Subspace-based model identification of a hydrogen plant startup dynamics

•A detailed UniSim design model of the hydrogen plant is developed.•Plant standard operating procedure is adapted for simulation.•LTI model of the startup process using subspace identification is identified.•The framework is successfully validated against simulated and industrial data.

This work addresses the problem of determining a data-driven model for the startup of a hydrogen production unit, and demonstrates the approach both on a detailed first principles simulation model and by application to real data. To this end, first a detailed first principles model of the hydrogen plant is developed in Honeywell's UniSim design by adapting the plant standard operating procedure (SOP). Illustrative simulations are next presented to establish the meaningfulness of approximating process nonlinearity with a (higher order) linear time invariant (LTI) model. Then an LTI data-driven model of the hydrogen unit startup process using subspace identification based methods is identified. The framework is then implemented and successfully validated data on simulated data and on data from an industrial hydrogen unit.