{"id":2404,"date":"2026-05-06T07:27:51","date_gmt":"2026-05-06T07:27:51","guid":{"rendered":"https:\/\/boshiya.com\/?p=2404"},"modified":"2026-05-06T07:49:02","modified_gmt":"2026-05-06T07:49:02","slug":"reduced-iron-process-explained","status":"publish","type":"post","link":"https:\/\/boshiya.com\/es\/blog\/reduced-iron-process-explained\/","title":{"rendered":"\u00bfqu\u00e9 es el hierro reducido? Explicaci\u00f3n del proceso DRI para plantas sider\u00fargicas"},"content":{"rendered":"

Direct Reduced Iron (DRI): Process, Properties, and Steelmaking Applications<\/span><\/p>\n

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Note:<\/strong> If you searched for reduced iron<\/em> as a food-label ingredient (e.g., in fortified cereals), see our brief clarification below<\/a>. This article covers industrial Direct Reduced Iron (DRI) used in steel production.<\/div>\n

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Reduced iron, also referenced as Direct Reduced Iron or sponge iron, is metallic iron produced by chemically e\u00d7tracting the o\u00d7ygen from iron ore in the solid state, without going through the liquid stage of pig iron. Solid state iron making occurs at temperatures below the melting point of iron, 1,5\u00b38C, by using a reducing gas\u2014either reformed natural gas or hydrogen. Total global reduced iron production is approximately 140.8-million tonnes in \u00b2024. Its 10-year CAGR stands at 6.6 per cent \u2014 three times the growth rate of the global steelmaking industry overall<\/p>\n

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\n\n\n\n\n\n\n\n\n\n\n\n\n
Direct Reduced Iron \u2014 Quick Specs<\/caption>\n
Parameter<\/th>\nValue<\/th>\n<\/tr>\n<\/thead>\n
Fe (Metallic) Content<\/td>\n86\u201394% Fetot (DRI) \/ \u226590% (HBI)<\/td>\n<\/tr>\n
Operating Temperature<\/td>\n700\u2013900\u00b0C (gas shaft); up to 1,200\u00b0C (coal kiln)<\/td>\n<\/tr>\n
Primary Feed<\/td>\nIron ore pellets, lumps, or fines<\/td>\n<\/tr>\n
Reducing Agents<\/td>\nReformed natural gas (H\u2082+CO), H\u2082, coal syngas<\/td>\n<\/tr>\n
Product Forms<\/td>\nDRI (sponge iron), HBI (hot briquetted), HDRI (hot discharge)<\/td>\n<\/tr>\n
Carbon Content<\/td>\n0.02\u20134.5% C (process-dependent)<\/td>\n<\/tr>\n
Global Production<\/td>\n140.8 million tonnes (2024, Midrex)<\/td>\n<\/tr>\n
Dominant Process<\/td>\nMIDREX (~54% global share, 2024)<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

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What Is Reduced Iron? Definition and Industrial Context<\/h2>\n

\"What<\/p>\n

Within the field of metallurgy, the precise definition of reduced iron is tailored to the specific parameters of the process in question. Reduced iron refers specifically to oxide compounds whereby chemical reduction has been achieved; this entails the removal of oxygen chemically bonded to the Fe metal in the alloy, yet the iron itself remains in a silty, porous, solid state which has not melted. Resembling a sponge in structure, each piece of DRI carries ~47% void porosity and contains 86\u201394% metallic iron by weight.<\/p>\n

Within the steelmaking industry, ‘direct reduced iron’ (DRI) is the accepted designation to distinguish this feedstock from pig iron and scrap steel. Minimal tramp elements \u2014 copper, tin, nickel, and chromium \u2014 make this material ideal as a virgin iron source for producing special bar quality (SBQ) steel in electric-arc furnaces. As a feedstock category, DRI manufacture has grown faster than any other iron input to steelworks over the past decade, rising from 75 to 140.8 million tonnes in 2024<\/a><\/p>\n

