WO1999039821A1

WO1999039821A1 - Absorbent

Info

Publication number: WO1999039821A1
Application number: PCT/SE1999/000141
Authority: WO
Inventors: Gunnar KÄLLSTRÖM
Original assignee: Storsjohus Byggkomponenter AB
Current assignee: Storsjohus Byggkomponenter AB
Priority date: 1998-02-03
Filing date: 1999-02-03
Publication date: 1999-08-12
Anticipated expiration: 2000-08-03
Also published as: SE9800303D0; NO20003834D0; SE9800303L; WO1999040163A1; NO20003834L; NO314187B1; SE511486C2; AU2648999A; AU2648899A

Abstract

An absorbent comprising at least one wood-chip product, ash and slaked lime is described. The absorbent may also comprise ground dusted paper. The described absorbent is especially suitable for collecting oil from a surface of water.

Description

ABSORBENT

Field of the Invention

The present invention relates to an improved absorbent for absorption of oils and other hydrophobic liquids. Background art

Japanese patent specification JP 8103764 A discloses a method for treating, for instance, waste oil. According to this patent specification, the waste oil is mixed with combustion ash and sawdust, and then the mixture is dried. It is also possible to use limestone together with the ash and the sawdust. The method can be used, for instance, for treating waste oil at petrol stations, in garages or on roads. The method can also be used to remove different types of waste solutions, such as clay water.

A drawback of the method described in the above Japanese patent specification is that the mixture of combustion ash, sawdust and possibly limestone that is used absorbs water together with the oil . The method according to the Japanese specification is based on water being absorbed together with any pollutants, such as oil. The water is then removed by drying and leaves a pulverulent material consisting of combustion ash, sawdust, pollutants and possibly limestone. The removal of water by drying may cause certain environmental problems since also highly volatile organic substances can evaporate in the drying process.

Moreover, the method according to the Japanese patent specification is not suitable for absorption of oil swimming on a surface of water since the mixture used will then absorb very large amounts of water, which on the one hand deteriorates the absorption of oil and, on the other hand, finally results in the product sinking and thus being difficult to collect. 2

There is thus a need for a more efficient absorbent, especially an absorbent that can be used to absorb oil in water, which may originate from, for instance, discharge of oil from ships. Summary of the Invention

An object of the present invention is to provide a new, improved absorbent for absorption especially of oils .

A further object of the invention is to provide an absorbent for absorption of oils swimming on a surface of water.

A further object of the invention is to provide an absorbent which is an extremely small strain on the environment . The objects are achieved by an absorbent comprising a mixture of at least one wood-chip product, preferably sawdust, slaked lime and ash, preferably ash from bio- fuels. The absorbent may also comprise ground dusted paper. The inventive absorbent enables quick and effective absorption of oil and oil-like products as well as other hydrophobic liquids in various surroundings. An important feature of the absorbent according to the present invention is that it does not absorb water or absorbs water but to a small extent, thereby avoiding the above problems of the method according to the Japanese patent specification.

The inventive absorbent is very lenient with the environment. For instance, renewable raw materials are preferably used to a great extent. The absorbent also has low density, which means that transports and other handling consume a small amount of energy. Moreover, the raw materials can in many cases be collected in the areas where the composition is intended to be used, which also reduces the consumption of energy for transports. 3

Detailed Description of the Invention

As mentioned above, the inventive absorbent comprises at least one wood-chip product, ash and slaked lime. It is possible to use many types of wood-chip products and also other similar products, such as finely chopped straw. The wood-chip product preferably used is sawdust . It is of no technical significance from which species of wood the sawdust is prepared but essentially any species of wood is appropriate. However, it is important from the economic point of view that the wood raw material is as cheap as possible. From the environmental point of view it is also important that the wood raw material is available in the areas where the absorbent is intended to be used, thus minimising the - number of transports. Consequently the species of wood spruce, pine and birch are particularly preferred although it is conceivable to produce the sawdust from species of wood such as alder, elm, aspen, ash, beech, oak, lime, larch tree, maple etc. The size of the sawdust may also vary but the diameter is preferably in the range 0.1-5.0 mm. Sawdust of a suitable size can be obtained from, for instance, saw mills using circular saws. The saw dust can also be collected from raw materials that are otherwise not used or that have a low refinement value, such as brushwood, twigs etc., which additionally contributes to the environmental advantage of the absorbent .

It is also possible to use other wood-chip products, such as bark. The ash in the absorbent according to the present invention is preferably ash from combustion of biofuels or heating using biofuels. For environmental reasons, it is desirable for the amount of non-combustible substances that are harmful to the environment, such as heavy metals, in the fuel to be as small as possible. For this reason, ash from incineration or combustion of fossil fuels is preferably not used. By the term biofuels is here meant 4 different kinds of wood, such as wood from pine, spruce, birch, alder, elm, aspen, ash, beech, oak, lime, larch tree, maple, raw materials from energy forests (willow, sallow, poplar) etc. Also straw, brushwood and other vegetable raw materials can be used.

Both the ash and the sawdust used are biodegradable, which contributes to making the absorbent harmless to the environment .

The third component in the absorbent according to the invention is slaked lime. The slaked lime is preferably used in a finely divided state. The particle size is not decisive, but the important thing is that the product is well mixed and approximately homogeneous. All this results in the absorbent being considered highly environ- mentally friendly.

It is the slaked lime that gives the absorbent according to the invention its excellent behaviour in water and contributes to the fact that the absorbent does not absorb essentially any water at all. The inventive absorbent comprises preferably the three ingredients in the following amounts: slaked lime: 1-50% by weight, ash from combustion of biofuels: 1-25% by weight, and sawdust: the balance for the sum to be 100% by weight. Preferably, the amount of slaked lime is 1-25% by weight.

A typical composition of an absorbent according to the invention is 5 parts by volume of sawdust, 1-2 parts by volume of slaked lime and 1 part by volume of ash from combustion of biofuels. The above proportions of the ingredients are only stated as an indication. For instance, it is also possible to use 1 part of sawdust, 1 part of ash and 1 part of slaked lime. Suitable amounts are decided, among other things, by what type of oil is to be absorbed and from which kind of environment it is to be collected.

The composition is produced according to a preferred embodiment of the invention by introducing sawdust, slaked 5 lime and ash into a mixer with a certain excess of lime and ash. Then the components are mixed by means of the mixer. By mixing, the components aggregate so that ash and lime adhere to the surface of the sawdust. This process can be resembled to glazing of the sawdust with lime and ash so that an encapsulating layer of lime and ash forms on the sawdust. The fact that the slaked lime which is hydrophobic, and also the ash which to some extent is hydrophobic, encapsulate the sawdust, results in the ab- sorbent as a whole being hydrophobic. In a last step of production, the excess of ash and lime is removed and returned to the beginning of the production.

The absorbent can, in addition to the three ingredients stated above, also contain finely divided paper, such as ground dusted recycled paper. Such an addition of paper is advantageous since a smaller amount of dust is generated when using the absorbent, which is particularly important for indoor use. Besides, the product will be lighter per unit of volume when it contains paper, which can be an advantage, for instance, when the product is to be used for absorption of oil swimming on water. Pel- letised recycled paper is preferably used, to which it is possible to add a colour pigment as well. This is an additional advantage when collecting waste oil swimming on water since the pigment makes it easier to distinguish the absorbent and the absorbed oil from the surface of water. Preferably, use is made of an amount of finely divided paper which corresponds to the used amount of sawdust. When collecting oil from a surface of water, the absorbent should, however, contain only a small amount of paper since otherwise the absorbent loses its hydrophobic properties .

The inventive absorbent is suitable for absorption of oil and petroleum waste outdoors as well as indoors. The absorbent can be used to absorb, for instance, oil on gravel pitches, asphalt, concrete and water. 6

Since the absorbent has hydrophobic properties, above all when it does not contain any paper product, it is particularly advantageous when collecting oil swimming on a surface of salt water and fresh water. Since the product does not absorb any water, or absorbs merely very small amounts of water, it does not settle and is therefore easy to collect after the absorption of oil.

After the absorption of oil, the product is removed and destroyed or buried in some suitable manner. The inventive absorbent has excellent storage properties. The contents of ash imply that vermin does not thrive in the absorbent, which means that indoor storage is possible. The composition is also stable at any temperatures occurring in reality indoors and outdoors, and there is no formation of lumps at temperatures below the freezing point. An additional advantage in storage is that the absorbent does not absorb any moisture. It is possible to pelletise, granulate or sinter the composition by applying techniques which are well-known to those skilled in the art. Such a form further increases the user-friendliness .

One more advantage of the inventive absorbent is that when being spread over a surface of oil , it prevents air from being supplied to the oil. This property makes it possible to use the absorbent also for extinguishing and collecting a burning oil product. When the absorbent is applied to the burning oil, the supply of oxygen is throttled and the fire thus goes out. When the fire has gone out, the absorbent immediately begins to absorb the oil.

The invention will now be described in more detail by way of the following examples. These examples are only intended to illustrate the invention and do not in any way restrict the scope of protection. Example 1

5 1 of pine sawdust with an average diameter of 9 mm, 1 1 of powdered slaked lime and 1 1 of finely 7 divided ash from the combustion of birch wood were carefully mixed in a vessel and then pelletised. The resulting composition had a density of 0.3 kg/m³.

The composition was spread over waste oil on the floor of a workshop. 1 kg of the composition was sufficient to absorb the oil on 21 m² of floor covered with waste oil. Subsequently, the oil could easily be removed from the floor together with the absorbent . Example 2 The absorbent used in this example consisted of 5 parts by volume of sawdust, 1 part by volume of ash and 1 part by volume of slaked lime.

The sawdust that was used had been supplied by Rδdnins Travaru AB at Skanderasen, Sweden. This saw mill produces sawdust which consists of essentially equal parts of spruce and pine, with a dry solids content of 68.3% and a density of 174.9 kg/m³.

The ash used was wood ash from the district heating power plant Jamtkraft at Lugnvik, Sweden, which uses biofuel consisting of forest raw materials with about 20% peat added. The density of the ash was 609.2 kg/m³.

The slaked lime [Ca(0H)₂] that was used had been supplied in finely divided state by Nordkalk, Sweden. Its density was 444.5 kg/m³. With a view to determining the absorption capability of the absorbent according to the invention, absorption tests were carried out with the nine different oils that are stated in Table 1 below. 1 1 of each oil was poured onto a hard surface where building protective plastic had been applied to protect the base. 1 1 of each of the oils was poured onto the base, and 3 parts by volume of the absorbent were added to each oil. 2 min after the adding of the absorbent, the treatment of the waste oil with a squeegee began, and 5 min later, the absorbent together with absorbed oil was swept up. The results are shown in Table 2 below. Table 1

Type of oil Density Viscosity (g/dm³) at 20°C

(cSt)

Synthetic Hypoid syntol 861.5 550 75W/140 (Statoil)

Synthetic motor oil 870.5 250 (Mobil 1)

Transformer oil 868.4 (not determined) (Nynas Naphynycs)

Mineral motor oil Max-Way 872.8 320 15W/40 (Statoil)

Biodegradable hydraulic oil 816.0 60 Hydro-Way Pa 32 (Statoil)

Unmixed glycol 1 123.4 (not determined) (Statoil)

Hydraulic oil SHS 32 855.4 65 (Agrol)

Diesel oil 803.7 (not determined) (Neste)

Waste oil 868.3 (not determined)

Table 2

Oil Result

No.

