Refining Community Logo

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


Charles Randall

Again let me say slowly so you get it – there isn’t a standard and the test isnt ran because getting green coke density is ~ meaningless number. Yes, most solids from coal to natural & synthetic graphite to green petcoke ect can yield a density value from pycnometer but its not going to have reproducibility or repeatability for coking unit. You need to understand the materials property and operation a lot better before you use some half-cooked value to plug into calculation. There are enough screwed up LP models in this world already from engineers that have no idea what process or product is like.
The one thing I can guarantee is that your going to have meaningless number that wont help calculate whatever your trying to plug that number into & for whatever reason (doesnt sound like you even know what you want to use it for either).
If your just looking for a bulk density number to try calculate tons made in drum during cycle then you can use rough estimates of  sponge coke at 46-52 lb/ft3 (on 10.0 mm average size particles), or shot coke at 52-65 lb/ft3 (on 1.0mm average size particles) or fluid coke at 63-72 lb/ft3 (on 0.1 mm average size particles) – I use these with angle repose to get max tons in petcoke storage piles as estimate.
Back to trying do green coke test – whenever someone wants get real values on petcoke for shipment or sales they take running sample from conveyor or loading  method and then they composite & reduce it down and run test for metals, sulfur & ect.  Lot times in refineries they just do grab samples off top truck/rail car/barge & do composite (its better nothing but just barely) – its ballpark for big problems but it isnt going be representative & most times clients take delivered samples or off vessel loading by  independent surveyor & lab. So you just grabbing some different size coke particles isnt going to work & there can be lot difference from big pieces from coke packed in middle drum vs fluff small size particles at top vs average particles between. Every coke drum has distribution curve range on sulfur, volatile matter and hardness that is different, these and particle size affect petcoke density. 
Let’s say the average works for your purpose – it isnt going to tell you much of anything about the next drum because the operating conditions, crude mix, run length and dozen other variables are going to shift the final VM, Sulfur and hardness. If your plant is lucky one with  just couple crudes that are very consistent (most crudes are actually blends these days even ones like WTI or Brent), and you have big coker for size of Vacuum unit so it isnt pushed and same with your furnace – the average just might work……but you would be 1 in 100 plants.
There have been lots studies by calciners looking to use green density to get better control on calcined densities, there have been lots research groups looking at impact of changes in sulfur, VM and HGI upon final calcined densities and correlations were too fuzzy to use for controls.  They often had better results using the VM & HGI values.

Refining Community