bluuebunny/crossref_metadata_2025 huggingface dataset:
Particle effects on free jet entrainment
Authors: Tatterson D. F. , Marker T. L. , Forgac J. M.
Published: March 2009

The effect of particles on entrainment into free jets has been reexamined. As previously reported, particles can increase, decrease or have no effect on jet entrainment. This study suggests that the effect correlates with the ratio of particle stopping distance to nozzle diameter. For values of this ratio less than 3 entrainment increases due to the presence of particles. For values of the ratio between 3 and 65, entrainment is decreased. For values greater than 65, the presence of particles in the jet has no effect on entrainment. If the suggested correlation proves to be correct, it will assist the design engineer who wishes to rapidly mix particles with surrounding gas in a free jet. In particular, the region where a decrease in entrainment is observed should be avoided as there will be a corresponding decrease in mass and heat transfer.
The redistribution of trace and minor elements during coal liquefaction
Authors: Pringle T. G. , Jervis R. E.
Published: March 2009

Radioactivation analysis of four sets of coal liquefaction feed and product materials provided information on the concentrations of forty trace and minor elements. Coal‐derived oil was found to have low levels of most elements, comparable to crude petroleum. Aqueous process effluents were shown to have potentially troublesome levels, especially of Cr and Ba. The concentration data derived in this study and relevant process data were combined to construct elemental mass balances around the liquefaction process; these varied widely between about 80 and 140%, depending mostly on analytical errors. Enrichment of chromium and other transition metals in the conversion residues indicated a possible source through equipment erosion while consistent depletion of barium suggested a loss to aqueous stream particulate matter or possible reactor deposits.
Numerical simulation of a pressure swing air separation systemndasha comparative study of finite difference and collocation methods
Authors: Raghavan N. S. , Hassan M. M. , Ruthven D. M.
Published: March 2009

The efficiency of three different numerical methods (single and double collocation and 3‐point central finite difference) is compared for the solution of the set of partial differential equations describing the performance of a pressure swing adsorption (PSA) system for air separation on a carbon molecular sieve. It is shown that in terms of computer time there is little difference between single and double collocation methods but for comparable accuracy both these methods are very much faster than the finite difference method.
Fischer‐tropsch synthesis in a stirred tank slurry reactorndashreaction rates
Authors: Bukur Dragomir B. , Brown Russell F.
Published: March 2009

The effect of process variables (temperature, pressure, space velocity, and H2/CO feed ratio) on the Fischer‐Tropsch synthesis on a promoted fused iron catalyst was studied in a slurry phase stirred tank reactor (STR). Operating conditions were chosen such that some of the data could be compared with previously reported results, but experiments were also performed at more extreme conditions (temperatures up to 280°C and pressures up to 2.86 MPa) than previously studied in a slurry phase STR. The catalyst activity compares well with previous studies at an H2/CO feed ratio of 1.0 and 1.8, but the activity is lower than previously reported values in the 0.64‐0.72 range of H2/CO feed ratios. Spacetime‐yield increases with pressure, and reactor productivity is best increased by increasing pressure at a constant pressure to space velocity ratio. The water‐gas‐shift reaction is near equilibrium at high conversions, and always proceeds at a slower rate than the Fischer‐Tropsch synthesis in a STR.
Pyrolysis of 1,3‐butanediol as a model reaction for wood liquefaction in supercritical water
Authors: West Mary Ann B. , Gray Murray R.
Published: March 2009

1, 3‐Butanediol was pyrolyzed at 425°C in a batch reactor as a model system for liquefaction of lignocellulosic materials such as wood. The observed gas and liquid products were consistent with fragmentation, dehydration, and condensation/polymerization reaction pathways. Reaction in supercritical water altered the selectivity of the reactions to give mainly propene and formaldehyde. Dehydration and the formation of two‐carbon products were suppressed by water. The conversion of 1, 3‐butanediol in dilute aqueous solutions increased three to four fold when the reaction density was increased by 33%. Trace oxygen was an important inhibitor, particularly in the dilute solution, but had only a minor effect on the reaction selectivity.
The phenomenon of thermal channelling in countercurrent gas‐solid heat exchangers
Authors: Wonchala E. P. , Wynnyckyj J. R.
Published: March 2009

Maldistributed flow in moving‐bed reactors and heat exchangers is recognized to be a serious problem. Heat exchanger equations do not provide a clue to the cause. In this paper it is shown that maldistributed flow can occur even in perfectly homogeneous packed beds and that this arises because of inherent temperature non‐uniformities. The term thermal channelling is introduced to describe this effect.

