摘要:

AbstractThe batch crystallization of potassium chloride from aqueous solution is investigated without impurities, with zinc chlorideI(30, 100, 1000 ppm), with sodium hexametaphosphateII(100 ppm) and potassium hexacyanoferrate (II)III(100, 500, 1000, 16 × 25 ppm). The dominant particle size of the pure systemLN, D= 427 μm increases by 40% by addition ofIand by 250% by addition ofII. WhileIdoes not affect the habitIIchanges it from cubes to octahedrons. In cases of low concentration,IIIleads to dendrites.It is shown that addition ofIIIdecelerates growth and increases the metastable zone width. Hence a high supersaturation is formed, the solution impoverishes fast whileIIIgets incorporated and therefore a strong nucleation starts in a relatively pure solution. By quasi‐continuously adding 16 × 25 ppm ofIIIthe dominant particle size increases by 160% with little fines. In this case the content ofIIIin the product is relatively

ISSN:0930-7516    

DOI:10.1002/ceat.270180502

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractA phenomenological approach to evaluating the agglomeration rate of growing crystals is presented. Crystals larger than the Kolmogoroff microscale collide because of the fluctuating velocity field. Bridges between the crystals form as a result of competition between crystalline growth and the turbulent velocity fluctuations on the opposite sides of the agglomerate.Crystals smaller than the Kolmogoroff microscale collide because of viscous laminar microshear stresses within the same turbulent eddy, are kept close together by Van der Waals forces and are joined together by crystalline bridges that grow between them. The strength of these bridges depends on the supersaturation level during the moments following the collision.These two sets of phenomena lead to two different preferential generation mechanisms for agglomerates. One example involving important agglomeration effects is developed for each case: the crystallization of adipic acid belongs to the first group (large crystals), whereas the precipitation of calcium oxalate monohydrate is typical of the second case (small crystals).

ISSN:0930-7516    

DOI:10.1002/ceat.270180503

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractWays, benefits and limitations of extracting the form and size of single latex particles or particle size distributions out of the surface topography of non‐coalesced latex films obtained by atomic force microscopy (AFM) are discussed. The general ways to generate the desired information out of topographical information in terms of height, surface curvature and lateral extensions are shown for idealized particles and measurement conditions. The different sources of information are evaluated for practical use and the analysis of particle size distributions is demonstrated by practical examples. The information content in lateral particle dimensions is shown to be the most advantageous for practical use.Determination of latex particle size distributions by AFM is shown to be an interesting alternative to the arsenal of available methods with respect to exactness of results, time consummation and instrumentation cost

ISSN:0930-7516    

DOI:10.1002/ceat.270180504

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe safe operation of a batch polymerisation reactor assumes sufficient knowledge about all the possible reactions. An investigation has been made in order to predict, with the aid of a mathematical model based on a detailed reaction mechanism, the runaway ability of a styrene batch suspension polymerisation reactor. The results of the simulation were compared with the experimental data obtained from a bench‐scale test cel

ISSN:0930-7516    

DOI:10.1002/ceat.270180505

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe performance of packed bed adiabatic gas absorbers has been analyzed using the enthalpy and material balance equations incorporating a new parameter,fr, defined as the fraction of the heat of absorption that is accounted for in the gas stream. An experimental programme to evaluatefrwas carried out and the data correlated. It was found thatfrwas dependent on the thermo‐physical properties and the hydrodynamic conditions. It is postulated that the mechanism by which this heat transfer occurs is by turbulence at the interface and by entrainmen

ISSN:0930-7516    

DOI:10.1002/ceat.270180506

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractIndustrial product quality control is a typical mathematical programming and optimization problem. Unfortunately, complete and precise models are not always available for many industrial processes. A fuzzy relation modelling approach is proposed to describe approximate relationships among system variables and reconcile empirical equations. Symmetric fuzzy decision‐making is transformed into a non‐linear function maximization problem. The approach is applied to optimization of a wood chip refining process. It is used either to improve pulp quality within the refiner operation range, or to reduce operation costs while maintaining an acceptable pulp qual

ISSN:0930-7516    

DOI:10.1002/ceat.270180507

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractNeural networks can be an attractive alternative to mathematical modelling of complex and poorly understood processes if input/output data can easily be obtained. Woodchip refining falls into this category. The mechanism of the refining process is still being studied and no thorough models have yet been developed. A feed‐forward neural network is proposed for modelling of woodchip refiners. The outputs predicted by the neural network are compared with industrial refiner data. It is also shown that a modified neural network structure can be used to optimize refiner operation and product quality. The advantages and disadvantages of neural network model application in simulation and optimization of industrial processes are discusse

ISSN:0930-7516    

DOI:10.1002/ceat.270180508

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractA high temperature coal pyrolysis reactor was developed and its operation demonstrated on a scale of 8 t/h. Pyrolysis is performed in a circulating fluidized bed reactor at 850–950°C. The developed process was integrated into smokeless fuel production technology and tested. Experimental data and reactor performance are present

ISSN:0930-7516    

DOI:10.1002/ceat.270180509

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe kinetics of methane pyrolysis were studied in a tubular flow reactor in the temperature range 1200 to 1500°C at atmospheric pressure. To avoid excessive carbon formation the reaction time was short and the methane feed was diluted with hydrogen. Ethene, ethyne, benzene and hydrogen were the main gaseous products. Ethane was observed as a product at very low conversions of methane. More than 90% selectivity was obtained for C2products. The ratio of ethyne to ethene increased with increasing temperature. The yield of C2products is limited by gas‐phase equilibrium at lower temperatures. Formation of carbon was strongly depressed by hydrogen at higher temperatures. The maximum yield of ethyne was found to increase from about 10% to about 50% when the temperature was increased from 1200 to 1500°C, with hydrogen dilution H2: CH4= 2: 1. A mechanistic reaction model was used to simulate the pyrolysis of methane at the actual conditions. A sensitivity analysis was performed to evaluate the elementary reactions which influence the formation and consumption of the species in the model sys

ISSN:0930-7516    

DOI:10.1002/ceat.270180510

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY

摘要:

AbstractThe thermal decomposition of hydromagnesite has been studied using thermogravimetric analysis. The experiments were conducted in a nitrogen atmosphere with pellets of hydromagnesite in the temperature range 300 to 550°C, and also with powder samples under non‐isothermal conditions at a heating rate of 10°C/min. It is found that the reaction proceeds in two stages: dehydration followed by decomposition. The dehydration reaction is controlled by external mass transfer whilst the decomposition reaction is controlled by both external and internal mass transfer. The activation energy for the dehydration reaction was found to be 2.67 × 107J/kmol. From the non‐isothermal analysis the activation energy for the decomposition of magnesium carbonate was found to be 1.62 × 10

ISSN:0930-7516    

DOI:10.1002/ceat.270180511

出版商:WILEY‐VCH Verlag    

年代:1995

数据来源: WILEY