GB2053883A - Removing oil pollution - Google Patents

Abstract

The method of removing oil or similar liquids from the surface of water or a solid material comprises absorbing the liquid by means of granulated mineral wool and separating the liquid from the mineral wool material by subjecting it to a centrifugal force or a pressure difference.

Description

SPECIFICATION A method of removing oil or similar liquids from the surface of water or a solid material The present invention relates to a method of removing oil or similar liquids from the surface of water or a solid material, and to its regeneration.

It is an object of the present invention to provide a new method which, in case of a leak, makes the oil removal possible, especially to a tanker by its own crew; or similar oil prevention actions.

Most of the oil accidents on the water areas happen so that a tanker springs a leak and a limited amount of oil runs into the water. Relatively seldom the leak is so large that whole of the tanker runs empty, although this is really very disastrous. The major part of the oil damages is thus to be prevented, if the tanker itself has been provided with the proper prevention equipment and material and the prevention acts can be started immediately during the first minutes of the accident.

The process of the preventing actions are as follows: When the oil leak has happened the leakage area is surrounded by e.g. boom nets in order to master the spreading of the oil and in order to be able to carry out the preventive actions. Granulated glass wool is spread by e.g. a blower over the area surrounded by the booms. The material, into which the oil is absorbed and which gathers towards the booms, forms kind of miniature mountains, the tops of which go under the surface of the water.

This combination of the boom and the granulated glass wool forms a protective structure which prevents the further spreading of oil, even when the sea is rough. From the area limited by the booms, it is possible to lift the oily wool back to the vessel with e.g. a grab bucket fixed to a hydraulic crane boom, or with a nylon net. The catch is emptied into a funnel leading it into a centrifuge or on to a suction wire.

After the centrifugalizing or the suction process, where the oil is separated by means of centrifugal force or suction air from the granulated mineral wool, the oil is led to a separate container, which can be either a big, floating "sock" made of rubber or some other container. The granulated wool can be e.g.

blown or otherwise conveyed to the surface of the sea for a new recovery process. This can be repeated over and over again. Thus it is possible to master a limited leakage with this method until the leakage is stopped or the whole bunker in the vessel is emptied to the sea level and other actions to save the situation have been organized.

It is already known to use mineral wool to absorb and to retain oil from the surface of the water (the Finnish Patent No 43289, the US Patent No 3,933,632 and the British Patent No 1 235 463), both glass wool and rock wool. The great capacity of the mineral wool to absorb oil has been demonstrated in these methods.

In these methods the used mineral wool has been regarded as a non-recurrent material, which is burned together with the oil absorbed in it. When the material is burned, the binding material on the fibre is destroyed and the material loses its good absorptive and floating qualities. The binding material is a very important factor as to the absorbtion process. To coat the burned fibre anew is very laborious and in the field work of the oil prevention practically impossible, as the covering requires, among other things, an accurate heat treatment. The coal which remains on the fibre after the burning is not good enough as to its absorbtive qualities, and furthermore, it can be washed away.

When the mineral wool is used as a non-recurrent material there are no specific requirements as to its oil retaining capacity. One has been satisfied with the absorbtive or absorbent capacity, which is inherent in most mineral wool materials. With the oil retaining capacity it is thus meant its ability to retain oil in itself when lifted up in the air. This property is essential in the method, where granulated glass wool is used as a "transfer vessel", when the oil is removed from the water to the tanker. The retaining of the oil, on the other hand, must not be excessive, as in some well know; methods, where heavy metals are added to the fibre structure of the mineral wool in order to improve the absorbtion and retaining capacities.By so doing the material loses most of its floating capacity and thus makes it difficult to remove the oil by other methods than by burning. It is known, as well, that mineral wool whose volume weight is relatively small, absorbs more oil in comparison to its weight than a heavier wool, but, correspondingly, the retaining capacities decrease so much that this prevents the transference of oil from one place to another, as the material acts like a leaking "transfer vessel". The use of non-recurrent material in the vessel presupposes a very large storage of mineral wool, and this is why its use as a preventing material has not reached the level which its properties imply.

The present invention is based on the discovery that one particular glass wool material in the form of granulated glass wool possesses such an inner structure - after having been made of a proper glass wool blank bound with plastic resin and heat-treated -- that it has a notable capacity of retaining oil and that it is possible to remove oil mechanically out of the structure by using earlier known methods such as suction and centrifugalizing so that both the structure of the glass wool is preserved as well as the resin on the fibres after the oil removal treatment. This makes it possible to use the same glass wool material repeatedly, and, consequently there is needed only a limited storage of glass wool on e.g. a tanker, which, further, makes it possible for the crew itself to carry out the prevention actions with proper equipment.

It is a characteristic feature of the method according to the invention that by using the already known method of suction or centrifugalizing it is possible to remove and to recover at least 90% of the oil absorbed in the granulated wool providing that the degree of absorbtion into the wool is adequate. It has been proved by experiments that by squeezing the oil out it is impossible to remove the same quantity of oil without breaking the structure.

It is a characteristic feature of the granulated mineral wool used in this method that after the described oil removal it can absorb essentially the same quantity of oil as the removed one once again.

A characteristic feature of the granulated wool used in this method is also the fact that the oil is absorbed from the surface of the sea to the free spaces in between the fibres and that when the wool is lifted from the sea permitting it to drain for one minute, the major part or at least 60% of the absorbed oil remains in it.

A characteristic feature of the granulated wool used in this method is also that a limited amount of moisture in the wool does not essentially impair its utilization in this method.

A characteristic feature of the granulated wool used in this method is also that the absorbed oil does not significantly flow away with the slow passing through of the water caused by the rough sea.

It has been discovered that the best material for this purpose is granulated wool which consists ot minor, one-size mineral wool pieces, and where the amount of loose fibres is small. The average diameter of the fibres must be from 3 to 20 jim. There should not notably be so called pearls. The volume weight of the granulated wool should preferably be from 40 to 120 kg/m3 and most suitably from 70 to 110 kg/m3. The fibres must be coated with plastic resin, which, at the same time, bonds the fibres together. The granulate is made by cutting a mineral wool blank in pieces.

A characteristic feature of the granules of the described material is their elasticity which arouses from the homogenity of the structure and which makes it possible that it including the coating material can endure mechanical treatment such as lifting out of the water by drug bucket, net or the like; centrifugalizing, suction or blowing by a fan or some other kind of spreading it out without being damaged.

It has been proved by experiments that the granulate used in the method blown on the surface of the water will float on the water at least 6 months and that the portion sinking is appr. 1%.

It has also been proved experimentally that the properties of the granulate used in the method are not essentially impaired after having been stored even for several years tightly packed.

Although, in the described embodiments of the invention, the material used has been glass wool it does not range out the possibility of using other mineral wools as well, if only their properties meet the requirements of the method. Although in the described embodiment oil is removed from the surface of the water back to the tanker, from where the leakage has taken place, the method of the invention is not restricted to this application but can also be used in other kinds of vessels, especially in vessels built for oil removal purposes. In this latter case it is possible to use a wire sunk into the water as an oil collecting means. It can also be used on harbour docks and equipments, in oil recovery actions taken from the ice or any other firm base or for removal of oil from ditches and pits, etc.

The method according to the invention can also be used for removal of other liquids similar to oil, such as: combustible oils, kerosene, metanol, alcohols, solvents and paints.

EXAMPLES 1. The capacity of absorbtion and of retention was measured with the equipment which consisted of an absorbtion vessel of 6.8 litres furnished with a bottom with holes having the diameter of 260 mm and of an oil container having a diameter of 300 mm. Granulate of glass wool of various volume weights were placed in the absorbtion vessel which was placed into the oil container. After the absorbtion the bottom tap of the oil container was opened and the amount of the absorbed oil was measured. The absorbtion vessel was lifted out of the container and the oil was allowed to drain during one minute of time, after which the oil retained by the wool was measured. The used oil was commercial diesel fuel.

The experimental temperature was +200 C.

The results are presented in the table below: Volume Weighed Absorbed Retained Retention weight granulate Absorbed Retained I of o/ I of o/ of absorb Test kg/m3 (9) ml ml kg of g kg of g tion % 1 120 816 5930 4580 7.2 5.6 78 2 100 680 6280 5240 9.2 7.7 84 3 62 422 5930 4710 14.0 11.2 80 4 52 354 6100 4250 17.2 12.0 70 5 20 136 4750 2370 34.9 17.4 50 I ofo = litres of oil kg of g = kilogrammes of granulates 2. A centrifugalizing experiment was carried out by using a washing machine, whose rotational speed was 2700 r/min, the centrifugalizing time was one minute, the temperature was +20 C. The oil used was diesel fuel and as absorbtion material granulated glass wool having a volume weight of 48 kg/m3 was used.

TEST 1 Weight of Retained Centri- Oil re- Separated original oil + Retained fugalized Separated mained in oil of granulate granulate oil granulate oil granulate retained Phases (g) (9) (9) (9) (9) (9) 1 500 3803 3303 612 3191 112 97 2 612 3580 3080 603 2977 103 97 3 603 3419 2919 602 2817 102 97 4 602 3386 2886 611 2775 111 96 TEST 2 1 500 3800 3300 607 3193 107 97 2 607 3607 3107 607 3000 107 97 3 607 3607 3107 615 2992 115 96 4 615 3615 3115 603 3012 103 97 5 603 3603 3103 605 2998 105 97 6 605 3605 3105 602 3003 102 97 3. The use of moist wool in absorbtion and its floating capacity.

The experiment was carried out in the laboratory for the combustible and lubrication materials of the Technical Research Institute of Finland in Espoo, on the 7th of April, 1978. The volume weight was defined by weighing and by measuring and with the method of Klein and Ander. The percentage of the moisture was defined according to DIN 51718. The oil retention capacity was defined by the method of Sturz and Klein. The experimental temperature was +20 C and the oil diesel fuel.

RESULTS: Oil Volume retention Floating Volume weight of capacity capacity weight Moisture dry substance I of oil/kg of 1 h after Sample kg/m3 % kg/m3 granulate the mixing 1 59.2 0.4 59.0 10.5 > 99 2 59.7 0.72 59.0 10.9 > 99 3 93.6 23.7 71.4 5.87 > 99 4. 10.3 9 of granulated glass wool in which 49.8 9 of crude oil had been retained was placed in a glass tube having a diameter of 40 mm and a height of 300 mm. 10 I of water was poured through the tube with a speed of 5 I/h. The separated quantity of oil was 3.6 9 or 7% of the retained oil.

5. Suction tests were carried out by using a vessel with a screen bottom, in which a vacuum of 900 mm water was maintained. The volume weight of the granulate was 48 kg/m3 and diesel fuel was used as oil, the temperature was +20 C. The suction time was 1 min.

Weight of Oil Weight of Retained granulate retained original oil + Retained aft suction Separated in the Separated/ Phases granulate granulate oil treatment oil granulate retained (9) (9) (9) (9) (9) (9) TEST 1 1 80 503 423 178 325 98 76.8 2 178 480 302 175 305 -3 100 3 175 461 286 186 275 11 96 4 186 457 271 179 278 -7 102.5 TEST 2 1 60 404 344 146 258 86 75 2 146 385 239 139 246 -7 103 3 139 382 243 135 247 -4 102 4 135 368 233 136 232 1 100 TEST 3 1 40 269 229 81 188 41 82 2 81 268 187 81 187 - 100 3 81 256 175 81 175 - 100 4 81 246 165 80 166 -1 100

Claims (5)

1. A method of removing oil or similar liquids from the surface of water or solid material, in which the liquid is absorbed in granulated mineral wool and is separated from it in order to recover the liquid and in order to reuse the granulated mineral wool for absorbtion of liquid, characterized in that the liquid in the granulated mineral wool is separated from the granulated mineral wool without breaking down the structure of the mineral wool by subjecting it to the influence of a centrifugal force or a pressure difference.

2. The method according to claim 1, characterized in that the liquid in the granulated wool is separated by centrifugalizing.

3. The method according to claim 1, characterized in that the liquid in the granulated mineral wool is separated by means of suction.

4. The method according to claims 1, 2 and 3, characterized in that at least 90% of the liquid retained in the granulated mineral wool is separated.

5. A method of removing oil or similar liquids from the surface of water or solid material substantially as herein described.