1) Snowman formation occurs when dusty clinker blows back from the cooler into the kiln, creating a cycle that increases dust levels. 2) High secondary air velocities above 5m/s can carry finer dust from the kiln into the burning zone, stealing liquid and creating stickier clinker dust. 3) This dust builds up on the cooler surfaces, forming snowman-like structures, worsened by the presence of alkalis or sulfur that increase melting. Maintaining a short, radiant flame with oxidizing conditions and optimizing air flow can help control clinker dust levels.

1. Snowman formation

2. Dusty clinker
More melt due to alkali or sulfur recycle
Distorted flame
Disintegration of clinker due to reduced conditions
Blow back of dust from cooler to kiln and recycling
High air flow rate in first portion of clinker (, incorrect air distribution)
Causes

3. Dusty clinker formation
When the kiln is dusty the snow man problem starts. The dust falls on the cooler
and blows back into the kiln which is carried away by secondary air stream. If
secondary velocity is more than 5 m/s the finer dust is carried into the kiln and the
velocity of combustion air and combustion products further shoots up near the flame
which carries the dust further in side the burning Zone. This dust steals some liquid from
the burning zone and falls on the cooler and the cycle continues between cooler to kiln.
It reaches a stage the clinker dust becomes so sticky that it sticks to the side and
vertical wall of the cooler and dust build –up called snow man forms. If horse shoe
is there in the front side of the it has favorable base to form. If sulfur and alkali
recycle is there inside the kiln the melt increases , which does not reflect in
the calculated liquid , the minor low melting compounds concentrate more on dusty
fraction of the clinker.
Though we donot have much control on minerlogy some critical parameters can
be controlled by operating the kiln with good quality liquid and good flame with
oxidised conditions. A short radiant flame forms relatively better clinker. A long
flame increases the burning zone length which allows the low melting consitituents
to volatilize and recycle.

4. It is often misunderstood that long flame gives good refractory life and hence to
form a lazy flame . This makes the kiln more dusty. Then the momentum is
often is interpreted in a very wrong way even by more experienced operating people.
. The momentum for conventional burner Is totally different from the modern
multi channel burner. The momentum is maintained to improve the rate of mixing
of coal and combustion air there by improve the combustion efficiency . The momentum
with low primary air percentage and high velocity is much better than with high Primary
air and low velocity. The shorter black jet (plume) and good radiant convergent flame
make the kiln much efficient .
The flame is the Victim of many hands and so the kiln.
Flame has to be monitored often and so the shell temperature which is good reflection
of the good shaped flame. If flame is wrong every thing goes wrong . We immediately
blame the chemistry and demands more liquid to form good nodules which aggravates
the situation.
If coal falls on the charge the liquid quality changes and the same wrong
interpretation about the chemistry and liquid. If char gets into the charge , which is
invisible,the same misinterpretation starts.
. One thing we have to remember is that with a good flame, short radiant flame we can
reduce the liquid % . Short radiant flame gives dense and better shaped nodules than
long lazy flame..

5. 1
2
3

6. Why the dust blow back ?
The dust is the main culprit of the snowman formation and then the uneven
distribution of air further aggravates the situation. The red river area is aerated
more, the dust Is blown back into the kiln. In modern beam aerated cooler the sand
blasting effect must be low. If it is so then the cooler plates slaught profile needs
check. Air flow in the front portion of the cooler has to be redistributed to avoid
sand blasting. More airflow does not mean more recuperation .

7. Remedies
Form a short radiant flame . Avoid char entrapment in charge .
Burner can be pushed inside the kiln by 500 to 1000 mm if there is
margin in % calcination. If calciner does not have margin it leads to loss
of production.
Avoid CO formation
Optimum liquid < 29 % including sulfur and alkalis
Optimum air flow for recuperation zone in cooler
Slopy horse shoe , as in the picture, with right oriented shock blasters
make the, hot dust slide and dislodge .