In the game a piece of ore is a container for exactly one substance. One piece of Ore (Iron) holds one unit of iron, one piece of Ore (Coal) one unit of hydrocarbon. Furnaces and printers only count these units. On top of that almost every ore carries gas that is released when it melts. Both together decide what happens in the furnace.
What each ore contains
Gases in mol per piece, as they are released while melting:
| Ore | Contents | Gases when melting | becomes |
|---|---|---|---|
| Ore (Iron) | iron | 0.5 CO₂, 2 pollutant | Ingot (Iron) |
| Ore (Copper) | copper | 0.5 N₂, 1 CO₂, 1 pollutant | Ingot (Copper) |
| Ore (Gold) | gold | 0.2 O₂, 0.5 N₂, 0.2 CO₂, 2 pollutant | Ingot (Gold) |
| Ore (Silver) | silver | 0.4 N₂, 1 N₂O, 1 pollutant | Ingot (Silver) |
| Ore (Lead) | lead | 0.4 N₂O, 1 N₂, 0.4 CO₂, 2 pollutant | Ingot (Lead) |
| Ore (Nickel) | nickel | 0.5 N₂, 1 CO₂, 1 pollutant | Ingot (Nickel) |
| Ore (Silicon) | silicon | 1 N₂, 1 CO₂, 1 pollutant | Ingot (Silicon) |
| Ore (Cobalt) | cobalt | 3 N₂, 1 methane | super alloys only |
| Ore (Coal) | hydrocarbon | 3 pollutant, 10 CO₂ | steel, solid fuel |
| Charcoal | carbon | 3 pollutant, 3 CO₂ | steel |
| Ore (Uranium) | uranium | 35 pollutant | no furnace recipe |
A few things stand out:
- Coal is the most gas-rich ore after uranium: 13 mol per piece, 10 mol of it Carbon Dioxide.
- Uranium releases 35 mol of Pollutant but has no furnace recipe in this version and is not used in any printer recipe either.
- Cobalt has no ingot of its own. You put the ore straight into the advanced furnace when a super alloy asks for it.
- Silver and lead carry Nitrous Oxide, gold even a little Oxygen.
- An ingot holds the same substance as its ore, but no gas. If you want less exhaust in the furnace, use ingots instead of ore.
- Ore from the centrifuge brings no gas along either: the game remembers that it has already been processed once.
In the gas furnace a piece only melts once the chamber is at least as hot as its flash point: metal ores from 373.15 K (100 °C), coal and charcoal from 323.15 K (50 °C). The gas enters much cooler than the furnace and cools it a little. Every unit of substance counts as one unit of mix in the furnace – with normal recipes it makes one ingot.
Ice
Ice is an ore item as well, but it only contains gas. According to the game data it melts at 273.15 K (0 °C):
| Ice | Gases per piece |
|---|---|
| Ice (Water) | 20 mol Water, 5 mol Nitrogen |
| Ice (Oxite) | 22.5 mol Oxygen, 2.5 mol Nitrogen |
| Ice (Volatiles) | 20 mol Methane, 2 mol Hydrogen |
| Ice (Nitrice) | 22.5 mol Nitrogen, 2.5 mol Nitrous Oxide |
So every ice yields 22 to 25 mol. The easiest way to turn it into gas is the Ice Crusher, which sends gas and liquid into separate pipes. According to the game data Ice (Volatiles) also has an autoignition temperature of 305.15 K (32 °C) – store it cool.
Worked example: how much pressure does a stack of ore make?
A full stack is 50 pieces. 50 iron ore release 50 · 0.5 = 25 mol of CO₂ and 50 · 2 = 100 mol of pollutant, 125 mol in total. In the 1,000 litre chamber of the Furnace that gives, even at 20 °C:
p = n · R · T / V = 125 · 8.3144 · 293.15 / 1,000 ≈ 305 kPa
With 50 pieces of coal it is 650 mol, about 1,584 kPa – before the furnace is even hot. Heating raises the pressure further, because it grows with temperature: at 900 K it is about three times as high as at 293 K.
That is why every gas furnace needs a gas outlet. Without one the pressure rises with every batch until it leaves the window of your alloy. Gas pipes hold 60,795 kPa at most.
Where the exhaust goes
The furnace exhaust is a mix of pollutant, carbon dioxide, nitrogen and, depending on the ore, nitrous oxide or methane. You can
- send it into a tank and use it later,
- split it with a Filtration and use the pure gases one by one,
- or vent it outside when the outside air is unbreathable anyway.
In any case keep the exhaust out of your breathing air – it contains neither enough Oxygen nor anything you want to inhale.
Contents from other sources
Ore is not the only source. According to the game data an iron ingot also holds exactly 1 iron, a steel ingot 1 steel, charcoal 1 carbon and solid fuel 1 hydrocarbon. The recycler and the deep miner deliver mixtures that only the centrifuge separates back into pure ores – more on that in Recycling and centrifuge: getting material back. Careful with Dirty Ore from the deep miner: in the furnace and the arc furnace it counts as melted but adds no substance. It always goes into the centrifuge first.
Further reading
- Finding and extracting ore: Mining: finding and extracting ore
- Which mix every alloy needs: Furnaces and alloys
- Gases, phases and combustion: Gases
- Work out a furnace charge: Furnace calculator