This paper is concerned with the mathematical modeling and simulation of the steady-state operation of an industrial moving bed heterogeneous reactor for the kraft pulping of Eucalyptus globulus. The cooking takes place in a single-vessel hydraulic digester adapted for isothermal cooking (ITC), a further development of the modi"ed continuous cooking (MCC) process. A heterogeneous model is used to take into account the di!erent phases, each with distinct pro"les of temperature and concentration of organic (lignin, cellulose and hemicellulose) and inorganic (e!ective alkali and sul"de) compounds. The numerical solution of the model is based on a non-uniform discretization strategy to cope with special geometric and operational features of the digester. The decrease in bulk porosity caused by the compaction of the bed and the progressive increase in the voidage of chips as a result of chemical reactions are incorporated into the model as well as the resulting implications in the entrapped and free liquor #ows. The model presented here can be used in optimization studies and has been validated with data from an industrial mill.

In the process industry, it is crucial to ensure safety, high product quality, strict environmental compliance, and optimum economics. Among other important factors, this calls for high performance of the control loops. One of the main root causes for poor performance is control valve malfunctions. In particular, stiction is a long-standing valve problem in the process industry, causing limit cycles with a negative impact on process performance. Therefore, it is important to detect this phenomenon as early as possible, to distinguish it from other oscillation causes, to determine the correct maintenance measures, and, if applicable, to apply proper stiction compensation. The present survey covers the field of stiction modeling, detection, and compensation, encompassing main research directions and significant contributions that have been reported in the literature. The relationship among different approaches is outlined showing their strengths and weaknesses. The review is complemented with a description of academic and commercial software packages that incorporate stiction diagnosis. Finally, a view on possible future research directions is provided.

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