Specialist tank cleaning composition

Abstract

A composition suitable for cleaning tanks, in particular those with hydrocarbon pollutamts comprises i) an alkyl sulphate or alkyl benzene sulphonate anionic surfactant, ii) an alky polyglucoside noni

Description

The present invention relates to a specialist detergent composition for the removal and recovery of oil-based materials, such as used in tank cleaning and component degreasing. Background Detergent compositions for the removal of oil-based materials are well established and many formulations are available tailored to different end uses, such as dictated by the form of the oil-based material to be removed, the method of removal, the placement where removal needs to take place and so forth. There is an ongoing need to provide specialist and effective compositions as to improve efficiency and reduce waste. US3535160A discloses a hydrocarbon tank washing composition comprising a solvent and chlorinated hydrocarbon. US20210261889A1 provides a solvent composition for removing petroleum residue from a substrate and methods of use thereof. Non-solvent General detergent composition may also be used but it is likely that these are less than optimal. Specific reasons are that many compositions create high levels of foam and this is difficult to pump out of a tank being cleaned at any volume, whereas the absence of foam reduces the available contact area for cleaning, such as by emulsification. There is therefore a balance to be made between these features. In addition, it is also desirable that the compositions have reduced environmental impact. In particular tank cleaning compositions often comprise solvents. Similarly, general detergent compositions are typically configured such that the incoming detergent composition is intended to remove as much of the soil, residue et cetera as possible and take it away with the composition for subsequent disposal, such as in water treatment. This is also suboptimal as it displaces the environmental burden to another place. There is therefore the need for an improved tank cleaning composition, such as for the cleaning of tanks containing oil-based compositions. For example, a tank which is used for containing diesel fuel may require cleaning prior to repair or internal inspection and detergent compositions to address this are desirable. Tank cleaning compositions The present invention The present invention in its various aspects is as set out in the appended claims. The present invention provides a tank cleaning composition for the removal of hydrocarbons from a storage tank, the cleaning composition comprising: a. an alkyl sulphate anionic surfactant and an: b. an alkyl polyglucoside nonionic surfactant; c. an alkyl sorbitan nonionic surfactant; and d. water. The cleaning composition of the present invention preferably consists of the above components A, B, C in an amount of not less than 95 parts out of 100, preferably not less than 98 parts as active components. The remainder of the active components to 100 parts of active components comprising optional minor components, such as antifoams, colourants, preservatives. The composition also comprises water d., considered as a non-active component) in various levels for ease of use, transportation etc. to provide 100% by weight. For example, at 3% active components then composition would comprise The remaining 97% represents 3233.33 parts of water. Examples herein assume no minor components unless otherwise specified The detergent composition of the present invention, in many applications may not be considered an advantageous detergent composition as it is relatively medium foaming. This is generally not desirable for many detergent products such as domestic products. The composition also has low foam stability, so that what form is generated does not persist and the foam rapidly collapses. However, in the present invention this is beneficial as the purpose of the foam is not for aesthetics but to produce a higher surface area and lower density whilst the cleaning composition of impinges upon a surface, such as a vertical surface and produces sufficient form in that high shear environment. However, subsequently low foam stability is beneficial as mechanical pumping of spent cleaning composition, typically in the form of an emulsion with hydrocarbon which has been cleaned, such as from a storage tank, is facilitated due to reduced occlusion air. Low foam levels are also beneficial in any subsequent separation of a broken emulsion. Further, the composition of the present invention is optimised so as to have low emulsion stability with typical hydrocarbons. Typical hydrocarbons for the purposes of the present invention are C8 to C 22 hydrocarbons. Again, emulsion stability is normally considered undesirable for detergent compositions. However, the cleaning composition of the present invention is primarily intended for use in industrial cleaning in conjunction with a subsequent separation phase in which emulsified hydrocarbon emulsion is assisted in, or at least allowed to collapse and hydrocarbon separates from the cleaning composition. This then allows the cleaning composition to be reused in the hydrocarbon