Iron Ore Pelletizing Process: 7 Steps With Costs

Iron ore pelletizing turns very fine iron ore concentrate into hard, round pellets about 8 to 16 mm across that a blast furnace or direct reduction plant can use. Pellet feed is ore finer than 0.15 mm, and the process takes it through seven steps: prepare the concentrate, mix in binder, roll green pellets, fire them, cool them, screen them and ship them (de Moraes et al., IntechOpen, 2018). Firing happens at roughly 1,290 to 1,400°C in US taconite plants (US EPA AP-42, section 11.23). This page gives the typical numbers for each step, compares the three furnace types, and includes a calculator for the bentonite and limestone bill.

It is written for mining consultants, plant engineers and project teams who need to check a pellet flowsheet, a supplier claim or a feasibility assumption. Every number carries its source and date. Plant results vary by ore, so treat the ranges as starting points for test work, not design values.

Why fine iron ore is pelletized

Grinding ore to release the iron minerals makes fine particles. Fines pack tightly, block the gas flow in a furnace and blow away as dust, so they need to be agglomerated (joined into larger lumps). The size classes used in ironmaking are lump at 6.3 to 31.7 mm, sinter feed at 0.15 to 6.3 mm and pellet feed below 0.15 mm (IntechOpen, 2018). Coarser material is usually sintered, while very fine ore is usually pelletized, and pellets generally travel and handle better than sinter (AusIMM Minerals Processing Toolbox).

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US iron ore production, 2021 to 2025

Million metric tons of usable ore; 2025 is an estimate

The idea of rolling damp fine ore into balls and then firing them was patented in Sweden in 1912, and commercial plants started in the 1950s. The same chapter estimates world installed pelletizing capacity at 480.7 million tonnes a year, with China, the United States and Brazil holding the most (IntechOpen, 2018). In the United States, eight open pit mines in Michigan, Minnesota and Utah, each with concentration and pelletizing plants, shipped 98% of domestic usable iron ore products in 2025 (USGS, Mineral Commodity Summaries 2026).

The iron ore pelletizing process in 7 steps

The steps below follow the order of the plant. The numbers come from the US EPA description of taconite plants (1997 text, still the standard US reference for plant layout) and a peer-reviewed overview of the process.

Step 1: Prepare the concentrate

Ore is crushed, ground wet in rod and ball mills, then upgraded by magnetic separation or flotation, or both. Concentrate coarser than about No. 10 mesh can go to a blast furnace without further treatment, but finer material has to be agglomerated (US EPA AP-42, section 11.23). Grind size matters for strength: in one study on specular hematite, more particles below 44 micrometres improved green and fired pellet strength and abrasion resistance (IntechOpen, 2018). Ask your lab for a size distribution and a surface area test on every new concentrate.

Step 2: Mix in binder, flux and water

A binder is a material that holds the damp particles together. Powdered bentonite clay is the usual choice and is mixed with the carefully moistened feed at 5 to 10 kg per tonne (10 to 20 lb per ton). Plants that make flux pellets add 1 to 10% limestone; acid pellets use ore and binder only (US EPA AP-42, section 11.23). Even mixing is important, because uneven moisture or binder creates lumps before the pellets form. The calculator further down prices this step.

Step 3: Roll the mix into green pellets

Green pellets are the unfired balls. They are formed on a balling drum or an inclined balling disc, at 8 to 16 mm in diameter. Pellets below 8 mm or above 16 mm leave the disc circuit at the screen and go back to the start (IntechOpen, 2018). Moisture is a trade-off: less water gives higher compressive strength, while more water gives better drop resistance, so operators tune it to the ore.

Step 4: Dry, preheat and fire the pellets (induration)

Induration is the heat hardening step. Green balls are dried and heated in an oxidizing atmosphere to an incipient fusion temperature of 1,290 to 1,400°C for several minutes, with acid pellets at the lower end and flux pellets at the higher end (US EPA AP-42, section 11.23). A separate review gives drying temperatures up to about 300°C, preheating of 1,000 to 1,100°C in the grate-kiln route and firing up to 1,350°C, with most strength developing above 1,200°C as grains neck together and the pellet densifies (IntechOpen, 2018). Natural gas was the most common fuel in the EPA description.

Step 5: Cool the fired pellets

Fired pellets leave the hot zone and are cooled with ambient air, usually on the grate extension or in a separate cooler. Grate-kiln plants use an annular cooler with counter-current airflow (US EPA AP-42, section 11.23). The heated air is sent back upstream to the firing and drying zones, which saves fuel (IntechOpen, 2018).

Step 6: Screen and recycle

Cooled pellets are screened. Fines and broken pieces are removed, and on a straight grate a share of fired pellets is kept back as a hearth layer, a 10 to 15 cm bed that protects the grate (US EPA AP-42, section 11.23). Product size is checked against the sales contract with a sieve test.

