CA1319016C - Ore pelletisation - Google Patents
Ore pelletisationInfo
- Publication number
- CA1319016C CA1319016C CA000562249A CA562249A CA1319016C CA 1319016 C CA1319016 C CA 1319016C CA 000562249 A CA000562249 A CA 000562249A CA 562249 A CA562249 A CA 562249A CA 1319016 C CA1319016 C CA 1319016C
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- polymer
- ore
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- weight
- binder
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-
- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B1/00—Preliminary treatment of ores or scrap
- C22B1/14—Agglomerating; Briquetting; Binding; Granulating
- C22B1/24—Binding; Briquetting ; Granulating
- C22B1/2406—Binding; Briquetting ; Granulating pelletizing
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- C—CHEMISTRY; METALLURGY
- C22—METALLURGY; FERROUS OR NON-FERROUS ALLOYS; TREATMENT OF ALLOYS OR NON-FERROUS METALS
- C22B—PRODUCTION AND REFINING OF METALS; PRETREATMENT OF RAW MATERIALS
- C22B1/00—Preliminary treatment of ores or scrap
- C22B1/14—Agglomerating; Briquetting; Binding; Granulating
- C22B1/24—Binding; Briquetting ; Granulating
- C22B1/242—Binding; Briquetting ; Granulating with binders
- C22B1/244—Binding; Briquetting ; Granulating with binders organic
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- Chemical & Material Sciences (AREA)
- Manufacturing & Machinery (AREA)
- Geochemistry & Mineralogy (AREA)
- Geology (AREA)
- General Life Sciences & Earth Sciences (AREA)
- Life Sciences & Earth Sciences (AREA)
- Environmental & Geological Engineering (AREA)
- Materials Engineering (AREA)
- Mechanical Engineering (AREA)
- Metallurgy (AREA)
- Organic Chemistry (AREA)
- Manufacture And Refinement Of Metals (AREA)
Abstract
ABSTRACT
Ore Pelletisation Finely divided mineral ore is pelletised using a soluble synthetic polymer. Preferably the polymer is in the form of beads made by reverse phase polymerisation and all having a size of below 300µm. When the ore gives a pH in water of below 8 the soluble polymer is preferably cationic.
Ore Pelletisation Finely divided mineral ore is pelletised using a soluble synthetic polymer. Preferably the polymer is in the form of beads made by reverse phase polymerisation and all having a size of below 300µm. When the ore gives a pH in water of below 8 the soluble polymer is preferably cationic.
Description
~3:l9~
Allied Colloids I,imited 60/2669/02 Ore Pelletlsation Iron ore needs to be in the form of agglomerates of substantial size when it is charged into a blast furnace.
If the available ore is in the form of particles that are too small for direct feed to the blast furnace it is necessary to convert them to a sinter or to pellets.
With the increasing use of lower grade ores it has become necessary to grind the ore more finely and, for these fine particles, pelletisation is the only satisfactory method of production of feedstock for the furnaces.
The pellets are made by adding binder to the fine particulate ore and stirring in the presence of a small amount of water (generally moisture in the ore) to form a moist mixture, and then pelletising the mixture, e.g., in a balling drum or disc pelletisPr. The green pellets are then fired in a kiln through a temperature range that extends from an inlet temperature typically in the range 200-400C up to a final temperature of e.g., 1~00C.
Important properties of the pellets are the initial or wet strength, the dry strength (after drying the green pellets in an oven at 105C) and the tendenc~ of ~he pellets to spall (or burst) upon exposure to firing temperatures. The tendency for spalling can be defined ~5 by determining the minimum temperature at which spalling occurs or by observing the percentage of fines formed during a particular firing cycle. The moisture content of the mixture and the porosity of the pellets must be chosen carefully. A high "drop number" for the green pellets is desirable. For cost reasons the amount of binder should be as low as possible and, to ensure uniform properties, its flow propertiPs must be such that it can easily be added uniformly in these low quantities.
Although many binders have been proposed in the literature, (e.g., bentonite and other clays, ferrous 13~9~6 sulphate, lignin sulphate, asphalt, starches, calcium and sodium compounds, and certain polymers) in practice , bentoni~e is the binder t~a~ is ge~rally used.
i~f n~blis ~d ~ J~ lql~
In GB 1,324,838~ work ~as desc~ibed that was ~5 conducted in or before 1970, more than 15 years ago.
Thls used, as binder, a water soluble linear organic polymer having a molecular weight of 1 million to 20 milllon. Suitable polymers were modified natural polymers such as starch and sodium carboxymethyl cellulose and various non-ionic, anionlc or cationic synthetic polymers. The process lnvolved forming a solutlon of the polymer and spraying the solution on to the particulate lron ore. The patent noted that the sprayed solutlon was viscous and that this could b~ a problem, but that the viscosity could be reduced by lncluding sodium chlorlde, sodium sulphate or potassium chloride in the water used for making the solution.
Although dlrect comparisons o~ the polymers in GB
1,324,838 lS di~icult it appears ~rom the patent that various non-ionic, anionlc and cationic polymers can be used to give improved green strength and/or spalling properties compared to bentonite, at very much lower dosages than bentonite. For instance a straight chain polyethylene oxide was reported as giving improved strength and spalllng values and a cationic copolymer and a polymer formed ~rom about 8~ sodium methacrylate and 92~ acrylamide were reported as giving improved strength values.
A disadvantage of the process in GB 1,324,838 is that it is necessary to introduce substantial amounts of water with the polymer and so the initial iron ore must be very dry (involving the use of drying energy) or the final pellets will be very wet ~increasing the risk of spalling).
3 ~3~90~
In Aus.I.M.M. Newcastle Pellets and Granules Symposium October 1974 pages 151 to 156 R.L.Smythe describes what appears to be the same work as is discussed in thls patent. It describes the problems that had been incurred with converting dry powder polymer into the polymer solution that could be sprayed on to iron ore. The article proposed the use of polymer supplied as a 35% solution (necessarlly therefore involving bulk handling problems) and the use of polymer supplied as a liquid suspension, that presumably was converted to an aqueous solution before use. The article warned about handling problems of the resultant pellets and the risk of blockage of chutes and referred to the study of alternatlve polymers, namely "natural polymers and derivatives of petroleum products".
Desplte all this work in the early 1970's an authoritative review of iron ore pelletisation by G.K.Jones in Industrial Minerals March 1979 pages 61 to 73 mentlons, as binders, only Portland cement, lime and bentonlte, and emphasises the large amount of bentonite that is used and predicts that it will continue to be used despite the shortages o~ bentonite.
Despite the acceptance by Jones, and the whole industry, that bentonite would continue to be the most widely used blnder it has, for very many years, been recognised to incur varlous problems~ Thus some grades o~ bentonite give satls~actory pellet propertles but others are less satisfactory. A prGblem with all grades of bentonlte is that the bentonlte lS not combustible and so contr1butes to the gangue ln the furnace, and thls gangue tends to be corrosive to the lining o~ the furnace. Another problem with bentonite is that the optimum grades are becoming less avallable. Bentonite must be present in the pellets in quite large amounts, thus reducing the iron content of the pellet ~319~
significantly and increasing the amount of gangue. Lime and some inorganic salts have been proposed as alternatives to bentonite, but again they cause the ~ormation of unwanted gangue and can be less satlsfactory than bentonite. The added gangue constituents require increased energy consumptlon ln the furnace.
A problem with bentonite and other hindars lS that the spalling temperature is low. Typlcally the inlet temperature of the kiln has to be ln the range 200 to 400C to prevent spalling. Higher inlet temperatures would be economically desixable if spalling could still be avoided~
ln Mlning Engineering October 1984 pages 1437 to 1441 de Souza et al reported that organic binders would have the inherent advantage, over inorganlc binders, of being eliminated during ~lring. Results were reported on the use of polymers based on cellulose, in partlcular the material sold under the tracle ~ k Perldur and which ~``.1~
is believed to be carboxymethyl cellulose. The article reported adding Peridur powder to an aqueous pulp of iron ore before ~iltration and also reported adding the powder manually to the ore flow. The article noted the need ~or water soluble polymers to be hydrated and dissolved during mixing and pelletising. Spalling at 250C was reported, but this is unsatis~actorily low.
A difficulty with powdered cellulosic blnders such as carboxymethyl cellulose lS that the irregular partlcle shape and size dlstribution is such that the powder does not flow ~reely. Instead the dry particles tend to clump together rather than flow over one another. As a result it is difficult to achieve uniform supply o~ the low dosages that are required. Another problem is that the amount o~ cellulosic binder that has to be used for adequate strength tends to be too high to be cost e~ective. Another problem with some cellulosic 1319~
polymers is that they can reduce surface tension, and this appears to be undesirable in pellet formation.
In practice the use of cellulosic binders has not been widely adopted, presumably because of these or other problems. At present therefore there is very little use of organic binders and bentonite is still very widely used, despite the long-recognised disadvantages and decreasing availability of suitable grades of bentonite and despite the long-established possibility of using organic binder.
In EP 0203855A2 published in 3 December 1986 it is proposed to use a water soluble high molecular weight polymer in the form of a dry powder or, preferably, a water-in-oil emulsion that preferably contains both water-in-oil and oil-in-water surfactants. Non-ionic, anionic and cakionic polymers are proposed. The use of the polymer in combination, with an inorganic salt, to increase strength, is also proposed.
Spalling properties are not discussed in a manner that allows judgement as to whether these polymers could give impro~ed spalling properties compared to the spalling properties of bentonite.
The only dry powders that are specifically proposed in EP 0203855A2 are Rhone Poulenc AD10 which is said to be a non-ionic polyacrylamide having intrinsic viscosity (IV) 15.4dl/g and which we beliave to be a coarse crushed gel product, and Percol*725 and Percol*726, both of which are made by the assignees of the present application. Percol*
725 is a crushed gel copolymer having IV about. 18 of 80%
acrylamide and 20% by weight sodium acrylate and Percol 726 is a bead copolymer of about 65% acrylamide and 35% by weight sodium acrylate and has IV about 17. In particular the bead form of Percol 726 is made by reverse phase polymerisation and a signi~icant amount of * Trademark 13190~6 the particles have a dry sl~e above 450~m and up to about 800~m, and the crushed gel of Percol 725 also has a particle size ot up to about 800~m.
When considering possible binders that might be used there are several critical factors that have to be recognised. The iron ore always has a very small particle size, and therefore a huge surface area. The binder must be lntroduced with the absolute minimum of water in order that the pellets can conveniently have a total moisture content of not more than about 15~. The duration and energy of mixin~ the binder with the iron ore particles must be as short as possible in order to maximise production and minimlse capital costs. The amount of binder must be as low as possible in order to minimise cost and to avoid the risk of excess binder accentuating the stlckiness problems noted in the article by R.L.Smythe.
Bentonite has a very small particle slze (typically below lO~m) and adequate admixture of these very small particles with the partlculate iron ore is acnieved because the bentonite is used ln a relatively large amount (typically 1~). However it would be expected that the use of a blnder that is substantially coarser and/or present in a substantlally smaller amount would tend to give less satis~actory results, due to non-uniform mixing o~ the binder with the relatively large volume of very fine particulate iron ore.
The use of cellulosic binders or the powder or emulsion binders proposed in EP 020385~A~ lS inconvenient from the point of vie~ of application methods that give reasonable results. ~lso the results are, at best, generally no better than those obtainable with bentonite, and they are often worse. It has been our object to improve application methods and/or obtain better results.
7 13~9~
In the methods of the invent.ion mineral ore pel:lets are made by adding binder comprisiny organic polymer to particulate mineral ore having substantially all particles below 250~m and stirring in the presence of about 5 to about 15% by weight water (based on total mixture) to form a substantially homogeneous moist mixture and pelletising the moist mixture.
Canadian Patent Application No. 523996 claims a process in which iron ore pellets are made by adding binder comprising organic polymer to particulate iron ore having substantially all particles below 250~m and stirring in the pres~nce of 5 to 15% by weight (based on total mix) to form a substantially homogeneous moist mixture and pelletising the moist mi~ture, and the process is characterised in that the binder comprises up to 0.2% by weight, based on total mix, of a water soluble synthetic polymer that has intrinsic viscosity 3 to 16dl/g and that is an anionic polymer of one or more water soluble ethylenically unsaturated monomers comprising an anionic monomer and that is added to the iron ore as a dry, free ~lowing, powder having substantially all particlles above 20~m and below 300~m.
Although that process is very successful for pelletising conYentional iron ores it has been found that less satisfactory results are obtained with some unusual ores, for instance one particular of haematite iron ore in Canada. It has been as~ertained that this particular ore as supplied is acidic, in that has a much lower pH than normal pelleting ores.
In the invention pellets are made from mineral ore by adding binder comprising organic polymer to acidic particulate mineral ore having suhstantially all particles below 250~m and stirring in the presence of 5 to 15% by weight water (based on total mix) to form a h~
8 ~31~0~ 6 substantially homogeneous moist mixture and pelletising the moist mixture, and in this process the binder comprises about 0.02~ to about 0.5~ by weight, based on total mlx, of water soluble polymer that is cationic.
When a small amount, e.g., 2 to 10% by weight, of partlculate ore is slurried with water the pH of the resultant water may depend upon the amount of ore that is used but at higher amounts of ore, typically 30 to 40%
solids, the pH becomes substantially independent o~ the amount o~ ore. It is this pH, that lS substantially independent o~ ore concentration, whlch lS intended herein when re~erence is made to the ore glving a speci~led pH. Normal ores give a pH of above 8.1, typically 8.2 to 8.4 or higher. The invention is of part1cular value when the ore lS acidic and thus gives a pH in this test o~ below 7, and often below 6.
By the lnvention it is possible to obtain very good pelletlsing results even at very low pH values. Th1s lS
in marked contrast to existing systems, and especially systems us-ing bentonlte, where reasonable results are sometimes obtainable at p~ values 7 to 8 but the results at lower pH values, for instance 6.~ to 4 or even down to 3, are totally 1nadequate in most instances. Thus the lnvention permits, ~or the first time, satis~actory pelletising of acidic, and often highly acidic, ores.
The mineral can be any acidic ore, e.g., a zinc ore, but is preferably an iron ore, normally a haematite, magnetite or tachonlte. The ore may be naturally acidic or may have been rendered acidic by some treatment prior to blending with the binder. For 1nstance the ore may have been washed with acid to remove acid soluble components, typlcally to produce a pH o~ ~rom 5 to 6 if manganese is being washed out o~ the ore.
The ore may have acquired an acidic pH during other processing treatments. For instance the ore may be 9 131~
dried under conditions that xesult in the dry ore ~iving the speclfied relatively low pH in water. This may be because, for instance, the drying is conducted using hot gases that contain sulphur or other impurities that cause acidification of the ore during drying or may be due to chemical changes in the surface properties of the ore that are caused by dehydration.
As a result of the invention it is possible, for the first tlme, to use for pelletising ores that hitherto would have been rejected, either because of their acidity or because of their low grade. The reason why lt lS now possible to use low grade ores for pelletising is because a preferred process of the invention comprlses forming acidlc particulate ore from the mineral ore (that can be of low grade) by a process comprising washing or leach`ng the mineral ore ln acid, and thereafter using the resultant, enrlched, acidic partlculat~ ore for pelletisln~. It has not previously been practicable to use acld washed or acid leached ores for pelletising.
The ore that is acid washed or leached is normally an iron ore.
Numerous methods of purifylng or enriching mineral ores by acid treatment are well known, and can be used in the inven~i~n.
The soluble cationic polymer is forme~ by the polymerisation of cationlc ethylenically unsaturated monomer, optionally with other ethylenically unsaturated monomers. The monomer or monomer blend will normally be water soluble. One sultable class of cationic monomers are the dialkylaminoalkyl ~meth) acrylates, especially dimethylaminoethyl (meth) acrylate (DMAEA or DMAEMA~.
Another suitable class are the dialkylaminoalkyl (meth) acrylamides. A suitable material is dimethylaminopropyl (meth3 acrylamide. All such monomers are generally present in the ~orm of acid addition or quaternary ~,3:L~a~
ammonium salts. For instance a suitable monomer is methacrylamido propyl trlmethyl ammonium chloride ~MAPTAC). Other sultable cationic monomers lnclude diallyl dialkyl quaternary monomers, especially diallyl dlmethyl ammonium chloride (DADMAC). Preferred cationic polymers are polymers having recurring quaternary ammonium groups. Blends of cationic polymers (e.g., a blend of svnthetic catlonlc with natural or modl~ied natural cationic polymer) can be used.
The polymers can be copolymerised with non-ionic monomers, generally (meth) acrylamide (ACM). Other suitable catlonic polymers are polyethylene imines and epichlorhydrin polyamine reactlon products made in bead torm. We find that homopolymers and other polvmers having a very high catlonic content can be of relatively low molecular weight, for instance having intrinsic ViSCOSlty below 5 dl/g, often ln the range 0.4 to 2 dl/g.
When such polymers are ~ormed from ethylenically unsaturated monomers at least 70 weight percent, and preferably at least 90 weight percen~, o~ the monomers should be cationic, and preferably the polymer is substantially a homopolymer.
Other preferred polymers have medium to high molecular weight and medium cationic content. For in~tance the IV may be from about 3 to about 20 dl/g or higher, generally 3 to 12 dl/g, preterably from 5 to 9 dl/g. Such polymers are best made by copolymerisation ot about 20 to about 75, pre~erably about 25 to about 60, we1ght percent cationic monomer with a non-ionic monomer such as acrylamide. Best results are generally obtained with about 35 to about 55 welght percent cationic monomer, with the balance non-ionic.
Although best results are achieved most easily wheri the cationic polymer is added in the f~rm of water soluble beads all below 300 microns, as discussed below, 11 13~9~6 in some instances the cationic polymer can be added in other ~orms. Thus it can be added ln ~he form of particles that are within the size ranges discussed above ~or beads but which have been made by comminution o~ gel in air or, preferab1y, in an organic liquid ~or lnstance as described in EP 169674. It may be necessary to sieve the particles to give the desired particle range and to exclude oversize particles.
Instead of beiny a synthetic polymer, it can be a naturally occurring polymer (or a modlfied natural polymer) such as Chitosan or catlonlc starch~ but this usually less satisfactory than the use of synthetlc polymers.
When the ore is wholly dry, or is drier than is required in the molst pelleting mixture, it is n~cessary to add water to the ore in order to ~orm the moist mixture and it lS then possible to incorporate the polymer as a solution in thls water. For this purpose the polymer can initially be provided in any suitable physical form. When the polymer is being added as a solution, the aqueous polymer solution may be sprayed on to the ore prior to pelletingO The solution can be made from polymer in the form o~ a concentrated solution, a polymer-in-oil dlspersion or powder. A1ternatively the polymer-in-oil disperslon of the polymer can be added dlrect to the ore. The polymer particles in any such disperslon can be dry or can be swollen gel particles.
Preferablv however the polymer is added ln the form of dry, free flowing powder having substantially all partlc1es below about 300~m, usually in the range about 20 to about 300~m. The particles can be comminuted gel, especially l~ the comminuted gel partlcles had been ~ormed or treated in known manner so as to promote their ~low, but preferably the particles are beads, ~or instance as made by reverse phase bead polymerisati~n.
~ ~3 ~ ~3 0 :~ ~
Reverse phase bead polymerisation is a well known process. Thus an aqueous solution of the chosen monomer or monomer blend is dispersed in water immisci~le llquid, generally ln the absence of an emulsl~ying agent but often in the presence of an amph1path1c polymeric stablllser, the polymerlsatlon is induced in convent1onal manner to provide a suspension of gel part1cles in the non-aqueous llqu1d, the suspension lS then dried by azeotropLc distillation and the particles are separated from the non-aqueous liquid in conventional manner. The desired part1cle size range is controlled in known manner, for instance by the choice of stablliser, emulsi~ying agent ~if present) and, especially, the degree o~ agitation during the ~ormation of the initial suspension of aqueous monomer partlcles in the water immiscible liquld. The beads a;e substantially spherical.
