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       Listing of PAPERS and ABSTRACTS published in:

		SPECULATIONS IN SCIENCE & TECHNOLOGY
      		     (Volumes 14 & 15, 1991/92)

       In the section:

           "DEVELOPMENTS IN CHEMICAL ENGINEERING"


 (Book Reviews and a Conference Listing are also included in each issue)

 (* Author to whom correspondence should be addressed)


 VOLUME 14, Issue no.2, 1991

 TWO CONCEPTUAL PROBLEMS IN HEAT OR MASS TRANSFER TO ARRAYS OF
 PARTICLES

 R Ocone*  and G Astarita
 Dept of Chemical Engineering, Princeton University, Princeton, NJ
 08544, USA

 Abstract.  It is shown that the limit where the Peclet number
 approaches zero in an array of particles is a singular one.  A
 simple cellular model is used, and the correct driving force for
 such a model is derived. When the Peclet number is finite, the
 Archimedes number is shown to determine the local relative motion;
 a modification of its definition is suggested for stirred tanks.
 An estimate of the dependence of the Nusselt or Sherwood number on
 the Archimedes number is derived from a scaling argument, and this
 is shown to be in reasonable agreement with published experimental
 data.  (pages 83-93)


 A NOVEL APPROACH TO FLOW REGIME PREDICTION IN GAS-LIQUID SYSTEMS

 P L Spedding*  and D R Spence
 Dept of Chemical Engineering, The Queen's University of Belfast,
 Belfast BT9 5AG, UK

 Abstract.  Existing flow pattern maps and flow regime transition
criteria are shown to be unable to successfully handle the effects
of geometrical variations and changes in the physical properties
of the phases.  A new method is presented which is based on the
separation of the flow patterns into either gas or liquid
turbulence dominated flow.  The individual flow regimes were
identified by use of a number of parameters which together
uniquely characterised regimes.  Tests against crude oil/natural
gas high pressure data were shown to be successful.  (pages 94-
116)


 DISPERSION IN PACKED BEDS: DOES THE FLUID ELASTICITY PLAY A ROLE?

 K R Westerterp*  and R J Wijngaarden
 Dept of Chemical Engineering, University of Twente, PO Box 217,
 7500 AE Enschede, Netherlands

 Abstract.  For axial dispersion of mass in a packed bed athighfluid flow rates, the Bodenstein number is equal to two.  This
means that each cavity between two particles behaves as one mixing
cell.  In the region for turbulent flow for Reynolds numbers below
1000, the Bodenstein numbers for liquid flow and for gas flow
differ by a factor of about 4.  This indicates that axial
dispersion of mass in a packed bed is not exclusively determined
by the Reynolds number, i.e. the ratio of the kinetic energy over
the viscous dissipation.  Some other property, being different for
gases and liquids, must also play a role.  On the basis of the
experimental observations of other scientists, and on the basis of
own work on the axial dispersion of heat, it is speculated that in
this case it might be the ratio of the intertia forces over the
elastic forces, and not the Reynolds number, that governs axial
dispersion in packed beds.  (pages 117-128)


 THE EFFECT OF HEAT ON COAL: AN ANNOTATED BIBLIOGRAPHY (PART 1)

 C Davies,*  A I Porter and G J Rees
 Dept of Science and Chemical Engineering, The Polytechnic of
 Wales, Pontypridd, Mid Glamorgan CF37 1DL, UK

 Abstract.  A survey has been carried out of the effect of heat on
coals up to approximately 900 degC.  The results have been
interpreted in terms of the activation energies for the three main
decomposition zones.  The first decomposition zone appears to be
associated with diffusion of trapped water and lighter components;
the second by liberation of oily components; and finally the third
region by active decomposition of the coal substance.  The rate of
heating, pre-treatment and physical structure of the coal, all
influence the activation energies reported for the reactions.
Catalysts influence the activation energies for the decomposition
zones.  (pages 129-136)


 HEAT EXCHANGER DESIGN (1966-1990): A BIBLIOGRAPHY (PART 1)

 Martyn S Ray
 Dept of Chemical Engineering, Curtin University of Technology,
 Perth, Western Australia

 Abstract.  Heat exchanger design is of fundamental importance to
both chemical and mechanical engineers.  The evaluation,
specification, and design of heat transfer equipment occurs in
many unit operations of chemical processes.  Over the past 50
years a significant proportion of the published technical
literature has been concerned with heat transfer fundamentals and
applications, and heat exchanger design and operation.  This two-
part article is a bibliography of published papers (and some
books) on selected heat exchanger topics for the period 1966-1990.
The topics included are:
   Part I: Heat Exchanger Design;  Part II: Heat Exchanger
Operation, Heat Exchanger Applications, Plate Heat Exchangers
The information contained in this paper provides an in-depth
coverage of heat exchanger design for the past 25 years.References
for the past two years (1988-1990) were included to
update those taken from a new bibliography prepared by the author.
The recent paper by Eckert et al. is a useful review of
thefundamental heat transfer literature (for 1989).  (pages 137-147)


