BE642015A - - Google Patents

Description

       

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 EMI1.1
 

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   The present invention relates generally to metallurgy and more particularly relates to the preparation of metallurgical reduction feeds of a type ideally suited as a feedstock for electric melting towers. In particular, the invention is principally directed to the preparation of hot reducing charges, presumably reduced, stabilized and capable of free flowing, from a wide variety of raw materials, by application of a unique and differential mechanism for heat treatment and gas reduction in a rotary kiln.



  The invention also relates to improved furnace structures and to improved operating techniques.
As a rule, a metallurgical reactor will work most efficiently when using a material whose chemical and physical properties do not vary appreciably over an extended period of time.



  Moreover, in such a reactor, a high quality raw material always allows a higher production than a low quality raw material. These principles have been conclusively demonstrated in recent years by the application of numerous concentration, enhancement and sintering techniques to poor quality ores such as taconites and ore. analogues, these techniques.

   giving rise to the obtaining of reduction charges

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 prepared or synthetic which, in many cases, have almost doubled the efficiency of conventional blast furnaces.



   The gas- or oil-fired rotary kiln has long held an enviable position in this field, but due to the inherent operational nature of this type of kiln, the number of desirable functions it can perform in a single kiln. given process is necessarily limited.

   The functions for which a rotary kiln is most commonly used include dehydration and calcination, roasting of otter and arsenic under oxidizing conditions and pre-reduction of metal products under reducing conditions * It is common practice in many installations to combine the first of these objectives with either of the other two, but the latter two functions are obviously mutually exclusive. This restriction inherent in oxidizing or reducing conditions places a severe limitation on the usefulness of rotary lathes.

   since many starting materials containing sulfur, arsenic etc. would constitute a much better load for the furnace if sulfur and the like could be removed and if the metal products could be pre-reduced to a substantial extent in one operation.



   Most of the improvement operations in use today relate primarily to increasing the quality of the ore itself and preparing the charge for the furnace comprising reducing agents and fluxes as well as ore is done either in the kiln or just before:

  loading into the furnace * A notable exception to this practice is constituted by the slag (self-melting ", in

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 EMI4.1
 which lime or other suitable flux is mixed with the ore before sintering. Preparation of other. constituent of the kiln, the carbon eookéfaotloa and the combustion of lime and similar materials do separately in the installations of ('ook'taot:

  1oD, of. lime towers or other. devices which all increase the cost of the product, both in terms of the capital employed and the actual production costs. This obviously adds to the cost of the sintering machines, lathes and other devices used to prepare the ore itself.



   Another problem which arises during the operation of conventional ovens is that the speed of the
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 Exit gas is usually sufficient to drive fine particles of ore and reducing agent out of the lathe.



    This gives rise to substantial losses in dust, particularly in the case of processing fine ores. The
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 recovery and reloading of these fine materials has proved inadequate .., because these fine materials constitute
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 a circulating charge which does not accumulate rapidly to a magnitude such that this charge cannot be sorted out.



  In the normal course of the towers. ratotifta, the chaut- 'luge is provided by combustion of pulverized coal of oil or gas at the discharge end, in a combustion hood *
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 The combustion air is sucked into this hood and into the oven by natural draft using a chimney or by an induced draft fan.

   Additional air t.
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 is generally pr4-m'11at1gé to fuel using a pressure-pressure blower @
In order for the lathe to operate efficiently, a sufficient amount of air must enter it at the location of the

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 combustion to completely burn the fuel This is
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 why, the end where the combustion takes place of the furnace hot bed at a much higher temperature than the rest of the furnace, since most of the combustion takes place in the first quarter or in the first fifth of the furnace * To reduce the temperature in this part of the tour,
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 excess air, put lirl <'0.11'11 "in the, x1 ..;

  1I1t 'of combustion in so 41. \' UI .. atllo81! Mu .., oxidants is maintained * over the entire length of the oven. As noted above, when a
 EMI5.3
 total reduction or tartiells of the ores must be obtained in the oven an oxidizing atmosphere is not desirable * The melting point Qes many types of mixes of cineraig de tondant, ooabuatibloo etc ,. oocQmunimant utilities in towers vary between approximately 950 * 0 and 1260 * 0.
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  He .' a, '1 t of the incipient melting temperature @ in the furnace tenlidrature at which a deposit of molten ore and flux * and observed on the walls of the furnace * For the operation of the lathe to be free * of cloudiness, it is necessary to operate at a time
 EMI5.5
 somewhat lower than this critical temperature at the combustion end of the lathe.



  Until now, the pre-reduction in tower 8 'was carried out mainly using carbon # a cuurante measurement has conuietdi, for example, to compress finely divided coal into finely divided coke and ore, l1uS. . "re to form briquettes, thus ensuring an in-
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 time between solids * When operating with the combustion extract <6 of the tower at a temperature between 955 and 126000 approximately, the temperature mid-length of the furnace * and normally do 427 to 64900 approximately. At neck temperatures,

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 the reduction of iron oxides by means of carbon is very slow. Thus, when the total residence time is three hours in an oven with a length of about 24.4 m, the affective time for reduction of the minorai is one and a half hours or less.

   As the temperature increases, the rate of reduction also increases until it is very rapid at a temperature of about 982 C. However, even at this temperature it takes time for the 00 to diffuse into the particles of. ore, to form 002 and for C02 to diffuse out of the feed, so that the reduction operates according to the following equations for iron ore:

   
Fe2O3 + CO - 2FeO + C02 Ci.7
FeO + CO = Fe + CO2 [2]
To obtain higher temperatures at mid-length of the furnace, air can be admitted through a damper near the top of the combustion hood. However, this air becomes stratified in the furnace and flows along of the vault of the latter over a quarter to a third of the length of the towers At this point, this air apparently diffuses throughout the cross section of the furnace and reacts with part of the carbon and with the residual volatile gases from the char- good in the ore pot,

   creating an excessively hot combustion. As a result, donut-shaped rings tend to form, these rings being made up of ore, fondant and coal ash.



  These rings may not extend for 20 to 50 of the length of the lathe from the discharge end of the lathe and may be of such magnitude as to cause a complete interruption of the march of the lathe.



   For a reduction in solid and gaseous phase of

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 ore due to a rotary kiln, carbon must be given priority for the following additional reactions to take place:
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 'e0 * * 2 "eG + 00'. 7,700 tz le + 00 4.7 of uau present carbon in the form of coal or coke is generally mixed with the ore and in the castings and the mix at the feed end of the
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 tower.

   With air, which contains only $ 1 to $ 2 volatile matter, oao constitutes a satisfactory method of supplying carbon. Low volatile carbon of the Pocohontas type containing 16 to 19 volatile dobby can also be introduced at The feed end, b although the use of such charcoal gives less pleasant results: when the charcoal advances through the furnace and reaches the hottest parts of it, it is * strikes off volatiles and, since there is little oxygen in the reducing atmosphere of the furnace, most of the volatiles leave the furnace as gas.
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 OO, H2 and Ch4 mbrle8.

   However, only a small amount of heat is lost in the distilled tars, since the volatile matter from this coal contains only
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 7.56 to 11 t; about 4 liters of tar. Or ton of coal, The use of oharbon with a high content of volatile matter !, which generally contain about p2 to 40 of the material, is not considered. oopuae practice at the end u1 feeding a furnace, because of the fact that the amount of relative gas ve is almost doubled and because of the large amount of
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 tar produced (?, 8 5,, 6 liters per tonne of coal).

   Unbrayed volatiles and tars not only represent a large additional heat loss! but these materials charge the smoke which leaves the tower in

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 Adding to difficulties by plugging and adhesion in the dust collector and the auxiliary equipment, the lignites can contain 40 to 50 volatile matter. and yield up to 75.6 liters of tar or more by distillation in the absence of oxygen.

   The heat losses and tar impediments experienced when attempting to use lignites at the feed end of the furnace are even greater * in a neutral or reducing atmosphere furnace than when using coals with a high volatile content * However, the lignites do not melt and the problems of adhesion or inorustations do not arise as with * coking coals with a high volatile content *. the aforementioned seemingly insurmountable problems associated with the use of high-material coal:

     volatiles in a rotary kiln led the researchers not to use such a carbon in this kiln and when it came to using strongly reducing gases such as hydrogen and methane in such a kiln, these researchers have uses separate gas generators producing mutants of these gases, or, in some cases, processes requiring the use of relatively high purity hydrogen, leaving others to put in / a device to produce this gas them an economic basis.

