US2940735A

US2940735A - Heat exchange apparatus

Info

Publication number: US2940735A
Application number: US692701A
Authority: US
Inventors: Marsh Kirtland
Original assignee: Aluminum Company of America
Current assignee: Howmet Aerospace Inc
Priority date: 1957-10-28
Filing date: 1957-10-28
Publication date: 1960-06-14
Anticipated expiration: 1977-06-14

Description

June 14, 1960 I K. MARSH I 2,940,735

HEAT EXCHANGE APPARATUS Filed Oct. 28, 1957 5 Sheets-Sheet 1 INVENTOR.

KIRTLAND MARSH I ATTOR N EY June 14, 1960 K. MARSH 2,940,735

HEAT EXCHANGE APPARATUS Filed Oct. 28, 1957 5 Sheets-Sheet 2 INVEN TOR.

KIRTLAND MARSH BY azgw ATTORN EY June 14, 1960 K. MARSH 2,940,735

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- l I 'm my 4 K92 \90 RTLfrlf li F isH 4 k I6 BY fizr/ 414-.

i j ATTORNEY K. MARSH HEAT EXCHANGE APPARATUS 5 Sheets-Sheet 4 INVENTOR. KIRTLAND MARSH jar/414b,

ATTORNEY June 14, 1960 Filed Oct. 28, 1957 June 14, 1960 Filed 001; 28 1957 5 Sheets-Sheet 5 000000000090 OOOODOOOOO D O0 9000 OOOOOOOQODO INVENTOR.

KIRTLAND MARSH Xx axzp R ATTORNEY HEAT EXCHANGE APPARATUS Kirtland Marsh, Pittsburgh, Pa., assignor to Aluminum Company of America, Pittsburgh, Pa., a corporation of Pennsylvania Filed Oct. 28, 1957, Ser. No. 692,701

2 Claims. (Cl. 257-235) This invention relates to indirect heat exchange between a fluidized, pulverulent material and a fluid medium. More particularly, it relates to novel features of construction in a fluidized heat exchange apparatus whereby great difierentials in temperature may be accommodated.

Many industrial operations require theme of heat exchangers for cooling or heating finely divided material. Various methods and types of apparatus have been devised for effecting such heat exchange, among which are the rotary cooler and the fluidized heat-transfer apparatus.

In one form of the fluidized unit, the heat transfer medium passes through the device in a plurality of tubes around which the pulverulent material flows in its fluidized state. Intermediate tube-supporting plates are employed as baflies to cause the material to flow in a sinuous path and in close contact with the tubes.

Apparatus of this type is subject to several diificulties when considerable gradients in temperature are tometal sheets employed as tube supports expand and lose.

mechanical strength, and the tubes themselves also expand, often causing buckling of the parts and rupture of the joints between thetubes and the end tube sheets.v

It is an object of this invention .to provide a fluidized States Patent great difierentials in temperature.

It is also an object of this invention to providea fluidi.

ized heat exchanger, in which heat exchange tube'sextend through transverse baffles, the baflies being maintained under tension vertically to avoid buckling thereof, and the tubes being movable endwise relative to the baflies, whereby creation of stresses in the tubes, bafiles, and end tube sheets, as a result of expansion orcontraction thereof is minimized.

It is a further object of this invention to provide a fluidized heat exchanger, in which heat exchange tubes are mounted at one end in a tube sheet which is movable longitudinally of the exchanger in response to expansion or contraction of the tubes.

A further object is to provide a simple and rugged diffusion grid for a fluidized heat-exchange apparatus,

through the apparatus, the left hand portion illustrating a flow-over baffle, the right a flow-under baffle.

Figure 5 is a sectional view of a spring assembly along the line 55 of Figure 4.

Figure 6 is a side elevational view of the structure shown in Figure 5.

Figure 7 is a top plan ponents broken away.

Figure 8 is a side elevational view of a difi-usion grid box assembly with sections of the side wall broken away.

Figure 9 is a detail view in cross-section of a joint between the interengaging, perforated topplate members of the grid assembly.

Figure 10 is a detail view of' a heat-transfer tube and baifle juncture.

Figure 11 is a side elevational view of a bafiie suspension hanger assembly.

