WO2016089748A1 - Usines d'asphalte en mélange chaud (ou tiède) produisant jusqu'à 100 pour cent de mélanges d'asphalte recyclé rap - Google Patents

Usines d'asphalte en mélange chaud (ou tiède) produisant jusqu'à 100 pour cent de mélanges d'asphalte recyclé rap Download PDF

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Publication number
WO2016089748A1
WO2016089748A1 PCT/US2015/062944 US2015062944W WO2016089748A1 WO 2016089748 A1 WO2016089748 A1 WO 2016089748A1 US 2015062944 W US2015062944 W US 2015062944W WO 2016089748 A1 WO2016089748 A1 WO 2016089748A1
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WO
WIPO (PCT)
Prior art keywords
hma
producer
inner drum
screw
heating
Prior art date
Application number
PCT/US2015/062944
Other languages
English (en)
Inventor
Jung Do Huh
Original Assignee
Jung Do Huh
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by Jung Do Huh filed Critical Jung Do Huh
Priority to CN201580065443.1A priority Critical patent/CN107000252B/zh
Priority to DE112015005403.0T priority patent/DE112015005403T5/de
Publication of WO2016089748A1 publication Critical patent/WO2016089748A1/fr

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Classifications

    • E—FIXED CONSTRUCTIONS
    • E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
    • E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
    • E01C19/00—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving
    • E01C19/02—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving for preparing the materials
    • E01C19/10—Apparatus or plants for premixing or precoating aggregate or fillers with non-hydraulic binders, e.g. with bitumen, with resins, i.e. producing mixtures or coating aggregates otherwise than by penetrating or surface dressing; Apparatus for premixing non-hydraulic mixtures prior to placing or for reconditioning salvaged non-hydraulic compositions
    • E01C19/1013—Plant characterised by the mode of operation or the construction of the mixing apparatus; Mixing apparatus
    • E01C19/1027—Mixing in a rotary receptacle
    • E01C19/1036—Mixing in a rotary receptacle for in-plant recycling or for reprocessing, e.g. adapted to receive and reprocess an addition of salvaged material, adapted to reheat and remix cooled-down batches
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
    • B01F27/05—Stirrers
    • B01F27/11—Stirrers characterised by the configuration of the stirrers
    • B01F27/114—Helically shaped stirrers, i.e. stirrers comprising a helically shaped band or helically shaped band sections
    • B01F27/1141—Helically shaped stirrers, i.e. stirrers comprising a helically shaped band or helically shaped band sections having holes in the surface
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
    • B01F27/05—Stirrers
    • B01F27/11—Stirrers characterised by the configuration of the stirrers
    • B01F27/114—Helically shaped stirrers, i.e. stirrers comprising a helically shaped band or helically shaped band sections
    • B01F27/1143—Helically shaped stirrers, i.e. stirrers comprising a helically shaped band or helically shaped band sections screw-shaped, e.g. worms
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
    • B01F27/05—Stirrers
    • B01F27/11—Stirrers characterised by the configuration of the stirrers
    • B01F27/114—Helically shaped stirrers, i.e. stirrers comprising a helically shaped band or helically shaped band sections
    • B01F27/1144—Helically shaped stirrers, i.e. stirrers comprising a helically shaped band or helically shaped band sections with a plurality of blades following a helical path on a shaft or a blade support
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
    • B01F—MIXING, e.g. DISSOLVING, EMULSIFYING OR DISPERSING
    • B01F27/00—Mixers with rotary stirring devices in fixed receptacles; Kneaders
    • B01F27/05—Stirrers
    • B01F27/11—Stirrers characterised by the configuration of the stirrers
    • B01F27/114—Helically shaped stirrers, i.e. stirrers comprising a helically shaped band or helically shaped band sections
    • B01F27/1145—Helically shaped stirrers, i.e. stirrers comprising a helically shaped band or helically shaped band sections ribbon shaped with an open space between the helical ribbon flight and the rotating axis
    • E—FIXED CONSTRUCTIONS
    • E01—CONSTRUCTION OF ROADS, RAILWAYS, OR BRIDGES
    • E01C—CONSTRUCTION OF, OR SURFACES FOR, ROADS, SPORTS GROUNDS, OR THE LIKE; MACHINES OR AUXILIARY TOOLS FOR CONSTRUCTION OR REPAIR
    • E01C19/00—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving
    • E01C19/02—Machines, tools or auxiliary devices for preparing or distributing paving materials, for working the placed materials, or for forming, consolidating, or finishing the paving for preparing the materials
    • E01C19/10—Apparatus or plants for premixing or precoating aggregate or fillers with non-hydraulic binders, e.g. with bitumen, with resins, i.e. producing mixtures or coating aggregates otherwise than by penetrating or surface dressing; Apparatus for premixing non-hydraulic mixtures prior to placing or for reconditioning salvaged non-hydraulic compositions
    • E01C2019/1081—Details not otherwise provided for
    • E01C2019/109—Mixing containers having a counter flow drum, i.e. the flow of material is opposite to the gas flow
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02A—TECHNOLOGIES FOR ADAPTATION TO CLIMATE CHANGE
    • Y02A30/00—Adapting or protecting infrastructure or their operation
    • Y02A30/30—Adapting or protecting infrastructure or their operation in transportation, e.g. on roads, waterways or railways

Definitions

  • the present invention relates to the field of asphalt mix production and more specifically relates to a plant producing up to 100% recycled mixes of reclaimed asphalt pavement (RAP) and asphalt roof shingles (ARS) as well as 100% virgin asphalt mixes as the final product.
