We can help our customers to determine which process is the best for their ore, fuel and pellet requirements. Our systems combine the best features of both technologies to provide the most modern plant and to produce pellets at the lowest cost and highest quality.
This process generates iron ore filter cake which needs to be pelletized to be used in the steel making process. Also during the processing of high grade iron ores which dont need beneficiated, fines which are generated can be pelletized and used instead of being disposed of.
Iron Ore Pellets are formed from beneficiated or run of mine iron fines. The iron is usually ground to a very fine level and mixed with limestone or dolomite as a fluxing agent and bentonite or organic binders as a binding agent. If the ore is a Hematite ore, coke or anthracite coal can be added to the mix to work as an internal fuel to help fire the pellets. This mixture is blended together in a mixer and fed to balling discs or drums to produce green pellets of size typically about 9-16mm. The green pellets are then fed to the induration machine. Both straight grates and grate kilns dry the pellets out in a drying section, then bring the pellets up to a temperature of about 800-900 Cin a preheat zone, then finish the induration process at roughly 1200-1350 C. The pellets are then cooled to a suitable temperature for transporting to a load out facility. Both processes recycle the heat from the pellet back through the process to aid in energy efficiency and decrease fuel usage.
Both processes can be used to generate almost any type of desired pellet chemistry, from direct reduction pellets (DR pellets) to blast furnace pellets. By adjusting the amount of fluxing agent or limestone added, pellets can be made that are anywhere from acid (or non-fluxed) pellets to heavily fluxed pellets.
Mixing is where the properly ground ore is combined with binding agents like Bentonite or organic binders, fluxing agents like limestone or dolomite, and if the ore is a Hematite with coke or anthracite coal as an internal fuel. The mixing is done usually in vertical or horizontal high intensity mixers to achieve a homogenous blend of ore and additives.
From mixing the filter cake is sent to the balling area where the ore is agglomerated on balling discs or balling drums into green(or unfired) pellets. Both drums and discs ball the ore to about 9-16mm size. Drums typically have very high recycle rates so have a screening circuit to screen out undersize and oversize pieces to be put back through the drum. Discs usually do not have a separate screening circuit at the disc.
Green pellets are then transported to the induration process. Pellets that are oversized or undersized and any fines generated during the balling or transporting process are screened right before entering the induration machine and sent back to the mixer or the balling area. The on-size pellets are then fed to the induration machine. Both straight grates and grate kilns dry the pellets out in a drying section, then bring the pellets up to a temperature of about 800-900 Cin a preheat zone, then finish the induration process at roughly 1200-1350 C. The pellets are then cooled to a suitable temperature for transporting to a load out facility. Both processes recycle the heat from the pellet back through the process to aid in energy efficiency and decrease fuel usage
Ankerite is a carbonate of lime, magnesia, manganese, and iron. It is of valuable composition, carries only 14 or 15% of iron, and is used more for its lime and magnesia as a flux than for its iron-content. Goethite and turgite come between hematite and limonite in composition, and are found with both, but are comparatively rare.
Iron ores cannot be profitably mined unless they occur in large bodies. The discovery of a few thousand tons, or a vein-like body four or five feet wide, is usually unimportant. To be worth while, the tonnage must be counted in millions of tons.
There are certain impurities that lower the value of iron ores or may even make them valueless. Sulphur in the ore goes partly into the iron and steel and makes them brittle. While it is possible by roasting the ore and by other means to remove the sulphur, the presence of any considerable amount is objectionable. Phosphorus in steel makes it brittle. For steel-making the limit for phosphorus is one hundredth of one per cent for ten per cent of iron in the ore; this is the so-called Bessemer limit. A Bessemer ore carrying 52% of iron must not have more than .052% of phosphorus and the sulphur should not exceed .04%. But since the presence of phosphorus in pig iron increases the fluidity and tends to make sound castings, ores high in phosphorus are used in making foundry pig iron. Titanium is objected to by users of iron ores, because it is said to make a pasty slag and to interfere in other ways with the smooth running of the blast furnace. At present, ores containing more than 5% or 6% of titanic acid (TiO2) are not saleable.
