The Miaogou Iron Mine, part of the Hebei Iron and Steel Group, is located in China’s Qinglong County, some 300 kilometers east of Beijing. Its annual iron concentrate production is 800,000 tons.
Due to the recent downturn in the iron and steel industry, Miaogou’s concentration costs were exceeding the price of iron concentrate. This put significant pressure on the company’s operations. Something had to be done.
Improved recovery, less energy
The mine’s original grinding circuit consisted of ball mills exclusively. The primary stage comprised 5 ball mills, the secondary stage 3 ball mills, and the final, tertiary stage 2 ball mills. The original tertiary grinding fineness was -325 mesh with 71-73% passing. Iron concentrate grade was 65% and the average recovery rate 87%.
Since the technological transformation, the concentration costs have basically paralleled the current price of iron concentrate. Under the current market situation, the normal production of the mine can still be guaranteed. Through the introduction of Metso’s Vertimill® VTM1500 vertical grinding mill, Miaogou Iron Mine has not only successfully achieved the goal of the technological transformation, it has also laid the foundation for smoothly riding out the current market's difficulties.
“After replacing the original tertiary ball mills with a Vertimill VTM1500, the grinding fineness was increased from 71-73% to 88-90% passing -325 mesh, the iron concentrate grade from 65% to 66%, and the average recovery from 87% to 89%. At the same time, the silica content was decreased by 1%,” says Zhang Runshen, General Chief of Miaogou Iron Mine Project and Chief of Concentration Plant.
In addition to having helped improve the recovery rate, the Vertimill has a lower energy and grinding media consumption rate than the ball mill. It also takes up much less space.