  • RAP reclaimed asphalt pavement
  • ARS asphalt roof shingles
  • the present invention is about a next-generation hot mix asphalt (HMA) producer that is the main unit in the innovative next generation HMA plant whose processing mechanism excels over any other existing HMA plants available nowadays. It should be noted that the principles of this invention may also be utilized in warm mix asphalt (WMA) production. Therefore, for purposes of this Application, and unless otherwise noted, the term HMA should also be understood to include WMA.
  • HMA next-generation hot mix asphalt
  • the existing HMA plant has the following common units. Cold bins and belt conveyors supply virgin aggregates to the hopper of the mixing drum (or a producer).
  • a mixing drum is the main unit that produces HMA product.
  • a conventional burner consuming oil fuel generates the horizontal hot air stream along the mixing drum.
  • the horizontal hot air stream that passes through cold aggregates vertically falling down from the top toward the bottom, heats each cold aggregate. During this passage, the horizontal hot air stream picks up substantial amount of dust falling down with aggregates. Dust collector units facilitated at the end of the mixing drum eliminate most of dust before discharge of the hot air stream into the ambient air.
  • Pocket flights attached on the inside of the mixing drum initially transfer cold aggregates forward in the hot air stream for heating by circular tumbling caused by rotation of the inclined mixing drum in the heating zone, and then heated aggregates reach in the mixing zone.
  • a RAP adding equipment inputs RAP at the mixing zone located at the almost end portion of the mixing drum, and an asphalt storage tank also feeds asphalt binder at the same mixing zone. Heated virgin-aggregates and cold RAP-aggregates, and the hot asphalt binder meet at the mixing zone and mix together there to produce HMA product at a given high temperature (usually 160°C).
  • a storage silo stores HMA transferred from the exit of the drum mixer by a belt conveyor, before loading into the dump truck that carries HMA on the construction site.
  • the cold RAP begins to receive heat upon contacting both heated virgin aggregate and hot asphalt binders by exchanging heat with them, and gradually reaches the uniformly high mix temperature (160°C).
  • the amount of cold RAP input cannot exceed more than 50% of the total mix due to heat exchange requirement.
  • the 30% RAP use is the common practice instead of 50% in the present RAP recycling industry. This is the one of the major limitations to be resolved immediately in the existing HMA plants.
  • the heating energy of the oil burner used in the 100% RAP recycling plant should be 3.28 times higher in heating the regular aggregates. Also the parallel heating method adopted in all those 100% RAP recycling plants provides a lot less efficient heating compared to the perpendicular heating on materials, and also indirect heating of multiple RAP particles in those RAP recycling plants requires further more energy compared to the direct heating of individual particle in the existing plant. All these factors negatively affect the success of the new 100% RAP recycling plants developed so far. Use of the higher heating energy burner and design of the efficient heating system are prerequisite for successful development of the 100% RAP recycling process.
  • a conventional oil burners or oil pipes used in those 100% RAP recycling plants make combustion of only 80% oil fuel, and produce more air pollutants like NOx, SOx, CO, C0 2 , etc.
  • this invention provides the following innovations.
  • the main producer in this invention consists of a rotating inner drum and a stationary outer housing surrounding the inner drum for the indirect heating system.
  • the indirect heating system is possible by locating the surface combustion burner at inside of the inner drum and material flow at outside. Heat generated from the surface combustion burner at inside of the inner drum arrives at the inner wall and then the heat passes through the wall by heat conduction to arrive at the outside surface. Heat arrived there conducts further to segmented screw flights and directional flights sitting on the outside surface of the inner drum. Thus, materials contacting by rotation of the outside surface of the inner drum, the segmented screw flights and the directional flights receives convectional heating just like the circulating air (materials) heated by the protruding thermal fins upon contact in the heat exchanger.
  • the outside surface of the rotating inner drum, the helically aligned segmented screw flight and the directional flight can make the helical material transfer, frictional shear mixing and convective heating all taking place at the same time.
  • the shear friction occurring between the material transfer tools (segmented screw and directional flights) and transferring materials creates another heating called frictional shear heating to contribute to more efficient heating.
  • the heating system in this invention is far effective over the any existing heating method.
  • a surface combustion burner adopted first time in this new HMA plant accomplishes 100% fuel consumption with perpendicularly oriented heating direction that leads to fuel saving as well as considerably reduced air pollution, and provides high energy density on diverse geometrical heating surface including a cylindrical shape.
  • the heating energy from the infrared and the blue flame mode in the surface combustion burner is very powerful in meeting all kinds of heating requirement.
  • Figure 1 is a schematic of a production plant utilizing the present invention.
  • Figure 2 is a schematic of a mobile production plant utilizing the present invention.
