Abstract: China' vigorous promotion of the construction of LNG import and LNG receiving stations, will from will form a natural gas pipeline network structure mainly for LNG and PNG supply in coastal cities. This research is aimed at the problem of collaborative LNG and PNG supply of natural gas pipeline network design optimization. On the basis of pipeline network design optimization, the influence of collaborative LNG and PNG supply on the pipeline network is included in the constraints, and the lowest annual equivalent cost is the objective function to establish a general MINLP model for the design and optimization of the natural pipeline network of the mixed gas source of LNG and PNG. Taking a coastal area as an example, two solution strategies, hierarchical optimization and overall optimization, are proposed to solve the above model. In the first stage of hierarchical optimization, the layout optimization will take the minimum flow length and the objective function line, and the mathematical programming solver GUROBI for solution, and in the second stage, the mathematical programming solver CONOPT is used. The overall optimization uses incremental piecewise linearization to linearize the pressure drop constraint, and the mathematical programming solver DICOPT for solution. Finally, two pipeline network design schemes of hierarchical optimization and overall optimization were obtained. The analysis found that the overall optimization solution time was longer than that of hierarchical optimization. The annual equivalent cost of overall optimization was reduced by RMB 7.4916 million per year, a decrease of 1.41%, which verified the reliability of the established general model, and can provide a reference for the design of the natural gas pipeline network for the collaborative supply of LNG and PNG.

Key words: LNG, PNG, mixed gas source, natural gas pipeline network, MINLP