It is shown that simultaneous consideration of both the heat and the mechanical energy (the Ergun equation) balances predicts that the gas, in cooling a hot bed, divides into a multiplicity of stable channels with significantly differing mass velocities. This does not, however, occur for the inverse case of heating the bed. Further, it is shown that the system conditions where a multiplicity of states is stable can be defined in terms of an integral mean temperature and two dimensionless variables, NTU and the bed Reynolds number. In general tall beds with large temperature differences are most prone to thermal channelling.
Kinetic modelling of a fluidized bed claus plant
Authors: Birkholz Robert K. O. , Behie Leo A. , Lana Ivo G. Dalla
Published: March 2009

A kinetic model of a fluidized bed Claus reactor was developed using the Modified Bubble Assemblage Model (MBAM) to establish the practical implications of fluid bed technology for this new application. Simulations predicted that a two stage sub‐dewpoint fluidized bed Claus plant is capable of achieving a recovery efficiency of 97.1%, which is comparable to a conventional three stage fixed bed plant, but considerably less than the overall equilibrium conversion of 99.5%. Conversion is limited by gas‐bypassing, particularly in the downstream sub‐dewpoint reactor. In the fluidized bed process, about half the catalyst is required and the pressure drop is significantly lower compared with a conventional plant of equivalent capacity. Moreover, the capital cost estimate for a two reactor fluid bed Claus plant (200 t/d sulphur) was estimated to be $20 million (Can) which is within 10% of a conventional plant.
The influence of geometrical factors and feedstock on gasification in a high temperature fluidised bed
Authors: Tomeczek J. , Kudzia W. , Gradonń B. , Remarczyk L.
Published: March 2009

Results are presented for gasification of coal and char by means of air or air‐steam mixtures in fluidised bed reactors of three different volumes. Two sizes of coal feedstock particles, 0.5‐1.0 mm and 1.0‐1.5 mm, and one size of char particles, 0.5‐1.5 mm, were used. The calorific value of generated gas and the carbon conversion are presented as a function of particle residence time. For coal gasification higher carbon conversion has been obtained at the same particle residence time than for char gasification. For the steam gasification, a lower gas heating value of about 4 MJ/m3 (S.T.P.) was obtained.
Application of parametric control concepts to decoupler design and heating control design for a batch reactor
Authors: Jutan Arthur , Rodriguez E. S.
Published: March 2009

Parametric control involves expressing the manipulated variables of a process in terms of a new set of variables, called parametric variables. The control engineer can choose the functional relationships between the two sets of variables to provide added flexibility in control loop design. The design of a static decoupler and the linearization of a batch reactor heating system are provided as examples.
Development of a procedure for selecting the optimum adsorbent for abs removal
Authors: Chiang P. C. , Lou J. C. , Tseng S. K.
Published: March 2009

The objective of this paper is to demonstrate the capability of some commercially available adsorbents (XAD‐2, XAD‐8, Activated Carbon) to treat waste water containing ABS (Alkyl Benzene Sulfonate). Laboratory experiments were performed to determine the adsorption capacity, effective diffusion coefficient and activation energy for each adsorbent. As a result, the AC‐B and XAD‐2 adsorbents were selected as potential adsorbents to run column tests i.e., service and regeneration cycles. Based on the results of treatability studies the optimum adsorbent was chosen. The most effective regenerant (CH3OH) was found on the basis of the extraction (distillation) efficiency and unit price associated with each organic solvent.
Kinetics of and catalyst decay accompanying the gas phase rearrangement of cyclohexanone‐oxime over a hy ultrastable zeolite
Authors: Burguet M. C. , Aucejo A. , Corma A.
Published: March 2009

The kinetics of the rearrangement of cyclohexanone‐oxime has been studied in a fixed bed, glass tubular reactor at atmospheric pressure and temperatures of 240, 270, 300 and 335°C, using ultrastable HY zeolite catalyst. Several kinetic models, including the Langmuir‐Hinshelwood type, have been derived and the best statistical fit has been obtained with a pseudo‐first order kinetic equation. The rate constants and activation energies for the formation of the products caprolactam, cyclohexanone and 5‐cyanopent‐l‐ene have been calculated. Based on the evolution of the selectivity with temperature, and the I.R. spectra of the poisoned catalyst, different decay models have been deduced and discussed.
Rising velocity of a swarm of spherical bubbles in a power law non‐newtonian liquid
Authors: Gummalam S. , Chhabra R. P.
Published: March 2009

Previous work on the rise of a swarm of bubbles in non‐Newtonian media has been reviewed. Variational principles have been combined with the Happel free surface cell model to obtain upper and lower bounds on the swarm velocities of bubbles rising slowly through power law liquids. The predictions presented herein encompass wide ranges of gas holdup and shear‐thinning behaviour.
Heat transfer coefficients in coiled stirred‐tank systems
Authors: Aksan Devlet , Borak Fahir , Ilsen önsan Z.
Published: March 2009

Steady‐state and transient heat transfer coefficients were determined in coiled, stirred‐tank systems with single‐tank and two‐tanks‐in‐series arrangements, using flat‐blade turbine impellers and water. Flowrates, hot water temperature and agitator speed were varied for Re between 19,000 and 77,000 for the agitated side, covering the Re = 20,000–40,000 range for which published data are not available.
Dispersing behaviour of droplets in suspension polymerization of styrene in a loop reactor
Authors: Tanaka Masato , O'Shima Eiji
Published: March 2009

Suspension polymerization of styrene was performed using a loop reactor. The dispersing behaviour of the droplets in the course of the reaction was observed. The mean droplet diameter was determined by the energy level at the impeller region. Moreover, the final particle size distribution and mean particle size were also determined after an elapsed time of 1‐2 hrs.

