Method for desiliconizing, demanganizing, dephosphorizing and desulfurating molten iron

The invention discloses a method for desiliconizing, demanganizing, dephosphorizing and desulfurating molten iron, which includes the following steps of: (1) pre-desiliconizing and pre-demanganizing molten iron in a blast furnace iron runner; spraying sintering ore dedusting powder on the surface of the molten iron by a spray gun and then entering a hot metal mixer car along with the molten iron flow to generate silicon oxides and manganese oxides which finally enter slag; wherein the desiliconizing rate is 60 percent to 78 percent and the demanganizing rate is 42 percent to 46 percent; removing manganese reversion sources in follow-up processing procedures by slagging off the molten iron; (2) continuously desiliconizing and demanganizing the molten iron; and spraying desiliconizing agent and demanganizing agent into molten iron by the spray gun, oxidizing all silicon elements and the demanganizing rate reaches 50 percent to 65 percent; and (3) dephosphorizing and desulfurating the molten iron with the dephosphorizing rate of 47 percent to 80 percent, the desulfurating rate of 54 percent to 83 percent, and manganese reversion amount of less than or equal to 0.03 percent. By combining with the desiliconization, dephosphorization, desulfuration and demanganizing technology of molten iron, the invention can preprocess the common blast furnace molten iron to keep the manganese content, phosphorus content and sulfur content in the molten iron within the required range simultaneously.