Retrofit And Operation Optimization Of Hydrogen System In Petrochemical Complex

Hydrogen is a very important raw material and by-product in the current production of petrochemical complex.The design,retrofit,and operation optimization of hydrogen systems are also receiving increasing attention.In previous researches on hydrogen system design optimization,the optimal setting of compressors and the optimal use of compression power have always been addressed,but the utilization of hydrogen turbines for pressure energy recovery and optimization has not been considered.In addition,most of the existing hydrogen system optimization work is focused on the optimization design of the pipeline network,and there is not much research on the retrofit and optimization of the hydrogen system in the existing pipeline network.In the operation optimization of hydrogen systems,accurate prediction of hydrogen consumption and flow rates and concentrations of gas streams from high-pressure and low-pressure separators,and dry gases during the hydrogenation process is a key issue.To provide models and guidance for the design,retrofit,and operation optimization of hydrogen systems in petrochemical complex,the main research content of this thesis is presented as follows:(1)A new type of refinery hydrogen system superstructure integrating hydrogen compressors and turbines was proposed,and mathematical models were established with optimization objectives of minimum hydrogen utility usage,minimum compression power consumption,minimum power consumption,and minimum annual total cost of the system.In the scenario of minimum annual total cost of the system,the comparison of the impact on the annual total cost of the system before and after adding hydrogen turbines to recover expansion work was considered.Results show that the total energy consumption of the system can be reduced by 3.9% by adding hydrogen turbines to recover hydrogen expansion work in the hydrogen network system.(2)A multi-component hydrogen system integration optimization model for integrated hydrogen pipeline network was established based on the existing and expanded operating conditions of the hydrogen system in actual refineries.The optimization objective function was to minimize the annual total cost and flowrate of hydrogen utility.The optimization and retrofit strategies for recovering and purifying hydrogen under different supply conditions was studied,and the effectiveness of the model was validated.The results show that the system operating cost and hydrogen utility usage have significantly decreased after optimization and retrofit,with a maximum of 18.25%.The cost of hydrogen utilities accounts for the majority of the system operating costs under various optimization conditions,reaching a maximum of 87.16%.It indicates that in retrofit optimization of the hydrogen network,the major consideration should be given to the changes in the cost of hydrogen utilities.To reduce the usage of hydrogen utilities in the system,the optimization model minimizes the hydrogen concentration in the inlets of hydrogen sinks as much as possible,while meeting the requirement that the impurity concentration at the inlet of the hydrogen sink is below the upper limit in each scenario.At the same time,results show that the production capacity of the existing hydrogen production unit and hydrogen purification unit should be fully utilized before a new hydrogen production unit is constructed,to reduce the investment cost.(3)The mechanism models are established for the hydrogen production unit,main hydrogen consuming units,hydrogen compressors,and pipeline network in a hydrogen system of certain Petrochemical Complex.Furthermore,a hydrogen system scheduling optimization model was established,with the optimization goal of minimizing the total operating cost of the hydrogen system.The process simulation software data interface was collected,and the entire hydrogen system process simulation model was integrated.The genetic algorithm is selected to be the solving algorithm to obtain the optimal operation plan of the hydrogen pipeline network.The optimization calculation results show that,under different production plan conditions,by optimizing and adjusting the load of the hydrogen production unit,the proportion of by-product hydrogen from the reforming unit,and the supply of by-product hydrogen from the methyl ethyl ketone unit to different pipeline networks,the total operating cost of the hydrogen system can be reduced by 3.36% to 4.96%,and an optimization benefit of 28.98 million to 44.52 million CNY per year can be reached.The case study demonstrates the effectiveness of the optimization model in solving the scheduling optimization schemes of hydrogen systems under different production conditions in petrochemical complex.