The per cent of iron in the ore as mined must be not less than 50%, if it is to be used without being first improved (beneficiated) by cobbing, washing, calcining, or magnetic concentration. Leaner ore is found in very large quantities; and in a favorable situation, it may be workable by some concentrating process.
Hematite is sometimes found in vein-like deposits which are not usually large enough to be important. Such ore-bodies have been found nearKitchener, B.C. and in the Matachewan area, Ontario. Deposits of considerable size have been found at the contacts of igneous intrusions, generally basic, with crystalline limestone, dolomite, and limey shale; the ore is usually of the specular variety, and it is apt to be partly magnetite. The most important hematite deposits are of a sedimentary origin, the ore forming beds in stratified rocks. The hematite beds of the Wabana Mines, Newfoundland, extend for miles under the ocean. They are found in sandstone and shale of Ordovician age. In Nova Scotia, smaller deposits have been found in Devonian and Silurian stratified rocks. The hematite deposits of the Lake Superior region are of sedimentary origin, but the rich ores have undergone natural concentration from the lean ores of the iron formation. These formations are widespread in eastern Canada and the United States; but in only a very small part of the known areas (about 2% in the U.S.A.) have merchantable ores been discovered. The immense iron range in the Labrador peninsula about 400 miles in length has begun to produce high grade hematite from open pits, and in time will rival the famous Mesabi range in Minnesota. At Steep Rock Lake in northwestern Ontario hematite of similarly high grade is being mined from deposits that stand vertical, having been formed by replacement of the rock along a contact of volcanics with crystalline limestone.
Iron formation consists of iron ore such as siderite, magnetite, and hematite, with silica in the form of chert, jasper, etc., generally in bands, but sometimes not distinctly so. Thebands of iron ore are at times high-grade, but are often mixed with a good deal of silica, the whole making an ore too lean for use without concentration. Iron formation is believed to be of sedimentary origin. In Ontario three epochs of deposition are known:
Only one deposit of the second kind has so far been found in Ontario, that at Loon Lake, east ofPort Arthur. In the United States, they have been found mostly in hilly regions and toward the bottom of the slopes. Another common condition is a tight trough, or basin, formed by the iron formation and an intruding dike. Important ore-bodies have been found that were completely without, or almost without, outcrop, in some cases being covered by slate. The hematite is sometimes mixed with enough magnetite to make possible a discovery by means of a magnetic survey.
Limonite, or brown ore, is to be found at the bottom of some bogs and shallow lakes, in favorable situations, where the weathering rocks have yielded iron to the water draining into these basins. The limonite accumulates so fast in some places that a lake bottom may be cropped again after a number of years, as at Radnor Forges,Quebec. Considerable deposits of limonite have been found in places where there is no standing water at present. Limonite is sometimes formed in large quantities by the weathering of the sulphides of iron; such gossan has occasionally been used as an iron ore. At Bannockburn, in the Madoc area, a pyrite deposit was discovered below the limonite, which was being mined as an iron ore; this gossan capping of the pyrite was from eight to fifteen feet deep. In the old iron mines near Londonderry, Nova Scotia, the ore was limonite in fissures originally filled with siderite and other carbonates.
Limonite varies a great deal in its appearance. In color, it may be light rusty brown, dark brown, or even black on a fresh fracture. It is sometimes in round grains (shot ore), or in porous round lumps or flat cakes. When ground fine, it forms a yellow powder.
Siderite or spathic iron ore, isusually gray or white; but at the surface it weathers to limonite, and the weathering may extend to a considerable depth. A rusty capping may cover a deposit of siderite. Where the ore forms the face of a cliff, the limonite may wash away as fast as it forms, leaving the siderite clean. The ore is found in vast quantities in the iron formation of the Michipicoten District, Ontario; the quantity around the Helen Mine is estimated at not less than 100 million tons; the ore is high in sulphur, owing to the presence of pyrite, and requires to be roasted to remove sulphur as well as to remove carbon dioxide.