Note: Descriptions are shown in the official language in which they were submitted.
285
~ 1 --
1 BACKGROUND OF THE INVENTION
2 1. Field of the Invention
3 This invention relates to the use o~ specific
~ zirconium salts in residual fuel oil to reduce the amount
of particulate matter formed during combustion.
6 2. Brief Description of the Prior Art
7 Residual fuel oils, including Grades Nos. 4, 5
8 and 6 (ASTM D-396), are widely used in a variety of
g industrial heating and steam boiler applications. A
particularly desired fuel oil is No. 6, which is exten-
11 sively used by utility and power companies.
12 State and federal EP~ emission standards are
13 currently limiting the use of residual fuels which produce
14 excessive amounts of particulate emission during combus-
tion and thus are not in compliance with standards.
16 However, the situation is relati~ely complicated,
17 since state-to-state emission standards tend to be differ-
18 ent and compliance by a residual fuel oil in one state may
1~ not necessarily be achieved in another, and further, since
standards are continuously subject to change, a fuel oil
21 currently in compliance may not be in compliance in the
22 near future in the same location and under the same
23 end-use conditions.
24 Fuels which tend to produce excessive amounts of
~5 particulate emission generally have one or more character-
26 istics associated with them: a sulfur content above about
27 1 percent; a Conradson Carbon Residue (ASTM D-189, also
~8 termed NCon CarbonN in the art) above about 7 percent; or
29 a high asphaltene content. Fuels yielding particulate
emissions that surpass the existing standards can't be
31 directly used, but in some cases can be blended in admix-
32 ture with fuels that do meet existin~ standards, which are
33 generally low in sulfur and/or low in ~Con Carbon" and
3~ asphaltene content. This situation has resulted in an
overall increased demand for fuel oils which meet emission
36 standards despite their diminishing supply and attendant
37 increase in cost.
38 What is desired is a process for increasing the
s~
~8~;
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utility of these high ~mission yielding residual uel oils
for industrial heating purposes in a manner that resulta
in acceptable particulate emissions, despite a high sul~ur
content, a high Con Carbon residue and/or high asphalten~
content.
In the area of related proble~s, it is known in
the art that the use of specific additives in certain
hydrocarbon fuels, can reduce smoke or soot upon combus-
tion, in certain instances. It is also known to use
specific additives in fuels to inhibit corrosion, inhibit
slag formation in boilers and to reduce the deleterious
efect of vanadium present in such fuels.
However, it has not been shown to use selected
additives to reduce particulate emission during combustion
of residual fuel oil, and particularly No. 6 fuel oil.
;Summary of Invention
;~t has unexpectedly been~found that by adding a
selected oil soluble zirconium salt of an alcohol/phenol
or sulfonate to a residual fuel oil, and particularly ~o.
.20 6 fuel oil the amount o~ particulate matt~r formed during
combustion can be significantly reduced in ~mounts of 10
to 25 p~rcent or greater.
In accordance with this in~ention, there is
provided a process for reducin~ the amount of particulate
matter ormed during the combustion o a residual fuel oil
which comprises combusting a residual ~uel oil which con-
tains an effective amount of an additive selected from the
group consisting o~:
n oil soluble zirconium salt of an alcohol or
phenol havin~ the ~ormula:
ROH
where R is a hydrocarbyl group of 2 to 24 carbon atoms: i
or
(ii) an oil soluble zirconium salt of a sulfonic acid
having the formula:
RSO3H
.~
_ 3 ~8~
where R is an alkyl, cycloalkyl, aryl, alk~ry1, or ar~lk~l
group and said salt has a molecular ~"ei~ht of about 100
to about 2500;
said amount bein~ effective in reducing the amount of
particulate matter formed during combustion
In another aspect the invention provides a com-
position comprising a residual fuel oil and an effective
trace amount of the additive previously described.
DESCRIPTION OF THE INVENTION AND PREFERRED EMBODIMENTS
- .. ... ~ .
10The novelty of the present invention resides in
the discovery that zirconium salts of certain alcohols/
phenols or sulfonic acids exert a beneficial efect on
; residual fuel oil, particularly No. 6 fuel oil/ in
reducing the amount of particulate matter formed during
combustion. The term nresidual fuel oil" as used herein,
is well-known and as described hereinabove, and includes
Grades No. 4, No. 5 and No. 6 residual fuel oils, mee~ing
tha specifications o ASTM D-396. Particularly preferred
is No. 6 fuel oil.
20The reason these particular zirconium additives
exhibit this surprising effect is not clearly understood.
It may be that the subject compounds promote and acti-
vate the complete oxidation of hydrocarbon and sulfur-
containing constituents in the fuel ~o volatile or gaseous
compounds during combustion, in a highly specific mannerO
The subject zirconium salts or compounds~ also
termed "additives~ herein, opera~ive in the instant in-
vention, comprise oil soluble zirconium sal~s of an
alcohol/phenol or sulfonate~ The zirconium salt of
30selected alcohols or phenols will be a 2irconium salt of
an alcohol or phenol having the formula:
ROH
where R is a hydrocarbyl group o 2 to 2~ carbon atoms.
More particularly R is a branched or unbranched, hydro-
carbyl group preferably having 2 to 13 carbon atoms.
Preferred compounds are those where R is a sa~urated or
Z3~5
-- 4 --
1 unsaturated aliphatic group having 2 to 8 and more pce~er-
2 ably 3 to 4 carbons. Most preferred are those coMpounds
3 where R is a saturated aliphatic group, and particularl~
4 those having 3 to 4 carbons. Compounds of this t<Jpe
include R groups which may be alkyl, aryl, alkar~l,
6 aralkyl and alkenyl. Illustrative alcohol or phenol
7 compounds oE this type include ethanol, propanol, butanol,
8 hexanol, decanol, octadecanol, eicosanol, phenol, benzyl
9 alcohol, xylenol, naphtholv ethyl phenol, crotyl alcohol
etc. Further information and description of the useful
11 alcohols of this type may be found in Kirk-Othmer,
12 "Encyclopedia of Chemical Technology" ~econd Edition,
13 1963, Vol 1, pp 531-&38.
14 The zirconium salt of sulfonic acids useful in
this invention are the zirconium salts of sulfonic acids
16 having the formula:
17 RS03H
18 where R is a hydrocarbyl group having 2 to 200 and prefer-
19 ably 10 to 60 car~on atoms. More particularly, the R
group in said sulfonic acids will be an alkyl, cycloalkyl,
21 aryl, alkaryl or aralkyl and said salt ~ill have a molec-
22 ular weight of about 100 to about 2500, preferably about
23 200 to about 700.
24 The sulfonic acids are characterized by the
presence o~ the sulfo group -SO3H (or -SO2OH) and can
26 be considered derivatives of sulfuric acid with one oE the
~7 hydroxyl groups replaced by an organic radical. Compounds
28 of this type are 9enerally obtained by the treatment of
29 petroleum fractions (petroleum sulfonates). Because of
the varying natures of crude oils and the particular oil
31 fraction used, sulfonates generally constitute a complex
32 mixture and it is best to define them in a general manner
33 giving the molecular weight as defined above. Partic-
34 ularly preferred sulfonates are those having an alkaryl
group, i.g. alkylated benzene or alkylated naphtalene.
36 Illustrative examples of sulfonic acids useful
372~S
in this invention are: dioctyl benzene sulfonic acicl,
2 dodecyl benzene sulfonic acid, didodecyl ben-zelle sulfonic
3 acid, dinonyl naphthalene sulfonic acid, dilauryl benzsne
4 sulfonic acid~ lauryl cetyl benzene sulfonic acid, pol~-
5 ole~in alkylated benzene sulfonic acid such as pol~-
6 butylene and polypropylene, etc. Further details regard-
7 ing sulfonic acids may be found in Kirk-Othmer, "Encylo-
~ pedia of Chemical Technology", Second Edition, 1969,
g Vol. 19, pp 311 to 319 and in NPetroieum Sulphonates'1 by
10 R. Leslie in Manufacturing Chemist, October 1950 (XXl, 10)
11 pp 417 to 422.