to be recovered. This greatly improves the environmental profile of the product as less waste is created. The cleaning composition of the present invention is primarily directed towards tank cleaning but may be equally effective in oil spills or other situations where a notable hydrocarbon content is present. Anionic In the present invention the anionic is preferably a C8 to C18 alkyl sulphate. The anionic may be a C8; C10; C12 (Dodecyl); C14 (Tetradecyl); C16 (Hexadecyl or Cetyl); C18 (Octadecyl or Stearyl) alkyl. Preferably the anionic is a C10 to C16 alkyl sulphate. In the present invention the generation of foam is preferably limited or avoided. In this respect at first you the use of C8 and C 10 alkyl sulphate would be counterintuitive as these are high forming, however they have low foam stability and in between antifoam generation and impinging upon a surface to be cleaned the composition may effectively de-foam. The mid-range C 12 to C14 alkyl compositions are less preferred as they are foaming and provide relatively stable foams. The higher alkyl C16 and C 18 can also be preferable in some situations as they are lower forming even if the foam is relatively stable. These are preferable where the application of the composition to a surface to be cleaned involves relatively little physical agitation to enable the entrainment of air. This is particularly useful when air entrainment in the pressurised spray of the composition in any method of use is not actively present. Preferably the alkyl sulphate is one or more of; Sodium lauryl sulphate (C12); Sodium myristyl sulphate (C14); Sodium cetyl sulphate (C16); Sodium stearyl sulphate (C18); Ammonium lauryl sulphate (C12); Potassium lauryl sulphate (C12); Sodium lauryl ether sulphate (C12, with ethoxylation); Sodium oleyl sulphate (C18:1 unsaturated); Potassium cetyl sulphate (C16); and Sodium palmityl sulphate (C16). Suitable commercial material include: Texapon® K12 (Sodium Lauryl Sulphate); Texapon® K14 (Sodium Myristyl Sulphate); Texapon® K16 (Sodium Cetyl Sulphate); Texapon® K18 (Sodium Stearyl Sulphate); Stepanol® WA (Ammonium Lauryl Sulphate); Texapon® K OS (Potassium Oleyl Sulphate); Empicol® LS (Sodium Lauryl Ether Sulphate); Hostapur® SAS (Sodium Alkyl Sulphate mixtures); and Crodet® SLS (Sodium Lauryl Sulphate). In the present invention the anionic may comprise a C8 unsaturated alkyl sulphate. Texapon 842 UP and Syntapon 0 are suitable commercial materials. The use of a C8 alkyl sulphate facilitates low emulsion stability, which is one reason why short-chain alkyl sulphates are not commonly used in detergent compositions. This is advantageous in the cleaning composition, particularly when used with the method of the present invention. Even without use of the method breaking of the emulsion will take place sufficiently long after the emulsion has been removed from the cleaning situation in a normal situation, such as in a tank that the composition is still effective. In the present invention the anionic comprises a C18 unsaturated alkyl sulphate. The use of an unsaturated alkyl sulphate such as based upon, Oleyl (C18:1) Linoleyl (C18:2) or Linolenyl (C18:3) is preferable. Suitable commercial materials include Stepan Olin Olefin Sulfonate; Clariant Texapon K OS; Croda Tween Oleyl Sulphate. Whilst a mixture of alkyl sulphates may be used it is preferable to use either the C8 or C18 alkyl sulphate composition, i.e. the anionic surfactant may consist of a C8 or a C 18 alkyl sulphate, preferably a C8 alkyl sulphate. The use of unsaturated alkyl sulphate is preferred as this gives rise to a less dense and less stable foam which more readily collapses for use in a subsequent separation phase 4 to recover the cleaning composition from the cleaning site; such as by pumping, preferably low shear pumping. This facilitates emulsion breakdown to provide separate phases so as to enable hydrocarbon recovery. In the present invention the alkyl sulphate is preferably the potassium or trialkylamine salt. Preferably the alkyl sulphate is the potassium or triethyl amine salt, most preferably the triethylamine salt. This reduces foam production for what is otherwise a relatively high foaming alkyl sulphate surfactant. The benefits of this are as previously mentioned. As an alternative to in combination with an alkyl sulphate alkyl benzene sulphonate may be used. The alkyl of the alkyl benzene sulphonate may be linear or branched. A branched alkyl benzene sulphonate is preferred. Specifically, a secondary alkyl, alkyl benzene sulphonate is preferred (i.e. a single branch in the chain). C 10 to C 18 alkyl, alkyl benzene sulphonates are preferred more preferred are C 10 to C 13 alkyl, alkyl benzene sulphonates. Suitable commercial materials are available with the tradenames; Petro® LAS (Stepan Company); Nansa® (BASF I formerly Cognis); Softanol® (Nippon Shokubai); Sulfopon® (BASF); Alconox® LABS (industrial cleaners); Ultra® LABSA (Godrej). A branched chain secondary alkyl, alkyl benzene sulphonate is available under the tradename Biosoft® (Stepan). In the present invention the alkyl sulphate is preferably the potassium or trialkylamine salt. Preferably the alkyl benzene sulphate is the potassium or