WO2003093144A2

WO2003093144A2 - Conveyor with heat transfer arrangement

Info

Publication number: WO2003093144A2
Application number: PCT/US2003/012995
Authority: WO
Inventors: Richard W. Kauppila; Raymond W. Kauppila
Original assignee: Individual
Current assignee: Individual
Priority date: 2002-04-29
Filing date: 2003-04-28
Publication date: 2003-11-13
Anticipated expiration: 2004-10-29
Also published as: CA2485686C; CA2485686A1; AU2003239181A1; US20040055738A1; WO2003093144A3; AU2003239181A8

Abstract

A conveyor (10) for moving hot or cold material along a trough (12) receiving the material. One or more heat transfer fluid flow tubes (36) extend over the outer surface of a trough liner wall (38) to indirectly cause cooling or heating of the liner wall (40). A series of wear plates (76) are clamped to a pushing side of a helical tube (74) of an auger type conveyor (52), which tube can also receive a flow of heat transfer fluid. A mass (92) of conductive beads can alternatively be used to transfer heat into or from the heat transfer fluid.

Description

CONVEYOR WITH HEAT TRANSFER ARRANGEMENT

Background of the Invention

This invention concerns conveyors and more particularly, conveyors such as

auger or recirculating chain flight conveyor used to convey hot (or cold) crushed or granular material, such as in cement plants, lime kilns, coal clinkers from power plants, etc.

Conveyors for such hot materials have in the past had short service lives and were prone to

failure. This is because of the effect of the high temperatures reached by the conveyor parts

as a result of conduction of heat from the conveyed material. Such conveyors have sometimes incorporated liquid cooling j ackets within a conveyor trough along which the hot

material is conveyed by an auger extending along the length of the trough. The trough and

jacket have been constructed as a weldment, and since the cooled liner is in direct contact with the hot material conveyed, the trough is severely stressed by gross thermal expansions

and contractions . The resulting expansion and contraction of the trough and coolant j acket leads

to cracking, buckling, weld failures and similar structural failures. Since very hot material is conveyed liquid in direct contact with the cooling j acket wall is heated to boiling, so that

vapor is generated in the jacket, greatly reducing the rate of heat transfer into the cooling

liquid. Since the trough cooling jacket is constructed as a weldment, it often is not

designed or approved for use as a pressure vessel, allowing only very low coolant pressures

and flow rates. Similarly, conveying augers have also often been constructed as a weldment,

with a central tube having radial spokes welded to a central tube forming a triangular cavity.

Liquid coolant has sometimes been circulated through such a screw, with direct contact of the coolant in the metal screw in direct contact with the hot material conveyed, leading to the same problems described above in connection with the conveyor trough.

Direct air cooling of the hot material requires dust collection equipment and

baghouses and necessitates government permits, as pollutants may be mixed with the

exhausted cooling air. Similar problems exist where a cool material is to be heated to elevated

temperatures during the passage through the conveyor.

It is an object of the present invention to provide a liquid cooled conveyor for

hot material of the type described, in which direct contact of coolant with the structure

defining a confinement of the hot material is avoided. It is a further object to provide a conveyor which avoids the use of a weldment

structure subjected to thermal stresses induced by a large temperature differential between the conveyor and the material conveyed, and uses material that are capable of withstanding such

thermal stresses . Yet another obj ect is to provide a conveyor having heat exchange fluid

passages which can withstand high ^'pressures, and pass a high velocity flow of a heat transfer

liquid to improve the heat conduction capacity of the unit.

Summary of the Invention The above objects as well as other objects which will be understood upon a reading of the following specification and claims are achieved by a conveyor including a

trough, with separate heat transfer fluid flow pressure vessels passing over an outside trough

surface. The fluid flow vessels may be supported on an outer structural trough wall by heat conducting connections such as interposed heat fins, angled metal strips and curved thin metal standoffs, or conductive beads (aluminum or other) metal filling the air space.

Optionally, air flow can be established over the fluid flow vessels, fins or beads to enhance the cooling (or heating) effect.

