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RE: Need a method for determination of Green Coke Density

Home Forums Coking Operations Coke Product, Feedstock, Storage, Handling Coke Product Need a method for determination of Green Coke Density RE: Need a method for determination of Green Coke Density

#5381

Charles Randall
Participant

I belive the ASTM 941-88 is for spent coke off catalysts and doesnt relate to green delayed coke test. Since most coke on catalysts is burnt off to regenerate the catalysts about the only use would be to identify the stream coking out and spending the catalysts.
 
Delayed petcoke often runs both Bulk Density (~0.8 gm/cm3) – often called VBD for Vibrated Bulk Density,  and Real Density (~2.06 gm/cm3) on Calcined Delayed Coke (~Anode or Sponge type and Needle coke is similar). I am not sure what purpose it would serve to run this test on green petcoke (both VM & HGI often correlate well with Bulk Densities).
 
Previous guest is right and ASTM D4292 is what is currently has been used for VBD but I understand this years TMS 2011 is presenting a paper on the ASTM D7454 that was approved by ASTM in 2008. It was proposed by Rio Tinto and uses semiautomatic equipment and tighter controls on sample prep.
 
The delayed coke particle size and crushing size have a strong effect on the VBD/Real Density results. Natural occuring particles tend to have higher packing density compared to particles crushed to same size. And most refinery crushing for green coke only goes to 6inches and down because every handling step tends to grind up big particles and customers dont want dust. Whereas CPC Anode/other applications often require controlled particle size with lots “fresh” crushed surface showing.
 
Both VBD/Real density test for CPC are really just indicators for Delayed Calcined Petroleum Coke (CPC) strength and porosity which determine how strong the baked anode for use Aluminum/other industries will be and also how much pitch it will soak up to make the prebaked anode block (usually about 60% CPC & 40% Pitch ratio). The higher porosity (ie holes left by Volatile Matter or Sulfur or Moisture being driven off from heat/calcining) means more pitch it will soak up.  Now if you try do green cokes these poors will likely be filled with either uncooked resid or volatile matter which will go away when its calcined and hence give false or bad indication (also reason VM and HGI tend correlate).  Also reason it isnt done on fuel cokes other than that market only cares about the BTU value – is that higher sulfur delayed cokes have higher decrease in density due lose of some sulfur on calcining that isnt seen on the -3.5% Sulfur CPC Anode cokes because most that sulfur is bound in petcoke matrix insteadk of fuel cokes where some exist as possible radical attached to matrix.
 
So your original statement is right – it wouldnt be that difficult to do a VBD/Real density test. The question is what use is it ?  ……sort like putting doors on a motorcycle you can but why hell would you want to?
Regards
 
 
 
 

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