摘要:

AbstractCyclic regeneration of activated carbon containing adsorbed sodium dodecyl‐benzene sulfonate (DBS) was studied in fluidized beds at 1119 K and 101.3 kPa. Optimum restoration of adsorption capacity (97.2% per cycle) resulted when gasification with 21.5% steam was continued for 200 s. At that time, about 85% of the DBS added to the carbon during the adsorption process had been removed. Because of the adsorbed inorganic residue from DBS, these results are somewhat different from earlier studies with the sucrose‐carbon system. With sucrose, maximum restoration of adsorption capacity was achieved when a weight equivalent to 100% of the adsorbed sucrose was removed by thermal decomposition and steam gasificat

ISSN:0001-1541    

DOI:10.1002/aic.690300202

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractThermodynamic property computations using equations of state first require computation of the density root. Since higher level calculations such as single‐stage flash, distillation and data regression are usually performed iteratively, properties are often demanded at conditions where the appropriate density root does not exist. A strategy of returning suitable pseudoproperties under such conditions is proposed. It has been successfully used in ASPEN (Advanced System for Process Engineering), a general process simulator developed at the Massachusetts Institute of Technolog

ISSN:0001-1541    

DOI:10.1002/aic.690300203

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractThis study is focused on deposition rate processes leading to inefficiency and “hot corrosion” in fossil‐fuel‐fired furnaces and engines. The inorganic compounds which deposit on heat exchanger surfaces and blades are formed in combustion product gases when the fuel and/or ingested air contains inorganic impurities. An improved understanding of the coupled thermodynamic, kinetic, and transport processes governing the deposition rate of inorganic oxides and salts from hot gases containing these compounds (or their precursors) can suggest more efficient test strategies and control measures. Accordingly, an optical interference method for accurately measuring the growth rate of deposits well before the onset of run‐off under laboratory burner conditions has been developed.To demonstrate the technique and provide data suitable for theoretical model development, a deliberately simple chemical system and target geometry are used. BCl3(g) is introduced into a premixed C3H8‐air flat flame at atmospheric pressure. The growth rate of B2O3(I) on an electrically heated platinum ribbon is then measured interferometrically over a range of fuel/air ratios and seed levels. However, the very existence of B2O3(I) deposition at the present seed levels and surface temperatures (about 1,200–1,300 K) clearly demonstrates the importance of kinetic restrictions on B2O3(I) gasification reactions. Optically measured film growth rates are obtained at film thicknesses small enough to neglect condensate run‐off, hence they yield vapor deposition rates directly. These deposition rates are found to be in good agreement with the predictions of a recently developed multicomponent mass‐transfer boundary layer (BL) theory, with a constrained equilibrium ((HBO2)3precluded) boundary condition. Remarkably, at a constant value of the BCl3flow rate, the Pt ribbon temperature above which there is no B2O3condensate (i.e., the so‐called dew point) is observed to depend on the fuel/air ratio. Whereas previous equilibrium‐based deposition models cannot embrace such phenomena, a semi‐quantitative argument, based on the nonequilibrium chemistry of B2O3precursor formation and (HBO2)3‐formation barriers, explains these potentially significant trends. These encouraging results suggest a more general applicability for the optical methods and chemically frozen (CF)BLtheory described herein, and demonstrate the important role of heterogeneous and homogeneous kinetic barriers in determining dew points and deposition ra

ISSN:0001-1541    

DOI:10.1002/aic.690300204

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractPreferential adsorption of organic compounds onto activated carbon from dilute aqueous solutions is studied to develop a comprehensive theoretical basis for predicting the adsorption of structurally different isomers for different homologous series. The fundamental multidimensional approachof the solvophobic (cϕ) thermodynamic theory is further refined and used to correlate the extent of adsorption for the comprehensive theory with the overall standard net free energy change (ΔGnet/RT) for the association‐adsorption reaction in solution, and for the simplified theory with the cavity surface area of the solute (TSA).Experimental adsorption isotherms of two homologous series (12 aliphatic alcohols and 21 aliphatic ketones) were measured and used to test and compare thecϕ theory with seven independent parameters characterizing the sorbates. Several experimental innovations for measuring equilibrium adsorption isotherms are introduced to reduce the possible loss of sorbate during the procedure and to provide reproducible and reliable results.Comparing the coefficients of linear correlation (r), the results for 12 aliphatic alcohols give greater than 99% confidence that ther‐values are different for ΔGnet/RTand molecular weight (MW). For the 15 aliphatic ketones, greater than 90% confidence interval is obtained for differentr‐values forTSAandMW.These results support the contention that simple structural modifications of aliphatic homologous compounds can be used to predict the effect of solute‐solvent‐sorbent interactions on adsorption. Thecϕ theory can thus be used to rank‐order adsorption intensity of these compounds from the aqueous phase onto