Alternatively, noncontact cooling methods are employed including cooling fins attached to the trough, interposed metal beads, or high temperature heat conducting

mediums.

The heat transfer fluid flow vessels can be arranged in longitudinal or

transverse loops or longitudinally extending straight sections can also be used, supplied with

a heat transfer liquid from a manifold at one end of the conveyor trough.

A helical auger tube used in an auger conveyor is constructed with mechanical connections to radial spokes to avoid thermally stressed welds. A side-to-side series of

clamp-on wear plates of a durable material can be installed on the pushing side of the helical

auger tube to prevent excessive wearing of the auger tube. Optionally, a heat transfer fluid can also be circulated through the helical auger tube, or a second tube can be inserted in a

larger outer helical tube with fins or beads, conducting the heat between the outer tube and

the heat transfer fluid in the inner tube.

Description of the Drawings Figure 1 is a perspective view of an auger conveyor according to the present

invention showing a portion of a helical tube auger included in the conveyor in broken lines.

Figure 2 is an enlarged partially broken away end view of the conveyor shown

in Figure 1. Figure 3 is an end view of the conveyor of Figure 1, with the trough outer wall partially broken away and showing further details of a coolant flow tubing installation for the trough.

Figure 4 is an end view of the conveyor with the outer wall broken away

showing another form of coolant flow tubing installation for the trough.

Figure 5 is a perspective partially fragmentary view of another embodiment of

the conveyor according to the present invention.

Figure 6 is an enlarged fragmentary perspective view of one end of the conveyor shown in Figure 5 with the outer wall of the trough partially broken away.

Figure 7 is an enlarged perspective view of the end of the conveyor shown in

Figure 5 with both walls of the trough partially broken away to show the helical tube auger.

Figure 8 is a fragmentary perspective view of the helical tube auger shown in Figure 7 with a single wear plate shown in solid lines and a phantom line depiction of the

entire series of wear plates. Figure 9 is an enlarged transverse section taken across the helical tube auger

and clamp on pusher blade of the type shown in Figure 7. Figure 10 is an enlarged transverse sectional view across a square section form

of the helical tube auger. Figure 11 is an enlarged transverse sectional view of a trough coolant tube of

the type shown in Figure 7. Figure 12 is a sectional view of an inner round tube nested within a round outer tube using an interposed mass of beads as the heat transfer medium.

Figure 13 shows an outer square tube having an inner tube carrying a heat transfer fluid, and with a mass of heat conductive beads interposed. Figure 14 shows a double walled conveyor trough having a mass of interposed beads as a heat transfer medium.

Figure 15 is a diagram showing the relationship between thermal conductivity and the void space defined within a mass of heat conductive beads.

Detailed Description

In the following detailed description, certain specific terminology will be

employed for the sake of clarity and a particular embodiment described in accordance with

the requirements of 35 USC 112, but it is to be understood that the same is not intended to be limiting and should not be so construed inasmuch as the invention is capable of taking many

forms and variations within the scope of the appended claims.

Referring to the drawings and particularly Figure 1 , a conveyor 10 is shown

which includes an inclined trough 12 provided with optional covers 14 installed except at a loading opening 16. The trough 12 is supported to be upwardly inclined by means of frame

supports 18, 20 at either end. A discharge chute 22 is at the upper end. A helically wound auger tube 24 is

disposed lengthwise in the trough 14 and rotated by a rotary drive 26. A heat transfer liquid

is typically introduced at the discharge end through an axial inlet 32 and through a side inlet 34, and exits outlets 28, 30 at the lower end of the conveyor 10.

A source 34A, 32A of heat exchange fluid such as a liquid coolant is

respectively connected with each inlet 34, 32 and a coolant recycler (such as cooling towers) may be connected with each outlet 28, 30.

Figure 2 shows further details. U-shaped loops of fluid flow tubing 36 are located between an inner trough wall 38 and an outer wall 40. The inner wall 38 is made of

heavy gauge metal to provide adequate structural support and durability as the conveyed

material is in direct contact therewith and its weight supported thereby. The outer covering

wall 40 can be of light gauge sheet metal or even mesh material as indicated.

