Magnesium metal is widely used in industries such as automotive and aerospace due to its lightweight and high-strength properties. With the continuous development of magnesite mining, the beneficiation of low-grade magnesite has become a major research focus in the magnesite ore processing industry. This article takes a low-grade magnesite ore as an example to introduce the process of desilication and decalcification using reverse flotation.
The main component of the ore is MgO, with impurities mainly consisting of SiO2 and CaO. According to the technical specifications of magnesite ore products, the MgO grade of the sample basically meets the requirements of industrial grade four. However, the mass fraction of SiO2 in the original ore is slightly higher than 2%, exceeding the grade requirement. Therefore, the main purpose of this study is to reduce the mass fractions of SiO2 and CaO in the ore and increase the MgO grade.
The project adopts a reverse flotation process, which first removes most of the silica-bearing minerals and some calcium-bearing minerals through reverse flotation, and then further removes calcium-silicate minerals through positive flotation to improve the quality and reduce impurities of the low-grade magnesite ore.
(1) Reverse Flotation Condition Test
In the reverse flotation condition test, the fineness of grinding was first tested. The pH of the pulp was adjusted to about 6 with sulfuric acid, and a small amount of glass water was added. Dodecylamine was used as the collector for the test, and the grinding fineness was determined to be -0.074mm, with a mass fraction of 79.8%.
Further pH value and reagent dosage tests were conducted. After data comparison, the pH value was determined to be 6. Sodium silicate is a dispersant widely used in ore dressing. It reduces foam viscosity, increases fluidity, and avoids losses caused by foam carrying useful minerals, thereby improving the concentrate grade. After comparing the test data of ore dressing, the dosage of sodium silicate was determined to be 500g/t.
The collector was determined to be dodecylamine, and its dosage has a significant impact on the flotation recovery rate. After experimentation, the optimal dosage of dodecylamine was determined to be 300g/t.
(2) Positive Flotation Condition Test
After reverse flotation, most of the silica-bearing gangue minerals can be removed, and the MgO grade of the reverse flotation concentrate can reach 44.21%. However, the content of dolomite in the concentrate is still relatively high. To further reduce the content of calcium-bearing silica impurities in the reverse flotation concentrate (product in the reverse flotation cell) and increase the MgO grade of magnesite, a positive flotation decalcification test was conducted.
Through pH value and reagent dosage tests, the pH value of positive flotation was determined to be 9, and the dosage of the inhibitor sodium hexametaphosphate was 150g/t. The dosage of frother 2# oil was 100g/t, and the collector for positive flotation was determined to be oleic acid, with a dosage of 1500g/t.
(3) Closed-circuit Flotation Test Flowchart
In order to further improve the MgO recovery rate of magnesite ore, reduce the MgO grade of tailings, and increase the utilization rate of magnesium resources, a closed-circuit flotation test was conducted based on the open-circuit test. The test flowchart is shown in the figure below:
After the above reverse flotation condition tests and closed-circuit flotation tests, the flotation process and reagent dosages were determined. Finally, in the concentrate product, the MgO grade reached 46.12%, and the MgO recovery rate was 75.88%. The mass fraction of dolomite minerals was 0.92%, with a removal rate of 68.33%, and the mass fraction of CaO was 0.81%, with a removal rate of 88.60%. The concentrate grade reached the first-grade magnesite ore requirement.
For low-grade magnesite ore, high silica and calcium content are the main impurities affecting purity and quality. Therefore, the research direction of beneficiation process for low-grade magnesite ore mainly focuses on desilication and decalcification. The rationality of the beneficiation process and the dosage of beneficiation reagents are crucial for the final beneficiation results. If you need ore beneficiation design or purchase magnesite ore beneficiation equipment, you can contact Xin Hai!
