Optimization of Process Parameters for Glycol Unit to Mitigate the Emission of BTEX/VOCs

Abstract

Recent developments in environmental regulations on the emissions of aromatic compounds including benzene, toluene, ethyl benzene and xylene isomers (BTEX) and other volatile organic compounds (VOCs) have made these emissions a major concern in the natural gas industry. In particular, one of the sources of emissions is glycol dehydration units. During the dehydration of natural gas, the BTEX and VOC compounds in it are absorbed by the glycol solvent, and subsequently emitted to the atmosphere during the thermal regeneration of glycol. As a result, quantification and means of reduction and ultimately elimination of these emissions is gaining importance in the industry. This problem requires careful attention during the design phase. The environmental considerations mentioned above are increasingly driving the selection and operation of process alternatives to reduce the BTEX/VOCs emissions to the atmosphere. This paper focuses on the glycol dehydration unit for one of the onshore oil and gas processing facilities in Abu Dhabi operated by Abu Dhabi Company for Onshore Oil Operations (ADCO). Firstly, the BTEX/VOCs emission levels vented out to atmosphere are quantified, and a description given of the sampling/measurement technique. Secondly, the process parameters associated with all major equipments in the glycol dehydration unit, i.e. the absorber, the flash tank, and the regenerator that may lead to the reduction in BTEX/VOC emissions, are optimized. The optimization study involves building a process simulation model based on actual design data/parameters provided by the glycol unit vendor and verified by operational data.