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#1
01-16-2012, 01:01 AM
 warifir Junior Member Join Date: Jan 2012 Posts: 10 Rep Power: 0
g/kWh to mg/nm3 for diesel generator

Dear All,

can any body help me to convert the following,

there is a diesel engine of 440 kwe (550 KVA), its NOx emissions are 444 g/kWh.

your prompt cooperation in this regard would be much appreciated.

waiting....
#2
01-16-2012, 02:16 AM
 JohnS Moderator Join Date: Dec 2007 Location: SE Michigan, USA Posts: 9,442 Rep Power: 19
Re: g/kWh to mg/nm3 for diesel generator

Quote:
 Originally Posted by warifir Dear All, can any body help me to convert the following, there is a diesel engine of 440 kwe (550 KVA), its NOx emissions are 444 g/kWh. Please convert it in mg/nm3. your prompt cooperation in this regard would be much appreciated. waiting....
That figure seems incredibly high. Are you sure that isn't the fuel consumption? If it is NOx, it is perhaps the worst engine ever built.

Anyway 440 kW x 444 g/kWh = 195360 g/h = 195.360 kg/h. You would have to determine the total exhaust volume during the hour to calculate concentration.
#3
01-16-2012, 08:57 AM
 warifir Junior Member Join Date: Jan 2012 Posts: 10 Rep Power: 0
Re: g/kWh to mg/nm3 for diesel generator

Quote:
 Originally Posted by JohnS That figure seems incredibly high. Are you sure that isn't the fuel consumption? If it is NOx, it is perhaps the worst engine ever built. Anyway 440 kW x 444 g/kWh = 195360 g/h = 195.360 kg/h. You would have to determine the total exhaust volume during the hour to calculate concentration.
Dear JohnS,

thank u so much for your reply. basically the diesel engine is from Germany. and the value of NOx was written like this way "4,44 g/kWh" and i couldn't understand whether the value is "444 or 4.44" that's why i had the big value. Anyways thank u so much for your reply. i will get the exhaust volume and then check the final value in mg/nm3. ok tc cya...thanks once again.
#4
01-16-2012, 09:26 AM
 JohnS Moderator Join Date: Dec 2007 Location: SE Michigan, USA Posts: 9,442 Rep Power: 19
Re: g/kWh to mg/nm3 for diesel generator

Quote:
 Originally Posted by warifir Dear JohnS, thank u so much for your reply. basically the diesel engine is from Germany. and the value of NOx was written like this way "4,44 g/kWh" and i couldn't understand whether the value is "444 or 4.44" that's why i had the big value. Anyways thank u so much for your reply. i will get the exhaust volume and then check the final value in mg/nm3. ok tc cya...thanks once again.
It is a decimal comma. Many European countries (other than English speaking ones) use a comma as the decimal marker. It is 4.44, so divide by 100.

The figure is still VERY high. Heavy truck engines manufactured in 2007 and after are spec'd at 0.2 g/bhp·h, about 0.27 g/kWh, about 16-fold better. I don't know what standards apply to staionary engines.

Last edited by JohnS; 01-16-2012 at 09:32 AM.
#5
01-16-2012, 07:15 PM
 warifir Junior Member Join Date: Jan 2012 Posts: 10 Rep Power: 0
Re: g/kWh to mg/nm3 for diesel generator

Quote:
 Originally Posted by JohnS It is a decimal comma. Many European countries (other than English speaking ones) use a comma as the decimal marker. It is 4.44, so divide by 100. The figure is still VERY high. Heavy truck engines manufactured in 2007 and after are spec'd at 0.2 g/bhp·h, about 0.27 g/kWh, about 16-fold better. I don't know what standards apply to staionary engines.
Dear JohnS,

Please assist that below calculations are correct or not? because Nox values looks under the limit,

Nox = 4.44 g/kWh

Power = 440 kWe

Required: NOx value in mg/nm3

therefore,

440 kWe x 4.44 g/kWh = 1,953.6 g/hr

Now, the total exhaust gas volume in one hour is = 4,980 m3/hr

1,953.6 g/hr
------------
4,980 m3/hr

Ans: 0.392 g/m3

and so we get, 392 mg/m3

JohnS, if my answer is right then the NOx value is under control without any catalytic converter. please reply me ASAP i will be very thankful to you.

if answer is not correct and i did a mistake then plz assist.

Last edited by warifir; 01-17-2012 at 12:15 AM.
#6
01-17-2012, 01:33 AM
 JohnS Moderator Join Date: Dec 2007 Location: SE Michigan, USA Posts: 9,442 Rep Power: 19
Re: g/kWh to mg/nm3 for diesel generator

Quote:
 Originally Posted by warifir Dear JohnS, Please assist that below calculations are correct or not? because Nox values looks under the limit, Nox = 4.44 g/kWh Power = 440 kWe Required: NOx value in mg/nm3 therefore, 440 kWe x 4.44 g/kWh = 1,953.6 g/hr Now, the total exhaust gas volume in one hour is = 4,980 m3/hr 1,953.6 g/hr ------------ 4,980 m3/hr Ans: 0.392 g/m3 and so we get, 392 mg/m3 JohnS, if my answer is right then the NOx value is under control without any catalytic converter. please reply me ASAP i will be very thankful to you. if answer is not correct and i did a mistake then plz assist.
The calculation looks correct. I don't know what your limit is for a stationary engine.
#7
01-17-2012, 03:08 AM
 warifir Junior Member Join Date: Jan 2012 Posts: 10 Rep Power: 0
Re: g/kWh to mg/nm3 for diesel generator

