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The mixing/agitation of time independent non-Newtonian fluids can be a challenge in many technological processes. In the present study, the influence of rheological parameters, K and n, on Reynolds number, power number and power consumption, for different concentration of carboxymethyl cellulose (CMC) solutions, 1%, 2%, 3%, 4 % and 5%, with shear-thinning behaviour, was analysed. The power consumption obtained by theoretical model and by an appropriate curve Po = f(Re) from experimental data, found in literature, was compared. The results have shown good agreement between calculated power number and the graphically determined values, and also minimal power consumption values comparable with those founded for the agitation of non-Newtonian liquids. [ABSTRACT FROM AUTHOR]

The paper presents the drying model proposed for sugar beet pulp in the presence of hydrated lime within a range temperature of 333 and 368 K. The experimental results were used to identify the coefficients in the two-term exponential model, choose as the most appropriated model for our case. The relationships for the variation of the coefficients with temperature were determined. The equations of the mathematical model were used to establish the optimal drying time. [ABSTRACT FROM AUTHOR]

The aim of this study is to investigate the hot air drying kinetics of sugar beet pulp, without and with dolomite addition, in order to establish the drying mechanism. The influence of temperature and dolomite addition on the drying rates is observed. The drying constant rates and the activation energies for different working conditions are determined. The obtained results show that the drying took place in falling rate period. The obtained activation energy values correspond to the mechanism mass transfer at low amount of dolomite addition and combined mechanism, mass transformation (evaporation process) - mass transfer, at higher amount. [ABSTRACT FROM AUTHOR]

The paper presents a comparative study of some physical properties, microstructure and antioxidant capacity of soluble coffee obtained at laboratory scale using spray-drying (SD) and freeze-drying (FD) as dehydration techniques. SEM was used for monitoring structures and size of the coffee powder. The results of SEM show the difference in the microstructure with the used drying technique. SD dried coffee has only spherical shape, narrow distribution, with the particle mean size of about 10 µ.m and smooth surface. The FD dried coffee has spherical shape with the size of about 40 µm and flaky structure, non-spherical shape, with the dimensions between 10 x 20 µm and 30 x 90 µm. EPR was used for the determination of coffee antioxidant capacity. SD coffee powder shows a higher antioxidant activity in comparison with FD dried coffee. [ABSTRACT FROM AUTHOR]

The present paper presents the freeze-drying kinetics of soluble coffee in order to determine the mass transfer parameters. Several semi-theoretical and empirical models were used to find the best fit to the experimental data. The applied models were compared using the coefficient of determination (R2), the mean relative percent error (P), the root mean square error (RMSE) and the reduced chi-square (x2). The Midilli model was found to fit better to the experimental freeze-drying data comparative to other models. The Fick’s second law was employed to determine the effective diffusion coefficient (Deff). [ABSTRACT FROM AUTHOR]

The aim of this study was to develop an ecological method for the removal of Pb2+ ions from industrial wastewater. The electrocoagulation (EC) process of Pb2+ has been studied, using an electrolytic flow cell (flow rate of 20, 40, 60 mL/min) equipped with sacrificial Al electrodes, operated under galvanostatic mode (current density of 5, 10 and 15 mA/cm2). In all experimental conditions the concentration of Pb2+ was lowered below the maximum allowable concentration (0.5 ppm). The experimental results showed that the performances of the process are more strongly dependent on the applied current density than on the applied flow rate. The electrolytic flow cell has proved to be quite effective, allowing the complete removal of lead with a specific energy consumption of 3.08 kWh/kg Pb removed. [ABSTRACT FROM AUTHOR]

The efficiency of Purolite A103S resin for zinc removal (as zinc chloride complexes) has been studied using different resin quantities and temperatures in a batch adsorption system. The experimental data were analyzed using pseudo-first-order, pseudo-second-order forms, Elovich, and intra-particle diffusion models. Kinetic studies showed that the adsorption followed type 1 pseudo-second-order reaction model. The results obtained from the kinetics models were examined by the most common error functions (e.g. ERRSQ/SSE, HYBRID, ARE, EABS, MPSD, rs, sRE, S.E., RMSE, APE, and Δq). Thermodynamic parameters, enthalpy, entropy, and Gibbs free energy were calculated in order to determine the adsorption behavior. The enthalpy value indicated an exothermic reaction. The activation energy value suggested that the process that rules over the zinc sorption on the Purolite A103S resin is physical. [ABSTRACT FROM AUTHOR]

