Astec Industries, Inc.

John Milstead

A dryer drum coater reduces blue smoke emissions by evacuating the blue smoke from the dryer drum coater independently of the exhaust of combustion products. The blue smoke, produced when heated and dried aggregate is mixed with other asphaltic products such as RAP or liquid asphalt, is preferably evacuated from a vapor outlet formed remote from the exhaust products outlet of the coater and adjacent the heated and dried aggregate inlet of the mixing chamber. Evacuating the blue smoke at this location obviates the need to separate the blue smoke from the combustion products and also prevents the introduction of excess oxygen into the combustion zone of the dryer drum coater. In a particularly preferred arrangement, the evacuated blue smoke is fed directly to the combustion air inlet of the coater's burner blower and is thereby incinerated.

Dryer drum coater having vented outer shell for VOC/NOx reduction

A rotary drum dryer has devices for cooling shielding flights located in the combustion zone of the drum. The devices comprise cooling flights which rotate with the drum to scoop up relatively small amounts of virgin aggregate from aggregate accumulated in the lower portion of the drum and to shower this aggregate over the outer radial surface of the shielding flights upon further rotation of the drum, thereby cooling the shielding flights without substantially decreasing the mean temperature of the aggregate. Cooling efficiency is enhanced by the continuous cascading of fresh aggregate over the shielding flights from the cooling flights through a substantial portion of the drum's rotation. The cooling flights and shielding flights preferably cooperate to limit or even prevent the showering of materials into the burner flame and thus inhibit burner flame quenching and accompanying emissions. Particularly preferred cooling flights take the form of auxiliary flights which can be easily adapted to existing shielding flight designs.

Rotary drum dryer having aggregate cooled shielding flights and method

Transport and erection of a portable asphalt plant are facilitated by transporting upper and lower subassemblies of the plant to a worksite on a single portable frame towed by a tractor. Once at the worksite, the frame is detached from the tractor and the upper plant subassembly is moved on the frame from a lowered transport position generally beside the lower plant subassembly to an intermediate position directly above the lower plant subassembly. The plant assembly is then completed by attaching the upper plant subassembly to the lower plant subassembly and raising the lower and upper plant subassemblies as a unit to a raised position which is sufficiently high to permit trucks to pass beneath the lower plant subassembly. An elevator is preferably transported to the worksite via another vehicle, then mounted on a pivot axis of the frame, and then pivoted about the pivot axis from a horizontal transport position to an upright operative position.

Method of erecting a portable asphalt production plant

A designated amount of recycled asphalt product (RAP) is fed to the pugmill of a batch asphalt plant during the production of hot mix asphalt (HMA) at a controlled rate so as not to overload the pugmill scavenging system. The designated amount of RAP is metered in a RAP weigh hopper, stored temporarily in a RAP holding hopper, and is then fed from the RAP holding hopper to the pugmill at a controlled rate. The feed of RAP to the pugmill, though electronically initiated, is preferably manually or automatically adjustable so as to avoid overloading the pugmill scavenging system while at the same time assuring adequate mixing of the RAP with the virgin aggregate and liquid asphalt. The scavenging system directs vapors removed from the pugmill to the dryer and preferably includes electronically operated dampers connecting the combustion air inlet of the dryer to the pugmill only during the mixing operation and otherwise connecting the combustion air inlet to the ambient atmosphere.

Batch asphalt plant having RAP weigh hopper and pugmill scavenging system

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.

