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Steelmaking
Blast Furnace Coke Rate & Reductant Ratio Simulator
A tool for designing the mass balance of a blast furnace. Change hot metal production, ore grade, PCI, hot blast temperature and oxygen enrichment to see the coke rate, reductant rate, CO₂ emission and energy intensity update in real time — and intuitively evaluate the economics and environmental footprint of ironmaking.
Parameters
Hot metal production
t/day
Iron ore grade
%Fe
Typical: hematite 62-67%, magnetite 65-70%
Ore type
Affects gas permeability, reducibility and strength
Pulverized coal injection (PCI)
kg/tHM
PCI rate at the tuyere. Substitutes coke at 0.85 kg/kg
Hot blast temperature
°C
Tuyere air temperature preheated in the hot stove
Oxygen enrichment
%
Pure O₂ enrichment added to the blast (ambient air: 21%)
Sinter basicity
CaO/SiO₂ ratio. Optimum 1.8-2.0
Results
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Ore required (kg/tHM)
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Coke rate (kg/tHM)
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Reductant rate (kg/tHM)
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Daily coke (t/day)
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CO₂ emission (kg-CO₂/tHM)
—
Energy intensity (GJ/tHM)
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Blast furnace cross-section & mass flow animation
Ore, coke and flux are charged from the top; hot blast and PCI are injected from the tuyeres; hot metal is tapped from the hearth. Colors indicate temperature zones of the reduction stack.
Coke rate starts from a baseline $C_{\text{base}}\approx 500$ kg/tHM and is reduced by PCI (0.85 kg/kg), hot blast temperature (~30 kg per 100 °C above 1100 °C) and O₂ enrichment (~4 kg per %).
Reductant rate is the sum of coke and PCI. Ore requirement is set by the iron mass balance between Fe in hot metal (94%) and the ore grade $w_{\text{Fe}}$.
Direct CO₂ from fuel combustion based on the carbon content per unit mass. Indirect emissions (electricity, stove preheat) are not included.
Blast Furnace Coke Rate & Reductant Ratio — Ironmaking Mass Balance
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A "blast furnace" — that's the huge chimney-like thing you see at steelworks, right? What does it actually do inside?
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Yes, the symbol of the steelworks. Over 100 m tall, with an inner volume of 5,000-6,000 m³ — it's a massive reactor. The principle is surprisingly simple: from the top you stack alternating layers of iron ore, coke and limestone, and from the bottom you blow in 1,200 °C hot air. As the burden descends, iron oxides (Fe₂O₃) are reduced by CO from the coke and finally collect at the bottom as molten "hot metal" (Fe ~94 %). A single furnace produces several thousand tonnes a day, continuously, for ten years or more between relinings.
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Got it! So "coke rate" is basically how much coke we burn per tonne of iron? On the left it says 331 kg/tHM.
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Exactly — the coke mass per tonne of hot metal (tHM). Modern large furnaces operate at 280-500 kg/tHM, and that number maps directly to cost and CO₂. Coke plays two roles: (1) chemically, it supplies the CO that reduces iron oxide; (2) physically, it forms a porous bed (the "deadman") that keeps the column permeable so gas can rise. Push the coke rate too low and the furnace chokes — you lose permeability and can stall the whole operation.
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When I raise the "PCI" slider, coke rate drops. What is PCI doing?
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PCI is pulverized coal injection. Coke is expensive and very energy-intensive to make, so since the 1980s cheap coal has been pulverized and blown directly into the tuyeres to replace some of it. Empirically, 1 kg of PCI substitutes about 0.85 kg of coke. PCI rates of 150-200 kg/tHM are standard, and the leading furnaces push above 250. But PCI is not a structural support, so it can't go to zero. The sum of coke and PCI — the reductant rate — should land in 480-560 kg/tHM for a good operation.
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Why do higher hot blast temperature and oxygen enrichment make things more efficient?
