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  • Chemical Engineering  (3,542)
  • 2020-2020
  • 1985-1989  (3,542)
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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 875-876 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 2
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 3
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 877-877 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 4
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 5
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 877-877 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 6
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 908-922 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Erosion in bubbling fluidized-bed combustors is a serious issue that may affect their reliability and economics. Available evidence suggests that the key to understanding this erosion is detailed knowledge of the coupled and complex phenomena of solids circulation and bubble motion. A thin transparent “two-dimensional” rectangular fluidized bed with an obstacle served as a rough model for a fluidized-bed combustor. This model was studied experimentally and computationally using two hydrodynamic equation sets. The computed hydrodynamic results agree reasonably well with experimental data. Bubble frequencies and sizes compare well with those obtained from analyzing a high-speed motion picture frame-by-frame. Time-averaged porosities computed from both models agree with time-averaged porosity distributions measured with a gamma-ray densitometer. The principal diferences between the data and the computations in this paper are due to asymmetries present in the experiment and to the simplified solids rheology used in the hydrodynamic models.
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  • 7
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 959-966 
    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 is developed for applying ideal and real adsorbed solution theory models to the description of multicomponent adsorption equilibria at fixed pressure. This allows ignoring single-component behavior in the Henry's law region, P → O, but introduces new parameters that must be evaluated from binary equilibrium data. Comparisons with various sets of experimental data show that the new approach gives results as good as the classical one, but without requiring knowledge of the single component behavior in the Henry's law region; more over, it removes the sensitivity to the type of model adopted in fitting single-component equilibrium data.
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  • 8
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 988-994 
    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 extent of high temperature (900-1,300°C), short time (〈1 s) SO2 capture was found to be limited by temperature-dependent losses in the porosity of calcium based sorbents. At 970°C these porosity losses were caused by CO2-activated sintering. Sulfation of the sorbents either prevented or reduced the extent of porosity losses. Differences in SO2 capture between hydroxides from different commercial sources, and significantly lower levels of capture by calcium carbonates compared to hydroxides were attributed to differences in particle size and the degree of porosity loss.
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  • 9
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    AIChE Journal 35 (1989), S. 1017-1028 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Systems having transfer functions of the form \documentclass{article}\pagestyle{empty}\begin{document}$$ G_P (s) = \frac{{P_1 (s) - P_2 (s)e^{ - t_d s} }}{{Q(s)}}, $$\end{document} where P1(s), P2(s) and Q(s) are polynomials, are called quasirational distributed systems (QRDS). They are encountered in processes modeled by hyperbolic partial differential equations. QRDS can have an infinity of right half-plane zeros which causes large phase lags and can result in poor performance of the closed-loop system with PID controllers. Theory on the asymptotic location of zeros of quasipolynomials is used to predict the nonminimum phase characteristics of QRDS and formulas are presented for factoring QRDS models into minimum and non-minimum phase elements.A generalized Smith predictor controller design procedure for QRDS, based on this factorization, is derived. It uses pole placement to obtain a controller parameterization that introduces free poles which are selected to satisfy robustness specifications. The use of pole placement allows for the design of robust control systems in a transparent manner. Controller selection is generally better, simpler and more direct with this procedure than searching for optimal PID controller settings.
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  • 10
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1049-1052 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 11
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1053-1053 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 12
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    AIChE Journal 35 (1989), S. 1097-1106 
    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 sorption of toluene, dilute in CO2, and likewise the distribution coefficient of toluene between silicone rubber and CO2 have been explored from gaseous to supercritical fluid conditions. Sorption and desorption isotherms were determined by frontal analysis using a new inverse supercritical fluid chromatography technique at 35 and 70°C up to 250 bar. Complementary swelling data are presented for pure CO2 in silicone rubber up to 315 bar. A new result is that the sorption of toluene goes through a maximum and is highly adjustable over a continuum in the highly compressible region of carbon dioxide. This behavior is explained physically and predicted quantitatively with the Flory equation and the Peng-Robinson equation of state using only information from binary systems. These results are useful for a wide variety of applications including impregnation of polymers with pharmaceuticals, fragrances and other additives, and polymer purification.
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  • 13
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1137-1147 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Detailed mathematical models, pore or grain based, describing diffusion, reaction, and pore structure evolution in pellets of porous solids are used to simulate, along with a macroscopic reactor design model, the transient phenomena that take place during desulfurization of coal gas in fixed-bed reactors of pellets of metal oxide sorbents. Our computer simulation results show that the form of the pore- or grain-size distribution strongly influences the predictions of the overall reactor design model.
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  • 14
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    AIChE Journal 35 (1989), S. 1186-1194 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Vapors of alkali metal compounds can be removed from coal combustion and gasification flue gases using high-temperature aluminosilicate sorbents. The fundamentals of alkali adsorption on kaolinite, bauxite, and emathlite are compared and analyzed both experimentally and through theoretical modeling. The results show that the process is not a simple physical condensation, but a complex combination of diffusion and reaction. The kinetics of adsorption on these sorbents have similarities: the process is diffusion-influenced, the rate decreases with time, and there is a final saturation limit. There are, however, differences in reaction mechanisms leading to potentially different applications for each sorbent. In adsorbing alkali chloride vapors, kaolinite and emathlite release all the chlorine back to the gas phase while bauxite retains some of the chlorine. Moreover, the products of reaction with emathlite have a melting point significantly lower than those for kaolinite and bauxite. Therefore, emathlite is more suitable for lower-temperature sorption systems downstream of the combustors/gasifiers, while kaolinite and bauxite are suitable as in-situ additives.