Quote:
 Originally Posted by JohnS The calculation looks correct. I don't know what your limit is for a stationary engine.
Dear JohnS,

can you tell me the limits of diesel NOx in USA, in mg/nm3?

and please let me know whether natural gas produces higher NOx or Diesel fuel?

your kind cooperation in this regard will be highly appreciated.
#8
01-17-2012, 04:41 AM
 JohnS Moderator Join Date: Dec 2007 Location: SE Michigan, USA Posts: 9,442 Rep Power: 19
Re: g/kWh to mg/nm3 for diesel generator

Quote:
 Originally Posted by warifir Dear JohnS, can you tell me the limits of diesel NOx in USA, in mg/nm3? and please let me know whether natural gas produces higher NOx or Diesel fuel? your kind cooperation in this regard will be highly appreciated.
The US does not specify it that way. For passenger car and light truck, the limits are in grams per mile. For heavy truck (and coach), off-road equipment, marine, and stationary engines, the limits are grams per brake horsepower hour, regardless of how the shaft power is used. The regulations do not consider the volume of exhaust. Each category above has its own limits by year of manufacture, with stationary engine the least regulated. (the above "mixed" units are easily converted to SI; divide approximately by 1.61 km/mi or 0.746 kW/bhp)

Natural gas is normally burned at stoichiometry (or very nearly) and has low NOx. It naturally produces lower CO and HC than gasoline and is easily cleaned up with after-treatment. Diesel is normally burned lean (excess air) to control CO, HC, PM, but this tends to produce high NOx. With tighter NOx regulation, after-treatment is required in heavy truck and coach. The other limits are lax enough that after-treatment may be avoided. Probably in the future, all of the limits in various categories will converge towards those for heavy truck engines.

There are so many categories and years (and power level) with different limits you will have to Google to find what you want. The EPA has pretty good lists.
#9
01-17-2012, 07:14 AM
 warifir Junior Member Join Date: Jan 2012 Posts: 10 Rep Power: 0
Re: g/kWh to mg/nm3 for diesel generator

Quote:
 Originally Posted by JohnS The US does not specify it that way. For passenger car and light truck, the limits are in grams per mile. For heavy truck (and coach), off-road equipment, marine, and stationary engines, the limits are grams per brake horsepower hour, regardless of how the shaft power is used. The regulations do not consider the volume of exhaust. Each category above has its own limits by year of manufacture, with stationary engine the least regulated. (the above "mixed" units are easily converted to SI; divide approximately by 1.61 km/mi or 0.746 kW/bhp) Natural gas is normally burned at stoichiometry (or very nearly) and has low NOx. It naturally produces lower CO and HC than gasoline and is easily cleaned up with after-treatment. Diesel is normally burned lean (excess air) to control CO, HC, PM, but this tends to produce high NOx. With tighter NOx regulation, after-treatment is required in heavy truck and coach. The other limits are lax enough that after-treatment may be avoided. Probably in the future, all of the limits in various categories will converge towards those for heavy truck engines. There are so many categories and years (and power level) with different limits you will have to Google to find what you want. The EPA has pretty good lists.
Dear JohnS,
Thank u so much for ur prompt replies. U know y i m confuesd for diesel cuz we r the dstrbutor of both gas n diesel generators. For gas generators,we have nox values in mg/nm3 and these are around 1200 mg/nm3. But for diesel we have the values in g/kwh n when i convert it according to the method which u have checked then it gives around 400 mg/nm3. That's y i m much confued that how a diesel engine can give lowest values of nox than gas engine, even without catalytic convertr. Even the size of both engines r same n both are power generation units. That's y i m keep asking. Sorry for any inconvenience this may have caused.

Last edited by warifir; 01-17-2012 at 07:21 AM.
#10
01-17-2012, 08:48 AM
 JohnS Moderator Join Date: Dec 2007 Location: SE Michigan, USA Posts: 9,442 Rep Power: 19
Re: g/kWh to mg/nm3 for diesel generator

Are the gas engines operated lean or at stoichiometry? Lean raises NOx substantially and generally requires active NOx aftertreatment (as it does in diesel, the problem is the excess O2)

Here is an example of a commercial natural gas engine (rated for heavy vehicle use) that meets 0.2 g/bhp·h NOx (about 0.27 g/kWh). It uses a conventional three-way catalyst.
http://www.cumminswestport.com/products/islg.php

Edit: May I suggest checking the exhaust flow calculation. That seems very high. At 25:1 air/fuel, which is pretty lean, it would suggest around 280 L of diesel per hour. I'm not sure how you derived it, but I think something is off.
(I assumed air mass 1.2 kg/m³, 25:1 mass air fuel ratio, and diesel density 0.85 kg/L) If you overstate the exhaust volume, the NOx concentration is understated.

Last edited by JohnS; 01-17-2012 at 08:58 AM.

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