GB2234052A

GB2234052A - Aggregate dryer

Info

Publication number: GB2234052A
Application number: GB8908018A
Authority: GB
Inventors: Katsuhiko Nishio
Original assignee: Nikko KK
Current assignee: Nikko KK
Priority date: 1988-06-14
Filing date: 1989-04-10
Publication date: 1991-01-23
Anticipated expiration: 2009-04-10
Also published as: CH677528A5; DE3912012A1; FR2632715A1; DE3912012C2; JPH01315502A; GB8908018D0; SE508395C2; SE8901095L; FR2632715B1; GB2234052B; AT397807B; SE8901095D0; ATA90689A; JPH0515844B2

Abstract

An internally bladed elongate inclined rotary drum 14 for a dryer 10 of an asphalt plant is partitioned at 26 into the cold hopper side 30 (upper rear section) and hot hopper side 30 (lower front section). Duct 28 extends through partition 26 to convey hot gases from one section to another. New aggregate feed holes 38 and waste material discharge holes 40 are provided in the circumferential walls of the drum below and above position 26 respectively, with a common non-rotary cover housing 42 around their peripheries. A new aggregate feeder 44 above cover 42 selectively feeds new aggregates into the feed holes 38 until they discharge from the new aggregate discharge part 24 a waste (recycle) material removal discharge port 50 at the base of the cover 42 selectively discharges the recycle materials fed into the rear upper section of the drum and escaping through the discharge holes 40. If port 50 is shut, recycle materials accumulates within the cover 42, eventually being taken up by holes 38 to be part of the material laid. Thus new aggregate only, or a mixture of new and recycled, can be laid as desired. <IMAGE>

Description

1 Dryer of Asphalt Plant The present invention relates to a dryer for

heating the aggregates of an asphalt plant for manufacturing asphalt mixtures used as a road paving material. More particularly. it relates to a dryer of an asphalt plant capable of heating both new aggregates and waste asphalt paving materials.

Waste asphalt paving materials from road construction and the like (hereinafter referred to as "waste material") are conventionally reheated and reclaimed for reuse. In general. a dryer having more or less the same construction as that used for heating new aggregates of an asphalt plant is employed. The heating dryer for waste material is thus frequently constructed together with the new aggregate dryer of the asphalt plant.

However. when the new aggregate dryer and the waste material dryer are constructed on the same site, construction and arrangement of the system can be complicated and the site area cannot generally be used with maximum efficiency.

It is a primary object of the present invention to provide a dryer for an asphalt plant. comprising:

an internally bladed elongate inclined rotary drum divided by a transverse partition into an upper rear section and a lower front section:

the upper rear section having an upper end feed hopper and lower end discharge holes in its circumferential wall and the lower front section having upper end feed holes in its circumferential wall. and a lower end discharge hopper; a common non-rotary cover housing extending around the drum to cover both feed and discharge holes; selectively operable feed supply means for the feed holes and selectively operable discharge removal means for the discharge holes being located generally above and generally below the cover housing respectively:

heat-supply means at the lower-end discharge hopper:

and a duct for passage of hot gases extending from intermediate the length of the lower front section through the partition and just into the lower end of the 1 4 3 upper rear section: whereby, as desired. (a) fresh aggregate can be selectively supplied through the feed holes. heated. and discharged from the lower end discharge hopper. (b) recycled aggregate or a mixture of fresh aggregate and recycled aggregate can be supplied through the upper end feed hopper. heated, and. selectively. either removed from the discharge holes for further recycling by opening the removal means or caused to accumulate within the lower housing by closing the removal means. and consequently to enter the feed holes for eventual discharge, in admixture with any new aggregate also fed through the feed holes, from the lower end discharge hopper.

As long as the discharge removal means under the cover is opened. and the hot air generated by the aggregate heating burner disposed at one end of the drum is fed into the drum to pass through the front half section of the drum. a portion of the hot air can readily be guided to the rear section and out to the cold hopper at the other end of the drum.

