Coke separation process in paste plant

1. A process for separating a dense coke fraction from a first particulate coke stream for carbon anode production by providing a first particulate coke stream having a first average density and a first average particle size distribution, the process comprising steps of:

feeding the first particulate coke stream to a density separator at an incoming flow rate;

stratifying the first particulate coke stream in a density separator into a bed of graded density comprising at least two separate particulate fractions of different average density using an upward flow of gas, the at least two fractions comprising a light coke fraction and the dense coke fraction, wherein the dense coke fraction is found in a layer at the bottom of the graded bed; and

separating the light coke fraction in the density separator, the dense coke fraction having an average density which is greater than the first average density and an average particle size distribution substantially equivalent to the first average particle size distribution, wherein the dense coke fraction is discharged from an upper end of an inclined oscillating table of the density separator.

2. The process of claim 1 , further comprising

establishing a preset flow rate for the dense coke fraction corresponding to a desired density for the dense coke fraction, and

adjusting the density separator such that the dense coke fraction attains the preset flow rate.

3. The process of claim 2 , wherein the preset flow rate is at least 50% of the incoming flow rate.

4. The process of claim 3 , wherein the preset flow rate is at least 70% of the incoming flow rate.

5. The process of claim 4 , further comprising

feeding the dense coke fraction from the density separator at the preset flow rate into a storage vessel;

dosing the dense coke fraction from the storage vessel at a constant flow rate;

maintaining an amount of the dense coke fraction in the storage vessel within a predetermined level range by adjusting the density separator.

6. The process of claim 5 , wherein adjusting the density separator is through adjustment of at least one operating parameter selected from the group consisting of: oscillation speed, oscillation frequency, oscillation eccentricity, vibrational amplitude, height of the exit dam, deck inclination and a gas flow through pervious deck.

7. The process of claim 6 , wherein a percentage change between the preset flow rate and the constant flow rate is obtained by a level measurement control in the storage vessel.

8. The process of claim 7 , wherein the level measurement control acts on the at least one operating parameter to control the preset flow rate.

9. The process of claim 8 , wherein dosing the dense coke fraction from the storage vessel is volumetric.

10. The process of claim 8 , wherein dosing the dense coke fraction from the storage vessel is gravimetric.

11. A process for separating a dense coke fraction from an incoming particulate coke fraction for carbon anode production, the process comprising steps of:

providing the incoming particulate coke stream,

combining the incoming particulate coke stream with a recycle stream to produce a combined feed coke stream,

feeding the combined feed coke stream to a particle size separator, separating the combined feed coke stream into one oversize coke fraction, at least one mid-size coke fraction, and an undersize size fraction,

wherein the mid-size coke fraction has a first average density and a first average particle size distribution;

feeding the mid-size coke stream to a density separator at an incoming flow rate; and

stratifying the mid-size coke stream in the density separator into a bed of graded density comprising at least two separate particulate fractions of different average density using an upward flow of gas, the at least two fractions comprising a light coke fraction and the dense coke fraction, wherein the dense coke fraction is found in a layer at the bottom of the graded bed; and

separating the light coke fraction from the dense coke fraction in the density separator, the dense coke fraction has an average density which is greater than the first average density and an average particle size distribution substantially equivalent to the first average particle size distribution, wherein the dense coke fraction is discharged from an upper end of an inclined oscillating table of the density separator.

12. The process of claim 11 , wherein grinding the oversize coke fraction produces the recycle stream.

13. The process of claim 12 , further comprising

establishing a preset flow rate for the dense coke fraction corresponding to a desired density for the dense coke fraction, and

adjusting the density separator such that the dense coke fraction attains the preset flow rate.

14. The process of claim 13 , wherein the preset flow rate is at least 50% of the first rate.

15. The process of claim 14 , wherein the preset flow rate is at least 70% of the first rate.

16. The process of claim 15 , further comprising

feeding the dense coke fraction from the density separator at the preset rate into a storage vessel;

dosing the dense coke fraction from the storage vessel at a constant flow rate; maintaining an amount of the dense coke fraction in the storage vessel within a predetermined level range by adjusting the density separator.

17. The process of claim 16 , wherein adjusting the density separator is through adjustment of at least one operating parameter selected from the group consisting of: oscillation speed, oscillation frequency, oscillation eccentricity, vibrational amplitude, height of the exit dam, deck inclination and a gas flow through pervious deck.

18. The process of claim 17 , wherein a percentage change between the preset flow rate and the constant flow rate is obtained by a level measurement control in the storage vessel.

19. The process of claim 18 , wherein the level measurement control acts on the least one operating parameter to control the preset flow rate.

20. The process of claim 19 , wherein dosing the dense coke fraction from the storage vessel is volumetric.

21. The process of claim 19 , wherein dosing the dense coke fraction from the storage vessel is gravimetric.