Note: Descriptions are shown in the official language in which they were submitted.
: .
- ` ~06242~
.. ` . . . . . . . .
. . .
,,. . . . , ................................................ ~
This application ls a di~ision.o~ co-pendlng
252 920 ~i~ed ~ay 20, 1976.
Canadian Application No,
CKGROUND OF THE INVENTION
Sponge tron, metali ked pellets or reduc~d metal materials are
~, proiuced by the dtrect retuctton o~ ores. "Metallized" ;n this sense
r.~. ~ ~ doos not mean coa~ed with metai, but means nearly complete!y ~duced to
- ~ ~etal, f.e., always tn excess of 75~, metal, and normally in excess o~ 8~L
~ctal In the praduct. Tht5 metalli~ed product ;s suitable for charging
dlrectly to a me~al refining furnace as the feed matertal. In ferrous
;~ metallurgy, the product refcrred to Ts m~talltzed iron material, which Is
ehargcd dlrectly to a steelmaklng Furnace, such as an clectric arc furnaça.
Stc~l ptants whlch utlltzQ mct~lllz~d Iron as a feed matcrial have no necd
~ for ~etallurglcal coal or coke. Further, such plants are economtcal at
;r,~ ` ~' , SH11 capacTtles and thus do not require the blgh capltal Investment of
~ A~ en P ~ t ~
~ 1~ 6Z~28
One of the prob1ems assoclated with the use of sponge Iron as
a raw materlal In steelmaklng is Tts inherent tendency to reoxtdTze upon
exposure to atmospheric condTtions. Hot sponge iron is extremely reactTve
and oxidlzes spontaneously If contacted by oxygen Tn any form~ Thus, sponge
Iron must be cooled in a reducing or neutral atmosphere. At room temperature,
- . sponge iron ts so reactTve that It oxTdkes even when stored tn the open air.
Contact with water, likewise, causes rapld oxidation, which is commonly
termed rustTng. STnee the oxidatTon of sponge iron i5 an exothermic
reaction, thTs oxidatlon can result Tn spontaneous heatTng and ignition of -
tO the sponge iron durTng storage or transport. For this reason, metallized
sponge Tron has been classified a hazardous mat~rTal by the U~S. Coast 6uard,
and Its bulk shipment tn the unstabilized condltion is prohibited.
~1 in some tnstances, reduced Iron in such form as sponge Iron or
metallized iron pellets is produced in an Tntegrated steel plant as a raw
rnaterial for the steelmaking furnaces. If it were possible to feed the hot
¦ reduced tron, at a temperature above 500 C ~about 930 F), dtrectly tnto
¦ the steelmakTng furnace, thls would result in a more economlcal steelmiaklng¦ process, inasmuch as the energy requTrelr.ents would be groatly reduced and
- 1 ¦ hlgher producttvity would be obtained. it would be Imporative that hot
2C I spo~ige iron materTal be transported and handled In a controlled atmosphere,
I as ~posure to atmospherTc aTr would result Tn an extremely hazardous
¦ sltuation. If the hot sponge tron could be passlvated sufftciently that
it could b- transported by conventlonal equlpment wTth a mlnimal heat 1055,
the steelmaklng process for whtch It sorves as a raw materlal could reallze
¦ the full beneflt of its heat content with attendant savings In onergy
~ ¦ eonsumptlon.
3 I Passlvi3tlon of sponge Iron is also desirablo becau~ oxldatTon¦ of sponge Tron, aftor havlng once been raduced, requTres a socond
I reductton wlth an attendant Increase In energy consumptlon and C05t.
I Many att mpts have been made In the past to overcome, or
. I ~ . .
