Method of utilizing furnace off-gas for reduction of iron oxide pellets

Abstract

The invention relates to the use of off-gas from furnaces (2) for the process of reduction of iron oxide. The bypass duct leads off-gas with reduction atmosphere directly into the reactor, passing through and back to join the main duct of dedusting system using negative pressure of the primary dedusting system. The off-gas directly heats up the iron oxide pellet and maintain the reduction atmosphere in the reactor and allow the reaction to proceed and prevent re-oxidation.

Claims

1. A method of using an apparatus for the reduction of pellets comprised of iron oxide and carbonaceous material, comprised of a pellet storage (1), a bypassed duct (3) a steelmaking furnace (2) having an off-gas outlet, a reactor (5), a burner (6) inside the reactor (5) and a main duct of a primary dedusting system, wherein the bypassed duct (3) and the main duct are connected to the off-gas outlet of the steelmaking furnace (2) independently of each other, and wherein the reactor (5) comprises at least one inlet duct connected to the bypassed duct (3) and at least one outlet duct connected the main duct, the method comprising the steps of: discharging pellets and direct reduced iron from the pellet storage into the reactor (5) via a discharging mechanism; using the by-pass duct (3) to lead a portion of steelmaking furnace (2) off-gas directly into a reactor (5) via the inlet duct; wherein the off-gas flows from the reactor (5), via the outlet duct, to the main duct of the primary dedusting system; wherein the off-gas heats up the reactor and keeps it under a reducing atmosphere; wherein the primary dedusting system induces off-gas flow from the steelmaking furnace (2) to the reactor (5) by negative pressure (7); wherein iron pellets are directly heated by the off-gas under the reducing atmosphere in the reactor (5) preventing re-oxidation; and wherein the burner operates to supplementary maintain the temperature and reducing atmosphere in the reactor, in addition to the off-gas.

2. The method of claim 1, wherein the at least one inlet duct has at least one damper to control the flow of off-gas into the reactor from the bypassed duct (3) and the at least one outlet duct has a least one damper to control the flow of off-gas out of the reactor (5) and into the main duct.

3. The method of claim 1, where the reactor (5) is installed above the furnace (2) offset to the side so that it can discharge a direct reduced iron into the furnace by gravity without blocking furnace operation.

4. The method of claim 1, wherein the furnace is a basic oxygen furnace.

5. The method of claim 1, wherein the furnace is an electric arc furnace.

6. The method of claim 1, wherein the bypassed duct is located within the main duct.

7. The method of claim 6, wherein the bypassed duct leads off-gas into the reactor from the furnace, and wherein negative pressure in the main duct minimizes penetration of external air into the reactor.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) FIG. 1 Shows the process of Method of Utilizing Furnace Off-gas for reduction of Iron Oxide Pellets

DETAILED DISCLOSURE

(2) FIG. 1 Shows the process of Method of Utilizing Furnace Off-gas for reduction of Iron Oxide Pellets

(3) The invention utilizes the off-gas from furnaces (2), which could be Electric Arc Furnace or Basic Oxygen Furnace or other types of furnace with reducing off-gas, for reduction of pellets incorporated with iron oxide and carbonaceous material.

(4) The reactor (5) is located above the furnace not directly on top but offset to aside so it does not obstruct operation when charging input material into the furnace.

(5) A portion of the off-gas is led into the inside of reactor (5) entry the bypass duct (3) and out of the reactor (5) to rejoin the primary duct. The bypass duct (3) allows utilization of existing primary suction (7) that is usually required in all furnaces (2) to induce a portion of primary off-gas flow into Reactor (5) without dedicated fan or equipment to produce suction (7) or negative pressure specifically for Reactor.

(6) Off-gas from furnace, as it goes into Reactor (5), heats up the reactor (5) and keeps it under reducing atmosphere. At the high temperature, the reaction goes and iron oxide pellets are reduced to direct reduced iron (DRI). The re-oxidation of iron in DRI is prevented by the reducing atmosphere in the reactor (5). There is a burner (6) inside the reactor (5) to operate as supplementary to the off-gas to maintain temperature and reducing atmosphere inside the reactor (5). Discharging pallets from storage (1) into reactor (5) is made via a discharging mechanism as well as discharging of direct reduced iron into the furnace. The timing of the is to be made in the right sequence with the process of the furnace (2) in order to allowing sufficient time for melting DRI into liquid and for decarburizing to reach desired carbon content of liquid steel.

(7) It is important that the penetrating of external air into the reactor (5) is minimized. Most of the furnaces (2) need to have movements to accommodate several steps of the steelmaking process (i.e. input material charging, de-slagging or tapping) whereas the primary dedusting system is in fixed position. This makes a split or a gap between the primary duct and the off-gas outlet of the shell is inevitable. The inlet of the bypass duct (3) is made as inner duct of primary duct, therefore, the external air coming via the gap between furnace and primary duct tends to flow along the suction (7) of primary dedusting line. The inner duct, is protected by negative pressure of the outer duct, receive mainly off-gas from the furnace. There are also dampers (4) at the inlet and outlet duct of the reactor (5) to control flow rate and to isolate the reactor (5) when required.