  • Figure 3 is a schematic of a screw conveyor-type HMA producer.
  • Figure 4 is various views of three kinds of screw conveyor outer housings.
  • Figure 5 is a collection of side elevation views depicting various kinds of shafted screws.
  • FIG. 6 is a schematic of an HMA plant representing the present invention.
  • Figure 7 is a side elevation and photograph depicting material transfer by frictional shearing of a rotating shaft and a screw flight.
  • Figure 8A is a side elevation view of an inner drum with an alternate directional flight.
  • Figure 8B is a side elevation view of an inner drum with two different directional flights.
  • Figure 9 is a side elevation view of an inner drum having an exemplary directional flight with no screw flight.
  • Figure 10 is a side elevation view of an inner drum having a segmented screw flight and plate-type directional flight.
  • Figure 1 1 is a schematic of several views of an inner drum having segmented screw flights and several plate-type directional flights in a single pitch.
  • Figure 12 is a schematic of several views of an inner drum having segmented screw flights and inclined several plate-type directional flights in a single pitch.
  • Figure 13 is a schematic drawing depicting the inside structure of an inner drum and other units relating thereto.
  • Figure 14A is a perspective view of a motor, a chain and a sprocket to roatate an inner drum.
  • Figure 14B is a perspective view of an idler assembly for use with an inner drum.
  • Table 1 depicts thermal properties of RAP, Granite Aggregate and Carbon Steel.
  • Table 2 depicts a comparison between surface combustion and conventional gas burners.
  • HMA producer is herein described. It should be clear that the articles “a”, “an”, and “the”, as used in this specification, include plural referents unless the content clearly dictates otherwise.
  • the present invention is related to a next generation HMA plant capable of producing the virgin HMA using virgin aggregates as well as the recycled HMA using up to 100% RAP aggregates for construction of all kinds of new and maintenance asphalt pavements including highways.
  • a revolutionary asphalt plant utilizing the teachings of the present invention may consist of an HMA producer (called as the drum mixer) as a main facility, cold aggregate bins for storage of virgin or RAP aggregates or both, a hot asphalt binder storage tank, and a storage silo for storing HMA produced.
  • Figure 1 represents such a revolutionary central HMA plant. This new central plant seems to be identical to the present central continuous HMA plant in the view of both having asphalt storage tank (1 ), cold bin for virgin and RAP aggregates (2), belt conveyor (3), storage silo (4), and HMA producer (5). Note that, as described above, the prior art central continuous HMA plant requires dust collectors and RAP- feeding facility in addition to plant units mentioned above.
  • the units of (1 ) to (4) are auxiliary to the main HMA producer (5) and have identical functions in both the prior art and present invention.
  • the revolutionary HMA producer (5) in this invention demonstrates quite different mechanical structure and processing mechanism from all existing ones such that it can eliminate dust collectors and RAP- feeding facility essential in all existing HMA plants.
  • Figure 2 represents a revolutionary mobile/in-place HMA production plant.
  • This unique mobile plant is different from the existing hot in-place recycling plant (i.e., remixing and repaving plant) because the former uses the cold RAP collected by the cold milling in contrast to the latter that uses the hot RAP collected by hot milling. Note that RAP collection by the cold milling is easier and faster than the hot milling. Thus, the production capacity of the formal mobile plant is a lot more than the existing hot in-place recycling plant.
  • This new mobile HMA plant is identical to the revolutionary central HMA plant shown in Figure 1 , except additional units such as loading frame (6) and tires (7) to make the plant be mobile.
  • the revolutionary HMA producer (5) shown in Figures 1 & 2 is independent of the plant type, the central or the mobile.
  • the unique revolutionary HMA plant producer (5) in this invention taking a key role in HMA production plant, is going to describe in more detail hereafter.
  • Figure 3 manifests one embodiment of a revolutionary HMA plant.
  • the main unit of the plant is a screw conveyor-type producer (8) that is a unique combination of several screw conveyors (9) running by the screw driving device (10).
  • the surface combustion burner (1 1 ) heats the outside bottom of the screw conveyors, and a feed (or a belt) conveyor (12) feeds materials (13) into the inlet of the producer.
  • a gas purifier (14) cleans gases (15) evolved in the producer (8). The following paragraphs explain operation of each unit.
  • Raw materials (13) arrived at the hopper of the feeding screw (or belt) conveyor (12) that controls the amount of raw materials (13) entering into the inlet of the producer and therefore the production rate of HMA (16).
  • Materials (13) entered into the inlet hopper proceed helically to reach the second conveyor by shearing force of the rotating full screw (17) attached on the screw shaft (18).
  • the shaft rotates by the screw driving device (10) composed of a motor (19) and a reducer (20).
  • Materials (13) passed through the second conveyor enter into the third conveyor and finally reach the outlet to produce a well-mixed hot HMA product (16).
  • materials (13) experience frictional shear mixing by rotation of the full screw (17) and the screw shaft (18). They receive frictional shear heating as well as indirect heating coming from a surface combustion burner (1 1 ) located at the outside bottom half of a screw conveyor (9) and a feed conveyor (12). Enough heating and mixing ensures asphalt binders and organic additives among entering materials (13) to be melted and coated on aggregate surfaces and produces uniformly mixed hot HMA products (16) at the exit of the final screw conveyor (9) in the producer (8).
