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  • 1
    Electronic Resource
    Electronic Resource
    Modeling and dynamic simulation of a bleach plant (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 2603-2613 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A dynamic model of five-stage (C+D)EDED bleach plant was developed using SIMNON a dynamic simulation language developed at Lund Institute of Technology, as a platform. The model is composed of individual modules that represent each bleaching stage. Each module includes chemical addition and mixing, diffusion and reaction in a retention towel, and washing. These unit operations are coupled with chemical kinetics for each bleaching stage using appropriate models. A relationship between the (C+D)E Kappa number and the input absorption coefficient to the D1 stage was used to link the delignification and brightening partial sequences of the bleach plant. The model, verified using steady-state data, was used to model the dynamic response of the plant to step changes in production rate, (C+D) chemical addition, and incoming Kappa number, as well as the open-loop response of the plant to a simulated variation in incoming Kappa number. The modular structure of the program allows a variety of bleach plants to be assessed once flow parameters and chemical kinetics are known. The dynamic model can also be used to develop and compare control strategies before being implemented at the mill.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690411209
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  • 2
    Electronic Resource
    Electronic Resource
    Screw design in injection molding (1989)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 29 (1989), S. 479-487 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The performance of screws of advanced design in injection molding has been investigated with respect to four different objectives: (1) improvement of distributive mixing; (2) improvement of dispersive mixing; (3) increase of plasticating capacity; and (4) reduction of inhomogeneity of melt temperature.The screws used are three zone screws with different compression ratios, screws with pineapple or Maddock/Egan mixing elements, with one or two channel barrier sections, with static mixers mounted in the valve or in the nozzle, or with combinations of these different elements. The best mixing quality is obtained with multi-channel Maddock sections. The highest plasticating capacity and, consequently, the shortest cycle times are achieved with the barrier screws. Temperature measurements show that these screws improve melt homogeneity considerably with a relatively small loss of plasticating time. In all cases, increasing the back pressure gives inferior results compared with improvement of the screw design.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760290708
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  • 3
    Electronic Resource
    Electronic Resource
    Crystallization and structure-mechanical property relations in poly(aryl ether ether ketone) [PEEK] (1990)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 30 (1990), S. 860-869 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: In the development of advanced composite materials, the mechanical behavior of the matrix is of critical importance. The next generation of composite materials will be based on high modulus tough matrices, of which poly(aryl ether ether ketone) [hereinafter, referred to as PEEK] is one of the first crystalline thermoplastics to receive serious attention. As in all crystalline polymers, the matrix is itself a composite material whose properties depend significantly on the crystalline morphology developed during processing. In this contribution, the current understanding of crystallization in PEEK and its influence on mechanical properties is reviewed. Problems yet to be resolved are highlighted.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760301409
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  • 4
    Electronic Resource
    Electronic Resource
    Viscosity effects in cocurrent three-phase fluidization (1990)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 36 (1990), S. 1613-1616 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690361024
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  • 5
    Electronic Resource
    Electronic Resource
    Effects of operating conditions on stability of gas-phase polyethylene reactors (1995)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 41 (1995), S. 868-879 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Fluidized-bed polyethylene reactors are prone to unstable behavior and temperature oscillations (Choi and Ray, 1985b). Their work is extended to show the effects of ethylene feed system operation, reactor cooling system design, catalyst properties, and gas composition on reactor stability and dynamics. The analysis is performed using a well-mixed model, because heat- and mass-transfer resistances between multiple phases are small and are not required to account for the observed bifurcation phenomena. The addition of a gas recycle and heat exchanger system to the model significantly affects dynamic performance, including the formation of limit cycles. The size and dynamics of the heat exchanger, however, have little effect on the overall stability. In contrast, automation of the ethylene feed system to replace the monomer in the reactor as it is consumed leads to substantially different dynamic behavior than if the ethylene feed is maintained at a constant rate. Catalyst properties (multiple sites, activation energy, and deactivation) significantly affect dynamics and stability, whereas comonomer and other gases affect them only mildly. The results confirm that without proper temperature control, gas-phase polyethylene reactors are prone to instability, limit cycles, and excursions towards unacceptable high-temperature steady states.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690410414
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  • 6
    Electronic Resource
    Electronic Resource
