US1790012A - Condensing metallic vapors - Google Patents

Description

Jan- 27, 1931. G. T. MAHLER ET AL L792 CONDENS ING METALLIC- VAPORS Filed May 5' 1925 2 Sheets-Sheet l Jan. 27, 1931.

G. T. MAHLER ET AL CONDENSING METALLIC VAPORS 2 Sheets-Sheet '2 Filed May 5, 1925 INV NTO S Gl. me, JJM

ATTORNEYS ratus for Patented Jan. 27, 1931l UNITED STATES PATENT l'OFFICE GEORGE T. MAKLER, ERWIN C. HANDWERK, .AND EARL H. BUNCE, OF PALMRTON,

PENNSYLVANIA, ASSIGNORS TO THE N. Y., A CORPORATION OF NEW JERSEY NEW JERSEY ZINC COMPANY, OF NEW YORK,

. CONDENSING METALLIC VAPORS ,v Application filed May 5,

This inventiourelates to the condensation of metallic vapor, and Amore particularly zinc vapor, and has for its object the provision of an improved method of and appacondensing metallic vapor and especially zinc vapor. y

Metallic zinc or spelter, when producedby the reduction of oxidized zinc ores at high temperatures, is almost universally made at the presenttime in zinc distillation or spclter furnaces having a number of relatively small retorts to the outer ends of which condeusers are attached. The retorts are usually mounted at a slight inclination, usually inclined downward from'the butt or closed end towards the open or outer end. The condenser is in effect an extension or elongation of the retort, although usually mo nted in a substantially horizontal position, and hence not in exact alignment with the elongated axis of the retort. The zinc vapor and other gases pass in a substantially horizontal line from the retort through the condenser, and the exhaust gases escape through the open end of the condenser. The eiliciency of this present customary condensing apparatus is far from satisfactory, only about 6() to 65% of thev the remainder metallic zinc vapor passing out of theretort being condensed as metallic zinc or spelter, being condensed as "blue powder or burning at the mouth of the condenser to zinc oxide andlost.

l/Ve vhave discovered that the eliiciency of u condensation of zinc vapor can be very substantially improved by appropriately circulating the vapor over a lm of molten zinc. of suitable area and held at a carefully controlled temperature. The necessary filmv of molten zinc is preferably provided and maintained upon the ceiling and the upright Wall `Aor walls of the condensing chamber, and thezinc vapor entering the chamber 1s caused to repeatedly circulate and Contact r with the ilm of molten zinc. The desired` circulation of the zinc vapor is advantageously brought about by passing a stream or current of zlnc vapor mto the condensing chamber and causing this stream of vaporfto impingefagainst al ceiling so disposed as to 1925. .Serial N'o. 28,056.

uniformly defiect-the zinc vapor against the film of molten right wall or chamber.

In our preferred practice, the condensing chamber' is disposed so that the stream of zinc vapor passes upwardly through the bottom thereof and impinging against the ceilmg is uniformly deflected outwardly and. downwardly over the film of molten zinc on= the ceiling and the upright (preferably ver-v tical) Wall or walls of the condensing chamber. The zinc vapor is thus'caused vto re'- peatedly circulateover and in Contact with the 'film of molten zinc, of appropriate area, and at the proper temperature, and condenses thereon. .The condensed zinc serves to maintain on the ceiling and on the upright wall or Walls of the condensing chamber the desired^film of mol-ten zinc, and the excess zinc drops off or Hows down these walls toan appropriate well at the bottom of the condensing chamber and is there collected.

We have found that in addition to the area of the condensing surface careful controlof the temperature of the ceiling and upright wall or Walls of the condensing chamber is necessary forthe optimum efficiency of condensation of the zincvapor. When the temperatureof the ceiling and upright wall (or walls) is properly controlled substantially allvof the zinc vapor is conzinc on the ceiling and'up-l walls of the condensing densed as metallic zinc or liquid spelter, and

less than 10% and frequently as little as 1 to 2% of the total zinc entering the chamber condenses as fblue powder or uncoalesced zinc droplets, the balance of the, zinc being con ensed as metallic zinc or liquid spelter.

In the accompanying drawings, we have illustrated what we now consider the best modes of practicing the invention. In these drawings, we have shown our improved condenserfin conjunction with a verticalretort or shaft furnace, but We desire to have it'understood that the invention is not limited to this particular type of zinc distillation furnace but, on the contrary, the invention is of general applicability and can be advantageously used for 'condensing zinc or other me 100 tallic vapor without regard to the source of the vapor.

