Patent Description:
The resurfacing involves, as a first step, the milling of the top surface of the asphalt wherein the surface is ground through the use of a cold plane milling machine and removed, leaving the underlying roadbed upon which fresh asphalt can be deposited.

The asphalt millings, sometimes referred to as bituminous concrete, are an environmental concern. The problem with asphalt millings is that the bitumen binder used in asphalt paving applications contains a relatively large concentration of a family of carcinogenic compounds which can pose serious human health and environmental concerns in certain circumstances, such as when the asphalt millings are blown off or washed from the surface of the waste material. These compounds, known as polycyclic aromatic hydrocarbons (PARs), are specified as targeted pollutants by the U.

Environmental Protection Agency (USEPA), and are present in asphalt at much higher levels than the criteria established by most states for general use on land. Such materials have the potential to significantly contaminate surrounding soils and/or surface water sediments.

To a certain extent, asphalt millings may be recycled in accordance with many state's regulations for recycling. Of course, the use of loose unbound asphalt millings on roadway surfaces without the placement of a paved top surface is not appropriate for the reasons noted above. Although many states permit millings to be used by road asphalt manufacturing plants for direct incorporation into new asphalt, the amount of millings per new asphalt that can be used is typically <NUM>% or less. Thus, at least <NUM>% of the millings are effectively wasted and cannot be used due to state environmental restrictions. As such, there is a need for a system for recycling asphalt millings and methods thereof.

A solution to this problem has been proposed by the present inventor, in <CIT>. That invention included an initial step of churning the asphalt millings using a liquid compound and optionally, the external application of heat. Although a significant advance in the recycling of asphalt millings, the mixture was required to sit for an extended period of time to cause the oil to loosen from the stone. This process would then create a liquid residue that would require further disposal.

<CIT> discloses an apparatus and a method for fragmenting and re-mixing agglomerated pieces of rubberized asphalt material. A random mixture of agglomerated pieces and rubberized asphalt material is delivered to a job site, forming a windrow, and an elevator picks up the mixture. The elevator carries the mixture upwardly, and delivers it to the upper portion of a cylindrical housing. An auger and tine assembly having a common drive shaft is mounted within the housing. The assembly includes auger sections mounted along the drive shaft in spaced relation. A rotating tine section is mounted on the drive shaft between the auger sections. The auger sections have converging handedness effective to transport the agglomerated pieces and the material toward the rotating tine section.

<CIT> discloses an asphalt material recycling system and a method with ball screener and impact and cutting choppers. The system comprises an asphalt material recycler having a recycling chamber, at least one motor and at least one chopper. The system further comprises a vibrating screener coupled to the asphalt material recycler and configured for receiving recycled asphalt material from the recycling chamber.

The present invention is directed to a significant improvement to the technology set forth in the above application, and to a method and apparatus that have the ability to cleanly and efficiently separate stone from bitumen to thereby recycle effectively <NUM>% of the asphalt millings.

In accordance with a first aspect of the invention, apparatus for recycling asphalt millings containing bitumen and stone comprises a milling tube having an outer tube and an inner tube axially aligned with and substantially contained within the outer tube, the inner tube having a diameter less that a diameter of the outer tube to thus define a mixing space between the inner and outer tubes. At least one of the inner and outer tubes is adapted to rotate relative to the other. An inlet is provided to the mixing space to receive the asphalt millings. A plurality of inner tube projections project radially outward from a surface of the inner tube toward the outer tube, and a plurality of outer tube projections project radially inward from a surface of the outer tube toward the inner tube. The milling tube facilitates the separation of the asphalt millings into bitumen and stone as one of the inner and outer tubes rotates relative to the other. Preferably, at least one of the outer and inner tubes contains an abrasive coating on a surface thereof, the inner tube projections and outer tube projections are comprised of wire rope. According to the invention, an inlet is provided in the outer tube through which cold air is applied to the mixing space. In accordance with an embodiment of the invention, the inner tube rotates within the outer tube, and the abrasive coating is located on an interior surface of the outer tube. An input conveyor adapted to feed the asphalt millings to the inlet to the mixing space can also be provided.

