US3637367A - Process and device for the distillative purification of metals, especially of zinc - Google Patents

Process and device for the distillative purification of metals, especially of zinc Download PDF

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Publication number
US3637367A
US3637367A US746191A US3637367DA US3637367A US 3637367 A US3637367 A US 3637367A US 746191 A US746191 A US 746191A US 3637367D A US3637367D A US 3637367DA US 3637367 A US3637367 A US 3637367A
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packing
metal
process according
column
zinc
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US746191A
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English (en)
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Norbert Lowicki
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Grillo Werke AG
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Grillo Werke AG
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Priority claimed from DE19671583880 external-priority patent/DE1583880A1/de
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    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B5/00—General methods of reducing to metals
    • C22B5/02—Dry methods smelting of sulfides or formation of mattes
    • C22B5/16—Dry methods smelting of sulfides or formation of mattes with volatilisation or condensation of the metal being produced
    • C—CHEMISTRY; METALLURGY
    • C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
    • C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
    • C22B19/00—Obtaining zinc or zinc oxide
    • C22B19/04—Obtaining zinc by distilling
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10S—TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10S203/00—Distillation: processes, separatory
    • Y10S203/11—Batch distillation

Definitions

  • ABSTRACT Metal especially zinc, is purified by distillation of the metal in the fused state in a packed column.
  • the fused metal is introduced at the top of the packing so that a coherent stream of the metal flows through a considerable height of the packing.
  • Heat is supplied to the packing to provide a temperature gradient across the packing so that the temperature of the vapor remote from the coherent stream is relatively high with respect to the temperature of the coherent stream.
  • the invention relates to a process for the distillative purification of metals, especially from their mixtures or alloys with less volatile metals.
  • the invention relates to the distillative production of pure zinc from its alloys with, for example, lead, iron, aluminum and/or copper, for example for the manufacture of zinc white and pigment zinc dust.
  • the distillation columns are equipped with dishlike plates through which liquid zinc is passed in countercurrent to the stream of metal vapor.
  • Such a rectification presumes that the less volatile accompanying metals which contaminate the zinc are liquid and/or soluble in the zinc at the process temperature and can be continuously removed in this form.
  • this zinc refining process requires a special process stage separate from the actual production of the zinc.
  • 586,627 proposes refining hard zinc by means of an unheated insulated packed column. Since however a solid iron sponge remains on distillation of hard zinc, continuous distillative working-up of hard zinc in the manner described is not possible. The distillation retort must frequently be mechanically cleaned. The air which hereupon enters oxidizes the metal remaining in the packed column and the oxide products thus produced block the column.
  • a coke column here serves as the heating resistance and the current is supplied by an electrode which reaches into the column from above.
  • the crucible at the lower end serves as the counterelectrode.
  • the heat required for the vaporization of the zinc is here produced by the electric current mainly in the thin layers of zinc metal on the surface of the pieces of coke. It is therefore stated to be essential to the process that the metal to be refined is distributed very uniform from four charging orifices, over the entire surface of the coke column.
  • Hard zinc to be processed is comminuted, mixed with clay, briquetted and introduced together with the coke. The remaining iron is removed together with the clay as the charge migrates downwards and is then separated from the coke.
  • U.S. Pat. specification No. 2,939,783 describes a further process variant for the distillative refining of zinc shot, pressure-casting alloys and the like. This is effected in two stages, and in the first stage the vaporization of the zinc is only taken to the point that the metal vapor, after passing through a column with guide walls arranged zigzag fashion, is completely pure. The sump alloy, in which the impurities have become enriched, is then further distilled in the second stage and these vapors are condensed via a packed column. The prepurified zinc alloy thereby produced is returned to the first distillation stage. The mode of action of the packed column is not explained further.
  • the invention is based on the fundamental new recognition that in order to have effective rectification of a mixture of materials it is not only necessary to provide adequate material exchange between the vapor phase and liquid phase and preferably at the same time to set up a temperature gradient in the direction of the stream of vapor, that is to say to provide a vertical temperature gradient, but that beyond this the action of the rectification unit must be decisively influenced by the fact that additionally a horizontal temperature gradient, that is to say a radial temperature gradient at right angles to the direction of flow of the gas phase and vapor phase, is provided within the rectification unit.
  • the subject of the invention is a process for the distillative purification of metals and especially for obtaining zinc from its alloys with the conjoint use of fractionating columns, characterized in that the fused crude metal which is to be purified is introduced in the form of at least a coherent stream of liquid from above into an externally heated vertical packed column in such amounts that at least a coherent stream of fused crude metal flows through at least a considerable part of the length of the packed column, while the vaporized metal is passed upwards through the packed column in countercurrent thereto and is withdrawn at the top.
  • the vapor stream withdrawn at the head of the column can if desired to be freed of metal droplets which have been carried along.
  • the essential feature of the invention thus resides in a fractionation stable.
  • This fractionation stage takes place in a packed column into which the fused crude metal introduced is at the top as a coherent stream of liquid.
  • the amount of liquid crude metal introduced is at the same time metered in such a way, especially matching it to the heating-up temperature in the column and the amount of vapor passing upwards through the column, that a coherent stream of the fused metal flows downwards through the packed column like a rivulet or brook.
  • the formation of such a continuous rivulet passing downwards right through the packing is favored by the characteristics of the liquid phase, especially probably by the high specific gravity of the fused metal and by its surface forces.
  • the essentially continuous downward-flowing rivulet of the fused metal which has actually not yet been heated to vaporization temperatures, is comparatively colder than the ascending metal vapor and than the externally heated wall of the packed column.
  • this comparatively cool downward-flowing rivulet of the continuous stream of metal is more or less fixed in its position in the cross section of the packed column. If for example the stream of fused crude metal is charged centrally into the packed column, then the rivulet also flows downwards approximately centrally through the vertical packed column.
  • a quasi'static condition as regards the radial temperature gradient in the column can in this way result, and this leads to the metal vapor passing upward through the column being constantly exposed to the influence of this virtual fixed radial temperature gradient.
  • the desired fractionating action of the column is hereby surprisingly increased relative to the usual operation with a horizontally uniform temperature or only a statistically distributed and constantly changing temperature gradient.
  • a temperature drop in the direction of the stream of vapor that is to say a vertical temperature gradient, also establishes itself in the packed column. This occurs automatically as a result of the fact that the colder liquid phase is introduced at the head of the column. In this way the stream of vapor can be cooled down to a temperature below the evaporation temperature of the-less volatile components which are to be separated off.
  • the most volatile components that is to say for example zinc in the particular case, leaves the packed column at the head.
  • the temperature gradient at right angles to the direction of flow of the liquid and vapor phase is appropriately established to the extent that the temperature of the colder part of the column which extends vertically through the packed column, that is to say the downwardflowing rivulet of the fused initial material-lies below the boiling point of the most volatile impurity which is to be removed.
  • a temperature difference which is not too small is at the same time chosen.
  • radial temperature gradients in the horizontal cross section of at least C. are preferred.
  • the radial temperature gradient can for example assume values of between l50
  • a definite temperature gradient directed towards the center of the packedcolumn develops between the heated outer wall and the preferably centrally introduced stream of metal, and this temperature gradient forms even if only such an amount of metal is charged into the column that on passing through the entire heated column height it can be evaporated approximately completely.
  • a larger quantity of fused crude metal is thus introduced at the head of the packed column than is withdrawn in the vapor phase from the head of the column.
  • the equilibrium ratios between the liquid phase and the vapor phase may, in a preferred embodiment, be so adjusted that to 90 percent by weight, preferably to 70 percent by weight, of the desired metal from the crude metal charged into the column are evaporated and withdrawn at the head of the column.
