WO1999040163A1

WO1999040163A1 - Composition

Info

Publication number: WO1999040163A1
Application number: PCT/SE1999/000140
Authority: WO
Inventors: Gunnar KÄLLSTRÖM
Original assignee: Kaellstroem Gunnar
Priority date: 1998-02-03
Filing date: 1999-02-03
Publication date: 1999-08-12
Also published as: SE9800303D0; AU2648899A; NO20003834L; AU2648999A; NO314187B1; WO1999039821A1; NO20003834D0; SE9800303L; SE511486C2

Abstract

The invention relates to a de-icing composition containing sawdust, lime and ash from combustion of biofuels. The invention also concerns use of such a composition as protection against skidding, caused by frozen water, on a ground surface.

Description

COMPOSITION

Field of the Invention

The present invention relates to a de-icing composition, i.e. a composition for increasing the friction on ground surfaces . Background Art

In many parts of the world, problems with slippery ground surfaces, especially roads, pavements, parking spaces and the like, arise periodically owing to the temperature falling below the freezing point of water. With a view to reducing this problem owing to slippery conditions, large amounts of de-icing agents are currently being applied.

De-icing agents in the form of compositions based on calcium chloride, or road salt, are common. The de-icing effect of road salt is caused by the fact that a salt solution melts at a temperature below 0°C. However, road salt cannot lower the melting point more than a few degrees and is therefore not used at temperatures below -10°C.

The use of road salt is disadvantageous in many respects. Chloride ions have a negative effect on plants. Great damage is done to vegetation, for instance, along roads that are treated with salt regularly. Since the salt also accompanies melted snow and ice, damage can arise even at a distance from the roads. Examples of typical such damage are water that has become unfit in wells close to roads and wetlands that have become affected. At the same time as the salts reduce the risk of accidents caused by slippery roads, it increases the risk of accidents caused by wild animals since animals tend to move to salt-treated roads to eat salt. Besides, the handling of road salt is heavy and energy-consuming. Moreover the road salt causes corrosion on vehicles and 2 application equipment and also costly damage caused by corrosion on concrete structures and reinforcement.

Experiments with other de-icing agents have therefore been made. Examples of variants of less aggressive, salt-based de-icing compositions are described in, for instance, patent application SE 9404184-5, in which wood ash is mixed with the salt, and in US-4,400,285 in which lime is mixed with the salt. However, none of these is a perfect alternative in actual practice. Both suffer from several of the drawbacks of salt.

Salt -free variants that have been used are sand and, in recent years, for instance, crushed stone and crushed shells, but also these materials suffer from drawbacks. Admittedly, they are not aggressive and harmful to the environment in the same way as road salt, but they are not as effective either. However, like road salt they are heavy to handle in connection with the application. Moreover, lumps frequently form owing to the freezing of water between the particles. This causes great wear to machinery. The above materials also cause damage by flying up from the road and hitting vehicles.

Thus, there is a need for an effective, light de- icing agent which has more advantages and fewer drawbacks than the prior art de-icing agents. Summary of the Invention

An object of the invention is to provide a de-icing composition which is a very small strain on the environment .

A further object of the invention is to provide a de-icing composition which is easy to handle.

One more object of the invention is to provide a de- icing composition which does not cause damage to vehicles or handling machines.

According to the invention, the objects are achieved by a de-icing composition which consists of a mixture of sawdust, lime and ash from the combustion of biofuels. In the mixture, the sawdust constitutes a base which pro- 3 vides volume. At the same time it has a low density which obviates the problems of the heavy handling. The ash has the property of adhering well to the base and has in itself a rough character. Also the ash has a low density. The lime acts as a binding agent. This de-icing composition is considerably more lenient with the environment than all prior art de-icing agents. For instance, use is largely made of renewable raw materials and the composition has a low density, which means that transport and other handling require less energy than the heavier prior art compositions. Moreover, the raw materials can in many cases be collected in the areas where the use of the composition occurs, which also reduces the consumption of energy for transports . The ingredients have no known negative effect on the environment surrounding the ground surfaces on which the composition is applied. In addition, the wear to machinery is small, the composition has no negative effect on vehicles etc.

According to an advantageous embodiment of the co - position according to the invention, lime is included to a part by weight of at least 1% and at most 50%, ash to a part by weight of at least 1% and at most 25%, sawdust constituting the balance up to 100%. The amount of lime preferably is 1-25% by weight. Below the lower limits for lime and ash, they have no noticeable effect on the properties of the composition. If the upper limit for lime is exceeded, the composition tends to be user-unfriendly. This also applies to ash.

According to another advantageous embodiment, the lime consists of slaked lime [Ca(OH)₂], which has an excellent de-icing effect. Moreover, the slaked lime is considered water repellent, which contributes to giving the composition the property of swimming on the top of a ground surface coated with ice and/or water and remaining on the surface as frost forms again, for instance at night or when the weather changes to colder weather. Thus, the de-icing composition acts actively in weather that knocks out the function of traditional de-icing compositions.

According to one more advantageous embodiment of the inventive de-icing composition, it also contains sand. Sand adds a certain weight which facilitates the application and initially contributes to the composition staying more easily on the ground surface. Detailed Description of Embodiments

The de-icing composition contains at least the three ingredients sawdust, lime and ash from combustion of biofuels. It is not technically important from which species of wood the sawdust is prepared, but essentially any species of wood will do. 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 important that the wood raw material is, if possible, available in the areas where use of the product occurs, thereby limiting the transports. Thus, the species of wood spruce, pine and birch are particularly preferred, but the sawdust may also be prepared from species of wood such as alder, elm, aspen, beech, maple, larch tree etc. The size of the sawdust may vary but the diameter should preferably be within the range of 0.1- 5.0 mm. An environmental advantage is that the sawdust can be collected from raw materials that are otherwise not used or have a low refinement value, such as brushwood, twigs etc.

The lime preferably consists of slaked lime. Except that the lime generally binds the various ingredients together, the slaked lime has a moisture-repelling effect which gives the composition a good storage life. The lime is included in the composition in a finely divided state.

The used ash is a residual product from heating by using biofuels. For environmental reasons, it is desir- able for the amount of environmentally harmful, non- combustible substances such as heavy metals in the fuels to be as small as possible. For this reason, use is pre- 5 ferably not made of, for instance, ash from incineration or combustion of fossil fuels. By the term biofuels is here meant different kinds of wood, such as wood from pine, spruce, birch, alder, elm, aspen, ash, beech, oak, lime, larch tree or maple, raw materials from energy forests, such as willow, sallow or poplar etc. Also straw, brushwood and other vegetable raw materials can be used and are here included in the term biofuels.

The proportions in which the ingredients appear may vary as follows, the figures indicating % by weight:

Lime at least about 1 and at most about 50

Ash at least about 1 and at most about 25

Sawdust the balance for the sum to be 100.

The amount of lime as well as the amount of ash are preferably at least about 10% by weight. A typical composition of the de-icing composition, or the de-icing agent, according to the invention is in respect of volume 5 parts by volume of sawdust, 1 part by volume of lime and 1 part by volume of ash. To provide a picture of the connection between volume and weight, the following examples can be mentioned. When producing the composition, use was made of sawdust supplied by Rόdnins Travaru AB at Skanderasen, Sweden. This saw mill produces sawdust which consists of essen- tially equal parts of spruce and pine, having 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 bio fuel consisting of forest raw materials with about 20% peat added. The density of the ash was 609.2 kg/m³.

The slaked lime [Ca(OH)₂] that was used was supplied in finely divided state by Nordkalk, Sweden. Its density was 444.5 kg/m³.

The above proportions are valid in general . In some cases or for certain types of base and other conditions, also other proportions can be usable or even preferred. An important factor in the context is also the properties 6 of the sawdust, such as surface structure, type and size, and, above all, the ratio of surface area to weight. For a high-density species of wood, this ratio is comparatively low whereas a species of wood having a low density and/or a porous surface structure has a high ratio. For instance, a composition with equal parts of sawdust, lime and ash has been found to function well .

