The ore characteristics mainly refer to the material composition of the ore, the grain size composition of the ore and the composition of the gangue minerals, as described below:
1. The influence of the material composition of the ore on the reduction roasting. The ore material composition mentioned here mainly refers to the type and structure state of the mineral. Reduction calcined minerals are mainly hematite, limonite and siderite and the like, containing hematite ores, because of their different structure, reducing performance is also very different. For example, quartz magnetite, some have a layered structure, and hematite and quartz appear cracks due to different expansion changes during heating. This facilitates the diffusion of the reducing agent molecules, increases the reduction rate of the ore and the quality of the calcined ore.
The ore structure is dense block, and tuberculous, and the reduction performance is poor.
For limonite, since the limonite molecule contains 10%-15% or more of crystal water, when the temperature reaches 100 °C, the crystal water begins to volatilize, which increases the porosity of the ore and is beneficial to increase the reduction rate. .
After the siderite is heated to 350 °C, it begins to decompose a large amount of CO and CO2 gas, which increases the porosity of the ore on the one hand, and increases the concentration of the reducing agent in the reaction on the other hand, which is beneficial to the reduction process. Going on.
2. The effect of the ore particle size composition on the reduction roasting, the larger the ore particle size, the smaller the specific surface area, the less the contact surface with the reducing agent, the slower the reduction process, and the often the surface layer and internal reduction of the nugget in production. Uniform phenomenon. The larger the ore particle size, the more serious this phenomenon is.
The reduction heterogeneity of the ore block is closely related to the reduction temperature and the reduction event. The larger the size of the nugget, the higher the reduction temperature and the longer the reduction time, the more significant the non-uniformity.
In order to improve the calcination quality, the upper limit of the particle size of the ingot should be lowered, and the lower limit of the particle size (the particle size is too small, and the gas permeability of the layer is poor) should be increased. For the shaft furnace, it is suitable to have a baking particle size ranging from 75 to 20 mm. In addition, the shaft furnace should be prevented from segregating the ore, and the ore particle size salt furnace body should be evenly distributed in order to obtain better roasting quality.
3. The influence of the composition of gangue minerals on reduction roasting, the iron mineral with quartz as the main gangue. During the roasting process, quartz transforms into quartz at 570 °C, absorbs part of the heat, and has 2% linear expansion. It is transformed into a larger volume of phosphorus quartz at 870 ° C or higher, which contributes to the bursting of the ore during heating, accelerates the reduction roasting, and reduces the reduction unevenness of the surface layer and the interior of the roasting ore.
In addition, quartz reacts with iron oxide at 900 ° C to form a low melting point of iron silicate, which is weak in magnetic properties and affects the magnetic separation recovery, so the baking temperature cannot be too high.
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