US2380548A - Zinc condenser - Google Patents

Description

2 Sheets-Sheet l INVENTORY lwwmvlmu/umQui wzm QUENEAU ZINC CONDENSER Filed April 16, 1942 July 31 July 31, 1945. A. L. J. QUENEAU 2,380,548

ZINC CONDENSER Filed April 16, 1942 2 SheetsSheet 2 l N V E N T O R m lion/dulvwmma,

2 m if) Q MW J m PN Patented July 31. 5

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coNnnNsaa Auguatin up... Jean-Queneau, Morriltown, NQL, "assignor to United States SteeI Corporation of Delaware, a corporation of Delaware Application April 16, 1942, Serial No. 439,266

' a s Claims. (crass-17 In zinc metallurgy, many forms of condensers ror evolved zinc vapors produced by thereduction of zinc ores have been evolved for thepurpose of condensing the zinc vapors to liquid zincwhich and shaft furnaces is of increasing importance.

In all of these operations, the'heat required for the reduction is supplied from the. outside of the retort either by conduction, convection, or. radiation, or by electrical heat liberated in situ within the charge itself. 7 e I The process of the reduction of the zinc-vapors in accordance with the present invention is based upon the reduction of the zinc oxide in a shaft furnace heated by direct internal combustion of carbon produced by pure anhydrous oxygen giv-. ing rise to a widely different set. of conditions from those existing in any other type of zincreduction furnace. The present'improvedreduction process eifects the reduction of zinciferous materials in a shaft furnace internally heated by "the combustion ofcarbon v(metallurgical coke) in a blast at appropriate pressurev (for example. 10 to 12 pounds) of pureanhydrous oxygen.

The various types of condensers proposed or in use for the condensation of"the zincvapor from the streams of zinc vapor and gases, carbon monoxide and occasionally hydrogen in small amounts. issuing from large industrial furnaces externally heated. as in the caseof vertical zinc retorts, orinternally heatedby electrical resistance of the furnace charge or by an electric arc. as in the case of electrothermic zinc processes. are not applicable to the special problemof the condensation of zinc vapor from the streams-of zinc vapor, and carbon monoxide issuing from a shaft furnace of the type herein described, heated internally by the combustion of carbon in a blast of oxygen, for-while the samecarbon monoxide and zinc vaporare present, they are present.in this specific instance in widelyldifferent volumes from the vapor-gas; stream from the classic Belgian retort process. or from the vapor-gas ess or of the furnaces utilizing eiectrothermic reduction. e

In all of these instances the maior chemical reactions are the same, namely,

COs-i-Ca-ZCO (2) secondary reactions here being neglected, such as the reduction of-iron and/or manganese oxides 0 present in minor quantities in the zinc ore of the furnace burden. In the foregoing procedures, for one pound of reduced zinc'vapor, there are 5.4.8 cubic feet of carbon monoxide, volume taken at standard conditions of temperature and pressure.

15 However. in the, case of the present process in which all of the heat requirements are produced within the reduction shaft furnace by the combustion of carbon in pure oxygen, the ratio is as follows: For one pound of zinc vapor there are 0 26.32 cubic feet of carbon monoxide. Thus. there is an increase for the" same pound of zinc, from 5.45 cubic'feet to 26.32 cubic'feetor an increase of substantially 1 to 5. e

This enormous increase in the volume of uncondensable gas, accompanyingthe condensable zinc vapor. gives rise to conditions in the zinc condenser which cannot be handled by the heretoiore proposed-condenser constructions, either thoseof the surface condenser type. or the con- 0 densers wherein a large body of molten zinc is "sloshed" back and forth by the hilh suction created by a vacuum pump. g

Itis found in practice that the use. of pure oxygen in a shaft furnace for .zinc produces oper- 35 ating eili'ciency highly above those obtainable by the usual operations. However, inyiewof the enormous increase in the volume of uncondensable gas accompanying the condensable zinc va-. pors there has been necessitated the construction 0 of a new type of condenser in which the mixture of zinc vapor and carbon monoxide is not passed into a body of zinc in liquid form, but is made to pass over a body of liquid zinc, as is done in the Belgian zinc condenser.

