摘要:

AbstractUsing pilot‐scale test plant, the interfacial area per unit volume was investigated in different gasliquid reactors, i.e. packed column, bubble column and free jet reactor. The interfacial area was studied as a function of liquid viscosity and of operating parameters. As a rule, identical test conditions were maintained in all the measurements, in order to obtain comparable results. The interfacial area was determined by chemical means using the sulphite system (a solution of sodium sulphite in water as model liquid and air as gaseous medium). The viscosity of the solution can be increased by adding carboxymethyl cellulose without significantly affecting the reaction kinetics. The addition of a surfactant to the sulphite system allowed comparative measurements at reduced surface tension. Based on a large number of measurements, the correlations of the interfacial area are expressed as power laws. The inclusion of experiments with a jet tube reactor and a stirring vessel allows an extensive comparison of all reactors. All tests were carried out with the same material system and the same method was used to determine the interfacial area per unit volume. Therefore, a comparison with respect to mass transfer is possibl

ISSN:0930-7516    

DOI:10.1002/ceat.270100102

出版商:WILEY‐VCH Verlag    

年代:1987

数据来源: WILEY

摘要:

AbstractAlthough carbon dixoide is important as an abundant carbonaceous raw material, so far, its utilization in chemical processes has been rather limited. This review covers the reactions of CO2employed in industry, such as the production of urea, the Kolbe‐Schmitt reaction, the synthesis of cyclic organic carbonates and the use of CO2in methanol synthesis. Interesting recent developments in CO2chemistry, such as the reactions catalyzed by transition metals, are also described. Apart from the synthesis of polymers and hydrocarbons, the production of oxygen‐containing substances appears to be very profitable and attractive for future industrial applications. Not only can derivatives of formic and carbonic acids be produced but also longer‐chain carboxylic acids and their derivatives by reactions of carbon dioxide with hydrocarbons such as alkynes, alkenes and1,3

ISSN:0930-7516    

DOI:10.1002/ceat.270100103

出版商:WILEY‐VCH Verlag    

年代:1987

数据来源: WILEY

摘要:

AbstractA new measurement method for determining the local liquid‐phase velocities in multiphase flows is presented. It is based on a tracer technique, using heat introduced into the flow, seemingly at random, instead of a material tracer. The input of heat pulses and measurement of temperature at an adjacent point is performed by small probes. As an intermediate result, the flow time distribution of the heat‐labelled fluid elements is calculated on‐line as a cross‐correlation function between the pseudo‐random input and the measured output signals. This calculation and the automatic control of measurements is carried out by a simple microprocessor unit. The device produced excellent results in gas‐liquid flows at high gas throughputs and high liquid‐pha

ISSN:0930-7516    

DOI:10.1002/ceat.270100104

出版商:WILEY‐VCH Verlag    

年代:1987

数据来源: WILEY

摘要:

AbstractAll the present experiments confirm that there is some liquid channelling on trays. Liquid channelling is extensive on trays of large diameters. It largely depends on the tilting of the plate, modifications of the inlet weirs and on non‐uniform bubble cap spacing. Consequences of liquid channelling for plate efficiency are clear; the higher the degree of liquid channelling the lower the plate efficiency. However, own experimental and theoretical investigations indicate that plate efficiency never falls below the value of point efficiency. Therefore, liquid channelling only affects the crossflow on trays. Liquid channelling reduces the mass transfer performance to a similar extent as does the backmixing of liquid. Consequently, plate efficiency is not very sensitive to liquid channelling. Since the liquid is completely mixed in the downcomer, the effects of liquid channelling are restricted to a single tray. The behaviour of tray columns completely differs from that of packed columns, where the effects of liquid channelling are cumulative over the packed height. Consequently, trays represent a suitable design for columns of large diameter

ISSN:0930-7516    

DOI:10.1002/ceat.270100105

出版商:WILEY‐VCH Verlag    

年代:1987

数据来源: WILEY

摘要:

AbstractThe present contribution illustrates a way of developing a continuous separation process for near critical fluid extraction, on the example of separation of soya oil from lecithin. First, a suitable solvent was selected. Phase equilibria were measured in autoclaves. Operating conditions for a pilot plant were derived from the phase equilibrium data. The pilot plant experiments provided the necessary data for designing a production plant. Computer programs for phase equilibrium, stage to stage and mass and heat balance calculations were used in order to minimize the number of experiments. A production plant with a capacity of 500 t/a of raw lecithin was designed on the basis of experimental and computational results. A cost estimation, based on tenders, showed that it is more economical to produce lecithin by near critical fluid extraction than by conventional acetone extraction.

