CA1064706A - Process of olivine useage in blast furnace, agglomerates containing olivine and process for their preparation and use - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
A process for the reduction of iron oxides to produce molten iron in which olivine is introduced into a blast furnace in addition to iron oxide bearing materials and in which there is a high content of alkali metal oxides in the materials charged into the furnace, resulting in minimizing or preventing "scaffolding"
and improving the operation of the furnace. The disclosure further includes improvements in which olivine is mixed with iron bearing materials or with coke and such mixture is formed into agglomerates having improved properties and in which such agglomerates are charged into the furnace.

Description

1~164~1a 6 Thts i,n~ention rclates to ~ process for producing molten iron in a blast furnace in which olivine is charged into a blast furnace in addition to iron ore or other iron oxide bearing materials. The invention relates particularly to such a process in which agylomerates containing mixtures of olivine with iron bearing materials or mixtures of oli-Yine with coke,are rharged into the furnace, and further re-lates to agglomerates containing such mixtures and to processes ' for the preparation of such agglomerates'.
B~CKGROUND
The operation of the blast furnace in the'pro-duction of iron ~nvolves processes of chemical reduction in which oxides o~ iron and other metals are reduced and oxygen removed. The blast ~urnace is charged with four basic ingredients: (1) iron oxides, in the form ol ~aw orel ~ene-~iciated pellets, hri~uettes, nodules, sinters, or other agglomerates; ~2)' calcium carbonate tthe term calcium carbonate is used to include'either limestone or dolomitè~; ~3~ a ~uel usually in the ~orm of coke; and t4) air which proYides oxygen to support the combustion. The raw iron as it comes' from the Lake Superior region has contained approximately 50 percent iron in the form of iron oxide (Fe~03), with ~he rem~inder ; being silica (SiO2), aluminum (A1203), magnesia (MyO) r lime (CaO), sulfur (S) and phosphorous (P), and manganese'oxide (MnO). The sulfur and phosphorous are eommonly considered impurities.

The iron oxides', ~x other met~llie charged materlals, ph: C ,~ 1 ~6~6 coke and calcium carbonate are charged into the blast fur-nace, one at a tima, in measuxed amounts, to form layers of iron ore, limestone or dolomite, and coke; and air (wind) is passed through these layers and the coke is burned. Burning of the coke produces heat and carbon monOxide which has a part in the chemical reduction o~ the iron oxides. As the coke burns the iron oxides are reduced and come into the form of molten iron. The limestone or dolomite, along with quanti-ties of impurities such as sulfur and phosphorous form a slag. The hearth which is located in the lower part of the furnace, is the hottest part of the furnace and the layers of ore, coke and calcium carbonate keep moving downwardly within the furnace to the hearth.
At some point in this movement downwardly in the furnace slag is formed, and after its full passage downwardly in the ~urnace it is withdrawn from the furnace in the form of liquid slag. The slag is important to the operation of the furnace because it carries with it many unwanted impurities and so separates these from the iron anA removes them from 2Q the furnace.
When the downward movement of the iron bearing charged materials, the coke and the calcium carbonate pro-ceeds in a uniform way with the movement taking place con-stantly and evenly on all sides of the furnace, th s is eyidence of good operation, Unfortunately, this is not al~a~s the case.
As is well known to blast furnace operators there

- 2 ph~
, ~6~7~6 are times when the downward movement of the ingredients charged iII~O the furnace is no~ xegular and uni~orm or when the movement at some place within the furnace is greater than at other places, making the furnace unbalanced. There are even times when at substanti~l areas the movement becom2s ~estric-ted, and then after operation for a time under such condi-tions the whole mass may let loose, descendiny at once into `
the hot part of the fu~nace with the result that the hearth temperature is reduced below an operable temperature, someti~es almost extinguishing the fire. When this happens, the fur-nace may have to be shut down, cleaned and restarted,which is a time-consuming and expensive operation.
It is our belief that the faulty operation above referred to is due in large part to the presence in the charged materials of alkali metal oxides such as Na20, K20 and Li20. These oxides appear to pass downwardly to hot^ter parts of the furnace and there become volatilized after which they pass upwardly in the furnace with the wind and then condense above the mantle of the furnace forming stable-alkali-alumino silicates. Such silicates are believed to lead to a scaffolding effect which prevents the layered burning material from descending in a regular, uniform manner.
A continuation of this action develops a situation where the mass will collapse of its own weight, chilling the furnace hearth where the most important smelting reactions take place.
DESCRIPTION
In our U.S. Patent No. 3,966,456 (June 29, ph~