In the accompanying drawings Fig. 1 is a front sectional elevation of a vertical retort or shaft furnace for reducing oxidized zinc ores provided with Athe im- Figs. 1, 2` and 3 of the drawingscomprises a vertical retort 10 of tire-clay or other appropriate material. The retort 10 is surrounded, for the greater part of its length, by a laboratory or heatingchamber 11. The heating chamber 11 is built Within a furnace structure comprising an outer steel shell or casing 12,

van intermediate layer 13 of heat-insulating material, such as Sil-o-cel, and a lining made up of lire-brick 14 covered with graphite blocks or plates 15. Appropriate openings 16 are provided through the Wall of the furnace structure for permitting the insertion of pyrometers Within the laboratory or heating chamber 11, for ascertaining and controlling the temperature throughout the length of this chamber.

The furnace structure is mounted on an appropriate foundation 17. 'Ihe bottom of the retort 10 opens into a closed chamber or pit 18 having a clean-.out door 19.

Any appropriate means may, of course, be employed for heating the retort. 10. Thus. for example, ire gases may be conducted through the laboratory 11 and around the retort 10. In the apparatus illustrated in Figs.'1, 2 and 3, the heating of the retort is effected by electric energy. The electric heating or resistance element comprises` two graphite rods 20 extending through the top of the furnace structure and resting on graphite blocks 21 slightly below the center of the chamber 11. The lower portion of the rods 2() are hollow and have a spiral slot sov as to provide a helical resistance path for the flow of the electric current. One terminal of the source of electric energy is connected to one of the graphite rods 20 and the other terminal of the source of electric energy is connected to the other graphite rod 20. the electric circuit between the lower ends of the two rods 2O being completed through the graphite blocks 21 and the graphite lining l5. Either direct or alternating current may be used for supplying electric energy to the graphite rods 20. 1

The bottom 'of the chamber 11 is provided with two graphite resistance rods or elements tically disposed wall 25. A flat circular ceil' ing 26 covers the top of the cylinder 25, and an annular plate 27 partially closes the bottom of the cylinder. The cylinder 25 and plates 26 and 27 are made of heat refractory `Inaterial, such as fire clay, carborundum,

mixtures of the same, or the like. These three elements may be integrally united or separately formed and joined together to constitute the novel and improved plug-hat condenser of ourI invention.

A nozzle 28 is attached to the bottom plate 27. The diameter of the central opening in the plate 27 and the internal diameter of the nozzle 28 are less -than the diameter of the retort 1() and these three elements are axial# ly in alignment. The nozzle 28 extends upwardly to about midway of the condensing chamber provided within the cylinder 25.

The ceiling 26 -has a `central opening 30 loosely covered by a plate 31. The exterior of the condenser (cylinder 25 and ceiling 26) is covered with an appropriate layer 29' of heat insulating material. In practice, we have found dust coal admirably adapted as the heat insulatingV covering for the con.- denser. From the loosely packed insulating material (coal) around the plate 31, the carbon monoxide gas escapes from the opening 3() of -the condensing chamber and burns in the air.

The annular space between the nozzle 28 and the cylinder 25provides a well for collecting molten zinc, and molten zinc is tapped from this well, from time to time, through a taphole 32.

The mixture of zinc vapor and carbon monoxide gas (resulting from the reduction of the oxidized zinc ore in the retort 10) passes out of the top of the retort into the nozzle 28. A11-upwardly flowing stream or current of zinc vapor thus passes through the bottom of the condenser and4 into the condensing chamber. This stream of zinc vapor impinges against the fans out over the ceiling 26, and is uniformly deflected down the side of the upright wall 25, as indicate-d by the arrows in Fig. l of the drawings.

drafted across this constantly renewed fresh film 'of molten zinc and condense thereon.

, Thus, the tihn of molten zinc provides a nucleus upon which condensation of the zinc vapor readily takes place. The exhaust gases, Ior`tne most part carbon monoxide, escape through the opening 30, passing underneath the loose plate 31 and through tallic zinc or liquid spelter.

.The metallic zinc condensing on the Wall of the cylinder flows down this wall `into the molten metal well at the bottom of the condensing chamber. The molten zinc accumulates in this well and is periodically removed therefrom through the tap-hole 32.

The film of molten zinc on the condensing walls -need not be continuous, and in practice may consist of minute drops or globules of molten zinc which substantially cover the innersurface of the wall or Walls. By a film of molten zinc, we mean a thin layer of molten zinc, not necessarily continuous, but sutliciently extensive in area to substantially cover the inner or condensing surface of the cylinder 25 and ceiling 26.