Some reverse phase polymerisation methods lnvolve the use of relat1vely large amounts o~ emulsifiers or other materials that depress sur~ace tension. It is particularly desirable 1n the invention to make the polymer particles in the substantial absence o~ any such material. In particular, it is deslrable that the entire blnder (and also the polymer component of the binder) should have substantially no depressant ef~ect on surface tension. Thus if binder is dissolved with water a~ 20C at 0.075% ~y weight concentration the surface tension of the solution should be above 65, and preferably above 70 dynes/cm. Thus it is pre~erred to avoid the use of amounts o~ surfactant that would depress surface tension significantly and reliance should be placed lnstead on agitation or stabiliser, in known manner, to control bead slze.
Although it might have been expected to be deslrable to use swellable but insoluble particles (in an attempt 13 1 3 1 ~
at matching the properties of hentonite) in fact the use of such polymer as ~he only polymer 1s unsatisfactor~ and soluble polymer must be used.
The failure of the cross-linked polymers, and the artlcle in Mining Engineering October 1984 page 1438, might have indicated that it is necessary ~or the polymer to go into solution and/or to form a viscous phase during mlxing, but results can be 1mproved (or the requ1red polymer dose reduced~ by the presence in the water of certain simple compounds. Many of these are monomeric, usually inorganic, electrolyte that can be shown experimentally to reduce the rate of solution and the viscosity when the polymer is dlssolved into bulk water.
However it appears that some mechanism other than depression of solubllity or viscosity is involved. In practice the water is generally moisture that is present in the ore, remalning from a previous ~lltration stage, and thls water is itself normally a solution of one or more lnorganic electrolytes.
Although this contamlnation appears satls$actory results are improve~ ~urther, and often synergistically, i~ the powdered binder that lS added to the ore includes addltlonal monomeric compound that is usually an inorganic or organic electrolyte but can be a non-electrolyte.
The compound is normally water soluble and inorgan1c and so lS prefera~ly a water solubLe salt o~ an acid.
However salts o~ strong acids (e.g., sodium chloride, sulphate or nitrateJ are less satisfactory than salts of wea~ organic acids or carbonic acid. The strong acid salts may generate corrosive aclds during smelting or firing. Accordingly preferred compounds that are ncorporated as part o~ the binder are orgarlic molecules such as urea, inorganlc water soluble salts o~
carboxyllc, dlcarboxylic and trlcarboxylic acids such as 14 ~31~16 sodium acetate, sodium citrate, sodium oxalate, sodium tartrate, sodium benzoate and sodium stearate, other sodium salts of weak acids such as sodium bicarbonate and sodium carbonate, other miscellaneous sodium salts such as sodium silicate or phosphate, the corresponding ammonium, potassium, calcium or magnesium salts of the preceding salts and calcium oxide. Sodium carbonate, bicarbonate or silicate are generally preferred as they give the best anti-spalling and dry strength results.
An important advantage of the use of beads made by reverse phase bead polymerisation ls that they can readlly be added in very unl~orm and very small amounts to the ore that is to be pelleted, because of the substantially spherical shape o~ the beads. If the binder is to be a blend of the polymer with other material such as any of the compounds dlscussed above then this other material should also be added in a form that is easily flowable on to the ore. Preferahly the compound is incorporated 1n the beads. For instance a salt of a weak acid can be present in the aqueous monomer during polymerisation. Alternatlvely the compound can ~e added separately to the ore or it can be preblended with the polymer beads, but in either instance the compound itsel~ is preferably put lnto a free flowable, ~generally bead, form, by known techniques.
The optimum amount of added salt or other compound can be found by experimentation. For many purposes it is in the range 0 to about 60% by weight based on the blnder (~elow 0.1% and usually below 0.02% based on ore).
In some instances amounts of from about 10 to about 30%
based on soluble polymer are the most cost effective but usually greater amounts, ~or instance 30 to about 100% or even 150~, preferably 50 ~o 90%, based on soluble polymer are pre~erred.
:~3i~0~ ~
The soluble polymer ~in bead or other form), optionally wi.th the added salt or other compound, can be used in combination with other binders. In particular, desplte the fact that cross lin~ed polymers have proved, by themselves, to be unsatisfactory we ~lnd valuable results are achieved if a cross linked, swellable, particulate organic polymer lS included with the soluble polymer. The cross linked polymer must have a small particle size, below lOO~m and often below 50~m. The size can be as small as lS commercially available, e.g., down to lO~m or l~m. The particles are normally introduced as dry powder and preferably this powder is in the form of bead tines separated during the production of coarser particulate swellable polymer as produced by bead polymerisation. The inclusion of the cross lin~ed polymer partlcles can give surprisingly improved dry strength and drop number values and so a blend of so~uble particles and cross lin~ed particles can give an excellent combination of dry strength, wet strength and spalling properties. Also the pellets tend to have improved sur~ace appearance, such as smoothness.
The cross linke~ polymer may be non-ionlc (e.g., polyacrylamide), but when the soluble polymer is ionic lt is pre~erably of the same ionlc type as the soluble polymer and 50 may be ~ormed from the same monomers as are discussed below $or the preparation o~ the soluble polymer. Preferably 20 to loo~ by weight, most preferably 60 to 100% by weight, are ionic. The use of homopolymer, e.g., cross llnked sodium polyacrylate, is very satis~actory. Cross linking may be by any of the conventlonal cross linking agents used in the production o~ swellable or absorbent polymers. Thus it may be by an ionic cross linking agent but is preferably covalent, e.g., methylene bis acrylamlde or other polyethylenically unsaturated monomer. The amount of cross lln~lng agent 16 13~9~16 is generalL~ in the range 20 to 1,000 ppm, preferably 50 to 500 ppm, and must be such that the particles are lnsoluble but highly swellable in water, e.g., having a gel capacity in water above 50, and pre~erably above 200, grams per gram.
The amount of cross linked polymer partlcles may be relatively low, e.g., 10 to 30~ based on soluble polymer, but generally greater amounts, e.g., up to 300% or even 600% based on soluble polymer are pre~erred. Amounts of 0 to 80% often 20 to 50%, based on total binder are suitable. Part1cularly preferred binders consist essentlally of 1 part by welght soluble polymer, 0.3 to 1.5 parts by weight sodium carbonate or other added salt or simple compound, and 0.3 to 5 parts by weight cross lin~ed anionic homopolymer or copolymer, with proportions of about 1:1:1 often belng convenient.
Substantially all the particles of the soluble polymer (and of other binder particles) must be below about 300~m ~or good results, presuma~ly since otherwise the partlcle size is too large to establis~ adequate contact with the very large ~umber of very small lron ore particles. Preferably substantially all the polymer particles are below about 200 a~d preferably below about 150 microns. Although it might be expected to be necessary to have exceedingly small polymer partlcle size, similar to bentonite, this is unnecessary and it is satisfactory for most or all of the par~icles to be above microns. Best results are o~ten achieved when substantially all the polymer particles are in the range 20 to 100 microns bUt a satisfactory fractlon is 100 below about 200~m and at least 50% below about lOO~m.
Good results are achieved at very low soluble polymer additions. The amount, therefore, lS usually below about 0.2% and generally it is below about 0.1~ (by weight based on the total mix). It lS often prefexLed 17 ~3~
for the amount to be below 0.05% by welght, but amounts below 0.01% are usually inadequate except when the soluble polymer is used with significant (e.g., at least 20% by weight) other binder components. the amount of soluble polymer may then sometimes be reduced, e.g., to 0.005~.
The particle size of the ore is generally less than 250 micron.s, usually 90% or 80~ by weight of the particles being less than 50 microns. The ore is preferably an iron ore such as magnetlte, haemetite or taconite, but can be any other mineral ore that needs to be put lnto the form of pellets, ~or instance a zinc ore.
Satisfactory results can be obtained even 1~ the ore is contaminated with clay.
Before adding binder in the form o~ dry polymer, the ore usually already has the desired final moisture content of 5 to 15%, preferably 8 to 10%, by weight based on the weight of iron ore. This moisture content is the moisture as measured by heating up to 105C. However if the ore is too dry then water may be added to it, e.g., be~ore or after the addition of polymer binder (or the binder may be predissolved).
The binder can be blended with the ore in the same manner as bentonlte lS blended, prefera~ly ~y scattering the polymer particles on to the ore as it is carried towards a mixer, for instance a paddle mixer provlded with stators. It may be mixed for the same duration as when bentonite lS used, for instance 2 to 20, generally about 10, minutes.
The damp blend of ore and polymer is converted to pellets in conventional manner, for instance by balling in conventional manner. This may be effected using a rotating tilting disc but generally is condueted in a balling drum. The size of the pellets is generally from 35 5 to 16 mm, preferabLy 8 to 12 mm.
18 ~3~901~
Be~ore the resultant green pellets can be ukilised for the production of metal they need to be fired, generally at a temperature up to above 1000C, for instance up to 1200C. For this purpose they can be introduced into a kiln or other firing apparatus and fired in conventlonal manner. It is deslrable to be able to lntroduce them into thls ~urnace at the highest possible inlet temperature with the minimum risk o~
spalling. The inlet temperature at which spalling becomes signl~lcant can be referred to as the spalling temperature and a particular advantage of the inventlon is that it lS possible to make pellets having a spalling temperature higher than can conveniently be obtained by the use of bentonite and other known binders.
Good results can be achieved while using easy application techniques and low amounts o~ polymer. It lS easy to make pellets which have satisfactorlly high wet strength and dry strength (measured after drying in an oven) and a satisfactorily high drop number when wet (lndlcating the number o~ drops before they shatter).
In particular it lS possible to obtain excellent spalling properties, often much better than are obtalnable with bentonite.
