Reactor performance, comparison

The distribution of residence times of reactants or tracers in a flow vessel, the RTD, is a key datum for determining reactor performance, either the expected conversion or the range in which the conversion must fall. In this section it is shown how tracer tests may be used to estabhsh how nearly a particular vessel approaches some standard ideal behavior, or what its efficiency is. The most useful comparisons are with complete mixing and with plug flow. A glossary of special terms is given in Table 23-3, and major relations of tracer response functions are shown in Table 23-4. 

The computer simulation study of the operation of the tubular free radical polymerization reactor has shown that the conversion and the product properties are sensitive to the operating parameters such as initiator type, jacket temperature, and heat transfer for a reactor of fixed size. The molecular weight-conversion contour map is particularly significant and it is used in this paper as a basis for a comparison of the reactor performances. 

GP18][R6] Experiments atfixedfiiowrate allowed a comparison of reactor performance over a VO /Al203 catalyst of a multi-platelet-stack micro-channel reac-torandaconventionalfixedbedasafunctionoftheinlettemperature[133,134j. 

The cyclohexene hydrogenation is a well-studied process especially in conventional trickle-bed reactors (see original citations in [11,12]) and thus serves well as a model reaction. In particular, flow-pattern maps were derived and kinetics were determined. In addition, mass transfer can be analysed quantitatively for new reactor concepts and processing conditions, as overall mass transfer coefficients were determined and energy dissipations are known. In lieu of benchmarking micro-reactor performance to that of conventional equipment such as trickle-bed reactors, such a knowledge base facilitates proper, reliable and detailed comparison. 

Figure 5.29 Special-type multi-purpose micro devices and mixing tee used for investigation of CO2 absorption. Comparison of their reactor performance as a function of the residence time. Micro bubble columns ( ) 1100 pm x 170 pm, (A) 300 pm x 100 pm and (T) 50 pm x 50 pm Interdigital mixer ( ) (40 pm) caterpillar mixer (A) (850 pm ramp) mixing tee (0) (1 mm) [5],...

Table 41.3 shows a performance comparison of Pt/Pd TUD-1 with a commercial Pt/Pd catalyst (26). The feedstock is a typical straight run gasoil ( SRGO ), a distillate precursor to diesel fuel. Under identical test conditions, the TUD-1 catalyst achieved 75% aromatics saturation versus 50% for the same volume of commercial catalyst. This superior result is particularly interesting because the TUD-1 catalyst had a much lower density than the commercial material, so that less catalyst by weight was required in the reactor. 

A performance comparison between a BR and a CSTR may be made in terms of the size of vessel required in each case to achieve the same rate of production for the same fractional conversion, with the BR operating isothermally at the same temperature as that in the CSTR. Since both batch reactors and CSTRs are most commonly used for constant-density systems, we restrict attention to this case, and to a reaction represented by... 

Comparison may be made of the reactor performance of tanks in series and tanks in parallel, in light of the different RTDs shown in Figure 17.4. If the two tanks shown in Figure 17.3 are arranged in parallel, and the flow, q, is split evenly between them, they act together... 

A system of N continuous stirred-tank reactors is used to carry out a first-order isothermal reaction. A simulated pulse tracer experiment can be made on the reactor system, and the results can be used to evaluate the steady state conversion from the residence time distribution function (E-curve). A comparison can be made between reactor performance and that calculated from the simulated tracer data. 

With Eqs. 6b and 7 we can compare performance of N reactors in series with a plug flow reactor or with a single mixed flow reactor. This comparison is shown in Fig. 6.5 for first-order reactions in which density variations are negligible. 

Table 1. Performance comparison between the monolith reactor and the conventional trickle bed reactor.

In Section 8.3.3, the safety performance of the tubular reactor was compared to the stirred tank reactor. This comparison can now be extended to a micro reactor. For this, we take a 10 m3 stirred tank vessel, a tubular reactor with 10 mm tube diameter length 1 m, and a micro reactor with 0.1 mm tube diameter and length 1 cm. We compare the following criteria that are important for the reactor safety ... 

Only very low catalyst concentrations down to 5 x 10-5 kmol/m3 are consumed that keeps also the catalyst inventory very small [266], Only 0.08 mg of Rh and about 0.2 mg-13 pg of the very expensive chiral ligands (about 300-1000 /g), depending on their molecular weight, are consumed. Finally, a performance comparison for three different reactors was made for the substrate methylacetamidocinnamate and the two rhodium diphosphine complexes Rh/Josiphos and Rh/Diop (see Figure 4.57). The first reactor was a commercial Caroussel reactor (Radleys... 

Figure 4.57 Reaction performance comparison of three reactors with the most active catalysts Rh/Josiphos and Rh/Diop. Caroussel (car), helical falling-film microreactor (p) and Parr (batch) reactor (by courtesy of Elsevier) [266]. 9% conv. and 46% conv. denote a fixed conversion of 9 and 46%, respectively, which have to be achieved.

Lerou and Froment [10] found by calculations that a reactor may ignite under non constant flow conditions while it is still stable if constant flow is assumed. Kalthoff and Vortmeyer [11],(Figure 4) found an improved agreement between measured and calculated ranges of multiple solutions for non -uniform flow. From the previous work therefore can be concluded that non-uniform porosity and flow distributions effect the chemical reactor performance. The question however, whether real improvements are obtained has to be subject to a comparison of experimental results with calculations. 

Kim, S. H., Han, S. K., and Shin, H. S. 2005. Performance comparison of a continuous-flow stirred-tank reactor and an anaerobic sequencing batch reactor for fermentative hydrogen production depending on substrate concentration. Water Sci. Technol., 52 (10-11), 23-29. 

Table 3 Comparison of reactor specifications, experimental conditions, and reactor performance efficiency for photocatalytic decomposition of Orange II dye...

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