RU2514645C1 - Method of localising oil spills in aquatic medium - Google Patents

Abstract

FIELD: chemistry.

SUBSTANCE: invention relates to techniques for removing oil and oil product spills and can be used in the oil extraction and oil refining industry, as well as in transportation. A sorbent is fed to the site of the oil or oil product spill in the water using a flexible or rigid line. The sorbent used is an aqueous solution of microgels of polysaccharides with molecular weight of 20000-200000 Da. Concentration of microgels of polysaccharides at the spill site is kept at least equal to 0.1 g/l. The jelly-like agglomerates formed are then mechanically collected.

EFFECT: high efficiency of localising and collecting underwater and subglacial oil spills while simultaneously increasing the amount of recovered oil, easier assembling of the equipment.

9 cl, 5 ex

Description

The invention relates to technologies for the elimination of emergency oil and oil product spills and can be used in the oil and refining industries, as well as in transport.

Currently, three main methods have been widely used to localize and collect emergency oil and oil product spills in water: the use of sorbents, surface-active compounds, and mechanical devices. All these methods work well on the water-air interface, preventing the oil film from spreading. At the same time, a limited number of methods are known that are suitable for localizing oil spills in the water column. The use of such methods can prevent the formation of large oil stains on the surface of the water, since the liquidation of the accident is carried out in the immediate vicinity of the accident under water, man-made structures and under ice.

A known method of collecting oil under water directly above its emergency release from the main oil pipeline by installing flexible screens in combination with instrumentation and equipment for pumping oil. In this method, a sealed tubular frame with supports and intake pipes in its lower part is lowered from a floating platform to the place of pipeline rupture. An elastic shell is provided on the inside of the frame perimeter, fixed inside the floating chamber on one side, and on the other hand, connected to the floating platform using an elastic sleeve. The method is implemented in a device for collecting oil under water [Patent RU No. 2247807 C1, IPC E02B 15/04, 03/10/2005].

The disadvantages of this device are the complexity of the design, as well as the inability to use during periods of freezing and ice drift.

Also known is a method of collecting oil under water, which consists in installing a catching arch made of elastic material under water, as well as mine wells on float elements, through which pollution can be evacuated to reserve tanks and anchor ballast. In the internal space of the device there is a telemetry instrumentation with a transmitting antenna brought to the surface in the area of the manhole cover of the shaft of the mine well. The method is implemented in a device for protecting the aquatic environment from pollution coming from underwater sources [Patent RU No. 2268338 C1, IPC E02B 15/04, 01/20/2006].

The disadvantages of this technical solution are a large amount of diving work during installation and a significant lag in time from the development of the accident, since the device is installed after oil leakage from the emergency facility.

Closest to the proposed method is a method of collecting oil spills in the area of the underwater trench passage of the main oil pipeline. The method includes the localization of an oil spill in the area of the trench underwater passage of the oil pipeline with a waterproof and oil-tight canvas covering the trench. A perforated tube filled with a non-woven sorbent material is placed under the web. The sorbent material is fixed on a cable through which the sorbent can be removed from the pipe and, after regeneration, by pressing or replacing, can be returned back for repeated use. Thus, this method allows to prevent the ingress of oil into the water, since the device for localization and collection of oil acts immediately when the pipeline breaks and oil spills [Patent RU No. 2439244 C1, IPC E02B 15/04, 01/10/2012].

The disadvantages of this method are the need to install bulky structures (domes, nets) under water, a significant time to eliminate the accident, the need to use additional equipment for collecting oil and separating oil from the sorbing material. All this requires large capital investments, therefore, the collection of oil in the water column with the help of such devices can only be used for large trunk pipelines. In addition, a significant part of the oil is irretrievably lost, and the resulting contaminated sorbent material must be disposed of in some way.

The objective of the present invention is to increase the efficiency of localization and collection of submarine and under-ice oil spills with a simultaneous increase in the proportion of returned oil and a decrease in the amount of installation work.

The problem is solved in that an aqueous solution of polysaccharide microgels with a molecular weight of 20,000-200,000 daltons is supplied to the place of the leakage of oil or oil products into the water column, while the concentration of polysaccharide microgels at least 0.1 g / l is maintained at the place of the leakage of oil or oil products.

Colloidal solutions of preferably natural polysaccharides selected from the following series are used as microgels of polysaccharides in the invention: low-substituted (<40%) salts of carboxymethyl cellulose with aliphatic amines, where butylamine, benzylamine, ethylenediamine, hexamethylene diamine are used as aliphatic amines; chitosan with a degree of deacetylation of 90-97%; pectin substances with a residual amount of methoxy groups <25%; alginic acid. To obtain polysaccharide microgels that are more stable for a long time, chemical crosslinking of the polymer chains of polysaccharides is carried out using anhydrides and activated esters of dicarboxylic acids, diisocyanides, diisocyanates, and other crosslinking agents. The particle diameter of the microgel polysaccharides vary preferably in the range of 0.1-1 μm.

