A study to reduce atmospheric emissions of an existing natural gas dehydration plant using multiple thermodynamic models

Abstract

Using Aspen Plus, operating parameters of an existing triethylene glycol natural gas dehydration plant including the solvent circulation rate, stripping gas flow rate, regenerator reboiler duty, solvent temperature, absorber (contactor) pressure, flash unit pressure and regenerator pressure were optimized to reduce BTEX, VOCs and CO2 emissions. The plant consists of an absorber, a flash tank, a stripper and a regenerator. Two thermodynamic models including PRMHV2 and PSRK were utilized for this plant. The sensitivity analysis study was conducted using two methods, namely Method A and Method B. Method A considered the effect of an individual parameter on the emissions, while other parameters were set at their base case values. Method B studied the impact of a given parameter, while other parameters were at their optimum values. Using the two methods, BTEX emission reduced more than 40%, while VOCs and CO2 emissions were decreased more than 60%. However, the moisture content of the dehydrated gas was higher when Method A was applied (249.9 × 10−6 kg H2O/m3) compared to Method B (65.7 × 10−6 kg H2O/m3). Method B was found to be a more precise approach to achieve the optimum plant operation.