Calibration of Gas and Liquid in Online GC

[JasGill]

Hi,

I have a reactor connected to an online GC.

What I need cto calibrate the GC for known amount of CO+CO2+O2+PROPANE+ACRYLIC ACID+ACETIC ACID.

1. I have a standard gas cylinder with co/co2/o2 at 10/10/20 mol% mixture

2. I also have prepared a standard solution of acetic acid/acyrlic acid of 50/50 mol% mixture.

I'm planning to inject liquid standard and and gas standard separately to get a normalised 100% calibration of all compounds.

Problem is how do I get 100% normalised amount. Is there a calculation spreadhseet that can be used to calculate these kind of calibrations.


Thanks..

[chromatographer1]

When you test the contents of your reactor is the sample and your reactor contents all in one phase?

If not, (which seems likely) then there is no spreadsheet because the calculation is not possible.

Think about it and you will agree (I hope).

For example:

I have a bottle containing water and gases. Tell me how much is water and how much is gas?

Well, tell me the answer. Isn't there a spreadsheet to calculate how much is water and how much is each of the gases?

Gosh, I wish the real world would be simple and straightforward but it isn't.

I hope I am understood.

I have been in situations where the contents are to be measured and normalized (not trended). Unless you know:

EVERYTHING that is in a sample

and can separate it, and can measure it, you can't calibrate the measurements and transform it into an answer of wt% or vol% or mol%. Even then the sample has to be entirely in one phase, all liquid or all gas.

Sometimes this is possible, but not in this case I suspect. (water, acid anhydrides, peroxides, etc)

You can trend the content of each phase of a two phase system but you can't normalize it as you don't know the AMOUNT of each phase present at any one time.

Knowing the limitations of a situation is almost as good as knowing the true answer.......

almost.

best wishes,

Rod

[JasGill]

thanks bro..

actually all my products ex-reactor are in gas phase(heated line to online GC at 180degC).


So my problem now is that I cant do the same for standard calibration solution which I prepared. Hence my earlier query...


Any solutions...

[DSP007]

Hello
Well, if all of the products outside the reactor ... vaporize them "nafig in vapor phase, and deal with it. At 150 and vinegar flies ...
But if you pick apart the gas and liquid phase directly into the reactor, "in process " - a task not for the average mind.

[chromatographer1]

No solutions.

You can trend the analysis, but you can't normalize.

have a great day,

Rod

[GasMan]

If you convert your calibration mixtures to absolute amounts in weight this should work. You would first need to convert your gas mixture in mol% to absolute weight injected, taking into account the volume, pressure and temperature of your gas sample. You would then get a response factor per unit weight. You do the same for your liquid sample. If you then run your sample, you would get a report in absolute weights present in your sample. This can then be converted to weight per cent and then to Mol%.

Gasman

[chromatographer1]

To Normalize Gasman you have to know all the components in the sample and to be able to measure them. This was hammered into me constantly when I worked for Philips Petroleum.

It isn't what you think is present in the sample, it is what is actually present in the sample.

OTHERWISE, it is only an approximation.

Not that that is a bad thing.

That is why in process control most analyses are trend analysis. It is not necessary to perform normalization to monitor a process. Normalization is for bean counters who like to be told the absolute truth when the absolute truth is not available. And they don't care if it is true or not, just so they can quote YOU saying it is true, even though it is not.

Guess who gets blamed when it isn't true and someone finds out, the bean counter? NOPE.

Now I am not saying that you can't get a close approximation, but IT IS AN APPROXIMATION.

I understand your thinking and I used to think that way myself. But professional chemical engineers with decades of experience beat it out of me.

Have a great day, everyone. It is spring.

Rod