RU2759712C1 - Method for collecting oil spill under ice cover - Google Patents

Abstract

FIELD: environmental protection.

SUBSTANCE: invention relates to the field of environmental protection; it can be used in the liquidation of emergency spills of oil and petroleum products under the ice cover of mainly flowing reservoirs. A method for collecting an oil slick in a localization zone and subsequent collecting in oil receivers is proposed. The method includes the creation of cavities and guide channels in the ice across a water stream at an angle to its dynamic axis using a natural snow cover as thermal insulation, allowing oil spilled under the ice cover to be moved into lanes with subsequent removal. In addition, on the surface of the cleared ice, on the border with snow thermal insulation, it is possible to create recesses for faster and deeper freezing of ice and, thereby, the formation of a more expressed ice channel.

EFFECT: method minimizes the negative impact of oil spill on the environment and simplifies the process of collecting oil spilled under the ice of the flowing reservoir.

1 cl, 4 dwg

Description

The field to which the invention relates

The invention relates to the field of environmental protection and can be used in the elimination of emergency spills of oil and oil products under the ice cover of mainly flowing water bodies. A method is proposed for directing an oil slick to the localization zone and subsequent collection.

The method includes creating guide channels in the ice, allowing the oil to be transported into the lanes for subsequent removal.

The method allows to minimize the negative impact of the oil spill on the environment and to simplify the oil recovery process.

State of the art

Ice regime in flowing water bodies is a complicating factor in the elimination of emergency oil spills. In the presence of ice cover, one of the mandatory stages of liquidation of emergency oil spills on water bodies is the stages of containment and subsequent collection of oil products.

For example, there are known methods of collecting oil from under the ice cover of a flowing reservoir (RF patent No. 2224842 "Method of collecting oil from under the ice cover of a flowing reservoir"; Ivanov VA and others. Elimination of emergency spills of oil and oil products. Textbook. - Tyumen: TyumGNGU, 2004.). Oil collection using these methods is carried out by creating slots in the ice cover, upstream of the oil spill spot, and installing barriers of various designs and materials in them perpendicular to the water flow (elastic screens with weights along the lower edges, rigid structures made of metal or wooden sections , shields, etc.). At the end of the slot, a lane is constructed to accommodate the oil skimmer and auxiliary equipment.

Their main disadvantages are limited efficiency and significant costs of accident elimination.

There is also known a method and device for collecting oil and oil products from under the ice cover of a reservoir (RF patent No. 2604931 "Method and device for collecting oil and oil products from under the ice cover of a reservoir"), including the localization of a spot of oil or oil products and the subsequent removal of oil or oil product by pumping into the oil receiver. At the same time, at least one pontoon is supplied to the area of localization of the oil or oil product slick under the ice cover, and it is pumped with air in an amount sufficient to create a lifting force for deformation of the ice cover. At the same time, a dome is formed at the site of localization of the oil or oil product slick, providing the collection of oil or oil product, which is between the water surface and the ice cover.

The main disadvantage of this method is its low productivity, labor intensity, the impossibility of using it in flowing water bodies, as well as the limitation on the thickness of the ice.

The closest to the claimed technical solution is a method of collecting oil from under the ice cover of a flowing reservoir (RF patent No. 2176701), which provides for breaking the ice cover and collecting the accumulated oil in storage tanks. The opening of the ice cover is carried out in such a way that the edge of the ice forms either a wedge opposite the current of the river, or an acute angle with one of its banks. The oil accumulated in the coastal zone is taken away, directing it to the accumulators prepared in advance on the shore, the bottom of which is made with a slope opposite to the reservoir. Communication between the reservoir and the reservoirs is provided by a system of pipelines, with the help of one of which oil is taken from the coastal zone, and with the help of the other, water is supplied to the reservoir to ensure a constant level of liquids in the reservoir, they are kept until ice crystallization at the interface between the liquids and oil is collected from the surface of the ice.

This method is also not effective enough, because under freeze-up conditions at negative air temperatures, water and oil in the slot freeze quickly and oil that has not surfaced continues to move under the ice. In addition, breaking the ice cover and creating a slot several meters wide requires significant time and labor.

Disclosure of invention

The objective of the proposed present invention is to provide simplicity, reduce labor intensity, efficiency and economy of the process of collecting an accidental oil spill on flowing water bodies in ice conditions.

The technical result of the invention is the creation of a method for collecting oil from under the ice cover of a flowing water body, which ensures prompt removal and localization of oil in ice conditions.

The advantage of the proposed method in comparison with analogues is the lesser impact of oil pollution on a water body, since it acts immediately upon a breakthrough of an oil pipeline and oil leakage. All preparatory work is carried out once and in the future is reduced only to periodic control. In addition, the advantage of the method is the possibility of using it during the freeze-up period, when many methods are practically not applicable.

Essential features characterizing the invention.

Restrictive: a method of localizing and collecting oil under the ice cover across the water flow at an angle to its dynamic axis.

Distinctive: localization and diversion of emergency oil under the ice cover to the collection zone and subsequent removal is carried out using ice channels created in the ice cover of a flowing reservoir by creating a natural snow cover downstream of the accidental oil spill site on the prospective path of the oil slick of snow thermal insulation and clearing the surface of the ice cover at the border with the snow insulation to increase its thickness under the cleared surface.

Brief Description of Drawings

Figure 1 shows a diagram of the formation of a guide channel in the ice cover using the snow cover. Figure 2 shows examples of localization and collection of oil spills at the boundaries during the ice period on flowing water bodies, depending on their width. Figure 3 shows a diagram of the location of the holes and the thickness of the ice. Figure 4 shows a comparison of ice thickness measurements at control points.

Implementation of the invention

Due to the fact that the thermal conductivity of ice exceeds the thermal conductivity of snow and water by an order of magnitude and four times, respectively, the authors propose a method for creating cavities and guide channels in the ice cover through which the collection and localization of oil spilled under the ice will be carried out.

The method is carried out as follows (Fig. 1). By clearing the surface of the ice cover of the reservoir (1) downstream from the site of the accidental oil spill, snow insulation is created from the natural snow cover on the supposed path of the oil slick (2). Thus, conditions will be created for increasing the thickness of the ice cover under the cleared area and, conversely, slowing down the increase in the thickness of ice under the snow insulation. In addition, on the surface of the cleared ice, on the border with the snow thermal insulation, it is possible to create depressions (3) for faster and deeper freezing of ice (4) and, thereby, the formation of a more pronounced ice channel (5). At the end of the ice channels, lanes are built, in which oil skimmers and auxiliary equipment are placed to remove oil into oil skimmers.

The number and shape of ice channels can vary depending on the width of the flowing reservoir (Fig. 2). For watercourses of small width, the oil slick (1) is diverted by an ice channel (2), which completely overlaps the channel. For medium and wide watercourses, it is possible to partially block the channel on the proposed paths of the oil slick (1) with subsequent diversion and collection into oil collectors (3).

To confirm the possibility of using the proposed method in real conditions, a full-scale experiment was carried out in a closed stagnant reservoir. For the experiment, a working zone with a diameter of 20 m was cleared from the snow cover.In the center of the zone, artificial insulation was formed from dome-shaped snow with a height of 1 m and a base radius of 3 m.At the beginning of the experiment, the thickness of the ice cover and the depth of the reservoir were 0.24 and 1.65 m respectively. The water temperature in the reservoir was 2.5 ° С, at the border between the snow cover and ice -4 ° С, the ambient air temperature was -23.5 ° С. As the snow fell, the territory of the zone was cleared. Also, to build a mathematical model during the full-scale experiment, the temperature of the ambient air and water, the thickness of the natural snow cover, the density of artificial snow insulation, and the wind speed were recorded.

On the 36th day from the beginning of the experiment, changes in the thickness of the ice cover were recorded under the snow insulation, as well as from the area cleared of snow and under natural snow cover. To measure the ice thickness, holes were drilled at 6 points (Fig. 3).

The data obtained show that the increase in thickness in the center of the isolated part of the ice cover was 7 cm (point 1), while the thickness of the uninsulated part increased by 50 cm (point 4), the difference between them was 43 cm. The air temperature during the experiment was dropped below -40 ° С.

The height of the snow insulation up to 1 m is sufficient to significantly slow down the growth of the ice cover during freeze-up.

To describe a full-scale experiment, a mathematical model was built that allows predicting the process of ice cover formation in a confined reservoir, depending on environmental conditions.

The problem was described by the heat conduction equation taking into account a phase transition in an axisymmetric form in a cylindrical coordinate system; traditional boundary conditions of the 1st and 3rd kind were set at the boundaries.

This task is Stephen's task of freezing water, the phase transition occurs in a small temperature range [Tf - Δ; Tf + Δ], thereby the enthalpy of the phase transition is "smeared" in this interval.

The geometrical dimensions adopted in the model problem are comparable with the geometrical dimensions of a full-scale experiment.

The heat transfer coefficients were calculated by the following formulas:

,

- высота и теплопроводность снежного покрова k-ой границы, ν_air - скорость ветра. Проведением натурного эксперимента зафиксированы значения T_ice, T_w, T_air,

и ν_air. Теплопроводность снега

зависит от плотности

и вычислялась выражением:where

,

- the height and thermal conductivity of the snow cover of the k-th boundary, ν _air - wind speed. By carrying out a full-scale experiment, the values of T _ice , T _w , T _air ,

and ν _air . Thermal conductivity of snow

depends on density

and was calculated by the expression:

FIG. 4 shows a comparison of the ice cover thickness at the control points obtained by solving the Stefan problem and in the course of a full-scale experiment. The deviation of the calculated results from the experimental data is about 4.8%, which confirms the adequacy of the mathematical model.

Claims (1)

A method for localizing and collecting oil spills under the ice cover of reservoirs across the water flow at an angle to its dynamic axis, characterized in that the localization and removal of emergency oil under the ice cover of a flowing reservoir into the collection area and subsequent removal are carried out using ice channels created in the ice cover by creating snow insulation from natural snow cover downstream of the accidental oil spill on the proposed path of the oil slick and clearing the surface of the ice cover at the border with the snow insulation to increase its thickness under the cleared surface.

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