An expression which correlated the final mean particle size with the operating conditions, such as the mixing conditions at the impeller region and the initial physical properties of the suspension system, was derived. The deposition of polymers on the reactor wall was found to be prevented due to the high fluid velocity.
Mixed convection heat transfer in porous media in the non‐darcy regime
Authors: Islam Rafiqul M. , Nandakumar K.
Published: March 2009

In this study mixed convection heat transfer in a homogeneous porous duct of square cross section in a horizontal orientation is examined. Results from a generalized Forchheimer model are compared with that from the Darcy model. The heat transfer rate and the flow behavior depend on the following parameters: Grashof number, Gr = Q'gβKa/kv2, an axial flow pressure drop parameter, ζ = (aK/vμ)dp'/dz', an inertial parameter ξ = mK/a, appearing in the Forccheimer model and the Prandtl number, Pr = Cpμ/k. In the Darcy limit, ξ → 0, the role of the axial flow parameter, λ is reduced to a mere scale factor and the flow behavior is determined by a single parameter, λ = Gr · Pr. Both the Darcy and the Forchheimer models exhibit dual solutions and a hysteresis behavior over a certain range of Gr. Such parametric dependence can be used as an additional tool along with carefully designed experiments to determine the importance of inertial and Prandtl number effects on convective heat transfer in porous media.
Oxygen transfer into newtonian and non‐newtonian fluids in mechanically agitated vessels
Authors: Ogut Ali , Hatch Randolph T.
Published: March 2009

Oxygen transfer into Newtonian and non‐Newtonian fluids was studied in stirred tank vessels of 0.0018, 0.006 and 0.036 m3 operating volumes. Emphasis was given to the rheological effects of the pseudoplastic medium on the volumetric oxygen transfer coefficient, KLa. Results indicate that KLa is a strong function of gassed power input per unit volume (Pg/V) for the Newtonian fluid, but a weak function of Pg/V for the non‐Newtonian fluid, and a strong function of superficial gas velocity (Vs) for both fluids for paddle‐type impellers. KLa is found to decrease rapidly with an increase in apparent viscosity for values of μa greater than 2.0 Pa · s. In addition to various correlations, a dimen‐sionless correlation including the impeller Reynolds number, impeller Weber number, and the aeration number is presented for the prediction of KLa in a gas‐liquid non‐Newtonian system.
A scanning electron microscope study of structural changes during the liquefaction of poplar sticks by rapid aqueous thermolysis
Authors: Boocock David G. B. , Kosiak L.
Published: March 2009

Scanning electron microscopy shows that the liquefaction of poplar sticks (6.35 mm square cross section) by aqueous pyrolysis first involves the surface disruption of the middle lamella. The latter and cell walls then fuse, and the flowing matrix then engulfs the cells. At surface temperatures of 280°C spherical structures appear within the stick, particularly on vessel walls. Flowing matrix fills irregular cavities within the stick and gas or vapour bubbles are formed. The spherical structures are insoluble in ether, which dissolves monomeric material, but are disrupted by chloroform which dissolves oligomers. Acetone which dissolves higher molecular weight material, removes the spheres.
Suboptimal control through model reduction
Authors: Gupta Y. P.
Published: March 2009

There has been a growing interest in control strategies that optimize a given performance criterion to improve process efficiencies. Optimal control techniques, such as LQP, have been available but did not find much acceptance in process industries because of certain problems that are involved in their application. In this paper an approach is presented which alleviates these problems. Simulation results show that the proposed approach works well for servo and regulatory control problems.
Gas‐solid contacting in a two‐dimensional fluidized bed containing mobile internals: Non‐reactive tracer studies
Authors: Gbordzoe E. A. M. , Littman H. , Bergougnou M. A.
Published: March 2009

The effect of 50.8 mm diameter disc shaped mobile internals (MIs) on gas‐solid contacting was studied in a large two‐dimensional fluidized bed by means of non‐reactive tracers. MIs were found to improve substantially the mass transfer coefficient between the bubble and dense phases. However, they also increased the gas dispersion in the dense phase.
Modified oil agglomeration process for coal beneficiation. I. Mineral matter liberation by fine grinding with the szego mill
Authors: Bajor Oliver , Trass Olev
Published: March 2009

The spherical oil agglomeration technique developed at the National Research Council of Canada (NRC) is an excellent method for cleaning and recovering very small coal particles. The finely ground coal, dispersed in water, is contacted with oil by intensive mixing. The hydrophobic coal particles collect onto the oil droplets to form the agglomerates which are then separated from the aqueous phase by screening.

A Szego Mill was used to wet grind Minto (New Brunswick) coal which was then subjected to laboratory agglomeration by the NRC procedure. A comparison with coal ground in a ball mill indicated superior ash rejection. The improved performance is attributed to better mineral liberation which is enhanced by the more flaky particles produced in the Szego Mill.
Kinetics of the methanation of carbon dioxide over a supported Ni‐La2O3 catalyst
Authors: Kai Takami , Takahashi Takeshige , Furusaki Shintaro
Published: March 2009

The kinetics of the methanation of carbon dioxide was investigated using an alumina supported Ni‐La2O2 catalyst in a differential and integral reactor. In the differential reactor the molar ratio of H2 to CO2 was varied from 0.6 to 30. In the integral reactor the rates were measured with up to 90% conversion. Both reactor tests were carried out at temperatures between 513 and 593 K. The experimental results were described by a Langmuir‐Hinshelwood type equation. The kinetics can be explained by assuming equilibrium of dissociative carbon dioxide and hydrogen adsorption, and assuming hydrogenation of surface carbon as the rate determining step.
The effect of surfactants on peat dewatering
Authors: Cooper D. G. , Eccles E. R. A. , Sheppard J. D.
Published: March 2009

