CSTR autothermal operation

Consider the reaction studied in Illustration 10.1. Autothermal operation is to be achieved using a CSTR with an effective volume of1000 gal followed by a PFR of undetermined volume. Pure species A enters at a rate of 40.0 gal/hr and at a temperature of 20 °C. The overall fraction conversion is to be 0.97. This flow rate and conversion level will suffice to meet the annual production requirement of 2 million lb of B. Both the CSTR and the PFR are to be operated adiabatically. What PFR volume will be required, and what will be the temperature of the effluent stream ... 

Professor Viejo Dinosaurio wishes to utilize this reaction as the basis for a laboratory demonstration that would illustrate both autothermal operation of a CSTR and reactor stability concepts. He plans to use a well-insulated reactor with an effective liquid volume of 1.0 L. The feed is to consist of a mixture of the hydroperoxide (HP), acetone (A), and acid catalyst at 25°C. Initial concentrations of hydroperoxide and acetone are 0.5 and 1.0 mol/L, respectively. The following property values are available the standard heat of reaction at 25°C (estimated) = -60.5 kcal/g-mol and the heat capacity per liter of fluid (estimated) = 406 cal/(L-°C). This value may be taken as independent of the fraction conversion. 

Jaisinghani and Ray (40) also predicted the existence of three steady states for the free-radical polymerization of methyl methacrylate under autothermal operation. As their analysis could only locate unstable limit cycles, they concluded that stable oscillations for this system were unlikely. However, they speculated that other monomer-initiator combinations could exhibit more interesting dynamic phenomena. Since at that time there had been no evidence of experimental work for this class of problems, their theoretical analysis provided the foundation for future experimental work aimed at validating the predicted phenomena. Later studies include the investigations of Balaraman et al. (43) for the continuous bulk copolymerization of styrene and acrylonitrile, and Kuchanov et al. (44) who demonstrated the existence of sustained oscillations for bulk copolymerization under non-isothermal conditions. Hamer, Akramov and Ray (45) were first to predict stable limit cycles for non-isothermal solution homopolymerization and copolymerization in a CSTR. Parameter space plots and dynamic simulations were presented for methyl methacrylate and vinyl acetate homopolymerization, as well as for their copolymerization. The copolymerization system exhibited a new bifurcation diagram observed for the first time where three Hopf bifurcations were located, leading to stable and unstable periodic branches over a small parameter range. Schmidt, Clinch and Ray (46) provided the first experimental evidence of multiple steady states for non-isothermal solution polymerization. Their... 

Figure 14.6 Illustration of range of feed temperatures (T 0 to T ) for multiple stationary-states in CSTR for adiabatic operation (autothermal behavior occurs for T0 > T )...

Consider the cascade of two nonidentical CSTRs and associated heat exchangers shown in Figure P10.13. In particular, consider the problem of steady-state operation of this cascade in an autothermal mode in which the feed stream flows in countercurrent fashion through heat exchangers in each reactor so as to be heated to a temperature at which the reaction becomes self-sustaining. The areas of the heat exchangers in the two reactors differ appreciably. 

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