Sour Gas

Sour Gas is an intermediate gaseous element used as the transition product between Petroleum and Natural Gas. It appears in systems where heavy hydrocarbons are vaporized and can be processed by extreme cooling to extract Liquid Methane and Sulfur, and by reheating to obtain Natural Gas. Sour Gas requires specialized thermal handling because its useful phase changes occur at very low temperatures.

When cooled to approximately -163.5 °C, Sour Gas undergoes phase separation: about 67% of its mass becomes Liquid Methane and about 33% becomes Sulfur. Liquid Methane can be reheated and vaporized back into Natural Gas. If cooled further at sufficiently low pressure, Sour Gas can condense differently: at very low densities (reported around 5 g or less per tile), it can condense almost entirely into Methane. A documented bug causes a 1:1 phase product ratio when the gas density is at or below 3000 mg/tile, which can in turn trigger issues such as the disappearance of liquid tiles smaller than 10 g.

Producing Sour Gas occurs as part of high-temperature processing of heavier hydrocarbon sources; in practical base designs it is the link used to convert Petroleum into Natural Gas when heated above its vaporization threshold.

Processing Sour Gas is thermally demanding. The extreme cold required makes direct handling difficult with ordinary cooling methods. Viable cooling and phase-extraction strategies documented in-game include:

• Using a Thermo Aquatuner cooled by Super Coolant to reach the required temperatures for phase separation. This is the common method but requires Super Coolant and careful heat isolation.
• Using an Anti Entropy Thermo-Nullifier to reach very low temperatures, noting that it must be well heat-isolated and may still take time to reach target temperature.
• Running Thermo Regulators with Hydrogen Gas (Hydrogen Gas) as the working coolant and an efficient heat exchanger; this can work but often consumes large amounts of power and requires careful engineering to yield net energy gain.

Because of the thermal extremes, the game’s documentation recommends postponing handling Sour Gas until you have the infrastructure to reliably reach and maintain the required low temperatures.

Practical and technical notes:

• Gas pipe segments hold 1000 g of gas and the pipeline throughput limit is 1 kg/s (one packet per second). Plan transport and buffering accordingly.
• Heat exchange between the gas and its environment depends on pipe segment thermal conductivity; among common materials Granite has the highest thermal conductivity and Ceramic the lowest before Thermium or Insulation become available. Note that a pipe segment exchanges heat with its tile but not with neighboring pipe segments.
• In the ventilation overlay, gas pipes, intakes and outputs are highlighted; gas pipes can occupy the same tile as other buildings except other gas pipes.
• Because Sour Gas creation and processing involve precise temperatures and densities, small-scale quantities can trigger edge-case bugs (see the low-density 1:1 product bug) — designs that rely on tiny amounts of liquid or gas should be tested carefully.

Sour Gas is primarily valuable for extracting Liquid Methane (and thus producing Natural Gas) and Sulfur, but extracting these reliably requires late-game cooling technology and careful engineering to avoid energy losses and known low-density bugs.