ارزيابي فرآوري فسفات از سنگ سبز با استفاده از مدار فعلي كارخانه فرآوري فسفات اسفوردي

Evaluation of green phosphate rock benefication by the present processing circuit of Esfordi phosphate plant

مجتمع فسفات اسفوردي به‌عنوان مهم‌ترين توليدكننده فسفات در ايران، از ذخيره‌اي با منشأ آذرين، به روش فلوتاسيون كنسانتره آپاتيت توليد مي‌كند. مدار فعلي اين كارخانه براي جدايش فسفات از كاني‌هاي آهن‌دار طراحي شده است. بخشي از ماده معدني، داراي كاني‌هاي سيليكاته منيزيم‌دار به‌عنوان باطله مي‌باشد كه به سنگ سبز معروف است. تا به امروز از سنگ سبز به‌عنوان خوراك كارخانه فرآوري استفاده نشده است. درحالي‌كه پنج ميليون تن از ذخيره معدن را سنگ سبز با عيار متوسط 7 درصد P2O5 تشكيل مي‌دهد. در اين تحقيق فرآوري سنگ سبز با استفاده از مدار فرآوري فعلي بررسي شد. براي اين منظور نمونه سنگ سبز مورد شناسايي قرار گرفت و كاني‌هاي موجود و درجه آزادي آن‌ها مشخص شد. نتايج نشان داد كه بخشي از كاني‌هاي آهن‌دار به‌صورت مگنتيت مي‌باشند. آزمايش‌هاي جدايش مغناطيسي شدت بالا مشخص كرد كه بخشي از كاني‌هاي سيليكاته به كنسانتره جدايش مغناطيسي آهن راه مي‌يابند (بازيابي 38/10 درصد MgO درشدت 5000 گوس). آزمايش‌هاي فلوتاسيون نشان داد كه بازيابي براي نمونه سنگ سبز بسيار پايين است و در شرايط معمول بازيابي و عيار P2O5، 39/7 و 11/21 درصد به دست آمد كه بعد از نرمه گيري به 65/38 و 98/27 درصد ارتقا يافت. پايش كارايي مدار فعلي با خوراك‌دهي سنگ سبز انجام شد و بازيابي كم فلوتاسيون، همراه با پايداري زياد كف مشاهده گرديد. همچنين كارايي مدار آسيا كني و سيكلون‌هاي نرمه گيري بررسي شد. در ادامه پيشنهادهايي جهت بهبود مدار فعلي كارخانه براي فرآوري سنگ سبز ارائه گرديد.

As the most important phosphate producer in Iran, the Esfordi phosphate complex produces apatite concentrate from the igneous ore by the flotation method. This plant is designed to separate phosphate from iron minerals. There is a type of rock in the Esfordi deposit that contains magnesium-bearing silicate minerals as gangue, which refers to green rock. Although the green rock includes five million tons of the mine reserve with an average grade of 7% P2O5, it has not been fed to the beneficiation plant, so far. In this research, the green rock processing was investigated using the current processing plant. A representative sample of green rock was prepared and characterized to evaluate the chemistry, mineralogy, and degree of freedom of apatite minerals. The laboratory magnetic separation and flotation tests along with the plenary sampling and characterization from the processing plant were performed. Introduction Esfordi Phosphate Mine has the largest reserves of igneous phosphate in the country. At present, the feed for the dressing plant is supplied from apatite and iron-apatite. The green rock is an alternative feed for the beneficiation plant. The presence of magnesium-bearing silicates and fine particles are the two main obstacles of green rock flotation. In this research, flotation experiments were performed to process green rock, and the performance of the current phosphate processing plant was assessed. Methodology and Approaches Sampling was performed in two stages. In the first step, a sample was taken from the stock to identify the characteristics of green rock. The laboratory magnetic separation experiments at different magnetic field intensities and flotation experiments were performed. Fatty acid collector (to float apatite) and corn starch (for depressing iron ores and silicate minerals) were used in the flotation tests. The industrial-scale investigations were made by feeding the green rock to the plant, and sampling procedures were performed from different grinding, classification, and flotation streams. Results and Conclusions The results of High-intensity magnetic separation experiments showed that some of the silicate minerals found their way to the iron magnetic separation concentrate (recovery of 10.38% MgO at 5000 gausses). Flotation experiments showed that the recovery for green rock samples was very low and under normal conditions, recovery and P2O5 grades of 7.39 and 21.11% were gained, which increased to 38.65 and 27.98% after desliming. The efficiency of feeding green rock to the current circuit was monitored and low flotation recovery was observed along with high froth stability. The efficiency of the grinding circuit and desliming cyclones was also evaluated. Then, suggestions were made to improve the current processing circuit for green rock beneficiation