ITMI20111353A1 - ROTARY CYLINDER DRYER FOR MIXTURES OF VIRGIN INERTES AND RECOVERY MATERIALS FOR THE PREPARATION OF BITUMINOUS CONGLOMERATES - Google Patents

Description

DRYER WITH ROTATING CYLINDER FOR BLENDS OF VIRGIN INERT AND RECOVERY MATERIALS FOR THE PREPARATION OF BITUMINOUS CONGLOMERATES.

The present invention refers to a rotary cylinder dryer for mixtures of virgin aggregates and recovery materials (RAP) for the preparation of bituminous conglomerates.

In the packaging of bituminous conglomerates, as known, mixtures of virgin aggregates have been used for some time, which are made up, for example, of gravel, sand and rock grit, and recycled materials, which are made up, in particular, of materials deriving from the dismantling of old asphalt pavements and commonly referred to with the acronym RAP (Reclaimed Asphalt Pavment).

Before amalgamating these mixtures with a bituminous binder, the humidity present in them must be eliminated by means of a drying process.

To this end, dryers generally of the rotary cylinder type are used.

A dryer of this type is, for example, described in patent application no. MI2008A02312 (EP2202473) in the name of the same Applicant and comprises a cylinder with an axis inclined with respect to the horizontal, placed in rotation around its axis by motor means and provided, in correspondence with one of its two opposite heads, with an inlet of the virgin and recovered materials to be dried already mixed with each other and, in correspondence with the opposite head, of an exit mouth of the dried materials.

The heat necessary for drying is generated by a burner which is placed at the head where the outlet of the dried materials is defined and which is coaxial to the cylinder.

The combustion and drying fumes, on the other hand, are evacuated through an opening which is obtained at the head where the inlet of the materials to be dried is defined and which flows into a chamber which is associated with a group of aspiration. Thanks to the inclination of the cylinder and the presence inside it of suitable handling means, the materials introduced in it advance from one head to the other, counter-current with respect to the combustion and drying fumes, drying and heating.

A tubular and open body at opposite ends is fixed inside the cylinder. One of the two open ends of the tubular body faces the burner and placed at a defined distance from it, so that the flame and the combustion fumes are directed inside the tubular body, while the opposite open end of the tubular body faces the inside the cylinder.

The burner and tubular body together define a combustor or post-combustor crossed by both the combustion fumes of the burner and the drying fumes which are sucked into it by a dynamic effect. The drying fumes derive, in particular, from the drying of recycled materials containing aged bitumen (RAP) which, together with the virgin materials, advance to the bottom of the interspace defined between the cylinder and the tubular body.

The tubular body, in fact, forms a hot combustion and / or post-combustion chamber.

Along the cylinder there is a series of treatment zones at different temperatures; in particular, starting from the head in correspondence of which the inlet mouth of the mixture to be dried is obtained and proceeding towards the head in correspondence of which the outlet mouth of the dried mixture is obtained, the following are followed:

- a first inlet zone in correspondence with which on the internal lateral surface of the cylinder there are helical blades which favor a first mixing of the virgin inert materials and the recovery materials which form the mixture; along this zone the average temperature is of the order of 120 ° C; - a second evaporation zone of the humidity present in the virgin and recovery inert materials and in correspondence with which on the internal lateral surface of the cylinder there are cups or cups for lifting the material which, then, falls in "rain"; along this zone the average temperature is of the order of 200 ° C;

- a third zone where the amalgamation of the virgin aggregates and the recovery material (RAP) takes place with the formation of their aggregates and in correspondence with which on the internal lateral surface of the cylinder there are cups or lifting cups of the material, of greater dimensions to those present along the second zone and which extend along generatrices of the cylinder; along this zone the average temperature is of the order of 300 ° C;

- a fourth final heating zone of the dried and amalgamated mixture and in correspondence with which the burner flows; on the internal lateral surface of the cylinder, in correspondence with this fourth zone, helical blades are arranged.

