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The feedback control of temperature in a simulated batch reactor was studied in a class of the master’s degree in Chemical Engineering for educational purposes. The process was simulated in real-time by means of the software Simcet developed by PiControl Solutions LLC where a step test was performed in open-loop. The dynamic response of the process output (temperature) was observed and transfer function parameters were visually estimated and discussed. In the second part of the work, the dynamic response was fitted by a First Order Plus Dead Time model in the software PITOPS, by using the System Identification module. Determined transfer function parameters were compared to the ones visually estimated. Finally, the second module available in PITOPS, PID/APC Optimization allowed for determination of PID tuning parameters for several different tuning criteria (e.g. IAE, RO). The dynamic response of the process upon a set-point change was simulated in closed-loop, i.e., with controller in automatic mode. Finally, outputs for all tuning criteria applied were compared and discussed in detail. The use of mentioned software as a teaching tool in Process Control course was found to be quite beneficial. Students were given an opportunity to gain basic but very practical skills which are essential for future process engineers. Also, the fact that these programs were used for optimization of processes in several large industrial plants in Croatia (Rijeka Refinery, Pliva, Cemex, Hospira/Pfizer, Xellia, etc.), made students involved in the exercises, but also more interested in the Process Control co [ABSTRACT FROM AUTHOR]

The aim of this work was to determine the influence of cooling rate on the nucleation and crystal growth of borax decahydrate. All experiments were carried out in baffled stirred crystallizer with the volume of 2.14 dm³. Mother liquor saturated at 30 °C was cooled down at 3 different cooling rates in the range from the 4 to 9 °C/h. In order to analyze and compare the influence of fluid flow pattern in the crystallizer on product properties, examinations were performed using two different impeller types; radial straight blade turbine (SBT) and axial pitched blade turbine (PBT). Mixing with both of impellers was carried out at constant impeller speed of 300 rpm. Concentration of the solution was measured in line by potentiometric method, while the changes of crystal size over process time were determined by optical microscope and image analysis software. The nucleation and crystal growth behaviors for borax-water system in a batch cooling crystallizer were estimated according to Mersmann's criteria. From the results obtained, it was found that cooling rate has great impact on nucleation and crystal growth kinetics. Moreover, in all system investigated nucleation was heterogeneous and crystal growth integration limited, its rates differed with cooling rates. The changes of those parameters with cooling rates in the systems with radial and axial impeller were similar. Nucleation and crystal growth reflected on the crystal size distribution as well. Increasing cooling rate crystal mean size decreases while crystal agglomeration increases, indicating the importance of cooling rate of batch crystallizer in the production of the crystals of desired properties. [ABSTRACT FROM AUTHOR]