摘要:

AbstractAdiabatic cocurrent flow of air and water through a narrow passage between two flat plates 240 mm long and 99mm wide with gap‐widths of 0.778 mm and 1.465 mm was investigated for six different orientations: Vertically upward and downward, 45°inclined upward and downward, and horizontal flows between horizontal plates and between vertical plates. Except for horizontal flow between vertical plates, the effects of gap width and flow channel orientation on flow pattern, void fraction and friction pressure drop were found to be small in narrow channels. The void fraction and two‐phase friction multiplier data could also be reasonably correlated in terms of the Martinelli parameter. For horizontal flow between vertical plates, both the void fraction and friction multiplier data showed strong mass velocity effects. Several friction pressure drop correlations were tested for applicability to the narrow channels including a separated flow model proposed in this

ISSN:0008-4034    

DOI:10.1002/cjce.5450710502

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe competitive, consecutive chemical reactions between 1‐naphthol and diazotized sulfanilic acid were utilized to study the mixing of a pulp fibre suspension in a 22 L stirred tank reactor. Mixing quality was determined from the distribution between the mono and bis substituted reaction products once a correlation was made for the adsorption of the product dyes onto the suspended fibres. The technique was found to be adequate for assessing micromixing and turbulence intensity within a fibre suspension provided the measured product distribution, Xs, was between 0.4 and 0.01. Thus the mixing conditions that could be assessed depended on both the energy dissipation within the mixer and the amount of the fibre present. For the experimental conditions chosen for this study energy dissipation rates would typically have to be less than 80 W/kg and the suspension mass concentration less than 2.5%. When compared with water, a reduction in turbulence levels at both the impeller zone and a remote zone in the stirred vessel was observed for fibre mass concentrations as low as 0.5%. The turbulence decreased as the suspension mass concentration was increased. This decrease is attributed to energy dissipation by friction at fibre‐fibre contact points as the fibres move relative to one another in the flow. This sink removes energy from the turbulence cascade which never shows up as small‐scale fluid deformations leading to better m

ISSN:0008-4034    

DOI:10.1002/cjce.5450710503

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe dynamic viscoelastic properties of pulp suspensions having consistencies, cm3ranging from 2‐13% were measured using a Weissenberg Rheogoniometer. A special reservoir‐type parallel plate fixture was designed to minimize oozing and compression during sample loading. Data for the complex modulus, G*, were obtained for a chemical thermal mechanical pulp and a pine sulfate pulp as functions of strain and frequency. Results for the elastic part of the modulus, G', show a relative insensitivity to frequency over the range l0‐* to 5s‐'. The applied strain has a significant effect, in some cases reducing the modulus by half. This effect was most pronounced at the lower consistencies where it is postulated that the suspension consists of small flocs loosely connected by individual fibres. At small strains, the linkages are disturbed elastically, whereas, as the strain increases, the connections are broken and must reform. At higher consistencies there is a continuous network of fibres, and this breakage‐reformation mechanism is not active. This view is supported by nonlinear effects observed in the suspensions (harmonic stresses produced in response to a single frequency strain) which are largest at the low consistencies. The measured yield stress values, as determined from the storage modulus data, are shown to agree with earlie

ISSN:0008-4034    

DOI:10.1002/cjce.5450710504

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractA unique characteristic linear dimension (d), defined as the cube root of the specific liquid holdup (hsp) in the packed column, was used to correlate successfully the liquid film mass transfer coefficient kLa for gas absorption‐desorption for sparingly soluble gases in liquids below loading. To produce this simple, dimensionless correlation, kLa data reported in literature were used, covering a wide range of physical properties of liquids, packings and operating conditions. This new approach showed operating holdup as an important factor in gas liquid mass transfe

ISSN:0008-4034    

DOI:10.1002/cjce.5450710505

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractKinetics of aggregation, nucleation and growth of canola protein particles were developed in a 100 mL mixed‐suspension mixed‐product removal precipitator (MSMPRP) using isoelectric precipitation with HCI at pH 4.2. Protein yield in terms of total nitrogen was measured by Kjeldahl system. The size distribution of protein aggregates was determined by a Coulter counter. The effects of pH, protein concentration driving force, mean residence time, agitation rate, ionic strength of the solution, and the operating temperature on the size distribution and yield of protein particles were investigated. Population balance on the protein particles was used to derive empirical correlations for the index of aggregation, nucleation rate of primary particles and growth rate of protein aggrega