  • the excess of crude metal introduced serves to form the downward-flowing liquid cooler core of the rectification column and at the same time takes up the higher-boiling impurities which are to be separated out and leaves the packed column at the bottom together with these impurities.
  • the less volatile alloy constituents which have become enriched in the sump product withdrawn at the base of the column can be in part separated from the sump product in a conventional manner, for example by refining. Fine refining is not necessary. In the continuous process it is merely necessary to ensure that no undesired enrichment in impurities takes place. This is because in that case the sump product which has been partially freed of impurities is preferably returned to the column head and here returned to the separation process, mixed with fresh fused crude metal. This circulation of the stream of metal makes it possible to remove the less volatile impurities of the alloy, which have been separated out during the material exchange in the column, from the rectification process in a controlled manner and to enrich them in the sump product in the desired manner.
  • the evaporation of the desired metal constituent from the stream of crude metal is, according to the invention, preferably effected within the packed column by adjusting the amount of heat introduced relative to the amount of the crude metal introduced, taking the equipment constants into ac count. Admittedly such evaporation of the metal within the packed column is not necessary. It is also possible to provide a separate evaporation unit at the base of the packed column and then to introduce the metal vapor into the packed column from below. As a rule however this requires greater expenditure on apparatus.
  • the packed column approximately into at least 2 sections which are distinguished by differing heating.
  • the lower section is adjusted to be hotter than the section arranged above it and serves as the evaporator zone. It is here that the major part of the metal vapor is thus produced from the crude metal stream.
  • the cooler part arranged above it serves for the fractionation and is accordingly described as the fractionating zone.
  • the task of this section of the column is to ensure that the desired exchange processes take place and these should be disturbed as little as possible by additionally evaporating metal.
  • a far-reaching control of the effective throughput as well as of the purity of the product distilled off can be effected by controlling the heat input in the lower evaporator part and in the superimposed fraetionating part, of the column.
  • the metal vapor issuing at the head of the column is not passed to the cooling directly but is further passed through an additional process stage for separating off the mechanically entrained, droplet impurities.
  • conventional methods for separating off a very finely divided liquid phase from a vapor plane can be chosen.
  • particularly simple means are here used which can effortlessly be joined onto the process means hitherto described.
  • the stream of vapor, after leaving the packed column is passed from below into a further packing layer.
  • the separation of the metal droplets is effected by a filtration effect.
  • the temperature of this part of the column can be so adjusted by appropriate regulation of the external heating that it is approximately the same as the temperature of the stream of vapor.
  • the packing layer exclusively acts as a kind of filter which very largely retains the liquid particles.
  • the temperature of the packing layer can however also be chosen to be somewhat lower.
  • a particularly preferred embodiment of the invention provides that a radial temperature gradient is also formed in this packing layer which is used for the purification of the vapor.
  • this can be achieved in a simple manner by placing the packing layer onto which there is no trickling directly on top of the packed column charged wit the crude metal and creating a colder zone extending from the top through to the bottom in the interior of the packing layer, such as for example centrally.
  • This formation of the colder zone is very simply achieved by passing a tube through the packing layer from top to bottom and passing the stream of crude metal to the head of the packed column through this tube.
  • the rectification of the metal thus takes place in a two-part or three-part rectification column which is characterized in that a feed tube for the fused crude metal alloy reaches into the layer of poured-outmaterial (i.e., packing material) from above.
  • This feed tube is preferably arranged to be adjustable in height and it is appropriate to adjust the depth of penetration into the layer of poured-out material to a range of about one-third to one-eighth of the entire height of the poured-out material layer.
  • This column of poured-out material is then divided into 3 zones by differential heating.
  • the fractionation zone in which the material exchange processes occur, is formed above this with gentler heating. It finishes, in the upper direction, at the mouth of the feed tube for the crude metal alloy which is to be purified and is followed there by the uppermost zone of the poured-out material column which is again adjusted to be hotter than the fractionating zone below it. This uppermost zone serves for the separation of metal vapor and liquid impurities which has been described.
