Optimization Algorithm Research Of CO₂ Pipeline Transportation System Under Uncertain Design Conditions

With the continuous increase of greenhouse gas emissions,extreme events caused by flooding,land drought,snow storm disasters and so on,have appeared continuously in public observation.Carbon capture,utilization,storage?CCUS?technology is one of the major means to reduce the CO₂ emissions.CCUS is to separate CO₂ from industrial or other emission sources,to transport the captured CO₂ to specific sites,and to utilize or store,thus to achieve a long-term isolation of CO₂ from atmosphere.Existing studies have shown that pipeline is an effective way to transport large-scale,long-distance CO₂,it is an important link for the capture source and storage location,as a vital part of CCUS investment,CO₂ pipeline transportation cost should not be neglected.However,in the engineering practice for transporting,there inevitably exist multiple engineering and economic uncertainties including the temperature,pump efficiency,electricity price,operation and maintenance costs,and so on,which seriously affect the pipeline optimization design performance.The CO₂ pipeline transportation system is studied in this paper,which focuses on the optimization algorithm research of pipeline transportation system under uncertain design conditions.The main contents are as follows.?1?The mismatch problem is researched between the calculated and engineering pipe diameter,based on the analysis of the differences and relations of engineering and calculated pipe diameters,a stepwise optimization algorithm is proposed,in the first step,the pipe diameter and wall thickness are optimized,in the second step,the inlet pressure and number of pump stations are optimized based on the optimized engineering pipe diameter and wall thickness.The CO₂ pipeline transportation system optimization problem is researched in the presence of temperature uncertainty,the paper analyzes the effect of temperature on the optimization problem of the pipeline transportation system,a piecewise design philosophy is proposed,which classifies the temperature range of the soil around the pipeline,further a corresponding optimization criterion is presented.?2?The CO₂ pipeline transportation system optimization algorithm is studied in the presence of multiple uncertain conditions.In the presence of multiple uncertainties,a robust optimization model is proposed.The model is linearized and then transformed into a quadratic programming problem,linear matrix inequality?LMI?is used to solve the proposed robust optimization problem.Compared with the sensitivity analysis approach,the proposed algorithm can effectively address the pipeline transportation system optimization problem under multiple uncertain design conditions.?3?CO₂ pipeline transportation is a multi-input and multi-output complicated nonlinear system,the optimization problem is difficult to be solved in the presence of multiple uncertainties.In light of the established robust optimization model of the pipeline transportation system,a co-evolutionary particle swarm optimization?PSO?algorithm is developed,compared with the robust optimization algorithm based on LMI,the proposed algorithm does not need the model linearization,which can avoid the model accuracy loss and obtain efficient solution,the optimization performance is improved.?4?CCUS system includes three sub-systems of CO₂ capture,transportation,utilization and storage,pipeline transportation system is the middle link of CCUS,whose optimization is closely connected with the other two sub-systems.However,there inevitably exist uncertainties in the pipeline transportation system,these uncertainties effectively affect the optimization design performance of the pipeline transportation system,which lead to unnecessary expenditure.The levelized cost of the pipeline transportation system is variable under the multiple uncertain design conditions,which affects the design of the other sub-systems.In turn,the design of the other sub-systems affects the design of the pipeline transportation system.Therefore,there are some flexibilities for the CCUS overall design and sub-systems designs.In order to solve the flexible optimization design problem of CO₂ pipeline transportation system,this paper proposes an interval number optimization algorithm,average levelized cost and system robustness are given as the optimization objectives,a two-objective,two-level,two-step optimization problem is established and solved by using quantum genetic algorithm?QGA?.The proposed interval number optimization algorithm has good decision space,the decision makers can flexibly make decisions based on the experimental analysis and the subjective preference,the designed pipeline transportation system is more flexible,which can be combined with the optimization of the other sub-systems,further,realize the coordination and unification of the CCUS optimization.In this paper,the optimization algorithms of pipeline transport system are studied under uncertain design conditions.Four algorithms are proposed including stepwise and piecewise optimization algorithm,robust optimization algorithm based on LMI,co-evolutionary algorithm,interval number algorithm,the uncertainties assumption and the use range are different for the four algorithms.The piecewise optimization algorithm is used to address the optimization problem of the pipeline transportation system under design condition of the temperature around the pipeline,however,in the presence of multiple uncertainties,this method is difficult to be used.To solve this problem,robust optimization algorithm based on LMI and co-evolutionary algorithm are proposed.By using the robust optimization algorithm based on LMI,the model should be linearized,which inevitably lead to model accuracy-loss,the algorithm is suitable to be used in the situation with the requirements of low precision and quick calculating speed.Co-evolutionary PSO algorithm doesn't need the model linearization,which is suitable to be used in the situation with the requirement of high precision and low calculating speed.Interval number algorithm is used to solve the flexible optimization design problem of CO₂ pipeline transportation system under multiple uncertain design conditions,which makes the system design with good decision space.The algorithm makes the CCUS optimization realization with good adaptability,which is suitable to be used in the situation of the coordination and unification of the pipeline transportation system and the other CCUS sub-systems optimization,however,it needs the decision maker with abundant CCUS design experiences to make decisions flexibly.