed: ZnO 94.80 per cent; SiOzAlzOa Since carbon monoxide is the principal reducing agent for the zinc, the use of the carbon monoxideV atmosphere introduces no extraneous material into the reacting system; and with the intimate contact between the carbon and the zinc oxide, which is provided by the present invention, .there are provided optimum conditions for the maintenance of the producer gas reactions.
  • ther improvements which consist in producing zinc oxide containing not more than substantially 0.6% of contaminants that are reactive towards silicon carbide at elevated temperatures intimately mixing and impregnating the resulting zinc oxide with a -bituminous material high in fixed carbon and adapted to bind-the zinc oxide, by' kneading together the zinc oxide and bituminous material into an extrudible material, .extruding the resultingl mixture, briquetting the extruded mixture, coking 'the resulting briquettes thereby carbonizing the bituminous material, commmuting the briquettes, whereby each resulting particle is acomposite particle of zinc oxide and carbon, and showering the resulting comminuted material through a vertical'silicon carbide retort externally heated to a sufficiently high temperature to reducethe zinc oxide to metallic zinc vapors while the amongl are in free suspension.
  • said pure zinc oxide by mixingit with a bitum'i-v u founded material including tar, kneading the tar" ofthe zinc oxide with thev tar is eifected, heating the resulting mixture to a coking temperature material, maintaining the coke and oxide in continuous contact, showering the resulting into the zinc oxide until thorough impregnation mixture through a ash reduction environment having surfaces in contact with the material Icomposed of silicon carbide heated to reducing temperatures, and eiecting a reduction of the charge to elemental zinc while the charge is infree movement inthe environment.