A method is described for recycling asphalt millings containing bitumen and stone, comprising delivering the asphalt millings to a mixing space having an abrasive surface, mixing the asphalt millings in the mixing space during which the millings are exposed to the abrasive surface, applying cold air to the asphalt millings during at least a portion of the mixing step, wherein the steps of mixing and applying cold air facilitate the separation of the bitumen and stone. The step of mixing the asphalt millings heats the millings through friction, before the step of applying cold air to the millings. The step of mixing occurs in the mixing space defined between an outer tube and an inner tube axially aligned with and substantially contained within the outer tube, the inner tube having a diameter less that a diameter of the outer tube. The step of mixing preferably comprises rotating the inner tube within the outer tube, and the step of applying cold air comprises the application of one of liquid nitrogen or dry ice to the asphalt millings.

These and other aspects of the invention will be described with reference to the following drawing figures, of which:.

As will be described, the present invention is directed to an apparatus that cleanly and efficiently separates stone from bitumen in asphalt millings, that does not require the application of external heat, liquid, churning, or processing time, that is free from run off, that can be implemented in a mobile apparatus on project sites, and which will yield <NUM>% recyclable materials, namely bitumen and stone. The present invention can also be utilized within asphalt plants, landfills, and/or any location permitted by state and local ordinances.

With reference to <FIG> and <FIG>, an example of an apparatus <NUM> in accordance with the present invention is shown. A hopper <NUM> is provided for accepting the asphalt millings by physical or automated means. The asphalt millings are passed through hopper <NUM> where they flow onto an auger or screw conveyor <NUM>, where the asphalt millings are spread and dried. Although not shown, the conveyor <NUM> is preferably provided with perforations, allowing air to be passed therethrough to facilitate the drying of the millings. The conveyor <NUM> may also be provided with grates placed to allow for any obstruction materials to be discarded and/or collected. At this point, the conveyed and dried the asphalt millings can be inspected by physical or automated means, if desired, and then passed into controlled hopper <NUM>. Controlled hopper <NUM> can be manned physically and/or automated, and functions to meter an appropriate amount of dried asphalt millings into asphalt milling tube <NUM> (at inlet <NUM>), which will be described with reference to <FIG> and <FIG>.

As shown in <FIG> and <FIG>, milling tube <NUM> is comprised of an outer tube <NUM> and an axially aligned inner tube <NUM> which is rotatable within outer tube <NUM>. Outer tube <NUM> may be constructed of steel in various thicknesses (for example, one-quarter to one-half inch), and may be approximately <NUM> inches in diameter, for example, although other materials, diameters and thicknesses may be employed if desired. Inner tube <NUM> may also be constructed of steel, have various thicknesses (for example, one-quarter to one-half inch) and may be approximately <NUM> inches in diameter for an outer tube <NUM> inches in diameter, although other relative dimensions may be selected if desired. Inner tube <NUM> rotates within outer tube <NUM> by means of axial shaft <NUM>, best shown in <FIG>. Shaft <NUM> can be approximately <NUM> inches in diameter, although other sizes may be used if desired. The overall length of the milling tube <NUM> can be approximately <NUM> to <NUM> feet, although other dimensions may be used, if desired, whereby an inch corresponds to <NUM>,<NUM>, a foot to <NUM>,<NUM> and a pound (lbs) to <NUM>,<NUM>.

As best shown in <FIG> and <FIG>, outer tube <NUM> is provided with wire rope "bullets" <NUM> that protrude radially into the interior of the tube. Bullets <NUM> may be arranged in the configuration shown in <FIG>, where <NUM> x <NUM> matrices of bullets can be placed at various locations along the tube <NUM>, as desired, depending upon the asphalt millings that are processed. Each bullet <NUM> can be formed of one-half inch steel wire rope crimped at about <NUM>,<NUM> lbs. in a steel pipe having an outside diameter of <NUM>,<NUM> and a wall thickness of <NUM>,<NUM> (half inch Schedule <NUM> steel pipe) and will protrude approximately one-half inch into the interior of the tube (beyond the abrasive coating, discussed below).