 VOLUME 14, Issue no.3, 1991

 OXYGEN CHEMISORPTION ON A LABORATORY-COKED RESID HDS CATALYST

 Y Wang, J Baumgart, W R Ernst*  and J D Carruthers
 School of Chemical Engineering, Georgia Institute of Technology,
 Atlanta, Georgia 30332-0100, USA

 Abstract.  Samples of a commercial Co/Mo/alumina resid HDS
catalyst were coked to progressively higher levels with styrene at
425 degC.  TGA was used to determine coke content of the samples.
Oxygen uptake at 0 degC increased with increasing coke content,
while BET surface area decreased.  The results suggest that coke
preferentially blocks surface which has the lowest density of
oxygen adsorption sites.  (pages 164-170)


 THE EFFECT OF HEAT ON COAL: AN ANNOTATED BIBLIOGRAPHY (PART 2).
 C Davies,*  A I Porter and G J Rees
 (pages 171-176)



 HEAT EXCHANGER DESIGN (1966-1990): A BIBLIOGRAPHY (PART 2)
 Martyn S Ray
 (pages 177-185)


 VOLUME 15, Issue no.1, 1992

 EFFECTS OF THE MICROPOROUS POLYMER-SUPPORTED CATALYST ON THE
 ALLYLATION OF 2,4-DIBROMOPHENOL

 M-L Wang*  and C-C Yu
 Dept of Chemical Engineering, National Tsing Hua University,
 Hsinchu, Taiwan

 Abstract.  The reaction of allyl bromide with 2,4-dibromophenol in
an organic solvent/aqueous solution to synthesize 2,4-
dibromophenyl allyl ether by triphase catalysis was studied.  The
microporous polymer pellet which served as the support of the
catalyst was prepared by reacting styrene monomer with
chloromethyl styrene and divinyl benzene in a suspension
polymerization reaction.  Tri-n-butyl amine was then immobilized
on the surface of the polymer pellet to form the three-phase phase
transfer catalyst.  Immobilization of the catalyst on the polymer
support should be carried out by mechanical agitation in order to
obtain a high catalyst reactivity.  In the three-phase reaction,
the effects of agitation speed, solvents, alkali concentration and
the characteristics of the triphase catalyst on the conversion of
allyl bromide were investigated in detail.  On the basis of the
experimental data (using 2.28 g of 2,4-dibromophenol), the optimum
operating conditions for preparing the triphase catalyst in order
to get a higher yield of 2,4-dibromophenyl allyl ether were: (a)
using a low degree of polymer cross-linking (2%); (b) a smaller
particle size; (c) 2 g of KOH (50 ml of H2O); (d) 1.5 g of
triphase catalyst; (e) 50 ml of dichloromethane solvent; (f)
stirring speed greater than 400 rpm.  (pages 3-14)


 PROPERTIES OF THE CRYSTAL SIZE DISTRIBUTION ESTIMATED FROM
 DENSITY-DISTRIBUTION FUNCTIONS

 J Mydlarz*  and D Briedis
 Institute of Chemical Engineering and Heating Equipment, Technical
 University of Wroclaw, ul. Norwida 4/6; 50-373 Wroclaw, Poland

 Abstract.  A discussion of the properties of the crystal size
distribution (CSD) estimated from both simulated and real MSMPR
crystalliser population density distributions is presented.  In
the case of simulated linear log population density versus
sizedata, estimation of characteristic parameters of the particle
distribution from the population density distribution give values
of the parameters which are close to their theoretical values.
Calculations indicate that for real CSD-MSMPR crystalliser data,
the values of the means of particle population are significantly
related to the particle size range measured.  This is particularly
important in the lower range of the estimated means of
experimental population density data.  Estimation of the kinetics
of growth and nucleation also confirms that values of crystal
growth and nucleation rates for the same run are substantially
related to the crystal size range measured.  (pages 15-23)


 PREDICTION OF EMULSIFIABILITY OF VISCOUS CRUDE OILS WITH
 ALKALITREATMENT FROM INTERFACIAL TENSION MEASUREMENTS

 J P Giordano, S Magdassi, S G Frank, D H Fruman and J L Zakin*
 Dept of Chemical Engineering, The Ohio State University, Columbus,
 Ohio 43210, USA