- ~6~7~;
1976) we set forth the improvement in blast furnace operation where the charged mater.ials contain in excess of about 1 pound of alkali metal oxides per net ton of molten iron produced by charging into the furnace a special mineral called olivine, to improve the furnace operation, removing a substantial part of the alkali metal oxides in the slag and preventing the occurr-ence of falling burden as above described.
The olivine above referred to is a special mineral in the form of an ore which may be crushed and sized and which has the following analysis:
MgO 40 to 50 weight percent SiO2 35 to 45 weight percent Fe23 6.5 to 10 weight percent The te~m "olivine" as used in this specification and claims is in the form of an ore which contains MgO, SiO2 and Fe203 in the proportions above-stated and which contains forsterite in an amount of 80 percent or more, usually.about 88 to 90 percent and contains iron silicate (2Fe-sio2~ in an amount of from 3 to 12 weight percent, usually about 8 to 9 percent, and which is substantially free of alkali metal com-pounds less than O.S weight percent and contains more than . ~0 percent nesosilicates, these percentages ~eing based on the ; total weight of the olivine.
The olivine may be charged into the furnace along..
with the iron oxide bearing materials and in the amount of from 0.10 to 10.0 weight percent of the iron bearing charged materials, preferably in an amount of from 0.25 to 5.0 weight ph:~

- ~6~7~6 percent o~ the iron oxide bearing charged materials. Charged materials having higher alkali metal oxide content (in excess of 1 pound per net ton o~ molten metal produced) may be treated to produce molten metal in a ~last furnace with much less difficulty when the olivine is also included.
We do not know with certainty the exact reason for such improvement, but a possible theory explaining the improved results is that the olivine provides a source of useful oxides (MgO, FeO and SiO2) without the evolution of carbon dioxide which is associated with dolomite, for example, and results in ra;sing the point in the geometry of the fur-nace at which the slag becomes fused, or in other words, causes the slag to be formed higher in the furnace which means that the slag is formed earlier in the total reduction process. This allows more time for the slag reactions to take place and for the impurities to be converted to stable compounds, thus making the process more effective for the ~` removal of sulfur and alkali metal compounds. Also, the tendency for previously fused slag to resolidify is reduced.
Further, we believe the earlier slag formation resulting from the introduction of olivine causes the slag to react with more iron oxide surfaces and more Fe203 to be reduced FeO.
Also, the olivine itself contains up to 10 percent of Fe203 which also is reduced in the course of reduction processes.
The olivine has a tough durable grain with a hardness of about 6.5 to 7.0 on the Mohs Scale and is mechanically strong as compared to limestone or dolomite, and ~ 5 ` .

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` . ~L616gL7~16 has an advantage in burden permeability and gas-solid contact.
~nother benefit from the introduction of olivine is in the area of iron chemistry control. ~ess dust loss and increased carbon monoxide evolutlon mean that control of silicon and manganese reduction are more precise. Heat losses due to calcination are lessened and slag mineralogy improved along with the better con~rol obtained in this improved operation.
The e~rlier formation of liquid slag further permits a more acid slag composition thus lowering the requirement for basic oxides such as limestone-or dolomite.
To demonstrate more specifically how to practice the improved process in which olivine and charge materials having a high alkali metal oxide content are introduced to a blast furnace, we set forth tests which may serve as specific illustrations of how the invention may be practiced and the results which are to be exp~cted.
The following Table 1 describes a program to be followed over a 30-day period in which the amounts of the materials for one~complete charge are listed in the left-hand column. It should be understood that the same amountsand relative proportions of charge materials are continued duriny the day listed in the table until the time a different amount of the various charges is prescribed and carried out.
The test is begun by accumulating data during a base period.
After this the change in the charge is made and continued long enough to provide an evaluation of the operation.

ph:G~l ~31647~
~ABLE I
B e period - ~uantities of char~e in~redients or one cha _ Pellets 29,550 lbs.
Mn-bearing ore 450 lbs.
Scrap 2,000 lbs.
Coke 14,000 lbs.
Dolomite 3,000 lbs.
Limestone 2,000 ]bs.
First day of olivine test - quantities/charge Pellets (same as in base period) Mn-bearing ore (same as in base period) Scrap (same as in base period) Coke (same as in base period) Olivine 125 lbs. of size -2~1/2 Dolomite 2,650 lbs.
Llmestone 2,250 lbs.
Third day of olivine test - quantities/charge Pellets (same as in base period) Mn-beaxing ore (same as in base period) Scrap (same as in base period) Coke (same as in base period) .
Olivine - 250 lbs.
Dolomite 2~300 lbs.
Calcite Stone 2,500 lbs.
Fifth day_of olivine test - quantities/charge Pellets (same as in base period) Mn-bearing ore (same as in base period) , . . ', , .

~i47~

TABLE I (continued) Scrap (same as in base period) Coke (same as in base period) Olivine 375 lbs~
Dolomite 1,950 lbs.
Limestone 2,750 lbs.
Seventh day of olivine test - quantities/charge Pellets (same as in base period) : Mn-bearing ore (same as in base period) Scrap (same as in base period) Coke (same as in base period~
Olivine 500 lbs.
Dolomite 1,5Q0 lbs.
Limestone 3,100 lbs.
Seventeenth day of test - quantities/charge , Pellets . (same as in base period) ,~ Mn-bearing ore (same as in base period) Scrap tsame as in base period) , Coke (same as in base period) ; 20 Olivine 600 lbs.
Dolomite ~ 1,200 lbs.
. Limestone .3,400 lbs.
.
;i Eighteenth day of test - quantities/charge Pellets(same as in base period) Mn-bearing ore(same as in base period) Scrap(same as in base period) . Co~e(same as in base period) : - 8 -ph~

L7~36 TABLE I_(_ontinued) Olivine 600 lbs.
Dolomite 800 lbs.
Limestone 3,800 lbs.
Nineteenth day of test - quantities/charge ...
Pellets(same as in base period) Mn-be~ring ore(same as in base period) Scrap(same as in base period) Coke(same as in base period) OIivine 600 lbs.
Dolomite400 lbs.
Limestone4,200 lbs.
'l~entieth_day of test - quantities/charge Pellets(same as in base period) Mn-bearing ore(same as in base period) Scrap(same as in base period) Coke(same as in base period) Olivine 600 lbs.
Limestone 4,200 lbs.
Twenty-lfth day of test - quantities/charg Pellets(same as in base period~
Mn-bearing ore(same as in base period) Scrap(same as in base period) Coke(same as in base period) Olivine 600 lbs.
Limestone 4,600 lbs.
Thirtieth day o~ test - ~uantities/char~e Test terminated.

_ g _ , ph~

.

64~06 The purpose of the test set forth in Table I
is to demonstrate the effect of the olivine on the operation of the blast furnace. As shown in this Table the olivine is increased during the first seven days of the test. The vol-ume o~ slag may be expected to increase during the test but the basicity and V-ratio will decli~e. The Na20 and K20 content of the slag may be expected to increase. Since the A1203 content of the slag should be substantially constant the increase in the NaO and K20 content of the slag may be established by plotting the Wa20/A120 and the K20/A1203 ratios. Also the ratio of CO to C02 may be determined and plotted to measure furnace efficiency, and if it is deter-mined that more Fe203 is being reduced to FeO during the reference period, this is an indication that the olivine is promoting early slag formation, and an improvement in the coke rate will result. Further~ if the furnace starts to peel early in the test, this is an indication the oli-vine is having a favorable effect.

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~i4~06 Table II describes another series of tests of blast furnace operation in which the ingredients cilarged in one charge are given for a base E~eriod in which no olivine is included, and then during subsequent periods in which the olivine is first included at 1,000 lbs./charge and in subsequent periods increased up to 2,000 lbs.charge.
~ s shown by the chemical calculations given in`
Table II the slag volume may increase with increased amounts of olivine, and the base/acid ratio decreases. An increase of the alkali metal component in the slag may be expected, and a noticeable improvement in the operation of the fur-nace.
It is an added feature of our invention and a further improvement that instead of charging a self con-tained volume of olivine into the furnace we may prepare an agglomerate which contains iron oxide containing mater-ials mixed with olivinç or which contains coke mixed with olivine, said agglomerate containing such mixtures in a solid, discrete form, and chargi~g agglomerates into the furnace. As used in this specification and claims, the term "agglomerate" refers to a feed material which has been prepared by mixing particles of relatively small size and forming the mixtu~e into discreie particles of relative--ly large size. The agglomerates may take the form of a ball, a lump, of pillow shape or any other such shape into which the mixture may be formed.
The primary purpose of using iron bearing ma-pl~

~1647~6 terials in the form of agglomerates is to improve burden per-meability so as t:o permlt a higher xate of gas flow and better gas-solid contact within the furnace. The principal types of ore bearing agglomerates which have been used in the past are sinters, pellets, nodules, and briquettes.
The making of sinters has commonly involveA the mixing of finely divided iron ores along with a small per-centage of fuel such as coke and depositing the mixture on a moving grate. The mixture is ignited at thP feed end of the grate and air is,pulled down through the mixture.
The temperature rises to about 24~0 to 2700 F and the final ore particles fuse together ln porous coherent lumps called sinters. In our improved sintering operation we mix with thè finely divided iron ores to be discharged onto the sintering grate a quantity of olivine ore in a finely divided state. The quantity may be from about 0.1 to 10.0 weight percent based on the total weight of the materials placed on the grate and subjected to the sintering opera-tion. We prefer to use about 0.5~ to 5.0 percent of oli-vine based o~ the total weight of the material mixture. Theolivine when mixed into the sinter feed material should ; preferably be ground to a fine particle size which will pass a 4 mesh size screen. In this way we produce an improved sinter containin~ from about 0.5 to 5.0 weight percent of olivine which is continuously dispersed throughout the internal area of the formed sinter. The hot sinter may be -cooled, sized, suitably to about 1/2 to 3" and fed along ph:C~r~

!L~647C~6 with other materials into a blast :Eurnace.
One of the best agglomerates containing iron ore is known as pellets. Since much of the raw ore made into pellets is of relatively low iron content, the raw ore is usually concentrated to increase the iron content to something like 50.0 to 60.0 or greater weight percent before ; the pelletizing process begins. Concentration may be accomplished, for example, by magnetic separation, by washing, or by flotation separation. After concentration the ore usually has an iron content of above 50 weight percent.
In the pelletizing process the iron bearing ore or concentrate which may consist mainly of magnetite or hematite is ground to about minus 200 mesh and mixed with water and bentonite. It is then rolled into balls in a bal-ling drum or disc. The balls may ~e approximately 0.25 to 1 inch in diameter. The "green pellets" so formed are then dried and heated to about 2200F to 2500F bonding the tiny yrains together within each pel]et. Because the heating step uses air for co~bustion the process is an oxi-dizing process and the heat generation is adequate to con-vert nearly all of the magnetite to hematite:~
Bondlng within the pellets is a cr~stalline bond which is due to the grain growth from the oxidation of magnetite to hematite. In the case of a hematite pellet, grain growth is due to recrystallization. In the case o$
both magnetite and hematite recrystallization of gangue ph~

~6~ 6 silicates and aluminates (slag bonding) will promote more rapid strengthening at lower temperatures, and if the magnitude o~ slag bonding could be increased by any means the process energy requirements would be reduced~
In our improved pelletizing process there is mixed with the finely ground magnetite or hematite a quantity of olivine. Suitably the olivine to be so mixed is in a finely divided state, preferably in a form in which most of it will pass a 200 mesh screen~ When the mix-ture containing the olivine has been balled and heated ac-cording to the steps above described, the pellets so for-med may be cooled, sized suitably to from 3/8" to 1" and i utilized along ~ith other feed materials in charging a blast furnace.
The peilets so formed containing olivine are stronger by reason of their olivine content. Olivine's melting point is drastically decreased in the presence of iron oxide and its inclusion in the concentrate mix pro-vides an excess of energy units to further recrystalli-zation.
In addition, both the co~position and structureo~ olivine are such that they duplicate the primary slag silicatesl thus adding an amount of slag "pre-formation", which in turn will lower energy requirements in the furnace to which the improved pellets are fed.
Advangates of including olivine in the mix to be formed into pellets are:
1. The olivine produces an increase in the drop , ph:(`"~

~69~706 and compressive green ball strength of the agglomerate enabling a reductlon in bentonite usage. In the blast furnace this effects a reduction in both alkali and alumina load in the furnace.
2. Olivine increases the fired strength of the pellets, resulting in pellets having increased resistance to degradation and lowered fines generation.