The flow tubing 36 is supported by transverse fins 42 contacting the tubing 36,

the outside of the inner wall 38 and the outer wall 40. Thus, fluid does not directly contact

the hottest surfaces, but rather there is an indirect heat conducting connection.

The fins 42 may extend longitudinally so that an air flow can optionally be blown through the interwall space and over the fins 42, from an air source 39.

Heat transfer fluid may also be circulated through the helical auger tube 24 introduced via a rotary fluid coupling 44 into a central support tube 46 rotated by the rotary

drive 26 and supported by a rotary bearing 48 (Figure 1). Fluid is directed into the helical tube 24 via a radial support tube 50

mechanically attached to the support/drive tube 46. The support tube 46 is blocked so as to avoid circulation through the support tube 46. Outlet flow is directed out into a support tube

46 at the lower of the conveyor. Figure 3 shows another view of the trough fluid tubes showing the U-shaped

loops and inlet, the loops extending transversely to the axis of rotation of the tube 24, i.e., in circumferential directions, although occupying only a portion of the perimeter of the trough

12.

Figure 4 shows a variation in which the fluid tube loops 36A are arranged longitudinally, and the fins 42A are oriented transversely.

Figure 5 shows another form of the conveyor 52 in which an inlet manifold 58

is connected to an inlet 60 at the upper end and an outlet manifold 54 is connected to an outlet 56. A series of straight longitudinal flow tubes 62 (best seen in Figure 6) extend the length of the trough 64 in the space between a inner wall 66 and outer wall 68.

As shown in Figure 7, the tubes 62 are supported on the liner wall 66 by thin

metal straight strips 70 and curved thin metal stand offs 72 (Figure 11).

Thus, the fluid does not directly contact the hottest surfaces, i.e., the trough liner wall 66, but rather has an indirect heat conductive connection thereto. This prevents a

loss of conductivity which would result from boiling of the cooling fluid.

In order to reduce abrasion wear of the auger tube 74, a series of wear plates

76 are clamped on the pushing side of the tube 74, edge to edge along the length of the helical

tube 74 (Figure 8). The hot granular material 80 being conveyed could otherwise rapidly wear the

tube 74 depending on the material characteristics, temperature, as well as the volume

conveyed. Figure 9 shows details of the attachment clamps for the wear plates 76 which

are preferably constructed of a material such as an Nichrome alloy which is wear resistant at

elevated temperatures. A U-bolt 82 passes through a clamping piece 84 and is secured by nuts 86.

A pair of opposing legs 88, 90 on the wear plate 76 and clamping piece 84

have cut outs mating with the auger tube 74. Figure 10 shows a square section tube 74A, such that a flat wear plate 76 A and clamping piece 84A can be secured with the U-bolt 82A and nuts 86.

Both forms of wear plates 76 and 76 A can have an angled portion 94 to assist in effectively pushing the material by rotation of the auger tube 74 or 74A. The clamp-on

design avoids the problem of weld failure resulting from the high temperature experienced by the tube 74.

Figures 12-15 concern the use of an interposed mass of beads rather the fins to create a proper heat transfer path to a fluid coolant tube so as to not boil the fluid by a too

rapid transfer of heat thereinto, hi Figure 12, a round tube 88 (used for auger tube 24)

receives a smaller inner coolant circulating tube 90. An intermediate space is filled with a mass 92 of heat conducting beads to establish a heat transfer path which can be controlled by

controlling the proportion of void space, in turn varying with the bead size. The material would be selected depending on the selected design parameters, but would typically be a

durable conductive material such as aluminum. The bead size would likewise be set to

achieve the desired coefficient of thermal conductivity. A series of centering webs 94 should be provided to maintain the tubes

centered with respect to each other while being loaded with the beads. Figure 13 allows a round inner tube 96 and square outer tube 98 and centering

webs 100. Figure 14 shows a portion of a trough inner wall 102 and outer wall 104 with an intervening space filled with a mass of beads 106. Spacer webs 106 are also provided.