In a second aspect of the invention, a modification lS provided in the process described in EP2~5171 for the treatment of conventlonal ores, especially lron ores, e.g., those giving a pH above 8. Although optimum results are more easily obtained, with or without added sodium carbonate or other inorganic salt, when using a soluble anionic polymer having intrinsic viscosity of about 3 to about 16, as in that U.S. patent, it has now been found that it is possible to obtain useful pelletising with other anionic pol~mers under particular clrcumstances.
19 ~319~g In particular, the inventlon also includes a process in which organic polymer lS added to conventional particulate iron or other ore having substantially all particles below 250~m and stirring in the presence of 5 to 15% by weight water (based on total mix) to form a substantially homogeneous moist mixture and pelletising the moist mixture, the process being characterised in that the binder comprlses up to 0.2% by weight, based on total mix, of water soluble synthetic polymer that has intrinslc VlSCoSity above about 17dl/g and -that is an anionic polymer of one or more water soluble ethylenically unsaturated monomers comprlsing an anionic monomer and the binder also comprises about lO to about lSO~, based on total binder, o~ added salt or other monomeric compound as discussed above. Although the high IV anionic monomers cannot be used alone, adequate results are obtainable when blended with such salt or other monomerlc compound, for instance ln proportions by weight 2:1 to 1:2. The very high molecular weight polymer is introduced ln the form of fine powder which can be beads or crushed gel. The particle sizes and other characterisitcs of the anionlc polymer, suitable inorganic matexials and cross linked polymes and other additives may all be as described above for the cationic binders.
In a third aspect of the invention, that is applicable to all types of ores, the b1nder comprises about 0.005~ to 0.5~ by weight, based on total mix, of a water soluble synthetlc polymer that is added to the ore as dry, free flowing, beads that are substantlally all above 20~m and below 300~m and that are made by reverse phase bead polymerisation from water soluble ethylenically unsaturated monomer or monomer blend.
The polymer of the beads pre~erably is not anionic polymer of intrinsic viscosity 3 to 16. Thus it may be 20 ~319~6 anionic below 3 and preferably below 2, anionic above 16 and preferably above 17, nonionic or cationic. The bead polymer may be mixed with othex polymer particles and/or add salts, for instance as described above.
In examples 1 and 2 below the binders were each scattered on to acidic moist partlculate haematite iron ore at an appropriate dosage. The molsture content was 8.3~. The blend was then converted to pellets ln a balling drum, the pellets having a size typically of about 5-16mm.
The following synthetic cationic polymeric binders were used. They were made by reverse phase polymerisation to a bead size below 200~m and the beads were dried and separated.
Polymer A : copolymer o~ 40% methyl chloride quaternised dimethylaminoethyl acrylate (MeCl.q DMAEA) 60% acrylamide (ACM) IV ~ 7-B dlg 1 Polymer B : copolymer of 50~ MAPTAC with 50~ ACM
IV =-6.9 dlg 1 Polymer C : 100% PolyMAPTAC
IV = 1.3 dlg Polymer D : copolymer o~ 60~ MeCl q DMAEA with 40% ACM
IV ~ 6-7 dlg Polymer E : copoLymer of 80~ MeCl q DMAEA with 20% ACM
IV ~ 8-9 dlg Polymer F : 100% Poly-diallyldimethyl ammonium chloride solid grade IV = 0.7 dlg 1 Example 1 An ore ~rom the Wabush mine was dried, giving a pH
o~ ~.2, and was blended whlle moist with the blnder.
The wet strength, dry strength, drop number and spalling 21 ~31~
temperatures were recorded, as shown in Tables 1 and 2 below.
Table 1 Dose Wet Dry Drop 5% w/w Stren~th/k~ Strength/k~ Nm~er Mbisture Blank - 0.56 0.59 7.9 8.0 Bentonite 0.7 1.17 8.20 18.5 10.0 Peridur0.04 0.56 0.14 9.2 8.7 Polymer A 0.04 0.92 1.24 22.7 8.8 10 Polymer B 0.04 0.72 1.82 19.2 9.4 Polymer C 0.1 0.86 3.31 8.2 8.2 Table 2 % Spalled 700~C 850C 1000C
Blank 0 70 100 Bentonite 40 50 100 Peridur - 100 Polymer A - 0 80 20 Polymer B - 10 100 Polymer C 0 0 70 Example 2 An acid leached iron ore having pH about 5 was used and the following results were obtained.
Table 3 Dose Wet Dry Drop %
% w~w Strength/kg Strength/k~ Number oisture Polymer A 0.04 0.49 1.61 8.2 8.9 B0.04 0.50 2.15 16.9 9.1 D0.04 0.58 2.11 6.8 8.0 E0.04 0.51 1.94 5.4 7.8 F0.1 0.48 3.50 4.2 7.9 22 1 31 9 ~1 ~
Spalling was tested for all binders a-t 850C and for binders B, E and F at 1000C. No spalling occurred.
Example 3 A gel polymer o$ 60% acrylamide 40% sodium acrylate having intrinslc viscosity 23.9dl/g was dried and comminuted in conventional manner to a particle size of around lOO~m and is blended with an equal amount by weight of sodium carbonate particles. Thls binder was blended with iron ore glving a conventional alkaline pH, at a dosage of 0.04%. The spalling properties o$ the anionic synthetic polymer binder system at 1,000C were excellent relative to the other systems and the other properties were satls$actory, although the molsture content was slightly hlgner than with the other systems.
Allied Colloids I,imited 60/2669/02 Ore Pelletlsation Iron ore needs to be in the form of agglomerates of substantial size when it is charged into a blast furnace.
If the available ore is in the form of particles that are too small for direct feed to the blast furnace it is necessary to convert them to a sinter or to pellets.
With the increasing use of lower grade ores it has become necessary to grind the ore more finely and, for these fine particles, pelletisation is the only satisfactory method of production of feedstock for the furnaces.
The pellets are made by adding binder to the fine particulate ore and stirring in the presence of a small amount of water (generally moisture in the ore) to form a moist mixture, and then pelletising the mixture, e.g., in a balling drum or disc pelletisPr. The green pellets are then fired in a kiln through a temperature range that extends from an inlet temperature typically in the range 200-400C up to a final temperature of e.g., 1~00C.
Important properties of the pellets are the initial or wet strength, the dry strength (after drying the green pellets in an oven at 105C) and the tendenc~ of ~he pellets to spall (or burst) upon exposure to firing temperatures. The tendency for spalling can be defined ~5 by determining the minimum temperature at which spalling occurs or by observing the percentage of fines formed during a particular firing cycle. The moisture content of the mixture and the porosity of the pellets must be chosen carefully. A high "drop number" for the green pellets is desirable. For cost reasons the amount of binder should be as low as possible and, to ensure uniform properties, its flow propertiPs must be such that it can easily be added uniformly in these low quantities.
Although many binders have been proposed in the literature, (e.g., bentonite and other clays, ferrous 13~9~6 sulphate, lignin sulphate, asphalt, starches, calcium and sodium compounds, and certain polymers) in practice , bentoni~e is the binder t~a~ is ge~rally used.
i~f n~blis ~d ~ J~ lql~
In GB 1,324,838~ work ~as desc~ibed that was ~5 conducted in or before 1970, more than 15 years ago.
Thls used, as binder, a water soluble linear organic polymer having a molecular weight of 1 million to 20 milllon. Suitable polymers were modified natural polymers such as starch and sodium carboxymethyl cellulose and various non-ionic, anionlc or cationic synthetic polymers. The process lnvolved forming a solutlon of the polymer and spraying the solution on to the particulate lron ore. The patent noted that the sprayed solutlon was viscous and that this could b~ a problem, but that the viscosity could be reduced by lncluding sodium chlorlde, sodium sulphate or potassium chloride in the water used for making the solution.
Although dlrect comparisons o~ the polymers in GB
1,324,838 lS di~icult it appears ~rom the patent that various non-ionic, anionlc and cationic polymers can be used to give improved green strength and/or spalling properties compared to bentonite, at very much lower dosages than bentonite. For instance a straight chain polyethylene oxide was reported as giving improved strength and spalllng values and a cationic copolymer and a polymer formed ~rom about 8~ sodium methacrylate and 92~ acrylamide were reported as giving improved strength values.
A disadvantage of the process in GB 1,324,838 is that it is necessary to introduce substantial amounts of water with the polymer and so the initial iron ore must be very dry (involving the use of drying energy) or the final pellets will be very wet ~increasing the risk of spalling).
3 ~3~90~
In Aus.I.M.M. Newcastle Pellets and Granules Symposium October 1974 pages 151 to 156 R.L.Smythe describes what appears to be the same work as is discussed in thls patent. It describes the problems that had been incurred with converting dry powder polymer into the polymer solution that could be sprayed on to iron ore. The article proposed the use of polymer supplied as a 35% solution (necessarlly therefore involving bulk handling problems) and the use of polymer supplied as a liquid suspension, that presumably was converted to an aqueous solution before use. The article warned about handling problems of the resultant pellets and the risk of blockage of chutes and referred to the study of alternatlve polymers, namely "natural polymers and derivatives of petroleum products".
Desplte all this work in the early 1970's an authoritative review of iron ore pelletisation by G.K.Jones in Industrial Minerals March 1979 pages 61 to 73 mentlons, as binders, only Portland cement, lime and bentonlte, and emphasises the large amount of bentonite that is used and predicts that it will continue to be used despite the shortages o~ bentonite.
Despite the acceptance by Jones, and the whole industry, that bentonite would continue to be the most widely used blnder it has, for very many years, been recognised to incur varlous problems~ Thus some grades o~ bentonite give satls~actory pellet propertles but others are less satisfactory. A prGblem with all grades of bentonlte is that the bentonlte lS not combustible and so contr1butes to the gangue ln the furnace, and thls gangue tends to be corrosive to the lining o~ the furnace. Another problem with bentonite is that the optimum grades are becoming less avallable. Bentonite must be present in the pellets in quite large amounts, thus reducing the iron content of the pellet ~319~
significantly and increasing the amount of gangue. Lime and some inorganic salts have been proposed as alternatives to bentonite, but again they cause the ~ormation of unwanted gangue and can be less satlsfactory than bentonite. The added gangue constituents require increased energy consumptlon ln the furnace.
