DE2045645C - Process for increasing the chromium / iron ratio of iron-rich chromite ores - Google Patents

Description

1 to

^a0

reduce c «. _Divide groups.

^we ™ ^en ™ 7 «" triggering the reduced iron off As for the « ^e _cnlnit , stood by

° ^em _ ^b . ^{r /} .f ^ " _such jo _C r procedure the improvement of the ^E " ^tw ^, ^ "^ _{in the} foreground, while the ^" ngsvern actual reduction the ^we '"^r;" ^ ^C "" f _ord eter remained meaning. ^from £ ^an 8 " ^from fjSA patent specification 2 197146, the following takes place ■ mixing of

^ iikt.on de ,, bi-en ^ ^ ^ _meshes .

mahle partners ^on ™ £ ^^ ^ ^ _konlenstoff. wide range of u, iw _t ^l _unienha iüger carbon dust, 5, ^old J ^gen _p ^S ^ iilkrack-Prückstands, etc.) and about coke, «cn, _this mixture im

* 1300 ⁰ C. After the

J ^^^ , Schut / eas or clearing slow channels' - ¹ ^ _{116 rctiuziert} e iron in

™ ^l , - "/ ™ _BH SCM dissolved. According to the British mineral acid (z. 0. t ₂ <- & ^ _{Reduküon the ge} .

^P ? * ^N * f "Vinnttn" from chromites (aimed at ™ "^ ^te " ^Ε '* ^η ^ ratio of 3 or more) becomes em ■ hrom-E. En Λ , r ^ _{water; tofTgas);}

A ₅ with a H'KevonGa s U ^J ^ _{m temperature range} from 900 to ^ l ^e _r n _e m reduced product, a favorable structural cooling in wa _{dued iron becomes by perIVh ^ cooling in water}

_increased temperature in Mig ^ or higher P. ^ _{the iron}

Precipitated by oxidation; after that it becomes through uxyaauon du s reduced chrome

together with the E ^ en ie.L * .ise

scanned every. British patent specification

^ ^e Jij, g ^B _{differs from} the above ge1 ^ _f ^ {«hSl primarily in that the above-mentioned process is in <^ ^ ^ _{that a}

8? ™ * «« ^ SeUe of 76 μ / 53 μ is passed) Sieve of a meshwork ^ graphite, starch,

4 «and ^ das Redukt.onsm UeI (Holzk ° ™> J _Dje

Mda ^ ^ j bnkctjert or ^ l ^

- ^ 1 μ; i T ^ temperature range from 1000 to usually ^m . ^^ "^ S 1450 ° C) through-1200 ⁰ C tojjm ^« reduceiee iron is in

30th

35

^SET

The invention relates to a method for increasing the chrome-iron ratio of iron-rich chromite ore, in which contained in the ore 55 is then excess iron by treating an overall '' ¹ - ^1-mixture of finely divided carbonaceous reducing agent and ground ore or Reduced concentrate in a suitable temperature range and

End product SiSSs:

The reduced iron is often very finely divided in the form of "fillings" or lamellae on the surface ^^^^ ΑΪΏΐ

g ^e » ^hiede _I ⁿ · P ^^ J ^? ^ _β1 Γ _Γ ^ ILlich da ζ ldl by Lo: sen JJ ¹ ^ '^

Results. Jas is loose

expensive ^W ^. ^^ ^mm J ^ ₀ solution going iron and chromium '

one

"'The aim of improving the chromium-iron ratio has so far always been unsatisfactory, if so After the epne process developed by Chromil ores, conventional k "» '™?' ™ -S , = according to whether the physical nature of the reducing agent has been reduced

took place. Working with different types of reduction on the resulting metal deposition. By means of detergents, for example ferrous mixtures, suicides and the like, the effect of the reduction carbide in pure form or in a mixture with carbon, the Cr _a O ₃ content of the end product to substances containing carbon is also often lost in patents. In Examples 2 and 3 of the above described. 5 patent in which the ferrochrome amount 10

According to the Norwegian patent specification 49 505 or 2.5%, based on the weight of the ore, if the production of metallurgical amounts occurs, chromium remained in the end product in a suitable chrome ore in the electric furnace (or an amount of 84 or 39% / ₀ , based on the device otherwise suitable for reduction) by reduction medium, and correspondingly 16 or 2%, based on iron / charcoal (coke or anthracite) gel, the chromium of the concentrate. With increasing amounts mixed with 60 to 70% chromium-containing iron to be reduced and increasing reductant-containing iron (e.g. 6 to 10% C) ferrochrome, 80% ion temperature, it comes because of the increasing manganese-containing ferro-manganese or a Ni - Cr content of the metal phase to a rapid mixture of the aforementioned compounds. This decrease in the percentages given.
Process provides alloyed iron (e.g. 20 to 30% Cr) 15 Working with ferrous or alloyed steel (e.g. Nt and 10 to 15% Cr) with a high content of silicon is because of the resulting eras and for the production of Ferrochrome (or manganese) aggravation of the further treatment of the slag suitable for re-use (Cr or Mn content> 30 until the production process concentrate only be-50% and SiO ₈ <20%). The reaction mixture can be possible to a limited extent; this also applies to a very special degree in the form of briquettes and the like, which are derived from the fine ao for silicon reducing agents. The disadvantage is when distributed components are produced in which this method is also used compared to the coal furnace. substance carried out gas phase reduction process

In Swedish patent specification 126 620 and the slow course of the reduction process that is carried out by corresponding German patent 821 719 is the relatively low temperature used and the a process has been described in which the iron oxide consequently runs in the solid phase Chrome ore in the electric furnace with the help of chrome production is conditional.

or ferrochrome using lime as the method according to the invention enables

Slag forming is reduced. The resulting reduction of that contained in the chromite ores The slag phase is cooled, and the over 20% egg ice and the separation of the reduced metal Metal containing Cr is magnetically separated from the remaining iron-poor metal separated from the slag. The chromite ore freed from iron in an advantageous way with physical Slag phase is further reduced to ferrochrome, means and without the disadvantages that have been described with the chromium iron silicide is used as a reducing agent. known processes occur.

In the Swedish patent specification 203 775 an object of the invention is a method for

Process described which differs from the previously described 35 Increase in the chromium-iron ratio of iron-written Processes mainly include chromite ores in which part of the in the ore separates that the reduction of the excess iron contained iron for the purpose of physical separation takes place from the chromites in the solid state. converted into metallic form by reduction

The reducing agent used is carbon and / or that the chromium-iron ratio is 3 or more silicon-rich ferrochromium or a mixture of 40, and the ore to be reduced, the carbon-containing substance required for the Rediesem and a carbon-containing substance (including production) CaC ₁ and Si are suitable) used. For the area the other necessary supplements mixed with the reduction, the limit temperatures will be 950. This process is characterized and called 145O ° C. The process runs smoothly that sulfur-containing additives before the reduction but below the temperature limit 1300 ⁰ C, where 45 tion phase of the iron are added, the temperature of the carbon-containing ferrochromium does not form a melt on the Fe-Cr-S melt solubility range. In the German in the patent up is increased from 1400 to 1500 ° C, then slowly to about-run examples, the freeness of the con- 100 is cooled to 200 ⁰ C so that the main centrate such that it partially a sieve having a mesh the sulphide phase containing aggregates still passes 0.23 mm, and the reducing agent has melted 50, and is finally cooled rapidly, to such a degree of grinding that it finds a sieve according to the method according to the specification

Mesh size 0.23 mm happens and at a start the time and temperature controlled reduction width of 0.149 mm is retained. Re-des Eisens under a sufficiently large ore mengj Production temperature and duration are 1200 ° C or use of solid carbon instead. The re-10 Hours. The iron removed by this process is not produced in the conventional way, separating metal phase has a coarser d. H. by dissolving in mineral acid, of the end product division on as separated when using carbonaceous, but the structure of the reduction Reducing agent, so that here a sufficiently effective standing metal phase is rather by before dei magnetic separation is possible. Reduction among the ore mixed activators and

The ferrochrome 60 used as a reducing agent is influenced by heat treatment in such a way that this (60% Cr, 12% Si, 6% C) as such naturally increases the chromium-iron ratio of the end product in a physical way; _{However, the Cr 2} O ₃ content can be recovered before being deposited and as a chromium-containing by-product, especially in the case of ore with a high gangue content, i.e. it is not lost,
of the end product on the metallurgical point of the invention, sulfur is in the form of voi

required minimum value (48% Cr ₂ O ₃ ) brought 65 sulfur-containing aggregates as basic. Used when the proportion of ferrous mixture in the activator decreases. This is, together with the reducing agent mixture, a decisive return to the reduction carbon in the form of a course of the inoculation effect of the iron contained therein for the system thermodynamically suitable Ver

3125

\ r

binding to the finely ground He /, added. That so The reduction mixture obtained is directly as such or in the form of briquettes or pellets subjected to two-stage heat treatment. Both stages usually take place in the same furnace, for example in a drum furnace instead of.

The first heat treatment stage comprises the surface disulfidation of the grain and pore surfaces of the iron oxide niche contained in the ore by the sulfur in the aggregate and the reduction of the iron in the oxide niche; both reactions run partially in parallel. During the first duration of annealing, the temperature depending on the ore and slamming usually between 900 and 1200 ⁰ C. The reduction is carried out for a sufficiently slow schedule to a uniform sulfidation, reduction, coating the metal phase to the Oxydkörner and cleaning of the inner parts of the chromite grains of the metal separations (sulfide formation, reduction, contact melting, effect of the additives on the surface properties of the melt as well as delaying the reduction reactions through the effect of sulfur as a catalyst poison on the Boudouard reaction which controls the reduction process).

The second heat treatment stage comprises the structural reshaping of the metal phase, which can be reduced in the form of thin layers on the surface of the chromite grains, into sufficiently large grains that can be easily removed from the oxide surfaces by gentle mechanical processing (e.g. coarse grinding of the pellets), which are suitable for magnetic or other mechanical Suitable for deposition. If sulfur is used exclusively as an additive, the heat treatment is carried out by raising the temperature of the reduced mixture to 1400 to 1500 ^° C. for a short time. This leads to the melting of the sulfur-containing metal phase, and the surface properties of the melt compared to the spinel phase allow small droplets of melt to filter through the oxide framework and merge to form larger droplets of melt (the movement of the skin, e.g. when working with a drum furnace, promotes the collision of the droplets ). Due to the melt solubility gap characteristic of the Fe-Cr-S system, the low-sulfur, iron-containing and the high-sulfur, chromium-containing melt separate from one another. The temperature of the system is then lowered, the high-volume low-sulfur melt disappearing with the separation of the chromium-containing iron phase and the much smaller high-sulfur melt containing only a small amount of separated metal phase wets the primarily formed metal. A change made in the temperature range of about 1350 to 120O ⁰ C rapid cooling (eg., In water) causes a disordered sulfide layer of desired thickness is left between the metal and Oxydphasen.

The course of the reduction processes and the change of the metal phase structure (i.e. speed, treatment temperatures, composition the phases, extent of the phases, etc.) can be controlled by adding sulfur to the system as additional activators substances, which the emergence of Schinel solubility gaps, add to the scope and influence the temperature range of the Fe-Cr-S systems and at the same time have an increasing effect on the sulfur and chromium activity of the resulting system.

In the following the invention will be explained with reference to the drawings, diagrams and photographic Illustrations described.

F i g. 1 shows line analyzes of the partially reduced Chromite grain;

F i g. 2 shows the stability ranges of the Fe-SO systems; Cr-SO; Na-SO (-SiO ₂ ) and Mg-SO (-SiO ₂ ); ίο F i g. 3 shows X-ray photographs of the chromite grain and its immediate surroundings (distribution ii / Cr, / VO, r / Fc and r // S. 750x magnification);

F i g. 4 shows X-ray images of the chromite grain and its immediate surroundings (distribution <; / Cr, A / Al, f / Fc and rf / S, 600x magnification);

F i g. 5 shows metallographic structure images of reduced chromite samples; a) no structure activation, b) structure activation with sulfur, c) metal deposition and d) metal deposition in such a spin matrix; a) and b) 500 times, c) 400 times and d) SOfachc magnification;

F "i g. (I shows the state diagram of the system

Fe-Cr-FeS-CrS (in diagram A are the sections

the 9/1 and 4/1 eCr-Systcme functions of the

as sulfuric temperatures and temperature; in diagram B

are (lic sizes of the solubility gap of the for the

Cr-F c-S-S) -Mem characteristic, from Cr-CrS-Bi-

naren outgoing and up to the concentrated

Fe mixture in the melted state as

Function of the I V-Cr-Vsrhähnisses and the S-üerriiics

shown I.

Fig. 7 drew; n ^ taHosraphischc structure record: ien of reduced, ChronMp ^ en (used structure activation; a) Sehu _C iei; ,, sulfur and manran,

c) sulfur

\ hngHii un

d d) sulfur, boron;> nd

Manganese; 300fai-h. ^ Mmg);

Fi g. S show Ju r,.,,. ,,. Reduction attempts g <..:> B present Fiiiü.'i.r.t! i-used furnace system in the Side view.

Fig. 9 shows! the r r.lnkuon of chromite iron in the drum furnace;

Fig. 10 shows the magnetic separation of van reduced chromii mn function of field strength. In the investigated cases the chromite was "

from a complete solution of chromite and aluminate spinello.1, which is more the ferrite spinel or were dissolved less evenly. The composition of the chromites varied with the individual ores within the limits

(Fe _{o. 5} _ _{o, 9} Mg _1, .. ,,) [Cr _{1-0. lt4} ΑΙ _βι4 _ _β . _β Fe _0. , -, ..] O ₄ η _ ^The Cr-Fe ratio of the ores varied between 0.8 and 1.9. The proportion of ferrous iron in the chromites makes up about 14 to 29% of the total iron content

H ^US \ v ♦ η, ^S1 and ^{ken of the M} "- ^In dex of Chromite below the value of 0.2 started the iron in the spinels of the mile of magnesium to contact the spinels occur as impurities, the Mn, Zn and Ni. -Spinels of the three groups mentioned above, likewise

S '^ ^{V d TS} ^ ^ ⁱ

The reduction of iron is particularly important in the case of s with a low Cr-Fe ratio to zone structure. The magnetite surrounding the inelle (often also breaking through, etc.) is a matter of magnetite with a chromium content of less than 3 ⁰ Z ₀

3125

often a thin (Jbergangsschicht constructed primarily from FciTociiromit-Magnctit mixed crystals and usually contains more than 10 ° / ₀ chromium.

The gangar, which binds the spinel mixture, consists of water-containing, very magnesium-rich sulphide minerals, usually of calcium carbonate and serpentine. ■ ··. : nngleich sometimes small amounts ^T remo encountered ith and chlorite.

When reducing iron oxides with the help of solid carbon, the following partial reactions can be achieved differentiate:

1. -xC _(ä) + FeO.V ("
, 2. VA-CO (J, -I- FeOx ( _S)
! 3.1 aC0 _{2 (i} ,) f .rC <"

Pe ₍ «) + x CO ₂ (tr)

■ 2ACO (S,) is the determining position. The speed of Uoudouard-Rcaktion can also use Iv: r ~ kömmlicher AklivMoren (Π alkali metals, Fc, Pb, Cu, V ".nd appropriate S i / e of said metals ¹ are accelerated Hei?..!.!. The method according to the invention must, however, be added to the syj-lem anions, e.g. S \ P ³ , B- ³ , which have an inherent effect on the partial reactions 2 and 3.

In Fig. 1 is one with a microprobe on one partially reduced (1175 ° C) chromite Line analysis - ■ analysis values without absorption and other corrections - reproduced. This analysis / uiolgc remain chromium and Aluminum in the grain proportionally over the entire, area almost constant, whereas the Magnesiuin- and iron content in the reducing zone of a considerable amount Subject to change.

_the

f s £ 5ä

The need for coal occurring in part

monoxyJ you throw the Boudoua ^

reaction 3) covered. Be. der Rcduktiotr * »

Chromite «using solid

the same MeUianism was established by experiments

placed. In the temperature range of 10000 ms ^ _hicdencn iron phase a sharply demarcated

_Tue | _llslon5hö f lies in which the original Εική-

_{hold on} until that remains unchanged

g ^ _{s ine} " _{mixture mined} , st.

»5 g _q ^ ^ _{? I | together with dcm Elsen} reduce

_{{ ch of the} mixture determines the reaction

C. The

Equilibrium constant

g-aton. C. The low ^Al "? I ^hu" i ^ _e effectively Gleichgewichlskonstante

'i-ÄE £ ÄÄs "' - * · -.« ■ ■ * ·

aaf attributed to the Boudouard reaction. In the case of 35 _traversing the held in weight

Reducing chromite iron with the help of a ^ _α ^ ^ _{jn your metal content} results in:

IiSiSSÄ SKÄ ^ iU _{r β Fe3} (Cr) Z (Fe) ₈ Ο-

the huh

IiSiSSÄ SKÄ U _r () Z

g-atom C so that * e TOTpeiatu «bhajOTk« t _{where the code number} ^ _{as a function of} the temperature ction MeO / Oas ακ; ^ ^cu j _{di form}

'Son ™ ble ^e ibt ^e in the shadow of this slower

Partial reaction 3. Oxvdsvstem

The removal of oxygen from dcirι O ^ dsy: stern

however, is only at the ^{phas 'n} ß ^r ^ ^z ™' S [to oxidation and desorption

ieduziere'nd gas possible. I ™ jg ^ Oxygen almost immobile so that the re

reaction from the diffusion of solids is dependent on the spinel mixture to be reduced Diffusion temperatures following Dinusion Kemc consequence:

r>Dc>£>Mn>Dm> Do,

so that it applies to the

diffusing ion mainly around 'E' ^se ™ üe according to the contained contamination levels

. the diffusion coefficients (D) over K-ac · _10,. a temperature of 1250 ° C in the range iu ΙΟ " ¹ · cm '/ sec- ¹ _{.. c} .""""j. ,, _7Ur

The structural acceleration, that is, of foreign cations (e.g. alkalis and alkaline earths), often accruing in the gas ^{reduction of} * ^ * ° ™ £ {_ formation of adsorption centers

the Oxydflächen has no ^{B "ch} S ™ ction 3 a result overall process because the Tsilreaktion a ^ha y _{ber5chreitel the} chromgelialt the Metallphasc the 5 percent limit, the almost constant 5 ^ _{code in Red} varies only uktionsbereich

as a function of the temperature between the values. _An increase in temperature reduces the JT value, ie. the chromium content of the metal

_{the chrome content of GeraiS} ches

p ^^ ^ ₅ . _percent . _{Limit) the} value of the

_{Code number with} decreasing chromium content strongly on ^ ^. ^ Damjt ^ _{d & Q dic G} j _{calibration) in this}

Range determines the solubility of the chromium, _{deviates from the} preceding one (this is obvious., Analogous to the melting processes, derived from the appearance of FeO-Cr ₂ O _{3 of} the spinel as an equilibrium phase in place of the distorted spinel ^ g ^ of _the ^H _O xyds Cr ₈ O ₈ or can also be traced back to the occurrence of _{the oxide} of divalent chromium as an intermediate form).

If the carbon _{is evenly distributed in the} mixture of residues, the iron content of the _diffusion chamber is primarily determined by the temperature _{MH as the} temperature increases, on the other hand. I do that in the re-

metal mixture with the iron de =.

3O ₉₆₁₈ ^ r

3125

Diffusion zone in equilibrium (if the right time for learning with carbon below a temperature of 900T and temperature rise - with MgO (j) or MgS (i) as the end product, the gas plan is adhered to), so that according to the phases above (in percent by volume) : 77.6 CO, 1.6 CO ₂ , 11.0 runs low temperature and correspondingly COS, 8.8 CS ₂ , .1.0 S ₂ and P _n ,, r ..: 4.1 '10 ²⁰ atm or high A lowering 5 corresponding to 97.1 CO for the iron content of the diffusion zone. 2.9 CO ₂ and'Pn, --- ΊΑ- ΙΟ " ² '"' Effect on the chromium content of the metal mixture atm. (Bu a temperature of 1150 * C la'uicn. If the reducing carbon is used up, values of the gas phase correspond to · 84 0 CO 0. "O ₂ , the temperature of the system can, if necessary, be 2.8 COS, Ί 1.5 CS, , 1.61 S, and P _0. , = ■ '3.0 · 10 ¹⁸ atm, the chromium content of the metal or 99.9 CO, 0.1 CO ₂ and P ₍ >"- 4.4 x 10 ^I6 atm. phase remains almost constant, since experience shows that 10 I _n the two cases can the "gas phase or the increase in the chromium content very reduce the mixture to the solid MgS the iron oxides (and chromite) to the equilibrium corresponding stand and sulfide
slowly goes by. Like the results of tests carried out

The increase in the magnesium content in the area of the show, the disintegration of the MgSO ₄ in the reduction diffusion zone according to the line analysis (Fig. 1) 15 system proceeds relatively slowly with increasing temperature, is primarily a consequence of the decrease in iron When the temperature rises, the reduction quantity. In the case of a mixture sufficient for a "solid" diffusion at a certain rate over the glowing period, the proportion of the sulphate-sulfur spinel mixture and the direction of the total sulfur content was 68% of the total sulfur content and the equilibrium was reached between the unreduced value of 95 ° C. From the thermodynamic * o of the total sulfur content, determined in relation to its primary activities, a part of the initial value is connected. 6 · / ,. When the reduction in chromium oxide "released" was reached at a temperature of 1150 C, the corresponding Penklas sulfur values for the aluminum phosphate deposited were 28 <V _O or n <y _{The ante} ^H _{jle dcs re} . to chromospinella The remaining oxides of reduced iron (measured by mixing mineral acids to (Cr.AO ^ solution of a certain a ₅ solution) on the total iron content amounted to the ge-composition ratio, which is then called the temperature 5 or 23 ° / In Fig. 3 the prism-shaped grain splitting pieces are separated from the distribution of the chromite grain and the knots lying in its spinel matrix

The behavior of additives during the re- a Reduk.mnsnrnh, T-JIl ^ ".!" O ^ T ¹ ?? 1. ™

production as well as its influence on the structure of the results of a X-ray analysis shown _{in the 3 p}

Reduction of the standing metal phase during the re-uptake results in <! STu ^ d Sauers? Off I nd

production is shown below. M j _m grain vr '^ i ύ ^MU ")"

First, the behavior of the sulfur-containing Schweb Z

Aggregates MgSO ₄ and Na ₂ S in the reduction system strips on the Sn

considered. In Fig. 2 are the ranges of stability of the 35 grain Td £ ', ^ S ₁ SaS ^ S MiS-

