Patent Application
20080081773
Various preferred features and embodiments are described below by way of non-limiting illustrations.
The present invention provides compositions as described above. The compositions are compatible for use in the natural gas processing fields with natural gas compressors and natural gas engines that power the compressors. Furthermore, the compositions of the present invention comprise an amount of one or more demulsifiers that are sufficient and competent to inhibit or reduce the amount of emulsions formed in the dehydrators and other downstream machines.
As discussed above, natural gas-fired engines are typically used in the oil and gas industry to compress natural gas at wellheads and along pipelines. This practice requires the engines to run continuously at or near full load, shutting down only for maintenance procedures such as oil changes. The need to run continuously near full load places severe demands on the suitable lubricating oils for those engines.
The increased operating severity has first lead to added incidents of engine exhaust valve wear commonly known as “valve recession” or “valve sink.” These terms refer to the rapid wear of the exhaust valves and/or the exhaust valve seats experienced by engines operating under high load conditions. It is known in the art that metallurgical improvements in valve and valve seat materials did little to relieve the wear. Certain lubricating oils, on the other hand, were found to effectively resolve the valve recession problem. U.S. Pat. No. 3,798,163, for example, disclosed a composition as well as a method of maintaining a lubricating amount of an oil composition comprising a base oil of lubricating viscosity; at least one alkaline earth metal sulfonate in an amount sufficient to improve the detergency of the composition; and at least one alkaline earth metal salt of a condensation product of an alkylene polyamine, an aldehyde, and a substituted phenol, in an amount sufficient to inhibit recession of the engine's exhaust valve into the engine's cylinder head.
Moreover, because the lubricating oils used with these engines are subject to high temperatures, the lives of the oils are often limited by oxidation. Additionally, natural gas engines run with high emissions of nitrogen oxides. Thus, the lives of the lubricating oils may also be limited by nitration. Accordingly, it is desirable that the gas engine oils have long life through enhanced resistance to oil oxidation and nitration. Engine oils having the desirable levels of resistance have been described in the prior art. For example, U.S. Pat. No. 5,726,133 disclosed a long-life and low-ash gas engine oil that has improved oxidation- and nitration-resistance. That oil comprised a major amount of a base oil of lubricating viscosity; and a minor amount of an additive mixture selected from at least one alkali or alkaline earth metal salt having a total base number (TBN) of about 250 or less, and a second alkali or alkaline earth metal salt having a TBN of about 125 or less. Moreover, U.S. Pat. No. 6,140,282 disclosed another long-life, low-ash gas engine oil that comprised a major amount of a base oil of lubricating viscosity; and a minor amount of a mixture of several metal detergents, such as a metal salicylate detergent, a metal sulfonate detergent, and/or a metal phenate detergent.
On the other hand, the combustion of natural gas is often complete, generating virtually no incombustible materials. Thus the durability of the cylinder head and valve is controlled by the properties of the lubricant and its consumption rate. Consequently gas engines typically have specific ash content requirements because it is the ash that acts as a solid lubricant and protect the valve/seat interface. Running the engine with too low an ash level results in shortened life for the valves or cylinder head, while running the engine with too high an ash level causes excessive deposits in the combustion chamber and piston areas. Accordingly, the ash level is often the focus in formulating natural gas engine oils.
In comparison, natural gas compressors have their own lubrication needs. The factors to consider in formulating compressor lubricants may or may not overlap those in formulating gas engine lubricants. Compressor lubricants must protect rotating bearing and/or sliding screws, pistons, crankcase components and other parts. Depending on the compressor design and type, high temperatures may be generated from adiabatic compression or friction of moving parts. Adequate thermal and oxidative stabilities are therefore required for compressor lubricants, just as they are required for gas engine oils. Rust and oxidation inhibited lubricants are also desirable, and antiwear protection is often needed.
