Boreskov Institute of Catalysis of the Siberian Branch of Russian ...

PP-II-3THERMAL MODES FOR THE CSTR WITH COMPLEX CHEMICALREACTIONSSamoilenko N.G., Deyun E.V., Korsunskiy B.L., Andrianova Z.S., Kustova L.V.Institute of Problems of Chemical Physics, Russian Academy of Sciences142432 N. Semenov avenue, Moscow region, Chernogolovka, Russia.E-mail: kors@polymer.chph.ras.ruThe investigation of thermal modes for continuous stirred-tank reactor (CSTR) is usefulin two aspects. First, it gives a contribution in the scientific basis of the safety of industrialprocesses, and, second, it widens our knowledge on the mechanisms of the birth/death of thee. g. self-oscillation regime. The dynamic behavior of CSTR with a simple reaction is wellinvestigated [1]. However the problem of the dynamic behavior of CSTR remains still nonsolved.In this work, some results of investigations of CSTR with complex reactions havebeen obtained.Autocatalysis. It was shown that, depending on the determinant parameters, either one orthree steady states can be realized in CSTR with an autocatalytic reaction. Unlike wellinvestigatedfirst-order kinetics, for an autocatalytic reaction at certain values of parameters(in particular, at not very high values of Semenov criterion), there is a restricted temperaturerange that is fundamentally inaccessible under stationary conditions. This result is a sequenceof the non-linearity of the autocatalytic kinetics, and in the coordinates temperature –conversion it appears as isola. The mechanism of isola formation has been formulated. It isshown that for a strongly exothermal reaction there is possible the existence of self-oscillationregimes only for steady states that are located on the unstable part of the right branch of athermal isoclinal line (the limit cycle on the phase plane).The mechanism of stability change has been investigated. Depending on the values ofparameters (in particular, at the variation of the Damköhler criterion), both soft and stiff deathof the limit cycle can be realized.Concurrent reactions. For CSTR with two concurrent exothermal first-order reactions,the investigation of the mechanisms of birth and death of self-oscillations has been carried outusing third focus coefficient, whose sign is an indication for the mechanism of the birth ofself-oscillations. The calculations have been carried out for the steady states that are locatedon the unstable part of the thermal isoclinal line. It was shown that, in case that a steady stateis located near the borders of the unstable part of the thermal isoclinal line, so the birth ofself-oscillations proceeds by a stiff mechanism, resulting from the closeness of trajectories.The arising self-oscillations have right away final amplitudes. In this case two limit cycles277