3. Olivine increases the amount of alkali metal , oxides (Na20)and (K20) removed in the furnace slag system and so minimizes swelling of the pellets bv alkali reflux condensation. Aero-dynamically this increases permeability of the blast furnace burden.
4. The eutectic temperature of olivine is high enough 50 that its stability is retained longer .
than any other mineral in the pellet mix.
This results in increased gas-solid contact when ~20 the pellet is used in the operation of furnacés.

5. Introduction of olivine to an iron bearing pellet reduces the iron content and increases silica and magnesia content. The increase in magnesia is greater than in silica, resulting in an increase of basic oxides. This improves the self fluxing properties of the pellets. This ; may be demonstrated by a reference to the ' ph: ~r~

~6~71~6 compositions of Major magnetite pellets without olivine as compared to the expected composi-tions of pellets from the same sources with olivine included.
;~ CO~POSITIONS O~ SOME MAJORiMAGNETITE PELLETS (1968)l Fe P , Si02 Mn A123 CaO MgO S
~ Minntac Pellets 65.12 0.011 5.50' 0.16 ; 0.42 0.25 0.59 0.002 Reserve Pellets 62.56 0.028 8.76 0.27 0.47 0.44 0.51 10 Erie Pellets, 63.91 0.012 7.22 0.23 0.31 --- ---Eveleth Pellets 65.39 0.023 5.50 0.14 0.29 0.19 0.30 EXPECTED COMPOSITIONS OF MAGNETITE PELLETS FROM THE
SAME SOURCES CONTAINING ABO~T 1.0 PERCENT ADDED OLIVINE
~, Minntac Pellets 64.46 ~ - 5.90 - - - - 1.04 Reserve Pellets 61.90 - 9.16 - - - - 0.96 Erie Pellets 63.25 - 7.62 Eveleth Pellets 64.72 - 5.90 - - - - 0.75 The amount of olivine introduced into the mix in the manufacture of pellets, and also in the manufacture of other iron bearing agglomerates, may vary between 0.10 and - 15.0 weight percent based on the iron content of the mix, preferably betweell 0.25 and 5.00 weight percent, and may be ground to a size of about minus 200 mesh or as close as is practicable to the si~e of the iron concentrate. The,olivine is mixed with the bentonite feed mix before the balling sequence.
' In the case of a specular hematite concentrate the olivine may '~ be added at the mineral blending stage. Specular hematites are usually difficult to ball because of their plate-like - structure, but the addition of olivine by reason of its ' ~ 18 -ph ~1 ~L~6~7(~ .
stability and hardness is useful in abrading the platey struc~
ture to facilitate the balling operation.i Cyanide emission in the blast furnace is a normal by-product of its high temperature ~lame, and its potentiation has a direct correlation with the alkali load a furnace is carrying at any given time. Although the, amount of cyanide ionization cannot be diminished, the fixation of the cyanide radical with alkalis may be reduced through slag removal.
Olivine bearing iron pellets accomplish this by reducing the availability of the alkali ions to react. This produces a more readily degradable and simpler cyanide compound, such as hydrocyanic acid, rather than a more complex alkali salt.
It will be understood that the basic steps in-volved in the production of pellets are in many respects utilized in the manufacture of other iron bearing agglome -ates such as sintering, nodulizing and briquetting, and the advantages above set forth in connection with pellets containing olivine are in most respects applicable to the other agglomerates which contain olivine.
In the nodulizing process, fine iron bearing ma-terials are introduced into a rotary kiln and formed-into nodules or lumps. The nodules are heated as they are rolled. In our improved nodulizing-process olivine in an amount of from 0.10 to 15.0 weight percent, preEerably from 0.25 to 5.00 weight percent, based on the total weight of the nodule is mixed in and the mix introduced into the kiln. In the nodulizing process the feed moisture and ph ~