Description

A. y L. `J. QUENEAU ZINC METALLURG'; Filed uay 17, 1941 Feb. 22, 1944.
SSN.
` WNS gl MMHWJML. A :Ally www@ Pnented Feb. 2z, 1944 UNirED s'rirrrasg PATENT 'ori-'ica 2,342,368 l l I znw METALLURGY Augustin Leon Jean Queneau, Peapack, N. J.
Application May 1v,-1941,'seriai No. 394,009 f 4 claims. (cl. 'z5-2e) Inainc metallurgy, it is not an entirely new conception to proceed by what may be termed a "fiashyreduction operation for winning zinc from zinciferous metallurgical materials.
In accordance with such flash reduction" procedure, oxidic zinc material,I together with carboniferous reducing agent, is showered through an environment which `is heated to temperatures above the reduction and volatilization temperatures of zinc, the reduction taking place in the freely falling charge while the particles are in suspension in the environment. The carbon must be present in suillcient excess to contact efficiently with the zinc oxide particles during their fall, so that reduction and volatilization of the zinc will proceed before the charge reaches the bottom of the reactant environment.
In carrying out the flash reduction process, it
has been the practice to shower the zinc oxide-- carbon mixture through a vertical columnar retort composed of a monolithic structure of essentially silicon carbide. The retort is fired externally, and preferably a reducing environmentis maintained in the retort in order to facilitate the reduction of the zinc oxide while it is freely falling. Propane gas has been employed for the maintenance of this reducing atmosphere, a propane atmosphere apparently tending to reduce the amount of blue powder produced during the operation. The formation of this blue powder has been one detriment to the flash reduction operation as has been practiced heretofore. This has led to various proposalsx for conditioning and scrubbingthe emergent zinc stream .as it passes l to the condenser to remove various vsuspensoids in the gas stream which appear to act as nucleiA for blue powder production.
Additionally, it has been proposed to increase the reduction rate by using activated, or alpha, carbon as the reducing agent.' In Vprior procedure, the elciency of the process is found to be increased thereby. l
These specialized provisions of the'prior practice are required because of certain existent factors:
l. The presence of suspensoids in the exit gases is due to entrained soiled particles from the of carbon arises because of imperfect physical contactbetween the particles oiA zinc oxide and the particles of carbon.
`3. This imperfect physical contact requires forefilciency a speeding up of the reduction speed,-
which is attained by the use of highly reactive (activated) carbon, materially increasing the cost of the procedure.
4. The life of the silicon carbide "ash" column is not sufficiently satisfactory to make a flash reduction procedure competitive with respect to costs,. with standard vertical retort operations.
In accordance with the present invention, the cause of the unsatisfactorily shortened life of the 'silicon carbide "flash columns employed in flash reducing operations as practiced prior to the present invention, now is found to be due to the presence of materials associated with zinc oxide, which even though present in sulcicntly small amounts so as to enable the zinc oxide .being employed to be classed as substantially pure zinc oxide, nevertheless, under the conditions existing in the ash column where the entire charge is being made up of continuously y swirling particles being continuously introduced j into the flash column, which particles` intimately engage the hot silicon carbide surfaces of the column and come into wiping contact therej with, such materials under these ideal conditions for reaction attack both the silicon carbide of the column and the binder employed to bond the silicon carbide during the manufacture of the column, lthe-resulting reactions causing a markedly quick disintegration and deterioration of the column. Such materials are found to be.
importantly, certain slag-forming materials normally present with zinc oxide produced from zinc ores or concentrates, among which materials may be mentioned, importantly. lime, magnesia, iron bide bricks which oxides, lead, cadmium, silver and alkalies, which under the conditions.. maintained in the retort,-
react with the silicon. carbide to produce silicates' of the respective metals.
While the silicon carbide shells which form the fiash"column in the usual type thereof are found to be destroyed with marked rapidity by the presence of even small amounts of such materials A in the zinc oxide being reduced, the same type of attack is observed inthe case of the silicon carve been employed in the construction of vertical retorts using briquetted charges of zinc oxide 'and carbon, although in such installations, the attack is much slower, as
the conditions for reaction with silicon carbide are much less favorable than are the conditions ex,-
istent in a flash reduction column. However, even in the carborundum brickwork of vertical zinc retorts, in time there becomes a very appreciable attack on the surfaces of the brick that are exposed to the briquetted charges being processed.
The procedure of the present improved process is found to obviate these, and other, difficulties which have made impracticable a process which should be an attractive procedure from the standpoint of costs, as well as the yield and purity of the condensed metal. l
