Flow of materials in rotary kilns used for sponge iron manufacture: Part III. Effect of ring formation within the kiln

The formation of accretions or ’rings’ in rotary kilns used for the manufacture of directly reduced iron (sponge iron) affects the residence time of the charge, kiln hold-up, and the kiln output to a great extent. In this part of the work, the effect of ring formation was simulated at room temperature in a scaled-down model of a rotary kiln by inserting conical dams in the shape of frustrums of cones through the feed end of the kiln. The influence of such conical dams on various operating parameters was evaluated.     

The use of Bassia indica for salt phytoremediation in constructed wetlands

The treatment and reuse of wastewater in constructed wetlands offers a low-cost, environmentally-friendly alternative for common engineered systems. Salinity in treated wastewater is often increased, especially in arid and semi-arid areas, and may harm crops irrigated from wetlands. We have strong evidence that halophyte plants are able to reduce the salinity of wastewater by accumulating salts in their tissues. Bassia indica is an annual halophyte with unique adaptations for salt tolerance. We performed three experiments to evaluate the capability of B. indica for salt phytoremediation as follows: a hydroponic system with mixed salt solutions, a recirculated vertical flow constructed wetland (RVFCW) with domestic wastewater, and a vertical flow constructed wetland (VFCW) for treating goat farm effluents. B. Indica plants developed successfully in all three systems and reduced the effluent salinity by 20-60% in comparison with unplanted systems or systems planted with other wetland plants. Salinity reduction was attributed to the accumulation of salts, mainly Na and K, in the leaves. Our experiments were carried out on an operative scale, suggesting a novel treatment for green desalination in constructed wetlands by salt phytoremediation in desert regions and other ecosystems.     

Surface modified mesoporous silica polymer nanocomposites for adsorption of dyes from aqueous solution

Functionalized mesoporous silica nanocomposites were synthesized via in situ radical polymerization of vinyl monomers (vinylcarbazole, vinyl imidazole and vinyl sulphonic acid) and characterized for adsorption of dyes from aqueous solution. Physicochemical characterization (PXRD, SEM, adsorption studies etc.) of the functionalized nanocomposites showed the presence of mesoporous nature of the nanocomposites. Different adsorption parameters such as adsorption weight, adsorption time, temperature, pH etc., were optimized for adsorption of dyes under environmental friendly conditions. The adsorption studies showed 96.8 and 80.49 % removal for cationic and anionic dyes respectively. Adsorption kinetics of the dyes on the functionalized nanocomposites can be well depicted theoretically by using pseudo-second-order kinetic model.     

Adenosine deaminase activity in protein-energy malnutrition

Cell-mediated immunity (CMI) was evaluated in 69 children with protein-energy malnutrition (PEM) and 20 healthy controls. Significantly decreased responses to purified protein derivative (PPD) (p < 0.02) and absolute lymphocyte count (ALC) (p < 0.01) and increased serum adenosine deaminase (ADA) activity (p < 0.001) were observed in PEM cases compared with the controls. The mean values of ALC and ADA activity in PEM patients were 85.9% and 158.7% of the normal mean, respectively. A significant negative correlation was observed between the two parameters (r=- 0.2765, p < 0.01). The CMI tests were abnormal in all three grades of PEM, except for the response to PPD in grade I, when compared with the controls. No significant differences were found between infected and uninfected PEM cases. Thus, impaired CMI was observed not only in grades II and III but also in grade I PEM patients and the concomitant infection did not affect its status. However, ADA activity demonstrated a more pronounced change than the other tests.     

Three-dimensional rainbow schlieren tomography of a temperature field in gas flows

We present quantitative rainbow schlieren deflectometry with tomography for measurements of temperature in three-dimensional gas flows. The schlieren apparatus with a continuously graded spectral filter of known transmissivity was used to create color schlieren images of the test media. These images at multiple viewing angles were used to infer beam deflection angles by the medium. The deflection data were used with a tomographic technique to reconstruct the refractive index and thus the temperature field. The temperature distributions obtained by the rainbow schlieren tomography agreed with those measured by a thermocouple probe. This research demonstrates that tomography can be used with full-field schlieren deflectometry to measure quantitatively temperature in asymmetric gas flows. The technique could be used to obtain related properties such as pressure, density, and gas composition.     

Bromate removal from water by granular ferric hydroxide (GFH)

The feasibility of granular ferric hydroxide (GFH) for bromate removal from water has been studied. Batch experiments were performed to study the influence of various experimental parameters such as effect of contact time, initial bromate concentration, temperature, pH and effect of competing anions on bromate removal by GFH. The adsorption kinetics indicates that uptake rate of bromate was rapid at the beginning and 75% adsorption was completed in 5 min and equilibrium was achieved within 20 min. The sorption process was well described by pseudo-second-order kinetics. The maximum adsorption potential of GFH for bromate removal was 16.5 mg g⁻¹ at 25 °C. The adsorption data fitted well to the Langmuir model. The increase in OH peak and absence of Br–O bonding in FTIR spectra indicate that ion-exchange was the main mechanism during bromate sorption on GFH. The effects of competing anions and solution pHs (3–9) were negligible. Results of the present study suggest that GFH can be effectively utilized for bromate removal from drinking water.     

Microwave Effects in Lead Zirconium Titanate Synthesis: Enhanced Kinetics and Changed Mechanisms

A novel, simple, and fast solid-state procedure has been demonstrated for the synthesis of Pb(Zr,Ti)O₃ (PZT), using microwave radiation. The process consists of starting with the respective oxides mixed in the required proportions and exposing the charge to the microwaves. By making one or more of the constituent oxides slightly nonstoichiometric, enormous enhancement in reaction rates has been achieved, and single-phase PZT can be synthesized at temperatures as low as 600°C. Moreover, it has been shown that the combined use of nonstoichiometric precursors and microwave irradiation leads to different reaction pathways for the formation of PZT. Further, the microwave method diminishes PbO loss.     

Measurement of hydrodynamic data of gas-phase polymerization reactors using non-intrusive methods

The hydrodynamic characteristics of polyethylene resins are studied in detail through a combination of different techniques in our laboratory. Computer Assisted Tomography is used to determine voidage distribution under different operating conditions. Radioactive particle tracking is used to determine the solid particle trajectories, the horizontal and vertical velocities of the solids and the residence time distribution of the solids. X-ray fluoroscopy is used to determine bubble frequency and velocity. All these techniques are then combined with the information obtained through monitoring pressure fluctuations in the fluidized bed columns. All experiments are performed in Plexiglas columns of diameters that vary between 10 and 30 cm in diameter. The materials used are polyethylene and air, respectively. The combination of these techniques provides the unique opportunity to study the fluidized bed systems in great detail. Unfortunately, all techniques cannot be implemented in a single experiment. As a result, the same experiment is repeated as many times as necessary to collect the required data. The column is moved from one imaging system to the next and the experiment is repeated under the same operating conditions. It is believed that the data collected can be used as if all the data were collected during the same test. This paper presents preliminary experimental results for each set of experiments along with the nature and limitations of each set of experimental data. The results from each different system are combined in an effort to describe the complex hydrodynamics of the bed. The incremental information obtained in each set of experiments compared to the macroscopic measurements (flow rate and pressure drop) is demonstrated.