Method for improving quality, reducing emissions and increasing the RAP rate in the production of recycled bituminous mixtures

Abstract

The invention relates to an optimised method for producing recycled bituminous mixtures (RBMs), thus improving the homogeneity of the product and therefore the quality thereof, and which increases the reclaimed asphalt pavement (RAP) percentage. The RAP fractions are classified according to density using a densimetric table, forming divisions with a homogenous grain size and bitumen content. Additionally, flexible mesh sieves are used to obtain sub-fractions, and a ballistic separator ("destoner") is used to separate the bituminous filler, with the same aim of controlling the RAP composition. Each sub-fraction and densimetric division is functionally allocated to different supply lines of the plant. Also included is a new system for incorporation using a reactor (MCRL), designed to heat, add additives and mix the fine RAP, controlling the residence time thereof. This integrated solution improves quality control, reduces bitumen oxidation, enhances rejuvenation, lowers emissions and enables greater RAP incorporation.

Description

[0001] METHOD FOR IMPROVING QUALITY, REDUCING EMISSIONS AND INCREASING THE RAP RATE IN THE MANUFACTURE OF RECYCLED BITUMINOUS MIXTURES

[0002] TECHNICAL FIELD

[0003] The present invention relates to the general technical field of devices, installations and methods for manufacturing recycled bituminous mixtures (MBR).

[0004] MBRs are obtained by adding materials recovered from the demolition of aged asphalt pavements, called RAP for "Reclaimed Asphalt Pavement", as a component of new asphalt mixtures for paving.

[0005] STATE OF THE ART

[0006] CONVENTIONAL BITUMINOUS MIXTURE

[0007] In general terms, a conventional bituminous mixture—also called asphalt mixture—is defined as the combination of:

[0008] • a natural or synthetic bituminous binder - usually bitumen -,

[0009] • Mineral powder - known as mineral filler - which are stone aggregates smaller than 0.063 mm

[0010] • the rest of the stone aggregates —known as aggregates— with a certain size distribution, commonly called granulometry,

[0011] • filler material, which can be cement, lime, calcium carbonate or others, and

[0012] • eventually additives.

[0013] All components are mixed in known proportions, which determines their physical properties and behavior under the stresses of a specific use—such as road pavement. Once spread and compacted in their application location, an aggregate structure is formed, bound by bituminous mastic, which is a matrix of bitumen and filler—both mineral and additive—and air voids dispersed between the aggregates and the mastic. Asphalt mixtures are used in pavements—roads, ports, airports, etc.—and other paved surfaces.

[0014] RAP GENERATION

[0015] Pavement maintenance involves planned conservation and rehabilitation operations to extend its lifespan and maintain its proper functional performance over time. Some of these operations involve milling away layers of bituminous mixtures from the pavement to be rehabilitated. This material resulting from the milling process is called RAP (Reclaimed Asphalt Pavement).

[0016] During this pavement demolition, many of the original, larger mineral particles are broken down, resulting in smaller particles and even mineral dust. Therefore, the particle size distribution of the material before and after milling will change, with a decrease in larger aggregates (coarse fractions) and an increase in smaller aggregates (fine fractions).

[0017] In addition, a large amount of RAP particles smaller than 0.5 mm are generated, henceforth referred to as "bituminous filler", which largely remains attached to the larger particles as dirt.

[0018] It can be stated that RAP is made up of stone materials of different sizes surrounded by bituminous mastic - which gave them cohesion before the demolition of the asphalt layer from which it comes - whose bitumen is aged with deterioration of its properties as a binder.

[0019] The particles that make up RAP vary from each other in both their size and density, determined by the proportion and size of the stone materials that make them up, the amount of mastic they contain, and the air gaps trapped inside.

[0020] Therefore, there will be RAP particles composed of coarse aggregate surrounded by a thin layer of mastic, similar in size to others that are the union of two or more aggregates surrounded by mastic, or others that are actually an amalgam of sand and mastic. These particles, although not differentiated by size, do differ in density.

[0021] RECYCLED BITUMINOUS MIXTURE (MBR) MBRs are made up of: all the virgin components of a conventional bituminous mixture,

[0022] • the aggregates, filler and aged binder, derived from the RAP particles, and

[0023] • eventually, additives that allow improvement of the RAP binder (chemical rejuvenators).

[0024] To properly dose an MBR, the first step is to readjust the particle size distribution of all the aggregates, formed by combining the virgin aggregates and filler with the aggregates and filler from the RAP, to achieve the required distribution. Second, the amount of binder is controlled, which includes both the aged binder from the RAP and the newly added virgin binder. Third and finally, the aged binder may require chemical rejuvenators to partially restore its initial properties. For this to occur, these additives must come into direct contact with the RAP binder under specific conditions of time, agitation, and temperature.

[0025] In a conventional bituminous mixture, manufactured entirely from virgin materials, the aggregates, filler, and bitumen are materials of known composition and are dosed separately with great accuracy during the mix design. However, the variability in RAP particles increases the uncertainty in the composition of the future recycled bituminous mixture (RBM) to which the RAP is added. Due to this inherent variability, the higher the RAP content added to a bituminous mixture, the greater the uncertainty regarding its resulting composition. Therefore, in practice, RAP variability limits the rate or percentage of this material that can be incorporated into RBMs when it is desired to preserve the quality and homogeneity of the RBM typically produced at an asphalt plant.

[0026] MANUFACTURING OF CONVENTIONAL BITUMINOUS MIXTURE

[0027] To manufacture a conventional bituminous mixture, several processes are necessary depending on the manufacturing temperature.

[0028] In the case of hot mix asphalt (HMA) - manufactured between 150 9 C and 190 9 C- and semi-hot mix asphalt (SMA) - between 100 9 C and 150 9C- Both the aggregates and the bitumen that make up the mix must be heated. For the aggregates, a heat transfer system using radiation and convection is employed, through direct exposure to a flame inside a rotating drying drum that stirs them and promotes heat distribution (aggregate line). The binder, in turn, is heated by contact with the surface of heat transfer circuits, generally with pipes containing thermal oil, electric heating elements, or another type of heat vector (binder line). The mineral filler is largely carried from inside the drying drum and conveyed to a collection system (mineral filler line) for subsequent reincorporation into the mix (recovery filler) or for removal in the desired proportion.

[0029] To manufacture warm mix asphalt (WMA) - manufactured between ambient temperature and 100 9C-, only the aggregate needs to be heated. As a binder, they use bitumen emulsions or other bituminous products that are sufficiently fluid at room temperature.

[0030] Cold bituminous mixtures (MBF) - manufactured at room temperature - do not require heating of the aggregates and use binders similar to MBT, which are sufficiently fluid at room temperature.

[0031] The aggregate and binder lines converge in the mixer, where the filler and recovery filler are added, along with any additives dosed according to a pre-established formula. All materials are mixed to achieve proper distribution and homogeneity, ensuring the mastic covers the entire surface of the aggregates to provide cohesion to the mix.

[0032] MANUFACTURING OF RECYCLED BITUMINOUS MIXTURE

[0033] The manufacturing processes for recycled bituminous mixtures (MBR) are similar to those for conventional bituminous mixtures, but in addition to the aggregate line, binder line, and filler line, there must be a RAP line through which it is introduced into the manufacturing process.

[0034] RAP lines are of two types: those that incorporate the RAP at room temperature (cold RAP) and those that preheat the RAP (hot RAP) before its incorporation into the MBR manufacturing system.

[0035] This patent relates to the manufacture of hot recycled bituminous mixtures (HRM), semi-hot recycled bituminous mixtures (SRMRM), warm recycled bituminous mixtures (HRMRM), and cold recycled bituminous mixtures (CRMRM). The processes for incorporating hot RAP must ensure that the aged binder it contains does not oxidize excessively upon heating, thereby preventing the loss of its remaining characteristics.

[0036] All cold or hot RAP lines must also ensure that the aged binder recovers its original properties as much as possible through the application of rejuvenating additives.