It is important that the temperature ofthe walls of the condensing chamber (25 and 26) be` carefully controlled. If the temperature of these walls is too high, the gases escaping through the opening will carry too much zinc vapor, and if the temperature of these Walls is too low an excessive amount of blue powder will be formed. l/Ve have found a temperature of from 500 to 850o C. satisfactory,'and when the condensing Walls are maintained Within this temperaturey range,

' very eicient condensation of the zinc vapor to metallic zinc or liquid spelter results.

Ve prefer to regulate and control the tem perature of the condensing wall or walls by regulating the amount of external heat insulation on these walls. In practice, we periodically insert a pyrometer (thermo-couple) into the condensing chamber (preferably .through the top opening 30) and when the temperature within the chamber is too high,

we decrease the amount of external heat insulation, and when the temperature is too low,

We increase the amount of this external heat insulation. This external heat insulation may advantageously consist of a layer of dust coal, or other appropriate heat insulating material, loosely packed around the outside of the condenser. The amount of external heat insulation about the condenser is then varied by varying the thickness of this layer of heat insulating material. Y.

The size and proportions of the condenser s are varied in accordance with the amount of zinc vapor to be condensed. Vorking with a retort (10) 8 inches in internal diametei-.and

10 feet long, charged with zinc silicate ore (containing approximately 45-50% zinc) .andy dust coal in about equal amounts, and

Working off the charge in 8 hours, we have secured excellent results with a condenser built of a mixture' of carborundum and ireclay, approximately 12 inches in internal diameter and 11 inches high (internal), the walls of the condenser being 1 inch in thickness. The nozzle 28 was approximately 3 inches in internal diameter and extended about 4 inches Within the condensing chainopening.30 and into the top of the retort through the nozzle 28. Too large a nozzle,

however, is not desirable, since a. certain amount ot the condensed zinc drops oit the ceiling 26, and it the diameter' otl the nozzle- 28 is too large, an objectionable amount of molten zinc dro-ps back into the retort and has to be redisti'lled.

The condenser of Fig. 5 is relatively higher and narrower than the condensers of Figs. 1 and' 4. Care must be taken not to unduly lengthen the condenser, since under such circumstances the topof the condensing chamber' becomes relatively cool and an excessive amount o f blue powder may be formed. In the condenser of Fig. 5 vthe same reference characters have been used ,to designate The nozzle 28 of the condenser l corresponding or equivalent parts as in Fi g.' 1.

lVhile we prefer to arrange thc entrance nozzle or orifice of the condenser so that it is coaxial with the condensing chamber, such an arrangei'neut is not necessary. In Fig. G

the nozzle 28 for conveying the zinc vapor y to the condensingchamber is disposed at'one side of the chamber.

The condenser of Fig. 7 is provided with spaced Walls. The exhaust gases from the condensing chamber vpass through the space between the' two walls and thus promote the heat insulation of the condensing chamber. Corresponding Ior equivalent parts of the condenser ot' Fig. 7 are indicated by the saine reference characters asin Fig. l. The 'condenser proper (25-26) is surrounded by a spaced shell 33, of fire-clay or the like.4 The gases' escape `from the condensing chamber through openings or ports 35 in the cylinder 25. The gases then How through the space between t-he shell 33 and the condenser (25-26) and escape to the atmosphere positioned openings trated a multiple condenser adapted to be condensed.

used with a vertical retort or shaft furnace of relatively large diameter.A As illustrated in Fig. 9. this condenser consists of three or more units, and vembodies theA general structural features of the condensers of Figs; 1 and 7. l

. The condensers herein illustrated and described are generally of circular section.`

However, it is to be understood that this configuration is not an essential part of the invention, but is adopted in practice principally because of its practical convenience. The improved condenser of our invention maybe square, rectangular, oval and indeed of any desired, sectional configuration.

The improved condenser of our invention is principally characterized by its upright and preferably vertical condensing Wall (or walls) and substantially horizontal ceiling. The condensing surface or area of the upright Wall (or walls) and ceiling are carefully proportioned with respect to the amount of zine vapor to be condensed'in a unit of time and this condensing surface is held at a carefully controlled temperature. The current or stream of entering zinc vapor is con# ducted into the condensing chamber through an opening, preferably constricted, in the bottom of t-he condenser. and rising upwardly in'lpinges against the ceiling and is deflected over the condensing surface. The zinc vapor repeatedly circulates over the condensing surface` covered with a film of molten zinc, until The exhaust gas is preferably "permitted to Vescape through the looselv covered opening in the top of the condenser.

