Plug flow reactor advantages

In principle, TPD can also be applied to high-surface area catalysts in plug-flow reactors. Often, however, the curves are seriously broadened by mass-transport phenomena. Hence, the use of single crystals or particles on planar supports offers great advantages for these investigations. 

In certain situations it is found to be advantageous to divide the product stream from a plug flow reactor and return a portion of it to the entrance of the reactor. Let the recycle ratio R be defined as... 

The representation of different types of reactor units in the approach proposed by Kokossis and Floudas (1990) is based on the ideal CSTR model, which is an algebraic model, and on the approximation of plug flow reactor, PFR units by a series of equal volume CSTRs. The main advantage of such a representation is that the resulting mathematical model consists of only algebraic constraints. At the same time, however, we need to introduce binary variables to denote the existence or not of the CSTR units either as single units or as a cascade approximating PFR units. As a result, the mathematical model will consist of both continuous and binary variables. 

An important advantage of the use of EOF to pump liquids in a micro-channel network is that the velocity over the microchannel cross section is constant, in contrast to pressure-driven (Poisseuille) flow, which exhibits a parabolic velocity profile. EOF-based microreactors therefore are nearly ideal plug-flow reactors, with corresponding narrow residence time distribution, which improves reaction selectivity. 

For normal reaction kinetics the plug flow reactor is smaller than thecontinuous-stirred tankreactor under similar conditions. This gives the PFR an advantage over... 

In a recycle reactor, part of the exit stream is recycled back to the inlet of the reactor. For a stirred-tank reactor, recycle has no effect on conversion, since we are essentially just mixing a mixed reactor. For a plug flow reactor, the effect of recycle is to approach the performance of a CSTR. This is advantageous for certain applications such as autocatalytic reactions and multiple reaction situations where we have a PFR but really require a CSTR. 

The tubular plug flow reactor is relatively easy to maintain with no moving parts, and it usually produces the highest conversion per reactor volume of any of the flow reactors. Other advantages are ... 

The advantages of the ring-shaped particles are also found for other type of reactions. To demonstrate this, consider an adiabatic plug flow reactor assuming that the external mass and heat transfer limitations are negligible. Equations for fluid-phase concentration and temperature (which are equal to the concentration and temperature at the surface of the pellet) are... 

The plug-flow reactor has the following advantages for laboratory purposes ... 

CSTR to minimize the inventory of intermediates. A plug-flow reactor would also typically have smaller volumes, hence a smaller inventory of reactants, intermediates, and products than a CSTR for the same throughput. This can be a big safety advantage. 

In the case of product inhibition, the plug flow reactor is advantageous, as the concentration of the inhibiting product slowly increases along the reactor length, whereas in a CSTR the product concentration is at the maximum value in the whole reactor. Therefore, the average reaction rate is higher in the PFR. 

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