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Hot blast is the air burning carbon at the tuyere. If it's already hot, less coke needs to be sacrificed to heat it. Roughly +100 °C of hot blast saves 30 kg/tHM of coke, which is why operators worldwide invest in better hot stoves. Oxygen enrichment is more direct — adding pure O₂ removes nitrogen and raises both the reaction rate and the flame temperature, saving about 4 kg/tHM per 1 % O₂. But oxygen costs money and high flame temperatures shorten refractory life, so 3-5 % is usually the sweet spot.
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And what about decarbonization? Steelmaking is famously CO₂-heavy.
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That's the biggest challenge in the industry. 70 % of the world's crude steel comes from the BF route, with about 1.4-1.8 t-CO₂ per tonne of steel — this tool's default settings give 1441 kg-CO₂/tHM. The roadmaps to net-zero by 2050 rest on three pillars: (1) hydrogen reduction (SSAB HYBRIT in Sweden, ThyssenKrupp tkH2Steel in Germany, COURSE50 / Super COURSE50 in Japan); (2) DRI + electric arc furnace; (3) CCUS integration. Use this tool as a baseline of today's BF performance before you compare against those alternatives.
Frequently Asked Questions
Coke rate is the mass of coke used per tonne of hot metal (tHM), expressed in kg/tHM. Modern large blast furnaces operate at 280-500 kg/tHM. Reductant rate is the sum of coke and pulverized coal injection (PCI) treated as a carbon reductant, typically 480-560 kg/tHM. Coke is essential as a permeable structural support inside the furnace, while PCI is a cheaper substitute that replaces coke roughly at a ratio of 0.85 kg PCI per 1 kg coke.
Hot blast is the air injected into the tuyeres to burn coke. The hotter it is, the less coke is needed to supply the required heat. As a rule of thumb, increasing hot blast temperature by 100 °C reduces coke rate by about 30 kg/tHM. Oxygen enrichment removes nitrogen and raises reaction efficiency: each 1 % of O₂ enrichment cuts coke by about 4 kg/tHM. This tool lets you feel both effects via the sliders.
Ore type affects gas permeability, reducibility and mechanical strength. Sinter dominates in Japan, China and Korea — fine ore is granulated and fired into porous lumps with good reducibility. Pellets are spheroidized fine ore with high strength and permeability, cutting coke rate by about 5 %. Lump ore is mined as natural lumps with lower preprocessing cost but worse reducibility, raising coke rate by about 5 %. The tool lets you switch among the three types.
The BF route accounts for 70 % of global crude steel and the bulk of steelmaking CO₂. Alternatives include (1) direct reduced iron (DRI, e.g. SSAB HYBRIT in Sweden) plus an electric arc furnace, (2) hydrogen reduction (voestalpine in Austria, ThyssenKrupp tkH2Steel in Germany, COURSE50/Super COURSE50 in Japan), and (3) CCUS integration. They target net-zero by 2050. Use this tool to baseline today's BF intensity before evaluating these transitions.
Real-world Applications
Steelworks operation design: Nippon Steel (Oita, Kimitsu, Nagoya), JFE Steel (Kurashiki, Fukuyama) and Kobe Steel (Kakogawa) operate 5,000 m³-class blast furnaces with world-leading coke rates of 290-330 kg/tHM. Mass-balance calculations like this tool's are used daily for new furnace start-up, mid-life relining and operating-condition optimization.
Raw material procurement: Integrated steelmakers import millions of tonnes of iron ore and metallurgical coal each year from Australia (BHP, Rio Tinto, FMG), Brazil (Vale) and Canada. Because ore grade and ore type both swing coke consumption and CO₂ noticeably, procurement teams use sensitivity analyses like this one when building long-term contract portfolios.
Carbon neutrality strategy: ArcelorMittal, ThyssenKrupp, SSAB, Nippon Steel, JFE, Kobe Steel, POSCO and China Baowu all target ~30 % BF CO₂ intensity reduction by 2030. They combine near-term efficiency moves (more PCI, oxygen enrichment, higher reductant rate operation) with longer-term shifts to hydrogen reduction, EAF and CCUS. This tool is useful as a baseline against which to test those scenarios.
