Effects of ultrasonic waves on enhancement of relative volatilities in methanol-water mixtures

The application of ultrasonic wave in various fields including separation process has increased predominantly. This paper reports the practicability of using ultrasonic wave to enhance separation of binary mixtures by distillation. The binary mixture utilized was methanol-water. The effect of different ultrasonic intensity at 50, 100, 200 and 250 W/A.cm2 with frequency of 40 kHz to vapor-liquid equilibrium (VLE) of methanol-water was investigated to obtain the most suitable operating intensity. Experimental studies were also carried out to investigate the frequency effect (25 and 68 kHz) to VLE data. It was found that the use of ultrasonic wave enhanced the separation process by increasing the relative volatility of components. The highest average relative volatility of methanol-water at 29.413 was obtained from experimental study using intensity 200 W/A.cm2 and frequency of 25 kHz. The changes in relative volatility and VLE were caused by cavitational activities and vacuum effect that occur during transmission of ultrasonic wave in liquid medium. The results from this study proved the practical feasibility of using ultrasonic wave to enhance separation of binary mixtures in distillation column

Properties of microwave-assisted spray dried pineapple juice powder

There is considerable interest and research into the intensification of processing methods that offer better product quality and energy efficiency at reduced costs and better yield. Microwave-assisted spray drying is one such potential process. Microwaves were integrated into the spray drying process of juice feeds in a laboratory scale spray drier to produce dried powder. The juice feeds comprise pineapple-maltodextrin mixtures that were spray dried in a concurrent air flow using microwave frequencies of 915 MHz and 2450 MHz and an inlet air temperature range of 105 oC – 130 oC and. The powder yield using the different microwave frequencies were analyzed for moisture content, bulk density and solubility. The differences in the dried powder yield was negligible while observed differences in the measured powder properties for the microwave frequencies used varied from 2% to 5% for similar inlet drying air conditions

Numerical estimation of moisture content in spray dried juice powder

The moisture contents of powders is an important parameter that affects the quality and commercial value of spray dried products. The utility of predicted moisture content values from two droplet drying models were compared with experimental data for spray dried pineapple juice, using the Ranz-Marshal and its modified variants for the heat and mass transfer correlations. The droplet Diffusion model, using the Zhifu correlation, gave estimates with errors of about 8 at 165 °C, 9 at 171 °C, 26 at 179 °C and 2 at 185 °C. The Ranz-Marshal correlation also gave comparable results with this model while results using the Downing and modified Ranz-Marshall correlations widely diverged. The Energy balance model predicted completely dried juice particles, and short drying times, in contrast to the experimental data. The small error sizes of the Diffusion model improves on the wide error sizes of an earlier process model, making is useful as a first approximation choice, for spray drier design and simulation, especially for juices under comparable operating conditions

Process simulation of pineapple juice spray drying

Pineapple juice is one of the known natural sources of bromelain, a bioactive compound beneficial to health. The dried powder has potential commercial value and is a convenient source of the juice drink. The quality of spray dried pineapple juice is dependent on the powder moisture content. Spray dried pineapple powders with low moisture contents were produced in a lab-scale spray dryer in this study. Powder production of 25% of total solids were obtained by use of DE6 maltodextrin to solids ratio of 0.41:0.59. A heat and mass transfer model of the spray drying process was implemented in Matlab and solved to determine its predictive utility. The simulation results showed agreement with experimental data at high inlet air temperatures but widely diverged at other air temperatures. The error size in predicted product moisture varied from 73% at 165 oC to almost zero at 185 oC while that for the predicted exit air temperatures varied from about 38% to zero over the same temperature range. Accuracy can be improved if transient heat effects, and sub models for the feed drying are included in the model

Effects of Ultrasonic Waves on Vapor-Liquid Equilibrium of Cyclohexane/Benzene

Separation of azeotropic mixtures is one of the most challenging separation processes in chemical industry. Special separation techniques such as azeotropic and extractive distillation are required to separate these mixtures. In this work, an innovative technique which incorporates ultrasonic waves during separation of Cyclohexane (Chx)/ Benzene (Bz) via distillation process was explored. The effects of ultrasonic wave at different intensities at 50, 100, 200 and 250 W/A.cm2 and at a fixed frequency of 40 kHz on vapor-liquid equilibrium (VLE) of Chx/ Bz were investigated. Studies were also done to examine the effects of ultrasonic frequencies on the VLE data at 25 and 68 kHz. It was found that ultrasonic waves at 100 W/A.cm2 intensity and 25 kHz frequency gave the highest relative volatility, α at 2.505 and completely eliminated the azeotropic point. The results revealed that ultrasonic waves had potential to favourably manipulate α, and hence, the VLE of Chx/ Bz

