The object of this invention is a method for preventing the migration of material particles into the air from the material during belt conveyance or corresponding material transport.

Belt conveyors are used for material transport in many places. The materials to be transported often include: coal, different rock materials, wheat, fertilizers, salt, ash, puritan filler, different industrial chemicals, etc. Conveyor lines and corresponding transport methods comprise an open upper part thereof. Due to the open structure it has not been possible to prevent environmental hazards caused by belt conveyors, with official regulations, but air pollution which cause health hazards have been spread to the surroundings during transport, mainly in the form of particles. The most common hazard is contamination of the environment which has caused suffering to both plants and the landscape. Belt conveyors which are permanently in the same place have been provided with a tubular or other corresponding structural forms to be sealed in order to prevent the spreading of dust and other ingredients into the surroundings. A drawback in many cases is the maintenance. A completely sealed structure should be so dimensioned that it endures the steps of a service man and the entire belt conveyor system as an economical investment may be too expensive to implement. In practice, accidents happen, especially at long transport distances, in which the material to be transported such as coal begins to fall off the conveyor belt because of damage and begins to fill the protective structure. This results in stoppage of the transport system and environmental hazards because the blocked part is often

emptied to be repaired, by dropping the accumulated material down. With respect to permanent conveyors it is possible to use the above-mentioned encapsulation of the conveyor with related difficulties.

When it comes to general, transportable belt conveyors which continuously need to be transported, sealed structures cannot be applied. It is obvious that dust-formation, for instance, when using belt conveyors in harbors, factories, in processing of stone material, etc., cannot be prevented very easily. The most frequently used method to prevent dust-formation is to wet the transported material. Wetting cannot be applied to anywhere near all the transferred materials. Other preventive methods for belt conveyors are not available on the market for preventing environmental hazards. The purpose of the invention is to eliminate the above drawbacks.

The method according to the invention is characterized in that ion yield tips are placed above the material to be transported in such a manner that an intensive ion field is provided over the material being transported. The conveyor structures are grounded. The material being transported can be grounded with the aid of an earth drag, for instance. The intensive ion field above and the grounded transport material cause the dust, droplets or other ingredients breaking loose from the transport material to become electrically charged in the ion field while trying to become detached from the transported material and return back to the material being transported. Depending on the quality and moisture of the transported material, the voltage level of the ion yield tip and its distance to the material being transported, the vertex of the detachment of the material particles from the material is about 2 mm - 30 mm before returning to the source material.

An embodiment of the invention is characterized in that ion

yield tips are installed to a high tension cable. In its simplest use, the high tension cable is installed above the belt conveyor so that ion yield tips are installed to the lower surface of the cable. The distance between the tips are determined by the voltage used and the distance of the tips from the transport material. In practice, the smallest possible voltage to provide the protection is preferred. For instance, if the voltage of the ion tips is about 50 kV and the distance from the tips to the material to be protected is about 50 cm, a suitable distance between the ion tips would be about 50-70 cm.

The model of the invention which gives more protection against atmospheric conditions is a load-bearing supporting structure extending along the whole length of the conveyor in question, giving support through insulating intermediate parts to both the protecting roof structure and the ion yield tips. The above embodiments can be used in connection with both permanent conveyors and those continuously moved. The structures of the invention are simple and light-weight. The high voltage can be provided by a 12 V supply voltage, whereby a 12 V car battery can be used as the source of reserve power. The need for energy is extremely low. For instance, a conveyor of 0.5 m of width and 20 m of length requires about 10-20 W for the protection.

The invention is described in the following with the aid of an example with reference to the appended drawings in which:

Fig. l represents a cross section of the protection in a simple form,

Fig. 2 represents a longitudinal section of the protection in a simple form,

Fig. 3 represents a cross section of the structure regarding atmospheric conditions, Fig. 4 represents a longitudinal section of the structure

regarding atmospheric conditions,

Fig. 5 represents the impact of the ion protective field on the material being transported,

Fig. 6 represents a belt conveyor provided with the prevention of detachment of material particles according to the invention.

The equipment used in the method is comprised of ion field 2 which protects material 1 to be transported, the ion field being provided by ion yield tips 3. Ion yield tips 3 are installed above surface 1 of the material to be transported, generally in form of a row, so that the ion beams coming from the ion yield tips cover the material being transported. The required high voltage for ion yield tips 3 is provided by a high voltage source from which it is conducted using high voltage cable 4 along the area above area 1 to be protected, in accordance with one of the most simple modes.

Conveyor belts 5 or other low loaders and the supporting structures are grounded. Protective structure 6 of the ion yield tips can be built from insulating material, as shown in Fig. 3. The light-weight high voltage cable can be supported using tubular, wire rope 7 or other structures.

Fig. 5 shows by arrows the detachment of material particles and the return thereof to the surface of the material.