Adsorbents for the natural gas drying at CNG stations

Humidity present in the natural gas causes problems by its compression at CNG filling stations. Therefore, the natural gas has to be dried before compression. For this reason, the water adsorption from the gas is mostly used as a suitable adsorbent. A device for drying compressed natural gas at high pressure is, therefore, an important part of the CNG filling station and affects the quality of produced CNG. For the correct operation of the drying equipment is decisive the selection of the suitable material for the adsorption of water vapor from the gas. As adsorbents for the removal of water from the gas, molecular sieves 4A, 5A, and 13X are primarily used. Molecular sieve 4A has a high sorption capacity for water vapor, which is, however, significantly reduced by co-adsorption of methane at high pressures. Other molecular sieves have not so high sorption capacity for water, but the influence of co-adsorption of methane at high pressures is by these adsorbents not so significant. The article is focused on selection of commercially available adsorbents having a high capacity for water steam and high efficiency of its removal from the gas. The results of laboratory tests of methane drying have been used in the selection of best adsorbent for natural gas drying at CNG stations.