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  • 15
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1203-1206 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 16
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1210-1210 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 17
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989), S. 1211-1214 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 18
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    AIChE Journal 35 (1989), S. 1245-1252 
    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 rates of reduction of hematite to magnetite and of magnetite to iron in hydrogen / nitrogen / water vapor atmospheres were each studied with respect to variation in temperature, gas composition, and solid pore structure. It is shown that at temperatures below 350°C, the reactions are under chemical kinetic control, and diffusional limitations are negligible. The activation energies for the reduction of hematite to magnetite and of magnetite to iron were found to be 185 kJ / mol and 76.6 k J / mol, respectively. Both reactions exhibit first-order behavior for hydrogen partial pressures less than 76 kPa. The conversion and rate data for each reaction were interpreted in terms of the random pore model of Bhatia and Perlmutter (1980), which takes into account the detailed pore structure of the starting material as well as the changes that occur as the reaction proceeds. The model predictions of conversion with time agree with the measured data to within 2%, and the rate vs. conversion predictions agree to within 5%.
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  • 19
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    AIChE Journal 35 (1989), S. 1282-1292 
    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 macroscopic model based on the volume-averaged equations of motion is presented for countercurrent gas-liquid flow in a packed bed. The model yields a column-limited flooding point as the loss of existence of uniform states. It correctly predicts the existence of two uniform states below the flooding point. The lower branch corresponds to the trends commonly observed experimentally. It is shown that the upper branch is made unattainable by the gas distributor/support plate at the bottom of the column. The occurrence of premature flooding induced by the support plate is also explained. It is suggested that the occurrence of spontaneous liquid segregation, necessitating frequent liquid redistribution in columns with large dumped packings and porosities, is a consequence of the loss of stability of the uniform state in the lower branch.
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  • 20
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    AIChE Journal 35 (1989), S. 1337-1345 
    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 recent model of partial internal wetting of catalyst particles (Bhatia, 1988) is extended to allow for pore-size distribution, multicomponent diffusion, and nonlinear kinetics for spherical particles exposed to condensible vapor undergoing an exothermic reaction. Profiles of liqid filling of the pores are computed, and the influence on mass transfer and effectiveness factor is determined. Under certain circumstances, the effectiveness factor has a maximum with respect to the mole fraction of condensible component suggesting an optimum vapor-phase composition. As the bulk vapor approaches saturation the effectiveness factor and particle temperature can drop sharply because of precipitious increase in liquid filling. However, a significant fraction of the pore space is still dry in contradiction to prior models assuming complete internal wetting of catalyst particles. The new model is more realistic than earlier attempts and lays the framework for proper representation of the physical phenomena involved.
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  • 21
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    AIChE Journal 35 (1989), S. 1346-1350 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Andritsos and Hanratty (1978b) have shown that the increase in interfacial drag caused by waves in stratified gas-liquid flows is related to the wave steepness. Recent analyses of finite amplitude Kelvin-Helmholtz waves are used to develop a correlation for the ratio of the wave height to wavelength.
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  • 22
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    AIChE Journal 35 (1989), S. 1328-1336 
    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 solid circulation in the annular region of a 0.146 and a 0.292 m ID semicylindrical and cylindrical air spouted beds was investigated for different spouting conditions. Stroboscopic photography, stopwatch and fiber optic methods were used to measure the vertical particle velocities in the annular region. The optical fiber probe enabled the measurement of particle velocities inside the dense annular phase and was validated at the walls. Velocity profiles in half beds were very different from those found in full beds. The work was then limited to full beds. Experimental results show that the solids flow is characterized by a point sink at the nozzle entrance with the solids moving almost in plug flow higher in the bed. There is negligible entrainment of solids along the spout wall and slow, thin wall layers are observed near the walls and spout. The velocity profiles are independent of the total height of the bed. A kinematic model successfully describes the observed velocity field.
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  • 23
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    AIChE Journal 35 (1989), S. 1370-1375 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 24
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    AIChE Journal 35 (1989), S. 1398-1398 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 25
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    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 35 (1989) 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 26
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    AIChE Journal 35 (1989), S. 1437-1444 
    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 periodic water flow on SO2 oxidation in a trickle bed of activated carbon catalyst was investigated, whereby gaseous reactants were introduced into the trickle-bed reactor continuously, but water was turned on and off. Mean liquid superficial velocities of 0.86 and 1.65 mm/s were used. At the latter, an increase in the oxidation rate of about 30 to 45% was found within a range of cycle periods from 2 to 80 min. A temperature change of up to 7°C was observed in the bed during periodic operation. An explanation of the improved average oxidation rate under periodic operation is developed in terms of the steady-state rates with and without water flow for symmetrical and asymmetrical cycles.