The effect of cationic, anionic and neutral surfactants on the mechanical dewatering of a highly decomposed fuelgrade peat has been examined. Surfactant adsorption and zeta potential of the peat particles correlated with dewatering of peat samples. The cationic surfactants had large positive effects on dewatering, the anionic surfactants had a negative effect while the neutral surfactant had no effect. The effects of the surfactants could be explained by charge neutralization and double layer suppression. The cationic surfactants were superior to analogous organic salts because of enhanced interaction by the hydrophobic effect.
Regeneration of cracking catalyst influence of the homogeneous CO postcombustion reaction
Authors: Morley K. , De Lasa H. I.
Published: March 2009

Accompanying the fast burning of coke on a cracking catalyst is the oxidation of the coke burning product, carbon monoxide. This carbon monoxide combustion involves a homogeneous and a catalytic reaction. The homogeneous reaction was isolated by injecting pulses of CO, CO2 and O2 into a laboratory scale reactor at controlled temperature and pressure. The coke burning and catalytic CO combustion reactions were studied by oxidizing coke deposited on a zeolitic catalyst in the same microcatalytic reactor. The role of homogeneous CO oxidation during coke combustion under these conditions was determined.
Use of nonlinear transformations and a self‐tuning regulator to develop an algorithm for catalytic reactor temperature control
Authors: Onderwater D. , Macgregor J. F. , Wright J. D.
Published: March 2009

Prior to developing a multivariable control scheme for conversion and production rates in a packed bed tubular reactor carrying out highly exothermic reactions, it was important to stabilize the reactor temperature. In this paper we illustrate the use of a self‐tuning regulator to develop an inner loop controller that satisfies some necessary conditions on temperature response, and that is capable of controlling the reactor over a wide range of operating conditions. The importance of using a nonlinear transformation of the reactor hot‐spot temperature is demonstrated. Varying the input constraining parameter in the “one‐step optimal” self‐tuning controller is shown to be a very effective way of achieving a controller with the desired properties for response smoothness.
A model for microencapsulation in polyurea shell by means of interfacial polycondensation
Authors: Sirdesai Mayur , Khilar Kartic C.
Published: March 2009

A quasi‐steady state model, based on two parallel modes of diffusion and a polycondensation reaction at the inside surface of a microcapsule, is formulated to compute the time of this microencapsulation process. The predicted times of encapsulation are in agreement with observed values reported in patents. It is also shown that, for small shell thickness, the process is reaction‐controlled.
Economic aspects of wood‐burning installations
Authors: Fels M. , Cooper D.F. , Patterson M.N.
Published: March 2009

Economic data were obtained from 15 industrial wood burners. The capital cost was correlated by:

Cost = $7870 (kW)0.59.

Operating cost varied between $ 0.64 and $ 2.65 per kWhr output, payback times between 3.5 and 11 years and internal rates of return between 6.3% and 28%. Using average values of economic parameters, these results were recalculated on a common basis as a function of wood and electricity costs.
Solubility of H2S and CO2 in sulfolane
Authors: Roberts B. E. , Mather A. E.
Published: March 2009

The solubility of H, S and CO2 in sulfolane (tetrahydrothiophene‐1, 1—dioxide) has been measured at 40°C and 100°C at pressures up to 2350 kPa and 5900 kPa respectively. The Henry's constants obtained from the data are in agreement with those of Rivas and Prausnitz.
Displacement of bitumen from reconstituted oil sands by aqueous solutions
Authors: Margeson J. L. , Hornof V. , Neae G. H. , Faurschou D. K.
Published: March 2009

A simple method has been developed for modelling the recovery of bitumen from packed beds of oil sand by water or caustic solution displacement. Batches of reconstituted oil sand were prepared by intimately mixing predetermined amounts of sand, water, and bitumen, thereby permitting the composition of the oil sand to be controlled and varied within a wide range. Dilution of the bitumen with hexadecane facilitated the mixing process and allowed experiments to be performed at low temperatures while maintaining oil‐water viscosity ratios comparable to those prevailing at the higher temperatures encountered during hot water or steam displacements in the field. The effects of a wide range of compositional and operational variables were studied using a two‐level fractional factorial design technique and the findings are discussed. Of particular interest are the observations that the density and initial connate water saturation of the oil sand exert significantly more effect on bitumen recovery efficiency for the case of water displacement than for caustic solution displacement.
Optimal design of a heat exchanger undergoing reaction fouling
Authors: Fryer P. J. , Hobin P. J. , Mawer S. P.
Published: March 2009

The design of heat exchangers which resist fouling is examined. It is shown that for asymptotic reaction fouling in a uniform wall temperature exchanger with outlet fluid temperature kept constant, it is possible to obtain an optimum combination of exchanger size and tube‐side temperature. This optimum minimises the amount of fouling in the system. An equation which gives a good approximation to the optimum is derived, and its limitations discussed.
Reactions of cyclopentane on HY Zeolite
Authors: Abbot J. , Wojciechowski B. W.
Published: March 2009

