17 replies to this topic

[ankur2061]

Dear All,

This question has been raised often on the forum and even now I see a lot of process engineers failing to understand the concept and making mistakes in conversion.

An important point is to note that a majority of the times when you are dealing with gaseous air pollutants in the atmosphere, the reference condition of temperature and pressure needs to be clearly specified. Most agencies involved in air pollution regulation and control use reference conditions of 25°C and 101.325 kPa(abs). A prime example is the United States Environmental Protection Agency (EPA). The European "Air Quality Directive" also uses reference conditions, however, these are not specified at their website. . The links for US EPA and European Air Quality Directive are provided below:

http://www.epa.gov/

http://ec.europa.eu/...y/standards.htm

An link for an online calculator for converting ppm (v) to mg/m³ and vice-versa is provided which uses reference conditions of 25°C and 1 atmosphere. This calculator has been found to provide satisfactory results:

http://www.cdc.gov/n...04-101/calc.htm

Regards,
Ankur.

[pavanayi]

The one that I use (and which I have confirmed with tech support of ADMS software), in which temperature is also a variable is (at 101.325 kPa(abs)):

ppm (v) = mg/m³ * T/(12.187*MW)

where MW is the molecular weight of the component and T is the temperature in K

so if the temperature is 25°C, the constant becomes (25+273.15)/12.187 = 24.46 as shown in the link given by Ankur.

Edited by pavanayi, 06 January 2012 - 05:35 AM.

[kkala]

Way of calculating the conversion based on ppm (v) definition is judged useful, especially when you are far from office. Actually ppm on volume basis is also ppm on molar basis for pressure = 1 Atm a of ambient air.
1. Concerning X ppm(v) of gas, of molecular weight MW; and temperature T oK for ambient air:
X ppm(v) = XE-6 kmol / kmol air = XE-6*MW kg/ kmol air = X*MW mg / kmol air.
But 1 kmol air has a volume of 22.414*T/273.15 m3 =T/12.187 m3.
So X ppm(v)=X*MW/(T/12.187) mg/m3 air.
2. Similarly X mg/m3 air = XE-6 kg/m3 air = XE-6/MW kmol/m3 air.
But 1 m3 air contains 1/(22.414*T/273.15) kmol air =12.187/T kmol air.
So X mg/m3 air = XE-6/MW/ (12.187/T) kmol/ kmol air = X*T/(12.187*MW) ppm (v) .This is the formula used by pavanayi.
3. In practice arithmetic operation using the specific figures may be more convenient, after finding molar volume at reference conditions. No need to know the formulas by heart, just apply the ppm (v) definition.
An example of similar conversion (as per para 1) can be seen at http://www.cheresour...6-stack-height/, where an arithmetic error occurred (convering kg to μg).

Edited by kkala, 06 January 2012 - 09:26 AM.

[kkala]

Way of calculating the conversion based on ppm (v) definition is judged useful, especially when you are far from office. Actually ppm on volume basis is also ppm on molar basis for pressure = 1 Atm a of ambient air.
1. Concerning X ppm(v) of gas, of molecular weight MW; and temperature T oK for ambient air:
X ppm(v) = XE-6 kmol / kmol air = XE-6*MW kg/ kmol air = X*MW mg / kmol air.
But 1 kmol air has a volume of 22.414*T/273.15 m3 =T/12.187 m3.
So X ppm(v)=X*MW/(T/12.187) mg/m3 air.
2. Similarly X mg/m3 air = XE-6 kg/m3 air = XE-6/MW kmol/m3 air.
But 1 m3 air contains 1/(22.414*T/273.15) kmol air =12.187/T kmol air.
So X mg/m3 air = XE-6/MW/ (12.187/T) kmol/ kmol air = X*T/(12.187*MW) ppm (v) .This is the formula used by pavanayi.
3. In practice arithmetic operation using the specific figures may be more convenient, after finding molar volume at reference conditions. No need to know the formulas by heart, just apply the ppm (v) definition.
An example of similar conversion (as per para 1) can be seen at http://www.cheresour...6-stack-height/, where an arithmetic error occurred (convering kg to μg).

Above post has received a negative feedback by ankur2061. Why? Ankur2061 is requested to justify the reason.