Referring in particular to Figures 1 and 2, the heat exchange apparatus is shown as an elongated closed, vessel 1 which is provided with a porous base or diffusion grid designated generally as 2. A plurality of heat-transfer tubes 4 anchored to a wall of the hottube sheet and plenum chamber assembly 6 extend the:- length of the vessel 1 and are supported intermediately by a plurality of suspended plates or bafiies 8 (8a and 8b) which define stages of the'apparatus. At the left or cold end, the tubes 4 undergo a substantially directional change and extend upward where they are T fixed to a wall of the oscillatably mounted cold tube,

sheet and plenum chamber assembly designated generfully hereinafter.

it exits at .the discharge opening 20. a

The unit is framed by vertic al buckstays,22, longi tudinal tie members- 24 supported thereon, and horizontal cross-ties .26. The outer side walls Of: th apparatus; are 'metal sheets .28. Forming the roofof the unit are refractory slabs 30 into which are anchored transverse,

beams 32, and intermediate tie beams 34, thetransverse beams 32 resting on the longitudinal tie members 24.. Fluidizing air discharge vents 36 are provided in each stage except the last or discharge stage, and preferably connect with a dust collector system. Flared inspectionports 38 in the slabs 30 may also be provided.

Referring now to Figure 3, the oscillatably-mounted cold tube sheet and plenum chamber assembly ,10 is shown in cross-section. the cold tube sheet 40 which is pivotally-suspended, bythe posterior hanger arm 42 and the pair of anterior walls 50 .and the end wall 52 which are joinedat, their lower end to the tube sheet 40 and at their upper end'toj. the angles 48, and the cover'plate 58 which is retained between the "anglesf48. Joinedto thefside walls "50 the bottom. closure plate 60 which is also joined to' thef tube sheet 40 and the top closur'eplate 62ivhich isfalsol' joined to the angle 48. The tube sheet 4i} is peripherallyi reinforced by the box girder 46. p An expansion joint 64 fixed at one end view of a difiusion grid box assembly with fragmentary sections of various com- The tubes 4 are anchored to l v to: issus plates 60 'and62 and side walls 50, and at theo'ther' 't'o 3 the" fixed sleeve '66 accommodates longitudinal move ment; The closure plates 60'and 62 and'the side walls 50 are in telescopic engagement with the sleeve 66 which is joined to the cold air duct 68. A substantially im- '-,perineable joint-between the'body of'the-apparatus 1 and the cold'tube sheet and plenum chamber assembly- 10' is' provided: by the fiexibl e-closure sleeve 70 attached at its upper end to the girder 46 and having its lower por I don bentbacleon itself clamped between the members '71.

. Referring now to'Figure 4, a frag mentaryviewof a flow-#under tensioned-batfle 8a is shown at the right, and a fragmentary view of a flow-overtensioned .baflie 8b af-t'h'e lefti The'spring assembly 12 supports the weight of the bathe: and the portion of the'tubes' carried there-- r by, and takes up the expansion of the bathe sheet 8 through the additional upward thrust of the enclosed spring, as illustrated in detail by Figures 5 and'6. Thethreaded spring':assemblysupport members 72 are adjustably joined to the intermediate support member 74, a

from which a plurality of intermediate hangers 76 depend'which are joined to the bafiie hangers 78. The

1 b'afiie 8" is attached at'itsbase to the anchors Sty-whose base of the tangs being spaced slightly from the edge of the adjoining plate to accommodate expansion of the '7 plates. In this manner, the plates are disposed'in a V common plane and yet portions ofadjacent edges are in 10 overlapping relationship. y

As shown in Figure 10, a smallclearance is provided between the tubes 4 and the baflles 8 through which they pass, to facilitate assembly and tow provide a slidable support. r K

lower 'ends areattached to the-base of the cooler 1. The

anchors have slotted bolt holes 81 therein in which the bolts 83 carried by the bafile are'free to slide to allow' limited vertical movementof-the bathe; ,In this manner; 1 movement :of the bafile downward underthe weight of theunflu'idized material -may beaccommodated, thus preventing buckling; theslot further limits upward move-" ment under operating conditions so as to prevent stress upon the tubes, thereby preventing undue deflection.