 Abstract.  Viscous crude oils will provide a valuable source of
future oil supply as low viscosity crudes are depleted.  A
promising technique for transporting them to refineries is as low
viscosity concentrated oil-in-water emulsions.  Of six heavy
crudes tested, 60% oil-in-water emulsions could be prepared from
three of them by treatment with sodium hydroxide over a fairly
wide alkali/total acid number (TAN) range.  Relatively unstable
emulsions over a narrow range of sodium hydroxide addition could
be formed from one crude, and emulsions could not be formed with
the other two at any alkali level.  Interfacial tension
measurements of 90% crude in toluene solutions against 0.01%
sodium hydroxide solutions gave results below 0.003 N/m for the
three crudes that could be emulsified, and over 0.0068 N/m for the
other three, indicating that such measurements can be used to
predict the feasibility of preparing emulsions by alkali
treatment.  Measurements at 77% crude in toluene confirm these
findings but the absolute values are generally somewhat higher.
(pages 24-29)


 LENTICULAR DROPS: A KEY TO IMMISCIBLE-LIQUID TRANSPORT IN
 AQUIFERS?

 C D Rugge, R C Ahlert*  and J M Zukowski
 Dept of Chemical and Biochemical Engineering, Rutgers University,
 Piscataway, NJ 08855-0909, USA

 Abstract.  Denser-than-water, immiscible chlorinated solvents
(DNAPLs) may spread through the unsaturated zone after spillage,
eventually penetrating the saturated zone.  A tendency of DNAPLs
to float on air-water interfaces may cause these liquids to be
distributed at the capillary fringe.  A study was performed with
1,1,1-trichoroethane, 1,1,2-trichloroethane, tetrachloroethylene,
carbon tetrachloride and trichloroethylene to investigate the
mathematical dependence of the maximum stable volume (MSV) of
solvent that can remain floating at an air-water interface with
the Bond number (Bo), a dimensionless quantity incorporating
density, interfacial tension, and aperture radius.  It is proposed
that MSV is a function of (Bo - Bo*), where Bo* is a critical Bo
below which no MSV forms.  This critical-mass model may have
application in describing DNAPL transport in aquifers,
incorporating both fluid and aquifer properties.  (pages 30-39)


 VOLUME 15, Issue no.2, 1992

 PRESENT TRENDS IN PROCESS SAFETY

 Trevor A Kletz

 Senior Visiting Research Fellow, University of Technology,
 Loughborough, Leics LE11 3TU, UK
 Address for Correspondence: 64 Twining Brook Road, Cheadle Hulme,
 Cheadle, Cheshire SK8 5RJ, UK

 Abstract.  Recent developments in process safety are reviewed.
Hazard and operability studies (hazop) and hazard analysis
continue to grow in popularity and computerised aids are now
available.  The limitations of the conventional hazop of a line
diagram are becoming recognized: it is carried out too late in
plant design for fundamental changes to be made.  If we can carry
out similar studies earlier in design then we can design
inherently safer and more user-friendly plants which can tolerate
human error or equipment failure without serious effects on safety
(and output and efficiency).  It is now recognized that we should
remove opportunities for error and not expect people to be error-
free.  Computer control has provided new opportunities for old
hazards.  Companies are still reluctant to learn the lessons of
the past and many senior managers do not see that they have a part
to play.  (pages 83-90)


 RELATIONSHIP BETWEEN DROP-SIZE AND FIELD STRENGTH IN ENHANCED
 WHOLE-BROTH LIQUID-LIQUID EXTRACTION

 L R Weatherley
 Dept of Chemical Engineering, Heriot Watt University, Riccarton,
 Edinburgh EH14 4AS, UK

 Abstract.  Recovery of products from microbiological fermentation
systems by direct solvent extraction offers significant scope for
process simplification and reduction in production costs.  The use
of electrical fields to accelerate the slow kinetics of whole-
broth extraction offers the potential for a viable and cheap
alternative to mechanical enhancement methods.  This study was
aimed at determining the drop behaviour during extraction by
comparison with a known model system.  The relationship between
drop size, nozzle velocity, physical properties and applied field
strength was explored for single aqueous drops dispersing from a
nozzle into an organic solvent under the influence of a constant
electric field.  The behaviour of the system ethanol-water/n-
decanol was compared with that of fermented malt extract liquor/n-
decanol in the presence of Saccharomyces cerevisiae.  The
experimental measurements of drop size were compared with
theoretical predictions based on a model in which the effect of
electrostatic forces acting upon detaching drops is described in
terms of the nominal field strength and the length of the charged
nozzle.  Good agreement between the experimental and predicted
drop sizes was found for both liquid-liquid systems.  (pages 91-100)