The reaction of cyclopentane has been studied on HY zeolite at 500°C. Initial reaction processes included ring cleavage to acyclic C5 species, and cracking to produce fragments in the range C1 ‐ C4. Hydrogen transfer accompanied those processes, so that paraffins as well as olefins were observed as initial products. Cyclopentene was formed as an unstable initial product by the dehydrogenation of the feed, although molecular hydrogen was not found as a primary product. Other dehydrogenated species initially formed included coke and aromatics in the range C6 ‐ C10.
A general solution for the transient response of heterogeneous continuous‐flow stirred reactors
Authors: Datta Ravindra
Published: March 2009

A general time‐domain analytical solution is provided for the step‐response of a continuous‐flow stirred reactor containing catalyst particles of arbitrary shape in which one‐dimensional diffusion and first‐order irreversible reaction is assumed to occur. The results reduce to the corresponding known solutions for the planar, cylindrical and spherical geometries.
Tube‐wall reactor modelling for multiple reaction networks with non‐linear kinetics and volume change
Authors: Goyal S. K. , Esmail M. N. , Bakhshi N. N.
Published: March 2009

Tube‐wall reactors are gaining importance for highly exothermic and fast chemical reactions because of their simple construction and improved temperature control. A generalized mathematical model of the non‐isothermal annular tube‐wall reactors for simultaneous catalytic reactions with mixed type non‐linear reaction kinetics and volume change is developed. Numerical solutions of two‐dimensional component transfer equations, heat transfer equation and fluid flow equation may be obtained with appropriate boundary conditions using a recently developed orthogonal collocation method for annular geometries. The model has been successfully applied to the tube‐wall reactors for the Fischer‐Tropsch Synthesis. Comparison between model predictions and previous experimental results is good.
Kinetics of methyl tertiary butyl ether synthesis catalyzed by ion exchange resin
Authors: Al‐Jarallah Adnan M. , Siddiqui Mohammed A. B. , Lee A. K. K.
Published: March 2009

This paper presents the results of an experimental investigation of the kinetics of liquid phase reaction between methanol and isobutene, catalyzed by an acidic ion‐exchange resin, to form methyl tertiary butyl ether (MTBE). A one litre Parr batch reactor was used. Experiments were carried out at 70, 80, 90 and 100°C and at pressures sufficient to maintain liquid phase at those temperatures. Initial methanol/isobutene mole ratios of 1.0 and 2.0 were used. The catalyst amount was also varied.

These kinetic data were used to model the reaction kinetics, by non‐linear least squares regression technique. The reaction was found to follow Rideal‐Eley kinetics. The values of the rate constants are reported.
Studies of the fischer‐tropsch synthesis on a cobalt catalyst i. evaluation of product distribution parameters from experimental data
Authors: Sarup B. , Wojciechowski B. W.
Published: March 2009

Two models describing the distribution of linear and monomethyl alkanes in Fischer‐Tropsch products from a cobalt catalyst are formulated. Distribution parameters for monomethyl isomers are derived by assuming either a post‐branching effect on linear chain growth or a decreasing reactivity toward branching with increasing chain length. Distribution parameters for each of the models have been extracted from an extensive experimental data set. We find that the experimental results are well represented by both the models.

A “break” in the distribution of linear paraffins has also been observed and is modelled as a sum of the yields of two Anderson‐Schulz‐Flory distributions. We postulate that the two chain growth processes which produce the distributions are governed by two kinds of termination.
Study of the hydrodynamics within a draft tube spouted bed system
Authors: Matthew Mani C. , Morgan Morris H. , Littman Howard
Published: March 2009

Two dimensional Darcy and Ergun models are used to describe the hydrodynamics within the annulus of a spouted bed equipped with a draft tube. Experimental pressure and stream function data for water spouting are shown to be in good agreement with theoretical predictions. Verification of a general spout‐annulus interfacial boundary condition is also established and it is shown that the entry region below the draft tube functions as a classical spouted bed. In addition, an experimental procedure for determining the location of the spout‐annulus interface is presented. Fluid residence time distributions are calculated for a few cases of practical interest.
Hydrogen production by the catalytic steam reforming of methanol: Part 3: Kinetics of methanol decomposition using C18HC catalyst
Authors: Amphlett J. C. , Mann R. F. , Weir R. D.
Published: March 2009

The rate of catalytic decomposition of methanol in the presence of steam has been studied using a commercial CuO‐ZnO‐Al2O3. low temperature shift catalyst from 150‐270°C at one atmosphere pressure in a fixed bed reactor. Mole ratios of steam to methanol of 0.66. 1.0 and 1.5 and catalyst mass to molar feed rate ratios of 25 to 1025 kg. s. mol −1 were utilized. The data were correlated and equations developed to successfully predict methanol conversions and carbon monoxide concentrations in the product gas stream over the temperature range studied. No evidence of mass transfer limitations was observed.
On boundary conditions to the film model of mass transfer in chemical absorption
Authors: Starzak Maciej , Ledakowicz Stanisuw
Published: March 2009

