Many hydrocarbon gases (APG, natural gas, biogas, and others) contain a substantial amount of acidic components, the most common of which are carbon dioxide (СО2) and hydrogen sulfide (H2S), however organic sulfur compounds such as carbon sulfide (COS), carbon disulfide (CS2), mercaptans (RSH), thiophenes and other impurities can be found as well. Such impurities are toxic substances tending to put strains on gas transportation and processing as they impair effectiveness of the catalytic processes and give rise to gas pipelines and equipment corrosion.
One of the processes used to remove acidic impurities from hydrocarbon gas is СО2 и H2S chemical sorption with water solutions of various amines, monoethanolamine (MEA), diethanolamine (DEA) and methyldiethanolamine (MDEA).
Brief Process Description
Absorption gas treating with amines is based on the understanding that when interacting with acidic gas components amines form chemical compounds easily decomposed into primary components when rising temperature and decreasing pressure.
To carry out the process, feed gas is heated to a temperature approximately equal to the ambient temperature and fed into the absorption column where it contacts amine solution. The purified from acidic impurities gas then passes through a separator where dropping liquid is separated, and fed for further treatment. The saturated amine solution is degassed, heated in a recuperative heat exchanger, and comes into desorber for regeneration. The regenerated amine solution is afterwards cooled and pumped back into absorption column.
Advantages of Amine Treatment Units:
- Such units ensure fine gas purification from hydrogen sulfide and СО2, at various pressure values, flowrates and concentrations of acidic components in the feedstock
- Simple and reliable unit performance
Main Process Shortcomings Include:
- Low extraction level of mercaptans and some other organosulfur compound
- Heavy heat and power expenses for process implementation
- Absorbents and products of their reaction with impurities contained in crude gas are rather commonly known for excessive corrosion aggressiveness
- Deterioration in process performance at high heavy hydrocarbons content
- The need for gas drying and acidic gases disposal upon amine treatment
Absorption technology (amine treatment) is applicable in a broad range of sulfur compounds and СО2 concentrations. MEA, DEA, TEA, MDEA solutions are used for various applications. Other absorbents tend to be usable in certain cases. With a view to cutting down operating expenses this technology can be combined with membrane and adsorption treatment.
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