 EFFECT OF ENERGY INPUT ON BUBBLE COALESCENCE IN BUBBLE COLUMNS

 M Jamialahmadi and H Muller-Steinhagen*
 Dept of Chemical and Materials Engineering, University of
 Auckland, Auckland, New Zealand

 Abstract. This paper combines the results of several
investigations aimed at obtaining a better understanding of bubble
coalescence in order to control this unwanted phenomenon in bubble
columns.  The effects of different methods of energy input, i.e.
heating, vibration and agitation on bubble coalescence and bubble
break-up have been analysed.  Gas and liquid-phase flow patterns
have been examined.  From these results, it was found that if
liquid backmixing can be reduced in some way, such as radial baffling 
or decreasing column height, then the bubble coalescence decreases 
and therefore, the gas hold-up increases significantly.(pages 101-110)


 DESIGN OF DECOUPLERS AND FEEDFORWARD COMPENSATORS IN THE PRESENCE
 OF UNREALIZABLE TIME DELAYS

 P R Krishnaswamy,*  N V Shukla and P B Deshpande
 Dept of Chemical Engineering, National University of Singapore,
 Kent Ridge, Singapore 0511

 Abstract.  Unrealizable time delays (positive dead time) can cause
a significant deterioration in the performance of feedforward
compensators employed in multivariable decoupling control and SISO
applications.  In this paper it is shown that the performance of
such systems can be considerably improved, contrary to general
belief, by judicious addition of pure time delay to the system.
This concept is illustrated with two simulation examples.  One is
a 2 x 2 boiler control system exhibiting one way interaction, and
the other is a heat exchanger operating under combined
feedback/feedforward control.  The results from the boiler example
show that loop interaction can be completely eliminated while at
the same time loop integrity is preserved.  In the case of the
heat exchanger, a remarkable improvement in feedforward action is
realized without affecting the stability of the closed loop
system.  (pages 111-119)


 VOLUME 15, Issue no.3, 1992

 CHEMICAL PROCESS SIMULATION PACKAGES

 PART I:  A GUIDE TO SELECTION

 M A Hussain
 Dept of Chemical Engineering, University of Malaya, Kuala Lumpur,
 Malaysia

 Abstract.  Computer-aided chemical process modelling and
simulation has become an integral part of chemical engineering
practice.  It is widely used in academic institutions and by many
engineers in research and development, as well as in process and
plant engineering situations.  Many simulation programs are now
commercially available, coupling the technical rigour of the most
sophisticated modelling and simulation systems with ease of use.
The range of simulation packages now available has created a need
to choose the right software at the right time with the right
cost.  This paper discusses the important factors to be considered
when choosing a general process simulator, with more emphasis
towards the personal computer-based programs.  An example of the
use of such a simulator for a particular application, and to
demonstrate certain features, is described in Part II of this
paper.  (pages 163-170)

 PART II:  A CASE STUDY EXAMPLE
 Abstract.  Many chemical process simulation packages have
been developed in the universities and industry since the 1960's,
mainly for use on mainframe or minicomputers.  However, with the
latest upsurge of powerful microprocessor technology many of these
simulators have been converted for use on the personal computer.
This paper assess the salient features of the PC-based DESIGN II
simulation package, with a case study application for a plant
producing cyclohexane by catalytic hydrogenation of benzene.  A
comparison with results obtained using the FLOWTRAN simulator is
included.  (pages 171-178)


 CONTINUOUS ELECTROLYTIC OXIDATION/REDUCTION OF Fe(II)/Fe(III) IONS
 IN URANIUM ORE LEACH SOLUTIONS

 I Nirdosh
 Dept of Chemical Engineering, Lakehead University, Thunder Bay,
 Ontario P7B 5E1, Canada

 Abstract.  In the ferric chloride leaching process of uranium
ores, uranium dissolves predominantly in the uranyl cation form
UO2(2+).  Reduction of the abundant ferric ion present in the
solution to the ferrous state is necessary prior to the recovery
of uranium from the leachate by solvent extraction, in order to
minimize the uptake of ferric ions by the solvent.  The recycle of
aqueous solution for leaching after the solvent extraction
operation requires re-oxidation of the ferrous ions to the ferric
state.  A continuous flow-through diaphragm electrolytic cell has
been tested for simultaneous oxidation of the ferrous ions in the
anodic side, and the reduction of the ferric ions in the cathodic
compartment of the electrolyzer.  It was found that the cell
operates successfully and the cell voltage depends primarily on
the ohmic losses.  (pages 179-185)
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