Disclosed are degassers, couplings, impeller shafts and impellers for use in molten metal. One such coupling transfers gas into an impeller shaft, the coupling having a smooth, tapered internal surface to align with a corresponding surface on the impeller shaft and help prevent gas leakage and to assist in preventing damage to the impeller shaft. Improved impellers for shearing and mixing gas are also disclosed, as is a degasser including one or more of these components.

Disclosed are degassers, couplings, impeller shafts and impellers for use in molten metal. One such coupling transfers gas into an impeller shaft, the coupling having a smooth, tapered internal surface to align with a corresponding surface on the impeller shaft and help prevent gas leakage and to assist in preventing damage to the impeller shaft. Improved impellers for shearing and mixing gas are also disclosed, as is a degasser including one or more of these components.

Disclosed are degassers, couplings, impeller shafts and impellers for use in molten metal. One such coupling transfers gas into an impeller shaft, the coupling having a smooth, tapered internal surface to align with a corresponding surface on the impeller shaft and help prevent gas leakage and to assist in preventing damage to the impeller shaft. Improved impellers for shearing and mixing gas are also disclosed, as is a degasser including one or more of these components.

A load current value I of a motor rotationally driving an impeller is read out when the impeller is rotated at a predetermined set rotational speed X.sub.0, and the rotational speed of the impeller is increased so that the load current value I becomes equal to or larger than a threshold value I.sub.0 when it is determined that the load current value I is smaller than the predetermined threshold value I.sub.0.

A load current value I of a motor rotationally driving an impeller is read out when the impeller is rotated at a predetermined set rotational speed X.sub.0, and the rotational speed of the impeller is increased so that the load current value I becomes equal to or larger than a threshold value I.sub.0 when it is determined that the load current value I is smaller than the predetermined threshold value I.sub.0.

A method for iron making by continuous smelting reduction, including: (1) mixing iron-containing mineral powder with a reducing agent and a slag former to obtain mixed powder materials; (2) placing furnace startup materials in a reducing furnace, and heating the furnace startup materials to be in a molten state to form a furnace startup molten pool; (3) conveying the mixed powder materials into the reducing furnace, and blowing oxidizing combustibles into the reducing furnace for heating; (4) performing stirring by a stirring paddle to form a molten slag layer and a molten iron layer; and performing stirring so that a vortex is formed in the molten slag layer; and (5) adjusting a position of the stirring paddle, a stirring speed and a conveying quantity of the mixed powder materials to enable the molten iron and the reduced molten slag to be respectively continuously discharged.

A method for iron making by continuous smelting reduction, including: (1) mixing iron-containing mineral powder with a reducing agent and a slag former to obtain mixed powder materials; (2) placing furnace startup materials in a reducing furnace, and heating the furnace startup materials to be in a molten state to form a furnace startup molten pool; (3) conveying the mixed powder materials into the reducing furnace, and blowing oxidizing combustibles into the reducing furnace for heating; (4) performing stirring by a stirring paddle to form a molten slag layer and a molten iron layer; and performing stirring so that a vortex is formed in the molten slag layer; and (5) adjusting a position of the stirring paddle, a stirring speed and a conveying quantity of the mixed powder materials to enable the molten iron and the reduced molten slag to be respectively continuously discharged.