A problem with bentonite and other hindars lS that the spalling temperature is low. Typlcally the inlet temperature of the kiln has to be ln the range 200 to 400C to prevent spalling. Higher inlet temperatures would be economically desixable if spalling could still be avoided~
ln Mlning Engineering October 1984 pages 1437 to 1441 de Souza et al reported that organic binders would have the inherent advantage, over inorganlc binders, of being eliminated during ~lring. Results were reported on the use of polymers based on cellulose, in partlcular the material sold under the tracle ~ k Perldur and which ~``.1~
is believed to be carboxymethyl cellulose. The article reported adding Peridur powder to an aqueous pulp of iron ore before ~iltration and also reported adding the powder manually to the ore flow. The article noted the need ~or water soluble polymers to be hydrated and dissolved during mixing and pelletising. Spalling at 250C was reported, but this is unsatis~actorily low.
A difficulty with powdered cellulosic blnders such as carboxymethyl cellulose lS that the irregular partlcle shape and size dlstribution is such that the powder does not flow ~reely. Instead the dry particles tend to clump together rather than flow over one another. As a result it is difficult to achieve uniform supply o~ the low dosages that are required. Another problem is that the amount o~ cellulosic binder that has to be used for adequate strength tends to be too high to be cost e~ective. Another problem with some cellulosic 1319~
polymers is that they can reduce surface tension, and this appears to be undesirable in pellet formation.
In practice the use of cellulosic binders has not been widely adopted, presumably because of these or other problems. At present therefore there is very little use of organic binders and bentonite is still very widely used, despite the long-recognised disadvantages and decreasing availability of suitable grades of bentonite and despite the long-established possibility of using organic binder.
In EP 0203855A2 published in 3 December 1986 it is proposed to use a water soluble high molecular weight polymer in the form of a dry powder or, preferably, a water-in-oil emulsion that preferably contains both water-in-oil and oil-in-water surfactants. Non-ionic, anionic and cakionic polymers are proposed. The use of the polymer in combination, with an inorganic salt, to increase strength, is also proposed.
Spalling properties are not discussed in a manner that allows judgement as to whether these polymers could give impro~ed spalling properties compared to the spalling properties of bentonite.
The only dry powders that are specifically proposed in EP 0203855A2 are Rhone Poulenc AD10 which is said to be a non-ionic polyacrylamide having intrinsic viscosity (IV) 15.4dl/g and which we beliave to be a coarse crushed gel product, and Percol*725 and Percol*726, both of which are made by the assignees of the present application. Percol*
725 is a crushed gel copolymer having IV about. 18 of 80%
acrylamide and 20% by weight sodium acrylate and Percol 726 is a bead copolymer of about 65% acrylamide and 35% by weight sodium acrylate and has IV about 17. In particular the bead form of Percol 726 is made by reverse phase polymerisation and a signi~icant amount of * Trademark 13190~6 the particles have a dry sl~e above 450~m and up to about 800~m, and the crushed gel of Percol 725 also has a particle size ot up to about 800~m.
When considering possible binders that might be used there are several critical factors that have to be recognised. The iron ore always has a very small particle size, and therefore a huge surface area. The binder must be lntroduced with the absolute minimum of water in order that the pellets can conveniently have a total moisture content of not more than about 15~. The duration and energy of mixin~ the binder with the iron ore particles must be as short as possible in order to maximise production and minimlse capital costs. The amount of binder must be as low as possible in order to minimise cost and to avoid the risk of excess binder accentuating the stlckiness problems noted in the article by R.L.Smythe.
Bentonite has a very small particle slze (typically below lO~m) and adequate admixture of these very small particles with the partlculate iron ore is acnieved because the bentonite is used ln a relatively large amount (typically 1~). However it would be expected that the use of a blnder that is substantially coarser and/or present in a substantlally smaller amount would tend to give less satis~actory results, due to non-uniform mixing o~ the binder with the relatively large volume of very fine particulate iron ore.
The use of cellulosic binders or the powder or emulsion binders proposed in EP 020385~A~ lS inconvenient from the point of vie~ of application methods that give reasonable results. ~lso the results are, at best, generally no better than those obtainable with bentonite, and they are often worse. It has been our object to improve application methods and/or obtain better results.
7 13~9~
In the methods of the invent.ion mineral ore pel:lets are made by adding binder comprisiny organic polymer to particulate mineral ore having substantially all particles below 250~m and stirring in the presence of about 5 to about 15% by weight water (based on total mixture) to form a substantially homogeneous moist mixture and pelletising the moist mixture.
Canadian Patent Application No. 523996 claims a process in which iron ore pellets are made by adding binder comprising organic polymer to particulate iron ore having substantially all particles below 250~m and stirring in the pres~nce of 5 to 15% by weight (based on total mix) to form a substantially homogeneous moist mixture and pelletising the moist mi~ture, and the process is characterised in that the binder comprises up to 0.2% by weight, based on total mix, of a water soluble synthetic polymer that has intrinsic viscosity 3 to 16dl/g and that is an anionic polymer of one or more water soluble ethylenically unsaturated monomers comprising an anionic monomer and that is added to the iron ore as a dry, free ~lowing, powder having substantially all particlles above 20~m and below 300~m.
Although that process is very successful for pelletising conYentional iron ores it has been found that less satisfactory results are obtained with some unusual ores, for instance one particular of haematite iron ore in Canada. It has been as~ertained that this particular ore as supplied is acidic, in that has a much lower pH than normal pelleting ores.
In the invention pellets are made from mineral ore by adding binder comprising organic polymer to acidic particulate mineral ore having suhstantially all particles below 250~m and stirring in the presence of 5 to 15% by weight water (based on total mix) to form a h~
8 ~31~0~ 6 substantially homogeneous moist mixture and pelletising the moist mixture, and in this process the binder comprises about 0.02~ to about 0.5~ by weight, based on total mlx, of water soluble polymer that is cationic.
When a small amount, e.g., 2 to 10% by weight, of partlculate ore is slurried with water the pH of the resultant water may depend upon the amount of ore that is used but at higher amounts of ore, typically 30 to 40%
solids, the pH becomes substantially independent o~ the amount o~ ore. It is this pH, that lS substantially independent o~ ore concentration, whlch lS intended herein when re~erence is made to the ore glving a speci~led pH. Normal ores give a pH of above 8.1, typically 8.2 to 8.4 or higher. The invention is of part1cular value when the ore lS acidic and thus gives a pH in this test o~ below 7, and often below 6.
By the lnvention it is possible to obtain very good pelletlsing results even at very low pH values. Th1s lS
in marked contrast to existing systems, and especially systems us-ing bentonlte, where reasonable results are sometimes obtainable at p~ values 7 to 8 but the results at lower pH values, for instance 6.~ to 4 or even down to 3, are totally 1nadequate in most instances. Thus the lnvention permits, ~or the first time, satis~actory pelletising of acidic, and often highly acidic, ores.
The mineral can be any acidic ore, e.g., a zinc ore, but is preferably an iron ore, normally a haematite, magnetite or tachonlte. The ore may be naturally acidic or may have been rendered acidic by some treatment prior to blending with the binder. For 1nstance the ore may have been washed with acid to remove acid soluble components, typlcally to produce a pH o~ ~rom 5 to 6 if manganese is being washed out o~ the ore.
The ore may have acquired an acidic pH during other processing treatments. For instance the ore may be 9 131~
dried under conditions that xesult in the dry ore ~iving the speclfied relatively low pH in water. This may be because, for instance, the drying is conducted using hot gases that contain sulphur or other impurities that cause acidification of the ore during drying or may be due to chemical changes in the surface properties of the ore that are caused by dehydration.
As a result of the invention it is possible, for the first tlme, to use for pelletising ores that hitherto would have been rejected, either because of their acidity or because of their low grade. The reason why lt lS now possible to use low grade ores for pelletising is because a preferred process of the invention comprlses forming acidlc particulate ore from the mineral ore (that can be of low grade) by a process comprising washing or leach`ng the mineral ore ln acid, and thereafter using the resultant, enrlched, acidic partlculat~ ore for pelletisln~. It has not previously been practicable to use acld washed or acid leached ores for pelletising.
The ore that is acid washed or leached is normally an iron ore.
Numerous methods of purifylng or enriching mineral ores by acid treatment are well known, and can be used in the inven~i~n.
The soluble cationic polymer is forme~ by the polymerisation of cationlc ethylenically unsaturated monomer, optionally with other ethylenically unsaturated monomers. The monomer or monomer blend will normally be water soluble. One sultable class of cationic monomers are the dialkylaminoalkyl ~meth) acrylates, especially dimethylaminoethyl (meth) acrylate (DMAEA or DMAEMA~.
Another suitable class are the dialkylaminoalkyl (meth) acrylamides. A suitable material is dimethylaminopropyl (meth3 acrylamide. All such monomers are generally present in the ~orm of acid addition or quaternary ~,3:L~a~
ammonium salts. For instance a suitable monomer is methacrylamido propyl trlmethyl ammonium chloride ~MAPTAC). Other sultable cationic monomers lnclude diallyl dialkyl quaternary monomers, especially diallyl dlmethyl ammonium chloride (DADMAC). Preferred cationic polymers are polymers having recurring quaternary ammonium groups. Blends of cationic polymers (e.g., a blend of svnthetic catlonlc with natural or modl~ied natural cationic polymer) can be used.
The polymers can be copolymerised with non-ionic monomers, generally (meth) acrylamide (ACM). Other suitable catlonic polymers are polyethylene imines and epichlorhydrin polyamine reactlon products made in bead torm. We find that homopolymers and other polvmers having a very high catlonic content can be of relatively low molecular weight, for instance having intrinsic ViSCOSlty below 5 dl/g, often ln the range 0.4 to 2 dl/g.
