摘要:

AbstractUp to now, the only equations that were known for calculating mass transfer during two‐phase countercurrent flow in packed columns were those that apply to the range extending up to the loading point. The gas and liquid streams flow separately through the column below but not above this point. Above it, the shear stress in the gas stream supports an increasing quantity of liquid in the column, with the result that the liquid holdup greatly increases. Finally, at the flood point, the liquid accumulates to such an extent that column instability occurs. Mass transfer in this upper loading range can be described if these fluid dynamic relationships are taken into consideration. The algorithm that is presented here for its prediction is based on theoretical and experimental studie

ISSN:0930-7516    

DOI:10.1002/ceat.270180602

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractPackings with vertical walls, especially structured packings, are distinguished by their high efficiency and low pressure drop per mass transfer unit. Yet for these types of packings there is still no universal relationship for calculating gas‐film‐controlled mass transfer coefficients. The present work proposes such an equation. For arranged and structured packings the new equation fits the experimental data, both new results and those taken from the literature, with a mean error of

ISSN:0930-7516    

DOI:10.1002/ceat.270180603

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this article we present results for the viscosity and the mass transfer rates of hydrogen/air, hydrogen/oxygen, methane/air and methane/oxygen mixtures in the temperature range from 1000 to 7000 K and a pressure range from 103to 106Pa. In addition, the combustion ratio is varied from 0 to ∞. The transport properties are calculated from the first order solution of the Chapman Enskog approach to the Boltzmann equation, assuming chemical equilibrium composition. An extensive literature study was performed to derive experimental and/or theoretically based data for the respective binary interaction potentials. The values of the collision integrals, as derived from a complex numerical integration procedure, are correlated to an approximation formula. In addition, the exact solutions of the kinetic theory are compared to frequently used empirical mixture rules. For the mixture viscosity an easy approximation formula is deduced from the gas‐kinetic the

ISSN:0930-7516    

DOI:10.1002/ceat.270180604

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractA computer program has been developed for the simulation of gas‐liquid absorption columns. The calculations are based on known assumptions and methods – the two‐film theory. Mass and energy balances together with chemical reactions are carried out for each tray of the column. The results obtained from the simulation procedure are compared with those measured at industrial plants. For the items “rich solution temperature” and “calculated number of trays” the agreement of calculated and measured results are satisfactory. However, for the CO2and H2S content of the streams only few comparisons could be made due to the fact that no measured values

ISSN:0930-7516    

DOI:10.1002/ceat.270180605

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this work, the influences of inert diluents, N2and CO2, on the explosion limits of benzene‐air mixtures were investigated at two different initial temperatures. The model of constant flame temperature was tested for the simulation of the experimental data. It was seen that the model fitted the data of the lower explosion limits, but didn't correlate with the data of the upper explosion limit

ISSN:0930-7516    

DOI:10.1002/ceat.270180606

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractAn advancing reaction‐front model has been proposed in the present study of facilitated transport through liquid surfactant membranes by taking into consideration a size distribution of emulsion drops. The model takes into account the continuous and outer liquid membrane phase resistances along with diffusion through composite emulsion drops. The effect of various dispersion phenomena on the mass transfer rate of solute has been discussed for two different operating conditions corresponding to different drop size distributions but having the same Sauter mean diameter. Membrane leakage is assumed to be negligibl

ISSN:0930-7516    

DOI:10.1002/ceat.270180607

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractEthane was converted into aromatic hydrocarbons on H‐ZSM‐5 and Zn‐ZSM‐5 at 773 K in a flow reactor system using nitrogen and hydrogen as carrier gases. Residence time was varied by changing catalyst weights to obtain information about primary and secondary reaction steps. On H‐ZSM‐5 ethane conversion proceeds via formation of ethene and subsequent oligomerization. Oligomers undergo fast isomerization, cracking and cyclization leading to a broad spectrum of aromatics. Methane is a secondary product. Dehydrogenation reactions proceed irreversibly. Introduction of zinc species significantly enhances the aromatization activity of H‐ZSM‐5 on the one hand and causes a change of reaction mechanism on the other. Oligomerization of olefinic intermediates can take place at zinc sites. In nitrogen, aromatization of C6olefins is faster than isomerization and cracking of these oligomers. Dehydrogenation steps proceed reversibly. On using hydrogen as the carrier gas over Zn‐ZSM‐5, the conversion of ethane as well as the formation of aromatics decrease. Furthermore, aromatics richer in hydrogen (especially C8aromatics) are then fo

ISSN:0930-7516    

DOI:10.1002/ceat.270180608

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractHydrodesulfurization of thiophene in n‐heptane, using a mixture of cobalt and molybdenum oxides as catalyst, has been studied in a fixed bed integral reactor, 200 mm long, 30 mm outer diameter and 20 mm inner diameter. It has been shown that, under experimental conditions employed in this study, neither external nor internal diffusion had been effective in the process and isothermal conditions prevailed in both gas and solid phases. A three step mechanism has been proposed for the hydrodesulfurization of thiophene. According to such a mechanism the diluent (n‐heptane) acts as an inhibitor by occupying free active sites. In further steps, thiophene is adsorbed on the catalyst surface and then undergoes reaction with hydrogen gas. Based on this scheme a rate model has been derived and verified by experimental resu

ISSN:0930-7516    

DOI:10.1002/ceat.270180609

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractTurbidimetry has proved to be an efficient method for the quantitative study of powder agglomeration for particle sizes in the region of 1 μm. This work presents a new application of the technique for the agglomeration of α‐alumina in water and inn‐heptane. The method of determining the kinetic parameters of agglomeration from the initial time‐evolution of turbidity is explained.Turbulent flow in the reactor has also been characterised by laser anemometry. From the turbulence intensity, the number of collisions per unit time is calculated and the agglomeration rate can therefore be determined.Good agreement is found between the values obtained respectively from turbidimetric and hydrodynamic measurements. Addition of KOH modifies the zeta potential of alumina in water and influences the agglomeration kinetics. This can also be quantitatively characterised by turbidimetry. The experimental results obtained for alumina particles of diameter 0.3 μm and 1 μm are interpreted according to the DLVO model of interaction between

ISSN:0930-7516    

DOI:10.1002/ceat.270180610

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractA theoretical analysis is presented for the time‐dependent vertical motion of spherical particles in a gas stream. Laminar, transitional and turbulent flows are considered, and equations are developed to predict particle velocity and distance travelled as functions of time in both stagnant and slowly‐moving gases. In both cases the equations are shown not to be universally applicable, and algorithms for estimating the limits within which they remain valid are briefly presen

ISSN:0930-7516    

DOI:10.1002/ceat.270180611

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY