Classifications

• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10L—FUELS NOT OTHERWISE PROVIDED FOR; NATURAL GAS; SYNTHETIC NATURAL GAS OBTAINED BY PROCESSES NOT COVERED BY SUBCLASSES C10G OR C10K; LIQUIFIED PETROLEUM GAS; USE OF ADDITIVES TO FUELS OR FIRES; FIRE-LIGHTERS
  • C10L1/00—Liquid carbonaceous fuels
  • C10L1/32—Liquid carbonaceous fuels consisting of coal-oil suspensions or aqueous emulsions or oil emulsions
  • C10L1/328—Oil emulsions containing water or any other hydrophilic phase

Definitions

• the present invention relates to a fuel oil composi ⁇ tion comprising an emulsion of water and a fuel oil which is used as a combustion fuel for a gas turbine. More particularly, the present invention relates to lubricity agents which can be incorporated in the noted emulsion to permit operation of the gas turbine when firing a water and fuel oil emulsion.
• Nitrogen oxides can form from the combustion of organic and inorganic nitrogen compounds in fuel and, at higher temperatures, from thermal oxidation of nitro- gen in combustion air. Combustion or gas turbines are considered to be even more prone to the generation of NOx because of the "favorable" high temperature and pressure conditions existing therein, as well as their more oxida- tive operating conditions.
• gas turbines are often also used by electric power generating utilities for emergency or peak load generation of elec ⁇ tricity.
• gas turbines can be either industri- al units made primarily from steel, or jet airplane en ⁇ gines made primarily from aluminum and aluminum alloys.
• the excessive NOx generation of gas turbines has often prevented their use as base load units because of regulations limiting the amount of nitrogen oxides which can be emitted and resulted in limitation of their use to peak periods or emergencies.
• Nitrogen oxides are troublesome pollutants and com ⁇ prise a major irritant in smog. It is further believed that nitrogen oxides can cause or enhance the process known as photochemical smog formation through a series of reactions in the presence of sunlight and hydrocarbons. Moreover, nitrogen oxides are a significant contributor to acid rain and have been implicated in the undesirable warming of the atmosphere through what is known as the "greenhouse effect" and in the depletion of the ozone layer. In addition, gas turbines often emit a visible plume which is highly undesirable since it causes concern among the general population in areas surrounding the facility.
• the emulsified fuel was believed to also create a secondary atomization because of the heat of vaporization from the burning fuel, which causes the emulsified water droplets to become steam.
• This second- ary atomization is thought to improve combustion and increase the gas volume.
• the heat required to change the water to steam is felt to be the basis for the reduction in flame temperature which leads to reduced formation of nitrogen oxides.
• Dainoff/Sprague/Brown has been found to lead to improved engine fuel system integrity and cooler engine burning temperatures (which leads to a reduction in thermal stress). Also, a higher load capacity is believed possi- ble in the gas turbine, and compliance with environmental regulations more easily obtained.
• Dubin and Wegrzyn have developed an emulsification system which is surprisingly effective at maintaining water and fuel oil emulsions for extended periods of time. This is espe ⁇ cially significant when the gas turbine in question is being used as a peaking or emergency unit, since the emulsion can often sit for extended periods of time with only occasional recirculation.
• the Dubin/Wegrzyn emulsi- fication system disclosed in U.S. Patent Application entitled "Emulsification System for Light Fuel Oil Emul ⁇ sions", having Serial No. 07/770,979, filed October 1, 1991, generally comprises an amide, a phenolic surfac ⁇ tant, and, optionally, a difunctional block polymer ter- minating in a primary hydroxyl group.
• the present invention relates to an enhanced lubric- ity water and fuel oil emulsion for reducing nitrogen oxides emissions and improving combustion efficiency in a stationary, electric power generating source, especially a gas turbine (the term “gas turbine” will be considered to be interchangeable with the term “combustion turbine” for the purposes of this disclosure).
• this invention relates to a water and fuel oil emulsion comprising an agent which provides lubricity to the emul ⁇ sion comparable to that of #2 fuel oil alone.
• the sub ⁇ ject emulsion can be either a water in fuel oil or a fuel oil in water emulsion, although water in fuel oil emul ⁇ sions are generally preferred for most applications, and can be used as the fuel for a gas turbine.
• the oil phase in the inventive emulsions comprises a light fuel oil, by which is meant a fuel oil having lit- tie or no aromatic compounds and consists essentially of relatively low molecular weight aliphatic and naphthenic hydrocarbons.
• the fuel oil can generally be referred to as a light crude naphtha fuel oil.
• light crude naphtha refers specifically to the first liquid distillation fraction, which has a boiling range of about 90°F to about 175°F. This is distinguished from heavy crude naphtha, which is the second distillation fraction, with a boiling range of about 325°F to about 425°F.
• Nephthenic is an industrial term which refers to fully saturated cyclic hydrocarbons having the general formula C n H 2n .
• Aliphatic is an industrial term which refers to fully saturated linear hydrocarbons having the general formula C n H 2n+2 .
• Suitable light fuel oils are those having a viscosi ⁇ ty of about 5 SSF to about 125 SSF, preferably about 38 SSF to about 100 SSF, at 100°F and a specific gravity of about 0.80 to about 0.95 at 77°F.
• Such fuels include fuels conventionally known as diesel fuel, distillate fuel, #2 oil, or #4 oil, as defined by the American Soci ⁇ ety of Testing and Measurement (ASTM) standard specifica- tion for fuel oils (designation D 396-86).
• ASTM American Soci ⁇ ety of Testing and Measurement
• distillate fuels Included among these are kerosene (or ASTM grade no. 1 fuel oil) and jet fuels, both commercial and military, commonly referred to as Jet-A, JP-4 and JP-5.
• the subject emulsions advantageously comprise water- in-fuel oil emulsions having up to about 90% water by weight.
• the emulsion comprises about 60% to about 90% water, more preferably about 70% to about 80% water.
• the emulsions which have the most practical significance in combustion applications when being combusted alone are those having about 5% to about 50% water and are preferably about 10% to about 35% water-in-fuel oil by weight.
• discontinuous phase i.e., the water in a water-in- fuel oil emulsion
• inversion will cause the emulsion to become a fuel oil-in-water emulsion compris ⁇ ing about 35% of the discontinuous oil phase.
• demineralized water is not required for the successful control of nitrogen oxides and opacity
• the use of demineralized water in the emulsion formed accord- ing to the process of this invention is preferred in order to avoid the deposit of minerals from the water on the blades and other internal surfaces of the gas tur ⁇ bine. In this way, turbine life is extended and mainte ⁇ nance and outage time significantly reduced.
• the inventive emulsions are prepared such that the discontinuous phase preferably has a particle size where ⁇ in at least about 70% of the droplets are below about 5 microns Sauter mean diameter. More preferably, at least about 85%, and most preferably at least about 90%, of the droplets are below about 5 microns Sauter mean diameter for emulsion stability.
• Emulsion stability is largely related to droplet size.
• the primary driving force for emulsion separation is the large energy associated with placing oil molecules in close proximity to water molecules in the form of small droplets.
• Emulsion breakdown depends on how quick- ly droplets coalesce.
• Emulsion stability can be enhanced by the use of surfactants and the like, which act as emulsifiers or emulsion stabilizers. These generally work by forming repulsive layers between droplets, pro- hibiting coalescence.
• an emulsification system is most preferably employed to maintain the emulsion.
• a desirable emulsification system which can be uti ⁇ lized comprises about 25% to about 85% by weight of an amide, especially an alkanolamide or n-substituted alkyl amine; about 5% to about 25% by weight of a phenolic surfactant; and about 0% to about 40% by weight of a difunctional block polymer terminating in a primary hy- droxyl group. More preferably, the amide comprises about 45% to about 65% of the emulsification system; the pheno ⁇ lic surfactant about 5% to about 15%; and the difunc ⁇ tional block polymer about 30% to about 40% of the emul- sification system.