  • the feed tube fed with the stream of molten metal effects a sufficiently large temperature gradient from the heated wall to the center to allow the gradually accumulating droplets of less volatile impurities to trickle down on the outer wall of the feed tube.
  • the possibility of changing the depth of penetration of the feed tube into the column and hence of adapting it to the particular composition of the crude metal which is to be purified leads to a further possible variation in the new process.
  • the depth of penetration of the feed tube can be adapted to the nature and amount of the contents of impurities in the starting alloy.
  • the crude metal predominantly contains elements which are particularly extensively entrained mechanically in zinc droplets (for example aluminum and copper) the depth of penetration of the feed tube and hence the height of the overheating zone or filter zone should be made large.
  • elements are predominantly present which have to be separated out by condensation or solution in the reflux stream (for example lead or iron) the depth of penetration can be made less and the fractionating zone accordingly larger.
  • the heating zones along the column are appropriately regulated and set to the particular temperature level required.
  • the head of the rectification column preferably remains empty, and thereby a streamlining space for the metal vapors is produced and dust from the packing which may have been entrained can be separated out. This is under certain circumstances of importance in the manufacture of pigment zinc dust from the zinc vapor or in the case of high exit speeds of the zinc vapor for special methods of manufacture of zinc white.
  • the zinc vapor exit speed from the column can be regulated to meet requirements, apart from doing so by the distillation speed, also by the choice of the diameter of the vapor exit pipe as well as by optional arrangement of one or more of these in the lid of the column.
  • the process according to the invention is not only distinguished by the fact that it permits a particularly effective and simple purification; it is now possible to solve, in terms of distillation, problems which could not be solved according to the prior technique of distillation of metals, espe cially easily volatile metals such as zinc.
  • the distillative purification of zinc in dish columns only produces high grade zinc from foundry red zinc which has been prepurified by refining.
  • the amount of the impurities of the zinc which are first runs before this rectification is limited and should if possible not exceed l.5 percent in the case of the main impurity, lead.
  • the contents of other impurities are then significantly lower, for example 0.2 to 0.5 percent in the case of Fe and 0.005 percent and below in the case of Cu and Al. Against this there is for practical purposes no limit to the content of higher-boiling impurities for the process according to the invention.
  • the level of the lead and/or iron may be 6 percent and copper and/or aluminum 10 percent and even above.
  • the invention furthermore relates to an apparatus for carrying out the new process.
  • FIGURE shows a schematic designed drawing of the part of the column which is essential for the distillation.
  • the feed device for recharging the packing reaches into the retort to an extent such that the conically widened head 6 remains empty and can serve as a streamlining space for the metal vapors. These are removed through one or more exit pipes 3 into the condenser 16 or into a combustion chamber for the manufacture of zinc white, not shown in the drawing.
  • the widened-out column head 6 is closed by a lid through which, inter alia, the feedpipe 2 for the crude metal which is to be purified projects downwards into the interior of the column.
  • This feedpipe 2 can be adjusted in height in a conventional manner which is not represented in the drawing. it is encased in a refractory and corrosion-resistant insulating material 4, at least over the part which projects into the column. It is continuously fed with crude metal via the supply chute 1. This crude metal can be prefused by means of waste heat, in a fusing kettle which is not represented in the drawing and which is arranged in the stream of waste gas.
  • the metal which trickles down the packed column and is enriched in the higher-boiling impurities which have separated out is withdrawn continuously or batchwise through the syphon 8/9, in a manner corresponding to the amount introduced and the distillation conditions.
  • the latter can be removed through the orifice 10 as required and be reintroduced through 5 after having been cleaned.
  • the column is externally heated by means of several burners ll, 12 and 13 arranged vertically above one another or arranged staggered. In practice it is appropriate to use more than the 3 burners represented here. These burners are built into a jacket of refractory material. The latter can be constructed in such a way that not only one but two or more distillation columns can be simultaneously operated in parallel. This permits more economical utilization of heat as well as a simplification of the feed and of the other servicing processes. The prefusing of, for example, zinc shot can then take place centrally at one point by means of utilization of waste heat.
