WO2005024096A1

WO2005024096A1 - Method and composition for cleaning metals

Info

Publication number: WO2005024096A1
Application number: PCT/GB2004/003816
Authority: WO
Inventors: Paul Lambart; Satinder Singh Chagar; Thomas Ivor Jones
Original assignee: R-MC POWER RECOVERY Ltd
Current assignee: R-MC POWER RECOVERY Ltd
Priority date: 2003-09-08
Filing date: 2004-09-07
Publication date: 2005-03-17
Anticipated expiration: 2006-03-08
Also published as: GB0320981D0; GB0607083D0; GB2421736A; GB2405639A; GB2421736B

Abstract

Metal cleaning compositions and their uses, for example for the cleaning of engines (especially on-line cleaning of gas turbines and turbo chargers). The compositions may comprise at least one surfactant selected from non-ionic and amphoteric surfactants; at least one terpene solvent; and at least one glycol. The compositions preferably include tar acid.

Description

METHOD AND COMPOSITION FOR CLEANING METALS

The present invention relates to metal cleaning compositions (for example, for cleaning steel and its alloys such as aluminium alloys, titanium alloys etc.) and to their use for the cleaning of engines (especially gas turbines and turbo chargers) . For gas turbine and turbo chargers, the composition according to the invention may be injected as a spray or aerosol into the air-flow system of the running turbine or engine/turbo charger ("on-line cleaning") ; the composition may be inserted while the turbine or engine/turbo charger is in idle mode ("off-line cleaning") .

Cleaning compositions for use in on-line cleaning of engines, running compressors and turbo chargers have to be both effective cleaners and stable at the high temperatures at which they are required to function. In use, removal of the soil from the blades of the compressor or turbo charger is achieved by penetration and dispersion of the soil by the cleaning composition. The dispersed soil may then be rinsed off by, for example, a liquid flush, which may also be performed while the engine is running. Thus, with on-line cleaning, the cleaner and the soil are likely to pass into the combustion side of the running engine, which is at high temperature. For this reason, the manufacturers of turbochargers and gas turbines have strict rules covering the use of cleaning chemicals, in order to limit the amount of material (s) which may have a detrimental effect on the engine or engine components . Some of the most obvious compounds for cleaning metals, such as caustics and ionic surfactants (for example, halides and alkali metals), are prohibited because they are reactive at the temperatures encountered in the hotter sections of the engine, and may react with engine component (s) resulting in damage such as "hot end corrosion".

^'There is a need for an engine, turbine and turbocharger cleaning composition which is effective for on-line (and/or off-line) use and which does not initiate or cause damage to the engine (e.g. does not corrode the engine in use). There is a need for a cleaning composition with, for example, a level of alkali metal content (combined Na/K level) no greater than 50 ppm (parts per million) , which satisfies the requirements of the original equipment manufacturers (OEMs) , and is effective as an engine, turbine and turbocharger cleaning composition.

The metal cleaning composition according to the invention comprises at least one surfactant selected from non-ionic and amphoteric surfactants; at least one terpene solvent and at least one glycol . Preferred compositions further comprise tar acid and/or inhibitor. The invention also provides a method of cleaning an engine which comprises spraying a composition of the invention into the air-flow system of a running engine, and optionally rinsing by spraying a second composition into the running engine. The invention may permit reduction of operational costs of e.g. gas turbines by the in service (off-line) removal of efficiency reducing deposits, and/or by the reduction of the need for, and/or frequency of, full shut downs for cleaning purposes. The metal cleaning compositions of the invention may be suitable for use for cleaning engines where the soil is carried through into the combustion area. The compositions of the invention may be formulated so that they are acceptable within the restrictions imposed by the engine manufacturers, for example they may have low alkali metal content .

Preferred compositions have a level of alkali metal content (combined Na/K level) which is no greater than 50 ppm (parts per million) .

