Natural gas is usually transported by pipeline networks. This paper presents a multi-objective optimization model in optimizing the operation of natural gas pipeline networks. A mathematical model is established for different network configurations, namely linear, branch and looped topologies. Two conflicting objectives, power consumption minimization and gas delivery flow rate maximization, are considered subjected to pipeline and compressor constraints. The decision variables are the pressure at the nodes and the rotational speed of the compressors. A set of constraints is developed based on gas flow equations and compressors operating conditions. Due to the nonlinearity of the constraints and the objective, the developed model is a Nonlinear Programming problem. The optimization of the models is performed with NSGA-II algorithm. The solution obtained is a set of Pareto optimal points from which a decision maker can select a specific preferred solution. Sensitivity analysis was performed to determine the impact of parameter changes.
Pipelines are one of the most efficient means for transporting hydrocarbons from one point to the other. However, there is a great risk of pipelines operation failure due to the detrimental effects of corrosion. At the point of corrosion, the pipe wall becomes thinner and loses its mechanical resistance. In such cases, reliable defect assessment methods are necessary to decide whether to resume continual operation or to shut down for maintenance or replacement. However, the available assessment methods are over-conservative, which enforce either unnecessary maintenance or premature replacement. Furthermore, the defect assessment methods should not only ensure safe operation, but also optimized operation cost. Therefore, a new assessment method was developed based on the nonlinear finite element (FE) analysis and a parametric study of geometric parameters related to the corrosion defect. The new method was validated with burst test database, which can predict the burst pressure of corroded pipelines with better accuracy and consistency.
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