Tubular batch reactor analogy

For gas-phase reactions this tubular reactor-batch reactor analogy may not be valid since the volmnetric flow rate of the gas, and therefore the gas velocity, can vary along the reactor length as a result of mole number changes accompanying chemical rea-... 

The tubular flow reactor is a convenient means of approaching the performance characteristics of a batch reactor on a continuous basis, since the distance-pressure-temperature history of the various plugs as they flow through the reactor corresponds to the time-pressure-temperature protocol that is used in a batch reactor. Although this analogy is often useful,... 

At constant pressure and granted ideal plug flow, the behavior of a tubular reactor at steady state is mathematically analogous to that of a batch reactor A volume element of the reaction mixture has no means of knowing whether it is suspended tea bag-style in a batch reactor or rides elevator-style through a tubular reactor being exposed to the same conditions it behaves in the same way in both cases. As in a batch reactor, what is measured directly are concentrations—here in the effluent—and a finite-difference approximation is needed to obtain the rate from experiments with different reactor space times and otherwise identical conditions. For a reaction without fluid-density variation ... 

A tubular prereactor, in series with CSTR system, can offer stability advantages, which will he discussed later. A number of other flow alternatives are also possible with a CSTR-series system but these alternates are not widely utilized. An obvious flow alternative for a reactor system consisting of a series of CSTRs would he to introduce some portion of the total recipe at places other than the front end of the reactor train. These intermediate feeds would, in many respects, be analogous to semicootinuous operation of batch reactors. 

In ihe three idealized types of reactors just discussed (the perfectly mixed batch reactor, the plug-fiow tubular reactor (PFR). and the perfectly mixed con-tinuous-siirred tank reactor (CSTR), the design equations (i.e.. mole balances) were dei doped based on reactor volume. The deris ation of the design equation for a packed-bed catalytic reactor (PBR) will be carried out in a manner analogous to the development of the tubular design equation. To accomplish this derivation. we simply replace the volume coordinate in Equation (MO) with (he catalyst weight coordinate H (Figure - 4). 

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