Systems Fe-SO (B ₁ ). Cr-SO (B ₂ ), Mg-SO (B ₄ ) and penetrated AnI mfih Ϊ, _t T

Na-SO (B ₅ ) as a function of oxygen and nX, Ncm Ltr ^^ ^? I ^} \ ° ~

Sulfur pressure shown. The binary equations to beöbncl cn di Z f F ^ i ^Sa ^ ⁱ

Weights were deconstructed for a temperature of 100'C S ilh -Z _n TTu ϊ Τ

calculates, however, the univariate equilibria for 40 talliÄ r "sen sinTSn ^ t Γ ^

the temperatures 500'C (a), HOO ⁰ C (6), 1250 ⁰ C (c) _F i Ϊ 4 ze e He, in τ ^Ζ "" ^ "Τ" «^

and 1400 ⁰ CW, so that the temperature speaking | «Ϊ́veΓ ^ ύηΓ ^ Αηΐϊ d« Sü -'- '

shows the dependency of the stability areas. schuefeN der Pmh "1 1 ^g 'Ante 1 des Su! .u-

Also the influence of silica on the oxide phase production _antc 1 Je ^ EiAT "£ itbild ^ e -. ■ '

the aggregates are based on FIG. 2 emerges. Conditional 45 sequences are with;, "" n * u £ . ^G λ

Due to the structure of the chromite in the area of aluminum («and M ^ ^etrach , t" ng, chrome. .d

between the dissociation pressures of the pure Mawä \ m Zi _n 2 r ^ ^ T ^{equally vert} , ^{C; !!} -

gnetits and the pure chromium oxide worked (HOO'C 1 K'S a me? n 'K ^ ^(C) ϊ " ¹ ? ^' ^S ° ^? a

- Fe ₃ O ₄ G): P ₀₂ = 2.60 · 10 "atm or PCO ₂ / z ^ ^ schefk ztere Γη ΐϊ e iron deposition and PCO 2 61 CrO and Π- Pn - 4 30 × 10 ²⁰ atm so η « ν ^1Uzt er and the unreduced center odTpCO; PCO = ϊ £ ^Λ ά>% DissociationdrS "^ f ^ ™] ^ Tä

the iron phase of FeCr ₂ O ₄ G) - B ₃ - is entangling "(df Ae-FeS

speaking: 2.19. 10-atm or PCOJPCO - 2.40. speaking .Bidte ^^ ASSi? αΪ 7 «

The sulfur pressure is at values below ₅₅ SciSd ^ m ^ TößS ¹ TT ^hcn S ^r ' ^da ° ^ ^Sul - ^fat ü

Dissociation pressure of the pyrrhotite maintained (HOO ⁰ C remains at the beginning Z '"""· ^Reduktl0ns g ^emisch

- FeS (I): P "= 1.61 ■ 10-atm and CrS (s) : P _{> 2} = are also sufficient Af-) _Βε ^^ Ph T" ϊ Γ "η 2.81 · 10-iOatm.) which then result from the sulfur activities at the RedukS £ ^ ^hrOmit j. ^{migrates u "d} Reduktionsproduktr. arise. The grain surface fS ^^ 'Μ' ^ Γ S

According to the stability diagram, the reduction 60 or dissolves in! Air ?!

range of iron and chromium in the relevant Na tr um'ulnd (Sdίί ΐ "

Temperature range in the Mg-OS system MgO _(j) sets, leads to the same Sh T

(partly also against FeS and CrS) stable. The sulfate, i.e. Z Frei, l, f ^E ^ * ⁵ cT Yf ^ T

Carbon of the "reduction mixture (or its penetration at the tops" de 7f Γ M)

volatile components) reduces the oxygen of the 6 ₅ phases and in dfcMik ™? n: ♦ ⁽ 'c

Sulphate, so that the end result is MgO and gas phase material) and disposing ^ ^, ^ ^{zen of Sa. ueP}

develop. Assuming that the iron does not re-sulphidation of the ^ Rednw ""'"'""ί ^statl ° ^narer

is reduced, result in the M _g SO ₄ reduction _On According to ^^ Α ^ ϊ ^ ¹ ^ Κ

3125

Ii

. · Iciii Na ₂ S (I) ü'ni-r den
richly stable. TioizJem
i,: ijlie as in the previous
■ _ -r Erz-Gangart Io .-> en da
:. -feld (Fig. 2) er.upre-c
-cherer Verbir.diüipt-nj ■
: -rich the stability

is;
he:

g -.- sanuen Uedukuons- ' ikr Me.huni.mLs the f-aü. The Siükatphasen

obtained samples can be considered as a function of the temperature.

The VcrsuuisrcJuktionen were in a drum furnace felt through; since, starting mixture was in Γοπη .o “Pellets put in the stove. The Chromu. whose spinel phase has the shape

. (Fe _{o 71} Mg _0,,;... Cr ₁₁₂₁₁ AI _Oiie Fe ₀ ,, O ₁ had was ground so that he u falls through a sieve de, mesh size 105, the pulverized coal War_ ground so that it diich a sieve of mesh size μ falls 5J the magnesium sulfate v, urde the mixture in connection with the Hersteilung the pellets ah added to aqueous solution, and thus served as a binder..

In relation to the ore weight, the carbon solids and the MgSO ₁ -AaIeUe of the arei test samples as well as the analytical values of the metal phases formed during the reduction (analytical values in% of the components; all data in percent by weight):

NaO ;. S ₀ dal ', the SiabiliciiJ Na _; SiG.,! .. the SiO ₂ -ι ¹ * :: ¹ · /! and in the ^Reduktiousf: e-Cr-i-eS-CrS-Na ₂ Si0 ₃

.:being. From the drawing, analogous values of silicic acid in the Mg-S-o system emerge, ...- however, due to the different poles in the formation of silicates. occurs in much weaker ■ rm (Na ₂ SiO ₃ : I ■ ', .-. -52 C3ü cul / mol and ■; j.SiO ₃ : JG --- -739OCaI ₁ InOl. Condition for the Üidierung with the ^ - In addition, the sulphate reduction is carried out at low temperature (900 "C) iso-./.iseh or stationary at rolati ^1. Lan", at increasing temperature, so that no large ir.vefel losses c 't are verairt due to excessively high pressure of the react./isg gases and their outflow from the system.

After the sulphidation of the surface particles and pore channel surfaces of the chromite grains. ; chen de. FeS and Fe phase to form ^: .:% Sulfur containing, melt at 985 Cii! Futectic that is diluted to equilibrium melt and ■ i ^r .en. The atomic path

ikeit significantly improved. The self-diffusion heat treatment took place in all samples

The same conditions as the sulfur-free deposition take place, only in the case of the sample (solid) y-iron at 115O ⁰ C No. 3, which has a higher carbon ^{addition than = 2.2 · 10 1X} cm- / s . Corresponding to the other samples received, the temperature of the iron in a 29% sulfur in the final phase of the reduction was increased by about 50 "C, S!) / Cr (total) from 4.6% to ■ ature D = Il, 9cm ² / s, that is, it is about 5 · 10 ⁿ times 35 d_n V / ert 7.3 and the degree of reduction of the

Iron accordingly from 74% to the value 80%

sample Filling mixture MgSO ₁ Fc Metal pliase S. No. C-fix- 2.0 89.7 Cr 2.6 1 44 4.0 87.5 ι 7.7 ' 5.0 2 4.7 4.0 84.9 7.5 4.5 5.5 10.6

larger than for pure y-iron. Iron and its sulphide i: network is known to be complete, besides are Surface tension and viscosity of the in the melt state Fe-S system located extremely low.

If the temperature is really wet, the main reason for the process is that both the iron and the sulphide melt retreat to the grain surface as the temperature rises (and that the solid iron is correspondingly wetted by the sulphide melt). In the metallographic illustration (Fig. 5) is shown the structure of a sodium chloride (a) and one with magnesium sulfate (b) treated reduction system at a temperature of about 120O ⁰ C; the reduction of iron

rose.