ISSN:0001-1541    

DOI:10.1002/aic.690300205

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractA new approach to the characterization of flow patterns and mixing through analysis of regional tracer dilution data obtained with a gamma camera is presented. Studies performed in a small, two‐dimensional, multiple‐inlet vessel demonstrate the experimental technique and how data are analyzed to determine the intravessel spatial distribution of fluid deriving from the traced stream. Good agreement is shown between calculated values of the flow distribution and visually observed flow patte

ISSN:0001-1541    

DOI:10.1002/aic.690300206

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractUntil now the oxygen transfer in viscous non‐Newtonian solutions has been studied only in bubble columns of about 0.14‐m diameter. Recently Godbole et al. (1982) reported much smaller gas holdups in Carboxy Methyl Cellulose solutions (CMC) for a large‐diameter column. Therefore, the gas holdups, volumetric mass transfer coefficients, and specific gas‐liquid interfacial areas are measured in CMC solutions using a bubble column of diameter 0.305 m and height 3.4 m. The transition from churn‐turbulent to slug flow regime occured at higher viscosities and the gas holdups and volumetric mass transfer coefficients were lower in both flow regimes than reported for smaller column diameters. Empirical correlations are presented for the gas holdup, volumetric mass transfer coefficient, and specific gas‐liquid interfacial area which would be suitable for the design of

ISSN:0001-1541    

DOI:10.1002/aic.690300207

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractA multivariable stochastic controller is implemented on a pilot scale, plug flow, butane hydrogenolysis reactor. In the synthesis of the controller, a multivariate time series model of the process disturbances is used. The success of this controller is compared to a previous controller where the process disturbances are not directly modeled.

ISSN:0001-1541    

DOI:10.1002/aic.690300208

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractA method for tracking the economically optimal operating conditions of a chemical process in the presence of constraints is developed. The technique is based on an on‐line search rather than a fundamental model. The most profitable operating point is found by fitting a dynamic model of the process based on data obtained from experimental moves on the plant.This model is used to compute gradients of the economic objective and of the constraints so that a direction of economic improvement inside the allowed operating region of the plant is always obtained. Constraint violations during the transients are prevented by a multivariable regulator. A new regulation method (Internal Model Control) is used which permits explicit handling of constraints and which can be made robust against modelling errors. This combined optimization/regulation approach is tested in a demonstrative simulation example and shown to be reliable for following a moving optimum and safely handling complex constraint move

ISSN:0001-1541    

DOI:10.1002/aic.690300209

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractThe convective dispersion theory of Gill and Sankarasubramanian is extended to allow for multiphase mass transfer interactions in column‐type contactors, and for multisolute, reversible and irreversible, homogeneous and wall‐catalyzed heterogeneous chemical reactions in the individual phases. This theory can now be applied in any transverse average, not just the area average used in the past, and additional interactions between the phases not normally accounted for in the traditional axial dispersion model are indica

ISSN:0001-1541    

DOI:10.1002/aic.690300210

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY

摘要:

AbstractA Numerical study, based on the theoretical developments of Part I of this series, has demonstrated that the chemical activity of a solute can have a significant effect on the convective dispersion behavior of multiphase reactors, and that the dispersion parameters estimated using inert tracers for the individual phases may not be representative of the parameters that should be used in the design of reactive systems. Moreover, the use of different transverse averaging procedures for the individual phases can give rise to additional interaction effects between the phases which are not accounted for in the traditional axial dispersion models. The predicted differences in dispersion parameter values depending on whether the solute is inert or not, are in qualitative agreement with published experimental results.

ISSN:0001-1541    

DOI:10.1002/aic.690300211

出版商:American Institute of Chemical Engineers    

年代:1984

数据来源: WILEY