Volume 60, Issue 6

A coupled membrane process of membrane distillation and osmotic evaporation, where the solutions were thermostated separately at different temperatures, was developed. Enhanced water flux was obtained since the total driving force of the coupled process was higher than the sum of the driving forces of single processes. Apple, raspberry, sour cherry, red, and black currant juices were concentrated by the novel, mild technique.

Residence time distribution (RTD) experiments were carried out using the catalytic packing MULTIPAK® in a 250 mm inner diameter column. The axial dispersion coefficients and dynamic liquid hold-up were derived from the RTD curves. Both hold-up and axial Péclet number were correlated in terms of gas and liquid Reynolds numbers. Free-draining experiments were performed to determine the dynamic and static liquid hold-ups. The measured axial dispersion coefficients were higher than those presented in other studies. The dynamic hold-up derived from RTD agreed with total hold-up from free-draining experiments. The static hold-up was found very high, even higher than the dynamic one, due to the liquid accumulated inside the catalyst bed. Possibly, the liquid considered “static” from the viewpoint of the free-draining experiments becomes “dynamic” during the normal column operation.

A novel technique based on artificial intelligence methods able to predict pollutant emission concentrations from industrial stacks is presented. This procedure combines regression and classification problems into a unified technique, named minimax decision procedure. The core of this procedure is based on the minimax probability machine regression model. Using experimental databases, the trend of pollutant emissions and the level of pollution for one industrial thermal power station stack were presented. Based on this unified technique, numerical experiments provided the estimates of concentrations of CO, NOx, NO, and SO2 confirming the predictive power of this procedure.

Application of ultrafiltration, nanofiltration, reverse osmosis, membrane distillation, and integrated membrane processes for the preparation of process water from natural water or industrial effluents was investigated. A two-stage reverse osmosis plant enabled almost complete removal of solutes from the feed water. High-purity water was prepared using the membrane distillation. However, during this process a rapid membrane fouling and permeate flux decline was observed when the tap water was used as a feed. The precipitation of deposit in the modules was limited by the separation of sparingly soluble salts from the feed water in the nanofiltration. The combined reverse osmosis—membrane distillation process prevented the formation of salt deposits on the membranes employed for the membrane distillation. Ultrafiltration was found to be very effective removing trace amounts of oil from the feed water. Then the ultrafiltration permeate was used for feeding of the remaining membrane modules resulting in the total removal of oil residue contamination. The ultrafiltration allowed producing process water directly from the industrial effluents containing petroleum derivatives.

The pyrolysis of rubber from the sidewall and tread of a passenger car tire was carried out in a nitrogen flow at a wide range of final temperatures. Derivative thermogravimetric analysis (DTG) was applied to examine the kinetics at the different process conditions of completed pyrolysis. Two characteristic stages were observed in the DTG curves. The first stage corresponded to the decomposition of processing oil, plastifier, and additives, whereas the rubber polymer was decomposed in the second stage. Several properties of the carbon black formed by the pyrolysis such as ash content, specific surface area, and pore size distribution were determined. A change of the internal structure of the rubber particle in the meso-and macroregions of the pore size was observed.

The mechanism of Re(VII) extraction from sulphate-containing solutions using primary amine Primene JMT, trioctylphosphine oxide (TOPO), tributyl phosphate (TBP), and their mixtures was investigated. It was found that the ratio of Re(VII) with Primene JMT and its sulphate in the organic phase was 1:1. The composition of Re(VII) complexes with TOPO depended on the acidity of solution ranging from about 1:1 to 2:1. When the extraction was carried out by TBP the mole ratio of TBP to Re was approximately 4. Primene JMT proved to be the most suitable agent for Re(VII) extraction with the exception of strongly acidic solutions, in which TOPO provided better results. The mixed solvents Primene JMT and TOPO as well as Primene JMT and TBP presented a slight synergism in weakly acidic solutions.

