NO122874B - - Google Patents

Description

Process for encasing powdery to granular particles with bituminous binders.

The present invention relates to a method for coating powdery to granular, moist, unheated solid particles with bituminous binders using metal compounds*

The invention is primarily intended to provide a method in which, in the production of bituminous mixed materials, e.g. for road construction, avoids the otherwise usual road development, i.e. a passing of very fine particles below

the drying process.

In known methods for producing bituminous mixed material, e.g. for road construction, it is preferably sorted to a low residual water content of approx. 0.5% dried and mostly up to 160-200°C heated mineral is fed over a weight into a mixer and coated here with bituminous binder. A prerequisite for the coating is, as discussed, a thermal pre-treatment of the mineral, during which pre-treatment a separation of the fine particles carried in by the drying gas flow takes place. In order to free the exhaust gas space from its dust content and to be able to add this dust to the mixture, in which it has an important function, as well as to prevent unacceptably high dust emissions,

often complicated technical aids are required, such as cyclones, wet scrubbers, filters etc. to such an extent that an economical treatment of such mixed goods, especially in residential areas, industrial agglomerations, nature conservation areas etc., for which the maintenance of certain permitted emission values is prescribed , is no longer possible* According to the invention, during the encapsulation of the particles, excretion of fine particles is avoided, i.e. formation of stciv, in that mineral solid particles, which in their mineral structure contain water and/or moisture on their surface, are first mixed in a cold state with a liquid bituminous binder, preferably with the addition of basic chromium salts that improve adhesion, and that in addition to that the obtained mixed goods. in a drying device, preferably a dryer, is subjected to a heat treatment at a temperature of over 80°C, preferably 140°C.

When using high temperatures and/or using suitably coordinated binders, it is possible in some cases to refrain from adding adhesion-improving additives and still achieve coatings that fulfill the intended purpose."

When carrying out this procedure, e.g. for road construction, it is practical in practice to add the not yet dried mineral substances, which normally have a moisture content of 3-5JC H•WO, in a mixer, preferably over fine distribution devices, at the same time as the binder and the aforementioned additives, so that the a sufficient static distribution of these substances on the surface of the mineral substances is achieved. After the addition has taken place and the desired mixing state has been achieved, the mixture is fed - in discontinuous operation - via a leveling container and a removal device continuously to a drier, preferably a drier, and is heated in this to a temperature of over 80°C, preferably 140°C. Already when the 80°C threshold is exceeded, the activation process begins, i.e. the chromium salt solution displaces the water adhering to the surface of the mineral substances and embedded in the pores and makes the individual mineral particles permanently water-repellent. In contrast to many known adhesive additives, the effect of the chromium salts is not reduced by the high temperatures.

The surfaces pre-treated in this way bind the binder through the activation of the adhesion forces and, at the same time as the previous extra rolling of the goods in the drum, result in a complete envelopment of the individual mineral particles.

If, after the end of the heat supply, the mixture is cooled to 60°C or below this temperature, a storable and strobeable mixture is obtained, but at outside temperatures below 10°C it can be densified.

The material activated according to the described method surprisingly allows an additional solution of interesting problems, of which one in particular will be mentioned in this context. It concerns the bringing together of these activated minerals, preferably pike perch, with mineral oils, other oils or oily substances, whereby a permanent bond is created between the mineral substances and the oils.

When lining with activated sand or spraying activated sand can, for example, cause liquid mineral oil on water to sink permanently (tanker accidents), as practical trials have shown.

Should the binding of the mineral substances take place through an emulsion,

is it appropriate to encase the solids using an alkaline bitumen emulsion overstabilised on the basis of hydrolysed protein compounds,

which is activated by metal salts, preferably chromium salts,

and to which is added borax and a water solution of formaldehyde.

When using such an emulsion is practically eliminated

mentioned the difficulties occurring at temperatures above 25°C, especially above 40°C, without the amount of activator needing to be covered. The addition of borax to the basic chromium salt solution makes the emulsion insensitive to temperatures within the practical working range. Likewise, the beneficial influence of the addition of a water solution of formaldehyde has been established by practical research.

Furthermore, it has been shown that in the production of

such mixtures, for example also when producing slurries, it is appropriate to add cement to the emulsion in accordance with the plasticity of the binder in an amount necessary for the desired stiffness of the mixture.

With such an emulsion, it is e.g. possible to produce

a stopeasphalt that can be installed in a cold state, which exhibits hitherto unknown properties, such as e.g. extremely fast binding up to in the case of a large build-in thickness and a practically insignificant shrinkage during drying or the curing process.

It is particularly appropriate that it is added to the emulsion

a mixture of quick-setting cement and lime in a ratio of one hundred parts by weight of quick-setting cement to thirty to one hundred parts of lime. With this addition, the road surfaces can be loaded after a short time" The depth of penetration is thus directly related to the amount of biturne in the emulsion and to the amount of lime-cement mixture"

A further positive influence on the setting time when using regular cement instead of quick-setting cement can be achieved by iron sulphate (FeSO^7 HO) is added to the cement in such a ratio that the acidity of the iron sulphate easily exceeds the alkalinity of the cement.

In addition, barium sulphide can be used instead of chromium salt as an activating agent and instead of cement as a hydraulic binder. In this case, the reaction takes place according to the formula BaS + 9 HjO ■ Ba(OH)27 H20 + H2S. This is also particularly advantageous in the production of slurries and cold-build asphalt.

The method can also be used for enveloping substances other than mineral, e.g. crushed hard pitch of all kinds, hard pitch granules, inflated polystyrene or other plastics, sawdust and the like. Such mixtures are excellently suited for use as insulating material and also allow the production of shaped pieces, e.g. cylinders or half-cylinders for insulations.

In this context, for example, the possibilities associated with the crushed sheathed hard beaker should also be mentioned.

If hard pitch is encased, a hardenable, agglomerable mixture is formed under pressure and/or elevated temperature, which, placed around hot pipe surfaces, exhibits interesting effects, namely melting of the mass closest to the hot contact surface and sintering of part of the longer ones away from the hot flat lying enveloped pitch grains while maintaining a certain pore proportion, whereby an excellent insulating effect occurs. A similar result is also achieved without increasing the temperature by applying pressure, e.g. if one embeds in roughs in the ground for laying down certain rudders in shrouded pitch masses and in addition loads with the backfilling material.

These special emulsions allow the coating of all powdery to granular materials through their strongly thixotropic properties, which occur when the emulsions are acidified.

Thereby, e.g. mineral mixtures also without sand and filler material are encased, without even if large emulsion dosages are needed, there is a fear that the emulsion will float away. On the other hand, mineral finds from the smallest to the coarsest grain form, including powder, such as iron oxide, limestone or quartz, are individually and completely enveloped in grain form, without the emulsion being divided into its components during this encasing process and without diluting the emulsion with water. necessary. The same of course also applies to organic substances, for example for encasing wood powder. It has also been established that all classic asphalt mixes can be mixed cold instead of hot with the same mineral and binder quantities through the use of the described

it^ed

emulsions, whereby/the post-drying, which can only take place by sunlight or at temperatures up to approximately 160°C, a bituminous mixed material is formed, which in terms of its appearance does not differ from classical, hot-mixed mixed material, but which exhibits hitherto unknown properties ; the adhesion, especially on acidic rock types, such as quartz or silica, is improved so considerably that the material forms a cold storable and non-dissolving mixable material that can also be incorporated at temperatures from 10 to 30°C. Thus

in practice, two increasingly frequent shortcomings are eliminated, namely, firstly, the poor adhesion of the binder to various minerals, especially quartz-containing minerals, and secondly, the unusability of hot-mixed but cooled-down bituminous mixture* The mixture according to the above-described method remains , as mentioned, in the form of free grains but in a densifiable state.

It has also been shown that cold mixed materials produced with these emulsions by open or closed construction with or without the addition of cement, lime or such fillers, dried in the air or through direct or indirect heating, to the extent that they pass through a critical condition such as mineral substances after evaporation of 80-90JÉ

of the water when moving is progressively shed. This phenomenon quickly disappears again with rising temperature and advancing degree of drying by simultaneous further movement of the mixing material. A drying with or without heating of a bituminous mixture produced on the basis of this emulsion without movement of the material also allows a complete envelopment of the solids, as soon as more than 90% of the water has evaporated, without the aforementioned critical unwrapping phase.

As already mentioned earlier, the method according to the invention practically means an upheaval of the classic hot mixing process, whereby the mineral dried and heated in the dryer is mixed in a mixer with the bituminous binder. On the contrary, in the present method, the moist mineral is mixed in the mixer together with the binder and the aforementioned additives and first passes through the dryer in connection with this. Then herewith also the mineral adhering resp. added fine particles have already come into contact with the binder, they are no longer entrained in the dryer by the hot gas drum and carried away, so that the hitherto unavoidable, expensive dedusting facilities become redundant. This means that already existing mixing plants that work according to the hot mixing method can be converted to the method according to the invention without expensive rebuilding work. It has therefore proved advantageous when using ro tas jonst rommel dryers to equip the drum with drag chains, which firstly promote the movement of the mineral and secondly protect the drum from contamination.

With regard to the economy of the method, e.g. in the case of stdv-free production of hot asphalt, it is worth noting that even if the highest possible adhesion is required, only a small amount of additives is necessary. Thus, e.g. for a quartz-containing material 125 g of basic chromium sulphate with grain size from 0 to 12 mm, dissolved in 375 cm^ of water, sufficient per tons of mixed goods. This addition is sufficient to achieve absolute water tolerance for the mixed material.

Claims (4)

1. Process for encasing powdery to granular, moist, unheated solid particles with bituniw»inose binders using metal compounds, characterized by mineral solid particles, which in their mineral structure contain water and/or moisture on their surface, first in a cold state is mixed with a liquid bituminous binder, preferably with the addition of basic croin salts as an adhesion improver, and that in addition to that the resulting mixture in a drying device, preferably a dryer, is subjected to a heat treatment at a temperature of over 80°C, preferably 140°. 2. Method according to claim 1, characterized in that the bituminous binder is an emulsion. 3. Method according to claim 1 or 2, characterized in that, after the end of the heat supply, the mixture is cooled to 60°C or below this temperature, 4. Method according to claims 1 to 3, characterized in that a bitumen emulsion is used for encasing the solid particles, based on hydrolyzed protein compounds, overstabilized alkaline, with borax or a formaldehyde-water solution added, which is activated through basic chromium salts and optionally contains cement, f .ex. a mixture of 100 parts quick-setting cement and 30 - 100 parts lime or barium sulphide.