摘要:

AbstractA simple and inexpensive Pbs‐FET with high sensitivity and short response time was developed which consists of a PbS layer on a pH‐sensitive gate of a field effect transistor. The PbS‐layer was prepared with simple wet precipitations technique. The PbS‐FET has about the same selectivities for Pb2+‐and for Cu2+‐ions, but only slight sensitivity for Cd2+‐and Zn2+‐ions. The sensor was integrated in a FIA system. By variing the injection time the measuring range varied between 10−1‐10−6and 10−2‐10−8mol Pb2+/1. The PbS‐FET‐FIA system is suitable for monitoring of Pb2+c

ISSN:0930-7516    

DOI:10.1002/ceat.270180402

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractFor the design, simulation and optimization of sulphur retention in atmospheric fluidized bed coal combustors, a mathematical model is needed that would be able to predict the behaviour of the combustor in a wide range of operating conditions. In this work, a sensitivity analysis of the sulphur retention predictions of the different hypotheses, equations and parameters, which define the different submodels and phenomena occurring in the combustor, has been carried out. It has been found that the hypotheses related to the gas flow, devolatilization type and sulphur distribution in the pyrolysis products imply an important division among models. The greatest effect on sulphur retention predictions is exercised by the parameters defining the fines elutriation and sorbent sulphation capacity. However, those corresponding to the bed hydrodynamics (minimum fluidization velocity and bed expansion) do not have a significant effect on the sulphur retention predictions.The sulphur retentions obtained in the combustion of high sulphur lignites with eight different limestones were used for model validation. A good fit of the experimental sulphur retentions was found, without using any adjustable parameter. Finally, a simulation of the process was made. The great effect of the bed height, air velocity and the particle size distribution of the limestone must be pointed out, as well as the effect of its reactivity through the maximum conversion attainable by each particle size.

ISSN:0930-7516    

DOI:10.1002/ceat.270180403

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe apparatus described allows successive TPR/TPO experiments on the same sample. A calibration method for the reducing or oxidizing gas mixture is described. The best operating conditions for optimal results and sensitivity are discussed. We have studied the application of TPR/TPO to bulk V2O5and to the redox behaviour of CuIIions on silica‐alumina. The procedure resulted in reproducible TPR/TPO profile

ISSN:0930-7516    

DOI:10.1002/ceat.270180404

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractIn this work a Sulzer structured packing, Mellapak 250Y, was studied for applications in the field of absorption. A new model was proposed which makes it possible to estimate the packing surface that actually takes part in the process. In the course of these studies, new experimental data were obtained relating to the absorption of 1,1,1‐trichloroethane using Genosorb 300, a mixture of polyethylene glycol dimethyl ethers produced by Hoechst S.p.A., as absorption liquid. The results obtained with the proposed model are in agreement both with the experimental measurements made in the course of the work and with experimental absorption measurements reported by other authors on water system

ISSN:0930-7516    

DOI:10.1002/ceat.270180405

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe efficiency of 6‐aminopenicillanic acid (6‐APA) production by enzyme‐catalyzed hydrolysis of penicillin G using penicillin G amidase (E. C. 3.5.1.11) immobilized in polyacrylamide gel can be improved by using a lower substrate concentration and an optimized low buffer concentration. In a continuous process the combination of a stirred‐tank reactor and a plug‐flow reactor gives optimum productivity. Since precipitation of 6‐APA is the crucial step in downstream processing, the product concentration has to be as high as possible. This can be achieved by concentrating the product solution by reve

ISSN:0930-7516    

DOI:10.1002/ceat.270180406

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractLarge quantities of sludge containing considerable amounts of zinc are obtained on treatment of waste water from the production of viscose fibres for textiles and industrial applications. A process has been proposed [7, 10] for the recovery of zinc from one such sludge, in the first step of which zinc is transferred to the liquid phase with liberation of hydrogen sulphide. In connection with this work a model was developed which provides a kinetic description of zinc liberation from various sludges and the parameters of this model fitted to the measured data by means of linear regression.

ISSN:0930-7516    

DOI:10.1002/ceat.270180407

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractEthyltert‐butyl ether (ETBE) is an alternative fuel oxygenate that can be produced in the liquid phase by addition of ethanol to isobutene catalyzed by sulfonic acid ion exchange resins. A generalized Langmuir‐Hinshelwood rate expression is formulated in terms of the liquid phase activities of the reactants that is quasi‐autocatalytic due to ethanol. This microkinetic model is combined with the generalized Maxwell‐Stefan equations for a detailed investigation of the influence of multicomponent mass transfer limitations inside the macropores of the heterogeneous catalyst. The model is used for revision of experimental rate data for ETBE synthesis in the literature. The analysis reveals that reverse diffusion of isobutene can occur by strong interaction with ethanol and the catalyst effectiveness factor can excee

ISSN:0930-7516    

DOI:10.1002/ceat.270180408

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractDeactivation kinetics and coke removal kinetics were derived from experimental studies on the disproportionation of ethylbenzene with a protonated Y‐faujasite (Z‐14) in a loop reactor under supercritical conditions. Derivation of the steady state kinetics of ethylbenzene disproportionation permitted determination of the catalyst activity. At small educt mole fractions of ethylbenzene, owing to the modest removal of coke the deactivation kinetics can be described by a power relationship. The rate of coke removal can be correlated with the activity and the deactivation rate of the catal

ISSN:0930-7516    

DOI:10.1002/ceat.270180409

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractAn experimental investigation in a tube wall reactor with catalyst‐coated inner wall is presented. Yields of formaldehyde of more than 70% can be obtained in the selective methanol dehydrogenation over alkalialuminate. Models for the reactor and the system of most important homogeneous reactions are derived. Different models describing the catalytic action are proposed. The results can only be explained by a new type of catalytic reaction, not described so far in the literature. Reducing gases like hydrogen and methanol lead to a volatilization of material from alkalialuminate which apparently catalyzes the dehydrogenation in the gas phase. Calculations and experimental evidence lead to the conclusion that this material should be sodium atoms. These are engaged in the homogeneous radical chain reaction by regulating the concentration of hydrogen atom

ISSN:0930-7516    

DOI:10.1002/ceat.270180410

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe determination of the composition of multi‐component mixtures is the basis by which a number of technical and physical problems in the field of power and process engineering are modelled. In order to calculate chemical states of equilibrium in the gas phase, a calculation method will be presented which is founded on a minimization of the Gibbs enthalpy. This method is characterized by a high reliability in convergency, considerable independence of starting vectors and by a moderate requirement for programming. These characteristics are achieved by a transformation of variables which results in numerically more favourable solutions to the non‐linear equation system. Calculated equilibrium compositions (including dissociation and ionisation) for a stochiometric mixture of hydrogen and oxygen in a temperature range of 300–12000 K and a pressure of 105Pa as well as the application of the method will be demonst

ISSN:0930-7516    

DOI:10.1002/ceat.270180411

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY