Plug flow reactors defined

As described above, the activity of a catalyst can be measured by mounting it in a plug flow reactor and measuring its intrinsic reactivity outside equilibrium, with well-defined gas mixtures and temperatures. This makes it possible to obtain data that can be compared with micro-kinetic modeling. A common problem with such experiments materializes when the rate becomes high. Operating dose to the limit of zero conversion can be achieved by diluting the catalyst with support material. 

Quantitatively, the efficiency at a specified conversion level, x, is defined as the ratio of the mean residence time or reactor volume in a plug flow reactor (PFR) to that of the reactor in question,... 

For the plug flow reactor or any similar adiabatic system, it is also possible to define an average specific heat that takes its explicit definition from... 

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... 

These assumptions lead to the picture of the flow as that of a plug of fluidum with uniform properties being pushed through the tube. In a plug flow reactor the mass balance for a component A over an infinitesimal reactor element, as defined in Figure 7.1, gives ... 

SPACE VELOCITY. In design treatment for plug-flow reactors, the concept of space velocity is often used where space velocity is defined as the ratio of the volumetric feed rate to the volume of the reactor, or... 

The production of copolymers leads to some additional constraints to reactor design beyond what is required for homopolymer. The most important of these is composition drift. The reactivity ratios of a monomer mixture define the composition of a copolymer that is instantaneously produced from a given monomer mixture. This is true in a plug flow reactor or a backmixed reactor. However, in the plug flow reactor, the copolymer composition drifts from that produced from the initial monomer composition to that produced by the monomer composition at the end of the polymerization. In contrast, in the backmixed reactor, all copolymer produced is of the same composition, which... 

Plug flow reactor (PFR) for which defined volume elements flow through a column without mixing with other volume elements. A liquid element will travel from the inlet to the outlet for a period of time equal to the reactor volume (V) divided by the flow rate (Q). 

A computational model for wastewater disinfection was developed by Emerick et al. (28). The user can define multiple equations for UV disinfection reactions. The reaction vessel is simulated as a plug flow reactor. A similar model called BioSys was developed by Zeidan (34). 

Comparison with Eqn. (8.8) for a batch reactor shows the mathematical analogy between plug-flow and batch reactors. The batch reactor results obtained in the preceding paragraph can be transposed to the plug-flow reactor, provided that a space time tq is defined for the plug-flow reactor as ... 

The application of the equations to chemical reactions requires the proper definition of the above quantities as well as correctly defining the transition probabilities pjj and pjk this is established in the following. It should also be noted that the models derived below for numerous chemical reactions, are applicable to chemical reaction occurring in a perfectly-mixed batch reactor or in a single continuous plug-flow reactor. Other flow systems accompanied with a chemical reaction will be considered in next chapters. 

Deflnitions. The basic elements of Markov chains associated with Eq.(2-24) are the system, the state space, the initial state vector and the one-step transition probability matrix. Considering refs.[26-30], each of the elements will be defined in the following with special emphasize to chemical reactions occurring in a batch perfectly-mixed reactor or in a single continuous plug-flow reactor. In the latter case, which may simulated by perfectly-mixed reactors in series, all species reside in the reactor the same time. 

In treating a certain configuration, the first step is to define the states that the system can occupy. By a state is meant, the concentration Ci in a perfectly mixed reactor i or at the inlet or the exit of a plug-flow reactor, that the system (fluid element) can occupy. The states will be designated by Ci, C2,... whereas the state space SS, will read ... 

Chemical reaction and mass transfer are two unique phenomena that help define chemical engineering. Chapter 8 described problems involving chemical reaction and mass transfer in a porous catalyst, and how to model chemical reactors when the flow was well defined, as in a plug-flow reactor. Those models, however, did not account for the complicated flow situations sometimes seen in practice, where flow equations must be solved along with the transport equation. Microfluidics is the chemical analog to microelectro-mechanical systems (MEMS), which are small devices with tiny gears, valves, and pumps. The generally accepted definition of microfluidics is flow in channels of size 1 mm or less, and it is essential to include both distributed flow and mass transfer in such devices. 

In the figure, a link type called PFRLink is defined. This example link type expresses that exactly one instance of the specific reactor type PFR (plug flow reactor) can be simulated by exactly one instance of the specific reactor block RPlug in the simulation model. The reactors in both documents can have an arbitrary number of ports which are mapped by the link as well. To assign corresponding ports, the link may have sublinks each mapping pairs of ports . Both reactors are referenced as dominant increments. This link type is rather specific, as it forms relatively tight constraints for all of its instances. 

Ideal mixing and plug flow. The batch, contlnuous-stirred-tank, and plug-flow reactors are defined by certain idealized assumptions on the fluid flow. The batch and continuous-stirred-tank reactors are assumed to be ideally well mixed, which means that the temperature, pressure and species concentrations are independent of spatial position within the reactor. The plug-flow reactor describes a special type of flow in a itube in which the fluid.is well.mixed in the radial direction and varies... 

The conversion of component j for a plug-flow reactor operating at steady state Is defined as... 

We will begin with the case of the batch reactor. In this case the vessel defines the control volume. We will move to systems with flow in and both flow in and out. The former is the case of semibatch operation while the latter will be treated as the continuous stirred tank reactor (CSTR) and the plug flow reactor (PFR). All the chemical kinetics that we will need can be introduced within the context of these four different kinds of reactors. 

In this section the size requirements for CSTR cascades containing different numbers of identical reactors are compared with that for a plug flow reactor used to effect the same change in composition. One may define a space time for an entire cascade (x, ) in terms of the ratio of the sum of the component reactor volumes to the inlet volumetric flow rate. Hence,... 

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