Steady state reactors

The tubular reactor, steady-state design equation is of interest here. The dimensional and dimensionless forms are compared for an nth-order reaction. 

Comparison of tank and tubular reactors steady-state. 

Batch reactors are frequently operated by chemists who are responsible for obtaining the (boring) prelirninary kinetic data on a process. Chemical engineers get involved when a continuous process is being considered because chemists do not understand anything beyond batch reactors. Steady-state continuous reactors are the subject of the next chapter. 

The reactor steady state is described by three algebraic balances a total mass balance, a component balance (since there are only two components), and an... 

There is a voluminous literature on steady-state multiplicity, oscillations (and chaos), and derivation of bifurcation points that define the conditions that lead to onset of these phenomena. For example, see Morbidelli et al. [ Reactor Steady-State Multiplicity and Stability, in Chemical Reaction and Reactor Engineering, Carberry and Varrria (eds), Marcel Dekker, 1987], Luss [ Steady State Multiplicity and Uniqueness... 

Figure 4. Model predictions of reactor steady-state temperature with experimental results.

III. Continuous Stirred-Tank Reactors Steady-State... 

III. Continuous Stiited-Tank Reactors Steady-State Operation 333... 

Morbidelli, M., Varma, A., and Arts, R., Reactor Steady-State Multiplicity and Stability, in Chemical Reaction and Reactor Engineering, 973-1055, New York Marcel Dekker, 1986. 

A more quantitative feehng for what is expressed in the analysis above can be obtained by another look at the sodium thiosulfate-hydrogen peroxide reaction illustrated in Figure 6.2. Consider the relationships possible between qg and for this reaction (computed for a feed mixture of 0.8M sodium thiosulfate and 1.2M hydrogen peroxide) shown in Figure 6.8. The only variable here is f, the holding time in the reactor. Steady-state operation corresponds to the intersection of the qg and q curves, so it is apparent that three steady states are possible between t = 6.8 and 17.8 s. From the analysis of the previous section we would expect the intermediate steady state to be inherently unstable and not observable in unconstrained operation. 

Results from the previous section in this chapter illustrate how and when interpellet axial dispersion plays an important role in the design of packed catalytic tubular reactors. When diffusion is important, more sophisticated numerical techniques are required to solve second-order ODEs with split boundary conditions to predict non-ideal reactor performance. Tubular reactor performance is nonideal when the mass transfer Peclet number is small enough such that interpellet axial dispersion cannot be neglected. The objectives of this section are to understand the correlations for effective axial dispersion coefficients in packed beds and porous media and calculate the mass transfer Peclet number based on axial dispersion. Before one can make predictions about the ideal vs. non-ideal performance of tubular reactors, steady-state mass balances with and without axial dispersion must be solved and the reactant concentration profiles from both solutions must be compared. If the difference between these profiles with and without interpellet axial dispersion is indistinguishable, then the reactor operates ideally. 

In contrast to the ideal CSTR, backmbdng is excluded in an ideal tubular reactor, characterized by a plug flow pattern of the fluid, with uniform radial composition and temperature. The material balance for a small volume system element (AV) shown in Figure 2.9 at the reactor steady state is written as... 

Incoloy reactor showed an initial activity profile similar to that of Inconel reactor. Steady-state activity was reached after 40 minutes, and the results were similar to those obtained in the reference reactor. The initial activity profile of Incology is shown in Figure 4. 

The three main types of immobilized enzyme reactors used are batch (Fig. 9.1), plug-flow (Fig. 9.2), and continuous-stirred (Fig. 9.3). In both batch and plug-flow reactors, non-steady-state reaction conditions prevail, while in continuous-stirred reactors, steady-state reaction conditions are prevalent. 

In a continuous-stirred reactor, steady-state reaction conditions prevail. Therefore, the model used is different from the one used for batch and plug-flow reactors. For the case of a continuous-stirred reactor, the reaction velocity (u) equals the product of the flow rate (Q) through a reactor... 

The temperature profile along the reactor was continuously monitored to check on the isothermality of the reactor. Steady-state runs were conducted at four residence time levels 0.273, 0.352, 0.54 and 1.33 seconds. For each residence time, a set of ten runs were made at different H2 Ci,H6 ratios, keeping the diluent composition (nitrogen) always constant at 60%. For all runs, the operating conditions were a temperature of 70 C ( 0.5 C) and a pressure of 1 psig (1.07 bar). 

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