how to cal heat loss due to low excess air in coal burner

[sircrazyhorse]

I work at a cement plant where we have 2 rotary kiln. From several projects I’ve noticed that the excess air within in the kiln was low. I know from college that this lowers the flame’s temperature. Currently we don’t have a way to accurately measure the temperature. However it’s vital to get some type of indication of how the flame is being affected. plese help

Thanks

 

[25362]

The adiabatic flame temperature in combustion of hydrocarbon fuels in refinery heaters comes down with an increase in excess air. One must consider that the xs air acts as an additional heat sink. See, for example, the adiabatic temperatures for a refinery fuel with a lower calorific value of 9,750 kcal/kg, with varying xs air %:

xs air,% adiab. temp., ^oC

0 2,000
20 1,800
40 1,640
60 1,480
80 1,360
100 1,250

In practice, these temperatures aren't attainable because of the immediate flame heat release "in status nascendi" by radiation.

If we assume that this "loss" is, say 35%, the above temperatures would come down to something as 1,450, 1,265, 1,140, 1,010, 920, and 850^oC, respectively.

Higher flame heat "losses", of around 50%, can be attained in refinery furnaces by preheating the air to combustion and having a low % of xs air which, as we saw, affects the flame temperature, and thus the flame radiation heat flux.

 

[cougarfan]

The few rotary kilns I have seen have a sight glass or some type of camera to see the flame. The bluer the flame the better. Check also the exhaust gases to see if their is any extra oxygen out the stack.