Certain features distinguish the present invention:
A. A careful purifilation of the zinc-bearing materials to eliminate associated impurities, thereby yobviating the necessity for special conditioning or scrubbing ofthe zinc-bearing gases passing from the flash retort to the condenser.
B. The production and maintenance of a homogeneous and intimate contact of the reactive carbon with the oxidic component of the charge,
to eliminate the necessity of utilizing specially prepared activated or alpha carbon.
-tage in the operation of other zinc metallurgical processes, including the usual type of vertical retort practice. v
The invention will be understood more readily by reference tothe accompanying drawing, which illustrates a diagrammatic flow-sheet of the process.
'I'he present process may be divided into several cooperating parts, the interrelationship of which will become apparent from a consideration of the accompanying drawing which illustrates a` diagrammatic flow sheet of the entire process. These cooperating parts are indicated in the diil'erent stages set forth in the description which follows hereinafter.
Preparation of the charge One of the important features of the present invention is the preparation of the charge for the reduction.
.Zinc ores occur in nature mixed with gangue materials and usually carry too low a percentage ,ofzinc to allow for economicaltreatment for reduction to metal or chemical compounds. The crude ores, therefore, are processed so as to; yield high grade concentrates; in the case of .sulphide ore, of 60 per cent zinc or better. ,'Even these high grade zinc concentrates contain substantial amounts of contaminating chemical elements or compounds, such as sulphur, iron, silica, lime,
cadmium, lead, etc.
In many instances, it is of economic interest to increase further the zinc contents ofl the mill concentrates mentioned above. Thus, the sulphur may be eliminated by suitable oxidizing treatment, such as roasting; In accordance with the present process, there are concentrated further the zinc contents of roasted zinc concentrates by the further elimination ofthe remaining vimpurities by a suitable pyro-metallurgical treatment described herein'.
2 as-iases The roasted zinc concentrates containing as main impurities iron and/or manganese oxides, lead sulphate, and small amounts of cadmium and precious metals, in accordance with the present invention are mixed with a suitable proportion of carbonaceous material, such as coke 6r anthracite coal, or other carbonaceous material high in fixed carbon, and the resulting mixture is fed into an inclined rotary kiln of the general type used inthe well-known Waelz process for producing zinc oxide. The heat gradient required for .the operation is maintained principally by the combination of the fuel addition to the zinc ore charge and, in addition, if required, by a burner supplying additional heat through the burning of powdered coal, fuel oil, or other suitable fuel, the selection of the fuel supply for the burner being largely a question of convenience and costs.
In its passage through the rotary kiln, the zinc oxide is reduced within the body of the charge, tumbling and rolling in contact with the lower and rising part of the kiln lining, principally in accordance with the reaction:
As there is of lnecessity an excess of carbon present in the kiln charge, a.' secondary reaction also takes place:
COa-I-C-)ZCO 'I'he metallic zinc vapors, together with the carbon monoxide issuing from the highly heated charge, burn freely in contact with the current of highly heated air admitted 'at the discharge end of the kiln. It may be noted in passing that that heat liberated by the combustion of zinc vapor to zinc oxide and of the carbon monoxide to carbon dioxide is substantially equivalent to the amount of heat required for the reduction of' zinc oxide in the roasted ore, with allowance for the heat which is carried away from the kiln by the gases of combustion, and also for the heat that must be supplied to the radiating outer surface of the kiln.
Now, as the vapors of the reduced zinc are burned, zinc oxide is re-formed. But now this zinc oxide is liberated almost completely freed from gangue impurities, except a small amount thereof that is carried as ne dust by the gas stream sweeping through the kiln to its exit. However, the resulting zinc oxide usually contains some lead, cadmium, and silver, since lead is reduced with the zinc and volatilizes as leadA retaining the precious metals in a complex ironcopper matte which is an active absorber of gold and silver. If copper is absent in the zinc calcines, an addition of copper-bearing material to the charge may be found to be advantageous.
The initially puried zinc oxide is collected in any suitable way, as in textile bags, or in -a Cottrell precipitator. This zinc oxide contains substantially all of the zinc content of the roasted ore charge with its lead and cadmium contents. It also includes a small amount of fine particles of gangue, of carbon, and also a comparatively large volume of sulphur dioxide and other gases s occluded and adsorbed on the zinc oxide particles, so that further treatment of the zinc oxide is required for the elimination of the lead. cadmium, silver, and the occluded gases.
For this purpose, the crude zinc oxide is mixed thoroughly with a halide compound, preferably sodium chloride. The resulting mixture is fed onto the bed of a blast sintering machine, such as a Dwight-Lloyd machine, with the salt presentV in the charge in slight excess of the stoichiometric requirements of the lead, cadmium, and silver. The charge is sintered,
This sintering removes al1 of the contaminating metals, lead, cadmium, and silver, as chlorides and/or sulphates, together with the Whole of any sulphur present. These contaminants are carried /away from the sinter bed by the gases sweeping at high velocity through the bed. The resulting gases pass through a suitable Cottrell precipitator in which the metal compounds are collected. i
The sintering operation is carried on in such a way as to produce a light porous sintered product, this being obtained by adding to the charge of the sintering machine a strict minimum amount of xed carbon, such as coke or anthracite coal, for minimizingI the maximum temperature reached in the bed of the sinteringmachine.
The resulting sintered product consists of substantially pure zinc oxide which is highly suitable for further metallurgical treatment for the production of high grade zinc metal by flash or suspensionv reduction or in a vertical continuous retort, or other procedure.
The residual gangue matter in the rotary kiln charge is discharged at its lower end, together -with any excess of carbon that may be present.
If the kiln charge contained suilicient values of precious metals, together with an adequate amount of copper, the resulting complex ironcopper matte carrying the precious metals may be separated readily from the otherwise valueless slag by crushing and treatment by the usual oredressing methods,'such as tabling, but preferably by flotation.
It will be seen, therefore, that from a complex zinc ore carrying gangue materials, such as iron, manganese, silica, lime, etc., together withadditional metal values, such as lead, cadmium, and
tions amounting to from about 15 parts by weight to about 20 parts by weight.
The mixture then is passed through a steam jacketed pug mill from which the thoroughly lneorporated mixture is extruded in the form of a hollow cylindersix inches in diameter with one and one-half inch central perforation, and cut into twelve-inch lengths orbriquettes. 'I'hese briquettes are piled on a platform car and run into a tunnel furnace, heated indirectly, in which there is maintained a maximum temperature of from about 600 C. to 800 C., the briquettes being brought slowly to full temperature until al1 volatile ymatter has been expelled and the briquettes are coked.
` The coked briquettes are crushed all through 4a one-inch screen, the crushed product then being fed to a rodmill operating in a closed circuit with an air classifier to give a iinal product,- about 85 per cent of which passes through a 20D-mesh screen. I
The particles of this product consist principally of puritled zinc oxide completely permeated with xed carbon deposited during the distillation and coking of the briquettes. There is provided thereby completely intimate contact between the reducing material and the zinc oxide. 'I'his contact, it is to be emphasized, is not the haphazard Vcontact between nite and separate particles of zinc oxide and carbon, as has been employed in reduction processes prior hereto, but, on the contrary, it is an actual finite zinc oxide-'carbon contact existing within each concrete particle of zinc oxide, thus providing optimum conditions for the rapid reduction of the zinc oxide when these pulverized zinc oxide-coke briquettes are brought up to the required zones of temperature for reduction.
-The charge of pulverized briquettematerial is passed into a preheater consisting of a rotary kiln which is ilred externally and in which a temperature of from about '100 C. to about 800 C. is maintained.
^ Reduction of the charge The charge, -prepared as above, and heated to from about 700 C. to about 800 C. (the temperature may vary according to the nature and characteristics of the zinc oxide to be reduced), is
duction operations# with the exception that in In order to .effect the improvements of the present process.' the purified sintered zinc oxide prepared'as'above, "together with coke, low-ash anthracite coal, or other carbonaceous material lowin mineral matter, and in the proportion of about 100 partsby weight of the zinc oxide sinter to from about-20 vto 25 parts byweight of the low-ash vcarbonaceous reducing material, are' mixedtogethenthoroughly while water-free hot tar is introduced into the mixture. the tar addicontinuously fed and showered into a vertical reducer furnace or retort Vcomposed of silicon carbide, maintained at a temperature of from about.1100 C. to about 1250" C., in which the reduction of the zinc oxide-carbon complex is eiected principally according to the reaction:
zno+C'ozn+co2 1) Since, however. there is an excess of carbon at a glowing temperature in the furnace "charge, the producer-gas reaction becomes eiective:
The value of the presence oi' carbon particles in intimate contact with the zinc oxide of the sinterV is indicated by Reaction 2. A It is known that the speed of Reaction 1 is as possible. The carbon present within each concrete particle of zincslnter offers immediate contact with the liberated C02.