[ankur2061]

Dear kkala,

Your post does not add any value to my original post. As I have mentioned in my blog entry refer comment # 2, a response to any query needs to add value to the original post which your post does not. Also the post is misleading in terms of not mentioning the correct units as mg/ Nm³ since the standard volume of a kg-mole of air is mentioned as 22.414 m³ which is the volume of 1 kg-mole of air at normal conditions of 0 deg C and 101.325 kPa (abs). My original post mentions the reference conditions of temperature as 25 deg C and 101.325 kPa(abs) for measurement

Regards,
Ankur.

[kkala]

Response to the post No 5 by ankur2061 is as follows.
Your post does not add any value to my original post. As I have mentioned in my blog entry refer comment # 2, a response to any query needs to add value to the original post which your post does not.
Although a block entry does not express orders, some value is added by the specific post. It explains how to make the conversions using only elementary knowledge. This is especially practical when far from office. A lot of errors occur in the relevant application.
Also the post is misleading in terms of not mentioning the correct units as mg/ Nm³ since the standard volume of a kg-mole of air is mentioned as 22.414 m³ which is the volume of 1 kg-mole of air at normal conditions of 0 deg C and 101.325 kPa (abs). My original post mentions the reference conditions of temperature as 25 deg C and 101.325 kPa(abs) for measurement.
The correct units are mg/m3, (as written) since there is temperature adjustment to molar volume. Air is considered at T oK and P= 1 Atm a (it is written). If someone wishes T=298.15 oK = 25 oC all right, other air temperatures are also covered. Once temperature of 15 oC was adopted here (annual mean).

I think argumentation is not objective, not revealing real incentives.
It is also noted that "Negative feedback on replies for posts is provided when the reply is either offensive or it is totally irrelevant to the subject and not at the whims and fancies of an individual" http://www.cheresour...-system-design/, post No 4 by ankur2061.

Edited by kkala, 06 January 2012 - 04:57 PM.

[ankur2061]

The correct units are mg/m3, (as written) since there is temperature adjustment to molar volume. Air is considered at T oK and P= 1 Atm a (it is written). If someone wishes T=298.15 oK = 25 oC all right, other air temperatures are also covered. Once temperature of 15 oC was adopted here (annual mean)

Ambient air emissions are reported at 25 deg C and 101.325 kPa (abs) by US EPA and the website of European "Air Quality Directive" web site does not specify the reference conditions of temperature and pressure. Please clarify with supporting evidence where other temperatures specifically 15°C has been used. The statement "other air temperatures are also covered" is meaningless since amient air emissions are not reported at various temperatures by monitoring and regulating agencies for ambient air emissions. For example, air emissions are not reported at 40°C which is a commonly observed temperature in many parts of the world during hot seasons. Thus the statement "other air temperatures are also covered" conveys no meaning.

Ankur.

Edited by ankur2061, 07 January 2012 - 01:53 AM.

[kkala]

Ambient air emissions are reported at 25 deg C and 101.325 kPa (abs) by US EPA and the website of European "Air Quality Directive" web site does not specify the reference conditions of temperature and pressure. Please clarify with supporting evidence where other temperatures specifically 15°C has been used. The statement "other air temperatures are also covered" is meaningless since ambient air emissions are not reported at various temperatures by monitoring and regulating agencies for ambient air emissions. For example, air emissions are not reported at 40°C which is a commonly observed temperature in many parts of the world during hot seasons. Thus the statement "other air temperatures are also covered" conveys no meaning. Ankur.
You could say the above as an opinion (that would be commented on), but it does not justify the negative feedback. It seems an excuse rather than an argument. The general case of T oK covers the specific case of 25 oC (molar volume 24.06 m3/kmol), and "standard" conditions for EU have not been found. That is why 15 oC (mean annual) was reasonably considered for the dispersions of a Seveso II safety study (2007).
I believe the negative feedback expresses just discomfort because of kkala's intervention and his willingness to do so. Any comments on this? But any member deserves contribution to any post, subject to fair criticism.

Note: let glc be 200 μg/Nm3 = 190 μg/std m3 = 183 μg/m3 air (25 oC, 1 Atm a); uncertainty of a dispersion model is wider than these differences.
Besides mentioned conversions can have wider application than in conversion models.

Edited by kkala, 07 January 2012 - 05:24 AM.

[ankur2061]

kkala,

You have contributed more than 1000 posts on the forum in a span of less than 2 years. That is appreciable. However, your penchant of mentioning in a majority of your posts about certain engineering design practices recommended by you as local practices and projects done in your area without providing any documentary evidence or backup is what is not correct.