triethyl amine salt, most preferably the triethylamine salt. This reduces foam production for what is otherwise a relatively high foaming alkyl sulphate surfactant. The benefits of this are as previously mentioned. Nonionic The anionic of the present invention is preferably used in conjunction with a nonionic, this improves hydrocarbon emulsification in conjunction with the anionic which is particularly suitable for suspending solids materials and adhering to services due to its charge. In the present invention the alkyl polyglucoside nonionic surfactant is preferably a C8 to C10 alkyl polyglucoside. In the present invention the degree of polymerisation of the alkyl polyglucoside nonionic surfactant is preferably from 1.0 to 2.2 more preferably the degree of polymerisation of the alkyl polyglucoside nonionic surfactant is preferably from 1.1 to 1.8. This provides improved emulsification in conjunction with the other surfactant components. In the present invention the anionic to nonionic surfactant is preferably present from a 2:1 to a 7:1 weight ratio; more preferably the anionic to nonionic surfactant is present from a 4:1 to a 6:1 weight ratio; most preferably the anionic to nonionic surfactant is preferably present as a 5:1 weight ratio. The composition of the present invention may be wherein the alcohol sorbitan nonionic surfactant is a C 8 to C 18 alkyl sorbitan. The alkyl sorbitan may be C 14 to C 18 as this improves emulsion stability and can therefore provide a more stable product, particularly during storage. Preferably the alkyl sorbitan is a C 10 to C 14 alkyl sorbitan which gives a balance between foaming and stability. In the present invention the alcohol sorbitan nonionic surfactant is preferably a C10 to C14 unsaturated alkyl sorbitan. Further components In the present invention further comprising one or more co-solvent selected from glycols, diols and polyethers. In the present invention co-solvent is preferably a glycol. In the present invention when the glycol is preferably an ethylene glycol or propylene glycol. In the present invention comprising between 10 and 50% by weight water, as a concentrate for dilution before use. Preferably the anionic to nonionic surfactant is present in a 1: 1 to a 10:1 weight ratio. Preferably the weight ratio is 1:3 to 1: 7, most preferably the weight ratio is a 5 : 1 weight ratio. This has been found to maximise heat transfer and minimise foaming. The composition of the present invention may be wherein the degree of polymerisation of the alkyl polyglucoside nonionic surfactant is from 1.1 to 1.8. This has been found to be the most synergistic with the alkyl sulphate in terms of the balance of desirable properties. It is important to note that whilst there is some technical underpinning for the choice of materials the particular blends of materials are themselves important and in particular in conjunction with the intended method of use by application in a pressurised waterjet. The composition of the present invention may include a polymeric thickener. The use of a polymeric thickener reduces the retention time of the cleaning composition upon contacting a surface, such as a surface being cleaned. This is important in terms of pressure washing vertical tank walls as it increased the time of contact in which emulsification can take place. The cleaning composition as applied in the cleaning process, such as after dilution to a concentration of 0.1 to 3% by weight cleaning composition (that is components other than water), preferably has a viscosity of between 20 and 1,000 mPa.s. However, only a small increase in the viscosity can greatly assist and higher viscosities are generally undesirable as they reduce emulsion recovery times. Preferably the viscosity of the cleaning composition is between 20 and 10OPa.s this can be achieved by the addition of the polymeric thickener. Suitable thickeners for use in the concentration range 0.05 to 0.1% are preferably carbomers, otherwise known as cross-linked polyacrylic acid polymers. Suitable preferred examples are Carbopol® Aqua SF-1 Polymer; Carbopol® Aqua SF-2 Polymer; Carbopol® Aqua CC Polymer; Carbopol® 676 Polymer. Other polymeric thickeners include xanthan gum, carboxymethyl cellulose, hydroxy ethyl cellulose or Hydroxypropyl Methylcellulose. The use of these polymeric thickener enables the composition to be more stable upon storage with a reduction in separation of components particularly on long-term storage and freeze thaw stability. Without being bound by theory these specific polymers add beneficial surface associations and viscosity, maximising agent effectiveness. The composition of the present invention preferably comprises between 10 and 50% water, which may preferably be used by further dilution upon spray application, such as to 0.1 and 3% by weight. This level of water represents a concentrated composition particularly suitable for use in dilution upon application. The composition of the present invention may comprise a concentrate for pre-dilution before application with between 51 and 99% water. The composition of the present invention may further comprise an anti-foam. However, it is preferable that an antifoam is not present as