Patent Publication Number: US-2017356143-A1

Title: Mobile planing machine and planing method for roadways with reduction in dust by a mobile planing machine

Description:
The present invention relates to a method of pavement planing with dust abatement by means of a mobile planer. It has applications in particular in the field of maintenance of traffic lanes and especially during the planing of pavement materials. 
     During road maintenance, it is sometimes necessary to remove the structure of the existing pavement, either because its state is unsuited to the traffic, or due to a change in its layout. 
     To remove the pavement structures, it is commonly used a machine that is called a planer and that includes a rotary planing-milling tool arranged in a casing. The tool has teeth that will progressively attack the pavement materials and disintegrate them during the rotation of the tool. Millings are then produced and are generally recovered thanks to a conveyor belt system sending them to a semi-trailer. This planing process causes the warming of the tool, which must be watered with a little quantity of water in order to cool it down during the planing. 
     It has hence been proposed in the documents EP 1 367 176 A1, EP 0 182 748 A2, EP 0 282 381 A1 and DE 42 06 994 A1 pavement planing methods and machines, some of which allow the recovery of the millings and others the reuse thereof in situ. 
     The planing process also produces dusts. However, the tool being housed in a casing, the emissions of dusts remain tolerable for roadworks relating to pavements containing no toxic constituents as silica or asbestos dusts. On the other hand, for pavements containing toxic constituents, in particular asbestos fibres or silica, the public health requirements and the legal constraints entail the implementation of means for reducing the exposition of the workers and the local residents to these dusts. 
     Besides the individual protection means, it is preferable to reduce the dusts at source. It has hence been proposed to implements water curtains, in particular by atomization, around the planer. 
     It is desirable to implement still more efficient means and that is what proposes the present invention with a system that allows the dust abatement and the re-agglomeration of the silica and/or asbestos dusts with the produced millings to form aggregates. The method of planing with dust abatement claimed in the present patent application hence allows evacuating the millings recovered to a landfill centre duly authorized to receive the bonded asbestos wastes. 
     Hence, the invention relates to a method of pavement planing by a mobile planer with reduced dust emission, and in particular by a mobile planer producing millings and dusts, method in which a rotary planing-milling tool housed in a casing of the planer is implemented, the tool receiving water to allow the cooling down thereof. 
     According to the invention, to perform an abatement of the dusts, at least one additive is further introduced into the casing with the water, forming or to form therein an aqueous composition intended to agglomerate the dusts with the millings produced to form bonded aggregates. 
     The aqueous composition may hence be introduced ready-made or not into the casing. 
     In various modes of implementation of the invention, the following means, which can be used alone or according to any technically possibly combinations, are used:
         the additives are additives against dust emission, in particular by wetting and/or agglomeration of the dusts,   the aqueous composition includes additives with mineral and/or organic fillers and constitutes an aqueous solution with mineral and/or organic fillers,   the aqueous composition includes bituminous additives,   the aqueous composition includes bituminous additives and constitutes a bitumen emulsion or a bitumen foam,   the water and the additive(s) are introduced into the casing in such a manner that the rotation of the tool causes a mixing of the millings, the dust and the aqueous composition,   the dusts contain asbestos fibres and/or silica,   the aqueous composition is chosen alone or in a physically/chemically compatible combination among: a bitumen emulsion, a bitumen foam, an aqueous solution with mineral and/or organic fillers,   at least two of the aqueous compositions chosen among: a bitumen emulsion, a bitumen foam, an aqueous solution with mineral and/or organic fillers are introduced into the casing,   at least two of the aqueous compositions chosen among: a bitumen emulsion, a bitumen foam, an aqueous solution with mineral and/or organic fillers are introduced into the casing, at different places of the casing for each one,   the aqueous solution with mineral and/or organic fillers, on the one hand, and an aqueous solution with bituminous additives, on the other hand, are introduced into the casing,   the aqueous solution with mineral and/or organic fillers is introduced at the planing-milling tool and on the planer casing in order to cool them down,   at least two of the aqueous compositions chosen among: a bitumen emulsion, a bitumen foam, an aqueous solution with mineral and/or organic fillers are introduced into the casing and at different places of the casing for each one, the aqueous solution with mineral and/or organic fillers being preferably introduced at the planing-milling tool and on the planer casing in order to cool them down,   the aqueous composition includes a foaming product intending to create foam at least in the casing,   the aqueous composition includes mineral and/or organic fillers,   the organic filler is tall oil or tall oil derivative(s),   the mineral filler may be calcareous filler,   the mineral filler is calcareous filler,   the mineral and/or organic filler is a surfactant,   the planing-milling tool includes an elongated, horizontal toothed rotor,   the planer is an automotive machine including control and guiding means,   the planer is an automotive machine on lateral caterpillars, the casing of the planing-milling tool being arranged under the machine, between the lateral caterpillars,   the aqueous composition includes a bitumen emulsion, its temperature being of about 60° centigrade,   the bitumen emulsion is proportioned with an ad hoc determined bitumen percentage,   the bitumen foam introduced into the casing is hot, its maximum temperature being of about 160° centigrade and its minimum temperature being of about 100° centigrade,   each additivated water forming the aqueous composition is stored in a tank of the planer, said aqueous composition being stored ready-made,   the water, on the one hand, and the additive(s), on the other hand, being stored separately in tanks of the planer, said additives being in concentrated form, the aqueous composition being made on demand in the planer,   the or at least one of the tanks of the planer is a buffer tank and said buffer tank is connected by a supply line to an external transportation tank truck that follows or precedes the planer during its displacement,   a water atomisation is further implemented, at least within the planer casing and at the planer fairing,   the water atomized in the planer casing and at the planer fairing includes at least surfactants and/or mineral and/or organic fillers,   the aqueous solution with mineral and/or organic fillers is moreover spread, in particular atomized, at the external perimeter of the planer fairing,   a component is further implemented for the recovery and the evacuation out of the casing of the aggregates produced, said component including an inclined, endless conveyor belt conveying said aggregates from an upstream end, on the side of the planer casing, to a downstream end, on the side of a storing component into which said produced aggregates flow down,   it is further implemented a water atomization on the conveyor belt component,   the atomized water for the conveyor belt component includes at least surfactants and/or mineral and/or organic fillers,   an aggregate flow down chute is placed at the downstream exit of the conveyor belt component,   the flow down chute is elongated downward in order to pass through a filling opening of the storage component.       

