GAS GUIDE
Biogas Compression
Raw biogas carries H₂S and water together — that combination decides the machine before pressure does.
Raw biogas carries H2S and water together, which is the combination that does the damage. Whether the gas has been desulfurised, and to what residual level, determines everything from material choice to whether oil-free is even worth paying for.
The properties that drive the choice
| Molecular weight | 27.2 |
|---|---|
| Isentropic exponent k (ambient) | 1.3 |
| Hazard profile | flammable |
| Autoignition temperature | 537 °C |
| Oil-free | Not required by the gas |
| Corrosion | Aggressive when wet |
Which families serve it
| Family | Role in this service | Envelope | |
|---|---|---|---|
| Oil-injected screw | Digester and landfill gas boosting where oil contact is acceptable | to 50 bar(g) | family page → |
| Dry screw | Wet, swinging flows without oil in the gas path | to 45 bar(g), differential ≤ 15 bar | family page → |
| Liquid ring | The wettest and dirtiest end of the stream | to 13 bar(a) | family page → |
Where the boundaries sit
- Assume 316L minimum unless the gas is demonstrably dry and desulfurised — H₂S plus water is the damaging combination
- Define the H₂S residual in ppm and where in the train it is removed; both belong in the enquiry
- Droplets and carry-over change the family answer — say so on the form rather than discovering it on site
Materials
Assume 316L minimum unless the gas is demonstrably dry and desulfurised; define the H2S residual in ppm and its removal point.
Related reading
Running a duty point on this gas? The selector on the home page maps gas, pressures, flow and temperature to a machine family with its boundary conditions — free.
Open the tool →