If by quoting that these are "local practices", design / installation / commissioning / operations can be successfully executed than there would be no need for engineering standards or guidelines either international, European, American, Greek, Luxembourgian, Asian, Japanese. The fact of the matter is that engineering may not be even based on a freely available article on the internet despite it's very informative and instructive nature because every engineer wants to go for proven and established practices. The codes, guides and standards including the one's from reputed companies just provide that confidence for an established and proven design as well as successful installation and operation.

Even considering that you have had a certain experience in the past, any information which is disseminated on the forum has to be backed up. If you are referrring local practices in Greece than back them up with reference to relevant documents (title, number etc.) which mentions those "local practices". In fact, it would be prudent to ask or instruct the OP to check regulations, laws and guidelines applicable in his or her country instead of telling him or her about local practices in Greece. Greece, I believe folllows ISO guidelines on oil and gas, which you could refer in your posts when discussing a critical issue. Otherwise, readers of your posts over a period of time will realize that he or she is being bluffed behind the cliched "local practices".

Another thing which you fail to notice is that you try to divert from the subject posted by the OP by inserting something irrelevant to the subject. This can happen a few times, but unfortunately it happens too often for you. Sticking to the point should be the motto of an intelligent and measured response.

Since you have a penchant for writing about your experiences as a process engineer, you should utilize the blog section of the forum for sharing your experiences. I am sure readers and members of "Cheresources" will be quite interested in reading and understanding your experiences.

Hopefully, you will take this on a positive note and try to improve on your responses. You are also free to point out any omissions and commissions which I make while posting responses to others.

Regards,
Ankur.

[kkala]

kkala,
You have contributed more than 1000 posts on the forum in a span of less than 2 years. That is appreciable. However, your penchant of mentioning in a majority of your posts about certain engineering design practices recommended by you as local practices and projects done in your area without providing any documentary evidence or backup is what is not correct.
If by quoting that these are "local practices", design / installation / commissioning / operations can be successfully executed than there would be no need for engineering standards or guidelines either international, European, American, Greek, Luxembourgian, Asian, Japanese. The fact of the matter is that engineering may not be even based on a freely available article on the internet despite it's very informative and instructive nature because every engineer wants to go for proven and established practices. The codes, guides and standards including the one's from reputed companies just provide that confidence for an established and proven design as well as successful installation and operation.
Even considering that you have had a certain experience in the past, any information which is disseminated on the forum has to be backed up. If you are referrring local practices in Greece than back them up with reference to relevant documents (title, number etc.) which mentions those "local practices". In fact, it would be prudent to ask or instruct the OP to check regulations, laws and guidelines applicable in his or her country instead of telling him or her about local practices in Greece. Greece, I believe folllows ISO guidelines on oil and gas, which you could refer in your posts when discussing a critical issue. Otherwise, readers of your posts over a period of time will realize that he or she is being bluffed behind the cliched "local practices".
Another thing which you fail to notice is that you try to divert from the subject posted by the OP by inserting something irrelevant to the subject. This can happen a few times, but unfortunately it happens too often for you. Sticking to the point should be the motto of an intelligent and measured response.
Since you have a penchant for writing about your experiences as a process engineer, you should utilize the blog section of the forum for sharing your experiences. I am sure readers and members of "Cheresources" will be quite interested in reading and understanding your experiences.
Hopefully, you will take this on a positive note and try to improve on your responses. You are also free to point out any omissions and commissions which I make while posting responses to others.
Regards, Ankur.

No comments, just noted. Please respond specifically to the post No 8 by kkala.

[ankur2061]

kkala,

Well, it seems my advice hasn't gone down well with you and I wasted my time in trying to make you mend your ways.

Coming to specifics, I missed out on something. The reference conditions used by the "European Environment Agency" (EEA) are 15°C and 101.325 kPa (abs).

What this indicates is that the US uses 25°C and Europe uses 15°C. Based on these standard conditions the molar volume of 22.414 m³ used in post # 3 is incorrect. The molar volume with 25°C as a reference temperature is 24.46 m³ and with 15°C as reference temperature is 23.64 m³. There is no evidence of any other reference temperature including 0°C being used for reporting ambient air pollutants in USA and Europe. In case you are able to furnish documentary evidence that ambient air pollutants are reported with a reference temperature of 0°C which provides a molar volume of 22.414 m³, then let me know and I will remove your negative feedback. Till then the negative feedback stays.

