Chinthapudi Eswaraiah

Settling characteristics of ultrafine iron ore slimes

The slurry settling characteristics are the most important to design a thickener in process industries. In this work, the iron ore slurry from the screw classifier overflow was used for the settling study. It was observed that the original slurry exhibited a low settling velocity and a turbid supernatant during the settling process. Commercial flocculating agents with anionic, cationic, and nonionic characters were used to improve the settling behavior of suspensions, which were added into the slurry at different ranges of slurry pH values, respectively. The settling results show that the use of flocculants increase the settling rate by several times. Compared with the cationic and nonionic flocculants, the anionic flocculant is more effective in enhancing the slurry settling rate. The small dose of the anionic flocculant is found to be more effective, but the other flocculants are less effective even at higher dosages. The simulation of an industrial thickener was carried out based on the laboratory settling data, and the appropriate design and selection parameters of the industrial thickener were estimated.

Selection of Gravity Separators for the Beneficiation of the Uljin Tin Ore

ABSTRACT Gravity separation is typically used in the beneficiation of tin ores as the density difference between the valuable and associated gangue minerals is significant. In the present investigation, a cassiterite sample collected from the Uljin deposit in South Korea has been subjected to different gravity separators to evaluate the separation efficiency. The selection of gravity units has been made based on performance evaluation following heavy liquid separation and assessment of grade/recovery curves and Tromp curve methods. In addition, a gravity separation index (GSI) has been proposed that is simpler than other methods for assessing the performance of gravity separators.

A Comparative study on a vertical stirred mill agitator design for fine grinding

Comminution is an energy intensive process. A small change in efficiency can lead to substantial benefits in an overall economy of the process plant. This study focused on the comparison of vertical stirred mill agitator designs. A double helical screw agitator was designed for this purpose. A series of stirred mill experiments were performed with two types of agitator designs a standard pin type and CSIRO’s designed double helical screw stirrers. The effects of operating parameters such as grinding time, stirrer speed, and pulp density on grinding performance was investigated using a magnetite concentrate. Grinding performance was analyzed by considering the product fineness and the energy consumption. The test results show that the grinding time and stirrer speed played a significant role; however, the pulp density had little impact on grinding performance in both cases of agitator designs. The 80% passing target product size of 38 μm was obtained with double helical screw agitator in 20 min of grinding with an expend of 10.53 kWh/t specific energy, whereas, the target product size of 38 μm was achieved with the pin type stirrer at the rate of 21.73 kWh/t. It is evident that grinding in a vertical stirred mill with a double helical screw is more efficient than that using a pin type stirrer in terms of the product size distribution and the specific energy consumption. It is concluded that the double helical screw design provides better energy efficiency compared to the pin type stirrer design. The models were developed for the responses P80 and Ecs. Both models show high regression coefficients thus ensuring a satisfactory of models with experimental data. The model equations developed were then optimized using a quadratic programming to minimize the P80 size at minimum specific energy.

Milling and Classification of Printed Circuit Boards for Material Recycling

Recycling of waste electric and electronic equipment (WEEE) is an emerging issue due to its hazardous nature. It is important to identify an appropriate environment-friendly process to recover the valuables and for safe disposal. The present work deals with the two-stage crushing process followed by a circulating air classifier for the separation of metals and nonmetals from the printed circuit boards (PCB). The two-stage crushing process is deployed to liberate the valuables for an appropriate progeny size distribution. The metal content decreases as the particle size decreases below 0.5 mm. However, it increases metal content above 500 µm up to 1,800 µm. It is concluded that the metals primarily enriched in the size range of −1.8 + 0.5 mm. The amount of metals and plastics present in each fraction is estimated. Among the classifier parameters, air flow velocity played a dominant role in metal enrichment. The material feed rate and rotating guide vane angle have no a significant effect on the enrichment of metals and nonmetals. The air flow velocity found was to be one of the crucial parameters for enrichment of metals. The superficial air flow velocity is optimized for efficient separation of metals and nonmetals of PCBs.

Grinding characteristics of coal and petroleum coke/coal blends on utilization for combustion

ABSTRACT Petroleum coke (PC) blend with coal is an attractive feedstock for combustion process. The present work investigates the grinding characteristics of PC blend with coal in a laboratory ball mill to meet an industrial tube mill conditions. Tests were carried out using a laboratory batch ball mill for optimal production of −200 mesh size product. The ground products at different combinations were subjected to sink-float tests. Experimental results suggested that the petcoke with coal at 5.0% blend ratio was optimum for generation of −200 mesh size product. It was also observed that increasing coal/petcoke blend ratio beyond 5.0% leads to a decrease in −200 mesh size generation. The better performance could be achieved at the blending ratio of 5%, perhaps resulting from the synergistic effect of the blends. With the aforementioned blend ratio, the optimal condition of the milling time was found to be 3 h. The percentage of coal to the total charge and percentage of petcoke to the total charge of the ball mill product at various blends were also calculated for all the blends and at all grinding time intervals. The results obtained could provide a useful insight to predict the industrial mill performance.

Optimization of Process Parameters Using Response Surface Methodology for Enrichment of Rice Bran Oil

Contamination of rice bran with the husk adversely affects the efficiency of an oil extraction process. The efficient separation of husk from the rice bran prior to an oil extraction process is of great benefit. In the present work, a three-factor-three-level Box–Behnken design of experiments combining Response Surface Methodology (RSM) is being employed to optimize the air classifier parameters. Three independent variables (i.e., wheel speed ranging from 800 to 1200 RPM, guide vane angle ranging from 13 to 65°, and the feed rate ranging from 12 to 24 kg/h) are consecutively coded as x1, x2, and x3 at three levels (i.e., −1, 0, and 1). Models were developed to demonstrate the effect of each parameter and their interaction effects on the responses. The second-order polynomial regression equations were derived from the data to predict the classifier cut size and the percentage of oil content. The significance of independent variables and their interactions are being tested by the analysis of variance at 95% confidence level (α = 0.05). The predicted values of responses obtained from the models were in good agreement with the experimental values. For the improvement of the oil extraction process, a pre-concentration methodology by a circulating air classifier is demonstrated and recommended to the industry for optimal separation of the rice bran/husk.

Experimental and Simulation Studies on Milling of Rice Husk

A study was conducted to investigate the size reduction characteristics of rice husk in a batch ball mill. The most popular population balance model was chosen for the analysis. The model parameters are the breakage distribution function (β) and breakage rate function (α). Experiments are conducted with three different feed sizes of rice husk at three different ball charges. From the experimental data, the best fitting breakage distribution function parameter is found. The breakage rate function parameters with process variables such as feed size, ball charge were calculated. The best correlation for the parameter with process variables was obtained by multiple linear regression analysis. Additional experiments were also conducted at different process conditions to verify the correlation. The accuracy of the correlation is also verified for pet coke data of Ray (2000). The correlation describes the experimental data with acceptable accuracy for rice husk and also for pet coke data within the range of process variables studied in this investigation. The calculated values of the breakage rate obtained through the developed correlations have been compared with the respective experimental values with root mean square error of 1.25% and correlation coefficient of 0.95. It is also found that the calculated values agree well with the experimental values.