Molecular sieves are crystalline compounds created from alumina silicates, with controlled and precise structures, which contain pores of uniform size. These compounds have an affinity for various molecules, especially for polar compounds such as water, hydrogen sulfide and carbon dioxide. Molecular sieves can therefore be used for removing water from sour gas, or they can also be used for sweetening sour gas that exceeds the hydrogen sulfide specification by a few ppm.
An adsorption unit used for water removal in natural gas dehydration and sweetening is called a dehydration unit (DHU). A DHU often consists of two or more vessels, filled with molecular sieves, that adsorb water during an adsorption period and are subsequently regenerated using a heated stream of treated gas.
Molecular sieve is a preferred adsorbent when deep removal of water is required (below 1 ppmv).Besides removing water from a feed stream, sometimes they can also remove additional contaminants (e.g., mercaptans). Luoyang Jianlong has specially designed molecular sieve high water adsorption and carbon dioxide capacity, excellent hydrothermal stability and good dynamic characteristic for natural gas dehydration.
Natural gas must be dehydrated to remove water vapor. Water vapor causes the formation of hydrates, over saturation of natural gas, and corrosion of equipment. The high pressure increases saturation and creates more water vapor. Hydrates cause freezing and blocking of pipelines, valves, and other equipment, bringing production to a halt. Oversaturated gas does not meet pipeline specifications, which must be removed in order to sell.
Natural gas compositions can vary over a wide concentration of hydrogen sulfide and carbon dioxide and a wide concentration of hydrocarbon components. If the hydrogen sulfide content exceeds the sales gas specification limit, the excess hydrogen sulfide must be separated from the sour gas. The removal of hydrogen sulfide from sour gas is called “sweetening”.