This paper focuses on the fluid catalytic cracking (FCC) process and reviews recent developments in its modeling, monitoring, control, and optimization. This challenging process exhibits complex behavior, requiring detailed models to express the nonlinear effects and extensive interactions between input and control variables that are observed in industrial practice. The FCC models currently available differ enormously in terms of their scope, level of detail, modeling hypothesis, and solution approaches used. Nevertheless, significant benefits from their effective use in various routine tasks are starting to be widely recognized by the industry. To help improve the existing modeling approaches, this review describes and compares the different mathematical frameworks that have been applied in the modeling, simulation, control, and optimization of this key downstream unit. Given the effects that perturbations in the feedstock quality and other unit disturbances might have, especially when associated with frequent changes in market demand, this paper also demonstrates the importance of understanding the nonlinear behavior of the FCC process. The incentives associated with the use of advanced model-based supervision strategies, such as nonlinear model predictive control and real-time optimization techniques, are also presented and discussed.

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There are currently no studies in the literature on the use of natural waste marble powder (WMP) resources as inexpensive sorbents for looping cycle CO2 capture. The high volume of marble production is associated with considerable amounts of WMP generated as byproduct during cutting and polishing procedures, which negatively impacts the surrounding environment. The main goal and innovative idea addressed in this study consists of investigating if solid wastes WMP from marble producer sources can be used as possible inexpensive and effective solid materials to be used as precursors of CaO-based sorbents in Ca-looping cycle CO2 post-combustion capture process. The cyclic carbonation–calcination reactions were experimentally studied in a laboratory-scale fixed-bed reactor unit for 10 and 20 cycles. The innovative and interesting results obtained show that Portuguese WMP represents a category of promising natural inexpensive solid sorbents to be used as effective CaO-based sorbents for looping cycle CO2 post-combustion capture, because of their increased CO2 carrying capacity and better cyclic stability with lower sorbent deactivation with the number of cycles, when compared with commercial CaCO3 reference sorbent precursor and with other natural and synthetic CaO-based sorbents, and other CaO-solid-based materials from industrial and natural wastes recovery, reported in the literature. The WMP resources have potential to be an economically attractive option thus contributing to reduce the cost of the Ca-looping cycle CO2 capture process, as well as to minimize the adverse environmental impacts of the high volume of WMP generated in the marble producers.

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