U.S. patent application number 10/528079 was filed with the patent office on 2006-03-23 for fuel additive composition and its preparation.
Invention is credited to Bjorn Forsberg, Gunnar Strom, Anders Wallenbeck.
Application Number | 20060059768 10/528079 |
Document ID | / |
Family ID | 20289021 |
Filed Date | 2006-03-23 |
United States Patent
Application |
20060059768 |
Kind Code |
A1 |
Wallenbeck; Anders ; et
al. |
March 23, 2006 |
Fuel additive composition and its preparation
Abstract
A fuel additive composition for the reduction/removal of
vanadium-containing ash deposits in gas turbines and other by
combustion of vanadium-containing fuel driven apparatuses, which
composition as its active ingredient comprises a compound of a
metal capable of forming a vanadate with vanadium of said ash
deposits is disclosed.
Inventors: |
Wallenbeck; Anders;
(Uppsala, SE) ; Forsberg; Bjorn; (Uppsala, SE)
; Strom; Gunnar; (Uppsala, SE) |
Correspondence
Address: |
MCDERMOTT WILL & EMERY LLP
600 13TH STREET, N.W.
WASHINGTON
DC
20005-3096
US
|
Family ID: |
20289021 |
Appl. No.: |
10/528079 |
Filed: |
September 16, 2003 |
PCT Filed: |
September 16, 2003 |
PCT NO: |
PCT/SE03/01446 |
371 Date: |
March 17, 2005 |
Current U.S.
Class: |
44/354 |
Current CPC
Class: |
C10L 1/1216 20130101;
C10L 10/04 20130101; C10L 1/1233 20130101; C10L 10/06 20130101 |
Class at
Publication: |
044/354 |
International
Class: |
C10L 1/12 20060101
C10L001/12 |
Foreign Application Data
Date |
Code |
Application Number |
Sep 17, 2002 |
SE |
0202760-5 |
Claims
1. Fuel additive composition for the reduction/removal of
vanadium-containing ash deposits in gas turbines and other by
combustion of vanadium-containing fuel driven apparatuses, which
composition as its active ingredient comprises a compound of a
metal capable of forming a vanadate with vanadium of said ash
deposits, which composition comprises a) as the active ingredient
either al) an inorganic oxygen-containing compound of said metal in
particle form, which oxygen-containing compound, when heated up in
a combustion flame, liberates a gaseous substance by evaporation
and forms the corresponding metal oxide having a crystalline porous
low density structure or a2) said corresponding metal oxide having
a crystalline porous low density structure, said inorganic
oxygen-containing compound a1) and said corresponding metal oxide
a2) having a particle size distribution essentially within the
range of from 0,1 to 2 micron, preferably from 0,1 to 1 micron and
said corresponding metal oxide a2) having a density of at most 2.0
g/cm.sup.3, dispersed in b) at least one liquid selected from the
group consisting of liquids soluble in oil, by means of c) at least
one dispersant selected from the group consisting of low molecular
weight dispersants and high molecular weight dispersants.
2. Fuel additive composition according to claim 1, wherein said
metal is capable of forming vanadates having a melting point within
the range of from 650.degree. C. to 2000.degree. C.
3. Fuel additive composition according to any of claims 1 and 2,
wherein said metal is magnesium or yttrium.
4. Fuel additive composition according to any of claims 1 to 3,
wherein said inorganic oxygen-containing metal compounds or oxide
has a particle size distribution which is adapted to be most
effective at the temperature at which a solid, porous metal
vanadate is formed and to form ash particles which deposit as
little as possible and form as loose deposits as possible.
5. Fuel additive composition according to any of claims 1 to 4,
wherein said liquid is selected from the group consisting of
mineral oils, highly aromatic naphtha, diesel fuel, vegetable oils,
esterified vegetable oils, animal oils and esterified animal
oils.
6. Fuel additive composition according to claim 5, wherein said
vegetable oils and esters thereof are selected from peanut oil,
coconut oil, corn oil, linseed oil, rape-oil, palm oil, sunflower
oil, olive oil, tall oil and esters thereof.
7. Fuel additive composition according to claim 5, wherein said
liquid is rape-oil methyl ester or diesel fuel.
8. Fuel additive composition according to any of claims 1 to 7,
wherein said inorganic oxygen-containing metal compound or oxide
comprises from 10 to 65% by volume, preferably from 20 to 50% by
volume and more preferably from 30 to 40% by volume, and most
preferably from 40 to 50% by volume, calculated on the total volume
of the composition.
9. Fuel additive composition according to any of claims 1 to 8,
wherein said at least one dispersant is an anionic or amphoteric
low molecular weight dispersant.
10. Process for the preparation of a fuel additive composition as
defined in any of claims 1-8, which process comprises mixing a
powder of an inorganic oxygen-containing compound of a metal
capable of forming a vanadate with vanadium of ash deposits from
vanadium-containing fuel and which inorganic oxygen-containing
compound when heated up in a combustion flame liberates a gaseous
substance by evaporating to form to the corresponding oxide having
a crystalline porous low density structure or a powder of said
oxide having a crystalline porous low density structure into a
mixture of at least one liquid selected from the group consisting
of liquids soluble in oil with at least one dispersant for said
inorganic oxygen-containing metal compound or oxide selected from
the group consisting of low molecular weight dispersants and high
molecular weight dispersants using shear forces to form a
homogenous pumpable premix and subjecting the premix to a treatment
comprising size degradation and dispersant coating to a particle
size distribution of the inorganic oxygen-containing metal compound
and oxide essentially within the range of from 0.1 to 2 micron,
preferably from 0.1 to 1 micron, under centrifugal or oscillation
forces in the presence of a grinding medium and/or ultrasonic
treatment until a plot of the sediment height in samples taken
periodically during said treatment and centrifuged at a fixed rate
for a fixed period versus time plateaus and the viscosity has
decreased and come into a steady state.
11. Process according to claim 10, wherein the size degradation and
dispersant coating is carried out in a basket mill with zirconium
balls as a grinding medium.
12. Process according to claim 11, wherein size degradation and
dispersant coating is carried out at an accelerative force within
the range of from 50 g to 70 g on the liquid.
13. Process according to any of claims 11 and 12, wherein only part
of said at least one liquid and/or said at least one dispersant has
been used when preparing the mixture of said at least one liquid
soluble in oil and said at least one dispersant, the remainder of
the dispersant and liquid being added after said graph over the
sediment height in samples taken periodically and being centrifuged
at a fixed rate for a fixed period has reached a plateau.
Description
TECHNICAL FIELD
[0001] The present invention relates to a fuel additive composition
for the reduction/removal of vanadium-containing ash deposits, a
process for the preparation of such a composition and the use of
certain inorganic oxygen-containing metal compounds as a component
of such a composition. More particularly the present invention
relates to a fuel additive composition for the reduction/removal of
vanadium-containing ash deposits in gas turbines and other by
combustion of vanadium-containing fuel driven apparatuses, a
process for its preparation and the use of certain inorganic
oxygen-containing metal compounds as an active component
thereof.
