A simple and general scale-up procedure, based on boundary and temperature diagram safety criteria for exothermic semibatch reactors (SBRs), has been developed. Such a procedure is based on a few graphical correlations that allow end users, dealing with homogeneous as well as heterogeneous SBRs (with or without autocatalytic behavior), an easy selection of safe operating conditions at the laboratory scale and for their scale-up to the industrial one, maximizing at the same time the industrial reactor productivity.

In this work a simple and general procedure, for optimally scaling-up exothermic semibatch processes, has been applied to the analysis of a nitration reaction performed in the agrochemical industry for the production of an important class of herbicides. Such a reaction is performed in indirectly cooled semibatch reactors in which the species to be nitrated is added to a mixture of sulfuric and nitric acid, forming an heterogeneous (liquid-liquid) system. Adiabatic calorimetric experiments performed in an ARC equipment showed that the reaction in question belongs to the most critical class of exothermic reaction processes, for which maximum attainable temperature due to synthesis reaction (MTSR) is, at the same time, higher than system decomposition temperature and lower than boiling temperature of the reaction mass. It has been verified, through reaction calorimetry experiments (performed in an RC1 equipment), that the optimization -scale-up procedure previously developed allows, with a minimum calculation and experimental effort, both for a selection, at laboratory scale, of operating conditions characterized by a rapid coreactant consumption and for their safe scale-up, maximizing industrial reactor productivity.

Safe operating conditions, for strongly exothermic chemical systems involving multiple reactions, are particularly critical to be obtained, because of the complex interactions between selectivity and safety constraints. In this work, new criteria, which are useful for isoperibolic semibatch processes involving consecutive reactions and based on the topology of a particular phase space, are presented. Such criteria are able to detect both the runaway boundary and the so-called "quick onset, fair conversion, smooth temperature profile" (QFS) operating region by performing a topological analysis of the phase space of the system of ordinary differential equations (ODEs) that describe the analyzed process. Moreover, a safe optimization procedure, the objective of which is to obtain the optimum values both of the dosing time of the dosed reactant and the initial reactor temperature, based on such criteria, has been developed. Finally, such a set of optimum operating parameters has been validated through a comparison with experimental data from published literature.

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Safe and productive operating conditions for complex exothermic chemical processes are difficult to obtain because of the strong interaction between selectivity and safety constraints. In this work a generalization of the topological criterion to nonautocatalytic, chain, and autocatalytic catalyzed reaction schemes is presented. Such a criterion, useful for isoperibolic semibatch processes, is able to detect the so-called QFS boundary by performing a topological analysis of a suitable reduced phase portrait of the system of ordinary differential equations describing the process. Moreover, a safe and general procedure aimed to obtain the optimum values of both the dosing time and the initial reactor/coolant temperature, based on such a criterion, has been proposed and validated through the use of literature experimental data and laboratory tests concerning the case studies analyzed.

In this paper, a laboratory-scale experimentation allowed comparing the performances of two upflow anaerobic packed-bed filters filled with different packing materials and operating at mesophilic conditions (30 degreeC) for treating slaughterhouse wastewaters. Methane production was experimentally evaluated considering different volumetric organic loading rates as well as feeding overloading conditions. Although filter performances declined with loading rates higher than 6 kg CODin m-3 d-1 , the chemical oxygen demand (COD) removal efficiency remained always above 60%. The experimental results allowed for determining kinetic parameters for bacterial growth rate and methane production, following Monod and Chen-Hashimoto models, respectively. Results demonstrated that the reactors reached a cellular retention time significantly greater than the hydraulic retention time. The kinetic parameter values (Ks, l/max) revealed the low microorganisms' affinity for the substrate and confirmed the moderate biodegradability of slaughterhouse wastewater. The kinetic analysis also allowed the comparison of the filters performances with another anaerobic system and the assessment of the parameters useful for real-scale plant design. The system design, applied to a medium-sized Argentinean slaughterhouse, demonstrated to (i) be energetically self-sufficient and (ii) contribute to the plant's water heating requirements.

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