     The invention also relates to a mobile planer for pavement planing and including a rotary planing-milling tool arranged in a casing, the planing producing millings, and means for introducing cooling water on the tool, and the planer includes dust abatement means, including means for introducing into the casing at least one additive with the water forming, or to form therein, an aqueous composition intended to agglomerate the dusts with the millings, to form bonded aggregates. 
     In a particular modality, the aqueous composition is chosen alone or in a physically/chemically compatible combination among: a bitumen emulsion, a bitumen foam, an aqueous solution with mineral and/or organic fillers. 
     Traditionally, the methods of planing coated materials containing asbestos cause an emission of fibres measured by a META method at a level 1 comprised between 30 and 50 fibres per litre of inhaled air. Thanks to the invention, it is possible to pass to a level of less than 5 fibres per litre of inhaled air, and possibly less by adding other barriers to the emission of dusts. 
     It is to be noted that the term “bonded” for the aggregates is used to mean that the invention is implemented in a context where the asbestos is linked to certain components. Moreover, an official text (a modified order of Sep. 9, 1997) mentions the “ Asbestos wastes bonded to inert materials: wastes containing asbestos bonded to inert building materials having kept their integrity ”. Thanks to the dust abatement planing method proposed, it is possible to evacuate the millings produced to a landfill centre duly authorized to receive the bonded asbestos wastes. 
    
    
     
       The present invention will now be exemplified, without being limited thereby, by the following description, in relation with the following FIGURE: 
         FIG. 1 , which shows a sectional schematic view of a planer according to the invention, in operation on a pavement. 
     
