FR3067371A1 - INSTALLATION AND PROCESS FOR PRODUCING COILS - Google Patents

Abstract

The installation comprises a rotatably mounted drum (4), a burner (10) configured to generate a flow of hot gas flowing in the drum (4) from a raised end (4A) to a lowered end (4B) of the drum (4). ), at least one recycling ring (12, 14) for the introduction of recycled asphalt aggregates (AE) into the drum (4), a filtering device (28) configured to filter hot gases collected at the lowered end ( 4B) of the drum (4), and a kneader (20) separate from the drum (4) and configured to mix aggregates (G) and recycled asphalt aggregates (AE) exiting the drum (4) with a binder.

Description

The present invention relates to the field of asphalt production facilities, in particular asphalt for road surfaces, with recycling of asphalt aggregates.

To produce asphalt for road surfaces, it is possible to dry and heat aggregates, then to mix dry and hot aggregates with binder, in particular a bituminous binder, to produce a road surface asphalt.

For the drying and heating of the aggregates, it is possible to introduce the aggregates into a drying drum mounted to rotate around its central axis, the axis of the drum being inclined relative to the horizontal plane, and to circulate a flow of gas. hot in the drying drum to dry and heat the aggregates.

The fresh aggregate is introduced into the drying drum at the raised end thereof, and the hot aggregate is collected at the lowered end of the drying drum.

Due to the rotation of the drying drum, the aggregates are raised and fall back forming a curtain of aggregates inside the drying drum, the flow of hot gas passing through the curtain of aggregates.

Due to the inclination of the drying drum, the aggregates introduced through the raised end of the drying drum progressively move towards the lowered end of the drying drum.

In a “co-current” or “parallel current” drying drum, the gas flow circulates in the drying drum in the direction of advancement of the aggregates, i.e. from the raised end to the lowered end.

In a "counter-current" drying drum, the gas flow circulates in the drying drum opposite to the direction of advancement of the aggregates, i.e. from the lowered end to the raised end.

The mixing of dry and hot aggregates with the binder is carried out in a mixing section of the drying drum, in which case the drying drum is called "dryer-mixer" or in a separate external mixer separate from the drying drum.

Advantageously, it is possible to mix the aggregates with "mix aggregates" originating from the recycling of mixes.

To do this, it is possible to provide a co-current dryer-kneader drum comprising successively, from its raised end towards its lowered end, a drying section for drying the aggregates, a recycling ring for introducing asphalt aggregates in the dryer-kneader drum, a drying section for mixing and drying the aggregates and asphalt aggregates, and a mixing section for kneading the mixture with a filler binder, the filler binder being introduced into the section mixing. The hot gases circulating in the dryer-mixer drum are generated using a burner located inside the dryer drum, near the raised end of the dryer drum.

It is also possible to provide a drying drum and an external mixer, the aggregates being heated in the drying drum, and the asphalt aggregates and the supply binder being introduced into the mixer. The aggregates are overheated in the dryer drum to provide the amount of heat needed to heat the mix aggregates.

It is also possible to provide a counter-current mixer-dryer drum comprising successively from its raised end to its lowered end, a drying section for drying the aggregates, a recycling ring for introducing asphalt aggregates into the dryer drum -mixer, a mixing section for mixing the aggregates and the asphalt aggregates, and a mixing section for mixing the mixture with a filler binder, the filler binder being introduced into the kneading section. The hot gases circulating in the drying drum are generated using a burner arranged inside the drying drum, generating a flame upstream from the point of introduction of the asphalt aggregates, the hot gases circulating towards the upstream.

It is also possible to provide a drying drum for drying the aggregates, and a mixing drum separate from the drying drum, the aggregates and aggregates and the binder of feed being introduced into the mixing drum. The aggregates are for example superheated in the drying drum in order to provide the quantity of heat necessary for heating the aggregates of mixes in the mixing drum.

It is also possible to provide a counter-current dryer drum for drying the aggregates and a counter-current or co-current dryer drum for drying the asphalt aggregates, the aggregates and the asphalt aggregates and the filler binder then being introduced into an external mixer separate from the drying drums. The flow of hot gas circulating in the drying drum for drying the asphalt aggregates is generated by a burner disposed in this drying drum or by a hot gas generator comprising a separate enclosure from the drying drum and a burner for generating the hot gases , the enclosure being fluidly connected to the drying drum to convey the hot gases into the drying drum.

