Conversion of Natural Resources through Waste reduction at the Processing Step by Briquetting Technique

India is gifted by nature by way of large quantities of high grade nonferrous mineral resources like barite containing more than 90% barium sulphate. The processing of barite to win chemicals from it requires its carbotherrnic reduction at high temperatures being carried out in rotary furnaces. The powdered charge containing barium sulfide is prone to get damaged due to reverse reaction caused by infiltered oxygen at the end of reduction state. This hampers the yield of water soluble barium sulfide.The paper discusses about the means of achieving favourbale kinetics and high recovery of water soluble barium sulphide in the carbothermic reduction of barite at high temperatures. The reaction rate of reduction step was enhanced many folds by using briquetting technique. Even with barite containing large amnount of harmful impurites, the yield of barium was improved considerably on pilot plant scale, thus achieving better utilisation of natural resoures such as barite and coke

Waste Reduction at the Source and Waste Recycle through Briquetting of the Reduction Charge in the black- ash process

Physical losses of material as flue dust in the oil fired rotary furnaces of black ash process for barite reduction have been arrested using briquetted charge. Similarly fine particles of barium sulphate obtained in the purification of barite could be recycled as a resource by exploiting advantages of catalysis and briquetting techniques

Mapping Site-Specific Changes that Affect Stability of the NTerminal Domain of Calmodulin

Biophysical tools have been invaluable in formulating therapeutic proteins. These tools characterize protein stability rapidly in a variety of solution conditions, but in general, the techniques lack the ability to discern site-specific information to probe how solution environment acts to stabilize or destabilize the protein. NMR spectroscopy can provide site-specific information about subtle structural changes of a protein under different conditions, enabling one to assess the mechanism of protein stabilization. In this study, NMR was employed to detect structural perturbations at individual residues as a result of altering pH and ionic strength. The N-terminal domain of calmodulin (N-CaM) was used as a model system, and the 1H-15N heteronuclear single quantum coherence (HSQC) experiment was used to investigate effects of pH and ionic strength on individual residues. NMR analysis revealed that different solution conditions affect individual residues differently, even when the amino acid sequence and structure are highly similar. This study shows that addition of NMR to the formulation toolbox has the ability to extend understanding of the relationship between site-specific changes and overall protein stability

Solid-gas reactions: effect of solid shape on proposed diffusion model

The diffusion model for gas-solid reactions, proposed by Phadtare and Doraiswamy [9] and applied for the oxidation of zinc sulphide by Gokarn and Doraiswamy [6] for spherical pellets, has been extended to include different geometrical shapes. Model equations have been derived for the long cylinder, right circular cylinder (L = D), infinite cylinder and flat plate. Cylindrical ZnS pellets have been prepared at three different compression pressures, and oxidation carried out at various temperatures for each compression pressure. It has been confirmed that there is a definite shift in the controlling regime and that the "critical temperatures" [i.e. the temperature at which the shift occurs] is dependent on the porosity of the ZnS pellet, shifting to a lower temperature as the porosity is decreased. It has also been observed that the modified kinetic and diffusion models satisfactorily represent the experimental data in the respective zones of control for all the shapes studied. The value of the effective diffusivity obtained by the application of the model to the experimental data for various shapes at a particular temperature has been found to be the same irrespective of the pellet geometry, thus providing further confirmation of the proposed models. In the kinetic regime the activation energy of the reaction has been estimated to be 7.55 kcal/g mole and in the diffusion regime 1.92 kcal/g mole. The Aris approximation for the diffusion length has been found to be applicable to the various geometrical configurations examined, thus proving that this useful approximation, which was so far limited to catalytic reactions, can also be employed for gas-solid reactions

A model for solid-gas reactions

Studies on the oxidation of zinc sulphide spheres suggested kinetic control in the temperature range 600-670°C and diffusion control in the range 740-820°C. In the intermediate range probably both chemical reaction and diffusion are simultaneously operative. In the kinetic regime, experimental data could be fitted to the established Levenspiel model, while in the diffusional regime the model represented by the following equation depicted the data very well: 3θ/AM=x+Bi[1.5-x-1.5(1-x)2/3]. This equation has been derived on the assumption that diffusion of oxygen through the "ash" layer (zinc oxide shell) controls the overall reaction. The effective diffusivity of the reacting and product gases through the ash layer was measured experimentally in a newly developed diffusion cell. The value of the tortuosity parameter (α) thus estimated form an independent set of diffusion experiments and that obtained from kinetic data by using the model represented by the above equation agreed very closely. The external mass transfer coefficient (kg) calculated from the model also need with the values calculated by standard methods. It may therefore be concluded that the above equation (based on the retreating core model) is an adequate representation of the diffusional regime. Similar equtaions can be readily written for other systems starting from Eq. (2) of the text

Effect of particle size on thermal decomposition of lime shells: Suitability of calcined lime shell for pollution control and energy storage

137-140Lime shells obtained from the lagoons of Kerala Coast have been decomposed with a view to study the effect of particle size. A modified TGA has been used to study the decomposition kinetics at various temperatures. Conversion time data obtained showed typical sigmoidal behaviour and the decomposition kinetics could be fitted to the Prout-Tompkins model at all temperatures and for all particle sizes studied. Arrhenius kinetic parameters showed normal type of compensation behaviour indicating an isokinetic temperature of 730°C. A theoretical explanation for these observed compensation behaviour and isokinetic temperature has been given. Further, the calcined lime shell has been tested for the capture of CO2 and SO2 using TGA. Effects of temperature of decomposition and particle size have been studied in this case. A theoretical, explanation based on pore size distribution of the calcined lime for this special behaviour has been given

A novel regenerable sorbent for SO<SUB>2</SUB>

A detailed study was undertaken to examine the potential of iron oxide present in red mud - a waste product from Bayer's alumina process - as a sorbent for SO2 capture by dry process. The other constitutents present in the red mud can bring about enhanced utilization of the active component provided they are almost completely inert. The practical use of the process has been explored and a few batchwise cyclic operations of SO2 capture and regeneration have also been carried out. A kinetic model of the reaction has been proposed