1~647~6 particle size are not so important as in the pelletizing process.
In the briquetting process, finely divided iron bearing materials such as flue dust, certai.n coal or coke materials, etc., may be utilized, and in our improved process the iron bearing materials and olivine are mixed in the proportion of from about 0.10 to 15.0 weight per-cent of olivine, preferably from about 0.25 to 5.00 weight percent of olivlne, based on the total weight of the mat-erial which goes to form the briquette, and the resulting iron-olivine mixture is passed lnto a press such as a roll press or punch press to form the briquettés. The briquettes may be heated or formed cold, but cold briquettes especially as previously produced have been found to be low in strength and not very useful because of this failing. Our improved briquettes containing olivine have greater strength and are deemed more useful in furnace operation for this reason.
In the preparation of ~ur improved sinters or briquettes we may start with the materials heretofore ; used in making sinters such as ore fines, mill scale blast furnace flue dust, llmestone or dolomite. The olivine so obtained may be fired to produce the sinters. The sinters thus pro-duced may then be used as an ingredient in the charging of the blast furnace.
The olivine may also be used in a similar way ; starting with similar materials to produce the improved ph~

~6~16~706 briquettes, and either the sinters or the briquettes con-stitute agglomerates which may be charged into the furnace.
To demonstrate the starting materials used in such pre-paration of agglomerates we set forth typical ingredients in proportions in the following Table III,.
TABLE III
Materials Weight Percent Ore Fines 30 to 50 Mili Scale 10 to 25 Blast Furnace Flue Dust 5 to 15 Coke Breeze 1 to 5 Limestone Fines 1 to 10 Dolomite Fines 1 to 10 Olivine Fines 0.10 to 1500 The improved agglomerates above described whether prepared by sintering, pelletizing, nodulizing or bri-quetting, normally will contain iron principally in the form of Fe203, but still further improvement may be had by concentrations by pre-reducing the iron oxides and in this way making the agglomerates more desirable as a charge in blast furnaces. After the iron ore and the olivine have been ground to the desired fineness and mixed as we have explained in the foregoing description for making the agglomerates, the mixture may be treated by any of the processes heretofore utilized for pre-reducing the iron content. Such processes may involve the heating of the iron ore-olivine mixture in the presence of a carbon- -: ' .

ph :~; `, t1 .
.

~64~06 aceous reducing agent with an excess of air suitably in a rotary kiln. Alternately, the iron ore-olivine mixture may be heated in a retort to produce sponge iron.f Chemically, the iron in the form of Fe203 is converted to Fe304 and Fe304 is converted to FeO. Pre-reduction o~ the iron ore may be conducted to the desired extent to partially pre-reduce the ore, and following the pre-reduction treatment brought to the form of sinters, pellets, nodules or briquettes using the technology above set forth.
In the above description we have referred to agglomerates which essentially contain a quantity oE iron bearing ore. Another type of agglomeratelis that containing essentially a fuel such as coke, and olivine. To prepare this type of agglomerate, the coke, or other such fuel, is ground into fine particles and mixed with olivine also in fine particles in a proportion, for example of about ~.10 to 15.0, preferably from about 0.25 to 5.00 weight percent of olivine based on the total weight of the mixture, with the addition of an amount of water necessary to a briquetting procedure, and a mixture thus prepared may be pressed to make briquettes which may be pillow shaped or of any other desired shape and suitably may be o~ a size such as 1" to 3" square. Alternately, the coke-olivine mixture may be nodulized or otherwise treated to bring it into agglomerate form.
The coke-olivine agglom~rations may be fed along with iron bearing ingredients into a blast furnace. They ph (i ~

.

