Manganese ore sintering technology

1. Purpose and characteristics of manganese ore sintering

The sintering of manganese ore can be carried out on a belt sintering machine or by sintering, sintering or earth sintering. Due to environmental reasons, the sintering of manganese ore is usually carried out by a belt sintering machine, and other methods are rarely used. The process flow of the belt sintering machine is shown in Figure 1.

After all kinds of raw materials are discharged from the silo according to the ratio, they are transported to the cylinder mixer through the belt, mixed with the hot returning of the hot screen and the cold returning of the cold screen, and then enter the sintering section of the sintering machine for sintering; After the mine is unloaded at the tail, it is broken by a single-roll crusher and then enters the hot sieve. The small particles under the sieve enter the cylinder mixer. The upper part of the sieve enters the belt cooler, after cooling, and then through the cold screen, less than 8mm into the cylinder mixer. A part of 6~15mm is used as the bottom material, and the remaining part is more than 15mm into the finished product warehouse.

Manganese ore has a variety of mineral forms, some containing crystal water, some containing carbonate, manganese oxide is also prone to redox reaction when heated. The manganese ore structure is loose and porous, and has high water absorption. The soft manganese ore has a water content of up to 50%. The manganese ore is subjected to high temperature during the sintering process, the water will evaporate, the carbonate will decompose, and the manganese oxide will undergo a redox reaction. While the reaction of ethylene oxide and manganese tetroxide and manganese in the manganese ore gangue silica easily form manganese olivine [MnSiO3], Fe, Mn or olivine [(MnFe) SiO4], when there is the presence of CaO, There is also a low-melting liquid phase such as calcium manganite [(CaMn)SiO4], which becomes a sintered binder phase.

The purpose of sintering is to make the powdered manganese ore that cannot be directly fed into the furnace into a block charge having a certain particle size and meeting the smelting requirements, in order to improve the gas permeability of the blast furnace charge. At the same time, the physical properties and chemical composition of the powdered manganese ore are changed by sintering, and the metallurgical properties are significantly improved.

The mechanism of manganese ore sintering is basically the same as that of iron ore sintering. That is, the mineral particles are mainly bonded by the liquid phase generated during sintering to form a coke -like porous sintered rock having sufficient strength. According to the smelting requirements, the chemical composition can be made into manganese sinter with different chemical composition and different alkalinity.

In manganese sinter, manganese exists in the silicate state, and its reduction performance is much worse than that of free manganese oxide. It consumes more heat during smelting and affects the recovery rate of manganese. However, by increasing the alkalinity of the sinter, the basic oxide is combined with the acidic oxide to displace the manganese oxide in the acidic liquid phase, which is beneficial to the reduction of manganese during the smelting process.

The natural alkalinity of manganese sinter can be stored for a long time due to the absence of dicalcium silicate and free calcium oxide, but the self-fluxing, especially the high alkalinity manganese sinter, both of which exist, due to hydration and crystal The sinter is severely caused to cause spontaneous fragmentation, forming a large amount of powder, and thus is not suitable for long-term storage.

Studies have shown that any manganese ore decomposed during sintering has a strong affinity for oxygen, which rapidly oxidizes manganese into higher valence oxides, and also easily forms a stable silicate liquid phase with SiO2. Due to the large amount of MnO present in the sintered ore, the liquidus viscosity and the crystallization temperature are greatly reduced. During the sintering process, a liquid phase having a low melting point, a small viscosity and a good fluidity is formed, and when a high-speed gas stream (1.4 to 1.6 m/s) passing through the layer is encountered, a large-porous thin-walled sintered ore structure is easily formed. Therefore, in the case where the strength of the liquid phase is weaker than that of the iron ore during the sintering of the manganese ore, the stress is to avoid supercooling of the sintered ore, to ensure the formation of liquid phase crystals, and to obtain a sintered ore having sufficient strength.

Compared with iron ore structure, manganese ore sintering has the characteristics of large burning loss, high heat consumption, narrow softening temperature range, small loose density, good gas permeability, low product strength and large returning rate (Table 1).

Manganese ore sintering consumes a large amount of heat, and at the same time, the burning loss is large, and the product structure is loose. In order to produce more liquid phase in the sintering to ensure sufficient strength of the product, it is necessary to appropriately increase the fuel ratio. In general ingredients, the fuel ratio is 8% to 10%.

If the manganese ore is decomposed by heat, the mineral will burst. The cracked fine particles will easily cause the igniting of the igniter wall and reduce its life. Therefore, the length of the igniter of the manganese ore sintering machine should be extended appropriately, increase the preheating section and slow down the burst.

The powdered manganese ore has a small bulk density, a large burning loss, and a good gas permeability of the material layer, so that proper pressing and thickening of the material layer can achieve good results.

A part of manganese in manganese ore is present in low-oxide oxide manganese ore (MnO) and manganite (Mn2O4). At low temperature, it has a large affinity with oxygen. During the ventilation and cooling process, oxidation reaction will occur and release. The heat makes the cooling process of the manganese sinter complex complicated and the cooling rate slows down.

