Advances in Gas Treatment

The most common unwanted compounds that are part of natural gas are water, nitrogen, carbon dioxide, hydrogen sulfide, carbonyl sulfide, helium, and other heavier hydrocarbons. Any or all of these compounds may be found in natural gas from almost any gas field at various concentrations. 

The presence of water, as mentioned earlier, can have several detrimental results among which is the formation of gas hydrates—snowlike, crystalline compounds composed of small amounts of methane, ethane, propane, or isobutane and water. The formation of these hydrates is aided by the presence of liquid water and areas of turbulence. The formation of these hydrates increases the pressure drop along the pipeline, thereby decreasing its capacity the presence of liquid water also can contribute to some corrosion. The formation and inhibition of these hydrates will be discussed in Section XII. In this section about gas treatment, the removal of hydrogen sulfide and other sulfide forms from the natural gas is discussed along with removal of carbon dioxide. A number of processes have been commercialized in this area and a few of them will be described here. 

Propylene carbonate is an efficient medium for the removal of carbon dioxide from high pressure natural gas streams with reasonably high carbon dioxide contents. The application of propylene carbonate for this application is based on several of the following aspects  

low solubility for hydrogen and other low molecular weight hydrocarbons of the gas stream 

The process is widely accepted because of its simplicity, low thermal energy and pumping requirements and overall low cost of operation. Propylene carbonate is an efficient solvent to remove carbonyl sulfide [10]. 

---