Natural gas dryers remove water vapor prior to storing or using natural gas for a vehicle fuel. High water content can cause blockage of CNG in fueling systems and can contribute to corrosion in storage vessels and piping.
The need for a dryer is determined by the water content of the incoming gas and the minimum ambient temperature. In cooler climates using standard pipeline natural gas, a dryer is likely required. A dryer may also be required in warmer climates.
Dryers operate on the low pressure side of the compression process. The low pressure dryer uses molecular sieve adsorbent desiccants to remove water vapor to extremely low levels. After operating for a period of time, the dryer has removed so much water that it requires regeneration or replacement of the desiccant. The dryers may include a hygrometer which confirms the gas has been sufficiently dried.