We are pyrolyzing sewage sludge in a fluidized bed pyrolyzer. We are using nitrogen as an inert atmosphere. Before every experiment we check the purging of lines by checking the bubbles in water at the end of gas tubes (which are very fast depending upon the flowrate of gas). The reactor has a cooling and clean-up unit which uses an ethanol and two distilled water washing bottles. During experiment the bottles with water has bubbles (which is not similar to the one we check while purging, they are slow and soapy). Also these bubbles does not rise from the beginning of experiment, they always start arising somewhere in between. I am not sure what is rising these bubbles? Can anyone help with clarification?
Is it because the bottles we are using are small and gas velocity is high? But then why the bubbles are different than purging?
Or may be they are because the temperature of cooling system gets high and need to be cooled down?
Or any other?
TIA
https://www.sciencedirect.com/search?qs=bubbles%20in%20condensing%20bottles%20during%20pyrolysis%20of%20sewage%20sludge&show=25&sortBy=relevance
Dear A. Siddiqui,
The appearance of the bubbles in the condensing bottles may be due to a number of reasons.
Firstly, this could be due to the formation and build up of NOx, CO2 or CH4 in the fuel gas mix produced during pyrolysis of sewage sludge (SS). The slow bubbles are akin to the bubbles formed in anaerobic digesters which are attributed to CH4 and CO2 whereas the soapy bubbles may be due to NOx or NHx. One way to confirm this will be collect and analyze the pyrolysis gas in a gas chromatography. Alternatively, you can conduct a TG-MS study of the SS and perform a detailed characterization of its fuel properties.
Secondly, this may be due to the fluidization conditions used in the process. However, the effect of this will be based on the dimensions of the reactor and its ancillary components, the heat transfer material (sand) and the particle size distribution of the SS. That said, I will suggest you try argon as the fluidizing gas, small sized SS particles and lower fluidizing numbers.
Hope this helps.
BBN
Bemgba Bevan Nyakuma.
Thank you Sir. Production of NOx or NHx might be the factor, I will confirm it with further analysis. You have made the reasons and explanations much simpler. Thank you
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