Chemical Engineering & Technology

In many grinding processes, wet-operated mills are used. An approach was derived to simulate a wet mill using a modified contact model in a discrete-element method. The model was compared with bead-bead simulations. The calculated bead movement could then be used to compute stress energy distributions. The gained results show that this approach is a possibility to calculate a wet-operated mill.

Flow fields in a straight, an orifice, a z- and a y-microchannel were investigated. Stationary particle tracking leads to the acting stresses. These stresses (tensile, shear, turbulent and compressive stress) are compared with the results of previously conducted dispersion experiments. Distributions of stresses and particle sizes were compared. Good agreement was found between experiments and simulations, but the predominant mechanism could not be identified.

Colloidal drug particles can be produced by wet-media milling using charged nanoparticles to enable drug particle stabilization. Such stabilization was facilitated using dissolved nonionic polymer molecules and highly charged nanoparticles. The general applicability of charged nanoparticles for colloidal drug stabilization combined with an industrially relevant production technology is demonstrated.

The reliability of the grindability test according to Zeisel is affected by a number of influencing parameters but also by the applied measurement techniques. The precise measurement of the grinding work by a load cell is introduced which replaces the traditional measurement by a protractor. Vibration during the test could be reduced and detailed data of the energy consumption could be obtained.

Using laboratory scale trials the influence of media density and friction coefficient on energy consumption in a M4 laboratory scale IsaMill™ is demonstrated for a number of ceramic media in a water environment. The experiments lead to a better understanding of the effect of media properties on the power draws.

The hydrodynamics of the fungi system Beauveria bassiana has been experimentally evaluated for different conditions in a mixing tank with a two-impeller configuration and Newtonian as well as non-Newtonian model fluids. Numerical simulations are essential to understand and optimize these systems. The simulation of streamlines for a radial-axial Rushton-Maxflo impeller configuration is presented.

Supported ionic liquid phase (SILP) catalysts consist of a homogeneous catalyst that is dissolved in an ionic liquid and dispersed on a porous support material. A novel preparation method for SILP catalysts is presented that is scalable for larger batches, as required for industrial use. Different types of support materials such as powders, spheres, agglomerates, and extrudates were successfully impregnated by the novel fluidized-bed impregnation method. The distribution of the ionic liquid and catalyst was analyzed by SEM-EDX.

Ilmenite has been found to release gas phase O₂ during chemical-looping combustion experi-ments. The phenomena manifested itself as an O₂ concentration of 1.0–1.5 vol. % when fluidizing the air reactor with air and the fuel reactor with steam. The O₂ release is small, but due to the presence of steam as fluidization medium, considerable O₂ concen-trations could be obtained if analyzed on dry basis.

Gas hydrate formation in natural gas and in the ternary gas mixture of CH₄, C₂H₆, and C₃H₈ was performed with a fixed amount of water with and without the addition of porous media. The addition of colloidal silica media increased substantially the gas storage capacity of the hydrate phase. The purification factor of CH₄ became significantly higher in the presence of silica-based porous media.

Computational fluid dynamics (CFD) simulations and experimental studies were developed in order to analyze the pressure drop through two eccentric annuli with variable eccentric motion of the inner cylinder, using xanthan gum solutions. The effects of four important operating variables were quantified. The comparison between CFD simulations and experimental data indicated a very good agreement.

The effects of temperature on the synthesis of 1,1-dibutoxyethane (DBE) in a fixed-bed adsorptive reactor were studied by performing both adsorption/desorption and reaction/regeneration experiments at 15 and 35 °C. Isothermal and nonisothermal mathematical models were used to simulate the reactor operation with different Damköhler numbers. The simulated results suggest that the reactor productivity can be improved by using the adiabatic operation mode on the fixed-bed adsorptive reactor.

The effects of fluidizing and pressurizing gas flow rates on the pneumatic conveying characteristics in a top discharge blow tank pneumatic conveying system were discussed. Pulverized coal and glass beads were used to investigate the influence of powder properties on conveying performance. Powder flow patterns in the tank were evaluated under different operating conditions.

The process of Fe(III) adsorption from water was modeled and optimized by means of multilayer perceptron (MLP) and central com-posite design (CCD). Bentonite clay was applied as a cheap and effective adsorbent. Compared with CCD, MLP proved to be a better tool for prediction of the adsorbed amount of Fe(III) from water and provided the best perfor-mance. The optimal adsorption conditions for both models were determined.

Thermo-responsive composite polyethersulfone (PES) membranes blended with monodisperse homogeneous poly(N-isopropylacryl-amide) (PNIPAM) nanogels were prepared from blends of PES solution and PNIPAM nanoparticles by phase inversion technique. The membranes exhibit satisfactorily reversible and reproducible thermo-responsive permeation performance.

Experimental work and the corresponding scale-up are presented to overcome the challenge of removing volatile siloxane compounds in a complex exhaust air from a synthesis process of an active pharmaceutical ingredient. The capability of 96 % H₂SO₄ for the removal of hexamethyldisiloxane from an exhaust air on a technical scale is presented.

H₂S decomposition into its constituent elements H₂ and S in a nonthermal plasma dielectric barrier discharge reactor has been investigated. Based on the Michaelis-Menten/Langmuir Hinshelwood model, a reaction rate model for H₂S decomposition was developed confirming that the reaction order approaches zero with increasing inlet concentration.

A fluid-dynamic cavitation model for reciprocating positive displacement pumps could be verified and established by means of high-speed particle image velocimetry (PIV) measurements. The PIV results demonstrate that the proposed model corresponds with the physical reality. It offers an excellent possibility for manufacturers to predict a limit for the extent of occurring cavitation in fluid handling.

A series of biodegradable polymer microspheres was prepared by solvent evaporation. The dimension of these microspheres was found to be depending on fluid-dynamic parameters of the dispersion process. The polylactic-co-glycolic acid microspheres obtained in this way may be applied for fabrication of biodegradable scaffolds for tissue engineering.

In the mining industry, grinding media wear versus cost is a key optimization consideration. Quantification of wear can be done indirectly via small-scale laboratory mill tests or potentially via measurement of the physical and mechanical properties of the media. The importance of hardness and toughness of grinding media in the stirred-mill environment are explained.