Method for removing manganese from molten iron in top and bottom combined blown convertor

The invention discloses a simple, efficient and low-cost method for removing manganese from molten iron in a top and bottom combined blown convertor. The final manganese content of the convertor is controlled to be less than 0.05 weight percent. The method comprises the following specific steps of: adding steel scrap into the convertor, adding the molten iron into the convertor, adding a demanganization agent into the liquid level of the molten iron, supplying oxygen to the liquid level of the molten iron by using an oxygen lance from the top, supplying stirring gas into the molten iron from the bottom, monitoring the CO content of converter gas, and pouring initial slag out when the inhibition of the carbon oxidation is converted into intense carbon oxidation, wherein the amount of poured slag is not less than 60 percent of the total slag amount; and adding the demanganization agent into the liquid level of the molten iron. Compared with the conventional method for removing manganese by a common blowing process or a convertor duplex manganese removal process, the method has the advantages that: special manganese removal equipment is not required, a mature top and bottom combined blown convertor blowing technology is fully utilized, and the dynamical condition for removing manganese from the molten iron is fully met, the common demanganization agent used as the raw material is used, sources are wide, and price is low.