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Fireside deposits
Fireside deposits are undesirable because they may lead to:
1) Loss of superheat temperature
2) Draft loss
3) Unset boiler circulation
4) Tube failure due to high or low temperature corrosion
5) Increase in sulfur trioxide formation
6) Lost efficiency
The primary cause of fireside deposits is the ash constituents of the fuel
oil. As discussed previously, the ash content of fuel oil may range typically
between 0 and 0.3%. Some of the constituents of oil ash are:
 | silicon, |
| Iron, |
| aluminum, |
| titanium, |
| calcium, |
| magnesium, |
| manganese, |
| vanadium, |
| nickel, |
| sodium, |
| potassium, |
| sulfate, and |
| chloride. |
|
POSSIBLE ASH CONSTITUENTS FORMED DURING COMBUSTION AND
THEIR MELTING POINTS |
|
Compound |
Chemical Formula |
Melting Point (OF) |
|
Aluminium Oxide
Aluminium sulfate
Calcium oxide
Calcium Sulfate
Ferric oxide
Ferric sulfate
Magnesium oxide
Mangesium sulfate
Nickel oxide
Nickel sulfate
Silicon dioxide
Sodium sulfate
Sodium bisulfate
Sodium pyrosulfate
Vanadiun trioxide
Vanadiun tetroxide
Vanadium pentoxide
Zinc oxide
Zinc sulfate
Sodiun metavanadate
Sodium pyrovanadate
Sodium orthovanadate
Nickel pyrovanadate
Nickel orthovanadate
Ferric metavanadate
Ferric vanadate
Sodium Vanadic
Sodium vanadyl vanadates |
Al2O3
Al2(SO4)3
CaO
CaSO4
Fe2O3
Fe2(SO4)3
MgO
MgSO4
NiO
NiSO4
SiO2
Na2SO4
NaHSO4
Na2S2O7
V2O3
V2O4
V2O5
ZnO
ZnSO4
Na2O.V2O5
2Na2O.V2O5
3Na2O.V2O5
2Ni2O.V2O5
3Ni2O.V2O5
Fe2O3*V2O5
Fe2O3*2V2O5
Na2O*V2O4*5V2O5
5Na2O*V2O4*11V2O5
|
3720
Decomposes at 1418 to Al2O3
4662
2642
2849
Decomposes at 896 to Fe2O3
4532
Deconposes at 2055 to MgO
3794
Decomposes at 1544 to NiO
3128
1616
482*
752**
3578
3578
1247
>3270
Decomposes at 1364 to ZnO
1166
1184
1562
>1650
>1650
1580
1571
1157
995
|
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* Decomposes at about 480°F to Na2S2O7 and H2O
** Decomposes at about 860°F to Na2SO4 and SO3 |
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