Hello Everyone
I would like to ask if anybody knows a technique to remove N2 from a mixture of biogas.. Its because I am working with a system for hydrogen production and my biogas produced is composed by H2, CO2, produced by bacteria and N2 that i used to sparge my reactor. I want to have only H2 in my biogas, so I can remove CO2 with an NaOH solution but I still have N2 in my biogas. Does someone knows how can I remove it???
Thank you in advance.
Kind regards
Hi Erika,
try to purge your reactor with CO2 instead of N2.
Kind regards, Rob.
The response by Mr. Bachmann is probably the most efficient way to solve your problem. If it's a continuous biogas process the nitrogen content should eventually go to zero. Other more complicated and expensive solutions involve cryogenic techniques (nitrogen condensate at -196 degree centigrade).
Thank you very much for your answers, will be very useful for my work.
Kind regards :)
Robert Thomas Bachmann Thank you for your reply. I am concern that maybe if I use CO2 to sparge my reactor it may lead to a change in the pH solution, and it can affect my hydrogen production.. do you have any suggestion to solve this problem?
thank you in advance.
Hi Erika,
assuming you use batch reactors filled with a solution that contains dissolved oxygen you could try to partially degas the solution by vacuum. To remove residual DO add an oxygen scavenger. Then you optimise the time (for given CO2 flowrate and temperature) required to remove the air from the headspace. If the buffer capacity of your solution is insufficient increase it.
By the way have you tried to run your reactor without sparging? If your inoculum is a mixed culture there may be some facultatives that can mop up the DO.
Hope this helps/makes sense?
All the best Rob.
Just for curiosity. Commonly, methane is the main component of biogas. If only H2 and CO2 are produced under anaerobic conditions, then the remaining material should be significantly enriched in carbon. Thus, you are dealing with a carbonization of biomass. Why the production of H2 and coal is better than the production of CH4 with small amount of inorganics ?
Good point raised by @yurii geletii. How do we know that the gas is N2 and not CH4? Pure H2 and CO2 production has not been reported in literature as far as I know. If H2 is produced in batch reactors I presume that gas is periodically sampled? If confirmed we can expect that N2 is flushed out with first 1-2 gas samples?
Read this article, it maybe helpful for you.
The removal of CO2 and N2 from natural gas: A review of conventional and emerging process technologies. Article The removal of CO2 and N2 from natural gas: A review of conv...
Erika Mendoza, I think the recommendation from Robert Thomas Bachmann is the best. Try to run your batch tests without flushing with N2. I am almost sure the facultative communities will deplete quickly the O2. Also try to reduce as much as you can the headspace in your bottles/reactors.
Regards
try adsorption by activated carbon for low concentrate ( 2% . volume)
Pressure Swing Adsorption and cryogenic separation are the 2 most popular commercial method to make pure H2. A membrane separation could get a high purity H2 product - but not 100%
Robert Thomas Bachmann , Yurii V Geletii Thank you for your replay. I am working with a pure culture of a non methanogenic bacteria, that is the reason why only H2 and CO2 is produced. I know that methane is not produced because I have analyzed some samples in the past by GC and its concentration was insignificant. But right now I most perform some experiments and I don't have the instrument for gas composition analysis. For this reason I want to calculate the hydrogen produced only by volume displacement, for this I should remove CO2 and N2 from the biogas.
Muhammad Asim Khan , Guillermo Quijano @khaled and @Rick, thank you for your responses. Kind regards
Press the mixtures in high P and low T, each component would be liquefied in different point (P,T) but it might be more expensive...
The measurement of hydrogen production by volume displacement does not require the removal of N2.
You could selectively scrub out the CO2 with an amine or potassium carbonate solution (Benfield/Catacarb ). If you are left with a mixture of only H2 and N2. you can determine the MW by a simple measurement of mass and volume at known conditions and calculate the composition from the MW.
Hi @Erika
N2 showed air were exist in your digester or GC analyser, i think your gas sample was contaminated by air
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