US1894215A - Pipe still furnace - Google Patents

Description

Jan. 10, 1933. D G, BRANDT 1,894,215

PIPE STILL FURNACE Filed Dec. 4, 1925 z'sheets-sheet 1 Jan. 10, 1933. D. G. BRANDT 1,894,215

PIPE STILL FURNACE Filed Dec. 4, 1925 2 Sheets-Sheet 2 Snug/w50@ FDAV/D G. BRAM/D7 idw Patented Jan. 10,

lUNITED STATES '.IO FOSTER WHEELER CORPORATION, NEW'YORK I Application le'd December method and apparatus for controlling the fire box temperature in pipe still furnaces such as are used for heating petroleum.

When fuel is burnedin a furnace the -re fractory walls and roof thereof absorb a good deal of heat from the burning fuel until they reach a certain temperature, dependingfcprimarily on the temperature generated by the burning of the fuel, after which they become sources of radiant heat. If the radiant heat is not absorbed and taken out of the tire boXthe heat then generated by the burning fuel is all converted into sensible heat carried by the products of combustion, resulting in hightemperatures of these products and in the fire box.

In pipe still furnaces having the still tubes in a bank at one side ofthe furnace, the usual practice is to circulate the convection gas i. c., the products of combustion, downwardlly through the bank on their way outof the furnace. In pipe still furnaces of this ytype difficulty is experienced in preventingthe upper row of tubes of the bank from becoming overheated and burning out, whereas no such ditliculty is experienced with the tubes therebelow. This failure of the upper row of tubes-is primarily due to two causes, namely, the high. temperature of theconvection gases and the high temperature of thelradiant surfaces-more particularly, the roof of the fur.- nace. Moreover,when the bank of tubes is i located at one side of a conventional bridge wall, the convection gases, in passing downwardly, through the bank, tendto How along that side of thebank remote from the bridge wall. This is due to the fact that the gases in moving upwardly from the fire-box sweep along the arched roof of the furnace and down along the wall forming the boundary at that side of the bank remote' from the bridge wall. It vfollow'stherefore, that those tubes adjacent to the brfdge wall do not receive as much heat from the convection gases as. do the tubes more remote therefrom.

The present invention aims to'overcome in [a novel manner the difficulties above indicated, Overheating vof the upper row of\tubes of the bank is prevented by reducing the tem- PATENT oil-Fica f nAvInG. BRANDT, or wEs'rrIELD, NEW JERSEY, AssIGNoR, RY MEsNE ASSIGNMENTS, or NEW YORK, N. Y., A CORPORATION 0E PIPE srI'LI. EURNACE 4perature of the convection gases and by shielding said tubes from highly heated radiant surfaces. The shielding means absorbheat from the burning gases and reduce fire-box temperature by absorption of heat therefrom,-the net result being a reduction of the temperature of the convection gases before they reach the tubes. The fireboX temperature is further controlled by injecting into the fire-box some of the convection gases after they have passed through the bank of tubes. Such gases will be relatively 'cool and L-hence will eXert ya cooling` effect within `the fire-box.'Y The gases arexreturned to the fireboX independently ofthe fuel gases to permit completecombustfon of the fuel to take place without being affected by the returned gases.' The deiciency'of heat supply to those I tubes nearest the bridge wall is overcome by constructing the bridge wall in such a manner that it will absorb heat from the fire-box and transmit it to the adjacent tubes. The improved bridge wall is therefore also a fact-or in the control of firebox temperature.

The above and otherobjects of the invention and features of novelty, will appear from l the detailed description ta-ken in connection with the accompanying drawings, forming pa'rt'of this specification., y A' Referringto thedrawings,Fig-1` is a verthrough .the preferred.

tical section taken form of pipe still furnace, embodying the nov'el features of the present invention and Fig. 2 is a horizontal section taken through the furnace, certain parts thereof being broken away to more fully show the preferred construction. j v

At one' side of the furnace chamber is ar., ranged a bank of tubes, generally indicated at lO, which it is desired to heat by the products of combustion i. e. therconvection gases coming from the -fire boX at one side of said bank. VJ"The bank is arranged over a longitudinally extending conduit 12, into which the convection gases are received after having passed downwardly'through the bank. The gases pass out of the conduit byway of a `pair'of flue passages 14, which lead from the conduit adjacent each end thereof. These Hue passages 14 may come together be-l `20 tor. To this end thereof and passes downwardly between the flue passages of which the recuperator is composed. Upon reaching the bottom of the recuperator the heated air passes therefrom through va pipe 20, `which leads vto an air `l0 chamber 22 within the furnace construction.