BACKGROUND ART
[0002] Fuels such as unrefined crude oil and residual oil
containing large amounts of impurities, which result in corrosive
deposits in apparatuses driven by the combustion of such fuel. One
such impurity is vanadium, which forms catastrophically, corrosive
low-melting slag. Said slag can destroy vital parts within a short
time. Crude oils usually contain vanadium in an amount within the
range of 1-500 ppm depending on the source of the oil. Because of
its origin as a concentrate from the refining process, residual oil
contains several times more vanadium than the crude from which it
is derived. Combustion of such vanadium-containing fuels primarily
results in the formation of vanadium pentoxide, V.sub.2O.sub.5,
which melts at about 675.degree. C. In molten state V.sub.2O.sub.5
behaves as an excellent solvent for e.g. the metal oxides that high
temperature alloys used in the hot section of gas turbines form in
order to protect their surfaces. Thus molten V.sub.2O.sub.5, acting
as a solvent, strips away said metal oxides. The metal atoms on the
surface of the gas turbine section in contact with the combustion
gases respond by forming a new layer of oxide coating which is
again stripped away by the V.sub.2O.sub.5 and so on.
[0003] In gas turbines metal temperatures can be higher than
1000.degree. C. at which temperatures corrosion can proceed very
fast so that the hot section may be destroyed within a week if no
measures are taken to inhibit the corrosion cycle.
[0004] In order to overcome the corrosion problems caused by
V.sub.2O.sub.5 the so-called oil soluble magnesium products were
developed. These products are based on the ability of magnesium
compounds to react with V.sub.2O.sub.5 to form a vanadate. Early
products belonging to this group contained magnesium naphthenates
which in the next step of development were replaced by compositions
based on magnesium sulfonates. The third generation of oil soluble
magnesium products comprises magnesium carboxylate products.
[0005] Thus, for instance, U.S. Pat. No. RE 32653 discloses a
method for the preparation of a magnesium-containing complex by
heating, at a temperature above about 30.degree. C. a mixture
consisting essentially of [0006] (A) at least one of magnesium
hydroxide, magnesium oxide, hydrated magnesium oxide or a magnesium
alkoxide; [0007] (B) at least one oleophilic organic reagent
consisting essentially of an aliphatic cycloaliphatic or aromatic
carboxylic acid containing at least eight carbon atoms or an ester
or alkali metal or alkaline earth metal salt thereof; [0008] (C)
water; and [0009] (D) at least one organic solubilizing agent for
component B.
[0010] The oil soluble magnesium products are added to the fuel in
an amount sufficient to convert V.sub.2O.sub.5 to magnesium
orthovanadate, Mg.sub.3V.sub.2O.sub.8, which melts at above
1100.degree. C. Said temperature is below the typical gas turbine
temperature when introducing the additive composition in the
combustion chamber, but above the turbine gas inlet typical
temperature due to the flame cooling process. Thus there will be no
liquid V.sub.2O.sub.5 that will act as a solvent for the alloy
surface metal oxides and thus corrosion caused by V.sub.2O.sub.5 is
inhibited.
[0011] The first generation of oil soluble magnesium products had a
concentration of magnesium as low as about 4%. The concentration
was increased in the second generation up to about 14% magnesium
and in the third generation the concentration could be raised
further. However, there is a continued need for fuel additive
compositions with still higher concentrations of magnesium or other
metals capable of forming vanadates having a melting point above
that of vanadium pentoxide.
[0012] Moreover, these prior art compositions give a dense vanadate
deposit the removal of which may cause some trouble.
[0013] As an alternative to oil soluble magnesium products U.S.
Pat. No. 4,412,844, issued Nov. 1, 1983, suggests oil dispersible
aqueous dispersions of magnesium hydroxide comprising in
percentages by weight: [0014] (a) 20-70% magnesium hydroxide having
particle size from 1.0-50 microns; [0015] (b) 29-79% water; [0016]
(c) 1.0-8.0% of a water-dispersible, oil-soluble, water-in-oil
emulsifying agent having an HLB value of from 4-10; [0017] (d)
0.1-6% of a water-soluble, oil-dispersible emulsifying agent having
an HLB of from 20-40.
[0018] Such slurries do not allow chemical high efficiency
inhibition for ash melts due to the large crystal size. This patent
states the preferred particle size to be in the range of about 30-2
microns, which makes the composition only practically applicable
per se to boilers. Thus it is expressly stated that the magnesium
hydroxide slurry specifically disclosed in the working example
"would be utilized to control vanadium corrosion in a utility
boiler".
[0019] In addition such slurries have a limited stability.
[0020] Accordingly, it is an object of the present invention to
provide a fuel additive composition containing a high concentration
of magnesium or other metal capable of forming vanadates having a
melting point above that of vanadium pentoxide.
[0021] It is another object of the present invention to provide a
fuel additive composition, which on use gives a porous vanadate
deposit that is easily removed.
[0022] It is a further object of the present invention to provide a
fuel additive composition, which is stable for a long time such as
12 months and longer at ambient temperature.
[0023] These and other objects are achieved by means of the fuel
additive composition and the process for its preparation according
to the present invention.
SUMMARY OF THE INVENTION
[0024] The present invention is based on the discovery that
crystalline particles of inorganic oxygen-containing metal
compounds which when suddenly being subjected to high temperatures
almost "explosively" liberate a gaseous substance by evaporation,
such as water vapour or carbon dioxide in case of e.g. magnesium
hydroxide and magnesium carbonate, respectively, and are converted
to particles of the corresponding metal oxide having a structure of
increased porosity and reduced density when compared to a
corresponding oxide prepared by evaporation of gas at considerably
lower temperatures. This makes the oxide better suited for reaction
with vanadium pentoxide will percolate easier into the more porous
particles. The presence or formation of such more porous particles
admits a faster chemical reaction due to the fact that the ions of
V.sub.2O.sub.5 can travel much faster from the surface of the
porous particles along the pores surface of the lattice of said
particles as vanadate forms than in the denser lattice of non or
low porous crystalline oxide.
[0025] It was also surprisingly found that when using an inorganic
oxygen-containing metal compound, which liberates a gaseous
substance by evaporating when being suddenly subjected to the heat
of a combustion flame, or a porous low density oxide with a
particle size distribution essentially within the range of from 0.1
to 2 micron as the active ingredient of a fuel additive composition
the vanadate deposit formed was much easier to remove than the
vanadate deposit formed when using prior art compositions.
[0026] The said particle diameter less than 1-2 .mu.m as a
measurement of particle size is just a rough indicative
measurement, as total mass, density, shape and porosity are
important "size" properties to be considered as optimizing a fuel
additive dispersion and its functional properties on ash melts and
corrosion inhibition as well as deposit problems concerned. The
optimal "size" in all the size dimensions named will minimize
deposit buildups due to the particles kinetic adsorption/desorption
rate, preferably approaching 1.0 and thereby avoiding high
adsorbing atomized and <.about.100 nm and avoiding high
impaction rate into deposit by dense particles above the upper,
>-1000 nm, micron sized limit.
[0027] Moreover, it was found that by proper selection of the
dispersing system, for an oil soluble solvent system, avoiding
water to the largest extent possible and using a specific process
for the preparation of the fuel additive composition, it was
possible to increase the level of the concentration per volume unit
of the metal to a level not having been disclosed previously for
submicron and nano-sized additives. Thus, according to the
invention a combination of at least one liquid selected from the
group consisting of liquids soluble in oil on one hand and at least
one dispersant selected from the group consisting of low molecular
weight dispersants and high molecular weight dispersants on the
other is used as the dispersing system.
[0028] Thus, in accordance with a first aspect of the present
invention there is provided a fuel additive composition for the
reduction/removal of vanadium-containing ash deposits in gas
turbines and other by combustion of vanadium-containing fuel driven
apparatuses, which composition as its active ingredient comprises a
compound of a metal capable of forming a vanadate with vanadium of
said ash deposits, which composition comprises [0029] a) as said
compound of a metal capable of forming a vanadate with vanadium of
said ash deposits al) an inorganic oxygen-containing compound of
said metal in particle form, which oxygen-containing compound, when
heated up in a combustion flame, liberates a gaseous substance by
evaporation and forms the corresponding metal oxide having a
crystalline porous low density structure, or a2) said corresponding
metal oxide having a crystalline porous low density structure, said
inorganic oxygen-containing compound al) and said corresponding
metal oxide a2) having a particle size distribution essentially
within the range of from 0.1 to 2 micron, preferably from 0.1 to 1
micron and said corresponding metal oxide a2) having a density of
at most 2.0 g/cm.sup.3, dispersed in [0030] b) at least one liquid
selected from the group consisting of liquids soluble in oil, by
means of [0031] c) at least one dispersant selected from the group
consisting of low molecular weight dispersants and high molecular
weight dispersants.
[0032] According to another aspect of the present invention there
is provided a process for the preparation of a fuel additive
composition according to the invention, which process comprises
[0033] mixing a powder of an inorganic oxygen-containing compound
of a metal capable of forming a vanadate with vanadium of ash
deposits from vanadium-containing fuel and which inorganic
oxygen-containing compound when heated up in a combustion flame
liberates a gaseous substance by evaporation to form the
corresponding oxide having a crystalline, porous low density
structure or a powder of said oxide having a crystalline porous low
density structure into a mixture of at least one liquid selected
from the group consisting of liquids soluble in oil with at least
one dispersant for said inorganic oxygen-containing compound or
oxide selected from the group consisting of low molecular weight
dispersants and high molecular weight dispersants using shear
forces to form a homogenous pumpable premix and
[0034] subjecting the premix to a treatment comprising size
degradation and dispersant coating to a particle size distribution
of the inorganic oxygen-containing metal compound and oxide
essentially within the range of from 0.1 to 2 micron, preferably
from 0.1 to 1 micron, under centrifugal or oscillation forces in
the presence of a grinding medium and/or ultrasonic treatment until
a plot of the sediment height in samples taken periodically during
said treatment and centrifuged at a fixed rate for a fixed period
versus time plateaus and the viscosity has decreased and come into
a steady state.
[0035] In accordance with a further aspect of the present invention
there is provided the use of an inorganic oxygen-containing
compound of a metal selected from the group consisting of metals
capable of forming vanadates having a melting point within the
range of from 650.degree. C. to 2000.degree. C. with vanadium of
ash deposits from vanadium-containing fuel, which inorganic
oxygen-containing compound when heated up in a combustion flame
liberates a gaseous substance by evaporation to form the
corresponding oxide having a crystalline, porous low density
structure, or the corresponding oxide obtained by heating the
inorganic oxygen-containing compound at a temperature which is high
enough to give the oxide in crystalline porous low density state
but is below the melting point of the oxide, said inorganic
oxygen-containing compound and said crystalline porous low density
oxide having a particle size distribution essentially within the
range of from 0.1 to 2 micron, preferably from 0.1 to 1 micron, as
a component of fuel additive compositions for the reduction/removal
of vanadium-containing ash deposits.
DETAILED DESCRIPTION OF THE INVENTION
[0036] Vanadium-containing fuels are used within several fields of
apparatuses driven by the combustion of fuel. The corrosion
problems caused by the presence of vanadium may be most serious in
the case of gas turbines but such problems also exist in connection
with e.g. boilers and diesel engines, wherein the metal
temperatures are lower than in gas turbines and relatively less
hazardous but still serious corrosion problems compared to gas
turbines exist.
[0037] According to the present invention the metal of the
inorganic oxygen-containing compound or oxide to be used in the
invention should be chosen so that on reaction with the vanadium
pentoxide a vanadate is formed that has a melting point exceeding
the temperature at which the composition is used. Thus, in case of
gas turbines a metal should be chosen the melting point of the
vanadate thereof preferably exceeds 1100.degree. C. Examples of
such metals are magnesium the vanadate of which melts above
1100.degree. C. and yttrium the vanadate of which has a melting
point above 1800.degree. C., magnesium being the preferred metal of
these two metals for economical reasons. Examples of other
vanadates having melting points enabling their use in the
compositions according to the invention to be used in connection
with apparatuses of lower temperature are among others, solely or
in combinations, aluminum, zirconium, manganese, iron, copper,
nickel and calcium. Often other metals than e.g. magnesium are
either both rear and expensive or are environmental polluters, e.g.
manganese etc.
[0038] Depending on the specific field of use generally metals
capable of forming vanadates having a melting point within the
range of from 650.degree. C. to 2000.degree. C.
[0039] Due to contaminants present in the fuel the vanadates formed
may be contaminated therewith resulting in a decrease or an
increase of the melting point in comparison with 100% pure
vanadate. Consideration should be paid thereto when selecting the
metal compound or oxide used in the composition according to the
present invention.
[0040] In accordance with one embodiment of the fuel additive
composition according to the present invention the active
ingredient thereof comprising an inorganic oxygen-containing
compound of a metal capable of forming a vanadate with vanadium of
ash deposits is a hydroxide of said metal which hydroxide when
heated up in a combustion flame is converted to the corresponding
oxide having a crystalline porous low density structure.
[0041] As indicated previously, hydroxides such as, for instance,
magnesium hydroxide, may be dehydrated almost "explosively" at very
high temperatures (over 1000.degree. C. and below 2800.degree. C.)
to form the corresponding metal oxide. Unlike the oxides formed by
dehydration of hydroxides at lower temperatures (such as just above
the dehydration point of 350.degree. C. for the conversion of
magnesium hydroxide to magnesium oxide) resulting in oxides with a
more dense crystalline structure the oxides formed at the higher
temperatures [below the upper limit in the "dead burned" range
where the oxide density closely approaches the maximum density] are
more porous and have a less dense crystalline structure than
else.
[0042] According to another embodiment of the fuel additive
composition according to the present invention said inorganic
oxygen-containing compound of a metal capable of forming a vanadate
with vanadium of ash deposits is a metal carbonate. When suddenly
being heated at high temperatures such as in a combustion flame the
carbonate will liberate carbon dioxide and form the corresponding
metal oxide having a crystalline porous low density structure
analogously to the formation of the oxide from an hydroxide at very
high temperatures.
[0043] According to a further embodiment of the fuel additive
composition according to the present invention said compound of a
metal capable of forming a vanadate with vanadium of ash deposits
is a metal oxide having a crystalline porous low density structure.
Such oxides may, for instance, be prepared from the corresponding
hydroxides or carbonates by heating at a high temperature. In order
to obtain maximum porosity of the oxide the conversion of the
hydroxide or carbonate should be carried out below the point at
which the oxide tends to increase in density, but close thereto and
far below it starts melting. Above said point at which the oxide
"tends to start melting" the pore structure continually decreases
as approaching the critical melting point, at which maximum density
will be reached, for e.g. magnesium oxide at 2750.degree. C. Such a
heat treatment to achieve minimum porous density oxide may be
performed by passing a dry powder of an optimal size distribution
of the hydroxide or carbonate through a flame having a temperature
suitably adapted below the density decreasing point of the oxide as
indicated above.
[0044] Alternatively, low density metal oxides may also be prepared
by suddenly subjecting submicron sized crystals of an inorganic
oxygen-containing metal compound, preferably a hydroxide or a
carbonate, which when heated to a high temperature liberates a
gaseous substance by evaporation, to heating at an appropriately
high temperature in an oven. Thus, for instance, the present
inventors rapidly heated sub-micron sized particles of magnesium
hydroxide in an oven at a temperature of 1000.degree. C. for a
short time which resulted in the conversion of the magnesium
hydroxide into magnesium oxide having a density of .about.1.4
g/cm.sup.3. Similar heating of magnesium carbonate in an oven at a
temperature of 1300.degree. C. resulted in magnesium oxide having a
density as low as 1.03 g/cm.sup.3
[0045] According to the present invention the low density metal
oxide should preferably have a density of at most 2.0 g/cm.sup.3,
more preferably below 1.5 g/cm.sup.3 and most preferably below 1.0
g/cm.sup.3.
[0046] The inorganic oxygen-containing metal compounds and porous
low density metal oxides incorporated in the fuel additive
composition according to the invention should have a particle size
distribution essentially within the range of from 0.1 to 2 micron,
preferably from 0.1 to 1 micron, preferably narrowly distributed
close to the optimal size within that range of 0.1 to 1 micron.
Preferably said compounds and oxides should have a particle size
optimal distribution which is adapted to be most effective at the
temperature at which a solid, porous metal vanadate is formed and
to form ash particles which deposit as little as-possible [due to
thermodynamic surface adsorption and desorption properties of the
particles] and form as loose a deposit as possible [due to the
porosity of the particles and thereby the epitactic and topotactic
deposits lattice build-up structure].
[0047] According to the high initial flame maximum temperature in
the range of 1600-2000.degree. C. before cooling the gas the
particle size distribution should be selected so that the metal
vanadates formed in the flame are not given sufficient time to melt
before reaching areas of the apparatus having a temperature below
the melting point of the vanadates. Moreover, the porous oxides
added to the fuel are not delayed in their reaction to the
formation of the vanadates in the heat zone compared to the porous
oxides formed from, for instance hydroxides or carbonates bypassing
the heat zone. This means that in case of gas turbines in which the
temperature of the flame may be as high as around 2000.degree. C.,
a hydroxide or a carbonate should be used which has a particle size
which is greater than that of the same hydroxide or carbonate to be
used in apparatuses operating at a lower heat zone flame
temperature. Furthermore, due to their higher reactivity surface
enlarged porous metal oxides should be used at temperatures lower
than those prevailing in gas turbine heat zones, i.e. they may
preferably be used in boilers and diesel engines if an
extraordinarily low operating temperature in the heat zone would be
a disadvantage of the addition of the heat zone by passing metal
hydroxide into the fuel.
[0048] Moreover, it was found that conversion of magnesium
carbonate into magnesium oxide at a given temperature is a slower
process than the conversion of magnesium hydroxide to the oxide due
to the difference in energy required to evaporate the carbon
dioxide from the carbonate in comparison with water from the
hydroxide. This means that in apparatuses working at relatively low
temperatures (e.g. boiler and diesel engines) the use of magnesium
hydroxide particles may be the preferred choice whereas magnesium
carbonate might be preferred for use in connection with gas
turbines having an extremely high temperature in the flame in order
to obtain a low density of the oxide formed.
[0049] Of specific importance is that the size of the oxide
particles is in the range not below 0.1 micron and not above high
density impacting 2 micron, preferably exhibiting a particle size
distribution injected into the fuel around 0.4 to 0.5 micron, in
order to reduce the deposit accumulation due to the Brown Movement
Kinetic affecting the particles surface adsorption and desorption
rate on the deposit surface and that the said particles have a
surface area including internal pores surface interface area
comparable to that of crystalline high density oxide particles of a
particle size far below 0.1 .mu.m to maximize the reactive surface.
Such a high surface area will solely be achievable by porous
particles.
[0050] The inventors have noted that dehydration or evaporation of
magnesium hydroxide particles at high temperature causes a split
size reduction and volume expansion and agglomeration into a less
tight particle size distribution depending on the particles
individual initial size. For this reason the particle size of the
particles used in the fuel additive compositions according to the
invention will generally be distributed in a somewhat enlarged size
range below and above when using the hydroxide in comparison with
the use of a size tailored oxide.
[0051] The particles of the inorganic oxygen-containing compound as
well as the oxide particles should preferably have a narrow (low
variance) particle size distribution, preferably around a cross
section largest distance arithmetic mean in the 0.2 to 0.5 micron
range and with a variance for a lognormal distribution in the range
.about.0.2<.delta.<.about.0.6.
[0052] In the fuel additive composition according to the present
invention the inorganic oxygen-containing metal compound or oxide
particles are dispersed in at least one liquid selected from the
group consisting of liquids soluble in oil.
[0053] Contemplated for use in the fuel additive composition
according to the invention are liquids selected from the group
consisting of mineral oils, synthetic oils, highly aromatic
naphtha, diesel oil, vegetable oils, esterified vegetable oils,
animal oils and esterified animal oils.
[0054] Examples of vegetable oils and esters thereof to be used in
the fuel additive compositions according to the invention include,
but are not limited to, peanut oil, coconut oil, corn oil, linseed
oil, rape-oil, palm oil, sunflower oil, olive oil, tall oil and
esters thereof, the preferred representative thereof being rape-oil
methyl ester (RME).
[0055] Examples of animal oils to be used in the fuel additive
compositions according to the invention include, but are not
limited to, fish liver oil, train-oil and liquid modified fat from
slaughter-houses.
[0056] The preferred representatives of the liquids soluble in oil
to be used in the present invention are diesel oil and rape-oil
methyl ester.
[0057] According to the present invention the inorganic
oxygen-containing metal compound particles or metal oxide particles
have become dispersed in at least one liquid which, as stated
above, is selected from the group consisting of liquids soluble in
oil by means of at least one dispersant selected from the group
consisting of low molecular weight dispersants and high molecular
weight dispersants.
[0058] The term "low molecular weight dispersants" as used here and
in the claims is used to designate dispersants having a molecular
weight usually within the range of from 1.000 to 2.000g/mole. In
addition, dispersants may be classified to manifold properties as
described below.
[0059] The term "high molecular weight dispersants" as used here
and in the claims is used to designate dispersants having a
molecular weight usually within the range of from 5,000 to 30.000
g/mole.
[0060] In addition. the conventional low molecular weight
dispersants are categorized according to their structure as
anionic, cationic, amphoteric and nonionic. Their efficiency is
defined by a) absorption of polar groups to the surface of the
particles to be dispersed and b) the behavior of a non-polar chain
of the medium surrounding the particle.
[0061] The dispersant industry supplies a huge variety of efficient
steric dispersants that enables stable solid particle dispersions
for colloid oil and aqueous systems. A colloid is a liquid droplet
or a solid particle in the size range of at most 1-2 Am but
normally submicron or in the range of one molecule to many
molecules forming a size of 2-999 nm in average diameter. Steric
dispersants adsorb and coat the particle surfaces. A surface is an
interface between two non-soluable compounds, one liquid and one
solid state or two liquid states. As no interface or surface occurs
between the dispersant-particles-layer-tails penetrating into the
particles ambient solvent the colloid dispersion is a true
dispersion formed of particles and such dispersions is commonly
defined as a micelle dispersion. A huge group of steric dispersants
forms micelles both in oil and water systems.
[0062] Most steric dispersants form micelles in a selected oil
soluble solvent, when the hydrophobic tail penetrates into the
solvent. The stability of such dispersions is depending on many
different forces defining the stability boundaries for the other
unit tail. The other said molecular hydrophilic tail adsorbs to the
particle surface and will be bondable to the surface of the
particle in many different ways due to the kind of (1) anchor
groups, (2) the number of repeating units in the polymer and (3) if
the dispersant is a homo polymers dispersants whereas the repeating
units are of one kind or is a co-polymer of two different kinds and
(4) the electrostatic properties.
[0063] The known art of the described colloid dispersion systems
admits a suitable tool to tailor a stable composition of solid
particles suitable as a fuel additive. In the range of suitable
compounds magnesium carboxylates and magnesium sulfonates has been
widely used to create stable metal oxide dispersions in fuel
additives. In the disclosed invention the kind of dispersants
suitable is enlarged to admit higher concentrations of stable solid
dispersions. Among others we have tested Hypermer.RTM. LP4 (amine
derivate of a fatty acid condensation polymer, from UNIQEMA,
Everberg, Belgium) EFKA 4010 (modified polyurethane, from EFKA
Inc., Heerenveen, the Netherlands) and Rhodafac.RTM. RE 610
(nonylphenol ethoxylate based phosphate esters, from Rhodia Inc,
France). All of these dispersants among others fulfill the claim to
form stable dispersions of magnesium oxides and magnesium
hydroxides and other particles if a suitable solvent and dispersion
technology is applied.
[0064] The selection of a dispersant for a specific application has
to be done due to the different claims of stability due to ambient
boundaries i.e., solid concentrations, temperature, g-forces and
the desired viscosity for the composition. To achieve maximum
particle concentration the dispersant layer that coats the
particles has to be thin. This is achieved by a small low molecular
weight dispersant as characterized by Rhodafac.RTM. RE 610 having
two tail units penetrating into the solvent or Hypermer.RTM. LP4.
When the volume of solvent in the composition increases and the
particle concentration is lower it is suitable instead to choose a
high molecular weight dispersant for instance EFKA 4010. When low
particle concentrations are desired other dispersants may be
preferably applied, but for such applications the particle size
range is of basic importance due to solvent molecules Brown
Movement Kinetics. In addition simple non-steric solely and
electrostatic dispersants, such as low molecular waxy compound e.g.
modified or non modified lanoline extracts from sheep wool
fat-layer may be applied.
[0065] High molecular weight dispersants have pendent anchoring
groups, which adsorb to the surface of the particles to be
dispersed. Their mechanism of action is by hydrogen bonding,
dipole-dipole interactions or Van der Waal forces. The polymeric
framework is sufficiently great to give an effect called sterical
stabilization.
[0066] The preferred dispersants to be used in the present
invention are anionic and amphoteric low molecular weight
dispersants.
[0067] Although, anionic low molecular weight dispersants to be
used in the present invention include magnesium soaps of carboxylic
and sulfonic acids. Such dispersants and comparable dispersants
containing magnesium are not preferable, as they may comprise atom
sizes magnesium that depart from the scope of porous oxides
feature, as a partial or total disadvantage to the aimed
invention.
[0068] The fuel additive composition according to the present
invention will generally comprise the submicron or nano-sized
inorganic oxygen-containing metal compound or oxide (component a))
in a concentration of from 10 to 65% by volume, preferably from 20
to 50% by volume and more preferably from 30 to 50% by volume, and
most preferably from 40 to 50% by volume, calculated on the total
volume of the compositions, the balance to 100% by volume
essentially consisting of components b) and c) and possibly a minor
amount of water (generally less than 0.5% by volume) such as
moisture emanating e.g. from the use of not fully dry starting
materials, such as the hygroscopic substance magnesium hydroxide or
deliberately added to regulate the viscosity and stability of the
composition.
[0069] The upper limit of the concentration of inorganic
oxygen-containing compound or oxide in each specific case is
defined by the particle volume size and specific dispersants
depletion limit due to the specific particle size that may
destabilize the dispersion. Thus the upper limit will increase with
increasing average particle size. Thus, for instance, the upper
limit will be around 50% by volume in case of particles having a
particle size low variance distribution, as a distribution having
variance from .about.0.2 to .about.0.6 for the log-normal
distribution around a mean size from 500 to 200 nano-meters (nm)
respectively
[0070] The volume ratio component b) to component c) generally
depends on the specific substances used as those components and the
amount of particles to be dispersed. The optimum ratio in each
specific system may easily be determined in a series of experiments
varying said ratio for which experiments no inventive activity
should be required.
[0071] The fuel additive composition according to the invention is
prepared according to said another aspect of the invention by means
of the process according to the invention, which process
comprises
[0072] mixing a powder of an inorganic oxygen-containing compound
of a metal capable of forming a vanadate with vanadium of ash
deposits from vanadium-containing fuel and which inorganic
oxygen-containing compound when heated up in a combustion flame
liberates a gaseous substance by evaporation to form the
corresponding oxide having a crystalline, porous low density
structure or a powder of said oxide having a crystalline porous low
density structure into a mixture of at least one liquid selected
from the group consisting of liquids soluble in oil with at least
one dispersant for said inorganic oxygen-containing compound or
oxide selected from the group consisting of low molecular weight
dispersants and high molecular weight dispersants using shear
forces to form a homogenous pumpable premix and
[0073] subjecting the premix to a treatment comprising size
degradation and dispersant coating to a particle size distribution
of the inorganic oxygen-containing metal compound and oxide
essentially within the range of from 0.1 to 2 micron, preferably
from 0.1 to 1 micron, under centrifugal or oscillation forces in
the presence of a grinding medium and/or ultrasonic treatment until
a plot of the sediment height in samples taken periodically during
said treatment and centrifuged at a fixed rate for a fixed period
versus time plateaus and the viscosity has decreased and come into
a steady state.
[0074] Metal compound particles to be used in the process according
to the present invention should not contain crystal water and have
a low moisture content, if necessary obtained by a drying process,
preferably a moisture content far below 0.5% by weight.
[0075] The particle size of the metal compound or oxide particles
should not be exceedingly greater than the size of the particles of
composition prepared by means of the process and generally particle
sizes within the submicron range should be used, but small
particles of a substantial amount below 0.1 microns easily
adsorbing the deposit areas and having a low desorbtions rate
should be avoided.
[0076] According to a preferred embodiment of the process according
to the present invention the particles of the metal compound or
oxide are added to a vessel containing a mixture of said at least
one liquid selected from the group consisting of liquids soluble in
oil and at least part of said at least one dispersant under mixing
to form a premix allowing the temperature to rise during the
mixing, e.g. to a temperature within the range of from 50.degree.
C. to the upper limit .about.85.degree. C. defined by the
centrifugal forces and the viscosity to avoid cavitation of the
grinding media in order to reduce the viscosity of the premix.
[0077] For the procedure of the second step of the process
according to the present invention preferably a basket mill is
used. Such mills are available on the market and are, for instance,
sold in different models under the trade name Turbomill by Mirodur
SpA, Aprilia, Italy.
[0078] The grinding media used are e.g. small zirconium balls, the
diameter of which is chosen in accordance with the intended
particle size of the metal compound and oxide particles,
respectively, after grinding so that said diameter is increased
when larger particles are wanted. Generally said diameter will be
within the range of from 0.8 to 1.2 mm, however, balls of uniform
size being used in each specific case. Balls of other materials
known as suited for use as grinding media, e.g. steel and glass,
can also be used in the process according to the invention.
[0079] A zirconium ball size of 0.8 mm is, for instance, sufficient
to reach the desired size for e.g. Mg(OH).sub.2-particles and
efficiently disperse the particles in accordance with the
invention.
[0080] The premix mentioned above is filled into the basket mill
vessel and rotating is started and speeded up to full power loading
allowing temperature to rise to about 75-85.degree. C. All moisture
that evaporates during the basket mill operation should be
evacuated from the vessel.
[0081] Samples are taken at intervals of 30 to 70 minutes such as 1
hour and centrifuged at a fixed rate, e.g. within the range of from
2000 rpm to 4000 rpm, such as 3000 rpm, for a fixed period within a
range of from e.g. 30 minutes to 1 hour, such as 45 or 50 minutes,
and the height of the sediment of each sample measured. During
rotation of the basket the height of the sediment of the different
centrifuged samples will start to decrease rapidly as sampling
proceeds. Rotation is continued during a constant temperature
operation phase until the plot of sediment height versus time
plateaus and thereby the basic viscosity has decreased and come
into a steady state.
[0082] As an alternative to the rotating basket mill operation
grinding may be performed by means of oscillation buckets.
Alternatively or as a supplement to grinding ultrasonic treatment
may be applied.
[0083] The design of grinding mills commonly supplied has to be
adjusted for the engine effect upwards to achieve at least an
accelerative force above 50 g on the liquid to reach the limit
force needed to override the tensions to disaggregate the present
smallest nano particles. Preferably 70 g is needed as desired to
economically optimize the capacity dispersed per kWh etc.
[0084] The liquid lubricant film must hold the balls of e.g. a
basket mill apart from each other. Otherwise the cavitating balls
will degrade themselves rapidly. There is no possibility to achieve
static pressure to degrade agglomerates and grind nano-scaled
particles. The force here transmitted, to achieve degradation has
to be transmitted to the electromagnetic interference between
particle surfaces and the intermediate liquid.
[0085] A media mill optimizing the following parameters preferably
achieves this.
[0086] 1. Temperature
[0087] 2. Relative content of solids in the liquid
[0088] 3. Ball size
[0089] 4. Ball density
[0090] 5. Ball volume relative to inlet power to be
transmitted.
[0091] 6. Accelerative force in g-number (Af)
[0092] Media disc mills are not suitable as accelerative force
achievable is to low.
[0093] Commonly in the color industry applied basket mills e.g. a
Turbomill is suitable for the present purpose. But other kinds of
mills as e.g. high frequency oscillation ball media vessels as e.g.
the Colorox mill may be applied. By rotating the ball filled basket
in a Turbomill the acceleration force (a) will be distinctly
controlled by the rotation speed. a=(.omega..sup.2*r*2*.pi.);
m/s.sup.2 Equation (1)
[0094] Where: r=peripheral radius in meter for the basket or a body
orbit [0095] .omega.=angular velocity=rpm/60=cycles per
second=Hertz [0096] and 1 Newton=1 m/s.sup.2; and Af=a/9.82; g
[0097] As recognized by equation (1) the acceleration force is
proportional to the radius for a body motion in a circular orbit
and proportional to the square power for the angular velocity.
Thereby, the needed rpm or frequency for different orbits to reach
the acceleration to override the tension is given by:
.omega.=Square root of (Af*9.82*/r) divided by (2*.pi.*60) Equation
(2)
[0098] An acceleration force (Af) of 70 g is preferable to exceed
the tensions in the crystal aggregate. Thereby equation (2) tells
us the orbit frequency for different kind of mills and other kinds
of power transmission facilities. As we decrease the orbit radius
to a certain limit e.g. 10 mm we cannot apply the power by
centripetal force as in a basket mill of understandable reasons.
Instead an high frequency oscillatory or vibrato vessel is
preferable. A 210 mm radius basket needs a rotating speed of 546
rpm to achieve a peripheral force of 70 g. A small body in 10 mm
radius oscillatory vessel needs a rotation speed of 3541 rpm or 59
Hertz.
[0099] To roughly define the velocity property limit to be override
for different kinds of force transmission equipment in accordance
with the invented process to prepare the dispersion for the
invented composition we need the illustrative tube. Imagine a tube
that enables to apply accelerative force in inversed direction for
the liquid in one direction and the tube wall in the other
direction. Thereby the relative speed and the tension between the
liquid and the tube wall will define the sheer forces interfering
the particles. As the entire volume in an oscillatory vessel will
oscillate in small orbits the relative speed will reach
approximately a maximum of twice the peripheral oscillation speed.
Thereby the shear force limit will be reach at a frequency of 2504
rpm or 42 Hertz for a 10 mm radius oscillatory vessel instead of
said frequency of 59 Hertz above for a single small body
acceleration of 70 g.
[0100] In addition ultrasonic methods may be used, as dispersion
par se is desired. Similar to the oscillatory vessel case equation
(2) will help us to define the frequency for different ultrasonic
amplitudes or wavelengths to be applied. As a conventional
ultrasonic frequency is 20-40 kHz for e.g. 35 kHz the desired
amplitude is 15 nm, but a substantially higher amplitude in the
range above 1-10 microns is a necessity due to achieve sheer beams
for the entire particles and not only for a small limit part on a
particles surface area. The amplitude has to substantially exceed
the particles size to admit surface coating and particles to
cavitate. Thereby, ultrasonic equipment is also contemplated for
use in the present invention, especially as increased power density
is needed to achieve efficient fast coating on the small part of
the very small nano particles to get a fully stable dispersion not
reaggregating.
[0101] The invention will now become illustrated by means of a
number of non-limiting working examples illustrating the
preparation and use of the compositions according to the
invention.
EXAMPLES
Materials used in Examples 1 & 2
[0102] The magnesium hydroxide used was Ankermag.RTM.-HH from
Magnifin Magnesiaprodukte GmbH, Austria. The magnesium powder
contains >98.0% by weight (wt %) Mg(OH) .sub.2 and <0.5 wt %
water. Specific surface 9-12 m.sup.2/g equivalence a mean size for
a dense sphere diameter range from 200-260 nm or in fact the
largest diameter of the thin flakes crystals average .about.500 nm.
The crystals D50 diameter is .about.900 nm, i.e. the median size
diameters in the distribution. In addition the crystal agglomerate
upper limit diameter is less than approximately 50 microns. The
preparation process according to the invention admits feeding by
much larger particles, preferably a surface area above >3-4
m.sup.2/g.
[0103] The dispersant used was Rhodafac.RTM. RE 610, from Rhodia
Inc, France, which is characterized by the manufacturer as
nonylphenol ethoxylate based phosphate esters.
[0104] Rape-oil methyl ester was supplied by Svenska Ekobranslen
AB, Sweden.
Example 1
Preparation of Fuel Additive Composition-Batch of 1000 kg
[0105] 20 kg of Rhodafac.RTM. RE610 and 270 kg of rape-oil methyl
ester (RME) having a moisture content of <0.05% by weight were
mixed in a dissolver vessel (Disolver DTM49 from Westerlins
Maskinfabrik AB, Malmo, Sweden) to a homogenous mixture.
[0106] Then 690 kg of magnesium hydroxide powder dried to a
moisture content of <0.5% by weight were gradually added under
continued mixing allowing the temperature to rise to about
50.degree. C. to form a premix.
[0107] The premix was then transferred to the vessel of a basket
mill (Turbomill.RTM. 2, from Mirodur SpA, Aprilia, Italy, with an
engine effect of 55 kW) containing balls of zirconium having a
diameter of 0.8 mm as the grinding medium and rotation of the
basket was started and speeded up to full power loading.
[0108] The temperature was allowed to increase to 75.degree.
C.-85.degree. C., i.e. securely below the upper limit where the
reduced viscosity achieved by the increase in temperature will
allow the balls of the milling medium to touch each other by
chance.
[0109] The temperature was kept stable until the samples taken at
intervals of 1 hour and centrifuged at a rate of 3000 rpm for 50
minutes indicated a rapid decrease in the height of the pellet
obtained by such centrifugation after approximately 4-6 hours, due
to operation temperature and the applied centrifugal force. The
basket mill was kept running until the premix was fully dispersed
which occurred as decreasing the rotation in accordance to the
decrease in the height of the pellet obtained by centrifuging
samples as above until approaching a steady state. Then additional
20 kg of Rhodafac.RTM. RE610 and 20 kg of rape-oil methyl ester (in
addition, if desired 1-5 liter water may be added per ton to
achieve increased stabilization of the particles) were added and
the grinding process continued for approximately 15 minutes.
[0110] The completed process was shut down and the composition
liquid was pumped into barrels and samples were collected. If
desired for the specific applications the liquid composition is
diluted by RME before barreling it up.
[0111] The Mg content by ash test was .about.29% by weight and the
Mg(OH).sub.2 content was 69% by weight (.about.46% by volume) and
the upper tail of the size distribution was below 1,0 micron and
the main particle flakes shown by a standard scanning
electronmicroscope were in the range 0.2-0.5 micron.
Example 2
Preparation of Fuel Additive Composition-Batch of 1000 kg
[0112] 40 kg of a Rhodafac.RTM. RE610 and 270 kg of diesel (class
1) were mixed in a dissolver vessel (Disolver DTM49 from Westerlins
Maskinfabrik AB, Malmo, Sweden) to a homogenous mixture
[0113] Then 690 kg of magnesium hydroxide powder dried to a
moisture content of <0.5% by weight were gradually added under
continued mixing allowing the temperature to rise to about
50.degree. C. to form a premix
[0114] The premix was then transferred to the vessel of a basket
mill (Turbomill.RTM. 2, from Mirodur SpA, Aprilia, Italy, with an
engine effect of 55 kW) containing balls of zirconium having a
diameter of 0.8 mm as the grinding medium and rotation of the
basket was started and speeded up to full power loading.
[0115] The temperature was allowed to increase to 75.degree.
C.-85.degree. C., i.e. securely below the upper limit where the
reduced viscosity achieved by the increase in temperature will
allow the balls of the milling medium to touch each other by
chance.
[0116] The temperature was kept stable until the samples taken at
intervals of 1 hour and centrifuged at a rate of 3000 rpm for 50
minutes indicated a rapid decrease in the height of the pellet
obtained by such centrifugation after approximately 4-6 hours, due
to operation temperature and the applied g-force. The basket mill
was kept running until the premix was fully dispersed which
occurred as decreasing the rotation in accordance to the decrease
in the height of the pellet obtained by centrifuging samples as
above until approaching a steady state. Then additional 40 kg of
Rhodafac.RTM. RE610 (in addition, if desired 1-5 liter water may be
added per ton to achieve increased stabilization of the particles)
were added and the grinding process continued for approximately 15
minutes.
[0117] The completed process was shut down and the composition
liquid was pumped into barrels and samples were colleted. If
desired for the specific applications the liquid composition is
diluted by dieseloil before barreling it up.
[0118] The Mg content by ash test was .about.29% by weight and the
Mg(OH).sub.2 content was 69% by weight (.about.46% by volume) and
the size distribution of the upper tail was below 1.0 micron and
the main particle flakes shown by a standard scanning
electronmicroscope were in the range 0.2-0.5 micron.
Example 3
Comparison of Structures of Magnesium Oxide
[0119] In order to compare the structure of magnesium oxide having
an porous structure formed by subjecting magnesium hydroxide to a
high temperature with that of magnesium oxide prepared by
dehydrating magnesium hydroxide at a comparatively lower
temperature the following experiment was carried out.
[0120] Three samples of magnesium hydroxide powder having a
particle size distribution of mean 400 nm, an .delta.=0.4 for the
lognormal estimated cross-section function and a moisture content
of <0.5% by weight and equal in weight were used. The samples
were rapidly heated in an oven at a temperature of 450.degree. C.
1000.degree. C. and 1300.degree. C., respectively.
