Typical Chemistry of Coal Fly Ash(in Wt.%)Atomic Absorption


 
ClassF ClassF ClassC Class C
low-Fe high-Fe high-Ca low-Ca
SiO2 46-57 42-54 25-42 46-59
Al2O3 18-29 16.5-24 15-21 14-22
Fe2O3 6-16 16-24 5-10 5-13
CaO 1.8-5.5 1.3-3.8 17-32 8-16
MgO 0.7-2.1 0.3-1.2 4-12.5 3.2-4.9
K2O 1.9-2.8 2.1-2.7 0.3-1.6 0.6-1.1
Na2O 0.2-1.1 0.2-0.9 0.8-6.0 1.3-4.2
SO3 0.4-2.9 0.5-1.8 0.4-5.0 0.4-2.5
LOI 0.6-4.8 1.2-5.0 0.1-1.0 0.1-2.3
TiO2 1-2 1-1.5 <1 <1

Note: Chemical analysis by atomic absorption, ICP, or "wet" methods. Much of SiO2, Al2O3 and Fe2O3 is present in glassy amorphous form. SO3 is usually present as calcium sulfate or alkali sulfates. Most of the CaO/MgO is not free. LOI is presumed to be carbon (check with LECO Carbon Analyzer.) Class C fly ashes are usually self-cementing (hydraulic.)

Class F fly ash has a glassy phase and inert crystalline phases: quartz, mullite, magnetite spinel, hematite. For example, it has been reported for a high-Fe Class F fly ash from Eastern Canadian bituminous coal : 9.6% quartz, 20.4% mullite, 4.5% magnetite spinel, 5.4% hematite, and 58% glass.(Hemmings, Berry, Cornelius, Sheetz, "Speciation in Size and Density Fractionated Fly Ash. Characterization of a Low-Calcium, High-Iron Fly Ash", Materials Research Society Symposia Proceedings, Fly Ash and Coal Conversion By-Products: Characterization, Utilization and Disposal, Vol. 86, 1987.)

Class C fly ash may have the above as well as: anhydrite, alkali sulfates, dicalcium silicate, tricalcium aluminate, lime(Portlandite if ash has been exposed to moisture), melilite, merwinite, periclase, sodalite. For example, it has been reported for a low-Ca Class C fly ash from western Canadian subbituminous coal: 6% quartz, 14% mullite, and 80% glass.(Berry, Hemmings, Cornelius, "Speciation in Size and Density Fractionated Fly Ash. The Influence of HCL Leaching on the Glassy constituents of a High-Ca Fly Ash", Materials Research Society Symposia Proceedings, Fly Ash and Coal Conversion by-Products: Characterization, Utilization and Disposal, Vol.113, 1988.)

See properties of Japanese fly ash.

SRM 1633a SRM 2689 SRM 2690 SRM 2691 lignite
SiO2 48.8 51.5 55.3 36 28.9
Al2O3 27.0 24.5 23.3 18.5 11.1
Fe2O3 13.4 13.3 5.1 6.3 11.1
CaO 1.6 3.0 8.0 25.8 18.9
MgO 0.8 1.0 2.5 5.2 6.0
Na2O 0.2 0.3 0.3 1.5 8.0
K2O 2.3 2.6 1.2 0.4 0.9
TiO2 1.3 1.3 0.9 1.5
P2O5 0.2 1.2 1.2
SO3 0.7 2.1 6.83
LOI 1.76 0.52 0.23 0.42

Trace Elemental Analysis Coal Fly Ash (Class F)

in mg/kg(NA= Not Available)


 
(Range)
aluminum 140000 (80000-140000)
arsenic 286 (100-300)
barium 1003 (100-1000)
boron 290 (NA)
cadmium <0.5 (NA)
chromium 218 (NA)
cobalt NA (10-90)
copper 185 (30-200)
lead 114 (120-270)
lithium 270 (NA)
manganese 290 (NA)
molybdenum 46 (NA)
nickel 169 (30-200);
selenium 11 (5-30);
silver 14 (NA);
P2O5 3800 (NA);
strontium NA (200-2600);
titanium 8500 (NA);
zinc 254 (200-450);

FLY ASH RESOURCE CENTER


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