the combination of surfactants in the present invention enables a suitable level of unstable foam to be produced such that a high surface area is created by application using a pressurised yet but that the foam relatively rapidly collapses for easy recovery of the resulting emulsion suitable for use in the subsequent separating stage. A significant feature is that antifoams in acting on the air water interface are not typically effective in re-use of a detergent composition, as intended by the present invention and therefore foaming characteristics can change markedly upon re-use. The composition of the present invention may be wherein the antifoam is selected from one or more of Silicone-based Defoamer; Mineral Oil-based Defoamer; Polyether-based Defoamer; Alkylbenzene-based Defoamer; Fatty Acid-based Defoamer; Alcohol-based Defoamer; Silica-based Defoamer; Propylene Glycol-based Defoamer; Organic Ester-based Defoamer; Natural Oil-based Defoamer; Amide-based Defoamer and fluorocarbon particulates. The preferred defoamer is a silicon-based defoamer, such as based upon polydimethylsiloxane. An example of a Silicone-based Defoamer is Polydimethylsiloxane (PDMS), Silicone emulsions. An example of a Mineral Oil-based Defoamer is White mineral oils. An example of a Polyether-based Defoamer is Polyethylene glycol (PEG), Polypropylene glycol (PPG). An example of a Fatty Acid-based Defoamer is Stearic acid, Oleic acid. An example of an Alcohol-based Defoamer is Higher molecular weight alcohol such as octanol and decanol. An example of a Silica-based Defoamer is Hydrophobic silica. An example of an Organic Ester-based Defoamer is Esters of fatty acids. An example of a Natural Oil-based Defoamer is Vegetable oils like soybean oil. An example of an Amide-based Defoamer is an Alkanolamide. Method of use The composition of the present invention is particularly effective when used in a defined method, namely: a method of cleaning a hydrocarbon composition from a surface the method comprising: a. contacting the hydrocarbon composition with the cleaning composition as herein described under pressure so as to entrain air and to emulsify a portion of the hydrocarbon and thereby create an emulsion; b. recovering the emulsion; c. placing the emulsion in a low shear environment to permit breaking of the emulsion and thereby creating at least two liquid layers, one of which being recovered hydrocarbon composition the other being recovered cleaning composition ; d. separating the two recovered compositions; e. recovering at least one of the recovered compositions for further use. In the present invention may comprise the subsequent step of: f. recovering the cleaning composition and re-using it, such as by further contacting it with hydrocarbon composition under pressure so as to entrain air and to emulsify a portion of the hydrocarbon and thereby create an emulsion. In the present invention comprising the precursor step of: a’, entraining air into the cleaning composition to create a foam to impinge, under said pressure, upon a surface in contact with said hydrocarbon composition. This has the advantage that the composition on impinging upon a surface is already foamed as opposed to being entrained upon impinging upon the surface which may mean that foam is distributed elsewhere and not present on the surface at which a waterjet may be aimed. In the present invention the air entrainment is preferably performed using a venturi nozzle. Venturi nozzle has the advantage that both air and detergent may be entrained into a stream of water simultaneously and in proportion as the degree of entrainment is rated to the liquid flow and the consequent pressure drop across the venturi and hence more entrainment gives rise to higher detergent entrainment at consequent higher flow rates. In the present invention said pressure is preferably between 7.0 MPa AND 27 MPa, preferably between 13.0 and 19.0 MPa. It is been found that, in particular in the central range of pressure foam generation and stability is generally optimal, i.e. sufficient foam is generated but there is less splash back to distribute the foam where it may not be required. In the present invention the cleaning composition is preferably diluted before use to comprise between 0.1 and 3% by weight of the cleaning composition, preferably between 0.25 and 1 % by weight of the cleaning composition. These weights relate to the non-water components of the composition as defined herein, i.e. 1 % by weight means 1 % by weight of the relevant surfactants (and any minor components) in the total amount of water in the composition is distributed during a cleaning operation. Compositions the present invention are preferably initially delivered in a concentrated form such as comprising up to 50% water. These are then diluted, such as using the aforementioned Venturi nozzle, into a water stream to create a detergent flow. When the cleaning composition is recycled then the same nozzle can be used to introduce air but without introducing further detergent. In a preferred form of the method between 10 and 20% of the original detergent composition (as measured by surfactant) is subsequently included with recovered cleaning composition