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List of Papers and Abstracts published during 19911992 in Speculations in Science and Technology in the section УDevelopments in Chemical EngineeringФ.

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List of Papers and Abstracts
published during 1991M992 in
Speculations in Science and
Technology, in the section:
"Developments in Chemical
(BookReviews and a Conference Listing are also included in each issue)
Volume 14, Issue No.2,1991
Two Conceptual Problems in Heat or Mass Transfer to Arrays of
R. Ocone* and G. Astarita
Department of Chemical Engineering, Princeton University, Princeton, NJ 08544,
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
Department of Chemical Engineering, The Queen $ University of Belfast, Belfast
BT9 5AG, U K
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 oilhatural gas high pressure data were shown to be successful.
(Pages 94-1 16).
* Author to whom correspondence should be addressed.
Dispersion in Packed Beds: Does the Fluid Elasticity Play a Role?
K.R. Westerterpl and R.J. Wijngaarden
Department of Chemical Engineering, University of f i e n t e , PO Box 21 7, 7500
AE Enschede, Netherlands
Abstract: For axial dispersion of mass in a packed bed at high fluid 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
Department of Science and Chemical Engineering, The Polytechnic of Wales,
Pontypridd, Mid Glamorgan CF37 lDL, UK
Abstract: A survey has been carried out of the effect of heat on coals up to
approximately 900°C. 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
Department 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 11: Heat Exchanger Operation, Heat Exchanger Applications, Plate Heat
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 the
fundamental heat transfer literature (for 1989). (Pages 137-147).
Volume 14, 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, GA
30332-0100, USA
Abstract: Samples of a commercial CoNolalumina resid HDS catalyst were
coked to progressively higher levels with styrene at 425°C. TGA was used to
determine coke content of the samples. Oxygen uptake at 0°C 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, No.l,1992
Effects of the Microporous Polymer-Supported Catalyst on the
Allylation of 2,4-Dibromophenol
M.-L. Wang' and C.-C. Yu
Department of Chemical Engineering, National Tsing Hua University, Hsinchu,
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 ally1 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
H20); (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
Department of Chemical Engineering, Michigan State University, East Lansing,
MI 48824-1226, USA
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 size data, 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 Alkali
Treatment from Interfacial Tension Measurements
J.P. Giordano, S. Magdassi, S.G. Frank, D.H. Fruman and J.L. Zakin'
Department of Chemical Engineering, The Ohio State University, Columbus, OH
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 Lmmiscible-LiquidTransport in Aquifers?
C.D. Rugge, R.C. Ahlert' and J.M. Zukowski
Department 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
Volume 15, No.2, 1992
Present Trends in Process Safety
Trevor A. Kletz, Senior Visiting Research Fellow
University of Technology, Loughborough, Leics LEI1 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
Department of Chemical Engineering, Heriot Watt University, Riccarton,
Edinburgh EH14 4AS, U K
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-waterh-decanol was compared
with that of fermented malt extract liquorh-decanol i n 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. Miiller-Steinhagen'
Department 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 101-1 10).
Design of Decouplers and Feedforward Compensators in the Presence
of Unrealizable Time Delays
P.R. Krishnaswamy', N.V. Shukla and P.B. Deshpande
Department 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 111-1 19).
Volume 15, No.3, 1992
Chemical Process Simulation Packages
M.A. Hussain
Department of Chemical Engineering, University of Malaya, Kuala Lumpur,
Part I: A Guide to Selection
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 I1 of this paper. (Pages 163-170).
Part 11: 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 I1
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 OxidatiodReduction of Fe(II)/Fe(III) Ions in
Uranium Ore Leach Solutions
I. Nirdosh
Department 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 U02 ’+. 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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