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  • 27
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    AIChE Journal 35 (1989), S. 1509-1520 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Differences in the dispersion and/or catalytic pellet size between laboratory and commercial reactors, operating at the same average residence time, may lead to differences in the yield of a desired product. Bounds are developed for predicting the maximal design uncertainty introduced by these phenomena for a network consisting of an arbitrary number of irreversible first-order reactions. A major advantage of these bounds is that they do not require any knowledge of the rate constants. It is shown that in a packed-bed reactor, the fractional yield loss is smaller than: \documentclass{article}\pagestyle{empty}\begin{document}$$ 0.5{\rm }(m - 1){\rm }\left[{\sigma _\theta ^{\rm 2} + \left({1.2 + \frac{2}{{Bi_m }}} \right)p^2 } \right] $$\end{document} where m - 1 is the number of reaction steps involved in converting a reactant to the desired product, σθ2 is the dimensionless variance of the residence time density function, Bim is the Biot number, p2 = [(Vp/Sx)2(1/Deτ)], and τ is the average residence time.
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    AIChE Journal 35 (1989), S. 1521-1526 
    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 purpose of this study is to observe the dynamic wetting process of a slide coater flow (Ca = 0.16; Re = 14.4; St = 0.0142; ΔeP = 2.5), using a specially-developed Laser-Doppler measuring technique.The measurements, carried out with glycerol solutions, reveal that the observed contact line is apparent and that a thin air film is entrained between the web and the liquid surface. The liquid is accelerated along the lower free surface and attains approximately 50% of the web velocity at the apparent contact line. Downstream from the apparent contact line, the liquid is further accelerated along the air film to the web velocity at the real contact line.The apparent contact angle increases with the capillary number Ca and air entrainment occurs at Ca = 0.25.
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    AIChE Journal 35 (1989), S. 1551-1554 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 35 (1989), S. 1564-1568 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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  • 31
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    AIChE Journal 35 (1989), S. 1582-1582 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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  • 32
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    AIChE Journal 35 (1989), S. 1602-1616 
    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 systematic method for synthesizing feedforward/state feedback controllers for a broad class of SISO nonlinear systems with measurable disturbances is presented. Depending on the structural characteristics of the system, the control law can be static or dynamic. The closed-loop system is independent of the measurable disturbances and linear with respect to set point changes. The performance of the proposed control scheme is illustrated through an example of composition control in a system of three CSTR's in series.
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  • 33
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    AIChE Journal 35 (1989), S. 1639-1650 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Steel bars in reinforced concrete are protected from corrosion by the high pH environment of the surrounding concrete. This alkaline environment is destroyed by the reaction of atmospheric CO2 with the Ca(OH)2 of the concrete mass. When this process, called carbonation of concrete, reaches the reinforcing bars, corrosion of the latter may commence. In this paper, the physiochemical processes in this phenomenon are presented and modeled mathematically. The mathematical model is fairly complex, but certain simplifying assumptions are possible, which lead to the formation of a “carbonation front” and to a simple analytical expression for the evolution in time of this front, in terms of the composition parameters of cement and concrete and of the environmental conditions. This simple expression is in very good agreement with experimental results obtained in this and in previous studies. The effect of some parameters on the carbonation front propagation is also discussed.
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    AIChE Journal 35 (1989), S. 1667-1677 
    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 study was made of the effect of design and operating parameters on the regeneration of a fixed bed of activated carbon. Two adsorbed species were removed by a hot gas purge, making the study relevant to thermal swing cycles used commercially. The analysis utilized direct experimental results as well as simulated results using a model described earlier by the authors (Huang and Fair, 1988).Regeneration parameters studied were: type of purge gas, purge gas contact time and velocity, regeneration temperature, initial bed loading, and bed pressure. These were related to certain parameters influencing the adsorption step: type of carrier gas, feed concentration, contact time and velocity, pressure, and initial bed temperature. The results are summarized in the form of guidelines for optimal regeneration cycle specification.
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  • 35
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    AIChE Journal 35 (1989), S. 1710-1718 
    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 one-dimensional isothermal transient two-phase flow model of gas and liquid in a low-permeability medium has been developed from the general mass and momentum balances.The characteristic roots of the governing differential equations are real and distinct. Therefore, solution of the flow equations may be attempted by a stable initial-value finite-difference scheme. A numerical solution was obtained using the method of lines.Calculated two-phase flow parameters are consistent with expected flow behavior and reflect the sensitivity of fluid flow to porosity, gas and liquid permeability, and capillary pressure in a tight sands porous medium. Calculated gas flow rates compared well with experimental data obtained at the Institute of Gas Technology (IGT) for low-permeability sandstone.
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    AIChE Journal 35 (1989), S. 1739-1741 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 35 (1989), S. 1756-1756 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 35 (1989), S. 1770-1778 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Previous work has shown that in a standard stirred tank, the three-dimensional velocity field in the discharge flow of the stirrer is characterized by a strong deviation from homogeneous isotropic turbulence. By means of a two-component laser Doppler velocimeter (2D-LDV), the \documentclass{article}\pagestyle{empty}\begin{document}$ \overline {v'_r v'_\theta} $\end{document} Reynolds stresses are measured in a 6.3-dm3 standard tank stirred by a six-flat-blade Rushton turbine. Obviously, these stresses must be known to better understand the turbulent mixing in such a configuration. Moreover, the 2D-LDV appears to be an efficient tool for characterizing, from an energy viewpoint, the type of agitator used and, in principle, is confirmed to be useful to accurately obtain the length scales of turbulence which are fundamental parameters for the study of the micromixing processes.
