In the past few years, the numerical solution of non-linear equations for natural gas network optimization has proven to be useful. This paper presents: (1) a sensibility analysis for the most important flow equations defining the key parameters in the optimization process, and (2) a software "GasNet" based in the Stoner method, improved with several techniques to solve the equations system, allowing until an error of 50% in the initial values which avoids the divergence and accelerates the convergence.

GasNet is a powerful tool for design and optimization because it has advantages such as many routines for handling the specific gravity of the natural gas mixture composition; in addition it includes correlations used to obtain other properties. It also has graphic utilities that make easier the detection and solution of problems.

With information from the network as: flow rate, input and/or output pressures, features of the pipelines, compressors, valves and regulators, etc., we perform a sensibility analysis in order to get which flow equation: Weymouth, Panhandle, AGA, etc., is best at predicting the natural gas flow behavior in the pipeline (also this adjustment is applied to the PVT correlations and the equations of state by determining the Z-factor). The variation between the predicted and measured values with two parameters was estimated using the coefficient of multiple correlation and the X2-distribution.

The optimization process is performed with two criteria: the maximum operational permissible pressure and the gas flow velocity. These criteria allow for security in the facilities and suppress the harmful bottle-neck.

Two field examples are considered to illustrate the applicability of the proposed algorithms: distribution of a high pressure natural gas network in the Mexico Valley, Mexico and a network in Michigan State, USA.

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