Optimization of Gas Transmission Networks under Energetic and Environmental Considerations
Résumé
The transport of large quantities of natural gas (NG) is carried out by pipelinenetwork systems across long distances. Pipeline network systems include one orseveral compressor stations which compensate for pressure drops. A typical net-work today might consist of thousands of pipes, dozens of stations, and manyother devices, such as valves and regulators. Inside each station, there can be sev-eral groups of compressor units of various vintages that were installed as the ca-pacity of the system expanded. The compressor stations typically consume about3 to 5% of the transported gas. It is estimated that the global optimization ofoperations can save considerably the fuel consumed by the stations. Hence, theproblem of minimizing fuel cost is of great importance. This study presents amathematical formulation for NG transport through pipelines and compressors byconsidering the mass and energy balance equations on the basic elements of a di-dactic network from the literature. First, a deterministic optimization procedure isimplemented. The objective of this formulation is the fuel minimization problemin the compressor stations for a fixed gas mass flow delivery. A second example isdevoted to the simultaneous consideration of gas mass flow delivery maximizationand fuel consumption minimization. In that case, two procedures are compared:a genetic algorithm coupled with a Newton-Raphson procedure and the scalariza-tion method of ?-constraint. In both monobjective and biobjective cases, a studyof carbon dioxide (CO2) emissions is carried out. The Pareto front deduced fromthe biobjective optimization can be used either for identifying the minimum andmaximum network capacity in terms of CO2 emissions and mass flow delivery or for a given mass flow delivery for determining the minimal CO2emissions froman appropriate operating of the compressor stations.
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