The parts of the state diagram discussed here

_, _ ^ or state diagram of the Fe-Cr-FeS-CrS system

Sulphide melt the low-silicate spinel sediment 40 are shown in the drawings A and B in FIG. 6 shown. Drawing A shows the sections of the 9/1 and 4/1 Fe / Cr systems as a function of the sulfur content and the temperature. In drawing B , the limits of the solubility gap of the melting state characteristic of the Cr-Fe-S system, starting from binary Cr-CrS mixtures and extending to the Fe-rich mixtures or alloys (approx. 1400 ^: 'C) are as a function of the Fe / Cr

- .— _, _._ ratio and the sulfur content shown. the

corresponds approximately to the original 50 limits (/) of the weakly sulphurous part of the carbon-solid part. In the partial figure α is solubility gap are imprecise, which is obviously due to the reduction of iron in the form of fine (solid) impurities in the particles subject to the measurement in the chromite pores and the spinel matrix mixtures. The analysis can clearly be seen at the presence of sulfur at the extreme point (g) of the phases of the solubility gap (b) , on the other hand, the grain is to a large extent free of 55 (in percent by weight): 79.0 Fe, 4.5 Cr and iron. The iron deposits are in the shape of a round - 16.5 S; the corresponding temperature is 139O ^G C licher (diffusion of the iron through the sulphide melt, the Fe-Cr ratio 17.55. Melts c and d correspond to the average co-wetting) lamellae on the surface of the chromite aggregates 17.6 S, 16.7 Cr and 17.1 S, 8.3 Cr grains - and thus the sulfur content 16.7% (Fe / Cr 4i mentioned deposition of magnesium-free oxide and 17.1 (Fe / Cr = 9) from drawing A. The chromium mixture of the form (Cr _Ol5 - _Oi, Al _OlS - _0il ) ₂ O ₃ from the poor metal melt is thus to be seen in the same-spinel matrix. The amount of melt weight with the sulfur and chromium rich.-ii Miifid: the reduced mixture is because of the low 65 the difference in content increases with increasing: Fisen- Reduction temperature still low . The equilibrium connections dei

On the basis of the state diagram, the process should be able to take place in the molten state the metal phases different from reductions thus the drawing /? can be removed.

The Drelibi . Λ U- egi - !: g clci "I I'rcmmi ! often · :: · - promotes dic ^ e Verei: iii-unt ^: he ier melt n. In t iereiei; der Lösii · :! - V.eiMiieU · '. re. HC ii, he -! -.! i 'J: : Sch mc ! zer S _: and S ₂ vc-r- a.ndei il : ■. ', .P. - ie, ilrv.'l Sulfur ^ ■ ;. ' {e ν • ^: maclv · H; , '· Uf bra uciien of Schrriei2.-i S _; .He sici- ! i ■ .ei ab-. ^ lekieudi : i - [- "i; ·. ■ e (which because of the ras-ehe: ". Ό: Γι ' ¹ , · u e sillii ul; d d he full '.: indi; 2ep Benetzu, - the SuH ^: .d-ch! .r : ie :. "" '' -in:! i'acku.i- nia .-. iüialer dich: e turn on! eiw: ι isO bi> I) ", ΜΊ'ί '. iü'.viclH of the Me.a'i- genvvche-. a 'he , Mj that ei; e: ^ eats.riia! b permanent tendon. ■ - ze S, before. i ! tiger Μίΐν.: - ; st VuV. .1 it's early from «; - say goodbye I'imia.ab-c heidunü fully suindifi bt-net / i. Da, rCn-: a ..i!: insnre; you ! -α the " Melt:, _{2 e.ihUt} at Eq.-i-.iii •.; J; l> / i; ^: iiii .i in the V : rglic'rt to the SuIn ri- Phase, u.r ■. ir ".1 ¹ Ii: a% -i Fe, C: ti- Phasc. Bc; raseüejn Ahki'iMen r I'i'iibe a; :: · de ι Λ r -.- i! i - ;. eritiarbere '.'; L between ck Liiviich'r.eits HlCKC U! ■ α the Fuekukerr! crst-.rl Jv. ■ ei in lib ';: i:' i iah C- ¹¹ Ir ) gei-er him 'ipröJer Form ai-i ( ^: OH-rOa'.he Read abu eschicdenen Meiall-

13 14

whereas those depending on the Te nine rat.; - 'iHric: ^ n o.rcn the spherical bodies unite

Any changes occurring on the first day of the month. ge-.muü'i-.vic, -. .'hsehc-idimgen r \ large dropper.

Drawing A can be seen. ih 'i Tlf fdt di

The composition of the Meu.Uphase cKt'er · milk sample No. 3 is in the range of solubility. · .-! If the temperature rises above the R ^ ciuV.tion ^ - temperature; on, -o take the ^r : -clirru '! / e-Ant-.il the mixture of metals or the alloy. Bib is the mixture at about J400 Γ, finally in its: entirety is in the state of melting i and the melted phases take the same-.iichiiZiiS-.and according to the determining conode. : -J-Sch:; itl / ei S ./^ be ^ lreb ■, sicii von der Mjhv.ereii schwcielarmtn Meiaii-Schpiel / e (S ₁ ) zu iren> v? N. Fill ¹ . iiv.r _s -i ^; , \; Termwrauu v.ieder, so iö .-. Can be found in the area of Luilichkeilsüxkc (Fig. 6,.-I) of both: öd.me ^ en λ! Lc, C.rJ mixed crystals. In doing so, the MLSbe of the melts is reduced (the melt S, v-irJ is completely rebuilt). With further temperaurabful! and Aujkri taliize dci ix-Bhase from the melt S ₂ other - Lh die Zu ^ ain-

Meiiserung the lei ^ g-jiiannten melt until the phascntrunii:;: · ,.

F i g due to the binary Cr / CrS and re / ieS. 5 shows what happened in the process

eutectic line is erreidii (Fe-Cr ratio tem- relatively large C / sulfur Gev.'ichtsprozen ¹ "\ 'EUTL particle ί · ■■■ inside which periitur!".. 0/1350 / 32.5; 25 sich klen.j divisions of (Cr, Fe) S-phase and

1 / 1350.32 ^: 4/1255 / 32.4 and 9 / 116U .11.4, being on its surface, i copious (Cr. Fe) S-Ph-Se

the phases x (Fe, Cr) NND 'hfcr, Fe] S) he ¹ further be'inden. The assignment of the samples in the oven and one

Decreases in temperature in the direction of eutectic suitable cooling then also have a beneficial effect

Line deposit together until the melt is completely off, when the composition of the reduce is used up. 30 metal phase lies outside the solution gap (in

The composition of the metal phase of the mixture are always impurities, their

search sample no. 1 lies outside the solubility gap overall effect cannot be determined), since m this too

in the ternary prism, in an area drawn from the surface of the metal drop

Binary FdCr as well as the metal-ripe surface of the clear sulphide layer can be observed, which limits the solubility gap. When cooling down, the more sulfur-containing the probes, the more it is.

