US3313618A - Method and apparatus for making steel continuously - Google Patents

Description

A yifi H, 3196'? J.FEINMAN ETAL 3,3135% METHOD AND APPARATUS FOR MAKING STEEL CONTINUOUSLY Filed June 11, 1964 I6 2/ I9 23 20 I4 I/l/l/E/t/TOHS. JEROME FEl/VF/MN and DAVID A. MUSKAT A f rorney United States Patent Office 3,3l3,5l8 Patented Apr. ll, 1967 3,313,618 METHGD AND APPARATUS FGR MAKHNG STEEL CONTINUOUSLY Jerome Feinman, Monroeville Borough, and David A.

Muskat, ()akrnont, Pa., assignors to United States Steel Corporation, a corporation of Delaware Filed June 11, 1964, Ser. No. 374,452 1 Claim. (Cl. 75-60) This invention relates to the manufacture of steel and, in particular, to a continuous process for the smelting of iron from its ore and refining the iron into steel, and apparatus for carrying out said process.

It is the object of our invention to achieve, in the manufacture of steel, the increased efiiciency and reduced cost characteristic of continuous processing as compared with the batch processes which are now universal in existing steel-production facilities. A further object is to provide an iron-smelting method and apparatus which do not require the use of metallurgical coke or stoves for preheating combustion-supporting gas.

In a preferred embodiment and practice of our invention, we provide a smelting shaft standing on one end of a reverberat-ory furnace chamber. We charge iron ore, coal and limestone into the top of the shaft and supply a reducing blast to the base thereof at a temperature sufficient to smelt the ore. Molten metal formed in the shaft drains into the furnace chamber where it is subjected to an oxygen jet for the oxidation of impurities. An oxygen fuel flame is fired into the furnace chamber and the gases of partial combustion are discharged up the stack with the off-gases from the oxygen refining, constituting the aforementioned reducing blast. Slag and metal are tapped separately at intervals from the furnace chamber.

A complete understanding of the invention may be obtained from the following detailed description and explanation which refer to the accompanying drawing, the single figure of which is a vertical section, largely diagrammatic, through one form of apparatus which may be used for our process.

Referring now in detail to the drawing, a smelting stack 10 rises from one end of an elongated reverberatory furnace chamber 11. The stack is a shell of steel plate having a refractory lining. It is surmounted by a top 12 provided with conventional solids-charging mechanism 12a such as the usual bell-and-hopper, and gas-ofitake means 13. At the bottom of the shaft is a hearth 14 sloping towards and opening into chamber 11. Chamber 11 is defined by walls 15 of refractory brick assembled within a conventional binding, a bottom 16 and is closed by an arched roof 17 of similar brick. A transverse partition 18 extends between the side walls but terminates below the roof 17. It is pierced by a port 19 at the level of the bottom 16.

Partition 18 divides chamber 11 into a metal-collecting portion 20 and a refining portion 21. Portions 20 and 21 are connected by port 19 in the partition and are in full communication above the level thereof. A burner 22 fires an oxygen-fuel fiarne through roof 17 into collecting portion 2!) and the gases of partial combustion pass upwardly through stack 19 making intimate contact with the burden of ore, coal and limestone therein, under the positive pressure maintained in chamber 11. The stone fluxes the ore for reduction by the products of partial combustion from burner 22 which are strongly reducing. These products, after the initial oxidation incident to reduction of the ore, are again reduced by the carbon content of the burden as they pass upwardly therethrough. Burner 22 and the supply of oxygen and fuel thereto are controlled to give a temperature of from 3400 to 4300 F., preferably about 3900 F., in the combustion product The burden as charged comprises from 200 to 600 lbs. of coal, preferably 350 lbs., and from to 500 lbs. of stone, preferably 300 lbs., per ton of hot metal or pig iron (l4% carbon) produced. The off-gases from the top of the stack are cooled and cleaned for use as fuel.

As the fusion and reduction of ore proceed in stack 10, molten iron accumulates in portion 20 of chamber 11 with a layer of molten slag floating thereon. The latter is damned by partition 18 but the metal passes through port 19 into portion 21. Slag is tapped periodically through port 23. The molten iron reaching portion 21 of chamber ll is subjected to oxygen refining by an oxygen lance 24 blowing downwardly thereinto through roof 17. A sampling port 25 permits the decarburization of the iron and the refining process generally to be checked. Alloy additions are made at regular intervals by a conventional charging device 26 (bell-and-hopper or star valve) through a port in roof 17. As a result, the metal in portion 21 is continuously converted into steel and may then be tapped through port 27 when desired slag and metal levels are achieved, such as when the slag level reaches the top of partition 13. The off-gas from the oxygenrefining process in portion 21 mixes with the products of combustion from burner 22 and the mixture ascends stack 10 through the burden therein as aforesaid.

Slag should be tapped from port 23 simultaneously with the tapping of steel from port 27. This causes the liquid levels in chamber portions 2% and 21 to descend together, reducing the chance of backfiow of metal through port 19. Port 27 should be above the top of port 19, as shown and port 23 even higher. The height of partition 1 3 should be sutficient to permit equalization of the hydrostatic heads on opposite sides thereof without overflow.

The operation of the refining portion 21 is controlled to produce continuously :a final steel product at a temperature between 2800 and 3400 F. and preferably at about 2950 F. This temperature may be controlled at the desired level by adding steam with the oxygen introduced through lance 24, by introducing a continuous flow of charge ore with the oxygen introduced through the lance, or by introducing cold scrap continuously through charging device 26. It is preferred to control the steel temperature by introducing steam and/ or charge ore because these methods permit better control over the steel composition.

Our invention is characterized by important advantages. The continuous processing eliminates handling hot metal from blast furnace to open-hearth furnace as in current practice. The use of oxy-fuel combustion gases as the reducing agent makes it unnecessary to include coke in the burden of the smelting shaft. Hot-blast stoves are no longer needed to achieve the temperature required for reducing the ore. The sloping hearth of the smelting shaft provides support for the shaft burden outside of the molten phases.

Although we have disclosed herein the preferred embodiment of our invention, We intend to cover as well any change or modification therein which may be made without departing from the spirit and scope of the claim.

We claim:

A method of making steel comprising charging iron ore, coal and limestone to the top of a stack in proportions of 200 to 600 pounds of coal and 150 to 500 pounds of limestone per ton of iron to be produced, discharging impure molten iron and slag from the bottom of said stack into one end of a metal-collecting chamber, discharging molten iron from the other end of said metalcollecting chamber into one end of a refining chamber, introducing a stream of oxygen to said refining chamber, partially burning fuel with oxygen in said metal-collecting chamber above the molten iron and slag therein to produce a reducing gas at a temperature of 3400 to 43 00 F, mixing oil-gas from said refining chamber with products of combustion in said metal-collecting chamber, maintaining gas in both chambers under a positive pressure which forces the gas mixture from said metal-collecting chamber up said stack to reduce the ore and be reduced by carbon in the coal, sealing both chambers to confine discharge of the gas to said stack, and periodically tap- References Cited by the Examiner UNITED STATES PATENTS FOREIGN PATENTS 3/1965 Great Britain.

ping slag from said metal-collecting chamber and steel 10 BENJAMIN HENKIN Examiner from said refining chamber.

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