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reduce, the rèoxidatlon of metalllzed pellets and to passîvate spongo Iron, ~ I
Illustratlve examples include the proposal to cover a bulk shlpmont of
sponge lron wlth a thln polyurethane foam coating or other type of plastlc I,
film to prevent oxygen or molsture from contactlng the spongo iron. It
has also been suggested to cover such a bulk shipment with a thtn glass
coating. U.S. Pa~ent No. 3 125 437 teaches a process for pass;vatlng
sponge iron agalnst oxldatton in air by creating a thln protectlve skin on
the sponge iron surface. Hot briquetting with roll type briquetting
machTnery are taught ln U.S. Patents 3 116 996 and 3 174 846 to densify the ,
sponge iron, thereby mintmizing the suriace area of the reduced iron orc
exposed to the oxldlzlng elements. These illustratlve, but ~ot exhaustivo
examples demonstrate the many attempts to solve the prob1em.
Coatings on sponge iron require the use of a forelgn material
which contaminates sponge iron without guaranteeing passivationO Such
coatings are easily damaged, for ;nstance, a mere shiftlng of the
materlal in Its contalner durlng transit may rupture the coat7ng. Although
a protectlve oxlde skin ls a proven inhibitor to oxldation ln alr, It is
subject to rustlng to hydrated ferric oxlde. Thus, such skln doos not
prevent further oxldatlon by rusttng.
Heretofore, the hot briquetting of sponge iron has been a very
; promtsing process for passivation Inasmuch as It can be used to passivate
bulk shlpments to a htgh degree, as well as to passivate hot sponge lron :
with temperatures as high as 900 C (about 1650 F), so that ;t can be
transported on conventlona1 hot convoylng systems at hlgh temperature wtth-
~ ~S out elther a prohlbitlvely high loss of m~tallizatlon or spontaneous !gnltlon.
; ~ens7flcatlon of sponge Iron, at least on tts surface, ls accompllshed by
hot brlquettlng. The extorlor of the brlquet Is compressed to a denso
layer whlch Is stable or passlvated. The Interlor of the brlquet remains
less dense, I.e., spongy, and thus Is actlve and readily oxidtzed, but ls
protectod by the more dense surface layer.
., , ' . .
Pletsch
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106Z~Z8
Hot briquet~ing encounters certain mechanical problems.
Before the briquetting rolls start to wear, single briquets are
easily produced. As soon as wear beings, briquets become connected
to each other by webs, which requires that they be broken apart
prior to shipment or handling. As roll ~ear lncreases, the problem
of-breaking the briquets apart becomes more and more di~ficult. In
addition, the breaking procedure produces fines and exposes the
less densified interior of each briquet to oxidation, particularly
if the breakage occurs through the briquet rather than through the
` 10 web. With increasing web thickness due to increasing wear, this
occurs more and more frequently, Thus, although the greater pro-
portion of each briquet is passivated, there is still a sufficient
proportion of the briquet which is less passivated and subiect to
reoxidation with a high loss of ~etallization.
For known strip breaking mechanisms, see German Patent
1,533,827.
- OBJECTS OF THE INVENTIO~
It is an obJect of this invention to provide a simpli~ied
' ~ and efficient method and apparatus for the passivation of sponge
iron.
BRIEF SUMMARY OF THE I~V~TIO~
; The aforesaid ob~ects o~ this invention, and other ob~ects
~'~ which will become apparent as this de~cription proceeds, are achieved
; by providing hot 8pon~e iron compacting apparatus ~ollowed by a
shearing apparatus. The hot compacting apparatus rolls the sponge
iron into an elongated mass. The shearing apparatu~ cuts the mass
across its longitudinal dimension, compacting the newly exposed
edge~, and creating.small "compacts" which are easily handled,
- tran8ported, and used in subsequent processes.
`
il/J~ 4-
:-` 1062~28
Where the compacting apparatus produceæ a relatively wide
strip, ap~aratus may be provided for slittlng the elongated mass
longi~udinally to produce a plurality of elongated masses.
In one particular aspect the parent application, afore-
mentioned Canadian Application No. 252,920, is concerned with the.
provision of a method for forming a plurality of small, passi- .
vated, compact products from hot reacti~e particulate sponge
iron comprising:
a) feeding said particulate sponge iron at a temperature
of at least 600~C to a compacting apparatus;
b) compac~ting said particulate.sponge iron to form a
continuous densified elongated metal strip;
c) longitudinally cutting said densified elongated strip
si into a multiplicity of Iongitudinal strips; and
d) further dividing said multiplicity of longitudinal strips
at regular intervals by shearing them transversely to their
longitudinal dimension and simultaneously densifying the newly
. created surfaces normal to the longitudinal dimension, thus pro-
ducing a plurality of small compacted sponge iron products, each
20 . having a dense skin on all faces, whereby the products are
. resistant to atmospheric oxidation and suitable for bulk handling,
storing, and shipping without additional passivating steps.
