Amer El-Hamouz

Effect of surfactant concentration and operating temperature on the drop size distribution of silicon oil water dispersion

The effect of sodium lauryl sulphate (SLES) surfactant and the operating temperature on the drop size distribution of a 350 cSt Dow Corning 200 series oil water dispersion was successfully studied. The dispersion was prepared in a standard 6 litres mixing tank at different impeller speeds. A measurement of the SLES critical micelle concentration (CMC) at 25°C was carried out. The interfacial tension of silicon oil water under various SLES concentration at a temperature range of 25 to 80°C was accomplished. Results showed that the interfacial tension of the silicon oil water decreased as the operating temperature increased and as the surfactant concentration increased. When the operating temperature was increased at the highest SLES concentration tested, a decrease of d 32 was observed. This was attributed to the possibility of hydration of the surfactant at high temperature. Same behavior was observed when measuring the drop size distribution at constant temperature but different SLES concentration. It was found that the mean drop size decreases with mixing time. Different slopes of the change of the median drop size with time were obtained for different SLES concentration. For the same concentration, the slope changes after 1 hour. The degree change of the slope is due to the change of interfacial area of the oil water as mixing time elapsed and the depletion of the surfactant concentration.

Computational fluid mixing for stirred vessels: progress from seeing to believing

Abstract Quantitative visualization of chemical processes and the consequent incorporation of images into process control loops was an idea that E.T. Woodburn et al. pioneered in mineral processing. This approach is based on the notion that many chemical processes possess intrinsic visual indicators which are otherwise difficult to instrument. Stirred vessels used as chemical reactors have the same potential to benefit from quantitative imaging, although, in this case, not just for control purposes but also as a powerful adjunct to model development and validation. This review outlines developments pursued at UMIST which seek to utilize image reconstruction modelling of mixing to interpret simple tracer diagnostic tests and thereby to predict chemical reactor behaviour under semi-batch operation. Progress from small two-dimensional axisymmetric networks-of-zones, through larger three-dimensional networks-of-zones to computational fluid dynamics predictions in full three dimensions are outlined. Problems requiring more advanced techniques and models to link macro-scale mixing to micro-mixing form a wide set of challenges for future research.

A new pair of reactions to characterize imperfect macro-mixing and partial segregation in a stirred semi-batch reactor

Abstract A new pair of reactions has been developed based on a first order decay (an internal clock) and a parallel second order diazotisation coupling reaction, represented by A → S and A+B → R. By adjustment of concentrations and pH, the pair of rate constants can be ‘tuned’ to various reaction speeds giving scope for assessing various rates of mixing and agitation. When B is added semi-batchwise to A, any region rich in A favours the decomposition reaction. Imperfect macro—mixing therefore leads to an increase in the less desirable by—product S. Experiments have been performed using different rates of stirring and different addition points (liquid surface or impeller). The pair of reaction show sensitive yield variations under these different mixing conditions. Quantitative interpretation of the experiments has been based on a networks—of—backmixed zones model, using networks of size (20×20)+(20×40) comprising some 1200 zones. Individual species concentrations in space are presented as sectional image reconstructions. The model helps the understanding of the experimental results and reasonable agreement is obtained.

HYDRODYNAMICS AND MASS TRANSFER OF TEXTILE VIBRATING-VALVE TRAYS

New types of vibrating-valve trays with textile valves were investigated to determine their optimal construction. Hydrodynamic and mass transfer measurements were carried out in a pilot plant with different vibrating-valve and conventional valve trays under identical experimental conditions. The total tray pressure drop (Δ P ), column efficiency (η), volumetric mass transfer coefficient ( K G a ) and pressure drop per theoretical tray ( Δp/N th ) were measured and compared. The high mass transfer rate, the low investment and operating costs, the corrosion and heat resistance make the vibrating-valve trays attractive for gas absorption and air cleaning in environmental protection.

Improvements of the Tensile Properties of Recycled High Density Polyethylene (HDPE) by the Use of Carbonized Olive Solid Waste

Recycling of plastic poses several concerns to manufacturers. The most important concern is the unpredictable of their mechanical properties (modulus of elasticity, tensile strength and ductility). Olive solid waste, an abundant material usually thrown into land causing harms to environment was mixed with HDPE plastic and used as a filling material. The mixture was fed to a house made extruder operating at different speed and temperature. Two carbon particle sizes range (less than 150 µm and 180–250 µm) were used. The effect of carbon contents from 0 to 10% wt/wt and operating conditions were tested on the mechanical properties of the recycled HDPE plastic. It was found that up to 5% wt/wt carbon of less than 150 µm resulted in a noticeable improvement of modulus of elasticity and tensile strength. The optimum value of modulus at carbon particle size 180–250 µm was found at 2.5 olive solid carbon content. Increasing screw speed was found to increase tensile modulus and strength of used plastic. This was related to melt viscosity and reduction in particle size. An increase in processing temperature was found to improve tensile properties up to certain point where degradation of polymeric matrix begins to occur and therefore tensile properties deteriorate.