Source of NOx in Cement Plants:
- Flame Characteristic –Shape, Flame temp,
- Higher Flame momentum
- Adjustment to axial/swirl air % & Velocity
- Burner position within Kiln
- Quantity of Transport air & Primary air %
- NOx formation mechanism in Calciner
- Kilns with Inline Calciners have higher potential for NOx reduction
- BZ temperature, Burnability, Fcao, LSF, MS, Fineness, Expert system
Impact of NOx - Acid rain
- Damage to vegetation
- Damage fertility of soil
- Damage to aquatic life
Affects Ozone balance in Troposphere - Depletes Oxygen content in water-biological disturbance to water bodies and
species like fish - Photochemical smog in the troposphere
- Damages human respiratory systems (lungs)
8.2 Control of NOx
a. Design of Low NOx burner – Burner to be designed in such a way so the
required fuel can be burnt fully before kiln inlet, zero CO % at kiln inlet, so
oxygen requirement at kiln inlet can be minimized resulting in lower NOx
generation.
The primary air requirement should be as minimum as possible, minimum the
PA and conveying air, lower will be the NOx generation inside kiln.
Also with optimum flame momentum unnecessary burning of material can be
avoided resulting in lower thermal NOx generation inside the kiln.
b. Low NOx calciner – Precalciner to be designed in such a way so that
where fuel is fired, which should be below TA duct entry. Basically
optimization of feed pipe position, coal firing position and TAD duct entry
should be in such a way so that coal should find proper reducing
one in calciner for reduction of NOx generated in the kiln , and at the same
time CO generation must be zero so no coating formation will take place.