In another particular aspect the parent application, afore-
mentioned Canadlan Application No. 2521920, i9 concerned with
the provision of a compactedt passivated, metallized lron product
useful as a feed material for a steelmaking process, said product
having dense, substantially pore-free faces with a densified
surface layer on each face, a less dense center with an average
.. : . . .
. ~ . density of
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`~ at l~ast 4.5 ~/cct and whereln from abou~ 75X to about 96~ of the
total iron present is in the metallic state.
The present application, a division of aforementioned
~':" , . .
~` Canadian Application No, 252,9~0, is particularly concerned with
," the provision of an apparatus for continuously passivating hot,
reactive particulate metal material comprising: a) means for feeding
... .
said particulate metal material to a compacting apparatus, said
feeding means including means for excluding substantially all
; ., ! ~
~~ atmospheric air therefrom; b) means for compacting said particulate
.....
~ lO metal to form a dense elongated metal mess; c) means for longi-
:j ~ tudinally cutting said mass while simultaneously passivating its
'k". ` .'
~` newly cut edges immedlately after said compacting apparatus; and
d) shearing means comprising t~o opposed cutting edges of metal
.~ coacting along a shear plane ~or simultaneously dividing said
. ~ .
~ elongated metal mass substantially normal to its longitudinal
~ , .
~ dimension and densifying the newly created surface by induced high
:............... .
shear forces, whe~eby a completely passivated product is produced
suitable for bulk handling, storing and shipping.
-~ While this invention is described in terms of sponge iron,
it will be readily understood~by those skilled in the art that the
~: . .
.
invention is equally applicab}e to the compaction of metallized iron
material in other forms such as pellets or fines, as well as other
I metals whlch have been directly reduced from their oxides, or ores
,.
and which metals react in the same ~anner as and have comparable
properties to sponge iron under oxidizing conditions.
.1 BRIEP DESCRIPTION OF THE DRAWINGS
For better understandlng of this invention, reference should
be had to the accompanylng drawlngs, wherein:
. ~ . , .
~ ~ Figure 1 ls an elevatlonal view of the preferred embodiment
. . .~ - .
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.. . . .
~ `. lO~Z~2~3
.;
of my lnvention with some parts removed.
' Figure 2 is a plan view of a pair of slitter rolls showing
..
t their interfltting configuration.
. Figure 3 is a plan view similar to Figure 2 on a larger
,....
; scale taken through the workpiece.
Figure 4 is a sectional view taken along the line IV-IV
. . .
:~ of Figure 3.
, ;. .,:~, . .
~' Figure 5 is an end view of the compactor rolls and their
e associated parts.
Figure 6 is a sectional view taken along the line VI-VI
of Figure 5, -
,;'f'! Figure 7 is a schematic cross-sectional view of a workpiece
about to be sheared longitudinally.
~`~ Figure 8 is a schematic view of a workpiece undergoing
,1 longitudina~ shearing and concomitant densification of its sheared
edges.
; Figure 9 is a schematic elevational view of a workpiece
1 about to be sheared transversely,
.. . .
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Figure 10 Ts a schematic elcvational vi~w of a workplece undor-
;~ golng transverse shearing and concomltant denslflcat70n of Its shearod
, edges.
