Sour Gas

Sour Gas is a gas element that appears as an intermediate product in the transition from Petroleum to Natural Gas, and it is also the high-temperature state used in methane-based refining chains. It is produced when Petroleum or Plastic is heated to 541.85 °C, just above its vaporization point. From there, its practical use is almost entirely as a material to be cooled and condensed into other resources.

When Sour Gas is cooled to its phase-change temperature of -164.5 °C, it converts into 67% Liquid Methane and 33% Sulfur by mass. If the Liquid Methane is heated again, it becomes Natural Gas. Because of this, Sour Gas is mainly valuable as a way to produce Natural Gas and Sulfur through controlled cooling. The exact transition can also depend on density: when Sour Gas is sufficiently low density, the phase-change result becomes a 1:1 split, which can also interact badly with very small liquid tiles.

Handling Sour Gas requires extremely strong cooling. In practice, this usually means using Super Coolant in a Thermo Aquatuner loop. The temperature target is so low that other approaches are less convenient: an Anti Entropy Thermo-Nullifier can work, but it usually takes careful setup and heat isolation to reach the required temperature, while Thermo Regulators running Hydrogen Gas as coolant consume a large amount of power. Sour Gas can theoretically be used as an alternative coolant in some setups, but only with an efficient heat exchanger strong enough to recover more power than the cooling costs.

Useful notes for working with it:

• Sour Gas is best treated as a conversion product, not as a final storage state.
• Its main pipeline role is as an intermediate between Petroleum and Natural Gas.
• Cooling it below the phase-change point yields Liquid Methane and Sulfur, with the methane side then available for conversion into Natural Gas.
• The cooling demand is extreme enough that most practical builds rely on late-game cooling technology.
• Gas pipes can transport it like other gases, with a throughput limit of 1 kg/s per pipe segment.
• Gas pipe segments exchange heat with the gas and their tile, and Granite has the highest thermal conductivity among common qualified pipe materials before Thermium and Insulation become available.

Because of its narrow use case and severe temperature requirements, Sour Gas is generally something to process only when the colony has the infrastructure to manage deep freezing efficiently. It is most valuable in systems designed specifically to extract Natural Gas and Sulfur from high-temperature petroleum products.