Pre-concentration of complex refractory iron ore - three-stage suspension roasting - magnetic separation treatment method

Abstract

A pre-enrichment-three-stage suspension roasting-magnetic separation treatment method for complex and difficult-to-separate iron ore, which belongs to the field of mineral processing technology. It is carried out according to the following steps: (1) Grind the complex and refractory-to-separate iron ore into weak magnetic fields. The tailings are separated by strong magnetic separation; (2) Put the strong magnetic separation concentrate into the suspension roasting furnace, and heat it to 450~800°C in the suspended state for pre-oxidation roasting; (3) Pour in nitrogen to replace the air; Inject reducing gas to reduce in a suspended and loose state; (4) When the temperature drops to 250~400°C, air is introduced for reoxidation, and when the temperature drops below 100°C, the secondary grinding is taken out; (5) The third magnetic separation is performed , the third magnetic separation concentrate and the weak magnetic separation concentrate are obtained as the final concentrate. The method of the invention is simple in process, improves the recovery rate of highly refractory ores, has strong adaptability, safe and reliable process, uniform and stable product quality, and has the advantages of energy saving and consumption reduction.

Description

Technical field [0001] The invention belongs to the technical field of mineral processing, and particularly relates to a pre-enrichment-three-stage suspension roasting-magnetic separation treatment method of complex and difficult-to-dress iron ore. Background technique [0002] With the rapid development of my country's steel industry, the demand for iron ore has risen sharply. China’s low iron ore grade, poor endowment, and high mining and dressing costs have caused domestic iron ore production to be far from meeting the needs of the development of the steel industry; in 2014, China imported 933 million tons of iron ore, and its foreign dependence was as high as 78.5%. The excessive dependence of iron ore on foreign countries has further reduced China’s steel’s international voice and safety; the price of imported iron ore in 2014 has been reduced from USD 130 / t at the beginning of the year to below USD 70 / t, and domestic iron ore is also corresponding A price cut of more than ...

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Problems solved by technology

[0003] Hematite-siderite-limonite-magnetite mixed ore is a typical complex refractory iron ore resource, widely distributed in Liaoning, Shanxi, Shaanxi, Gansu, Xinjiang and other places; the mineral composition of this type of iron ore is extremely Complex, the main minerals are hematite, magnetite, siderite, quartz, iron dolomite, etc., of which iron in hematite accounts for 30-80%, iron in siderite accounts for 5-20%, limonite The iron in the ore accounts for 5-20%, and the iron in the magnetite accounts for 5-20%. Due to the complex mineral composition and close symbiotic relationship of the ore, there are many types of iron-containing minerals, and the separation properties vary greatly. Technology is difficult to obtain better technical and economic indicators; Northeastern University and Dong'anshan Sintering Plant adopt "step-by-step flotation" technology to process Dong'anshan carbonate-bearing iron ore (belonging to hematite-siderite-limonite-magnetic Iron ore mixed ore), obtained the industrial technical index of TFe grade 63.37%, recovery rate only 60~65%

[0004] Magnetization roasting-magnetic separation refers to heating materials or ores in the corresponding atmosphere to perform complex physical and chemical actions, so that weak magnetic iron minerals can be transformed into strong magnetic iron minerals (Fe 3 o 4 ), and then use the magnetic difference between minerals for magnetic separation; common methods of magnetization roasting include shaft furnace roasting, rotary kiln roasting, fluidized roasting, etc. 3 Shaft furnace roasting technology processes this type of ore. The roasted ore can be subjected to weak magnetic separation to obtain iron concentrate with a TFe grade of 55%-56%, and the iron recovery rate is 70-80%. However, the ore size suitable for shaft furnace processing is 25-75mm. About 40% of the 0-25mm ore in Jiuquan Iron and Steel Concentrator can only use the strong magnetic separation process, which can only obtain iron concentrate with a TFe grade of 49.06%, and the iron recovery rate is 66.59%, resulting in a large waste of resources; and the shaft furnace roasting process There are problems such as high energy consumption, long roasting time, uneven product quality, etc.

[0005] When the above magnetization roasting technology is used to process hematite-siderite-limonite-magnetite mixed ore, there are three problems as follows: 1. Due to the inconsistency of iron mineral properties, the reactions of different minerals under the same reduction conditions are not synchronized , the reducing material cannot completely react to generate magnetic Fe 3 o 4 , or there is over-reduction to generate non-magnetic FeO, which leads to poor sorting indicators; 2. The heating and reduction of materials are carried out simultaneously, and the reduction atmosphere is difficult to guarantee, and it is difficult to implement industrialization; 3. It cannot handle 0~25mm fine-grained materials

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