Mineral Processing
Jiaye Li; Jing Zhao; Zebin Wang; Huan Liu; Qing Wen; Jinling Yin; Ze Li; Yang Lei; Guiling Wang
Abstract
Traditional graphite has safety and environmental issues, associated with fluorine purification. To address these issues, an energy-saving and efficient graphite purification process can be explored through the acid leaching method with composite additives. The acid leaching process was studied and optimized ...
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Traditional graphite has safety and environmental issues, associated with fluorine purification. To address these issues, an energy-saving and efficient graphite purification process can be explored through the acid leaching method with composite additives. The acid leaching process was studied and optimized in detail using the controlled variable method including the effects of the soaking time and temperature on the graphite purification process. Then the response surface method was used to simulate the orthogonal experiment of graphite purification to verify the correctness of the single-factor, experiment. The purity and micromorphology of the graphite samples at each stage were characterized and tested. The experimental results showed that the optimal liquid-to-solid ratio of the acid solution and graphite was 20:1, which could make the fixed carbon content reach 99.77%. On the basis of these optimal process conditions, the addition types were further explored. The experimental result showed that the best addition was ascorbic acid and EDTA, which could reduce the content of various impurities in the graphite raw material without destroying the microstructure of the graphite. Benefitting from the addition of compound additives in the two-step process, almost all the metal ions were leached from the graphite. After the acid and water leaching, the fixed carbon content of graphite could reach 99.96%. The process parameters proposed in this paper were scientifically verified by both the single-factor and multi-factor experiments, and innovative and effective additives were introduced in different steps to make the graphite purity break through 99.9%, which was difficult to reach by the traditional method.
H. Sarfaraz; M. H. Khosravi; T. Pipatpongsa
Abstract
One of the most important tasks in designing the undercut slopes is to determine the maximum stable undercut span to which various parameters such as the shear strength of the soil and the geometrical properties of the slope are related. Based on the arching phenomenon, by undercutting a slope, the weight ...
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One of the most important tasks in designing the undercut slopes is to determine the maximum stable undercut span to which various parameters such as the shear strength of the soil and the geometrical properties of the slope are related. Based on the arching phenomenon, by undercutting a slope, the weight load of the slope is transferred to the adjacent parts, leading to an increase in the stability of the slope. However, it may also lead to a ploughing failure on the adjacent parts. The application of counterweight on the adjacent parts of an undercut slope is a useful technique to prevent the ploughing failure. In other words, the slopes become stronger as an additional weight is put to the legs; hence, the excavated area can be increased to a wider span before the failure of the slope. This technique could be applied in order to stabilize the temporary slopes. In this work, determination of the maximum width of an undercut span is evaluated under both the static and pseudo-static conditions using numerical analyses. A series of tests are conducted with 120 numerical models using various values for the slope angles, the pseudo-static seismic loads, and the counterweight widths. The numerical results obtained are examined with a statistical method using the response surface methodology. An analysis of variance is carried out in order to investigate the influence of each input variable on the response parameter, and a new equation is derived for computation of the maximum stable undercut span in terms of the input parameters.
Mineral Processing
M. R. Khani; M. Karamoozian
Abstract
In the present work, we investigated and optimized the digestion efficiency, A/S (Al2O3/SiO2 in red mud), and N/S (Na2O/SiO2 in red mud) of mixed bauxite in Iran Alumina Company using the Bayer process. Digestion experiments were carried out in an induction rotary autoclave on a mix of Jajarm, Yazd, ...
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In the present work, we investigated and optimized the digestion efficiency, A/S (Al2O3/SiO2 in red mud), and N/S (Na2O/SiO2 in red mud) of mixed bauxite in Iran Alumina Company using the Bayer process. Digestion experiments were carried out in an induction rotary autoclave on a mix of Jajarm, Yazd, Tash, and Shirin Cheshmeh bauxites. A 4-factor 3-level response surface methodology was applied for the design and analysis of the experiment with the optimization of Na2O concentration, digestion temperature, residence time, and amount of lime addition. Towquadratics and one linear model were derived for the prediction of digestion efficiency, and A/S and N/S responses. The results obtained showed that the optimum amounts for Na2O concentration, temperature, amount of lime addition and residence time were 180 g/L, 275°C, 7.73%, and 50 minutes, respectively, in which the digestion efficiency, A/S, and N/S reached 72.05%, 1.169, and 0.27, respectively. Validation experiment showed that the digestion efficiency, A/S, and N/S were 72.24%, 1.162, and 0.28% respectively, which meant a 2% increase in digestion efficiency and a 0.09 and 0.02 decrease in A/S and N/S, respectively, compared to the current operating condition.
