Chemical Engineering & Technology

Microbial fuel cells (MFCs) are a promising technology for the production of electricity from waste-activated sludge (WAS). A critical review on recent progresses in MFCs powered by WAS summarizes related publications on MFC reactor designs, MFC performan-ces, and sludge degradation efficiencies. Challenges and corresponding enhancement measures of MFCs applying WAS as fuel are discussed as well.

Copper cementation is a useful technique for the recovery of copper from a variety of waste solutions. Here, copper cementation on iron substrates in batch process was investigated. Various parameters played a major role on the yield of copper-iron cementation. A statistical full factorial design was carried out and optimization studies were done.

A mathematical model for the formation of CO₂-hydrate in sand sediment is proposed for sub-seabed geological storage of CO₂ in the form of gas hydrate, considering gas diffusion through the CO₂-hydrate film and the presence of a fresh reaction interface. CO₂-hydrate formation was numerically simulated by solving a heat transfer equation.

A cost-effective optimization design of the boil-off gas (BOG) reliquefaction process for liquefied ethylene vessels is proposed. The performances of the reliquefaction system and refrigeration cycle are investigated based on the exergy analysis. The exergy efficiency of the improved refrigeration cycle is significantly increased as well as the energy utilization efficiency of the BOG reliquefaction process.

Modeling equations were developed theoretically for the temperature distribution and temperature polarization profiles in a laminar concurrent-flow parallel-plate direct-contact membrane distillation (DCMD) module. The feed velocity effect on the temperature profiles and average Nusselt number was examined. Good agreement between the experimental results and the theoretical predictions was achieved.

A method based on experimental breakthrough curves for quickly evaluating adsorbents for a defined separation in terms of selective volume, capacity, selectivity and productivity is demonstrated under the conditions of the Parex process. Fixed-bed experiments are carried out in order to assess a barium-exchanged faujasite-type zeolite as adsorbent for the separation of p-xylene from its isomers.

The potential of a model based process design is demonstrated. Hereby, it will be shown that the sum of the single optima of each unit operation is not equal to the total process optimum. Using the example of a combined chromatographic two-step separation the resulting benefits will be pointed out.

Maximum specific growth rate and succinic acid production could be increased by reducing the salt concentration, optimizing the organic nitrogen source and adjusting the pH. In fed-batch experiments, the final succinic acid concentration was 25.6 % higher compared to the reference. Furthermore, the results indicated that A. succiniciproducens consumes only organic nitrogen.

The transient period of water evaporation and drying of different solutions was studied to describe the fluid dynamic behavior of a vibrofluidized bed operating with inert particles. The pressure drop and air velocity on the bed were investigated as function of the amplitude, frequency, and dimensionless vibration number.

The Sauter mean drop sizes of the dispersed phase in a three-stage modified Scheibel extraction column with no mass transfer were investigated. A precise correlation with operation conditions and system physical properties applied to liquid-liquid systems with low interfacial surface tension was proposed for calculating the dispersed-phase mean drop size.

A modified approach is proposed to improve the accuracy of CGCC generation. For the feed stage treated as a stripping (or rectifying) section stage in the existing top-down (or bottom-up) approaches leading to ambiguity at the feed stage, new calculation equations for the f-1^th and f ^th stage are formulated and an indicator is defined and used to evaluate these approaches.

Equilibrium conversion and product selectivity in methane dehydroaromatization is strongly influenced by reaction conditions. The use of common coke-removing agents such as steam and hydrogen severely impact the equilibrium methane conversion and/or product selectivity rendering this approach unsuitable to cope with the main technical problem of the process, namely coke formation.

Gas permeation through a membrane was analyzed by comparing three combinations of a mass transfer model with a thermodynamic model. The differences among the three model combinations increase with gas solubility. Among the considered model combinations, Maxwell-Stefan equation with the UNIQUAC equation gives the least prediction deviation.

The effects of reactor configuration and operation conditions on mass transfer performance were investigated in a new medium-sized rotating-drum bioreactor (RDB). Compared with the stirred bioreactor and traditional RDBs, the novel bioreactor exhibits a better mass transfer performance. An empirical correlation to predict the volumetric mass transfer coefficient is proposed for the design of a bioreactor.

A comprehensive investigation of the catalytic hydrogenation of cumene hydroperoxide in cumene over a Pd/Al₂O₃ catalyst is presented, including the effects of residence time, reaction temperature and H₂ pressure on conversion and catalyst deactivation. Attempts are made to simulate the performance of operating conditions with kinetic models.

For hydrogen production by methanol steam reforming, Cu/ZnO/Al₂O₃ nanocatalysts modified by adding small amounts of Ba, Zr, and Ce oxides were prepared by coprecipitation and oxalate coprecipitation. Catalysts obtained by means of the coprecipitation method exhibited a better performance. Selected promoters (Zr, Ce, and Ba) had a noticeable impact on the properties of the Cu/ZnO/Al₂O₃ catalyst.

The development of stainless-steel microchannel emulsification chips, each consisting of uniform-sized parallel channels and a terrace, is described. The production of highly monodisperse O/W emulsions with controllable droplet size demonstrated the usability of these stainless-steel chips. The influence of the dispersed-phase velocity in a channel on droplet generation characteristics is discussed.

A solid-liquid fluidized bed of inert particles was used to separate a pure object from a mixture. Pieces of plastic sheet were used as the objects for separation. When the bed was stirred, the existing height of the object in the bed changed with the liquid velocity, i.e., the separation of pieces of plastic sheet by density was possible.

The effects of several influencing factors (CaO and H₂O₂ concentration, gas flow, solution temperature, NO, SO₂, O₂ and CO₂ concentration) on the simultaneous removal of NO and SO₂ from flue gas by using a UV/H₂O₂/CaO process were studied in a UV bubbling column reactor. It was found that, under all experimental conditions, this process achieved a SO₂ removal efficiency of 100 %.

Adhesion is the most important factor when dealing with particle resuspension from a membrane surface but a direct, online measurement of the acting adhesion forces during a filtration process seems technically not feasible. Experiments are introduced that enable a time-resolved measurement of particle resuspension from a membrane surface and the possibility to estimate the acting adhesion forces.