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The rates of carbon-steam (C-H20) and carbon-carbon dioxide (C-C02) reactions were studied in a laboratory fluidized bed with coke breeze over a temperature range of 920 to 1040 °C at 1013 kPa. Rate equations suggested by a simplification of the Langmuir-Hinshelwood rate expression and also Ergun's model for a fully back-mixed fluidized bed were developed for both reactions, with rate as a function of temperature and gas composition. The success of these equations in fitting gasification results affords some support for Ergun's model but not In all details, and no attempt is made to prove the detailed mechanisms for the reactions In the present study. The reaction rate was found to be independent of the particle size and the inert gas concentration. The variation of the reaction rate with carbon conversion was also studied. This study forms a basis for interpreting char reactivities to be used in projecting plant performance within the range of experimental conditions studied here.

The major parameters in the design of spray dryers are discussed. A Lagrangian approach, combining experimental data with theoretical concepts, is proposed to develop design methods. Vortex flow patterns, obtained experimentally in a laboratory size chamber, are correlated and presented. Based on this design methodology, computational methods are given to calculate droplet trajectories and hence to predict the optimum chamber dimensions and operating conditions for maximum thermal efficiency and/or minimum operating cost. Application of these basic principles is illustrated by the design of an industrial size, spray drying chamber for a specific feed solution and production rate.

Equations are proposed to predict the three‐dimensional motion of droplets in a spray dryer, based on a knowledge of the characteristics of the atomizing device and of the gas flow patterns in the drying chamber. If the droplet size distribution produced by the atomizing device is known or can be assumed, the trajectories of the droplets can be calculated throughout the drying process and hence the evaporative capacity and thermal efficiency of the spray dryer can be predicted. Experimental verification of this theoretical approach was obtained from a study of the drying of calcium lignosulfonate solutions of various concentrations in a 122‐cm diam. × 183‐cm high laboratory circular concurrent chamber with a conical bottom where the drying air was introduced tangentially near the top. An experimental study of the effects of a number of operating variables on the capacity and the efficiency of the spray dryer was also carried out. These effects were interpreted in terms of the droplet trajectories obtained in each case.

The flow of air through packed beds of solid and hollow particles of a wide range of geometries was studied, with particular reference to the effect of the particle shape on the pressure drop in the turbulent range. A method of analysis based on the concept of stagnant void fraction and the principle of drag additivity has been developed. Equations for estimating the stagnant voidages for various particle shapes arranged in a random pattern in a packed bed were derived. A new type of friction factor based on this approach was correlated satisfactorily with a shape factor. The momentum transfer data were also correlated with the sphericity of the particles. SCOPEPacked beds play a far greater role in many aspects of chemical and metallurgical processing than commonly realized. Simple in design, low in capital cost, and of rugged construction, they find application in a wide variety of operations such as absorption, drying, dust collection, separation, combustion, filtration, catalysis, and solid-fluid contacting in general. Their major operating cost is directly related to the pressure drop they create in the fluid-handling system. It is therefore surprising to note that the latter can be predicted with so little reliability when the particles in the bed depart somewhat from the spherical shape.The objective of this work was to investigate and correlate the effect of particle shape on the behavior of fluid flow through beds of solid and hollow shapes arranged in isotropic randomness in the turbulent range. To this end, a wider range of particle shapes has been investigated than has been hitherto reported in the literature and particular attention has been paid to the behavior of mixtures of particles of different ihapes and sizes.Numerous investigations were carried out in the past on momentum transfer through packed beds. Scheidegger (1961) critically reviewed the earlier models which have been proposed to account for the flow behavior through packed beds and porous media. Of these, the most widely used is the channel model, which envisages the packed bed as consisting of an assembly of tortuous conduits.Typical of this school is the correlation developed by Ergun (1952).At a very early stage, Burke and Plummer (1928) had proposed a discrete particle model which regards the system as consisting of an assembly of particles submerged in the flowing fluid, each possessing its own individual boundary layer. This approach was later expanded somewhat by Ranz (1952). Both models provide reasonably good pressure drop predictions for spheres or nearspherical shapes but are inadequate for particles of low sphericity.The next advance in the field was provided by Kusik and Happel (1962) who proposed yet another model, based on the consideration that the particle wake effectively decreases the area available for flow, thus creating stagnant regions in the fluid, of void fraction € b e Galloway and Sage (1970) reported the values of Eb for different particle shapes from available transport data on single particles and on pack...