Abstract:
A drum mixer for recycling old asphalt pavement features a stationary shroud enveloping a series of circumferentially spaced feed ports medially of the drum. The old pavement is introduced tangentially into the shroud and then into a series of "hoppers" within the shroud formed about the feed ports and revolving with the drum. The old pavement falls through the feed ports onto the exterior of a conical inner drum and is directed to the downstream end of the latter by flighting thereon where it joins virgin aggregate emerging from the interior of the inner drum.
Abstract:
An elongated drum for mixing asphalt materials has a rear inlet end, a front outlet end and a side wall concentric to a substantially horizontal axis about which the drum rotates. For feeding salvaged asphalt material into the drum, the side wall has circumferentially spaced ports in a zone intermediate said ends. As ports move upwardly in their orbits, material falls toward them from the bottom outlet of a hopper above the drum and is guided into them by chutes, one for each port, that are fixed to the side wall and project out from it. Also, fixed to the side wall is an inwardly projecting spout for each port whereby material entering the port is deflected forwardly to fall to the bottom of the drum in front of the ported zone. Material moving forward from the rear of the drum is deflected around the ports by the spout walls. An annular trough-like shroud encircles the drum at said zone, embracing the chutes as they move orbitally and preventing incursion of external ambient air into the ports. A hole in the shroud, in line with the upper outlet, is either blocked by salvaged material in the hopper or is closed by a gate for use with all-virgin materials.
Abstract:
A method of hot mix recycling of old asphaltic concrete paving heats the old pavement, after it has been removed and sized, to a temperature below its firing point and heats fresh aggregate to a greater temperature before combining the two and adding new asphalt. The method is embodied in a drum-mixer type of apparatus modified by inserting a smaller drum in the upstream portion of the large drum. The burner fires into the smaller drum into which the fresh aggregate only is introduced while the old mix (plus additional fresh aggregate in certain cases) is introduced into the annular space between the two drums, the fresh aggregate and the old mix being thereafter combined in the large drum, new asphalt added and the mix further heated.
Abstract:
The device includes in a rotary cylindrical drum (1) a zone for transfer and heating (11) where the inner surface of the drum (1) is fitted with sections of blades (17) wound in a spiral across the drum (1). These blades (17) arranged projecting with respect to the inner surface of the drum (1), by their edges remote from the drum support baffleplates (18) in a longitudinal direction. The drum (1) likewise exhibits an isolation and drying zone (12) where the inner surface of the drum (1) is fitted with lifter devices (20-21) having a high retention capacity for lifting materials (25) up to the upper portion of the drum (1) and the formation by falling back of these materials (25) of a continuous screen isolating the flame (5) of the burner (4) from the next zone of the drum (1).
Abstract:
In a continuous drum mix asphalt plant, dust is exhausted from an intermediate zone of the drum mixer between its drying and mixing zones. The dust is exhausted radially through openings into a collection housing, which communicates with a dust collector and exhaust blower. An end housing at the discharge end of the drum communicates with the same dust collector and blower. Dampers are provided to control the relative proportion of air exhausted from the drum through the respective housings. Aggregate deflectors on the interior wall of the drum at the intermediate zone allow air and dust to flow while inhibiting the flow of aggregate. The collection housing surrounding the intermediate zone is of a size such as to produce a reduction in the velocity of the air as it passes out of the drum. Consequently, it serves as a knock-out box for the collection of larger particles which are carried out of the drum, but which settle out of the air stream as a result of the velocity decrease. These collected particles are reintroduced into the drum by scoops on the exterior of the drum. These scoops are also used for the introduction of recycled asphaltic concrete.
Abstract:
In recycled asphalt-aggregate compositions prepared by adding a suitable amount of make-up asphalt to pieces of the used composition and heating the mixture in a rotating cylindrical drum by tumbling the composition over heated pipes as it is gradually directed towards an output end of the drum, the improvement comprising adding an amount of petroleum hydrocarbon to achieve a laid down asphalt penetration of between 25 and 300 dmm at 77.degree. F. A further embodiment of the improved process comprises venting a mixture of hydrocarbon gases and moisture vaporized from the hot composition mixture at the output end of the apparatus, condensing the moisture and removing it and returning the hydrocarbon gases to a combustion chamber for providing heat to the apparatus tubes. Still another improvement comprises an apparatus modification wherein a plurality of relatively short pipes are disposed in the forward ends of the heating tubes through a front plate displaced from the forward end wall of the drum with the open pipe ends exposed to the combustion chamber for providing heat to the interior of the heating tubes.
Abstract:
In a process for producing asphalt-aggregate compositions in a conventional type dryer-mixer drum in which aggregate is exposed directly to flame and hot gases of combustion while it cascades in the rotating drum, and in which the flame and hot gases of combustion are directed into an input end of the drum, the improvement comprises separating the aggregate into a plurality of different portions or increments each having different particle size ranges, introducing the coarse or larger aggregate particles into the drum and directly exposing them to the flame, its radient heat, hot gases of combustion at the input end, and introducing the finer or smaller aggregate particles downstream from the input end and away from direct exposure to the flame and extremely hot gases in a temperature zone which will avoid overheating the fine particles. The improved apparatus includes means for introducing the coarse particles at the input drum end for direct exposure to the flame or hottest gases and means for introducing the fine or smaller particles in a cooler zone of the apparatus.
Abstract:
In a process for recycling asphalt and aggregate containing composition, the improvement comprises separating the composition into a plurality of portions having different particle sizes, ranging from coarse to fine, introducing the particle portions into different mixing and heating drums, one of the drums being for the coarse particle portion, and one or more additional drums for smaller particle portions, and heating the particles in the respective drums with hot gases of combustion at temperatures below that which will burn the asphalt particles in each of the respective drums.