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    AIChE Journal 35 (1989), S. 1813-1820 
    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 generalized algorithm has been developed for solving simultaneous chemical and phase equilibrium equations of two-phase systems. By rearranging convergence loops of the algorithm of Sanderson and Chien (1973), this new approach shows improved robustness and speed. Solutions to the material balance and chemical equilibrium equations are obtained with an improved Marquardt method (Zhan, 1976). An esterification reaction and dissociation reactions of electrolytes in phase equilibrium are presented as examples.
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    AIChE Journal 35 (1989), S. 1845-1855 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Continuous-phase backmixing coefficients have been determined by continuous tracer injection for pulsed-plate extraction columns of 72-, 152- and 300-mm-diameter. Both single-phase water and two-phase kerosene-water were studied in all three columns, together with four other solvent-water systems in the smallest column; in all cases, water was the continuous phase. Evidence of maldistribution of the phases was obtained in the largest column. The backmixing coefficient was found to increase with column diameter in single-phase operation, but was diameter-independent in the two-phase case. Alternative correlations of the data were based on dimensional analysis and on a physical model, respectively. The influence of different systems was accounted for in the latter in terms of droplet size and terminal velocity, dispersed phase holdup, and density difference. Qualitative color tracer tests on the dispersed phase gave no evidence of backmixing of this phase, although strong forward dispersion was observed in the emulsion regime.
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    AIChE Journal 35 (1989), S. 1883-1893 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Partition coefficients are computed for hard spherical solutes in equilibrium with sponge-type matrices containing randomly-placed spherical cavities or pores using grand canonical Monte Carlo simulation. The random pore model is representative of a variety of disordered porous solids including porous glasses and some polymeric materials. The algorithm used brings additional realism to the problem by rigorously distinguishing between accessible and inaccessible pore space. The simulation results display significant concentration effects which are often observed experimentally and are compared to data obtained by Brannon and Anderson (1982) for the partitioning of bovine serum albumin into controlled-pore glass.
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    AIChE Journal 35 (1989), S. 1899-1902 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 35 (1989) 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 35 (1989), S. 1933-1941 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Many industrial proceses require the circulation of particles between reacting fluidized compartments at a stable, but flexible rate, so that the processes can be operated at different solids rates. In order to understand the phenomena involved in the circulation and its control, circulation of sand particles has been studied through a new experimental approach, using an open-loop two compartment circulating system.Experimental results show that the control of the circulation rate depends on three phenomena: the vertical resisting force in the fluidized compartments, the contraction of flow in the communication zone, and the bypass of gas between the compartments. For industrial purposes, the first appears to be predominant in the control of the solids rate. The second ensures neither the strict control of this rate nor the required flexibility. The link between the gas bypass and the circulation phenomena is explained and recommendations for the design and operation of circulating systems are given.
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    AIChE Journal 35 (1989), S. 1975-1979 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Notes: A model is developed describing consecutive gas-solid reactions occurring in porous media. The model calls for independently measurable parameters and predicts two maxima in the reaction rate at intermediate conversions. The low temperature (350°C) reduction of hematite to iron in a hydrogen-nitrogen atmosphere was used to test the model. The experimental data confirmed the expected rate maxima. The conversion predictions are very close to the data for conversions below 30%, but are systematically somewhat lower than the experimental values for higher levels of conversion. An explanation for the discrepancy is offered in terms of the description of the pore structure.
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    AIChE Journal 35 (1989), S. 2013-2027 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In this paper, a simple procedure based on fast and slow reaction asymptotics has been employed to derive first-order closure models for the nonlinear reaction terms in turbulent mass balances from mechanistic models of turbulent mixing and reaction. The coalescence-redispersion (CRD) model, the interaction by exchange with the mean (IEM) model, the three-environment (3E) model, and the four-environment (4E) model have been used to develop closure equations. The closure models have been tested extensively against experimental data for both single and multiple reactions. The closures based on slow asymptotics for the CRD, 3E and 4E models provide very good predictions of all of the experimental data, while other models available either in the literature or derived here are not adequate. The simple new closure equations developed in this paper may be useful in modeling systems involving turbulent mixing and complex chemical reactions.
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    AIChE Journal 35 (1989), S. 2058-2060 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 35 (1989), S. 1052-1052 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 35 (1989), S. 1535-1542 
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    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Many industrially important processes feature both nonlinear system dynamics and a process deadtime. Powerful deadtime compensation methods, such as the Smith predictor structure in state space for linear systems is presented first and then directly extended to nonlinear systems. When combined with input/output linearizing state feedback, this Smith-like predictor makes a nonlinear system with deadtime behave like a linear system with deadtime. The control structure is completed by adding an external linear controller, which provides integral action and compensates for the deadtime in the input/output linear system, and an open-loop state observer. Conditions for robust stability with respect to errors in the deadtime and more general linear unstructured multiplicative uncertainties are given. Computer simulations for an example system demonstrate the high controller performance that can be obtained using the proposed method.
