Influence of process parameters on thermodynamic efficiency of expander-generator units at the plants for technological decompression of transported natural gas

Abstract

The article presents the research results of the influence of process parameters on the thermodynamic efficiency of expander-generator units, used as an alternative to throttling devices for technological reduction of pressure of transported natural gas at the plants of technological decompression of the gas supply system–gas distribution stations (GDS) and gas control points (GCP). The process parameters are the temperature of the outside air, the ratio between the pressures of the transported gas at the outlet and inlet of GDS and GCP, and the temperature of the gas heating before the expander. Various circuit designs of expander-generator units for generating either only electricity or electricity and cold are considered. Exergy efficiency is taken as a criterion for evaluating thermodynamic efficiency. The calculation results for the changes in flow exergy and exergy efficiency at changing process parameters are presented in graphical form. The thermodynamic efficiencies of throttling devices and expander-generator units are com-pared. It is shown that the replacement of the throttling device by the expander-generator unit for all the considered process parameters leads to an increase in the exergy efficiency of the stations for technological decompression of the transported gas in all the considered schemes of this unit inclusion: without heating the gas in the expander-generator unit, with heating the gas after the expander, as well as with heating before and after it.