Lubrication requirements differ with different compressors because of their distinct structural features. For example, lubricants that are used in reciprocating gas compressors must have two separate functions: (1) providing lubrication for the crankshaft and other portions of the drive train and transmission parts for the compressor; and (2) providing lubrication for the compression chamber. The lubrication of the drive train and transmission requires a stable material that retains its viscosity and lubricating properties under various severe operating conditions. Materials meeting these requirements include, for example, high-performance ester-based lubricants that have been disclosed in the prior art as turbine engine lubricants or oils for jet aircraft engines. The second function, i.e., providing lubrication of the compression chamber, is specific to this type of compressor. Unlike lubricants for internal combustion engines, the cylinder lubricant in reciprocating gas compressors is injected into the piston chamber, is not recycled subsequently, and exits with the compressed gas. Thus, lubricants for these compressors must not only have high resistance to degradation under extreme temperatures and pressures, but also refrain from forming sludge or varnish in the valves. They must also be effective in small amounts in order to avoid excessive contamination of the exhaust compressed gas. In addition, lubricants for reciprocating compressors must have low vapor pressure and good viscosity stability. An example of a suitable lubricating oil composition for a reciprocating compressor was disclosed in U.S. Pat. No. 4,111,821.
In the rotary screw compressors, rotors are exposed to a mixture of gas and the lubricant. In addition to providing a thin film on the rotor to prevent metal-to-metal contact, the lubricant must provide a sealing function to prevent gas recompression, which occurs when high-pressure, hot gas escapes across the seals between the rotors and other meshing surfaces and is compressed again. The lubricating oils for these compressors often serve as coolants, removing the heat generated during gas compression. These oils must also be suitable for lubricating the bearings at the inlet and outlet of the compressors. And because the lubricants are in contact with the gas being compressed in these compressors, the lubricants experience high shearing force between the intermeshing rotors. Suitable lubricating oil compositions for rotary screw-type of compressors have been disclosed in the prior art, for example, in U.S. Pat. No. 4,302,343.
A conventional gas engine lubricant therefore may not necessarily be suitable for use interchangeably with a compressor. However, in accordance with the present invention, a person skilled in the art will be able to formulate lubricating oil compositions that are suitable for such interchangeable uses without undue experimentation, because the criteria against which the performances of the desired compositions are evaluated are known.
The lubricating oil composition of the present invention typically comprises one or more base oils that are present in a major amount (i.e., an amount greater than about 50 wt. %). Generally the base oil is present in an amount greater than about 60 wt. %, or greater than about 70 wt. %, or greater than about 80 wt. %, based on the total mass of the lubricating oil composition. The base oil used in the lubricating composition of the invention may be a natural oil, a synthetic oil, or a mixture thereof, provided that the oil exhibit the requisite thermal stability and resistance to oxidation and nitration. Base oils contemplated for use with the present invention include animal, vegetable, mineral or synthetic hydrocarbon oils of lubricating viscosity and mixtures thereof. Synthetic hydrocarbon oils include long-chain alkanes such as, for example, cetanes, and olefin polymers such as, for example, oligomers of hexene, octene, decene, and dodecene. Synthetic oils may also include (1) fully esterified ester oils, with no free hydroxyls, such as pentaerythritol esters of monocarboxylic acids having 2 to 20 carbon atoms, trimethylol propane esters of monocarboxylic acids having 2 to 20 carbon atoms; (2) polyacetals; and (3) siloxane fluids. Especially useful among the synthetic esters are those made from polycarboxylic acids and monohydric alcohols. Particularly preferred are the ester fluids made by fully esterifying pentaerythritol or its mixtures with di- and tripentaerythritol, with an aliphatic monocarboxylic acid containing from 1 to 20 carbon atoms.