The new aggregates fed from the new aggregate feeder at the upper portion of the cover are guided into the drum through the new aggregate feed holes opened in the drum so as to be subjected to heat exchange with the hot air while being rolled and rendered fluid in the front 1 4 half section of the drum on the burner side to the desired temperature. and discharged from the new aggregate discharge port under the hot hopper.

The waste i.e. recycle materials can be fed into the cold hopper, heated to the desired temperature by the hot air passing through the cylinder, rolled and rendered fluid within the rear half section of the drum and discharged from the waste material discharge port under the cover through the waste material discharge holes near the center of the drum.

When heating only new aggregates, these can be fed from the cold hopper with the discharge gate closed to prevent the aggregates from flowing out from the waste material discharge port. and heated in the rear half section of the drum so as to drop through the waste material discharge holes but be sent toward the burner side in the cover as being accumulated in the lower portion thereof of the cover. They are in such an instance transferred to the front half section of the drum through the new aggregate feed holes. heated to the desired temperature while being rolled and rendered fluid in the front half section of the drum. and discharged from the new aggregate discharge port under the hot hopper.

t Thus, both new aggregates and waste (recycle) asphalt materials can be heated simultaneously by one dryer. or the respective materials can be heated independently. This results in a compact system. Construction and arrangement of the system can be simplified and space can be saved.

Preferably, the upper end feed hopper and/or the cover housing have exhaust gas flues.

With this arrangement. an exhaust fan on the end of the exhaust gas flue connected to the cold hopper i.e. upper end feed hopper. can exhaust both this gas and passing through feed or discharge holes into the cover.

In the dryer of the asphalt plant. it is preferred for the feed holes and the discharge holes to be arranged at constant intervals in two separate rows.

Smooth feeding of new aggregates-and discharging of waste materials from the cover housing are thereby facilitated. and the new aggregates can also be transferred smoothly from a the upper to the lower section via the the cover.

Preferably, a plate for adjusting a flame is installed to cover the lower end of the duct extending through the partition. and/or a damper plate for 4 6 adjusting air flow passing through such a duct is installed at the upper end thereof.

The hot air temperature can thereby be regulated by adjusting the burner flame properly by the shield plate, and the hot air temperature and flow to the rear half section of a drum can be regulated by adjusting the damper of the cylinder, to heat the materials suitably.

The present invention will be further described with reference to the accompanying drawings, showing preferred embodiments in which:

Figure 1 is a partially cutaway diagrammatic front view of one embodiment of a dryer of the present invention.

Figure 2 is an enlarged sectional view taken along the line A-A of Figure 1, Figure 3 is an enlarged sectional view taken along the line B-B of Figure 1. and Figure 4 is a section of another embodiment of a dryer of the present invention.

k 7 Figure 1 to Figure 3 show one preferred embodiment of the present invention, and like numerals refer to like parts. A dryer 10, for heating new aggregates and waste materials, comprises an elongate inclined rotary cylindrical drum 14 provided with a number of lifting blades 12 disposed in circumferentially extending groups at its inner surface. The drum 14 is supported rotatably by support rollers 18 on bases 16 to lie at a small angle to the horizontal. and is rotatable at a predetermined speed by a driving unit (not shown). A hot lower end discharge hopper 20 is disposed at one end of the drum. and an aggregate heating burner 22 is installed thereon to send hot air into the drum 14, at the lower portion thereof. A new-aggregate discharge port 24 for discharging the heated new aggregates is located at the lower end of the hopper 20.

Generally near the center portion of drum 14 is secured a transverse parting plate 26 to partition the drum into a front and rear section. Cylindrical duct 28, of suitable diameter for guiding part of the hot air supply from burner 22 to the rear section of the drum is provided to extend along the front section of the drum 14, starting near the burner 22 and passing through the parting plate 26 at its other end. Part of the hot air is sucked into the cylinder duct 28 and thence to the upper rear section of the drum by an exhaust fan 34 at 1 4 8 end of an exhaust gas flue 32 connnected via a cold upper end feed hopper 30 to the drum end. Shield plate 36 may be mounted at the burner end of cylinder 28. for additional hot air control.

