Kiln and method for burning carbonate rock

A method of burning material, such as carbonate rock, in a parallel-flow regenerative shaft kiln having two shafts which are operated alternately as burning shaft and as regenerative shaft and are connected to one another by a connecting duct, wherein the material flows to a material outlet through a material inlet into a preheating zone for preheating the material, a burning zone for burning the material and a cooling zone for cooling the material, the method comprising:

• admitting a cooling gas into the cooling zone;
• and
• discharging offgas from one shaft of the kiln via an offgas outlet disposed within or above the preheating zone;
• wherein the offgas discharged from the shaft via the offgas outlet is branched into a first portion of the offgas and a second portion of the offgas;
• wherein the first portion of the offgas is fed via a first offgas inlet to an upper region of the preheating zone;
• wherein the second portion of the offgas discharged from the shaft is fed to the preheating zone downstream of the first offgas inlet via a second offgas inlet.

A parallel-flow regenerative shaft kiln for burning and cooling material, such as carbonate rock, comprising:

• two shafts that are operable alternately as burning shaft and as regenerative shaft and are connected to one another by a connecting duct;
• wherein each shaft has, in flow direction of the material, a preheating zone for preheating the material, a burning zone for burning the material and a cooling zone for cooling the material;
• wherein at least one shaft of the PFR shaft kiln has an offgas outlet disposed within or above the preheating zone for discharging offgas from the shaft and a first offgas inlet for admission of offgas;
• wherein the offgas outlet is connected to the first offgas inlet for admission of a first portion of the offgas into the preheating zone;
• wherein the shaft has, within the preheating zone, a second offgas inlet which is beyond the first offgas inlet in flow direction of the material and which is connected to the offgas outlet for admission of a second portion of the offgas into the preheating zone.