Combined direct reduction technology of blast furnace gas ash and refractory low-grade iron ore in tunnel kiln

Abstract

The invention provides a combined direct reduction technology of blast furnace gas ash and refractory low-grade iron ore in a tunnel kiln. The combined direct reduction technology mainly comprises the following processing steps: (1) burdening and mixing the iron ore with grain sizes of 0-3mm and the blast furnace gas ash so as to obtain fine-graded materials; grading the iron ore with grain sizes of above 1mm according to different grain size ranges, burdening and mixing the iron ore and reduced coal in the same grain size range so as to obtain coarse-graded materials; (2) sequentially laying the fine-graded materials and the coarse-graded materials on a fire-resistant thermal conducting plate of a kiln car of a tunnel kiln from top to bottom; and (3) placing the materials in the tunnel kiln along with the kiln car so as to carry out high temperature reduction. The combined direct reduction technology has the advantages that the blast furnace gas ash is effectively utilized, and the utilization efficiency of carbon in the blast furnace gas ash is greatly improved; by adopting a layering distribution step-by-step oxygenation reduction method, the metallization ratio of iron ore direct reduction is increased, and the reduction time is shortened; and the iron grade of metallizing iron powder produced by the technology reaches above 84%, and the metallization ratio reaches above 88%.

Description

technical field [0001] The invention belongs to the technical field of metallurgy and mineral engineering, and relates to a combined direct reduction process of blast furnace gas ash and refractory low-grade iron ore tunnel kiln. Background technique [0002] At present, the development and utilization of blast furnace gas ash and refractory low-grade iron ore generally adopt a single material treatment method in China. The treatment method and utilization status are as follows: [0003] (1) Current status of blast furnace gas ash treatment [0004] With the rapid development of the iron and steel industry, the annual discharge of blast furnace gas ash is very huge. At present, this kind of dust has not been effectively treated for a long time, and it has piled up like a mountain near many steel mills. Valuable resources such as carbon. [0005] In order to make reasonable use of blast furnace gas mortar, domestic iron and steel enterprises have done a lot of work in the...

AI Technical Summary

Problems solved by technology

At present, this kind of dust has not been effectively treated for a long time, and it has piled up like a mountain near many steel mills. Carbon and other valuable resources

[0005] In order to make reasonable use of blast furnace gas mortar, domestic iron and steel enterprises have done a lot of work in the utilization of sludge, dust and other wastes in the past ten years, changing the original practice of using dust and sludge as sintering raw materials. There are: steelmaking dust is used to press into cold solidified pellets and add to steelmaking for utilization. Although this method makes good use of iron oxides and calcium oxide in steelmaking dust, it is difficult to The reduction amount of iron oxide is limited, so it can only be added in a small amount during smelting. At the same time, the cold solidified pellets added in steelmaking are prone to pulverization; When recycling carbon-containing resources, there is a problem of ring formation in the rotary kiln; when the blast furnace gas ash is removed by a rotary hearth furnace to remove Zn and Pb and utilize the carbon and iron oxides, it is generally achieved by adding a certain amount of iron oxide scale. Make carbon-containing pellets and make them reduce at high temperature. Although this method can dispose of iron-containing dust in large quantities, two kinds of high-purity secondary dust rich in zinc and lead and metallized pellets for blast furnaces can be obtained. products, but the main problem is that the carbon utilization efficiency in blast furnace gas ash is not high, the raw materials need to be roasted after pelletizing, and the metallization rate of the reduced products is not high

[0006] (2) Current status of refractory low-grade iron ore processing

①Siderite is one of the low-grade complex refractory minerals with relatively abundant resources. Its theoretical iron grade is only 48.2%, and it often coexists with calcium, magnesium and manganese in the same quality. %, plus the poor sintering performance of siderite concentrate, therefore, it is difficult for iron and steel companies to accept siderite concentrate

②Limonite is also one of the complex refractory minerals. Limonite is rich in crystal water, easy to muddy, and the specific magnetic susceptibility coefficient is very low. Usually, the grade of iron concentrate recovered by physical beneficiation is lower than 60%, and it is difficult to obtain High metal recovery rate

③ The beneficiation process of mixed fine-grained low-grade iron ore is complex and the separation efficiency is poor

[0008] The content of iron oxides in refractory low-grade iron ores is low, resulting in a low concentration of carbon oxides in the iron ore reduction process. Grinding magnetic separation, reverse flotation, magnetization roasting, direct reduction and other processes all have problems such as low metal recovery rate, low iron grade of products produced, long reduction time and high production cost, resulting in some iron A large amount of fine-grained low-grade iron ore stripped out during the mining process has been piled up for unutilization, and there are still a large amount of fine-grained low-grade iron ore that has not been developed yet.

[0009] From the above treatment methods of blast furnace gas ash and refractory low-grade iron ore, it can be seen that the single treatment of blast furnace gas ash and refractory low-grade iron ore cannot achieve satisfactory treatment effect

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