This is not the case when the carbon is present in the charge only as particles separate and distinct from the zinc calcine particles of the susdenser for zinc maintained at the optimum temperature for the condensation of the zinc vapor s to liquidzinc.
The residual carbon monoxide stream, carrying a small proportion of zinc dust and blue powder,
passes through a small column through which flows counter-currently aspray of'water.
This collected zinc dust and blue powder mud- (zinc dust, zinc oxide, and blue powder) is returned to the pug mill for afurther treatment with the following charge of purified sintered zinc oxide, while the washed carbon monoxide issuing from the zinc condenser is utilized to provide a controlled non-oxidizing atmosphere in both the coking briquette furnace and the preheating rotary kiln for the charge of pulverized briquettes of zinc oxide-carbon. The carbon monoxide, after its passage through both furnaces, is burned to supply additional heat units in both furnaces.
In the flash reduction furnace, there may be provided an incandescent column of coke, although the presence thereof is not obligatory by any means. But where such coke column is provided, its temperature is at the high heat level required (1200 C.1300 C.), which is maintained by indirect heating, as when adjacent to the flash reduction furnace wall, by electrical resistance,
or by direct partial combustion by the admittance at a point above the bottom of the coke column of a strictly metered amount of atmospheric air.
The sized coke (all through a Z-inch ring and plus 3A inch) is fed to the coke column at a continuous rate through a gastight seal 'and there is withdrawn at an equal rate and continuously an equal amount from the foot of the .column also through a gas-tight seal, and quenched. The coke also may be supplied to the reduction furnace in the form of briquettes. J
As has been pointed out above, the present invention provides means for maintaining carbon in intimate contact with the zinc oxideof the charge; and it has been pointed out above that the reduction of the zinc oxide, proceeds in accordance with the two reactions:
zno+co+zn co2 k1) CO2+C 2CO f (2) producer reaction` g furnace is brought to a temperature of 800 C.' 900 C. before introduction to the flash reduction metal.
coke that is being withdrawn continuously. The
withdrawn solids, coke, and residues, are screened,
all material passing a '3A-inch screen is separated,.
and the v-i-r'inch coke is returned to the feed of the coke column, while all V2-inch materialis crushed and passed to the feed of the rotary kiln as reducing and heating fuel. The 9A-inch and +1/2-inch material is sent to a crusher for addition as fuel to the reduction furnace charge preparatory to the tar addition.
The coke fines also carry the residues from the zinc charge of the suspension zinc reduction furnace. These nes pass to the rotary kiln and are mixed with the incoming charge of crude zinc ore calcines and coke.
This procedure enables the residual zinc values to be utilized, together with the withdrawn undersized coke.
The purified zinc vapors and gases now consisting substantially wholly of carbon monoxide with a small percentage of nitrogen (from tue air, admitted in regulated amount to the base of the incandescent coke column), pass 'to the condenser wherein the zinc vapor is condensed to liquid The residual gases, mainly C0, issuing from the scrubbing tower ofthe zinc condenser, are returned in the volume required to the top of the flash reduction furnace to provide the carbon monoxide atmosphereequired for the zinc reduction process and arepreheated to 1000" C.- 1100 C. before admission to the furnace. The admission of a regulated amount of air at the base of the incandescent coke column serves the further purpose in helping to scavenge and evacuate therefrom any zinc vapor that might have a tendency to concentrate at the bottom of the furnace within the,coke column. This function is in addition to its assistingl in maintaining the temperature of the coke column at the level desired.
After passage through the zinc condenser, the
residual gases and zinc vapors go through an adsettling in the condenser. Any uncondensed zinc vapor is oxidized partly or wholly in the scrubbing tower and is collected as a mud consisting of zinc oxide and zinc dust. The product is removed at intervals from the bottom settling tank, which also forms a gas seal.
The clean residual gases, which consist principally of carbon monoxide, pass through a preheater, a portion thereof passing thence to' the preheating furnace in which the' finely com' minuted charge of the suspension zinc reduction furnace. l
The following products are obtained from the mixed pug mill in which the zinc oxide sinter is with coke'and hot anhydrous tar, as has been described above, for further treatment in the flash furnace.
Product 3, above, passes to the rotary kiln for the recovery,of the zinc and carbon contained '.cautions must be taken to assure the producer gas reaction proceeding in 'the iiash column through interaction of the carbon ofthe charge with any carbon dioxide tending to be formed, which, however, cannot exist as such. Consequently, sufllcient carbon in the charge must be provided to maintain the gas producer Reaction 2, above, for minimizingl blue powder formation. Also, of course, the elimination of the coke column obviates introduction of air into the environment in the flash reduction shaft. Otherwise, the operation is in accordance-with the description given above. Y'