[0121] Analyses of the 1000.degree. C. treated sample showed that
the surface area increased from BET 8.66 m.sup.2/g for the
hydroxide particles to BET, 10.38 m.sup.2/g for the porous oxide
particles. The density decreased from approximately 2.3 g/cm.sup.3
for the Mg(OH).sub.2 to 1.36 g/cm.sup.3 (measured by a pyknometer)
for the converted MgO crystals. This is below 40% of the density of
nonporous MgO of 3.58 g/cm.sup.3 and a remarkably low density.
[0122] The specific surface area for Mg(OH).sub.2 and MgO was
measured by Multipoint Surface Area N.sup.2-gas at 77.degree.
Kelvin adsorption isotherm and pore distribution. The pore diameter
at surface had its distinct high frequency with as micropores
within the range 3.5-6.5 nm for the almost fully dense Mg(OH).sub.2
and for the converted low density MgO as mesopores within the range
of 10-60 nm with the mode-frequency just below 30 nm
[0123] It was confirmed by X-ray diffraction (Cu, K; .alpha.=1.54
.ANG.) that MgO has a solely crystalline lattice structure whereby
the crystals are not to any degree an amorphous unordered
structured crystal. Thereby the expanded and to some extent
sintered crystals contain open pores through the crystal surface as
well as closed pores within the crystals due to the low density and
the small 20% increase in specific surface area as loosen 3/5 atoms
out of the crystal volume.
[0124] The other two samples treated at 450.degree. C. and
1300.degree. C. confirm that the MgO density is temperature
sensitive as density decreases by temperature within the
temperature range below the high temperature dead burned range
above approximately 1600.degree. C. Thereby there my be a need to
tailor size low density MgO particles for certain applications as
the operating combustion temperature will be below the optimal
temperature to form desired low density MgO particles to reduce
deposit buildups
[0125] Similary, magnesium carbonate was rapidly heated in an oven
at a temperature of 1300.degree. C. and the density of the
magnesium oxide thus formed was measured by a pyknometer and found
to be 1.03 g/cm.sup.3
[0126] The results of the density measurements together with
density values found in literature are summarized in the following
table.
Table
[0127] Density of magnesium oxide formed by heating magnesium
hydroxide and magnesium carbonate at different temperatures at
ambient atmospheric pressure. TABLE-US-00001 Density of MgO from Mg
Density of Temp. (OH).sub.2 MgO from MgC0.sub.3 [.degree. C.]
[g/cm.sup.3] [g/cm.sup.2] Remark 450 2.13 -- 1000 1.36 -- 1300 2.45
1.03 2750 3.58 3.58 from literature
Example 4
[0128] A fuel additive composition according to the present
invention was used in a large-scale comparative test in a power
plant, wherein two comparable 120 MW gas turbines were applied in
parallel, both being fed with the same fuel until injecting the
composition according to the invention and a prior art composition
(KL 200 from Baker Petrolite, USA), one for each gas turbine with
the same present common pumps into the oil flow on its final short
way into the combustion chamber. The gas turbines were completely
up kept at onset including new turbine blades.
[0129] The fuel additive composition according to the invention
used in this experiment had a density of .about.1.56 g/cm.sup.3 and
contained .about.69% by weight of magnesium hydroxide particles and
thereby 29% Mg by weight having a particles size distribution
around mean .about.300-500 nm with a variance mean for the
lognormal distribution of .about.0.4 and 4% by weight of
Rhodafac.RTM. RE610 from Rhodia Inc, France and 27% by weight of
REM.
[0130] KL 200 is a magnesium oxide over-based magnesium carboxylate
vanadium inhibitor with a density of 1.22 g/cm.sup.3 containing 20%
Mg as specified by the supplier.
[0131] Based on laboratory test figures every second hour the dose
rate was maintained at the level of 2 grams of magnesium per 1 gram
of vanadium inherent in the washed heavy fuel oil containing 20-30
ppm vanadium and .about.2% sulfur.
[0132] Inspections were made after each wash cycle.
[0133] The wash cycle is the time range from start of operation
until the gas turbine needs to be cleaned up for deposits due to
technical and economical disadvantages from the accumulated
deposits of ash compounds.
[0134] It was found at the inspections for the 1.sup.st wash cycle
before auto wash that the deposits were easy to remove by hand in
case of using the composition according to the invention but could
not be removed by hand in case of using the prior art
composition.
[0135] During the 1.sup.st wash cycle in this comparative
large-scale test, the input-output efficiency rate adjusted by
uncontrolled variables shows an increase in average MWh output per
unit oil of approximately 1% in favor to the turbine injected with
the additive in accordance with the invention. Thereby, it was
assumed that the gas turbines run in parallel with the same fuel
was comparable. The 1% efficiency difference between the gas
turbines was an underestimation of the true benefits of the
invented composition as illustrated in the next paragraph.
[0136] During the 4.sup.th and 5.sup.th wash cycles both turbines
were run with the prior art fuel additive to indicate the
comparability. A difference was found. Instead of the comparison
after the 1.sup.st wash cycle the 3.sup.rd and 6.sup.th wash cycles
for the gas turbine run by the fuel additive according to the
invention were compared to the 4.sup.th wash cycle run by the prior
art fuel additive. It was found that the average efficiency
increased in an amount of at least 2-4% by using the fuel additive
composition according to the present invention.
[0137] Of special interest is the effect occurred as the turbine
was tripped on the day 8 and the booster effect increased the
efficiency by more the 2% units.
[0138] The volume of the pores in the deposits was estimated before
auto wash. By letting a liquid be absorbed into deposit pieces it
was found that deposits in accordance with the invention were
substantially more porous in the range of an additional pore volume
for deposit comparable locations of 30-115% and in accordance with
that a decreased density in the rage up to 25% was reported. In
addition the liquid absorbance speed was much faster for the
deposits in accordance with the invention.
[0139] Of great importance is the ability of the deposits to absorb
aerosol water during auto wash and booster tripping a gas turbine.
Indicatively this feature is in proper advance for deposits formed
by applying the invented composition as the absorbance of H.sub.2O
from ambient 60% relative humidity air rapidly reaches a steady
state of 2.9% compared to the absorbance of deposits formed by the
prior art conventional composition which was more than 10 time less
or 0.25% H.sub.2O at room temperature.
Conclusions
[0140] The findings illustrated in the examples show and fully
explain the better off for gas turbine input-output efficiency for
the porous MgO-particles applied in accordance with the present
innovation to react in the combustion chamber instead of MgO
dense-structured crystals as mainly is inherent in the combustion
chamber for prior art compositions. These findings may be
generalized to other solid metal-oxides, from the scientific common
sense in chemistry and physics. Thereby, additional metals not
tested may be applied in accordance with the disclosed invention to
reduce the negative efficiency impacts of hard ash deposits in oil
power transformation.
[0141] As will be apparent to those skilled in the art in the light
of the foregoing disclosure, many modifications, alterations and
substitutions are possible in the practices of this invention
without departing from the spirit or scope thereof as defined in
the appended claims.
* * * * *