Pulse reactor evaluation

We thank K. S. Patel and D. M. DiCicco for providing the dynamometer-aged catalysts and sweep evaluation data. E. Gulari and C. Sze (U. of Michigan) assisted with the design of the pulsed reactor system. 

Evaluation of the kinetic order of the various constituents in a PN hydrocyanation was carried out by monitoring the temperature after injecting small portions of HCN into a pulse reactor (Section I,D) containing NiL4... 

We continue to rely extensively on the two-step (initiation - propagation or autocatalytic) model 4) to evaluate data on coking rates. Two rate constants are involved fc for the deposition of coke on a "clean" surface, i.e., with no coke around and k2 when coke is deposited adjacent to another coke deposit. The former rate constant is for an initiation step (or "non-catalytic" coking), while the latter is for the propagation step (or coking catalyzed by the presence of the coke "product") hence, typically, k2 > ki. A third parameter used in the model is M, which represents the maximum amount of coke which can be deposited on the catalyst. In terms of these three parameters, the coke level expected in a pulse reactor after the passage of R amount of reactant is given by ... 

The mechanical system used for this evaluation consisted of several automated components feed control, reactants preparation, synchronized injected reactant pulses, reactor temperature and pressure and residence time control, on-line analytical, fraction collector for product sample collection, as well as programming for multi-system coordination. 

In service inspections of French nuclear Pressure Water Reactor (PWR) vessels are carried out automatically in complete immersion from the inside by means of ultrasonic focused probes working in the pulse echo mode. Concern has been expressed about the capabilities of performing non destructive evaluation of the Outer Surface Defects (OSD), i.e. defects located in the vicinity of the outer surface of the inspected components. OSD are insonified by both a "direct" field that passes through the inner surface (water/steel) of the component containing the defect and a "secondary" field reflected from the outer surface. Consequently, the Bscan images, containing the signatures of such defects, are complicated and their interpretation is a difficult task. 

Via a passive scalar method [6] where or, denotes the volume fraction of the i-th phase, while T, represents the diffusivity coefiBcient of the tracer in the i-th phase. The transient form of the scalar transport equation was utilized to track the pulse of tracer through the computational domain. The exit age distribution was evaluated from the normalized concentration curve obtained via measurements at the reactor outlet at 1 second intervals. This was subsequently used to determine the mean residence time, tm and Peclet number, Pe [7]. 

Stimulus-response experiments were used to evaluate the operation of a 1.465L laboratory stirred-tank reactor as a CSTR. The response curves were obtained (a) by using acetic acid (A, ca = 0.85 mol L-1) as a tracer chasing water in step-change experiments, and (b) by using a small pulse of glacial acetic acid (density = 1.05 g cm-3, M = 60 g mol-1) on a... 

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. 

Ghommidh et al. [45] investigated the performance of Acetobacter ctWs immobilized in a monolith reactor operated with a pulse flow. A very high productivity up to 2.9 X 10" kg m see" of acetic acid was achieved due to the very intensive transfer of oxygen from the gas to the solid. Oxygen transfer in the microbial film was evaluated as controlling the reactor productivity. 

The variation in residence times of the molecules in the reactor will disperse the input pulse, giving a response curve like that in Fig. 6-Ab. To evaluate the RTD we proceed as before and formulate two expressions for the marked molecules at some time 0. Since C is the concentration of marked molecules at 6, the number of such molecules leaving the reactor in the time period 6 to 6 + dd will be CQ dd. All the marked molecules in the effluent will have a residence time 9 to 6 + dd because they were added only at 0 = 0. By definition, the fraction of the effluent stream consisting of such molecules will be dJ 9) or J 9) dO. The number of such molecules will be MJ 6) dd. Equating the two expressions for the number of marked molecules gives... 

With this result we can evaluate J (9) for any reactor, using only the measured response curve to a pulse input. Since dJ 9) = J (9) d9, the RTD in terms of J(9) is given by... 

Benzene hydrogenation activity evaluation of the catalysts was carried out by a pulse and continuous testing method and the results are indicated in Table-2 and Figure 1. Activity is represented as percentage of benzene converted to cyclohexane. Activity results as per evaluation in pulsed microcatalytic reactor indicated a similar trend as obtained from continuous testing of samples. 

In Illustration 11.1 we considered the response of an arbitrary reactor to a pulse stimulus and used these data to determine the average residence time and the F(0 curve. If the pulse is assumed to be perfect, what value of T)JuL gives a reasonable fit of the experimental data Use the slope and variance methods to evaluate this parameter. 

In evaluating the residence time distributions in a continuous system oper> ating without recycling, for the case of the ideal discontinuous stirred vessel the curve with an exponential decay of the dilution process normally appears. But it appears in such a way that the pulse functions do not overlap (see Fig. 3.6 and also Blenke, 1979). This means that mixing and dilution processes are superimposed, and that in reactors that deviate from the ideal continuous... 

Figure 3.7. The longitudinal Bodenstein number of the total pulse function, BOtot for the liquid phase of a tube-type reactor with recycling as a function of the recycle ratio, r. The evaluation of the experimental results are compared with the theoretical calculation, Equ. 3.15b. (From Moser and Steiner, 1974 and 1975).

Data generated using the experimental techniques described above are used to formulate hydrodynamic models that may be used to predict reactor performance. In this section, studies that employ chemical reactions to evaluate mass transfer and contacting efficiency are described. Selected references are shown in Table 7. Dry et al. have applied hot air pulses as a reacting tracer [87]. Chemical reactions used to probe gas phase hydrodynamics include thermal decomposition of sodium bicarbonate, ozone decomposition, coal combustion, and FCC coke combustion. 

In this contribution we discuss the opportunities of pulsing flow and a cycled liquid feed strategy, both resulting in a non-steady state behavior of the trickle-bed reactor. The focus is on the hydrodynamics and its effect on catalytic reactions is evaluated. 

The fast camera data must be evaluated while you are in the laboratory, using the proprietary software that came with the camera. From the camera data you can determine how long after the transient rod was fired until the transient rod started to move, when the transient rod reached the full out position, when the reactor power became high enough to see the Cherenkov radiation, when the peak of the pulse occurred. This data will be useful in interpreting the data from the TestLab. 

Bubble columns. Tracers are used in bubble columns and gas-sparged slurry reactors mainly to determine the backmixing parameters of the liquid phase and/or gas-liquid or liquid-solid mass transfer parameters. They can be used for evaluation of holdup along the lines reviewed in the previous Section 6.2.1. However, there are simpler means of evaluating holdup in bubble columns, e.g. monitoring the difference in liquid level with gas and without gas flow. Numerous liquid phase tracer studies of backmixing have been conducted (132-149). Steady-state or continuous tracer inputs (132,134,140,142) as well as transient studies with pulse inputs (136,141,142,146) were used. Salts such as KC Jl or NaCil, sulfuric acid and dyes were employed as tracers. Electroconductivity detectors and spectrophotometers were used for tracer detection. The interpretation of results relied on the axial dispersion model. Various correlations for the dispersion... 

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