Comparison of equilibrium and nonequilibrium models of a CSTR with total condenser focused on the multiple steady states and dynamic behaviour was carried out. The steady-state behaviour of the model system, MTBE synthesis from methanol and isobutene in a reactive distillation column, was studied in terms of the input parameters, i. e. feed flow rate of methanol or butenes, reflux ratio, and mass of catalyst. The dynamic behaviour of the system during the start-up was investigated and perturbations of manipulated variables were found to cause transitions between the parallel steady states.

The effect of the biomass presence on the overall circulation velocity, the linear velocities both in the riser and the downcomer and the overall gas hold-up was studied in a three-phase internal loop airlift reactor (ILALR). The measured data were compared with those obtained using a two-phase system (air—water). All experiments were carried out in a 40 dm3 ILALR at six different biomass concentrations (ranging from 0 g dm−3 to 7.5 g dm−3), at a temperature of 30°C, under atmospheric pressure. Air and water were used as the gas and liquid model media, respectively. Pellets of Aspergillus niger produced during the fermentation of glucose to gluconic acid in the ILALR were considered solid phase. In addition, liquid velocities were measured during the fermentation of glucose to gluconic acid using Aspergillus niger. All measurements were performed in a bubble circulation regime. At given experimental conditions the effect of the biomass on the circulation velocities in the ILALR was negligible. However, increasing of the biomass concentration led to lower values of the total gas hold-up.

Gas-liquid reaction carried out in an internal loop airlift reactor was modelled and subjected to the scale-up procedure. Homogeneous oxidation of glucose to gluconic acid catalyzed by Gluzyme 10000 BG, a commercial product containing the enzymes glucose oxidase and catalase as active components, was chosen as the model system. The kinetic parameters were obtained using a 12-L airlift reactor considered as a CSTR. The behaviour of a large-scale internal loop airlift reactor was modelled dividing the reactor sections into a series of tank reactors. The reliability of the model was verified by comparing experimental measurements with the simulation results obtained employing 40-L and 200-L airlift reactors. The designed model could be suitable to predict the behaviour of large-scale internal loop airlift reactors.

A model approach to Hazard and Operability (HAZOP) analysis is presented based on the mathematical modeling of a process unit where both the steady-state analysis, including the analysis of the steady states multiplicity and stability, and the dynamic simulation are used. Heterogeneous tubular reactor for the ethylene oxide production from ethylene and oxygen was chosen to identify potential hazards for real system. The computer code DYNHAZ was developed consisting of a process simulator and a generator of the HAZOP algorithm.

Content of fluoride compounds in some typical Ethiopian water sources was analysed and several commonly available soils were characterized for their adsorption properties regarding the water defluoridation. Various soils were collected in different Ethiopian sites and the samples were analysed by X-ray diffractometry for their mineralogical composition. Batch experimental runs at room temperature were performed to evaluate the adsorption capacity of each soil sample as well as to deduce the adsorption isotherms of fluoride ions with respect to the examined soils. The best soil was identified in terms of adsorption capacity and considered for the design of two different adsorption apparatuses. Considering the water consumption of a small rural community, the capacity of the adsorption unit was selected to assure a reduction of the fluoride concentration in drinking water to the limits recommended by the World Health Organization and to allow a suitable working time of the adsorption unit before the replacement of adsorbent would be necessary.

Five hydroxyanthraquinone derivatives physcion, emodin, fallacinal, teloschistin, and 1,3-dimethoxy-8-hydroxy-6-methyl-9,10-anthraquinone were isolated from the lichen Caloplaca cerina growing in Serbia. Three anthraquinone derivatives, namely physcion, emodin, and rhein were isolated and identified from the Thai medicinal plant Cassia tora.

The study deals with the development of an immobilized biocatalyst for the production of fructooligosaccharides. Several commercial anion-exchange resins and polymethacrylate carriers were tested for the immobilization either by the direct attachment of fructosyltransferase or by the attachment accompanied by simultaneous glutaraldehyde crosslinking in the pH range from 5.7 to 7.1. On the basis of the efficiency of immobilization and the storage stability, Amberlite IRA 900 and Dowex Marathon MSA were selected as the best carriers for fructosyltransferase immobilization by direct attachment at pH 5.7.