ISSN:0008-4034    

DOI:10.1002/cjce.5450710506

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractA laser particle analyzer was used to study the formation of asphaltene agglomerates from Cold Lake bitumen due to the introduction of paraffinic diluents. The growth of the particles over time was investigated, and it was found that asphaltene particle growth is essentially an instantaneous process; that is, the final agglomerate size is reached within 5 seconds.The type of diluent used to precipitate the asphaltenes was determined to have a major effect on the size distribution of asphaltene agglomerates. The average particle size of asphaltene agglomerates ranged from 169 ptn for n‐hexadecane to 299m for n‐pentane. A relationship is shown to exist between the average particle size of asphaltene agglomerates and the carbon number of the diluent u

ISSN:0008-4034    

DOI:10.1002/cjce.5450710507

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractCommercial activated alumina and titanium dioxide catalysts were treated with Teflon to reduce the negative effects of water vapour on the oxidation of hydrogen sulphide by sulphur dioxide (Claus Reaction) near the sulphur dew point. The tests were conducted at 200°C and 130°C (108 kPa), with and without 30% water vapour in the feed gas. An alumina/Teflon composite catalyst was found to be superior to both untreated commercial catalysts at 130°C. This improvement was probably due to an increase in macroporosity rather than to a wetproofing effect. At 200°C, the performance of the composite was similar to that of the untreated titanium dioxide which in turn was superior to the untreated activated alum

ISSN:0008-4034    

DOI:10.1002/cjce.5450710508

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe calculation of product composition, flow rate and temperature of the modified Claus process reaction furnace is typically done by assuming either thermodynamic equilibrium or by empirical methods fitted to plant data. This paper extensively reviews the literature on the Claus reaction furnace and compares equilibrium and empirical results of the predicted concentrations of the key components: hydrogen (H2), carbon monoxide (CO), carbonyl sulphide (COS) and carbon disulphide (CS2). The implication of the reaction furnace model on the overall plant design and sulphur recovery is subsequently presented. It is well known that results of equilibrium calculations do not match plant data taken both before and after the waste heat boiler (WHB). Moreover, even though results of empirical methods do not match plant data taken before the WHB, one empirical method provides the best fit of highly scattered data taken after the WHB and provides a conservative plant design and estimates of sulphur recovery and emissions.

ISSN:0008-4034    

DOI:10.1002/cjce.5450710509

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractThe formation of sulphates in an industrial Ni‐W Hydroprocessing (HP) catalyst was investigated by X‐ray Photoelectron Spectroscopy (XPS). A small fluidized bed test unit with on‐line sampling device was constructed to simulate industrial sulfidation and oxyregeneration processes of HP catalysts. The results obtained show that the sulfates observed on the surface of sulfided catalysts are not formed during the sulfidation process. Two oxidation processes seem to be responsible for the formation of sulfates. One of the processes happens when the catalyst is exposed to air before it is properly cooled. The other is a slow conversion at ambient temperature. The two different processes might be associated to different sulfidic species formed during the sulfidation processes, with the sulfides in the bulk of catalyst particles being more easily oxidized than the ones on the external surface of the catalyst particles. The sulfate formed during the air oxidation of sulfided catalysts, as well as that after oxyregeneration is not aluminum sulfate but nickel sulfate in both cases. XPS results also indicate that oxygenates in the feedstock are not directly involved in the sulfate form

ISSN:0008-4034    

DOI:10.1002/cjce.5450710510

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY

摘要:

AbstractA variable diffusivity shrinking‐core model that allows for temporal and spatial variation of the effective diffusivity in the solid product layer was developed in this study. The model was used to analyze a set of experimental data for the direct sulfation of three limestones (that is, their reaction with SO2 under noncalcining conditions), and a parameter estimation procedure was formulated for extracting the effective diffusivity as a distributed parameter from the experimental conversion vs. time curves. Very strong effects of temperature, concentration, and depth in the product layer on the effective diffusivity were revealed by the analysis. On the basis of the obtained results, it was concluded that despite being essentially nonporous, uncalcined limestones can react with SO, under noncalcining conditions at rates comparable to those of calcined samples because they present much lower resistance for diffusion of SO2 through the product layer than the latte

ISSN:0008-4034    

DOI:10.1002/cjce.5450710511

出版商:Wiley Subscription Services, Inc., A Wiley Company    

年代:1993

数据来源: WILEY