- The fresh air is forced through the recuperator bymeans of a blower 24 having a suitable intake 26. The recuperator is preferably provided with a plurality of baille plates -28 arranged in staggered relation, so as to cause `the incoming air to travel through a' circuit ous path toward the bottom of the recuperator. It may sometimes be desirable to pass all or some of the lases around the recuperaiere is provided a vpassa e 30 whichby-passes the recuperator. At te v lower end of the bypass 30 is a damper 3 1 for regulating the flow of gases around the recuperator. Leading forwardly fromthe conduit 12 below the banklO is a passage y32 dis'posedcenL trally ,of the ire box` and below the floor 33 thereof. This passage 32 opens onto a transversely extending passage 34, which extends 50 across the/entire width of the fire box, and:

y which is roofed over with tile members 35 havlng openings 36 extending therethrough.

Arranged at the inlet end of the passage 32v 1s a fan 37 adapted to draw gases from the 85 conduit 12 and force them into the re box through the perforated tiles 35.r The fan is rotated by a motor 38 located outside of the furnace proper, the motor beingconnected to the fan by a shaft 39 'supported in suitable bearings, one of which isY indicated at 40 within the conduit-12. In order to prevent the bearing 40 from becoming overheated and. also to keep the shaft 39 cool, there is vided va tube 42 through which the shaft 4.15.y 9 extends.y This tube is o en at both ends and cool air may therefore ow thro h it to the bearing 40. The fan is preferzliliy rotated at a constant rate of speed..

For controlling the amount of the gasestre- 50 turned or injected into the fire box, suitable dampers are provided at the outlet end of the passage 32. 'The dampers'have. been shown as constituting a pair of doors 44, mounted on a common upright-hinge 46.' The doors are adapted to be operated from the outside lof the furnace by any suitablemechanism as 'by a hand lever 48 suitably mounted on the outside of the furnace and connected by a 'link 50 which passes through the furnace wall, said link eing connected to lever 51 which inturn connects by'means of a-link 52 kwith a to gle mechanism 53 which is connected to t e doors 44.

The furnace as shown. is designed^to be heated by a fluid fuel,preferably gas.' The fuel gases preferably enter'the fire box in such a manner that they will not pla directly on the bank of tubes at rthe side o the furnace, but will be directed-away therefrom. Extending upwardly from the bottom of the 'bank of tubes, and in front thereof, is a wall 63. In front of this wall is located a fuel,

gas manifold 54 in connection with a gas suppl not shown. Projecting from the l'mani old is a`plurality of gas jets 55. In front of the gas jets is a perforated tile 56 through the perforations of which the gas jets discharge into the lire box.` The air supply chamber 22 is located in front orf the upright wall-63 and is adapted to supply the necessary amount of air to the fuel gas to insure completeconlbustion of the fuel. The amount of air supplied to the incoming gas is controlled by al damper 57 which is adaptedto be operated from' the'putside of the furnace in any suitable manner, as by means of a hand lever A58to which is vconnected a link 59 which in turn is operatively connected tol r the damper' 57 by any suitable link and lever mechanism generally indicated at 60.

- In order to permit the furnace to be fired with fuel oil, should circumstances require, there is provided ay battery or rowof oil burners shown as conduits 61 which have their burner ends behind the tile 56 in front of .Openings therein, air being supplied to the oil vfrom the air chamber 22. The oil conduits areso arranged that they maybe pulled away from' the tile 56 when gas is being burned so as to avoid overheating the burner endv of the tubes.

It will be noted that'the convection gases taken fromthe conduit 12 are returned to the fire box remote from the point where the combustion of the fuel gases takes place. By enteringthe convection gases at a point remote from `the place of combustion of thel fuel gases, the returned gases do not interfere with4 the rapid and complete burning of the fuel.-