A sample from a high temperature causes the precipitation to occur. The increase in the grain size of the metal precipitate

Melt Sj only secondarily in the form of drops, which and the formation of a metal and the spiral

between the primarily separated "mixed cri- phase separating sulphide layer errrög-

remain stable, in appearance (Fig. C, A). The calibration lent a slight detachment of the metal phase from the ό phase, which is primarily deposited by the droplets, is 40 oxide matrix in its pure form with the help of simple physical

on the already existing primary separation of local separation methods (e.g. coarse breaking of the

layered; the same is true for the resulting pellets and sifting through the large metal droplets

eutectic crystallization separating »phase and / or fine breaking and grinding as well as weakly

to. In the solidified structure there is no formation of layers Magnetic separation of the small Metalliropl'en ¹ ). determine, and the Λ-phase is in tropic form in 45. According to the basic mechanism described above

the Λ matrix. nisnns becomes the structure of the metal deposit and

At low temperatures and slowly evacuating this layer of sulphide from the temperature

Under certain circumstances, cooling can, after a strong decrease in the melt solubility gap of the system

the chromium content in the metal mixture (e.g. by Fe-Cr-FeS-CrS, its location and scope as well as the excessive carbonization and binding of chromium 50 surface phenomena that occur between sulfide scr.mel-

on carbides and the like) occur in the structure in the matrix ze, metal and oxide phase. To

Daubroelith in the form of long lamellae as a result of the method according to the invention can be applied to all

Reaction mentioned factors by adding appropriate amounts

TC c r> c jc "i;r> ς j ρ »^ ^er named active gates or their mixtures

55 influence. Below Nvsrden

appear. considered some of the tried and tested options. the

If the temperature of the sample after the reduction is suitable activators, which in addition to Cr are soluble

increases, the amount of melt in the metal gap in the Fe-S-

phase, which induce diffusion rates of the grain system, and which tend to be alone or Components rise and the viscosity of the melt goes 60 as a mixture or mixture of this gap or theirs

back accordingly. On the other hand, increasing the upper temperature range will be hi: r in

The surface energy of the melt compared to the gas phase is divided into the following two groups:
because of their increasing metallization depending on the temperature, and because of the
correspondingly changing adsorption enables 65

the change in the contact angle - between the substances in the first group show d -,

the chromospine, together with the pre-corona, on the iron-rich rope of the solubility

We called a spontaneous "infiltration". When there is a gap in the same direction as with Fe-Cr-S-SysUnn,

Al. Ce . Cu, Mn, Ti, Zr G sip point B, < V, Sb . Si, Sn, Zn the Sl open minded det first

$ o that these substances tend to concentrate primarily in the sulphide system.

In the case of the substances of the second group, the conodes point in the opposite direction, so that these substances tend to migrate into the metal shell. Accordingly, the representatives of this group, especially those at the beginning of the series, a strong one that increases the thermodynamic activity and thus lowers the sulfur content Effect to own.

As an example, consider the Fe-S-Mn-C (Cr) system serve (the stability ranges of the system Fe-M n -.> in the reduction phase are shown in FIG. 2 calculated). The rivet-side limit of the melt solubility gap of the Fe-Mn-S system is fixed at about 1600 ° C. by the following values: S, percent by weight / Mn, percent by weight

3.0 / 0.5; 1.7 / 1.0; 0.8 / 2.0; 0.7 / 3.0.

The manganese causes a slight decrease in sulfur activity; but since the carbon itself has a very strong increasing effect in this regard, an increase in the S activity and thus a proportional decrease in the sulfur in the molten metal are the result (the logarithms of the activity coefficients are additive: 2% C, log / i ' = 0.25; l ° / ₀ Mn, log / ^ "----- -0.02 and thus log / i ¹ ""= • 0.23).

The shift in the clearance gap of the carbonized Mn-Fe-S melt towards the iron side is evident from the analytical values for 1600 ° C (data as above):

1.1 / 0.5; 0.65 / 1.0; 0.40 / 2.0; 0.30, '3, O.

Also, the temperature dependence of the above Löslichkeitslücke is the carbon greatly affected (shift between 1650 ^0C and 1150 "C) at 1250 ⁰ C, the values of the noisy metallssitigen limit Löslichkeitslücke (details above).:

0.15 / 0.5; 0.08 / 1.0; 0.04 / 2.0; 0.03 / 3.0.

Boron has an effect analogous to that of the carbon atom, but has a more powerful effect in this system (log / "/ log /" - ■ 1.6), while silicon and phosphorus have a weaker effect.

F i g. 7 shows the results of tests with various structurally activating substances. The same ore powder was used for these tests as in the previous test series. The grain size of the powder wai selected so that it happened 149 μ to 100 ° / ₀ ^ n-mesh screen. A stationary furnace system was used for the reduction. The heat treatment during the reduction was carried out according to the following program: 2 Siundcn / 1175 ° C. and an additional 0.5 hours / 1450 ° C. After the temperature of the batch had freely fallen to 1350 ° C., rapid cooling was carried out.

In the sample of the part of Figure disnte MgSO ₄ α as an aggregate, wherein the Schweiclmenge 1.06 constituted ° / ₀ of the Erzgewichtes. According to the figure, the metal phase is completely covered by a relatively thick ^r sulfide layer. Although it is a static system, a confluence of metal droplets can be observed as a result of filtering through (α). The interior of the spinel bodies is to a high degree free from metal deposits.

_{MgSO 4} and MnSO ₄ were used as aggregates in the sample in partial illustration /), the Mn and S amounts making up 0.73% and 0.96% of the ore weight, respectively. According to the figure, this sample corresponds largely to sample a. The sulfide surrounding the metal phase contains approximately 0.5% Mn at the metal boundary and approximately 1.0% Mn at the spin boundary.

In the sample of partial images c , only Mn and S are used as aggregates in amounts of 0.73% and 0.42% of the ore weight, respectively. The sulfide layer surrounding the metal phase continues to be without gaps, but is thinner than in the previous samples and, according to probe analyzes, has a zone-like structure compared to chromium and manganese. Furthermore, the sulfide sits less firmly on the spinel surfaces than in the previous samples. Partial figure d shows the structure of the metal phase of a sample containing 0.73% Mn, 0.42% S and 0.22% B. The sulfide layer on the surface of the metal phase is extremely good, but thin.

The metal deposits are lower compared to those of the previous samples Size. Also, to a greater extent than in earlier spinel grains, finely divided, spherical metal phase separators; nevertheless, the overall result is good.

With the help of aggregates, the surface energy ratios can also be influenced prevail between the solid and molten phases of the system. In the inventive! proceedings they are extremely complicated! Energy conditions are also subject to constant change, partly from the temperature changes, but especially from the fluctuations in the mixture or the alloy results. In the initial phase of reduction after the formation of contact melt the effect of the sulfur creates a complete wetting between the melt and the growing metal phase as well as moderate wetting between the melt and the still iron-containing one Oxide phase. As the reduction continues, the metallization increases rapidly the melt, so that the surface energy values (melt / gas, melt / oxide) despite the inclusion of the compensating chromium with a corresponding increase in the edge angle A temperature increase carried out after the reduction causes an increase in dci Amount of melt and. due to their increasing metallization, an increase in energy values, which, of course, is caused by the rise in temperature ζ. Τ is compensated. With the complete melter The metal phase in the area of the solubility gap leads to the formation of equilibrium energy between the deposited melts and oxide phases. Compared to the previous state of the Melt, the degree of metallization of the low-sulfur melt causes high Greiullächeri energy values Because of the stagnation of the metallization of the sulphurous melt and the formation of a conode equilibrium corresponding chronicity. if the interfacial energy V values are low enough that: the partial wetting that takes place between the melt and the oxide surface, the filtering through Melt system allowed.

With the help of surface-active activators, both the melt-gas and the melt-oxide-oxide surface energy values affect

flows, since the wetting of the melt / metal is of sufficient intensity throughout the entire process is. The aforementioned activators from the first group are surface-active in this system Mn and Ti age, which at the melt / oxide boundary mainly at the areas occupied by oxygen ions Places in the oxide lattice to stabilize its crystal structure are deposited, thereby wetting and work of adhesion increase. The substances of this group have on the melt gas energy values an insignificant influence. Exercise an extremely strong influence on both limit energy systems the very strongly adsorbed on the surface of the melt (monoatomic surface layer) components the activator group 2 (especially components B, C, S, P). The substances mentioned increase the thermodynamic activity of sulfur, so that with their help the course of the isopotential curves the effective components of the multicomponent systems to be treated can easily be manipulated and thus, by regulating the absorption in a wide range, influence on the surface energy and contact angle values can be taken.

