Advice on choosing a GC

[Nurrie]

Hello Everyone,

Our lab is currently shopping for a GC that would help us accurately analyze the products of Steam Methane Reforming. The products we need to look at are pretty simple, mostly just refinery gas products and hydrogen. Even though this is a fairly easy task for a gas chromatograph equipped with a TCD detector, the concerns arise when attempting to detect H2 and refinery gas products simultaneously due to their drastically different thermal conductivities.

One setup we used to use was dual TCD, one running Argon carrier to detect H2, and the other running Helium for everything else. The issue with this is a complicated method that led to 20 min run times due to a column isolation step (piping diagram below).



The other setup was one TCD running just Argon carrier, and dealing with the low responses from the refinery gases. This was not ideal, but might do the trick.

With the SMR reaction we also need to worry about moisture getting into the system, so a good condenser upstream would be required.

When looking for quotations, various companies have said the first setup is probably the best, but maybe use an FID for the refinery gases.

Agilent suggests the 490micro, which im apprehensive about due to its limitations, but seemingly offers the fastest run times and most accurate results. Reminds me kind of a laptop vs a desktop pc. The desktop pc offers much more customization, cheaper components, and you can maintain it much easier yourself. What are your experiences with these microGCs?

Any help or suggestions would be much appreciated.

N.

[James_Ball]

Would it be more simple to use the dual TCD setup or a TCD/FID setup and just place a simple flow switch at the end of the column, and switch from one detector to the other after the H2 elutes?

http://www.gmu.edu/depts/SRIF/equipment ... atures.pdf

Look at pages 6-8 of the brochure, I think it would do exactly what you are wanting with just a little tweaking. With either the TCD/TCD or TCD/FID setup.

[rb6banjo]

I'm with James. I'm not that familiar with your analysis and these columns. Are you saying that you can separate H2 from O2, CO, CH4, and CO2 on the Haysep and the rest on the Poraplot Q?

If yes, then what if you purchased a 2 detector system and the Agilent Dean's switch set up to do heartcuts. Inject your sample on the Poraplot Q column but cut the really light part of the chromatogram to the Haysep, then back to the FID or second TCD to get the rest?

https://postimg.org/image/rbtq58389/

My system is set up similarly but most of my work involves aroma and flavor. My columns are a 5-phase where the Poraplot Q is and a wax phase where the Haysep Q is. I also have the effluent from the wax going to a mass spectrometer.

Additionally, you might consider substituting a pulsed-discharge helium-ionization detector for the TCD. It's a great detector for fixed gases.

[GasMan]

To make the decision on which GC to order you will first need to define exactly what you are trying to accomplish.

1. Is the time of analysis important.
2. A list of all possible compounds in your sample.
3. A list of the compounds that you wish to measure in this sample and the levels that they will be present, maximum and minimum.

Then a decision can be made on the correct GC.

Gasman

[Nurrie]

I really like the idea of the flow switch, it's simple and would "de-clutter" so much of the previous plumping, plus shorten the run time. I'll mention this when getting quotations.

I am still stuck on dual TCD, mostly because I have the most experience with them and they are simple. I've had some experience with HIDs and FIDs but not sure if they are necessary in my case, but I could be convinced.

I will include the information that GasMan suggested in case anyone has anything else to add:

1. Time of analysis is preferred to be 15 min or faster. In the past, typical runtimes with this set of gases took about 15-20 mins, and it would be a great if that could be cut in half or more. It's a "faster the better" scenario, since this is for research/product development purposes.

2. List of potential compounds:

• Methane 0-100%

• Hydrogen 0-100%

• Nitrogen 0-100%

• Oxygen 0-10%

• Carbon Monoxide 0-100%

• Carbon Dioxide 0-100%

• Ethane 0-10%

• Ethylene 0-10%

• Acetylene 0-10%

• Propane 0-10%

3. All compounds above need to be detected. The levels are unknown, but will vary greatly depending on the efficiency of the reaction. In the past our ranges were quite large depending on what we were doing. Since this is for product development, flexibility is necessary. I don't think the TCD will have much trouble dealing with large ranges assuming we calibrate properly, but in the past we ran into peak overlap for some compounds if the levels were too high. Accuracy only needs to be within 0.1%, so TCD is quite good for this as well.

I am relatively new to gas chromatography, but I am always interested in learning as much as I can. I am curious if any of you could refer me to any good resources that have helped you in the past, or possibly any seminars that were particularly good.

Thanks again,

N.

[AIM]

Would you be interested in a custom configured refurbished Agilent GC system. We can setup it up to meet your exact criteria and save you money. Please feel free to call Travis at 303-730-4136 ext. 903 or visit our website and request a quote. www.aimanalytical.com