1156 posts
Air emission control Question 3
Our government is starting to limit NOx emissions from cement kilns and the regulation, as I heard, was more severe than in the European countries. I think the best way for reducing NOx emission with no further cost is to use fuels that contain the lower nitrogen content, especially coal and residual fuels. Am I correct?
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1156 posts
Re: Air emission control
The NOx emissions arise from two sources: (i) the nitrogen in the fuel as you say, and (ii) "thermal" NOx from the breakdown of atmospheric nitrogen at the high temperatures in the burning zone. Usually the thermal NOx is much higher than the fuel NOx and the best way to reduce NOx emissions is to reduce this thermal NOx. Low NOx burners reduce the temperatures in the flame and produce less NOx by using less primary air. Low NOx calciners burn some of their fuel in a depleted oxygen environment to cause NOx degradation by the following reaction: NO + CO -> 0.5N2 + CO2. These are the best way sto reduce the NOx emissions of the kiln.
1156 posts
1156 posts
Re: Air emission control
The sizing of the tower is determined by a heat balance which tells you the amount of water which would need to be evaporated to realise a certain fall in temperature of the gases entering the tower. The results of this heat balance are then used with the Ideal Gas Laws which allow you to calculate the contraction in volume of the gases caused by the reduction in temperature. This contraction creates a negative pressure. This then needs to be compared with the negative pressure rating of the tower.