[0037] THE FIVE CHALLENGES IN THE CURRENT STATE OF THE ART

[0038] The reuse of RAP in the manufacturing process of recycled bituminous mixtures (MBR) involves five challenges that are not fully resolved with current manufacturing systems:

[0039] 1. Quality control in the composition of recycled asphalt mixtures (MBR): Virgin materials—mineral aggregates, fillers, and bitumen—are dosed with sufficient precision to ensure that conventional asphalt mixtures are homogeneous within the tolerances required by various technical standards. The composition of MBRs—to which RAP is added in addition to virgin materials—must achieve homogeneity with tolerances similar to conventional bituminous mixtures. This is achieved by adding the fractions of aggregate materials, fillers, and aged binder from the RAP to the new recycled asphalt mixture (MBR) in the correct proportions. This ensures that, when the RAP is incorporated, the required gradation and precise bitumen content of the resulting bituminous mixture are met.In practice, the uncertainty caused by the lack of homogeneity in the composition of RAP particles is limited by restricting the RAP rate allowed in the MBR by the different technical pavement regulations.

[0040] 2. Minimize the oxidation of the binder contained in the RAP: For the manufacture of MBRC, MBRSC, and MBRT, virgin aggregates need to be preheated. The RAP will be preheated or heated at the time of its incorporation when mixed with the preheated virgin aggregates. In both cases, additional oxidation of the aged binder can occur if the RAP is exposed to very high temperatures. This results in improved MBR quality, since the oxidation of the binder reduces the MBR's lifespan.

[0041] 3. Rejuvenating the RAP binder: The properties of the bituminous binder contained in the RAP must be restored by incorporating chemical additives, commonly called rejuvenators. These additives need to come into contact with the aged bitumen at a sufficient temperature and for a sufficient time to be effective. Similarly, rehabilitating the bituminous binder improves the quality of the MBR by increasing its service life.

[0042] 4. Reduce energy consumption and pollutant emissions generated in the manufacturing processes: Generally, cold RAP recycling systems require greater heating of some of the remaining components of the asphalt mixtures, resulting in increased heat loss and unwanted emissions. Furthermore, hot RAP also produces emissions when heated above 150°C. 9 C

[0043] 5. Increase the percentage of RAP in the MBR (RAP rate), to take advantage of or valorize as much of the waste from road rehabilitation as possible, reusing it for the same purpose.

[0044] To address the first challenge as much as possible—meeting the required particle size distribution and binder content—RAP is typically classified into different "RAP fractions" based on particle size using the same methods employed for virgin aggregates—"aggregate fractions"—that is, using wire mesh screens. Combining the RAP fractions with the virgin aggregate fractions helps to approximate the required particle size distribution as closely as possible.

[0045] The fractions are named "F(d / D)" according to the sizes of their particles, where "d" is the nominal size of the smallest particles belonging to that fraction and "D" is the nominal size of the largest particles:

[0046] - "d" is the nominal minimum size of the fraction, defined as the maximum opening in millimeters of the UNE EN 933-2:96 sieve through which less than 10% by weight passes (the percentage of particles smaller than "d" is less than 10%). Therefore, it should be understood that every fraction contains particles smaller than "d" in a relatively small proportion.

[0047] "D" is the nominal maximum size of the fraction and is defined as the smallest opening in millimeters of the UNE EN 933-2:96 sieve through which more than 90% by weight passes (the percentage of particles larger than D less than 10%), when the entire fraction also passes through the double-opening sieve (the percentage of particles larger than "2D" equal to 0%). Therefore, it should be understood that every fraction contains particles larger than "D" in a relatively small proportion.

[0048] From now on, we will refer to both the RAP fractions and the aggregate fractions as follows:

[0049] • Fine fractions: whose maximum nominal size (D) is less than or equal to 6mm, e.g. F(0 / 2), F(2 / 4), F(0 / 6).

[0050] • Coarse fractions: those whose minimum nominal diameter (d) is greater than 6 mm, e.g. F(6 / 12), F(8 / 10), F(10 / 20). • Intermediate fractions: all other fractions that do not meet the above requirements, e.g. F(4 / 8), F(5 / 10), F(5 / 11).

[0051] The metal mesh screens used in the asphalt mix manufacturing industry are not designed to classify materials with the moisture content typical of RAP stockpiles. Therefore, the fine fractions of RAP become clogged during their production. The smallest mesh size typically used to separate RAP is between 10 and 12 mm.

[0052] "Dmax" refers to the maximum nominal particle size of RAP that can be processed for MBR manufacturing. RAP particles larger than Dmax are referred to as "RAP rejects," which are typically crushed and recirculated to the screening process.

[0053] In a given RAP fraction, the amount of mastic in the RAP particles is greater the larger the specific surface area of ​​the aggregates that compose it. Fine RAP fractions are typically made up of smaller aggregates than the constituents of coarse RAP fractions. This characteristic is taken into account when designing MBRs.

[0054] The particles that make up RAP, despite being separated by size, are not homogeneous in composition—as we saw earlier—resulting in particles of similar size but with different densities. Therefore, the amount of bitumen, filler, and aggregate gradation added to the MBR with the RAP cannot be determined solely by its size.

[0055] Patent WO2014168478A1 advances the separation of RAP particles by impact crushing. Once classified by size into fractions, this allows for the production of fine and coarse RAP with more controlled bitumen content, as the impact process breaks down the mastic-like agglomerations. However, this solution requires that the impact not cause the rupture of mineral aggregates, which is not being achieved in practice, and therefore it is not a widely used system.

[0056] Furthermore, in standard size separation methods, the fractions into which RAP is classified are not precise enough for manufacturing some bituminous mixtures. For example, several common mixtures are dosed by separately adding virgin aggregate fractions F(0 / 2) and F(2 / 4), which are smaller than those achievable with current RAP screening techniques due to the mesh size. Moreover, the smallest RAP fraction, F(0 / 0.5) mm – bituminous filler – is present in all RAP fractions, adhering to the surface of larger particles, and cannot be separated from them by screening.

[0057] For these reasons, the proportion of RAP relative to the total MBR (RAP rate) is currently limited due to the variability and uncertainty that its poor knowledge of its granulometry and filler and bitumen content induces in the MBR thus manufactured.

[0058] To try to solve the second challenge - minimizing the deterioration due to oxidation of the bitumen contained in the RAP - there are several techniques that depend on the RAP being integrated into the manufacturing process at room temperature (cold RAP) or preheated (hot RAP).

[0059] Systems for incorporating cold RAP into recycled bituminous mixtures introduce the RAP directly into the asphalt plant mixer, where heated virgin aggregates and filler have already been added. The RAP is then heated by heat exchange with the aggregates. Subsequently, new binder and, if necessary, rejuvenating additive—either premixed or added separately—are introduced, as described in EP0114118A1.

[0060] In the production of MBRC, MBRSC, and MBRT, the virgin aggregates must be superheated depending on the amount of cold RAP incorporated and its moisture content. The superheated aggregates then transfer heat by contact to the RAP, achieving the correct outlet temperature from the mixer. For example, when adding 20% ​​RAP with a moisture content of 5%, the aggregates should enter the mixer at approximately 225°C. 9 C to obtain an MBRC at the mixer output of 150 9 C. However, when the cold RAP comes into contact with the superheated aggregates, a sudden rise in its temperature occurs, known as thermal shock. If the temperature increase is very high, it aggravates the aging of the RAP bitumen and can even cause irreversible damage.

[0061] There are three additional problems with this cold RAP aging technique: First, when the RAP is heated by contact with the superheated aggregates, the bitumen in the RAP generates volatile organic compounds (VOCs) that partially condense, commonly known as blue smoke, and pollute the atmosphere. Second, the energy efficiency of the virgin aggregate heating systems decreases as the desired temperature at the dryer drum outlet increases, since heat losses increase with higher system temperatures. And finally, the plants' production capacity decreases because the virgin aggregate heating cycle in the dryer drum takes longer.Hot RAP incorporation systems are of two types: "mixed drum" where the RAP is heated in the same device, but in a different space than the virgin aggregates, so that the RAP is heated both by contact with hot aggregates and by convection in the dryer drum itself; and "RAP drum", where the heating of RAP occurs in a different device than the one that heats the virgin aggregates.

[0062] In mixed drums, to minimize bitumen oxidation and therefore aging, the RAP (Reclaimed Asphalt Pavement) is introduced at ambient temperature to an area of ​​the drum either away from the flame or protected from it. The RAP heats up inside the drum without overheating the virgin aggregates and avoiding significant thermal shock. The temperature reached by the virgin aggregates in the hottest section of the drum is also used to further raise the temperature of the RAP through contact with the aggregates in the section of the drum with lower thermal radiation.

[0063] In this regard, patent FR2632669A1 has had the greatest application, advancing the flame inside the dryer drum and introducing the RAP behind it so that it mixes with the virgin aggregates.

