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NOx Emissions From Large Stationary Engine

NOx Emissions From Large Stationary Engine

NOx Emissions From Large Stationary Engine

Have measured NOx emissions from engine exhaust but analyzer units are in PPM. Need to convert to g/Bhp-Hr. Seeking formula for units conversion. Thank you!!!

RE: NOx Emissions From Large Stationary Engine

It's not ordinarily done the way you are proposing. I'll assume you mean ppm "by weight" b/c it could also be by mole.

First: you need to know the NO/NO2 ratios of your NOx. Then also realize that EPA assumes all the NO goes to NO2 in the atmosphere. E.g. if you produce NOx with 90% NO, you will be "credited" with .1 * x + .9 * (46/30) x, or 1.48 g NOx emissions per 1.0 g NOx measured.

So - you measure 100 g NOx, convert to 148 g NOx equivalent, and then you have to know how many hp-hr were used in generating that much NOx.

e.g. - let's say your engine runs 23,000 g/min exhaust flow at 200 hp, and you measure 200 ppm (weight) NOx; your g/hp-hr is: 23,000 * 60 * (200/1,000,000) * 1.48 / 200 = 2.04 g/hp-hr

RE: NOx Emissions From Large Stationary Engine

take PPM, multiply by average molecular mass of NOx constituents (30 to 46), divide by average mass of exhaust constituents (including NOx, say 30-ish), you get lb NOx per lb exhaust.  

multiply the above by mass flow rate of exhaust (lb exh /hr) to get lb NOx per unit time (lb/hr)

divide by the corresponding horsepower to get brake-specific NOx emissions per unit time (lb/hp.hr)

in the end you'll get an answer that says 10ppm is about 0.03 gm/bhp.hr, depending on the above

RE: NOx Emissions From Large Stationary Engine

ivymike- there's nothing wrong with your math, but that method will underestimate the EPA-reported NOx due to the EPA correction as noted in my post above.

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