  • the packed column can also be constructed as a long rectangle, viewed in a horizontal section, and in that case several inlet pipes 2 are arranged at a certain distance from one another and preferably centrally between the two nearest external walls.
  • the 3 zones of the column are schematically represented by the 3 burners 11, 12 and 13.
  • the burner 13 covers the hottest evaporation zone, the burner 12 heats the fractionating zone which is set to the lower temperature and which ends at the mouth of the inlet pipe 2, and finally the burner 11 heats the layer of poured-out material (i.e., packing), onto which there is no trickling, above the fractionating zone to the desired temperatures.
  • EXAMPLE 1 A hard zinc of high lead content, containing 2.6% Pb and 3.3% Fe, is refined in the distillation column described above.
  • the depth of penetration of the feed pipe was set to oneseventh of the total height of poured-out material in the column and the fractionating part was lengthened to half the height of the.column. Coke in small pieces, of particle sizes between 12 and mm., served as the packing.
  • the temperatures in the evaporator part of the column were set to 1,230l,250 and those in the fractionating part to 1,100P-1 ,l20, in each case measured at the inner wall of the column.
  • the metal reflux was regulated to 50 60 percent relative to fresh alloy.
  • the distillation product contained 0.008% Pb and 0.0003% Fe and corresponded to a normal quality of high grade zinc.
  • EXAMPLE 2 A zinc pressure casting alloy shot contaminated with brass, containing 5.2% A1, 3.8% Cu, 0.5% Pb and 0.3% Fe was converted into pigment zinc dust by means of a rectification column. Because of the high first-run of impurities, which are easily mechanically entrained, the depth of penetration of the feedpipe was adjusted to one-third of the total height of poured-out material (i.e., packing). The temperatures of the individual burner planes were regulated in such a way that the evaporator and the fractionating part also each amounted to one-third of the column height. The temperatures in these zones were as in example 1 and the temperature in the over heating part was set to l,150-l,200. The metal reflux was 25-30 percent.
  • the pigment zinc dust obtained contained less than 0.001% Cu, 0.015% A1, 0.1% Pb and 0.001% Fe.
  • EXAMPLE 3 A mixture of hard zinc, pressure-casting shot and other shot was worked up into zinc white by rectification and subsequent combustion.
  • the starting alloy contained 2.2% Pb, 3.7% A1, 2.3% Fe and 1.4% Cu.
  • the depth of penetration of the feedpipe as well as the heights of the evaporator and fractionating part were set as in example 2. The temperatures in these parts were retained and the overheating temperature was raised to l,250-1,280. The metal reflux was increased to S060 percent.
  • the zinc white obtained contained: 0.02% PbO, 0.0017% A1 0 Cu and Fe each less than 0.0005 percent. It thus met the quality requirements of the rubber industry.
  • EXAMPLE 4 A hard zinc contaminated with brass, which was unusable for the usual manufacture of zinc white, was worked up into rolling zinc with the aid of the rectification column according to the invention.
  • the starting alloy contained 1.1% Pb, 6.2% Fe, 1.3% Cu and 0.8% A1.
  • the distillation conditions were set as described in example 1 but the depth of penetration of the feedpipe was increased to one-fourth of the column of poured-out material (i.e., packing). The process was carried out without reflux and the amount of metal run in 'was set for maximum distilling-out of the zinc content.
  • the distilled-off zinc contained 0.104% Pb, 0.003% Cu, 0.025% A1 and 0.0005% Fe.
  • EXAMPLE 5 An alloy containing 75.5% Zn, 9.1% A1, 9.0% Cu, 3.4% Pb and 1.4 Fe was worked up into rolling zinc. The distillation conditions and the depth of penetration of the feedpipe were set as described in example 3 but the process was carried out without reflux.
  • the sump alloy which was withdrawn discontinuously, contained: 7.2% Zn, 42.2% A1, 30.6% Cu, 12.4% Pb and 5.9% Fe.
  • the zinc distilled off corresponded to a good quality of rolling zinc, as in example 4. it contained: 0.37% Pb, 0.032% A1 0.0027% Cu and 0.0008% Fe.
  • the packing was freed of metal droplets and oxidic impurities as well as other mechanical impurities by sieving and was reused.
  • said body of column packing includes an upper portion defining a fractionation zone, and a lower portion defining an evaporation zone and maintaining the lower portion at higher temperature than the upper portion.
  • the radial temperature gradient between said stream and the wall of the column containing the packing being at least 1008 C.
  • the radial temperature gradient between said stream and the wall of the column containing the packing being at least C.
  • the radial temperature gradient between said stream and the wall of the column containing the packing being at least 100 C.