12 Methods of preparing the subject zirconium salts
13 described above are well known in the art and generally
1~ said salts are commercially available.
The zirconium additive is incorporated into the
16 residual fuel oil by dissolving therein. This is accom-
17 plished by conventional methods as by heating, stirring
18 and the like.
19 The amount of zirconium additive to be used is
20 an "effective trace amount" that will reduce the amount of
21 particulate matter formed during combustion of the resi-
22 dual fuel oil as compared to the combustion o said fuel
23 oil in the absence of said additive. By the term "effec-
24 tive trace amount" is quantitatively meant an amount of
25 about 1 to 1000 ppm by weight and preferably 10-500 ppm
26 by weight, 2irconium additive, taken as metallic zirconium,
27 in said fuel oil, and particularly preferred about 50 to
28 150 ppm by weight zirconium additive, taken as metallic
29 zirconium, in said uel oil. However, lower and higher
30 amounts than the 1-1000 ppm range can also be present
31 provided an effective trace amount, as defined herein, is
32 present in the residual fuel oil.
33 By the term "reduce the amount of particulate
3~ matter formed during combustion", as used herein, is meant
35 that at least about a Eive percent reduction in formed
36 particulate matter, and preferably from about 10 to 25
37 percent and greater, reduction in formed particulate
38 matter is achieved as compared to the combustion of the
~g ~37~35
6 --
1 residual fuel oil in the absence of the subjec~ zirconium
2 additive.
3 In the process, the fuel oil containing said
~ additive is generally mixed with ox~gen, usuall~ in the
form of air, to form a fuel/air mixture prior to combus-
6 tion. Generally, the amount of air utilized is an excess
7 over the stoichiometric amount to completely combust the
8 fuel oil to carbon dioxide and water. The reason for
g utilizing this excess is that complete mixing does not
always occur between the fuel oil and the air, and that
11 also a slight excess of air is desirable since it serves
12 to reduce the tendency of soot and smoke formation during
13 combustion. Generally, the excess of air used is about 2
14 to 35 percent (0.4 to 7 percent basad on oxygen) over
the stoichiometric amount depending upon the actual
16 end-use conditions which may vary considerably from one
17 type of industrial boiler to the next. One disadvantage
18 in using a large excess of air is that a greater amount of
19 heat is lost through entrainment that would otherwise be
utilized for direct heating purposes. We have found
21 that by use of the subject zirconium additives, less
22 excess air is required to reduce smoke and soot formation
23 and thus the heating efficiency of the residual fuel oil
24 is greater, as well as resulting in a reduction of par-
ticulate emission.
26 The above-described step of mixing fuel oil and
27 air is conventional and is usually accomplished for
28 example, by steam or air atomi~ation to produce a fine
29 spray which is then combusted to maintain and support a
flame. The combustion is controlled and conducted
31 at a particular "firing rate" which is usually expressed
32 as lbs/minute of fuel oil combusted.
33 The combustion of residual fuel oil is usually
3~ carried out in conventional industrial boilers, utility
boilers, refinery furnaces and the like.
36 The amount of particulate matter formed during
37 combustion of residual fuel oil will vary over a broad
38 range and is dependent upon a number of factors such as
37Z~
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1 type of boiler, boiler size, nuMber and tt~pe of burners,
2 source of the residual fuel oil used, amount o~ e~cess air
3 or oxy~en, firing rate and the like. Generall~, the
4 amount of particulate matter formed wilL be in the range
of about O.01 to l.O weight percent of the fuel oil used
6 and higher. One weight percent corresponds to one gram
7 particulate matter formed from the combustion of 100 grams
8 of fuel oil. The amount of particulate matter formed,
g herein termed "total particulate matter ,n is actually
the sum of two separate measurements; "tube-deposits,'l the
11 amount of particulate matter deposited inside of the
12 boiler, and two, ~filtered stack particulate," which is
13 the amount of particulate matter formed which escapes the
1~ boiler and is actually emitted out of the stack into
the air. EPA measurements are generally only concerned
16 with filtered stack particulate which is directly released
17 into the air environment and contributes to a decrease in
18 air quality. However, "tube deposits" lead to corrosion
19 of the equipment, frequent "clean-outs~ and add to the
total opera~ing costs. Furthermore, as tube deposits
21 collect on the inside of the apparatus, a critical crust
22 thickness is reached and ~urther tube deposits are then
23 entrained in stack particulate, which signiicantly
24 increases th~ amount of particulate emission. Thus r in
order to fully assess the overall operating advantages of
26 a particular residual fuel oil in a boiler operation, the
27 amount of tube deposits should also be considered, as well
28 as total stack particulate for compliance with emission
29 standards~
The amount o allowed stack particulate will
1 vary from state to state and is also subject to a minimum
32 amount allowed under Federal EPA standards. For example,
i 33 in Florida, the currently allowable limit for existing
power plants is 0.10 lbs. particulate emission per million
BTU, which is equi~alent to about 0.185 weight percent of
36 particulate stack emission per weight of combusted fuel
37 oil. Since the allowable emission standards will vary
38 from jurisdiction to jurisdiction, dif~erin~ amounts of
28S
the subject zirconium additive will be necessar~ to
2 produce a residual fuel oil composition in compliance ~/ith
3 those standards.
4 Measurement of the amount of "stack particulate
matter" is conducted by EPA Method t~5 Stack Sampling
6 System, "Determination of Particulate Emissions from
7 Stationary Sources" and is described in the Federal
8 Register~
g The particulate stack emissions are generally
comprised of particulate carbon, sulfur-containing hydro-
11 carbons, inorganic sulfates and the like.
12 The following examples are illustrative of this
13 invention and should not be construed as being limitations
14 on the scope and spirit of such invention.
Example 1
16 Combustion runs were carried out in a 50 horse-
17 power ABCO, 2-pass, water jacketed forced draft boiler
18 with an air-atomizing burner and a nominal firing rate of
g 1.2 lbs/min. of residual fuel oil. The boiler was modi-
fied so that closure on each end could be opened easily
21 for recovery of deposits laid down in the boiler. TS~1Q
22 other modifications included installation o a second fuel
23 system so the boiler could be heated to operating tempera-
24 tures on No. 2 oil and then switched over to the test fuel
without shutting down or upsetting the boiler operation
26 unduly and installation of a two foot length of firebrick
27 linin~ at the burner end of the iretube and a Cleaver-
28 Brooks noz~le assembly in place o the Monarch nozzle~
29 These modifications eliminated oil pooling and rapid
carbon deposits on the firetube walls when residual uel
31 was fired. The first pass is a ~9 cm (18.375 in.) diameter
32 x 178 cm ~5 ft. 10 in~) long fire tube; the second pass
33 consists of 52 tubes each ~ cm (2.375 in.) diameter x 188
34 cm (6 ft. 2 in.) lon~.
Atomization of the fuel was accomplished using a
3~ low pressure air-atomizing nozzle. Viscosity of the fuel
37 oil a~ the nozzle was maintained at 30 centistokes by
38 heatin~ the oil to a predetermined temperature (about
~37~8~i;
1 105C). Prior to contacting the burner gun, the a~oM-
2 ized fue~ oil was mixed with a meas~lred amount of excess
3 "secondary" air which was forced through a diffuser
4 plate to insure efficient combustion. The secondary air
was provided by a centrifugal blower mounted in the boiler
6 head. The amount of secondary air was controlled by means
7 of a damper which was regul3ted to keep the oxygen level
8 in the atomized fuel at about 1.5% in excess (over that
9 needed stoichiometrically to completely combust the fuel).
A run was started by firing the boiler and
11 heating it to operating temperature or 55 minutes using
12 No. ~ oil. The feed was then switched to test fuel and
13 after allowing suficient time for conditions to stabilize
14 (about 25 minutes) samples of about 10 minutes duration
were collected isokinetically from the stack on tared,
16 Gelman, Type A (20.3 x 25.4 cm) fiber glass filters. The
17 test fuel was a No. 6 fuel oil.
18 Total particulate matter formed was determined
19 by adding the amount of Stack particulate measured iso-
kinetically (EPA Method 5 Stack Sampling System) to the
21 amount deposited in the tubes of the boiler i.e. "tube
22 deposits".
23 The EPA Method 5 Stack Sampling System was
29 conducted with a commercially available system for this
purpose. This unit consisted of an 18-inch glass lined
26 probe, a cyclone, a 125 mm glass fiber filter and four
27 impingers. ~he first two impingers contained water, the
28 third was empty and the last one contained silica gel.
29 With the exception o the impingers, the entire sampling
train was ~aintained at about 175C to insure that the
31 stack gases entering the sampling system were above
32 the H2S04 dew point.
33 The deposits laid down in each of the 52 tubes
34 is collected on a separate, tared 20.3 x 25.4 cm fiber-
glass filter. Deposits are collected by positioning a
36 specially-designed filter holder against the end o each
37 tube in turn, pulling air through the tube and the filter
38 using a high-volume vacuum pump and manually brushing the
~ ~t372~35
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1 tube from end-to-end ten times with a 2.50 inch diameter
2 wire shank brush. The brush is mounted on a 8 ft. long,
3 0.25 in. diam. SS rod driven by an electric drlll. This
4 method gives almost 100% recovery of the deposits laid
down in the tubes. All the tubes are sampled because for
6 a given run there are large differences in deposit weight
7 from tube-to-tube in each row of tubes across the boiler
8 and from top row to bottom row and there is no consistent
g ratio of the weight of deposit collected from a given tube
from run-to-run.
11 The fuel oil used (Test Fuel) in the runs
12 analyzed for the following constituents:
13 Analysis of Test Fuel
14 Sulfur 2.0 wt~
ConCarbona14.8 wt%
16 Ashb .1 wt~
17 ~anadium469 ppm
18 Nickel 70 ppm
19 Iron 2.9 ppm
aASTM-D-189
21 bASTM-D-482
22 The zirconium additive used in tbe run was
23 zirconium propoxide an alcohol salt and was present in a
24 concentration of 100 ppm taken as metallic zirconium.
For test fuel alonel the stack particulate was
26 0~34 wt~ on uel, while the tube deposits was 0.20 wt% on
27 fuel for a total test particulate wt% of 0.54. The sample
28 o fuel containing the zirconium propoxide measured a
~9 stack particulate of 0.24 wt~ on uel and tube deposits of
0.16 wt% on fuel for a total particulata wt% of 0.40. The
31 improvement in usin~ the zirconium additives was a reduc-
2 tion in total particulates of 25.9%.
Example 2
34 Following the same general procedure and using
the ABC0 boiler described in Example 1 r a sample run using
36 100 ppm of a zirconium sulfonate additive, i.e. zirconium
-- 1 1 --
1 salt of dodecyl benzene sulfonic acid, ~"as made with the
2 same No. 6 fuel oil as in said Example 1.
3 The results for the sample containing zirconiurn
4 sulfonate were a stack particulate of 0.29 wt~ on ~uel and
tube deposlts of 0.18 wt~ on fuel for a total particulate
6 of 0.47 wt% on fuel. The improvement in using the zir-
7 conium additive was a reduction in total particulate of
8 13.0 %.
