Hydrocarbon Emission Estimates and Controls for Natural Gas Glycol Dehydration Units

Abstract

ABSTRACT The evaluation and reduction of hydrocarbon emissions from glycol dehydration units has required a concerted effort in the areas of methods development, emission measurements and field testing, and control technology evaluation and application. Of five emission estimate methods evaluated, excellent estimates of benzene, toluene, ethylbenzene, and toluene (BTEX) and good estimates of total volatile organic compounds (VOC) can be achieved with rich/lean glycol mass balance. Rich/Lean glycol BTEX emission estimates are independent of atmospheric and pressurized sample collection, whereas, higher estimates of VOC are obtained from pressurized samples. Confirmation of the rich/lean glycol method has been made from total capture stack condensation on small glycol units (< 15 MMSCFD) and from partial-stack condensation on large units. BTEX emission data obtained from total capture condensation and rich/lean mass balance are in excellent agreement. The agreement in total VOC emissions from the two methods is dependent on the inlet gas composition. From total capture stack condensation field tests, a combination of condensation and use of the non-condensible gases as fuel to the reboiler has been determined to be the most cost effective method to reduce emissions. Prototype units have been developed and are presently in operation in Louisiana and Oklahoma.