   When volatile hydrocarbons have been used in rotary kilns, their application has heretofore been limited to providing the thermal units necessary to maintain carbon and carbon monoxide reductions. Of course, this use was always limited by the above / described problems.

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 EMI9.1
 



  Certain iron and coal minarais contain aoufrt mud 1a volume of pyrite (the 2) * In a reduetriect atmosphere 1 "sulfur cannot be burnt efficiently in a ydnatt atmosphere, sulfur can be burnt *
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 belon the following $ reactions t
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 ? os2 # 302 a 760 + 230 2 4c5l 2 Jib + 1120 2? O 203 C 6-7 DUO c CM .e aoufr-9 is eliminated from the ore and is 4 charged in turn forms us do 302 caseuxo As on 1 # 4 dt jà aignaldt it would be very desirable from an economic point of view to:

  'asr lc phew this by combustion in the tower
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 reduction*
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 In the development of the fusionproods of the tra Po f3tr & tegio-Udy, the desirable caraoteriatics * as well as the operational problems are very diverse. rotary kilns have been produced to an extended extent
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 in that a rotary kiln has been used @ at various times *
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 with all the wadi charges - described both early * oxidizing $ and end * rdtuotrioosis In general, on the basis of studies and observation @ limitations imposed @ on the totio- '
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 operation of rotary lathes <, the present invention has for '
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 object an integrated process, in which all the functions
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 ruedeority, including the use of the entire duo's capabilities,

   coal with a high volatile content *
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 can be performed simultaneously in a single oven,
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 so that the additional advantage is obtained, that the
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 the product discharged from the lathe constitutes a full charge
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 containing all the dldpentates including the reducing agent oarbani-t
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 as necessary for an efficient reductive melting operation

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 It thus becomes possible in a single continuous operation
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 to calcine the charge of the rotary lathe by stripping the ft4 and the other volatile fibers of this charges; to dehydrate the charge to oxidize and to remove the sulfur and the etartioj of elie miner the oxygen from the ore by carrying out a partial reduction.

   
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 to crumble the fine $ ilartiCUles so as to form larger agglomerations, which eliminates the beading by entrainment of dust, to use the volatiles of the drafting agent
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 in order to efficiently handle jar craoking dot hydrocarbons and coking of the reducing agent, to adjust the final residual carbon content of the product discharged from the lathe to a value
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 desired and, in general, to obtain at the end of the discharges of the lathe a complete charge of constant and precisely regulated composition for subsequent reduction.

     So in comparison with classic devices $ @
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 the only rotary kiln functions as a desoicatourp as a sintering plant, as a coke oven and as the top of a blast furnace.



   The reduction capacities of a turn operate according to
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 the principles of the present invention constitute a very substantial o- ration compared to the methods of the prior art ** They are based on the recognition
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 and the adjustment of two factors which were either ignored or treated orrondly by previous researchers. The first of these factors is the relation between the atmosphere of the tower and the atmosphere of the layer or charge contained therein.

   Although the character of the atmosphere prevailing in a furnace is easily determinable, with regard to the oxidation or reduction capacities, the atmosphere prevailing in the layer or charge
 EMI10.8
 is much more complex, t this / atmosphere being intimately

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 EMI11.1
 bed;;;

   "the totality of all the internal chemical reactions * l.nnt in this layer By adopting the system of approach which coneiste to analyze first all the possible reactions which could take place C (±" ltl the layer and by postulating a model laait we 5. had to compare this one with what we obier * ve been practical and we can thus determine the phaf fJf! 1! I 1! h; '8i <!! ü néc (Jofla:!. rQB for to realize the conditions 14 '.... the \ !; e! 1st year. the studies to which it will be asked * aleot 11 ²l'etlo one leads to the eeoond oruoial factor, which is the factor -, the load. the expression nfactour of load * is used 63M the reent mmo1re to set the percentage
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 .t .1 <. section "11I ': Total HBvereale of the fout which is occupied by 3.:.,.". î, 0 t â .., r. The present invention is bandgon part, ILr '.-. dJl uv;

  rr = c according to which by a precise adjustment of the JY .'aa de ehaege 1 ')' of the length of stay as well as by "JI!:; r, s '} <la: T) 1'nt \ .u' e over the entire length of the turn, we "'1'11. l '.l!' '' 1l} sort or @ dqg hydrogen, uu methane and au-. y i ',' rKt = .. F;, are produced by 1 \ 8; ;; materials with a strong tvîiôu ';; H ,,; I, t; ** "v-'JlIj.t1..i <:" P end l :) 't use 0'1 gaI for pn', '<' '..j' .. #} - l ", '' '' 0! 4j "1i heard, this adds to the Lj6Q \ - ni",:,:, bzz:, ". # '<#' Ion ..i.UJ !! "'..rE'! '\ lUe of contact reduction tJo-'! 1 ''" <- ''> .y Útr '! \ r \ 1'Af! fvee the ore t'1. du ruduotion iU; 'fJUtu r3t rt. ,, rE.xrrr: ^' ic a: x'37t7p .1.1 <::; .... '1; oviJust that the chemical reactions x are that, '"u,.; ax k:. (: T1IÀl \ ilt ea pre-reduction of a tuur ru.



  \ ü1; U '' 1. ,, .. 'n J.> f),' III.iH.> <the chemical and mechanical properties of millet,;: .. 'b \ $ JH.r'.) '.1']) '.. : l1V J.uuet Thus, the ideal system and, nr oonfl + 5 \ .l .. "'t J. \ factor t.1' squash the, temperature and the duration of stay in the oven will vary by a ore to another, where 1.1 peml f; \ nv; .. 1). deuamiereeue in no case had the factor

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 EMI12.1
 and load should read eupdrluur at 15 th and, in the majority of ores processed, the load factor of between 6 Jf and 11% has been found to be satisfactory.

   It is interesting to note
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 that the charcheure have, when they spoke of a
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 load generally determined a figure between 25 and 35 i * t The Applicant has found that with such. load factor * The atmosphere in which the furnace has virtually no effect on the concentrations in the layer or load and very little reduction can take place.

   This is due to the fact that a thick film cannot be controlled with regard to temperature and reducing character by the atmosphere.
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 sphere of the lathe * On the other hand, the present invention allows a
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 precise adjustment of the C0nalT.inB uano the layer by adjusting the. temperature f <t bond reduction capabilities. moophére lying or '}' 1 ': l! \ H'1 (the said layer, in aorta
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 that none of the 01 sort, <,: 5 "=" 'u.oH, ent1onnÓeEJ is met with the mechanism of re;: lnE-: .. <,,,, and more in detail o1-d8880U8.



  Day tl .t. a..4 ..) ni "f,;,.: i '. s?! s C'i'ii'lète of the hematite reaction u.tvi' 4 sic '1, (. (' '1 <-H, e,:!.' Ef!
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 D <: 6 r; °,. = Tn; d- received tien intermediates such as rt1aotior.eo trM &! U:; m1 '.. i: .J CIO Tla: tite in magnetite, from! agnotite in wuetit;>, if not III'18tHe In proud ae produce dga- lM: Mtt avço ie l '' l ,: c1l "o: hl" t 'lu !!! (' thf..ne and / or carbon monoxide, 11 and well ton than lorequ 1 in the absence of oxygen These coals are chs-turf4and hydrogen, methane, carbon monoxide and other gases are released to a lesser extent.

   Groin:!., Loroqt4e {ÎIAf.I charhone are carbonized, the distillation gas> ç-ut n4, ci4 20 b. 60? ' of hydrogen, 25 il 50 ±

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 EMI13.1
 of a4thane and 9 * 7 '- of carbon monoxide' The composition
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 depends on the type of charcoal, the temperature of the
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 bonus, the type of carbon11'u and other * monk factors
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 important *
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 During the process of washing, part of the gas is cracked to form one carbon molecule and two hydrogen molecules. The tar * present in the distillation gas undergoes an oraokase in carbon and hydrogen.

