New research questions has arose from previous ones.
Q1: https://www.researchgate.net/post/Is_it_possible_to_carry_out_Proximate_analysis_via_Thermogravimetric_analysis_TGA
Q2: https://www.researchgate.net/post/N2_gas_or_Air_should_be_used_for_TGA_of_CARBON_BLACK_CHAR_and_PYRO-OIL
Attached are the TGA results I obtained (for proximate analysis purposes) on the pyrolysis char and pyrolysis oil.
N2 gas of 99.99% purity was used for one test and air the other.
However, both seems to generate almost identical weight reduction curves.
1. Is there a logical reason behind the similarity?
2. How to determine the percentages of
i. moisture
ii. fixed carbon
iii. volatiles
iv. ash?
Dear Teo,
The answer of (2.) is pretty straight forward that the standard conditions for the proximate analysis are seldom achieved in an open TG experiment.
For (1.): TG/DTG curves of char, the release of volatiles starts quite early which brings in a confusion as if char is a torrefied residue instead. Could have been clearer if TG/DTG curves of the precursor and ultimate analyses of the precursor, pyrolysis char and pyrolysis oil were made available. Anyhow, regarding pyrolysis char, I can make a wild hunch perhaps
1. The precursor pyrolysis was carried out in a closed system or under pressure. The obtained char contained trapped and condensed volatiles.
2. The pyrolysis of the precursor may have been carried out under O2/CO2 rich environment or the system was not purged properly with inert gas (N2).
3. The oxygen content of the precursor may have been quite high, either it contained a lot of embedded organic oxygen in the polymer matrix or present in the form of inorganic ash.
Having similar residue at the end could be due to one or more of the described reasons (ash in both cases with air or N2) or perhaps the flow of oxygen during TG was limited (ash+FC in both cases with air or N2).
Good day Mr Imtiaz Ali .
Is it possible that the heating rates performed on the products via TGA were too high that the details of thermal degradation weren't observable?
It might sound dumb, but it is worth asking: are you 100% sure you are correctly switching to Air on your TGA tests? If yes, then consider the following:
Have you calculated the stoichiometric air needed to fully combust your sample or the produced volatiles during your TGA tests? It seems that the amount of air you are using is less than the stoichiometric amount for any of your tests, so the volatiles produced during them are combusted, consuming any available oxygen. If this is true, the oxidizer could not react with the actual sample. Having no O2 to consume the sample material causes both N2 and Air tests to have similar rates of mass loss. Additionally, I think the heat produced by the combustion is less than the one needed to follow the programmed temperature history, so it does not speed up the thermal degradation of your samples.
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