However, if desired, the upright4 Wall of the condenser may be provided with suitable openings or ports for the escape of the exhaust gas. i

The zinc vapor enters the condensing chamber at an approximately right angle to the surface of the molten zinc in the collecting Well. The molten zinc in this-Well preferably surrounds the conduit through which the zinc vapor passes on its wayinto the condensing chamber. The temperature of the Vmolten zinc in the collecting Well is controlled to prevent boiling oft-he Vmolten' zinc. This may be conveniently accomplished by appropriate control of the amount of external Aheat insulation about this portion of the condenser.

The upright wall or Walls of the condenser are preferably cquidisjtant from theentering de nsation.

yissue from the top of the vertical' retort 10,

the two factors that play a great part in the efficiency of condensation are the temperature and pressure Within the condensing chamber. Both of -these factors are controlled by the size and the proportions of the condenser. If the temperature of the condensing Walls is too great, zinc vapor will escape and be lost. If the temperature is too low, the zinc will condense in the form of blue powder. rather than molten metal. If the pressure in the condensing chamber becomes too great, it Will have a deadening effect on the velocity of the reaction Within the vertical retort, and will, therefore, ad-

' verselyaffect the recoveries. Ifthe pressure in the condensing chamberbecomes too low,

the zinc will condense as blue powder,

amount of zinc vapor may be held fairly con-v stant and uniform, and a condenser of appropriate size and proportions may he provided for this uniform set of conditions.

ico

lu the case of' hatch or intermittent chargmixed gases passing from the muflle or re-.

tort is than in the second four hours of the operation. ,During the first four hours ofthe operation, the condenser, therefore, should have a relatively large radiating surface and relatively large volume in order to keep the temperature and pressure down to Within the limits for efficient condensation.

During the latter four hours of the operation. theratio of zinc in the gases increases and the quantity decreases so that it is necessaryr to provide more external heat insula- Vtion for the condenser in order to maintain a high` enough temperature for efficient con- It is impossible to change the volume of the' condensing chamber and, therefore, during this latter stage of the operation the pressure in the condensing chamfrom said last mentioned opening into thc ber is too low for efiiciet condensation, and condenser.

some of the zinc may, therefore, be con- In testimony whereof We atix our signadensed as blue poWder.- tures.

In constructing a condenser for batch or GEORGE T. MAHL'ER. 70 intermittent operation, 'it is preferable tol ERWIN C. HANDWERK. compromise between the two extreme condi- EARL H. BUN CE.

. ing therein, a plate loosely covering saidv tions, rather than to provide a condenser of appropriate size and proportions for one or the other extreme conditions.

Weclaim v 1. A condenser for metallic vaporscomprising a substantially upright enclosing wall, a ceiling for said wall havingan opening therein, a plate loosely covering said opening, and a closure at the bottom of said wall having an opening for the passage of metallic vapor into the condenser.

2; A condenser for metallic vapors comprising` a substantially upright enclosing Wall, a ceiling for said Wall having an opening therein, a plate loosely covering said opening, an external covering of heat-insulating material for said Wall and ceiling, and a closure at the bottom ofA saidwall having an opening for the passage of metallic vapor into the condenser.

3. A condenserfor metallic vapors comprising a substantially upright enclosing wall, a ceiling for said wall, an external covering ofloosely packed granular heat-insulating material for said wall and ceiling, and

. a closure lat the bottom of said wall having an opening for the passage of metallic vapor into the condenser.

4. A- condenser for metallic vapors comprising a substantially upright enclosing Wall, a ceiling for said wall having an openopening, an external covering of loosely packed granular heat-insulating material for said Wall and ceiling, and a closure at the bottom of said Wall havingan opening for the passage of metallic vapor into theconenser. 1

5. A 'condenser for metallic-vapors comprising a -vertically disposed cylindrical en@ closing wall, a ceiling for said Wall having aff opening therein, a plate loosely covering said opening, an externalvcovering of heat insulating material for said Wall and ceiling, a closure at the bottom of said wall having an opening therein, and a nozzle extending up- Wardly from said opening into the con-v denser.

6. A condenser for. metallic vapors comprising a vertically disposed cylindrical enclosing Wall, a ceiling' for said Wall having an opening therein, a plate loosely covering said opening, an external covering of loosely packed granular heat-insulating-material for said wall and ceiling, a closure at the bottom of said Wall havingian opening therein and a constricted nozzle extending upwardly los

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