But in the present improved construction the vapor-gas stream is divided into a number of smallerstreams by windows cut into walls extending transversely to the longitudinal axis of the condenser. Owing to the velocity of these gas streams, the surface of the molten lincis depressed and pushed toward the exit end of'the condenser. Also. the violent and turbulent passage of the gas streams, tears bodily from the molten zinc, drops-and splashes which are pro- I stream from the continuous vertical retort proc lected against the forward plit i mie m ppfl of the zinc ores free surfaces of the condenser. The zinc so pro- Jected drops back into the main body and efilcicntly scrubs the passing stream of vapor and gas. These steps are repeated at each condenser wall.

'Theoxygen blast for effecting the reduction in the shaft furnace is blown through the tuyeres of the furnace at a pressure suiflclentto overcome the resistance offered-to its passage by the burden within the shaft furnace; as well'as the resistance of the condenser itself and of the scrubbing system through which the carbon monoxide with any small proportions of uncondensed zinc vapor is made to pass before reaching the gas holder for; the purified carbon monoxide. This initial oxygen pressure supplies vthe energy necessary for the operation of the condenser.

Buch operating conditions are not present elther'in-the procedures involving the use of a vertical retort. a flash reduction" column. nor

"in shaft'furnaces employed for ejle'ctrothermic zinc reduction operations. In the present process new conditions 'are'set up which require new meansfor handling.

In all prior procedures as noted above.'the pressure of the zinc vapor and carbon monoxide, liberated by the reducing-Reactions l and 2 noted above herein. is that of the furnace atmosphere that is slightly above atmospheric pressure. It

is insufficient to force the passage of the gas and zinc'vapor through any depth of moltenzinc.

Therefore. in some operations a vacuum pump 'is' employed to'draw the gas and zinc vapor through a collected body of molten zinc, for-effecting condensation. In other operations using the socalled vertical retort in order to increase the volume of the retort reduction gaseous products, there is introduced by means ofa positive blower a metered amount'of air at the base of the vertlcal retort at a point above the water seal. This air coming in contact with the carbon of the hot briquettes forms additional carbon monoxide:

which helps to sweep upwardsto the condenser the reduction gases. zinc vapor and carbon monoxide. Additiorraliythere is 'a certain amount of steam generated by the exiting'spent hot briquettes falling into the water of the water seal; This steam rises through the verticalretort and in contact wi'ththe hot carbon of the briquettes forms additional carbon monoxide andhydrogen:

C+H :O-'C0+Hz v v This additional gas volume assists in the evacuation of the gaseous products of the zinc reduction. But there is nothing which approaches the posithe view being taken on the longitudinal center.

line .of the condenser;

, l"ig.-2 is a transverse sectional elevation through the condenser of Fig. 1. the view being taken on scans the line 11-11 of Fig. 1, looking in the direction of the arrows: and.

Fig. 3 is a sectional plan view of a modified form of condenser.

Referring more particularly to the drawings and to Figs. 1 and 2. the condenser construction illustrated therein comprises a metal shell I such as sheet steel or the like, which is lined with a suitable number of courses of refractoryv brick I.

which may be made of siliconcarbide or ,carbon.

Extending transversely across the interior of the condenser is a. plurality of transverse partiticns 9. each of which is provided with a plurality of rather large openings or windows ii, the level of which above the condenser floor is raised from I the inlet end l3 of the condenser to the outlet end It so as to maintain a uniform depth of molten zinc tube depressed and agitated by the flowing stream' of vapor and gas throughout its length. The outlet end I! is provided with a suitable tap hole ll, for providing drainage for the condenser at the end of a run. hole is provided conventionally in all types of zinc condensers.