This is intended to produce a controlled coefficient of thermal conductivity which does not

cause boiling of the coolant and prevents the resultant loss of heat conductivity into the

coolant. Figure 15 shows the relationship between the proportion of void space and thermal conductivity.

Loosely packed spherical particles will properly conduct the heat while still

allowing relative movement without causing excessive stresses. Other shaped particles could be selected that serve the same basic purpose of controlling thermal conductivity.

The proper selection of the spherical shaped particles involves diameter,

^■ material, and relative pipe sizes. If the space were filled with particles that would

approximate air, the thermal conductivity would be very low. However, if the space were filled with very small particles, approaching a solid, the thermal conductivity would be high,

approaching that of the solid. Somewhere between these two extremes is a void ratio that would be in line with the desired heat transfer characteristics. By properly selecting the pipe

sizes, particle sizes and material and the overall geometry of the thermal screw, a desired

design should be achieved. It should be noted that with proper design of connections, forces due to

dimensional changes from thermal effects, as well as thermal stresses cause by thermal

gradients within structural members should be effectively controlled.

Claims

Claims:

1. A conveyor for handling hot materials or cold materials comprising:

an elongated conveyor trough having an inlet for receiving material to be

conveyed and an outlet whereat said material passes out of said trough; a conveyor member supported within said trough to extend along the length of

said trough, and a drive for moving said member to cause advance of material deposited in

said trough; said trough having an inner wall having an inside surface confining said

material; and one or more heat exchange fluid flow tubes extending over an outside surface

of said inner wall and having a heat conductive connection thereto, with a source of heat

exchange fluid suppling fluid to said one or more fluid flow tubes, whereby said heat exchange fluid may indirectly transfers heat to or from said trough inner wall.

2. The conveyor according to claim 1 wherein said one or more fluid flow

tubes have an array of heat transfer fins mounted thereto also in contact with said outer

surface of said trough liner wall.

3. The conveyor according to claim 1 wherein a plurality of lengthwise

extending tubes are arranged about said outside surface of said liner wall, each having a heat

conductive connection thereto.

4. The conveyor according to claim 3 wherein an inlet manifold at one end of said trough supplies fluid to all of said flow tubes.

5. The conveyor according to claim 3 wherein each of said fluid flow tubes is connected to said trough inner wall by a respective reversely angled thin metal piece

associated with each fluid flow tube.

6. The conveyor according to claim 2 wherein a single fluid flow tube is

transversely looped about said outside surface of said trough inner wall.

7. The conveyor according to claim 6 wherein said loops of said fluid

flow tube extend across said trough inner wall.

8. The conveyor according to claim 6 wherein said loops of said fluid

flow tube extend lengthwise along said trough inner wall.

9. The conveyor according to claim 1 wherein said conveyor includes a

helical auger tube located extending along the inside of said conveyor trough, and a drive for rotating said auger tube to convey material down said trough.

10. The conveyor according to claim 9 further including a series of wear

plates clamped onto a pushing side of said helical tube.

11. The conveyor according to claim 10 wherein said wear plates have an outer angled side to assist in pushing material.

12. The conveyor according to claim 10 wherein said wear plates are arranged side-to-side along the length of said helical tube.

13. The conveyor according to claim 1 wherein source of heat transfer

fluid is connected to said helical tube to be circulated along the length of said helical tube.

14. The conveyor according to claim 1 wherein an outer trough wall

overlies said at least one heat transfer fluid flow tube.

15. The conveyor according to claim 14 wherein said cover wall is comprised of an open material allowing air circulation therethrough.

16. The conveyor according to claim 14 wherein a mass of heat conductive

beads fills an intermediate space between said trough inner and outer walls.

17. The conveyor according to claim 13 wherein an outer tube surrounds

said helical tube and a mass of heat conductive beads fills an intermediate space

therebetween.

18. The conveyor according to claim 16 wherein said beads are spherical

and made of aluminum.

19. The conveyor according to claim 17 wherein said beads are spherical and made of aluminum.