Mineral oils are cost effective for applications where high-temperature stability is not required. Mineral oils may also be processed to reduce sulfur content, but hey generally contain residual sulfur in amounts of about 0.1 to 0.5 wt %. For this reason, synthetic base lubricating oils are preferred for the present invention because they are free of residual sulfur. Suitable synthetic base oils include, for example, polyalphaolefin (PAO) oils, ester (diester and polyolester) oils, polyalkylene glycol oils or mixtures having a kinematic viscosity of about 2 to 10 cSt at 100° C. These synthetic base oils are inherently free of sulfur, phosphorus and metals.
Polyalphaolefin oils can be prepared by the oligomerization of 1-decene or other lower olefin to produce high viscosity index lubricant range hydrocarbons in the C20 to C60 range. Other lower olefin polymers include, for example, polypropylene, polybutylenes, propylene-butylene copolymers, chlorinated polybutylenes, poly(1-hexenes), poly(1-octenes), alkylbenzenes (e.g., dodecylbenzenes, tetradecylbenzenes, dinonylbenzenes, di(2-ethylhexyl)benzenes); polyphenyls (e.g., biphenyls, terphenyls, alkylated polyphenols); and alkylated diphenyl ethers and the derivatives, analogs and homologs thereof.
Polyalkyleneglycol oils can be prepared by polymerization of alkylene oxide polymers and interpolymers and derivatives, wherein the terminal hydroxyl groups have been modified by a process such as esterification and etherification. Examples include polyoxyalkylene polymers prepared by polymerization of ethylene oxide or propylene oxide, the alkyl and aryl ethers of these polyoxyalkylene polymers (e.g., methyl-polyisopropylene glycol ether having an average molecular weight of 1,000, diphenyl ether of polyethylene glycol having a molecular weight of 500-1,000, diethyl ether of polypropylene glycol having a molecular weight of 1,000-1,500); and mono- and polycarboxylic esters thereof, for example, the acetic acid esters, mixed C3-C8 fatty acid esters, and C13 Oxo acid diester of tetraethylene glycol.
The ester oils may also serve as the solubilizing media between the synthetic lubricating base oils and the additive compositions. The ester oil may comprise, for example, an aliphatic diester of an aliphatic dicarboxylic acid, which may be selected from: phthalic acid, succinic acid, alkyl succinic acids and alkenyl succinic acids, maleic acid, azelaic acid, suberic acid, sebasic acid, fumaric acid, adipic acid, linoleic acid dimer, malonic acid, alkylmalonic acids, and alkenyl malonic acids. The alcohol precursors of the esters may include, for example, butyl alcohol, hexyl alcohol, dodecyl alcohol, 2-ethylhexyl alcohol, ethylene glycol, diethylene glycol monoether, propylene glycol. Specific examples of suitable esters include dibutyl adipate, di(2-ethylhexyl)sebacate, di-n-hexyl fumarate, dioctyl sebacate, diisooctyl azelate, diisodecyl azelate, dioctyl phthalate, didecyl phthalate, dieicosyl sebacate, the 2-ethylhexyl diester of linoleic acid dimer, and the complex ester formed by reacting 1 mole of sebacic acid with two moles of tetraethylene glycol and 2 moles of 2-ethylhexanoic acid.
Esters useful as synthetic oils also include those made from C5 to C12 monocarboxylic acids and polyols and polyol esters, such as, for example, neopentyl glycol, trimethylolpropane, pentaerythritol, dipentaerythritol and tripentaerythritol.
The additives that may be included in the lubricating oil compositions of the present invention include an effective amount of one or more demulsifiers to inhibit the formation or buildup of emulsions in the dehydrators and other machines that are downstream from the dehydrators. Additives suitable for the present invention may also include one or more of: viscosity index improvers, corrosion inhibitors, oxidation inhibitors, dispersants, lube oil flow improvers, detergents and rust inhibitors, pour point depressants, anti-foaming agents, anti-wear agents, seal swellants, friction modifiers, extreme pressure agents, color stabilizers, wetting agents, bactericides, and additive solubilizers. Some but not all of the suitable additives are described below. Persons skilled in the art will be able to select other additives without undue experimentation.