When choosing one or more activators for the structure of the metal deposition, in addition to the effectiveness of the activators, the amount of permissible impurities in the metal or spinel phases is of decisive importance. Usually activators are chosen which mainly accumulate in the resulting metal phase to be deposited (group 2), so that the spinel-oxide mixture phase to be further refined remains pure. The treatment of the metal phase to be deposited (recovery of the activators, extraction of chromium, etc.) always requires a separate process. It should be mentioned that in the case of small amounts of iron to be separated from the ore - this has been proven by tests carried out - small amounts of previously separated Cr and Fe-containing metal phases are advantageously mixed with the product to be reduced, which causes a temperature increase following the reduction The particle size of the metal phase to be deposited grows. In order to maintain the high chromium content of the end product, it is also otherwise advantageous to add chromium-containing salts or a ground metal mixture or metal alloy to the activator mixtures; especially when ores with a low CrO ₂ content are treated.

The practical implementation of the method according to the invention is explained below.

The reduction device and its mode of operation will first be described.

For the reduction experiments with chrome ore iron, the method shown in FIG. 8 furnace system shown is used. The furnace drum, equipped with speed regulation, η - 0.3 to 1.3 rpm, had a diameter of 1.00 / 0.77 m and a length of 12 m. "The inclination of the drum could be in the range of 2.5 can be regulated up to 5.0 ° / _0.

The concentrate pellets were filled in together with the accompanying coke by means of a vibrating feeder at the return end 2 of the drum 1. After passing the furnace, the pellets passed freely through the outlet end 3 into the drum cooling device 4, where they were extinguished with water. In the opposite direction to the pellets: A suitable fuel-air mixture was fed into the furnace via the burner. In order to achieve the correct temperature profile, additional air for the combustion of the accompanying coke was fed into the drum via d "air openings 6", depending on requirements. The combustion and reducing gases get through the exhaust pipe 7, -the dust separator. In the course of the Redukun, -, process, the individual process phases in /, were clarified through the openings 9 to 14 solid- _liii; , Gas samples taken from the drum.

Examples

The chroi used for the test batches -.;:. ore had the following analysis values (in weight percent ■■: ■

28.90 Cr: 21.00 Fc: VSO Fc ³ ': 12.30 Al ₂ O ₃ ; 0.77 Cu ₁ , 10.80 MgO and 4, / Vi SiO ₂ .

The content of nu-usüiic ¹ , 11 trace elements is low. Most strongly represented were Mn <0.15%, followed by (.-0.1 ⁰ I ₀ ) Ni / n. Ti, Co, V and Cu.

The ore hew something - a spinel part betnfli. shape

(Fe ₀ ,,, Mgo,: ₁ i '--ii. · ^ ^Λ ' ο.5β Fe _o ,, _e O,

The gait consisted mainly of TaH. Serpentine together, the serpentine part in., about 45 percent by weight of the gait.

The coal used for the reduction!, The following analysis values (in percent by weight):

88.0C (total carbon); 79.0 C (fix): 3. ¹ ^. 0.52 S and 7.58 ash. The analysis values of the /-.■■, .. · were accordingly:

8.6 FeA: 48.1 SiO ₂ ; 7.0CaO; 14.1 MgO: 9.5 , and 3 "3 NaO ₂ .

The analytical values of the eingei into _the oven; th Begleitkokses denominated (in weight percent):

88.0C (total); 84.8 C (fix); 1.10 H; 0.75 S and 9.8G ash. Purify the analysis values of the ashes.

14.1 Fe ₂ O 2: 50.6 SiO 2: 3.1 CaO; 1.8 MgO and 23.7 Al ₂ O;,.

The ore was of a fineness appropriate. that 80'V _{0 passed} a sieve with a mesh size of 105 μ!:. the Redul tion carbon was ground to a fineness level that 100 ° / ₀ a sieve with a mesh size of 53 μ. happened. The grain size of the accompanying coke was 20 to 40 mm.

B e i s ρ i e 1 1

Ground ore, reducing coal and magnesium sulphate as an additive were brought to the pelletizing plate via a mixer together with a suitable amount of water and processed there into pellets with a diameter of 10 to 15 mm. Reducing carbon and activator became 6 b: w. 2%, based on the malt weight, added. The pellets obtained in this way had a moisture content of 8 percent by weight. The test series was carried out with the following amounts of material (dry weight): 300 kg / hour pellets, 100 kg / hour accompanying coke (which served as an oxidation protection for the pellets and at the same time covered the furnace system's need for additional fuel) and 65 kg / hour butane. The butane was burned with an air coefficient of 0.75. The total amount of air was 920 Nm ³ Z hour.

The speed of the reduction drum was

20th

of the " fJ ⁵

0.8 rpm, their inclination 2.5 ° / ", The ^^ P ^ reduced product was m the drum 1430. after passing the cooling drum IMJ L. uie

of samples _nomme ent through openings in the drum were n, tracked.

^ ^ Reduction attempt as a function
^ _{Distance from the} charging end of the furnace see below
i "Table 1 and in F i _g . 9 compiled.

Reduction of chromite ores using carbon

Amount of reaction mixture
Distance from the loading end temperature
Analysis of the sample
Spinel and Oxide Mixtures
Cr (total)

Cr (acid soluble)

Fe (total)

Fe (acid soluble)

C-fix

Fe (hl) / Fe (ges)

Cr (born) / Fe (born)

let "the temperature of the ^" ^^ "'^ S ^ gJende

At a distance of about 8 "^ / 2K _n , the furnace was below 1200-C. The great terid ^ E""n_;

, was reduced in this interval. At the other br ^

• In the rotary kiln, the temperature Q

• niche quickly to the final value - 143Uj

; gert, with the reduction

Carbon equivalent (about 74 "/"). ^D ; J _acid .

Carbon, sulphite sulfur and aes

Chroms lived up to expectations Especially the = "" f "^ If n« nüto

eratu ^

143Uj- 8 The pellets obtained in the previous example were ground to such a grain size for attempts to separate the reduced metal phase. 80% a sieve with a mesh size of 53 μ

Separation tests were carried out on a P.lot scale _with a weak magnet separating device, the field strength of which could be regulated. The _decision was made from a wet scrubbing.

Analyzes of the Abschdderesuta.es _ind i ,. TabeHe 2

table table

nn dry reduced chromite concentrate depending on the wet magnetic separation of dry ^^., ^

Magnetic field strength, GauD

Material balance
magnetic deposition

magnetic part

non-magnetic part ...

Analysis:
magnetic part:

Fe-Cr ratio. -

Fe + Cr

Fe yield - Rre -

non-magnetic part:
Cr-Fe ratio

Fe + Cr

Cr ₁ O ₃ - calculated - · ■ ·
Cr yield - Rcr - · · ·
All figures include weight percentages

2.08 48.13 47.50 97.00

2.60 46.28 48.86 95.50

3.22 44.79 49.95 92.80

3.57 3.90 4.36 4.80 44.16 43.66 43.08 42.62 50.42 50.79 51.22 51.55 89.60 85.00 79.60 74.00 -

Both the magnetic and non-magnetic products were additionally tested with respect to iron and chromium analyzed. The theoretical deposition result given in the table was obtained, by calculating the analyzes and amounts of the metal phases of acid-soluble metals and sulfur and took this as the theoretical magnetic fraction of the deposition. From the deposition results are the Cr-Fe ratio of the non-magnetic deposition part as well as dieio, respectively Chromium output, as a function of the field strength used, is shown as curves I in FIG. 10. From the table and the drawing it can be seen that there is a relative field strength of approx 1.5 H Gauss for the non-magnetic product gives the Cr-Fe ratio of 3. The is Chromium yield about 94%. The Fe-f-Cr sum of the magnetic fraction is at the same time approximately 90%, so that the product is free of non-magnetic product to the highest degree. With awake-20 transmitter field strength, there is an improvement in the Cr-Fe ratio of the non-magnetic component, however, it also leads to a sharp drop in the chromium yield. At the same time the metal content goes of the magnetic part quickly returns, which is tantamount to a decrease in the selectivity of the Phases is. In the example, however, the chrome finish is ^ v'c with a Cr-Fe ratio of 4 still 84% and the metal sum of the magnetic part correspondingly 86%, see above that the deposition result can be described as good. So should be the Cr-Fe ratio of the non-magnetic Are partially increased, the separation of the magnetic fraction must be repeated and if necessary to undertake an additional grinding in order to increase the chromium yield of the non-magnetic part improve.

The same starting product is ground to such a grain size that 85% pass a sieve with a mesh size of 105 μ, and then the above is carried out the magnetic separation tests described in Table 3 and Fig. 10 - curves 11 - results presented.

table

Wet magnetic separation of dry reduced chromium concentrate depending on the

Magnetic field strength

οΐϋιι

magnetic deposition

Magnetic field strength, C-auB

3.5OH

4.0OH

4.9OH

6.50H

Thcroic

magnetic part

non-magnetic part ....

Analysis:

magnetic part:

Fe-Cr ratio

Fe + Cr

Fe yield - R " _C -

non-magnetic part:

Cr-Fe ratio

Fe + Cr

Cr ₂ O ₃ - calculated -
Cr yield - Rcr - ...
All information in percent by weight.

According to the figure, the chromium yield corresponding to the Cr-Fe ratio 3 is over 90%, but falls rapidly as the Cr-Fe ratio increases, apparently indicating a deterioration the separability is due, which in turn is based on the fact that part of the metal phase is not freely available for separation because of the relatively coarse grinding in the product. Will striving for higher Cr-Fe ratios and chromium yields, the grinding is to be continued and the magnetic component by repeating the deposition to clean.

It should be mentioned that the basic separation of the metal phase after the breaking or coarse grinding of the PeIIeLs can even be carried out by sieving, since the metal phase to be deposited z. T. in very large and loose deposits are present.

Example 3

In this series of experiments, separation experiments were carried out with a reduction product No aggregates that activate the structure of the metal phase were used.

15.38 25.44 39.04 84.62 74.56 60.96 6.53
89.14
53.86 2.92
74.75
64.15 1.72
65.12
72.83 2.80
45.74
49.26
94.00 3.22
44.79
49.95
84.00 3.50
44.28
50.33
69.20

43.45
56.53

1.56
03.43
76.04

3.71
43.95
50.57
64.50

18.47
81.53

11.68
96.41
73.93

5.03
42.78
52.15
95.40

In the reduction were 5.5% carbon and

as a binder 1% sodium chloride, calculated from

Ore weight, used. Loading quantities and

Heat treatments were the same as in the

Reduction experiments of example 1.

The starting mixture had the following analytical values (in percent by weight): 81.8 spinel and oxide mixtures; 27.14Cr (total); 0.03 Cr (Sl); 19.74 Fe (total); 1.02 Fe (Sl); 4.08 C (fix) and 0.03 S.
The analytical values of the reduced product were accordingly: 69.9 spinel and oxide mixtures; 30.74 Cr (total); 1.32 Cr (Sl); 22.36 Fe (total); 15.88Fe (SI): 0.19 C (fix) and 0.03 S.

Relative to the bound. Metals, the Cr-Fe ratio in the starting mixture was 1.45 percent by weight, 4.54 percent by weight in the end product

In terms of magnetic deposition (Separation) the reduced product was ground to such a grain size that 87% of the Mesh size 105 μ passed.

The results of the separation experiments are in TaUHe 4 and F i g. 10 - curves III - compiled.

table

^{lrat depending on}

Material balance
magnetic deposition

3.5OH magnetic field strength, GauB
4.75 H j 5.5OH | 6.50 H.

theory

magnetic part ....
non-magnetic part

Analysis:
magnetic part:

Fe-Cr ratio

Fe + Cr

Fe yield - Rpe -

non-magnetic part:

Cr-Fe ratio

Fe + Cr

Cr _a Ö ₃ - calculated - ....

Cr yield - Rcr -

All information in percent by weight.

25.44
74.56

2.00
68.86
52.22

2.33
47.72
48.80
81.00

31.40 67.60

1.80 66.93 62.34

2.73 46.46 49.70 74.80 36.80
63.20

1.66
65.45
67.15

2.95
45.91
50.11
70.50

44.62
55.38

1.38
62.33
72.15

3.06
45.65
50.29
62.00

17.41 82.59

12.00 98.82 71.04

4.54 43.45 52.05 95.69

On the basis of the results it can be determined that the metal phase adheres tenaciously to the spinel metrix. In the case of the best deposition with regard to the Cr-Fe-ratio, the proportion of the non-magnetic part was only 55 ° / ₀ compared to a theoretically calculated value of 83 ° / ₀ . Also, the corresponding chromium yield was only 62 ° / ₀ (theoretical value% ° / _0). The circumference of the magnetic part of 45% (theoretical value 17%) and its metal sum -on 62% (theoretical value 96%) indicate the presence of a large non-magnetic component. A change in the field strength does not lead to any major differences in the selectivity. Even further grinding of the starting product does not result in any noticeable improvement in the selectivity. Although the experiments were carried out with pellets, there is no doubt that powder or lump ore is also used

The raw material obtained by reduction without the addition of structural activators is therefore suitable for the unfavorable shape and position of the metal phase do not allow the metal phase to separate from the oxide phases with the help of physical processes.

It will be understood that the method described can be modified in many ways.

* 5 Annealing temperature and duration depend on the Additional geniuses, but already those in this context discussed substances: sulfur, carbon, boron and manganese offer regarding the process very extensive variation possibilities.

These simple annealing processes, which work with variable temperature, can also be used in technological very different furnace systems. If for the examples given here a rotary kiln and induction furnace system

mainly to highlight the differences between static and dynamic systems. The pilot test processes described as an example only show the basic mechanism of the process and this in particular with very low aggregate quantities. Along with the iron, the other metals such as nickel and cobalt also go away, completely regardless of the proportions of these metals. The process according to the invention can also be applied to the deposition of iron, nickel and cobalt, of aluminate, ferrite, titanium and vanadium spinous containing these metals and their mixtures, and of ores and latents formed _{from Al 2} O _{3 -containing sesquioxide mixtures} .

50

For this purpose 4 sheets of drawings 309 618/31

Claims (6)

Hanian classification process 1. Process for increasing the chromium-iron ratio of iron-rich chromite ores, in which part of the iron contained in the ore is converted into metallic form for the purpose of physical separation by reduction in such a way that the chromium-iron ratio? or more, and the ore to be reduced, the carbonaceous substance required for the reduction and the other necessary additives are mixed, characterized in that sulfur-containing additives are added before the iron reduction phase, the temperature to the Fe-Cr-S melt solubility range is increased from about 1400 to 1500 ⁰ C, is then slowly ^{cooled by about 100 to 200 0} C so that the sulfide phase containing the main part of the aggregates is still melted, and is finally cooled quickly. 2. The method according to claim 1, characterized in that that as additional activators elements of the group: Al, Ce, Cu, Mn, Ti, Zr and / or the Group: B. C, P, Sb, Si, Sn, Zn, which cause a melt solubility gap in the Fe-Cr-S system or increase these, preferably added as sulfur compounds. 3. The method according to claim 1 or 2, characterized in that Na ₂ SO ₄ , MgSO ₄ , ZnSO ₄ , Na ₂ S and / or MnSO ₄ are used as the sulfur-containing aggregate Lffe. 4. The method according to any one of claims 1 to 3, characterized in that the heat treatment taking place after the reduction ^ phase in the temperature range of the solubility gap determined by the activator, but below the calibration temperature of the relevant Spinel mineral body is carried out. 5. The method according to one.der claims 1 to 4, characterized in that the heat treatments dts English «in the same oven unit be performed. 6. The method according to any one of claims 1 to 5, characterized in that, if the ore is no 5, J ^g coke,