摘要:

Solvent sublation is a unique bubble-separation method which combines features of foam fractionation and solvent extraction in a single unit operation. Surfactant introduced into a flotation column serves to remove emulsions and other colloids, while simultaneously transporting dissolved organics into a solvent layer for retention. The extracting solvent is placed directly on the surface of the aqueous phase.

ISSN:0098-6445    

DOI:10.1080/00986448808940299

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Significant improvements in control system performance and robustness can be obtained if the major process nonlinearities are included in the control system design. Nonlinear model control achieves this through the use of simple parallel and series compensation. In the paper we demonstrate the use of this method. New theoretical results on controller robustness are presented; it is in particular shown how series nonlinear model compensation using state and disturbance feedback can be used to improve control system performance. The theoretical results are supported by simulation and pilot plant experiments using a modified version of the self-tuning regulator.

ISSN:0098-6445    

DOI:10.1080/00986448808940300

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The use of an elbow flowmeter for the volumetric flowrate measurements of water, a glass bead/water slurry, and a sand/water slurry was experimentally investigated. It was found that as long as the slurry behaved as a homogeneous single phase fluid, the calibration of the elbow flowmeter was the same as that for a single phase fluid and the pressure difference across the elbow was that expected from single phase correlations. The effects of concentration were accounted for by using the density of the slurry for these calculations. The coefficient of discharge was calculated and analytically predicted to within 5%. If the conditions were such that a considerable slip velocity existed between the fluid and the slurry particles, the flowmeter behaved differently from that expected for a homogeneous fluid. The flow of a sand/water slurry through the elbow flowmeter which consisted of large particles resulted in stratification of the sand in the elbow. This caused a substantial change in the value of the elbow flowmeter's discharge coefficient and the calibration of the elbow meter.

ISSN:0098-6445    

DOI:10.1080/00986448808940301

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The thermodynamic pressure effect on rate constants is reported in supercritical fluid carbon dioxide for a homogeneous reaction network over a wide density range. The selectivity, or ratio of rate constants, has been controlled over a continuum for the parallel Diels-Alder additions of methyl acrylate and cyclopentadiene by adjusting the pressure at constant temperature. This reaction network is well-suited to provide fundamental insight into the nature of supercritical solvent effects since three simplifications arise: the pressure effect on the selectivity is independent of the partial molar volumes of the reactants, the temperature effect on the selectivity is independent of the partial molar enthalpies of the reactants, and the ratio of the endo- to exo-rate constants based on mole fraction units is the same as that based on concentration units. The selectivity for the more polar product, the endo-adduct, increases as the pressure or density increases, which indicates that it has a more negative partial molar volume in the transition state due in part to stronger induction forces. The slope of the logarithm of the selectivity is shown theoretically to increase as a function of the isothermal compressibility at constant temperature. At constant pressure, the selectivity decreases with temperature which indicates that the magnitude of the partial molar enthalpy is greater for the more polar endo-transition state than the exo-state. Solvatochromic polarity scales may be used to correlate quantitatively the solvent on this reaction network at supercritical fluid conditions.

ISSN:0098-6445    

DOI:10.1080/00986448808940302

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Large scale spills of volatile cryogenic or pressurized ambient temperature liquids often produce denser-than-air clouds which disperse in the atmosphere in a manner that is different than trace gases. These differences are due to density or gravity-induced effects such as turbulence damping from the stable density stratification, alteration of the ambient velocity field due to gravity flow, and the source momentum flux. Also important are thermodynamic effects such as aerosol formation and flash vaporization upon release, evaporative cooling, or heat transfer from the ground modifying cloud buoyancy and turbulence. In addition, chemical reaction effects such as hydrolysis with atmospheric water vapor, polymerization, or decomposition which also affects cloud density and thermodynamics can be important. These effects are very important close to the release point but also can have dramatic effects on the cloud as it disperses downwind.

ISSN:0098-6445    

DOI:10.1080/00986448808940303

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The proper design and control of an indirect coal liquefaction process plant require an accurate knowledge of bubble sizes and size distribution. Of particular importance regarding proper design is the understanding of the complicated dependence of bubble dynamics on bubble column geometry, and of the nature of the solid-liquid phases. The nature of the products and their relative proportions, on the other hand, are seriously influenced by the bubbling characteristics of the reactor because the mass transfer behavior and mixing are dependent on the bubble size and velocity distributions. This report reviews experimental techniques that have been employed to measure bubble sizes in multiphase reactors. The methods, which fall in three different categories, namely, the photographic method, the optical probe, and the electrical conductivity (resistivity) probe, are described in a historical sequence; and in each case, their unique features and design details are discussed. A general methodology of data analysis in each category is given, together with a state-of-the-art technology assessment and, finally, relative merits and demerits of the methods.

ISSN:0098-6445    

DOI:10.1080/00986448808940304

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The flow behaviour of polymer solutions of non-hydrolyzed polyacrylamide and Xanthan was investigated in two rectangular and similar plexiglas models containing 3 cylindrical enlargements of the same dimensions. These three enlargements were located successively at the mid point of the first model length, whereas they were equally spaced along the second one. Only non-hydrolyzed polyacrylamide polymer solutions have shown viscoelastic behaviour in these plexiglas models. However, the behaviour of these polymer solutions in the first model was different from that in the second one.

ISSN:0098-6445    

DOI:10.1080/00986448808940305

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

The effect of imperfect mixing in a single batch reactor was studied using a two-tank system model with internal recycle and unequal volumes. The double-valued relationship between the reactant in each tank of the model for theA → Bbiochemical/chemical reversible and irreversible reactions was used to analyze mixing patterns in poorly mixed stirred-tank reactors.

ISSN:0098-6445    

DOI:10.1080/00986448808940306

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

A simulation of the polymerization of methylmethacrylate in a CSTR is adaptively controlled by two types of pole-placement algorithms. The strongly nonlinear polymerization process, exhibiting multiple steady states, presents difficult control problems for conventional feedback controllers. The performance of an adaptive explicit SISO controller and that of an adaptive implicit multivariable controller are compared and evaluated as applied to this process. The plant is identified by a recursive least squares estimator. Modifications made to the estimation algorithm help to maintain adequate closed-loop results. A simple warm-up procedure is introduced that successfully initializes the controller and estimator during plant start-up. Good servo and regulatory control are achieved by both pole-placement schemes.

ISSN:0098-6445    

DOI:10.1080/00986448808940307

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor

摘要:

Certain failures in absorption and distillation columns are attributed to flow induced vibrations. Mechanisms by which column pressure pulsations can occur are discussed. The mechanism most closely linked to the damage conditions is identified and its limits and characteristics defined. Interaction between the pulsation phenomenon and the mechanical damage is discussed.

ISSN:0098-6445    

DOI:10.1080/00986448808940308

出版商:Taylor & Francis Group    

年代:1988

数据来源: Taylor