The presence of impurities and moisture in natural gas is highly undesirable because it can adversely affect the transportation as well as complicates its operation as fuel and raw material. Also, this process removes pollutants of the environment. They are carbon dioxide, hydrogen sulfide and sulfur dioxide. Natural gas should be purified to the content of harmful impurities getting into the atmosphere not exceeding 500 ppm.
Often, natural gas purification is carried out directly during its mining. Purification process depends on the composition and concentration of impurities.
Ways to remove undesirable components :
- Chemical treatment;
- Physical absorption;
- Combination of physical and chemical methods;
- Oxidation of hydrogen sulfide compounds with the fallout of sulfur;
- Use of solid adsorbents.
Drying of natural gas is done by :
- direct cooling,
- a combination of these approaches.
Adsorption drying – is a selective absorption of solid parts of water. Other parts are extracted by means of external influences.
Adsorbing is done in units with a fixed absorbing layer. A full cycle of drying natural gas on this device – involves adsorption, regeneration and cooling of adsorbent. As absorbents are used bauxite, zeolite (molecular sieves), silica gels, alumina silica gel and activated alumina. The most expensive adsorbents are zeolites, but they are most effective in drying gases containing acidic components.
The adsorption method has a high degree of drying gas regardless of its initial state. The equipment is compact for its implementation. The disadvantages are – the high cost of adsorbent, the highest resistance to the flow of gas and high costs of high-power installations.