Refrigerated dryers stop at +3 °C PDP. −40 °C needs desiccant or membrane; the real cost is regeneration purge, not the dryer price.
- Heatless desiccant purges 12–15% of flow — compressor capacity must grow accordingly.
- At 100 Nm³/min that purge can cost ~CNY 610k/yr; heat-of-compression pays back in about a year.
- Stage drying: refrigerated pre-dryer + desiccant only on the instrument branch.
- Specify PDP, inlet temperature ≤40 °C and online dew-point metering.
- Membrane suits small dispersed points, not large continuous flow.
Full economic comparison in Chinese; we calculate purge cost from your hours and tariff.