The surfactant is a main cleaning and dispersing component. It may also aid wetting of the metal surface to be cleaned (by the composition) by changing the surface tension of the e.g. fluid/spray droplets of the composition.

Thermal stability is an important and preferred property of the surfactant, e.g. for temperatures of up to 300°C which can be achieved within a turbine or engine. The absence of highly active substituent groups such as halides, sulfates and sulfonates is also important and preferred since these encourage erosion at high temperatures. The presence of amino or amide groups in the surfactant can actively prevent corrosion of the metal surfaces being cleaned. Preferably the surfactant is a non-ionic surfactant. A preferred class of surfactants comprises the ethoxylated amines and ethoxylated amides, for example ethoxylated cocoamine, Ethylan TC-fatty amide, Ethylan TM-fatty amide, and Imbentin- cocodiethanolamide . Other suitable nonionic and amphoteric surfactants include alkylglucosides, alcohol ethoxylates, the betaines, glycines and polyethoxylated alkyl ethers and their derivatives .

Preferred ethoxylated amines for use as or in the surfactant for the composition of the present invention are of the formula

(CH₂CH₂0)_xH I N-R I (CH₂CH₂0)_γH wherein R is an alkyl group having 6 to 20, preferably 12-18 carbon atoms, and x and y are integers whose sum ranges from 2 to 50, preferably from 8 to 20, most suitably from 14 to 16. Preferred ethoxylated amides for this purpose are of the same formula but with 0 I II N-R replaced by N - C - R. Suitable ethoxylated amines for use as or in the surfactant in the present invention may be obtained from a large number of commercial suppliers. For example, there may be utilized ethoxylated amines/amides manufactured by Croda Chemicals Ltd. of North Humberside, England under the trademark "Crodamets"; or by Lankro Chemicals Ltd of Manchester, England under the trademark "Ethylan" - e.g. "Ethylan TC" "Ethylan TLM" and "Ethylan TT-15"; or by Libra Chemicals Ltd of Manchester, England under the trademark "V- Cam 150". Rohm and Haas Company of Philadelphia PA markets surfactants of this category under the trademark "Triton RW", "Triton RW-100" being particularly suitable. Also suitable are surfactants sold under the trademark "Ethomeen", in particular "Ethomeen C-25", manufactured by Armour and Co., Chemical Division of Chicago. Ethomeen C-25 contains 15 mols of ethylene oxide on average . The fatty acid component of the Ethomeen is a mixture of C₈ through Cie acids having approximately 50% by weight of lauryl (Cι₂) residue and approximately 20% by weight of myristyl (Cχ₄) residue. A particularly preferred surfactant comprises ethoxylated cocoamine which with its appropriate chain length, and preferably with 15 mole ethoxylation (i.e. x + y = 15 in the above formula), can optimise cleaning performance.

The terpene solvent aids in the dissolution of deposits/soil on the metal surface to be cleaned (e.g., a turbine blade) ; the deposit/soil may become at least partially dissolved so that it may be subsequently rinsed away. The terpene solvent may suitably be a citrus terpene solvent. A preferred terpene solvent is l-methyl-4- (1- methylethyl) cyclohexene, known as limonene. A particularly preferred terpene solvent is d-limonene. Suitable d-limonene for use in the invention is available from J & W hewell Limited of the UK.

The glycol (or glycols) acts as a high temperature carrier. It is stable and able to remain liquid at high temperatures so as to keep the remainder of the ingredients of the composition in solution for longer. This allows the composition to clean in the high temperature environments encountered in engines/turbines. The glycol component may have anti-freeze properties which are beneficial for storage in cold climates. The glycol component may also have surfactant properties to assist in cleaning and dispersion, and it may also dissolve organic soils. Suitable glycols for use in the composition according to the invention are mono-, di-, and tri-propylene glycol and polyethylene glycol. Other suitable glycols include for example monoethylene glycol and polyhexylene glycol. A preferred glycol is butyl diglycol. Preferred glycols (such as butyl diglycol) aid the solubilization of the soil/deposits on the metal surface. Preferred glycols (such as butyl diglycol) increase the flash point of the terpene solvent in the composition. The use of solvents such as terpene solvents may have a number of associated health and safety issues (due to the possibly low flash points and flammability classifications) ; preferred components of the composition according to the invention, for example butyl diglycol, may be chosen so that the flashpoint of the composition as a whole is greater than 65°C (so the composition is classified as non-flammable) . Butyl diglycol also has useful biodegradeability properties.