The following illustrative data show the results-obtained in the preparation of the zinc 'oxide for charging.
A zinc sulphide concentrate assaying Zn 61.77 per cent; S 30.82-per cent; Fe 1.15 .per cent; Pb 1.12 per cent; Cd 0.389 per cent; CaO 0.10 per cent; MgO 0.594 per cent; SiO: 3.26 per cent;
A1203 0.51 per cent, first was roasted.
The roasted concentrate analyzed: Zn 71.30
per cent; S 2.55 per cent; Pb 0.31 per cent; Cd 0.03 per cent; Fe 1.69 per cent; CaO 0.29 per cent; `Mg 0.70 per cent; S102 5.34 per cent; A1203 0.60 per cent; 017.45 per cent.
This roasted concentrate was' charged into the rotary kiln and the zinc oxide produced by the kiln in a procedure similarto the well knownl Waelz process.
This zinc oxide analyzed; ZnO 87.0 per cent (Zn 69.8 per cent) S 2.0 per cent; Pb0.03 per cent; Cd "0.31 per cent; SiOnJllzOa' 4.00 per cent; CaOMgO 0.50 percent; C 6.14 per cent.
This oxidlc material thenis sintered in the presence of salt, as described above, prior to the mixing with tar in the pug mill. The sintered product analyzed: ZnO 94.80 per cent; SiOzAlzOa Since carbon monoxide is the principal reducing agent for the zinc, the use of the carbon monoxideV atmosphere introduces no extraneous material into the reacting system; and with the intimate contact between the carbon and the zinc oxide, which is provided by the present invention, .there are provided optimum conditions for the maintenance of the producer gas reactions.
While the coke column may be omitted,`its
. use as described herein, is preferred.
' therein. The product is mixed with fresh incom- I claim:
1. The process of producing zinc, which coinprises converting an impure zinciferous material into vsubstantially pure zinc oxide free from cadmium, lead. silver, and lall other materials chemically reactive towards silicon carbide, preparing a charge of the said pure zinc oxide by intimately mixing it with a substantially anhydrous bituminous material including water-free tar, kneading the tar until complete impregnation with the tar is eiected, heating the resulting mixture to a coking temperature until the bituminous material is coked in situ in the zinc.
oxide, finely comminuting the resulting material, maintaining the coke and oxide in continuous contact. showering the resulting mixture through a ash reduction environment having surfaces in contact with the material composed of silicon carbide heated to reducing temperatures, and eiecting a reduction of the into a substantially pure zinc oxide free fromv materials chemically reactive towards silicon carbide, preparing a charge of the said pure zinc -oxide by intimately mixing it with a bituminous material adapted to form coke upon heating to` coking temperature,l kneading together the bituminous material and the pure zinc oxide until complete intermixing results, heating thev y resulting mixture to coking temperature until j' the bituminous material is coked in situ in the zinc oxide, finely commuting the resulting material maintaining the coke and oxide in continuous contact. showering the resulting `mixture as a charge through a flash reduction environment having surfaces in contact with the mixture composed of silicon carbide heated to reducing temperatures, and effecting a, reduction of the charge to elemental zinc, while the charge is in free movement in the environment.
3. In the metallurgy of zinc, ther improvements which consist in producing zinc oxide containing not more than substantially 0.6% of contaminants that are reactive towards silicon carbide at elevated temperatures intimately mixing and impregnating the resulting zinc oxide with a -bituminous material high in fixed carbon and adapted to bind-the zinc oxide, by' kneading together the zinc oxide and bituminous material into an extrudible material, .extruding the resultingl mixture, briquetting the extruded mixture, coking 'the resulting briquettes thereby carbonizing the bituminous material, commmuting the briquettes, whereby each resulting particle is acomposite particle of zinc oxide and carbon, and showering the resulting comminuted material through a vertical'silicon carbide retort externally heated to a sufficiently high temperature to reducethe zinc oxide to metallic zinc vapors while the partiel are in free suspension.
4. The process of producing zinc, which coinprises converting an impure zinciferous material into substantially pure zinc oxide free from cadmium, lead, silver, iron and substantiallyl all of any other materials chemically reactive to- -wards silicon carbide, preparing a charge of the. said pure zinc oxide by mixingit with a bitum'i-v u nous material including tar, kneading the tar" ofthe zinc oxide with thev tar is eifected, heating the resulting mixture to a coking temperature material, maintaining the coke and oxide in continuous contact, showering the resulting into the zinc oxide until thorough impregnation mixture through a ash reduction environment having surfaces in contact with the material Icomposed of silicon carbide heated to reducing temperatures, and eiecting a reduction of the charge to elemental zinc while the charge is infree movement inthe environment.'
AUGUSTIN LEON JEAN QUENEAU
US394009A 1941-05-17 1941-05-17 Zinc metallurgy Expired - Lifetime US2342368A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US394009A US2342368A (en) 1941-05-17 1941-05-17 Zinc metallurgy

