(170b) Dynamic Modeling and Explicit Model Predictive Control of Absorption of Hydrogen in a LaNi5 Bed
AIChE Annual Meeting
Monday, October 30, 2017 - 12:49pm to 1:08pm
The high-fidelity dynamic model described in this work is based on first principles according to [7, 9] and accounts for the spatial variations of some thermodynamic properties. The model makes the following assumptions; the ideal gas law holds in the gas phase, the solid and fluid temperatures are essentially equal, axial and radial dispersion are included in the mass balances for the interstitial fluid, the axial and radial pressure drops in the bed depend linearly on the superficial velocity through Darcy's law. The model is developed in gPROMS software and it is used to simulate the absorption process. It is subsequently validated with experimental data. An optimization procedure is implemented on the model to determine optimal operation condition and results of the optimization will be used to determine appropriate constraints for the control design. The optimization strategy minimizes the storing time and the output pressure while satisfying, a number of operating and safety constraints. In the second part of this work, we develop a reduced order approximate model suitable for multi-parametric model predictive control (mp-MPC) based on prior analysis. The reduced order state-space (SS) model (usually linear) is developed using model identification. The SS model is developed such that it can approximate the high fidelity model. The main contribution is the design of a multi-parametric/explicit model predictive controller to regulate the absorption of hydrogen in the LaNi5bed. Unlike the MPC the mp-MPC MPC avoids the online optimization procedure. The optimization is done offline to determine the control action at every state obtained while simultaneously accounting for physical and operational constraints. For system with faster dynamics (like the MH), mp-MPC is ideal. The explicit controller is designed in MATLAB and it is linked to gPROMS through gO:MATLAB.
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