Air and water pollution control., HTML programming, GNU Linux.

Thursday, 16 October 2008

How to convert from m3 to Nm3?

Many times when you see the different concentrations of any polluters you may see it in mg/m3. For people who are not familiar with terminology this could be a little bit disturbing because some norms and limits are granted in mg/Nm3 which in some cases could be totally differen t.Where is the difference in this upper case N? N means Normal and according to International Union of Pure and Applied Chemistry and their site these standard conditions are temperature 273.15 K (C) and pressure 10^5 Pascal’s.

And what we should to do if have a concentration of 300 mg/m3 and limit of 150 mg/Nm3. Is it possible to reach the norm and even to outrun it? Yes in some cases it is possible but not in any of course. We can look our concentration and just to imagine that this concentration had measured in some chimney where the smoke gases became from furnace with temperature of 850 – 950 (Klaus process for example). And you have measured something like:

T (average): 650 0C

P (average): - 3 mm Hg

To = 273 K – this is normal temperature – 0 0C

Po = 760 mm Hg – 1 atm.

Other common measured parameter is a flow of smoke gases which is possible to be something like 130 000 m3

Then from these we are able to find some coefficient (let’s name it - K)

K = (To * P)/( Po *T) = [273*(760-3)]/[760*(273+650)]= 0.29

Now we should convert 130 000 m3/h * 0.29 = 37 700 Nm3

See how low are now these – round three times less than before. If we have measured the humidity in the chimney gases in percent then we also should remove this. It happens at this pattern:

If humidity is 5 % for example so then 37 700 Nm3 must multiple to this 5% and

37 700 * 0.05 = 1 885 Nm3 and

37 700 - 1 885 = 35 815 Nm3

At the end from 130 000 m3 we receive 35 815 Nm3 of chimney gases.