Chemical Engineering & Technology

The inclusion of a washcoat model into the classical 1D monolithic catalyst simulation in order to create a 1+1D model of the channels using a minimum of parameters is reviewed. A 1+1D model can provide insight into kinetic- and mass transfer-limited regimes when implementing the catalyst in an industrial setting and is able to simulate a layered washcoat consisting of different catalytic materials.

Different mass transfer models were evaluated on the basis of zinc extraction with the liquid ion exchanger di(2-ethylhexyl)phosphoric acid. Comparison of the models showed that the film model only allows an approximate calculation of the measured concentration-time curves, whereas both the penetration and the film-penetration model adequately describe the time dependence of zinc concentration.

A systematic optimization approach is presented considering the multiple feeds in a steam reformer unit that provides optimum use of off-gases in the hydrogen network. The steam reformer is associated to the feedstock and linear programming is applied. It is concluded that low-pressure off-gases should be sent to the steam reformer.

The potential of a mesoporous ordered silica impregnated with the heteropolyacid H₃PO₄·12WO₃·xH₂O (PW₁₂) was evaluated to produce biodiesel from the solid sludge from wastewater treatment plants. Catalytic performances were investigated in a microreactor setup under different experimental conditions.

Sugarcane bagasse was treated by acetylation to improve its abilities for wicking oil and for promoting biodegradation in saturated environments. Partially acetylated bagasse proved to be highly effective due to enhanced hydrophobicity and oil-wicking ability and could be applied for remediation of oil-contaminated environments with high water saturation and strong binding between oil and sediment.

A systematic procedure to integrate the heat exchanger network (HEN) simultaneously considering heat and flow exergy consumptions is described. The overall flow exergy consumption by the HEN is calculated by means of pressure drop correlation and stepwise optimization. The exergoeconomic analysis based on both heat and flow exergy consumptions can provide a whole perspective for proper energy use and design of HEN.

Two different numerical criteria are proposed for determining the critical impeller speed for complete dispersion in a liquid-liquid stirred reactor. The simulated critical impeller speeds are in good agreement with those from empirical correlations when a fixed droplet size is properly selected. This demonstrates that the presented modeling approach and numerical criteria are promising for predicting the dispersion characteristics of liquid-liquid stirred tanks.

Al₂O₃ was used to deposit a film on the surface of diatomite for the efficient removal of linear anionic polyacrylamide (APAM). FT-IR, XRD, and SEM results show that Al₂O₃ was successfully coated on the surface of diatomite. The resultant Al₂O₃-coated diatomite was utilized to treat wastewater, which contained APAM and suspended solid particles.

Microarray surfaces and spacers may affect the binding efficiency and quality between aptamers and their corresponding targets. Various surfaces modified with amino, epoxy, and aldehyde functional groups with short, middle, and long spacers of linear and branched type were investigated. Spacers fused to the terminal end of aptamers were tested and compared with spacers fused on microarray supports.

The change of the surface gradient during a mass-exchange process influences the gas-liquid bubbling layer formed on the trays. In order to evaluate the effect of surface tension on mass transfer, a possible expression of the Marangoni efficiency enhancement ratio by experimental distillation data obtained under identical hydrodynamic conditions is presented.

Benzoic acid as an essential ingredient in many commercial products is expected to be of globally increasing demand, and therefore, innovations in benzoic acid and sodium benzoate production are a key issue. An overall kinetic model for sodium benzoate synthesis in heterogeneous media was developed. The results could be applicable for thermokinetic research, food, and pharmaceutical industries.

Hydrothermal carbonization is an attractive process for converting biomass with high water content into different products. The requirements on the products, which may be soil improvement or substitution of lignite or carbon black, are opposed to biomass as a feedstock that has a very complex and variable composition.

The results of investigations on the emission of particulate matter from outdoor firework displays are presented. During these events, possibly harmful and toxic aerosol emissions were measured. The values were compared to data published in the literature and to common threshold values, giving a state-of-the art overview about possible hazards arising from outdoor firework displays.

For the optimal design of dividing wall columns (DWC), a multi-objective genetic algorithm with restrictions is considered. Additionally, a methodology is proposed for sizing the DWC. The proposed design methodology shows robustness and it allows obtaining an adequate set of optimal designs for complex distillation sequences.

Modeling of gas-solid turbulent flow in a spout-fluid bed is very difficult because of the flow fields including turbulent gas jet or spout, gas and solid recirculation and boundary layer flows. A 3D CFD-DEM simulation of gas-solid turbulent flow in a cylindrical spout-fluid bed with conical base is established by incorporating various gas-particle interaction models.

As a real alternative to traditional inorganic metal coagulants in the removal of dyes and surfactants the tannin-derived optimum coagulant from Acacia mearnsii de Wild is characterized. Theoretical modeling, pilot plant implementation, and the influence of significant variables are investigated. This novel coagulant exhibits functional working advantages that may encourage further researches.

Several approaches to the electrokinetic treatment of soil polluted with diesel fuel were evaluated. The use of surfactants as processing fluid was tested with the aim of increasing desorption and the solubility of diesel fuel, leading to improved removal by electroosmosis. Additionally, the EK-Fenton process was investigated as a method of promoting in situ degradation of diesel fuel.

Microwave heating (MH) and convective heating (CH) are compared in order to calculate critical efficiency factors of microwave energy conversion into thermal energy for different operating conditions. The calculated critical efficiency factors indicate when MH is more energy efficient than CV. A simple approach for evaluation of an efficiency factor is presented.

Fluid-dynamic characterization of an oxyfuel combustion pilot plant is performed using a cold flow model scaled according to the laws proposed by Glicksman. Pressure profiles and circulation rates are determined experimentally in the cold flow model. Based on measurements, the fluid-dynamic limits of the operating ranges are identified and can be extrapolated to the original hot pilot plant.

The stability of jets in elongational flow is exploited to obtain thin threads before breakup. Fine drops can be generated in suitable geometries with comparably large ducts. The examination deals with the stability of liquid threads simultaneously extended with the continuous phase in convergent flow. Breakup limits and regimes are discussed.