Step 7: Store, load and ship

Finished pellets go by conveyor to stockpiles, rail cars or ships. Pellets generally travel and handle better than sinter (AusIMM), but they still wear in every transfer, so chute design and stockpile handling are part of quality control. Tumble and abrasion tests check how a lot holds up.

Straight grate, grate-kiln or shaft furnace: which induration system

Three kinds of furnace harden pellets. In a vertical shaft furnace, hot gas rises through a slowly descending bed of pellets. In a straight grate, a moving bed of pellets passes through drying, firing and cooling zones on one machine. A grate-kiln uses a short traveling grate for drying and preheating, then a rotary kiln for firing (US EPA AP-42, section 11.23).

The straight grate and grate-kiln comparison comes from the IntechOpen overview (2018); the EPA text, written in 1997, notes that most large and new US plants used the grate-kiln. Pick the system with test work on your own concentrate, because ore type changes the firing curve.

Bentonite and limestone cost per tonne of pellets

Bentonite has been the main binder since pellet production began in the 1950s. It is cheap, but it adds silica and alumina to the pellet, which increases slag volume and energy use in the furnace. One review puts the usual dose at about 0.5% by weight (IntechOpen, 2018), which equals 5 kg per tonne, the low end of the EPA range of 5 to 10 kg per tonne. Michigan Technological University researchers reviewed organic and inorganic binders and found bentonite the most commonly used, with many alternatives that could compete in some cases (Eisele and Kawatra, 2003). Organic binders burn out without leaving residue, but give less strength to preheated and fired pellets than bentonite, so combined binders are often tested.

For price, USGS reports an average ex-works unit value of US$110 per tonne for US bentonite in 2025 (estimate), up from US$105 in 2024 (USGS, Mineral Commodity Summaries 2026: Clays). Ex-works means before freight, and pellet plants often pay more for specification-grade binder delivered to site. Use your own quote in the calculator below.

Blast furnace pellets or direct reduction pellets

Both main iron-making routes accept pellets. In a blast furnace, iron is reduced and melted into liquid hot metal. In direct reduction, iron stays solid and the product is direct reduced iron (DRI) (IntechOpen, 2018). A 1993 AusIMM monograph describes major buyers negotiating a blast furnace pellet premium with pellet producers, with a separate direct reduction pellet premium agreed later (AusIMM Minerals Processing Toolbox).

Chart

Rio Tinto realised prices, first half

US$ per wet metric tonne, FOB; first half of 2025 against first half of 2026

Price reporters now publish those premiums. Fastmarkets launched a European blast furnace pellet premium on 1 July 2026, quoted over its 65% Fe Brazil-origin fines index for cargoes of at least 60,000 tonnes (Fastmarkets pricing notice, July 2026), and in 2023 it launched indices for 67.5% Fe pellet feed, the high-grade feed used for pellets (Fastmarkets pricing notice, February 2023). It also publishes a weekly direct reduction grade pellet premium indicator, launched in November 2022. For the direct reduction route, see our guide to a direct reduction plant. The United States also has one DRI plant in Louisiana and three hot-briquetted iron plants in Indiana, Ohio and Texas (USGS, 2026).

Pellet quality tests and what the numbers mean

Buyers write pellet specifications around physical, chemical and metallurgical properties, and most are standardized. The table lists the tests named in the IntechOpen overview (2018). Check which edition your contract cites, because ISO revises these methods.

Chemistry matters as much as strength. Silica and alumina from the ore and binder form slag, and bentonite is a known source of both (IntechOpen, 2018). Each buyer sets its own chemistry and strength limits in the contract, so the numbers on this page are not a specification.

Pellet prices and US output: what the data show

Pellets sell at a different price from the fines they are made from. Rio Tinto reported realised prices for its Iron Ore Company of Canada (IOC) pellets of US$124.9 per wet tonne FOB in the first half of 2026, against US$129.9 a year earlier. Its Pilbara iron ore (fines and lump, a different product from a different mine) realised US$85.2 per wet tonne, up from US$83.2 (Rio Tinto, 2026 half-year results). The two lines are not a like-for-like premium, because the mines, grades and shipping routes differ.

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US iron ore average mine value, 2021 to 2025

US$ per metric ton, average unit value reported by mines; 2025 is an estimate

US output fell in 2025. USGS estimates 38 million tonnes of iron ore, a 16% fall from 45.1 million tonnes in 2024, after two Minnesota mines were idled in March 2025. The average mine value fell to about US$89 per tonne. The same report notes a 7-million-tonne-a-year mine and pelletizing plant project in Minnesota with a start expected in early 2026 when USGS wrote in February 2026 (check the project’s current status) (USGS, Mineral Commodity Summaries 2026).

What to ask a lab or supplier before you specify a plant

A pellet flowsheet is only as good as the test work behind it. Before committing to a design, ask for the items below and compare them with the ranges on this page.

• A size distribution and chemical analysis of the concentrate, including silica and alumina.
• Balling tests that show green pellet strength at several moisture levels and binder doses.
• Firing tests on pot-grate or similar equipment at the temperatures the chosen furnace can reach.
• Results against each ISO test your buyer names, using the edition the contract cites.
• A binder comparison, including bentonite, an organic binder and a combined option, with cost per tonne of pellets.

Fixing common pellet problems

Most pellet faults trace back to the first three steps. Use the list as a checklist before changing the furnace.

• Weak green pellets: check moisture and binder mixing first. Water that is too low reduces drop resistance, and too high reduces compressive strength.
• Fines or oversize at the screen: if many pellets fall outside 8 to 16 mm, the disc angle, speed or feed rate needs adjusting.
• Uneven fired strength: on a straight grate, top and bottom layers see different temperatures. A grate-kiln mixes pellets in the kiln.
• High silica or alumina in the product: review the binder. Bentonite adds both, and an organic or combined binder may help if the buyer penalizes them.
• Uneven drying: straight grate plants dry in two stages, with hot air blown up from below and then down from above, so the whole bed dries evenly.

Emissions and energy at a pellet plant

The first dust source in the pelletizing section is bentonite transfer and blending. Other emission points include the main waste gas stream from the furnace, and plants use hood-and-duct systems feeding cyclones, scrubbers or fabric filters (US EPA AP-42, section 11.23). Because the ore is processed wet until the drying stage of induration, dust from the grinding circuit is small, the EPA notes.

Energy is mostly fuel for drying and firing. Heat recovery from the cooler reduces that load, and recovering hematite from old tailings basins and pelletizing it is one route USGS lists for adding supply (USGS, 2026). Mining also changes land and water, which is why permits and closure plans matter before a plant is built.

▶ Explains the main environmental impacts of mining in plain words, with satellite maps. · 2:31

Where the ore for a pellet plant comes from

A pellet plant is only as good as its concentrate, and concentrate depends on the deposit. Taconite, magnetite and hematite ores need different grinding and firing. Our guides on taconite pellets, the types of iron ore and iron ore exploration cover that side, and our post on pelletization innovations looks at newer plant ideas.

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Iron ore mine production, selected countries, 2025

Million metric tons of usable ore (estimates); a selection of the countries USGS lists

Before a drill goes in, a satellite screen can show iron-oxide and alteration signatures across a licence, as a target for field work and not as a resource estimate. Farmonaut’s satellite mineral detection takes a KML, KMZ or polygon for your area; you can request a quote on the mining query form or contact us.

▶ Shows how a satellite picture becomes a map of targets, tonnes and grade, and which inputs are measured or assumed. · 2:54

Related reading on this site: Copper Beneficiation Process: 7 Steps and Recoveries.

We cover a connected topic in Copper Smelting Process Control: Targets by Step.

Frequently asked questions

What is iron ore pelletizing?

It is the process of rolling fine iron ore concentrate with a binder into balls, then hardening them in a furnace so they can be shipped and fed to a blast furnace or direct reduction plant.

What size are iron ore pellets?

Green pellets are formed at 8 to 16 mm, and pellets outside that range are screened out and recycled (IntechOpen, 2018).

What temperature is used to fire iron ore pellets?

US EPA gives 1,290 to 1,400°C for taconite pellets, with flux pellets at the higher end. A peer-reviewed overview gives firing up to about 1,350°C.

Why is bentonite used in pelletizing?

It binds the damp particles so green pellets hold together and survive handling and drying. The downside is that it adds silica and alumina.

How much bentonite is used per tonne of pellets?

The US EPA gives 5 to 10 kg per tonne of concentrate, and one review gives about 0.5% by weight. Test work sets the plant value.

What is the difference between acid and flux pellets?

Acid pellets are made from ore and binder only. Flux pellets have 1 to 10% limestone added before balling (US EPA).

What is the difference between pellets and sinter?

Both agglomerate fines. Pellets suit very fine ore and handle better in transport, while sinter is usually made from coarser ore.

Which furnace is better, straight grate or grate-kiln?

Neither always wins. A straight grate is one machine but fires unevenly through the bed, while a grate-kiln mixes pellets in a rotary kiln and can use coal, at the cost of three machines.

What is the difference between blast furnace and direct reduction pellets?

Both go into ironmaking, and buyers agree a separate premium for each product (AusIMM). Chemistry and strength limits are set in each buyer’s contract.

How is pellet quality measured?

With standard tests for size, crushing strength, tumble and abrasion, swelling, low-temperature disintegration and reducibility, plus a chemical analysis.