HC and BTEX absorption into amine solutions has received increased attention over the last decade due to emissions to the atmosphere or to problems in downstream equipment. The collection of VLE and VLLE data by GPA and others have facilitated the development of a model for the absorption and removal processes. The amount of HC and BTEX emitted or passed to downstream equipment may be controlled by reducing the absorption or by removal from the rich amine.

Amine solutions absorb some amount of hydrocarbons and BTEX. These dissolved hydrocarbons that are obtained by contacting with the feed gas are ultimately released in the overhead of the regenerator. This overhead either vents to the atmosphere or feeds a sulfur recovery unit. Hydrocarbon content for regenerator vents discharging to the atmosphere must comply with recent stringent regulations. For acid gas feeds to a Claus unit, excessive hydrocarbons may result in catalyst fouling, sub-quality sulfur product, or more sophisticated burner design.

To better understand and quantify hydrocarbon and BTEX solubility in aqueous amines, the Gas Processors Association commissioned research Project 971. Preliminary results from this project have been used to improve models for hydrocarbon and BTEX solubility predictions. Model predictions are compared with operating facilities and guidelines for minimizing hydrocarbon absorption in amine facilities are presented.

The amount of BTEX components emitted from gas processing facilities has become a significant environmental concern. Recently, amine sweetening units have received the same environmental scrutiny as glycol units with regard to BTEX emissions. This paper compares the BTEX emissions from amine sweetening and glycol dehydration facilities as well as the methods available to minimize BTEX pickup in these systems. Reducing solvent circulation rates in both the amine and glycol units and minimizing the lean amine temperature were found to be the most effective ways of limiting overall BTEX emissions. Changing solvent type can also reduce emissions, but the effect on treated gas quality must be considered as well. In the cases investigated approximately 25% of the overall BTEX emissions came from the amine units, while the remaining 75% came from the glycol system

The amine process will absorb heavy hydrocarbons and aromatics from gas streams in addition to the acid components. Whether the acid gas is to be vented or fed to a sulfur plant, it is highly desirable to remove these compounds from the acid gas. A new, economical process has been developed to greatly reduce the aromatics and heavy hydrocarbons in the amine plant acid gas stream. In the test facility, the new BTEX-T. rex process decreased the level of aromatics in the acid gas stream by more than three quarters. The process utilizes the plant fuel gas as a stripping agent and the aromatics and heavy hydrocarbons which are removed are incinerated in the amine plant reboiler heater. Plant data collected before and after implementing the BTEX-T. rex process compare favorably with the results estimated using a recent version of TSWEET regarding BTEX concentration results.

Over the past several years, concerns about hydrocarbon emissions from the regenerator vent in glycol dehydrators has become a significant issue. This paper illustrates the prediction capabilities of PROSIM® for analyzing these concerns. First, the paper illustrates that predictions made by PROSIM compare favorably to data from the API Glycol Reboiler Emissions Work Group. Next, PROSIM shows that while a significant amount of non-aromatic VOC emissions are released in the flash separator, a small fraction of BTEX emissions are evolved at normal conditions. PROSIM indicates that over-circulation does not enhance dew point depression, but will cause a nearly linear increase in the amount of BTEX compounds emitted from the unit. Next, various contactor pressures are analyzed which show that higher emissions result from lower pressure units due to the increased amount of water that must be absorbed. Finally, a comparison between DEG and TEG facilities with similar circulation rates indicates that approximately 30-40% more BTEX emissions occur when using TEG than DEG.