• Suitable n-substituted alkyl amines and alkanol- amides which can function to stabilize the emulsion of the present invention are those formed by the condensa ⁇ tion of, respectively, an alkyl amine and an organic acid or a hydroxyalkyl amine and an organic acid, which is preferably of a length normally associated with fatty acids.
• They can be mono-, di-, or triethanolamines and include any one or more of the following: oleic diethan- olamide, cocamide diethanolamine (DEA) , lauramide DEA, polyoxyethylene (POE) cocamide, cocamide monoethanolamine (MEA), POE lauramide DEA, oleamide DEA, linoleamide DEA, stearamide MEA, and oleic triethanolamine, as well as mixtures thereof.
• alkanolamides are commercially available, including those under trade names such as Clindrol 100-0, from Clintwood Chemical Company of Chica ⁇ go, Illinois; Schercomid ODA, from Scher Chemicals, Inc.
• the phenolic surfactant is preferably an ethoxylated alkyl phenol such as an ethoxylated nonylphenol or octyl- phenol.
• ethylene oxide nonyl ⁇ phenol which is available commercially under the trade- name Triton N from Union Carbide Corporation of Danbury, Connecticut and Igepal CO from Rhone-Poulenc Company of Wilmington, Delaware.
• the block polymer which is an optional element of the emulsification system advantageously comprises a nonionic, difunctional block polymer which terminates in a primary hydroxyl group and has a molecular weight rang ⁇ ing from about 1,000 to above about 15,000.
• Such poly ⁇ mers are generally considered to be polyoxyalkylene de ⁇ rivatives of propylene glycol and are commercially avail- able under the tradename Pluronic from BASF-Wyandotte
• the emulsifica- tion system may further comprise up to about 30% and preferably about 10 to about 25% of a light fuel oil, most preferably the light crude naphtha fuel oil which comprises the continuous phase of the inventive emulsion. It has been found that inclusion of the fuel oil in the emulsification system can in some cases increase emulsion stability of the emulsion itself.
• other components such as salts of alkylated sulfates or sulfon- ates such as sodium lauryl sulfate and alkanolamine sulfonates may also be included in the inventive emulsi- fication system.
• the use of the noted emulsification system provides chemical emulsification, which is dependent on hydro- phylic-lipophylic balance (HLB), as well as on the chemi ⁇ cal nature of the emulsifier.
• HLB hydro- phylic-lipophylic balance
• the HLB of an emulsifier is an expression of the balance of the size and strength of the hydrophylic and the lipophylic groups of the com ⁇ position.
• the HLB system which was developed as a guide to emulsifiers by ICI Americas, Inc.
• the emulsifiers useful herein should most preferably have an HLB of 8 or less, meaning that after vigorous agitation they form a milky dispersion in water (HLB range of 6-8), poor dispersion in water (HLB range of 4-6), or show no dispersability in water (HLB range of less than 4).
• HLB range of 6-8 milky dispersion in water
• HLB range of 4-6 poor dispersion in water
• HLB range of less than 4 a milky dispersion in water
• the inventive emulsification system provides superior emulsification because it com- prises a plurality of components of different HLB values.
• the emulsification system has a combined HLB of at least about 4.0, more preferably about 5.1 to about 7.0 to achieve this superior emulsification.
• an emulsification system which com- prises 70% oleic diethanolamide (average HLB 6), 10% ethylene oxide nonylphenol (average HLB 13), and 20% #2 fuel oil has a combined HLB of about 5.5 (70% x 6 plus 10% x 13).
• An emulsification system which comprises 50% oleic diethanolamide, 15% ethylene oxide nonylphenol and 35% of a propylene oxide/ethylene oxide block polymer
• the emulsification system should be pres ⁇ ent at a level which will ensure effective emulsifica- tion.
• the emulsification system is present at a leVel of at least about 0.05% by weight of the emul ⁇ sion to do so.
• leVel of at least about 0.05% by weight of the emul ⁇ sion to do so.
• a physical emulsion stabilizer in combination with the emulsification system noted above to maximize the stability of the emulsion.
• Use of physical stabilizers also provides economic bene ⁇ fits due to their relatively low cost.
• physical stabilizers increase emulsion stability by in ⁇ creasing the viscosity of immiscible phases such that separation of the oil/water interface is retarded.
• Exem ⁇ plary of suitable physical stabilizers are waxes, cellu ⁇ lose products, and gums such as whalen gum and xanthan gum.
• the physical stabilizer is present in an amount of about 0.05% to about 5% by weight of the combination of chemical emulsifier and the physi- cal stabilizer.
• the resulting combination emulsi- fier/stabilizer can then be used at the same levels noted above for the use of the emulsification system.
• the emulsion used in the process of the present invention can be formed using a suitable mechanical emul- sifying apparatus which would be familiar to the skilled artisan.
• the apparatus is an in-line emulsifying device for most efficiency.
• the emulsion is formed by feeding both the water and the fuel oil in the desired proportions to the emulsifying apparatus, and the emulsification system can either be admixed or dispersed into one or both of the components before emulsification or can be added to the emulsion after it is formed.
• dimer and/or trimer acids sulfurized castor oil, phos ⁇ phate esters, and mixtures thereof will significantly increase the lubricity of the subject water and fuel oil emulsions and avoid the mechanical problems associated with such emulsions when combusted in a gas turbine.
• dimer and/or trimer acids or blends thereof are preferred among these.
• Dimer acids are high molecular weight dibasic acids produced by the dimerization of unsaturated fatty acids at mid-molecule and usually contain 21-36 carbons. Simi ⁇ larly, trimer acids contain three carboxyl groups and usually 54 carbons. Dimer and trimer acids are generally made by a Diels Alder reaction. This usually involves the reaction of an unsaturated fatty acid with another polyunsaturated fatty acid — typically linoleic acid. Starting raw materials usually include tall oil fatty acids. In addition, it is also known to form dimer and trimer acids by reacting acrylic acid with polyunsaturat ⁇ ed fatty acids.
• the product usually comprises a small amount of monomer units, dimer acid, trimer acid, and higher analogs.
• the product desired is primar- ily dimer acid (i.e., at least about 85% dimer acid)
• the reactant product is often merely referred to as dimer acid.
• the individual components can be separat- ed to provide a more pure form of dimer acid or trimer acid by itself.
• Suitable dimer acids for use in this invention in ⁇ clude Westvaco Diacid 1550, commercially available from Westvaco Chemicals of Washington Heights, South Carolina; Unidyme 12 and Unidyme 14, commercially available from Union Camp Corporation of Dover, Ohio; Empol 1022, com ⁇ surgeally available from Henkel Corporation of Cincin ⁇ nati, Ohio; and Hystrene 3695, commercially available from Witco Co. of Memphis, Tennessee.
• blends of dimer and trimer acids can also be used as the lubricity additive of the present invention.
• These blends can be formed by combining dimer and trimer acids, or can comprise the reaction product from the formation of the dimer acid, which can contain substantial amounts of trimer acid. Generally, blends comprise about 5% to about 80% dimer acid.
• Spe ⁇ cific blends include a blend of about 75% dimer acid and about ⁇ 25% trimer acid, commercially available as Hystrene 3675, a blend of 40% dimer acid and 60% trimer acid, commercially available as Hystrene 5460, and a blend of about 60% dimer acid and about 40% trimer acid, all com ⁇ dismissally available from Witco Co. of Memphis, Tennessee.
• Phosphate esters useful as the lubricity additive of the present invention can be prepared by phosphorylation of aliphatic and aromatic ethoxylates. These phosphate esters can be hydrophylic or lipophylic and include phos ⁇ phate esters of fatty alcohol ethoxylates. Suitable phosphate esters are commercially available as Antara LB700, a hydrophylic phosphate ester and Antara LB400, a lipophylic phosphate ester, both of which are commercial ⁇ ly available from Rhone-Poulenc Co. of Cranbury, New Jersey.
• the sulfurized castor oil which may be used in the present invention is commercially available as Actrasol C-75 from Climax Performance Materials Corpora ⁇ tion Co. of Summit, Illinois.
