Evaluation of laboratory reactors

The successful design of industrial reactors lies primarily with the reliabiliry of the experimentally determined parameters used in the scale-up. Consequently, it is imperative to design equipment and experiments that will generate accurate and meaningful data. Unfortunately, there is usually no single comprehensive laboratory reactor that could be used for ail types of reactions and catalysts. In this section, we discuss the various types of reactors that can be chosen to obtain the kinetic parameters for a specific reaction system. We clo.sely follow the excellent strategy presented in the article by V, W. Weekman of Mobil Oil. now ExxonMobil.  

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A variety of laboratory reactors have been developed for the determination of the kinetics of heterogeneous reactions, all with specific advantages and disadvantages. Several reviews of laboratory reactors are available [28-33]. The evaluations of the available methods in these reviews are different because of the variation of chemical reactions and catalysts investigated and the different viewpoints of the authors. It is impossible to choose a best kinetic reactor because too many conflicting requirements need to be satisfied simultaneously. Berty [34] discussing an ideal kinetic reactor, collected 20 requirements as set forward by different authors. From these requirements it is easy to conclude, that the ideal reactor, that can handie all reactions under all conditions, does not exist For individual reactions, or for a group of similar reactions, not all requirements are equally important. In such cases it should be possible to select a reactor that exhibits most of the important attributes. 

To analyze reaction mechanisms in complex catalytic systems, the application of micropulse techniques in small catalytic packed beds has been used. Christoffel [33] has given an introduction to these techniques in a comprehensive review of laboratory reactors for heterogeneous catalytic processes. Mtlller and Hofmann [59,61] have tested the dynamic method in the packed bed reactor to investigate complex heterogeneous reactions. Kinetic parameters have been evaluated by a method, which employs concentration step changes and the time derivatives of concentration transients at the reactor outlet as caused by a concentration step change at the reactor inlet. 

C. M. Barnes, Evaluation of Tubular Reactor Designs for Supercritical Water Oxidation of U.S. Department of Energy Mixed Waste, Idaho National Engineering Laboratory Report INEL-94/0223, December, 1994. 

The criteria used to evaluate various types of laboratory reactors are listed in Table 5-2. 

Central to the evaluation presented here is the assessment of the catalyst s reaction performance, carried out using one or more of the many forms of laboratory reactor available. 

Table I Classification of laboratory reactors for evaluation of reaction related parameters...

For the evaluation of reaction related parameters, a great variaty of laboratory reactors has been developed which can be classified according to the matrix given in Table I. 

The ROTOBERTY internal recycle laboratory reactor was designed to produce experimental results that can be used for developing reaction kinetics and to test catalysts. These results are valid at the conditions of large-scale plant operations. Since internal flow rates contacting the catalyst are known, heat and mass transfer rates can be calculated between the catalyst and the recycling fluid. With these known, their influence on catalyst performance can be evaluated in the experiments as well as in production units. Operating conditions, some construction features, and performance characteristics are given next. 

In this volume not all stress types are treated. Various aspects have been reviewed recently by various authors e.g. The effects of oxygen on recombinant protein expression by Konz et al. [2]. The Mechanisms by which bacterial cells respond to pH was considered in a Symposium in 1999 [3] and solvent effects were reviewed by de Bont in the article Solvent-tolerant bacteria in biocatalysis [4]. Therefore, these aspects are not considered in this volume. Influence of fluid dynamical stresses on micro-organism, animal and plant cells are in center of interest in this volume. In chapter 2, H.-J. Henzler discusses the quantitative evaluation of fluid dynamical stresses in various type of reactors with different methods based on investigations performed on laboratory an pilot plant scales. S. S. Yim and A. Shamlou give a general review on the effects of fluid dynamical and mechanical stresses on micro-organisms and bio-polymers in chapter 3. G. Ketzmer describes the effects of shear stress on adherent cells in chapter 4. Finally, in chapter 5, P. Kieran considers the influence of stress on plant cells. 

Equation (48) e ees with experimental results in some circumstances. This does not mean the mechanism is necessarily correct. Other mechanisms may be compatible with the experimental data and this mechanism may not be compatible with experiment if the physical conditions (temperature and pressure etc.) are changed. Edelson and Allara [15] discuss this point with reference to the application of the steady state approximation to propane pyrolysis. It must be remembered that a laboratory study is often confined to a narrow range of conditions, whereas an industrial reactor often has to accommodate large changes in concentrations, temperature and pressure. Thus, a successful kinetic model must allow for these conditions even if the chemistry it portrays is not strictly correct. One major problem with any kinetic model, whatever its degree of reality, is the evaluation of the rate cofficients (or model parameters). This requires careful numerical analysis of experimental data it is particularly important to identify those parameters to which the model predictions are most sensitive. 

FCC catalyst, supplied by Grace Davison, at three different cat-to-oil ratios, 4,6, and 8. The feed was injected at a constant rate of 3 g/min for 30 seconds. The catalyst to oil ratio was adjusted by varying the amonnt of catalyst in the reactor. Two catalysts used for this evaluation were laboratory deactivated using the cyclic propylene steaming (CPS) method [6]. Properties of these catalysts after deactivation are listed in Table 12.3. 

An advanced cracking evaluation-automatic production (ACE Model AP) fluidized bed microactivity unit was used to study the catalyst and feed interactions. The fluidized bed reactor was operated at 980°F (800 K). Every feed was tested on two different catalysts at three cat-to-oil ratios 4, 6, and 8. Properties of laboratory... 

HELP HEU HFO HFR HLW HREE HRL HT HTGR HWR Hydrological evaluation of landfill performance Highly enriched uranium Hydrous ferrous oxide or ferric hydroxide Hot fractured-rock High-level nuclear waste Heavy rare earth elements (Gd-Lu) Hard rock laboratory High temperature High-temperature gas-cooled reactor Heavy water reactor... 

Stewart, T. L., and J. N. Hartley. 1985. Evaluation of Improved Chemical Waste Disposal and Recovery Methods for N Reactor Fuel Fabrication Operations 1984 Annual Report. PNL-5294 and UNI-3204, Pacific Northwest Laboratory, Richland, Washington. 

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