Synthesis of activated carbon doped with transition metals for hydrogen storage

Carbon materials with high porosity and surface area such as activated carbons with a combination of metal possess great materials to obtain maximum hydrogen adsorption via the hydrogen spillover effect. The properties of activated carbon doped with metals (copper, nickel and palladium) were studied to evaluate the capacity of hydrogen sorption on the materials. Characteristics of the activated carbon doped with copper (AC-Cu), nickel (AC-Ni) and palladium (AC-Pd) were evaluated using particle density test, Fourier transform infrared spectroscopy (FTIR), x-ray diffraction (XRD) and surface and pore analysis (BET). The performance of hydrogen adsorption of the materials was carried out at different pressures of 50, 100 and 150 psi. Characterization of the materials shows that FTIR spectroscopy manage to detect surface functional groups meanwhile the carbon structure and metal content was determined using XRD. BET analysis shows the presence of oxygen groups was decrease the specific surface area whereas the presence of transition metals had increased the surface area. Hydrogen adsorption test at 150 psi indicates that oxygen groups are not a good adsorption characteristic with only a maximum of 0.39 wt% of hydrogen was adsorbed compared to pristine activated carbon’s 0.42 wt% at 150 psi. The presence of transition metals, copper, nickel and palladium increased the overall hydrogen uptake with 0.52 wt%, 0.44 wt% and 0.62 wt% respectively at 150 psi

State-of-the-art technologies for separation of azeotropic mixtures

Azeotropic separation technologies have been classified broadly into two major categories, i.e., distillation and membrane processes. Because normal distillation has limitations for azeotropic mixtures, enhancements have been proposed that either introduce a third component serving as an entrainer in extractive and azeotropic distillation processes or apply a pressure swing distillation system. Among the membrane processes, pervaporation was reported to be most promising for azeotropic separations. More recently, an approach known as process intensification has been proposed for combining multiple processes into single units such as a dividing wall distillation column or exploiting sonication phenomena to break an azeotrope in an ultrasonic distillation system. This article reviews the state-of-the-art technologies covering all the separation techniques mentioned here. Existing techniques are appraised, and technology gaps are identified. Based on these insights, areas for further development are suggested, aiming at satisfying the process objectives by inherently safer, environmentally benign and economically more attractive techniques

Electrooxidation of nitrite ions on gold/polyaniline/carbon paste electrode

Nitrite ions can penetrate from fertilizers into underground water and consequently contaminate the water and food sources. A facile two-step electrochemical method was used to fabricate gold/polyaniline/carbon paste electrode (Au/PAni/CPE) for nitrite sensing. The Au/PAni/CPE was visualized and characterized by scanning electron microscopy, energy-dispersed X-ray spectroscopy, X-ray diffraction and electrochemical methods. The electrocatalytic activity of bare CPE, PAni/CPE and Au/PAni/CPE toward the electrooxidation of nitrite was examined and compared via cyclic voltammetry. To obtain the optimal condition for fabrication of the electrode, the number of cycles in cyclic voltammetry for synthesis of polyaniline and the deposition time in potentiostatic deposition of gold were optimized with respect to the electrooxidation of nitrite. In a phosphate buffer solution (PBS, pH 7.0), the peak current was linear to the concentration of nitrite in the range from 3.8×10-5 M to 1.0×10-3 M with a detection limit of 2.5×10-5 M. The interference effect on the nitrite detection was also studied. The proposed method was also employed for the determination of nitrite in rain and lake water samples

Microwave assisted demulsification of water-in-crude oil emulsions

Emulsions are of considerable practical significance both in processing industry and in the consumer sector. In the petroleum industry emulsions phenomena are particularly aware because it can lead to upstream and downstream production upset. A recent report stated that about 80% of exploited crude oil exists in an emulsion state, all over the world (Xia et al., 2004)

In-situ ultrasonic cleaning of crossflow sintered tube microfiltration: effect of sonication cycle time

Membrane separation in general and microfiltration in particular is frequently employed in the dairy, pharmaceutical, food, fermentation and biotechnology, and chemical industries