Gas Turbine Vanadium Inhibition: G. E. Krulls
Gas Turbine Vanadium Inhibition: G. E. Krulls
Gas Turbine Vanadium Inhibition: G. E. Krulls
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$A p{l OEM THE AMERICAN SOCIETY OF MECHANICAL ENGINEERS
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G. E. Krulls
Gas Turbine Vanadium Inhibition
Consulting Engineer, The mechanism of gas turbine vanadium inhibition is discussed as well as corrosion,
Vidak Associates, hot gas path deposition and exhaust gas emissions. A cost comparison is presented
Delanson, N.Y. for the various types of inhibition based on a typical power plant situation. A brief
Mem. ASME description is provided of three different kinds of inhibition systems. The aim of
this paper is to provide the gas turbine user with a practical evaluation of the
various inhibition processes.
have been tried over the years but the Other numbers can be evaluated by the use of
magnesium compounds have been proven best. the equation shown below. See also Appendix
A.
HOT GAS PATH DEPOSITION 26.47V + 10 4 A = XH
When there is considerable vanadium where
present, then the problem of deposition also V = Vanadium in fule oil - PPM
increases as well as the amount of A = ash in raw fuel oil - %
particulates present in the exhaust. As long
as calcium is kept to a minimum, the deposits X = allowable particulates in exhaust -
can be fairly easily removed. This usually LB/MBTU
requires water washing and perhaps even nut- H = higher heating value of the fuel-
shelling equipment. If the turbine can not BTU/LB
be shut down and cooled frequently for wash-
ing then not-shelling can remove deposits This equation is based on particulates being
under load. Quite often both cleaning made up of:
techniques are used. 3MgO • V2O5 magnesium ortho vanadate
Ninety percent of the deposits formed MgSO4 magnesium sulfate
are magnesium oxide and magnesium sulfate.
Magnesoim oxide is by far the hardest to re- MgO magnesium oxide
move. Both species are in equilibrium ac- SiO2 silicon dioxide
cording to:
ash
where the magnesium compounds formed are
based on magnesium added to fuel being 4.643
MgSO4 MgO + So3 times the stoichiometric ratio which is an
addition rate of 3.25:1.00 Mq:V. The
magnesium that remains is assumed to form
compounds 90% of which are MgSO4 and 10% MgO.
Increased temperature drives the re- It can readily be seen that environmental
action to the right whereas increased sulfur regulations can radically affect allowable
and pressure drives it to the left, As one fuel quality. Without this factor the old
can see, this is in the right direction for limit of 500 PPM vanadium would be feasible.
modern gas turbines with increasing pressure
ratios. COST OF VANADIUM INHIBITION
SUSPENDED MAGNESIUM HYDROXIDE 13.6 0 3.31 -- --- $4.50/GAL 39,256 17,671 3140
POWDERED MAGNESIUM SILICATE 1820 2830 0.79 0.52 $0.15/GALL 29,660 4,452 3042
SUSPENDED MAGNESIUM SILICATE 6.27 9.57 0.79 0.52 /GAL 85,148 4,452 6812
Table No. 1 was generated based on the 9. COSTS HERE PRE CALCULATED EXCLUSIVE OF
following: SHIPPING.
BASIS: 10. THE FIGURES PRESENTED ARE FOR TYPICAL
PRODUCTS IN THE FORM THAT THEY ARE
1. FUEL FLOW - 200 GPM.
AVAILABLE.
2. OPERATING TIME - 173 HRS. MO .
11. THERE IS ALSO AN OIL SOLUBLE INHIBITOR
3. VANADIUM - 100 PPM. ON THE MARKET WHICH HAS BOTH MAGNESIUM
AND SILICON CONTAINING 6z% OF EACH AT
4. RATIO OF MAGNESIUM:VANADIUM - BY WT.
$10.00/GALLON.
3.25:1.
5. MAGNESIUM SULFATE CONCENTRATION IN 12. 75 PER CENT OF SPACE IS USED WHEN STOR-
ING DRUMS FOR 6 MO. STORAGE.
WATER (MgSO4) BY WT. - 25%.
6. MAGNESIUM SOLIDS SUSPENSION CONCENTRA- 13. 90 PER CENT OF SPACE IS USED WHEN
STORING BAGS SUCH AS MAGNESIUM SULFATE
TION IN OIL - BY WT. - 33%.
(TALC) AND MAGNESIUM SULFATE HEPTAHYDRATE
7. EPSOM SALT IS CALCULATED @ $6.00 PER (EPSOM SALT) FOR 6 MONTHS STORAGE.
100 LB.
14. LABOR COSTS FOR MIXING AND HANDLING ARE
8. EMULSIFIER IS CALCULATED @ $6.00 PER EXCLUDED.
GALLON.
atomic weight Mg = 72 or
atomic weight 0 = 48 + 80 V = X - 10 4 A
26.4
atomic weight V = 102
This can then be solved for various
atomic weight of molecule = 302 values of X and A to determine allowable
limits for V.
MgSO4
It is realized, that the formation of the
atomic weight Mg == 24 products of combustion is not as simple as
outlined here. Depending upon the amounts of
atomic weight S = 32 magnesium pyro and meta vanadates formed less
atomic weight 0 = 64 magnesium will go to the stoichiometric
protion of this reaction and more will be left
atomic weight. of molecule = 120 for the magnesium sulfate and magnesium oxide
products producing less total particulates
Mg 0 and somewhat increasing the allowable
vanadium. There are also secondary and
atomic weight Mg = 24 tertiary compounds formed which are not con-
sidered here. However this procedure should
atomic weight 0 = 16
give one a clearer understanding of how
atomic weight of molecule = 40 inhibition affects particulate emissions and
how to easily calculate vanadium limits.
Of the magnesium added, most of it does
not go for inhibition
Ma = 72 = 0.706
V 102
i.e. out of 3.25:1 Mg:V 0.706:1 Mg:V is
required for inhibition. Magnesium is added
at 4.6 times the stoichiometric ratio. This
means that 2.54:1 out of 3.25:1 is left to
produce MgSO4 and MgO particlulates.
Typically 90% of this would be MoSO 4 and
and 10% MgO.
V - _72 V ) 9 120
102 V + (3.25
1 102 24
+ V - 7 2 V) 0.1 40
1 102 24
+ 3.25 30 60 + 10 4 A = X
1 18 28
where
X= allowable particulates in exhaust
- LB/MBTU
A= ash in fuel -
V= vanadium in fuel - PPM