The diffusion controlled corrosion of a cooling system composed of an array of vertical tubes attached to the inner wall of a fixed bed reactor containing plastic Raschig rings was studied by a rapid technique which involves the diffusion controlled dissolution of copper in acidified dichromate. Variables studied were solution velocity, Raschig rings diameter, vertical tube height and the presence of surface active agent. The present data were correlated by a dimensionless equation. The presence of surface active agents decreased the rate of mass transfer by an amount ranging from 7.5 to 36.2 depending on the operating conditions. Implications of the present results for the design and operation of built-in cooling systems of fixed bed reactors was highlighted. Also the possible use of the obtained equation in calculating the rate of heat transfer by analogy was discussed.
The aim of the present work is to combine TiO 2 /Graphene to increase photo-catalytic activity and obtain efficient removal of direct red 23 azo dye without difficult synthesis. Many operating variables which affect the process and some design aspects were studied. Reactor geometry is the main design parameter where slurry rectangular reactor and bubble column were compared with respect to hydrodynamic regimes, overall degradation efficiency and applicability in industrial scale. The removal rate was found to increase with increase in TiO 2 concentration, approaching a limiting value at catalyst loads of 3g/L. For rectangular reactor only 0.005g/L of rGO able to enhance the activity of photo-catalysis. However, the optimum concentration of rGO is decreased in the bubble column reactor to be 0.001g/L. In both reactor systems, photocatalytic activity increase significantly by decreasing wavelength of the irradiated lamp from 365 nm to 254 nm. Also, results show the ability of bubble column reactor to treat high concentrations of dye up to 200 ppm. That makes it suitable to be integrated with biological system to convert non-biodegradable contaminates into biodegradable organics. That reduces the operating cost of the process and makes it more applicable in industrial scale. Rectangular reactor has the ability to be modified to use sunlight instead of artificial lamps because of high surface exposed to sunlight. In general the performance of bubble column reactor was better than rectangular reactor because it has excellent mass transfer characteristics, which enhance the efficiency of the process.
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