Operation Optimization And Simulation Of Central-Asia Gas Pipeline System With Crossover Valves

In this paper,a mathematical model for operation optimization of Central-Asia gas pipeline system is developed considering crossover valves between Line A/B and Line C,and the corresponding algorithm is put forward based on a two-level iterative procedure.In a particular iteration,at the first level,flow rates through crossover valves are optimized via golden section search or improved pattern search method according to the numbers of opening valves.At the second level,flow rates through crossover valves are given and optimal pressure variables are found via dynamic programming or non-sequential dynamic programming.A software for operation optimization of Central-Asia gas pipeline system is developed based on VB.NET.By means of the software,for a variety of source flow scenarios,the operation schemes are optimized considering opening a certain valve and unknown valve combinations respectively.The optimization results show the facts:(1)When Line C is at full capacity(250×10~8m~3/a),and source flow rate of Line A/B decreases progressively from its full capacity(300×10~8m~3/a)to 120×10~8m~3/a by a step of 20×10~8m~3/a,the energy consumption of combined operation is lower than that of independent operation,and the difference is about 5%~24%.(2)When Line A/B is at full capacity and source flow rate of Line C falls from its full capacity to 142×10~8m~3/a,the energy consumption difference is small.So,in this case,the valves between Line A/B and Line C are suggested to be closed.(3)When Line A/B is at full capacity and source flow rate of Line C falls from 142×10~8m~3/a to 70×10~8m~3/a,the reduction of energy consumption is about 4%~11%.(4)When source flow rate of Line C is no less than 80%of its full capacity,and source flow rate of Line A/B falls from 80%to 40%of its full capacity,the maximum reduction is about 21%.Besides,in order to improve the capacity of unfavorable conditions,the corresponding optimal valves combination scheme is obtained according to various failure scenarios of compressor station using SPS software.The results of 24-hour transient simulation using SPS software show that the change of total flow is little compared to no action on crossover valves when the station CS1 or CS4 in Line A/B or station CCS2 or CCS5 in Line C is shutdown.