Abstract:
An asphalt roofing material recycling system and method is used to recycle asphalt materials, such as asphalt shingles and tar paper that include granules, fibers or other particles. The asphalt material is simultaneously heated and milled in a heated milling apparatus, such as a heated ball mill, to reduce the asphalt material granules to a fine mesh in suspension in liquid asphalt. Excess moisture is removed from the asphalt material being recycled, either during heating and milling by continuously venting the heated milling apparatus, or before the heating and milling in a drying apparatus. The heated milling apparatus preferably includes a rotatable milling vessel rotated at an acute angle with respect to the horizontal plane and having an opening that provides continuous venting. The rotatable milling vessel includes a plurality of mixing members, such as rods or paddles, extending from an interior surface and preferably arranged in a helical pattern to force the asphalt material away from the opening. The asphalt material recycling system further includes a storage apparatus for storing reduced asphalt material and a filter apparatus for filtering reduced asphalt and removing foreign objects therefrom.
Abstract:
A method for reducing at production levels sticky, abrasive waste shingles and portions thereof into a reduced shingle material for use of a patch for potholes and cracks and as paving for roads and the like comprises shredding of the shingles to pieces, milling the pieces to particles and granules and impinging the particles and granules with intermittent blasts of compressed air to prevent clogging and sticking and to assist in discharging of the reduced shingle materials. The method may also include the step of spraying water upon the shingles and inside of the apparatus. The apparatus includes an improved hammermill with a compress air manifold with apertures therein for intermittently discharging compressed air which impinges upon the inner chamber of the hammermill and upon the pulverized waste materials. A pressurized water manifold with apertures may also spray the mill chamber of the hammermill with water to prevent clogging or sticking of the hammermill. A method is also provided for heating the reduced sticky, abrasive waste shingle granules for application as a patch as well as a paving for roadways, driveways, walkways and the like.
Abstract:
An asphalt drum mixer includes a rotating drum within a fixed sleeve which defines an annular chamber, and mixing tips mounted on the drum and in the annular chamber. The mixing tips pass through the hot mix asphalt laying in the bottom of the annular chamber and mix and shear the hot mix asphalt and increase its residence time in the drum mixer. In one preferred embodiment, the mixing tips may comprise curved scoop-like elements which lift the hot mix asphalt higher than conventional paddles and greatly increase residence time of the mix in the drum over conventional paddles. The quality of the mix is thus greatly improved. In another preferred embodiment the mixing tips may comprise curved scoop-like elements having slots which greatly increase sheering of the hot mix asphalt, thereby further improving the quality of the mix.
Abstract:
An apparatus and process is provided for the production of hot mix asphalt (HMA) by the treatment of virgin material alone or adding reclaimed or recycled asphalt pavement (RAP) of up to 100% of the HMA comprised of reclaimed asphaltic pavement (RAP). The HMA is first heated in either a parallel or a counter flow rotating drum which is supplied with hot combustion gases generated by a remote low NO.sub.x burner. The temperature of hot gases entering the drum is from about 400.degree. to 2,000.degree. F., and the temperature of gases exiting from the drum is from about 130.degree. to 220.degree. F. The HMA material optionally can be subjected to microwave radiation to raise the material to a final temperature, or optionally to only reorient the dipolar molecules of the material without any measurable heating of the material. The exhaust gas is treated and made environmentally safe. The hot gases exiting from the drum are passed through a knockout box and then through a baghouse having acrylic bags coated with a protective layer of particulate material. The gases exiting the baghouse are passed through an oxidizer to further remove smoke and asphaltic material and at least a portion of the gases from the oxidizer are recycled through a heat exchanger.
Abstract:
An apparatus for controlling the angular velocity and slope angle of a hot mix asphalt drum as a function of the temperature gradient across the drum outlet. Uneven gas outlet temperature indicates that the veil of RAP (Recycled Asphalt Pavement) in the drum is insufficient. The veil is increased by increasing drum speed. The complete recycled asphalt pavement hot mix asphalt plant uses uneven gas outlet temperatures to change drum operating parameters.
Abstract:
A drum mixer is useful in the continuous production of asphalt paving composition, and has provision for the accurate control of the final temperature of the composition being produced. The drum mixer comprises a fixedly mounted cylindrical sleeve disposed in a generally horizontal orientation, and rotating blades for conveying the heated aggregate longitudinally through the interior of the sleeve. An opening is provided in the side wall portion of the sleeve, and a box-like enclosure covers the opening and mounts a plurality of sensor mounting tubes, so as to permit one or more sensors to be positioned at a location within the enclosure. The enclosure is located where the blades or mixing action in the sleeve will supply a regular flow of the aggregate into the enclosure, and so that the aggregate then slides over the sensors. The sensors are thus subjected to a representative portion of the aggregate, and they are protected from both the radiant heat of the burner and the physical abuse of the mixing action.
