Isothermal continuous flow reactor

The information flow diagram, for a non-isothermal, continuous-flow reactor, in Fig. 1.19, shown previously in Sec. 1.2.5, illustrates the close interlinking and highly interactive nature of the total mass balance, component mass balance, energy balance, rate equation, Arrhenius equation and flow effects F. This close interrelationship often brings about highly complex dynamic behaviour in chemical reactors. 

Barnett et al. [AIChE J., 7 (211), 1961] have studied the catalytic dehydrogenation of cyclohexane to benzene over a platinum-on-alumina catalyst. A 4 to 1 mole ratio of hydrogen to cyclohexane was used to minimize carbon formation on the catalyst. Studies were made in an isothermal, continuous flow reactor. The results of one run on 0.32 cm diameter catalyst pellets are given below. 

This hypothesis has been corroborated in simulation studies based upon the kinetics of Komiyama and Inoue [8]. Lee s calculation noi indicates that substantial improvements in ethylene selectivity may be obtained by cycling the feed hydrogen concentration to a perfectly mixed, isothermal continuous flow reactor with a... 

Both kinetic and equilibrium experimental methods are used to characterize and compare adsorption of aqueous pollutants in active carbons. In the simplest kinetic method, the uptake of a pollutant from a static, isothermal solution is measured as a function of time. This approach may also yield equilibrium adsorption data, i.e., amounts adsorbed for different solution concentrations in the limit t —> qo. A more practical kinetic method is a continuous flow reactor, as illustrated in Fig. 5. 

In this chapter, we first consider uses of batch reactors, and their advantages and disadvantages compared with continuous-flow reactors. After considering what the essential features of process design are, we then develop design or performance equations for both isothermal and nonisothermal operation. The latter requires the energy balance, in addition to the material balance. We continue with an example of optimal performance of a batch reactor, and conclude with a discussion of semibatch and semi-continuous operation. We restrict attention to simple systems, deferring treatment of complex systems to Chapter 18. 

The partial air oxidation of 2-methylpropene to methacrolein in a constant and continuous supply of selenium dioxide was investigated in an isothermal integral flow reactor, constructed of 316 stainless steel. The schematic diagram of the apparatus used to study the reaction is shown in Figure 1. 

Continuous isothermal plug flow reactor (the reactor mixture is at thermal equilibrium with the surroundings). 

We consider that the chemical process studied takes place in an isothermal, continuous-flow stirred tank reactor (CSTR) operated with a constant total flow rate and with constant input concentrations. We assume that at least one of the chemicals entering the system is available in two different forms, unlabeled and labeled, respectively, and that the kinetic isotope effect can be neglected, that is, the kinetic parameters are the same for the labeled... 

The theorems by Feinberg, Horn, Jackson and Vol pert provide sufficient conditions to exclude multistationarity. These theorems can be applied in the case of homogeneous systems, and in the case of inhomogeneous systems, if the system can be modelled by formal elementary reactions as shown several times above. An especially important case of an inhomogeneous systems is the isothermal continuous (flow) stirred tank reactor (CSTR). By a CSTR we mean one in which there is perfect mixing and in which, at each instant, every component within the reaction vessel is also contained in the effiuent stream. 

The fixed-bed laboratory reactor is regarded as an ideal isothermal plug flow reactor. The reactor model consists of the continuity equations for (1) N2, CO, NO, O2, CO2, N2O and NO2 in the gas phase, (2) surface species adsorbed on the noble metal surface, (3a) surface species adsorbed on the ceria surface, (3b) species in the ceria sub-layer, (4) CO2 adsorbed on the y-AI2O3 support. A detailed description can be found in [28]. 

To illustrate the design of continuous flow reactors (i.e., CSTRs and PFRs). we consider the isothermal gas-phase isomerization... 

Continuous-flow stirred-tank reactors ia series are simpler and easier to design for isothermal operation than are tubular reactors. Reactions with narrow operating temperature ranges or those requiring close control of reactant concentrations for optimum selectivity benefit from series arrangements. 

CONTINUOUS FLOW ISOTHERMAL PERFECTLY STIRRED TANK REACTOR... 

CONTINUOUS ISOTHERMAL PLUG FLOW TUBULAR REACTOR... 

The experimental programme was mainly concerned with estimating kinetic parameters from isothermal steady state operation of the reactor. For these runs, the reactor was charged with the reactants, in such proportions that the mixture resulting from their complete conversion approximated the expected steady state, as far as total polymer concentrations was concerned. In order to conserve reactants, the reactor was raised to the operating temperature in batch mode. When this temperature had been attained, continuous flow operation commenced. This was... 

Consecutive reactions, isothermal reactor cmi < cw2, otai = asi = 0. The course of reaction is shown in Fig. 5.4-71. Regardless the mode of operation, the final product after infinite time is always the undesired product S. Maximum yields of the desired product exist for non-complete conversion. A batch reactor or a plug-flow reactor performs better than a CSTR Ysbr.wux = 0.63, Ycstriiuix = 0.445 for kt/ki = 4). If continuous operation and intense mixing are needed (e.g. because a large inteifacial surface area or a high rate of heat transfer are required) a cascade of CSTRs is recommended. 

Energy balances are needed whenever temperature changes are important, as caused by reaction heating effects or by cooling and heating for temperature control. For example, such a balance is needed when the heat of reaction causes a change in reactor temperature. This is seen in the information flow diagram for a non-isothermal continuous reactor as shown in Fig. 1.19. 

The F(t) curve for a system consisting of a plug flow reactor followed by a continuous stirred tank reactor is identical to that of a system in which the CSTR precedes the PFR. Show that the overall fraction conversions obtained in these two combinations are identical for the case of an irreversible first-order reaction. Assume isothermal operation. 

Some aspects of reactor behavior are developed in Chapter 5, particularly concentration-time profiles in a BR in connection with the determination of values of and k2 from experimental data. It is shown (see Figure 5.4) that the concentration of the intermediate, cB, goes through a maximum, whereas cA and cc continuously decrease and increase, respectively. We extend the treatment here to other considerations and other types of ideal reactors. For simplicity, we assume constant density and isothermal operation. The former means that the results for a BR and a PFR are equivalent. For flow reactors, we further assume steady-state operation. 

Stoichacmetry and reaction equilibria. Homogeneous reactions kinetics. Mole balances batch, continuous-shn-ed tank and plug flow reactors. Collection and analysis of rate data. Catalytic reaction kinetics and isothermal catalytic radar desttpi. Diffusion effects. 

The same reactions considered in Prob. 6.17 are now carried out in a single, perfectly mixed, isothermal continuous reactor. Flow rates, volume and densities are constant,... 

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