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In 1996, 217.97 million tons of iron ore was selected in the country, accounting for 85.2% of the country's total of 252.28 million tons of iron ore. Selected iron ore production of iron ore fines 85.857 million tons, of which the focus of the ore processing plant 10.961 million tons of raw ore processing, production of iron ore fines 41.85 million tons, accounting for 48.4% of iron ore fines production.
(A) ore crushing
China's ore dressing plants generally use broken, medium break, and fine broken three-stage crushing processes to break down iron ore. Roughly broken multi-use 1.2m or 1.5m gyratory crusher, medium break using 2.1m or 2.2m standard type cone crusher, fine break 2.1m or 2.2m short head type cone crusher. Through coarse broken ore, the block size is not more than 1m, and then after medium and fine crushing, the final product that is sieved with the ore size less than 12mm is sent to the grinding ore pit.
(B) grinding process
Most of China's iron ore grinding processes use two-stage grinding processes, and small- and medium-sized ore dressing plants often use a grinding process. Due to the adoption of fine sieving and new grinding technology, some ore dressing plants have changed from two-stage grinding to three-stage grinding in recent years. The grinding equipment used is generally small. The maximum ball mill is 3.6m×6m, the maximum rod mill is 3.2m×4.5m, the maximum self-grinding mill is 5.5m×1.8m, and the pebble mill is 2.7m×3.6m. The grading after grinding is basically a spiral classifier. In order to increase the efficiency, some hydromills in the beneficiation plant replaced the secondary spiral classifier.
(III) Sorting Technology
Magnetite mineral processing
Mainly used to select low-grade "Anshan-style" magnetite. Due to the strong magnetic properties of the ore and its good grinding and grinding options, the domestic magnetic separation plants have adopted stage grinding and multi-stage grinding processes. For the coarse-grained magnetite, the former is used (a section of grinding), and fine-grained and fine-grained inlays are used. The magnetite uses the latter (two-stage or three-stage grinding) (Figure 3.2.23). The series of permanent magnetization developed by our country has enabled the magnetic separator to achieve permanent magnetization. Since the 1970s, due to the promotion of the new technology of fine sieving and re-grinding at the national magnetite ore concentrator, the concentrate grade has been increased from 62% to about 66%, and the Ministry of Metallurgical Industry has proposed that the concentrate grade be up to 65%.
2. Weak magnetic iron ore beneficiation
It is mainly used to select hematite, limonite, mirror iron ore, siderite, imaginary hematite or mixed ore, also known as “red mineâ€. This kind of ore has a low grade, fine grain size and complex mineral composition, making it difficult to sort. After 1980s, the beneficiation technology has continuously improved the research on roasting magnetic separation, wet-type strong magnetic separation, weak magnetic floatation and re-selection and other technological processes, equipment, and new varieties of pharmaceuticals, so that the concentrate grade and metal recovery rate have been continuously improved. If the Anshan Iron and Steel Qi Dashan Concentrator adopts a new process flow of weak magnetic-magnetic-flotation (Figure 3.2.24), encouraging achievements have been made.
3. Polymetallic ore concentrates
This type of ore is complex in composition and diverse in type. Therefore, the methods, equipment, and processes used are also different. For example, the Baiyuebo Iron Mine uses reverse flotation—multi-gradient magnetic separation, flocculation, flotation, weak magnetic-reverse flotation, and strong magnetic Selecting, weak magnetic-positive flotation, roasting and magnetic separation and other different technological processes to improve the iron recovery rate and comprehensive recovery of rare earth oxides. About 53% of vanadium-iron ore concentrate is obtained through magnetic separation in Panzhihua Iron Mine. The magnetic tailings are subjected to weak magnetic sweep-strong magnetic separation-re-election-flotation-drying electrification to obtain titanium concentrate and thiocyanide Mine, recovery of titanium and cobalt. Daye Iron Mine uses weak magnetic-magnetism and flotation to recover iron, copper, cobalt, and sulfur.
(4) Sintering pellet technology
Sintering technology is the main means of man-made rich mines in China. In 1996, a total of 16.0965 million tons of man-made rich ore were produced, including 948.59 million tons of key enterprises, accounting for 58.9%, and 61.337 million tons of local state-owned enterprises, accounting for 38.1%.
China has reached a considerable level in the technology of fine concentrate sintering. As early as the early 1950s, Anshan Iron & Steel successfully changed the production method of acidic sinters to alkaline sinter production methods on sintering machines. In the world, slaked lime or lime was used as the flux to solve the problem of fine concentrate sintering.
The equipment level of sintering pellets has also been improved. There are 419 sintering machines in the country, with a total area of ​​15,522m. Among them, there are 22 sintering machines of 130m2 or more, with a total area of ​​4,107m2, and 197 sintering machines of 24 to 129m2, with a total area of ​​9,387 m2. There are 200 sintering machines of less than 24 square meters and the total area is 2028 square meters.The 300m2 sintering machine put into production at Maanshan Iron and Steel Plant on February 24, 1994 is the largest modern sintering machine designed, manufactured and constructed by China in addition to Baosteel.
The main technical and economic indicators for sintering in 1995 were: utilization factor 1.36t/(m2·h), sinter grade 53.00%, sintering machine calendar rate 80.94%, sinter qualification rate 84.92%, and labor productivity 2170t/ (h·a).
Iron ore beneficiation technology
China’s iron ore reserves are mostly poor (accounting for 97.5% of total reserves) and have more (or 1/3) of the total combined reserves (compared with 1/3 of total reserves), so most of the iron ore needs to be processed before smelting. .