Asphalt drum mixer with curved scoop-like mixing tips

A drum mixer for heating and drying stone aggregate as part of a process of continuous production of asphalt paving composition, the drum mixer including: an elongate hollow rotatable drum having a length and an outer surface, the elongate hollow rotatable drum defining a central axis, a sleeve having an inner surface, the sleeve being mounted coaxially with the elongate hollow rotatable drum about the central axis and around at least a portion of the length of the elongate hollow rotatable drum and so as to define an annular chamber having an entire distance between the outer surface of the elongate hollow rotatable drum and the inner surface of the sleeve, and structure for mixing hot mix asphalt in the annular chamber including rake flights mounted on the outer surface of the elongate hollow rotatable drum and in the annular chamber including scouring structure for lifting hot mix asphalt up from a lower portion of the annular chamber along the inner surface of the sleeve through the annular chamber and onto an upper portion of the outer surface of the elongate hollow rotatable drum, the scouring structure including a plurality of shaped scouring fingers extending radially toward the outer surface of the elongate hollow rotatable drum so as to break-up hot mix asphalt and allow hot mix asphalt to fall through the rake flights and onto the upper portion of the outer surface of the elongate hollow rotatable drum, thereby scouring the outer surface of the elongate hollow rotatable drum.

Asphalt drum mixer with self-scouring drum

A portable and self-erecting plant for the batch production of asphalt, and wherein the several components of the plant are split into two subassemblies which are initially mounted to the front and rear portions of a roadway transportable main frame. The front subassembly may be lifted to a first temporary position and then moved rearwardly to overlie the rear subassembly. The two subassemblies may then be interconnected to form an operational plant, which may be then lifted to its operating position as a unit. A separate elevator is provided which is also roadway transportable, and the elevator may be pivotally connected to the main frame so that it may be raised to an operative vertical position adjacent the plant.

Self erecting asphalt production plant

An apparatus for feeding preheated aggregate material, such as for the production of asphalt. A feed hopper includes a heater within its interior and positioned adjacent a slotted discharge opening at the lower end of the hopper. A tent-like cover is positioned above the heater to deflect aggregate material from contacting the upper portion of the heater and to transfer heat to the aggregate material in a uniform and efficient manner. The heater may preferably be a gas-fired radiant heater extending lengthwise parallel to and for the full length of the slotted discharge opening. A series of hoppers may be arranged in side-by-side relation and a common conveyor positioned beneath the individual feed conveyors of each hopper to direct the preheated aggregate material to a subsequent processing apparatus, such as a drum mixer or other dryer, used for the production of asphalt.

Feed hopper for providing preheated aggregate material

An asphalt production plant which is adapted to process mixtures of recycled paving and aggregate, and which comprises a rotary drum dryer for heating and drying stone aggregate, and an elevator for conveying the heated and dried aggregate to an elevated discharge location. A batch tower is positioned adjacent the elevator, and the batch tower comprises an aggregate sizing screen which receives and segregates the aggregate by size, and several underlying aggregate storage bins, with each aggregate bin receiving aggregate of predetermined average size from the sizing screen. Also, a recycle bin is positioned between and in alignment with the aggregate bins. A weigh hopper is provided for receiving the aggregate and/or recycle material from the bins, and a pugmill is positioned below the weigh hopper for mixing the material with hot liquid asphalt and then delivering the resulting mix into an underlying truck. A gate is provided for delivering the material from the elevator into either the sizing screen or the recycle bin. In addition, a weigh belt conveyor is provided for delivering the aggregate to the drum dryer at a predetermined feed rate by weight, and a weigh belt conveyor is provided for delivering the recycle material into the elevator at a predetermined feed rate by weight.

Asphalt plant adapted for the batch production of asphalt mix containing

An asphaltic mix batch apparatus which comprises a tower which mounts a number of aggregate storage bins, a weigh hopper underlying the storage bins, and a pugmill underlying the weigh hopper. Also, a screen assembly is positioned above the bins for segregating the aggregate by size, and such that the initial bin receives the more fine aggregate and the subsequent bins receive the more coarse aggregate. The initial bin has a relatively wide open top, and it receives a relatively broad gradation of the aggregate from its front to its back, with the front being disproportionately fine and the back being disproportionately coarse. A divider plate is positioned in the initial bin to prevent the gradation from interfering with the free discharge of the aggregate when the associated discharge port is opened, and to thereby provide a more uniform gradation being withdrawn through the discharge port.

Growing community of inventors

Chattanooga, TN, United States of America

John Milstead