   Thus, an additional amount of hydrogen becomes available when the distillation gas has heated to the cracking temperature. In the process according to the invention, coal at the highest material content. volatile have added in one or * vr6t'renoe, in several places. along the side of the tower, where the temperature is 8uttleammtnt high so that a 1'd1at distillation.

   of charcoal is primed, Quantities st urë 8 dtmlr compressed are admitted * in a large number of
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 point along side of turn before, between and after said '*
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 positive * of Helimentat10n in carbon @
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 Alone *, a small amount of air is injected into
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 a point determined in order to t # fish for a complete combustion of the carbon # of * volatiles ** or reduction yas (for example CQ) The air burns completely in the form of a flame in a gasstust atmosphere and being against the gas oven, <x <t0 "will tetont 1 lu ta $ m $ way that gas burning in air
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 following the load factor in question and the free clearance
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 of ga by the layer there was no air left for combustion
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 carbon or in the ore layer in the lathe.

   
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 when the incoming coal falls on the oily layer of ore, it immediately begins to distill in 11b'-

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 first of all higher hydrocarbons ranging from methane to tars * The air coming from the nearest air orifices partially burns and / or cracks these rich hydrocarbons and provides heat for the process * during carbonization of the coal. the richer or heavier hydrocarbons distil first and as the temple flows the hydrogen content gradually increases until towards the end of carbonization the hydrogen in the distillation gas eventually reaches 80 to 90%.

   It should be noted that there is time for carbonization, this temple depending on the temperature, the temperatures of the ore layer and the duration of stay of this one 4. ne turn are, therefore * regulated. , so that there is enough time so that there is always a set of hydrogen present in the ore layer throughout the furnace after the places where the coal is added.



   Due to the mixing action of the rotary kiln, the distilled coal mixes with the ore in the layer and releases hydrogen and methane in this layer, so that reduction of the ore occurs there. Gas samples taken from the layer at various points along the furnace confirm this theory and are shown in the examples.



   In addition to the process of producing a strongly reducing atmosphere in the layer consisting of hydrogen, methane and carbon monoxide from coal, lignite and others. solid carbonaceous materials with a high volatile matter content, the Applicant has also developed another method for injecting natural gas along the lathe,

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 EMI15.1
 so that this water enters the furnace below 1 * aoa * che and undergoes while it crosses this one from bottom to top, a craoking in carbon and hydrogen gateuxe Natural gas and other gas containing a licurcentage substantial of 4tbo, 4.

   can not be used to form the roaming hydrogen of reducing gas, as well as fuel for the aysteoe lerw- 'which it burned above the bed of minorai * We know that the rate of reduction of * ï'4 < Mr <d <t increases with temperature and that at a t..p4tIre 4oao4 lt humidity reduced at a rate ** a little higher than carbon monoxide * We also kept silent that the CO t CO2 ratio is high or the greater the ratio H2 * H2 0 * and <1 <!, the reduction is rapid.

   An important advantage of 1. pri ..... the invention lies in the fact that @ en tr1 ..., 1 & retains hydrogen in the ore layer at t .., 4mam the furnace)) lh rough reduction at a T1te ... pl 410 * and & a lower temperature qwt <c la was i aalt l la8CJ, lK'- 'present, Ainui, with a particulltc mttlaffl of 4 .. melting and coal ash * <Mt <comt \ 8W q qo 1. fusion patuan or rather the point ci. ± \ &, 108 Mi--. itut tlleorrâpw roll 102) -0.

   It was at '0 .. "" ". 1 ;," ""' n of 1 "atn walk the tourodi so that the t .... tar8, the triUc l% tm plus ohAU4..t .. t-d1 "to Ilextrfut + A of t4obume * qexz4g * stinks this value * In these 'OO8I1t10188 opdmtelx e 1 * enz dient de hltperature from the n1II1W <S 4 * ohws * turn was such that 18 has ta l tttt% 4 c * tt% atlWtW 60 deoharp, the Ullp4r. "ul" in * was plus *% xe te '110-0 * & v3xux, <3cMn <; it is, 1 .... 0 "" '' '' '4 * M4, tUq t8. tq | ii i 'at Itaitt of carbon and of i & onaxjr4 te 4 * rbb w #% T'taeMMtt !:

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 EMI16.1
 
 EMI16.2
 lentf at this temperature.

   However, by generating the 4. hydrogen dances the mineral layer itself, a
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 tooth a reaction rate higher than that of CO is
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 made available and the ratio of the reducers to 0 2 is
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 increased * This two factors tend to produce a significantly greater degree of reduction with respect to the preferred apparatus in which
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 the roo6d 'aunddescribed it must be exuouted, it is useful in accordance with the invention, a rotary kiln equipped with the pipes or inlet ports wait inside this tower and by the
 EMI16.7
 <tê <tl0t the combustion air ieout be admitted, as needed, from. * A ': 11'S orts which particular area of the turn.

   One or more
 EMI16.8
 other loading devices of the type generally used
 EMI16.9
 up to r'8Dt, 1 'occasion; by rotary kiln operators * are arranged along the kiln, while another type of 6: 1 Ojolti: t loading capable of projecting 114 .. materials of small dimeneione in the kiln only finds k the.xtr4 . mi "" 4th G8obuS8 of this one, sn mime tot; 4p than a long burner. gay or & high classical Ba J>: '81.iqu., an oxidizing atmosphere * and established rt Jtf.:1DwJJU. teeth the 1110: 1 t:

  14 of the furnace which does not find 1 * y2m & prba of the loading end ** admitting of 1 "* ver their inlet opening of this are, so that the mimr * l which can be lM1J" â due fondant and at a little '8 ent ritsuc * -ait initial ... t dârhydxti, cloni et "fJ8ri padMt sao pasalçs 41lne this part of the oven, Approla ntvsrri 81.10Dg.ur of the oven, due quantities ¯ub.tant1.1- them demand "U4WU. tu high volatile content * have 1ew6 1.

   a, xrg * by the 'di8pO, itit of loading oon- tim i-r (4v * state Ifs - "' 1'01 Su four ut a redduotrioe

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 EMI17.1
 , and Minai established as above, which entails a partial reduction of metal products
 EMI17.2
 are kept in the ore. According to another feature of the invention, the continuous charging device which is disposed along the length of the furnace is still used to recycle the fines which are collected in the outlets at the end. dlcharae of the furnace and to initially load the fias einerais whose particles have a size between 50 mesb and 1croD / 'By charging these .fines in the reducing and hot part of the lathe, these fines nvb1asent a rapid sintering, so as to foraer of 1 magnified, articulated,

   which eliminates any circulation of a charge of fines and generally increases the efficiency of the process further * These recycled fines or new linons can be introduced alone or in Mixture with a reducing agent, if desired * Mixing the recycled fines with a reducing agent is particularly advantageous when using certain coking coal
 EMI17.3
 With a high volatile content and high degree of fluidity, such coals tend to form annular deposits in the furnace which possibility is eliminated by mixing recycle fines therein.



   The new loading device provided at the discharge end of the furnace is used to introduce carbonaceous material at any point along: the reducing zone of the furnace, the quantity and the places where the additions are made. being determined by the precise practical needs of the feeding of the lathe, This amounts to saying that the material is introduced at a place such that it
 EMI17.4
 either properly charred or 00. 6tied as it is discharged from the rotary lathe.

   It has been found that the combustion of volatiles from the material

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 thus introduced is sufficient to maintain fuel equilibrium and ensure a suitable temperature at the discharge end of the furnace, which practically eliminates the need for the use of the gas or oil burner. In this way. the native finally discharged from the lathe contains all the * ingredient * necessary, including the stoecliometric quantity of carbon in the de-areal state, to constitute an optimum charge for a reduction furnace, in intimate mixing and at a temperature. properly adjusted.

   As will easily be understood, this feature of the invention constitutes a means of supplying the desired quantity of burnt carbon in the material finally discharged from the furnace and / or in the feed charge of the electric lathe, in the latter. where low volatile fuels such as anthracite or other forms of carbon containing less than about 15% volatile matter are not minimally available or not desired in the electrical tower. fusion * Moreover, the process provides an easy way to regulate, in a preaching manner. the residual carbon contained in the declared material of the rotary kiln,

   under conditions in which the carbon from bituminous or lignite coals, small coke etc. has been totally consumed in the rotary kiln or consumed to such an extent that there is a stoichiometric deficiency for the most efficient operation of the fusion tower.



