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The paper presents the application of two nonlinear model predictive control (NMPC) approaches:quasi-infinite horizon nonlinear MPC (QIHNMPC) and moving horizon estimator nonlinear MPC (MHE-NMPC) to the FCCU. A complex dynamic model of the reactor-regenerator-fractionator system is developed and subsequently used in the controller. The novelty of the model consists in that besides the complex dynamics of the reactor-regenerator system, it also includes the dynamic model of the fractionator, as well as a five lumps kinetic model for the riser. Tight control is achieved using the QIHNMPC NMPC approach. The MHE-NMPC considers important features of a real-time control algorithm, resulting in a framework for practical NMPC implementation, such as: state and parameter estimation and efficient solution of the optimisation problem. In the NMPC approach, only measurements available in practice are considered, whereas the rest of the states are estimated together with uncertain model parameters, via MHE technique. Using an efficient numerical implementation based on the multiple shooting algorithm real-time feasibility of the approach is achieved. The incentives of the proposed approaches are assessed on the simulated industrial FCCU.

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Gasification technology is a process in which solid fuel is partially oxidised by oxygen and steam/water to produce a combustible gas called syngas (mainly a mixture of hydrogen and carbon monoxide). Syngas can be used either for power generation or processed to obtain various chemicals (hydrogen, ammonia, methanol, etc.). This article evaluates the possibilities of solid fuel decarbonisation by capturing carbon dioxide resulted form thermochemical conversion of solid fuel using gasification. Evaluation is focused on power generation technology using syngas produced by solid fuel gasification (so-called integrated gasification combined cycle -IGCC). Case studies analysed in the article are using a mixture of coal and biomass (sawdust) to produce around 400 MW electricity simultaneously with capturing about 90% of the feedstock carbon. Various carbon dioxide capture options (post-and pre-combustion) are compared with situation of no carbon capture in terms of plant configurations, energy penalty, CO 2 emissions, etc. Plant options are modelled using ChemCAD, and simulation results are used to assess the plant performances. Plant flexibility and future improvements are also discussed. 