The problem of appropriate boundary conditions for mass transfer within the liquid film in chemical absorption ih reconsidered. It has been shown that the most general solution to the problem of mass transfer in the liquid film can be obtained if a fixed bulk composition is taken as a film‐bulk boundary condition to the differential balance equations of the film. This method leads to solutions which can be incorporated into absorber balance equations of any type. As an illustrative example, the simultaneous absorption of two gases which react together in a semi‐batch absorber is discussed. A new, approximate but very simple and accurate solution to this problem is proposed.
Viscosity and surface tension of p‐xylene‐ethylacetate liquid mixtures
Authors: Narayan Jyoti , Wanchoo R. K. , Razna G. K. , Wani G. A.
Published: March 2009

Experimental density, viscosity and surface tension data are reported for p‐xylene‐ethylacetate mixtures at 20°. 30° and 40°C. over the entire composition range. The presence of interactions has been studied in the light of excess properties.
The importance of real‐fluid behavior in predicting release rates resulting from high‐pressure sour‐gas pipeline ruptures
Authors: Picard D. J. , Bishnoi P. R.
Published: March 2009

The real‐fluid nonisentropic decompression model presented by Picard and Bishnoi (1988) has been used to evaluate the current practice of assuming perfect‐gas behavior when predicting release rates from high‐pressure sour‐gas pipelines. It is shown that use of perfect‐gas theory can result in the transient release rate being underestimated by 30 to 45 percent, and the total amount of fluid released, underestimated by 50 percent. Furthermore, perfect‐gas theory cannot consider condensation effects; more than 35 percent of the H2 S contained in a pipeline may be emitted as a liquid.

Use of the popular “double exponential” model, as presented by Wilson (1979), will result in similar errors. However, if the model is modified slightly so that the initial mass of fluid in the pipeline is determined based on real‐fluid theory, then a conservative estimate of the transient release rate may be obtained (i.e., the most rapid release of the fluid is predicted).
Studies of the fischer‐tropsch synthesis on a cobalt catalyst II. Kinetics of carbon monoxide conversion to methane and to higher hydrocarbons
Authors: Sarup B. , Wojciechowski B. W.
Published: March 2009

Six Langmuir‐Hinshelwood‐Hougen‐Watson models have been derived for the kinetics of conversion of carbon monoxide to hydrocarbons in the Fischer‐Tropsch synthesis. The models were fitted to experimental data obtained in an internal recycle reactor over a wide range of operating conditions. Two models, one based on the hydrogenation of surface carbon and the other on a hydrogen‐assisted dissociation of carbon monoxide as rate limiting steps were both able to provide a satisfactory fit to the experimental rate data.

A general model was also developed for the rate of methanation in the presence of higher hydrocarbons. The same two rate limiting assumptions as those used in formulating the rate of total CO conversion are used in these models. The two models were fitted to experimental data for methane formation.

It was the model assuming CH formation as rate limiting that showed the best fit for both CO conversion for CH4 formation.
Ignition characteristics of liquid hydrocarbon fuels as single droplets
Authors: Bergeron Carol A. , Hallett William L. H.
Published: March 2009

An investigation into the effects of fuel boiling point and chemical type on the autoignition of single droplets of a number of pure hydrocarbons is reported. Ignition delay times were measured using the suspended droplet technique, and a numerical model was developed to extract reaction rate constants for the fuels. The results show that both fuel boiling point and chemical kinetics are important contributors to the ignition delay.
Nonhydrogenative co‐processing of saskatchewan heavy oil and coal
Authors: Varma R. L. , Bakhshi N. N. , Ranganathan R.
Published: March 2009

A Saskatchewan heavy oil was processed with coal additives in a tubular reactor packed with procelain berl saddles at 400–480°C and atmospheric pressure. For comparison purposes, blank experiments in the absence of coal additive were also carried out. The results indicate that considerable reduction in viscosity and increased distillate yields can be achieved by processing heavy oil with coal additive. The API gravity of the liquid product is also improved. Increased amounts of gaseous products with changed composition are obtained in the presence of coal. Under certain conditions, significant dissolution of coal occurs even at the relatively mild conditions used.
Measurement of longitudinal distribution of solids holdup in a three‐phase fluidized bed by ultrasonic technique
Authors: Uchida S. , Katsumata T. , Okamura S.
Published: March 2009

A method of measurement of solids holdup in a three‐phase reactor by analyzing the shape and the phase lag or lead of an ultrasonic wave has been proposed. The solids holdup in a solids‐dilute three‐phase fluidized bed could be measured without being affected by the presence of gas bubbles. The experimental values of solids axial dispersivity measured by the ultrasonic technique are in reasonable agreement with an empirical correlation of previous data obtained by other methods. The possibility of the application of the ultrasonic technique to the measurement of solids holdup in a three‐phase fluidized bed has been suggested.
A phenomenological model for heat transfer in freeboard of fluidized beds
Authors: Biyikli Suleyman , Tuzla Kemal , Chen John C.
Published: March 2009

A phenomenological model was developed to predict heat transfer to tubes located in the freeboard region of gas fluidized beds. The model is concerned with the conductive/convective mechanism of heat transfer. For high temperature applications, an additional contribution by thermal radiation would need to be incorporated. The model considers that the tube surface experiences alternating contact with a dense emulsion phase and a lean void phase. Contributions by dense and lean phases are represented by transient conduction and convection mechanisms, respectively. Particletube contact information was obtained experimentally for a wide range of operating conditions at room temperature and pressure. Predictions of the model were compared with measured heat transfer coefficients. Over a 20‐fold range in magnitudes of heat transfer coefficients, the model successfully predicted the measured values with an average deviation of 44 percent.
Solids exit discontinuity in slurry bubble columns
Authors: de Bruijn T. J. W. , Reilly I. G. , Macintyre D. , Scott D. S.
Published: March 2009

The exit discontinuity in slurry bubble columns, i.e., the difference in the apparent solids concentration at the very top of the column (Ct) and the concentration in the effluent (Ce), was studied in a 0.3 m ID bubble column, using air as the gas phase, water, a light hydrocarbon oil (Varsol) and trichloroethylene as liquids and glass beads of different sizes and density as solids.