Education and training: University metallurgy / materials engineering courses and steelmaker new-hire training use BF mass balance — together with the Rist diagram — to teach how operating knobs map to outputs. Cross-checking textbook examples (e.g. Geerdes et al., "Modern Blast Furnace Ironmaking") against this tool is a useful exercise.
Common Misconceptions & Pitfalls
First, the idea that "less coke is always better". Coke has both a chemical role (CO reductant) and a physical role (porous structural support that keeps the furnace permeable). PCI can only replace the chemical role; the physical role is non-substitutable. Driving coke rate down toward 280 kg/tHM destabilizes the gas distribution and risks thermal swings, chilling and channelling. World-record low-coke operation (coke ~250-270 kg with PCI ~250 kg) only works with premium coke and very advanced controls — don't chase those numbers blindly.
Second, treating CO₂ as a "blast furnace only" problem. The 1,400-1,500 kg-CO₂/tHM this tool reports is direct combustion (Scope 1). Add coke oven combustion, sinter plant firing, hot stove gas combustion, electricity (Scope 2) and raw-material logistics (Scope 3), and you reach 1.8-2.2 t-CO₂ per tonne of crude steel. Always state the scope boundary when discussing decarbonization. This tool focuses on the blast furnace itself; upstream and downstream stages must be evaluated separately.
Finally, the oversimplification that "hydrogen reduction = instant decarbonization". Hydrogen direct reduction does not emit CO₂ from the reduction reaction itself, but (1) reliable supply and price of green hydrogen (today 5-8 USD/kg, target ~2 USD/kg), (2) capital cost of replacing existing BF assets (hundreds of billions of yen per furnace), (3) the surge in electricity demand from DRI + EAF, and (4) impurity control when EAFs have to handle ores and scrap previously processed by BFs are all serious challenges. SSAB HYBRIT, ThyssenKrupp tkH2Steel and Nippon Steel's COURSE50 / Super COURSE50 target commercial operation only in the early 2030s. During the realistic transition, the optimized BF operation modelled here — combined with CCUS — will continue to play a major role.
How to Use
Enter hot metal production target (e.g., 500 t/day) and iron ore grade as Fe content percentage (58-65% typical for pellets)
Set pulverized coal injection (PCI) rate in kg/t hot metal (0-150 kg/t reduces coke demand) and blast air temperature in °C (900-1300°C)
Click Calculate to generate coke rate (kg/tHM), total reductant ratio, daily coke consumption, CO₂ emissions per tonne hot metal, and energy intensity in GJ/tHM
Worked Example
A blast furnace producing 800 t/day hot metal with 62% Fe ore grade, 80 kg/t PCI injection, and 1150°C blast temperature requires approximately 490 kg/tHM coke, 590 kg/tHM total reductant (coke + PCI equivalent), 392 t/day coke consumption, 1.95 kg-CO₂/tHM direct emissions, and 13.2 GJ/tHM energy intensity. Increasing PCI to 120 kg/t reduces coke to 420 kg/tHM and energy intensity to 12.8 GJ/tHM.
Practical Notes
Higher ore grades (64-65% Fe) reduce slag volume and coke rate by 15-20 kg/tHM compared to 58% ore; screen supplier specifications
PCI substitution ratio typically 0.7-0.8 (80 kg injected coal replaces ~56-64 kg coke), but injection rates above 180 kg/t risk raceway blockage and increased CO production
Blast temperature increases of 50°C improve thermal efficiency ~1-2%, but require refractory upgrades; monitor stove performance limits
Daily coke × 365 days × 1.95 kg-CO₂/tHM estimates annual Scope 1 emissions for carbon accounting; compare against 1.9 kg-CO₂/tHM industry best practice