Rapid estimation of equilibrium water dew point of natural gas in TEG dehydration systems

Abstract

Evaluation of a triethylene glycol (TEG) system involves first establishing the minimum triethylene glycol (TEG) concentration required to meet the outlet gas water dew point specification. In the present work, simple-to-use correlation, which is simpler than currently available models involving a large number of parameters, requiring more complicated and longer computations, has been developed for the rapid estimation of the water dew point of a natural gas stream in equilibrium with a TEG solution at various temperatures and TEG concentrations. This correlation can be used to estimate the required TEG concentration for a particular application or the theoretical dew point depression for a given TEG concentration and contactor temperature. Actual outlet dewpoints depend on the TEG circulation rate and number of equilibrium stages, but typical approaches to equilibrium are 6–11 °C. Equilibrium dewpoints are relatively insensitive to pressure and this correlation may be used up to 10 300 kPa (abs) with little error. The proposed correlation covers VLE data for TEG–water system for contactor temperatures between 10 °C and 80 °C and TEG concentrations ranging from 90.00 to 99.999 wt%. The average absolute deviation percent from the data reported in the literature is 0.5% which shows the excellent performance of proposed correlation. This simple-to-use correlation can be of immense practical value for the gas engineers to have a quick check on equilibrium water dew point of natural gas at various temperatures and TEG weight percents. In particular, personnel dealing with natural gas dehydration and processing would find the proposed approach to be user friendly involving no complex expressions with transparent calculations.