     It is thus seen that the present invention encompasses a process for introducing solid carbonaceous materials with a high volatile content or even hydrocarbons! liquids in the rotary kiln, in such a way that these materials are brought to the ore layer.

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   is valid in the oven under optimum conditions so that the desired product is sealed at the discharge end of the rotary oven. In this way, the carbonated additive material is injected onto the surface of the active layer or onto the lining of the furnace in a position varying between
0.3 and 12 m upstream of the discharge end of the furnace.



   Thus, volatile gases, hydrocarbons and other vapors are distilled off and contribute to the reduction as described above. The residual charred coal or the whole partially coked remains in the charge and is thoroughly mixed with the product discharged from the furnace.

   The cost of carbonizing the high volatile reducing agents in separate equipment is thus avoided and the optimum conditions for a melting furnace feedstock can be achieved by treatment in a single rotary furnace,
It should be emphasized that any solid combustible carbonaceous material can be used in the process according to the invention, in particular anthracite, lignite and bituminous coals at any volatile matter content and in ash and in reasonable sulfur content, these materials having coking qualities ranging from those of oxidized non-coking coals to those of highly coking coals, small coke, peat, / sawdust, husks plant products,

   splinters of wood and; .. It is only necessary to know the composition of the reducing agent, so that the appropriate amounts of this agent can be used, as well as it is necessary to know whether such impurities. sulfur are present, so that appropriate adjustments can be made in the operation of the furnace, to remove impurities.

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 Of course, the requirements of the hydrogen reduction mechanism require the employment of at least some Malian veils when this profera mechanism is used.



   A preferred embodiment of the invention will now be described, with reference to the accompanying drawings in which - Figure 1 is, after partial section, an elevational view showing the structure of the rotary kiln used. readied for the practice of the invention; - Figure 2 is a section along line 2-2 of Figure 1, this view illustrating features of the structure of the furnace according to the invention; . Figure 3 is a section taken on line 3-3 of Figure 1, this view illustrating still other features of the structure of the furnace according to the invention;

   and FIG. 4 is a perspective view showing the preferred arrangement of the structure of the furnace according to the invention with respect to an electric rotary hearth lathe arranged to be loaded directly from the rotary furnace. Figure 1 shows a conventional rotary kiln 1 with a steel casing, provided with a refractory lining 2 and mounted so as to be able to rotate on journals 3, The tower has end walls 4, containing orifices for (a) loading from a loading hopper 5, (b) a cover for removing the% gold gas. tants 6, (c) a burner 7 supplied with gas or oil, (d) unloading into an insulated hopper (d)

   a special loading device for injecting a solid material into the interior 9 of the furnace. A fan 10 driven by a motor is mounted 1, outside the steel casing but is located at a certain distance from this casing.

 <Desc / Clms Page number 21>

 In order to avoid overheating, the fan 10 exits to inject air through a series of stainless steel inlet pipes 11, each pipe being fitted with valves (not shown) and passing through the casing of the furnace in various directions. places distributed along it,

   these pipes ending in orifices or holes directed in the direction of flow of the xaz inside the furnace 12. It is necessary that the orifices be directed in this direction so that a substantially negative pressure can be maintained. in the furnace and also to minimize turbulence which would cause fine induction doors. It is also possible to use a series of fans, so that an individual fan is associated with each inlet pipe 11.

   Likewise, for the injection of reducing gas below the load, pipes 18a can be fitted as shown in figure 2 and can be activated, when they are below the load, at each rotation of the load. oven. At mid-length thereof, a chute 13 is provided for the load. Continuous ment of a reducing agent in the reducing agent of the furnace.

   The operation of the chute is shown in detail in FIG. 2; the caster 13 is preferably made of stainless steel or brick and has a pipe 18 which extends inside the oven forming an elbow. The reducing agent 17 is introduced into an open hopper 14 from the tank 15 so that, at each revolution of the oven, the chute receives a predetermined quantity of reducing agent. When the chute i filled with reducing agent leaves the tank, the reducing agent; is distributed over the surface of the load in the furnace.

   The pipe 18 prevents the hot layer 16 from discharging * when; that the dipstick is in the pan, because it is always above the upper level of the oven load. @

 <Desc / Clms Page number 22>

 It has been found that by forming an elbow in the pipe as shown in Figure 2, a much better distribution of the reducing agent occurs than when the pipe enters the furnace in a straight line, while the formation dust is significantly reduced.

   The number of such rolls must obviously be determined by their dimensions and the volume of material to be loaded at each revolution (only one chute being shown) * If it is desired that a greater quantity of reducing agent be loaded at at a given moment, the rotation of the furnace can be interrupted and the reducing agent can be brought directly from the trial * into the furnace, Or, the speed of rotation of the furnace can be varied, so as to obtain a residence time For most applications and for the load factors described above, a residence time of the charge in the oven of 3 to 6 hours has been found to be satisfactory.

   The residence time is advantageously adjusted by varying the speed of rotation. The chute and the tank are arranged so as to provide passage for the conduits or pipes 11 made of stainless steel *
In use, a crushed ore or a mixture of ores is charged into the loading hopper 5 together with the essential fluxes and / or the carbonaceous reducing agent From the hopper 5 the mixture is continuously fed into the loading end of the tower, The temperatures suitable for the desired reactions are maintained by adding carbon through the chutes 13 and compressed air through the pipes 11 and / or by the gas or oil burner 7.

     The inlet pipes 11 can also be arranged to inject a reducing gas into the layer 16. To establish and maintain a

 <Desc / Clms Page number 23>

 oxidizing atmosphere above the sensitive layer 16.
 EMI23.1
 ment during the first half of the operation, the valves provided in the pipes 12 are opened and
 EMI23.2
 combustion air is admitted 1 enter the furnace and pass over the charge in it If the charge contains a high percentage of fines, the losses by entrainment in the hood 6 are high, but this dust by train'.

   can be collected in precipitation apparatus and / or suitable dust collectors (not shown), this dust being simple-
 EMI23.3
 ment returned to the furnace via hopper 15. Zn introducing the recycling fines into the middle part of the furnace alone or in combination with carbonaceous fuel
 EMI23.4
 solid, these fines quickly agglomerate, so as to form normal charges, which come out, at the end of. discharge from the furnace rather than trana forming into a circulating charge.

   The angle at which the pipe 18 enters the furnace ensures a gradual introduction of fines near the surface of the load.
 EMI23.5
 and thus contributes to preventing the formation of pouanièreas In the first zone or oxidizing zone of the furnace, the sulfur
 EMI23.6
 is removed both ore and reducing agent. In practice, it has been found that up to 90% of the total sulfur present in the ore of this ma-
 EMI23.7
 niàr8inal that 50 to 70% of the sulfur present in the reducing agent.

   Dehydration, agglomeration, and calcination of the charge also take place as the charge moves through the oxidizing zone of the tower.
 EMI23.8
 Substantially at mid-length of the taux, the reducing agent is introduced through the chute 13 of the annièra described above and the oxidizing atmosphere located above the load and in the latter becomes reducing ,,

 <Desc / Clms Page number 24>

 Reducing daring and freed by distillation of volatile hydrocarbons, owing to the annual high temperatures it is subjected and the gases produced,

   as well as the direct reactions between the carbon and the constituents of the iron, give rise to the reduction of metallic oxide * to interior oxide and elemental metal, as described above.
Without the particular embodiment illustrated in the drawing, the auxiliary charging device 9 * and equipped with a soft pressure gas supply line which charges compressed air or other gases used as a vehicle during the injection of the carbonaceous material necessary to adjust the composition of the charge, so that it is optimal.

   This device is powerful enough to project the charcoal over about half the length of the oven and it can be adjusted to introduce the material at any desired point along this half of the turn.
The feed rate and precise trajectory are easily determined by calculating the additional amount of reducing agent needed in the final charge for the melting furnace, based on the samples taken and the duration of the operation. stay necessary to properly coke the material thus introduced. It is obvious that any suitable mechanical projection device can be used for this purpose.

   Since the walking tour is conti. naked, the distances inside the furnace are proportional to the length of the day, provided that it is taken into account that the large particles move in the furnace at a speed slightly greater than that of the small *% particles ,
Figure 2 illustrates the structure of the loading device provided at mid-length of the oven.

   As one can see

 <Desc / Clms Page number 25>

 
 EMI25.1
 Easily the material during processing 16 occupies about 6 to 15th of the transverse action of the furnace,., loft the load fryer condi- tions sued4criteso 00 = 0 described in more detail, the panty 13 have elbows oetaae shown, so that when the material 17 is unrolled in the lathe it falls a short distance only on layer 16.

   The .ti, ura 3t which is a section through line 3-3 of figure lo shows the assembly and drive details of the lathe, this view showing the journals 3 # the drive motor 19 and
 EMI25.2
 the ring gear 20 connected to it,
 EMI25.3
 Lorol1ue matter * 'freely flowing reached
 EMI25.4
 the fallen end of the towers it can be collected doua *
 EMI25.5
 a trt, -Iaio isolated 8, to be transferred to the oven
 EMI25.6
 * However, it is preferred that the material discharged from the
 EMI25.7
 Holt rotary kiln introduced directly and continuously into a rotary kiln with rotary hearth. A fixed or rotary kiln can be used for this purpose. ensure an uai tome distribution of the oh.roe on the surface of the bath, the capacity and the.,

  1 tell "of furnace melting being proportional to the flow rate of the reduction furnace * When using a rotary melting tower, a truly continuous operation is aleuréa, the rotation only having to be interrupted from time to time to unload the furnace from The relations between the 414 constitutive tales of the installation appear the ancestors to
 EMI25.8
 figure 4.
 EMI25.9
 the following illustrative examples will make it possible to better understand the process according to the invention, including
 EMI25.10
 detailing past practice and improvements
 EMI25.11
 provided by the principles and operating methods following
 EMI25.12
 present * invention.

   

 <Desc / Clms Page number 26>

 
 EMI26.1
 1329LU -I &
 EMI26.2
 To obtain an appropriate comparison standard, a test was carried out before any modification $
 EMI26.3
 epient brought to an elastic rotary kiln. The ore consisted of a very finely divided, grate type magnetite iron ore concentrate was charged with flux and charcoal with a low volatile content at the end.
 EMI26.4
 power moth of the lathe.

   All combustion air
 EMI26.5
 has been loaded into the discharge end of the furnace by the combustion hood * The eucal results are shown in table 1 below t
 EMI26.6
 1 WLAU IJftb1tuo1e At1R1YBe from the chart!
 EMI26.7
 
<tb> Mnerai <SEP> Coal <SEP> (low <SEP> content <SEP> in
<tb>
 
 EMI26.8
 lli; III, .- ,,,,, #,. ,., ...,. ¯¯¯¯¯¯¯MRtieree volatile).



  Pe 46o6 Mat. Flight. 19. Gangue 34.0 Carbon 7493% Sulfur 00, Q # Ash 6 # 4th Sulfur 005% Data, l, .relative, to the functionnamtnt of the kiln Ore 860 kg / br.



  Weighting 167.6 Jcg / Jir Coal with low volatile matter content. 190 ttg / bre Natural gas consumed 890 8000? 020 Slag discharge temperature 1050'C Temperature in the middle of the furnace 585 # O
 EMI26.9
 
<tb> Temperature <SEP> of <SEP> gas <SEP> of <SEP> smoke <SEP> 365 * 0
<tb>
 
 EMI26.10
 1'1ragehdan. the ignition chamber 0.125 ounces of water? aot?! rr7 (discharge extrëait) 702% Retention time 3.0 hrs Analx9e, smoke ag¯ C02 18.1? J 2 1.



  CO 1,

 <Desc / Clms Page number 27>

 
 EMI27.1
 
<tb> Sulfur <SEP> in <SEP> the <SEP> slag <SEP> 0.11
<tb>
<tb> <SEP> reduction of <SEP> ore <SEP> 38 <SEP> to <SEP> 40%
<tb>
 
Despite a high slag discharge temperature (1050 C), only 39% of the oxygen contained in iron oxides ion was removed in the furnace.

   A considerable merger @ you an important agglomeration of the load at? the walls of the ae are produced up to about 7.5 m from the discharge end of the furnace, wrongly * that it has been frequently necessary to clean the furnace with a coring , in order to allow continuous operation, annular deposits forming from temple to temple * In short, the operation of the oven was not satisfactory.



     After discharging from the tower, the acorie at 1050 * 0 was collected in an insulated container.Letting them stand for half to 1 hour, while stirring them, the fine particles of slag containing the metallic iron melted and agglomerated , by forming a solid cake which could only be removed from the containers * with great difficulty *, using a corny.



   The proportion of 1.9% of 00 contained in the flue gas indicates that approximately 12% of the heat contained in the coal was lost in the form of 00 in the smoke chamber, while hydrogen and methane were also lost * The oxygen content from the incoming air at the discharge end indicates that an oxidizing atmosphere prevailed throughout the length of the tower.



   EXAMPLE 2,
5 7.5 cm air hoses were installed on the outside of the tower at 1.8 m intervals, starting about one third of the length of the furnace from the discharge end . the pipes were connected to conduits

 <Desc / Clms Page number 28>

   leading to a motor blower mounted on the side wall.



  Air subjected to a sufficient positive static pressure was introduced into the furnace at the five points in question, so as to create a long combustion period, by adjusting the composition of the gases and the temperature of the furnace in this zone, as well as in the entire oven.



   Furthermore, several Mont chutes were mounted on the side of the furnace substantially at ni ** length, so as to allow the furnace to be supplied with coal @ with a high content of matir. volatile and lignite. While working with the furnace, the chutes took their load of coal with a high volatile matter content from a fixed tank located below the furnace, as described above.

   Since no coal or other fuel was loaded at the feed end of the furnace, it had a combustion zone extending half its length from the point of 'Charcoal feed to feed end * In this zone, volatiles from charcoal have had sufficient time to distil, react and / or burn almost completely
The ore used consisted of an iron ore concentrate of the unroasted magnetite type with a high sulfur content, in the form of particles having the same particle size. Sorted than that of the concentrate used in Example 1, the ore from the same mine as in Example 1. The coal used was of the high volatile type.

   It contained a high proportion of sulfur, as shown in Table II.

 <Desc / Clms Page number 29>

 
 EMI29.1
 



  ¯¯¯¯ym? ïî-MMf ######### Anfrlyy, d o, la? haMt ..



  Ore Coal with high material content n plalap b. on 53,076 Mat- Vol. 52.8 * Qangue 2405e carbon bzz 3oufrf Ot92} <Ash 90 e 8oufr $ 2,9'A j'niyf 1 III * if, p ,. the 1! Yew fouf Mitieroti 660 te / bre Chn'uon with high volatile content # $ 162 kert natural gas consumed 12 $ 46% 3 / bre Discharge temperature of the * Cori # 971 * 0 temperature in the middle of the tower 905 '0 Temperature of t;

  as of tWD4, 7.12 ft5 / hrt Draft in ignition house 000500M water? tank actor ,, * {discharge end) $ t1t * Retention time 390 hrea Smoke gas analysis 002 1806% o2 009% 00 0.4% sulfur in 1001'1. 10010 Mineral reduction 51? Sulfur removal 22% mm-MMO-M Momm-
 EMI29.2
 In this 8 ... 1, using an r461 'power supply. side in air and a side supply in coal, the temperature of the unloaded cross * was 97040 # or about 6000 less than in 1 # exomple 1, in which the claloic process of supply and combustion at dtd used As a result of reduction by hydrogen based on tttaplraturi, it produced neither a6s1om4rat1on, nor fusion of the soorit

 <Desc / Clms Page number 30>

 on the walls 8 of the oven.

   Moreover, despite the high degree of reduction (giving a high percentage of metallic iron
 EMI30.1
 in the slag) no agglomeration or fusion of the iron pa! i1ou1 "has this produced in containers collecting the 4 * orlop the sedoculling material freely during its evacuation of the inner hopper *
Although the discharge temperature is sufficiently low * that the operation of the oven is free of cloudiness, the temperature in the middle of the oven has been increased by
 EMI30.2
 58500 (example 1) up to 905 * 0.

   Thus, the reducing agent present in the furnace has been lengthened and, as a result of the distillation of the hydrocarbons, the residence time in
 EMI30.3
 reducing conditions was increased at a corresponding rate * This explains the higher percentage reduction in min. rai z center 39? * h 8rat at lower discharge temperature *
By adjusting the air introduced laterally, it has been possible to maintain a reducing atmosphere in the discharge half of the furnace and yet add sufficient air in the supply half, so that the quantities ex-
 EMI30.4
 -help. of volatile matter and tar from coal with high volatile matter content are burnt.

