US2132858A - Process of continuously producing zinc in vertical reducing chambers and apparatus therefor - Google Patents

Description

Oct. 11, 1938. TT 's 2,132,858

PROCESS OF CONTINUOUSLY PRODUCING ZINC IN VERTICAL REDUCING CHAMBERS AND APPARATUS THEREFOR Filed June 9, 1957 F7191 F1912 A w//////// I i /]22 f *f A 9 9 Ir F Z n Y 1 Patented Oct. 11, 1938 UNITED STATES PATENT OFFICE.

PROCESS OF CONTINUOUSLY PRODUCING ZINC IN VERTICAL REDUCING CHAMBERS AND APPARATUS THEREFOR Application June 9, 1937, Serial No. 147,174 InGerinany June 10.1936

11 Claims.

The present invention relates to a zinc reducing process, and, more particularly, to a process for the continuous production of zinc in vertical reduction chambers.

5 Heretofore, numerous attempts have been made to smelt raw materials containing zinc in vertical inuiiles in a continuous operation. Most of these prior attempts have completely failed due to various serious practical difliculties. Even the 10 few methods which have attained some practical importance in comparison with the conventional smelting processes in the horizontal muifie, had very serious defects which rendered the production process diiilcult and expensive in practical 15 operation.

In view of the good results obtained with silicon carbide as a highly refractory structural material of good heat conductivity, the important problem of providing a suitable structural ma- 20 terial for muflles has been satisfactorily solved.

However, another equally important problem still remained in the construction of vertical mufiies, to wit: the satisfactory removal of the reduction gases from the heated muflle chamber into the condensing plant. Prior attempts of solving this problem involved internal, stationary, hollow or loosely filled structures in the mufile or .briquetting and coking of the ore-coal mixture. None of these prior attempts was completely satisfactory or successful, or free from drawbacks and dimculties. The stationary internal structures became obstructed and were diiiicultly accessible for the purposes of inspection and cleaning. Briquetting and coking, on the other hand, .3 were expensiveand had to be determiried by experiment for each kind of ore. Only suitably shaped solid ore-coal briquettes provided a sufliciently loose stratification in the vertical muille for the removal of the gaseous products of reduction to the condensing plant. They also presented great resistance to the conduction of heat in consequence of the desired small number of contact points of small surface and thus greatly increased the cost of heating.

It has been found that the above problem may be solved in a simple and eflicient manner.

It is an object of the present invention to provide an improved process for the production of zinc in vertical muflies which is free from the J disadvantages of conventional processes.

It is another object of the present invention to provide a novel and improved process for the continuous production'of zinc in vertical reduction chambers.

5 It is a further object of the present invention to provide a vertical muffle of novel and improved character which is capable of continuously producing zinc from zinciferous material on a practical and industrial scale.

Other and further objects and advantages of 5 the present invention will become apparent from the following description taken in conjunction with the accompanying drawing,- in which:

Fig. 1 illustrates a vertical and longitudinal sectional view of a vertical reduction chamber embodying the principles of the present invention; and

Fig. 2 depicts a section taken on line AA of Fig. 1

Broadly stated, according to the principles of the present invention a vertical muflie is provided for the continuous production of zinc, said muffle having its upper portion divided in three chambers down to about the heating chamber by means of two vertical partition walls. of these three chambers the middle one is charged with coarse granular pieces of a heat-resisting material forming no slag and which is not attacked by 'zinc vapors, the two chambers at each side of the center chamber are filled with a mixture of zinciferous materials and of a reducing agent. The zinc vapors produced in the heated portion of the mufile are removed into a condenser through the center column constituted of coarse pieces of an inert material extending downwards which due to its structure is readily permeable to gases, whereas the residues of the zinciferous charge and of the granular material containing no zinc may be withdrawn continuously or intermittently at the bottom of the reducing shaft.

It is generally preferred to provide a mufile shaft of quadrangular cross section and to divide the upper part thereof, for example the section located above the heating zone or a portion thereof, into three vertical chambers. In this manner one charging column lies against each of the two longitudinal walls of the shaft and a third column extending along the full height of the shaft in the core of the muflle is enclosed by these two lateral columns. These three charging columns are formed by the division of a section of the upper part of the mufiie by means of two longitudinal walls carried by supporting arches provided within the mufile. The supporting arches, in this type of structure, are advantageously located directly above the heated mu'file shaft so that the anchoring of the arches presents no dificulties. Preferably, at the same point, to wit: above the heated shaft few large pieces.

' with the condenser.

chamber, an opening is provided in one muflle wall of the center shaft, which communicates The whole mufiie shaft is preferably constructed.

of structural materials having good heat conductivity such as particularly silicon carbide bricks, or may be made of the same material in a different manner for example by means of ramming and other similar shaping methods either integrally formed in a single piece or in a The insulation of the outer walls of thevunheated top portion of the muflle shaft, the so-called charging shaft, greatly promotes the drying and preheating of the charge.

