JPH0159320B2 - - Google Patents

Description

[Detailed description of the invention]

This invention relates to a method for rationally cleaning oil adhering to, for example, the walls and bottom plate of an oil tank, and more specifically, it relates to a method for rationally cleaning oil adhering to the walls, bottom plate, coils, etc. of the oil tank using foam spray. The present invention relates to a method for easily cleaning and removing oil stains by spraying a cleaning agent having a composition in the form of foam and contacting the foam with attached oil. Oil tanks that store large amounts of oil must be inspected for corrosion and cracks after a certain period of time, as corrosion or cracks on their walls, bottom plates, etc. can cause major accidents. It is therefore compulsory. The fluorescent magnetic powder method, which is used as a method for inspecting the presence of cracks, involves dispersing fine powder of iron oxide whose surface is coated with fluorescent dye in water, pouring it onto the weld, and then dispersing it around the weld. It creates a magnetic field. If there is a crack, magnetic fluorescent iron oxide powder collects in the crack, making its presence known. In this case, if oil remains in the cracks, the adsorption of the fluorescent iron oxide powder will be poor, and there is a high possibility of misjudgment. Conventionally, as a detergent for oil present in cracks, there are known detergents containing nonionic surfactants as a main component, which cleanse by utilizing the emulsifying effect of oils. In this case, emulsification is performed by mechanical force such as high-pressure jetting or scrubbing, but if the oil tank is made of iron plate, there is so-called black crust or rust on the surface, and the oil seeps into the inside. Because of this, it is difficult to reach deep parts using only high-pressure spray or scrubbing with a cleaning brush. Furthermore, if the oil is not completely removed by washing, a phenomenon is observed in which the oil gradually oozes out onto the surface again after drying. Therefore, in the past, the surface was usually scraped off using wire brushes or puff polishing, etc. Therefore, when changing the type of oil stored, a turret was built in the oil tank and each level was removed. Another method is to arrange laborers to pour detergent from the top shelf and then start scrubbing each shelf at the same time. However, this method requires a large amount of preparation work and a great deal of labor, and has disadvantages such as the fact that it is difficult to completely remove the oil even by such means. On the other hand, when cleaning oil as mentioned above requires a long time, immersion cleaning is performed, but immersion cleaning is not possible for cleaning oil tanks, structures, and machinery as described above. A second drawback is that the cleaning waste liquid emulsifies. In other words, it is not possible to dispose of emulsified oil as it is due to pollution prevention ordinances, but it is extremely difficult to completely separate the emulsion and oil from emulsified cleaning waste, and it is difficult to dispose of emulsified cleaning waste. That is the reality. In particular, when changing cargo on a multi-purpose tanker, cleaning fluid is injected using a high-pressure pump installed onboard the ship, but if the cleaning agent is based on non-ionic surfactants, the oil will emulsify, making it difficult to dispose of it. However, when using anionic surfactants as the main ingredient, it is difficult to completely clean them. In view of the above-mentioned circumstances, this invention was developed as a result of intensive research into a cleaning method that can be completely cleaned with a small amount of cleaning liquid and prevents the oil in the cleaning waste liquid from turning into an emulsion, especially for cleaning the walls and bottom plate of the oil tank. If you spray a cleaning agent with a foamy composition onto the cleaning surface and keep the cleaning agent in contact with the cleaning surface for a long time, the cleaning agent will penetrate between the black scales and rust and the oil will be completely removed. It has been discovered that the cleaning waste liquid can be removed and the treatment of the cleaning waste liquid becomes extremely easy. The alkaline agents in the cleaning agent components according to this invention include caustic alkalis such as caustic soda and caustic potash;
Inorganic alkali salts such as secondary and tertiary phosphates, pyrophosphates, tripolyphosphates, metasilicates, orthosilicates, carbonates, triethanolamine, diethanolamine, monoethanolamine, isopropylamine, monoisopropanolamine, These are organic alkalis or organic alkali salts such as diisopropanolamine and triisopropanolamine. Ether alcohols are compounds that have a hydroxyl group and an ether bond in the same molecule and are compatible with water in any proportion. The simplest compound among alcohol ethers is diethylene glycol HO―CH ₂ ―CH ₂ ―O―
CH ₂ —CH ₂ —OH. This is obtained industrially by addition polymerizing two molecules of ethylene oxide to one molecule of water. Triethylene glycol, which is obtained by addition polymerizing three molecules of ethylene oxide to one molecule of water, can also be used in the present invention, but as the number of moles of ethylene oxide increases, it changes from a liquid state to a paste state or a solid state. Some polyethylene glycols cannot be used in this invention. The next simplest compound among alcohol ethers is dipropylene glycol.