   Since the smoke lock contains t7.47 of 00, only 2% of the total heat contained in the coal has been lost, forming us as fuel in the flue gas.



   At the end of the test, no accumulation of dust was observed in any part of the dust collector, blower, or other gas handling system, indicating that the tars were used substantially in an adequate manner. complete.



   No special attempt was made to remove the dhow from coal and ore in this trial, per

 <Desc / Clms Page number 31>

 Combustion * However, 22% of the sulfur from the coal and ore was burned in the lathe, even with the higher pre-reduction.



   By controlled combustion by the lateral air distribution and by almost complete use of the large quantity of tar and volatile matter * a high degree of pre-reduction has been obtained, a substantial percentage of the sulfur has been burnt and the discharge temperature was lowered enough to obtain a free flowing slag.

   the nearly complete combustion of the large amount of tar and volatiles provided such an amount of heat that the amount of natural gas burnt only half that used in Example 1, in which use was made of. low solids, volatile coal * In this example, only 8% of the total heat leaving the furnace was from natural gas. The remainder was from the high volatile coal. Only the fixed carbon in the coal was burned.



   EXAMPLE 3.



   In this test the same ore and the same coal was used as in Example 2. A significantly larger amount of air was injected into the furnace feed half in order to to remove sulfur from ore and coal by combustion. The results of this test are shown in Table III.

 <Desc / Clms Page number 32>

 



    TABLE III,
 EMI32.1
 Combined operation of oxidation and reduction) ..., .... i, l ... i 2Pnn4g8 Celatlvea au f2n2tlonei2elâj in oven.



  Ore 906 kg / hr Coal with high * content of volatile matter 181 7cg / la Natural gas oonsummé Ht 76 M3 / hra
 EMI32.2
 
<tb> Temperature <SEP> of <SEP> discharge <SEP> of <SEP> the <SEP> slag <SEP> 980 * 0
<tb> Temperature <SEP> at the <SEP> middle <SEP> of the <SEP> oven <SEP> 893 C
<tb>
 
 EMI32.3
 Gas temperature, fwnëe D5500 Draft in ignition chamber 0.05 oz of water
 EMI32.4
 
<tb> Factor <SEP> of <SEP> discharge <SEP> (end <SEP> of <SEP> discharge) <SEP> 7.0%
<tb>
 
 EMI32.5
 Retention time y25 hrea Flue gas analysis 00g 17 r 4 02 2, Ot
 EMI32.6
 
<tb> 00 <SEP> 0.2%
<tb>
<tb>
<tb>
<tb> Sulfur <SEP> in <SEP> slag <SEP> 0.40
<tb>
<tb>
<tb>
<tb> '<SEP> reduction of <SEP> Ore <SEP> 43%
<tb>
 
 EMI32.7
 72% sulfur extraction
As revealed by the flue gas analysis,

   an excess + air was injected into the feed half of the tower, so as to provide a 2.0% excess oxygen and an amount
 EMI32.8
 negligible CO. The excess O2 has exceeded the amount neon- en
 EMI32.9
 sary to burn the $ addition, The gases contained 0.5% of $ 020
During the test, 72 of the total sulfur contained in the coal and in the ore was burnt to SO2 and
 EMI32.10
 eliminated. of slag # It is notable that this figure can be raised up to a5 or more, provided that the bone sulfur has a form that can be burned (pyrite, organic sulfur in charcoal, eto ...).



   As in Example 2, a low discharge temperature (979 * 0) was maintained, while at mid

 <Desc / Clms Page number 33>

 
 EMI33.1
 length of the furnace a * temperature of approximately 893 * 0 was obtained ** This result was obtained, as before, by burning the wx- ebe of at1'rec.olt11. of the coal introduced laterally into a longer combustion, but no <xo <ûaiv <n <nt hot this combustion sound system being regulated by the side 1n.o'10n $
 EMI33.2
 of compressed air in several pointa.
 EMI33.3
 



  Use of a more oxidizing atmosphere in the furnace feed motor lowered the percent reduction by 1 µl. 43 <This situation can be corrected by using a longer furnace with a longer residence time * The heat loss in the fuel @ contained in the gas from tum4, was within about 0, If in this tone, Otpen > lant | the gas used for combustion in the nitvaueventé tt xaur relative to the quantity of gas used in the axa: ple 2.
 EMI33.4
 



  No agglomeration, no deposit or no adhesion
 EMI33.5
 load in the oven were not observed. jX '; M; PL 41- In this test an ore of far linin was used as well as lignite with a high ash content, eomrt
 EMI33.6
 are
 EMI33.7
 reducers' The results in Table IV.



  U.:Bj.iJ'\t1J -ivā
 EMI33.8
 t1't 1 nz da li ntt <for aliraanttr four nHÏy.8t ''. "de '\ a.'cmr & 9l Jl" ""' "'" llingrai it-nita # 39, Mat, see 42.9 Gangue 30, Carbon 31 # 10 Door by combUBtLon13r5> C Ctfndrt 26000 .3 besides 0, 3 Sulfur 0.9

 <Desc / Clms Page number 34>

 
 EMI34.1
 relative poeoe * to pond furnace Ore 736 kg / hr $ Lignite 263.6 kaam Natural Oez oonBOtnraé '13 w3 / hr <slag ddoliaret leak 010.10 Woulpêtaturs in Mid-round 839 C tomperuture of smoke case 501 * 0 ...

   d "has charcoal d 1 P.Ilitmotge 0.05 that of water <#"! t. <'ur de ctarge (discharge end) 6.0 *) r c îc retention 3910 hMe .4 !! 4.1 az of smoke COp 2195e 02 5> i CO 0.5 'Sulfur in slag 0,, 4Ce
 EMI34.2
 
<tb> <SEP> reduction of <SEP> ore <SEP> 68%
<tb>
 
 EMI34.3
 Elimination of the otter 45
 EMI34.4
 The much higher percentage reduction * "of the iron ore (66) obtained from this test was partly due to the porous texture of the ore, but mainly the substantial amounts of hydrogen and methane released in the layer, as well as the mineral. high reactivity of charred lignite, after distillation of volatiles in the
 EMI34.5
 tower.

   However, the excessively large amount of volatile matibr "was almost encroached upon as evidenced by the low CO content of the smoke eas. # After the eeee no tarry dust accumulation was observed in the dust collector or elsewhere.



   About 45 of the total sulfur contained in the ore and in the coal was burnt in the kiln.
 EMI34.6
 



  As previously, neither deposit nor agglomeration of slag is produced in the lathe.

 <Desc / Clms Page number 35>

 
 EMI35.1
 



  EISMPLB 5. during the pre-reduoUoa of an ore in a furnace, if seen from the subsequent melting in a foundry furnace, it is aouhnitable to provide carbon in an etodahlordi- tical quantity, to complete the reduction in the turn of thus killing , an 8corie prepared from a hematite ore and pre-redu1t. at a rate of 55% in the furnace still requires the addition of a considerable amount of carbon in the melting furnace, to complete the reduction.

   If the product contains
 EMI35.2
 50% fire 4 at a pre-reduction of 55, '28 kg of carbon per 45 kg of loaded carbon-free slag is required. in the oven to obtain a complete reduction in metal.
 EMI35.3
 Assuming that air is introduced in a suitably regulated quantity to the sides of the furnace at various points, only 5 to 10% of the fixed carbon contained in the reducing agent is burnt, even when using coals. high volatile content), or lignite, as a result of reduction with hydrogen and methane, When large coke or small coke with 85-95% fixed carbon is used
 EMI35.4
 or low m content coal:

  Ua.r. volatiles containing 75 to 82% fixed carbon, it is not difficult to obtain an / excess of carbon in the slag. However, as shown proceeds! - There is too little volatile matter in the combustible case to heat the furnace and contribute to the reduction and a large amount of gas or other fuel must be burned in the furnace discharge extract.

   In addition, the Fuel is
 EMI35.5
 loaded at the feed end or pure from ugly gully. However, the melting furnace requires a greater or lesser amount of carbon, because less or greater pre-reduction is desired in the pre-reduction furnace, a

 <Desc / Clms Page number 36>

   The change in the carbon content of the slag takes several hours, due to the extended residence time of the ore and the carbon in the pre-reduction furnace.



