The minimum gas temperature at the inlet of regulators in natural gas pressure reduction stations (CGS) for energy saving in water bath heaters

In this study a computational procedure for the computation of Joule-Thomson coefficient of natural gas has been developed using fundamental thermodynamic equations and AGA-8 equation of state, and then the minimum possible temperature of the natural gas entering to the pressure regulator of city gate stations (CGS) is calculated. As a case study, a CGS located in Bistoon (of Iran's CGSs) with nominal capacity of 20,000 SCMH has been considered. A comparison has been made between the calculated results and corresponding collected data from the station within 10 months. Results of this study help to determine the minimum temperature values of entering gas with different pressures to the regulator in order to avoid hydrate formation of the outlet gas, and can be used to design appropriate temperature control systems for water bath heaters and in turn save consumed energy for gas heating. The results show that heating the gas up to calculated minimum temperatures can save energy consumption of heaters by 43%. Also, it is indicated that by applying a control system, based on the result of this study, in the CGS the payback period would be less than a year.