Heterogeneous design

Within CRC IMPROVE, ConceptBase has been used as the basis to describe the interrelationships between heterogeneous design artefacts and some aspects of the semantics of design process guidance, mostly at the fine-grained level [193]. In the course of the CRC, a large number of improvements were made, including novel compilation and optimization techniques and new interfaces, e.g. for XML. A recent system overview can be found in [205]. 

Scheme 9.7 Enzyme-composite with heterogeneous design...

In some applications diffusion theory may be too approximate, especially if a pronounced angular dependence of the neutron flux exists in a reactor region. This situation becomes almost usual when analysing some new concepts, such as the axially heterogeneous design [4.55] with an axial uranimn layer inside the core and a sodium plenum above the core. 

For homogeneous NDT data and repeatable inspection conditions successful automated interpretation systems can relatively easily be developed. They usually use standard techniques from statistical classification or artificial intelligence. Design of successful automated interpretation systems for heterogeneous data coming form non-repeatable, small volume inspections with little a-priori information about the pieces or constructions to be inspected is far more difficult. This paper presents an approach which can be used to develop such systems. 

L. K. Doraiswany and M. M. Shamia, Heterogeneous Reactions, Hnaijses, Examples and Reactor Design, Vol. 2, Fluid—Fluid Solid Reactions, ]ohxi Wiley Sons, Inc., New York, 1984, pp. 299—300. 

Historically azeotropic distillation processes were developed on an individual basis using experimentation to guide the design. The use of residue curve maps as a vehicle to explain the behavior of entire sequences of heterogeneous azeotropic distillation columns as weU as the individual columns that make up the sequence provides a unifying framework for design. This process can be appHed rapidly, and produces an exceUent starting point for detailed simulations and experiments. 

This is an exothermic reaction, and both homogeneous (radical or cationic) and heterogeneous (soHd catalyst) initiators are used. The products range in molecular weight from below 1000 to a few million (see Olefin polymers). Reaction mechanisms and reactor designs have been extensively discussed (10-12). 

Clearly, these groupings are not mutually exclusive. The chief distinctions are between homogeneous and heterogeneous reactions and between batch and flow reactions. These distinctions most influence the choice of equipment, operating conditions, and methods of design. 

Designed to obtain such fundamental data as chemical rates free of mass transfer resistances or other complications. Some of the heterogeneous reactors of Fig. 23-29, for instance, employ known interfacial areas, thus avoiding one uncertainty. 

Two complementai y reviews of this subject are by Shah et al. AIChE Journal, 28, 353-379 [1982]) and Deckwer (in de Lasa, ed.. Chemical Reactor Design andTechnology, Martinus Nijhoff, 1985, pp. 411-461). Useful comments are made by Doraiswamy and Sharma (Heterogeneous Reactions, Wiley, 1984). Charpentier (in Gianetto and Silveston, eds.. Multiphase Chemical Reactors, Hemisphere, 1986, pp. 104—151) emphasizes parameters of trickle bed and stirred tank reactors. Recommendations based on the literature are made for several design parameters namely, bubble diameter and velocity of rise, gas holdup, interfacial area, mass-transfer coefficients k a and /cl but not /cg, axial liquid-phase dispersion coefficient, and heat-transfer coefficient to the wall. The effect of vessel diameter on these parameters is insignificant when D > 0.15 m (0.49 ft), except for the dispersion coefficient. Application of these correlations is to (1) chlorination of toluene in the presence of FeCl,3 catalyst, (2) absorption of SO9 in aqueous potassium carbonate with arsenite catalyst, and (3) reaction of butene with sulfuric acid to butanol. 

The express method of phenolic compounds determination was designed. It is based on heterogeneous azo-coupling reaction of phenols, which different extracts of fresh raw material contain, with aryldiazonium salts grafted on the silica surface. We can carry out phenols analysis on-site, as formation of immobilized azocompounds leads to a drastic change in the sorbent s color. Thus, we pui pose a new method, that allows to indicate herb phenols in aqueous and non-aqueous medias and to compare it with a well-known Folin-Ciocalteau method. 

Commercial or production reactors for heterogeneous catalytic processes are versions of the so-called integral reactors, so the fundamental process of design is integration. In particular, the necessary catalyst-filled reactor volume must be calculated that will give a desired production rate. This then includes finding conditions to achieve the desired production, at a certain selectivity and minimal operating costs and investment, to maximize the return on investment. 

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