as its efficiency is slightly degraded unless emulsion breakdown is complete, which takes some time and hence a quicker turnaround of use, recovery and reuse can take place if a small amount of additional cleaning composition is included in each recirculation. The maximum shear rate of the low shear environment in step c. is preferably less than 550s-1, more preferably less than 200s-1, most preferably less than 100s-1. By providing a low shear environment then the hydrocarbon emulsion more readily breaks, for this specifically designed low stability emulsion composition. Higher recovery rates of hydrocarbon are obtained at the lower shear rates. However, below 50s-1 the rate-limiting step is the ability to recover the hydrocarbon emulsion after step b. when using pumps and pipework of conventional sizes. These formulations are particularly effective at step a. shear rates above 550s-1. Shear rates above 550s-1 effectively stabilise the emulsion. The mechanism is not known; however, it is perhaps a balance between emulsion breakdown versus emulsion creation is mediated by emulsion instability mediated against emulsion creation. Since in a recovery step prior to step c. Some air is inevitably entrained then shear rates above 550s-1 / 500s-1 tend to create undesirable foam and reduce pumping efficiency. In the present invention step c. Preferably comprises passing the emulsion through a coalescing plate separator. The use of such a separator facilitates breakage of the emulsion formed between the cleaning composition and the hydrocarbon and hence faster turnaround of cleaning composition for reuse in the method. Examples The present invention will now be illustrated by means of the compositions shown in table 1. Compositions 1 to 9 are within the scope of the present invention. The further compositions are comparatives and are denoted by the suffix C Table 1 Formulation => 1 2 3 4 5 6 7 8 9 10C Material Trade Alkyl + APG (10:1) Alkyl + APG (1:10) Alkyl + APG (1:1) Alkyl + Sorbitan 10:1 Alkyl + APG + Sorbitan Alkyl + APG + Sorbitan + Salt Alkyl + APG + Sorbitan + Alternate Salt Alkyl + APG + Sorbitan +salt + Antifoam Alkyl + APG + Sorbitan + Alternate salt + Antifoam Tween 20 sodium n-octyl sulphate(C8) Texapon 842 UP 33.4 3.3 16.7 33.4 33.4 33.4 33.4 33.4 33.4 Sorbitan laurate C12 Polyoxyethylene (20) sorbitan monolaurate Surfacare S20 Veg FG Tween 20 1 0.4 0.4 0.4 0.4 0.4 15 Alkyl poly glucoside C8-10 Glucopon 225 DK 1.42 14.2 7.14 0.85 0.85 0.85 0.85 0.85 Ammonium Phosphate - 18 18 Ammonium bicarbonate - 1.5 1.5 Ammonium sulphate - 5 5 Sodium bicarbonate - 1 1 Potassium citrate - 40 40 Potassium bicarbonate - 3.5 3.5 Cetearyl Alcohol (and) Ceteareth-20 Promulgen D 3 3 Preferred Alkyl / APG ratio Inverted Alkyl / APG ratio Altered Alkyl / APG ratio Preferred Alkyl / Sorbitan ratio Preferred Alkyl / Sorbitan / APG ratio -sorbitan / APG blend more effective Preferred Alkyl / Sorbitan / APG ratio + enhancing salt -Salts add additional cooling qualities to the working fluid Preferred Alkyl / Sorbitan / APG ratio + alternative enhancing salt Preferred Alkyl 1 Sorbitan / APG ratio + enhancing salt + Antifoam -Antifoam improves performance of the working fluid Preferred Alkyl 1 Sorbitan / APG ratio + alternative enhancing salt + Antifoam Material only control The above compositions are presented as parts by weight. The compositions are made up to 97% by weight of water before testing. Formulation => 11 12 13 14 15 16 17 18 19 20C Material Trade Alkyl + APG (10:1) Alkyl + APG (1:10) Alkyl + APG (1:1) Alkyl + Sorbitan 10:1 Alkyl + APG + Sorbitan Alkyl + APG + Sorbitan + Salt Alkyl + APG + Sorbitan + Alternate Salt Alkyl + APG + Sorbitan +salt + Antifoam Alkyl + APG + Sorbitan + Alternate salt + Antifoam Tween 20 C12-14 sulphate salts neutralised with Sodium Stepanol WA Extra HA 33.4 3.3 16.7 33.4 33.4 33.4 33.4 33.4 33.4 Sorbitan laurate C12 Surfacare S20 Veg FG 1 0.4 0.4 0.4 0.4 0.4 Polyoxyethylene (20) sorbitan monolaurate Tween 20 15 Alkyl poly glucoside C8-10 Glucopon 225 DK 1.42 14.2 7.14 0.85 0.85 0.85 0.85 0.85 Ammonium Phosphate - 18 18 Ammonium bicarbonate - 1.5 1.5 Ammonium sulphate - 5 5 Sodium bicarbonate - 1 1 Potassium citrate - 40 40 Potassium bicarbonate - 3.5 3.5 Cetearyl Alcohol (and) Ceteareth-20 Promulgen D 3 3 Preferred Alkyl / APG ratio Inverted Alkyl / APG ratio Altered Alkyl / APG ratio Preferred Alkyl / Sorbitan ratio Preferred Alkyl / Sorbitan / APG ratio -sorbitan / APG blend more effective Preferred Alkyl / Sorbitan / APG ratio + enhancing salt -Salts add additional cooling qualities to the working fluid Preferred Alkyl / Sorbitan / APG ratio + alternative enhancing salt Preferred Alkyl 1 Sorbitan / APG ratio + enhancing salt + Antifoam -Antifoam improves performance of the working fluid Preferred Alkyl 1 Sorbitan / APG ratio + alternative enhancing salt + Antifoam Material only control The above compositions are presented as parts by weight. The compositions are made up to 97% by weight of water before testing. Formulation => 21 22 23 24 25 26 27 28 29 30C Material Trade Alkyl + APG (10:1) Alkyl + APG (1:10) Alkyl + APG (1:1) Alkyl + Sorbitan 10:1 Alkyl + APG + Sorbitan Alkyl + APG + Sorbitan + Salt Alkyl + APG + Sorbitan + Alternate Salt Alkyl + APG + Sorbitan +salt + Antifoam Alkyl + APG + Sorbitan + Alternate salt + Antifoam Tween 20 Sodium ethyl hexyl sulphate Sorbitan laurate C12 Primesurf 2EH40 Surfacare S20 Veg FG 33.4 3.3 16.7 33.4 33.4 33.4 33.4 33.4 33.4 1 0.4 0.4 0.4 0.4 0.4 Polyoxyethylene (20) sorbitan monolaurate Tween 20 15 Alkyl poly glucoside C8-10 Glucopon 225 DK 1.42 14.2 7.14 0.85 0.85 0.85 0.85 0.85 Ammonium Phosphate - 18 18 Ammonium bicarbonate - 1.5 1.5 Ammonium sulphate - 5 5 Sodium bicarbonate - 1 1 Potassium citrate - 40 40 Potassium bicarbonate - 3.5 3.5 Cetearyl Alcohol (and) Ceteareth-20 Promulgen D 3 3 Preferred Alkyl / APG ratio Inverted Alkyl / APG ratio Altered Alkyl / APG ratio Preferred Alkyl / Sorbitan ratio Preferred Alkyl / Sorbitan / APG ratio -sorbitan / APG blend more effective Preferred Alkyl / Sorbitan / APG ratio + enhancing salt -Salts add additional cooling qualities to the working fluid Preferred Alkyl / Sorbitan / APG ratio + alternative enhancing salt Preferred Alkyl 1 Sorbitan / APG ratio + enhancing salt + Antifoam -Antifoam improves performance of the working fluid Preferred Alkyl / Sorbitan / APG ratio + alternative enhancing salt + Antifoam Material only control The above compositions are presented as parts by weight. The compositions are made up to 97% by weight of water before testing. 5 Formulation => 31 32 33 34 35 36 37 38 39 40C Material Trade Alkyl + APG (10:1) Alkyl + APG (1:10) Alkyl + APG (1:1) Alkyl + Sorbitan 10:1 Alkyl + APG + Sorbitan Alkyl + APG + Sorbitan + Salt Alkyl + APG + Sorbitan + Alternate Salt Alkyl + APG + Sorbitan +salt + Antifoam Alkyl + APG + Sorbitan + Alternate salt + Antifoam Tween 20 Alkyl benzene sulphonate TEA Salt Stepan Biosoft 411-E / Abeson TEA 33.4 3.3 16.7 33.4 33.4 33.4 33.4 33.4 33.4 Sorbitan laurate C12 Surfacare S20 Veg FG 1 0.4 0.4 0.4 0.4 0.4 Polyoxyethylene (20) sorbitan monolaurate Tween 20 15 Alkyl poly glucoside C8-10 Glucopon 225 DK 1.42 14.2 7.14 0.85 0.85 0.85 0.85 0.85 Ammonium Phosphate - 18 18 Ammonium bicarbonate - 1.5 1.5 Ammonium sulphate - 5 5 Sodium bicarbonate - 1 1 Potassium citrate - 40 40 Potassium bicarbonate - 3.5 3.5 Cetearyl Alcohol (and) Ceteareth-20 Promulgen D 3 3 Preferred Alkyl / APG ratio Inverted Alkyl / APG ratio Altered Alkyl / APG ratio Preferred Alkyl / Sorbitan ratio Preferred Alkyl / Sorbitan / APG ratio -sorbitan / APG blend more effective Preferred Alkyl / Sorbitan / APG ratio + enhancing salt -Salts add additional cooling qualities to the working fluid Preferred Alkyl / Sorbitan / APG ratio + alternative enhancing salt Preferred Alkyl 1 Sorbitan / APG ratio + enhancing salt + Antifoam -Antifoam improves performance of the working fluid Preferred Alkyl / Sorbitan / APG ratio + alternative enhancing salt + Antifoam Material only control Formulation => 41 42 43 44 45 46 47 48 49 50C Material Trade Alkyl + APG (10:1) Alkyl + APG (1:10) Alkyl + APG (1:1) Alkyl + Sorbitan 10:1 Alkyl + APG + Sorbitan Alkyl + APG + Sorbitan + Salt Alkyl + APG + Sorbitan + Alternate Salt Alkyl + APG + Sorbitan +salt + Antifoam Alkyl + APG + Sorbitan + Alternate salt + Antifoam Tween 20 Alkyl benzene sulphonate Sodium Salt Stepan Biosoft 411-E 33.4 3.3 16.7 33.4 33.4 33.4 33.4 33.4 33.4 Sorbitan laurate C12 Surfacare S20 Veg FG 1 0.4 0.4 0.4 0.4 0.4 Polyoxyethylene (20) sorbitan monolaurate Tween 20 15 Alkyl poly glucoside C8-10 Glucopon 225 DK 1.42 14.2 7.14 0.85 0.85 0.85 0.85 0.85 Ammonium Phosphate - 18 18 Ammonium bicarbonate - 1.5 1.5 Ammonium sulphate - 5 5 Sodium bicarbonate - 1 1 Potassium citrate - 40 40 Potassium bicarbonate - 3.5 3.5 Cetearyl Alcohol (and) Ceteareth-20 Promulgen D 3 3 Preferred Alkyl / APG ratio Inverted Alkyl / APG ratio Altered Alkyl / APG ratio Preferred Alkyl / Sorbitan ratio Preferred Alkyl / Sorbitan / APG ratio -sorbitan / APG blend more effective Preferred Alkyl / Sorbitan / APG ratio + enhancing salt -Salts add additional cooling qualities to the working fluid Preferred Alkyl / Sorbitan / APG ratio + alternative enhancing salt Preferred Alkyl 1 Sorbitan / APG ratio + enhancing salt + Antifoam -Antifoam improves performance of the working fluid Preferred Alkyl 1 Sorbitan / APG ratio + alternative enhancing salt + Antifoam Material only control Tween 20, and Kotilen-20) is a polysorbate-type nonionic surfactant formed by the ethoxylation of sorbitan monolaurate. Tests are all scored on a scale of 1 to 5 with the most desirable result, for the purposes of the present invention, being 1 and least desirable 5. Test methodology ASTM D117 Ross Miles foam test (foam test in tables) Formulations at 3% by weight of active components were made up with water and the test carried out as in the standard ASTM D117. This is scored into our system by means of foam height, with 1 being the lowest foam volume observed and 5 being the greatest In summary, in the scoring system 1 has the Lowest foam volume, 5 has the highest foam volume. 