The tubular body that forms the combustor is located in the latter area.

This known type drier has proved to be particularly advantageous, allowing, in particular, to dry and amalgamate mixtures containing recovered materials (RAP) in percentages up to 40% by weight.

However, it has some drawbacks which make it susceptible to further improvements.

In particular, it has been found that the advancement and mixing inside the cylinder of the virgin and recovered aggregates (RAP) sometimes take place irregularly with the formation of an inhomogeneous mixture which negatively affects the quality of the bituminous conglomerate. with it realized.

The purpose of the present invention is to obviate the drawbacks of known dryers and in particular to propose a rotary cylinder dryer for mixtures of virgin aggregates and recycled materials (RAP) for the preparation of bituminous conglomerates which allows to improve the advancement and The amalgamation of virgin aggregates and recovery materials (RAP) to form a homogeneous dried mixture.

These purposes according to the present invention are achieved by making a rotary cylinder dryer for mixtures of virgin aggregates and recovery materials (RAP) for the preparation of bituminous conglomerates as set forth in claim 1.

Further characteristics are provided in the dependent claims.

The characteristics and advantages of a rotary cylinder dryer for mixtures of virgin aggregates and recycled materials (RAP) for the preparation of bituminous conglomerates according to the present invention will become more evident from the following description, exemplifying and not limiting, referring to the attached schematic drawings in which:

Figure 1 is a schematic side elevation view of the dryer according to the present invention;

Figure 2 is a schematic, longitudinal and partial section of the dryer according to Figure 1;

Figure 3 is an enlarged detail of the dryer of Figure 2;

Figure 4 is a schematic view of a detail of Figure 3 showing only the characteristic blading of the dryer according to the present invention;

figure 5 is a schematic section on the V-V plane of figure 4;

Figure 6 is a view of a portion of the plane extension of the portion of the cylinder of the dryer according to the present invention provided with the mixing blades characteristic of the present invention. With reference to the attached figures, the number 10 generally indicates a rotary cylinder dryer for mixtures of virgin aggregates and recycled materials (RAP) for the preparation of bituminous conglomerates.

The dryer 10 comprises a cylinder which is rotatably supported about its longitudinal axis A by supports 12 mounted on a frame 13 resting on the ground.

Mounted on the frame 13 are motor means 14 which, by means of transmission means 15, for example of the gear type, cause the cylinder 11 to rotate around its longitudinal axis A.

As is evident from Figures 1 and 2, the longitudinal axis A of the cylinder 11 is inclined with respect to the horizontal plane or the supporting plane of the frame 13 by an angle a of the order of some degree, typically 3 °.

The cylinder 11 is delimited at its opposite ends by two heads, respectively a first head 16 at a higher level and a second head 17 at a lower level.

An inlet 18 of a mixture of virgin aggregates and recycled materials (RAP, Reclaimed Asphalt Pavment) to be dried is defined in correspondence with the first head 16, while in correspondence with the second head 17 an outlet 19 of the mixture is defined dried.

The heat necessary for drying is generated by a corresponding group consisting of at least one burner 20 associated with the second head 17 and arranged coaxially to the longitudinal axis A of the cylinder 11 inside which it directs the flame. In correspondence with the first head 16, on the other hand, there is an outlet 21 for the exhaust fumes of the dryer 10 which communicates with an aspiration chamber 22 which in turn can be associated with a unit for the aspiration and treatment of the exhaust fumes of the The dryer 10 is not shown in detail, being known to the person skilled in the art.

In correspondence with the outlet opening 21 there are baffle plates and / or walls designed to prevent the fine dust of the treated materials from reaching, dragged by the aspirated fumes, the fumes filter unit located downstream of the dryer 10 and which are subject to a co-pending application in the name of the same Applicant.

On the internal lateral surface of the cylinder 11 are mounted means for mixing and handling the aggregates and the treated recovery material which mix them and accompany them in their forward motion along the entire cylinder 11, from the inlet 18 to the outlet 19.

As can be seen from Figures 1 and 2, the inlet 18 and the outlet 19 of the mixture are obtained at the opposite ends (heads) of the cylinder 11, as well as the burner 20 and the outlet 21 of the exhaust fumes. they are arranged at the opposite ends (heads) of the cylinder 11; this makes it possible to exploit the entire length of the cylinder 11 for the heat exchange between the heat generated by the burner 20 and the treated mixture.

Fixed inside the cylinder 11 is a tubular body 23 open at the opposite ends 23a, 23b and arranged coaxially to the longitudinal axis A of the cylinder 11 with one of its open ends 23a facing the burner 20 and at a defined distance from it and with the opposite open end 23b facing the first head 16.

The tubular body 23 has a maximum diameter smaller than the internal diameter of the cylinder 11 so as to form with it an annular gap crossed by the mixture being dried.

The combustion fumes and the flame generated by the burner 20 are axially directed inside the tubular body 23, inside which, moreover, the drying fumes of the drying mixture that advance on the bottom of the the gap defined between the cylinder 11 and the tubular body 23, without, however, impacting the latter.

In succession to the tubular body 23 and downstream of it with respect to the direction of the flow of the combustion and drying fumes, there is an auxiliary tubular body 24, also open at the opposite ends 24a, 24b, fixed inside the cylinder 11 and arranged coaxially to the longitudinal axis A of the cylinder 11 itself.

The auxiliary tubular body 24 is arranged with one of its two opposite open ends 24a facing the open end 23b of the tubular body 23 opposite to that 23a facing the burner 20 and at a defined distance from it and the opposite open end 24b directed towards the the inside of the cylinder 11 is facing the first head 16.

The auxiliary tubular body 24 has a maximum diameter smaller than the internal diameter of the cylinder 11 and with it defines a gap crossed by the mixture being dried.

The combustion and drying fumes that come out of the tubular body 23 are directed into the auxiliary tubular body 24, inside which, moreover, the fumes external to it are aspirated by a dynamic effect.

The tubular body 23 and the auxiliary tubular body 24 each define a respective hot chamber for combustion and / or post-combustion of the combustion fumes and drying fumes, where the latter are generated by the fraction of recovery material (RAP) present in the mixture being dried and, in particular, from the aged bitumen present in them.

Both the tubular body 23 and the auxiliary tubular body 24 are made of heat-resistant steel, even of a different type, since the second must withstand lower temperatures than the first. In a preferred embodiment, the tubular body 23 is made of AISI 310 S steel, while the auxiliary tubular body 24 is made of 304-306 steel.

The assembly consisting of the burner 20, the tubular body 23 and the auxiliary tubular body 24 forms a combustor or post-combustor unit; in particular, the tubular body 23 and the auxiliary tubular body 24 form two hot chambers inside which the flame and the combustion fumes are directed and the drying fumes generated by the recovery materials (RAP) or in any case the fumes present in the cylinder 11, allowing the completion of the combustion (oxidation) of the organic substances contained therein.

The distance between the tubular body 23, or rather between its open end 23a, and the burner 20, as well as the distance between the tubular body 23 and the auxiliary tubular body 24, or rather between their open and facing ends, 23b and 24a respectively, is determined in such a way as to ensure the desired suction effect of the fumes, in particular of the drying fumes, inside them.

The whole of the tubular body 23 and of the auxiliary tubular body 24 and the structure of these bodies is the subject of a co-pending application from the same Applicant.

Inside the cylinder 11 and along its longitudinal development there is a sequence of different zones for treating the mixture at different temperatures progressively increasing as the mixture introduced through the inlet 18 advances towards the outlet 19.