   When loading high volatile coal or lignite into the kiln, the amount that can be charged is limited by the heat generated by the combustion of the excess volatile matter, so more carbon is necessary for the melting furnace, it is sometimes not possible to load a larger quantity of these fuels at the feed end of the furnace or through the side chutes thereof; or the oven may be superheated to burn off additional volatiles.



   To ensure immediate control of the carbon content of the slag and to obtain more carbon in the slag, when using coals with a high volatile magnesium content or limits, the furnace was operated in a similar manner. such as coal with a high material content? volatiles is injected into the discharge end of the furnace on the hot slag layer and / or on the hot walls of the furnace, at a location between 0 and 9 m from the discharge end of the furnace.

   A sufficient quantity of coal or other fuel can be used so that the heat generated by the combustion of the volatile matter from the fuel not consumed in the reduction approximates the heat of combustion of the gas. natural replaced.



   When the slag is discharged at the rate of approximately 793 kg / hour and the natural gas is consumed or burned at the rate of 12.6 m3 / hour (460,000 Btu per hour), the gas supply is stopped and the high-grade injected carbon

 <Desc / Clms Page number 37>

 
 EMI37.1
 #n Jftatt.r81, olatiltee. ' bl '. At a rate of about 50 kg per hour, the coal was made up of pieces having a corner @ of 6 # 30 JUL. It contained 3.3% pieces of 100 weeh, most of which apparently were burnt suspended in the feed opening of the furnace. The mittiere plus 61'0'81'1 "fell on the bed or on the wall of the furnace, the discharge affecting the 103840 approximately at the beginning of the I.lai.

   This charcoal has been ddbarrals' prl, that 1mm'd1atement of the volatiles., And of the volatiles ** have been burnt ... with the air sucked in we form a large yellow flame filled. Being the whole section tran8vert'11 from the oven. Oomal pre-emptied, insufficient * air was aspirated to achieve complete combustion * due to volatile matter *,

     so that some hydrogen remains in the water. Oombuation of excess volatiles was ensured * by injecting air sideways into the whisk as described in * previous examples *
The carbonized residue or ooke coming from the injected carbon freed from volatile matter remained all fora *
 EMI37.2
 of a * layer on the charge, in order to prevent a rw-exydttier of the ore * This residue was discharged with the slag of man1'r.

   to supply a carbon wttoe to supplement the stoechlometric carbon requirements of the ditotriquet smelting furnace Thus, a complete charge for this latter furnace was prepared in the rotary furnace using coal at 36} <volatile matter *
Before coal injection, the carbon content
 EMI37.3
 dt the stable was 97% by weight or about 99% of the total amount of niacaaxi carbon, re to ensure complete reduction of an aoorie to z iron, with a pre-reduction of

 <Desc / Clms Page number 38>

 55%.

   After the start of the carbon inaction, the carbon content of the slag from the kiln was increased in a few minutes to 8% or a little more than the stoichiometric amount required to complete the metal reduction in the kiln. electric.

   By synchronous adjustment of the lateral coal supply and the coal supply by inaction, it has been possible (1) to maintain the desired percentage of carbon in the slag and to further heat the temperature in turn 4. desired combustion and (2) to maintain the desired combustion and the desired setting of the atmosphere to remove sulfur, to ensure pre-reduction, summer ... and to maintain a free flowing slag
In another test with a different ore and with a larger coal than that described above,

   it was found that 11% of carbon residue was discharged with the acorie; this is why finer coal was used to achieve the desired relationship between the carbon present in the slag and the heat released in the kiln. The charcoal consisted of lumps all less than 3.175 mm, this charcoal containing 16% lumps with a caliber of - 100 mesh. In this case the very fine particles burned in fl uence, forming a luminous flame. and hot for heating the furnace, while the larger coarse particles fell on the hot load and were stripped of volatile matter,

   to form a residue which was discharged with the slag * During this last period, the carbon content of the slag fell from 11% to about 7.5%, when finer coal was used instead of coal bigger $
Thus, it was found that by controlling the degree of pulverization of the coal, the proportion of carbon in the product discharged from the furnace could be effectively controlled.

 <Desc / Clms Page number 39>

 



   While the wrongly volatile coals were injected into the discharge end of the furnace, the furnace continued to operate by causing the middle chutes to introduce the high volatile coal :! with recycled fines from dust collectors
When melted, coking coals with a high volatile content are often very fluid.



  These coals generally melt at a temperature between 315 and 399 * 0, that is to say at a temperature much lower than the normal temperature of the lathe. according to the preferred practice of the present invention, when charcoal of this. Type is mixed with ore fines and / or smoke dust, the carbon particles are dispersed and no operational difficulties are observed.

   On the other hand, when coal with a high volatile content is loaded on its own, that is to say without a mixture of ore fines or smoke dust or other inert matter, the particles melt and agglomerate. , so as to form a melt and sticky mass which sometimes adheres to the side walls of the furnace * The mass can then be distilled, so as to form solid coke which increases in quantity as more coal is loaded * finally, an annular and thick deposit of coke can accumulate over the entire side wall of the furnace at the location of the loading openings * The flow of ore in the furnace can thus be partially stopped.

   In addition, the ore layer can be deprived of reducing carbon during this period of formation of an annular deposit and the. reduction can be stopped. Eventually, the annular deposit breaks and falls under its own weight, undesirable excess carbon being discharged with the reduced ore or

 <Desc / Clms Page number 40>

 slag. these difficulties are however easily avoided, even when the coal is not mixed with smoke dust or ore fines, by maintaining a sufficiently high temperature at the midpoint of the lathe.

   The distillation and cracking of volatile matter * then takes place before a melted and sticky manna can form *
EXAMPLE 6.



   Two tests were carried out to determine with exactitude the distribution of the reducing gases in the layer or filler. In these tests a significantly larger furnace (45m) was used, while the degree of reduction was kept constant at 35% in the first test and 40% in the second test. Table V indicates the operating conditions, as well as the temperature measurements and gas analyzes,
TABLE V.
 EMI40.1
 
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  MATERIALS <SEP> FLOW
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<tb> Ore <SEP> of <SEP> iron <SEP> (57.2% <SEP> Fe) <SEP> 4530 <SEP> kg / hre
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<tb> Bituminous <SEP> coal <SEP> 1291 <SEP> kg / hour
<tb>
<tb>
<tb>
<tb>
<tb>
<tb>
<tb> Anthracite <SEP> 271 <SEP> kg / hr
<tb>
<tb>
<tb>
<tb>
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<tb> Lime <SEP> 770 <SEP> kg / hr
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<tb>
<tb>
<tb>
<tb> Natural <SEP> gas <SEP> 73.3 <SEP> m3 / hr
<tb>
<tb>
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<tb>
<tb>
<tb> Factor <SEP> of <SEP>.

   <SEP> load <SEP> (end <SEP> of <SEP> discharge) <SEP> 8.6%
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<tb>
<tb>
<tb>
<tb>
<tb> <SEP> duration of <SEP> retention <SEP> 3.2 <SEP> hours
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<tb>
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<tb>
<tb>
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<tb> TEMPERATURES
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<tb> Meters <SEP> to <SEP> from <SEP> Tempe <SEP> from <SEP> the <SEP> load
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<tb> of <SEP> end <SEP> C
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<tb> End <SEP> of <SEP> discharge <SEP> 1.5 <SEP> 1010 C
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<tb> Torque <SEP> n <SEP> 3 <SEP> 11.1 <SEP> 910 * 0
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<tb> Torque <SEP> n <SEP> 2 <SEP> 20.1 <SEP> 899 0
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<tb> Torque <SEP> n <SEP> 1 <SEP> 32.1 <SEP> 749 C
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<tb> Power <SEP> end <SEP> 43.5 <SEP> 510 C
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 <Desc / Clms Page number 41>

 
 EMI41.1
 ;, 1 'a' ':

   A IY1; .t1 Ollàà2l Sample MttPM at S <3O2 S 00 * H2 * oïL jt pipe H * from # # # '* - * - # * # *
 EMI41.2
 
<tb> the end-
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<tb> mity <SEP> of
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 9 39 5689 boa 09) 2.1 13.5 15 * 5 16 * 7 44.6 11.8 13.4
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<tb> Device
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<tb> power supply
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 in coal n * 1506 # # - # 3 18 48.5 23.7 1395 0.9 11.0 4 2205 909 3.3 42.0 1995 24.4
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<tb> Device
<tb>
<tb> power supply
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<tb> in <SEP> coal <SEP> n 2 <SEP> 24.9 <SEP> -
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It can be seen that additional samples 2 and 4, located 2.1 and 2.4 m downstream of the oherbon supply device $,

     the proportion of methane contained in the
 EMI41.7
 layer was very high * (11 <8 and 19.5 respectively). At points 1 and 3 located 6.6 and 6.9 m downstream of the feeders
 EMI41.8
 there was very little methane in the layer, but the carbon in the process of carbonization also released hydrogen, as the analyzes revealed * There was therefore an appreciable amount of hydrogen in the layer between the coal feeder No. 2 and the point 1 for taking samples, i.e. over a distance of about 15 m.

