The pyrolyser/ pyrolysis reactor is heated to the pyrolysis temperature and feedstocks are fed into the system without purging of inert gases. What will happen?
Products obtained are PHYSICALLY similar to those of purged system,
- combustible pyrolytic vapour/ gas/ fumes
- combustible carbon black/ char
- combustible pyrolytic oil/ tar/ Rubber Processed Oil
If the inert gas is not purges, this could lead to:
1) Air could be trapped in the reactor which will lead to thermal oxidation of the feedstock and CO2 well as CO, NOx, SO2 will be generated.
2) Pyrogas will be contaminated with combustion products and this will lower the calorific value of the pyrogas.
3) The quality of the generated oil (tar) will degrade and its heating value as a fuel will also degrade.
4) Char will also be produced.
Hope this helps answer your question.
Professor Yehia Khalil, Yale University, USA
Fellow of the University of Oxford, UK
Adding Hydrocarbon to a hot vessel containing air could also cause a pretty significant explosion and fire.
Inert gas should not be much problem if the vessel is half full of tires, and the off gas has a way to exit the vessel through condensers and scrubbers. NOx might be evaluated further unless the scrubbers remove it.
Vacuum vessels always have the risk that air will leak in. Many pyrolysis systems start up by purging with steam while the vessel is heating up and even continuing to some extent during the pyrolysis. Results are different with more oxygenated products being made, but possibly gives a safer system, with less carbon dust. Risk with steam is that when shutting down the vessel, remaining steam may condense and draw vacuum and maybe air. So a secondary inserting system is indicated to prevent air from entering hot vessel.
It will lead to oxidation and combustion to some extent due to the presence of limited oxygen that has been trapped in a reactor during the operation.
Both the attached files (of the same main author) suggested
"Auger reactors use small amount of inert gas (typically at the ambient temperature) and that is only for purging the gaseous products out of the reactor."
Is it possible that nitrogen purging is only required for selected system setup/ reactor design?
For rotating cone design, no carrier gas is needed to transport the vapours and thereby reducing the operating cost (Wagenaar 1994, Bridgwater 2003, Butler 2011, Bridgwater 2012).
For ablative pyrolyzer, no carrier gas is required.
For screw conveyor, to ensure that the reactor remains oxygen free, nitrogen is introduced at the inlet. Additionally, product gases are swept from the reactor, so just a minimum amount of carrier gas is used compared to fluidized bed reactors.
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