1. Acid sinter:
The sinter with alkalinity (cao/sio2) less than 0.5 is sintered by sintering iron concentrate or rich ore powder without or less flux. Its iron bearing minerals are magnetite and hematite, and the main binding phase minerals are ferroolivine (2FeO SiO2) and cafeosio2. The natural pulverization of the red hot acid sinter does not occur during the cooling process. The mechanical strength of the product is high, but FeO is high, the reduction is poor, and the soft melt temperature is low; The ore is used alone to smelt in furnace, and a large amount of limestone is needed; The reduction of blast furnace is poor, which leads to low blast furnace production and high coke ratio. In addition to some special cases, this kind of sinter is not used in modern blast furnace.
2. Iron ore concentrates:
The iron ore powder with high grade obtained by fine grinding and selection of lean iron ore. Iron concentrate is a kind of iron and steel metallurgical raw material for producing man-made rich ore. Iron concentrate is divided into magnetite concentrate, hematite concentrate and brown iron concentrate according to the different iron bearing minerals; According to the different beneficiation methods, it can be divided into weak magnetic concentrate, strong magnetic concentrate, flotation concentrate and gravity concentrate. Usually, magnetic concentrate is obtained by magnetic separation method; Hematite concentrate is obtained by gravity separation, flotation, strong magnetic separation, magnetization roasting magnetic separation, or by combined process; The brown iron concentrate is obtained by the treatment of the brown iron ore by gravity separation, strong magnetic separation or magnetic roasting magnetic separation.
There are generally four requirements for iron concentrate:
(1) The iron content is high. The iron content of magnetite concentrate should be over 65%, hematite concentrate should be over 60%, brown iron concentrate should be more than 50%. The fluctuation of iron content is less than ± 0.5%。
(2) Water is low. Water has a great influence on storage and transportation, ore mixing and ball making. The moisture content of the general magnetite concentrate should be less than 10%, that of hematite concentrate and brown iron concentrate should be less than 12%.
(3) The granularity is suitable. The iron concentrate used for pelletizing is required to be less than 0.074mm in particle size accounting for more than 70%, and the specific surface area is 1200-2000cm2 / g.
(4) The lower the content of impurities (such as sulfur, phosphorus, lead, arsenic, zinc, copper and other harmful elements), the better. Generally, s ≤ 0.10% – 0.19%, P ≤ 0.05% – 0.09%, Pb ≤ 0.1%, as ≤ 0.04% – 0.07%, Zn ≤ 0.1% – 0.2%, Cu ≤ 0.1% – 0.2%.
The acid and alkali property of iron fine powder (including iron ore) refers to the acid-base of gangue composition in the ore, specifically refers to the ratio of calcium oxide to silica, and if cao/sio2 is greater than 1, it is alkaline ore, and cao/sio2 less than 1 is acid ore. If the content of magnesium oxide and alumina in the ore is higher, there are also alkaline ores with (CaO + MgO) / (SiO2 + Al2O3) greater than 1, otherwise, they are acid ores.
The acid base of iron powder is related to the ironmaking index of blast furnace. If the blast furnace adopts alkaline slag smelting (in order to better Desulfuration), it is hoped to use alkaline ore; If the blast furnace is smelted with acid slag (in order to improve the utilization coefficient and reduce coke consumption), it is hoped to use acid ore. At present, alkaline ore is commonly used in blast furnace in China, that is, the alkalinity of iron ore (cao/sio2) is higher.
The acid and alkali of iron powder is calculated by the following formula:
（CaO+MgO）/（SiO2+Al2O3）>1.2； Alkaline ore;
（CaO+MgO）/（SiO2+Al2O3）=0.8~1.2； Autosoluble ore;
（CaO+MgO）/（SiO2+Al2O3）=0.5~0.8； Semi autosoluble ore;
（CaO+MgO）/（SiO2+Al2O3）<0.5； Acid ore;
It can also be simplified to cao/sio2 ratio for evaluation.
Most of the iron ores in China are acid ores with low Cao, MgO, high SiO2 and Al2O3
1. Acid sinter: