Vibration assisted vacuum dewatering of fine coal particles
Fine coal particles are dewatered by mechanically removing water from the coal particles by vibration assisted vacuum dewatering to form a coal particle filter cake. The filter cake typically has a water content less than 35% by weight, suitable for extrusion to form discrete, non-tacky pellets. The vibration assisted vacuum dewatering may operate at a vibration frequency in the range from about 1 Hz to about 500 Hz. The vibration frequency may be adjusted during the dewatering process. In some embodiments, the vibration frequency is increased as the moisture content of the coal particle filter cake is decreased. Washing the filter cake during dewatering removes soluble contaminants. Various vibration assisted vacuum dewatering devices may be used, including a vibration assisted rotary vacuum dewatering drum, a vibration assisted vacuum disk filter, and a vibration assisted vacuum conveyor system.
1. A process for removing water from coal particles comprising:
obtaining a quantity of wet coal particles collected from coal fines that were processed to remove ash-forming component particles, wherein the coal particles have a particle size less than about 500 μm; and
mechanically removing water from the wet coal particles by vibration assisted vacuum dewatering to form a coal particle filter cake having a water content less than 35% by weight, the vibration assisted vacuum dewatering comprising:
placing at least one vibration source on a surface of the coal particle filter cake; and
vibrating the at least one vibration source at a frequency in the range of about 1 Hz to about 500 Hz.
2. The process according to claim 1 , wherein the vibration assisted vacuum dewatering further comprises increasing the frequency as the water content of the coal particle filter cake is decreased.
3. The process according to claim 1 , wherein the coal particle filter cake is formed on a vibration assisted rotary vacuum dewatering drum.
4. The process according to claim 1 , wherein the coal particle filter cake is formed on a vibration assisted vacuum disk filter.
5. The process according to claim 1 , wherein the coal particle filter cake is formed on a vibration assisted vacuum conveyor system.
6. The process according to claim 1 , wherein, after the vibration assisted vacuum dewatering, the coal particle filter cake has a water content suitable for extrusion to form discrete, non-tacky pellets.
7. The process according to claim 1 , wherein the coal particles have a particle size less than about 300 μm.
8. The process according to claim 1 , wherein the coal particles have a particle size less than about 150 μm.
9. The process according to claim 1 , wherein the coal particles have a particle size less than about 100 μm.
10. The process according to claim 1 , wherein the coal particles have a particle size less than about 75 μm.
11. The process according to claim 1 , wherein the step of mechanically removing water from the wet coal particles by vibration assisted vacuum dewatering forms a coal particle filter cake having a water content less than 30% by weight.
12. The process according to claim 1 , wherein the step of mechanically removing water from the wet coal particles by vibration assisted vacuum dewatering forms a coal particle filter cake having a water content less than 25% by weight.
13. The process according to claim 1 , further comprising, during the vibration assisted vacuum dewatering, washing the coal particle filter cake with wash water to remove soluble contaminants.
14. The process according to claim 13 , wherein the soluble contaminants include soluble sulfate salts.
15. The process according to claim 13 , wherein the soluble contaminants include soluble chloride salts.
16. The process according to claim 1 , wherein the vibration assisted vacuum dewatering causes water to initially be removed from the coal particle filter cake at a rate greater than 1.5 l/m 2 /min.
17. the process according to claim 16 , wherein the vibration assisted vacuum dewatering causes water to initially be removed from the coal particle filter cake at a rate greater than 2 l/m 2 /min.
18. The process according to claim 1 , wherein the vibration assisted vacuum dewatering causes the water content of the coal particle filter cake to be reduced by at least 10 wt. % within 15 seconds.
19. The process according to claim 18 , wherein the vibration assisted vacuum dewatering causes the water content of the coal particle filter cake to be reduced by at least 20 wt. % within 30 seconds.
20. The process according to claim 18 , wherein the vibration assisted vacuum dewatering causes the water content of the coal particle filter cake to be reduced by at least 30 wt. % within 60 seconds.
21. The process according to claim 1 , wherein the vibration assisted vacuum dewatering causes the water content of the coal particle filter cake to be reduced at an average rate greater than 2.3 liters/square meter/minute for a dewatering time of 2 minutes.
22. The process according to claim 1 , wherein the vibration assisted vacuum dewatering causes the water content of the coal particle filter cake to be reduced at an average rate greater than 1.5 liters/square meter/minute for a dewatering time of 3 minutes.
23. A process for removing water from coal particles comprising:
obtaining a quantity of wet coal particles collected from coal fines that were processed to remove ash-forming component particles, wherein the coal particles have a particle size less than about 300 μm; and
mechanically removing water from the wet coal particles by vibration assisted vacuum dewatering to form a coal particle filter cake having a water content less than 30% by weight such that the particle filter cake is suitable for extrusion to form discrete, non-tacky pellets,
wherein the vibration assisted vacuum dewatering comprises:
placing at least one vibration source on a surface of the coal particle filter cake;
vibrating the at least one vibration source at a first vibration frequency in the range from about 1 Hz to about 500 Hz for a first period of time; and
vibrating the at least one vibration source at a second vibration frequency higher than the first vibration frequency for a second period of time subsequent to the first period of time such that the vibration frequency is increased as the water content of the coal particle filter cake is decreased.
24. The process according to claim 23 , wherein the coal particles have a particle size less than about 150 μm.
25. The process according to claim 23 , wherein the coal particles have a particle size less than about 100 μm.
26. The process according to claim 23 , wherein the coal particles have a particle size less than about 75 μm.
27. The process according to claim 23 , wherein the step of mechanically removing water from the coal particles by vibration assisted vacuum dewatering forms a coal particle filter cake having a water content less than 25% by weight.
28. The process according to claim 23 , further comprising, during the vibration assisted vacuum dewatering, washing the coal particle filter cake with wash water to remove soluble contaminants.
29. The process according to claim 28 , wherein the soluble contaminants include soluble sulfate salts.
30. The process according to claim 28 , wherein the soluble contaminants include soluble chloride salts.
31. The process according to claim 23 , wherein the vibration assisted vacuum dewatering causes water to initially be removed from the coal particle filter cake at a rate greater than 1.5 l/m 2 /min.
32. The process according to claim 31 , wherein the vibration assisted vacuum dewatering causes water to initially be removed from the coal particle filter cake at a rate greater than 2 l/m 2 /min.
33. The process according to claim 23 , wherein the vibration assisted vacuum dewatering causes the water content of the coal particle filter cake to be reduced by at least 10 wt. % within 15 seconds.
34. The process according to claim 33 , wherein the vibration assisted vacuum dewatering causes the water content of the coal particle filter cake to be reduced by at least 20 wt. % within 30 seconds.
35. The process according to claim 33 , wherein the vibration assisted vacuum dewatering causes the water content of the coal particle filter cake to be reduced by at least 30 wt. % within 60 seconds.
36. The process according to claim 23 , wherein the vibration assisted vacuum dewatering causes the water content of the coal particle filter cake to be reduced at an average rate greater than 2.3 liters/square meter/minute for a dewatering time of 2 minutes.
37. The process according to claim 23 , wherein the vibration assisted vacuum dewatering causes the water content of the coal particle filter cake to be reduced at an average rate greater than 1.5 liters/square meter/minute for a dewatering time of 3 minutes.