For a mix, the "recycling rate" is the ratio of the quantity of mix aggregates to the sum of the quantity of mix aggregate and the quantity of fresh aggregates used in the composition of the mix.

For asphalt production with recycling of asphalt aggregates, it is desirable to achieve a high recycling rate, to increase recycling of asphalt aggregates and limit the amount of new aggregates used. At the same time, it is desirable to be able to limit the polluting emissions resulting from the coating.

One of the aims of the invention is to provide an asphalt production facility which can allow a high rate of recycling of asphalt aggregates while limiting polluting emissions.

To this end, the invention provides an installation for the production of asphalt mixes from aggregates and aggregates of recycled asphalt mixtures, comprising a drying drum rotatably mounted around a central axis of the drum, the drum having a raised end for the introduction of aggregates and a lowered end, a burner configured to generate a flow of hot gas circulating in the drum from the raised end to the lowered end, one or more recycling ring (s) arranged along drum for the introduction of recycled asphalt aggregates, the drum comprising an upstream drying section located upstream of the recycling ring (s) and a downstream drying section located downstream of the recycling ring (s) recycling, a filtering device configured to filter hot gases collected at the lowered end of the drum, and a mixer separate from the drum and configured to mix aggregates and aggregates gats recycled coated out of the drum with a filler binder.

The installation may include one or more of the following optional features, taken individually or in any technically possible combination:

- It comprises a plurality of recycling rings arranged along the drum being spaced apart, the drum comprising an intermediate drying section between each pair of adjacent recycling rings;

- It comprises exactly two recycling rings, the drum comprising an intermediate drying section located between the two recycling rings;

- It includes a recycling circuit configured to collect binder vapors present in the mixer and reinject them into the aggregate coating installation so that they are incinerated in a flame generated by the burner;

- the burner is arranged at the inlet of the drum so as to generate a flame inside the drum;

- It includes a heat exchanger configured for heat transfer from the gases filtered by the filtering device to an oxidant supplying the burner;

- the heat exchanger is arranged between the filtering device and a chimney for evacuating the filtered gases to the atmosphere.

The invention also relates to a method for producing asphalt mixes from aggregates and recycled asphalt aggregates, comprising the introduction of aggregates into a rotary drying drum, the drum having a raised end for the introduction of aggregates and a lowered end, the generation of a flow of hot gas circulating in the drum from the raised end towards the lowered end, the introduction of asphalt aggregates into the drum via one or more recycling ring (s) arranged along the drum, the drum comprising an upstream drying section located upstream of the recycling ring (s) and a downstream drying section located downstream of the recycling ring (s), recovery and filtering the hot gases leaving the drum in a filtering device, and mixing the aggregates and asphalt aggregates with a filler binder in a mixer separate from the drum.

The process may include one or more of the following optional features, taken in isolation or in any technically possible combination:

- it includes the introduction of asphalt aggregates via several recycling rings, the drum having an intermediate drying section between each pair of adjacent recycling rings,

- a first fraction of asphalt aggregates introduced via an upstream recycling ring has a lower binder content than that of a second fraction of asphalt aggregates introduced via a downstream recycling ring.

The invention and its advantages will be better understood on reading the description which follows, given solely by way of example, and made with reference to the appended drawings, in which Figures 1 and 2 are schematic overall views of '' asphalt production facilities.

The asphalt plant 2 of FIG. 1 is configured for the production of asphalt with recycling of asphalt aggregates, from fresh aggregates and from recycled fresh asphalt aggregates.

In the present application, the term "fresh" means that the aggregates or mixes are wet and cold and have not yet been dried - completely or partially - in installation 2.

The installation 2 comprises a drum 4 for drying aggregates by circulation of a gas flow in the drum 4.

The drum 4 extends along a central axis A and is rotatably mounted around its central axis A. The central axis A is inclined at a non-zero angle relative to the horizontal plane. The angle of inclination of the central axis A with respect to the horizontal plane is for example between 2 ° and 6 °.

The drum 4 therefore has a raised end 4A and a lowered end 4B. The raised end 4A is located at a level higher than that of the lowered end 4B.

The raised end 4A defines an inlet for fresh aggregates and the lowered end 4B defines an outlet for a mixture formed of aggregates G and aggregates of recycled asphalt mixes introduced into the drum 4.

The installation 2 comprises a supply device 6 configured to supply the raised end 4A of the first drum 4 with fresh aggregates G.

During the rotation of the drum 4, due to the inclination of the latter, the aggregates G introduced into the raised end 4A of the drum 4 progressively move towards the lowered end 4B of the drum 4.

In the following, the terms "downstream" and "upstream" are understood with respect to the direction of circulation of the aggregates G in the drum 4, from the raised end 4A to the lowered end 4B.

The installation 2 includes a hot gas generation device 8 configured to generate hot gases and to circulate the hot gases in the drum 4 from the raised end 4A to the lowered end 4B, ie in the same direction as the aggregates G. Drum 4 is a drying drum called "parallel currents" or "cocurrent".

In the example illustrated, the device for generating hot gases 8 comprises a burner 10 arranged to generate a flame F inside the drum 4. The burner 10 is configured to generate the flame F from a fuel and d 'an oxidizer. The oxidizer is for example air.

The installation 2 comprises one or more recycling ring (s) 12, 14 arranged along the drum 4 for the introduction of asphalt aggregates AE inside the drum 4. Each recycling ring 12 , 14 is arranged along the drum 4 at a distance from the raised end 4A and at a distance from the lowered end 4B.

The drum 4 comprises several consecutive drying sections TA, Tl, TB along the drum 4.

In known manner, in each drying section TA, Tl, TB, the drum 4 is provided, on its internal surface, with lifting blades 16 configured to raise the aggregates G and / or the asphalt aggregates AE, so to form, in operation, a curtain of aggregates and / or asphalt aggregates AE crossed by the hot gases circulating in the drum 4. According to their profiles, the lifting vanes 16 make it possible to create, respectively in each drying section TA, Tl, TB, a more or less dense curtain.

The drum 4 comprises an upstream drying section TA located upstream of the recycling ring (s) 12, 14, and a downstream drying section TB located downstream of the recycling ring (s) 12, 14.

Only the aggregates G are present in the upstream drying section TA, the asphalt aggregates AE being introduced into the drum 4 only downstream from the drying section TS.

When the drum 4 comprises several recycling rings 12, 14, the drum 4 comprises an intermediate drying section T1 between each pair of adjacent recycling rings.

The upstream drying section TA is located upstream of the recycling ring 14 located most upstream. The downstream drying section TB is located between the recycling ring 14 located furthest downstream, and the lowered end 4 of the drum 4.

The hot gases gradually cool down along the drum 4 due to the heat exchanges with the aggregates G and the aggregates of mixes AE present in the drum 4. The hot gases are therefore progressively less and less hot when passing from one drying section to the next, moving from upstream to downstream of the drum 4.

The provision of a plurality of recycling rings 12, 14 spaced along the drum 4 makes it possible to introduce the asphalt aggregates AE into the drum 4 selectively via one or more ring (s) from the plurality of recycling rings. recycling 12, 14.

The temperature of the hot gases gradually decreases along the drum 4 due to the heat exchanges, in particular with the aggregates G.

It is possible to introduce all of the AE mix aggregates selectively via only one of the plurality of recycling rings 12, 14. This makes it possible to subject the AE mix aggregates to hot gases at a temperature more or less high, depending for example on the content of binder of AE mix aggregates.

It is possible to introduce separate asphalt aggregate fractions via several recycling rings chosen from the plurality of recycling rings, each fraction of asphalt aggregates being introduced via a respective recycling ring.

A fraction of asphalt aggregates introduced further upstream will be subjected to hot gases at a higher temperature than that of the hot gases to which is subjected a fraction of asphalt aggregates introduced further downstream. This allows, for example, to submit fractions of asphalt aggregates having different contents by bonding to hot gases at different temperatures.

In the example of FIG. 1, the drum 4 comprises exactly two recycling rings 12, 14 delimiting between them an intermediate drying section T1. The drum 4 comprises, from upstream to downstream, the upstream drying section TA, the intermediate drying section Tl and the downstream drying section TB.

