Fluidized Bed Combustion

Fluidized Bed Combustion

1868 Book Reviews operation of experimental-scale units is described. Aspects of biomass hold-up and mass transfer limitations are reviewed but no n...

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Book Reviews

operation of experimental-scale units is described. Aspects of biomass hold-up and mass transfer limitations are reviewed but no new information is presented. Applications of immobilized-cell technology would seem to be- most advanced in the field of eflluent treatment. A detailed description of the use of fluid&d beds of sand particles for the treatment of wastewater both at laboratory and pilot plant scale is presented with tables of operating results. The use of polyurethane foam pads as additions to conventional activated sludge units is aho assessed with operating data. In direct contrast, but demonstrating the versatility of immobilization techniques, the section concludes with reports of immobilized enzymes making fructose and the potentials of immobilized plant and animal cells. The final section of the book is a collection of shorter contributionsdealing with a wide range of investigations such as the production of ethanol from yeasts and Zymomonas mobilis, of hydrogen from green algae, ammonia from Anabaenu and cellulase from Trichoderma reesei. Basic mechanisms of adhesion are discussed as well as physiological aspects of cells immobilized in aliginate beads. A number of

papers are also presented on the immobilization of plant cells, although they contain very little that could be described as process engineering. This publication represents the translation of a useful conference into a handy (A5 sized) manual on the subject. In addition to the actual papers presented at the meeting, usefully grouped into topic sections, there is a detailed contents, a glossary of terms for the uninitiated, a unified nomenclature and a satisfactory index. It is clear that immobilized-cell technology exists primarily at the laboratory scale and that process engineering aspects are rather limited. However, this publication represents a useful assessment of the state of the art and as such is both a good introduction to the subject and a reference for the expert.

Fluidized Bed Combustion. Edited by M. RADOVANOVIC Hemisphere Publishing Corporation, 1986,307 pp., DM 228

not yet able to provide data points for large-scale operation. Verhoeff’s account of the design of a large industrial fluidized-bed boiler is therefore of special interest: the approach and the data are both worth study. The author however leaves the reader in the air as to the source of further data, and without an indication as to whether the given case study measures up to any criteria that were specified. Professor Draijer’s contribution on heat transfer also emphasizes the gap between theory and practice in pointing out that boiler designers look first for “unprocessed data” from experiments carried out on pilot plants. It is therefore not particularly helpful to quote Broughton’s correlationwith its index to three decimal places-on the maximum (not optimum) obtainable heat transfer coefficient without a qualification, for example, as to its temperature dependence as shown in work using alumina. A book of this kind makes no claim to overall coherence and, therefore, if readers are to use it in part, a good index is essential. The tests I have made suggest that the moderate quality of the index here will reduce the effectiveness of the book as a whole. For example, the index carries entries on pressurized fluidized beds but the first major section on the subject (pp. 29-30) is not listed. The book’s price will not of course commend itself to the individual purchaser, but it has a claim to a place in the library as a summary of the state of the art to about 1982 and as a pointer to further work.

This book is made up of authors’ notes from a Course on Fluidized Bed Combustion given in Dubrovnik in 1984 by Twente University of Technology under the general auspices of the International Centre for Heat and Mass Transfer. It includes contributions on the fundamentals of fluidization, materials handling (including coal storage and feeders for solids), lluidized-bed combustors and the design of fluidizedbed boilers, fuel circulations and segregation in combustors, heat transfer in boilers, sulphur oxides reduction, and thermodynamic cycles with fluidized-bed combustion. These sections are intended as guides for further work in fluidizedbed combustion and as an addition to what the editor acknowledges is,an “impressive amount of information” on the subject already available in the literature: in my view the book succeeds rather better as a future guide than as a significant addition to present knowledge. The contributions vary widely in style. The substantial section on combustion in fluidized beds is in fact in several parts (fuels, coal devolatilization and ignition, fly ash recycling, and carbon particle combustion) with changes of author and separate references. In some contrast the contribution on fundamentals by van Swaaij and Prins is scholarly and wideranging. When these authors conclude, rightly, that the design of Buidized-bed combustors still largely depends on empiricism they probably undervalue the extent to which fluidization research in the last 25 years-to which they themselves have made considerable contributions-influences the overall approach to design even though laboratory experiments are

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DAVID HARRISON University of Exeter Northcote Elouse, The Queen’s Drive, Exeter, U.K.