2009, Vol.12, No.2, pp.119-129

An input/state/output control-oriented model, a controller design, and a simulation technique are presented to facilitate development of the closed-loop control system for the cold flow fluidized bed riser (CFFBR). The control-oriented model is obtained by augmenting the two coupled nonlinear partial differential equations (PDEs) describing the flow process in CFFBR with an integral pressure readout map. The controller design is carried out using the model linearization at a steady state, the finite-dimensionalization of the linearized model, and the finite-dimensional LQG synthesis. Two numerical simulation tools are developed, one based on a Lagrangian method and the other - on the direct spatial PDE discretization. Both simulation tools are applied to the closed-loop system consisting of the nonlinear PDE-based riser model and the linear finite dimensional control law. The simulation reveals that the Lagrangian based numerical technique overcomes computational difficulties arising due to the stiff source terms in a control-oriented model significantly better than the direct discretization technique and provides an adequate computational tool for the closed-loop system simulation. Using this simulation tool, the numerical performance assessment of the closed-loop system is carried out, demonstrating stable system performance under the proposed control law. The tools presented pave the way for improving, through the closed loop control, the performance of the gas/solid FB transport risers in the novel near-zero emission coal-based power generation processes currently under development.
Key words: fluidized bed, riser, control, sensing, actuation

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