Suitably spaced feed holes 38 for new aggregate. and suitably spaced discharge holes 40 for waste material are provided in two rows around the drum walls. one row to either side of the parting plate 26. The holes 38, 40 are surrounded peripherally by a cover 42 which is fixed, i.e. does not rotate with the drum 14.

Chute 44. for feeding new aggregates. is disposed at the upper part of the cover 42. The front end of the chute 44 extends to reach the feed holes 38 to feed the new aggregates into the drum 14. Guide chutes 46 are installed one on each hole 38 (as shown in Fig. 2) to facilitate smooth feeding of the new aggregates into the drum 14.

Waste material removal discharge port 48 at the lower portion of the cover 42 receives extending waste material from discharge ports 40. It is provided with a discharge gate 50. so that the waste material can be gravity discharged to the outside. If the discharge gate 50 is closed. part of the material in the rear section of the drum accumulates in the waste material r 1 9 discharge port 48. Eventually. it becomes transferred to the front section of the drum, through the new-aggregate feed holes 38, rising up via the guide chutes 46.

An exhaust gas bypass 54 is connected to the cover 42 and to the exhaust gas flue 32 connected to the cold hopper 30.

Numerals 56. 58, 60. 62 and 64 generally indicate air flow adjusting dampers. which are controllable at suitable openings. When the exhaust fan 34 is operated. the hot air flow sent from the burner 22 is split. Part of the hot air is led to the rear section of the drum. through the cylinder 28, while still hot and, via a dust collector 66, the cold hopper 30 and the exhaust air flue 32 is exhausted to the atmosphere. The other part of the hot air is led through the front half section of the drum without entering the cylinder 28. and is guided to the exhaust air flue bypass 54 from the newaggregate feed holes 38. being introduced into the dust collector 66 through the exhaust air flue 3?.

Numerals 68a 68d indicate aggregate hoppers for storing new aggregate separately in various particle sizes. The new aggregates, taken out from the aggregate hopper by take-out feeders 70a 70d in a 1 -X predetermined ratio, are fed to the new aggregate chute 44 via conveyors 72 and 74.

Numerals 76a - 76b are waste material hoppers for storing the waste materials separately in various particle sizes. The waste materials. taken out from the waste material hoppers by take-out feeders 78a, 78b in a predetermined ratio, are fed into the drum 14 via conveyors 80 and 82. When heating only new aggregates i.e. those stored in the aggregate hoppers 68a 68d, as for a start-up situation. a separate conveyer (not shown) is interposed between the conveyer 72 and conveyer 82 (as indicated by dotted lines) so that conveyer 82 can be fed and the cold hopper 30 filled to allow effective.heating throughout.

When new aggregates and waste materials are heated simultaneously, with the discharge gate 50 open and the hot air introduced into the drum 14 by the burner 22, the new aggregates (taken out in a predetermined ratio from the aggregate hoppers 68a - 68d and stored in their various particle sizes) are fed to the new aggregate chute 44 near the center portion of the drum 14 via the conveyors 72 and 74, fed into the drum 14 from via feed holes 38 so as to be heated to the desired temperature while being rolled and rendered fluid in the front half section of the drum 14, and discharged from A i 11 the discharge port 24 at the bottom of the hot hopper 20.

Also. a predetermined quantity of waste materials is taken out by the take-out feeders 78a, 78b from the waste material hoppers 76a. 76b. The waste materials are stored separately in various particle sizes. and fed via the conveyors 80 and 82 into the drum 14 from the cold hopper 30. The waste materials which are rolled and rendered fluid in the rear section of the drum are heated to the desired temperature by the hot air introduced into the rear section of the drum at high temperature through the cylinder 28. dropped through the waste material discharge holes 40 and discharged from the waste material discharge port 48 at the bottom of the cover 42.