Preferred compositions may also include at least one tar acid. The tar acid in the composition is able to penetrate and disperse carbon deposits. Tar acids generally have boiling points in the range of 230-280°C. They are generally derived from the middle oil range in the distillation of coal tar by reaction with caustic soda solution, removal from the tar fraction, followed by purification recovery from the aqueous solution by acidification. These tar acids are usually a complex mixture of diethyl phenols/methyl substituted dihydric phenols/propyl and butyl phenols/indenols/naphthols and tetralols. All are suitable for use in the invention, either alone or in combination. A preferred tar acid component for use in the invention is cresylic acid. Other tar acid components which are suitable (either alone or in combination) are phenol, o-cresol, m,p- cresol, 2-6-xylenol, o-ethylphenol, m-p- ethylphenol, 3,5- xylenol, o-isopropylphenol, m,p-isopropylphenol, trimethylphenol, 2-ethyl-4-methylphenol, o-propylphenol, methylethylphenol, 4-indanol, 5 indanol .

The composition according to the invention preferably includes at least one inhibitor - to inhibit metal corrosion and/or scale. The inhibitor suitably comprises at least one compound selected from organopolyphosphonic acids and/or at least one compound selected from dialkylamides of long chain unsaturated fatty acids .

The organopolyphosphonic acids are of formula RfP(OH) 0 _n where R is an n-valent organic moiety. R could for example be the divalent group 1-hydroxylethylidene, giving 1-hydroxyethylidene (1, 1-diphosphonic acid), compound (1) of the following formula

OH OH OH

or it could be the trivalent group trimethyleneamino, giving amino tri (methylenephosphonic acid), compound (2) of the following

0 Other di-, tri- and higher valent organic moieties R are possible, having correspondingly 2, 3, or more phosphonic acid groups attached thereto. A currently preferred organopoly-phosphonic acid inhibitor for use in the invention contains equal or nearly equal volumes of compounds (1) and (2) above. Suitable organo-polyphosphonic acid inhibitors for use in the invention are available from the company Solutia of Ghent, Belgium under the trade name DEQUEST. Amongst the DEQUEST products available, DEQUEST 2000 is an aqueous solution of compound (1) above and DEQUEST 2010 is an aqueous solution of compound (2) above/ these solutions can for example be combined in appropriate proportions to give a mixture containing about equal volumes of compounds (1) and (2) above. The organopolyphosphonic acids are useful as inhibitors in compositions for cleaning cast iron internal combustion engines.

Amongst the dialkylamide inhibitor compounds, the dimethylamide compounds are preferred. The hydrocarbon chain of the long chain unsaturated fatty acid is for example of 14 to 20 carbon atoms and a Cχ₇ hydrocarbon chain is one which is particularly suitable. Preferably the hydrocarbon chain has one or two sites of unsaturation. Mixtures of two or more dialkylamide inhibitors may be used. Preferred compounds for use according to the invention are N, N-dirnethyloleamide, compound (3) of the following formula

CH₃ - (CHi)/ - CH3 N

CH3 .1 (CHl)7 CH = CH

and N, N-dimethyllinoleamide, compound (4) of the following formula

CH. N - 5- ₍CHz - CH = CH - CH₂ - CH = CH - (CH₂ ⁾< - CH₃

( 4 )

Compounds (3) and (4 ) may be employed in admixture in approximately equal amounts by volume - e.g. in a volume ratio of 10 to 9. A suitable dialkylamide inhibitor for use in the invention is available under the trade name DMAD from Buckman Laboratories Limited of London; DMAD is a dimethylamide mixture consisting mainly of compounds (3) and (4) above in a volume ratio of about 10 to 9, together with a small amount (e.g. about 5%) of amides of saturated fatty acids. Compositions according to the invention containing dialkylamide inhibitor are particularly useful for cleaning engines and turbines containing aluminium components .