According to the principles of the inventicn, the middle shaft, formed at the top by the two partitions, isnow charged with, coarse granular pieces of a material which changes little or nothing in fire, and which may preferably be preheated'externally of the charging shaft, for example by the waste heat of the gases from the combustion chamber. The grain size of these pieces is about 20 to about 100 mm. but may be varied within wider limits. These pieces depending on the'nature of the zinciferous ore employed may consist of coke, preferably completely degasifled, shaped pieces of silicon carbide,

porcelain, quartzite stones (coarse gravel), or mixtures of these substances or similar materials. The shape and grain size of this material has to be of such nature that the charge arranged in the middle charging column is as loose and permeable as possible. For example, ring-like spherical, tetrahedron and cube-shaped bodies,

or bodies or lumps having angular edges may be employed having approximately equal piece size.

The two laterally disposed charging shafts of the subdivided upper portion of the muiiie are charged with a mixture of are and carbonaceous reducing agent such as is customary for horizontal muiiies, although any other desired zinciferous material such as roasted ore, zinc ash, zinc oxide ora mixture of these substances with the usual reducing agent, for example smail coke of a suitable grain size, may be employed as a charge material with equal or similar results. The charging openings or ports may be closed in the conventional manner. The muflle is emptied at its bottom end, for example by means of a cooled iron attachment having dimensions corresponding to the cross section of the mutlie or in any other conventional manner. At this point both the ash to be removed from the lateral charging columns and the stable or inert material from the middle charging column are withdrawn at a uniform rate. The coarse-grained material from the middle charging column can be constantly recovered by sifting and may be returned to the column and used over again. The removal of the burnt out charge from the iron attachment is carried out continuously or intermittently by mechanical means, for example rollers, or manually. The thickness or the charging columns of coal and ore sliding down the longitudinal walls of the muflie must be so selected that complete burning out is ensured for the selected muflle height and furnace temperature. Generally speaking, thicknesses of about 10 to about 20 cm. have been satisfactory However, this opening may.

in practical operation. The middle column of loosely packed stable coarse-grained material has to be so thick that the passage of the zinc vapors is rendered possible at any point of the muifle from the side columns into'the middle column and within the latter to the outlet pipe into the condenser, for example upwards. As a rule, a thickness of about 20 to about 40 cm. will be sufficient.

Tiie'thermal efliciency of the process of the present invention is a great deal better than in any of the conventional processes. In consequence of the more intimate contact, the orecoal mixture conducts the heat better and it is also unnecessary to heat the middle of the muiiie shaft to the same temperature as the outer wall of the muiiie, because the material of the middle core is not metalliferous but has a temperature which permits the zinc vapor to escape unhindered upwards into the condenser. Therefore, it is unnecessary to build the heated muflie shaft very high. As a rule, a heated muflie height of about 4 meters is sufficient. The length of the mufiie may be the usual, tor example, about 1.5 to about 3 meters. In the structure of the character described it. is also possible to efiect the removal of deposits, bridge formations and the like in the muflie shaft by means of iron tools or rods from the charging platform withcut the necessity of temporarily interrupting the operation of the mufile. Due to the fact that the process of the invention does not require briquetting or any other speciai preliminary treatment of the charge, the cost of smelting and the initial cost of the plant are greatly reduced and the process of the invention can be utilized with equal success for treating any raw materials encountered in practical operation.

In order that those skilled in the art may have a better understanding of the invention, the invention will now be more fully described reference being had to the accompanying drawing which illustrates diagrammaticallyand by way of example a preferred embodiment of an apparatus suitable for carrying the process of the invention into practice.

Referring now more particularly to Figs. 1 and 2 of the drawing, a bottom structure a is carried by a plurality of beams and supports furnace b having a heating chamber b -i and a cover c. In heating chamber b-l is located a reduction chamber d of quadrangular cross-section constituted of silicon carbide in the form of bricks or other shapes. The reduction chamber extends upwards through cover 0 and has its lower end resting on a base d-I supported by the bottom structure a. The lower end of the reduction chamber is connected to a discharge shaft m, constituted of iron. The upper portion of reduction chamber d and extending beyond cover c is protected by insulating waiis I from excessive radiation of heat. This upper portion of the reduction chamber is divided into three compartments by means of twointernal partition walls 9. Of these three compartments, the lateral chambers 51-4 and h -2 are located towards the cutside, and a third chamber 1' is formed between the partition walls and in the middle. Partition walls a rest on flat arches e the supports of which are carried by an anchoring i mounted on cover c 01' the furnace. An opening or port In is provided in middle chamber 2', and is connected to a condenser 12 for the zinc vapors. Chamber i is closed at the top by means of a cover in a gas tight manner. Instead of the cover, other suitable closure means may be employed or charging devices capable of being closed. Likewise, closure means of similar character may be provided at the top of chambers hl and h2. However, generally the columns of charge material located in the upper part of said chambers or shafts are themselves suflicient to provide thenecessary closure.