Specific settling tests have been made using diluted yeast suspensions coagulated/flocculated in the presence of FeCl3 at constant pH of 4.0 in order to determine the flocs/aggregates size and gel solid concentration, parameters which are necessary in numerical simulation and characterization of sedimentation processes. The sizes of the incipient aggregates and the gel point show to be dependent on coagulant concentration. The size of aggregates and the gel point has increased with the increase of coagulant concentration. [ABSTRACT FROM AUTHOR]

The present study presents the drying of carrot slices as thinlayer of 4 mm thickness in a laboratory dryer with the drying air temperature in the range of 40-0 °. The effect of drying air temperature on the drying kinetics, the drying rates, the effective diffusion coefficients and the activation energy were determined. The effective diffusivity was found to be between 2.6·10-10 and 5.2·10-10 m2/s. The Newton, Page, modified Page and Henderson & Pabis models available in the literature were fitted to the experimental data using nonlinear regression analysis. The models were compared using the coefficient of determination (R2). Henderson & Pabis model has shown a better fit to the experimental drying data as compared to other two models. [ABSTRACT FROM AUTHOR]

In order to characterize the hindered effect which appears by sedimentation of concentrated suspensions new experiments with quartz sand having equivalent size d90 = 170 μm and concentration 10 - 30 %, in volume, in ethylene glycol and aqueous solutions carboxymethylcellulose (CMC) 0.5%, 1.0%, in weight, were carried out. The drag coefficient, CD, as a parameter which quantifies the hindered effect, was calculated with particle terminal settling velocity. The hindered settling velocities predicted by Richardson-Zaki's equation were founded comparable with experimental results. [ABSTRACT FROM AUTHOR]

This paper presents the experimental data obtained in absorption process of SO2 into limestone suspensions. The absorption experiments have been performed in a 0.75 L reactor, fitted with mechanical stirring, at temperature of 293, 303 and 313 K. The consistency of limestone slurry expressed as solid-liquid ratio was: R1=1/30; R2= 1/15; R3=1/10 and R4= 1/7.5. The influence of the limestone content in the initial slurry and the operating temperatures on the total absorption capacity were determined and analyzed. The obtained results, absorption capacity between 0.49 - 2.14 mol SO2/L slurry, are comparable with those reported by other authors. [ABSTRACT FROM AUTHOR]

The behavior of polydisperse concentrated solid suspensions (ε smaller than 0.95) of quartz sand in carboxymethylcellulose (CMC) aqueous solutions (with 0.5%, 1.0% and 1.5%, in weight) during the sedimentation process was investigated. The influence of solid size, solid concentration and rheological parameters of CMC disperse fluid with a non-Newtonian behavior on the settling kinetics has been theoretically accounted. The experimental hindered settling velocities determined graphically by Kynch method and those expressed by Richardson-Zaki equation are compared and analyzed. [ABSTRACT FROM AUTHOR]

This paper presents the kinetic study of the dry desulphurization process at low temperature using solid adsorbents by thermogravimetric analysis technique. Experiments are performed in isothermal conditions, at three temperatures (373 K, 473 K and 573 K) with diameters of sodium carbonate granules of 31.5 μm and 900 μm and sulfur dioxide concentration of 0.5 % and 1.0 %. The particle size, temperature and gas flow rate show a dominant influence on the variation of carbonate conversion. The obtained activation energy values are in the range from 4.234 KJ/mol to 12.275 KJ/mol showing that the diffusion through the solid product layer is the determinate rate step of the process. The experimental results confirm that the shrinking Unreacted Core Model can be used to describe the sulfation of sodium carbonate at low temperature. [ABSTRACT FROM AUTHOR]

This study describes the physicochemical treatment applied to colloidal dispersion of carboxymethylcellulose (CMC) in order to improve the removal of colloidal particles from aqueous solution by sedimentation and pressure filtration. The physicohemical treatment consists in coagulation/ flocculation with different coagulants/flocculants at different concentrations. By coagulation-sedimentation combination the optimal parameters were established to be 5.9 for pH and 200 mg/g (FeCl3/CMC) for coagulant concentration. By coagulation-filtration the best result were obtained with the coagulant concentration of 200 mg/g (FeCl3/CMC) and pressure difference of 4 bar. [ABSTRACT FROM AUTHOR]

On the basis of mathematical modelling and numerical simulation the batch settling of coagulated yeast suspensions was analysed. Time and space behaviour of the solids height and critical height of sediment in gravitational settling, has shown similar results comparative to experimental data. The method offers the possibility to predict by simulation the settling rate for the consolidation region, a key settling variable difficult to be measured experimentally but important for the settler design. [ABSTRACT FROM AUTHOR]

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