In particular, starting from the first head 16 in correspondence with which the inlet mouth 18 of the mixture of aggregates and recycled materials (RAP) to be dried is defined, continuing towards the second head 17 in correspondence with which the inlet mouth 18 is defined. exit 19 of the dried mixture: a first zone 25 for the inlet of the mixture and in correspondence with which a plurality of helical blades 26 is distributed on the internal surface of the cylinder 11, a second zone 27 for evaporation of the humidity present in the mixture and in correspondence of which on the internal surface of the cylinder 11 there is distributed a plurality of lifting cups 28 for the aggregates and the recovery material (RAP) which fall like rain, a third zone 29 for mixing the aggregates and the recovery material (RAP) and in correspondence with which a plurality of mixing blades 30, 30 'and a fourth zone are distributed on the internal surface of the cylinder 11 31 for the final heating of the mixture and in correspondence with which a plurality of helical blades 32 are distributed on the internal surface of the cylinder 11.

As is evident from Figures 1 and 2, in a preferred embodiment, the tubular body 23 extends along at least a portion of the fourth heating zone 31 and the auxiliary tubular body 24 extends along at least a portion of the third mixing zone 29 .

The dryer 10 also comprises a heating unit for the combustion air fed to the burner 20. This heating unit comprises a pre-heating chamber 33 which extends behind the second head 17 and inside which the burner body 20.

Around the cylinder 11, for at least a portion of the length of the fourth zone 31, the one with the highest temperature, a skirt 34 is mounted which forms, around the cylinder 11, a cavity 35 which communicates, at one end, with the chamber. pre-heating 33 and, at the opposite end, with one or more inlet openings 36 of the ambient air.

An intake fan 37 is mounted below the frame 13 and communicates with the pre-heating chamber 33 so as to suck ambient air into it through the interspace 35.

Furthermore, sensor means for the temperature of the intake air are provided, such as, for example, a thermal probe, and means for measuring the flow rate of the intake air, such as, for example, a Pitot tube, so as to control and regulate the operation. of the burner 20.

The air sucked in from the external environment first passes through the interspace 35 from which it then enters the pre-heating chamber 33 to be then fed into the cylinder 11 to support the combustion of the fuel injected with the burner 20.

The heat of the walls of the cylinder 11, which in steady state reach temperatures of about 500-550 ° C, is transferred by convection to the intake air whose temperature is on average increased by about 45-50 ° C before being injected into the cylinder. , with obvious advantages in terms of combustion efficiency.

A peculiar characteristic of the present invention is the shape and arrangement of the mixing blades 30, 30 'fixed to the internal lateral surface of the cylinder 11 in correspondence with the third zone 29, i.e. in correspondence with the longitudinal portion of the cylinder which extends from the body. tubular 23 towards the first head 16 and inside which the auxiliary tubular body 24 is at least partially housed.

With reference to Figures 3-6, the mixing blades 30, 30 'consist of flat quadrangular plates which are arranged along a plurality of alternating rows Fi and F2 parallel to the longitudinal axis A of the cylinder 11.

In a plan view of the cylinder 11 (figure 6) the mixing blades 30, 30 'of each row F1 and F2 are orthogonal to the development plane of the cylinder 11, corresponding to the internal lateral surface of the cylinder 11, and are arranged between they are spaced apart and parallel to a respective plane P1 and P2 inclined with respect to the longitudinal axis A of the cylinder 11.

The mixing blades 30, 30 'of two adjacent rows FI and F2 are respectively parallel to a first plane PI inclined by a first angle β with respect to the longitudinal axis A of the cylinder 11 and to a second plane P2 inclined by a second angle γ with respect to to the longitudinal axis A of the cylinder 11.

In figure 6 the mixing blades 30 and 30 'and the first and second planes P1 and P2 are indicated by the respective projections on the plane.

The first angle β and the second angle γ are complementary to each other and, in a preferred embodiment, each of them has an amplitude of 45 °.

The mixing blades 30 of the rows Fi therefore have an opposite orientation to that of the mixing blades 30 'of the rows F2.

Along each of the rows Fi and F2 the respective mixing blades 30 and 30 'are arranged spaced apart at a constant pitch, where, in a preferred embodiment, the pitch between the mixing blades 30 of the rows Fi is equal to the pitch between the mixing blades 30 'of rows F2.

The mixing blades 30 and 30 'of two adjacent rows Fi and F2 are offset from each other by half a step.

Advantageously, the mixing blades 30, 30 'of the rows Fi and F2 are anchored to rods 38 parallel to the longitudinal axis A of the cylinder 11.

The mixing blades 30 and 30 'are fixed to the internal lateral surface of the cylinder with which, therefore, they are integral in rotation.

With reference to the attached figures, the operation of the dryer is as follows.

The virgin inert material and the recovery material (RAP) are fed into the cylinder through the inlet 18.

The materials thus fed pass through the first zone 25 being mixed and amalgamated by the helical blades 26.

The average temperature inside the cylinder 11 at the first zone 25 is generally of the order of 120-150 ° C.

The mixture then advances along the second zone 27, inside which there is an average temperature of the order of 280300 ° C, where the evaporation of the humidity contained in the materials and, in particular, in the recycled materials (RAP) takes place.

The lifting cups 28, or similar lifting means, for example with shovels or cups, lift the materials, which fall "like rain"; the mixing and amalgamation of the virgin inert materials with the recycled materials are thus favored. In particular, the bitumen fraction present in the recovery materials (RAP) softens, favoring the bond with virgin aggregates; thus, aggregates of virgin inert materials and recycled materials (RAP) are formed.

Along the third zone 29 there is a further mixing of the materials by the mixing blades 30, 30 'which, thanks to their particular arrangement and conformation, give the materials a controlled advancement motion such as to favor the formation of a substantially homogeneous mixture.

The alternating and opposite orientation arrangement of the mixing blades 30 of the rows F1 and of the mixing blades 30 'of the rows F2, in fact, generates a combined movement of advancement and withdrawal of the materials, favoring their mixing by overlapping of layers.

Along this third zone 29, the mixture advances into the interspace defined between the cylinder 11 and the auxiliary tubular body 24, without contacting the latter.

Inside this interspace there is a maximum average temperature of the order of 450 ° C, while inside the auxiliary tubular body 24 there is a maximum average temperature of the order of 550 ° C.

Finally, the dried and amalgamated mixture advances in the fourth final heating zone 31 to leave the outlet 19 at an average temperature of about 180-200 ° C.

The flame of the burner 20 flows into this fourth zone 31, the average temperature of which is of the order of 1000-1400 <0> C.

In particular, it is noted that the mixture advances without coming into contact with the flame or with the external wall of the tubular body 23.

The efficiency of the burner 20 is improved thanks to the pre-heating of the combustion air.

The flame and the combustion fumes are directed into the tubular body 23 (inside which there is an average maximum temperature of the order of 800-900 ° C) and from this into the auxiliary tubular body 24.

Furthermore, the drying fumes, ie the fumes generated by the recovery material, are aspirated inside the tubular body 23 and the auxiliary tubular body 24, due to a dynamic effect.

The two hot chambers in succession, formed respectively by the tubular body 23 and by the auxiliary tubular body 24, are crossed by the combustion and drying fumes and the volatile organic substances present in them oxidize thanks to the heat present inside these two chambers warm and on their walls.

The fumes are then evacuated through the outlet opening 21 and the chamber 22 and conveyed to a treatment and abatement unit.

The dryer object of the present invention has the advantage, thanks to the particular arrangement and conformation of the mixing blades 30, 30 ', of favoring the mixing of the virgin aggregates and the recovery material to form a homogeneous and uniform mixture, without penalizing the 'drying and production efficiency.

The presence of the auxiliary tubular body 24 in succession to the tubular choir 23, moreover, allows to further reduce, compared to known dryers, the percentages of volatile organic substances (VOC, COT) present in the exhaust fumes in compliance with the regulations in force, regardless of the nature of virgin aggregates and recovered materials (RAP) and also for percentages of recovered materials (RAP) higher than 25% and even of the order of 40%.

The pre-heating of the combustion air improves the combustion efficiency in terms of fuel savings of the order of 10% -20%.

Finally, thanks to the provision of baffle plates and walls placed in correspondence with the smoke outlet opening, fine particles of the treated materials are prevented from reaching the smoke filter unit, dragged by the aspirated fumes.

It should be noted that the temperatures shown in this description are purely indicative, depending on the flow rate and the type of both the virgin inert material and the recovery material (RAP), the fuel used, the ambient air temperature and the required temperature. heat the material.

The dryer thus conceived is susceptible of numerous modifications and variations, all of which are within the scope of the invention; furthermore, all the details can be replaced by technically equivalent elements. In practice, the materials used, as well as the dimensions, may be any according to the technical requirements.

Claims (8)

CLAIMS 1) Dryer (10) with rotating cylinder for mixtures of virgin aggregates and recycled materials (RAP) for the preparation of bituminous conglomerates, comprising a cylinder (11) which can be associated with motor means (14) able to rotate it around the its longitudinal axis (A) and which is equipped with two opposite heads (16, 17), an inlet (18) for a mixture of virgin aggregates and recovery materials (RAP) to be dried and which is defined in correspondence with one of said two heads (16), an outlet (19) of the dried mixture and which is defined in correspondence with the other of said two heads (17) and a heat generation unit associated with said cylinder (11) for the generation of drying heat of said mixture, characterized in that the internal lateral surface of at least one longitudinal section of said cylinder has a plurality of mixing blades (30, 30 ') which are arranged along a plurality of rows (FI, F2) parallel to de longitudinal axis (A) of said cylinder (11), in which, in a plan view of said cylinder (11), the mixing blades (30, 30 ') of each row (FI, F2) are arranged between they are spaced apart and parallel to a respective inclined plane (PI, P2) with respect to the longitudinal axis (A) of said cylinder (11) and in which the mixing blades (30, 30 ') of two adjacent rows (FI, F2) are respectively parallel to a first plane (PI) inclined by a first angle (β) with respect to said longitudinal axis (A) of said cylinder (11) and to a second plane (P2) inclined by a second angle (γ) with respect to said longitudinal axis (A) of said cylinder (11). 2) Dryer (10) according to claim 1, characterized in that said first angle (β) and said second angle (γ) are complementary to each other. 3) Dryer (10) according to claim 1 or 2, characterized in that the width of each of said first angle (β) and of said second angle (γ) is 45 °. 4) Dryer (10) according to one or more of the preceding claims, characterized in that said mixing blades (30, 30 ') of each said row (FI, F2) are arranged spaced apart at a constant pitch. 5) Dryer (10) according to one or more of the preceding claims, characterized in that said mixing blades (30, 30 ') of said two adjacent rows (FI, F2) are offset from each other. 6) Dryer (10) according to one or more of the preceding claims, characterized in that each of said mixing blades (30, 30 ') consists of a plate. 7) Dryer (10) according to one or more of the preceding claims, characterized in that said heat generation unit comprises at least one burner (20) associated with said head (17) in correspondence with which said outlet mouth (19) is defined ) and in that it comprises at least one tubular body (23), open at opposite ends (23a, 23b), fixed inside said cylinder (11) and arranged coaxially to the longitudinal axis (A) of said cylinder ( 11) with one of its open ends (23a) facing said burner (20) and at a defined distance from it, in which said mixing blades (30, 30 ') are fixed to the internal lateral surface of a section of said cylinder ( 11) which extends from said tubular body (23) towards said head (16) in correspondence with which said inlet (18) is defined. 8) Dryer (10) according to claim 7, characterized in that it comprises said tubular body (23) and at least one auxiliary tubular body (24), open at opposite ends (24a, 24b), fixed inside said cylinder ( 11) and arranged coaxially to the longitudinal axis (A) of said cylinder and in succession to said tubular body (23), in which said mixing blades (30, 30 ') are fixed to the internal lateral surface of the section of said cylinder (11) in which said auxiliary tubular body (24) extends at least partially.