# US 2013/0154167 A1 · Rotary hearth furnace exhaust gas duct apparatus and method for operating same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2013/0154167 A1 - Document ID: US20130154167A1 - Status: Published application - Kind: A1 - Application number: 13/820,174 - Filed: 2011-09-02 - Published: 2013-06-20 - Earliest claimed: 2010-09-02 - Assignees: Kabushiki Kaisha Kobe Seiko Sho (Kobe Steel, Ltd.) - Inventors: Noriaki Mizutani; Koji Tokuda; Osamu Tsuge - Web page: https://patentgrep.com/patent/US20130154167A1 ## CPC - F27D 17/302: {Constructional details of ancillary components, e.g. waste gas conduits or seals} - C21B 13/105: {Rotary hearth-type furnaces} - C21C 5/40: Offtakes or separating apparatus for converter waste gases or dust - F27B 9/16: the charge moving in a circular or arcuate path - F27B 9/30: Details, accessories or equipment specially adapted for furnaces of these types - F27D 17/22: for removing solid constituents - F27D 17/30: Arrangements for extraction or collection of waste gases; Hoods therefor - C21B 2100/44: Removing particles, e.g. by scrubbing, dedusting - Y02P 10/134: by avoiding CO2, e.g. using hydrogen - Y02P 10/25: Process efficiency - F27D: DETAILS OR ACCESSORIES OF FURNACES, KILNS, OVENS OR RETORTS, IN SO FAR AS THEY ARE OF KINDS OCCURRING IN MORE THAN ONE KIND OF FURNACE - C21B: MANUFACTURE OF IRON OR STEEL (preliminary treatment of ferrous ores or scrap C22B1/00) - C21C: PROCESSING OF PIG-IRON, e.g. REFINING, MANUFACTURE OF WROUGHT-IRON OR STEEL; TREATMENT IN MOLTEN STATE OF FERROUS ALLOYS - F27B: FURNACES, KILNS, OVENS OR RETORTS IN GENERAL; OPEN SINTERING OR LIKE APPARATUS - Y02P: CLIMATE CHANGE MITIGATION TECHNOLOGIES IN THE PRODUCTION OR PROCESSING OF GOODS ## Abstract An exhaust gas duct apparatus for use in a rotary-hearth furnace for heating a starting material including a carbonaceous reducing material and an iron-oxide containing material to produce reduced iron or granular metallic iron. In an exhaust gas duct for use in the rotary-hearth furnace, a cooling part for cooling an exhaust gas discharged from the rotary-hearth furnace to solidify a metal salt in the exhaust gas, a collision part for allowing the exhaust gas just after being cooled to collide therewith to drop down the metal salt solidified, and a direction change duct for guiding the exhaust gas after being collided, in a direction other than a direction of dropping the metal salt, are arranged in this order in two stages. ## Claims ### Claim 1 An exhaust gas duct apparatus for use in a rotary-hearth furnace for heating a starting material including a carbonaceous reducing material and an iron-oxide containing material to produce reduced iron or granular metallic iron, wherein, in an exhaust gas duct for use in the rotary-hearth furnace, a cooling part for cooling an exhaust gas discharged from the rotary-hearth furnace to solidify a metal salt in the exhaust gas, a collision part for allowing the exhaust gas just after being cooled, to collide therewith to drop down the metal salt solidified, and a direction change duct for guiding the exhaust gas after being collided, in a direction other than a direction of dropping the metal salt, are arranged in this order in two stages. ### Claim 2 (depends on 1) The exhaust gas duct apparatus for use in a rotary-hearth furnace according to claim 1, wherein the cooling part includes a first cooling part for cooling the exhaust gas discharged from the rotary-hearth furnace to a temperature of from 1000 to 1200° C., and a second cooling part for further cooling the exhaust gas after being collided, to a temperature of from 450 to 900° C. ### Claim 3 (depends on 2) The exhaust gas duct apparatus for use in a rotary-hearth furnace according to claim 2, wherein the collision part includes a first collision part placed just behind the first cooling part in the exhaust gas duct, and a second collision part placed to connect to a rear part of the second cooling part in the exhaust gas duct. ### Claim 4 (depends on 2) The exhaust gas duct apparatus for use in a rotary-hearth furnace according to claim 2, wherein the first cooling part includes a water cooling duct. ### Claim 5 (depends on 4) The exhaust gas duct apparatus for use in a rotary-hearth furnace according to claim 4, wherein the water cooling duct is arranged horizontally just before the first collision part. ### Claim 6 (depends on 5) The exhaust gas duct apparatus for use in a rotary-hearth furnace according to claim 5, wherein no water cooling structure is provided on an upper part of the water cooling duct. ### Claim 7 (depends on 4) The exhaust gas duct apparatus for use in a rotary-hearth furnace according to claim 4, wherein the water cooling duct has a lined refractory structure, and the lined refractory structure