Improving performance of absorption tower in natural gas dehydration process

Absorption tower is the most important section of a natural gas dehydration plant. In this paper the effect of some influential factors such as temperature and flow rate of TEG entering the tower, number of equilibrium stages and liquid fractional entrainment in gas phase on performance of dehydration absorption tower is investigated. Entrainment is one of the most effective factors on tray tower performance, particularly absorption towers where the liquid concentration is much higher than the vapor in equilibrium with it. The effect of this parameter has not been considered in commonplace simulating softwares. Having extracted an equation for the fractional entrainment factor with the aid of Fair empirical correlation, a simulator is prepared using VC++ program language in 9000 lines of source code which includes subprograms for simulating absorption, desorption and distillation towers, heat exchangers, condensers and flash drums. Input data corresponded to TEG dehydration unit of Asaloye gas field in Iran. The simulation results show that increasing TEG inlet temperature decreases water absorption efficiency while increasing TEG flow rate and number of stages increases this efficiency as well as absorption of pollutants like benzene and toluene. Finally it was observed that increasing entrainment decreases water absorption efficiency as expected.

Keywords:

Dehydration , Absorption Towers , TEG , Entrainment , Simulation