Since manganese ore sintering has some characteristics different from iron ore sintering, it should be fully considered when selecting manganese ore sintering process and design. Determined by experimental research and comparison.

Second, the progress of manganese ore sintering technology

The production process of manganese sinter is basically the same as that of iron sinter. As long as the characteristics of manganese ore sintering, the equipment and process are adjusted accordingly to suit the manganese ore sintering. With the development of science and technology, manganese ore sintering technology has also developed rapidly. The main advances in equipment and processes are as follows:

(1) The sintering machine has evolved from an old-fashioned curved type to a more advanced type of swing type and translation type.

(2) The production of hot ore is developed into cold mine production. A belt cooler replaces the vibrating cooler with more problems.

(3) Advanced pulping technology and granulation system are adopted. It can extend the life of the trolley, reduce the furnace consumption and reduce the dust content of the exhaust gas.

(4) Continuous improvement of production indicators:

The sintering utilization factor has reached 1.20 t / (m 2 · h).

The unit fuel consumption is gradually reduced. According to the raw materials and products, the fuel ratio is generally 120~150kg/t.

The operating rate of the sintering machine has increased by more than 90%.

The sintering back-return rate has been greatly reduced, reaching 10% to 15%.

(5) use of a thick layer of sintered material, the high alkalinity (high magnesium oxide) sintered mixture was added slaked lime enhanced sintering measures.

(6) Established a perfect dust removal system, improved the working environment and reduced dust pollution.

The development of manganese ore sintering technology has improved the output of manganese ore and improved the quality of manganese ore, thus providing high quality manganese ore raw materials for the smelting process.

Third, manganese ore sintering requirements for raw materials

The main raw material manganese sintered manganese ore powder (powder ore, manganese ore is selected), flux (limestone, dolomite), fuel (coke breeze, anthracite). Usually, during the sintering process, the thickness of the high temperature zone is only 15~40mm, and all sintering reactions are completed within 0.5~1.5min. At the same time, it is necessary to make the sinter layer have good gas permeability and finally obtain a sinter which meets the quality requirements. Therefore, there are corresponding requirements for the physical and chemical properties of the sintered raw materials.

(1) The upper limit of the particle size of manganese powder ore manganese ore should be strictly controlled. The suitable particle size for manganese ore sintering should be 0~6mm; it can also be sintered with a small amount of 6~10mm, but it should be less than 12%. If the particle size is too coarse, it will form a "sandwich" phenomenon during sintering. If the particle size is too coarse, the gas permeability of the material layer is too high, and the heat taken away by the air is too much, so that the coarse particle size is not completely reacted, or only the surface of the particle is sintered, which is bound to result in a loose structure and low quality product. If the particle size is too fine, the gas permeability of the sintered layer is severely lowered. At this time, the granulation work should be strengthened. If necessary, an appropriate amount of binder (lime, slaked lime, bentonite , lignin, etc.) may be added to form a fine-grained manganese concentrate powder to form a separate pellet or to return to the core. Outsourcing concentrate ball, but the ball requires sufficient mechanical strength and high temperature thermal shock resistance.

(2) Flux The type of flux added mainly includes limestone and dolomite, quicklime and hydrated lime, and the amount of addition is determined according to the requirements of smelting.

Limestone and dolomite are cheaper and have better working conditions. In order to ensure complete reaction of the flux during the sintering process, a particle size range of 0 to 3 mm is usually employed. When the particle size is too coarse, a large amount of free calcium oxide will appear in the sintered ore, which is prone to hydration during storage, and the strength of the sintered ore is deteriorated, and the powder is increased. In production, the more molten dose is added, the finer the particle size requirements. This will make it evenly distributed and complete in the sintering material.

In order to increase the amount of available calcium oxide in the flux, a flux containing as little acid gangue component as possible should be selected.

A certain amount of quicklime or slaked lime is added to the sinter to enhance granulation. This is very advantageous for improving the granulation and sintering properties of fine fines ore.

(3) The fuel blended with the sinter material requires low volatility, low ash content and high carbon content.

The fuel blended into the sintering mixture should ensure that the high temperature combustion zone reaches a temperature of 1300 ° C for about 1 min, so that the manganese powder ore is completely sintered. The fuel particle size control is usually 0~3mm and the average particle size is 1.2~1.5mm. If the particle size is too fine, flashing combustion will occur, and the high temperature holding time will be insufficient. If the particle size is too coarse, more local reduction zones will be formed, the high temperature retention time will be prolonged, the combustion zone will be enlarged, and the particle layer resistance will increase. Therefore, for the 0~6mm powder ore sintering, the fuel particle size is preferably 0~3mm. However, when the particle size of the fine ore increases to 0~10mm, the particle size of the fuel should be 0~5mm. At the same time, the choice of fuel particle size should also consider the reactivity of the fuel. The highly reactive anthracite particle size can reach 0~6mm, and the coke powder with weak reactivity should have a particle size of 0~3mm.

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