Pulverised coal injection, usually called PCI, lets a blast furnace replace part of its coke with coal blown in through the tuyeres. The saving only appears if the coal is ground fine enough to burn in the short time it spends in the raceway, injected steadily and blended to suit the furnace. Poor grinding or unstable injection can leave unburnt char that harms gas flow and stability. This guide covers grinding fineness, injection rate and coal blend choices. To see where your system could improve, you can review your PCI data with our team.
Coke and fuel rate optimisation
Get More Coke Replacement From Every Tonne of Injected Coal
iFactory AI combines grinding, injection and furnace data so teams can raise PCI rate safely and keep the furnace stable.
Three levers behind PCI performance
Grinding finenessInjection rateCoal blend
How PCI worksCoal Replaces Part of the Coke, Not All of It
Fine coal is blown into the raceway with the hot blast, where it burns and supplies heat and reducing gas. Coke still holds up the burden and keeps gas flowing.
Cost
Coal usually costs less than coke per unit of fuel
Carbon
Replacing coke can lower emissions per tonne
Flexibility
Different coals can be used
Limit
Coke is still needed for structure and permeability
The replacement ratio, meaning kilograms of coke saved per kilogram of coal injected, is usually below one and varies with conditions.
The key formulasReplacement Ratio and Net Saving
Replacement ratio = coke saved / injected coal added
Net saving = coke saved x coke price - coal added x coal price - added operating cost
Measure the replacement ratio on your own furnace. It changes with coal quality, blast conditions and furnace state.
BurnoutCoal Has Only a Fraction of a Second to Burn
The time coal spends in the raceway is extremely short. Finer particles burn faster and more completely.
1
Grind
Coal is milled to the target fineness.
2
Transport and inject
Coal is carried to the tuyeres in a steady stream.
3
Burn in the raceway
Particles heat, release gas and burn.
4
Leave unburnt char
Any unburnt coal travels up the furnace and can hurt gas flow.
Unburnt char is the main hidden cost of poor PCI. It can reduce permeability and limit how much coal the furnace tolerates.
See How Much Coke Your PCI System Really Replaces
Share your injection and fuel rate data and see how iFactory AI would estimate your replacement ratio and headroom.
GrindingFineness Is the First Lever
Coal is often specified so that most particles pass a fine sieve around 75 microns. Your mill and coal determine what is practical.
| Factor | Effect on PCI | What to check |
|---|
| Fineness | Finer coal burns more completely | Sieve results by mill and shift |
| Moisture | Wet coal is harder to grind and transport | Drying and storage |
| Grindability | Hard coals need more energy to mill | Coal test data |
| Mill wear | Worn parts change fineness | Maintenance records |
| Consistency | Swings upset injection and burnout | Trend of fineness over time |
Finer is not always better. Grinding energy and mill capacity set a practical limit, so optimise for the whole system.
Injection rateRaise PCI Rate in Steps, Not Jumps
More coal means more cooling and more load on the raceway. Furnaces respond best to gradual, monitored increases.
Watch hot metal temperature, permeability and top gas after each step. Pause if signs of instability appear.
Coal blendBlend Properties to Suit the Furnace
No single coal is perfect. Blends balance burning behaviour, ash, sulphur and cost.
Volatile matter
Higher volatile coals ignite quickly but may behave differently in the raceway.
Ash content
Ash adds slag volume and can reduce efficiency.
Sulphur and alkalis
Affect hot metal quality and furnace operation.
Grindability
Determines mill capacity and energy.
Moisture
Affects handling and burning.
Price and supply
Reliable supply and cost drive blend choices.
Test a new blend carefully. A cheaper coal that burns poorly can cost more than it saves.
Data sourcesBring Mill, Injection and Furnace Data Together
Mill and fineness dataInjection rate by tuyereFurnace and top gas data
PCI optimisation model
Injection setpointsBlend guidanceStability alerts
Tuyere-by-tuyere data is valuable. Uneven injection between tuyeres can upset local conditions.
StabilityTrade More Coal for Risk Only When the Furnace Is Ready
PCI strategy
Stable furnace
Unstable furnace
Gradual increase
Best path
Steady gains with monitoring
Stabilise first
Fix instability before adding coal
Rapid increase
Higher risk
Savings can be lost to upsets
Avoid
High risk of a serious upset
Treat stability as the limit. A smoothly running furnace tolerates more coal than a disturbed one.
Autonomy levelsTake Control Step by Step
Advise
The model suggests injection and blend settings.
Approved setpoints
The model proposes changes inside limits.
Closed loop
Selected setpoints adjust automatically inside strict bounds.
Many plants stay at the first two levels for a long time. To plan yours, ask our team about PCI control limits.
What improvement looks likeBefore and After a PCI Programme
Track the same measures before and after changes. This view is illustrative.
Before optimisation
Injection variation between tuyeres
After optimisation
Injection variation between tuyeres
RolloutFive Steps to Better PCI Performance
1
Baseline
Record PCI rate, coke rate, fineness and stability.
2
Check the mill and lines
Verify fineness, moisture and injection balance.
3
Review the blend
Compare coals on burning, ash and cost.
4
Raise rate in steps
Increase gradually with monitoring.
5
Measure the result
Calculate replacement ratio and net saving.
Baseline PCI rate, coke rate and stability recorded
Fineness measured regularly and trended
Mill condition and moisture checked
Injection balance across tuyeres reviewed
Coal blend properties documented
Rate increases made in small, reviewed steps
Replacement ratio measured on your furnace
Owner from furnace operations, PCI plant and raw materials
Expert reviewWhat a PCI and Ironmaking Specialist Would Check First
Expert review
PCI is limited by burnout and stability, not only by equipment capacity. Make sure fineness, injection balance and furnace condition are right before pushing the rate.
VerdictStrong when fineness and injection balance are monitored and rate increases are gradual.
Watch forChasing a higher injection rate while unburnt char builds up.
Do nextMeasure fineness and tuyere balance for a month before changing the rate.
Frequently asked questionsWhat Steel Plants Ask About PCI Optimisation
How fine does PCI coal need to be?
Many plants aim for most particles to pass a sieve around 75 microns, but the right target depends on coal properties and furnace conditions. Finer coal burns more completely but costs more to grind, so optimise the whole system.
Review your fineness data.
What limits how much PCI we can inject?
Common limits include burnout in the raceway, raceway cooling, gas flow and thermal stability. Unburnt char and uneven injection between tuyeres are early warning signs.
Ask about PCI limits.
How do we choose a coal blend?
Compare coals on volatile matter, ash, sulphur, alkalis and grindability, then trial blends carefully. Judge them on replacement ratio and stability, not price alone.
Plan a blend trial.
What is a good replacement ratio?
Can AI raise PCI safely?
It can help by showing headroom, spotting imbalance and advising on blends, but operators and engineers set the limits. Start in advisory mode and increase rate gradually.
Discuss a safe pilot.
More replacement, stable furnace
Make Every Kilogram of Injected Coal Count
Book a session with iFactory AI to review your grinding, injection and furnace data and plan a PCI programme that raises replacement without risking stability.