1 After treatment for about 3 min, all the oil was absorbed. After collection, there was no oil left on the base.

2 After collection, no oil was left on the base.

3 After treatment for about 3 min, all the oil was absorbed. After collection, there was no oil left on the base.

4 After collection, there was no oil left on the base.

5 After treatment for about 2 min, all the oil was absorbed. After collection, there was no oil left on the base.

6 After collection, there was no glycol left on the base.

7 After collection, there was no oil left on the base.

8 After collection, there was no oil left on the base.

9 After collection, there was no oil left on the base (the base, however, had been

discoloured by the oil) .

For comparison, the oils 8 and 9 were treated with sawdust only. Otherwise the tests were carried out as above. The results are shown in Table 3 below. 10

Table 3

Oil Reference results No.

8 The oil began to be absorbed immediately when adding the sawdust, which however was quickly saturated. After collection, a thin film was still left.

9 The oil began to be absorbed immediately when adding the sawdust, which however was quickly saturated. After collection, a thin film was

still left.

With a view to determining the behaviour of the absorbent in moist surroundings, equal parts of glycol and water were mixed, and the mixture was poured out and treated as described above. After collection, a thin film was still left on the base, which indicates that the water is not absorbed to the same extent as oils or unmixed glycol . Example 3

To further demonstrate the excellent function of the absorbent in the presence of water, 1 dl each of the oils 2, 5 and 8 from Example 2 was poured into a vessel containing 1.5 1 of water. Then 3 dl of the absorbent used in Example 2 was spread over the oil . The vessel was rocked back and forth to simulate wave motions. After 5 min, the absorbent together with the absorbed oil was ladled by means of a sieve into a glass bowl. The remaining water was then poured into a graduated glass (2 000 ml) and was allowed to stand for 4 h for separation of water and the remaining oil. The result is shown in Table 4 below. 11

Table 4

il Total amount of liquid Amount of oil of Absorption o. transferred to the the total amount of oil graduated glass (ml) (%)

(ml)

2 1 450 about 1 about 99

5 1 435 < 1 > 99

8 1 430 about 1-2 about 97-97

In this experiment, it is true that the absorbent absorbed a small amount of water, which, however, was caused by some ash and lime falling to the bottom and uncovering sawdust which thus could absorb water. Example 4 In this Example, 2 dl of diesel oil was poured into a sheet metal vessel and then ignited. When the flame of fire was about 3 dm high, 6 dl of the absorbent from Example 2 was thrown over the seat of the fire. The fire then went out, and all diesel oil was absorbed by the absorbent within about 3-4 min.

Claims

12CLAIMS

1. An absorbent for oils and other hydrophobic liquids, comprising at least one wood-chip product, ash and slaked lime.

2. An absorbent as claimed in claim 1 , wherein said wood-chip product is sawdust.

3. An absorbent as claimed in claim 2 , wherein the size of the sawdust is between 0.1 and 5.0 mm.

4. An absorbent as claimed in any one of claims 1-3, wherein the ash is ash from the combustion of biofuels.

5. An absorbent as claimed in claim 4 , wherein the ingredients are included in the following amounts: slaked lime: 1-50% by weight, ash from the combustion of biofuels: 1-25% by weight, sawdust: the balance for the sum to be 100% by weight.

6. An absorbent as claimed in claim 5, containing 1- 25% by weight of slaked lime.

7. An absorbent as claimed in claim 5 or 6, containing 5 parts by volume of sawdust, 2 parts by volume of slaked lime and 1 part by volume of ash from the combustion of biofuels.

8. An absorbent as claimed in claim 7 , wherein the amount of slaked lime is 1 part by volume.

9. An absorbent as claimed in any one of claims 1-8, further comprising ground dusted paper.

10. An absorbent as claimed in claim 9, wherein the amount of ground dusted paper is essentially the same as the amount of sawdust.

11. Use of an absorbent as claimed in any one of claims 1-8 when collecting oil from a solid base.

12. Use of an absorbent according to any one of claims 1-10 when collecting oil from a surface of water.

13. A method for collecting oil, charac t er i sed by the step of contacting the oil with a wood- chip product, such as sawdust, ash and slaked lime.