  • the HMA products (16) can be either stored at the storage silo (4) or loaded into trucks to transport them to construction sites.
  • the number of screw conveyors (9) required in constituting the screw conveyor-type producer (8) depends on whether provision of enough heating on materials is possible or not from the surface combustion burner (1 1 ) and the frictional shear heating to reach the desired material temperature at the exit of the final screw conveyor (9).
  • screw conveyors (9) in the screw conveyor-type producer (8) can have the inclined
  • the screw conveyor-type HMA producer in Figure 3 achieves the technical objectives set in this invention.
  • the first is an indirect heating system separating material flow from heat transfer passage.
  • the second is that RAP enters into the inlet of the producer and does not require an extra RAP feeding facility.
  • the third is the elimination of dust collectors due to no dust generated.
  • the fourth is the use of surface combustion burner giving high heating power on the cylindrical surface with vertical heating.
  • the fifth is the capability of 100% RAP recycling.
  • the sixth is the single process covering material transfer, heating, and mixing as a single process.
  • the seventh is the considerable reduction in environmentally polluting gasses.
  • the eighth is the fuel saving by consuming 100% fuel in the surface combustion burner.
  • the ninth is the screw and its shaft creating effective shear mixing and heating on materials. Any existing HMA producer has never shown such characteristics.
  • a typical single screw conveyor (9) commonly finds its use in conveying materials from a given inlet to the designated outlet usually under no heating environment. Note that combination of these screw conveyors (9) makes application first time to the screw conveyor-type HMA producer (8) by providing a heating system made of the surface combustion burner (1 1 ).
  • the screw conveyor (9) has a conveyor housing surrounding a screw (17) and its shaft (18).
  • Figure 4 manifests three types of conveyor housings often used.
  • a screw conveyor used in constructing the screw conveyor-type HMA producer (8) also can choose one of these housings.
  • the frictional shearing force of a given screw required in transferring materials against the stationary conveyor housing increases in the order of the V-shaped (27), the U-shaped (26) and the tubular trough (25).
  • the required power of the driving device follows the same order.
  • V-shaped (27) or U-shaped trough (26) is better choice for materials hard to move due to the less frictional contact area involved leading to decreased friction.
  • the driving device (10) rotating the screw shaft with the screw in figure 3 usually consists of a motor (19) alone, and sometimes combination of the motor (19) and the reducer (20) is necessary to overcome the strong rotational resistance of materials.
  • the amount of raw materials entering into the screw conveyor-type producer (8) determines the HMA production at the exit.
  • the feeding screw conveyor (12) in Figure 3 is the solution in determining the feeding material amount. Sometimes, a large material feeding requires a belt conveyor instead of the feeding screw conveyor (12). However, for accurate control of feeding rate and material preheating, the feeding screw conveyor is favorable.
  • the gasses evolved will be mostly volatile organic fumes having the low molecular weight and steams evaporated from water initially contained in materials (13).
  • the heat exchanger (21 ) in the purifier (14) makes these gasses (15) mostly liquefied and collected in the liquid container (24).
  • the DOC (Diesel Oxidation Catalyst) device (22) in the purifier (14) eliminates relatively small amount of CO x , NO x and SO x evolved from the surface combustion burner (1 1 ), compared to the large amount in the general oil burner.
  • the surface combustion burner (1 1 ) receiving the adjusted ratio of air-to-fuel to accomplish 100% combustion requires less fuel and less pollutants evolved accordingly, compared to the unadjusted fuel combustion of the general oil burner.
  • the blower (23) helps all gasses (15) produced in the producer (8) pass through the gas purifier (14) before discharging into the
  • Screws (17) in the screw conveyor (9) have two different kinds; the shafted and the shaft-less ones. Either one can be used in the screw conveyor (9).
  • the shafted screw has many different kinds according to different designs of pitches and flights as shown in Figure 5. One of those shafted screws (17) applies to make good material transfer.
  • a material heating source is a surface combustion burner (1 1 ) used, first time, in the HMA plant history.
  • Figures 3 and 4 demonstrate its application. Burners (like the general oil, the microwave, the heated oil, and the infrared) have been used to heat materials (i.e., virgin aggregate, RAP, HMA, and asphalt pavement) for HMA production in the existing plant, or pavement repair of damaged pavements.
  • the surface combustion burner (or the metal fiber burner) (1 1 ) finds its use first time for those purposes in this invention.
  • a screw conveyor-type HMA producer (8) requires a good heating source with high energy density to heat cold RAP or virgin aggregates located inside of the screw conveyor. Success of the screw conveyor-type HMA producer (8) largely relies on enough material heating in the mixing process. RAP that is not a good heat- conductive material compared to aggregates (about 3.3 times harder) should be heated, melted, and mixed well before discharging into the outlet. Thus, the heating process is the critical step in the screw conveyor-type producer (8), because material contact area for heating is limited to be the bottom half of the conveyor housing. Screw (17) and its shaft (18) that are away from the heating surface do not contribute to material heating at all. The possible heating surface of the screw conveyor is the bottom half of the cylindrical housing. The above two factors are the critical limitation in the screw conveyor-type producer (8).