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    AIChE Journal 35 (1989), S. 1543-1546 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 35 (1989), S. 1376-1379 
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    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 35 (1989), S. 1617-1624 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Notes: Ultrapyrolysis or ultrarapid pyrolysis is a hydrocarbon thermal cracking process which offers the promise of greater product selectivity, higher yield and feedstock flexibility. In this paper, ultrapyrolysis of propane in a spouted bed with a draft tube was used as a test system to demonstrate these advantages. Experiments, carried out on a 20-cm-diameter pilot-scale reactor, illustrate the spouted bed to be capable of achieving the extremely high reactant heating rates of up to 105 K/s and the short gas residence times of less than 500 ms necessary for this process. Moreover, reactant conversion and product yields can be enhanced by controlling the operating temperature of the bed. In addition, application of the propane pryolysis reaction scheme of Sundaram and Froment into a recently developed computer model indicates the ability to correctly simulate the spouted bed as an ultrapyrolysis reactor.
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    AIChE Journal 35 (1989), S. 1651-1658 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper focuses on the problem of scale-up of two-phase (e.g., solid-fluid) reactors. It outlines a class of such reactors which, for first-order reactions, scale in the familiar single-phase manner via an analog of the usual residence time distribution formula. The differences lie in the fact that the appropriate tracer experiment entering the formalism for this reactor class refers to a nonadsorbing tracer, and the analog of the plug flow solution is the solution for a fixed bed with fluid-phase plug flow. Surprisingly, unlike single-phase systems, there exist two-phase reactors, outside of the class defined, that do not scale in this manner, even when, say, the true catalyst surface chemistry is purely first-order. The paper discusses a few examples and implications for the design of two-phase reactors, including fluidized beds.
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    AIChE Journal 35 (1989), S. 1685-1691 
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    Keywords: Chemistry ; Chemical Engineering
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    Notes: Heat transfer coefficients were measured for ciculating beds of sand particles of mean size 222 to 299 μm at temperatures of 340-880° C. Transfer coefficients were obtained for both a 1.22-m-long, 12.7-mm-OD vertical tube and a 1.59-m-long, 148-mm-wide membrane wall near the top of a 152-mm-square by 7.32-m-tall combustion column. For both surfaces and all temperatures, average heat transfer coefficients increased almost linearly with local suspension density which ranged from 0 to 70 kg/m3. Radiation played a significant role, especially at high temperatures and low suspension densities. Heat transfer coefficients also varied significantly with the lateral position of the tube. The vertical length of heat transfer surface is shown to be an important parameter allowing seemingly discrepant published results to be reconciled.
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    AIChE Journal 35 (1989), S. 1719-1727 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An approximate equation for the evolution of finite-amplitude, long disturbances to Newtonian liquid films is found to be accurate over a wide range of Reynolds numbers. A long-wave expansion leads to a film profile equation asymptotically correct when wave number and Reynolds number are small. Solutions of the film profile equation are compared to exact and other approximate solutions of the Navier-Stokes system. An alternative form of the film profile equation results in remarkably accurate solutions, when Reynolds numbers are moderate, in the cases of standing or monotonically decaying waves in horizonatal films, rising film flow, final acceleration of a moving film, and film flow emerging from a slot coater.
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    AIChE Journal 35 (1989), S. 1742-1744 
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    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 35 (1989), S. 1753-1756 
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    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 35 (1989), S. 1592-1601 
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    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Various strategies for sequencing heterogeneous azeotropic distillations have been explored. The design and optimization of these systems by simulation-based methods is generally acknowledged to be a very difficult problem (Kingsley and Lucia, 1988). In this article, a simple and accurate design and optimization procedure has been developed. The method does not involve any recycle convergence loops and has been applied successfully to several test problems. Unlike the simulation-based methods, our method is robust to changes in the system optimization variables (e.g., reflux ratio in the azeotropic column).In order to demonstrate the method, we present design and optimization results for the dehydration of ethanol using a benzene entrainer. Our optimal designs consume significantly less energy than state-of-the-art designs reported in the literature.
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    AIChE Journal 35 (1989), S. 1625-1630 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The final properties and end use of many organic solids often depends on their crystal-size distribution (CSD), e.g., bioavailability for pharmaceutical solids. The objective of this study was to develop an alternate technology for crystallizing and manipulating size distribution of organic solids by crystallization from supercritical fluids. Such a technology might be superior to conventional-size manipulation techniques, such as milling and recrystallization from organic solvents, which might contaminate the products and affect their physical-chemical stability. Supercritical carbon dioxide was used as solvent to dissolve and then crystallize benzoic acid. A batch crystallizer was constructed and operated in the supercritical region. Seeded and unseeded crystallization experiments were performed. Different depressurization vs. time profiles for the supercritical fluid were used to produce crystals of various sizes.
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    AIChE Journal 35 (1989), S. 1962-1974 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A computer simulation of turbulent flow in a channel is used to detect flow patterns related to the production of Reynolds stress. It is found that quadrant 2 and quadrant 4 events possess a streaky structure in the viscous wall region and that these events can be best understood by examining the velocity field in the y-z plane. Large turbulence production in the viscous wall region is found to occur in updrafts and downdrafts associated with closed eddies. These eddies, on average, have a spanwise dimension of 50 wall units and a streamwise dimension of 400-450 wall units. They are often seen to originate from small attached eddies at the wall.