According to a preferred embodiment, the composition is produced by supplying sawdust, slaked lime and ash to a mixer. Subsequently, 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 water-repellent properties of the slaked lime and certainly also of the ash are used innovatively by achieving the above-mentioned advantage when changing between mild and cold weather. In addition, it will be possible to store the de-icing composition outdoors since it keeps the moisture away. The composition is stable at all temperatures appearing in reality, indoors as well as outdoors, and there is no formation of lumps at temperatures below the freezing point.

In a last step in the production, any excess of ash and lime, which has not adhered to the sawdust, is removed and returned to the beginning of the production process. This results in an efficient use of the raw materials and a product which is fairly free from dust, which facilitates the handling thereof. In an alternative production process, the aggregation is advanced one step further by granulating or sintering the mixture in a manner known to those skilled in the art. As a result, the final product becomes essentially completely dust-free, which makes it particularly user-friendly.

Alternatively, also sand can be added to the composition, in which case, in addition to the amount of saw- 7 dust, also the amount of the other ingredients may need to be modified in relation to the amount of sand. The sand yields a more homogeneous mixture, which may be advantageous in connection with the handling of the composition. In addition to the above-mentioned advantages, it can be mentioned that the sand further promotes to some extent the considerable increase in friction that the composition produces on the ground surface to which the composition is applied. The friction- increasing effect, however, is excellent also without sand in the mixture, which is accomplished by the ash "sticking to" the surface .

The inventive de-icing composition thus has many advantages. Besides those already mentioned, it should be pointed out that the inventive de-icing composition does not act by melting ice and packed snow but instead adheres well on top of the surface and forms a base with high friction compared with packed snow and ice. A difficulty in connection with prior art de-icing agents containing ice-melting components is that they tend to disappear in the slippery layer and thus have a considerably deteriorated effect some time after being applied. This effect is frequently particularly noticeable if the sun is shining. However, the inventive de-icing composi- tion retains its good properties even if subjected to the warmth of the sun or heated. Besides, the fact that the composition has no melting effect allows it to be applied as a preventive measure in good time before estimated problems caused by slippery conditions, which is particu- larly advantageous if there is a risk that the roads will become treacherously icy.

The ash and the sawdust are biodegradable. Also slaked lime has no negative effect on the environment. Owing to these conditions, the inventive de-icing agent must be considered to be very environmentally friendly.

Salt and salt -containing prior art de-icing compositions are pale or even transparent. This causes problems when treating slippery roads, abrupt changes frequently occurring between different districts. A treated road passes, without any previous warning, into an untreated one, which may have devastating accidental consequences. However, the ash in the present composition yields a dark tint which is in glaring contrast to pale snow and ice surfaces.

Finally, it can be mentioned that despite a large amount of biological substances, the composition has good storage stability outdoors as well indoors. The contents of ash cause vermin not to thrive .

The description above constitutes but a non-limiting example of how the inventive composition can be formed.

Many modifications are feasible within the scope of the invention as defined in the appended claims.

Claims

1. A de-icing composition, c h a r a c t e r i s e d in that it contains sawdust, lime and ash.

2. A de-icing composition as claimed in claim 1, c h a r a c t e r i s e d in that the ingredients are included in the following amounts: lime: >1% by weight and <50% by weight, respectively; ash: >1% by weight and <25% by weight, respectively, and sawdust: the balance for the sum to be 100% by weight.

3. A de-icing composition as claimed in claim 1 or 2, c h a r a c t e r i s e d in that the ingredients are included in the following ratio by volume: lime: 1 part; ash: 1 part and sawdust: 5 parts.

4. A de-icing composition as claimed in any one of claims 1-3, c h a r a c t e r i s e d in that in addition to the other ingredients, it also contains sand.

5. A de-icing composition as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that the lime is slaked lime.

6. A de-icing composition as claimed in any one of the preceding claims, c h a r a c t e r i s e d in that the ash is ash from combustion of biofuels.

7. Use of a de-icing composition according to any one of claims 1-6 to protect against skidding, caused by frozen water, on a ground surface.