  • the surface combustion (or metal fiber) burner (1 1 ) may be best suited. It is the new generation heating method to make the
  • the surface combustion burner has several advantages compared to other burners; that is, homogeneous and uniform combustion with high modulation rate, high efficiency with low emission rate, less pressure drop, flashback safety, thermal expansion control, resistance to thermal shocks, robustness, and quick response of high temperature arrival and cooling down.
  • the heating power of the surface combustion (or metal fiber) burner is impressive.
  • the combustion surface burner (1 1 ) can occur in two different modes.
  • One is the radiant mode whose infrared heating ranges from 100 to 500kW/m 2 .
  • the flame color is red or orange.
  • the other is the blue flame mode. It is the convection heating ranging from 500 to 10,000 kW/m 2 .
  • the blue flames hover above the surface and release the majority of the energy through convection. Flame color is blue.
  • the surface combustion (or metal fiber) burner geometry has diverse shapes to fit into various heating surfaces.
  • the heating geometry is the bottom half of the cylindrical screw conveyor that is hard for other burners to apply on.
  • the surface combustion burner (1 1 ) can satisfy both requirements of high energy density and curved heating surface.
  • the screw conveyor-type producer (8) chooses the surface combustion burner (1 1 ) as a heating system, first time, in this invention.
  • the fuel for the surface combustion burner can be either LNG (Liquid Natural Gas), LPG (Liquid Propane Gas), or possibly Waste Oil, all, mixed with air. LNG is the common energy source because it is more economical over LPG.
  • the surface combustion (or metal fiber) burner (1 1 ) has several other excellent heating performances. Table 2 compares the surface combustion burner to the existing general oil burner. The former burner exhibits many advantages over the latter.
  • Modification of the screw conveyor-type producer (8) is necessary in overcoming its drawbacks.
  • the modification is achieved by enlarging the shaft (18) of the screw conveyor (9) to a big drum size having screw flights on its surface, and by facilitating the surface combustion burner at both inside and outside of the drum.
  • FIG. 6 describes the next-generation HMA plant and its major units schematically.
  • the plant consists of the asphalt storage tank (1 ), the cold bins (2), the belt conveyor (3), the HMA silo (4) and the next generation producer (28).
  • the producer (28) is a unique and innovative unit.
  • the innovative producer (28) shows technical breakthroughs and possesses innovative mechanical structures that have never known before in the asphalt plant history. Its characteristic structure consists of stationary outer housing (29), rotating inner drum (30), segmented (or full) screw flight (31 ), directional flight (32), surface combustion burner (1 1 ), chain and sprocket (33), inner drum driving device (19), idler (34), gas purifier (14), axial thrust bearing assembly (35), cone connector, small diameter steel pipe, material inlet (36) and outlet (37).
  • the next generation producer fixed at a certain location can constitute the central plant as shown in Figure 1 , and the producer loaded on the frame (6) with tires
  • (7) can be a mobile plant as shown in Figure 2. Note that the mobile plant using the cold RAP as a processing material can find its appearance first time in this invention. This feature makes the mobile producer best suited for RAP recycling in the construction site where cold RAP generates.
  • next generation producer (28) in Figure 6 originates from the screw conveyor-type producer (8) in Figure 3.
  • the relatively big inner drum (30) in the former (28) accompanying with the large outer housing corresponds to the smaller screw conveyor (9) in the latter (8).
  • the surface combustion burner (1 1 ) heats only the outside of the screw conveyor (9) in the latter (8), while it heats both the inside of the inner drum (30) and the outside of the outer housing (29) in the former (28).
  • another flight called the directional flight (34) applies to the former (28) to improve mixing, heating, and material transfer.
  • the screw rotation device (19) directly connects to the screw shaft (18) on the one end and the thrust bearing assembly on the other end of the shaft in the latter (8), while the inner-drum rotation device (19) in the former (28) connects to the chain and the sprocket (33) circumferentially attached to the outside surface of the inner drum (32) just like the conventional drum mixer and serves to rotate the large inner drum (30) and the thrust bearing assembly is present at the other end. Effect of the better mixing, efficient heating and more material transfer in the formal (28) permit a single processor sufficient enough to produce good HMA product, compared to the latter (8) necessitating combination of several screw conveyors (9).
  • Raw materials (virgin aggregates, RAP, organic additives, etc.) in the cold bins (2) drop down on the moving belt conveyor (3) together with spray of hot asphalt binders from the asphalt storage tank (1 ) on the top of those incoming cold materials according to the HMA product composition.
  • These compositional materials on the moving belt conveyor (3) transfers and enters into the inlet (36) of the stationary outer housing (29).
  • the inner drum (30) constantly rotates by the chain and the sprocket (33) run by the driving device (19).
  • the idler (34) runs on the other side of the sprocket (35).
  • Entered materials into the inlet (36) make helical movement in the region between the stationary outer housing (29) and the rotating inner drum (30) by frictional shearing force of the helically aligned segmented (or full) screw flight (31 ) and the directional flight (32) attached on the drum's outside surface. Note that the frictional shearing enhances better material mixing compared to the simple mixing by tumbling in the conventional drum mixer.