When such polymers are ~ormed from ethylenically unsaturated monomers at least 70 weight percent, and preferably at least 90 weight percen~, o~ the monomers should be cationic, and preferably the polymer is substantially a homopolymer.
Other preferred polymers have medium to high molecular weight and medium cationic content. For in~tance the IV may be from about 3 to about 20 dl/g or higher, generally 3 to 12 dl/g, preterably from 5 to 9 dl/g. Such polymers are best made by copolymerisation ot about 20 to about 75, pre~erably about 25 to about 60, we1ght percent cationic monomer with a non-ionic monomer such as acrylamide. Best results are generally obtained with about 35 to about 55 welght percent cationic monomer, with the balance non-ionic.
Although best results are achieved most easily wheri the cationic polymer is added in the f~rm of water soluble beads all below 300 microns, as discussed below, 11 13~9~6 in some instances the cationic polymer can be added in other ~orms. Thus it can be added ln ~he form of particles that are within the size ranges discussed above ~or beads but which have been made by comminution o~ gel in air or, preferab1y, in an organic liquid ~or lnstance as described in EP 169674. It may be necessary to sieve the particles to give the desired particle range and to exclude oversize particles.
Instead of beiny a synthetic polymer, it can be a naturally occurring polymer (or a modlfied natural polymer) such as Chitosan or catlonlc starch~ but this usually less satisfactory than the use of synthetlc polymers.
When the ore is wholly dry, or is drier than is required in the molst pelleting mixture, it is n~cessary to add water to the ore in order to ~orm the moist mixture and it lS then possible to incorporate the polymer as a solution in thls water. For this purpose the polymer can initially be provided in any suitable physical form. When the polymer is being added as a solution, the aqueous polymer solution may be sprayed on to the ore prior to pelletingO The solution can be made from polymer in the form o~ a concentrated solution, a polymer-in-oil dlspersion or powder. A1ternatively the polymer-in-oil disperslon of the polymer can be added dlrect to the ore. The polymer particles in any such disperslon can be dry or can be swollen gel particles.
Preferablv however the polymer is added ln the form of dry, free flowing powder having substantially all partlc1es below about 300~m, usually in the range about 20 to about 300~m. The particles can be comminuted gel, especially l~ the comminuted gel partlcles had been ~ormed or treated in known manner so as to promote their ~low, but preferably the particles are beads, ~or instance as made by reverse phase bead polymerisati~n.
~ ~3 ~ ~3 0 :~ ~
Reverse phase bead polymerisation is a well known process. Thus an aqueous solution of the chosen monomer or monomer blend is dispersed in water immisci~le llquid, generally ln the absence of an emulsl~ying agent but often in the presence of an amph1path1c polymeric stablllser, the polymerlsatlon is induced in convent1onal manner to provide a suspension of gel part1cles in the non-aqueous llqu1d, the suspension lS then dried by azeotropLc distillation and the particles are separated from the non-aqueous liquid in conventional manner. The desired part1cle size range is controlled in known manner, for instance by the choice of stablliser, emulsi~ying agent ~if present) and, especially, the degree o~ agitation during the ~ormation of the initial suspension of aqueous monomer partlcles in the water immiscible liquld. The beads a;e substantially spherical.
Some reverse phase polymerisation methods lnvolve the use of relat1vely large amounts o~ emulsifiers or other materials that depress sur~ace tension. It is particularly desirable 1n the invention to make the polymer particles in the substantial absence o~ any such material. In particular, it is deslrable that the entire blnder (and also the polymer component of the binder) should have substantially no depressant ef~ect on surface tension. Thus if binder is dissolved with water a~ 20C at 0.075% ~y weight concentration the surface tension of the solution should be above 65, and preferably above 70 dynes/cm. Thus it is pre~erred to avoid the use of amounts o~ surfactant that would depress surface tension significantly and reliance should be placed lnstead on agitation or stabiliser, in known manner, to control bead slze.
Although it might have been expected to be deslrable to use swellable but insoluble particles (in an attempt 13 1 3 1 ~
at matching the properties of hentonite) in fact the use of such polymer as ~he only polymer 1s unsatisfactor~ and soluble polymer must be used.
The failure of the cross-linked polymers, and the artlcle in Mining Engineering October 1984 page 1438, might have indicated that it is necessary ~or the polymer to go into solution and/or to form a viscous phase during mlxing, but results can be 1mproved (or the requ1red polymer dose reduced~ by the presence in the water of certain simple compounds. Many of these are monomeric, usually inorganic, electrolyte that can be shown experimentally to reduce the rate of solution and the viscosity when the polymer is dlssolved into bulk water.
However it appears that some mechanism other than depression of solubllity or viscosity is involved. In practice the water is generally moisture that is present in the ore, remalning from a previous ~lltration stage, and thls water is itself normally a solution of one or more lnorganic electrolytes.
Although this contamlnation appears satls$actory results are improve~ ~urther, and often synergistically, i~ the powdered binder that lS added to the ore includes addltlonal monomeric compound that is usually an inorganic or organic electrolyte but can be a non-electrolyte.
The compound is normally water soluble and inorgan1c and so lS prefera~ly a water solubLe salt o~ an acid.
However salts o~ strong acids (e.g., sodium chloride, sulphate or nitrateJ are less satisfactory than salts of wea~ organic acids or carbonic acid. The strong acid salts may generate corrosive aclds during smelting or firing. Accordingly preferred compounds that are ncorporated as part o~ the binder are orgarlic molecules such as urea, inorganlc water soluble salts o~
carboxyllc, dlcarboxylic and trlcarboxylic acids such as 14 ~31~16 sodium acetate, sodium citrate, sodium oxalate, sodium tartrate, sodium benzoate and sodium stearate, other sodium salts of weak acids such as sodium bicarbonate and sodium carbonate, other miscellaneous sodium salts such as sodium silicate or phosphate, the corresponding ammonium, potassium, calcium or magnesium salts of the preceding salts and calcium oxide. Sodium carbonate, bicarbonate or silicate are generally preferred as they give the best anti-spalling and dry strength results.
An important advantage of the use of beads made by reverse phase bead polymerisation ls that they can readlly be added in very unl~orm and very small amounts to the ore that is to be pelleted, because of the substantially spherical shape o~ the beads. If the binder is to be a blend of the polymer with other material such as any of the compounds dlscussed above then this other material should also be added in a form that is easily flowable on to the ore. Preferahly the compound is incorporated 1n the beads. For instance a salt of a weak acid can be present in the aqueous monomer during polymerisation. Alternatlvely the compound can ~e added separately to the ore or it can be preblended with the polymer beads, but in either instance the compound itsel~ is preferably put lnto a free flowable, ~generally bead, form, by known techniques.
The optimum amount of added salt or other compound can be found by experimentation. For many purposes it is in the range 0 to about 60% by weight based on the blnder (~elow 0.1% and usually below 0.02% based on ore).
In some instances amounts of from about 10 to about 30%
based on soluble polymer are the most cost effective but usually greater amounts, ~or instance 30 to about 100% or even 150~, preferably 50 ~o 90%, based on soluble polymer are pre~erred.
:~3i~0~ ~
The soluble polymer ~in bead or other form), optionally wi.th the added salt or other compound, can be used in combination with other binders. In particular, desplte the fact that cross lin~ed polymers have proved, by themselves, to be unsatisfactory we ~lnd valuable results are achieved if a cross linked, swellable, particulate organic polymer lS included with the soluble polymer. The cross linked polymer must have a small particle size, below lOO~m and often below 50~m. The size can be as small as lS commercially available, e.g., down to lO~m or l~m. The particles are normally introduced as dry powder and preferably this powder is in the form of bead tines separated during the production of coarser particulate swellable polymer as produced by bead polymerisation. The inclusion of the cross lin~ed polymer partlcles can give surprisingly improved dry strength and drop number values and so a blend of so~uble particles and cross lin~ed particles can give an excellent combination of dry strength, wet strength and spalling properties. Also the pellets tend to have improved sur~ace appearance, such as smoothness.
The cross linke~ polymer may be non-ionlc (e.g., polyacrylamide), but when the soluble polymer is ionic lt is pre~erably of the same ionlc type as the soluble polymer and 50 may be ~ormed from the same monomers as are discussed below $or the preparation o~ the soluble polymer. Preferably 20 to loo~ by weight, most preferably 60 to 100% by weight, are ionic. The use of homopolymer, e.g., cross llnked sodium polyacrylate, is very satis~actory. Cross linking may be by any of the conventlonal cross linking agents used in the production o~ swellable or absorbent polymers. Thus it may be by an ionic cross linking agent but is preferably covalent, e.g., methylene bis acrylamlde or other polyethylenically unsaturated monomer. The amount of cross lln~lng agent 16 13~9~16 is generalL~ in the range 20 to 1,000 ppm, preferably 50 to 500 ppm, and must be such that the particles are lnsoluble but highly swellable in water, e.g., having a gel capacity in water above 50, and pre~erably above 200, grams per gram.
The amount of cross linked polymer partlcles may be relatively low, e.g., 10 to 30~ based on soluble polymer, but generally greater amounts, e.g., up to 300% or even 600% based on soluble polymer are pre~erred. Amounts of 0 to 80% often 20 to 50%, based on total binder are suitable. Part1cularly preferred binders consist essentlally of 1 part by welght soluble polymer, 0.3 to 1.5 parts by weight sodium carbonate or other added salt or simple compound, and 0.3 to 5 parts by weight cross lin~ed anionic homopolymer or copolymer, with proportions of about 1:1:1 often belng convenient.
Substantially all the particles of the soluble polymer (and of other binder particles) must be below about 300~m ~or good results, presuma~ly since otherwise the partlcle size is too large to establis~ adequate contact with the very large ~umber of very small lron ore particles. Preferably substantially all the polymer particles are below about 200 a~d preferably below about 150 microns. Although it might be expected to be necessary to have exceedingly small polymer partlcle size, similar to bentonite, this is unnecessary and it is satisfactory for most or all of the par~icles to be above microns. Best results are o~ten achieved when substantially all the polymer particles are in the range 20 to 100 microns bUt a satisfactory fractlon is 100 below about 200~m and at least 50% below about lOO~m.