Using demulsifiers to break water-in-oil emulsions are well known in the art, especially in the arena of crude oil production. It is known that demulsifiers break emulsions of polar solutes like water, and non-polar solvents like oil. They are commonly used in functional fluids (e.g., metal removal fluids, greases, rust and oxidation fluids, hydraulic oils, compressor oils, fuels, and transformer fluids) to inhibit formation of emulsions, break emulsions that have developed, and inhibit corrosion.
In their broadest conception, demulsifiers are made of amphiphilic compounds. See, e.g., Kwetkat et al., U.S. Pat. No. 5,997,610. The hydrophilic portion of a demulsifier may contain formally charged residues such as cationic, anionic, zwiterionic residues, or it may contain uncharged, polarized residues. The hydrophobic portion of a demulsifier may include long alkyl functional groups (>7 carbons), alkyl aryl functional groups, petroleum derivatives, or even polysiloxane functional groups.
The ASTM D-1401 is a standardized test typically used to evaluate the general effectiveness of a compound as a demulsifier. A description of this test may be found in the Annual Book of ASTM Standards, Vol. 05.01, which is incorporated herein by reference. ASTM D-1401 tests the relative speed and extent of demulsification among different demulsifiers. The standard ASTM D-1401 test procedure calls for the mixing of 40 mL of an oil phase and 40 mL of an aqueous phase (typically deionized water), followed by a period of time to allow the phases to separate. The results to ASTM D-1401 are usually expressed in the form O/W/E (T), where the O is the volume of the oil phase, W is the volume of the aqueous phase, E is the volume of the emulsion layer, and T is the time it takes to achieve stable separation of the two phases. The standard test is performed at 54° C. The standard testing conditions, however, are preferably modified to mimic the conditions under which the lubricating oil compositions and the demulsifiers contained therein will function. Specifically, the testing temperature is preferably lowered to about 20 to 27° C., and most preferably to about 24 to 25° C. Moreover, the aqueous solution added to form the test mixture is preferably a brine solution rather than distilled water because the constitution of a brine solution more closely resembles that of the emulsions. Particularly preferably, the proportion of the brine solution is adjusted so that the concentrations of the components in the test mixture mimic those in the actual emulsions.
The demulsifiers of the present invention may be selected from known demulsifiers that are stable and functional under various temperatures. Preferably, the demulsifiers of the present invention demonstrate good performance in the ASTM D-1401 test at the lower, modified testing temperatures, which simulate the actual operating temperatures in the dehydrators. Demulsifiers of the present invention are preferably low-ash, or most preferably ashless, to avoid clogging filters and orifices of the compressors and the engines. Such ashless demulsifiers may be based upon amine sulfonates, amine sulfates, amine phosphates, and amine carboxylates. The demulsifiers are preferably low foaming, with low viscosity and/or have the capacity to inhibit corrosion. An exemplary embodiment of the present invention comprises a polyoxyalkylene glycol as the demulsifier.
The amount of demulsifiers used in the lubricating oil compositions of the present invention may vary substantially. At the minimum, however, the amount of demulsifiers must be sufficient to inhibit or reduce the formation of emulsions in the dehydrators and other downstream components, for example, from about 0.01 to 2.0 wt. %, or preferably from about 0.1 to 1.0 wt. %, based on the total mass of the lubricating oil composition. Exemplary embodiments of the present invention comprise about 0.01 to 1.0 wt. % of demulsifiers, based on the total weight of the lubricating oil composition.