1 being the most desirable. Foam Breakage A relative score for the rate at which the foam reduces in volume. This uses the Ross Miles foam result and meaures the half-life to decay to half foam volume. Emulsification light absorbance test (Emulsification test in tables) Each formulation is formulation added to water at 3% by weight of active components to make up 100ml of test solution agitated in a vortex mixer for 1 minute with 24ml of 99.99% n-heptane. The emulsion is then characterised by looking at the change in backscattering of light over time using a Turbiscan TLAB spectrometer. This method can characterise; droplet size, migration velocity and emulsion stability globally and in a targeted area. In summary, in the scoring system 1 has the best emulsification, 5 has the lowest emulsification. HTC estimate This is the relative heat transfer coefficient as a surrogate for how effectively a waterjet impinging upon a surface retains heat in the liquid rather than displacing it to the surroundings. Retained heat provides an increase in the water temperature and improved emulsification. Hydrocarbon recovery test The aqueous cleaning composition as a surfactant weight inclusion level of 1% of active components is mixed with diesel fuel hydrocarbon, and a high agitation using an Ultra-turrax bench scale mixer for five seconds. The emulsion layer is then removed. The foam is allowed to collapse and the emulsion allowed to break. The amount of hydrocarbon recovered and the half-life, by volume of the foam breakage time measured. The two components tests are scored from 1 to 5. 1 being the fastest foam breakage and most hydrocarbon recovered and 5 the slowest foam breakage and lowest volume of hydrocarbon recovered, respectively. This is a pass or fail with a pass being a score of <3 for both tests. Heptane Foam test Requirements; 100ml beaker; 1000 ml measuring cylinder; 25ml graduated pipette and filler; 100ml test liquid; 24ml 99% n-Heptane; Magnetic stirrer Method for 3% use concentration Take test Products : for each. Make up 100ml of 3% test solution 2. Face labels on beaker away 3. Add 24 ml n-Heptane beaker (Take image before stirring) 4. Turn on stirrer to % (marked on unit) for 60 seconds 5. Control has colour change to solid milky and very faint odour - 6. Check sample and again after 3 mins 7. Pour into 1000ml measuring cylinder 8. Shake 10 times and document foam height - control @ 150 Emulsion stability This is a relative measure of the time at which a clear layer of separated hexane starts to form by observation in the measuring cylinder. Hydrocarbon Recovered This is a relative measure of the total amount of heptane clear layer that separates by observation in the minute measuring cylinder. In summary, in the scoring system 1 has the best emulsification shown by solid milky aspect and a foam height equal to or less than 150ml, 5 has the lowest emulsification shown by a lack of solid milky aspect and a foam height equal to or greater than 700ml. 5 For the purposes of this test 1 is the most desirable, 5 the least Formulation => 1 2 3 4 5 6 7 8 9 10 C 11 12 13 14 15 16 17 18 i 19 i20ci 21 22 23 24 25 26 27 28 29 30C Foam test 4 5 5 3 2 2 1 1 1 2 4 5 5 3 2 2 1 1112 4 5 5 3 2 2 1 1 1 2 HTC test 4 5 5 4 2 2 1 1 1 3 4 5 5 4 2 2 1 1 1 ; 3 4 5 5 4 2 2 1 1 1 3 Emulsification test 3 5 4 3 2 2 2 1 2 2 3 5 4 3 2 2 2 12 12 3 5 4 3 2 2 2 1 2 2 Hydrocarbon recovery test F F F F P P P P P P F F F F P P P p p ;p f F F F P P P P P P Foam Breakage 3 5 5 4 2 2 1 1 1 2 4 5 5 4 2 2 1 1 1 2 4 5 5 4 2 2 1 1 1 2 Hydrocarbon Recovered 3 5 5 4 2 2 1 1 1 2 4 5 5 4 2 2 1 1 1 2 4 5 5 4 2 2 1 1 1 2 Emulsion stability 4 5 5 3 2 2 2 1 2 2 3 5 4 4 2 2 2 1 2 2 3 5 5 4 2 2 2 1 2 2 Heptane Foam test 3 4 5 3 2 2 2 1 2 2 3 5 4 4 2 2 2 1 2 2 4 5 4 3 2 2 2 1 2 2 Estimated results. In this and the other tables 1 is a relative best score and 5 is a relative worst score. Score of 5 for emulsion stability indicates poor emulsion stability however in this instance this is considered positive. 5 F= Fail; P= Pass; C=Comparative Formulation => 31 32 33 34 35 36 37 38 39 40 C 41 42 43 44 45 46 47 48 49 50C Foam test 4 5 5 3 2 2 1 1 1 2 4 5 5 3 2 2 1 1 1 2 HTC test 4 5 5 4 2 2 1 1 1 3 4 5 5 4 2 2 1 1 1 3 The Emulsification test 3 5 4 3 2 2 2 1 2 2 3 5 4 3 2 2 2 1 2 2 Hydrocarbon recovery test F F F F P P P P P P F F F F P P P P P P Foam Breakage 3 5 5 4 2 1 1 1 1 2 4 5 5 4 2 2 1 1 1 2 Hydrocarbon Recovered 3 5 5 4 1 1 1 1 1 2 4 5 5 4 2 2 1 1 1 2 Emulsion stability 4 5 5 3 2 2 2 1 2 2 3 5 4 4 2 2 2 1 2 2 Heptane Foam test 3 4 5 3 2 2 2 1 2 2 3 5 4 4 2 2 2 1 2 2 Estimated results. As can be seen the compositions of the present invention and in particular compositions 5,6,7,8 and 9 are low foaming. Comparative composition 10C, 11C and 14C is also low foaming but as this represents polysorbate surfactant, APG surfactant alone and a competitor formulation respectively, they are not an effective extinguishing composition. The compositions of the present invention provide a high heat transfer coefficient, in particular compositions 5,6,7,8 and 9. Comparative composition 13C also provides a high heat transfer coefficient, however this is not an effective emulsifying composition. The compositions of the present invention provide effective emulsification, in particular compositions 8, 9. Comparative formulation 11C also provides effective emulsification but as this represents Sodium benzyl sulphonate surfactant alone, this is not an effective extinguishing composition.