Good results are achieved at very low soluble polymer additions. The amount, therefore, lS usually below about 0.2% and generally it is below about 0.1~ (by weight based on the total mix). It lS often prefexLed 17 ~3~
for the amount to be below 0.05% by welght, but amounts below 0.01% are usually inadequate except when the soluble polymer is used with significant (e.g., at least 20% by weight) other binder components. the amount of soluble polymer may then sometimes be reduced, e.g., to 0.005~.
The particle size of the ore is generally less than 250 micron.s, usually 90% or 80~ by weight of the particles being less than 50 microns. The ore is preferably an iron ore such as magnetlte, haemetite or taconite, but can be any other mineral ore that needs to be put lnto the form of pellets, ~or instance a zinc ore.
Satisfactory results can be obtained even 1~ the ore is contaminated with clay.
Before adding binder in the form o~ dry polymer, the ore usually already has the desired final moisture content of 5 to 15%, preferably 8 to 10%, by weight based on the weight of iron ore. This moisture content is the moisture as measured by heating up to 105C. However if the ore is too dry then water may be added to it, e.g., be~ore or after the addition of polymer binder (or the binder may be predissolved).
The binder can be blended with the ore in the same manner as bentonlte lS blended, prefera~ly ~y scattering the polymer particles on to the ore as it is carried towards a mixer, for instance a paddle mixer provlded with stators. It may be mixed for the same duration as when bentonite lS used, for instance 2 to 20, generally about 10, minutes.
The damp blend of ore and polymer is converted to pellets in conventional manner, for instance by balling in conventional manner. This may be effected using a rotating tilting disc but generally is condueted in a balling drum. The size of the pellets is generally from 35 5 to 16 mm, preferabLy 8 to 12 mm.
18 ~3~901~
Be~ore the resultant green pellets can be ukilised for the production of metal they need to be fired, generally at a temperature up to above 1000C, for instance up to 1200C. For this purpose they can be introduced into a kiln or other firing apparatus and fired in conventlonal manner. It is deslrable to be able to lntroduce them into thls ~urnace at the highest possible inlet temperature with the minimum risk o~
spalling. The inlet temperature at which spalling becomes signl~lcant can be referred to as the spalling temperature and a particular advantage of the inventlon is that it lS possible to make pellets having a spalling temperature higher than can conveniently be obtained by the use of bentonite and other known binders.
Good results can be achieved while using easy application techniques and low amounts o~ polymer. It lS easy to make pellets which have satisfactorlly high wet strength and dry strength (measured after drying in an oven) and a satisfactorily high drop number when wet (lndlcating the number o~ drops before they shatter).
In particular it lS possible to obtain excellent spalling properties, often much better than are obtalnable with bentonite.
In a second aspect of the invention, a modification lS provided in the process described in EP2~5171 for the treatment of conventlonal ores, especially lron ores, e.g., those giving a pH above 8. Although optimum results are more easily obtained, with or without added sodium carbonate or other inorganic salt, when using a soluble anionic polymer having intrinsic viscosity of about 3 to about 16, as in that U.S. patent, it has now been found that it is possible to obtain useful pelletising with other anionic pol~mers under particular clrcumstances.
19 ~319~g In particular, the inventlon also includes a process in which organic polymer lS added to conventional particulate iron or other ore having substantially all particles below 250~m and stirring in the presence of 5 to 15% by weight water (based on total mix) to form a substantially homogeneous moist mixture and pelletising the moist mixture, the process being characterised in that the binder comprlses up to 0.2% by weight, based on total mix, of water soluble synthetic polymer that has intrinslc VlSCoSity above about 17dl/g and -that is an anionic polymer of one or more water soluble ethylenically unsaturated monomers comprlsing an anionic monomer and the binder also comprises about lO to about lSO~, based on total binder, o~ added salt or other monomeric compound as discussed above. Although the high IV anionic monomers cannot be used alone, adequate results are obtainable when blended with such salt or other monomerlc compound, for instance ln proportions by weight 2:1 to 1:2. The very high molecular weight polymer is introduced ln the form of fine powder which can be beads or crushed gel. The particle sizes and other characterisitcs of the anionlc polymer, suitable inorganic matexials and cross linked polymes and other additives may all be as described above for the cationic binders.
In a third aspect of the invention, that is applicable to all types of ores, the b1nder comprises about 0.005~ to 0.5~ by weight, based on total mix, of a water soluble synthetlc polymer that is added to the ore as dry, free flowing, beads that are substantlally all above 20~m and below 300~m and that are made by reverse phase bead polymerisation from water soluble ethylenically unsaturated monomer or monomer blend.
The polymer of the beads pre~erably is not anionic polymer of intrinsic viscosity 3 to 16. Thus it may be 20 ~319~6 anionic below 3 and preferably below 2, anionic above 16 and preferably above 17, nonionic or cationic. The bead polymer may be mixed with othex polymer particles and/or add salts, for instance as described above.
In examples 1 and 2 below the binders were each scattered on to acidic moist partlculate haematite iron ore at an appropriate dosage. The molsture content was 8.3~. The blend was then converted to pellets ln a balling drum, the pellets having a size typically of about 5-16mm.
The following synthetic cationic polymeric binders were used. They were made by reverse phase polymerisation to a bead size below 200~m and the beads were dried and separated.
Polymer A : copolymer o~ 40% methyl chloride quaternised dimethylaminoethyl acrylate (MeCl.q DMAEA) 60% acrylamide (ACM) IV ~ 7-B dlg 1 Polymer B : copolymer of 50~ MAPTAC with 50~ ACM
IV =-6.9 dlg 1 Polymer C : 100% PolyMAPTAC
IV = 1.3 dlg Polymer D : copolymer o~ 60~ MeCl q DMAEA with 40% ACM
IV ~ 6-7 dlg Polymer E : copoLymer of 80~ MeCl q DMAEA with 20% ACM
IV ~ 8-9 dlg Polymer F : 100% Poly-diallyldimethyl ammonium chloride solid grade IV = 0.7 dlg 1 Example 1 An ore ~rom the Wabush mine was dried, giving a pH
o~ ~.2, and was blended whlle moist with the blnder.
The wet strength, dry strength, drop number and spalling 21 ~31~
temperatures were recorded, as shown in Tables 1 and 2 below.
Table 1 Dose Wet Dry Drop 5% w/w Stren~th/k~ Strength/k~ Nm~er Mbisture Blank - 0.56 0.59 7.9 8.0 Bentonite 0.7 1.17 8.20 18.5 10.0 Peridur0.04 0.56 0.14 9.2 8.7 Polymer A 0.04 0.92 1.24 22.7 8.8 10 Polymer B 0.04 0.72 1.82 19.2 9.4 Polymer C 0.1 0.86 3.31 8.2 8.2 Table 2 % Spalled 700~C 850C 1000C
Blank 0 70 100 Bentonite 40 50 100 Peridur - 100 Polymer A - 0 80 20 Polymer B - 10 100 Polymer C 0 0 70 Example 2 An acid leached iron ore having pH about 5 was used and the following results were obtained.
Table 3 Dose Wet Dry Drop %
% w~w Strength/kg Strength/k~ Number oisture Polymer A 0.04 0.49 1.61 8.2 8.9 B0.04 0.50 2.15 16.9 9.1 D0.04 0.58 2.11 6.8 8.0 E0.04 0.51 1.94 5.4 7.8 F0.1 0.48 3.50 4.2 7.9 22 1 31 9 ~1 ~
Spalling was tested for all binders a-t 850C and for binders B, E and F at 1000C. No spalling occurred.
Example 3 A gel polymer o$ 60% acrylamide 40% sodium acrylate having intrinslc viscosity 23.9dl/g was dried and comminuted in conventional manner to a particle size of around lOO~m and is blended with an equal amount by weight of sodium carbonate particles. Thls binder was blended with iron ore glving a conventional alkaline pH, at a dosage of 0.04%. The spalling properties o$ the anionic synthetic polymer binder system at 1,000C were excellent relative to the other systems and the other properties were satls$actory, although the molsture content was slightly hlgner than with the other systems.
Claims (22)
1. A process in which pellets are made from mineral ore by forming acidic particulate ore having substantially all particles below 250µm and that gives a pH in water of below 7 by a process comprising washing or leaching the mineral ore in acid and blending binder comprising organic polymer into the acidic particulate ore in the presence of 5 to 15% by weight water (based on total mix) to form a substantially homogeneous moist mixture and pelletising the moist mixture, and in which the binder comprises about 0.02% to about 0.5% by weight, based on total mix, of a water soluble polymer that is cationic.
2. A process according to claim 1 in which the polymer is synthetic and formed from ethylenically unsaturated monomers comprising a cationic monomer.
3. A process according to claim 1 in which the mineral ore is iron ore and the polymer is synthetic and is formed from ethylenically unsaturated monomer comprising cationic monomer.
4. A process according to claim 3 in which the cationic polymer is selected from polymers that have intrinsic viscosity 0.4 to 5dl/g and that are formed from monomers of which at least 70% by weight are cationic, and polymers that have intrinsic viscosity of 3 to 20dl/g and that are formed by copolymerisation of 20 to 75 weight percent cationic monomer with 80 to 25 weight percent non-ionic monomer.
5. A process according to claim 3 in which the cationic polymer is substantially a homopolymer having intrinsic viscosity 0.4 to 2dl/g.
6. A process according to claim 3 in which the cationic polymer is a copolymer of 25 to 60 weight percent cationic monomer with 75 to 40 weight percent acrylamide and has IV 3 to 12.
7. A process according to claim 3 in which the cationic polymer is a substantial homopolymer of monomers selected from diallyl dimethyl ammonium chloride and quaternised dialkylaminoalkyl (meth) acrylates and quaternised dialkylaminoalkyl (meth) acrylamides and has intrinsic viscosity 0.4 to 2dl/g.