In addition to the demulsifiers, oxidation inhibitors or antioxidants may be added to the lubricating oil compositions of the present invention because they reduce the tendency of base stocks to deteriorate in service, prevent the increase in viscosity, and avoid sludge or varnish deposits on metal surfaces. Such oxidation inhibitors may include one or more of hindered phenols, alkaline earth metal salts of alkylphenolthioesters having preferably C5 to C12 alkyl side chains, calcium nonylphenol sulfide, ashless oil-soluble phenates and sulfurized phenates, phosphosulfurized or sulfurized hydrocarbons, phosphorous esters, metal thiocarbamates, and oil-soluble copper compounds such as those described in U.S. Pat. No. 4,867,890. Phenols that are useful for this purpose include various alkylated phenols, hindered phenols and phenol derivatives such as t-butyl hydroquinone, butylated hydroxyanisole, polybutylated disphenol A, butylated hydroxy toluene, alkylated hydroquinone, 2,5-ditert-aryl hydroquinon 2,6-ditert-butyl-para-cresol, 2,2′-methylenebis(6-tert-butyl-p-cresol); 1,5-naphthalenediol; 4,4′-thiobis(t-tert-butyl-m-cresol); p,p-biphenol; butylated hydroxy toluene; 4,4′-butylidenebis(6-tert-butyl-m-cresol); 4-methoxy-2,6-di-tert-butyl phenol; and the like. Amino antioxidants include aldehyde amines, ketone amines, ketone-diarylamines, alkylated diphenylamines, phenylenediamines and the phenolic amines. An exemplary embodiment of the present invention comprises an overbased, sulfurized calcium phenate and an IRGANOX™ L-135 hindered phenolic propionate ester as antioxidants.
Frictional modifiers may also be included to improve efficiency of the natural gas engines and the compressors. Oil-soluble alkoxylated mono- and di-amines are well known frictional modifiers. The amines may be used as such or in the form of an adduct or reaction product with a boron compound, which may be, for example a boric oxide, boron halide, metaborate, boric acid or a mono-, di or tri-alkyl borate. Among other frictional modifiers, there may be esters formed by reacting carboxylic acids and anhydrides with alkanols. Other conventional friction modifiers generally consist of a polar terminal group (e.g. carboxyl or hydroxyl) covalently bonded to an oleophillic hydrocarbon chain. Esters of carboxylic acids and anhydrides with alkanols have been described in U.S. Pat. No. 4,702,850. Further examples of other conventional friction modifiers, including the often-used organo-metallic molybdenum, have been described by M. Belzer in the Journal of Tribology, Vol. 114, pp. 675-682 (1992), and M. Belzer and S. Jahanmir in Lubrication Science, Vol. 1, pp. 3-26 (1998).
The lubricating oil compositions of the present invention may also comprise a rust or corrosion inhibitor, which may be selected from nonionic polyoxyalkylene polyols and esters thereof, polyoxyalkylene phenols, and anionic alkyl sulfonic acids. Moreover, copper- and lead-bearing corrosion inhibitors may be used, but are typically not required with the formulation of the present invention. Examples of such compounds include thiadiazole polysulfides containing from 5 to 50 carbon atoms, their derivatives and polymers thereof, such as those described in U.S. Pat. Nos. 2,719,125; 2,719,126; and 3,087,932. Other additives, such as the thio and polythio sulfenamides of thiadiazoles described in UK. Patent Specification No. 1,560,830, and benzotriazoles derivatives may also fall within this class of additives. When these compounds are included in the lubricating composition, they are typically present in an amount not exceeding 0.5 wt % active ingredient.
Dispersants are also added to the lubricating oil compositions of the present invention. Preferably, the dispersants are of the ashless variety. Ashless dispersants typically comprise oil-soluble polymeric hydrocarbon backbones with attached functional groups that are capable of associating with the particles to be dispersed. The functional groups may be, for example, amines, alcohols, amides, and ester polar moieties, and they are attached to the polymer backbones via bridging groups. Suitable ashless dispersants may be, for example, selected from oil-soluble salts, esters, amino-esters, amides, imides, and oxazolines of long-chain hydrocarbon-substituted mono- and dicarboxylic acids or their anhydrides; thiocarboxylate derivatives of long-chain hydrocarbons; long-chain aliphatic hydrocarbons having a polyamine attached directly thereto; and Mannich condensation products formed by condensing long-chain substituted phenols with formaldehydes and polyalkylene polyamines. An exemplary embodiment of the present invention employs a bissuccinimide ashless dispersant.
