Activation Technology And Parameter Optimization Design Research Of Low-grade Boron And Magnesium Ore

In spite of abundant boron resources in China, much of ore resource condition and grade are severe. Nowadays the high-grade boron and magnesium ore which are generally processed and utilized in nature account for 6.64% of total reserves of boron ore in china. On the other hand, those low-grade boron and magnesium ore the reserves of which are more than half of the total reserves are abandoned and less used because of the limit of high-grade ore, resulting in much resource waste, huge land occupation and serious effects on environment. Obviously, the exploitation and utilization of low-grade ore resources should be taken into consideration due to the non-renewable resources of ore. Therefore, this study use the method of High-temperature and acid hydrolysis to activate necessary elements（boron, magnesium, calcium, silicon and so on） needed for plant growth and optimize relevant parameter with low-grade of boron and magnesium ore in Kuan dian of Liaoning province as raw materials, moderately made into products which not only contain the nutrient elements such as boron, magnesium, calcium, silicon and so on, but also owes the function of soil conditioner. Above all, the research provide reasonable technologies to utilize the low-grade boron and magnesium ore resources meanwhile make certain contribution to local agricultural development. The main findings are as follows:1. Chemical characteristics and components of low-grade boron and magnesium ore were analyzed. The results showed that the raw ore were mainly consisted of perovskite（MgSiO₃）, magnesite（MgCO₃）, forsterite（Mg₂SiO₄） and α-quartz（SiO₂）, the structure was relatively complex; The B₂O₃ content（9.69%） was not suitable for producing boric acids in industrial process. However, the ore still contained MgO（32.61%）, SiO₂（20.28%）, CaO（6.79%）, Fe₂O₃（2.2.3%） and Al₂O₃（1.08%）. Activated by certain technological process, the nutrient elements could be transformed from hardly-soluble form to plant-available form, then were made into a product which not only contained the nutrient elements such as boron, magnesium, calcium and silicon etc., but also possessed the function of soil conditioner. Therefore, its implications could be very broad.2. Sulfuric acid and nitric acid were respectively used for acid hydrolysis to figure out the different variables in acid hydrolysis process, including acid concentration, acid dosage, reaction time, granularity and clarify other factors. The results showed that: four factors had a certain influence on the activation process; compared with the nitric acid solution, the reaction process of the sulfuric acid solution was easier to be controlled and complete. Moreover, The production cost was lower, which was suitable for industrial production. The optimum conditions of the solution of sulfuric acid were confirmed via orthogonal test : sulfuric acid concentration of 75%, and the amount of sulfuric acid as the theoretical amount of 130%, the ore particle size of 100 mesh sieve, at 80r/min stirring speed with10 min reaction. Under these conditions, the content of water-soluble B₂O₃, MgO and CaO in the reaction products were respectively 4.92%, 15.37% and 2.93%. The effective SiO₂ content was 0.49% and the pH value was 3.27.The study also used the high-temperature calcination to activate the low- grade boron magnesium ore. Investigating the influence of calcination temperature, calcination time, calcination granularity on the slag calcination test and analysis of the phase of calcined product. Studies showed that, the magnesite（MgCO₃） in original was decomposed as a small amount of free magnesium oxide（MgO） during calcination process. The optimum conditions were confirmed via orthogonal test: calcining temperature（850?C）, calcination time（3h） and particle sizes（80-100 mesh）. Under these conditions, the content of water-soluble B₂O₃ reached 2.53%, effective MgO and CaO in the calcined material were respectively 25.35% and 6.34%, compared with the original ore, effective degree reached 78% and 93%. The effective SiO₂ content reached 5.55%, and the pH value was 11.50.3. The influence of calcined materials on the magnesium availability through ammonuim sulfate calcination process were researched. The results showed that: roasting temperature, roasting time and the addition of ammonium sulfate had influence on the reaction process, and the high reaction temperature might cause the burnt. The optimum technological conditions: calcination temperature（475?C）, n（（NH4）2SO₄）: n（MgO） were 1.4:1 under the calcinations time of 4h. Under these conditions, the product of the water-soluble MgO content reached the maximum of 16.11%, water-soluble boron, calcium contents were respectively 4.30% and 5.23%, more than that of the water-soluble content in samples before roasting. Effective SiO₂ content reached 5.56% and pH 6.14.4. The results from the Physical traits analysis of the two process samples showed that: the water content of different slag treatment processes were less than 5%, their particle size were greater than 80 mesh, matching the requirement of national standards.In summary, two methods could achieve the purpose of activating the low-grade boron and magnesium ore. Acid product’s pH was 3.27, which could be applied in alkaline soils in the North of China. The product’s pH of High-temperature method was 11.50, certainly used in South China’s acidic soils. Both of them could not only replenish soil boron, silicon, calcium magnesium and other trace elements, but also improve soil structure. In addition, the ammonium sulphate roasting method could be applied for the products of high-temperature method through this two ways. That makes effective magnesium into the water-soluble magnesium in order to improve the utilization ratio of elements, while the pH of the high-temperature calcined material could be lowered to achieve the normal growth range of the plant.