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The effect of the duration of the adsorption step and purge flowrate on the performance of a demand-driven pressure swing adsorption unit (PSA) was investigated. These two operating parameters were varied and examined by simultaneously varying the requested total productivities (demand) using a model for biogas upgrading. The considered biogas PSA application uses a FAU zeolite (13X) to separate CH4 and CO2. The performance is tracked by three key performance indicators (KPIs): purity, recovery and total productivity. Depending on the selected KPI and constraints, an optimum emerges for the adsorption duration and purge flowrate. The breakthrough of carbon dioxide and insufficient purging are key elements limiting the performance for adsorption durations above and below the optimum, respectively. The complex interplay among the KPIs for the PSA process is visualized using a three-dimensional representation. Here, the various operating parameter settings (duration of the adsorption step and purge flow) define curves on the 3D surfaces, visualizing the effect of the PSA settings on all KPIs simultaneously. From such graphs, contour plots are extracted to highlight Pareto frontiers for a constant productivity or purity constraint.
Witte et al. (Mon,) studied this question.