Viscosity index modifiers may also be added to the lubricating oil compositions of the present invention. These additives impart high- and low-temperature operability to lubricating oils. They may be the sole-function type or may be multifunctional. Suitable viscosity modifiers include, for example, polyisobutylene, copolymers of ethylene and propylene and higher alpha-olefins, polymethacrylates, polyalkylmethacrylates, methacrylate copolymers, copolymers of an unsaturated dicarboxylic acid and a vinyl compound, inter polymers of styrene and acrylic esters, and partially hydrogenated copolymers of styrene/isoprene, styrene/butadiene, and isoprene/butadiene, as well as the partially hydrogenated homopolymers of butadiene and isoprene and isoprene/divinylbenzene.
Metal-containing or ash-forming detergents function both as detergents to reduce or remove deposits and as acid neutralizers or rust inhibitors. Detergents generally comprise a polar head with long hydrophobic tail, with the polar head comprising a metal salt of an acid organic compound. The salts may contain a substantially stoichiometric amount of the metal in which they are usually described as normal or neutral salts, and would typically have a total base number (TBN), as may be measured by standard detergency tests such as ASTM D-2896. It is possible to include large amounts of a metal base by reacting an excess of a metal compound such as an oxide or hydroxide with an acid gas such as carbon dioxide. The resulting overbased detergent comprises neutralized detergent as the outer layer of a metal base (e.g., carbonate) micelle. Such overbased detergents may have a TBN of 150 or greater, and typically from 250 to 450 or more.
Suitable detergents include oil-soluble neutral and overbased sulfonates, phenates, sulfurized phenates, thiophosphonates, salicylates, naphthenates, and other oil-soluble carboxylates of a metal, particularly the alkali or alkaline earth metals. The most commonly used metals are calcium and magnesium sometimes also mixed with sodium, which may all be present in certain detergents. Particularly suitable metal detergents are neutral and overbased calcium sulfonates having TBN of from 20 to 450 TBN, and neutral and overbased calcium phenates and sulfurized phenates having TBN of from 50 to 450. An exemplary embodiment of the present invention comprises an overbased sulfurized calcium phenate with a TBN of about 120, as well as a low overbased sulfonate with TBN of about 20.
Pour point depressants, otherwise known as lube oil flow improvers, lower the minimum temperature at which the fluid will flow or can be poured. Such additives are well known. Examples of those additives include C8 to C18 dialkyl fumarate/vinyl acetate copolymers, polyalkylmethacrylates, and the like.
Dihydrocarbyl dithiophosphate metal salts are conventionally used as anti-wear and antioxidant agents. The zinc salts are the most commonly used in lubricating oil in amounts of 0.1 to 10, preferably 0.2 to 2 wt. %, based upon the total weight of the lubricating oil composition. An exemplary embodiment of the present invention comprises about 4.5 mM zinc (II) bis(O,O′-di(2-ethyl-1-hexyl)dithiophosphate) as an antiwear agent.
Foam control can be provided by many compounds including an antifoamant of the polysiloxane type, for example, silicone oil or polydimethyl siloxyane. An exemplary embodiment of the present invention comprises about 5 ppm of a silicon-based foam inhibitor in the lubricating oil composition.
Some of the above-mentioned additives can provide a multiplicity of effects. Thus for example, a single additive may act as a dispersant as well as an oxidation inhibitor. Multi-functional additives are well known in the art.
The lubricating compositions of the present invention are formulated by known methods. The formulating is typically carried out continuously at the additive manufacturing plant or blend facility. Alternatively, the compositions can be formulated in a semi-works by hand. The components of the additive composition are weighed individually on a scale and added to an amount of base oil in a steam-jacketed stainless steel kettle at or above ambient temperature, with stirring. When a homogeneous mixture is achieved, the base lubricating is added gradually, with continuous stirring. The result if the final lubricating oil composition, which is then packaged and shipped to point of use. At the point of use, the gas engine or the crankcase of a gas compressor is drained and then refilled with the lubricating oil composition of the invention.
