Smelting Without Smoke — Clean Furnaces for Steel & Friends
Coal made the first skyscrapers; electrons will make the next civilization. In our world, furnaces don’t cough — they hum. The only “smoke” is heat we harvest on purpose.
Why smelting without smoke (and why it’s easier than it sounds)
The “toxic” part of old metallurgy wasn’t metal itself — it was the combustion used to heat and reduce it: coal in blast furnaces, diesel in mine trucks, oil for process heat. We remove combustion, keep the physics. Electric arcs, induction coils, and hydrogen do the same jobs with fewer side stories.
- Same atoms, new fire: electrons and H₂ replace coke and diesel.
- Closed‑loop heat: off‑gas becomes steam and process heat, not a weather event.
- Power abundance: the solar seed factory (Part 3) prints the megawatts we need.
Steel without coal — the two clean routes
Route A — Scrap → EAF (Electric Arc Furnace)
We melt recycled steel with an electric arc. Add a pinch of lime and oxygen, skim, cast, smile. This is the lightest‑energy route when good scrap is available.
Electricity: ~0.35–0.60 MWh/t steel O₂ & fluxes: modest Electrodes: ~1–2 kg/tOptional: induction furnaces for smaller foundry runs (similar electricity per ton).
Route B — DRI(H₂) → EAF
When we need virgin iron, we reduce iron ore with hydrogen in a shaft furnace (DRI), then melt in an EAF. Hydrogen is just a temporary electron carrier. No coke ovens, no sinter stacks.
Hydrogen: ~50–60 kg H₂/t steel Electricity (incl. H₂): ~3.2–4.2 MWh/t Pellets: high‑grade, low impuritiesElectrolyzers at ~50–55 kWh/kg H₂. We oversize solar to feed them calmly.
Per‑ton cheat sheet (steel)
Inputs & energy (per 1 t liquid steel)
| Route | Electricity | Hydrogen | Notes |
|---|---|---|---|
| Scrap → EAF | ~0.35–0.60 MWh | — | Best where clean scrap is abundant |
| DRI(H₂) → EAF | ~3.2–4.2 MWh* | ~50–60 kg | Electrolyzer + compression + EAF |
*Assumes electrolyzers ~50–55 kWh/kg H₂ and clean electricity.
What we replace (for context only)
| Old route | Combustion energy | Main fuel |
|---|---|---|
| BF/BOF (blast furnace) | ~4–6 MWh/t (as heat) | Coke/coal |
| Diesel mine haul | — | Replaced by electric vans (Part 1) |
We keep the metallurgy, delete the fumes.
Pre‑calculated plant scenarios (shop‑friendly, no scripts)
Steel EAF (scrap route)
Electricity only. Range accounts for scrap mix and practice.
| Capacity | Avg load | PV min | 12 h storage | Notes |
|---|---|---|---|---|
| 1 Mt/yr | ~57 MW | ~300 MWp | ~0.68 GWh | 0.5 MWh/t design |
| 5 Mt/yr | ~285 MW | ~1.46 GWp | ~3.42 GWh | Multiple furnaces in bays |
PV “min” sized by daily energy: PVMWp ≈ Avg(MW) × 5.14 (5.5 PSH, 85% yield).
Steel DRI(H₂) + EAF
Electrolyzers dominate the load; EAF is the sprinter.
| Capacity | Avg load | H₂ needed | PV min | 12 h storage |
|---|---|---|---|---|
| 1 Mt/yr | ~400 MW | ~55 kt/yr | ~2.05 GWp | ~4.8 GWh |
| 5 Mt/yr | ~2.0 GW | ~275 kt/yr | ~10.3 GWp | ~24 GWh |
Electrolyzer power split (1 Mt/yr): ~330–360 MW; EAF + balance: ~40–70 MW. We run them on a calm microgrid, not a spiky one.
Space & kit (typical 1 Mt/yr campuses)
| Block | Area | Notes |
|---|---|---|
| EAF melt shop (2–3 furnaces) | ~3–6 ha | Enclosed, acoustic panels |
| DRI shaft + pellets yard | ~5–8 ha | If using Route B |
| Electrolyzer hall | ~2–4 ha | Containerized stacks |
| Cast/rolling prep | ~3–5 ha | Billets, slabs, blooms |
| PV field (min) | ~3.0–3.5 km² | For 2.05 GWp nearby |
| Storage yard | ~0.5–1 km² | 4.8 GWh containers |
We co‑site with the lake (Part 1) for cooling water & serenity.
Friends of steel (clean furnaces for other metals)
Aluminum — Hall‑Héroult, electrified end‑to‑end
Alumina (Al₂O₃) becomes molten aluminum in electrolytic cells. We pair it with electric calciners and, where available, inert anodes to eliminate perfluorocarbon spikes.
- Electricity: ~14–16 MWh/t aluminum (smelting)
- Refining & casting (electric): +2–3 MWh/t
- 500 kt/yr plant: ~800 MW avg • PV min ~4.1 GWp • 12 h storage ~9.6 GWh
Copper — pyro + electrorefining, tidy
Sulfide concentrates smelt exothermically. We capture SO₂ for sulfuric acid (a useful product), then finish with electrorefining.
- Electricity: ~2.5–4.0 MWh/t cathode
- 1 Mt/yr campus: ~340 MW avg • PV min ~1.76 GWp • 12 h storage ~4.1 GWh
- Byproduct: acid plant feeds leaching circuits and neighbors
Silicon — electrometallurgy
Quartz + carbon → metallurgical‑grade silicon in arc furnaces. With clean power and off‑gas capture, it’s a bright, controlled thunderstorm.
- Electricity: ~11–14 MWh/t
- 100 kt/yr plant: ~137 MW avg • PV min ~0.70 GWp • 12 h storage ~1.6 GWh
- Upstream to solar: routes into wafer fabs next door (Part 3)
Air, water & neighbors (boringly clean by design)
Air
- No coke batteries. EAF lids closed; fumes scrubbed & filtered.
- SO₂ capture. Copper off‑gas → sulfuric acid; no tailpipe drama.
- Arc flash, not smokestack. Noise and light contained by enclosures.
Water
- Closed cooling loops with dry coolers; the lake handles seasonal swings.
- Zero un‑treated discharge; we prefer “no discharge” as a lifestyle.
- Rain from PV fields becomes process make‑up via simple treatment.
Q&A
“Is hydrogen dangerous?”
It’s energetic and deserves respect — like electricity. We keep electrolyzers outdoors, pipes short, sensors everywhere, and designs boring on purpose.
“What about scrap quality?”
We pre‑sort aggressively (Part 2 energy in, energy out). When virgin iron is needed, DRI(H₂) fills the gap without importing a century of emissions.
“Isn’t this a lot of power?”
Yes — and that’s the point. The solar factory prints power at scale (Part 3). We build the collectors faster than excuses, then wire them straight into the furnaces.
Up next: Steel: Bones of Civilization — Casting Slabs, Billets & Beams (Part 5). We’ll pour sunlight into shapes strong enough to hold a century.