   There is no doubt that there was also some hydrogen in the layer over a distance of 9 m from the sample collection point to the discharge end. In the second test, the reduction was maintained.

   , 40%, but the throughput of ore and coal has been increased, while the supply of natural gas has been reduced in a

 <Desc / Clms Page number 42>

 
 EMI42.1
 dies corresponding The results are indicated in table VI uuîvemt # TASUSAU Vit ¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯¯
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 Kinerai (57t.1e Po) 5436 kg / h Bituminous coal 1404 kg / hr cox nenu 145 kt / bre
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<tb> Lime <SEP> 792 <SEP> kg / hr
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<tb> Natural <SEP> gas <SEP> 50 <SEP> m3 / hour
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 EMI42.4
 ? nctouy of charge (extracted from discharge) 10.5
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<tb> <SEP> duration of <SEP> retention <SEP> 4.0 <SEP> hours
<tb>
 
 EMI42.6
 Xeters from Twap. of the load end * 0 .. Ae ## r ...



  End of d4ch, r; e 1.5 1005 * 0 torque N # 3 11.1 671 f0
 EMI42.7
 
<tb> Torque <SEP> n 2 <SEP> 20.1 <SEP> 666 * 0
<tb>
<tb> Torque <SEP> n 1 <SEP> 32.1 <SEP> 689 * 0
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<tb> Power <SEP> end <SEP> 43.5 <SEP> 643 * 0
<tb>
<tb>
<tb> ANALYSIS <SEP> OF <SEP> GAS <SEP> OF <SEP> THE <SEP> CHARGE
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 EMI42.8
 Sample meters at f> 00g $ 00 fi j OH.

   H2 -t-u-vm u1; from "**" w * "1" '- "' *" "# '" "" * i *' i # '##
 EMI42.9
 
<tb> the end
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<tb> from <SEP> dump, <SEP>
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 <.5 2497 57.7 15tl 1.0 1.5 13.5 6.0 7.3 36.3 13o5 36.7
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<tb> Device
<tb>
<tb> power supply
<tb>
 
 EMI42.12
 in coal n't 't 5, d # 3 18 45.4 33.6 11.9 0.8 8.3 4 22.5 12.7 11.1 41.1 1'T,' i 1703
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<tb> Device
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 EMI42.14
 in charcoal n * 2 24, 9 - #

 <Desc / Clms Page number 43>

 
It should be noted that, under these conditions, there is almost twice as much hydrogen in the layer 9 m from the discharge end as in the previous test and that this increase in hydrogen occurs entirely at the expense of the quantity of CO2 present.

   At a temperature of around 1700 C, it can be seen that the added hydrogen and the decreased CO2 have a significant effect on the reduction conditions *
It is obvious that the invention is not limited to the details described above and that many modifications can be made to these details may go beyond the scope of the invention which involves the complete preparation of a load for an electric furnace of fusion, in a rotary lathe.



    CLAIMS.

** ATTENTION ** end of DESC field can contain start of CLMS **.


    

Claims (1)

1.- Process for the continuous pre-treatment of a metallurgical charge in a rotary kiln, characterized in that a mixture of ore, flux and a carbonaceous reducing agent is charged in the rotary kiln, oxidized by monk Partly this mixture at an elevated temperature in the oven, so as to ensure its dehydration and to remove the volatile and oxidizable constituents of said mixture, including sulfur and arsenio, an additional quantity of reducing agent is added to the mixture. Oxidized mixture directly from the furnace and the mixture obtained is subjected to reducing conditions in order to effect a filtering, an agglomeration and a partial metallization of this mixture, then additional amounts of carbon reduction are injected into the partially reduced mixture, so as to establish the total residual carbon content of this mixture discharged from the furnace at a value corresponding at least to the approximate toichiometric amount necessary to ensure total metallization of the metal contained in this mixture, during the subsequent melting of the material discharged from the rotary kiln, <Desc / Clms Page number 44> 2.- A method according to claim 1, characterized in that the additional reducing agent added to the partially oxidized mixture is a carbon reducing agent containing volatile hydrocarbons, the partial metallization of said mixture taking place by contact and by reaction with solid carbon, gaseous carbon monoxide, hydrogen, methane and other hydrocarbon type distillation products of said carbon reducing agent, 3.- A method according to either of claims 1 and 2, characterized in that the mixture of metallurgical charge, ore, flux and carbonaceous reducing agent does not occupy more than 15% of the section. cross section of the rotary lathe. 4.- Process according to one or the other of the claims. tions 1 and 2, characterized in that the mixture of metallurgical charge, ore, flux and carbonaceous reducing agent occupies about 6 to 11 of the cross section of the rotary kiln, 5. A method according to either of the preceding claims characterized in that the residence time of said mixture in the rotary kiln is approximately 3 to 6 hours. 6. A method according to claim 1, characterized in that the additional reducing agent added to the partially oxidized mixture is a gas containing hydrogen. 7. A method according to claim 1, characterized in that fine ores are added to the mixture with the additional reducing agent after the oxidation of the mixture, so as to ensure the sintering and an intimate mixture of fine ores in the material discharged from the furnace. $ 8.- A method according to either of claims 1 and 7, characterized in that the fine particles <Desc / Clms Page number 45> entrained boron from the furnace in the sa% effluent August picked up and re-introduced into the furnace charge, together with additional reducing agent after oxidation of the charge. 9.- A method according to one or other of the preceding claims, characterized in that the carbonaceous reducing agent injected into the partially reduced mixture contains constituents of the volatile hydrocarbon type, the injection being carried out at a point such as In the oven, this volatile component is substantially completely removed, by distillation of the reducing agent, before the total mixture is discharged from the tower. 10.- For rotary suitable for carrying out the method according to one or the other of the preceding claims characterized in that it comprises a tubular vent filled with refraotaire material, as well as closure elements * material. terminals lined with refractory and operatively connected to the tubular casing, means for rotating the casing around its central axis forming a small anle aveo the horizontal, means for heating the interior of the casing, loading means established at the ends @ and the loris of the casing to introduce the solid particles of the load and of the carbonaceous reducer inside the casing during the rotation of the latter, means for adjusting the residence time load in the envelope, means distributed along the envelope and communicating with the interior of oelle-oi, to establish and maintain Ions .. different oxidizing and reducing agents along respective portions of the interior of the furnace, in cooperation with the material charged in the lathe by the said charging means, as well as means for discharging said material at the lower end of the furnace. 11. A rotary according to claim 10, characterized in that the means for establishing and maintaining <Desc / Clms Page number 46> oxidizing and reducing agents comprise, in part, a series of pipes penetrating into the casing and having orifices arranged substantially on the central axis of this casing, these apertures being directed in the direction of flow of the gas in the tower . ohaoun of these pipes being connected outside the casing to means capable of injecting an oxygen-containing gas from a casing, ohaoun of these pipes being individually adjustable to adjust the entry of said gas into the casing. envelope. 12. Rotary oven according to either of claims 10 and 11, characterized in that loading means are arranged along the oven, these means comprising a pipe, one end of which is located outside the oven. and which extends through the tubular casing to the interior of the furnace, a collector provided at the outer end of the pipe being arranged to take the charge stored below the furnace and to deposit this charge in the furnace. furnace during rotation thereof, the inner end of the pipe being in reasonable proximity to the surface of the material being processed in the furnace, at the time when the pipe discharges material into the furnace. 13.- Process and oven, in substance, as described above, in particular in the examples *