in a lower part of the water cooling duct to which a dust can be easily adhered is constituted such that an inner surface temperature thereof is 600° C. or lower. ### Claim 8 (depends on 2) The exhaust gas duct apparatus for use in a rotary-hearth furnace according to claim 2, wherein the second cooling part injects a fluid directly into the exhaust gas duct. ### Claim 9 (depends on 4) The exhaust gas duct apparatus for use in a rotary-hearth furnace according to claim 4, wherein the direction change duct includes a first riser extending substantially vertically upwardly, the first collision part includes a first riser inner wall surface, and the first riser inner wall surface for allowing the exhaust gas existing at least just behind the water cooling duct to collide therewith is covered with an abrasion resistant refractory. ### Claim 10 (depends on 8) The exhaust gas duct apparatus for use in a rotary-hearth furnace according to claim 8, wherein the direction change duct includes a horizontal duct substantially horizontally arranged in a lowermost part of an inverted J-shaped duct connected to and descending from a top part of the first riser, the second collision part is a dust collecting tank placed in the horizontal duct, the second cooling part is placed in at least any one of the first riser and the inverted J-shaped duct, and the exhaust gas cooled through the second cooling part is allowed to be collided with the second collision part. ### Claim 11 (depends on 9) The exhaust gas duct apparatus for use in a rotary-hearth furnace according to claim 9, wherein the direction change duct includes a horizontal duct substantially horizontally arranged in a lowermost part of an inverted J-shaped duct connected to and descending from a top part of the first riser, the second collision part is a dust collecting tank placed in the horizontal duct, the second cooling part is placed in at least any one of the first riser and the inverted J-shaped duct, and the exhaust gas cooled through the second cooling part is allowed to be collided with the second collision part. ### Claim 12 (depends on 10) The exhaust gas duct apparatus for use in a rotary-hearth furnace according to claim 10, wherein the exhaust gas allowing to be collided with the dust collecting tank is allowed to rise through a second riser, and an air preheater is placed in a lowering duct connected to a rear part of the second riser. ### Claim 13 (depends on 11) The exhaust gas duct apparatus for use in a rotary-hearth furnace according to claim 11, wherein the exhaust gas allowing to be collided with the dust collecting tank is allowed to rise through a second riser, and an air preheater is placed in a lowering duct connected to a rear part of the second riser. ### Claim 14 (depends on 2) A method for operating the exhaust gas duct apparatus for use in a rotary-hearth furnace according to claim 2, wherein a cooling temperature of the cooling part for cooling the exhaust gas can be changed depending on a kind of the metal salt in the exhaust gas. ### Claim 15 (depends on 2) A method for operating the exhaust gas duct apparatus for use in a rotary-hearth furnace according to claim 2, wherein the second cooling part cools the exhaust gas by directly supplying any one or more of an inert gas, gas-water state water and air to the exhaust gas. ### Claim 16 (depends on 3) The exhaust gas duct apparatus for use in a rotary-hearth furnace according to claim 3, wherein the first cooling part includes a water cooling duct. ### Claim 17 (depends on 16) The exhaust gas duct apparatus for use in a rotary-hearth furnace according to claim 16, wherein the water cooling duct is arranged horizontally just before the first collision part. ### Claim 18 (depends on 17) The exhaust gas duct apparatus for use in a rotary-hearth furnace according to claim 17, wherein no water cooling structure is provided on an upper part of the water cooling duct. ### Claim 19 (depends on 16) The exhaust gas duct apparatus for use in a rotary-hearth furnace according to claim 16, wherein the water cooling duct has a lined refractory structure, and the lined refractory structure in a lower part of the water cooling duct to which a dust can be easily adhered is constituted such that an inner surface temperature thereof is 600° C. or lower. ### Claim 20 (depends on 16) The exhaust gas duct apparatus for use in a rotary-hearth furnace according to claim 16, wherein the direction change duct includes a first riser extending substantially vertically upwardly, the first collision part includes a first riser inner wall surface, and the first riser inner wall surface for allowing the exhaust gas existing at least just behind the water cooling duct to collide therewith is covered with an abrasion resistant refractory.