• the use of dimer or trimer acids is highly preferred as the lubricity additive of the present invention, as compared to phosphate esters or sulfurized castor oil. This is because the combustion of emulsions using the dimer and/or trimer acid lubricity additives produce less ash, with less than about 0.2% ash being highly preferred.
• the elimination of phos ⁇ phorous and sulfur compounds is also desired.
• the use of phosphorous- or sulfur-containing lubricity additives can lead to colored deposits on the turbine nozzle guide vanes and other turbine blades which can hinder efficient operation of the turbines and result in low electrical energy output. Although it is not clear how the use of phosphorous or sulfur compounds can lead to these depos ⁇ its, it is possible they act as binders. In any case, non-phosphorous and non-sulfur lubricity additives are preferred.
• the lubricity agent provided in the noted emulsions should be present at a level which varies between about 50 and about 550 parts per million (ppm) in the emulsion. Most preferably, the lubricity additive is present at levels of about 100 to about 400 ppm. At these levels, emulsions of up to about 85% water-in-fuel oil or as low as about 15% fuel oil-in-water will exhibit lubricities comparable to those of fuel oil alone.
• the lubricity agent is incorporated into the emulsification system and applied to the emulsion in this manner.
• the lubricity agent should be present in the emulsification system, which when applied at a level of about 1500 to about 3500 ppm, more advantageously about 2500 to about 3000 ppm, ensures the desired level of lubricity agent is present in the final emulsion.
• the lubricity gains provided by the inventive lubricity additive are relatively specific to fuel oil and water emulsions.
• the inven ⁇ tive lubricity additives in a fuel oil and water emulsion creates significant increases in the lubricity of the emulsion.
• the lubricity additives increase the emulsion lubricity to levels equivalent to those for fuel oil alone.
• Suitable corrosion preventing additives include filming amines, such as organic, ethox ⁇ ylated amines.
• N,N',N'-tris (2-hydroxy- ethyl)-N-tallow-l,3-diaminopropane commercially avail ⁇ able as Ethoduomeen T/13 from Akzo Chemicals, Incorporat ⁇ ed of Chicago, Illinois; an oleic diethanolamide which is the reaction product of methyl oleate and diethanolamine; an alkanolamide commercially available as Mackamide MO from Mclntyre Co. of Chicago, Illinois; and Ethoduomeen T/25, which is a higher ethoxylated version of Ethoduo ⁇ meen T/13.
• the emulsions prepared with the lubricity additives of the present invention can advantageously be used in a gas turbine which primarily fires natural gas, such as is taught by Brown and Sprague in U.S. Patent Application Serial No. 07/751,170, entitled “Reducing Nitrogen Oxides Emission by Dual Fuel Firing of a Turbine", filed August 28, 1991, the disclosure of which is incorporated herein by reference. In fact, such a "dual fuel" use is pre- ferred.
• the data is presented in terms of metal loss (grams/hour) , total running time (seconds), and a Wear Index which provides wear increments at 250 psi, 500 psi, and 750 psi.
• the Wear Index is presented in the format A/B(B)/Cx, where A represents increments to maintain 250 psi, B represents total increments from beginning of test through 500 psi, (B) represents increments to maintain 500 psi, and C represents total increments from beginning of test to failure as marked by the x.
• the individual runs made include
• Run 1 #2 fuel oil.
• Run 2 - 80% water-in-#2 fuel oil.
• Run 3 70% water-in-#2 fuel oil.
• Run 4 70% water-in-#2 fuel oil, further containing
• Run 7 70% water-in-#2 fuel oil, further containing 400 ppm of sulphurized castor oil.
• Example 1 The procedure of Example 1 is followed using an emulsion comprising 70% water in #2 fuel oil having lu ⁇ bricity additives set out below. The runs made are as follows:
• Run 16 400 ppm sulfurized castor oil. Run 17 - 100 ppm of Hystrene 5460 trimer acid and 100 ppm 'Ethoduomeen T/13.
• Run 34 400 ppm ethoxylated castor oil, 400 ppm #2 fuel oil, and 400 ppm Dowanol EB, 2-butoxyethanol/- ethyleneglycolbutylether.

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