[Formula]. This is produced by addition polymerizing 2 moles of propylene oxide to 1 molecule of water, but polypropylene glycol, which is produced by addition polymerizing 2 moles or more of propylene oxide to 1 molecule of water, has lower water solubility than polyethylene glycol and has a lower molecular weight. At 400, it is no longer compatible with water at any rate. Further, compounds having a plurality of hydroxyl groups or more, ie, compounds obtained by addition polymerizing ethylene oxide or propylene oxide to a polyhydric alcohol, also belong to the alcohol ethers of the present invention. Comparison of ethylene oxide addition polymers and propylene oxide for ethylene glycol, propylene glycol, butylene glycol, hexylene glycol, etc., which have two hydroxyl groups, glycerin, which has three hydroxyl groups, erythritol, which has four hydroxyl groups, and sorbitol, which has six hydroxyl groups. Commonly used are low addition polymers and the like. Addition polymerization of ethylene oxide to monohydric alcohol includes methyl monoethylene glycol ether, generally methyl polyethylene glycol ether, ethyl monoethylene glycol ether, generally ethyl polyethylene glycol ether, propyl monoethylene glycol ether, generally Propyl polyethylene glycol ether, butyl monoethylene glycol ether, generally butyl polyethylene glycol ether, amyl monoethylene glycol ether,
Generally, they are amyl polyethylene glycol ether, hexyl polyethylene glycol, etc. Addition polymerization of propylene oxide to monohydric alcohols include methyl monopropylene glycol ether, methyl dipropylene glycol ether, methyl tripropylene glycol ether, methyl tetrapropylene glycol ether, methyl hexapropylene glycol ether, ethyl monopropylene glycol ether,
Ethyl dipropylene glycol ether, ethyl tripropylene glycol ether, ethyl tetrapropylene glycol ether, propyl monopropylene glycol ether, propyl dipropylene glycol ether, propyl tripropylene glycol ether, butyl monopropylene glycol ether, butyl dipropylene glycol ether, etc. . In addition, methylbutylene glycol ether,
Examples include ethyl butylene glycol ether, propyl butylene glycol ether, methyl amylene glycol ether, and ethyl amylene glycol ether. If simple alcohols such as methyl alcohol, ethyl alcohol, ethylene glycol, propylene glycol, hexylene glycol, or glycerin are used instead of alcohol ethers, no foam will be generated or no foam will be generated even when applied to a foam spray machine. Even if oil is generated, the bubbles are large and easy to break down, and therefore remain on the wall for a short time, so oil removal is insufficient.
It is especially unsuitable for removing oil from iron tanks that have a lot of black crust and rust. The cleaning composition of the present invention containing alcohol ethers generates fine foam only when a foam spray machine is used, and foaming is not good even when the liquid itself is stirred. For example, generally speaking, the amount of foaming and the stability of foam are measured using a Rosmiles foaming tester, but as shown in Table 1, cleaning compositions containing alcohol ethers have a Rosmiles foaming ability. Almost no bubbles are generated in the tester. Compositions without alcohol ethers generate a large amount of very stable foam.

