DIY Gas cromathograph

[eslavko]

Hello...

My friend has farm and biogas power plant. Now we are just wonder if it's possible to make GC at home to compare quantity of CH4, CO2, H2S in biogas and maybe even the CH4, O2 in exhaust of generator.
We see that for diy people use cooper, stainless and PTFE for column. We are biased toward PTFE 2 mm inner diameter. For packing material they mostly use kitty litter and silica gel. I do read that diatomic earth and zeolite are the options too. What to use and how to prepare. I have access to zeolite, diatomic earth and silica gel (if old desiccant is usable). For detector we chose TCD as that I can made with ease with diode or bulb filament as detector. For carrier gas we don't know what to use. If air is possible then this is 1st choice. The gas cylinders are mostly out of questions. The option is with hydrogen generator (electrolysis) but I don't like that as in that case the only outdoor work is option for me.
I'm electronics engineer with just "google crash course" on GC theme.
Is that possible to work at all?
Does worth to try?

Thanks in advice

[Purexed]

It would probably be easier to just send it into a lab and have it analyzed for like $60-$100. We used Argon as a carrier, but if you don't care about nitrogen you could probably use that.

[James_Ball]

I was thinking nitrogen also as carrier since you don't seem to be looking for air gasses. I have seen a project for a home made nitrogen generator using the "pressure swing adsorption" method which will make highly pure nitrogen gas from compressed air. It will require some plumbing and switching valves but it is possible to make. You can probably find the plans online. The expensive part may be the molecular sieve used in the pressure cylinders to adsorb the oxygen from the air.

Long ago I made columns with 1/8 inch copper tubing, packing with a vacuum pump and frit at the bottom and funnel at the top, then wrapping it around a coffee can. The columns are the simple part. Injection port can be a simple Tee fitting with gas coming in one side, column connected to the other side and a septum in the third opening.

[eslavko]

It would probably be easier to just send it into a lab and have it analyzed for like $60-$100. We used Argon as a carrier, but if you don't care about nitrogen you could probably use that.

I mean to make measuerment daily or even multiple time per day. So lab test is out of question.

[eslavko]

I was thinking nitrogen also as carrier since you don't seem to be looking for air gasses. I have seen a project for a home made nitrogen generator using the "pressure swing adsorption" method which will make highly pure nitrogen gas from compressed air. It will require some plumbing and switching valves but it is possible to make. You can probably find the plans online. The expensive part may be the molecular sieve used in the pressure cylinders to adsorb the oxygen from the air.

This seems like a lot of work and money too. As I don't know much about GC I just wish to know if separation of required gases is possible at all with diy GC. And for example I don't know how long 1kg bottle of balon helium can work so I don't know if that can pass price range. And what carierr gas is best for required sample. And I assume that I need to run carrier gas much before injecting sample to purge column.

[eslavko]

What difference I can expect if I make heated column?

[antonk]

What difference I can expect if I make heated column?

Only repeatability and independence of ambient conditions.

You analysis would run perfectly @50-60C

Once I've seen portable russian chromatograph for home appliance natural gas leak detection.



Simple membrane pump getting air, filter, packed column in a coil around the heater, electrochemical detector (on separate heater), onboard microcomputer with LCD display.

All stuff in a box 300mm x 100mm x 250 mm

[eslavko]

Ok so temperature owen is not mandatory but with owen the results are more consistent and probably faster.

[eslavko]

Ok so temperature owen is not mandatory but with owen the results are more consistent and probably faster.

[dblux_]

...
Once I've seen portable russian chromatograph for home appliance natural gas leak detection.



Simple membrane pump getting air, filter, packed column in a coil around the heater, electrochemical detector (on separate heater), onboard microcomputer with LCD display.

All stuff in a box 300mm x 100mm x 250 mm

Actually no need to have gas chromatograph to find natural gas leaks from home installation.
This one serves as welding gas mixtures analyser according to vendor.

[James_Ball]

I was thinking nitrogen also as carrier since you don't seem to be looking for air gasses. I have seen a project for a home made nitrogen generator using the "pressure swing adsorption" method which will make highly pure nitrogen gas from compressed air. It will require some plumbing and switching valves but it is possible to make. You can probably find the plans online. The expensive part may be the molecular sieve used in the pressure cylinders to adsorb the oxygen from the air.

This seems like a lot of work and money too. As I don't know much about GC I just wish to know if separation of required gases is possible at all with diy GC. And for example I don't know how long 1kg bottle of balon helium can work so I don't know if that can pass price range. And what carierr gas is best for required sample. And I assume that I need to run carrier gas much before injecting sample to purge column.

Since Helium is normally separated from natural gas, I imagine balloon grade will have a lot of impurities of CH4 and O2 and possibly many other of the gasses you are looking for. You would need to place carbon and oxygen and probably moisture filters in the gas line to purify it before it goes into the GC.

Homemade GC are done all the time, there are a few threads here talking about it. Your sensitivity will depend some on the purity of your carrier. As long as your packing material is not sensitive to oxygenation then air could be used if you are not looking for any of its constituents. For air I would suggest an oil free compressor and place a carbon trap in the air to remove any traces of CH4 and CO2 that could be in the air.

A large cylinder of purified nitrogen would cost less than $200 and would last for several months in such a situation, or you can get the less pure nitrogen for less than $100 and use some purifier cartridges that will last several tanks and cut the overall cost a little more.

If you will be doing this over a long period of time you might want to look at a membrane nitrogen generator https://nitrogen-generators.com/generat ... enerators/

We use one of these that is just a small tube about a foot long that makes 99% nitrogen from compressed air and would probably be good for your needs.