| The production and sustainable development of manganese series products were restricted by poor resources of manganese ore in China. At the area of some manganese series products production concentrated in our country, the grade of manganese carbonate has been reduced from18%～20%to only12%～15%, and on the other hand, a large number of pyrolusite of manganese content in20%～25%can’t be used, because of the cost of reduction process is too high or the environmental pollution problems serious. Therefore, it has important strategic significance to research how to use the resources of manganese ore economically and legitimately in China for easing the contradiction of manganese ore resources short supply in our country, ensuring the sustainable development of manganese series products industry, and promoting the economic development of western region. In this thesis, the unmanageable complex low-grade manganese ore and manganese-containing dust as raw material, a new technology of pressure acid leaching-purification-extraction was developed.First of all, The analysis approaches such as chemical multielement analysis, physical phase analysis, XRD analysis, SEM images and energy spectrum analysis were used for the mineralogy analysis of complex low-grade manganese ore, manganese-containing dust and pyrite. The analysis results showed that manganese of complex low-grade manganese mainly existed in high valence manganese oxide (Mn3O4and MnO1.88), the content of manganese was17.64%. The major gangue mineral of complex low-grade manganese ore is CaO, followed by SiO2, Al2O3and MgO. The manganese of manganese-containing dust mainly distributed in the high valence manganese oxide MnO2and MnO1.88, the content of manganese was33.5%. The major gangue mineral of manganese-containing dust is SiO2, followed by Al2O3. The main phase composition of pyrite were FeS2, BaSO4, SiO2, ZnS and Al2Si4O10(OH)2.Thermodynamics and mechanism analysis were studied for the pressure leaching process of complex low-grade manganese and manganese-containing dust, the values of chemical reaction were negative. The potential-oxidation state-AG diagram of manganese in acid solution, the φ-pH diagram of Mn-H2O system, Fe-S-H2O system and Mn-H2O system, S-H2O system at298K and373K were analyzed. The analysis results showed that high valence manganese oxide was reducted and leaching by pyrite theoretically whether in room temperature or high temperature conditions. Pressure leaching in high temperature is based on the needs of the dynamics primarily, and it is helpful for the sulfur and iron of pyrite were translated into SO42-or H2SO4and Fe2O3respectively, thus the effect of increasing the leaching speed, decreasing the acid consumption and iron dissolving rate were achieved.The pressure leaching process of complex low-grade manganese ore in a sulfuric acid medium was studied by orthogonal experiments and single-factor experiments. And the optimum leaching conditions were determined to be:low grade manganese powdered ore of100g, initial acidity of120g/L, leaching temperature of120℃, pyrite amount of50g, liquid-to-solid ratio of5:1, leaching time of100min, pressure of0.7Mpa, the agitation speed of350r/min. The results of experiments indicated that this craft had good stability. Under the optimized leaching condition, the leaching rate of manganese was96%, and the leaching rates of Al and Fe were38.7%and7.12%. The concentration of Mn、Fe and Al in leaching liquid were19.87g/L、2.34g/L and0.74g/L respectively. The temperature, pressure and time had a great important on the behavior of aluminum.The optimum operating parameters of pressure leaching of manganese-containing dust were established as follows:the manganese-containing dust of100g; pyrite amount of50g; the liquid to solid ratio of5:1; the initial sulfuric acid concentration of120g/L, leaching temperature of120℃, pressure of0.8MPa, leaching time of2h, the agitation speed of350r/min. Under these conditions, the leaching rates of Mn and Fe arrive at96.1%and7%, the residual rate of final acid is about35%. The concentration of manganese and iron in leaching liquid were44.74g/L and2.52g/L.The kinetics of pressure leaching low grade manganese ore was studied. The effects of agitation rate, particle size,temperature, pressure, initial acid concentration and pyrite content in solid mineral on the leaching rate of manganese were examined. The experiment results indicate that the agitation rate had no effect basically on the reaction process, manganese leaching rate increases with a decrease of particle size and an increase of temperature, total pressure, sulfuric acid concentration and pyrite content in solid mineral. It was found that the reaction kinetic model follows the shrinking core model of chemical reaction control and the apparent activation energy was determined as43.4kJ/mol. The reaction orders with respect to sulphuric acid concentration total pressure and pyrite content were1.428、0.864and2.58, respectively. The kinetic equations for the effect of particle size, leaching temperature, total pressure, sulfuric acid concentration and pyrite content were obtained and a mathematical model of manganese leaching from low grade manganese ore was developed as:1-(1-x)1/3=(3824.8/HAir0.864·r0)·exp(-43.4×103/RT)·C1.428·P0.864·[FeS2]2.58·t This equation estimates the leaching of manganese with very good agreement between the experimental and calculated values.Considering the production, the purification process of manganese sulfate pressure leaching liquid has been studied. The method of oxidation and neutralization was used for removing Fe3+and Al3+ions, the concentration of Fe3+and Al3+ions in neutralization liquid were less than1mg/L and0.18mg/L respectively, the concentration of Cu2+and Zn2+ion were0.27mg/L and0.082mg/L respectively; Removal heavy metal ion by ammonium sulphide as the precipitating agent, the pH of the neutralization fluid was controlled less than6.0, the heavy metal ions were precipitate out and MnS precipitation was not generated, the concentration of Co2+Ni2+and Cu2+in filtrate were0.253mg/L、0.637mg/L and0.071mg/L; After concentration and standing for a long time, the concentration and removal rate of Ca2+and Mg2+ion were0.08g/L and85.63%、0.36g/L and83.22%.In view of the low concentration of manganese ions in leaching solution of low-grade manganese ore and manganese-containing dust, the technique of extraction-back extraction was used. Manganese can not be directly extracted from the leaching solution because of iron is extracted easily, and calcium and magnesium would lead to the emulsification of extracting agent. Therefore, the purification process was carried out before the process of extraction-back extraction.The optimum extraction conditions were determined to be:the saponification rate of extraction agent P204was80%, the extraction phase ratio (O/A) was1:1, the concentration of extraction agent (P204) was40%, the extraction pH value was5.0, the temperature was30～40℃, the extraction time was5min, the extraction stages was level1. In terms of the purification liquid that the concentration of manganese ion is21.20g/L, Mn extraction rate was above95%. The optimum back-extraction conditions were determined to be:the acidity of back-extraction was120g/L, the temperature of back-extraction was room temperature, the mixing time of back-extraction was3min, the phase ratio of back-extraction was2:1-3:1, the stages of back-extraction was level1. The back-extraction rate and the concentration of manganese were96.9%and42.16g/L respectively, and the concentration of other impurities has reached the requirement of electrolytic manganese. |
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