Claims

1. A tank cleaning composition for the removal of hydrocarbons from a storage tank, the cleaning composition comprising:a. an alkyl sulphate or an alkyl benzene sulphonate anionic surfactant and an:b. an alkyl polyglucoside nonionic surfactant;c. an alkyl sorbitan nonionic surfactant; andd. water.

2. The composition of any preceding claim wherein the alkyl sulphate or alkyl benzene sulphonate anionic surfactant is the potassium or trialkylamine salt.

3. The composition of claim 2 wherein the alkyl sulphate or alkyl benzene sulphonate anionic surfactant is the triethyl amine salt.

4. The composition of any preceding claim wherein the anionic is a C8 to C18 alkyl sulphate.

5. The composition of claim 4 wherein the anionic is a C8 alkyl sulphate.

6. The composition of claim 4 wherein the anionic is a C18 unsaturated alkylsulphate.

7. The composition of any one of claims 1 to 3 wherein the anionic is an alkyl benzene sulphonate, preferably a C 10 to C 14 alkyl benzene sulphonate.

8. The composition of any preceding claim wherein the alkyl polyglucoside nonionic surfactant is a C8 to C10 alkyl polyglucoside.

9. The composition of any preceding claim wherein the degree of polymerisation of the alkyl polyglucoside nonionic surfactant is from 1.0 to 2.2.

10. The composition of claim 7 wherein the degree of polymerisation of the alkyl polyglucoside nonionic surfactant is from 1.1 to 1.8.

11. The composition any preceding claim wherein the anionic to nonionic surfactant is present in a, from 2:1 to a 7:1 ratio by weight.

12. The composition of claim 11 wherein the anionic to nonionic surfactant is present in a, from 4:1 to a 6:1 ratio by weight.

13. The composition of any preceding claim wherein the alcohol sorbitan nonionic surfactant is a C10 to C14 alkyl sorbitan.

14. The composition of claim 11 wherein the alcohol sorbitan nonionic surfactant is a C10 to C14 unsaturated alkyl sorbitan.

15. The composition of any preceding claim further comprising one or more cosolvent selected from glycols, diols and polyethers.

16. The composition of any preceding claim further comprising polymeric thickener selected from one or more of Guar Gum; Xanthan Gum; Carboxymethyl Cellulose (CMC); Hydroxyethyl Cellulose (HEC); Hydroxypropyl Methylcellulose (HPMC); Agar-Agar; Pectin; Carrageenan; Alginate; Starch and Modified Starches; Chitosan.

17. The composition of any preceding claim comprising between 10 and 50% by weight water, as a concentrate for dilution before use.

18. A method of cleaning a hydrocarbon composition from a surface the method comprising:a. contacting the hydrocarbon composition with the cleaning composition of any of claims 1 to 17 under pressure so as to entrain air and to emulsify a portion of the hydrocarbon and thereby create an emulsion;b. recovering the emulsion;c. placing the emulsion in a low shear environment to permit breaking of the emulsion and thereby creating at least two liquid layers, one of which being recovered hydrocarbon composition the other being recovered cleaning composition ;d. separating the two recovered compositions;e. recovering at least one of the recovered compositions for further use.

19. The method of claim 18 comprising the subsequent step of:f. recovering the cleaning composition and re-using it by further contacting hydrocarbon composition under pressure so as to entrain air and to emulsify a portion of the hydrocarbon and thereby create an emulsion.

20. The method of claim 18 or 19 comprising the precursor step of:a’, entraining air into the cleaning composition to create a foam to impinge, under said pressure, upon a surface in contact with said hydrocarbon composition.

21. The method of claim 20 wherein the air entrainment is carried out using a venturi nozzle.

22. The method of any of claims 18 to 21 wherein said pressure is between 7.0 MPa and 27 MPa, preferably between 13.0 and 19.0 MPa.

23. The method of any of claims 18 to 22 wherein the cleaning composition is diluted before use to comprise between 0.1 and 3% by weight of the cleaningcomposition, preferably between 0.25 and 1 % by weight of the cleaning composition.

24. The method of any of claims 18 to 23 wherein step c. Comprises passing the emulsion through a coalescing plate separator.

25. The method of any of claims 18 to 24 wherein the low shear environment of step c. provides a shear rate of no higher than 100s-1.T +44(0)30 0300 2000A