Practice of Improving the Grade of Iron Concentrate

The ore processed by Shandong Jinling Iron Mine (referred to as Jinling Iron Mine) is a high-temperature hydrothermal contact metasomatic skarn type polymetallic magnetite. The ore type is mainly magnetite, followed by skarn magnetite and pseudo hematite. The main metal mineral is magnetite, followed by pyrite (containing cobalt), chalcopyrite, and pyrrhotite; The main gangue minerals are pyroxene, followed by chlorite, phlogopite, vermiculite, and a small amount of calcite. The original process flow and existing problems of the Jinling Iron Mine beneficiation plant are as follows: the crushing and screening process consists of two stages and one closed circuit. Pre screening is set before fine crushing, and the screened materials are pre selected and discarded by magnetic pulleys. After fine crushing, inspection and screening are set. The screened materials are pre selected by magnetic pulleys and returned to fine crushing, forming a closed circuit; The grinding and selection process consists of a closed circuit grinding process followed by a graded overflow followed by mixed flotation followed by separation flotation to recover copper and cobalt. The mixed flotation tailings are then subjected to three stages of magnetic separation to recover iron. The main problems with the original process are: (1) With the increase of processing capacity, the ball mill can no longer guarantee the fineness required by the grinding production process. (2) The working condition of the magnetic agglomeration machine is poor, and the grade of iron concentrate fluctuates greatly; The processing capacity of CTB1024 magnetic separator is severely insufficient, and the sorting effect is poor. (3) The auxiliary equipment also has varying degrees of insufficient production capacity, which restricts the selection effect of production processes. 2. Measures to Improve the Grade of Iron Concentrate 2.1. Production practice and experiments on improving the grinding fineness of ball mills have shown that within a certain range, for every 1 percentage point increase in grinding fineness, the grade of iron concentrate increases by 0.08 percentage points. Due to the needs of enterprise development, the production capacity of iron concentrate powder in the beneficiation plant increased from 50000 tons in 1997 to 675000 tons in 2001, and the hourly processing capacity of the ball mill also increased from 28 tons to 38 tons. 2.1.1 Reducing the particle size of the grinding mill increased the processing capacity of the beneficiation plant by 27% without significant changes in ore properties. Since 1998, Jinling Iron Mine has reduced the grinding particle size from 0-20mm to 0-14mm, achieving the goal of more crushing and less grinding, improving grinding efficiency, reducing production costs, and meeting production process requirements. 2.1.2 Reasonable ore blending: The ore from the beneficiation plant comes from three sub mines: Zhaokou, Houzhuang, and Tieshan. The ore properties of each sub mine vary greatly, and there are significant differences in their grindability and washability. In order to stabilize the feeding properties of the ball mill, strict ratios were made for the input ore volume of the three mining plants according to their production capacity. When the ore output of three mining plants is uneven, a buffer storage yard is established to ensure the ratio of ore to be ground. Through the above two measures, the grinding fineness of the ball cnc mill turn has been basically stabilized within the range required by the production process (see Table 1), creating conditions for stable improvement of iron concentrate grade.

2.2.2 Transformation of Iron Concentrate Filters From August 1998 to November 1999, four filters were renovated, increasing the magnetic envelope angle of the filters from 31 ° to 39 °. After the transformation of the magnetic filter, its adsorption area increased, and the unit processing capacity of the filter increased by 25%, effectively solving the pressure caused by the increase in processing capacity. At the same time, two sets of magnetic blocks were added along the circumference, increasing the number of magnetic rolling of the iron concentrate in the adsorption zone, which is conducive to cleaning out the gangue mixed in the magnetic minerals and further improving the grade of the iron concentrate. 2.3 Actively applying new equipment to improve equipment level 2.3.1 Application of CTDG1010N permanent magnet dry magnetic separator The original pre selection and waste disposal equipment was 1030mm × 1045mm water-cooled electromagnetic pulley. This device has many drawbacks: (1) the magnetic field force and its depth of action are small, causing metal loss; (2) The magnetic system design is unreasonable, and waste rocks are mixed in the middle of magnetic ore, affecting the quality of the concentrate; (3) The structure is complex, with frequent faults, which affect the normal production of the process flow. In August 1998, the CTDG1010N permanent magnet dry magnetic separator replaced the original electromagnetic pulley. The CTDG1010N permanent magnet dry magnetic separator has a reasonable magnetic system design, high field strength, and a large depth of magnetic field action. After the renovation, magnetic rolling occurred in the direction of circular motion, resulting in an additional 11520t of waste rock being thrown every year. At the same time, the iron grade entering the ground ore increased by 1-2 percentage points, which played an important role in improving the grade of iron concentrate. [next] 2.3.2 Transformation of Magnetic Separation Tailings Pump The tailings pump for the first and second magnetic separation operations was originally an 8/6E-AH slurry pump, with a maximum processing capacity of 400m3/h. After the processing capacity of the ball mill increased, the insufficient processing capacity of the slurry pump restricted the addition of dispersed water in the magnetic separator, affecting the operating concentration of the first and second magnets. In December 2000, an investment of 120000 yuan was made to complete the transformation of the magnetic separation tailings pump and switch to a 200ZGB slurry pump. After the renovation, the tailings pump met the production requirements, and the first and second magnetic separators achieved ideal working conditions, optimizing the sorting effect of the magnetic separator. Moreover, the actual power consumption of the tailings pump has been reduced by 40kW, saving over 300000 kW. h of electricity annually. The application of the above measures in the analysis of production indicators and economic benefits has led to an increasing trend in the grade of iron concentrate the classification of powder binders year by year. In 2001, the qualification rate of iron concentrate outward transportation (concentrate grade not less than 65.50%) reached 100%, with an average grade of 66.37%. It can be seen that from 1997 to 2001, while the production of iron concentrate steadily increased, the grade of iron concentrate powder increased by 0.83 percentage points. According to the sales contract, for every 0.1 grade increase, an economic benefit of 0.7 yuan can be obtained, resulting in an annual increase of over 1.6 million yuan in benefits.