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What does “reduced iron” mean in food and cereal products?<\/h3>\n
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Food grade reduced iron is a finely powdered elemental iron ingredient produced by hydrogen reduction of iron oxides \u2014 not a melt process. Food manufacturers use it to fortify breakfast cereals, flour, and infant formula as a dietary iron source, regulated under 21 CFR Part 184 (GRAS). Common forms of iron fortification include elemental iron (reduced iron), ferrous sulfate, and ferrous fumarate. Elemental iron powder has lower bioavailability than soluble iron salts because the body must absorb it after acid dissolution in the stomach; ferritin and serum iron tests will still respond to dietary iron absorption from this source. The nutrition label lists it simply as “iron.” Quantities are measured in milligrams per serving \u2014 no physical or steelmaking connection to industrial DRI exists.<\/p>\n<\/div>\n

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How Direct Reduced Iron Is Made \u2014 The Direct Reduction Process<\/h2>\n

\"How<\/p>\n

Industrial DRI manufacture begins and ends as a solid \u2014 iron oxide feed is progressively stripped of its bonded oxygen through a sequence of solid-state chemical reactions, bypassing the melt stage entirely. Raw materials \u2014 iron ore pellets or lumps (67% Fetot, size 9\u201316 mm, <0.008% sulphur, predominantly hematite or magnetite) \u2014 enter the hot upper region of a shaft furnace or rotary kiln, where gravity counter-preva iling downward against a stream of reducing gases. Reduction occurs through sequential oxygen debonding reactions across the vertical stabilization zones of the furnace.<\/p>\n

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Engineering Note \u2014 Reduction Chemistry<\/p>\n

With gas: Fe O FeO FeO Fe + HO (three-stage reaction mechanism)<\/p>\n

With another reducing gas, Carbon monoxide: Fe O FeO FeO Fe + CO<\/p>\n

In gas based shaft furnaces the reducing gas is a mixture of H and CO at a ratio of approximately 1.5-1.6:1 ( H:CO), entering the furnace at ~900 C.<\/p>\n<\/div>\n

MIDREX – the world leader in DRI direct reduction technology; responsible (by volume) for ~54% of all DRI produced worldwide in 2024 (76.2 million tonnes). Use a countercurrent shaft furnace where the reformed natural gas rises through the descending ore burden. A catalyst reformer converts methane and recycled top gas to H and CO at ~900 C. Material leaving the bottom of the shaft cools to ~50\u00b0C in the cooling zone, or is diverted at 650\u2013700\u00b0C directly into the briquetting press for HBI production.<\/p>\n

Energiron (HYL), developed jointly by Tenova and Danieli, used a pressure based shaft furnace and has gained market share especially on newer H-ready plants. MIDREX and Energiron together account for a (by volume) ~75% share of worldwide gas based DRI production: coal based processes are very much in the minority.<\/p>\n

What is the difference between gas-based and coal-based DRI production?<\/h3>\n

Gas based shaft furnace processes (MIDREX, Energiron) dominate in Middle East, Americas, and Northern Africa, where readily available cheap natural gas supports the generation of effective H+CO reducing gas. Coal based rotary kiln processes (SL \/ RN and variations thereof) dominate in India, which has now established itself as the world largest producer of DRI at 54.7million tonnes in 2024 – \u00b38.8% of the worlds DRI, mainly kiln based, is produced there. Gas based DRI, whether from MIDREX or Energiron, provides higher metallisation (92-96%), has a lower ash content, and a lower sulphur content that coal based DRI: on average each tonne of coal based DRI will carry about 2% more gangue \/ sulphur burden through to the steel resulting in a lower quality product. Consequently, DRI produced from gas in flat-rolled and SBQ steelmaking applications will generally command a higher quality premium.<\/p>\n

