Simulation And Optimization Of Hydrogen Storage And Purification Using Adsorbents And Metal Hydrides

Effective hydrogen storage and hydrogen purification play important roles in the hydrogen energy economy.Hydrogen can be stored using physical and chemical methods,such as the adsorption-desorption process based on adsorbents and the hydriding-dehydriding process based on metal hydrides.Hydrogen also can be purified from mixture gases using adsorbents through physical method and metal hydrides through chemical method.In this work,various models for the hydrogen storage system and the hydrogen purification system have been developed and validated in order to simulate and optimize the system performance.As for the physical hydrogen storage,the flow-through cooling method has been used in the adsorptive hydrogen storage delivery tank based on the activated carbon in order to improve the system efficiency.As for the chemical hydrogen storage,a lumped parameter model has been built for metal hydride hydrogen storage tank to investigate the system performance.Then the analytical solution for the lumped temperature of metal hydride bed is obtained which can be used as a benchmark for lumped/distributed parameter models.In addition,some distributed parameter models have been developed to research the thermal effect during hydriding on the system performance.Considering the huge reaction heat released during hydriding,the coiled-tube heat exchanger is applied into the metal hydride hydrogen storage tank.Complete 3D models have been used to investigate the performance of metal hydride reactor equipped with complicated heat exchanger.The reduced 2D models for coiled-tube heat exchangers have been presented and validated for calculation simplification.Phase change materials can be used to store the heat energy during phase transition process,which can be composited with various metal foams including aluminium foam and copper foam to improve the effective thermal conductivity.The commercial paraffin RT35 is used as the phase change material in the work.These composited phase change materials have been employed to the metal hydride hydrogen storage system for performance optimization.Hydrogen can be separated and purified from the gaseous mixtures through the physical method and the chemical method.The pressure swing adsorption(PSA)technology is widely used for hydrogen purification.As for the physical hydrogen purification,the adsorption isotherm model and the PSA model have been developed and validated in order to simulate the hydrogen purification process using zeolite 5A as the adsorbent.The performance of the vacuum pressure swing adsorption(VPSA)system has been compared with that of the PSA system.The results show that it is an effective method to improve the hydrogen purity through the VPSA method.Then,the validated PSA model has been used to generate a dataset for training the artificial neural network(ANN)model.The trained ANN model and the multi-objective optimization function have been used to obtain optimal operation conditions for the performance optimization of hydrogen purification system.As for the chemical hydrogen purification,the metal hydride has been applied in a similar PSA hydrogen purification system.A lumped parameter model for the metal hydride hydrogen purification system has been developed and validated,the performances of this system are researched through parametric study.