Packed-Bed Reactor PBR

Packed-bed reactors are tubular reactors filled with catalyst particles. In PBRs it is the weight of catalyst W that is important, rather than the reactor volume. The derivation of the dilTerential and integral forms of the design equations for packed-bed reactors are analogous to tho.se for a PFR [cf. Equations (2-15) and (2-16)). That is. substituting Equation (2-12) for Equation (1-15) gives 

The ditferential form of the design equation [i.e.. Equation (2-17)] must be used when analyzing reactors that have a pressure drop along the length of the reactor. We discuss pressure drop in packed-bed reactors in Chapter 5. 

Equation (2-18) can be used to determine the catalyst weight W (i.e., mass) necessary to achieve a conversion X when the total pressure remains constant. 

In this section, we are going to show how we can size CSTRs and PFRs (i.e., determine their reactor volumes) from knowledge of the rate of reaction, -r/, as a function of conversion, X [i.e., =y(AD]. The rate of disappearance of 

is almost always a function of the concentrations of the various species present (see Chapter 3). When only one reaction is occurring, each of the concentrations can be expressed as a function of the conversion X (see Chapter 4) consequently, -r can be expressed as a function of X. 

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In this study, Pt/AliOj having high activity for CO oxidation and different affinities for fee adsorption of CO and Hi was selected as a catalyst/adsorbent In a conventional packed bed reactor (PBR), fee surface of fee catalyst is dominantly covered by COads with small amotmt of Oads fee CO conversion is therefore low. Several investigations on periodic operation have illustrated feat fee reaction front wife comparable amount of fee two adsorbed species leads to enhancement of fee CO conversion. Conceptually, this type of the reaction front should be generated by application of a CMBR, as well. Figure 1 illustrates an image of... 

The decolorization of Orange II by immobilized P. chrysosporium in a continuous packed-bed reactor (PBR) was investigated [50]. Nearly complete decolorization (95%) with immobilized fungus on PuF was obtained when working at optimal conditions [dye load rate of 0.2 g/l/d, temperature of 37°C, a hydraulic retention time (HRT) of 24 h], and also oxygen gas in a pulsed flow was applied. A correlation between residual MnP activity and decolorization was observed, but no laccase and LiP enzyme activities were detected. 

If similar calculations are performed for the tubular packed-bed reactor (PBR), one finds that for the same catalyst weight the conversion and pressure at the exit are... 

Continuous flow reactors are almost always operated at steady state. We will consider three types the continuous stirred tank reactor (CSTR). the plug flow reactor (PFR). and the packed bed reactor (PBR). Detailed descriptions of these reactors can be found in both the Professional Reference Shelf (PRS) for Chapter 1 and in the Visual Encyclopedia of Equipinent on the CD-ROM,... 

Eigure 2 shows the bioreactor types which are most suitable for MTBE removal. The packed bed reactor (PBR), fluidized bed reactor (EBR) and the membrane bioreactor (MBR) are widely applied. Both the PBR and the EBR are often categorised as fixed film reactors in the literature. 

Table 4 Ranking of different reactor types suitable for MTBE biodegradation in terms of typical process characteristics. The reactors shown are the fluidized hed reactor (FBR), packed bed reactor (PBR), rotating biological contactor (RBC), membrane bioreactor and the aerobic upflow sludge bed reactor (AUSB)...

Plug flow reactors (PFRs) and Packed Bed Reactors (PBRs)... 

In packed-bed reactors (PBRs), the solid particulate catalyst particles forming the bed are fixed in an enclosed volume. The... 

PFR The one-dimensional design equation for an ideal catalyst-packed PFR (called a packed-bed reactor (PBR)) is obtained by making a component mass balance over a volume element extending over the entire cross section of the reactor ... 

Thus, for Michaelis-Menten kinetics, a PFR type reactor, predominantly a packed-bed reactor (PBR, Figure 9.1b) is preferred to the continuous stirred-tank reactor (CSTR, Figure 9.1a), since it requires less biocatalyst to reach the same level of conversion. In this case, ideal reactors are those with high space time/yield to increase the efficiency of the transformation. PBRs with immobilized catalyst have a clear advantage in that voidage is low 34% compared to over 80-90% for CSTR [35]. However, if pH control is required, the use of a PFR is not advised. In case of substrate inhibition, a CSTR (Figure 9.1a) operated at high conversion is to be preferred. On the other hand, when product inhibition is pronounced, a... 

Figure 9.1 Reactor types for continuous-flow operation with immobiiized/retained biocatalysts [33]. Continuously operated reactors with plug-flow behavior [feed one (S) or more (S. ..) substrates outflow one (P) or more (P. ..) products] (a) Continuous stirred-tank reactor (CSTR) (b) packed-bed reactor (PBR) (c) fluidized-bed reactor (FBR) (d) continuously operated membrane...

Figure 10.2 Potential reactor configurations. (a) CSTR in series using two soluble enzymes, (b) Packed bed reactor (PBR) configurations using immobilized and soluble enzymes. (1) PBR divided in sections using both enzymes immobilized, (2) PBR...

Oxidative coupling of methane using a catalytic-membrane reactor (CMR), catalyst packed-bed reactor (PBR), and catalyst packed-bed membrane reactor (PBMR), have been also compared. The authors conclude that the catalytic activity of PBR and PBMR (using Na-WMn/Si02) were lower than that observed for CMR (with a yield of 34.7%). 

Monoliths and microchannel reactors (MRs) are two of the different types of structured reactors. A thin layer of catalyst deposited on stiff 3D structures with channels or macro-pores and high lateral surface is characteristic of these catalytic devices. These structures overcome flow maldistribution, high pressure drop, and diffusional limitations in the pores that are frequently associated with the conventional packed-bed reactors (PBRs) commonly used for catalytic reactions. Compared with PBR, structured reactors have unquestionable advantages not only in lowering pressure drop and decreasing flow maldistribution, which... 

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