JPS6233364B2 - - Google Patents

Description

Detailed Description of the Invention The present invention provides a composition of asphalt and aggregate that is recirculated by heating and mixing the asphalt concrete used in a rotatable drum supplied with flame and high-temperature combustion gas. The present invention relates to a method and apparatus for manufacturing products.

No. 3,999,743 of the present assignee discloses a method and apparatus for recycling a spent asphalt, aggregate composition, which is comminuted and separated into different particle size ranges. This particular method involves introducing particles of coarse and fine asphalt and aggregate composition into a rotatable drum, in which they are directly exposed to flames and the hot gases of combustion. Including introduction into a separate heating zone. Because fine to small particles of asphalt-containing compositions are more easily heated than coarser particles, the small particles prevent the asphalt from degrading by burning and overheating, thereby reducing significant smoke and other It is introduced into the drum in a cold area so as to prevent the formation of undesirable contaminants.

It is an object of the present invention to provide a method that further improves the reduction of air pollutants generated during heating of asphalt, aggregate compositions during recycling processes. The present invention introduces asphalt-free aggregate particles into the hot region of a rotating drum, thereby exposing the aggregate directly to the hot gases of flame and/or combustion and recirculating the asphalt, aggregate composition. into one or more cold regions of the drum;
This includes preventing overheating of the recycled raw asphalt.

Referring to the figures, a rotatable dryer-type drum 10 having an outer cylindrical cover or surface 13 surrounding a hollow inner drum chamber, a stationary inlet end wall 47, and a stationary outlet end cover 45.
It is shown. A plurality of elongate lifters or vanes 18 are secured to the inner surface of the drum and extend substantially the length of the interior of the drum. The purpose of the lifter is to lift the aggregate and asphalt-containing composition as the drum rotates to facilitate mixing.
The raw material then cascades from the rising lifter and falls by gravity to the bottom of the rotating drum during the mixing and heating operations. The drum preferably has an inlet end 1
The drum is tilted as shown so that the aggregate introduced from 6 is progressively fed by gravity to the outlet end 17 of the drum.
The inlet end is therefore elevated relative to the outlet end. The degree of slope can be varied to change the rate at which the material flows through the drum.

The device comprises a device for rotating the drum (not shown), for example a motor or other drive, and a sprocket extending around the drum surface 13 to which is fixed a chain meshing with gears. The drum is supported on rollers and a suitable frame.
The specific apparatus for rotating and supporting the drum is not part of this invention and is within the skill of the art. In this device, the hot gases of combustion produced in the burner 12 are sent into the interior of the drum. The stationary outlet end cover 45 has a port 42 at its bottom through which the heated and mixed composition is withdrawn. The final composition simply falls through the port onto conveyor 38. Other equivalent product recovery equipment is available and the one shown is
Just an example. Both the inlet end wall and the outlet end cover are at least slightly spaced from their respective drum end surfaces so as not to inhibit rotation of the drum. A vent chimney 50 is located at or adjacent to the top of the outlet end cover and includes an exhaust fan 48 that draws hot gases from the burner 12 through a drum and forces them into the chimney for exhaust to the atmosphere. Collaborate.
Alternatively, the gas and the trapped dust can be sent to a dust collector or knock-out box that cooperates with the conduit. Other features of this device are disclosed in the above-mentioned patent applications, the relevant parts of which are described here for reference.

An important improvement in the method and apparatus of the present invention lies in the manner in which the aggregate and recirculated asphalt compacted particles are introduced into the heated mixing drum, the improved and advantageous results being thereby achieved. You can get it. By introducing the asphalt-containing recirculating particles into the colder region of the equipment compared to the hotter region where the aggregate particles are introduced, heating efficiency is improved and asphalt degradation is significantly reduced and improved, if not eliminated. It has been found that an air pollution problem based on smoke, unburned hydrocarbons, toxic gases and fumes emitted into the atmosphere is eliminated.

As shown, typically aggregate particles 25 of fresh aggregate
is delivered to the drum 10 at the inlet end 16 just inside the end wall 47 and is directly exposed to the hot gases from the burner 12 in the hottest drum first region.
The aggregate is heated by a flame having both a light-emitting part and a non-light-emitting part caused by combustion in the burner 12, radiant energy, and high-temperature gas.
is any suitable conventional oil or gas fired type that produces a flame and hot gases that are directed into the interior of the drum through a suitably located orifice funnel or opening in the inlet end wall 47. In this hot area of the drum, the ambient temperature is e.g.
It may be 1649°C (approximately 1000-3000°C), or even higher depending on the size and power of the burner as well as the distribution of the flame and hot gas. After being lifted along the inner surface of the drum, the aggregate particles fall or cascade through the hot gas, during which time they are gradually heated and advance toward the exit end of the drum.