Angle" clips 82 and angle members 84' on opposite s'id es of the bafiles 8 attached to the sides of the apparams prevent" movementYof-the baffles 8 longitudinally" 'of 'the apparatus and tendto prevent the pulverulent material from passing around the sides of the battles 8,-

' 'whiehare spaeed sjli'ghtlytfrom the'side walls so as to v l prsvrae sufiicient clearancefor'horizontalexpansion. 'Intheflow-ov enbafile 8b, a small amount of clearance is provided between its lower end and thertop' of thetdif a fusion- 50 'as td a'ccommodat'e some movementiin this'idirectionf 7 1 2' I v f The-diffusion grid :2 is constructed of a plurality'ef removable difiusion 'grid box assemblies 8'6, "shown in and SLJ 'Ihe refractory walls 104; outer netal;

casi'rigf'28 refractory 'roof slab j of'the: apparatus are supported by the verticalbuckstaysfil; "horizontal" In the operation of the apparatus'described, hot pulverulent material to be cooled is introduced through the inlet 18 and'is aerated or fluidized by air fed through the air inlets 14 and diffusing through the grid 2. In

" thisflu'idized'state, the material flows through the cooler to the discharge opening 20, and is induced to flow around the tubes 4' in a sinuous path by the transverse" The heattransfer mebafiless, first under then over. dium'enters the cooler 1 at theoscillatably-mounted cold tube sheet and plenum chamber assembly .10, travels countercurrent of the material flow in the heat-transfer tubes '4;- and is discharged at the hot tube plenum sheet and chamber assembly 6.

The fiuidizingair escapes from the air' discharge vents I 36 in the-various. stages, which preferably are connected to a duct collector system under negative pressure, The 1 volume'of the fluidizing airsupplied is preferably varied in thesuccessive stages to maintain an essentially uni form velocity at bed temperatures, increments in volume compensating for cooler temperature of the material.

This maybe" accomplished by'use of the valves 16, or

by varying the de'pthor permeability of the insulating material 94 in the difiusiongrid box assembly 86, or

The-'pulverulentmaterial may be introduced intermittently, or preferably it'may be fed continuously at a] substantially uniform rate, the rate of dischargebeing' governed by therate offeed. However, the'rateof feed should be controlled so as toallow' sufficient contact time 1 with the tubes" -ffo'r'the' desired degree of heat exchange.

crass-nemaand. the longitudinal tie 'members 245 j Referrin 11w to igures' 5 6- wherein the" spring" assembly '12 isshown in sectional detail; the spring 106" seateduon the tie 26 surrounds the lower'spring guide; 7

108,- and 'thestop 110 acts as an outer casting 'for the assembly. The threaded' adjustable spring assembly s'up' port member 72 'extends'"from' the intermediatejsupport member .74 through-the lower spring guide 108 and the flanged 'uppe'r spring guide 112; which forms a a top.

fastened 'intoithe studsi;ltltfwhichf ardlmoiin'tedtojh 2' .sns;192,anhsi the" sevei'all conlpofints"together 'A 's'uita 1e pattern 'oflinterengaging expansion joints lwefl perforated'gfid plates 963s depicted and the,

mitei'edxjorners. permit close fittin'ggof rtheplates,

Referrin new {9 F gures; ntimated is a sanitar :With increase intemper-ature, the baflles 8 and tubes ,4f-tend to expand; The average longitudinal expansion of the tubes '4 is translated intd and accommodated by movement 'oflthe 'oscillatably mounted cold tube sheet and plenum chamber assembly 10 longitudinally of. the

apparatus 1'. Difl erential expansion from tubeto tube is I compensated by :further deflection'of the individual tubes at'the '90? bend at the outlet ofthe cooler.

accommodated. e

spring assembly is employed. The wall of the hot tube plenum chamber assembly'd is fixed at its base and exp'a'fids upwa'rdly. The upwardly directed; force of the V compression springs- 106 on the spring assembly support members 72; through the spring zguides ll l and. the lock '-n-uts 114 isin .excess of the Weightof thejbafiles, their suspension assem blies and theportionpf the tubes carj riedl thereby; Under operating iconditions the spring compression permits vertical movement of the baflies 8 to. maintain substantialalignment between the openings in the baflles for the lowest row of 'tu-bes and their fixed end mountings in tl e wallof the hot tube plenum chamber;.assem bly 6. Ihe anchors StIsecure t-he bottomibf. the baffles 8 to the base of the cooler 1 but thejlost motion connections ;provi ded by the slots81 and the bolts 83 allow limited vertical movement of the baflles 1 to permit the alignmentydescribed above and to limit furi i As the 'tubes 4 are slidably supported intthe' baflies 8, substantially"all"longitudinal expansion of the tubes 4 is thus ther movement, thus preventing excessive stress upon the tubes.

Under operating conditions, the force of the springs 196 maintains the bafiies under tension causing them to expand upwardly, thus preventing buckling. The stop 110 and the flanged top of the spring guide 112 cooperating therewith upon downward movement of the support member 72 prevent excessive compression of the spring 106 when the bed is not fluidized and prevent damage in event of possible mechanical failure, and further permits the use of lesser spring force during operating conditions, thus substantially eliminating the effect of creep in the baflie and baffie suspension system. The bafiie 8 may expand horizontally in the clearance provided between it and the refractory wall 104, the angle members 84 and angle clips 82 securing the baflie 8 in place and preventing material flow around it.

In the cooler described, which is primarily designed for treating alumina being discharged from a kiln and which is at an entrance temperature of about 1400" F., it has been preferred to use a segmented baflle plate for the first or hottest stage, as described in copending application Serial No. 692,700, filed October 28, 1957, by Herbert M. Short, now Patent No. 2,876,975 granted March 10, 1959.

Further, the bafiies for the coolest stages may be fixedly suspended rather than supported by a pressureexerting spring assembly, as may be determined by the operating conditions.

For efiicient operation of the unit, the initial baffle should cause the material to flow thereunder so that the inlet feed material entering the first stage descends around and is in contact with the tubes 4. In the second stage, the baflie should cause the material to flow over; and in subsequent stages, this pattern of under and over should be repeated to secure the desired tortuous flow and the maxim-um contact, as is schematically illustrated in Figure l.

The diffusion grid 2 is preferably constructed of removable units of the type illustrated as the diifusion grid box assembly 86. The fluidizing air enters the assembly through the air inlet 14 and ditfuses upward through a permeable top closure consisting of a perforated bottom plate 92, an intermediate fibrous, permeable insulating material 94, and the perforated top plates 96. The insulating material may serve a dual purpose; i.e., its permeability or density may be varied to vary the fluidizing pressure, as well as the material acting as an insulator and membrane.

To provide a rugged and simple top element for the assembly, a perforated metal top plate 96 is employed. An interengaging expansion joint, illustrated in Figure 9, is preferably provided between the individual top plates 96 to accommodate the considerable expansion which takes place at operating temperatures.

The combination of the tube bend and the oscillatably-mounted cold tube sheet and plenum chamber assembly 10 has been found most etficient. The expansion of the tubes, which in tubes of long length can be considerable, is easily accommodated by longitudinal movement of the cold tube sheet and plenum chamber assembly 10 and by further deflection of the tubes 4 at the 90 bend.

Although but one specific embodiment of the invention has been shown and described herein, it will be understood that modifications may be made within the spirit of the invention.

Having thus described the invention, 1 claim:

1. In a heat exchange apparatus having a horizontally disposed vessel, an expansion accommodating heat transfer tube assembly comprising a plurality of heat transfer tubes in said vessel, a horizontally disposed tube sheet, each of said tubes having two portions connected by a substantially 90 angle in each tube below said horizontally disposed tube sheet, one of said two portions of each tube extending upwardly and having the end thereof joined to said horizontally disposed tube sheet, the other of said two portions of each of said tubes being horizontally disposed and extending longitudinally of said vessel, means pivotally suspending said horizontally disposed tube sheet above said horizontally disposed portions of said tubes for translation longitudinally of said vessel, and a vertically disposed substantially fixed tube sheet to which the end of each of said horizontally disposed portions of said tubes is joined.

2. In heat exchange apparatus, an expansion accommodating heat transfer tube assembly as defined in claim 1, wherein said tube sheet pivotal suspending means comprises pivotally mounted supports pivotally attached to said horizontally disposed tube sheet.

References Cited in the file of this patent UNITED STATES PATENTS 1,781,107 Grace Nov. 11, 1930 1,788,386 Ehrhart Jan. 13, 1931 1,809,915 Smith June 16, 1931 1,829,236 Perkins Oct. 27, 1931 2,032,413 Hall Mar. 3, 1936 2,232,936 Bimpson Feb. 25, 1941 2,336,879 Mekler Dec. 14, 1943 2,357,901 Lewis et a1. Sept. 12, 1944 2,501,487 Whitman Mar. 21, 1950 2,523,484 Walsh Sept. 26, 1950 2,797,908 Zubrzycki July 2, 1957 OTHER REFERENCES Unit Heaters Steam and Hot Water Types, J. E. York, Heating and Ventilating Magazine, April 1946; pp. 68-78, pp. 72-73 only relied on.