The results showed that the drop in solids concentration occurs in a very small layer at the gas/liquid interface. By changing the column exit configuration and removing the gas/liquid interface the exit discontinuity disappeared. The extent of the exit discontinuity depended on the liquid properties and appeared to be related to the foaming tendency of the liquid. In addition, in those systems where the exit discontinuity was significant, it depended on the solids properties and the gas and liquid superficial velocities.
Computation of solid circulation rates in a fluidized bed from tracer particle concentration distributions
Authors: Kececioglu Ifiyenia , Keairns D. L.
Published: March 2009

Experimentally measured profiles of tracer particle concentration inside a fluidized bed were employed to calculate rates of bed‐solid circulation induced by the presence of a central jet and by slug motion. Lagrangian minimization and direct pattern search techniques were used to determine the solids transfer rates, which should minimize the error in the tracer particle mass balance while satisfying the bed solid mass balance. Time‐average steady‐state mixing of bed solids and upstream weighting of tracer concentrations were employed in the formulation of the minimization scheme. Quantitative information on solid circulation for three nominal jet velocities of 52, 37 and 25 m/s is provided. The computed solid circulation rates show that there is a region of high circulation around the jet and a region of lower circulation induced by the slug motion.
Monte carlo simulation of a probability screen
Authors: Beeckmans J. M. , Jutan A.
Published: March 2009

The interaction of a probability screen with spherical particles was simulated in a computer model. Repeated runs were made using randomly selected, slightly differing initial conditions, from which the penetration probability was obtained at a particular particle size under given screen operating conditions. The calculations were then repeated with differing particle sizes and operating conditions, and the results were found to compare favourably with experimental data obtained in a previous study. It was shown that the stochastic model correctly predicts the effects of the principal operating variables (screen angle of inclination and aperture size, frequency and amplitude of vibration). Because of excessive computer time requirements of this model a second, semi‐empirical non‐stochastic model was developed whose results closely match those of the earlier model. The second model is suitable for incorporation into a plant simulation computer package.
Laminar mixed convection in the thermal entrance region of horizontal isothermal rectangular channels
Authors: Lin Jenn‐Nan , Chou Fu‐Chu
Published: March 2009

Laminar mixed convection in the thermal entrance region of horizontal isothermal rectangular channels for moderate and small Prandtl number (air) is investigated using the vorticity‐velocity formulation of the Navier‐Stokes equation. The numerical results, including the cross‐stream velocity vectors, local Nusselt numbers and local friction factor ratios are presented for the aspect (width/height) ratios 0.5, 1.0 and 2.0, Rayleigh numbers 0 ∼ 2 × 105 and Prandtl numbers 0.7, 5.0 and 100. The strength and pattern of the secondary flow induced by buoyancy effects is found to depend on the magnitude of Rayleigh number and aspect ratio, and the secondary flow leads to a significant enhancement of heat transfer in the entrance region. The classical Graetz problem is shown to be a limiting case which applies only when Ra ≤ 10.3 The behavior of the local Nusselt number for Pr = 100 compares well with the existing results for Pr → ∞.
Power law models as descriptors of the kinetics of complex systems: Temperature effects
Authors: Crickmore Peter J.
Published: March 2009

The effects of temperature on power law models for the kinetics of parallel first order systems are studied. The variation of the empirical power law parameters with temperature provides information on the relationship between the rate constant and activation energy distributions; in particular.

if the power law exponent increases with temperature, there is a positive correlation between the rate constants and the activation energies;

if the power law exponent decreases with temperature, there is a negative correlation between the rate constants and the activation energies;

Arrhenius plots will always be concave unless the activation energies for all the reactions are equal. Application of the techniques described here to data from the catalytic cracking of gas oil over LaY zeolite reveals a compensation effect among the reacting hydrocarbon species.
Maleic anhydride formation from 1, 3‐butadiene oxidation over a vanadia molybdate catalyst
Authors: Lang Xiaosu , Hudgins R. R. , Silveston P. L.
Published: March 2009

Steady‐state and transient studies of the partial oxidation of butadiene to maleic anhydride were performed over a Te‐promoted vanadia molybdate catalyst previously used by Fiolitakis et al. (1983) for a study of maleic anhydride production from benzene. Inhibition of the partial oxidation by butadiene was observed. Pathways for CO2 and maleic anhydride formation are different. False‐start behaviour for some products was observed and attributed to conflicting contributions of adsorption and catalyst reduction or oxidation. The reaction mechanism for butadiene differs from that reported from benzene oxidation by Fiolitakis et al. (1983).
Simultaneous correlation of excess gibbs energy and enthalpy of mixing by the UNIQUAC Equation
Authors: Demirel Yasar , Gecegörmez Hatice
Published: March 2009

