Galore Knowledge Publication Pvt. Ltd

Galore Knowledge Publication Pvt. Ltd

Chemical Engineering Some Selected Reviews

The emission of gases such as sulphur dioxide, nitrogen dioxide cause of concern from ecological perspectives. These gases can be scrubbed off by using gas absorption and other techniques. Removal of sulphur from fuel can reduce the emission of oxides of sulphur. Coal is one major fuel resource in many sectors. Sulphur can be removed from coal by leaching, bioleaching, precipitation etc. Second chapter is about Bubble Column Rectors. A multiphase reactor involves two or more phases. Most of these reactions involve gas and liquid in contact with solid. In these reactors the reaction takes place on the surface of solid catalyst. In slurry reactor, gaseous reactant is bubbled through a solution containing solid catalyst particles. The contacting equipment for gas liquid reactor includes trickle bed(packed bed), packed bubble column, agitated slurry reactors, slurry bubble column reactor and fluidized bed reactors.It is followed by a review on RTD Studies for Reactors. Reactor design for ideal reactors with ideal flow patterns for plug flow and mixed flow reactors are very useful tools for analysis, design and operation.

Fourth chapter is about Methane Reforming. Methane is favorite source of hydrogen. Fuel cells can directly convert chemical energy into fuel. Steam reforming of methane (SRM ) is well established process to produce H2 for FC. It is followed by review on catalyst deactivation. In catalyzed reactions the catalyst lowers energy of activation. Catalyst increases rate of reaction. The deactivation of the catalyst can happen because of poisoning, coking or fouling and ageing. It is essential to know the mechanism of deactivation. The recovery of catalyst is widely investigated area of research because it has environmental and economical significance. Sixth review in the sequences is related to crystallization. For crystallization, supersaturation and temperature are two imporant factors. Crystallization finds major application in food and pharmaceutical industry.Many investigators have carried out research on crystal size, growth and structure, factor affecting crystal growth and other important aspects of crystallization

Seventh and eighth reviews are related to important aspects in chemical engineering such as fluidization and heterogeneous reactions. Fluidized bed offers advantage of uniform temperature distribution and excellent contact between particles. It has been tried for adsorption and chemical reactions. Heterogeneous reactions can be catalytic and noncatalytic. The catalytic reactions involes gas solid and solid liquid reactions. Kinetic modeling is important aspect from controllability and optimality point of view. 11th and 12thchapters are about mass transfer aspects such as tray towers and pressure swing adsorptions. Tray columns are the most important contact mechanisms along with packed columns. Easy cleaning, high liquid hold up, side stream flexibility are some advantages of tray towers over packed columns. The regeneration of adsorbents and recovery of valuable gases is an important aspect of the adsorptive separation. Temperature and pressure swing (TSA and PSA) adsorption uses change in temperature and pressure respectively for regeneration.

Last three reviews discuss important chemical engineering topics such as boundary layers, diffusivity and process control. The boundary layer formation plays major role in momentum, mass and heat transfer. The concept and understanding of boundary layer is important to know the transfer phenomenon in fluids. In flow past immersed bodies, the formation of boundary layer is predominant phenomenon. Formation of boundary layer and its thickness depends on roughness, velocity of flow and fluid properties. About diffusivity, the molar flux in molecular diffusion is divided into two parts. One is due to bulk motion and other is due relative speed of particle or molecule. Diffusion plays major role in applications such as drying, catalysis and many other chemical engineering applications. Diffusion through solid is classified as diffusion through porous solid, diffusion through polymers and surface diffusion. Depending on size of molecule, porous diffusion is classified as Fickian, Knudsen diffusion and transient diffusion. One of the key aspects of processes is optimization and process control. Various control objectives such as optimizing temperature, pressure, conversion, flow, level are met by using different types of control systems. Feedback, feed forward and combination as a control strategy. Various control systems such as proportional (P), proportional integral (PI), and proportional integral derivative control systems can be used according to requirements. Nowadays Fuzzy logic control system is considered promising in many applications because of its advantages.


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