[Table] It is not clear why the cleaning composition according to the present invention, which has poor foaming power in the Ross Miles foaming power tester, generates stable foam in a foam spray machine. The larger the molecular weight of the alcohol ether, the finer and more stable the foam will be. For example, when polyethylene glycol molecular weight is 6000, the foam is extremely fine and stable. However, as the molecular weight increases, the blending ratio of the alkaline agent gradually decreases, and there are also disadvantages in that the molecules may disintegrate during storage of the product. On the other hand, the surfactant used in this invention must have a foaming action and at the same time, it must also have an action as a hydrotrope. Here, hydrotropy is a phenomenon in which the solubility of a substance that is poorly soluble in water is increased by the addition of a third substance. In this case, the alkaline aqueous solution and alcohol ethers do not mix and separate at high concentrations, but by adding a third substance, a hydrotrope, they mix and become a homogeneous liquid. . Suitable anionic surfactants that meet these conditions include those in which the hydrophilic group is a sulfate ester salt, an ethoxy sulfate ester salt, and a sulfonate. , alkyl sulfonate, alkylbenzene sulfonate, alkylnaphthalene sulfonate, etc., and in order to exhibit the action as a hydrotrope, it is preferable that the number of carbon atoms in the alkyl group is 14 or less. . Of course, since it is an industrial product, the number of carbon atoms in the alkyl group is not uniform, but has a certain distribution width, and the number of carbon atoms in the main alkyl group is
This means that it is 14 or less. Specifically, the main ones include dodecyl sulfate ester sodium salt, dodecyl ethoxy sulfate ester sodium salt, dodecyl sulfonate sodium salt, octylbenzenesulfonate sodium salt, and diisopropylnaphthalene sulfonate sodium salt. One type of anionic surfactant is phosphate ester salts, which foam well and have great ability as hydrotropes. In this case, examples of the hydrophobic group include higher alcohols and alkylphenols, and there is no particular limitation on the number of carbon atoms in the alkyl group. Since higher alcohols and alkyl phenols directly converted into phosphoric esters produce less foaming, phosphoric ester compounds of alkyl ethoxylates and alkylphenyl ethoxylates to which ethylene oxide has been added are used. In addition, the amphoteric surfactants used in this invention include alkyl betaine compounds, alkylimidazolinium compounds, N-alkyl-β-iminodipropionates, N-alkyl-β-aminopropionates, etc. The number of carbon atoms in the alkyl group is preferably about 8 to 18, and it is excellent as a hydrotrope and foams well. In this invention, the above alcohol ethers,
The four components of surfactant, alkaline agent, and water are absolutely necessary components, and even if one of these components is missing, the oil will not separate from the wall surface. For example, alcohol ethers, surfactants, and water alone produce extremely stable fine bubbles, but
There is no force to remove oil from the wall surface. If only a surfactant, an alkaline agent, and water are used, no bubbles will be generated and the ability to remove oil from the wall surface will be weak. It also does not dissolve oil. If the oil is oxidized, it will be saponified and dissolved in the cleaning agent, but mineral oil, animal oil, and vegetable oil, such as those that adhere to oil tanks, have few oxidized components, so they are not included in the cleaning agent of this invention. It does not substantially dissolve. The proportions of the above-mentioned alcohol ethers, surfactant, alkali agent, and water vary depending on the type of oil to be removed. For kerosene, 0.5 to 2% of alkali agents and 1 to 5% of alcohol ethers are sufficient. Therefore, sufficient detergency can be achieved with 0.2 to 1% surfactant and the rest water. However, light oil, animal and vegetable oil, A heavy oil, B heavy oil, C
Sufficient cleaning power cannot be obtained unless the concentration of alkaline agents and alcohol ethers increases as the oil gets heavier. Therefore, unless the amount of surfactant is increased,
It cannot be made into a homogeneous phase. For walls with a large amount of tar adhesion, it is desirable to have a high blending ratio of alcohol ethers.
Approximately 40% is necessary. In this case, the mixing ratio of the alkaline agent is limited to about 5%, and if the concentration exceeds 5%, even if the surfactant is mixed at 20% or more, the cleaning agent will not be uniform and will separate. For walls with a large amount of sludge adhesion, it is desirable to have a high proportion of alkaline agents, and there are stubborn sludges that require about 20%.In this case, the upper limit of the proportion of alcohol ethers is 5%, and if it exceeds 5%, even if 20% or more of the surfactant is added, the detergent will not be uniform and will separate. Therefore, alkaline agents are 0.5 to 20%, alcohol ethers are 1 to 40%, and the hydrophilic groups are sulfate ester salts, ethoxy sulfate ester salts, sulfonate salts,
Anionic surfactants consisting of phosphates, amphoteric surfactants consisting of alkyl betaine compounds, alkylimidazolium compounds, N-alkyl-β-aminopropionates, and N-alkyl-β-iminodipropionates. 0.2 for one or more types
A blending ratio of ~2.0% and the balance being water is preferred. On the other hand, the foam spraying machine used in the present invention is a commercially available foam spraying machine, and a small or large one is selected depending on the intended use. Then, the above-mentioned cleaning agent composition is stored in the foam spray machine and sprayed onto the inner wall surface of the oil tank, attached equipment within the oil tank, etc., and the cleaning agent is foamed and cleaned. The features of the foam cleaning according to the present invention are as follows: (1) There is no irritating odor. With regular sprays, it becomes a mist, and if it contains an alkaline agent like the cleaning agent of this invention, the mist particles floating in the space will irritate the respiratory organs of the workers, so they should continue working. becomes virtually impossible. Also, if you work while wearing a gas mask, it will be completely impossible to continue working in the summer when the temperature inside the oil tank becomes high.
In this invention, since the cleaning agent is sprayed in the form of foam by a foam spray machine, there is no irritating odor and work can be done easily in the oil tank. (2) Long contact time with wall surface. Since the bubbles attached to the wall have a small density,
The flow rate takes a much longer time than the almost instantaneous flow of liquid. That is, the contact time between the cleaning agent and the wall surface is long. Therefore, the contact between the foam-like cleaning agent and the oil becomes longer, and when the foam-like cleaning agent and the oil come into contact, the foam breaks down and becomes liquid, and the oil separates from the wall surface and flows down together with the cleaning liquid. The foam-like cleaning agent that has not yet been destroyed comes into contact with the remaining oil on the newly exposed wall surface, and releases the oil from the wall surface. In other words, as long as the bubbles remain, new cleaning agent is constantly supplied, so the oil on the surface is removed one after another, and the cleaning agent can finally reach the black scales and rust. It is also possible to remove the oil content. Therefore, it is possible to obtain the same effect as when cleaning a dirty surface by immersion in an oil bath filled with cleaning agent, without requiring the force necessary to simultaneously remove black scale and rust with a wire brush or the like. (3) There is no need to build a tower on the oil tank. The foam spray machine has a slight injection pressure of 0.5 to 3
The equipment is light, as it only requires about Kg/cm ² , and therefore, for example, it is possible to operate a foam spray machine by attaching it to the tip of a pole, which reduces the time and cost of assembling the turret, and the cost of installing it at each tier. Labor is unnecessary. (4) Processing of cleaning waste liquid is easy. Since the washing waste liquid is not emulsified, ordinary waste water treatment equipment can be used. In other words, after separating the upper layer of oil using an oil separator, the lower layer of wastewater is neutralized with acid, and the dissolved organic matter is removed using a decomposition device. Common wastewater treatment equipment can be used. The following method may be used to determine the end point of cleaning, when the oil adhering to the rusted iron tank has been removed and there is no need to spray any more cleaning agent with foam. That is, 0.1 to 5% of nitrite such as sodium nitrite is added to the above-mentioned cleaning composition and foam sprayed.
The end point of cleaning is determined by the phenomenon in which the foam turns brown. In other words, when the oil is completely removed from the rusted iron surface by spraying foam, the nitrite in the cleaning agent acts on the rusted iron surface, reducing some of the iron rust and at the same time reducing the rust. Particles are released and adsorbed to the bubbles,
It turns the foam brown. Therefore, the end point of cleaning can be determined by spraying a foam spray onto the wall of an iron tank or the like and observing the phenomenon in which the flowing foam turns brown. This phenomenon is not observed in detergents that do not contain nitrites, and for this reason, the blending rate of nitrites required is 0.1 to 5%, and below 0.1% there is almost no effect. If it is 5% or more, the cleaning agent will not be uniform and will easily separate. A more preferable range is 0.3 to 2%, and within this range,
In many cases, it is possible to make the cleaning agent uniform without reducing the blending ratio of alkaline agents or alcohol ethers. In summary, according to the present invention, since the foam spray is sprayed onto the surface to be cleaned and the cleaning agent is allowed to contact the surface for a sufficient amount of time, it is possible to achieve the same cleaning effect as immersion cleaning. Therefore, it is highly effective in cleaning the inside of oil tanks. Examples of this invention will be shown below. Example 1 Foaming quality and foam stability were measured by the following method. (1) Measurement method Mark the 500ml and 250ml marks on a glass cylinder with a diameter of 8cm, and measure the weight of this glass cylinder when it is empty. Next, foam was sprayed onto this, and when the foam reached 500 ml, the foam spray was stopped and a stopwatch was pressed at the same time to measure the time it took for the foam to disappear to 250 ml. After completing the measurement, the weight of the glass cylinder is measured to determine the weight of the contents (cleaning agent). (2) Cleaning agent composition A cleaning agent was prepared using the various alcohol ethers listed in Table 3 as the alcohol ethers in the formulation shown in Table 2 below. Table 2 Caustic soda 3wt% Lauryl sulfate ester soda salt 5wt% Alcohol ethers 10wt% Water 82wt% (3) Results The results are shown in Table 3. Here, foam weight = weight of cleaning agent required to create 500 ml of foam (g) Foam half-life = time required for 500 ml of foam to disappear to 250 ml.

[Table] Rule
(4) Conclusion As is clear from Table 3, monohydric alcohol isopropyl alcohol, polyhydric alcohols ethylene glycol, propylene glycol,
Glycerin and the like do not produce foam, but methyl monoethylene glycol ether, which is an ether-bonded compound of ethylene glycol and methanol, and polyethylene glycol 200 (ethylene glycol average degree of polymerization 4.4) produce sufficient foam. In other words, if it has a hydroxyl group and an ether bond in one molecule, it will foam. In particular, according to experiments conducted by the present inventors, among alcohol ethers, those that do not belong to surfactants have a remarkable foaming effect when used with a foam spray machine. Example 2 The hold of a tanker was cleaned. The cargo was coconut fatty acid methyl ester. The composition of the cleaning agent is shown in Table 4. Table 4 Caustic soda 0.5wt% Polyethylene glycol molecular weight 10000 1 〃 Potassium phosphate ester of 6 mole adduct of octylphenol ethylene oxide 2 〃 Water 96.5 〃 The tank is made of stainless steel, and conventionally cleaning was mainly done with sodium alkylbenzenesulfonate. Cleaning was carried out by spraying an aqueous solution at a pressure of 4 kg/cm ² at 70°C, but spraying the cleaning agent shown in Table 4 at room temperature with foam provides comfortable conditions and is popular among workers, as well as being oil-free. There was nothing left. Example 3 The hold of a tanker was cleaned. The cargo was dioctyl phthalate. The material was steel plate. Table 5 Caustic soda 2wt% Propylene glycol molecular weight 250 15 Sodium diisopropylnaphthalene sulfonate
2 〃 Water 81 〃 When I sprayed the cleaning agent in Table 5 with foam and then sprayed it with water, the entire wall got wet. Previously, a cleaning aqueous solution consisting mainly of sodium alkylbenzene sulfonate was sprayed at high pressure at 70°C, but there were many parts that repelled water even when rinsed. The dioctyl phthalate ester was cleaned well by foam spraying with the cleaning agent in Table 5, demonstrating that it is a far superior cleaning method to conventional cleaning methods. Example 4 In order to undergo an inspection of a light oil tank on land, the side and bottom plates of the tank were cleaned. The material is steel plate. Table 6 Caustic soda 1wt% 3-methyl-3-methoxybutanol
5 Lauryl sulfate ester soda salt 0.2 Water 93.8 Foam sprayed the cleaning agent shown in Table 6 on the side and bottom plates of the tank. Since the bottom plate also has some slope, foam spraying is a good method because it maintains contact time for a long time. It was inspected using the fluorescent magnetic powder method, but no problems were found. Example 5 A heavy oil tank on land was cleaned in order to fill it with gasoline. The cleaning agent has the formulation shown in Table 8. After spraying foam twice on all side panels and bottom panels, water was sprayed with a fire hose, and no water was found on any of the walls. Since the wastewater was separated into an oil layer and an aqueous layer without being emulsified at all, it was transferred to a wastewater treatment equipment and was treated without any problems. Table 8 Caustic soda 3wt% Butyl triethylene glycol 40 〃 Sodium N-lauryl-β-iminodipropionate 10 〃 Water 47wt% Example 6 For inspection of onshore C heavy oil tank The bottom 1/2 of the board above it, the bottom board, and the coil were cleaned. Foam spraying was repeated three times using the detergent formulation shown in Table 8, followed by washing with water. No water permeation was observed on any of the walls. The completely dry wall surface was observed the next day, but no oil was found to be seeping out. The conventional cleaning method was to apply a cleaning agent based on non-ionic activators and scrub with a wire brush or a dirt brush. Even when water was applied, water-repellent areas were observed on almost all walls. The welded parts that were to be inspected were carefully buffed. Furthermore, since the wastewater is emulsified, it is collected in a drum and put into an incinerator little by little for incineration treatment. After cleaning using the method of the present invention, the welded area was sprayed with a citric acid aqueous solution to remove conventional rust, water treated, and immediately subjected to a fluorescent magnetic particle inspection. Also, since the wastewater was not emulsified at all, normal wastewater treatment methods could be applied. Table 8 Caustic potash 20wt% Butyl diethylene glycol 10 Sodium lauryl sulfate 10 Sodium octylbenzenesulfonate
10 〃 Water 50 〃 Example 7 Using an empty lubricating oil tank,
A comparison was made between cleaning agent A, which does not contain sodium nitrite, and cleaning agent B, which does contain sodium nitrite. The first foam you spray has lubricant attached to it, so
Both A and B were light and dark brown in color, whereas the second sprayed foam was white in A, while B was brown due to the adhesion of free iron rust. The proof that it is iron rust is also evident from the results of collecting the foam and quantifying the amount of iron.

【table】

[Table] Example 8 Using a part of the side wall of an empty tank containing the lubricating oil "Lite", the cleaning power of a foam spray and a mist spray was compared. The cleaning area was 5 m ² and the cleaning agent was sprayed at a rate of 100 g/m ² . After leaving it for 10 minutes, I sprayed it with water and rinsed it. The area where I sprayed the foam was completely wet with water. That is, the lubricating oil "Light" was completely washed away. On the other hand, the sprayed area was sprayed, allowed to stand, and rinsed twice, but water-repellent areas remained. By the third washing, the oil could finally be completely removed. In other words, the foam spray can be cleaned with 1/3 the amount of cleaning agent, cleaning time, and cleaning effort compared to the spray spray.

Claims (1)

[Claims] 1. Alkaline agent 0.5-20wt%, alcohol ether 1-40wt, anionic surfactant whose hydrophilic group is sulfate ester salt, ethoxy sulfate ester salt, sulfonate salt, phosphate ester salt, alkyl betaine compound, alkylimidazolium 0.2 to 20 wt of one type or a mixture of two or more surfactants selected from amphoteric surfactants consisting of N-alkyl-β-iminodipropionate, N-alkyl-β-aminopropionate, and N-alkyl-β-aminopropionate. % and water is sprayed onto the cleaning surface in the form of a foam using a foam spray machine while blowing air into the cleaning composition to remove oil stains. A cleaning method for removing oil stains inside the oil tank.