BTEX EMISSIONS FROM ETHYLENE GLYCOL CIRCULATION IN NATURAL GAS REFRIGERATION PLANTS: A PROCESS SIMULATION STUDY

摘要

Monoethylene Glycol (EG) is widely used as a hydrate inhibitor in low-temperature refrigerated gas plants. One of the main environmental issues with the operation of glycol units is the release of BTEX (benzene, toluene, ethylbenzene, xylenes) emissions, which are controlled by federal and/or local regulatory agencies. Although the vast majority of glycol units use Triethylene Glycol (TEG) to remove water from natural gas, there are a significant number of refrigeration plants that rely on EG to ensure hydrate-free operation. Earlier reports have shown that the main process simulation tools used in the sector to predict BTEX emissions from TEG systems provide reasonably similar results and adequately match the available experimental data. EG systems however have not been extensively studied and it is well-known among practitioners that the simulation software tools generally used can produce widely different results, and in some cases even fail to produce results at all. In North America, HYSYS~(TM), ProMax~? and GRI-GLYCalc~? are the most common simulation tools used to predict BTEX emissions from glycol units. For HYSYS, a more recently added “Glycol” property package was developed with good results for predicting BTEX emissions from glycol units. ProMax has also been widely used with the recommended SRK equation of state incorporating fitted interaction parameters. GLYCalc has also been used in industry, but relies in part on simplified methods to calculate emissions. In this work, a set of refrigeration plants operating in Western Canada were simulated using these different approaches; results are presented in this report.