If only new aggregates are heated the discharge gate 50 of the waste material discharge port 48 is closed near the center portion of the drum 14 to prevent the aggregates from flowing out from the waste material discharge port 48. The new aggregates taken out from the aggregate hoppers 68a - 68d (and stored separately in various particle sizes by the take-out feeders 70a - 70d) are fed to the cold hopper 30 by switching the feeding direction from the conveyer 72 to the conveyer 82 by a separate conveyor (not shown) as indicated by the dotted lines. The new aggregates fed are folled and 1 k 12 rendered fluid in the rear section of the drum. When they arrive near the center portion of the drum 14, they are sent transversely toward the burner side in the cover 42 from the waste material discharge holes 40 in the circumferential wall of the drum 14, then pass up by the guide chutes 46 and finally transfer to the front section of the drum from the new aggregate feed holes 38. In the drum they are heated to the desired temperature while being rolled and in the front half section of the drum, and discharged from the new aggregate discharge port 24 at the bottom of the hot hopper 20.

It will be appreciated that the temperatures of the new aggregates and waste materials are controlled by the combustion capacity of the burner 22. openings of the air flow adjusting dampers 56 - 64 and feed quantities of respective materials.

As described heretofore, in the present invention. the new aggregates and waste materials can be heated simultaneously or independently. and not only the system can be made compact. but also the constructions and arrangements of the system are all simplified. saving the site area.

Figure 4 shows features of an alternative embodiment f 4.

13 of the present invention.

In the embodiment, a cap-shaped damper 84 for adjusting the hot air flow is mounted, on the cold hopper side, to the end of the cylinder 28. It can be adjusted freely in an open-and-close fashion. The damper 84 is mounted on a driving shaft 86 supported at its center between the side of cylinder 28 and the cold hopper 30 as shown in the figure. The driving shaft 86 is adjustible to open and close the damper by an opening drive cylinder 90 via a universal coupling 88. A driving shaft protecting cover 92 and a thrust bearing 94 complete the assembly.

In this embodiment the hot air flow to the rear section of the drum can be controlled particularly sensitively by the hot air flow adjusting damper.

Various embodiments have been described above to aid the understanding of the invention. Variations may be made by one skilled in the art without departing from the scope of the appended claims.

14

Claims

CLAIMS:

A dryer for an asphalt plant, comprising an internally bladed elongate inclined rotary drum divided by a transverse partition into an upper rear section and a lower front section:

the upper rear section having an upper end feed hopper and lower end discharge holes in its circumferential wall and the lower front section having upper end feed holes in its circumferential wall. and a lower end discharge hopper; a common non-rotary cover housing extending around the drum to cover both feed and discharge holes:

selectively operable feed supply means for the feed holes and selectively operable discharge removal means for the discharge holes being located generally above and generally below the cover housing respectively:

heat-supply means at the lower-end discharge hopper:

and a duct for passage of hot gases extending from intermediate the length of the lower front section r 1 is through the partition and just into the lower end of the upper rear section: whereby, as desired, (a) fresh aggregate can be selectively supplied through the feed holes. heated. and discharged from the lower end discharge hopper. (b) recyled aggregate or a mixture of fresh aggregate and recycled aggregate can be supplied through the upper end feed hopper. heated. and. selectively. either removed from the discharge holes for further recycling by opening the removal means or caused to accumulate within the lower housing by closing the removal means. and consequently to enter the feed holes for eventual discharge. in admixture with any new aggregate also fed through the feed holes, from the lower end discharge hopper.
2. A dryer for an asphalt plant as claimed in claim 1, wherein the upper end feed hopper and/or the cover housing have exhaust gas flues.
3. A dryer for an asphalt plant as claimed in claim 1 or 2, wherein the feed holes and the discharge holes are arranged at constant intervals in two separate rows.
4. A dryer for an asphalt plant as claimed in any one preceding claims wherein a plate for adjusting a flame is installed to cover the lower end of the duct extending through the partition.

-f AL 16
5. A dryer for an asphalt plant according to any one preceding claim wherein a damper plate for adjusting the air flow is installed to cover the upper end of the duct extending through the partition.
6. A dryer as claimed in claim 1 and substantially as herein described with reference to the accompanying drawings.

1 Publish d 1991 atThe Patent Office. State House, 66/71 High Holbom. LondonAVC11147P. Further copies Tn2y be obtained from ea Sales Branch. Unit 6. Nine Mile Point Cwrnfelinf2ch. Cross Keys. Newport. NPI 7HZ. Printed by Multiplex techniques ltd. St Mary Cray. Kent.