EP0032468A2 - Apparatus for producing bituminous mixtures from aggregates, bitumen and solid materials liable to deteriorate at high temperature - Google Patents

Abstract

The invention relates to a device for manufacturing bituminous coated products from aggregates, bitumen and solid materials liable to degrade at high temperature. The device consists of a rotary drum (1). Solid materials and hot gases from a burner (6) flow in the same direction. The drum has an introduction zone (16), a transfer zone (17, an intermediate zone (18) and a hot-mixing zone (19) for aggregates and bituminous materials. The intermediate zone (18) comprises a first part where lifting vanes (28) arranged on the internal wall of the drum (1) allowing the constitution of a continuous curtain of materials throughout the section of the drum (1) and a second part where the degradable solid materials are introduced In this second part, the drum (1) comprises a second internal casing (31) coaxial with its external casing (1), internally lined with lifting vanes (32). The invention applies in particular to the manufacture of coated products for road use, from recycled materials.

Description

The invention relates to a device for the production of bituminous coated products from bitumen aggregates and solid materials which can undergo degradation if they are exposed to a medium at high temperature.

In the processes for the preparation of hot bituminous mixes in which, on the one hand, aggregates which do not contain bituminous material and, on the other hand, bituminous products, are introduced into a rotary drum around its longitudinal axis. need to introduce bitumen-containing products inside the drum in an area protected from direct contact with the burner flame, which generally penetrates through the inlet end of the drum, to avoid causing degradation of these bituminous materials under the effect of an atmosphere at too high a temperature.

Thus in the French patent n ° 2.327.048 filed on October 8, 1975 by the Creusot-Loire Company, one recommended the introduction of the liquid bitumen for its incorporation in the aggregates having undergone drying in the tdmbour, in a zone of the drum protected from the burner flame by a continuous and opaque curtain formed by the aggregates in the course of drying falling down throughout the section of the drum.

To constitute this curtain of materials while allowing a development of the flame of the burner at the level of the drying zone, provision was made on the surface of the drum in this zone, a set of lifting devices of particular shape making it possible to constitute the curtain of materials progressively in the drying area, while leaving a central space free for the development of the flame.

Such a device also has the advantage of preventing the aggregates introduced into the drum from falling into the flame, which avoids the formation of dust by bursting of these aggregates under the effect of the heat of the flame.

However, such a device is not suitable in the case where it is desired to introduce into the drum solid materials containing bitumen, such as recovered bituminous mixes or any other solid material which can be degraded if it is exposed to a medium at high temperature.

Such solids can be, for example, compounds rubberized plastics, plastics, sulfur, coloring products such as a metal oxide, or bitumen in flakes.

Such materials, even if they do not fall back into the burner flame, can be destroyed by the heat of the flame if they are not protected from the radiation of the latter in the introduction zone and in the drying zone of the drum.

D ^t is known other devices for the production of asphalt from nine aggregates, bitumen as well as a certain proportion of recycled coated when recycled asphalt is introduced into the drum in an intermediate zone between 'entry end through which the new aggregates penetrate and the exit end of the drum through which the asphalt is discharged. In such devices, the principle of constituting a curtain is used with the new aggregates introduced into the drum, the recycled aggregates being introduced into an area of the drum protected from the flame by this curtain of materials.

The recycled materials are introduced into the drum through openings made in the wall of this drum. And mechanical devices, such as hatches which close by gravity, make it possible to prevent the material from coming out of the drum at this area. intermediary for the introduction of recycled materials.

Such devices have certain drawbacks since the new aggregates introduced by the inlet end of the drum fall back into the area of space where the flame develops and consequently cause the formation of dust which is transported by the gases coming from the burner and crossing the drum. In fact, in these devices, the drying zone for the new aggregates comprises revealing devices which allow the new aggregates to fall over the entire section of the drum and in particular in the flame of the burner.

This protects the intermediate zone where recycled materials are introduced against the burner flame but disturbs the development of this flame and causes the formation of dust which is found in the gases discharged into the atmosphere.

On the other hand, these devices require mechanical members such as hatches movable relative to the casing of the drum at the level of the intermediate zone for introducing recycled materials. Under the operating conditions of the drum, it is undesirable to use such movable closing devices.

