The purpose of the present invention is to provide a method for eluting calcium from steel slag such that more calcium can be eluted into an aqueous solution containing carbon dioxide from the steel slag. The present invention comprises carrying out, in the following order, a step of subjecting a calcium compound contained in the steel slag to hydration and a step of bringing the steel slag subjected to the hydration into contact with the aqueous solution containing carbon dioxide. Furthermore, in the present invention, the aqueous solution containing carbon dioxide is brought into contact with the steel slag while the steel slag is being pulverized or the surface of the steel slag is being ground. As a result of these methods, more calcium can be easily eluted into the aqueous solution containing carbon dioxide from the steel slag.

The present disclosure relates to a method for producing steel in an integrated metallurgical plant comprising at least one direct reduction reactor for directly reducing iron ore to give sponge iron, at least one electric furnace for melting the sponge iron to give pig iron or crude steel, at least one blast furnace for smelting iron ore to give pig iron, and at least one converter for refining pig iron to give crude steel. In accordance with the invention, the process gas discharged from the direct reduction reactor is admixed at least partly to the hot blast air and/or at least partly to an optional charging material, said air and/or said material being blown into the blast furnace.

The present disclosure relates to a method for producing steel in an integrated metallurgical plant comprising at least one direct reduction reactor for directly reducing iron ore to give sponge iron, at least one electric furnace for melting the sponge iron to give pig iron or crude steel, at least one blast furnace for smelting iron ore to give pig iron, and at least one converter for refining pig iron to give crude steel. In accordance with the invention, the process gas discharged from the direct reduction reactor is admixed at least partly to the hot blast air and/or at least partly to an optional charging material, said air and/or said material being blown into the blast furnace.

A method for refining molten iron that can stably produce low-nitrogen steel is proposed. In this method for refining molten iron, untreated molten iron with a carbon concentration [C].sub.i between 0.5 mass % and 3.0 mass %, both inclusive, is placed into a vessel, and oxygen is blown onto the untreated molten iron under atmospheric pressure while a hydrogen gas, a hydrocarbon gas, or a mixture gas of these gases is blown in to perform a decarburization and denitrification treatment of the untreated molten iron. It is preferable, for example, that a nitrogen concentration [N].sub.f in treated molten iron after being subjected to the decarburization and denitrification treatment be 30 mass ppm or lower; that treated molten iron after being subjected to the decarburization and denitrification treatment be further subjected to a vacuum degassing treatment; that the untreated molten iron include molten iron obtained by melting a cold iron source; that the untreated molten iron be a mixture of primary molten iron obtained by melting a cold iron source in a melting furnace and molten pig iron having a carbon concentration of 2.0 mass % or higher; that the cold iron source include reduced iron; and that the vessel be a converter.

A method for refining molten iron that can stably produce low-nitrogen steel is proposed. In this method for refining molten iron, untreated molten iron with a carbon concentration [C].sub.i between 0.5 mass % and 3.0 mass %, both inclusive, is placed into a vessel, and oxygen is blown onto the untreated molten iron under atmospheric pressure while a hydrogen gas, a hydrocarbon gas, or a mixture gas of these gases is blown in to perform a decarburization and denitrification treatment of the untreated molten iron. It is preferable, for example, that a nitrogen concentration [N].sub.f in treated molten iron after being subjected to the decarburization and denitrification treatment be 30 mass ppm or lower; that treated molten iron after being subjected to the decarburization and denitrification treatment be further subjected to a vacuum degassing treatment; that the untreated molten iron include molten iron obtained by melting a cold iron source; that the untreated molten iron be a mixture of primary molten iron obtained by melting a cold iron source in a melting furnace and molten pig iron having a carbon concentration of 2.0 mass % or higher; that the cold iron source include reduced iron; and that the vessel be a converter.

An immersion device for collecting a slag sample and measuring a molten metal parameter is provided. The immersion device includes an inflow conduit for directing the molten slag to a slag sample chamber and a measuring element for measuring the parameter of the molten metal. The inflow conduit and the measuring element are arranged in the top area of an immersion end of the immersion device and/or are facing towards an immersion direction. During immersion in the immersion direction into the molten slag and then the molten metal, the molten slag enters an external portion of the inflow conduit and is directed through an inner portion of the inflow conduit to the slag sample chamber. Reliable slag collection and molten metal measurement also in a converter can thereby be achieved. A method of collecting a slag sample and measuring a molten metal parameter is also provided.

The purpose of the present invention is to provide a method for recovering calcium-containing solid components from steelmaking slag, with which it is possible to easily increase the calcium recovery rate. With the method, steelmaking slag is immersed in an aqueous solution containing carbon dioxide, and calcium in the steelmaking slag is made to leach out into the aqueous solution. Next, the immersed steelmaking slag is removed from the aqueous solution, and, subsequently, the pH of the aqueous solution is increased. When solid components precipitated by doing so are recovered, it is possible to recover solid components containing 20% or more by mass in terms of calcium atoms.

The present disclosure addresses the deficiencies described above by providing systems and methods for enhancing the efficiency and yield of alkene production. The methods and systems provide for the use of activated CO.sub.2 in a dehydrogenation reactor along with an alkane stream. Through the use of the methods and systems of the invention, catalyst deactivation by coke deposition is reduced and the selectivity and efficiency of the dehydrogenation reaction is improved.

The invention relates to a method for operating a steelworks, for example in a blast furnace converter route, or with a direct reduction of iron ore with hydrogen with downstream electrical steel route, preferably additionally a secondary steel route. To carry out the method, the following are balanced: A) a number of starting material flows of supplied starting materials, B) a number of by-product material flows from emitted by-products, and C) a number of energy flows of used energy.

The invention relates to a method for operating a steelworks, for example in a blast furnace converter route, or with a direct reduction of iron ore with hydrogen with downstream electrical steel route, preferably additionally a secondary steel route. To carry out the method, the following are balanced: A) a number of starting material flows of supplied starting materials, B) a number of by-product material flows from emitted by-products, and C) a number of energy flows of used energy.