Reduce Emissions and Operating Costs with Appropriate Glycol Selection

Abstract

Glycol selection for natural gas dehydration applications may be based on a number of factors including dehydration capability, glycol losses in the contactor and regenerator, and absorption of volatile organic compounds (VOC’s). The most commonly used glycol is triethylene glycol1. Diethylene glycol and ethylene glycol may also be used in dehydration applications; however, DEG and EG are often not considered due to dry gas water content requirements. TEG has a higher degradation temperature and can be regenerated to a higher lean concentration with no modifications to the standard regenerator reboiler. However, EG and DEG can meet water content specifications when used with enhanced regeneration systems. Enhanced regeneration is any system that improves glycol regeneration to achieve a "leaner " or more concentrated glycol solution. Enhanced regeneration could be the injection of stripping gas into the reboiler, azeotropic regeneration2, or other proprietary processes. Glycols absorb aromatic compounds such as benzene, toluene, ethylbenzene, and xylenes (BTEX) from natural gas. BTEX, along with other organic compounds considered to be pollutants, such as hexane, cyclopentane, heptane, cyclohexane, etc. are collectively known as volatile organic compounds. Regulatory agencies limit emissions from dehydration units to 10 tons/year of any one pollutant or 25 tons/year of total pollutants3. BTEX is generally of greatest concern since these compounds are often found in natural gas and are soluble in glycols.