Low NOx calciner

1. A system for reducing NO x emission levels during the manufacture of cement clinker comprising a calciner unit further comprising:

an upper portion;

a lower portion;

a NO x reduction zone in the lower portion having a refractory layer on the inside surface thereof;

a tertiary air inlet in the upper portion for introducing tertiary air into the upper portion;

a main calciner meal inlet located above the NO x reduction zone for introducing a main calciner meal portion into the upper portion;

a first cooling calciner meal inlet located in the NO x reduction zone for introducing a first cooling calciner meal portion into a periphery of the NO x reduction zone for forming a peripheral layer of meal in the NO x reduction zone for protecting the refractory layer from hot kiln gas;

a second cooling calciner meal inlet located in the NO x reduction zone;

a fuel inlet located in or below the NO x reduction zone for introducing fuel into the NO x reduction zone for supporting a hot core of the hot kiln gas within the peripheral layer of the meal in the NO x reduction zone;

wherein the first or second cooling calciner meal inlets located in the NO x reduction zone are arranged such that the cooling calciner meal portion is introduced tangentially into the NO x reduction zone; and

a constriction located between the upper portion and lower portion for inhibiting the main calciner meal portion in the upper portion from entering the NO x reduction zone.

2. The system of claim 1 , wherein the main calciner meal inlet is located above the tertiary air inlet.

3. The system of claim 1 , further comprising a riser unit located below the NO x reduction zone wherein the fuel inlet is located below the NO x reduction zone in the riser unit.

4. The system of claim 3 , wherein a cross-sectional area of the NO x reduction zone is larger than a cross-sectional area of the riser unit.

5. The system of claim 1 , wherein the NO x reduction zone comprises a reduction zone inlet cone and wherein the fuel inlet is located immediately adjacent to and below the inlet cone.

6. The system of claim 1 , wherein the second cooling calciner meal inlet is positioned laterally opposite the first cooling calciner meal inlet for introducing a second cooling calciner meal portion into the periphery of the NO x reduction zone forming a peripheral layer of the meal in the NO x reduction zone for further protecting the refractory layer from the hot kiln gas.