From the above description the operation of the improved vertical muflle will be readily understood by those skilled in the art. After the furnace has been heated up, a normal zinciferous reduction charge is introduced into lateral chambers or shafts 71-! and h-2. The middle shaft i is charged with coarse-grained; inert material such as, for example, coarse pieces of coke. Charging of the lateral chambers hl and h2 and of the middle chamber i is continued until the charge will reach up to the upper edge thereof. Reduction chamber d is'now heated to the usual reducing temperature of zinc-reducing furnacesby means of suitable heating means such as, for example, ga's burners provided in the heating chamber b|. As the zinciferous reduction mixture is in direct contact with the heated walls of reduction chamber d, they will be heated by these to a high temperature, whereas the middle portion of chamber d down to its bottom is constituted of coarse grained coke sink ing downwards from chamber 2'. The furnace heat will cause reduction of the zinciferous material. The zinc vapors liberated thereby and the carbon monoxide gas produced during the reduction will enter the middle zone of coke pieces which is permeable to gases, and will rise unhindered until they arrive through port k into condenser n. In the'condenser the zinc vapor is condensed to liquid zinc while the carbon monoxide leaves the condensation space and is either combusted when it gets into contact with the outer air or may be recovered for further utilization and treatment. During the reduction, the charge goes down and accordingly new charge material is introduced into chambers h-l and h2 at the top thereof and also new pieces of coke in chamber i are added. The residues are intermittently removed through discharge shaft m, and their finer parts are separated from the coarse pieces of coke. The pieces of coke are reintroduced into the top of chamber out departing from the principles of the present invention. Thus, instead of dividing the top portion of a reducing chamber of rectangular cross section into three shafts, it is also possible to provide areducing chamber of circular, oval or polygonal cross section in which a corresponding central chamber is divided off by a cylindrical, oval or polygonal member filled with a suitable inert material in coarse lump form. In this case, this middle shaft is enclosed by an annular chamber, or a chamber corresponding in'cross section to that of the muffle, to hold the reduction mixture. All of these variations and modifications are considered as within the true spirit and scope of the present invention as disclosed in the present description and defined by the appended claims.

I claim v 1. The process for the continuous production of zinc in vertical reducing chambers which comprises establishing a central vertical column constituted of coarse refractory non-slagging lumps of a material not substantially attacked during reduction, establishing vertical columns of a mixture of zinciferous material and reducing agent in proximity to said central column, separating only the upper portions of said vertical columns from each other to prevent direct contact of said upper portions and to establish direct contact of their lower portions, heating said columns to zinc reducing temperatures, passing the zinc vapors produced through said permeable central column, and condensing said zinc vapors.

' 2. The process for the continuous production of zinc in vertical reducing chambers which comprises establishing a central vertical column constituted of coarse refractory non-slagging lumps of a material not substantially attacked during reduction, establishing vertical columns of a mixture of zinciferous material and reducing agent in proximity to said central column separating only the upper portions of said vertical columns from each other to prevent direct contact of said upper portions and to establish direct contact and communication between their lower portions, heating said columns to zinc-reducing temperatures, passing the zinc vapors produced through said permeable central column, and condensing said zinc vapors.

3. The process for the continuous production' of zinc in vertical reducing chambers which comprises establishing a central vertical column constituted of coarse refractory non-slagging lumps of a material not attacked by zinc vapors, establishing lateral vertical columns of a mixture of zinciferous material and reducing agent in proximity to said central column, separating only the upper portions of said vertical columns from each other to prevent direct contact of said upper portions and to establish direct contact, intimate heat exchange and communication between their lower portions, applying heat to the lower portion of said central column to heat said columns to zinc-reducing temperatures, continuously withdrawing zinc vapors produced through said central column permeable to gases, and condensing said zinc vapors.

4. The process for' the continuous production of zinc in vertical reducing chambers which comprises establishing a central vertical column constituted of coarse refractory non-slagging lumps of a material not attacked by zinc vapors, establishing at least one lateral vertical column of a mixture of ,zinciferous material and reducing agent in proximity to said central column, separating only the upper portions of said vertical columns from each other to prevent direct contact of said upper portions and to establish direct contact, intimate heat exchange and communication between their lower portions, heating said columns to'zinc-reducing temperatures, continu-- ously withdrawing zinc vapors through said permeable central column, condensing said zinc vapors, introducing fresh charge materials into said columns at the top thereof, and removing solid residual products at the bottom of said central shaft.-

5. The process for the continuous production of zinc in vertical reducing chambers which comprises establishing a central vertical column of coarse refractory non-slagging lumps of a material not substantially attacked during reduction, establishing vertical columns of a mixture of zinciferous material and reducing agent in proximity to said central column, separating only the upper portions of said vertical columns from each other to prevent direct contact of said upper portions and to establish direct contact, intimate heat exchange and communication between their lower portions, applying indirect heat to the lower portion of said vertical reducing chamber to cause reduction of the zinciferous materials to metallic zinc, withdrawing zinc vapors and reduction gases through said permeable central column, condensing said zinc vapors, feeding fresh charge materials into said columns at the top thereof, and removing residual products at the bottom of said central column.