The polysaccharide microgels used in the claimed invention have high surface activity and the ability to gel during contact with oil. Therefore, upon adsorption on the oil-water interface, these polysaccharide microgels form strong films that isolate oil droplets from the surrounding aqueous phase. In addition, individual drops of oil coated with these films stick together into larger agglomerates, which greatly facilitates their subsequent collection. Thus, localization of the spill is ensured by the formation of oil capsules with a size of 0.1-2 mm, coated with a polysaccharide shell, and larger agglomerates based on them 0.5-5 cm in size.

In the claimed invention, chemically bonded chitosan-based microgels with a degree of crosslinking from 1 to 15% or chemically bonded pectin-based microgels with a degree of crosslinking from 1 to 25% can also be used as polysaccharide microgels.

Polysaccharides with a low molecular weight (less than 20,000 daltons) cannot be used in the present method, since they have increased solubility in water. At the same time, polysaccharides with a high molecular weight (more than 200,000 daltons) have a high viscosity, making it difficult to obtain microgels based on them.

The inventive method can be used in two ways: to prevent oil leaks during its movement by pipeline and to localize oil leaks in hard-to-reach places (under ice and artificial structures).

In the case of oil transportation through pipelines, a permanent flexible or rigid line for supplying an aqueous solution of polysaccharide microgels is used to attach oil spills, attached to the pipeline surface and equipped with nozzles installed, for example, every ten meters. The supply of an aqueous solution of polysaccharide microgels to the line is carried out by pumps from tanks, also located along the pipeline line. In the event of an accidental oil spill under water, the oil concentration in the area adjacent to the accident site will increase. If an emergency spill is detected using automatic sensors located on the surface of the pipeline; during visual inspection or in any other way from the control panel of this system, the nozzle closest to the accident site will be turned on. In this case, a concentrated aqueous solution of the polysaccharide microgel will enter the zone contaminated with oil, and upon reaching the working concentration (0.1 g / l), oil capsules will begin to form.

When localizing individual oil spills in hard-to-reach places (under ice or artificial structures), a system consisting of a tank, a pump, a flexible or rigid solution supply line and nozzle is used. If a spill is detected, a flexible or rigid line goes down to the oil spill site, then the pump is turned on, and a concentrated aqueous solution of the polysaccharide microgel is fed to the accident site through the nozzle.

Capsule formation is equally effective in fresh and salt water. Therefore, the inventive method can be used for the localization of oil spills at sea and in freshwater bodies of water (lakes, rivers, swamps). Oil or oil products in the form of capsule agglomerates do not spread when they ascend to the surface of the water, do not harm the environment, do not burn and do not evaporate. They are easily collected using fine-mesh networks (1-2 mm), and oil and oil products can be returned back when processing agglomerates with alkali. The microgel of polysaccharides is to be reused. Thus, when using the proposed method does not generate waste that must be disposed of or incinerated.

The inventive method in comparison with the prototype is characterized by a number of new significant features: the use of a new localization method based on the prevention of oil spreading on the surface of the water, in the water column, including under ice; high percentage of oil return; lack of environmentally harmful waste.

Comparison of the proposed method with the known allows us to conclude that the claimed solution meets the criterion of "novelty."

Polysaccharides and their microgels with sizes from 50 to 500 nm are widely used in various fields of science and technology. However, the surface-active properties of these polymers are weakly expressed, until today they have only been used to a limited extent as colloidal emulsion stabilizers. In the inventive method for the first time used such a property of polysaccharides as the ability to be adsorbed on the interface in the form of microgels. In relation to the claimed invention, the use of polysaccharide microgels allows us to solve two problems at once: to isolate oil droplets from the aquatic environment due to the formation of an elastic film on their surface and to prevent the spread of oil on the water surface during ascent, under ice and artificial structures. Oil from a fluid with significant fluidity turns into an elastic gel, the mobility of which is much lower. In encapsulated form, oil / oil products do not spread over large areas, but are concentrated at the spill site, which greatly simplifies the process of its collection and significantly reduces the damage to the environment. For the localization of underwater spills of oil / oil products, the inventive method for the localization of oil and oil products is new and provides the claimed result.

The above allows us to conclude that the claimed technical solution meets the criterion of "inventive step".

The inventive method can be successfully used in the elimination of spills of crude oil, petroleum products and organic solvents with the possibility of returning a marketable product. The method is feasible in real conditions using known materials and substances.

The inventive method was used to localize leaks of crude oil in water in an amount of up to 50 liters in a test installation. The high efficiency of the proposed method is proved by tests.

This allows us to conclude that the proposed solution meets the criterion of "industrial applicability".

The inventive method is implemented as follows. A flexible or rigid line for supplying an aqueous solution of polysaccharide microgel with an nozzle, sediment and a container with a concentrated aqueous solution of polysaccharide microgel (5-30 g / l) is brought to the oil leak. The position of the nozzle relative to the emergency oil spill area is determined visually, based on the readings of the sensors or in some other way. After turning on the pump, a concentrated aqueous solution of the polysaccharide microgel is sprayed under water directly in the oil leak zone, where an oil-in-water emulsion is present. When the working concentration of the polysaccharide microgel aqueous solution (0.1 g / l) is reached in the rupture zone, the oil droplets are coated with a polysaccharide film and form jelly-like agglomerates that rise to the surface of the water. At a shallow depth (up to 20 m), gel-like pop-up oil is collected by fine-meshed nets and sent for regeneration. At large depths, a mesh screen with a load at the edges is installed above the accident site to reduce the oil collection area. During spills under ice and artificial structures, oil does not spread with a thin film along the surface boundary, but accumulates in the form of large clots that can be collected after a long time (2-3 months) after the accident is liquidated. At the same time, encapsulated oil does not cause significant damage to marine fauna and flora and does not interfere with gas exchange. The regeneration of the collected jelly-like agglomerates is carried out by treatment with an alkali solution. In this case, two phases are formed: crude oil and a polysaccharide microgel solution, which is reused for the implementation of the proposed method.

The inventive method is illustrated by the following examples of specific performance.

All tests of this method were carried out in a laboratory setup, which is a plastic tube with a diameter of 1 cm passing through the bottom of 10 l of a container filled with water. The tube has artificial defects that mimic ruptures in the pipeline. For testing, crude oil was pumped through the tube under pressure, some of which passed through defects into a container of water. An aqueous solution of the polysaccharide microgel in water was supplied directly to the rupture site using a lead-in flexible line in the form of a reinforced rubber tube 1 cm in diameter until a predetermined concentration was reached, which was determined by taking samples through a sampler. Agglomerated oil agglomerates floating onto the surface were collected using a fine mesh and analyzed.

Example 1 (according to the invention)

Localization of a spill of crude oil in the water column using a solution of a physically associated microgel based on chitosan.

Chitosan (1 g) with a deacetylation degree of 95% and a molecular weight of 60 to 200 thousand D was dissolved in 1 l of 0.01 M hydrochloric acid. To this solution was added a sodium hydroxide solution of 0.05 M to a pH of 7.5. The resulting suspension of chitosan microgel was centrifuged to obtain a more concentrated suspension (5 g / l), which was used to localize the oil spill. A suspension of chitosan microgel (5 g / l) was fed in a continuous stream to a laboratory setup to meet pop-up drops of oil. Upon reaching a concentration of 0.1 g / l, gel films were observed to form on the surface of oil droplets. When surfacing to the surface, individual droplets formed clots that were collected using a fine mesh. The total consumption of the suspension per 1 liter of crude oil was 120 ml (600 mg, calculated on dry weight).

Example 2 (according to the invention)

Localization of a spill of crude oil in the water column using a solution of a physically associated microgel based on carboxymethyl cellulose salts.

The sodium salt of carboxymethyl cellulose (25 g) with a degree of substitution on carboxymethyl groups in the range of 40-70% and a molecular weight of 30 to 120 thousand D was dissolved in 1 liter of water. To this solution 2.5 g of hexamethylenediamine and a concentrated hydrochloric acid solution were added successively to an acidic pH = 1-3 reaction. The resulting solution of carboxymethyl cellulose microgel with a concentration of 3% of the mass was fed in a continuous stream to a laboratory setup to meet the pop-up drops of oil. When the microgel concentration in water reached 0.1 g / L, gel films were observed to form on the surface of oil droplets. When surfacing to the surface, individual droplets formed dense agglomerates 3-4 cm in size, which were collected using a fine mesh network. The total consumption of the suspension per 1 liter of crude oil was 80 ml (2.4 g in terms of dry weight).

Example 3 (according to the invention)

Localization of a spill of crude oil in the water column using a solution of chemically bound microgel based on pectin.

Pectin (5 g) with a degree of methoxylation of 1-25% and a molecular weight of 20 to 100 thousand D was dissolved in 1 l of sodium hydroxide solution (2 g / l). To this solution was added 2 g of benzylamine hydrochloride and 200 mg of diisocyanopropylpiperazine. After complete dissolution of these reagents, 3 ml of formalin was added to the solution and left for 2 hours with vigorous stirring. The resulting solution with a concentration of 0.5% was acidified and centrifuged to obtain a more concentrated suspension (5 g / l), which was then alkalized with sodium hydroxide and used to localize the oil spill. A suspension of pectin microgel (5 g / l) was fed in a continuous stream to a laboratory setup to meet pop-up drops of oil. Upon reaching a concentration of 0.1 g / l, gel films were observed to form on the surface of oil droplets. When surfacing to the surface, individual droplets formed clots that were collected using a fine mesh. To obtain denser agglomerates, the surface of the encapsulated oil was additionally treated with a 1% hydrochloric acid solution. The total consumption of the suspension per 1 liter of crude oil was 100 ml (500 mg, calculated on dry weight).

Example 4 (according to the invention)

Localization of a spill of crude oil in the water column using a solution of chemically bound microgel based on chitosan.

Chitosan with a degree of deacetylation of 92% in an amount of 2.5 g is dissolved in 1 liter of a 0.2% solution of hydrochloric acid in water. The resulting solution is titrated with a 0.2% solution of sodium hydroxide in water until the solution becomes cloudy (pH 6.0-6.5). To the resulting solution add the calculated amount (to obtain 1-15% crosslink density) of a mixture of hexamethylene diisocyanide and formaldehyde in 20 ml of acetonitrile. The mixture is stirred vigorously for 1 hour. Then the pH of the mixture by adding triethylamine is adjusted to a value of 8.5, after which the resulting mixture was incubated for another 1 hour. The resulting solution with a concentration of 0.25% was made alkaline and centrifuged to obtain a more concentrated suspension (5 g / L), which was then acidified again with hydrochloric acid and used to localize the oil spill. A suspension of chitosan microgel (5 g / l) was fed in a continuous stream to a laboratory setup to meet pop-up drops of oil. Upon reaching a concentration of 0.1 g / l, gel films were observed to form on the surface of oil droplets. When surfacing to the surface, individual droplets formed clots that were collected using a fine mesh. The total consumption of the suspension per 1 liter of crude oil was 75 ml (400 mg, calculated on dry weight).

Example 5 (according to the invention)

Regeneration of a chemically bound pectin-based microgel.

After separating the encapsulated oil (Example 3), it was placed in a separate glass and concentrated sodium hydroxide solution (30%) was added to pH 8. At the same time, the gel was destroyed and the system was divided into two layers: the upper one was crude oil and the lower one was a polysaccharide microgel solution. After separation of the layers, the microgel solution was acidified with 10% hydrochloric acid to pH 3 and centrifuged to obtain a more concentrated suspension (5 g / l), which was then alkalized with sodium hydroxide and reused to localize the oil spill. When using this solution, indicators similar to Example 3 using the starting pectin were achieved. The number of regeneration cycles is 4-5.

The effectiveness of the proposed method depends on the consumption of microgel polysaccharides. We found: 1 kg of polysaccharide microgel (in terms of dry weight) is enough to collect 800-850 liters of crude oil. Given the possible regeneration of polysaccharide microgels, this indicator increases to 3200-3400 liters. The cost of the polysaccharide microgel is from 300 rubles / kg for carboxymethyl cellulose to 1600 rubles / kg for chitosan. Thus, the cost of collecting crude oil (without the cost of the work itself) varies between 0.1-0.5 rubles / liter.

Claims (9)

1. A method of localizing oil spills in an aqueous medium by reacting oil with a sorbent in the water column and subsequent mechanical collection, characterized in that an aqueous solution of polysaccharide microgels with a molecular weight of 20,000-200,000 daltons is used as a sorbent, which is fed to the oil spill zone, providing the concentration of polysaccharide microgels in the oil spill area is at least 0.1 g / l. 2. The method according to claim 1, characterized in that the physically associated chitosan-based microgel is used as polysaccharide microgels. 3. The method according to claim 1, characterized in that physically associated carboxymethyl cellulose-based microgel is used as polysaccharide microgels. 4. The method according to claim 1, characterized in that as the polysaccharide microgels, a chemically coupled chitosan-based microgel with a crosslinking degree of 1-15% is used. 5. The method according to claim 1, characterized in that as the polysaccharide microgels, a chemically bound pectin-based microgel with a degree of crosslinking of 1-25% is used. 6. The method according to claim 1, characterized in that when transporting oil through pipelines, a constant supply line of an aqueous solution of polysaccharide microgels is used, installed on the surface of the pipeline and equipped with nozzles. 7. The method according to claim 1, characterized in that when localizing oil spills in hard-to-reach places, a tank for an aqueous solution of polysaccharide microgels is used, which is connected to the pump with a flexible or rigid solution supply line equipped with a nozzle. 8. The method according to claim 1, characterized in that at a depth of 20 meters using fine mesh networks. 9. The method according to claim 1, characterized in that at a depth of more than 20 meters use a mesh screen with a load at the edges.