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 CO 2 emissions. The plant consists of an absorber, a flash tank, a stripper and a regenerator. Two thermodynamic models including PRMHV 2 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 CO 2 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 H 2 O/m 3 ) compared to Method B (65.7 × 10 −6 kg H 2 O/m 3 ). Method B was found to be a more precise approach to achieve the optimum plant operation.

Analysis Study of Available Alternatives for Mitigation of Aromatic Hydrocarbon Emissions from a Glycol Dehydration Unit

“…Amouei Torkmahalleh et al [38] observed that the infuence of the reboiler duty, which is related to the regenerator temperature, is insignifcant with a slight increase in BTEX emissions observed with increasing the regeneration temperature. However, it is noted that at lower reboiler duty values, the infuence of the reboiler duty on BTEX emissions is more signifcant.…”

“…Tey also found that the stripping gas fow rate signifcantly impacts VOC emissions. Amouei Torkmahalleh et al [38] examined the impact of solvent circulation rate, reboiler heat duty, stripping gas circulation rate, and lean TEG temperature on BTEX, VOCs, and CO2 emissions. Teir results showed that increasing solvent circulation rate decreases dry gas moisture content to some extent, and if a solvent fow rate up to 9.25 GPM is used, the moisture content starts rising.…”

“…On the other hand, Darwish and Hilal [29] found that increasing solvent fow rate could lead to a decrease in solvent purity due to chemical dissolution, and hence, moisture content decreases. Many works such as the research works of Amouei Torkmahalleh et al [38], Hlavinka et al [39], Braek et al [22], and Sony et al [40] have been directed toward studying the NG dehydration operating conditions. Siti et al [41] studied the efect of operational parameters on the performance of natural gas dehydration process and an optimization of the operational parameters using symmetry process simulation software was carried out.…”

Selection of Natural Gas Dehydration Process for Offshore Floating Production Storage and Offloading

“…The results show that when the flow rate of nitrogen is increased to 400 kg h −1 , the concentration of the lean liquid can reach 0.999 wt%, the moisture content in the dry gas is reduced to below 1 ppm, but the loss of TEG increases to about 2.2 kg h −1 . Amouei Torkmahalleh et al [ 19 ] used two methods for sensitivity analysis in Aspen Plus. The first one is single factor sensitivity analysis, which is more intuitive to study the influence of the parameter disturbance on the process by controlling a single variable; the second one is sensitivity analysis is performed for a given parameter when all other parameters are optimal.…”