DETAILED DESCRIPTION
~, . ~ ~ . . :
With speciflc reference to the form of the Inventlon iilustrated
tn the drawings and referring particularly to Figure 1, apparatus for
continuously passivating hot reactive particulate metal materlal conslsts
i essentially of three bas1c parts, a material accumulator 10, a compactor
¦ 12 and a divider-d~nslfier 14. ~ ;~
1 Accumulator 10 may take the form of a surge bin 15 having
slids valve 16 at ths bottom thereof positioned above a feed hopper 18,
which hopper is adapted both to con~ain hot feed materlal 20 and to control
the rate of feed of the materlal to the compactor apparatus 12. The feed
material 20 may be sponge iron, pellets or tump or~, or a combinatlon
~i~ 15 thereof, which material has been reduced In an assoclated direct reductlon
^~ furnace 8. Feed hopper 18 Includes cheek plates 22, sho~wn In Figure 7 and
8, whlch bear against the ends of the bodtes of power drlven, large diameter ,
$ ¦ compactor rolls 24 and 26 to seal the Tnterlor of the hopper 18 against
atmospherlc air. As shown, roll 24 is fixed in its chocks 28 wheraas roil
¦ 26 is movably mounted in horizontally movable roll chocks 30, the movement
~, I of which is controlled by hydrauiic cylinders 32. Rolls 24 and 26 may
¦ have a fiat contour or may have a sma11 collar at each end of the roll
¦ body~
~ ¦ The region from slide valve 16 to the nip of rolls 24 and 26 Is
;~ 25 ¦ deslgnated hereunder as the feedlng and compactlon zone.
1 ¦ ~ 5crapers 44a and 44b are plvotally mounted beneath the compacting
rolls at pivot points 46a and 46b respectively, each of which is w~11 below
~ the center of gravity of Its respective scraper. Thus, the upper edge
`r; of each scraper tends to maintain con~act wlth Its respectlve compactlng
~; roll. A tenslon sprlng 48 blases each scraper against Its compactlng
` ? -7-
¦ ~ Pletsch
',', ' '. ' ~ . i, ~ ,
o~a428 ,¦ ~
~; roll to ensure sure contact,
`, i~eneath the compactor rolls and aligned with the psss-11ne thereof
are a palr of hor;zontally opposed shearing or slTtting rolls 34 and 36 for
~ longltudina1 s!ltting of wtde strip. Roll 34 is mounted In ftxed chocks 38
t ;; whlle roll 36 Is mounted In horizontally movable chocks 40 the` motion of
~!~ ~hich Is controlled by hydraullc cylinders 4~tt~ The shearlng rolls
advantageously have a configuration as shown Tn Figures 2 and 3.
s A doctor device 50 which may also be known as a roll stripper
or guide is located on the discharge side or bottom of each roll 34 and
~; 10 36. Such a guide may have the full contour of the roll, extending compietely
~ , across the roll body. Alternatively, the device may constst of a number
æ . of guides each of whi~h fits into a recess 34a or snto a collar 34b
(Figure 3) of the roll, respectively.
~ Aligned wtth the pass-lines of the compactor rolls and the slitter
;,. t5 rolls is anvil ~ er54, whlch likewise may have a horlzontal ~ j/c4/~
contour matching that of roll 34. A rotatiny shear 56, contatning a number
of blade holders 58 with thetr assoclated blades 59, ts moùnted beneath ~ ;
the anvll 54 in such manner that the shear blades transversely cut the
workpieces by shearlng them against the anvll. ~lades 59 preferably have a
flat shearing face 60. A feed chute 61 may be provided beneath the rotary
c ~ shear to collect the metallized iron compacts 62 and direct them into a
~, cooling tank 64 which is fl11ed with water. An apron conveyor 66 removes
the compacts from the coollng tank, transferr7ng them to a belt conveyor 68
~,~ for transshipment to a stockpile 70, The small amount of flne mater7al that
may be produced by the shearing and abrasion of the compacts falls through
the perforattons in the apron conveyor and co71ects in a funnel 72 which
has a lock valve 74 at its lower extrem7ty, The funnel can be emptled Into
~n a trough car 76 per70d7cally to remove the f7nes from the system.
In operatlon, hot sponge Tron, pe71ets and/or lump material,
~;~ 30 Includtng flnes, 7s charged Into surge bln 12. Level control devlces
~ `; . ~ . ' . '
~'.n` -8- PIetsch
, . , . .