    Measure of closed-loop nonlinearity and interaction for nonlinear chemical processes (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 2261-2278 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A new approach for assessing nonlinear interaction effects and closed-loop nonlinearity in multivariable processes is presented. It is based on a differential geometric interpretation of the relative gain array that leads naturally to systematic procedures for describing interaction effects of higher order and for assessing closed-loop nonlinearity effects in nonlinear processes. Two types of nonlinear effects associated with the behavior of a process are introduced. Between-channel nonlinearity is associated with the nonlinear dependence of an output channel on other input - output pairings. Withinchannel nonlinearity is used to identify the nonlinear effects that result from the inherent nonlinearity of an individual output channel. A root-mean-squared measure of nonlinearity is introduced and is used to evaluate the significance of local nonlinear effects. Nonlinear interaction measures are derived that provide tools for assessing input - output pairings in a nonlinear process. This new approach extends the standard techniques and provides an estimate of the effect of nonlinearity on closed-loop interactions.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430912
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  • 7
    Electronic Resource
    Electronic Resource
    Particle-to-bubble adhesion in gas/liquid/solid slurries (1991)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 37 (1991), S. 1801-1809 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In gas/liquid/solid slurries, adhesion of small particles to gas bubbles is often encountered, for example, during flotation of finely divided minerals and in slurry reactors where particle-to-bubble adhesion may result in an enhanced gas absorption rate (Wimmers, 1987; Lindner, 1988). The adhesion of small particles to gas bubbles in water is studied with a modified bubble pick-up method. The extent of the particle-to-bubble adhesion is revealed in the angle αmax, by which the gas-bubble surface is covered by adhering particles under static conditions. It is shown that αmax depends on the modified Eötvös number, the ratio of the particle and bubble radii, and the effective contact angle θE. It is also found that θE is affected by the curvature of the three-phase contact ring and by the type of the gas.A “particle-to-bubble adhesion” model, indicated by PBA model, based on a balance of forces under static conditions, is developed to calculate the value of θE from the measured values of αmax. The measured values of cos(θE) appeared to be a linear function of the curvature 1/r of the three-phase contact ring which is in accordance with the extended Young-Dupré equation.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690371205
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  • 8
    Electronic Resource
    Electronic Resource
    Determining porosity profiles during filtration and expression of sewage sludge by NMR imaging (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 953-959 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The formation of a filter cake during mechanical dewatering (filtration and expression) of sludge is studied using one-dimensional nuclear magnetic resonance (NMR) imaging of porosity profiles. The experiments clearly showed the formation of a porosity gradient during filtration and the disappearing of this gradient during expression, forming a cake with a uniform porosity. This technique makes it possible to investigate the material behavior of the porous medium, which is needed before any model calculations can be performed. The results indicate that NMR imaging is useful in nondestructive monitoring of the filtration and expression process of sludge.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690420408
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  • 9
    Electronic Resource
    Electronic Resource
    Study of instabilities in film blowing (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 1388-1396 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Bubble instabilities observed in film blowing using four different polyolefins are discussed: high-density polyethylene (HDPE), low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE), and polypropylene (PP). Special attention is given to the effect of the frost line height on the bubble stability, an effect mostly ignored in the literature. A video-camera system was used to record the bubble shape and oscillations. In general, three forms of instabilities and combinations were observed: (1) axisymmetric periodic variations in the bubble diameter; (2) helical motions of the bubble; and (3) variations in the position of the solidification line. The four resins show different stability behaviors. The LDPE has the most stable operating space and the PP is the most unstable one. No correlation was observed between bubble stability and oscillatory shear rheological properties of the resins. Instability is enhanced by increasing take-up ratio, increasing blow-up ratio, and decreasing frost line height. Furthermore, for the LDPE, some operating points were not attainable and multiple steady states were observed. Our results are in a poor agreement with the predictions Cain and Denn's 1988 analysis.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690420519
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  • 10
    Electronic Resource
    Electronic Resource
    Effect of rhecological properties on power consumption with helical ribbon agitators (1993)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 39 (1993), S. 1421-1430 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The influence of shear thinning and viscoelasticity on the power required for the mixing of viscous liquids using six different helical ribbon agitators has been investigated. Four Newtonian and 12 non-Newtonian fluids prepared using several polymers dissolved in varying concentrations in different solvents cover a wide range of rheological properties. By a careful choice of test media, the specific and combined effects of shear thinning and viscoelasticity on the power requirement have been examined. Simple models are proposed to predict the effective shear rate in the tank from the knowledge of the torque or power number. The effective shear rate predictions compared with the effective shear rate estimated using the scheme of Metzner and Otto (1957) show that they slightly depend on the shear thinning properties. Fluid's elasticity increases appreciably the power requirement, and departures from the generalized Newtonian power curve in the laminar regime are observed at smaller Reynolds numbers for viscoelastic fluids. Bottom wall resistance of the mixing vessel makes a negligible contribution to the power consumption.
    Additional Material: 14 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690390902
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