ISSN:0930-7516    

DOI:10.1002/ceat.270100106

出版商:WILEY‐VCH Verlag    

年代:1987

数据来源: WILEY

摘要:

AbstractThe oxidation of carbon monoxide by air in a turbulent flow was investigated under experimental conditions where the rates of turbulent mixing and of chemical reaction are comparable. For this purpose, carbon monoxide was admixed into the completely burnt gas of a natural gas flame operated with excess of air. Measurements of mean values of axial velocity, temperature and volume fractions of carbon monoxide and oxygen were compared with computational simulations involving thek– ϵ turbulence model and several turbulent reaction models for the oxidation of carbon monoxide. The comparison of measurements and numerical calculations demonstrated that thek– ϵ turbulence model is suitable for prediction of the turbulent flow field in the flow system investigated. Furthermore, it could be shown that one‐variable turbulent reaction models, such as the flamesheet or the eddy‐break‐up model, cannot explain the measured carbon monoxide volume fraction profiles. Two‐variable turbulent reaction models with a probability density function closure of the source term of the transport equation for the mass fraction of the chemical species result in a better agreement between the measured and simulated volume fraction profiles, particularly in predicting the clear influence of the initial temperature on carbon monoxide volume fractions. Weighting of the kinetic rate expression for the oxidation of carbon monoxide with different presumed probability density functions yields slightly different predictions of the carbon monoxide volume fractions, reflecting the assumed different character of turbulent

ISSN:0930-7516    

DOI:10.1002/ceat.270100107

出版商:WILEY‐VCH Verlag    

年代:1987

数据来源: WILEY

摘要:

AbstractIdeal flow conditions are generally assumed for the reactor design. If stoichiometry, reaction mechanism and kinetics are known, the balance equations for the ideal flow tube, the ideal steady‐state continuous stirred tank reactor or the ideal, completely mixed stirred batch reactor are often applied. In many cases, formal kinetics, which forms the basis of reaction modelling, is so uncertain that the idealization of the flow field can be accepted. In practice, however, deviations from the ideally calculated conversions, yields and product qualities, often occur. In these cases, it is necessary to consider the real flow conditions. In general, a distinction is made between macroand micromixing processe

ISSN:0930-7516    

DOI:10.1002/ceat.270100108

出版商:WILEY‐VCH Verlag    

年代:1987

数据来源: WILEY

摘要:

AbstractAmong other processes, adsorption is used for the removal of hydrogen sulphide from natural gases. Hereby, competitive adsorption of the different gas components plays an important role, e.g., that of carbon dioxide. Data of equilibrium loading and adsorption kinetics are required for the design of adsorbers, filled with molecular sieve. In order to obtain these data under the prevailing operating conditions, hydrogen sulphide was removed from gas mixtures H2S/CH4and H2S/CO2/CH4, in a pilot plant, by adsorption on molecular sieve 5A. The equilibrium loading, the height of transfer zone, and the length of unused bed were determined from the measured breakthrough curves of H2S. With these data, the breakthrough time and the optimum process conditions were calculated for a practical example.

ISSN:0930-7516    

DOI:10.1002/ceat.270100109

出版商:WILEY‐VCH Verlag    

年代:1987

数据来源: WILEY

摘要:

AbstractAs a part of a research project on the mass transfer in liquid pulsed sieve‐tray extraction columns (PSE), the diameters and hold‐ups of the drops were measured: the drop size using a suction technique, with photoelectric detection, which was adapted to the special boundary conditions of the PSE; the integral hold‐up by the pressure difference between the lower and upper parts of the column. Since experimental results cannot be described by known calculation formulae for the Sauter mean diameter and the hold‐up, a new method of calculation was developed. It is phenomenologically based on high‐speed photographs of the drop motion on a sieve tray. The mathematical‐physical model allows the prediction of drop size and hold‐up within certain limits, while the possible different operating regimes of the PSE, i.e. the mixer‐settler and dispersion regimes can al

ISSN:0930-7516    

DOI:10.1002/ceat.270100110

出版商:WILEY‐VCH Verlag    

年代:1987

数据来源: WILEY

摘要:

AbstractThe Carman‐Arnell equation relates the rate of flow of a fluid through a packed bed to the pressure drop across the bed. This equation is the basis for surface area determination by permeametry. It is found that the surface area measured at sub‐atmospheric pressure varies with the bed porosity, so a porosity was selected where the rate of change was at a minimum. The study suggests that, at reduced pressures, the gas flow rate is a linear function of the mean press

ISSN:0930-7516    

DOI:10.1002/ceat.270100111

出版商:WILEY‐VCH Verlag    

年代:1987

数据来源: WILEY