~ ¦ ; 31062 42~3 RJJ
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¦ 80 ~such as a C-E Invalco Nuclear Level Control manufactured by C-E Invalco
¦ DivTsTon of Com~ustion Engineering, IncO, Tu1sa, Oklahoma, U.S.A.) may b~
,~ ¦ interlocked with the speed control on the roll drives for rolls 24 3nd 26
¦ to ensure sufficient volume of material to maintain a constant wldth of
¦ the elongated strips (Flgure 1).
: ¦ The hot sponge iron has a te~perature of at least 600 C
¦ preferably 700 to 800 C and an average metal!Tzation of at least about
¦ 75%, but normally at least 8~%, and preferably at least 9CP~O meta!llzed.
The hot sponge iron passes from the surge bln 12 through the region of the
`~ 10 ¦ 5 lide valve 16 into feed hopper 18. The slide valve is in the open positlon
¦ during operation of the apparatus, and is closed only wnen the machinery
¦ is shut down. The feed hopper, slide valve and surge bin must be gas tight
¦ to prevent ambTent atr from contacting the hot, extremely reactive material.
;iX` ¦ The flow rate of hot sponge iron to the nip of the two compactlng rolls 24
1 15 ¦ and 26 may be controlled by a movable feed tongue mechan7sm 86. This
~ , I controls the volume of sponge iron reaching ~ne rolls, and thus the thick-
;~, ¦ ness and density of the strlp produced by compactlon. If too great a volu~e
:; ` ¦ of materTal is fed into the ~olls, they will open, producing a thicker strip
;hl; ¦ havlng an unfavorable density distribution or gradient. The feed tongue ô8
1 Ts pivotally attached to the feed hopper, and has an adjustlng arm 90 whtch
¦ extends outside the hopper. The tongue may extend the full width of the
¦ hopper, or a number of narrower tongues may be employed.
¦ Hot sponge tron is fed to the compactlng rolls by gravity. An
alternative feeder arrangement such as a screw feeder may be used whlch wlll
¦ exert a positive feed pressure on the material enterlng the roll ntp. Thls
;; I wlll control both the rate and voiume of flow of the feed mater~al. .`
After entrainment of the hot sponge Iron Into the roll nlp, tha
ij ¦ sponge Iron is contlnuously denslfled by the counterrotatlng ro11s 24 and
" 26 whlch exert large compressive forces on the sponge iron causing formàtlon
;`1 30 of an Increa51ngly compacted Iron mass untll It reaches the narrowest gap
;.",,~ . ~ _g_ . ; '
~ Pletsch
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i at the hori~ontal center!tne of the rolls. During this denslfTcatlon
procedure, the indlvldual pellets or lumps are deformed and the spongy
structure of the iron is destroyed by the pressure of compaction exerted by
the compacting rolls, and the flnes 0re asslmilated into the densTfied mass.
; ~ 5 The gas which has been in the interstices between the hot pellets as well
as in the pores of the pellets, is foreeab1y expelled therefrom and escapes
~`; from the hopper 18 through gaps between the ends of the compacting rolls
~` and the cheek plates 22 as well as through gaps between the roll boiy and
, the base of feed hopper 18. This gas, which remained in and around the
0 pellets on discharge from the direct reduction furnace 8 is reducing in
character, and provides a steady stream of non-oxldizing gas to protect
the feeding and compaction zone against contact by the surrounding atmoshor7c
air. Thus it is unnecessary to provide a sophisticated sealTng system. At
Startup a nltrogen purge is used. Nitrogen or other non-oxidizlng gas is
Introduced to the feed hopper through orifice 92 ~Figures 5 and 6) in the
-~ cheek plates 22 near the nip of the rolls. ~fter a few feet of compacted
strlp has been formed, the nttrogen purge is stopped, as the reduclng gas
~ f orced out of t~e pores wlll displace the nitrogen and matntain a reduclng
!~' '. ' atmosphere.
~; 20 Compaction of the hot sponge iron forms a continuous strtp or sheet
S (Flgure 1~ having such high density that the formerly very high affinlty
of the iron for oxygen is so far reduced that it is no longer subject to
'l catastrophic reoxidation. In fact oxldation of the surface of thls
extremely dense materlal will now result In a very small loss of metalllzatlon
The mean denslty of the strip depends on the thlckness of the
: strlp. A pronounced density gradlent toward the less dense center of tho
i strlp reduces the mean denslty wlth IncreasTng strlp thlckness. The mean
i ~ density must be at least 4.5 grams per cubic centimeter, and preferably
should be between 5 and 6 grams per cubtc centimeter. Below a density of
4.5 grams per cublc centlmeter, passlvatton Is insufflclent for long-term
-tO- Pletsch
~"" . . .
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open bulk storage wlthout slgnlflcant loss of metalllzatlon. Note that
whlle themean density of a thick strtp may be only 4.5, the surface contacted
by the surrounding atmosphere has a very high densTty with an attendant
high degree of passlvatlon.
During compaction, the compactlng rolls 24 and 26 become heated
due to conduction of heat from the hot feed material Z0, ~he temperature of
; which has been increased by the extremely great amount o~ energy input that
has been transformed into heat and is absorbed by the feed materTal. Exhaust
fans 100 (Figures 5 and 6) may be employed to remove excess heat from the
rolls~ For the exhaust fans to work efficiently, the compacting rolls 24
and 26 should be surrounded by an enclosure 102 best shown In Figurc 5.
Enclosure 102 has at least one, but preferably a multiplicity of air intakos -
104 along ea h slde of its bottom face. The suction cr~ated by exhaust
fans 100 will circulate amblent air through intakes 104 around compactlng
~1 15 rol ls 24 and 26 and out of enclosure 102 through the exhaust fans 100.
;, These fans may be associated with a dust coliector, bag house or precipltator
to remove particulate material from the exhaust air.
~! Scrapers 44 act as roll gutdes for the compacting rolls 24 and ~,
- 26 to prevent the elongated strip from wrapplng around one of the rolls.
In additTon the scrapers assist in guiding the strip into the slitting rolls
34 and 36. The scrapers 44 are b7ased against the compacting rolls by
springs 48 and guide the strip into the pass-line of the slitting rolls~
,: Since the workplece is a wide strTp A upon exiting the densiflca-
iS; ~ tion rolls, it is cut into narrower S strips (Figure 4) by the roll
slltter 34, 36 which forces the hot, hlghly malleable strlp S Into the
alternating grooves in each roll. This process creates sufflclent compres-
,~ slve forces on the edges of the newly sl7t strips S to Increase the denslty
of the material on the strtp edges sufftclently to accompllsh the desired
passlvation along the longltudtnal edges. Deformation of the workpleces
by sllttlng is shown in Flgures 7 and ô.
:, .: ' . . .
, ~ ~ -11~ Pl etsch
... .
~.`;' ' . . . .,~
,.. !:; . _. . ' :,, . ' ~ '
i; '.,,.. ~ -,, . ., . . ., . ,; , . .. , , , ~ , , ....... ,. :
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.. , , . . . , .
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The strTps S produced Tn the sllttlng apparatus are subsequently
subdivided into small, completely passlvated pieces or corlpacts 62 which ~ -
can be handled, stored and shlpped in bulk without degradation, using o~ly
conventional equipment. The outer surface of each compact must be high1y
densified to achieve complete passivatlon. Since the center of the strlp
- is less dense than the strip surface, the dlviding process must sufficiently
densify the newly created transverse surfaces to obtain complste passivation.
The temperature of the strip at this point in processing is sufficiently
, ~ htgh to maintain the lron strip in a highly malleable rondition, particularly
?i 10 since the strip density is only about iO to 80% of its theoretical density.
- An alternative method of achieving simultaneous diviston and
densiflcation of passivated pieces of material is high speeci cutting in ~r
~ ~ whTch so much energy Is introduceci locally that the resulting heat melts a
i ~ thin layer of the metallic materialO Soltdification of the material forms
.~, 15 dense protective skin on the new surfaces.~, Simultaneous division and densification of the strlp Is accompllsh-
ed by moving the strlp p~st anvil 54 while drivlng blades 59 of rotary shear
. 56 against the strlp. This action and the deformatlon of the sheared faces
~, of the resulting compacts are shown in Flgures 9 and 10. The stresses from
deformation actually cause densification of that portton of the materlal
~,~ comprising the sheared faces. In fact, hot shearing compresses the matarlal
at each face, rendering the sheared dimension less than that of the normal
workpiece thickness.
If the compacts have been produced for shipment, they must be
cooled to amblent temperature. Slnce the compacts are completely passlvated .;
cooling can be accomplished by quenching In or by water, or by any other
~' ; avai!able means. Sultable apparatus for water quenchlng has been tllustrated
in Ftgure t and descrtbed above.
- Upon shearing, the compacted products rematn hot. If these
, 3 compacts are to be used In an adjacent steel productng mlll, the inherent
-12
Pletseh
,,, ,. . , , . .
, , , ' , ' , `: ,, . ~ ,~ . , , , . .. ',: . " , . ..
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; ~- I ~0~2428
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heat In the compacts may bq utllized to reduce the energy Tnput required In
~; ¦ the m~lt shop and Increaso productlvlty, To accompllsh thls, the compacts
; ¦ are transferred without quenchtng or cooltng to a heavy-duty steel apron
¦ conveyor to be transported directly to a melting furnace. Since the compacts
j ¦ ~ ¦ are In a passivated condttion, they can be transported with no speclal
precautions in ambient air. It is deslrable, however, to protect the compacts
I ~
; ¦ from cooling by wind, raln, snow, etc. Thus, the conveyor may be enclosed
¦ to protect it from cooling effects of the elements, and the conveyor may
~&~ ¦ be insulated to prevent heat loss from the compacts, particularly by con-
. 10 ¦ vec~ionO If waste gas is available having a temperature greater than 700 C
; I From elther the steel mlll or from the direct reduction facTlity, thls gas
may be introduced to the enclosure surroundtng the apron conveyor to
-~ ¦ minlmize heat loss of the compacts durTng transpore. Suitable gases are
~; ¦ blast furnace gas, waste gas or spent reducing gas from a dTrect reducelon
~5 ¦ furnace, off gas from a metal refining furnace such as an electrlc furnace,
¦ and gaseous hydrocarbons. It is preferable that the gas be non-oxidizTng
¦ in character, but this ts not necessary due to the passlvatlon of the
~; ¦ eompacts.
¦ In its simplest form, my method for continuously passlvating a hot
; 20 ~ reactlve particulate metal comprehends feeding the partlculate metal 20 to
~ ¦ a compacting apparatus such as compacting rolls 24 and 26, compacting the
6~s~ ¦ partlculate metal material to form a dense elongated metal mass, followed
~ i~ ¦ by the slmultaneous divisisn of the elongated metal mass by cutting It
;r;~. ¦ across Its longitudinal dimension by apparatus such as shear 56 and anvil 54,
,~ 25 ¦ whlle s7multaneously denslfylng the newly created surfaces caused by such
; ¦ cutting, thus producing a completely passivated product sultable for bulk
¦ handllng, storlng and shlpplng without addltional passlvatlng steps,
¦ The iron compacts produced by this process have generally
¦ rectangular faces which form a substantlally rectangular paraileleplped.
,II 30 l It Is clear from the foregolng that I have overcor~ the
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¦ dlfficulties of prior art practices and have invented a method and appar2tus
~ ` ¦ for passlvating metalllc materials which are highly reactive and readlty sub-
;i ¦ ject to oxidation. t have provided a slmplified and efflcient method and
, ¦ apparatus for the passivation of sponge metal, the product of whtch has
¦ eonsistently high quality and which epparatus requires a minlmu~ of matn-
- ¦ tenance. ~y passivating system produces a hot product that can be dtrectly
x I transported to a metal reftning facility at the high temperature at whtch It
¦ completed the passtvatton process whereby the Inherent heat content of the
,~;; ¦ product w;ll reduce the energy tnput required Tn the metal refining process
and reduce the melting time. A1ternatPvely the hot passivated product can
be cooled for safe storage, handllng and tulk shtp~ent.
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