An optimum design method for high pressure natural gas trunk-lines

Natural gas is rapidly growing in global importance both as a primary energy source and a feedstock for downstream industry. Therefore, needs for natural gas transportation from production zones to consuming areas are ever increasing. Natural Gas transmission through pipelines is the oldest and most common method for high capacities gas transmission. These transmission systems are very capital intensive, therefore, optimum designs for this method of transportation seems indispensable. In this paper, the optimum design for these pipelines has been investigated from technical and economical viewpoints. Different combinations of diameters, thicknesses, pipeline grades, number of possible compressor stations is considered in this optimization procedure and some major technical constraints are also included. The optimization criteria has been the minimization of pipeline life cycle cost consisting Capex and Opex of pipelines and compressor stations. An optimization method to find the optimum combination of operating and design variables for a gas transmission trunk-line has been developed. Based on this method, an algorithm has been written using VISUAL BASIC software. The effect of different operating variables on the life cycle cost could be investigated using this algorithm. The effect of maximum operating pressure on the life cycle cost for one of the Iranian Gas Tunk-Lines (IGAT II) has been investigated.