The installation 2 is configured for the introduction into the drum 4, selectively, of all of the asphalt aggregates AE via the recycling ring 12 located upstream, of all of the asphalt aggregates AE via the ring recycling 14 located downstream or from a first fraction of asphalt aggregates AE1 and a second fraction of asphalt aggregates AE2 via respectively the recycling ring 12 located upstream and the recycling ring 14 located downstream.

The first fraction of AE1 mix aggregates and the second fraction of AE2 mix aggregates have, for example, different binder contents.

Preferably, the first fraction of AE1 asphalt aggregates introduced further upstream has a lower binder content than that of the second fraction of AE2 asphalt aggregates introduced further downstream.

The hot gases being less and less hot along the drum 4, this makes it possible to expose the second fraction of asphalt aggregates AE2 having the highest content of binding to hot gases at a more moderate temperature, thus limiting the generation of binder vapor.

The drum 4 does not have a mixing section configured for the mixing of aggregates G and of asphalt aggregates AE.

The aggregate coating plant 2 comprises an external mixer 20 configured to knead the mixture of aggregates G and of aggregates of mixtures AE emerging from the drum 4, at the lowered end 4B thereof.

The mixer 20 is distinct and separate from the drum 4. It receives the mixture of aggregates G and of asphalt aggregates AE after it has left the drum 4.

The AE mix aggregates mixed with the G aggregates already contain binder, known as "recycling binder", coming from the AE mix aggregates. It may also be necessary to provide additional binder, known as "binder". The filler binder is for example bitumen.

The installation 2 includes a supply binder supply device 22 for introducing supply binder into the mixer 20.

Optionally, the installation 2 comprises a recycling circuit 24, configured to collect binder vapors present in the mixer 20 and to reinject them into the installation 2 so that the binder vapors are incinerated in the flame F of the burner 10.

The recycling circuit 24 is here configured to reinject the binder vapors into the drum 4, upstream of the flame F generated by the burner 10, so that the binder vapors are incinerated in the flame F.

More specifically, the recycling circuit 24 is here configured to reinject the binder vapors into the drum 4, at the raised end 4A of the drum 4.

The installation 2 comprises a gas manifold 26 arranged at the lowered end 4B of the drum 4 for collecting the hot gases leaving the drum 4, and a filtering device 28 fluidly connected to the gas manifold 26 for filtering the gases collected by the gas collector 26. The filtering device 28 is for example a bag filter.

The provision of an external mixer 20, distinct and separate from the drum 4, avoids exposing the supply binder to hot gases and makes it possible to collect the binder vapors generated in the mixer 20 and the hot gases leaving the drum 4 separately . In particular, the gas collector 26 and the recycling circuit 24 are distinct and separate.

Optionally, the installation 2 comprises a heat exchanger 30 disposed downstream of the filtering device 28 is configured for a heat exchange between the hot gases filtered by the filtering device 28 and an oxidant supplying the burner 10. The oxidant is here from the air.

The heat exchanger 30 is a separate flow. The hot gases and the oxidizer are not in contact during the heat exchange. They exchange heat through one or more walls.

The heat exchanger 30 is here a gas / gas heat exchange, configured for a heat exchange between the filtered hot gases and the oxidant which is in the gaseous state.

Preferably, the installation 2 comprises a chimney 32 for the evacuation of the hot gases filtered into the atmosphere. The chimney 32 is here arranged downstream of the heat exchanger 30.

In an embodiment in which the installation 2 does not have a heat exchanger 30, the chimney 32 is for example placed directly downstream of the filtering device 28.

In operation, the drum 4 is rotated about its central axis A and the hot gases generated by the burner 10 circulate in the drum 4 from the raised end 4A to the lowered end 4B.

Due to the rotation of the drum 4 and its inclination, the aggregates G and the asphalt aggregates AE1, AE2 introduced into the drum 4 progressively advance from the raised end 4A towards the lowered end of the drum 4.

The aggregates G are introduced at the raised end 4A of the drum 4. They are first dried alone in the upstream drying section TA. They are then mixed with aggregates of mixtures AE introduced into the drum 4 via one or more recycling rings 12, 14, which are mixed and dried with the aggregates in the or each possible intermediate drying section Tl and in the section of downstream drying TB.

The aggregates G and the aggregates of mixes AE mixed and dried emerge from the drum 4 by the lowered end 4B. The aggregates G and the asphalt aggregates AE are kneaded in the mixer 20, with filler binder.

The hot gases are collected at the lowered end 4 of the drum 4 by the gas manifold 26, then filtered by the filtering device 28.

As an option, heat exchange is carried out between the filtered hot gases and the oxidant supplying the burner 10, in the heat exchanger 30.

Optionally, the binder vapors recovered in the mixer 20 are reintroduced into the installation 2 so as to be incinerated by the flame F of the burner 10.

In the drum 4, the temperature of hot gases decreases from upstream to downstream due to the heat exchanges with the aggregates G and the aggregates of asphalt mixes AE.

The introduction of asphalt aggregates AE downstream of the upstream drying section TA into a parallel current drum 4 makes it possible to expose the aggregates of asphalt AE to hot gases at a moderate temperature compared to that of the hot gases. generated by the burner 10. In addition, when the flame F is generated inside the drum 4, the curtain of aggregates formed in the upstream drying section TA due to the rotation of the drum 4 protects the aggregates of coated materials AE radiation from flame F. This limits the emissions of binder vapors from the AE mix aggregates.

When a plurality of recycling rings 12, 14 are provided, the temperature of the hot gases in the successive drying sections gradually decreases. The selective use of one or more recycling rings among the plurality of recycling rings 12, 14 makes it possible to expose the aggregates of coated materials AE to hot gases at a more or less high temperature, and / or different fractions of asphalt aggregates to hot gases at different temperatures. This makes it possible to expose aggregates of AE mixtures having a higher content of binder to hot gases at very moderate temperature, further limiting the emissions of binder vapors by the mixtures of AE mixtures.

The mixer 20 separate from the drum 4 makes it possible to supply filler binder outside of the drum 4, this filler binder not being exposed to hot gases. In addition, the binder vapors generated in the mixer 20 are not carried to the filtering device 28 and are not ultimately released into the atmosphere. Thus, the separate mixer 20 limits the binder vapors in the hot gases collected at the outlet of the drum 4.

When a heat exchanger 30 is provided, the reduction in the binder vapors in the hot gases collected at the outlet of the drum 4 limits the risk of fouling of the heat exchanger 30 and preserves its efficiency.

The heat exchanger 30 makes it possible to recover part of the energy of the hot gases exiting in the drum 4 and to reinject it into the drum 4. It makes it possible to increase the efficiency of the burner 10, and therefore the efficiency of the installation 2.

Thus, the aggregate coating plant 2 makes it possible to obtain a significant recycling rate while limiting polluting emissions.

The installation 2 of Figure 2 differs from that of Figure 1 in that it comprises a single recycling ring 12. The drum 4 has exactly two mixing sections, namely the upstream drying section TA, located upstream of the recycling ring 12, and the downstream drying section TB situated between the recycling ring 12 and the lowered end 4B of the drum 4. The aggregates of mixes AE are introduced into the drum 4 by means of the recycling ring 12.

The provision of a plurality of recycling rings 12, 14 along a drying drum is advantageous regardless of the particular configuration of the installation 2 described above.

Thus, in general, the invention also relates to an installation for the production of asphalt mixes, comprising at least one drying drum mounted to rotate about a central axis inclined at a non-zero angle relative to a horizontal plane, the drum having a raised end and a lowered end, a burner configured to generate a flow of hot gas flowing through the drum, and a plurality of recycle rings disposed along the drum spaced apart, for the introduction of asphalt aggregates inside the drum via one or more of the plurality of recycling rings, the drum comprising a drying section intermediate between each pair of adjacent recycling rings.

Furthermore, the provision of a heat exchanger 30 arranged for a heat exchange between hot gases coming from the drum 4 and an oxidizer, for example air, supplying the burner 10, is advantageous independently of the particular configuration of installation 2 described above.

Thus, in general, the invention also relates to an installation for the production of asphalt mixes, comprising at least one drying drum mounted to rotate about a central axis inclined at a non-zero angle relative to a horizontal plane, the drum having a raised end and a lowered end, a burner configured to generate a flow of hot gas circulating in the drum, and a heat exchanger arranged for a heat exchange between hot gases having circulated in the drum and an oxidant, for example of air, feeding the burner.

The heat exchanger can be arranged downstream of a device for filtering the hot gases having circulated in the drum, in particular between the filtering device and a chimney for discharging the hot gases.

The drum can be co-current, the gas flow circulating in the same direction as the aggregates, ie from the raised end towards the lowered end, or against the current, the gas flow circulating in the opposite direction of the aggregates , ie from the lowered end to the raised end.

The drum can be a drying drum associated with a separate mixer, or a drying-mixing drum comprising a mixing section provided for mixing the aggregates and any asphalt aggregates introduced into the drum with a filler binder.

The aggregate coating plant can optionally include at least one recycling ring arranged along the drum for the introduction of mix aggregates inside the drum. The aggregate coating plant can for example comprise several recycling rings, for example two recycling rings.

Claims (10)

1. - Plant for the production of asphalt mixes from aggregates (G) and recycled asphalt aggregates (AE), comprising - a dryer drum (4) rotatably mounted about a central axis (A) of the drum (4), the drum (4) having a raised end (4A) for the introduction of aggregates and a lowered end (4B), - a burner (10) configured to generate a flow of hot gas circulating in the drum (4) from the raised end (4A) to the lowered end (4B), - one or more recycling ring (s) (12, 14) arranged along the drum (4) for the introduction of recycled asphalt aggregates (AE), the drum (4) comprising a section of upstream drying (TS) located upstream of the recycling ring (s) (12, 14) and a downstream drying section (TA) located downstream of the recycling ring (s) (12, 14), - a filtering device (28) configured to filter hot gases collected at the lowered end (4B) of the drum (4), and - a mixer (20) separate from the drum (4) and configured to mix aggregates (G) and asphalt aggregates (AE) recycled out of the drum (4) with a binder. 2. - asphalt production plant according to claim 1, comprising a plurality of recycling rings (12, 14) arranged along the drum (4) being spaced apart, the drum (4) comprising an intermediate drying section (Tl) between each pair of adjacent recycling rings (12, 14). 3. - asphalt production plant according to claim 2, comprising exactly two recycling rings (12, 14), the drum (4) comprising an intermediate drying section (Tl) located between the two recycling rings (12, 14). 4. - asphalt production plant according to any one of the preceding claims, comprising a recycling circuit (24) configured to collect binder vapors present in the mixer (20) and reinject them into the coating plant aggregates in such a way that they are incinerated in a flame generated by the burner (10). 5. - Asphalt production plant according to any one of the preceding claims, in which the burner (10) is disposed at the inlet of the drum (4) so as to generate a flame inside the drum (4 ). 6. - Asphalt production plant according to any one of the preceding claims, comprising a heat exchanger (30) configured for a transfer of heat from the gases filtered by the filtering device (28) to an oxidant supplying the burner ( 10). 7. - asphalt production plant according to claim 6, wherein the heat exchanger (300) is disposed between the filtering device (28) and a chimney (32) for evacuating the filtered gases to the atmosphere. . 8. - Process for the production of mixes from aggregates (G) and mixes of mixes (AE) recycled, comprising - the introduction of aggregates into a rotary dryer drum (4), the drum (4) having a raised end (4A) for the introduction of aggregates and a lowered end (4B), - the generation of a flow of hot gas circulating in the drum (4) from the raised end (4A) to the lowered end (4B), - The introduction of asphalt aggregates (AE) into the drum (4) via one or more recycling ring (s) placed along the drum (4), the drum (4) comprising a section of upstream drying (TS) located upstream of the recycling ring (s) (12, 14) and a downstream drying section (TA) located downstream of the recycling ring (s) (12, 14), - recovering and filtering the hot gases leaving the drum (4) in a filtering device (18), and - the mixture of aggregates (G) and asphalt aggregates (AE) with a filler in a mixer (20) separate from the drum (4). 9. - A process for the production of mixes according to claim 8, comprising the introduction of mixtures of mixes (AE) via several recycling rings (12, 14), the drum (4) having an intermediate drying section ( Tl) between each pair of adjacent recycling rings (12, 14). 10. - A process for the production of mixtures according to claim 9, in which a first fraction of mixtures of mixtures (AE1) introduced via an upstream recycling ring (12) has a binder content lower than that of a second fraction of asphalt aggregates (AE2) introduced via a downstream recycling ring (14).