Also as shown, recycled asphalt,
The aggregate particles 35 are introduced into a cooler second region a distance forward from the inlet end downstream or towards the outlet end of the device. The specific temperature of the low temperature region is
It depends on the power or capacity of the burner used in the device as well as the distance from the burner at which the asphalt-containing particles are introduced. The second region is cooler not only because of its distance from the burner 12, but also because the shielding of the aggregate particles that cascade in the hot region forms a heat sink such that the temperature of the hot gases is significantly reduced; This is because the asphalt-containing particles are exposed to the radiant energy of the flame. Although the second region is cooler than the hot region at the inlet end, the asphalt and aggregate particles are sufficiently heated by being exposed to the hot gas passing through this region and being mixed with the heated aggregate. be done. As the drum rotates, the asphalt-containing particles are lifted and then cascaded to mix with the heated aggregate particles coming from the hot area.

The preferred temperature in the second low temperature region is approximately 427°C (800°C).
〓) Below. High temperatures are preferably avoided so as to prevent combustion of the more easily heated fines, which usually contain significant amounts of asphalt.
The fines are small asphalt-containing particles of recycled crushed asphalt compacted material;
It passes through a US series No. 8 sieve and often accounts for about 20 to 60% by weight of the recycled composition. When there is a significant amount of fines, especially when the size of the fines particles is very small, it is desirable to introduce the asphalt-containing particles into the cold region at temperatures even lower than 316°C (600°C). The temperature of a particular cold region therefore depends on the size and amount of fines present.

Although one cold region is illustrated, two or more separate regions may be used to introduce particles of recycled asphalt-containing composition, each near the inlet end. It is cooler than the next adjacent region. Therefore, any number of multiple regions or locations for introducing the asphalt, aggregate composition particles may be used, depending on practical considerations of the construction of the equipment and the separation and handling of different particle sizes desired. It is recognized that it is good. One cold zone may be sufficient, but two cold zones may be used, the first for coarse asphalt, aggregate particles and the second to introduce fine particles. It is also an area of low temperature. Such multiple low temperature regions, along with the separation of different asphalt-containing particle size ranges, are described in the above-mentioned U.S. patent.
Described in No. 3999743. Furthermore, if the device has a device for introducing the composition into more than one zone, only two zones are actually required to be used. The distance between the inlet end wall 47 and the second region fed by the chute 24 as shown is for illustrative purposes only, as the specific distance between the regions will depend on the burner capacity, particle size. However, it is not a restriction. Therefore, the distance between the regions is selected to achieve the desired temperature in each region.

The amount of aggregate added in a recirculation process depends on several variables. It is understood that depending on the specifications and requirements of the paving or surfacing job, the final product will typically have from about 80 to 95% aggregate by weight, and typically any amount of aggregate, for example about 50% by weight. Or more aggregate may be used if desired. Combining fresh aggregate and asphalt in this way yields a high proportion of new mixture, so the amount of aggregate used depends on the amount of recycled composition available and its age. typically depends on available aggregates, price requirements, and air pollution regulations at the site or plant location.

The aggregate or recycled asphalt, aggregate particles are introduced in any suitable manner, such as a chute or hopper. A funnel chute 30 is conveniently used on a stationary inlet end wall to collect aggregate particles 2.
5 is introduced via conveyor 46. The particles are
As it falls through the hot flame of burner 12 and the combustion gases, it passes through an opening in end wall 47. In contrast, a scoping device is shown which is fixed to the outside of the drum and cooperates with a trough into which the composition is charged, so as to introduce aggregate and/or asphalt, aggregate particles into the drum cold region. has been done. As shown, the trough 36 is stationary and positioned around the rotating cylindrical drum 10. a plurality of spaced ports 20 are located around the drum surface;
It opens into the inside of the drum and communicates with the outside of the drum.
The scoop 31 is located above each port 20 and is fixed to the outside of the drum, and has a cavity communicating with the port;
and an edge having a surface that engages the composition during rotation of the drum. A trough 36 extends around the drum over the scop sp and forms a cavity in which the scop is located and through which the drum is rotated.
The chute 24 communicates with a trough 36 so that the composition particles introduced into the trough via the chute are then picked up by the scoop and fall by gravity into the interior of the drum via the port 20. The dimensions and shape of the trough must be such that the scoop can pass through it without resistance and pick up the composition particles introduced into the cavity of the trough. The sides of the gutter are preferably
It has an edge that follows the general shape of the outside of the drum it encloses, which edge is shaped as the drum rotates while the trough remains stationary.
At least slightly spaced from the drum surface to prevent contact. The device for introducing the particles into the gutter, eg via chute 24, is not particularly critical and any convenient device may be used. For example, a conveyor device 22 as shown may direct the composition particles to a chute 24, which is then routed to a hopper and trough.

