摘要:

AbstractStarting with a brief review of the development of the circulatingfluidbed (CFB) reactor principle, its main features as an important tool for efficient and thus environmentally acceptable processing of fine particulate solids, typically less than 150 μm diameter, are discussed. Various new industrial processes and high temperature process options starting with alumina calcination are described. Developing applications in the cement, metallurgical and chemical industries are approaching large‐scale industrial importance. Efficient combustion or pressure gasification of fossil fuels and carbon‐containing residues, fulfilling increasingly strict environmental legislation, is by far the most rapidly expanding field of application. In support of these developments our fundamental understanding of the fluid dynamics of CFB riser and of cyclone precipitation at high solid loadings has to be steadily improved. The reaction behaviour of aggregating fine particulate solids of varying size distributions also remains an open ques

ISSN:0930-7516    

DOI:10.1002/ceat.270180202

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe fluid flow in a filter chamber, consisting of a rotating disk and a stationary plate, has been numerically investigated. A proposed model provided acceptable predictions for shear rate and frictional torque in laminar and turbulent flow regimes. Owing to the pronounced effect of the shear stress on the filtration rate, the data obtained were used in analysis of the influence of hydrodynamics on the shear stress field in the filter chamber.

ISSN:0930-7516    

DOI:10.1002/ceat.270180203

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe modelling of pressures in silos has been attempted by numerous researchers using a variety of different methods. Starting with the work of Janssen, the slice element method, the method of characteristics, the finite element method and the method of granular dynamics are reviewed. Every model needs constitutive parameters which have to be found from experiments. A method to calibrate the more recent – and highly complex – constitutive models from general tests is presented. Besides the models for silo pressures, several models of flow in silos are conside

ISSN:0930-7516    

DOI:10.1002/ceat.270180204

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe octane enhancer tertiary amyl methyl ether (TAME) is produced by liquid phase synthesis from methanol and a mixture of isoamylenes, namely 2‐methyl‐1‐butene and 2‐methyl‐2‐butene, using a sulfonic acid ion exchange resin as catalyst. Three reactions take place simultaneously in TAME synthesis: etherification of the two methylbutenes and their isomerisation. In order to study the equilibrium of the multiple reactions in TAME synthesis, the thermodynamic properties of the compounds in the liquid phase and equilibrium constants were calculated using a modified UNIFAC method to describe the nonideality of the system. Four parameters influencing the equilibrium conversion were derived and discussed in detail. Supplemental experiments were performed at three temperatures in the range from 303 to 343 K and at different initial molar ratios of educts. Equilibrium conversions of methanol were determined from these experiments and compared with calculated values. At 298 K the predicted activity based equilibrium constant was 22.9 for TAME synthesis from 2‐methyl‐1‐butene and 1.6 for TAME synthesis from 2‐methyl‐2‐butene; for isomerisation of 2‐methyl‐1‐butene to 2‐methyl‐2‐

ISSN:0930-7516    

DOI:10.1002/ceat.270180205

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe effect of Cl−ion addition to a Li+‐ZnO catalyst has been studied with respect to the oxidative coupling of CH4and the oxidative dehydrogenation (OXD) of C2H6. Increasing the Cl/Li ratio from 0.65 to 0.90 had relatively little effect on the CH4conversion, whereas the C2H4/C2H6ratio was enhanced significantly as a result of an increase in the OXD reaction rate. Conversely, loss of Cl−from the catalyst during the reaction had a much more deleterious effect on ethane OXD activity than on methane coupling activity. Addition of Cl−ions at a Cl/Li ratio of 0.9 caused a decrease both in the number of basic sites and in the basic strength of these sites, as determined by temperature‐programmed desorption of CO2. The similarities between the results obtained over Li+‐ZnO‐Cl−catalysts and those previously reported for Li+‐MgO‐Cl−catalysts confirm that basicity of the host oxide plays only a minor role in determining the properties of thes

ISSN:0930-7516    

DOI:10.1002/ceat.270180206

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe hydrogenation of CO over supported cobalt catalysts has been studied using in situ FTIR spectroscopy and gravimetry atP= 6 bar,T= 473–723 K and H2/CO = 2–3. On both silica‐ and alumina‐supported catalysts IR absorption bands corresponding to linearly adsorbed CO on metallic cobalt were observed. On alumina an additional pair of bands at lower frequencies was attributed to bridge‐bonded CO. Absorption bands corresponding to adsorbed hydrocarbons (3050–2700 cm−1) and to oxygen containing species (1800–1200 cm−1) were found to correspond to adsorbed products or unreactive species. The gravimetric studies showed a significant difference between the supports. On the silica‐supported catalyst the weight uptake decreased with increasing temperature (473–573 K). The weight increase during reaction was attributed to adsorbed hydrocarbon reaction products. On the alumina‐supported catalyst the weight uptake increased with increasing temperature, and there was also a significant weight increase with the support alone. Most of the weight uptake can be attributed to the formation of stable formate and carbonate species on the alumina support. At 723 K the deposits formed were stable in H2, and the shape of the curves indicated different mechanisms for deposition of material. In particular the Co/Al2O3sample showed a very high and linear rate of weight gain, which was an order of magnitude higher tha

ISSN:0930-7516    

DOI:10.1002/ceat.270180207

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractResults are reported for the oxidative coupling of methane on silica‐supported alkaline earths prepared from either their acetates or chlorides with and without alkali metals as dopants and in the absence or presence of carbon tetrachloride (TCM). The addition of small quantities of TCM to the methane feedstream produces increases in the conversion of methane and the selectivities to C2hydrocarbons which correlate with the increase in cation size and thus are inversely related to the polarizing abilities of the cation

ISSN:0930-7516    

DOI:10.1002/ceat.270180208

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractA solid state electrochemical reactor is described in which reactants can be oxidised at high temperatures over an anode/catalyst using co‐fed oxygen gas as well as electrochemically supplied oxygen. The setup permits injection of isotopic pulses in the reactant streams. The composition and isotopic distribution in the products are recorded with a quadrupole mass spectrometer. The use of the system is exemplified by oxidation of methane over a Au + SrFeO3−δ//YSZ anode at 800–850°C. Pulses of18O2in the stream of co‐fed O2were used to study the reactivity and products of gaseous oxygen as distinguished from the electrochemically supplied oxygen. The results indicate that the anode used supports oxygen pumping, but is only moderately active for methane oxidation. The products are mainly CO and CO2. The content of18O in the products is low, indicating that methane oxidation takes place by16O‐rich lattice oxygen. In comparison, a reference Au//YSZ electrode was found to be a slower anode for oxygen pumping, but a better catalyst for the reaction between CH4and gaseous O2, seemingly involving adso

ISSN:0930-7516    

DOI:10.1002/ceat.270180209

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

ISSN:0930-7516    

DOI:10.1002/ceat.270180201

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY