Using system analytical method, a mathematical model for evaluating the efficiency of gas-distribution piping system was established, and the illation was made about efficiency of it in the realm of evaluation.

Based on the affect of the different lay mode of pipeline in investment,and the objective function was the shortest length of the layout pipeline,the layout optimizes model of the city gas pipelinenetwork was set up.

A tentative programme for electric disposition of 150 kt/a PET unit;