6. The process for the continuous production of zinc in vertical reducing chambers which comprises establishing a central vertical column of coarse refractory non-slagging lumps of a material not attacked by zinc vapors and having a to prevent direct contact of said upper portions and to establish direct/contact, intimate heat exchange and communication between their lower portions, applying indirect heat to the lower portion of said vertical reducing chamber to cause reduction of the zinciferous materials to metallic zinc, withdrawing zinc vapors and reduction gases through said permeable central column, condensing said zinc vapors, feeding fresh charge materials into said columns at the top thereof, removing residual products at the bottom of said central column, recovering the coarse lumps of the central column from said residual products by sifting, and returning the same to said vertical column for further use.

7. A vertical muffle for the continuous production of zinc comprising a vertical reducing shaft, a'heating chamber externally surrounding the lower portion of said shaft, partition walls dividing the upper portion of said shaft into vertical central and lateral chambers, a port at the top of said central chamber to introduce coarse refractory non-slagging lumps of a material not substantially attacked during reduction, openings atthe top of said lateral chambers to fill the same with a mixture of zlnciferous material and reducing agenta'heating means in said heating chamber to heat said vertical reducing shaft to zinc-reducing temperatures, and a port at an intermediate portion of said central chamber to withdraw zinc vapors therefrom.

8. A vertical mufile for the continuous production of zinc comprising a vertical reducing shaft constituted of a highly refractory structural m'aterial having good heat conductivity, a heating chamber externally surrounding the lower portion of said shaft, partition walls within said shaft chamber to heat the vertical reducing shaft to zinc-reducing temperatures, and a port in an intermediate portion of said central chamber to withdraw zinc vapors therefrom.

9. A vertical muflle for the continuous production of zinc comprising a quadrangular vertical reducing shaft constituted of a highly refractory structural material having good heat conductivity, a heating chamber externally surrounding the lower portion of said shaft, a pair of partition walls within said shaft dividing the upper portion thereof into a vertical central chamber and a pair of lateral chambers, a pair of arches within said shaft for supporting said partition-- walls, a port at the top of said central chamber to introduce coarse refractory non-slagging lumps of a material not substantially attacked during reduction thereinto, openings at the top of said lateral chambers to fill the same with a mixture of zinciferous material and reducing agents, heating means in said heating chamber to heat the vertical reducing shaft to zinc reducing temperatures, and a port in an intermediate portion of said central chamber to withdraw zinc vapors therefrom.

10. A vertical muflie for the continuous production of zinc comprising a quadrangular vertical reducing shaft constituted of a highly refractory structural material having good heat conductivity, a heating chamber externally surrounding the lower portion of said shaft, a pair of partition walls within said shaft dividing the upper portion thereof into a vertical central chamber and a pair of lateral chambers, a pair of arches within said shaft for supporting said partition walls, a port at the top of said central chamber to introduce coarse refractory nonslagging lumps of a material not attacked by zinc vapors thereinto, ports at the top of said lateral chambers to fill the same with a mixture of zinciferous material and reducing agents, heating means in said heating chamber to heat the vertical reducing shaft to zinc reducing temperatures, a port at an intermediate portion of said central chamber to withdraw zinc vapors therefrom, and a condenser connected to said port to condense said vapors.

11. A vertical mufile for the continuous production of zinc comprising a vertical reducing shaft constituted of a highly refractory structural material having good heat conductivity, a heating chamber externally surrounding the lower portion of said shaft, a cover for said heating chamber having said shaft protruding therethrough, a 'pair of partition walls within said shaft dividing the upper portion thereof into a vertical central chamber and a pair of lateral chambers, a pair of arches within said shaft for supporting said partition walls, a charging port at the top of said central chamber to introduce coarse refractory non-slagging lumps of a material not attacked by zinc vapors thereinto,

charging ports at the top of said lateral cham-- bers to fill the same with a mixture of zinciferous material and reducing agents, closure means for said charging ports, heating means in said heating chamber to heat said vertical chambers to zinc-reducing temperatures, a discharge port in an intermediate portion of said central chamber to withdraw zinc vapors therefrom, a condenser for condensing said vapors, and a discharge shaft connected to the bottom end of said vertical shaft for the removal of residual materials.

HERMANN MA'I'IHIES.

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