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  • Engineering & Computer Science (AREA)
  • Chemical & Material Sciences (AREA)
  • Manufacturing & Machinery (AREA)
  • Materials Engineering (AREA)
  • Mechanical Engineering (AREA)
  • Metallurgy (AREA)
  • Organic Chemistry (AREA)
  • Vaporization, Distillation, Condensation, Sublimation, And Cold Traps (AREA)
  • Manufacture And Refinement Of Metals (AREA)
US746191A 1967-07-20 1968-07-19 Process and device for the distillative purification of metals, especially of zinc Expired - Lifetime US3637367A (en)

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DE19671583880 DE1583880A1 (de) 1967-07-20 1967-07-20 Verfahren und Vorrichtung zur destillativen Reinigung von Metallen,insbesondere von Zink

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0026560A1 (en) * 1979-07-24 1981-04-08 Isc Alloys Limited Boiler for molten metals and a method of boiling and refining a molten metal
CN113350821A (zh) * 2021-05-28 2021-09-07 鲁西化工集团股份有限公司硅化工分公司 一种提高精馏系统运行效果的装置

Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1086452A (en) * 1912-08-16 1914-02-10 Bernhard Benedix Rectifying apparatus.
US1941569A (en) * 1930-02-24 1934-01-02 New Jersey Zinc Co Manufacture of zinc oxide
US2183535A (en) * 1938-02-18 1939-12-19 American Smelting Refining Recovering zinc
US2433615A (en) * 1945-03-27 1947-12-30 New Jersey Zinc Co Treatment of dross for the recovery of zinc
US2674609A (en) * 1951-07-10 1954-04-06 Robert E Beal Deodorization process
US2915883A (en) * 1953-06-22 1959-12-08 Philips Corp Gas-fractionating column
US3325376A (en) * 1963-05-08 1967-06-13 Us Stoneware Co Distillation column

Patent Citations (7)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US1086452A (en) * 1912-08-16 1914-02-10 Bernhard Benedix Rectifying apparatus.
US1941569A (en) * 1930-02-24 1934-01-02 New Jersey Zinc Co Manufacture of zinc oxide
US2183535A (en) * 1938-02-18 1939-12-19 American Smelting Refining Recovering zinc
US2433615A (en) * 1945-03-27 1947-12-30 New Jersey Zinc Co Treatment of dross for the recovery of zinc
US2674609A (en) * 1951-07-10 1954-04-06 Robert E Beal Deodorization process
US2915883A (en) * 1953-06-22 1959-12-08 Philips Corp Gas-fractionating column
US3325376A (en) * 1963-05-08 1967-06-13 Us Stoneware Co Distillation column

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
EP0026560A1 (en) * 1979-07-24 1981-04-08 Isc Alloys Limited Boiler for molten metals and a method of boiling and refining a molten metal
CN113350821A (zh) * 2021-05-28 2021-09-07 鲁西化工集团股份有限公司硅化工分公司 一种提高精馏系统运行效果的装置

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GB1239053A (enrdf_load_html_response) 1971-07-14
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