Pancione, Esther (2025) Experimental and modelling optimization of a VPSA process for Biogas Upgrading. [Tesi di dottorato]

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• Nonlinear homogenization. (deposited 21 Mag 2010 11:26)
  • Experimental and modelling optimization of a VPSA process for Biogas Upgrading. (deposited 26 Gen 2026 11:49) [Attualmente visualizzato]

Abstract

The global transition toward carbon-neutral energy has intensified the need for efficient biogas upgrading technologies capable of delivering grid-quality biomethane with minimal methane losses. Vacuum Pressure Swing Adsorption (VPSA) represents a solvent-free, modular, and energy-efficient solution, yet its industrial deployment remains constrained by limited experimental validation and incomplete understanding of material–process interactions, living room for further process optimization. This PhD project, developed as an industrial doctorate with Oiltech S.r.l., addressed these gaps through an integrated experimental–modeling approach aimed at designing and optimizing a VPSA process for biogas upgrading. The work combined materials characterization, cyclic testing, and dynamic simulation to establish quantitative links between adsorbent properties, operating conditions, and process performance. Two adsorbents were investigated, the metal–organic framework UTSA-089 and the carbon molecular sieve CMS CT-350. Breakthrough experiments on a lab-scale VPSA unit provided equilibrium and kinetic data for CH₄/CO₂ mixtures (1–8 bar, 20–80 °C), enabling the determination of isotherm and mass-transfer parameters, while complementary desorption and cyclic tests on a single-column were performed to assess regeneration kinetics and define the optimal regeneration strategy. Multi-column VPSA cycles were designed through a fine tuning based on the measured adsorbent properties and systematically tested to assess the influence of operating conditions, cycle configuration, and step sequencing on overall process performance. UTSA-089 exhibited high CO2 capacity but slow regeneration and poor cyclic stability, while CMS CT-350 achieved superior performance, achieving CH₄ purity above 97% and recovery up to 95% with moderate energy demand (≈ 9–11 kJ mol⁻¹). A one-dimensional non-isothermal model was developed and implemented in Aspen Adsorption, incorporating multicomponent Sips isotherms, LDF kinetics with Darken correction, coupled with full mass-, momentum-, and energy-balances. The model was calibrated using the experimental data set, and accurately reproduced the measured transient profiles of pressure, flowrate, and composition as well as the overall process performance (with deviation up to 3%). Beyond validation, the simulator acts as predictive design tool, enabling virtual testing of operating scenarios and advanced VPSA configurations that cannot be readily implemented experimentally. By allowing systematic variation of key process parameters (pressure, flowrate, feed composition, and step durations), the model minimizes trial-and-error experimentation and guides targeted optimization, thereby reducing development costs and accelerating industrial scale-up. Overall, this industrial PhD establishes a validated workflow that directly supports the deployment of VPSA technology for biomethane production at industrial scale. For the industrial partner, the experimental database and the calibrated Aspen Adsorption model now constitute a decision-making tool for the design and de-risking of a pre-commercial VPSA prototype and for planning subsequent scale-up steps, including the evaluation of advanced configurations such as VPSA units in series or partial recycle of the waste stream, with the ultimate goal of limiting CH₄ slip and improving overall energy utilization.

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