Multipurpose Utilization Of Ascharite With Magnesite

The world's boron resources are mainly distributed in the Pacific Rim and Mediterranean countries, including Turkey, the United States, South America, Russia and China.Compared with the other countries and regions rich in boron resources, the majority of boron minerals in China are low grade boron ores which is difficult to process. Take the solid boron resources for example, the average grades of the foreign tinca, colemanite and ulexite ores are around 25%, while the average grade of ascharite in Liaoning Province is only about 10%, indicating that both the boron ore reserves and grade of China are in disadvantage campared to the other countries rich in boron resources. As the development of the gloabalization, the boron chemical companies in China are facing unprecedentedly fierce competion. Therefore, how to improve the competivity of chinese companies is becoming a very crucial problem. Considering the current circumstance, the only solution is to maximize the utilization of the usefull elments in the boron minerals. In this paper, both high and low grade ascharite rich in magnesite were studied, respectively.The research object of the first part in this paper is the multipurpose utilization of the low grade ascharite rich in magnesite from Kuandian. The ascharite raw ore was calcined, slaked, carbonated and pyrolyzed to lead to basic magnesium carbonate (4MgCO3·Mg(OH)2·4H20), the slime obtained from the process was provided as the raw materials for producing borax. The effects of re-calcining temperature of the raw ores and the solid to liquid ratio in the process of carbonation on extracting magnesium were invetigateded. The effects of calcining temperature and the carbonation process on the reaction activity of ascharite ores were also studied. The reaction activity of the aschartie ores increases to the top then drops with the increase of the re-calcining temperature of the ascharite ores.The content of MgO in the carbonation mother liquor increases first to a maximum point then drops with the increase of the re-calcining temperature of the ascharite ores. The content of MgO in the carbonation mother liquor increases first to a maximum point then drops with the increase of the solid to liquid ratio. The reaction activity of the aschartie ores decreases a little bit after carbonation. It is concluded that the best calcination temperature is 700℃, at which the reaction activity of ascharite and the amount of MgCO3 obtained are the highest, the reaction activity of ascharite reached the maximum 85.24%from 82.17%. When solid to liquid ratio is 160g/L, the reaction activity of ascharite after the carbonation process was 80.13%, indicating a little reactivity drop compared with that of 82.17%for the ascharite ores before the second recalcining. The separation of free MgO from the ascharite ores by carbonation process and transferring the MgO into basic magnesium carbonate (4MgCO3·Mg(OH)2·4H2O) could not only solve the problem of drying up and filtering difficulty in the production of borax by soda-CO2 method, but also afford valuable basic magnesium carbonate at the same time. Therefore, it is a feasible multipurpose utilization process for ascharite ores with magneite.In the second part of the paper, high grade ascharite ores rich in magnesite from Errengou with 18%B2O3 was studied. The XRD characterization of the ascharite ores indicates that there exists a quantity of magnesite in the ascharite ores. The TG-DTA analysis of the ascharite ores shows that magnesite starts to decompose at 600℃. The effect of calcining temperature of the ores on the decomposition of magnesite was studied. Most magnesite in the ores can be decomposed into MgO at appropriate calcining temperature for the appropriate time. MgO was transferred into valuable basic magnesium carbonate by the processes of slaking, carbonation and pyrolysis. The grade of slime after carbonation increases, it can be used to manufacture boric acid with sulfuric acid. The calcining temperature of the ores and solid to liquid ratio in the carbonation process have a great effect on extracting magnesium from the ores, the appropriate calcining temperature and solid to liquid ratio are 800℃and 60g/L, respectively. The most favorable carbonation time is 60min. The grade of slime increases from 18.48%to 25.95%after calcining and carbonation. The leaching rates of both boron and magnesium in the lime reach the maximum when the solid to liquid ratio and H2SO4/slime ratio of the decomposition of the slime by sulfur acid are 3:1 and 1.1:1.