摘要:

AbstractParticle velocities are measured for the cocurrent flow of air and coal particles through helical colis. The ratio of average particle velocity to gas velocity,Vg, is nearly independent ofVgat 0.25 ± 0.1. This ratio would be above 0.95 for similar flow conditions in straight, horizontal tubes. The particle velocities also depend slightly on other variables, decreasing with larger particles, larger solids feed rate, and smaller helix diameters. Visual observations reveal that the particles slide along the outer periphery of the coil, in a fashion similar to the sliding action at saltation conditions in horizontal flow. A model that permits prediction of particle velocity in helical geometries is proposed; this model is based on the modification of existing saltation velocity correlations by substituting centripetal acceleration for gravitational acceleration. Approximate agreement between experiment and prediction is obtained

ISSN:0001-1541    

DOI:10.1002/aic.690320402

出版商:American Institute of Chemical Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractAn analytical solution of thermally coupled system (TCS) optimization was found. Energy requirements of the TCS were minimized provided that the ternary solution being separated is ideal. The TCS is energetically profitable in comparison with other sequences of distillation columns. The solution method can be used for the synthesis of separation systems and for screening calculations, due to the great simplicity of the result.

ISSN:0001-1541    

DOI:10.1002/aic.690320403

出版商:American Institute of Chemical Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractIn solving the nonlinear algebraic equations that are normally used to model multicomponent separation processes, one is not guaranteed that Newton's method or any of its relatives will converge to the solution. This paper describes two homotopies and their use in the solution of difficult equilibrium stage separation process problems. The first, the Newton homotopy, is able to solve more problems than a standard implementation of Newton's method but is not the most reliable homotopy. Since the equations being solved no longer model a separation process unit, the Newton homotopy sometimes suffers from intermediate solutions that are physically meaningless. The second, the thermodynamic homotopy, is strongly based on the thermodynamic properties of the systems involved. This new homotopy is able to handle not only the more traditional distillation problems (hydrocarbon systems and mildly nonideal systems), but is also extremely effective at solving azeotropic and extractive distillation problems. The implementation of these methods requires only minor modifications to existing software.

ISSN:0001-1541    

DOI:10.1002/aic.690320404

出版商:American Institute of Chemical Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractA finite‐element method is used to solve the full Navier‐Stokes and energy equations for the problem of laminar combined convection from two horizontal cylinders in tandem arrangement. From comparisons with the previous theoretical and experimental results of a single‐cylinder situation, it is found that the behaviors flow and heat transfer in the upstream cylinder are close to those in a single‐cylinder, but this is not the case for the downstream c

ISSN:0001-1541    

DOI:10.1002/aic.690320405

出版商:American Institute of Chemical Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractHydrogenation of α‐methyl styrene with Pd/Al2O3catalyst was studied in a three‐phase stirred slurry reactor. Responses to step inputs of H2in N2carrier gas provided temporal moments that allowed estimation of separate values for reversible adsorption and irreversible surface reaction rates for reactant H2. Mass transfer resistances are either estimated from other sources and shown to be small, or are evaluated from the flow rate dependence of the moments. The adsorption equilibrium constant for H2on the catalyst was measured with reaction product cumene as the solvent. For temperatures between 290 and 322 K adsorption appears to have the dominant influence on the overall rate of hydrogenation. The energy of activation for the adsorption step was found to be 8 kcal

ISSN:0001-1541    

DOI:10.1002/aic.690320406

出版商:American Institute of Chemical Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractA procedure based on averaging the conservation equations in a homogeneous, disordered fibrous medium is used to demonstrate that in the limit of long times, macroscopic versions of Fick's and Fourier's laws may be used to relate the average flux to the average gradient in driving force. The asymptotic behavior in the limit of low volume fraction of the effective diffusivity (or conductivity) in such a medium is determined for all values of the Peclet number,P=Ua/Df, whereUis the average velocity through the bed,ais the fiber radius, andDfis the molecular diffusivity of the solute in the fluid. The convective disturbance caused by the fibers is found to have a large influence on the rate of mass transfer even at moderate Peclet numbers and low volume fraction.

ISSN:0001-1541    

DOI:10.1002/aic.690320407

出版商:American Institute of Chemical Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe problem of synthesizing processing systems via simultaneous structural and parameter optimization is addressed in this paper. Based on a superstructure representation for embedding alternative configurations, a general mixed‐integer nonlinear programming (MINLP) framework is presented for the synthesis problem. An efficient outer‐approximation algorithm is described for the solution of the underlying optimization problem, which is characterized by linear binary variables and continuous variables that appear in nonlinear functions. The proposed algorithm is based on a bounding sequence that requires the analysis of few system configurations, and the solution of a master problem that identifies new candidate structures. Application of the proposed algorithm is illustrated with the optimal synthesis of gas pipeli

ISSN:0001-1541    

DOI:10.1002/aic.690320408

出版商:American Institute of Chemical Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractThe thermal decomposition of Colorado oil shale was studied at subpyrolysis temperatures, 533 to 611 K, as part of an investigation of rates of supercritical extraction. Thermal degradation followed by solution in the solvent is a possible, partial explanation for the enhanced solubility at supercritical conditions for a complex mixture such as kerogen.In the region of the critical temperature of toluene, up to 26% of the kerogen in the original shale was converted by thermal reactions to gases and soluble (in toluene at 298 K and 101 kPa) products. The kinetics of the decomposition of the insoluble organics in shale could be explained by a combination of series and parallel reactions.

ISSN:0001-1541    

DOI:10.1002/aic.690320409

出版商:American Institute of Chemical Engineers    

年代:1986

数据来源: WILEY

摘要:

AbstractFlow rate and concentration measurements in a steady state process are reconciled by weighted least squares so that the conservation laws and other constraints are obeyed. Two projection matrices are constructed in turn, in order to decompose the problem into three subproblems to be solved in sequence. The first matrix eliminates all unmeasured component flow rates and concentrations from the equations; the second then removes the unmeasured total flow rates. The adjustments to component flow rates are iteratively determined, starting with guessed values of unmeasured total flow rates.Chi‐square and normal test statistics are derived by linearizing the equations, to allow detection of gross errors in imbalances and adjustments of measurement

ISSN:0001-1541    

DOI:10.1002/aic.690320410

出版商:American Institute of Chemical Engineers    

年代:1986

数据来源: WILEY

ISSN:0001-1541    

DOI:10.1002/aic.690320411

出版商:American Institute of Chemical Engineers    

年代:1986

数据来源: WILEY