摘要:

Correlations between pressure drop and hold-up for trickle-bed reactors operated in the low interaction regime, based on the Ergun-type model and a model of channels with constrictions, are compared. A simplified physical picture of the processes in the high interaction regime is given, allowing to suggest a pressure drop-hold-up correlation for this flow regime.

ISSN:0098-6445    

DOI:10.1080/00986448608911733

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

In a previous paper [5], it was shown how an arbitrary system of flow-mixing and splitting with plug sections in between could be modelled by a discrete residence time distribution (macro-mixing) and micro-mixing only between streams having equal remaining life. It is demonstrated in this paper how one may generalize these concepts to include the continuous descriptions of both of these mixing functions. These results are embodied in a mathematical model (General Mixing Model) which contains the macro-mixing and micro-mixing appearing as explicit functions and this model is valid for steady flow reactors in which systems of reactions with arbitrary kinetics (linear and non-linear) take place. This statement is true as long as there is no volume change on mixing or reaction, and we have a single unique residence time distribution for all the species in the system.

ISSN:0098-6445    

DOI:10.1080/00986448608911734

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Non-homogeneous drag reduction is obtained by injecting a polymer solution thread into the center of a turbulent pipe flow. Under the proper conditions the magnitude of this non-homogeneous drag reduction is much larger than that for the same polymer molecules uniformly distributed in the flowing solvent. In this work the axial velocities and velocity fluctuations near the wall were examined in such a non-homogeneous drag reduction and also in the flow of a homogeneous (pre-mixed) solution of poly(ethylene oxide). The drag reduction and the Reynolds number were the same for both fluids. Significant differences were found in the velocity profile and in the statistical analysis of the velocity fluctuations. The skewness profile for the non-homogeneous case remained positive to a much greater distance from the wall than the skewness profile for the premix solution. In the injection case the velocity fluctuation spectra had the same sharp peak at 5−10 Hz fory+between 11 and 50. This peak corresponded to the bursting frequency measured from the short time autocorrelation. In the pre-mix case a broad increase in velocity fluctuation spectra was seen aty+= 11 which was attributed to polymer molecule rotations in the laminar shear flow near the wall. This band was absent in the non-homogeneous drag reduction, suggesting that no polymers were present aty+= 11. The observations imply that non-homogeneous drag reduction involves a modification of the large eddy structure.

ISSN:0098-6445    

DOI:10.1080/00986448608911735

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Detailed analysis of biological processes for hazardous waste-water treatment presents extreme difficulty. Complexity of organic and inorganic solute mixtures in solution prohibits GC-MS analysis. Gross parameters must be used to monitor treatment process performance. Ultrafiltration, coupled with gross parameter estimation, provides enhanced definition of treatment. Results, employed to monitor in-situ biodegradation of a hazardous landfill leachate, are discussed.

ISSN:0098-6445    

DOI:10.1080/00986448608911736

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A correlation between the volumetric hydrogen mass transfer coefficient (KLa) in SRC-II process slurry and specific power consumption in mixing (E/VR) is developed. This correlation is independent of reactor configuration and it is also in very good agreement with the literature correlations forKLa. It is unified with an intrinsic hydrogen reaction rate expression to simulate the rate of hydrogen consumption in the SRC-II process. The simulation is validated by experimental data from an SRC-II continuous stirred tank reactor (CSTR). The mass transfer effects are interpreted and related to changes in product quality and a reduction in hydrogen reaction rate. Critical mixing power, required to maintain kinetically controlled operation of the process, is suggested.

ISSN:0098-6445    

DOI:10.1080/00986448608911737

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

The effects of hydrogen mass transfer resistance in large-scale SRC-II bubble column reactors (BCR), over large ranges of process variables, are studied. Due to the interactive effects of mass transfer resistance and gas hold up, the hydrogen consumption or liquid yield in a BCR has a maximum with respect to the specific mixing power. Under normal SRC-II process conditions a superficial gas velocity of about 0.01 m/s represents the optimum with respect to the hydrogen consumption or liquid yield. In general, the product quality requirement rather than the rate of hydrogen consumption determines the minimum specific mixing power requirement. Increase in hydrogen partial pressure can be used to reduce the level of mixing power required to maintain the desired product quality. Interrelations between mass transfer and gas hold effects and the variations in hydrogen concentration in slurry over large ranges of process conditions are also illustrated. This work provides some bases for the selection of reactor dimensions and process conditions for an SRC-II bubble column reactor (BCR).

ISSN:0098-6445    

DOI:10.1080/00986448608911738

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Pore size distribution of polyamide thin film composite reverse osmosis membranes and a cellulosic ultrafiltration membrane were obtained from vapor adsorption data of CO2and N2gases. The surface: force-pore flow model previously reported in the literature was utilized in this work. The pore distribution data were further used with solutes separation data at a particular pressure to obtain the values of solute-solvent-membrane wall forces involved. The interaction parameters were obtained by the simultaneous solution of the ordinary differential equations describing the model using the software package COLSYS. From the knowledge of the pore distribution data and the interactions forces, the solutes separation data (for nonionized organics and sodium chloride) were predicted over a wide range of pressures and showed excellent agreement with experimental separation data.

ISSN:0098-6445    

DOI:10.1080/00986448608911739

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

In previous papers, Monte Carlo simulations of the Knudsen diffusion of gases in porous solids having convex or concave pore walls have been performed. In the present paper, molecular trajectories inside pores are computed in the Knudsen region to obtain both collision density and collision numbers. It was found that these parameters were strongly dependent on the pore structure. The results obtained here will have applications to reactive flow and heterogenous catalysis.

ISSN:0098-6445    

DOI:10.1080/00986448608911740

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

Five mechanistic models of mixing and chemical reaction having an analogy with isotropic turbulent mixing are evaluated. The turbulence analogies, based on matching variance decay laws of models and turbulence theory, provide a physical basis for the models and a means of estimating their micromixing parameters apriori. Experimental data for single second order liquid phase reactions provide strong support for the analogies. However, it is demonstrated that in spite of their success for single reactions, the models may predict grossly different selectivities in the case of competing reactions in a plug flow reactor. This emphasizes the importance of certain structural features of the models which are independent of the existence of a turbulence analogy, such as: (i) reacting regions which are rich in each of the reactants of a two feedstream reactor, and (ii) unmixed regions in the reaction mixture. The importance of obtaining data for competing reactions in a highly segregated plug flow reactor for the purpose of model discrimination is made apparent.

ISSN:0098-6445    

DOI:10.1080/00986448608911741

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor

摘要:

A mathematical model is developed for an equilibrium stage analysis of nitrogen oxides absorption in nitric acid solutions. Using equilibrium data available from the literature, the model demonstrates that 15−35 wt% nitric acid may be efficiently used to reduce pollutant emissions in NOx-containing gases having low degree of oxidation. Lower oxides of nitrogen accumulate in the liquid as nitrous acid which is carried away by the nitric acid solution. The scrubbed gas contains a reduced concentration of nitrogen oxides and has a higher degree of oxidation than the feed gas.

ISSN:0098-6445    

DOI:10.1080/00986448608911742

出版商:Taylor & Francis Group    

年代:1986

数据来源: Taylor