Enhancement in NGL production and improvement in water dew point temperature by optimization of slug catchers’ pressures in water dew point adjustment unit

Abstract

The water dew point adjustment is one of the most important processes in all gas refineries which reduces the water content of gas to some allowable limit and separates the heavy hydrocarbons from gas. In Sarkhun gas refinery, natural gas dehydration and hydrocarbon dew point adjustment are performed by cooling method. Diethylene glycol (DEG) is injected to gas–gas heat exchanger and chiller to absorb water from wet gas and act as a freezing inhibitor. Hydrate formation in filter elements was observed in this gas refinery which has been investigated in this research. The pressure difference between slug catchers and well streams were optimized by steady state process simulation software in order to decrease the mole percentage of C 6+ exited along with the outlet gas stream from slug catcher and maximize the separation of liquid hydrocarbons. The pressure difference between the slug catcher unit and well streamlines was adjusted at optimized conditions and the experimental sampling was performed during modifications. The experimental results showed a considerable decrease in the mole percentage of C 6+ exited along with the outlet gas stream from slug catcher and the simulation results showed 16500 bbl/year increase in NGL production rate. Operating under optimized pressure in the dew point adjustment unit of Sarkhun gas refinery decreased the water dew point temperature to −26 °C and improved the hydrocarbon dew point temperature to −9 °C. Moreover, NGL and LPG production rates increased annually about 18672 ton and 6365 ton after modifications which results in $11million extra annual income for company.