The dimensions and shape of the scoop and gutter are not particularly critical, but preferably the outer edge of the scoop is
It is formed to have the same shape as the inner wall of the gutter, but slightly smaller. The scope tip is also preferably tilted so that particles easily fall along the inside of the scope tip into the port by gravity. Further details of scoops, ports, and troughs for use in cold regions are described in U.S. Pat. No. 4,034,968, a description of which is incorporated herein by reference. However, any device may be used to introduce the particles into different areas, such as one extending from the outlet end through the outlet end cover 45 into the drum.
or more conveyors may be provided. Accordingly, the device is not critical and what is shown is for illustrative purposes only.

The device may include one or more tubes 14 with one or more openings 15 or similar devices for charging the asphalt into the drum. The asphalt is preferably heated to a more liquid consistency as it is fed through such a tube and sprayed onto the particles in the drum to obtain the desired asphalt-aggregate product properties. . The asphalt is preferably used in the burner 12 so as to prevent possible combustion or deterioration thereof.
is added to the heated granular mixture at a distance from the forward outlet end. However, the asphalt is thoroughly mixed into a compositional mixture of recycled asphalt and aggregate, which is gradually conveyed to the outlet end as it cascades and tumbles in an inclined rotating drum. must be introduced far enough into the drum to This distance, as well as the quality of the asphalt, can be easily determined in the art. Of course, the amount of asphalt added will depend on the ratio of aggregate to recycled asphalt-containing feedstock being mixed, with higher amounts of aggregate requiring more asphalt. Preferably, the tube and asphalt outlet opening 15 extend into the drum so as to discharge the liquid asphalt adjacent to the point where the asphalt-containing particles are introduced, as shown. Also, the asphalt is preferably added far into the drum so that proper mixing is effectively provided prior to the composition being recovered at the exit end. Tube 14 may be extendable to different lengths to provide flexibility in discharging liquid asphalt to different predetermined locations.

The resulting composition that is recovered is at a temperature of at least about 93°C.
(200〓), preferably 107°C (225〓) or higher. The desired temperature is obtained by varying the pitch or inclination of the drum, the rotational speed of the drum, the heating of the burner, and the raw material charge ratio. If desired, aromatic hydrocarbon softeners may be used in the final product, as disclosed in US Pat. No. 4,000,000. The flexibility of this method and apparatus, as well as other modifications within the scope of this invention and its advantages, will be apparent in the art.

[Brief explanation of the drawing]

The drawing shows a partially cut away elevational view of an apparatus according to an embodiment of the invention. 10...Dryer type drum, 12...Burner,
13... Cylindrical cover of the drum, 14... Asphalt charging tube, 20... Port, 24... Chute, 25... New aggregate particles, 30... Funnel chute for aggregate, 31... Scot tip , 35...Recirculating asphalt, aggregate particles, 36...Gutters.

Claims (1)

[Claims] 1. Introducing asphalt-free aggregate particles into a hot region of a rotatable drum, gradually heating the aggregate and sending it toward the drum exit end, so that the high temperature region is injected into the drum. asphalt comprising introducing particles comprising a mixture of asphalt and aggregate in a downstream cold region and gradually mixing and heating said aggregate into said mixture of asphalt and aggregate to produce an asphalt concrete composition. Method of manufacturing concrete compositions. 2. The method according to claim 1, comprising the step of adding and mixing asphalt to the composition in the low temperature region. 3. The method of claim 1, comprising the step of supplying hot gases of combustion into the drum, thereby exposing the aggregates directly to the gases. 4. The method according to claim 1, wherein the mixture of asphalt and aggregate includes the asphalt and aggregate composition used. 5. The asphalt and aggregate mixture is introduced into the drum through radially extending ports, such that the asphalt-free particles in the hot area are shielded from the asphalt and aggregate particles in the cold area. A method as claimed in claim 1 for forming. 6 (a) an elongated rotatable drum having an inlet end and an outlet end opposite thereto; (b) a length of the drum from the inlet end to the outlet end for supplying the drum with hot gases of combustion at said inlet end; (c) feeding particles of asphalt-free aggregate to the drum in a hot region, thereby: (d) introducing solid particles used in asphalt concrete having a mixture of asphalt and aggregate into the drum in a low temperature region to heat the asphalt concrete in the low temperature region; An apparatus for producing asphalt and aggregate compositions, comprising: a second apparatus for direct exposure to gas; and (e) a apparatus for recovering the heated and mixed composition at the outlet end. 7. The manufacturing apparatus according to claim 6, further comprising a device for introducing asphalt into the drum in the low temperature region. 8. The manufacturing apparatus of claim 6, wherein said second apparatus comprises a radial port of said drum. 9. The manufacturing apparatus of claim 8, wherein the second apparatus comprises a plurality of inlet ports extending around the outside of the drum and communicating with the interior of the drum. 10 comprising a plurality of scoops each fixed to the outside of the drum and overlapping one of the ports, and a trough extending around a portion of the outside of the drum to receive the mixture of asphalt, aggregate particles; 9. The apparatus of claim 8, whereby said scoop moves along said trough to pick up said particles and introduce said particles into said drum through said port.