Study On Chlorination Roasting-Water Leaching-Carbonizing Process For Lowgrade Manganese Ore

Lean ores are the main type of manganese ores in China, the average grade of manganese is only about 20%. With the rapid development of manganese industry, the demand of manganese grade are gradually increased during the process of modern production.However, the amount of medium and high grade manganese ore are too little to meet the requirements of industry. Therefore, Using advanced technology improving low grade manganese ore to prepare the high grade manganese are of great significance.Direct acid leaching method and preroasting leaching method are commonly used in the treatment of low-grade rhodochrosite. The preroasting leaching method process includes chlorination roasting, water leaching and carbonization, the main principles are as follows: rhodochrosite in chlorination roasting process ture into the soluble calcine mainly with manganese chloride, then MnCl₂ is separated by soaking the calcine into the water, finally, Carbonate concentrate are obtained by applying carbide agent to carbonize the immersion of manganese chloride. Compared with traditional direct acid leaching process, the preroasting leaching method primary advantages are as follows: 1) water leaching treatment can avoid using HCl or H2SO4, thereby reducing the environmental pollution from direct discharging containing acid wastewater; 2) the tail gas from roasting process and the filtrate from carbonization both can be recycled to reduce raw material consumption. Therefore, it is very important to study the low grade manganese ore by chlorination roasting, water leaching and carbonization process, which is of great academic significance and economic value.For Sichuan Wanyuan area rhodochrosite having the characteristics of complex composition and low manganese content, this article uses the chlorination roasting, water leaching and carbonation method to research it. The effects of technological parameters from above-mentioned three procedures on manganese recovery rate were systematically studied.The results showed that rhodochrosite's manganese grade were increased from 17.83% to 41.78% depending on this method, and the obtained manganese carbonate ore concentrate can reach the standard of the chemical industry. The conclusions are as follows:?1? The X-ray fluorescence analysis and X-ray diffraction analysis were used to study the original ore. The results showed that the manganese grade of rhodochrosite is 17.83%, which belongs to the typical low grade rhodochrosite and main phase includes MnCO₃, CaMg?CO₃?₂, SiO₂, and a small amount of FeCO₃.?2? Thermodynamic calculation and analysis were applied on the chlorination roasting process of manganese ore, and the results show that it is feasible to use ammonium chloride as additive in the roasting process. The starting decomposition temperature of NH₄ Cl and MnCO₃ are 623 K and 621 K respectively. Therefore, according to the point of thermodynamics analysis, it's more beneficial to get MnCl₂ when reaction temperature is controled in 623K⁷86K, and also to reduce the formation of impurities, such as the ferric chloride, magnesium chloride, calcium chloride and so on.?3? Using ammonium chloride as the additives,the influence of the amount of ammonium chloride, the roasting temperature and roasting time in the calcine quality?the manganese leaching rate as index?were studied. The optimized conditions of chlorination roasting process were established in the same condition of water immersion.When calcination temperature is 459?, ratio ammonium chloride and rhodochrosite power is 1.59 and roasting time is 83 min, the manganese leaching rate can be reached to 93.8%.?4? The water leaching experiment of containing manganese calcine were conducted under the optimal chlorination roasting conditions,and the effect of liquid-solid ratio, temperature of water leaching process and time on the leaching rate of manganese were studied. The results showed that the leaching rate of manganese can reach 93.8% when.the ratio of liquid to solid is 4:1, the water immersion temperature is 50?, the leaching time is 30 min.?5? By adding ammonium hydrogen carbonate solution into containing manganese leaching, the carbonation experiments were studied. Meanwhile the influence of each parameter involving in carbonization process in manganese grade were analyzed.The results show that the preparation of manganese carbonate concentrate ore grade can be increased to 41.78% when NH₄HCO₃ solution concentration is 1 mol/L, the molar ratio of [NH₄HCO₃]: [Mn²⁺] is 2.2:1, water extract pH value is 7.0, the reaction time is 80 min, the reaction temperature is 30?.?6? The leaching residue, filtrate and tail gas from the whole process of the chlorination roasting,water leaching and carbonization were analyzed. In addition to discharge the leaching slag, the filtrate and tail gas can be recycled again. The whole process is not noly environmental protection,and can realize the recycling of resources.