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    AIChE Journal 35 (1989), S. 1993-2002 
    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 ability of knowledge-based expert systems to facilitate the automation of difficult problems in process engineering that require symbolic reasoning and an efficient manipulation of diverse knowledge has generated considerable interest recently. Rapid deployment of these systems, however, has been difficult because of the tedious nature of knowledge acquisition, the inability of the system to learn or dynamically improve its performance, and the unpredictability of the system outside its domain of expertise.This paper proposes a neural-network-based methodology for providing a potential solution to the preceding problems in the area of process fault diagnosis. The potential of this approach is demonstrated with the aid of an oil refinery case study of the fluidized catalytic cracking process. The neural-network-based system successfully diagnoses the faults it is trained upon. It is able to generalize its knowledge to successfully diagnose novel fault combinations it is not explicitly trained upon. Furthermore, the network can also handle incomplete and uncertain data. In addition, this approach is compared with the knowledge-based approach.
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    AIChE Journal 35 (1989), S. 2037-2039 
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    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 35 (1989), S. 1895-1898 
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    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 35 (1989), S. 2029-2032 
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    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 35 (1989) 
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    AIChE Journal 35 (1989), S. 923-930 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This paper presents an efficient method for the design of controllers for integrating and runaway processes. The method is based on model matching in the frequency domain. The presence of open-loop instability as well as pure time delay in the process models make the design task challenging for these classes of processes.The goal is to achieve low-order, easily implementable cascade controllers in a unity-output-feedback configuration. It is shown that the central problem is in the selection of appropriate reference models. Several key constraints are developed which relate a given process model to a class of reference models for achieving total stability. Typical design examples are presented to clearly illustrate the various mathematical techniques.
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    AIChE Journal 35 (1989), S. 951-958 
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    Keywords: Chemistry ; Chemical Engineering
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    Notes: Models are developed for isothermal desorption in a fixed bed of adsorbent particles. While more general models require numerical solution of the governing equations, two practically important cases have analytical solutions: (1) an equilibrium desorption model where the rate of desorption is controlled by external and intraparticle mass transfer; and (2) a kinetic model where external and intraparticle mass transfer and a first-order irreversible desorption step control the overall process.Recent experimental data (Tan and Liou, 1988) for the desorption of ethyl acetate from activated carbon with supercritical carbon dioxide are found to fit the local-equilibrium model. Data for the effect of temperature on fractions desorbed indicate a reversal of the temperature dependence of the adsorption isotherm as the supercritical pressure is increased. This phenomenon is analogous to the observed cross-over region for the effect of temperature on the solubility of a solid at supercritical conditions.
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    AIChE Journal 35 (1989), S. 995-1002 
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Experimental data on silicon nitride film growth have been obtained from a radial-flow, plasma-enhanced chemical vapor deposition reactor. A nonisothermal mathematical model has been developed consisting of Navier-Stokes, energy, and species balance equations taking into account the temperature dependence of physical properties. The model is predictive at various power input levels for film compositions and growth rates.
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    AIChE Journal 35 (1989), S. 1039-1043 
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    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 35 (1989), S. 1057-1072 
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    Keywords: Chemistry ; Chemical Engineering
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    Notes: We have developed an analytical solution which describes mineral zonation caused by diffusion in permeable media. For a semiinfinite domain, the species conservation equations transform into ordinary differential equations that yield a closed-form solution. The solution exhibits shock dissolution/precipitation fronts and gradual (nonshock) precipitation fronts. The solution can exhibit regions (gaps) containing no reactive solids which separate moving dissolution and precipitation fronts. The analysis is, in principle, extendable to include intraaqueous reactions, although the mathematics quickly becomes intractable.Numerical simulation exhibits all of the features of the more restricted analytical solution and is in good agreement with the data on hydroxyapatite dissolution taken by Kim and Cussler (1987).
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    AIChE Journal 35 (1989), S. 1107-1114 
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    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The extent of diffusion limitations in the catalytic conversion of synthesis gas to hydrocarbons by the Fischer-Tropsch reaction has been established for a number of iron- and cobalt-based catalysts. The studies were performed in a fixed-bed microreactor system at temperatures in the range 473-523 K. Variation of catalyst particle size in the range 0.2-2.6 mm shows that the conversion of synthesis gas decreases considerably when the average particle size is increased. The effects of variation of particle size and pore diameter have been quantified with the Thiele model for diffusion limitations. Evidence has accumulated that the limited mobility of reactant molecules in the liquid-filled pores of Fischer-Tropsch catalysts is the main cause of retardation of the reaction rates. The experimentally determined reaction rates with various catalysts operated under different conditions show an excellent fit with the theoretical model.
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    AIChE Journal 35 (1989), S. 1148-1156 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Large transient temperature excursions may be caused by a sudden reduction in the feed temperature to a packed-bed reactor operating at an intermediate conversion. When a unique steady state exists for all feed temperatures, the magnitude of the wrong-way behavior predicted by a two-phase model is very close to that predicted by a pseudohomogeneous model if PeH is equal to the dimensionless heat transfer coefficient H. The two-phase model enables a more efficient numerical simulation in such cases. The predictions of these two models may be rather different when steady-state multiplicity exists for some feed temperatures. In such cases, a two-phase model, which accounts for the axial dispersion of heat, should be used to simulate the transient behavior. The wrong-way behavior may lead to an ignition of a low-temperature state or an upstream propagation of a transient temperature wave.
