a Mohajeri - Department of Industrial Engineering, Mazandaran University of Science and Technology, Babol, Iran
i mahdavi - Department of Industrial Engineering, Mazandaran University of Science and Technology, Babol, Iran
n Mahdavi-Amiri - Faculty of Mathematical Sciences, Sharif University of Technology, Tehran, Iran
r Tafazzoli - Mazandaran Gas Company, Sari, Iran

An Ant Colony Optimization (ACO) algorithm is proposed for optimal tree-structured natural gas distribution network. Design of pipelines, facilities, and equipment systems are necessary tasks to configure an optimal natural gas network. A mixed integer programming model is formulated to minimize the total cost in the network. The aim is to optimize pipe diameter sizes so that the location-allocation cost is minimized. Pipeline systems in natural gas network must be designed based on gas flow rate, length of pipe, gas maximum pressure drop allowance, and gas maximum velocityallowance. We use the information regarding gas flow rates and pipe diameter sizes considering the gas pressure and velocity restrictions. We apply the Minimum Spanning Tree (MST) technique to obtain a network with minimum number of arcs, spanning all the nodes with no cycle. As a maincontribution here, we present and use an ant colony optimization algorithm for solving the problem. The proposed method is applied to a real life situation. Our obtained results are compared to the ones obtained by an exact method. The results show that ACO is an effective approach for gas distribution network optimization. A case study in Mazandaran Gas Company in Iran is conducted to illustrate thevalidity and effectiveness of the proposed approach.

Natural-gas network; Minimum spanning tree ; Location-allocation; Ant colony optimization