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US394009A US2342368A (en) 1941-05-17 1941-05-17 Zinc metallurgy

Publications (1)

Publication Number Publication Date
US2342368A true US2342368A (en) 1944-02-22

Family

ID=23557157

Family Applications (1)

Application Number Title Priority Date Filing Date
US394009A Expired - Lifetime US2342368A (en) 1941-05-17 1941-05-17 Zinc metallurgy

Country Status (1)

Country Link
US (1) US2342368A (en)

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2475607A (en) * 1947-08-26 1949-07-12 American Metal Co Ltd Fluidization in zinc production
US2560175A (en) * 1948-05-12 1951-07-10 American Metal Co Ltd Fluidizing reduction of zinc compounds with stagewise feeding of solids
US3271134A (en) * 1962-08-20 1966-09-06 Nat Smelting Co Ltd Extraction of zinc
US3850613A (en) * 1973-05-14 1974-11-26 Ferro Carb Agglomeration Treatment of steel mill waste dusts containing zinc
US4021530A (en) * 1970-01-02 1977-05-03 The Dow Chemical Company Preparation of metal fluorides
US4070160A (en) * 1977-05-09 1978-01-24 Phillips Petroleum Company Gasification process with zinc condensation on the carbon source
US4073630A (en) * 1976-10-26 1978-02-14 Phillips Petroleum Company Production of carbon monoxide
US4112058A (en) * 1976-08-23 1978-09-05 Phillips Petroleum Company Production of carbon monoxide from carbonaceous material and zinc oxide
US4115524A (en) * 1977-02-02 1978-09-19 Phillips Petroleum Company Production of carbon monoxide
US4132764A (en) * 1976-08-23 1979-01-02 Phillips Petroleum Company Production of carbon monoxide from carbonaceous material and zinc oxide
US4309397A (en) * 1980-07-28 1982-01-05 Phillips Petroleum Company Production of carbon monoxide from carbon
US4382915A (en) * 1981-10-13 1983-05-10 Phillips Petroleum Company Quenching of ZnO-char gasification
US4422624A (en) * 1981-08-27 1983-12-27 Phelps Dodge Corporation Concentrate burner
US4496370A (en) * 1983-04-04 1985-01-29 Phillips Petroleum Company Zinc oxide-char gasification process
WO2017129816A1 (en) * 2016-01-29 2017-08-03 Ulrich Bech Method for the carbothermal reduction of zinc oxide to zinc
CH712284A1 (en) * 2016-03-21 2017-09-29 Bech Ulrich Process for the carbothermic reduction of zinc oxide to zinc.