Preferred compositions have a flash point greater than 65°C. Herein the amounts and proportions of components in the cleaning composition of the present invention are expressed as parts and percentage by volume. The composition according to the invention suitably includes, by volume, from to 5 to 15 parts of the surfactant. The composition suitably includes, by volume, from 40 to 70 parts of glycol. The composition suitably includes, by volume, from 0 to 3 parts, preferably 0.05 to 3 parts, of tar acid. The composition suitably includes from 20 to 40 parts terpene solvent. The composition suitably includes from 0 to 3 parts of inhibitor.

Preferred compositions include, by volume, from 10 to 15 parts of the surfactant. Preferred compositions include, by volume, less than 60 parts of glycol, more preferably 40 to 58 parts of glycol (preferably butyl diglycol). Preferred compositions include, by volume, from 30 to 40 parts terpene solvent (preferably d-limonene) , preferably more than 35 parts terpene solvent. Particularly preferred compositions include from 40 to 58 parts of glycol (preferably butyl diglycol) and from 30 to 40 parts terpene solvent (preferably d-limonene) . Preferred compositions include from 40 to 50 parts of glycol (preferably butyl diglycol) and from 30 to 40 parts terpene solvent (preferably d-limonene) and over 10 or more parts surfactant. The compositions may include other components (diluents, buffer acids etc.).

The composition may also include a buffer acid, such as one or more of orthophosphoric, phosphonic, glycolic, gluconic, glucoheptonic, acetic or citric acids. The buffer acid is employed to buffer the pH of the composition to the required value, which is usually pH 7 to 9 e. g. pH 8 ± 1. The buffer acid may also act in similar fashion to the tar acid and/or to chelate metal ions from the engine soil, thus assisting the cleaning performance of the composition. A preferred buffer acid is orthophosphoric acid. The composition suitably includes, by volume, from 0 to 3 parts, preferably 0.05 to 3 parts, of buffer acid.

According to the present invention in a further aspect, there is provided the use of a terpene solvent (e.g. d- limonene) for cleaning of engines, or in the manufacture of a composition for cleaning engines. According to the present invention in a still further aspect, there is provided the use of butyl di glycol for cleaning of engines, or in the manufacture of a composition for cleaning engines.

Herein, the term "engine" may be taken to mean any kind of machine that uses energy to develop mechanical power, including

(but not limited to) internal combustion engines and components thereof, diesel engines, turbines such as gas turbines, turbochargers, superchargers, oil refinery equipment or power station equipment etc..

The compositions according to the invention may enable cleaning of engines, for example, gas turbines and other turbo charging equipment that have become so fouled with oily hydrocarbon deposits that they are impossible (or inefficient) to clean using known off- or on-line cleaners and cleaning methods. Thus, the use of compositions according to the invention may increase efficiency by enabling cleaning without taking the equipment out of service for disassembly and manual cleaning using chemicals and hand abrasives. With the introduction of new emission regulations engine manufacturers are now recirculating crank case gases into turbo chargers; this can result in turbo chargers becoming fouled very quickly leading to a significant reduction of efficiency. There is, therefore, increasing need for engine cleaning compositions which may be used without taking the engine out of service.