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    AIChE Journal 35 (1989), S. 1195-1198 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    AIChE Journal 35 (1989), S. 1219-1223 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 35 (1989) 
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    AIChE Journal 35 (1989), S. 1263-1270 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: When the ratio of the drop radius to the distance separating any two drops and the relative importance of gravitational to surface forces are both small, the small amplitude oscillations of a drop of one viscous fluid immersed in another fluid are governed by the nonlinear dispersion relation derived by Miller and Scriven (1968). The dispersion relation has been solved numerically to determine the character of oscillations for arbitrary values of drop size, physical properties of the two fluids, and interfacial tension. The new theoretical results determine the range of validity of the low-viscosity approximation of Miller and Scriven, and are also shown to be essential for proper interpretation of many previously reported experimental results. New experimental measurements of natural frequencies of oscillation of water drops falling in 2-ethyl-1-hexanol, a system having properties characteristic of many others in solvent extraction, agree well with the theoretical predictions when drop radius is smaller than a critical size. The frequencies of oscillations of larger drops are better described by the dispersion relation due to Subramanyam (1969), which accounts for the relative motion of the two phases.
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    AIChE Journal 35 (1989), S. 1304-1314 
    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 laser-Doppler velocimeter (LDV) was used in a cold-flow study of a simulated entrained-flow coal gasifier. The study was designed to provide fundamental information about the flows in such a gasifier and to provide data for the validation of a turbulence submodel used in modeling combustion processes. Measurements in 20 swirling and nonswirling flow cases were made with several levels of replication. This study emphasized the effects of inlet conditions on flow properties within the simulated reactor.Unsteady flow phenomena with time scales on the order of seconds to minutes were sometimes observed. The unsteadiness was apparently associated with relaminarization-type flow transitions.Comparisons were made with model predictions from PCGC-2, a model for combustion processes based on the k,  -  ∊ turbulence model. Several areas of weakness in the model results were observed, but the unusual flow regimes measured in this study may be beyond the abilities of practical computer models.
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    AIChE Journal 35 (1989), S. 1569-1571 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 35 (1989) 
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    AIChE Journal 35 (1989), S. 1391-1394 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 35 (1989), S. 1428-1436 
    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 magnetic thermometric method is used to determine cross-sectional average axial catalyst temperature profiles for superparamagnetic neckel catalyst beds during ethane hydrogenolysis, an exothermic reaction. Each solid temperature profile is determined from an axial profile of cross-sectional average magnetization and is represented by a polynomial. In turn, each magnetization profile is determined from voltage data obtained as the bed is moved through an AC permeameter. A Fredholm equation of the first kind, “regularized” using a minimum variance constraint, is inverted to determine the magnetization profile.The determination of the axial temperature profile for a reactor operating at 11.0% conversion is detailed. It provides a good test of the method used. Some limitations of the method are highlighted by attempts to analyze data from a reactor operating at complete conversion. The potential for model parameter estimation is discussed.
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    AIChE Journal 35 (1989), S. 1473-1486 
    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 theory is presented for the fully-developed flow of gas and particles in a vertical pipe. The relation between gas pressure gradient and the flow rates of the two phases is predicted, over the whole range of cocurrent and countercurrent flows, together with velocity profiles for both phases and the radial concentration profile for the particles. The gas and the particles interact through a drag force depending on their relative velocity, and there are mutual interactions between pairs of particles through inelastic collisions. This model is shown to account for marked segregation of gas and particles in the radial direction, and the predicted relation between the pressure gradient and the flow rates of the two phases is surprisingly complex.
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    AIChE Journal 35 (1989), S. 1445-1456 
    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 kinetics of a semibatch melt transesterification of dimethyl terephthalate (DMT) with ethylene glycol (EG) is studied with zinc acetate as a catalyst. This paper quantifies the effect of various reactor operating conditions on the transesterification rate and the product composition distribution. Our experiments support the assumption that the methylesters in DMT and growing oligomer chains have the same reactivities for transesterification with EG and that the reactivity of hydroxyl groups in pure EG for esterification with DMT is twice that of the hydroxyl group in oligomers. With a molecular species model in which various oligomers are identified by the type of functional end groups, the progress of the transesterification and the oligomer concentration distribution were estimated and the agreement between the model predictions and the experimental data were excellent. It has also been shown that 30 wt. % of oligomers are produced for [EG]/[DMT] molar ratio of three, and up to 70 wt. % oligomers are produced at the [EG]/[DMT] molar ratio of one.
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    AIChE Journal 35 (1989), S. 1547-1550 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 35 (1989), S. 1559-1563 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 35 (1989), S. 1575-1582 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 35 (1989) 
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    AIChE Journal 35 (1989), S. 1779-1790 
    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 kinetics of protein aggregation in salt-induced precipitation processes were studied as a function of salt type, salt concentration, temperature and protein concentration. α-chymotrypsin (αCT) was used as a model protein. Stopped-flow turbidimetry was used to monitor the progress of precipitations. Analysis of the linear portions of the turbidity trajectories indicates that temperature and salt concentration effects are related to protein solubility; the protein concentration dependence is well described by the Smoluchowski collision equation. The aggregation kinetics of partially-inhibited αCT exhibit poisoning behavior, underscoring the importance of dimerization and monomer addition in the precipitation of αCT. Solute particle radius distributions determined via dynamic laser light scattering for low salt and supernatant αCT solutions indicated that significant aggregation does not occur in the absence of supersaturation. A detailed population balance model was proposed that accounted for specific and nonspecific interactions and monomer addition. The model is expected to find general application to protein aggregation phenomena, in particular for proteins that have specific quaternary interactions.
