Advances in Chemical Engineering 

About: Advances in Chemical Engineering is an academic journal published by Elsevier BV. The journal publishes majorly in the area(s): Process (engineering) & Combustion. It has an ISSN identifier of 0065-2377. Over the lifetime, 262 publications have been published receiving 8273 citations.

Combustion Synthesis of Advanced Materials: Principles and Applications

Abstract: Combustion synthesis is an attractive technique to synthesize a wide variety of advanced materials including powders and near-net shape products of ceramics, intermetallics, composites, and functionally graded materials. This method was discovered in the former Soviet Union by Merzhanov et al. (1971). The development of this technique by Merzhanov and coworkers led to the appearance of a new scientijc direction that incorporates both aspects of combustion and materials science. At about the same time, some work concerning the combustion aspects of this method was also done in the United States (Booth, 1953; Walton and Poulos, 1959; Hardt and Phung, 1973). However, the full potential of combustion synthesis in the production of advanced materials was not utilized. The scientijc and technological activity in thejeld picked up in the United States during the 1980s. The signijcant results of combustion synthesis have been described in a number of review articles (e.g., Munir and Anselmi-Tamburini, 1989; Merzhanov, I990a; Holt and Dunmead, 1991; Rice, 1991; Varma and Lebrat, 1992; Merzhanov, 1993b; Moore and Feng, 1995). At the present time, scientists and engineers in many other countries are also involved in research and further development of combustion synthesis, and interesting theoretical, experimental, and technological results have been reported from various parts of the world (see SHS Bibliography, 1996). This review article summarizes the state of the art in combustion synthesis, from both the scientijc and technological points of view. In this context, we discuss wide-ranging topics including theory, phenomenology, and mechanisms of product structure formation, as well as types and properties of product synthesized, and methods for large-scale materials production by combustion synthesis technique.

Mass-Transfer Measurements by the Limiting-Current Technique

Abstract: Publisher Summary Limiting-current density refers to the maximum rate at 100% current efficiency, at which a particular electrode reaction can proceed in the steady state. This rate is determined by the composition and transport properties of the electrolytic solution and by the hydrodynamic condition at the electrode surface. It has been observed that in many cases mass transfer is not the sole cause of unsteady-state limiting currents, observed when a fast current ramp is imposed on an elongated electrode. Major conditions for valid measurement and interpretation of limiting currents include reaction characterized by slow surface kinetics, progress of the electrode position reaction, use of low concentrations of the reacting ionic species in free convection studies. This chapter outlines the underlying principles, discusses the conditions of validity, and highlights some selected applications and basic features of the limiting-current phenomenon. The chapter also illustrates a synopsis of electrochemical mass-transfer theory, to the extent required for analysis of limiting-current conditions. Various complicating factors—migration effects, the choice of appropriate diffusivity values, unsteady-state conditions, current distribution below and at the limiting current, and the effect of formation of rough metallic deposits—in the interpretation of limiting-current measurements are considered.

The Formation of Bubbles and Drops

Abstract: Publisher Summary This chapter describes the single bubble formation at isolated nozzles both under constant flow and constant pressure conditions, though considerable work still needs to be done in the intermediate region where bubble size is highly influenced by resonance effects. The method of dispersion through submerged nozzles, slots, or holes is the simplest and hence the most common. It permits equipment of extremely simple design and leads to reasonably large interfacial areas. Some industrial operations involving bubble and drop formation are extraction, direct-contact heat exchange, distillation, absorption, sparger reactors, spray drying and atomization, fluidization, nucleate boiling, air lifts, and flotation. In all these operations involving bubbles and drops, three stages have to be studied: the formation of bubbles or drops, the movement of bubbles or drops through the continuous phase and possible coalescence therein, and the formation of the interface. Various factors that influence bubble size are experimental set-up, effect of orifice characteristics, chamber volume, submergence, surface tension of the liquid and the wetting properties of the orifice, liquid viscosity, liquid density, gas properties, effect of gas-flow rates, and effect of continuous-phase velocity. The two-phase theory of aggregative fluidization considers the bed to be made up of two parts: a particulate phase wherein the gas flow rate corresponds to that required for incipient fluidization and a bubble phase, which conveys the extra gas through the bed in the form of bubbles.

Multiscale modeling of gas-fluidized beds

Abstract: Numerical models of gas-fluidized beds have become an important tool in the design and scale up of gas-solid chemical reactors. However, a single numerical model which includes the solid-solid and solid-fluid interaction in full detail is not feasible for industrial-scale equipment, and for this reason one has to resort to a multiscale approach. The idea is that gas-solid flow is described by a hierarchy of models at different length scales, where the particle-particle and fluid-particle interactions are taken into account with different levels of detail. The results and insights obtained from the more fundamental models are used to develop closure laws to feed continuum models which can be used to compute the flow structures on a much larger (engineering) scale. Our multi-scale approach involves the lattice Boltzmann model, the discrete particle model, and the continuum model based on the kinetic theory of granular flow. In this chapter we give a detailed account of each of these models as they are employed at the University of Twente, accompanied by some illustrative computational results. Finally, we discuss two promising approaches for modeling industrial-size gas-fluidized beds, which are currently being explored independently at the Princeton University and the University of Twente.

Mass-Transfer Rates in Gas-Liquid Absorbers and Reactors

Abstract: Publisher Summary At the heart of the liquid-phase processes, gas scrubbing process, manufacturing of pure products, and biological systems, there exists the absorber or the reactor of a particular configuration best suited to the chemical absorption or reaction being carried out. Its selection, design, sizing, and performance depend on the hydrodynamics and axial dispersion, mass and heat transfer, and reaction kinetics. This chapter focuses on the subject of mass transfer with chemical reaction. It presents the techniques, results, and opinions on mass-transfer coefficients and interfacial areas in most types of absorbers and reactors. To study gas–liquid mass-transfer phenomena, it is convenient to consider steady-state situations in which the composition of the gas and the liquid are statistically constant when averaged over time in a specified region, such as a short, vertical slice of a tubular column or the entire volume of a single-compartment agitated vessel. Useful predictions have been developed for describing the behavior of complicated systems, using highly simplified models that simulate the situation for practical purposes without introducing a large number of parameters. The procedure differs depending on whether physical or chemical absorption is involved.