Octave Levenspiel

Chemical reaction engineering

Partial table of contents: Overview of Chemical Reaction Engineering. HOMOGENEOUS REACTIONS IN IDEAL REACTORS. Introduction to Reactor Design. Design for Single Reactions. Design for Parallel Reactions. Potpourri of Multiple Reactions. NON IDEAL FLOW. Compartment Models. The Dispersion Model. The Tank--in--Series Model. REACTIONS CATALYZED BY SOLIDS. Solid Catalyzed Reactions. The Packed Bed Catalytic Reactor. Deactivating Catalysts. HETEROGENEOUS REACTIONS. Fluid--Fluid Reactions: Kinetics. Fluid--Particle Reactions: Design. BIOCHEMICAL REACTIONS. Enzyme Fermentation. Substrate Limiting Microbial Fermentation. Product Limiting Microbial Fermentation. Appendix. Index.

Drag coefficient and terminal velocity of spherical and nonspherical particles

Explicit equations are developed for the drag coefficient and for the terminal velocity of falling spherical and nonspherical particles. The goodness of fit of these equations to the reported experimental data is evaluated and is compared with that of other recently proposed equations. Accurate design charts for CD and ut are prepared and displayed for all particle sphericities.

Patterns of Flow in Chemical Process Vessels

Publisher Summary This chapter focuses on two idealized patterns (of all possible flow patterns), plug flow and back-mix flow. Plug flow assumes that fluid moves through the vessel “in single file” with no overtaking or mixing with earlier or later entering fluid. Back-mix flow assumes that the fluid in the equipment is perfectly mixed and uniform in composition throughout the vessel. All patterns of flow other than plug and back-mix flow may be called nonideal flow patterns because for these the design methods are not nearly as straightforward as those for the two ideal flow patterns. The treatment of nonideal flow patterns discussed in the chapter divides naturally into two parts: flow of single fluids and flow of two fluids. The main emphasis falls on the nonideal flow of single fluids through process equipment. Conversion in a reactor with nonideal flow can be determined either directly from tracer information or by use of flow models. The distribution of residence times gives information on how long various elements of fluid spend in the reactor but not on the detailed exchange of matter within and among the elements. The exact nature of the surrounding molecules is of no importance. Thus, the distribution of residence times yields sufficient information for the prediction of the average concentration in the reactor effluent. Because of a lack of applications, conversion expressions for two region models have not been developed for homogeneous systems. For heterogeneous systems, the appropriate expressions can be found in the works of the individual investigators.

Fluid dispersion-generalization and comparison of mathematical models—I generalization of models

Abstract Many models have been used to characterize dispersion of fluids in flowing systems. Some account for both transverse and longitudinal dispersion, while others account for longitudinal dispersion alone. In addition, the variety of experimental tracer methods used to find the parameters of the models makes the resultant analyses seemingly unrelated. We show here the relationship between these models and generalize all the previously presented measurement techniques. This gives a comprehensive picture of the field of dispersion, allows a quantitative evaluation of the error incurred when a simple model is used in place of a more exact but more unwieldy model, and gives future experimenters the necessary information to decide what combination of experimental set-up and mathematical model yields, within prescribed limits of error, an analysis of desired accuracy.

A Monte Carlo treatment for reacting and coalescing dispersed phase systems

Abstract The Monte Carlo method of digital computer simulation is used to study the influence of coalescence on the progress of reactions occurring in the dispersed phase of two-phase systems in backmix reactors. Three different types of chemical reaction of both one and two reactants are studied and performance charts are prepared and discussed. It is shown that depending on the system, coalescence can either increase or decrease the extent of conversion of reactants. The Monte Carlo method, because of its simplicity, is found to be especially suited to studying discrete systems of this type since analytical solution is not yet possible and other numerical methods are very cumbersome. Possible extensions are discussed and the possibility of using the dispersed phase model for studying mixing and reaction in homogeneous systems is pointed out.

Experimental search for a simple rate equation to describe deactivating porous catalyst particles

Abstract This paper concerns the experimental determination of the orders of reaction and deactivation in the n th order rate equation which represents the four broad classes of deactivation of catalyst particles: parallel, series, side-by-side, and independent. We discuss the various reactor types which may be used, both batch-solids and flowing solids. For batch-solids systems we show that when deactivation is concentration independent then using a batch of fluid or any flow of fluid gives results which are simple to interpret. However, when deactivation is concentration dependent then only one very particular form of contacting is recommended in that it alone allows decoupling of concentration and activity effects, and their study one at a time. In essence we show how the methods for n th order homogeneous reactions can be extended in a simple way to catalytic systems with deactivating porous solids.

Circulating fluidized-bed reactors

Abstract This paper develops a flow and contacting model to represent a CFB. Best estimates of contacting efficiencies are presented for the turbulent, fast fluidized, and pneumatic transport regimes of the CFB. Material balances are presented, ending up with conversion equations for first-order solid-catalyzed gas-phase reactions. Four examples show how to use this model and show its predictions.

New scale-up and design method for stirrer agitated batch mixing vessels

Abstract Residence time distribution theory and probability conditions predict that the infusion rate of a slug of tracer into a batch mixer can be characterized by a single quantity, a decay rate constant. This constant is then used to define a dimensionless mixing-rate number. Experiments in turbine-agitated and propeller-agitated fully-baffled tanks verify the theory, and relate this mixing-rate number to the stirrer Reynolds number and to the Power number for mixing. These new correlationships allow calculation of time needed or energy input needed to achieve any desired degree of uniformity of the mixture.

Entrainment of solids from fluidized beds I. Hold-up of solids in the freeboard II. Operation of fast fluidized beds

Abstract Part I: Kunii and Levenspiel proposed a flow model to represent the complex phenomena occurring in the freeboard above a fluidized bed. A somewhat more The key parameter emerging from this model is the decay constant for the fall off of bulk density of solids with height in the freeboard. Values for th Part II: Viewing the fast fluidized column as having a lower region of approximately constant bulk density and an upper region wherein the bulk density An example of a design calculation shows how the fast fluidized system responds to changes in operating variables. More importantly, it makes clear wha

Optimal temperature policies for reactors subject to catalyst deactivation—I Batch reactor

Abstract For a single irreversible reaction A → R subject to catalyst deactivation, the problem of finding the optimal temperature policy in a batch reactor was formulated as a Bolza problem of the calculus of variations. For reaction and deactivation kinetics described by Eqs. (2–10), an analytical solution was obtained for the optimal policy. Accordingly, depending on the relative sizes of the activation energies E (for reaction) and ϵ (for catalyst decay), the optimal policy is either to operate at the maximum allowable temperature (if ϵ E ), or with a rising temperature policy characterized by d k eff /d t = d( ka )/d t = 0 (if ϵ > E ). This result is applicable for arbitrary orders of reaction and deactivation. A simple equation was derived for the optimal temperature policy itself, and finally the effect of temperature constraints was examined.