Often all the additives, except for the viscosity modifier, are blended into a concentrate or additive package that is subsequently blended into base stock to make finished lubricant. Use of such concentrates is conventional and well known. The concentrates are formulated to contain the additives in proper amounts so as to provide the desired concentration in the final formulation when the concentrate is combined with a predetermined amount of base oils. The concentrate is preferably made in accordance with the method described in U.S. Pat. No. 4,938,880.
The present invention provides a method of inhibiting the formation of emulsions in a natural gas dehydrator and other downstream field processing machines by lubricating the compressors and the engines powering the compressors with a lubricating oil composition comprising:
The lubricating oil composition may also comprise one or more suitable additives selected from: a friction modifier, a viscosity index improver, a foam inhibitor, a rust/corrosion inhibitor, a pour point depressant, and the like.
The term “inhibiting the formation of emulsions” means reducing the level of emulsions or completely eliminating the formation of emulsions in certain machine compartments and vessels.
The invention will be further understood by referencing the following examples, which are not to be construed as limitative of its scope.
The following examples are provided to illustrate the present invention without limiting it. While the present invention has been described with reference to specific embodiments, this application is intended to encompass those various changes and substitutions that may be made by those skilled in the art without departing from the spirit and scope of the appended claims.
Oils A and B were prepared and tested for demulsing capabilities according to the modified, lower-temperature version of a standard ASTM D-1401 test. The components of Oils A and B are listed in Tables 1 and 2, respectively:
1See Table 3
Oil A concentrate has a sulfated ash content of less than 8.5 wt. % (0.51 wt. % in finished oil), a phosphorus content of about 0.46 wt. % (0.013 wt. % in finished oil), a sulfur content of about 1.76 wt. % (0.11 wt. % in finished oil), and a TBN of about 49 to 56. Various amounts of demulsifiers were added to Oil A, and corresponding amounts of diluent oil (to the concentrate) and base oil (to the finished oil) were also added to the mixture to bring the total amount of the lubricating oil compositions to 100 wt. %.
2See Tables 3, 4, and 5
Oil B concentrate has a sulfated ash content of about 6.4 wt. % (0.51 wt. % in finished oil), a phosphorus content of about 0.352 wt. % (0.03 wt. % in finished oil), and sulfur content of about 2.609 to 3.125 wt. % (0.21 to 0.25 wt. % in finished oil), preferably of about 2.867 wt. % (0.23 wt. % in finished oil), and a TBN of about 56. Various amounts of demulsfifiers were added to Oil B, and corresponding amounts of diluent oil (to the concentrate) and base oil (to the finished oil) were also added to being the total amount of the lubricating oil compositions to 100 wt. %.
The demulsibility tests were performed at 24° C. with one part of 40 ml of distilled water and another part of 40 ml of the oil samples. The oil and water mixtures were stirred at 1,500 rpm. The levels or amounts of emulsion were reported at 5 minute intervals for 30 minutes.
The results of the demulsibility tests are summarized in Table 3:
Oil B was used in this example. Compared to Example 1 above, an inlet brine solution rather than distilled water was mixed with the oil samples before testing. The brine solution was employed to simulate the actual components of the emulsions in the dehydrators. Equal volumes of the brine solution and the oil samples were mixed. The time to stable phase separation was also recorded. The results are summarized in Table 4.
Oil B was used in this example. Compared to Example 2 above, rather than using equal volumes of brine solution and oil, a 70-ml brine solution and a 10-ml oil sample were mixed to more closely simulate the typical brine-compressor oil concentrations in the dehydrators and other downstream components. The results are summarized in Table 5:
