Process Optimization Of Membrane-cryogenic Hybrid System For Carbon Dioxide Recovery

Continuous carbon dioxide emission triggers the greenhouse effect and leads to frequent occurrences of extreme climate phenomena worldwide.After years of rapid economic blooming,China has become the world's largest carbon emitter.To curb excessive carbon emissions and achieve sustainable development in society,economy and environment,it is necessary to promote the clean energy utilization and low-carbon technologies in the whole nation.Based on our national energy security condition,it is particularly important to popularize carbon capture technology in thermal power plants.In order to further reduce the process energy consumption in carbon recovery process,break through the development bottleneck of related technologies and reduce the construction and maintenance costs of separation system,this paper investigated the carbon dioxide recovery network in thermal power plants,especially focused on multi-units hybridization and multi-networks integration.Based on previous research,a set of systematic modeling and optimization approaches are proposed.These approaches can provide new ideas and methods for other related researches.First,based on the hybrid separation technique in carbon capture,this paper proposed a modeling and optimization method for separation network containing multi-units.On the basis of unit modeling,a superstructure model was built.Setting minimized total annual cost as objective function,a MINLP model can be established and calculated.The result showed that the optimized separation process could reduce the power consumption of backflow compressors effectively.In addition,a Pareto analysis was proposed to explore the relationship between carbon recovery rate and total annual cost.According to the energy consumption analysis,a suitable carbon recovery rate region was given.Secondly,this article integrated the design of separation network and heat exchanger network to improve the energy efficiency in carbon recovery network.Meanwhile,a piecewise approximation approach was proposed to deal with non-isothermal phase change in the multi-stream heat exchanger design;a stepwise optimization strategy was adopted to reduce the solving difficulty in multi-networks integrated model.The case results showed that separation system had no more need for low-temperature utilities after heat exchanger network design.The energy consumption in carbon recovery could be greatly reduced.Finally,the work exchanger network was introduced on the basis of separation-heat exchanger network.Meanwhile,temperature-varying membranes and modified heat exchanger network were appended to the original model.According to the separation requirements,each unit could adjust its own temperature and operating pressure.The optimization results of the separation-heat-work-exchanger network model showed that the multi-network integrated design could greatly improve the system economics and achieve the efficient separation of carbon dioxide.