[kkala]

A.

I believe the negative feedback expresses just discomfort because of kkala's intervention and his willingness to do so. Any comments on this? But any member deserves contribution to any post, subject to fair criticism.

You know the above is the essence, please respond to it.
We are not in negotiations for the negative feedback, justification is requested for placing it. Action is of interest, not the feedback itself. It should not be removed, history is history.
B. "Specifics" in post No 11 concern also previous posts already commented on. Anyway, explanations below are more detailed than before.
B1. Coming to specifics, I missed out on something. The reference conditions used by the "European Environment Agency" (EEA) are 15°C and 101.325 kPa (abs).
This was not known to me, please report reference.
G. Ulrich and P. Vasudevan in "Chemical Engineering, Process design and economics, a practical guide", PP 2004, p. 529, Table 11.3, converts μg/m3 to ppmv based on air at 1 Atma and 20 oC.
B2. What this indicates is that the US uses 25°C and Europe uses 15°C. Based on these standard conditions the molar volume of 22.414 m³ used in post # 3 is incorrect. The molar volume with 25°C as a reference temperature is 24.46 m³ and with 15°C as reference temperature is 23.64 m³.
Molar volumes are correct. According to Post No 3, molar volume at 25 oC is 22.414*298.15/273.15 = 24.47 m3 and at 15 oC 22.414*288.15/273.15 = 23.64 m3 per kmol. The factor 22.414 is not alone, take notice of the symbol T (oK) etc.
B3. There is no evidence of any other reference temperature including 0°C being used for reporting ambient air pollutants in USA and Europe.
What is the harm, if way of calculation can be also for other temperatures? Use what you wish. Also remember G. Ulrich above.
B4. In case you are able to furnish documentary evidence that ambient air pollutants are reported with a reference temperature of 0°C which provides a molar volume of 22.414 m³, then let me know and I will remove your negative feedback. Till then the negative feedback stays.
Irrelevant point, out of subject too. Look at B2 above (and at A for the feedback).

Edited by kkala, 07 January 2012 - 10:25 AM.

[ankur2061]

No comments on above litany.

European Environment Agency (EEA) reference conditions provided at:

http://en.citizendiu...re_and_pressure

[kkala]

No comments on above litany.

But the reason of negative feedback has not been clarified. Please do.

Edited by kkala, 07 January 2012 - 05:40 PM.

[kkala]

Concerning reference air temperature (t) for the ground level concentrations (glcs) used in dispersion models:
1. Greek legislation specifies t=273 oK ~ 20 oC, see post 32 of http://www.cheresou...-stack-height/ . This is copy from EU (European Union) legislation, so for EU it must be t=20 oC.
Web reference of post 13 (present thread) reports 15 oC as reference temperature of a gas by European Environmental Agency, but this does not necessarily refer to glcs. Legislation must be prevailing.
2. USA Environmental Protection agency reports t=20 oC or 25 oC as reference gas temperatures, see attachment to post 13 of present thread. Probably t=20 or 25 oC, but which of the two? G. L. Ulrich reports t=20 oC in his book, see post No 31 of http://www.cheresour...6-stack-height/.
3. Any specific evidence on reference air temperature (in EU or USA) for glcs would be appreciated. Dispersion models are not sensible to such small differences in t, as post No 8 (present thread) indicates. But clarification would help compare allowable glcs on the same basis. Since the matter has been touched, it had better be clarified.

Edited by kkala, 13 January 2012 - 05:18 PM.

[kkala]

No comments on above litany.

But the reason of negative feedback has not been clarified. Please do.

Unfortunately no sincere explanation has been given so far. Arguments of "no adding value" and "reference to 0 oC" are false (see previous posts). I believe post No 9 is a list of false accusations too. If there were a harmful post by kkala, you should refer to it.
Cold mind and good will (from all) are needed to approach correct answer.

[Qalander (Chem)]

Dear Kostas Hello/Good Evening,

• Just leave it,
• I consider this "at times" much better to leave.
• than responding!

Hope you forgive us all "Humans" like poor me, greats 'ankur'& 'you' both!

Edited by Qalander (Chem), 22 February 2012 - 11:10 AM.

[kkala]

Thanks, Qalander (Chem).
Last note: Supplementary info on the subject and mainly on "standard" conditions for air (and gases in general) can be found in http://www.cheresour...ard-conditions/.

Edited by kkala, 28 February 2012 - 02:17 AM.