Abstract:
An asphalt manufacturing assembly (10) is disclosed that includes a rotatable cylindrical dryer drum (11) having an opening (14) in the front (12) for receiving virgin asphalt aggregate and for permitting the exhaust of fumes and an opening (18) in the back (13) for discharging the heated aggregate and for permitting the introduction of air. A burner (41) adjacent the back (13) introduces a flame and heat into the dryer drum (11). A longitudinal air conduit (22) is formed by a stationary annular shroud (20) around the back portion of the dryer drum (11) that extends longitudinally beyond the dryer drum back end (13). The shroud (20) includes two controllable discharge openings (24,25). The assembly (10) further includes a separate rotatable cylindrical mixer drum (51) having a materials inlet (54) for receiving the aggregate discharged from the dryer drum (11), reclaimed asphalt pavement, liquid asphalt and fines and a discharge opening (58) for discharging asphalt. A scavenger fan ( 95) is disposed generally between the two drums (11,51). Each drum (11,51) further includes a plurality of longitudinally and radially projecting paddles (28,32) attached to each's back end (13,53).
Abstract:
An asphalt drum drying and mixing plant capable of using recycled pavement aggregate material includes two interacting drums, each being heated to different temperatures. A first drum is a parallel flow drying and mixing drum. The recycled material is introduced at the intake or feed end of this first drum and dried and heated to a comparatively low temperature in a first region of the first drum. A burner of relatively lower heat generation capacity furnishes heated gases. The recycled material is protected by supplying the gases through a cylindrical combustion chamber within which the fuel is completely burned such that no luminous gases enter the drum and contact the recycled material. A second, adjacent region of the parallel flow drum is the mixing region. The recycled material is transferred to the mixing region with close control over the temperature at which the material enters the mixing region. The parallel flow drum also has an intermediate feed chute through which virgin aggregate material is added. The virgin aggregate is heated in a counterflow drum to a temperature higher than the recycled material and the temperature of the final mix is controlled by changing the temperature of the virgin material. The exhaust from the mixing region is introduced as secondary air into the counterflow drum burner assembly. From the counterflow drum all gases are passed to a cleaning system including a cyclone separator and a baghouse filter. From the cyclone separator and the baghouse filter separated material and fines are routed into the mixing region together with liquid asphalt cement.
Abstract:
In a dryer apparatus including an elongated rotatable drum having an input end and an output end, a burner for directing hot gases into the input end of the drum, and an aggregate feed mechanism for supplying aggregate particles into the drum adjacent the input end and for conveying the aggregate particles toward the output end, an assembly adapted to introduce reclaimed asphalt pavement particles into the dryer includes an inner drum for introducing reclaimed asphalt pavement particles into the elongated drum at a position adjacent the output end of the elongated drum and for moving the recycled asphalt pavement particles within the elongated drum in a direction counter to the direction of flow of the hot gases so that the hot gases heat the recycled asphalt pavement particles during travel of the recycled asphalt pavement particles within the inner drum assembly. The inner drum is mounted for rotation with the elongated drum and has an inlet end, an outlet end, and flighting for moving the recycled asphalt pavement along the inner drum from the inlet end toward the outlet end such that recycled asphalt pavement falls from the outlet end of the inner drum into the elongated drum and mixes with aggregate particles which are introduced into the drum adjacent the input end. The particles are heated by the hot gases moving in and around the inner drum as well as by conduction heating carried out via the flighting within the inner drum.
Abstract:
A drum mixer is provided for producing an asphaltic composition. The drum mixer utilizes a first heat source located at an intermediate position within the drum mixer for producing a first current of hot gases directed towards the entry end of the drum mixer. The drum mixer also utilizes a second heat source located at the discharge end of the drum mixer for producing a second current of hot gases directed towards the entry end. Virgin aggregate is introduced into the drum mixer at the entry end of the drum mixer and is heated by the first current of hot gases. Recycle material is introduced into a mixing zone within the drum mixer between the first heat source and the discharge end. The heated virgin aggregate combines with the recycle material in the mixing zone and is further heated by the second heat source. Liquid asphalt is mixed with the virgin aggregate and recycle material in the mixing zone and the product is removed from the drum mixer at the discharge end.