Method and shaft furnace for burning carbon-containing material in a shaft furnace

A shaft furnace for firing material containing carbonate, the shaft furnace comprising:

• in a flow direction of the material, a preheating zone, a firing zone, a cooling zone, and a material outlet for discharging the material;
• burner lances that project into the firing zone, wherein a first of the burner lances has a first penetration depth into the firing zone and a second of the burner lances has a second penetration depth into the firing zone that is greater than the first penetration depth;
• a first ring conduit that extends around a circumference of a shaft wall of the shaft furnace;
• a second ring conduit that extends around the circumference of the shaft wall;
• a first primary air conduit that conveys primary combustion air through the first primary air conduit, into the first ring conduit and into the first burner lance;
• and a second primary air conduit that conveys primary combustion air through the second primary air conduit, into the second ring conduit and into the second burner lance, wherein the second primary air conduit extends at least partly through a preheating device that heats the primary combustion air in the second primary air conduit, wherein the primary combustion air conveyed by the first primary air conduit is not preheated by the preheating device.

A process for firing material that contains carbonate in a shaft furnace, the process comprising:

• causing the material to flow through a preheating zone, a firing zone, and a cooling zone to a material outlet;
• introducing fuel in the firing zone or adjacent thereto via burner lances, wherein a first of the burner lances has a first penetration depth and a second of the burner lances has a second penetration depth that is greater than the first penetration depth;
• conveying primary combustion air through a first ring conduit that extends around a circumference of a shaft wall of the shaft furnace to the first of the burner lances;
• and
• conveying oxygen along with the primary combustion air through a second ring conduit that extends around the circumference of the shaft wall to only the second of the burner lances that have the second penetration depth or conveying oxygen into a primary air conduit and through a second ring conduit that extends around the circumference of the shaft wall that conveys the primary combustion air only to the second of the burner lances that have the second penetration depth.

A process for firing material that contains carbonate in a shaft furnace, the process comprising:

• causing the material to flow through a preheating zone, a firing zone, and a cooling zone;
• directing fuel through (i) a first primary air conduit that conveys the fuel through a first ring conduit that extends around a circumference of a shaft wall of the shaft furnace;
• and (ii) a second primary air conduit that conveys the fuel through a second ring conduit that extends around the circumference of the shaft wall;
• introducing fuel in the firing zone or adjacent thereto via burner lances, wherein a first of the burner lances, receives fuel from the first ring conduit and has a first penetration depth and a second of the burner lances, receives fuel from the second ring conduit and has a second penetration depth that is greater than the first penetration depth;
• and
• conveying primary combustion air that has been preheated exclusively to burner lances that have the second penetration depth.