Chemical Engineering & Technology

The hydrodynamic and mass transfer characteristics of a novel tray with SiC ceramic foam (SFCT) are studied in different pilot plants. The SFCT provides better performances compared to the conventional F1 float valve tray. The corresponding mathematical relationships are evaluated to predict the hydrodynamic properties of this kind of novel distillation tray and the mass transfer efficiency results are discussed.

The recovery of nickel and cobalt present in spent NiMH batteries was performed by electrowinning. A two-compartment cell separated by an anionic membrane was constructed to avoid the usual problem of a laborious and reagent-consuming pH control. The results demonstrate the technical viability of this cell regarding current efficiency improvement, thereby recovering nickel and cobalt in an effective way.

Reaction kinetics and potential applications of carbon dioxide-binding organic liquids, a novel class of carbon dioxide capture solvents, are discussed. An analysis of the rate constants and activation energies of the reaction between carbon dioxide and the diazabicycloundecene/1-alkanol solutions is reported.

An analytical model, based on an equilibrium orbit concept, for calculating the separation efficiency of uniflow cyclones for the separation of solid particles from gases is proposed. The model predicts the main tendencies of the separation efficiency as a function of geometry and operation data. Its application to uniflow cyclones operated in test facilities indicates good agreement with experimental data.

A two-fluid 1D transient mathematical model to design a drying operation control was developed, validated with data from PVC drying in an industrial continuous fluidized-bed dryer, and applied to simulate responses to disturbance on the PVC moisture content at the dryer inlet. The drying operation could be predicted satisfactorily by this model which due to its simplicity enables fast responses to disturbances in the process.

The stability of immobilized Candida sp. 99–125 lipase was investigated. The lipase shows excellent stability in the biodiesel reaction medium. Methanol and glycerol showed the most negative effects on the lipase stability. Desorption was the main reason leading to lipase inactivation in the water system.

The performance of a pilot-scale solar reactor was compared for plug flow and mixed flow based on experimental results. Aqueous phenol solutions served as a model for industrial wastewater containing organic contaminants. Batch experiments carried out under clear sky achieved high removal rates. The dissolved organic carbon removal rate was simulated by an empirical model on the basis of neural networks.

A new type of tube with staggered twisted tapes with central holes is presented. Heat transfer and pressure performance of the new tube with the modified twisted tapes are investigated numerically. The criterion of the thermal-hydraulic performance is used to evaluate the heat transfer and pressure drop performance of the tube with staggered twisted tapes with central holes.

The utilization of CO₂ to industrially relevant products presents a major challenge. By use of ceria-based catalysts, carboxylation of methanol with CO₂ is possible up to equilibrium yields of dimethyl carbonate. A variation in reaction parameters and investigation of the catalyst properties can provide an insight into the catalyst's activity. Such activities are studied both in gas and liquid phase.

The o-xylene combustion in air over a Pt/γ-Al₂O₃ catalyst was studied under conditions typical for depollution applications. A kinetic model based on the Langmuir-Hinshelwood mechanism is formulated, accounting for the experimentally observed negative influences of o-xylene and water concentrations on process kinetics. The reliability of the proposed model is demonstrated by comparing its predictions with measurements.

The lowest heat treatment conditions required for the completion of the polycondensation of sol-gel derived hybrid silica particles prepared from vinyltrimethoxysilane and vinyltriethoxysilane were determined. The completion or incompletion of the polycondensation of the samples was evaluated using several instrumental methods in addition to light scattering tests.

The axial and radial velocity profiles in a filter bag have been experimentally measured under different loading conditions to verify the hypothesis that the local velocity through the filter elements depends on dust loading. The axial velocity is also modeled using a simple approach and compared to the experimental results. The actual velocity profile depends on the cake area load on the object bag as well as on its neighbors.

Pyrolysis is one of the promising routes for converting biomass into energy. The downer reactor offers significant advantages over conventional fluidized-bed reactors. The pyrolysis behavior of wheat straw is investigated in a bench-scale circulating fluidized-bed downer reactor to elucidate the effects of acid treatment on the pyrolysis product distribution and product properties.

Extraction of gold in a solution of n-heptane and synergistic extractants was studied using a membrane extractor consisting of the tube side, the membrane, and the shell side. Simulation results showed that increasing the feed flow rate reduces the extraction efficiency, while doing the same for the organic phase flow rate does not change the extraction efficiency.

The catalytic performance of a ZnO-Al₂O₃ catalyst for dimethyl carbonate (DMC) synthesis from methyl carbamate and methanol in a fixed-bed reactor was evaluated. DMC could be effectively synthesized by stripping off NH₃ from the reaction zone which simultaneously minimized the side reactions. The catalyst prepared by coprecipitation presents high stability and a DMC yield of ∼ 73 % could be achieved.

Copper hydroxy-phosphate, Cu₂(OH)PO₄, was synthesized through a hydrothermal route and the resulting hierarchical superstructures were characterized. The morphology of Cu₂(OH)PO₄ was found to change drastically with the addition of alcohol (ethanol, n-propanol, or ethylene glycol) as solvent. A possible mecha-nism for the formation of these copper hydroxyphosphate hierarchical superstructures is proposed.

Ni-MgO is a promising catalyst for methane steam reforming due to the high stability of the NiO-MgO solid solution formed in this catalyst. The high activity and stability of the catalyst coated on a metallic monolith are demonstrated for methane steam reforming working at 700 °C and a steam-to-carbon ratio as low as 1.5, thus enabling more energy-efficient reforming processes for hydrogen production.