The cleaning composition according to the invention, injected into the air intake of a running engine (iby methods well known in the art, e.g. a gas turbine, via e.g. spray nozzles) can penetrate and disperse soot, silica, scale and hardened carbonation deposits as well as accumulated deposits of atmospheric salts and dust, sulfur, metallic soil, vanadium oxide and oil and grease residues etc.. The small size of sprayed droplets and the low kinetic energy ensure that there is no damage to moving parts. The composition according to the invention is preferably introduced into the engine while the engine is cool (off-line) . Once injected, the composition is carried into the engine by the airstream where it dissolves and/or breaks down the soil, deposits etc . , to form a fluid/solution/emulsion or suspension which may be retained on the engine parts (e.g. turbine blades) .

The fluid/solution/suspension/emulsion retained on the engine/turbine parts is preferably rinsed away. Preferably, a rinse fluid (off-line or on-line wash fluid) is introduced (through e.g. the same spray nozzles) after a period of time, rinsing away the solvent and/or soil from the engine parts. A preferred rinsing step is an on-line or off-line rinse using a known aqueous surfactant. Preferably the rinse fluid is PowerBack (TM) available from R-MC Power Recovery, of Lincoln, UK.

The compositions according to the invention preferably have no harmful effects on engine components or lubricating oils .

The composition according to the invention is preferably applied as a spray by methods known in the art. Suitable applicators include pump-up sprays, aerosols and spray guns. For example, when using a pump sprayer, one may pump up the sprayer to achieve a gentle flow rate of approximately 0.2 litres per minute by turning down the lance delivery jet until a fine mist spray is obtained. In an alternative method the spray may be released in short bursts. For spray gun application, a gravity fed airgun with opaque cup may be used. The best overall results may be obtained by using 30 psig air pressure and a 1.1 mm paint nozzle to achieve a flow rate of .25 litres per 3 minutes delivery time; 1.2 to 1.3 mm paint nozzles may be used to obtain a faster flow rate.

For aerosol application (e.g. to a turbocharger) a 250 ml aerosol may be used. Continual spraying for 1 minute will dispense the entire contents, or .250 litres.

A preferred aerosol or droplet size is 50 to 300 microns .

The following Examples identify preferred cleaning compositions according to the invention. The percentages are by volume. The components are liquids and are prepared using methods well known in the art. EXAMPLE 1

10% ethoxylated cocoamine (15 mole ethoxylation) (V-Cam 150) (e.g. CAS 61791-14-8) 2% cresylic acid (tar acid component) (e. g. CAS 106-44-5) 30% d-limonene (e.g. CAS 5989-27-5) 57% butyl diglycol (e.g. CAS 112-34-5) 1% trimethylenephosphonic acid (DEQUEST) (e.g. CAS 6419-19- 8) .

EXAMPLE 1A The Example 1A composition is the same as that of Example 1 except that it substitutes 1% of a 10-9 v/v mixture of N, N-dimethyloleamide and N,N-dimethyllinoleamide for the trimethylenephosphonic acid.

The compositions of Examples 1 and 1A, together with additional Examples 3 to 8 are shown in the attached Table 1. Table 1 also includes the results of penetration and wetting tests, as discussed below.

Table 1

Example 9: Penetration and wetting tests

Examples 1, 1A and 3 to 8 were tested as follows

Example 9A Penetration: To Measure the Penetration Effectiveness Of Cleaning Fluids

A mild steel plate (100 x 100 mm x 0.91mm) is freshly burnished. The plate is degreased with a suitable hydrocarbon solvent, rinsed in an acetone solution mixture and dried in an oven 0 105+/- 2°C for 30 minutes. The plate is then cooled to room temperature in a dessicator. The plate is coated evenly with R-MC Oildag treatment Solution, and then dried in an oven @200°C for 24 hours, then cooled to room temperature in a dessicator. One end of the plate is elevated to 45 ° with the other end resting on a flat surface, and, with a pipette, 3 x 1ml of fluid is placed on top of the raised plate. The plate is allowed to stand for 60 minutes, washed gently with demineralised water using a wash bottle, and dried in an oven Q 105+/- 2°C for 30 minutes. The plate is cooled to room temperature in a dessicator. A clear acetate sheet, with a pre-printed grid 100 equally sized boxes (the gridlines must be <0.5mm thick) is placed over the plate, and the number of boxes that the fluid has entered is noted.