Cited By (16)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2475607A (en) * 1947-08-26 1949-07-12 American Metal Co Ltd Fluidization in zinc production
US2560175A (en) * 1948-05-12 1951-07-10 American Metal Co Ltd Fluidizing reduction of zinc compounds with stagewise feeding of solids
US3271134A (en) * 1962-08-20 1966-09-06 Nat Smelting Co Ltd Extraction of zinc
US4021530A (en) * 1970-01-02 1977-05-03 The Dow Chemical Company Preparation of metal fluorides
US3850613A (en) * 1973-05-14 1974-11-26 Ferro Carb Agglomeration Treatment of steel mill waste dusts containing zinc
US4132764A (en) * 1976-08-23 1979-01-02 Phillips Petroleum Company Production of carbon monoxide from carbonaceous material and zinc oxide
US4112058A (en) * 1976-08-23 1978-09-05 Phillips Petroleum Company Production of carbon monoxide from carbonaceous material and zinc oxide
US4073630A (en) * 1976-10-26 1978-02-14 Phillips Petroleum Company Production of carbon monoxide
US4115524A (en) * 1977-02-02 1978-09-19 Phillips Petroleum Company Production of carbon monoxide
US4070160A (en) * 1977-05-09 1978-01-24 Phillips Petroleum Company Gasification process with zinc condensation on the carbon source
US4309397A (en) * 1980-07-28 1982-01-05 Phillips Petroleum Company Production of carbon monoxide from carbon
US4422624A (en) * 1981-08-27 1983-12-27 Phelps Dodge Corporation Concentrate burner
US4382915A (en) * 1981-10-13 1983-05-10 Phillips Petroleum Company Quenching of ZnO-char gasification
US4496370A (en) * 1983-04-04 1985-01-29 Phillips Petroleum Company Zinc oxide-char gasification process
WO2017129816A1 (en) * 2016-01-29 2017-08-03 Ulrich Bech Method for the carbothermal reduction of zinc oxide to zinc
CH712284A1 (en) * 2016-03-21 2017-09-29 Bech Ulrich Process for the carbothermic reduction of zinc oxide to zinc.

Similar Documents

Publication Publication Date Title
US2342368A (en) Zinc metallurgy
US2855290A (en) Method of reducing iron oxide to sponge iron
US3185635A (en) Method for producing metallurgical coke and metal-coke from both coking and non-coking coals
CA1338126C (en) Continuous feed shaft retort process and apparatus for recovery of non ferrous metals
US3169055A (en) Process for producing pig iron in rotary furnace
US4323391A (en) Process for recovering zinc
US4519836A (en) Method of processing lead sulphide or lead-zinc sulphide ores, or sulphide concentrates, or mixtures thereof
KR100322393B1 (en) Method of making high grade nickel mats from nickel-containing raw materials, at least partially refined by dry metallurgy
US2598743A (en) Zinc smelting
US1858274A (en) Process for reducing oxide ores
US2823108A (en) Process for reducing ores and oxidic residues in rotary kiln
US2127633A (en) Smelting of zinciferous materials
JPS60169543A (en) Manufacture of ferromanganese
US3495973A (en) Gas-solid reaction
US4238222A (en) Waelz process of volatilizing zinc and lead from iron oxide-containing materials
US4369059A (en) Process of directly reducing iron oxide containing materials in a rotary kiln
US4394167A (en) Method of carbothermically producing aluminum
US1102339A (en) Process for treatment of minerals and extracting metal.
US2266816A (en) Manufacture of high grade iron and steel
US1174729A (en) Metallizing process.
US2442674A (en) Deleading zinc-lead fume
US2077651A (en) Treatment of zinciferous materials
US890234A (en) Method of treating iron ores.
US3175900A (en) Process for the recovery of iron and uranium from slags, boiler waste and the like
US1047360A (en) Process of separating zinc and lead from mixed sulfids.