8. A process according to claim 3 in which the cationic polymer is a copolymer of about 20 to about 60%
acrylamide with about 80 to about 40% by weight of a quaternised monomer selected prom dialkylaminoalkyl (methy acrylate and dialkylamino alkyl (moth) acrylamide and has intrinsic viscosity of from 3 to 12dl/g.
acrylamide with about 80 to about 40% by weight of a quaternised monomer selected prom dialkylaminoalkyl (methy acrylate and dialkylamino alkyl (moth) acrylamide and has intrinsic viscosity of from 3 to 12dl/g.
9. A process according to claim 3 in which the ore is iron ore which gives a pH in water of below 6.
10. A process according to claim 3 in which the polymer is added to the ore as dry tree flowing powder having substantially all particles above 20µm an below 300µm.
11. A process according to claim 3 in which the polymer is added in the form of beads made by reverse phase suspension polymerization and that are substantially all above 20µm and below 300µm.
12. A process according to claim 3 in which the binder gives a surface tension of above 70 dynes/cm at a concentration in water at 20°C of 0.075% by weight.
13. A process according to claim 3 in which the amount of polymer is from 0.01 to 0.05% by weight.
14. A process according to claim 3 in which at least 70%
by weight of the acidic particulate ore has a particle size below 50µm.
by weight of the acidic particulate ore has a particle size below 50µm.
15. A process according to claim 3 in which substantially all the polymer particles are below 150µm.
16. A process according to claim 3 in which substantially 100% of the polymer particles are below 200µm and at least 50% are below lOOµm.
17. A process in which pellets are made from mineral ore by adding binder comprising organic polymer to acidic particulate iron ore having substantially all particles below 250µm and stirring in the presence of 5 to 15% by weight water (based on total mix) to form a substantially homogeneous moist mixture and pelletising the moist mixture, and in which the binder comprises about 0.002%
to about 0.5% by weight, based on total mix, of a water soluble polymer that is cationic and the ore gives a pH
in water or below 7.
to about 0.5% by weight, based on total mix, of a water soluble polymer that is cationic and the ore gives a pH
in water or below 7.
18. A process in which iron ore pellets are made by adding binder comprising organic polymer to particulate iron ore having substantially all particles below 250µm and stirring in the presence of 5 to 15% by weight water (based on total mix) to form a substantially homogeneous moist mixture and pelletising the moist mixture, characterised in that the binder comprises up to 0.2% by weight based on total mix, of a water soluble synthetic polymer that has intrinsic viscosity above 17dl/g and that is an anionic polymer of one or more water soluble ethylenically unsaturated monomers comprising anionic monomer, and the binder also comprises 10 to 150%, by weight binder, of a compound selected from urea, sodium acetate, sodium citrate, sodium oxylate, sodium tartrate, sodium benzoate, sodium stearate, sodium bicarbonate, sodium carbonate, sodium silicate, sodium phosphate and the corresponding ammonium, potassium, calcium and magnesium salts of the preceding salts, and calcium oxide.
19. A process according to claim 17 in which the binder contains sodium carbonate, sodium bicarbonate or sodium silicate in an amount of 50 to 150% based on soluble polymer.
20. A process according to claim 17 in which the soluble polymer is added as a dry, free flowing, powder having substantially all particles above 20µm and below 300µm.
21. A process in which pellets are made from mineral particulate ore having substantially all particles below 250µm by adding binder in the presence of 5 to 15% by weight water (based on total mix) to form a substantially homogeneous moist mixture and pelletising the moist mixture, and in which the binder comprises about 0.02%
to about .05% by weight, based on total mix, of a water soluble polymer that is added in the form of dry, free flowing, beads that are substantially all above 20µm and below 300µm and that are made by reverse phase bead polymerlsation from water soluble ethylenically unsaturated monomer or monomer blend.
to about .05% by weight, based on total mix, of a water soluble polymer that is added in the form of dry, free flowing, beads that are substantially all above 20µm and below 300µm and that are made by reverse phase bead polymerlsation from water soluble ethylenically unsaturated monomer or monomer blend.
22. A process according to claim 21 in which the polymer of the beads is nonionic, cationic or anionic having IV
below 3 or above 16 dl/g.
below 3 or above 16 dl/g.
Applications Claiming Priority (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8706932 | 1987-03-24 | ||
| GB878706932A GB8706932D0 (en) | 1987-03-24 | 1987-03-24 | Ore pelletisation |
| GB878712552A GB8712552D0 (en) | 1987-05-28 | 1987-05-28 | Ore pelletisation |
| GB8712552 | 1987-05-28 |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CA1319016C true CA1319016C (en) | 1993-06-15 |
Family
ID=26292050
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CA000562249A Expired - Lifetime CA1319016C (en) | 1987-03-24 | 1988-03-23 | Ore pelletisation |
Country Status (3)
| Country | Link |
|---|---|
| EP (1) | EP0288150B1 (en) |
| AU (1) | AU613351B2 (en) |
| CA (1) | CA1319016C (en) |
Families Citing this family (15)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| GB8830383D0 (en) * | 1988-12-30 | 1989-03-01 | Allied Colloids Ltd | Process and composition for pelletising particulate materials |
| DD297773A5 (en) * | 1989-02-13 | 1992-01-23 | �����@������������������k�� | PROCESS FOR PREPARING IRON-CONTAINING OIL SLUDGE FOR PROCESSING |
| DD297772A5 (en) * | 1989-02-13 | 1992-01-23 | �����@������������������k�� | METHOD OF BONDING PARTICULAR WEAPON WASTE, SUCH AS DUST, METAL WASTE, FIBERS, PAPER WASTE OD. DGL. TO SOLIDS |
| GB8918913D0 (en) * | 1989-08-18 | 1989-09-27 | Allied Colloids Ltd | Agglomeration of particulate materials |
| GB9116700D0 (en) * | 1991-08-02 | 1991-09-18 | Allied Colloids Ltd | Ore pelletisation |
| US5685893A (en) * | 1991-08-02 | 1997-11-11 | Allied Colloids Limited | Ore pelletization |
| CA2082128C (en) | 1991-11-07 | 2002-12-31 | Henricus R. G. Steeghs | Process for agglomerating particulate material and products made from such processes |
| GB9721085D0 (en) | 1997-10-03 | 1997-12-03 | Allied Colloids Ltd | Mineral palletisation |
| GB9724032D0 (en) * | 1997-11-13 | 1998-01-14 | Allied Colloids Ltd | Ore pelletisation |
| EP2548978A1 (en) | 2011-07-21 | 2013-01-23 | Clariant S.A., Brazil | Binder composition for the agglomeration of fine minerals and pelletizing process using the same |
| EA201890549A1 (en) | 2015-09-02 | 2018-09-28 | Басф Се | APPLICATION OF HYDROPHOBIC-ASSOCIATING COPOLYMERS AS CONNECTING SUBSTANCES FOR LAYING METAL-CONTAINING ORES |
| CA3051646A1 (en) | 2017-02-22 | 2018-08-30 | Basf Se | Use of copolymers as binders for pelletizing metal containing ores |
| GB201813370D0 (en) * | 2018-08-16 | 2018-10-03 | Binding Solutions Ltd | Binder formulation |
| KR20220134012A (en) * | 2020-05-18 | 2022-10-05 | 닛폰세이테츠 가부시키가이샤 | Method for producing a condensed material and a condensed material |
| FR3135993A1 (en) | 2022-05-24 | 2023-12-01 | Snf Sa | BINDING COMPOSITION FOR AGGLOMERATION OF IRON ORE |
Family Cites Families (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US3180723A (en) * | 1963-05-27 | 1965-04-27 | Nalco Chemical Co | Metallurgical process |
| US3860414A (en) * | 1968-09-04 | 1975-01-14 | Int Minerals & Chem Corp | Use of graft copolymers as agglomeration binders |
| AU445417B2 (en) * | 1970-08-07 | 1974-02-21 | Catoleum Pty. Limited | A process of manufacturing indurated mineral agglomerates |
| US3893847A (en) * | 1970-08-07 | 1975-07-08 | Catoleum Pty Ltd | Composition of matter and process |
| DE2105932C3 (en) * | 1971-02-09 | 1975-04-17 | Bayer Ag, 5090 Leverkusen | Agglomeration of ferrous titanium ores |
| US3925060A (en) * | 1974-09-23 | 1975-12-09 | Timken Co | Compact containing iron oxide and carbon and method for its use in steelmaking |
| ZA774057B (en) * | 1977-07-06 | 1978-09-27 | Revertep South Africa Ltd | Process and composition for aggregating particulate materials |
| ZA776166B (en) * | 1977-10-17 | 1978-12-27 | Revertex Ltd | The treatment of particulate material to form aggregates |
| AU546359B2 (en) * | 1980-12-08 | 1985-08-29 | Revertex (South Africa) Pty. Ltd. | Briquetting of particulate materials |
| US4690971A (en) * | 1985-03-05 | 1987-09-01 | Allied Colloids Limited | Water absorbing polymers |
| CA1332514C (en) * | 1985-05-21 | 1994-10-18 | Meyer Robert Rosen | Process for agglomerating mineral ore concentrate utilizing emulsions of polymer binders or dry polymer binders |
| GB8529418D0 (en) * | 1985-11-29 | 1986-01-08 | Allied Colloids Ltd | Iron ore pelletisation |
-
1988
- 1988-03-21 EP EP88302455A patent/EP0288150B1/en not_active Expired - Lifetime
- 1988-03-23 CA CA000562249A patent/CA1319016C/en not_active Expired - Lifetime
- 1988-03-24 AU AU13705/88A patent/AU613351B2/en not_active Expired
Also Published As
| Publication number | Publication date |
|---|---|
| AU613351B2 (en) | 1991-08-01 |
| AU1370588A (en) | 1988-09-22 |
| EP0288150A1 (en) | 1988-10-26 |
| EP0288150B1 (en) | 1994-02-23 |
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