For the box to count the fluid must cross over the line. Each box represents 1%, thus 10 boxes = 10% penetration, 50 boxes = 50%, 70 boxes = 70%etc.

It can be seen that all the Example compositions provide some penetration of soil. Example 1, 1A, 4, 6 provide excellent penetration of soil (40% or over).

Example 9B Wetting: To Measure the of Wetting Effectiveness Of Cleaning Fluids

A mild steel plate (100 x 100 mm x 0.91mm) is freshly burnished. The plate is degreased with a suitable hydrocarbon solvent, rinsed in an acetone solution mixture and dried in an oven @ 105+/- 2°C for 30 minutes. The plate is then cooled to room temperature in a dessicator. The plate is coated evenly with R-MC Oildag treatment Solution, and then dried in an oven @200°C for 24 hours, then cooled to room temperature in a dessicator. 3 x 1ml of fluid is placed in the middle of the plate with a pipette and the plate is allowed to stand for 5 minutes. A clear acetate sheet, with pre-printed concentric circles covering its surface area, is used for the measurement. The distance between each pre-printed circle line must be 10mm; there will be a total of 5 circles; the lines must be <0.5mm thick. The acetate sheet is placed over the plate and the number of circles that the fluid has entered is noted. For the circle to be counted, the fluid must cross over the line. Each circle represents 20% coverage, thus : 1 circle = 20% wetting; 2 circles = 40% wetting; 4 circles = 80% wetting etc..

It can be seen that all the Example compositions provide some wetting. Example 1, 1A, 4, 6, 7 and 8 provide excellent wetting (35% or over) .

The above, and other, test work has found the compositions such as Examples 1, 1A, 4, 6, 7 and 8 etc. are most effective against oily deposits which have been baked on to turbine blades for a number of hours. Thus, compositions according to the invention may enable removal of oily hydrocarbon deposits from engine/turbine parts when injected into an engine or turbine, e.g. by the methods described above .

Claims

C A I M S :

1. A metal cleaning composition comprising at least one surfactant selected from non-ionic and amphoteric surfactants; at least one terpene solvent; and at least one glycol .

2. A composition according to claim 1 which further comprises a tar acid.

3. A composition according to claim 1 or 2 which further comprises an inhibitor.

4. A composition according to any preceding claim wherein the surfactant comprises one or more of an ethoxylated amine, an ethoxylated amide, an alkyl glucoside and an alcohol ethoxylate .

5. A composition according to any preceding claim wherein the terpene solvent comprises a citrus terpene solvent.

6. A composition according to any preceding claim wherein the terpene solvent comprises d-limonene.

7. A composition according to any preceding claim wherein the glycol comprises butyl diglycol.

8. A composition according to any preceding claim which further comprises a buffer acid.

9. A composition according to any of claims 2 to 7 in which the inhibitor is a buffer acid.

10. A composition according to any preceding claim for use in cleaning one or more components of an engine.

11. A method of cleaning an engine which comprises adding a composition according to any preceding claim into the airflow system of a running engine.

12. A method according to claim 10 which comprises a step of rinsing by adding a rinsing composition into the running engine .

13. A metal cleaning composition substantially as hereinbefore described with reference to the Examples.

14. A metal cleaning composition according to any of claims 1 to 10 or 13 which has an alkali metal content which is no greater than 50 ppm.

15. The use of a terpene solvent for cleaning of engines, or in the manufacture of a composition for cleaning engines.

16. The use of butyl di glycol for cleaning of engines, or in the manufacture of a composition for cleaning engines.