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    AIChE Journal 35 (1989), S. 1829-1834 
    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 low residence time flow method for the measurement of the critical temperatures and pressures of thermally-unstable fluids was developed in this work. The low residence time at elevated temperatures minimizes decomposition and other reactions, making it possible to measure the critical properties of many unstable fluids. An extrapolation procedure was developed to obtain the critical properties of rapidly reacting substances, based on the linear behavior of the apparent critical property with residence time. The measured critical properties of 14 n-alkanes (pentane through octadecane) using this method are reported in this paper. The results extend the available data on the critical properties of the higher alkanes and reveal a possible error in the literature value for the critical pressure of tetradecane.
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    AIChE Journal 35 (1989), S. 1835-1844 
    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 feedforward/feedback version of a single input/single output self-tuning controller has been developed and tested both via simulation studies and experiments on a section of an absorption/desorption pilot plant. The algorithm is based on the recursive least squares estimation of parameters for the linear models relating the output to the controlled input and to the disturbances; adaptation is achieved using a variable forgetting factor. The control input at each time interval is calculated using one of several single-step extended-horizon control strategies.The results show that the performance of the algorithm is insensitive to the choice of initial parameters, all of which have a readily identifiable intuitive basis. The algorithm is especially robust against deterministic disturbances (measurable and unmeasurable) and unknown and varying time delays. Computational load beyond that of a feedback-only version is minimal.
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    AIChE Journal 35 (1989), S. 1869-1875 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Equilibrium isotherms and kinetic data for sorption of ethylamine on two different H-form ion exchangers (a homogeneous gel type and a biporous MR type) have been determined experimentally by the gravimetric method. The gaseous amine is adsorbed on the dry resins according to an acid-base neutralization reaction, and the saturation capacity coincides with the exchange capacity of the resin. For the gel-type resin, the equilibrium is less favorable and the isotherm is almost linear over the experimental range.The kinetic data also reflect the structural difference between the two adsorbents. In the MR-type resin, the sorption rate is controlled by macropore diffusion with rapid equilibration of the adsorbed phase within the microparticles. Since the equilibrium isotherm is highly favorable, approaching the irreversible limit, the uptake curves are well represented by the ‘shrinking core’ model. Diffusion in the gel-type resin is much slower and the pore diffusivities are smaller by several orders of magnitude, presumably reflecting the smaller effective pore diameter.These results suggest that the MR-type resin is a potentially useful adsorbent for removal of traces of light amines from industrial gases.
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    AIChE Journal 35 (1989), S. 1903-1906 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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    AIChE Journal 35 (1989), S. 1915-1916 
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    AIChE Journal 35 (1989), S. 1927-1932 
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    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The model of uniform nonlinear kinetics recently developed for the continuous description of a multicomponent mixture reacting in a batch or plug flow reactor (Astarita, 1989) is applied to the analysis of a continuous stirred tank reactor (CSTR). It is shown that most of the equations can be solved in general, independently of the specific kinetic mechanism. Some specific mechanisms are discussed. The difference between the behavior in a plug flow reactor (PFR) and a CSTR turns out to be quite dissimilar from what one would expect by considering the single-component case.
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    AIChE Journal 35 (1989), S. 1921-1926 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: An assumption commonly, but by no means universally, made in the stability analysis of the homogeneously fluidized state is that the pressure field may be well approximated by its gravitational component alone. This assumption is critically examined: the results indicate that it is valid for most cases of practical interest but can lead to significant discrepancies for liquid fluidization of low-density particles.
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    AIChE Journal 35 (1989), S. 1942-1952 
    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 Monte Carlo (MC) technique involving explicit calculation of molecular trajectories in fibrous media is used to obtain effective transport coefficients in the Knudsen regime of gas diffusion. A fully penetrable cylinders (FPC) model is used to represent a fibrous substrate during the course of densification, as in composite fabrication processes such as chemical vapor infiltration (CVI). The calculated Knudsen permeabilities are in excellent agreement with available data. Accessible porosities are computed as a function of total porosity and are shown to depend on the fiber number density. The nonfiber phase is shown to percolate at φ ≈ 0.095, but the threshold is sensitive to the boundary conditions employed.
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    AIChE Journal 35 (1989), S. 2040-2042 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
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    AIChE Journal 35 (1989), S. 1351-1364 
    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 the present investigation, Taylor's analysis of the axial dispersion of a solute in a Newtonian fluid undergoing laminar flow through a circular tube was applied to dispersions of colloidal particles, in which effects of size exclusion, inertial and colloidal forces, and wall retardation must be considered. The results indicate that the product of the particle Reynolds and Peclet numbers determines the importance of the inertial forces on both the effective axial diffusion coefficient and the height of a theoretical plate.The height of a theoretical plate as a function of the eluant ionic strength and average velocity, particle diameter, and tube diameter was determined experimentally. Close agreement with the numerical calculations from the diffusion equation was obtained. The height of a theoretical plate was found to attain a maximum value when the product of Reynolds and Peclet numbers was approximately 10.5.
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    AIChE Journal 35 (1989), S. 1385-1390 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
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    AIChE Journal 35 (1989), S. 1402-1403 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
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