[0064] Within the mixed drums, patent US3999743 proposes incorporating the RAP fractions that are finer - higher bitumen content - further away from radiation, using several incorporation rings in the drum for this purpose.

[0065] In the case of RAP drums, these are drums specifically designed for preheating the RAP, where the flame is kept away from the RAP insertion points to prevent bitumen oxidation. Many variations exist.

[0066] US patent 4096588A introduces the use of different drying drums, each with the flame positioned further away as the RAP fractions become finer. These are commonly known as parallel drums. Since only two drums are used in parallel in practice, excessive heating occurs to the smaller RAP particles, which have a larger specific surface area and are therefore more exposed to radiation.

[0067] US patent 5522158A—a system known as "double barrel I"—develops a concentric outer drum into which the RAP (Reclaimed Aggregate Potential) is introduced. This drum utilizes the heat from the inner drum of virgin aggregate exposed to the flame, thus completely protecting the RAP from the flame and bonding it with the virgin aggregate afterward. WO2017173555A1 patent describes a RAP drum with an independent combustion chamber where the flame is generated and a subsequent chamber, connected in series, for drying the RAP. These chambers are separated by a variable opening system that allows for controlled regulation of the hot air entering the second chamber.

[0068] Both mixed drums and RAP drums present similar problems when working with RAP at temperatures where the binder adheres very easily to all types of surfaces. To prevent the RAP from cooling down and sticking to the walls of the systems that convey it to the mixer, all contact areas must be heated to avoid breakdowns and operational problems.

[0069] Conventional drums—for heating virgin aggregates—constitute the "aggregate line" in the bituminous mixture manufacturing process. RAP drums constitute a separate "RAP line." Combination drums combine the aggregate and RAP lines. All of them generate, through controlled combustion—a controlled flame—a stream of hot gases that raises the temperature of the aggregates and the RAP, carrying the smaller particles along in their flow—mineral filler from the virgin aggregates and bituminous filler from the RAP.

[0070] In conventional drums, before being released into the atmosphere, the gases pass through filtration systems that retain the mineral filler. A portion of this filler can be reincorporated into the asphalt mix, and the remainder becomes a byproduct of the process. When reused, it is stored in a silo and is called reclaimed filler. This constitutes the "mineral filler line" of the conventional asphalt plant. The systems currently used to retain the filler are textile filters, commonly called bag filters. Subsequently, the gas stream, once the filler has been retained in the filter, continues its path through the exhaust line to the atmosphere.

[0071] Whether using mixed drums or RAP drums, the bituminous filler is carried along with the mineral filler through the same line to the filtration systems, which creates several problems:

[0072] • The filler is a material with a large specific surface area and each particle collects a large amount of radiation, so there is a risk of combustion of the bitumen it contains.

[0073] • Before leaving the drum, the heated bituminous filler easily adheres to the drum walls, compacts and oxidizes, and causes the drums to lose effectiveness to the point that in many cases it has to be removed with a hammer drill, which increases the operating cost.

[0074] • In the filler line, bag filters are designed for powdered materials. The result is that the fabric filtering the mineral filler becomes clogged by the bituminous filler particles that adhere to it, eventually rendering it unusable.

[0075] • The filler line stream contains combustion gases, air, water vapor, volatile organic compounds (VOCs), and, if RAP or binder is introduced, vaporized heavy hydrocarbons (visible blue fumes) are also carried along. These vaporize at temperatures above 150°C. 9 These gases condense at room temperature, combining with dust and water particles, and have a characteristic fuel odor. Blue fumes also accumulate in bag filters with the same harmful effect as bituminous filler.

[0076] To reduce filter clogging, the mineral filler acts as a coating for the bituminous filler particles, helping to condense heavy volatile hydrocarbons. This prevents the filler particles from adhering to the filter cloth when they collide. However, this solution depends on the quantity and quality of the filler surrounding the binder particles and the hydrocarbons present, so it is not always effective.

[0077] Therefore, in the case of mixed drums, it is always necessary to have a portion of virgin aggregates with sufficient mineral filler in the drum. In the case of RAP drums, they must always be used in parallel with conventional aggregate drums that provide mineral filler, and the hot gas flow conduits of both drums must be connected. This limits the RAP rate in the production of bituminous mixtures with the drums described above and other similar solutions on the market, since the proportion of mineral filler must always be carefully controlled to slow down filter clogging.

[0078] To address the third challenge - regeneration of the binder present in the RAP - a rejuvenating additive is needed that comes into contact with the RAP for a minimum time and temperature so that its aged binder recovers, as far as possible, its initial properties.

[0079] One common technique involves premixing the rejuvenating additive with fresh binder in the binder tanks, which requires recirculating or stirring all the stored binder before adding it to the MBR. Another common technique is to use systems to dose the additive directly into the asphalt plant mixer.

[0080] In both cases, there is no direct contact of the rejuvenating additives with the RAP exclusively - in the mixer it comes into contact along with the rest of the components of the final mix - virgin aggregates, filler, and new bitumen - On the other hand, the mixing time is subject to the manufacturing process of the plant, so on many occasions it is insufficient for effective rejuvenation because it does not slow down the entire manufacturing line.

[0081] Therefore, there is no technique in which the additive comes into contact with the RAP bitumen in the first instance, controlling the temperature and mixing time.

[0082] To address the fourth challenge - reducing energy consumption and polluting emissions generated in manufacturing processes - several techniques are used.

[0083] On one hand, there are strategies focused on manufacturing at lower temperatures. This involves producing semi-warm recycled asphalt mixes (MBRSC) instead of warm recycled mixes (MBRC). Within this technology are chemical methods using workability-enhancing additives and physical methods of bitumen foaming. Both achieve the same effect and are complementary.

[0084] On the other hand, warm recycled mixes (MBRT) are manufactured with a binder in the form of an emulsion, but are currently out of use due to the additional cost involved.

[0085] On the other hand, combustion-based heat generation systems can be replaced by electric resistance heating, which produces no emissions in the mixture manufacturing area. For example, this could be used in thermal oil boilers to heat bitumen and process lines that require it.

[0086] For the fifth challenge - increasing the percentage of RAP in the MBR (RAP rate) - several of the previously mentioned systems are combined:

[0087] • Mixed drums and RAP drums help reduce thermal shock. The higher the RAP temperature before mixing with the preheated virgin aggregates, the lower the temperature of the latter needs to be. This reduces the temperature differential experienced by the RAP bitumen, allowing for a higher RAP content. • To increase the RAP content, it is necessary to improve both the particle size distribution of the RAP and its binder content. Increasing the number of fractions in which the RAP is introduced during the MBR manufacturing process helps in this regard. Currently, two RAP fractions are used: a fine fraction (up to 8 or 12 mm) and a coarse fraction (from 8 or 2 mm up to the maximum size allowed for each type of mix, typically between 20 mm and 32 mm). While this significantly improves the final particle size distribution, it can still be optimized to further increase the RAP content.

[0088] • Patent WO2014168479A1 proposes using the larger RAP fractions, which in principle have a lower bitumen content, by introducing them into the aggregate line, where they are directly exposed to flame radiation. As the RAP binder oxidizes, it loses all its properties. This increases the recycling rate of aggregates from RAP in MBRs by introducing a large quantity of material through the aggregate line, but at the cost of not recovering the bitumen content, which is then incinerated during heating in the aggregate line.

[0089] SUMMARY OF THE INVENTION

[0090] RAP particles of the same size can have different compositions, varying among themselves in the proportions and sizes of the stone materials that make them up, the amount of binder they contain, and the air gaps trapped inside, which consequently means that they differ in their density.

[0091] For this reason, characterizing RAP by particle size does not imply knowing the gradation of the aggregates that compose it, which depends both on the original pavement formula and the pavement milling process, since a portion of the original aggregates is broken down. To date, RAP has been classified only by size, that is, by grouping the particles into fractions—just as is done with virgin aggregates—which we call "RAP fractions." Therefore, introducing RAP into the MBR manufacturing process creates uncertainty in its final gradation, which limits the maximum RAP content to avoid exceeding the MBR composition tolerance.

[0092] The present invention, "a method for improving quality, reducing emissions, and increasing the RAP yield in the manufacture of recycled bituminous mixtures," is applicable to at least one of the RAP fractions and is based on classifying its particles according to their composition, using a separation process with a densimetric table. This achieves a dual objective: firstly, separating the RAP particles with the highest bitumen content; and secondly, gaining a better understanding of the particle size distribution of the aggregates present in the RAP particles and their bitumen content.

[0093] Regarding the first objective, it's important to remember that improving the RAP rate requires utilizing the maximum amount of bitumen present in the RAP. Therefore, it will be necessary to identify which RAP classifications have the highest bitumen content and apply bitumen rejuvenation techniques exclusively to these groups, thereby increasing their effectiveness, since current techniques apply rejuvenators to the entire set of MBR components.

[0094] Regarding the second objective, since pavements require a specific mineral structure and bitumen content, the correct manufacture of MBRs involves adjusting their particle size distribution and bitumen content with the same tolerance required for a bituminous mix of the same characteristics without RAP. This requires sufficient knowledge of the particle size distribution and bitumen content of both the newly added aggregates and the RAP itself.

[0095] Density tables separate particles into groups of homogeneous densities. This is achieved using a blowing process through a perforated, inclined tray subjected to a vibratory motion that propels the denser particles upwards. Therefore, when we refer to density separation from now on, we are referring to the separation resulting from the use of a density table.

[0096] The present invention comprises a process for separating at least a fraction of RAP - F(d / D) - using a densimetric table, by which at least four differentiated groups are obtained based on their composition, which we will henceforth call "densimetric divisions":

[0097] The densest particles are subject to the vibratory motion of the table, which forces them to rise up the slope of the perforated tray, settling on the upper side. These constitute the corresponding heavy fraction Dp(d / D). Their mineral aggregates will belong to the aggregate fraction F(d / D), and their bitumen content will be low or intermediate depending on the surface area of ​​these aggregates.

[0098] • The less dense particles, thanks to the airflow and gravity, settle to the bottom of the inclined tray. These form the corresponding light division, Dl(d / D). The RAP particles in this division will also be between dy and D mm in size, but the mineral aggregates that compose them will be mostly fine—less than 6 mm—and their bitumen content high. • The smallest particles, with a larger specific surface area, are carried away by the airflow and collected separately, for example, using a cyclone. They form what is called bituminous filler (FB). The size of these particles will mostly be between 0 and 0.25 mm, with the maximum nominal size increasing as the airflow velocity of the gravity table increases. Their bitumen content will always be very high.

[0099] • The denser, but sufficiently small, particles fall through the perforated holes in the tray, forming the through-division Dpas(h), where "h" is the diameter of these holes. These particles will be composed of mineral aggregates approximately the same size as the opening of the mastic air outlet on their surface, and their bitumen content will be intermediate. For example, with a 5 mm hole, aggregate up to 5 mm will be obtained.

[0100] In order to economize or make the process more efficient, the present invention preferably further comprises a process for separating at least one other fraction of the RAP by means of a ballistic separator, which we will hereafter call a "destoner," by which the bituminous filler adhering to its particles is extracted. We will hereafter call this process the "destonerization process."

[0101] Also preferably, for the manufacture of MBR, the present invention comprises a process prior to the two previously described, which, for at least one fraction of RAP, divides it using flexible mesh screens, resulting in one or more fractions with a maximum nominal size less than or equal to 12 mm, which we will henceforth call "sub-fractions". Following the same criterion as the fractions, we will name the sub-fractions "sF(d' / D')", where "d'" is the minimum nominal size and "D'" is the maximum nominal size. We will call this process "sub-fractionation by flexible mesh".

[0102] Both the fractions and sub-fractions of RAP that have undergone the destonering process will be named in the same way as the rest of the fractions and sub-fractions, but adding the term "dest" at the end. For example, F(d / D)dest or sF(d' / D')dest.

[0103] Preferably, the present invention also comprises a new process, subsequent to the densimetric table separation, in which the RAP sub-fractions and divisions with the highest bitumen content—including the bituminous filler—are fed into the MBR using addition systems and mixing and heating systems for a controllable residence time. This process is called "hot light RAP pretreatment" and is explained below.

[0104] The light sub-fractions and divisions, with high and very high percentages of bitumen - which we will henceforth call light RAP - have been incorporated into MBRs at very limited rates due to the problem of thermal shock, and because of their stickiness - problems of adhesion to the walls of the plants - which can lead to RAP scaling and breakdowns, which implies a very high preventive maintenance cost.

[0105] For the incorporation of lightweight RAP into the MBR manufacturing process, the present invention proposes the use of a mixing and heating reactor, widely used in other industrial sectors, but specifically prepared for RAP. This device will henceforth be referred to as the Lightweight RAP Mixer-Heater (LRMC).

[0106] The MCRL reactor comprises an elongated chamber, slightly inclined longitudinally, with a lower end corresponding to the beginning of the material flow and a higher end corresponding to the end of the material flow. Its outer casing houses non-radiative, temperature-adjustable heating systems. Inside, it contains propulsion and mixing systems (433 and 434).

[0107] The reactor is longitudinally subdivided into different zones where the various materials are incorporated, as well as additives that modify the mixture both physically and chemically, such that: in zone 1, next to the first end, the lightweight RAP is introduced; in zone 2 § In the adjacent zone, liquid material is introduced, preferably a rejuvenating additive and / or a liquid additive to reduce the viscosity of the mixture. 3 § In this area, additional powdered material is introduced, preferably bituminous filler, and optionally a special filler, powdered colorant, fibers, or other additive. 4 §In this area, additional solid material, preferably rubber pellets, is introduced to modify the rheology of the mixture; and at the second end there is an outlet gate that allows the residence time of all the introduced materials and additives to be controlled at will - controlled residence time - to finally obtain as a resulting product Hot Additive Light RAP, which we call RAPLAC, which is incorporated into the MBR manufacturing process.

[0108] The resulting product is a Light, Additive, Hot RAP (hereinafter RAPLAC), which is incorporated into the MBR during manufacturing.

[0109] In this MCRL reactor, heating is achieved by indirect heat transfer, preferably by external heating. For example, the reactor is jacketed with thermal oil heated externally by an electric or combustion boiler.

[0110] External to the indirect heating system, a heat insulation system is provided to operate efficiently.

[0111] To ensure that the appropriate temperature is reached and that the rejuvenation process is completed, the residence time is controlled. Additionally, a thermally insulated regulating hopper can be located between the MCRL reactor and the asphalt plant mixer. This facilitates coordination between the supply from the MCRL reactor and the demand from the MBR plant, and also increases the interaction time between the RAP and the additives, beyond the residence time in the MCRL.

[0112] The MCRL reactor achieves heating of the lightweight RAP particles without direct radiation, and allows for the dosing of all types of additives and bituminous mixture improvers. Subsequently, once heated, the lightweight RAP is introduced into the asphalt plant mixer using a standard lifting or conveying system that allows for the dosing of the required quantity for the MBR to be manufactured.

[0113] Therefore, the present invention—a method for improving quality, reducing emissions, and increasing the RAP yield in MBR manufacturing—makes use of this new RAP classification, which groups the material into sub-fractions, density divisions, and bituminous filler. The particle size distribution of the mineral aggregates and bitumen content of each of these components are now known thanks to the homogeneity of their composition. In this way, we can increase the RAP yield by knowing the final particle size distribution and bitumen content of the MBRs with sufficient precision. For each of these newly classified groups, the method indicates the most suitable incorporation system for MBR manufacturing processes from among those available at current asphalt plants.Heavy Dp (d / D) divisions from coarse RAP fractions or sub-fractions, with low bitumen content, can be added to the MBR manufacturing process using one of the following systems, listed in order of preference:.

[0114] 1. Incorporate the heavy Dp(d / D) divisions into a hot RAP line. This way, the recovery of their limited binder content is not compromised. The fact that these divisions contain little bitumen and very little bituminous filler makes them more favorable for preventing bitumen oxidation, potential emissions, and improving the particle size control of the bituminous filler. Furthermore, it prevents the filler from adhering to the various components of asphalt plants, significantly increasing the recycling rate in all current RAP preheating systems.

[0115] 2. If a hot RAP line is unavailable, the heavy Dp(d / D) fractions can be introduced through the asphalt plant's aggregate line, as if they were an aggregate fraction. This increases the RAP content in the MBR, since the coarser aggregates present in Dp(d / D) are very abundant in most common asphalt mixtures. The drawback is that the limited amount of binder contained in these heavy fractions is not recovered. This system is similar to that proposed by patent WO2014168479A1, but by removing the particles from the light fraction, it is possible to control the mix's gradation more precisely and to utilize the bitumen contained in the light RAP fractions separately in another incorporation system, representing a significant improvement over that patent.The only limitation to consider are the emissions produced in the combustion by direct exposure to the flame of the small amount of bitumen contained in this heavy division of RAP.

[0116] 3. Cold RAP systems can be used, with the aforementioned limitation of thermal shock, although it would facilitate granulometric control in any case.

[0117] i. Heavy divisions Dp (d / D) from fine fractions or sub-fractions and passing divisions Dpas(h) with intermediate bitumen content, which should not be introduced through the aggregate line as they could cause emissions -blue smoke-, should be incorporated using one of the following systems in order of preference:

[0118] 1. Introduce them through the hot RAP line, with the same limitations and advantages as the Dp (d / D) divisions from coarse RAP fractions or sub-fractions; or

[0119] 2. Introduce them through the cold RAP line, although we also encounter the limitation of thermal shock. iii. The RAP sub-fractions obtained with the flexible mesh screens, with a high bitumen content, must be incorporated through the cold RAP line as the only option. Therefore, the quantity will be limited by thermal shock in the mixer. iv. The light Dl(d / D) divisions, also with a high bitumen content, must be incorporated through the cold RAP line as the only option, which also entails a limitation due to thermal shock in the mixer. v. The bituminous filler extracted, either by Destoner or on the density table, with a very high bitumen content, should be incorporated through the hot light RAP pretreatment line as the preferred option. With current systems, it can only be incorporated through the cold RAP line, but due to its high bitumen content, the quantity that can be added would be very limited since thermal shock would be very detrimental.

[0120] The remaining RAP fractions, which can be retained when using the present "method for improving quality, reducing emissions and increasing RAP rate in MBR manufacturing", are those customary in the prior art: i. The coarse RAP fractions with intermediate bitumen content are incorporated using one of the following systems in order of preference:

[0121] 1. Insert them through the hot RAP line

[0122] 2. Introduce them through the cold RAP line, although we also encounter the limitation of thermal shock. i. The fine RAP fractions with intermediate-high bitumen content, whose limitation due to thermal shock and whose workability drawbacks are greater than in the coarse fractions, should be incorporated using one of the following systems in order of preference:

[0123] 1. Introduce them through the hot RAP systems, preferably, the further away from the radiation the better.

[0124] 2. Introduce them through the cold RAP line, although we also encounter the limitation of thermal shock.

[0125] In conclusion, the improvements that the present invention provides for each of the five challenges described above are outlined. i. The first challenge: Controlling the quality of the composition of recycled asphalt mixtures. The present invention, "method for improving quality, reducing emissions, and increasing the RAP content in the manufacture of recycled bituminous mixtures," allows for the control of the particle size distribution and bitumen content of the RAP, thanks to the incorporation of RAP particles classified into new groups: sub-fractions, density divisions, and bituminous filler, in addition to the fine and coarse RAP fractions—the only fractions currently used. Thus, it becomes possible to incorporate a higher percentage of RAP into the MBR while meeting the particle size distribution specifications of the bituminous mixtures.

[0126] The amount of bituminous filler contained in RAP typically exceeds that required for dosing MBR. Thanks to filler extraction, either on a density separator or a destoner, it can be controlled with high precision, separately from the other mineral aggregates, something not currently possible. The excess bituminous filler can be stored in silos or bagged for later use in other industries that may require this byproduct, e.g., the manufacture of bituminous mastic for sealing and waterproofing.

[0127] i. For the second challenge: minimizing the oxidation of the binder contained in the RAP, the present invention establishes which is the most suitable asphalt plant process line for the incorporation of each of the fractions, sub-fractions and divisions of RAP, based on its bitumen content.

[0128] Furthermore, for lightweight RAP—light sub-fractions and divisions with high and very high bitumen percentages—the present invention proposes a new process that we have called "hot pretreatment of lightweight RAP," which allows the lightweight RAP to be heated while practically preventing the oxidation of the bitumen it contains. iii. The third challenge: properly rejuvenating the binder, is achieved thanks to the MCRL system, which processes the RAP with controlled temperature and mixing time, adding the rejuvenating additives to the portion of the RAP with the highest bitumen content.

[0129] This represents a significant advantage over current methods where the rejuvenating additive is added to all MBR materials simultaneously, tending to interact with the virgin bitumen, as well as with the older and more viscous RAP bitumen. iv. The fourth challenge: reducing emissions in asphalt mixture manufacturing processes. This is achieved in several ways:

[0130] • In the case of asphalt plants with a cold RAP line, the method allows a large quantity of material (heavy division) to be fed directly through the drying drum. This means that the RAP particles from that division do not need to come into contact with superheated aggregates to reach the manufacturing temperature. Therefore, the heat losses due to the need to superheat the aggregates will be reduced.

[0131] • In asphalt plants with the hot RAP line, the method reduces blue smoke emissions by introducing only RAP with low bitumen content, since RAP particles with high bitumen content are processed through the MCRL (Mechanical Combustion Line Reactor). Similarly, the fractions that undergo filler extraction in the destoner contain less bituminous filler, which helps reduce emissions that would have been produced by these particles, which contain the highest percentage of bitumen and are therefore the most exposed to radiation.

[0132] • Being able to remove the bituminous filler from the hot RAP lines results in a decrease in emissions and also an improvement in efficiency because: in both the heating process of the mixed drums and the RAP drums, the accumulation of bituminous filler that adheres to their walls, causing inefficiency in the system, is reduced; in addition, the difficulties for precise dosing of the hot RAP in the transfer ducts from one part to another of the asphalt plant are minimized; and all this results in fewer technical stops to clean the bituminous filler before restarting production.

[0133] • In the preferred option of using the new MCRL reactor for the pretreatment of hot lightweight RAP, the need to heat RAP particles by contact with hot aggregates is reduced, avoiding overheating—with the consequent heat losses—and bitumen emissions, since part of the RAP is heated with emission-free systems through indirect heat transfer. Regarding the fifth challenge: increasing the percentage of RAP in MBRs (RAP rate), the new method achieves significant progress depending on the systems of each asphalt plant:

[0134] • In the case of asphalt plants that also have a cold RAP line, the RAP supplied by this line can consist of fractions and divisions with medium, high, and very high bitumen content. This way, more bitumen is recycled with the same amount of RAP limited by thermal shock. The heavy divisions, with low bitumen content, can be fed through the aggregate line. Therefore, a higher RAP recycling rate is achieved by using two RAP lines simultaneously.

[0135] • In the case of plants with a mixed RAP drum, the sub-fractions and divisions established in the present invention allow increasing the contribution made by the hot RAP line: if only the so-called Divisions and those fractions or sub-fractions processed by the Destoner -whose bituminous filler has been previously extracted- are used, the maintenance and operation of the drum improves significantly, so the RAP rate remains high for a longer time, without needing to stop and remove the deposits of bituminous fines from the inner walls of the drum, the heavy Divisions with low % bitumen can go through the aggregate line at the same time, so an additional RAP line is added.

[0136] • In the case of RAP drums—parallel, concentric, or in series—the improvement is considerable due to the significant advantage of removing the bituminous filler before the RAP enters the heating processes. Heavy divisions with a low bitumen content can then be processed on the aggregate line simultaneously, effectively creating an additional RAP line. • In the case of conventional asphalt plants, meaning those without a RAP line installed, the new method allows for the introduction of heavy divisions—with low bitumen content—through the virgin aggregate heating and processing line. This effectively transforms these plants from having zero RAP reuse to having a primary RAP line.

[0137] BRIEF DESCRIPTION OF THE FIGURES

[0138] Figure 1 shows RAP particles of similar size but with different internal compositions. All these RAP particles belong to a similar granulometric fraction but differ in composition, both in their mineral aggregates and bitumen content: particle A is a mineral aggregate coated with a thin layer of bituminous mastic; particle B is a mineral aggregate partially coated with a thicker layer of bituminous mastic; particle C is a mineral aggregate almost completely coated with mastic; particle D is composed of two mineral aggregates bonded together and surrounded by mastic; particle F is actually a group of fine aggregates surrounded by mastic; and particle G is mastic only.

[0139] Figure 2 is a schematic view of the process of separating a RAP(d / D) fraction into sub-fractions, using a flexible mesh screening system (1) so that it is divided into: sub-fraction sF(d / Dl) which accumulates in stockpile (13) and sF(d2 / D) which follows the treatment line with a RAP separation process into divisions using a densimetric table (2) with air outlet holes of diameter "h" mm. So that it is divided into: heavy division Dp(d2 / D) which accumulates in stockpile (21), light division Dl(d2 / D) also accumulated in stockpile (23), the through division Dpas(h) accumulated in stockpile (25) and the bituminous filler FB which is collected by means of a cyclone (26) to a collection box (27) to be subsequently stored in a silo (29).

[0140] Figure 3 shows an overview of the detonation process of the F(d' / D') fraction entering the ballistic separator or detonator (3). The bituminous filler surrounding the RAP particles is pushed upward by the detonator's steps (3) due to the adhesion of its particles. This results in the separation of the adhered bituminous filler, which is stored in silos (33) and (35). Meanwhile, the larger RAP particles, impacted by these steps, fall by gravity and are stored in stockpile (37).

[0141] Figure 4.1 shows an overview of the light RAP mixer-heater, MCRL (4), whose housing consists of the lid (41) and the main casing (42). The lid (41) includes the main material inlet (411), the chemical regeneration agent inlet (412), the first additive inlet (413), the second additive inlet (414), and the third additive inlet (415).

[0142] Figure 4.2 shows a longitudinal projection, two cross-sections, and a side view of the MCRL. Section AA shows the main housing (421), the housing (422) of the thermal oil heating chamber (423), and the gate guide (424) (425). Section BB shows the regenerator inlet (412) and the second additional material inlet (414), as well as part of the material handling and mixing system consisting of one of the main shafts (433) and a pusher blade (434). Projection C shows the drive for the material handling and mixing system (431), the support bearings for the lower end main shafts (435), and other previously defined parts.

[0143] Figure 4.3 shows a plan view, a section DD taken in the plane of symmetry, and a partial section EE showing the material outlet gate area. The latter section shows the gate (425) and its drive system (426). Section DD shows the entire material conveying and mixing system (413), consisting of the drive (431), the main shafts (433), the second-end bearing located at the top (432), the conveying and mixing blades (434), and the first-end bearing located at the bottom (435). Section EE shows a top view of the semi-closed gate (425) and its drive (426).

[0144] Figure 4.4 is a section showing the clamping and residence time measurement system. The reactor is supported by two hinges (442) at the first end and two load cells (441) at the second end. The material introduction system into the reactor also includes an inlet mass flow meter. In the preferred embodiment shown, a weighing belt (443) is also included.

[0145] Figure 5 is a schematic of an asphalt plant composed of: the aggregate line (51), the filler line (52), both recovery filler and addition filler; the bitumen line (53); the cold RAP line (54), with incorporation into the mixer; the hot light RAP pretreatment line (55) with incorporation into the asphalt plant mixer by an independent route.

[0146] PREFERRED MODE OF EMBODIMENT

[0147] According to the preferred manufacturing method, the process begins with the usual RAP fraction F(0 / 12) obtained by classification on a metal screen; the remainder is the rejection of RAP larger than 12 mm, Dmax=12 mm. This rejection may be used in another process or shredded and / or ground to a nominal maximum size of less than 12 mm to be reintroduced into the process.

[0148] OBTAINING SUB-FRACTIONS AND DIVISIONS

[0149] The fraction f (0 / 12) begins the process in equipment consisting of a flexible mesh screen

[0150] (1) and a density table (2). The F(0 / 12) fraction is placed in the receiving hopper (10) by mechanical means, e.g., from a stockpile using a conventional front-end loader. It is then conveyed by a conveyor belt (11) to the flexible mesh screen (1), where it is separated into the sF(0 / 6) and sF(6 / 12) sub-fractions. The sF(0 / 6) sub-fraction is transferred via a conveyor belt (12) to a stockpile (13) for further destonering. The sF(6 / 12) sub-fraction is then transferred to the density table.

[0151] (2) by mechanical means, e.g. gravity conveying from the outlet of the flexible mesh screens (1). The densimetric table (2) classifies the particles into the following divisions:

[0152] • The particles with the highest apparent density—which also have the lowest bitumen content—settle out through the upper area of ​​the densimetric table (2), resulting in the heavy fraction Dp(6 / 12) with mineral aggregates between 6 and 12 mm. These are then transferred, e.g., via a conveyor belt (20) to a stockpile (21) for later reuse in the manufacture of an MBR.

[0153] • Through the lower area of ​​the densimetric table (2) the particles with lower apparent density - which are also those with the highest bitumen content - are decanted, i.e., the light division Dl(6 / 12), with mineral aggregates between 0 and 6 mm, are conveyed through a conveyor belt (22) to stockpile (23) for subsequent reuse in an MBR.

[0154] • The denser, but sufficiently small, particles fall through the perforated holes in the densitometer tray (2) due to gravity. They accumulate beneath the densitometer, forming the through fraction Dpas(5), since the air outlet holes of the densitometer have a 5 mm diameter opening. These particles will be mostly composed of mineral aggregates between 3 and 5 mm. They are then conveyed via a conveyor belt (24) to a stockpile (25) for later use. • Particles carried by the air stream are drawn in through the upper part of the densitometer (2). This air stream has a variable speed, regulated according to the fraction or sub-fraction of RAP introduced. This results in the bituminous filler fraction FB, which is collected using a conventional system that separates it from the air stream, e.g.cyclone (26), with a collection space (27) and a conveying system, e.g. screw conveyor (28), for subsequent storage, e.g. in a silo (29).

[0155] DETONERIZATION PROCESS OF THE sF(0 / 6) SUB-FRACTION

[0156] The sF(0 / 6) sub-fraction is then transferred to the destonerization process in the Destoner (3), where some of the bituminous filler adhering to its particles is collected. Using conventional mechanical means, e.g., a front-end loader, the RAP particles are deposited into the receiving hopper (30) and then conveyed via a conveyor belt (31) to the ballistic separator or Destoner (3). Here, a large portion of the bituminous filler is separated by the impact of the Destoner plates on the RAP particles. Depending on which step or plate of the Destoner is used, different types of bituminous filler are obtained. The finest bituminous filler—fine FBdest—rises to the upper steps and is transported by a conveyor belt (32) to its storage in silo (33). The coarser bituminous filler - FBdest coarse - climbs the lower steps and is transported by a conveyor belt (34) to its storage in a silo (35).The remaining particles that form the sub-fraction sF(0 / 6) fall by gravity, bouncing off the steps and are collected by the elevator belt 36 to its stockpile 37.

[0157] LIGHTWEIGHT RAP MIXER-HEATER (MCRL).

[0158] The light division Dl(6 / 12) and the sub-fraction sF(0 / 6)Dest are combined in the appropriate proportion to meet the specified particle size range of the MBR and are passed on to the "hot light RAP pretreatment" process (55) by being introduced into the light RAP mixer-heater (553) through the starting hoppers (551).

[0159] According to a preferred embodiment, the MCRL(553) consists of a mixer-heater (4) in the form of an elongated chamber with a lid (41) and a main housing (42), with two longitudinal shafts along its longer dimension (433). Radial arms and paddles (434) are arranged on these shafts to mix the granular material and any fluid or solid additives. This chamber has two longitudinal ends, the first end and the second end. The reactor is inclined longitudinally, with the first end at the lower end and the second end at the higher end. The material moves from the first end to the second end in a continuous mixing and heating process.

[0160] This reactor is longitudinally subdivided into different sections where the additions of different materials are made, as well as additives that modify the mixture both physically and chemically.

[0161] 1. At the first end, the introduction of the light RAP (411) is carried out. In this preferred embodiment, the RAP comes from: The light division Dl(6 / 12) and the sub-fraction sF(0 / 6)Dest, critical to meet the granulometric range of the MBR.

[0162] 2. In the following section, liquid material is added through its inlet at the beginning of this section (412). In this preferred embodiment, a rejuvenating additive responsible for binder regeneration (chemical modification) and a liquid additive to improve the workability of the mixture are included.

[0163] 3. In the following section, additional powdered material is added through its inlet at the beginning of this section (413). In this case, the bituminous filler necessary to complete the particle size range of the MBR is added, for example, coarse FBdest.

[0164] 4. In the next section, additional solid material is added through the inlet at the beginning of this section (414), which can be supplied from a hopper. In this preferred embodiment, the product is pre-digested rubber, to modify the rheology of the mixture.

[0165] At the second highest point, at the bottom of the chamber, is the discharge gate (425) through which the resulting product is discharged, and whose opening is controlled to ensure the appropriate residence time.

[0166] Heating is achieved by indirect heat transfer. The reactor is heated, in a preferred embodiment, by a thermal oil jacket heated externally by an electric or combustion boiler. This heating is carried out by chambers (423) through which thermal oil is passed at a temperature between 180 9 C and 350 9 C. These chambers consist of the main casing (421) and the heating chamber casing (422). In another preferred embodiment, heating elements are located within the thermal oil jacket to heat the thermal oil. In a third preferred embodiment, electrical heating elements are used in direct contact with the metallic material forming the reactor walls.

[0167] Around the indirect heating system, a heat insulation system is provided to operate efficiently.

[0168] The chamber's discharge process control system ensures that the treated RAPLAC material exits at the appropriate temperature, while also guaranteeing that the rejuvenation process is complete. This is achieved by monitoring the residence time in the chamber.

[0169] In this preferred embodiment, the residence time is measured as follows:

[0170] 1. The incorporation rate of the different materials is measured using systems of type (443) for granular materials, and using Coriolis mass flow meters for liquid additives. The total incorporation rate is denoted (TI).

[0171] 2. The total mass in the mixer (MT) is measured. This is done using load cells (441), which, thanks to the reactor being supported on joints (442), provide a signal from which the mass of the material present in the reactor can be extracted.

[0172] 3. Dividing the total mass (MT) by the incorporation rate (TI), the residence time (TR) is obtained directly.

[0173] The control system specifies a setpoint residence time (SRT).

[0174] With a Proportional Integral Derivative (PID) Controller, the gate (426) is actuated in such a way as to reduce to zero the error between the setpoint residence time (TRO) and that determined by the sensors (TR).

[0175] Incorporation of RAP fractions and divisions for the manufacture of MBR in the preferred embodiment.

[0176] Using the preferred embodiment of the present invention, the following fractions have been collected: sF(0 / 6)Dest in stockpile, aggregate size between 0 and 6 mm; the heavy divisions Dp(6 / 12), with aggregates between 6 and 12 mm; light divisions Dl(6 / 12) with mineral aggregates between 0 and 6 mm; through divisions Dpas(5) with aggregates between 3 and 5 mm.

[0177] The different types of bituminous filler have also been stored in silos: the fine FBdest, the coarse FBdest, both from the Destoner; and the FB from the densimetric table.

[0178] The preferred embodiment comprises the use of these fractions and divisions in a batch asphalt plant (5) having the different process lines, which broadly comprise:

[0179] 1. Aggregate line (51), with five hoppers (511); conveyor belt (512) to the drying drum (513); inside the drum is the industrial burner where the flame is produced which has a fuel tank (514), aggregate elevator (515), tower (516) with screens, dosing system (517) and the mixer (518).

[0180] 2. Filler line (52), conduit from the drum (521), recovery system using a bag filter (522), and tower with recovery silo and feed silo (523). The air carried by the filler is drawn in by a fan (524) which creates an airflow from the beginning of the dryer drum (513) and expels it to a chimney (525) through which all the combustion gases—including water vapor—are expelled.

[0181] 3. Bitumen line (53), with two bitumen tanks (531), lift pump (532) and connecting pipes to the mixer. The bitumen tanks are heated with thermal oil by means of a boiler (533) with a small fuel tank (534).

[0182] 4. Cold RAP incorporation line (54), with three hoppers (541) and elevator belt to the mixer (542) with prior dosing system (543).

[0183] 5. and the hot light RAP pretreatment system (55) which receives thermal oil from the boiler via a connecting pipe (557). This system effectively constitutes a hot RAP line. From the hoppers (551), the light RAP enters the MCRL reactor (553) through the inlet (552). It also includes the liquid feeder (554), powder feeder (555), solid feeder (556), and lifting system (558) to the tower where, upstream of the mixer, the preheated light RAP feeder system (559) is located in the MCRL (553). The heavy Dp division (6 / 12) is incorporated via the aggregate line (51) using one or two hoppers (511) that feed the loader (57). Thus the RAP, together with the virgin aggregates, accesses the drying drum (513) via the conveyor belt (512) and follows the process line to the mixer in the tower (516).

[0184] 5 The through division Dpas(5) is incorporated through the cold RAP line (54), is placed in the hoppers (541) by means of a loader shovel (57) and through the elevator belt accesses the tower (516) directly to the mixer.

[0185] According to the preferred embodiment, the high and very high bitumen content fractions are incorporated into the MBR manufacturing process via the MCRL (553). The light fraction Dl(6 / 12), along with the high fraction passed through the destoner sF(0 / 6)Dest, is fed through the starting port (552) by means of a front-end loader (58). The rejuvenating additive is added via the liquid feeder (553). The coarser bituminous filler obtained from the coarse destoner FBdest enters the MCRL (553) via the powder feeder (554), and the pretreated rubber via the solids feeder (555). The heated RAP. At the end of the MCRL reactor (553) the RAPLAC passes through the lifting system (558) to the dosing unit (559) prior to the mixer tower of the asphalt plant where it is incorporated into the rest of the materials that make up the MBR to be manufactured.

[0186] The remaining FBdest fine and FBdest coarse bituminous filler is stored in silos and subsequently bagged for use in the manufacture of sealants and other bituminous applications.

Claims

A manufacturing process for recycled bituminous mixtures (MBR) from material recovered from the milling or demolition of asphalt pavements (RAP), wherein the RAP is classified by size into a number "r" of fine, intermediate, or coarse fractions, characterized in that it comprises the following steps: a) Selection of a number "n" of RAP fractions—fine, intermediate, or coarse—and stockpiling of the remainder "rn" for subsequent conventional use in the manufacture of MBR. b) Classification by density using a densimetric table (2) of each of said "n" RAP fractions, into at least four densimetric divisions of RAP—which, depending on their granulometry, will also be called fine, intermediate, or coarse—such that from each fraction F(d n / D N ) are created: a Heavy Division Dp(d n / D N ) (21), with low (<3%) or intermediate (3-5%) bitumen content; a Light Division DI(d n / D N(23) with high bitumen content (>5%); a through division Dpas(h) (25) with intermediate bitumen content (3-5%); and bituminous filler FB (29) with very high bitumen content; (>10%) c) Stockpiling of each of the generated density divisions (21) (23) (25) for use or storage, the bituminous filler being able to be stored in a confined deposit (29) d) Selection of the RAP fractions and density divisions necessary to ensure that, together with the aggregates and virgin bitumen, the required particle size distribution and bitumen content of the MBR to be manufactured are met. e) Incorporation into the asphalt mixture manufacturing plant of the selected RAP fractions using the RAP addition systems known in the standard technique. f) Incorporation of the densimetric divisions of RAP, according to their bitumen content, in the different RAP contribution systems available to the asphalt mixture manufacturing plant as follows: i. Plants with hot RAP and cold RAP incorporation systems • The light divisions DI(dn / DN) together with the bituminous filler FB, both with high bitumen content, will be introduced through the cold RAP system. • the heavy Dp(dn / DN) divisions with low bitumen content, by the hot RAP system. A portion of the heavy Dp(dn / DN) divisions with low bitumen content can be incorporated as an additional aggregate (aggregate line). • The through divisions Dpas(h) and the heavy divisions Dp(dn / DN) with intermediate bitumen content can be incorporated by either system. i. Plants with a single RAP incorporation system. • The light divisions DI(dn / DN) together with the bituminous filler FB, the through divisions Dpas(h) and the heavy divisions Dp(dn / DN) will be incorporated by the existing system, thus helping to meet the required granulometry. A portion of the heavy Dp(dn / DN) divisions with low bitumen content can be incorporated as an additional aggregate (aggregate line). iii. Plants without RAP incorporation systems A portion of the heavy Dp(dn / DN) divisions with low bitumen content can be incorporated as an additional aggregate (aggregate line).

1. A manufacturing process for recycled bituminous mixtures (MBR) according to claim 1, wherein a size sub-fractionation process is added to at least one of the "r" fractions into which the RAP has initially been classified, characterized in that it comprises the following steps: a) Selection of a number "s" of fine, intermediate, or coarse RAP fractions for a second size classification. The remaining "rs" fractions will follow the process defined in claim 1. b) Size classification using a flexible mesh screen known to a person skilled in the art, wherein each of said "s" RAP fractions F(ds / Ds) is separated into as many sub-fractions sF(ds' / Ds') as the number of elastic meshes in the screen plus one.c) Stockpiling each of the generated sub-fractions for incorporation into the manufacturing process according to claim 1, where they can be further classified by density, or stockpiled for direct incorporation into the MBR manufacturing process. d) Selection of the most suitable RAP sub-fractions, fractions, and density divisions so that, together with the aggregates and virgin bitumen, they meet the particle size distribution and bitumen content of the MBR to be manufactured. e) Incorporation into the asphalt mixing plant of the fractions and density divisions selected according to claim 1. f) Incorporation of the selected RAP sub-fractions, according to the type of RAP delivery system available at the asphalt mixing plant, as follows: i. Plants with hot and cold RAP delivery systems: the sub-fractions with high bitumen content (>5%) will be introduced through the cold RAP system.The sub-fractions with low bitumen content (<3%) will be introduced by the hot RAP system. Sub-fractions with intermediate bitumen content (3-5%) will be introduced by either of the two systems. A portion of the sub-fractions with low bitumen content (<3%) can be incorporated as an additional aggregate (aggregate line). i. Plants with unique RAP incorporation systems. The sub-fractions will be incorporated by the existing system, thus helping to meet the required granulometry. Sub-fractions with low bitumen content (<3%) can be incorporated as an additional aggregate (aggregate line). iii. Plants without RAP incorporation systems Sub-fractions with low bitumen content (<3%) can be incorporated as an additional aggregate (aggregate line).

3. Process for manufacturing recycled bituminous mixtures (MBR), according to claim 1 and 2, to which a "destonerization" process is added, by which part of the bituminous filler adhering to the larger RAP particles is extracted, characterized in that it comprises the following steps: a) Selection of a number "k" of RAP fractions together with a number "j" of RAP sub-fractions to carry out the destonerization process, chosen from among the group of fractions and sub-fractions that will not be subjected to the density separation process according to claim 1. b) Separate introduction of each selected fraction and sub-fraction into a ballistic separator, known to a person skilled in the art, which we call a "destoner" (3), which strikes the particles of each RAP fraction, extracting part of the adhering bituminous filler, generating "k" destonerized fractions and "j" destonerized sub-fractions, which will be stockpiled independently (37), as well as the generated bituminous filler that It will be collected by a transport system, e.g., a conveyor belt (32) (34), to a separate stockpile, or in a confined storage area (33) (35). c) Selection of the destoned fractions and subfractions, of the bituminous filler from the destoner, as well as the RAP fractions, subfractions, and density divisions generated in claims 1 and 2, which, together with the aggregates and virgin bitumen, meet the particle size distribution and bitumen content of the MBR to be manufactured. d) Incorporation into the asphalt mixture manufacturing plant of the fractions, subfractions, and density divisions selected according to claims 1 and 2.e) Incorporation of the destonerized fractions, selected destonerized sub-fractions, as well as the bituminous filler from the selected destoner, into the MBR manufacturing process according to the type of RAP contribution systems available at the asphalt mixing plant, as follows: i. Plants with hot and cold RAP incorporation systems: the destonerized fractions, destonerized sub-fractions -both with high bitumen content (>5%)- and the bituminous filler from the destoner -with very high bitumen content (>10%)-, will be introduced through the cold RAP system. the destonerized fractions and destonerized sub-fractions -both with low bitumen content (<3%), will be introduced through the hot RAP system. The destonerized fractions and destonerized sub-fractions - both with intermediate bitumen contents (3-5%) - will be introduced by either of the two systems. A portion of the destonerized fractions and destonerized sub-fractions with low bitumen content (<3%) can be incorporated as an additional aggregate. (aggregate line). i. Plants with a single RAP incorporation system. The destonerized fractions, destonerized sub-fractions and the bituminous filler from the destoner will be incorporated through the existing system, thus helping to meet the required granulometry. Destonerized fractions and destonerized sub-fractions with low bitumen content (<3%) can be incorporated as an additional aggregate (aggregate line). iii. Plants without RAP incorporation systems Destonerized fractions and destonerized sub-fractions with low bitumen content (<3%) can be incorporated as an additional aggregate (aggregate line).

4. Method for manufacturing recycled bituminous mixtures (MBR) according to claims 1 and 3, characterized in that the bituminous filler from the densimetric table (29) according to claim 1 and from the destonerization process (33) (35) according to claim 3, are incorporated into the manufacturing process of an MBR through the filler addition line (52).

5. Manufacturing process for recycled bituminous mixtures (MBR) according to claims 1 to 3, with a newly invented specific hot RAP feeding system, hereinafter referred to as "additive hot light RAP system (S-RAP-LCAD)" (55), comprising the following stages: a) Separation of the RAP classifications with higher bitumen content from among the RAP fractions, subfractions, densimetric divisions, destonerized fractions and subfractions and bituminous filler from the destoner, selected for the manufacture of the MBR, these being: The RAP fractions and the light RAP divisions with high bitumen content (>5%), and the bituminous filler obtained according to claim 1; The fine-grained RAP sub-fractions with high bitumen content (>5%) obtained according to claim 2; The destonerized fractions and destonerized sub-fractions of RAP with high bitumen content (>5%) and the bituminous filler resulting from the destonerization process according to claim 3; b) Incorporation into the MBR manufacturing process of the RAP classifications with lower bitumen content according to claims 1 to 3. c) Incorporation into the MBR manufacturing process of the RAP classifications with higher bitumen content by means of the new S-RAP-LCAD system, and said RAP incorporation system comprises the following elements: A. A pre-dosing system using hoppers with controlled discharge (551) and a material transport system, e.g. a collecting belt, known to a person skilled in the art, where they introduce these classifications of RAP with higher bitumen content. B. A newly invented reactor, which we call a mixer-heater of Light RAP (MCRL) (4), where the RAP heating process and the additive addition and mixing processes occur simultaneously, characterized in that said reactor: comprises an elongated chamber (41-42) slightly inclined longitudinally, with a first end (411) located at the lowest level, where the inlet opening is located, corresponding to the start of the material flow, and a second end located at the highest level (425), corresponding to the end of the material flow where the outlet opening with a gate is located; and in its outer casing (42), it has non-radiative heating systems (423) -by electrical resistances or by thermal oil conduits- with adjustable temperature, so as to allow heating the aged bitumen without causing its oxidation; and inside it houses pushing and mixing systems (433 - 434); and the residence time of the introduced materials is controllable thanks to the regulation of the thrust speed and the operation of the outlet gate at will; said reactor being subdivided longitudinally into different zones where the incorporation of the different materials takes place, as well as additives that modify the mixture both physically and chemically, so that: In zone 1 (411), next to the first end, the pre-classified RAP is introduced through an opening located at the top of the reactor. In zone 2 a In an adjacent zone (412), liquid material is introduced, preferably a rejuvenating additive and / or a liquid additive to reduce the viscosity of the mixture. 3 aIn zone (413-414), additional powdered material is introduced, preferably the bituminous filler from the density splitting according to claim 1 or from the destonering process according to claim 3, and optionally a special filler, powdered colorant, fibers, or other additive. In a 4th zone (415), additional solid materials are introduced, preferably rubber pellets to modify the rheology of the mixture; and at the second end of which is an outlet gate (425) located at the bottom of the reactor that allows its opening and closing to be controlled at will or on a programmed basis, thereby determining the residence time of all the introduced materials and additives – controlled residence time – to finally obtain as the resulting product the Hot Additive Light RAP, which we call RAPLAC, is incorporated into the MBR manufacturing process. C. A dosing system (559), which incorporates RAPLAC into the asphalt plant mixer, similar to those used in hot RAP incorporation systems by means of a "RAP drum", known to an expert in the field. [0001]A new set of claims 1 to 5 is presented, which completely replaces the original set of claims, keeping intact the structure of each claim and the invention addressed in each of them, i.e., the new claim 1 replaces the old claim [0002]1 and so forth up to claim 5. [0003]In response to the observations made by ISA / ES in the Written Opinion, a comprehensive review of the claims has been carried out in order to adapt them to the provisions of Article 6 and the [0004] PCT Rule 6.3, ensuring its clarity, conciseness and correspondence with the description. [0005]Likewise, all language of purpose or advantage has been eliminated, maintaining the strictly technical formulations that describe the operations corresponding to the processes, and unnecessary repetitions in the texts have been eliminated, leaving only those essential to define each process.

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