The object of the invention is therefore to propose a device for the manufacture of bituminous coated products from aggregates, bitumen and solid materials, such as recycled coated materials which can be degraded if they are exposed to a medium at high temperature, comprising a drum rotating around its axis, slightly inclined on the horizontal, inside which circulate, in the same direction, the solid products and the hot gases coming from a burner penetrating by the entry end of the drum through which also new aggregates penetrated by means of feeding into the first zone of the drum following this entry end, or introduction zone, the drum being supplied with solid materials such as recycled asphalt, at an intermediate zone arranged between the entry end and the outlet end through which the products circulating in the drum are evacuated and preceding in the direction of circulation of the products a hot mixing zone into which the bitumen is introduced and where the products s are lifted throughout the section of the drum by lifting devices and brought into contact with the hot gases passing through the drum, this device having to avoid contact of solid materials such as asphalt recycled with an atmosphere at too high temperature, -to avoid direct contact with the flame of the burner for new aggregates and to allow the introduction of solid materials into the drum with a simple device having no moving part with respect to the drum.

• - une première partie où la paroi interne du tambour porte des aubes releveuses pour la constitution d'un rideau continu de produits solides retombant dans toute la section du tambour,
• - et une seconde partie au niveau de laquelle le tambour, entouré par un dispositif d'introduction de matières solides fixe et présentant des ouvertures traversant sa paroi ou première enveloppe, comporte une deuxième enveloppe cylindrique coaxiale à la première enveloppe, de diamètre plus faible et garnie sur sa surface interne de dispositifs releveurs pour la constitution d'un rideau continu de produits solides retombant dans toute la section de la seconde enveloppe, cependant que des ailettes hélicoïdales disposées sont/entre la paroi interne du tambour et la surface externe de la deuxième enveloppe pour chasser les matières solides introduites à ce niveau dans le tambour vers la zone de malaxage à chaud.

For this purpose, the drum comprises, between the introduction zone and the intermediate zone, a zone for transferring new aggregates where screen vanes having a concave surface, directed towards the internal wall of the drum, are fixed on this internal wall. , and the intermediate zone successively comprises, in the direction of circulation of the products:

• - a first part where the internal wall of the drum carries lifting vanes for the constitution of a continuous curtain of solid products falling throughout the section of the drum,
• - And a second part at which the drum, surrounded by a fixed solid material introduction device and having openings passing through its wall or first envelope, comprises a second cylindrical envelope coaxial with the first envelope, of smaller diameter and furnished on its internal surface with lifting devices for the constitution of a continuous curtain of solid products falling throughout the section of the second envelope, while helical fins arranged are / between the internal wall of the drum and the external surface of the second casing to expel the solids introduced at this level into the drum towards the hot mixing zone.

In order to clearly understand the invention, there will now be described by way of nonlimiting example an embodiment of a device according to the invention as well as its use for the production of hot-coated materials from new aggregates. , bitumen and recycled materials.

Figure 1 shows a sectional view through a vertical plane of symmetry of the drum and the associated devices associated therewith.

Figures 2, 3, 4 and 5 are cross sections of the drum at sections 2-2, 3-3, 4-4 and 5-5 of Figure 1 ..

In Figure 1, we see a drum whose outer casing 1 of cylindrical shape has an inlet inlet 2 and an outlet end 3, the axis 4 of the cylinder constituting the drum being slightly inclined horizontally so the inlet end of the drum is again higher than the outlet end.

Through the inlet face 2 of the drum enters a burner 6, the flame 9 of which develops in part of the internal volume of the drum.

By the inlet end 2 of the drum also penetrate the new aggregates 7 brought to the drum by a belt conveyor 8 of conventional type.

The outlet end 3 of the drum opens into a hopper 10 which allows, on the one hand, the evacuation of the gases from the burner having passed through the drum and possibly entrained particles and, on the other hand, the outlet of the mixes (arrow 12).

By the outlet face 3 of the drum also penetrates into this drum a device 14 for supplying hot and molten bitumen which ends in a spraying ramp 15 making it possible to distribute the bitumen on the solid materials in the last zone of the drum.

The drum comprises successively from its entry to its exit, that is to say from the right to the left in FIG. 1, an introduction zone 16, a transfer zone 17, an intermediate zone 18 and a mixing zone 19 in which the addition of bituminous binder takes place via the spray boom 15.

The flame 9 of the burner extends in zones 16 and 17, that is to say in the introduction zone and in the transfer zone.

To describe these different zones successively, reference will be made to FIG. 1 and to Figures 2,3,4 and 5.

In the zone 16, the internal surface of the drum carries fins 20 arranged helically on the wall of the drum and projecting, so that the new aggregates 7 arriving by the entry face of the drum are rapidly introduced into the transfer zone 17 after an extremely short journey time in the zone 16 where these materials 7 remain in contact with the wall of the drum. During this rapid transfer to an area away from the flame, the materials undergo practically no drying and produce no dust.

As can be seen in FIG. 2.1, the drum is lined in the transfer zone 17 of blades 22 kept apart from the wall of the drum 1 by means of spacers 23, the blades 22 constituting screen blades being constituted by sheets folded in U whose hollow surface for receiving the material 7 is directed towards the wall 1 of the drum.

As can be seen in FIG. 2, the material 7 during the rotation of the drum in the direction of the arrow 25 is retained by this hollow surface directed towards the wall of the drum and driven upwards, then downwards inside the vanes 22, the sectbn of which has the shape of an asymmetrical U.

The vanes 22 constitute, by their flat surface directed towards the flame of the burner 9, screens protecting the material 7 constituted by the new aggregates.

In this way the new aggregates do not fall back into the flame of the burner 9 and do not undergo bursting under the effect of the heat which would produce dust particles.

Hot gases passing through the drum from the burner to the outlet end do not cause large amounts of dust.

In this zone, the aggregates contained in the screen vanes 22 also protect the wall 1 of the drum against the heat of the burner flame by absorbing part of the heat of this flame.

The aggregates therefore undergo heating and the onset of drying in this zone by conduction of heat through the screen vanes.

On the other hand, this arrangement improves the efficiency of the installation because the heat evacuated by the wall 1 of the drum at this zone is considerably reduced.

Because of the inclination of the drum, the new aggregates progress in this zone until they reach the intermediate zone 18.

To promote this progression we can have small horns on the inner wall of the drum.

As can be seen in FIGS. 3 and 4, the intermediate zone comprises two separate parts, the first part, the cross section of which is shown in FIG. 3, being an area for constituting a continuous curtain of materials and the second part, shown in Figure 4, an area for introducing solids fearing too high temperatures.

In the first part of the intermediate zone, the drum has on its internal surface several sets of lifting vanes 28 angularly offset along the length of the drum to form a continuous dense and opaque curtain of aggregates 7 throughout the cross section of the drum. These lifting vanes have a shape having a concavity towards the internal surface of the drum and are constituted by folded sheets. As can be seen in Figure 4, the drum is surrounded at the second part of the intermediate zone, by a fixed device for introducing recycled materials 29 comprising an introduction hopper 27 and a closed cylindrical body 30 surrounding the drum with a slight clearance allowing the rotation thereof.

The drum further comprises at this intermediate zone, in addition to its external envelope 1, an internal envelope or second envelope 31 coaxial with the first which extends over the entire second part of the intermediate zone up to the entry to the mixing zone 19.

This internal ferrule 31 carries on its inner wall sets of vanes 32 comparable to the vanes 28 of the first part of the intermediate zone.

On the wall 1 of the drum and on the outside of this drum are fixed, at the level of the fixed casing 30 of the device for introducing recycled asphalt, chutes 36 projecting outwardly making it possible to introduce the materials entering through the hopper 27, in the space between the drums 1 and 31, furnished with fins 35. The troughs 36 include guide surfaces 33 inclined for the introduction of the materials through openings 34 of the drum 1.

Between the external envelope 1 of the drum or first envelope and the ferrule 31 constituting the second envelope, the helical fins 35 are arranged so that during the rotation of the drum and of the ferrule 31 which is integral with the envelope of this drum, the fins helical 35 drive the recycled products 29 to the hot kneading zone 19 where these recycled materials 29 mix with the new aggregates 7 arriving through the internal part of the shell 31.

At the intermediate zone 18, the new aggregates undergo an intensive and complete drying since they are exposed throughout the section of the drum to hot gases coming from the burner both at the level of the first part and of the second part of this zone. intermediate.

The aggregates 7 which enter the hot mixing zone are therefore perfectly dry.

On the other hand, the curtain of materials which is formed over the entire length of the intermediate zone first at the level of the first part of this zone throughout the section of the drum, then inside the ferrule 31 of diameter less than diameter of the drum, perfectly isolates the hot kneading zone from the burner flame and therefore perfectly protects, on the one hand, the recycled materials arriving at the end = from the ferrule 31 and, on the other hand, the liquid bitumen distributed by the spray bar 15 on recycled materials and new aggregates in mixture.

As can be seen in FIG. 5, the internal wall of the drum comprises, at the level of the hot mixing zone, lifting vanes having a certain concavity making it possible to carry out a lifting of the materials and a fallout of these materials throughout the section of the drum where these materials are exposed to the gases circulating in the drum at the level of zone 19.

These gases are still hot but are already considerably cooled compared to the previous zones since they have already carried out the drying of the new aggregates in the intermediate zone. These gases are therefore capable of promoting the coating of the aggregates while avoiding destroying the bitumen of the recycled materials and the bitumen introduced liquid through the pipe 14 and the spray boom 15.

Hot mixing takes place in zone 19 so that the mixture of new aggregates, liquid bitumen and recycled aggregates joined to the action of hot gases circulating in the drum at this level produces coated materials of equivalent quality to materials produced only by mixing new dried aggregates and bitumen, the bitumen of recycled aggregates being remelted under the effect of heat.

The materials leaving by the face 3 of the drum in the hopper 10 are therefore constituted by coated materials completely comparable to coated materials obtained by a process without introduction of recycled materials.

We see that the main advantages of the device according to the invention are on the one hand to avoid the fall of new aggregates in the burner flame thanks to the screen vanes. which also produce with these other aggregates an insulation of the wall of the drum; on the other hand that the zone where recycled materials and liquid bitumen are introduced is perfectly isolated from the zone where the flame is located which is confined behind a very curtain. dense of materials and that the device for introducing recycled materials into the drum does not have any moving part with respect to the drum.

On the other hand, as in the previous devices where the flame and the hot gases are confined behind a curtain of extremely dense materials, the gases operate an extremely intense and extremely effective drying of the aggregate before the introduction of the liquid bitumen and the mix with recycled materials.

The invention is not limited to the embodiment which has just been described; on the contrary, it comprises all the variants thereof and one can imagine modifications of details without departing from the scope of the invention.

It is thus in particular that the shape of the trims described is by no means the only one possible and that lifting vanes having a shape with sharp angles or a curved shape with a greater or lesser radius of curvature can be used indifferently.

The screen vanes of the transfer area of the drum can have a shape with sharp angles and be made of folded sheets with a section comparable to that shown in FIG. 2 or, on the contrary, consist of a sheet folded along a curved surface. . In all cases, the hollow surface or the concavity of the curved surface is directed towards the internal wall of the drum.

In the example which has been described, the device was used to manufacture mixes from new materials and from a certain proportion of recycled materials. But it is also possible to use the device according to the invention to produce coated materials from new materials and from a certain quantity of additive elements fearing exposure to too dense heat, such as rubber compounds , plastics, sulfur, coloring products such as iron oxide or bitumen in flakes.

The invention applies in particular but not exclusively to the production of bituminous mixes for road surfaces.

Claims (4)

1.- Device for the production of bituminous coated products from aggregates, bitumen and solid materials liable to deteriorate if they are exposed to a medium at high temperature, comprising a drum rotating around its axis, slightly inclined on the horizontal, inside which circulates, in the same direction, the solid products and the hot gases coming from a burner penetrating through the inlet end of the drum, through which also new aggregates brought in by means of feeding into the first zone of the drum following this entry end, or introduction zone, the drum being supplied with solid materials such as asphalt recycled at an intermediate zone arranged between the entry end and the outlet end through which the products circulating in the drum are evacuated and preceding, in the direction of circulation of the products, a hot mixing zone into which the bitumen is introduced and where the products are s uplifted throughout the drum section by lifting devices and brought into contact with the hot gases passing through the drum, characterized in that the drum comprises, between the introduction zone and the intermediate zone, an aggregate transfer zone new ones where screen vanes having a hollow surface directed towards the internal wall of the drum, are fixed on this wall, and which the intermediate zone successively comprises, in the direction of circulation of the products: A first part where the internal wall of the drum carries lifting vanes for the constitution of a continuous curtain of solid products falling throughout the section of the drum, - And a second part at the level of which the drum, surrounded by a fixed solid material introduction device and having openings passing through its wall or first envelope, comprises a second envelope coaxial with the first envelope, of smaller diameter and packed on its internal surface of lifting devices for the constitution of a continuous curtain of solid products falling over the entire section of the second envelope, while helical fins are arranged between the internal wall of the drum and the external surface of the second envelope for expel the solids introduced at this level into the drum towards the hot mixing zone. 2.- Device for the manufacture of coated products according to claim. 1, characterized in that the screen vanes arranged in the transfer zone of the drum consist of sheets having a length approximately equal to the length of the transfer zone folded so as to present a hollow surface towards the internal wall of the drum and a protective surface serving as a screen towards the internal part of the drum where the flame develops. 3.- Device for the manufacture of coated products according to any one of claims 1 and 2, characterized in that the chutes are fixed to the outside of the drum, these chutes arranged between the openings made in the lateral surface of the drum constituting inclined surfaces for guiding solids towards the openings. 4.- Device for the manufacture of coated products according to any one of claims 1, 2 and 3, characterized in that a pipe for introducing the bitumen ending in a dispersion ramp is introduced through the outlet end of the drum, the spray bar being arranged in an area close to the entrance to the hot mixing area.

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