Method for producing metallic magnesium by vacuum circulating silicothermic process and apparatus thereof

Abstract

A method for producing metallic magnesium by vacuum circulating silicothermic process and apparatus thereof The method comprises the following steps: passing molten ferrosilicon ( 109 ) of 1350˜1600° C. and magnesium ore powder containing magnesia blended therein through a vacuum container ( 104 ) with a vacuum of 350˜10000 Pa periodically in a manner of circulating flow, and collecting liquid magnesium ( 201 ), i.e. the magnesium vapor released upon condensing. The apparatus comprises a heating container ( 101 ) and a vacuum container ( 104 ) connected with an elevating dip pipe ( 102 ) and a falling dip pipe ( 103 ) whose lower ends immersed into the molten ferrosilicon ( 109 ) in the heating container ( 101 ). An inert gas blowing device is inserted into the elevating dip pipe ( 102 ) wall. The method and apparatus thereof can improve productivity.

1 . A method for producing metallic magnesium by vacuum circulating silicothermic process, characterized in that, the method comprises the steps of:
 a first step of heating ferrosilicon to a molten state in a heating container communicating with the atmosphere, and maintaining the temperature at 1350˜1600° C.;   a second step of passing the molten liquid ferrosilicon and the MgO-containing powdered ore blended therein sequentially through a vacuum container under the dual action of vacuum suction and inert gas driving, and repeating the processes to form a continuous circulating flow, wherein the vacuum container is separated from the heating container, wherein the vacuum degree of the vacuum container is maintained at 350˜10000 Pa, and during the molten liquid ferrosilicon and the powdered ore periodically passing through the vacuum container in the continuous circulating flow, MgO in the powdered ore is reduced into Mg vapor by silicon in the molten liquid ferrosilicon;   a third step of collecting the liquid Mg, i.e. the Mg vapor released upon condensing.   
     
     
         2 . The method for producing Mg according to  claim 1 , characterized in that, in said second step, under the action of the vacuum suction and the driving force due to thermal expansion of the filled inert gas, the molten liquid ferrosilicon forms a circulating flow and passes through the vacuum container periodically. 
     
     
         3 . The method for producing Mg according to  claim 1 , characterized in that, in said second step, the powdered ore is sprayed into the circulating molten liquid ferrosilicon and circulates with the molten liquid ferrosilicon, and wherein in the vacuum container, MgO in the powdered ore chemically reacts with the ferrosilicon liquid and forms Mg vapor which rises to the upper part of the vacuum container. 
     
     
         4 . The method for producing Mg according to  claim 1 , characterized in that, in said third step, said Mg vapor is cooled to 650˜700° C. and captured by the sprayed liquid Mg droplets, and thus condenses into liquid Mg to be collected. 
     
     
         5 . The method for producing Mg according to  claim 1 , characterized in that, the molten liquid ferrosilicon in said heating container has Si percentage content of 30˜65% by weight, wherein in the process for producing Mg, solid state or molten state ferrosilicon alloy, which has Si percentage content by weight larger than that of the molten liquid ferrosilicon in the heating container, is regularly added to said heating container, or industrial silicon is added directly to said heating container. 
     
     
         6 . The method for producing Mg according to  claim 1 , characterized in that, upon the process for producing Mg is complete, one or more of industrial silicon, industrial pure iron, and iron alloy is added to the molten liquid ferrosilicon in said heating container, to adjust the chemical composition of the molten liquid ferrosilicon, thereby producing alloys comprising at least two elements of Si and Fe as by-products during producing Mg. 
     
     
         7 . The method for producing Mg according to  claim 1 , characterized in that, in the process for producing Mg, liquid waste slag is discharged regularly from the heating container. 
     
     
         8 . An apparatus for producing metallic magnesium by vacuum circulating silicothermic process, characterized in that, the apparatus comprises:
 a heating container, which contains molten liquid ferrosilicon comprising Mg powdered ore and communicates with the atmosphere;   a vacuum container, a lower end of which communicates with an upper port of a dipping pipe, wherein a lower port of the dipping pipe is inserted below the liquid level of liquid ferrosilicon including powdered ore contained in said heating container, wherein the internal space of the vacuum container is sealed by the liquid ferrosilicon including powdered ore contained in said heating container to form an enclosed space, the enclosed space becomes a vacuum environment under evacuating, and the liquid ferrosilicon including powdered ore in said heating container is suctioned upward into said vacuum container through the dipping pipe;   a blowing means, which communicates with said dipping pipe and is capable of blowing inert gas into the dipping pipe, wherein the liquid ferrosilicon including powdered ore which has been suctioned into said dipping pipe continues to rise to the vacuum container under driving of the thermal expansion of the inert gas, and then drops due to the gravity of the liquid ferrosilicon including powdered ore, so that the liquid ferrosilicon including powdered ore develops a repeated circulating flow between the atmosphere of the heating container and the vacuum environment of the vacuum container.   
     
     
         9 . The apparatus for including Mg according to  claim 8 , characterized in that,
 said vacuum container is arranged above the heating container,   said dipping pipe is placed at the lower side of the vacuum container and communicates with said vacuum container,   said dipping pipe is inserted into said heating container, wherein when said lower port of the dipping pipe is immersed below the liquid level of liquid substance in said heating container, the internal space of said vacuum container and its dipping pipe is isolated from the atmosphere to form an enclosed space,   the enclosed space becomes a vacuum vessel under evacuating action, and the liquid substance in said heating container is suctioned upward into said dipping pipe and said vacuum container.   
     
     
         10 . The apparatus for producing Mg according to  claim 8 , characterized in that, said dipping pipe has at least two manifolds, the blowing nozzle of said blowing means is provided under or aside the first manifold and is capable of blowing the inert gas into the first manifold, so that ferrosilicon liquid rises in the first manifold to said vacuum container, but drops in the second manifold to return to said heating container. 
     
     
         11 . The apparatus for producing, Mg according to  claim 8 , characterized in that, a condenser is provided on said vacuum container, said condenser communicates with the vacuum container, and said vacuum container is evacuated by a pump system via the condenser, so that Mg vapor is cooled into liquid and falls into a liquid Mg storage means under the condenser. 
     
     
         12 . The apparatus for producing Mg according to  claim 8 , characterized in that, said dipping pipe has three manifolds, wherein argon is introduced into one of the manifolds, so that ferrosilicon liquid rises in said one of the manifolds to said vacuum container, but drops through two other manifolds to return to said heating container. 
     
     
         13 . The apparatus for producing Mg according to  claim 11 , characterized in that, a cooling member and a Mg liquid spraying member are provided in said condenser, for cooling the Mg vapor passing through the condenser, and for condensing the passing Mg vapor to form liquid Mg by spraying Mg liquid, thereby forming liquid Mg to be collected. 
     
     
         14 . The apparatus for producing Mg according to  claim 8 , characterized in that, at least one plasma heating means, which is capable of heating the substance in the vacuum container, is provided on a sidewall of said vacuum container.