    
    
     In its principle, the invention consists in introducing water additivated with one or several types of dust stabilizing agents as a bitumen emulsion, a bitumen foam, an aqueous solution with mineral and/or organic fillers, into the casing of the planing-milling tool herein also called “mixing bell”. The bitumen foam and the bitumen emulsion are aqueous compositions within the framework of the invention because they include water. The tool is conventionally a planing drum. This additivated water may also be emitted at the external periphery of the planer and, in this case, it will preferably be the one in the form of an aqueous solution with mineral and/or organic fillers. 
     In particular, according to the quantities of coated material containing asbestos to be planed, the asbestos type and the quantity contained in the coated material, the planing speed of progression and/or the weather conditions, the method may use one, two or even three types of stabilizing agents. However, in case of physical/chemical incompatibility of these three types of stabilizing agents, it is provided that the respective introductions thereof are spatially separated from each other. For example, the aqueous solution with mineral and/or organic fillers may be introduced directly on the planing-milling tool, into the mixing bell. 
     The coated millings are hence re-agglomerated with a bitumen emulsion and/or a bitumen foam and/or an aqueous solution with mineral and/or organic fillers, allowing it to bond the asbestos and silica fibres to the materials and to eliminate the asbestos fibres free in the air or the free silica particles. Preferably, at least water additivated with bitumen, as a foam and/or as an emulsion, is implemented so obtain a still more efficient re-agglomeration. The so-processed aggregates are either evacuated on a conveyor belt or compacted at the rear of the recycling machine. 
     Dust abatement means may hence be implemented in different forms: essentially liquid, as an emulsion or as a foam, and that further allow the re-agglomeration of the millings and dusts, including fibres, into aggregates recoverable at the exit of the tool casing. The aggregates obtained are in the form of materials coated with the bitumen of the emulsion and/or of the foam and they hence recover a physical integrity similar to that they had in the pavement before the planing operation. Hence, during the later handling of these aggregates, in particular during the loading and unloading operations, the aggregates do no longer liberate asbestos or silica fibres/dusts. 
     Moreover, an atomization of the aqueous solution with mineral and/or organic fillers is implemented at the periphery of the planer fairing, out of the latter. 
     Due to the capture of the fibres and dusts and to the re-agglomeration thereof within the aggregates, it may be contemplated to lighten the protection devices for the workers working on such roadworks of removal of coated materials containing silica or asbestos, while respecting the legal obligations. It may also be contemplated to lighten the worksite marking and isolation arrangements thanks to the method of the invention. It may be contemplated to multiply by five the efficiency of the operations of removal of coated materials containing asbestos or silica with the method of the invention with respect to the conventional operations of removal of coated materials containing asbestos and/or silica. 
     An example of method and planer will now be described more precisely in relation with  FIG. 1 . 
     The schematized motorized planer  1  is provided with driving and guiding means, not shown, of the caterpillar type. It includes a casing  2  under which is transversally arranged a planing-milling tool  3  provided with teeth that tear off millings from the initial pavement  4 , which generates dusts. These dusts are abated by introduction into the casing of aqueous compositions intended to agglomerate the dusts with the millings produced in order to form aggregates  5  that will thereafter be taken by a conveyor belt  10 , to be recovered in a storing means  11  that is herein a transportation tank of a semi-trailer. Downstream from the planer, if considering the direction of displacement thereof schematized by an arrow in  FIG. 1 , the pavement is planed  4 ′. 
     In this example, a first aqueous composition is spread upstream from the tool  3  by a spraying ramp  6  and this is a bitumen emulsion or a bitumen foam. The bitumen emulsion or bitumen foam is stored ready-made in a tank, herein independent of the planer and that is an independent tank  8  that moves with the motorized planer. This solution with an independent tank  8  has for advantage that it is possible to implement a conventional motorized planer with a minimum of modification. In other variants, a specific planer may be made, with the tank  8  integrated thereto. 
     Still in this example, on the tool  3  itself, an aqueous solution with mineral and/or organic fillers is spread by a spraying ramp  7 . Water is stored in a tank  9  of the planer  1  so and the aqueous solution with mineral and/or organic fillers is made before introduction into the casing  2  by mixing of the water with a concentrated additive that is stored in a specific tank  12  of the planer  1 . In a variant that is not shown, the water and the concentrated additive are introduced separately into the casing on the tool  3  and mixed up into the casing due to the stirring produced by the tool  3 . 
     It is understood that other aqueous compositions may further be introduced into the casing  2 , either in replacement of one or of those of the example, or in addition. Likewise, the place(s) of spraying of the aqueous composition(s) may be different, for example downstream from the tool  3 . Finally, the aqueous composition(s) may be introduced ready-made/realized or, then, with their various separated constituents that are mixed up in the casing due to the stirring produced by the tool.