An Iranian EAF operator choosing the new direct reduction plant design and supply<\/a> route would default to MIDREX given Iran’s onshore and Kaspian base’s large availability of natural gas; a new greenfield plant in Odisha India would face a very different set of considerations where the availability of coal, and local grid costs, would favor the relatively less capital intensive rotary kiln process despite the poorer metallics of the resulting hot briquetted iron DRI.<\/p>\n

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DRI Product Forms: Sponge Iron, HBI, and Hot DRI Explained<\/h2>\n

\"DRI<\/p>\n

Leaving the shaft furnace in one of three commercial forms, DRI varies significantly depending on the degree of cooling between the high-temperature reduction zone and final discharge. Each type of DRI has specific physical properties, reactivities, and logistical implications: selecting the correct one (while balancing economic and metallurgical considerations) is critical.<\/p>\n

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\n\n\n\n\n\n\n\n\n\n\n\n\n\n
DRI Product Forms \u2014 Properties Comparison (Source: MDPI 2024, Kieush et al.)<\/caption>\n
Property<\/th>\nCold DRI (Sponge Iron)<\/th>\nHBI (Hot Briquetted Iron)<\/th>\nHDRI (Hot Discharge)<\/th>\n<\/tr>\n<\/thead>\n
Fetot<\/strong><\/td>\n86\u201394 wt.%<\/td>\n\u226590 wt.%<\/td>\n86\u201394 wt.%<\/td>\n<\/tr>\n
Metallization<\/strong><\/td>\n92\u201396%<\/td>\n90\u201394%<\/td>\n92\u201396%<\/td>\n<\/tr>\n
Bulk Density<\/strong><\/td>\n1.5\u20131.9 t\/m\u00b3<\/td>\n2.4\u20133.3 t\/m\u00b3<\/td>\n1.5\u20131.9 t\/m\u00b3<\/td>\n<\/tr>\n
Apparent Density<\/strong><\/td>\n3.2\u20133.6 g\/cm\u00b3<\/td>\n5.0\u20135.5 g\/cm\u00b3<\/strong><\/td>\n3.2\u20133.6 g\/cm\u00b3<\/td>\n<\/tr>\n
Porosity<\/strong><\/td>\n~47 vol.%<\/td>\n~21 vol.%<\/td>\n~47 vol.%<\/td>\n<\/tr>\n
Water Absorption (sat.)<\/strong><\/td>\n12\u201315%<\/td>\n~3%<\/strong><\/td>\nN\/A (hot, no storage)<\/td>\n<\/tr>\n
Reoxidation Risk<\/strong><\/td>\n\u26a0 High<\/td>\n\u2705 Low (1\u20132 orders lower)<\/td>\n\u26a0 High if cooled<\/td>\n<\/tr>\n
IMSBC Class<\/strong><\/td>\nGroup B \u2013 DRI(B)<\/td>\nGroup B \u2013 DRI(A)<\/td>\nNot shipped<\/td>\n<\/tr>\n
Typical Application<\/strong><\/td>\nLocal EAF delivery<\/td>\nLong-distance ocean trade<\/td>\nAdjacent on-site EAF<\/td>\n<\/tr>\n<\/tbody>\n<\/table>\n<\/div>\n

Hot briquetted iron (HBI) is produced by compacting roughly 650700 O C hot DRI at high pressures into cylindrical briquettes (90-140mm 48-58mm 20-50 mm, mass 500 700 g). Compaction reduces volumetric porosity from ca 47% to ca 21% and reduces maximum saturated water absorption from 12 15% to ca 3%. HBI thus becomes significantly less reactive than sponge iron DRI by two orders of magnitude, decreasing the safety for ocean bulk cargo and long duration storage. Legal IMSBC\/HBI specification requires briquetting above 650\u00b0C to an apparent density exceeding 5.0 g\/cm\u00b3. Cold-moulded briquettes (CBI) formed below this temperature retain the full DRI(B) hazard classification.<\/p>\n

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DRI Product Form Selection \u2014 Decision Framework<\/p>\n