The design'of these windows if in relation to the inlet pressure of the gas stream is such as to allow a depression of from approximately six to approximately eight inches in the bath of molten zinc of the condenser.

Each of the transverse partitions 9 has a. small port 11 which allows restricted communication between all'sections of the pool "of molten zinc.

-Thecondenscr communicates with a holdin furnace is for the zinc in a manner which now will be described. This communication is effected by providing graphite cylinders 2| and 23, which may be made from nine-inch square graphite electrodes. thefcylinder 2| being drilled with a hole extending partly thcre'through. and cylin- 40 der 23 having a; hole 21 drilled all the way therethrough. so that when the cylinder 23 is assembled the hole, 21 communicates with hole 25.;01111- ing a passage through which zinc may now from the condenser infcthc furnace l9.

The pipe 23 is covered by. a layer of refractory 29,-which is enclosed in a metal sheath 3I." Thc 4 furnace i9 is provided with a tap hole 33. shown it y zinc vapor-gas stream enters the condenser asclosed by a plug 35. opening of the tap hole 33 allowing'zinc to flow out of the furnace l9 over a lip'31 into a suitable large ladle from which the molten zinc is poured into the usual molds in which the zinc solidifies into slabs.

Aswill beseen from Figs. 1 and 2. a high velocthrough intake l3..which leads from the reduction zinc furnace not shown) which operates similarly toa blast furnace except thatcombustion is .supported by pure oxygen introduced through the tuyeres of the furnace under sufficient pressure to maintain" a super-atmospheric pressure of from about ten to about twelve pounds in the furnace.

After passage through suitable insirumcntalities for removing entrained solids fromthe vapor-g'asstrcam, this latter passes under high velocities induced by the. said pressure into the condenser, which condenses zinc from the stream to form the pool 20 of molten zinc in the condenser. i

The continued entry of the high velocity as stream.-which stream is subdivided by the windows ll into smaller streams. likewise of high velocity, results in-the pool so bcingswept by th incoming high velocity vapor-gasstr'eams. Ow-

ing to the high velocity or these vapor-gas Such a tap assasss plnges first mainly upon partition II, which, to-

streams, and in view of the ports llai'fording free communication betweenthe various sections of the pool, the surface of the pool "is depressed and pushed towards the exit. end [I of thecon- 'denser as shown inv the drawings. also, the

, violent and turb'ulentpassage of, the vapor-gas streams tears bodily from the pool, drops and splashes of the molten'zinc which are projected against the forward partitions, and uppenfree surface of the condenser. The zinc so projected drops backinto the main molten zinc body and emciently scrubs the passing streams of zinc vapor and gas, condensing the zinc therefrom. These actions are repeated at each condenser division walls 9.

The residual carbon monoxide with a small percentage of uncondensed zinc passes out from the condenser through a stack 3'. to suitable scrubbing instrumentalities of well-known type, such as a wet cyclone and scrubbing tower where it meets in its upward travel a washing stream of water. The resuiting'clean'carbon monoxide may be passed to a suitable gas holder.

A modified form of condenser is illustrated in Fig. 3, which operates in a manner similar to that described above. I

In the form of condenser shown in Fig. 3, instead of a long cylindrical condenser of fifteen or more feet "in length of the type shown in Figs. 1 and 2, the requisite length of travel of the vapor-ga stream may be attained by the use of two or more short chambers suitably com-.

municating so that the vapor-gas stream will be doubled back upon itself a suitable plurality of communicate at their far ends.

times. In Fig. 3 two chambers. are shown, which In Fig. 3 the condenser structure 4| is divided in raphitejp pe ljie respondins to pe which leads to. a holding furnace for molten zinc,

similar to fumaceifl but not shown in Fig. 3.

'I'hereformit-vvill-be seen that the direction j of now of the vapor-gas stream is reversed as it passes through-the condenser system, and the condensing chambers 43,", may be increased in number to whatever capacity may be required for agiven installation, the arrangement being such I that the direction of flow is reversed'for eachchamber.

