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.
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I work in the US. Other companies pay us to use their waste as fuels in some of our processes. Essentially, we are then generating revenue for the use of those specific fuels. Currently, the revenue is being accounted for as a contra expense on our income statement. Some believe that all revenue is revenue and the alternative fuels payment should therefore be accounted for as revenue on our income statement. Others argue that the alternative fuels process is taking place within a cost center, one of our manufacturing plants, and all revenues should role up into the costs of the of the plant, which is what we are doing now by treating the alternative fuels' revenue as a contra expense. Is there is an industry standard or norm for the accounting of this process
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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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The criteria for petcoke grinding should be the residue on a 90 micron sieve. You need to find the optimum by conducting trials however you can anticipate that you may need to grind the petcoke to less than 10 per cent residue on the 90 micron sieve. The problem with petcoke is the low level of volatiles. With a coal particle the particle "explodes" when it enter the kiln atmosphere due to rapid evaporation of the volatiles in the coal. This causes very rapid combustion. With the petcoke there are no volatiles so the particle can fall into the bed of material before fully combusting. This can cause locally reducing conditions and badly affect the clinker quality. This is why petcoke is usually ground to a high fineness.