Harmful elements generally refer to sulfur (S), phosphorus (P), potassium (K), sodium (Na), lead (Pb), Zn ( zinc ), As ( arsenic ), Cu. Iron ore blast furnace usually requirements are as follows: Pb<0.1%, Zn<0.1%, As<0.07%, Cu<0.2%, and K2O+Na2O≤0.25%. Sulfur (S): Sulfur is the most harmful component of steel, which makes the steel "hot brittle". The iron content in the iron ore is high, and the cost of desulfurization in the blast furnace is increased, so the less sulfur in the iron ore entering the furnace, the better. Phosphorus (P): Phosphorus is also one of the most common harmful elements in steel, which makes the steel "cold brittle". Phosphorus in iron ore is 100% into pig iron during smelting of blast furnace, and can not be dephosphorized by sintering. The phosphorus content of pig iron is mainly controlled by controlling the phosphorus content of iron ore. Dephosphorization can only be carried out by steelmaking, which increases the dephosphorization cost of steelmaking. Therefore, the lower the phosphorus content of iron ore, the better. Alkali metal: mainly alkali metals sodium and potassium. The effect of potassium and sodium on the blast furnace is not proportional to the nature. The blast furnace itself has a certain ability to discharge alkali, and the alkali metal has little effect on the blast furnace within the control range. However, the alkali metal content of the iron ore in the furnace is too much, and the alkali metal enrichment is formed beyond the capacity of the blast furnace to discharge alkali, resulting in the alkali metal content of the upper charge in the blast furnace greatly exceeding the original level of the charge. The iron ore contains more alkali metal, which is easy to cause the softening temperature to decrease, and the soft melt zone moves up, which is not conducive to the development of indirect reduction, resulting in an increase in coke ratio. The inclusion of an alkali metal in the pellet causes an abnormal expansion of the pellet to cause severe chalking and deteriorate the gas permeability of the pellet. Alkali metal coke performance damage is also very serious. In addition, the alkali metal compound in the upper part of the blast furnace adheres to the furnace wall, causing the furnace wall to thicken, nodule and destroy the brick lining. Therefore, the lower the alkali metal content of the iron ore, the better. Lead (Pb): Lead is almost completely reduced in the blast furnace. Because the density is as high as 11.34t∕m3, it sinks under the dead iron layer and easily breaks the brick bottom seam, which may cause the bottom of the furnace to burn through. Zinc (Zn): Zinc is easily vaporized. Zinc vapor easily enters the brick joint, oxidizes to become ZnO and expands, destroying the refractory brick lining on the furnace body. Arsenic (As): Arsenic is also one of the harmful elements in steel. It causes cold brittleness of steel and deteriorates the weldability of steel. The arsenic in iron ore is basically reduced into pig iron, which affects the quality of pig iron. In addition, arsenic volatilizes during the sintering process, which has a great impact on the environment. Copper (Cu): Copper makes the steel "hot brittle" and the steel is not easy to roll and weld. A small amount of copper can improve the corrosion resistance of steel. In blast furnace smelting, all copper is reduced into pig iron. Titanium improves the wear resistance and corrosion resistance of steel. However, in the smelting of the blast furnace, the properties of the slag deteriorate, and about 90% of the titanium enters the slag. When the content of titanium is low, it has little effect on the slag and the smelting process. When the content is high, the slag will become thicker and the fluidity is poor, which has great influence on the smelting process and is easy to form a furnace. Titanium has a role in protecting the furnace. Many blast furnaces specialize in buying titanium ore to join the blast furnace. In short, blast furnace smelting requires iron ore to have as low a component as possible.
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