Development of a dynamic multi-bed Pressure Swing Adsorption process for high purity hydrogen production from Coke Oven Gas

Abstract

Coal is certain to play a major role in the world’s energy future due to its low cost and widespread distribution around the world. At the same time, being the largest contributor to global CO2 emissions from energy use, coal faces significant environmental challenges in terms of air pollution and global warming. The study focuses on developing a pressure swing adsorption (PSA) technology that will allow for continued operation of coal, while improving its energy-efficiency by better utilisation of its by-product coke oven gas from steel industries. A generic, fast and robust simulation tool for simulating a variety of pressure swing adsorption processes considering both equilibrium and kinetic effects using a detailed non-isothermal and non-isobaric model is developed using MATLAB in the study. The adsorption equilibrium data required for the model are first calculated from experimental results using the non-linear regression data fitting method. Activated carbon and zeolite LiX adsorbents are modelled using Spartan molecular modeling software and simulated for estimation of the adsorption equilibrium data. The isosteric heat of adsorption values estimated from the simulation of molecular models matched well with the values calculated from experimental results showing the potential of molecular modeling tool in estimating the adsorption equilibrium data in a simple, fast and cost-effective way. A series of rigorous parametric studies and breakthrough tests are performed using the developed mathematical model for better understanding of the effects of different factors on the PSA process performance. With the better understanding obtained from the above-mentioned parametric studies, the model is optimised by performing several simulation tests to achieve the best possible process performance in terms of purity and recovery of the H2 product, productivity of the adsorbents and energy consumption for compression of gases. The optimised 14-step multi-bed PSA cycle developed in this study allows for an improved energy efficiency of coal usage by better utilisation of its by-product coke oven gas by converting it into valuable high purity (>99.999%) hydrogen fuel for mobility applications with a recovery of over 75%.