Rotary hearth furnace exhaust gas duct apparatus and method for operating same

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, comprising:

• an exhaust gas duct connected to carry exhaust from the rotary-hearth furnace,
• a first cooling part for cooling exhaust gas discharged from the exhaust gas duct to solidify a metal salt in the exhaust gas,
• a first collision part for allowing the exhaust gas, just after being cooled in the first cooling part, to collide with the first collision part, whereby the solidified metal salt drops from the cooled exhaust gas,
• a first direction change duct for guiding the collided exhaust gas in a direction other than a direction of dropping of the metal salt;
• a second cooling part for cooling exhaust gas discharged from the first direction change duct to solidify another metal salt in the exhaust gas,
• a second collision part for allowing the exhaust gas, just after being cooled in the second cooling part, to collide with the second collision part, whereby the solidified another metal salt drops from the cooled exhaust gas, and
• a second direction change duct for guiding the collided exhaust gas in a direction other than a direction of dropping of the another metal salt.