16~69~7~6 have special advankage in such operations. We have al~
ready discussed the action of olivine in overcoming the effect of the alkali metal oxides resulting in the elimi-nation or minimizipg the scaffoldiny effect which is so detrimental to the operation. A substantial quantity of such alkali metal oxides come into the furnace by way of ; the coke feed and this quantity has been increasing in recent years as the quality of the coke being used decrea-ses. From about 20 to 80 percent of these alkalis may be contained in the coke feed. By incorporating the oli-vine as a mixture in the coke agglomerates the olivine is thus brought into proximity with the highest concentration of alkali metal oxides and so functions to better advantage in overcoming the effect of these alkalis.
We believe that one important reason for the im-; provement when using olivine in the form of mixtures con-taining agglomerates is that the agglomerates are structur-ally stronger and better resist degradation in the course of tlle iron making process. Their improved strength may be demonstrated both by dropping the agglomerates or by compressing them until they begin to ~reak up. Another rea-son which we believe to be important in explaining the improved results obtained in using our agglomerates is that it is easier to distribute the olivine across the furnace and better distribution of the olivine can be brought about.
This makes for more uniform reactions and the minimizing of spots in the furnace where scaffolding may occur.
.

ph:c~1 ~63 647~6 While we have described our invention with respect to certain modes and embodiments it will be apparent to those skilled in this art that the invention may be embodied in many forms and many changes may be made all within the spirit of the invention and the scope of the appended claims.

ph~

Claims (22)

WE CLAIM:

1. In a process for producing iron in a blast furnace wherein charge materials including iron oxide bearing materials, calcium carbonate and coke, are charged into the blast furnace to form within the furnace layers of iron oxide bearing materials, calcium carbonate and coke and wherein air is passed upwardly through said layers, and said coke is burned to heat said materials and reduce iron oxides to produce molten iron, said charge materials having an alkali metal oxide content exceeding one pound per ton of molten iron produced, the improvement which includes charging into said blast furnace in addition to said iron oxide materials from 0.10 to 10.0 percent of olivine, said percentage being based on the weight of said iron oxide materials.

2. A process as set forth in claim 1 which in-cludes charging into said blast furnace agglomerates con-taining said olivine in said amount.

3. A process as set forth in claim 2 in which the said amount of olivine is from 0.25 to 5.0 weight percent.

4. A process as set forth in claim 2 in which said agglomerate is pellets.

5. A process as set forth in claim 2 in which said agglomerate is nodules.

6. A process as set forth in claim 2 in which said agglomerate is briquettes.

7. Agglomerates selected from iron oxide bearing materials and coke useful in the charging of a blast furnace and containing olivine in an amount of from 0.10 to 15.0 weight percent based on the total weight of the agglomerates.

8. Agglomerates as set forth in claim 7 in which olivine is contained in the agglomerates in an amount of from 0.25 to 5.00 weight percent based on the total weight of the agglomerates.

9. Agglomerates as set forth in claim 7 in which said olivine is contained in the agglomerates in a mixture with coke.

10. Agglomerates as set forth in claim 7 in which olivine is contained within the agglomerates in a mixture of iron oxide bearing material and olivine.

11. Agglomerates as set forth in claim 8, 9 or 10 in which said agglomerates are sinters.

12. Agglomerates as set forth in claim 8, 9 or 10 in which said agglomerates are pellets.

13. Agglomerates as set forth in claim 8, 9 or 10 in which said agglomerates are nodules.

14. Agglomerates as set forth in claim 8, 9 or 10 in which said agglomerates are briquettes.

15. A process for preparing agglomerates which are useful in the charging of a blast furnace comprising mixing olivine with an iron oxide bearing material or coke in a proportion of from 0.10 to 15.0 weight percent olivine based on the total weight of the mixture and forming said mixture into an agglomerate.

16. A process for preparing agglomerates which are useful in the charging of a blast furnace comprising mixing olivine and an iron oxide bearing material in the proportion of 0.25 to 5.00 weight percent of olivine based on the total weight of the mixture, and forming said mixture into an agglomerate.

17. A process for preparing agglomerates which are useful in the charging of a blast furnace comprising mixing olivine and coke in the proportion of 0.25 to 5.00 weight percent of olivine based on the total weight of the mixture, and forming said mixture into an agglomerate.

18. A process as set forth in claim 16 in which said mixture is sintered to form sinter agglomerates.

19. A process as set forth in claim 16 in which said mixture is pelletized to form pellets.

20. A process as set forth in claim 16 in which said mixture is formed into briquettes.

21. A process as set forth in claim 16 in which prior to its formation into agglomerates said mixture is subjected to a reducing procedure to convert iron oxide contained therein to a reduced form.

22. A process as set forth in claim 17 in which said mixture is pressed into briquette form.