  • the thrust bearing housing (35) is necessary to prevent such backward retraction force of the inner drum (30).
  • materials receive indirect heating initiated by a stationary surface combustion burner (1 1 ) located at the inside of the inner drum (30) and at the outside of the outer housing (29).
  • materials also experience heating from rotational contact by the hot segmented (or full) screw flights (33) and the directional flights (34) conductively heated from the surface combustion flame. Since these flights are metals that are an excellent conductive material, they receive heat about 32 times faster than poorly conductive materials in moving, and play a role of an efficient heating tool protruding on the rotating inner drum's outside surface.
  • the rotation of these flights through materials provides continuous chance of material heating and shear mixing upon contact. In other words, they provide the convective heating to moving materials that is further effective over the conductive heating shown in developing HMA producers. All these heating and mixing contribute to melting, mixing, and uniform coating of the organic materials (virgin and RAP asphalt binders, and organic additives) on aggregates.
  • the next generation HMA plant (28) excludes the dust collector unit that is essential in the conventional asphalt plants.
  • the next generation producer (28) also adopts the same surface combustion burner (1 1 ) as in the screw conveyor-type producer (8) because of high energy density, capability of cylindrical surface heating, and many other benefits indicated in Table 1 , compared to the conventional oil burner.
  • any materials including the RAP aggregates can enter into the inlet in the next generation producer (28), but the conventional producer (a drum mixer) only permits the RAP entry at the mixing zone due to the poor material transfer tool (or the pocket flight) together with the direct heating system, leading to necessity of dust collectors.
  • Cold RAP entering into the mixing zone that is almost at the end portion of the mixing drum restricts the regeneration of RAP percentage to be less than 50% due to heat exchange requirement.
  • the 100% RAP regeneration provides benefits of eliminating land pollution due to no RAP left over after production, significantly reducing the raw material cost for HMA production, and saving the expensive virgin materials (asphalt binder and aggregate), etc.
  • the outer housing (29) in the next generation producer (28) has three different shapes; that is, the tubular (25), the U- shaped (26) and the V-shaped trough (27) that are same as those in the screw conveyor-type producer (8) depicted in Figure 4. Only difference is the size.
  • the latter producer (8) has relatively small housing compared to the large housing of the former (30). As explained earlier, difficulty in material flow determines the shape of the outer housing among the three troughs shown in Figure 4.
  • the characteristics of the rotating inner drum (30) depend on kinds of the screw flight (31 ) and the directional flight (32) attached on the outside surface of the drum. As far as screw flight is concerned, this invention adopts either the full or the segmented screw flight (31 ).
  • the full screw flights (17) shown in Figure 5 for the screw conveyor-type producer (8) apply to the next generation producer as well, if they are present on the outside surface of the inner drum (30) instead of the screw shaft (18).
  • Another screw types in addition to full screw flights (17) are the
  • segmented screw flights (31 ). Many different screw segments with vacancy between two consecutive ones helically constitute the segmented screw flight on the outside of the inner drum surface. All kinds of full screws in Figure 5 can cut into segment shape to form segmented screw flight (31 ). They generally give better mixing, less driving force and easy to be fabricated, but less production compared to the full screw flights.
  • Figure 6 schematically displays one of segmented screw flights (31 ).
  • FIG. 6 displays the directional flights (32) located on the perpendicular line of a screw pitch expanded over the entire helical distance with a given interval to move more materials forward to the exit. Note that the directional flight (32) creates more shearing surface allowing better material transferring, promotes good shear mixing, generates higher frictional heating, and plays a role of an efficient material heating tool.
  • Directional and screw flights may also be used to prevent overflow of the HMA out of the open end of the outer housing (29) by channeling HMA towards the material exit (37).
  • Directional flights (32) attached on the outside surface of the inner drum (30) can have many different shape and arrangement as long as they can promote efficient material transfer, mixing and heating during rotation of the inner drum (30).
  • Figure 8 demonstrates an example of another shape of the directional flight (Figure 8A) and arrangement of two different directional flights ( Figure 8B).
  • this invention claims a segmented (or full) screw flight (31 ) together with a directional flight (32) to be an essential unit in the rotating inner drum (30).
  • utilization of the directional flight (32) alone without the screw flight (31 ) can be possible as indicated in Figure 9.
  • All kinds of directional flights (32) standing alone on the outside surface of the inner drum also belong to this invention.
  • Figure 10 demonstrates the plate-type directional flight that composes of the horizontal plate (38) with the vertical rod (39), and the vertical plate (40) with horizontal rod (41 ) to have better material mixing and heating. If materials flow the above and the below of the horizontal plate at one position, they do the left and the right of the vertical plate at the next position. This alternative flow derivation creates better mixing as well as effective heating by providing more shearing surface.
  • the pitch distance between adjacent two screw flights, and the flight height between the inner drum and the outer housing should be big enough to transfer large materials per a unit rotation.
  • mere increase of the pitch distance and the flight height for the segmented screw flight with the directional flight are not sufficient enough for good mixing and heating.
  • the directional flight (32) possessing structural security as well as more shearing surface is always desirable.
  • Figure 1 1 demonstrates such an example.
  • a single pitch (43) on the cylindrical inner drum (30) unfolds to make the flat surface for better understanding.
  • the segmented screw flight (31 ) has an inclined angle (44) against the vertical line
  • the directional flight (32) shows a repeating unit (42) that contains three horizontal plates (38) with a vertical rod (39) in the screw flight height, and three vertical plates (40) with a horizontal rod (41 ) in the screw pitch instead of using a big single horizontal plate with a vertical rod (39), and a big single vertical plate (40) with a horizontal rod (41 ).
  • the vertical rod (39) and both sides of screw segments across the pitch structurally secure three horizontal plates (38).
  • the horizontal rod (41 ) and the surface of the inner drum (30) secure three vertical plates (40).
  • each horizontal plate (38) The material flow on the top and below each horizontal plate (38), and the material flow to the left and to the right of each vertical plate (40) can provide more material shearing surface leading to more material transfer, better material mixing and effective heating.
  • the repeating unit (42) performs its function repeatedly from the starting pitch (43) to the final one. Facilitating more plates in the direction of the screw flight and the screw pitch with a given space between two adjacent plates can increase more material production.
  • the directional flight of the horizontal (38) and the vertical plate (40) in Figure 1 1 can change into inclined forms shown in Figure 12 because inclination creates higher shearing surface and larger material transfer compared to the normal un-inclined plate.
  • this invention includes all kinds of odd shape directional flights and different numbers in the direction of the flight height and the pitch distance with normal or inclined forms as long as they increase heating, mixing and production capacity.
  • this invention has claimed the next generation HMA producer (28) having unique mechanical units as shown in Figure 6 for production of the diverse HMA products including the 100% RAP (or ARS)-recycled one. Afterwards, each unit of the next generation HMA producer (28) begins to claim its innovative functional characters.
  • the outside housing (29) has claimed three different types according to difficulty in material transfer.
  • the second unit considered was the inner drum (30). All kinds of the segmented (or full) screw flight (31 ) and the directional flight (32) standing on the outside surface of the rotating inner drum (30) have claimed their characteristics in the view of material transfer, indirect heating and frictional shear mixing.
  • the length of the inner drum (30) is relatively long, and only two outside supporters (50) almost at the end of both sides (one for the sprocket (33) and the other for idler (34)) support the drum weight. Bending is possible at the middle of the drum due to no supporter in the middle. Such bending can strike the stationary outer housing (29) by the screw flight (31 ) and the directional flight (32) sitting on the rotating inner drum (30) during material processing. This can cause structural damage at the contacting point of the screw flight (31 ) and the directional flight (32) against the outer housing (29). To prevent such damage due to bending, the inner drum (30) necessitates installation of the inside supporter (49) as shown in Figure 13.
  • the shape of the inside supporter (49) can be either one of circular, rectangular, pentagonal, hexagonal, heptagonal and octagonal ones, or simply using the several rectangular bars (or strips) attaching on the inside wall of the entire inner drum (30) with the same interval in the circular direction.
  • Use of the inner drum (30) having a thick wall without any inside supporter (49) can be another alternative.
  • Surface combustion burner (1 1 ) is important in transferring heat energy to processing materials. As already indicated, the burner initially heats the inside wall of inner drum (30), and then the heat passes through the drum wall to arrive at the outside wall by conduction mechanism where the segmented screw flight (31 ) and the directional flight (32) stand. Further heat conduction through these units allows effective heat transfer to materials contacting during rotation of these units. This is a completely indirect heating system. The indirect heating generates no dusts and no slow-down of material production, even if materials are under the high temperature, differently from the existing producers. These characteristics make RAP entry possible at the material inlet and make 100% RAP recycled HMA production feasible in reality.
  • the only burner that can fit into the half-cylinder geometry is the surface combustion burner (1 1 ).
  • the surface combustion burner (1 1 ) place at the inside of the inner drum (30) as shown in Figure 13, and then each burner's temperature set differently to achieve the desired material temperature at the exit.
  • a single burner covering the whole drum length is also valid, but use of several burners with a certain length give more flexibility in controlling material temperature.
  • the stationary surface combustion burner (1 1 ) hangs down from the fuel pipe toward the inside drum wall, while the inner drum (30) rotates around the burner (1 1 ). This way makes sure that the surface combustion burner (1 1 ) can perpendicularly heat the rotating inner drum wall.
  • the perpendicular heating to the material flow direction is the better way of heating over the parallel heating.
  • the air- and-gas mixer (47) mixes air from air blower (45) and fuel gas from the LNG (liquid natural gas) or LPG (liquid propane gas) tank (46) to supply a proper composition to the burner (1 1 ) to make sure 100% fuel combustion.
  • the surface combustion-burner (1 1 ) receives the mixed air-and-gas fuel through the fuel pipe and break out the high temperature flame by achieving 100% fuel combustion.
  • the exhausted hot air (44) transfers to other units requiring heat and may provide a heat source for additional burners (1 1 ).
  • the idler (34) locates at the opposite side of the sprocket position in the drum to make balanced rotation.
  • the supporter of the sprocket (33) and that of the idler (34) are two supporting spots to endure the entire inner drum weight as mentioned earlier.
  • Two or three outer housing supporters (51 ) under the housing can support the entire weight of the stationary outer housing (29).
  • Driving of the motor (19) and ignition of the surface combustion burner (1 1 ) require electricity.
  • the electric generator (48) is an essential unit to generate and supply electricity needed.
  • the sectional screw flight (31 ) and the directional flight (32) attached on the outside surface of the inner drum (30) pushes material forward by the frictional shearing, but the inner drum (30) itself attaching those flights experiences the retraction force as much as the forwarding force of materials.
  • the axial thrust bearing (35) must install at the end of the material inlet side of the inner drum (30).
  • the inner drum diameter needs to be large enough to effectively transfer heat to the material.
  • the ideal diameter is estimated to be between 4' and 14', mostly due to mobility concerns.
  • an inner drum of any suitable size may be used, depending upon production needs. For this reason, the inner drum reduces to the smaller steel pipe or the tubing that can comfortably accommodates the thrust bearing assembly (35) around it.
  • the cone connector (52) finds its use by connecting the large inner drum to the large cone side and the small pipe to the smaller side.
  • closure of the end of the inner drum with the thick circular plate having the smaller pipe or the tubing attached in the center of the circular plate can be another choice.
  • the next generation producer (28) uses combination of the thrust bearing housing (35) from the screw conveyor technology, and the sprocket (33) and the idler (34) from the drum mix technology.
  • the next generation HMA producer (28) claimed in this invention has many benefits and advantages over the existing producers. They are significant reduction of environmental pollution, no dust generation, excellent frictional shear mixing, effective indirect convective heating caused by heated flights, fuel saving achieved by using a surface combustion burner, and production of 100% RAP-recycled mixes. One obtains additional benefits of excellent performance properties obtained by adding organic additives, decreased construction cost, elimination of waste disposal fee, saving of virgin raw materials relating to 100% RAP recycled mix production.
  • next generation HMA producer (28) constituting of rotational inner drum (30), stationary outer housing (29), segmented screw (or full screw) flights (31 ) and directional flights (32), sprocket with chain (33) and idler (34), thrust bearing assembly (35), and surface combustion burner (1 1 ) becomes a truly next generation producer.
  • the reason is that such a producer creates unique technical breakthrough never achieved in the history of asphalt mix plants and solves limitations of the existing HMA producer.
  • the present invention has industrial applicability in producing the regular and the modified HMA (or WMA) products and up to 100% RAP (or ARS) recycled ones, and disclosing apparatuses and methods for making such products.

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  • Chemical & Material Sciences (AREA)
  • Chemical Kinetics & Catalysis (AREA)
  • Engineering & Computer Science (AREA)
  • Architecture (AREA)
  • Civil Engineering (AREA)
  • Structural Engineering (AREA)
  • Road Paving Machines (AREA)
  • Working-Up Tar And Pitch (AREA)
  • Road Paving Structures (AREA)

Abstract

L'invention concerne une usine de production de mélange d'asphalte chaud ou de mélange d'asphalte tiède (28) caractérisé par un transfert de matériaux par l'action de cisaillement d'une vis segmentée (31) et de déflecteurs directionnels (32) sur un tambour interne (30) de l'entrée (36) à la sortie (37), le chauffage du matériau par convection indirecte initiée par un brûleur à combustion de surface (11) et le mélange du matériau par cisaillement de frottement. Ici, le mélange, le chauffage, la fusion et le revêtement uniforme du matériau, tous ont lieu sous la forme d'un seul processus simultané.
PCT/US2015/062944 2014-12-01 2015-11-30 Usines d'asphalte en mélange chaud (ou tiède) produisant jusqu'à 100 pour cent de mélanges d'asphalte recyclé rap WO2016089748A1 (fr)

Priority Applications (2)

Application Number Priority Date Filing Date Title
CN201580065443.1A CN107000252B (zh) 2014-12-01 2015-11-30 生产高达100％沥青路面回料再生混料的热(或温)拌装置
DE112015005403.0T DE112015005403T5 (de) 2014-12-01 2015-11-30 Hot (oder warm) asphaltmischanlagen herstellung bis zu 100 prozent rap recycelte asphaltmischungen

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US201462123866P 2014-12-01 2014-12-01
US62/123,866 2014-12-01

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CN110029556A (zh) * 2019-05-15 2019-07-19 成都广维重工科技有限公司 一种砂石自制间歇式沥青混凝土搅拌站
CN110201621B (zh) * 2019-07-04 2024-04-30 河北交科材料科技有限公司 一种管式改性沥青混料机
CN110656871B (zh) * 2019-10-24 2020-11-27 山东安舜消防设备有限公司 一种双轨双帘防火卷帘门
CN112064453A (zh) * 2020-09-14 2020-12-11 苏州三新路面工程有限公司 一种沥青混凝土拌和工艺

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US5547277A (en) * 1994-04-12 1996-08-20 Klockner-Humboldt-Deutz Ag Preheating screw
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