Each chamber is divided into section by transverse partitions which are similar to partitions 9 of the construction of Figs. 1 and .2, and which likewise are provided with windows II. which are similar to windows II and are placed likewise at increasing heights in the direction of gas flow, and are provided also with small ports corresponding to ports IT.

The operation of the condenser of Fig. 3 is' similar to the operation of the condenser of Fig. 1, described above, except that the high velocity vapor-gas stream, is subjected to centrifugal force in swervingaround and through the partitions, the carbon monoxide and the zinc vapor being thrown forcibly into contact with the walls of the condenser. This is due to the fact that the vapor-gas stream entering through intake ll im- 7 gether withsomewhat lessened velocities caused by the stream entering the 'enlargedchamber It produces a vigorous swirling of the stream as it passes through the condenser system, thoroughlywetting all'surfaces'with'droplets of molten zinc, which thus contact the walls and surfaces. wetting them andtrickling down'to-thefpool of molten zinc inthe bottom of the condenser.

The condenser structures herein shown and described operate very efficiently in practice in condensing zinc from high velocity vapor-gas streams entering the condenser in large volumes, from a nnc reduction shaft furnace operating on pure oxygen as the combustion-supporting agent.

Referring to'Fig. 3, the carbon monoxide stream carriesany small amounts of zinc vapors that before.

InJboth illustrated forms of the condenser, as

i the levelof the zinc pool in thecondenser rises through additions of molten condensate derived from the incoming vapor-gas stream, equivalent amounts of molten-zinc are forced throughthe outlets l8, channels II and 21. (II, Into the pool of the holding furnace.

Suitable clean-out doors with appropriate refractory plugs and covers, not shown, obviously may be provided as desired. a

I claim:

1. A condenser for condensing the zinc content of high velocity zinc vapor-gas streams from a blast furnace using pure oxygen as the supporter of combustion of reduction reactions. which com- ,lprises in combination, a condenser environment having refractory walls, an inlet for the zinc vapor-gas stream, partitionumeans extending transversely across the condensing environment dividing the environment into sections, bottom ports in each of the partition means providing communication from one of the said sections to adjoining sections, thereby enabling formation of a continuous pool of condensed molten zinc extending throughout the bottom of the condenser environment, and openings in the said partition means for subdividing the incoming zinc vapor-gas stream into a multiplicity ofsmaller high velocity streams.

2. A condenser for condensing the zinc content of high velocity zinc vapor-gas streams from a'blast furnace using pure oxygen as the supporter of combustion for reduction reactions. which comprises in combination, a condenser environment having refractory walls, an inlet for admitting the zinc vapor-gas stream into the .condenser environment, partition means extendins transversely across the condensing environment dividing. the environment into sections, bottomports in each of the partition means providing communication from one of the said sections to adjoining sections, thereby enabling fordenser environment, openings "in the said partiuously withdrawing condensed zinc from the condenser in conformity with the condensation of zinc from the zinc vapor-gas streams.

3. A- condenser for condensing the zinc content of high velocity sinc vapor-gas streams from a blast furnace using pure oxygen as the sup; porter oi combustion for reduction reaction); which comprises in combinaticn, a condenser environment comprising a plurality of condensing chambers, acommunication between the said chambers sothat the zinc vapor-gas streams reverse in direction of now through the chambers,.

an inlet for introducing the zinc vapor-gas stream into one of the chambers in a location remote irom the said communication, outlet means in another chamber also remote from the communi- 10 denser.

cation for removing stripped gas from the condenser. partition means in the chambers, dividing the chambers into sections, openings in the said partition means for subdividing the incoming zinc vapor-gas stream into a multiplicity 01! smaller high velocity streams, the said streams impinging upon condenser walls, and partition means under action of centrifugal force, and means for removing condensed zinc from the con suoos'rm LnoN JEAN QUENEAU.

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