Energy Regeneration in Natural Gas Pressure Reduction Stations by Use of Gas Turbo Expander

Natural gas is transported at high nominal pressure 1000 psi. In the City Gate stations (CGS) the pressure must be reduced from 1000psi to 250psi. Gas pressure reduction is accomplished in throttle‐valves, without producing any energy. The replacement of the gas‐throttling process by the process of its expansion in turbo expanders (TE) makes it possible to convert the pressure of the natural gas into the mechanical energy, which can be transmitted to an electric generator. In this paper we have evaluated this work. One computer simulation was developed to study the exact values of some parameters when an expansion turbine driving a generator is used in place of the throttle valve.From thermodynamics relations involving enthalpy, entropy, the work can be achieved.As a case study, we have evaluated one City Gate Station with the maximum capacity of 120,000 SCMH1. The statistical records show that the average pressure and temperature of the inlet gas during the year 2008, varies from 694‐780 PSIG and 8‐19.4ºC respectively. The temperature of the natural gas decreases averagely 18ºC as it expandsthrough the control valve. When the turbo expander is used, the temperature drop is much greater, as the gas is doing work in the expansion. In this way, the gas needs to be preheated. The results show that the TE can produce 1.8 Mw power (maximum power) and the total electricity produced in one year is nearby 6000 Mw‐hr. Economical analysis show that for initial plant outlay and O&M costs, the payback period will be less than 2 years

کلیدواژه ها:

Gas Pressure ، Turbo Expander ، Energy Regeneration