Inner tube <NUM> is provided with wire rope brushes <NUM> that project radially outwardly toward the outer tube. Different configurations and locations of brushes <NUM> can be used, but preferably, brushes <NUM> can be configured in a generally helical arrangement, so that they function as an auger to move the millings from the input end <NUM> of milling tube <NUM> to its output end <NUM>. Each brush <NUM> can be formed of one-half inch steel wire rope crimped at about <NUM>,<NUM> lbs. in a steel pipe having an outside diameter of <NUM>,<NUM> and a wall thickness of <NUM>,<NUM> (half inch Schedule <NUM> steel pipe) or a steel pipe having an outside diameter of <NUM>,<NUM> and a wall thickness of <NUM>,<NUM> (three quarter inch Schedule <NUM> steel pipe) and will protrude approximately one-half inch from the surface of tube <NUM>.

Thus, it will be appreciated that the combination of the bullets <NUM> and the rotating wire brushes <NUM> turbulently mix the millings during the separation process. It is again noted that other dimensions can be used in accordance with the present invention, as will be appreciated in view of the present disclosure.

Finally, the inner surface of the outer tube <NUM> is coated with an abrasive. For example, a mineral compound can be prepared by mixing an epoxy and hardener with a mixture of non-fibrous aluminum oxide, aluminum silicate, and/or titanium aluminum oxide, which may be obtained commercially in the form of Bauxite. Alternatively, instead of Bauxite, silicon carbide or diamond particles may be used. The above abrasive materials are mixed with the epoxy/hardener and coated on the inner surface of the outer tube <NUM> to thereby provide a coarse, abrasive layer which can be approximately <NUM>/<NUM> inch in thickness.

In operation, the asphalt millings enter outer tube <NUM> from controlled hopper <NUM> at a rate of approximately <NUM> pounds per second. Inner tube <NUM> is rotated at approximately <NUM> revolutions per minute, and wire brushes <NUM> spin the asphalt millings against bullets <NUM> and the abrasive surface. The friction resulting from this action creates heat which facilitates the separation process; depending on the climate and season of the year, the application of additional heat may be required. Outer tube <NUM> is then jetted with liquid nitrogen, dry ice or the like through jet inlet <NUM>, <FIG>, located downstream of the inlet <NUM>. This combination of the turbulent mixing of the millings against the abrasive coating, the generation of heat and the subsequent application of cold, causes the bitumen to separate from the stone, leaving a re-usable natural asphalt binder (bitumen), and stone. The natural asphalt binder is then removed from the output end <NUM> of milling tube <NUM> and collected through a series of grates, conveyors and possibly vacuums that function to separate the binder from the stone in a manner that will be understood.

Claim 1:
Apparatus (<NUM>) for recycling asphalt millings, said millings containing bitumen and stone, said apparatus comprising:
a. a milling tube (<NUM>) having an outer tube (<NUM>) and an inner tube (<NUM>) axially aligned with and substantially contained within said outer tube (<NUM>), said inner tube (<NUM>) having a diameter less that a diameter of said outer tube (<NUM>) to thus define a mixing space between said inner and outer tubes (<NUM>, <NUM>), at least one of said inner and outer tubes (<NUM>, <NUM>) adapted to rotate relative to the other,
b. an inlet (<NUM>) to said mixing space adapted to receive said asphalt millings;
c. the milling tube (<NUM>) having an output end (<NUM>);
d. a plurality of inner tube projections (<NUM>) projecting radially outward from a surface of said inner tube (<NUM>) toward said outer tube (<NUM>);
e. a plurality of outer tube projections (<NUM>) projecting radially inward from a surface of said outer tube (<NUM>) toward said inner tube (<NUM>);
f. an inlet (<NUM>) in said outer tube (<NUM>), located downstream of the inlet (<NUM>) to said mixing space through which cold air can be applied to said mixing space;
whereby said milling tube facilitates the separation of said asphalt millings into bitumen and stone as one of said inner and outer tubes (<NUM>, <NUM>) rotates relative to the other.