Using data for excess Gibbs energy, gE, and enthalpy of mixing, hE, temperature dependent parameters of the UNIQUAC equation have been estimated for twenty four systems of binary mixtures. Fifteen of them include data for gE and hE at more than one different isotherm. These parameters are later tested in predicting the gE and hE data simultaneously and representing the effect of temperature on such data. The UNIQUAC equation with temperature dependent parameters represents larger values of maximum heat of mixing than does the UNIQUAC equation with the parameters independent of temperature.
Optimization of non‐steady‐state operation of reactors
Authors: De Tremblay Michele , Luus Rein
Published: March 2009

Non‐steady‐state operation of reactors is approached from the optimal control point of view. To find the best type of input, dynamic programming is used. The results show that for some systems, the optimal input is oscillatory in nature as has been found experimentally by others. A modification to conventional dynamic programming is used to avoid the need for interpolation and thus allow high‐dimensional systems to be handled more readily. Three chemical engineering systems of different complexity were considered to test the computational aspect of the approach. In all cases, dynamic programming gives the optimum policy with respect to the period, cycle‐split and amplitude.
The particle collection efficiency of a cascade of cylinders
Authors: Ingham D. B. , Hildyard M. L. , Heggs P. J.
Published: March 2009

The entry flow and the trajectories of small solid particles into a fibrous filter, which is modelled as a single row or cascade of cylinders, is examined. Both large (potential) and small (creeping) Reynolds number flows through the cascade of cylinders are treated using the Boundary Element Method (BEM). Results for the collection efficiency are presented as functions of the Stokes number for both types of flow and are shown to be in excellent agreement with existing published results. An asymptotic expansion of the flow is developed both upstream and downstream of the cascade and it is shown to significantly affect the collection efficiency.
Improvement in separation of the batch‐type thermal diffusion column with impermeable barriers inserted between the plates
Authors: Weitsai Shau , Yeh Ho‐Ming
Published: March 2009

Rather than one impermeable barrier, the installation of more impermeable barriers between the plates in a batch‐type thermal diffusion column substantially enhances the separation efficiency by further properly reducing the remixing effect. Theoretical analysis shows that when the barriers are installed at the best positions, maximum degree of separation, maximum concentration of the top product or minimum concentration of the bottom product may be obtained. Considerable improvement is obtained especially when the ratio K'; of transport constants (i.e. Kc/Kd) is large.
Recovery of copper from copper concentrator tailings by leaching
Authors: Acharjee D. K.
Published: March 2009

Tailings from a chalcopyrite beneficiation plant (concentrator) have been leached with dilute ferric chloride in a packed bed. The effect of leaching time and packed bed height on the conversion of cuprous sulphide (present in tailings) has been determined. For predicting the conversion, an expression based on the shrinking core model has been derived and compared with the experimental data. At low conversion, the agreement is good, but at intermediate and high conversion the deviation is considerable.
Dissolution of spherical solid particles in a stagnant fluid: An analytical solution
Authors: Chen Yu‐Wen , Wang Pei‐Jan
Published: March 2009

Film theory has often been used to calculate the dissolution rates of solid particles. However, it is only good for the case of low solubility solids due to the assumption of pseudo‐steady state. In this study, we propose a more refined model to facilitate the characterization of the dissolution of spherical solid particles in a stagnant fluid. The results indicate that the film theory will overestimate the dissolution time for the case of high solubility, while for low solubility particles, the film theory is quite accurate in predicting the dissolution time.
The effects of clay fines on oil in water dispersions
Authors: Spence J. R. , Masliyah J. H.
Published: March 2009

The effects of the addition of clay on oil drop size were investigated for dispersions of oil in water in an agitated vessel. Three types of oil were used: hexane, a medium viscosity paraffin oil and a viscous Cold Lake bitumen. Pure kaolinite clay was used for the solids. Experiments were carried out with and without clay fines over a range of agitator speeds. The addition of kaolinite was found to increase the drop size for both the hexane and the paraffin oil, approximately doubling the drop size for hexane. The addition of the kaolinite to the bitumen/water dispersions was found to have no effect on the drop size.
Experimental study of an extruder‐feeder for biomass direct liquefaction
Authors: White D. H. , Schott N. R. , Wolf D.
Published: March 2009

A new type of feeding system by an extruder‐feeder was utilized to pump high concentrations of slurries into an advanced biomass liquefaction reactor operating at pressures of up to 25 MPa and temperatures of up to 400°C. The operability of such an extruder‐feeder and the design criteria for this type of unit operation are described, and operational data are reported. Three types of extruder‐feeders were used, and many different types of feedstocks were tested. The extruder‐feeder proved to be effective in the biomass direct liquefaction process and could prove applicable in many other processes where high concentrations of solids are to be pumped, thus reducing drastically the size of the plant and the need for recycle of large amounts of liquid carriers for the solids.

Typical experimental data and results of the flow rates and pressure generation for the various extruder‐feeders and their operational conditions for several feedstocks are reported. The theoretical models developed for plasticating extruders were found to be acceptable also for the extruder‐feeder of biomass feedstock, applying appropriate drag and pressure flow coefficients.