Instead of separating the bank of tubes from the fire box by means of a thick bridge wall, the present invention provides a bridge wall which is in effec-t a relatively thin curtain through which heat may be absorbed -from the frebox and transmitted to the adpr'eferably takes the form of a plurality of of relatively thin tiles 62 supported on the AOuter tubes of the bank. As shown, the tiles cated, access may/be had .to the tubes by simply removing the tile members. should jacent tubesfv The imp rovedl bridge wall be noted at this point that the'bank tubes run parallel with the tile members 62, or in other words, that the return bends of the tubes are at thel sides of the furnace. By providing a bridge wall of the character indicated, a more uniform heating of the bank is obtained than could. be obtained if the bridge wall were a thick non-conducting member. The reaSOn f heat of the convection for this will be seen when it is lremembered that the convection gases coming from the fire box tend to flow downward through the bank along the side wall of the furnace with the result that the tubes next to and in pr0X- imity to the bridge wall do not receive as muchheat as the tubes more remote from the bridge wall. As a consequence `the tubes adjacent to the bridge wall would ordinarily -be somewhat cooler than the tubes in closer proximity .to the opposite wall of the furnace. The heat transmitted through the thin bridge wall, therefore, supplements, as it Were,the

wardly through the ban In order to shield the uppe'r row of tubes of the bank from radiant heat from the roof of the furnace, there isl arrangedbelow-the' roof 65 of the furnace va series of tubes 66 which 'extend from wall to wall of the furnace, over the entire width of the same, said tubes preferably being in the same ,the tubes of the bank 10.' As shown, 66 are arranged in vertically spaced rows with the tubes in one row staggered with respect to the tubes in the adjacent row as indicated in Fig. 2. 'The roof tubes will: absorb the radiant heat from, the roof and will also absorb radiant heatvl from the walls of the furnace.` As a. result of this absorption of heat the firebox temperaturewill be lowered and the convection gases flowing to the bank will be suiciently reduced in temperature to prevent the upper tubes from becoming overheated.

The fluid to be heated will preferably enter the bank oftubes 10 at the bottom thereof and iiow upwardly through the tubes against the down-coming convection gases and'iiow will be little or no tendency for the fan to draw more of the convection gases downwardly alongione side or end of the bank of tubes, than at any other point of the same. Should any such tendency be indicated the flow of gases passing down- `air at the same'temperature,

circuit as i the tubes v v combustion are recirculated equlvalent amount of air, there 1s a further the gases may be readily controlled by dampers 7 0 placed one in each flue passage 14. The

tubes of the bank 10 maybe supported between their ends in any suitable manner but Y.preferably by spaced upright partitions as indicated at 7l through which the tubes pass.`

By providing upright partitions in the bank the convection gases will be obliged to flow through definite flow channels with the result that a more uniform distribution of heat may be had through thelength of the bank. Partimay likewise 4be protectedby partitions 73.

In order to prevent deterioration or failure of the still tubes due to their becoming oxidized, it is highly desirable that a nonoxidizing atmosphere be maintained within the furnace. By recirculating some of the hot products 'of' combustion for the purpose -of controlling the fire box temperature rather than by introducing'an equivalent amount of I am enabled to obtain a substantially non-oxidizing atmosphere withinthe furnace with the result that oxidation of the st ill tubes is-practically entirely avoided.

Aside from the fact that a substantially nonfoxidizing atmosphere may be obtained in the furnace when some yof the products of increase in efficiency of the operation of the furnace by reason of the fact thatno preheating of the gases is necessary. If air were to be introduced intothe `fire box for the purpose of. controlling its temperature, it will be readily appreciated that some of the heat of the fuel-heat taken from the waste gases passing through the Vrecuperat or-would have to be given over to preheating the air.

Vhat is claimed is:

1. In a pipe still furnace, the combination of a bank of tubes arranged at one side of the furnace fire-box, a conduit below the bank and extending lengthwise thereof, a. passage leading from said conduit midway r its ends, a second passage extending'parallel to the conduit and in communication with the first named passage and opening into the iirebox, means for introducing fuel into the fire-box in a direction away from said bank and towards the point where the second passage opens into the tire-box, means in communication with said conduit for leading products of combustion out of the furnace and means causing a flow into the fire-box of some of the products of combustionvwhich have passed through said bank.

2. -A method ofsupplying tempered heating gases to heat absorbing means behind a wall in a furnace' chamber, comprising ininthe first named passage forV tions 72 are preferably provided adjacent each end of the bank to protect the return bends of the tubes from the heat of the fur-V nace. The return bends of the. roof tubes 66` rather. than an ilo troducing into the furnace firebox at a lace remote from said wall a stream of pro` ucts of combustion which have previouslyl passed over one endof said-walland over said heatv absorbing means, and directing toward said stream and from a lpoint aodjacent the oppo- `V site end of said wall, a stream of burning 'l fuel.

lends whereby hot 3; In an oilfheating furnace, the combination ofa heating chamber. and irebx in communication with each other at their upper ases from the Virebox must pass throughsaid chamber on their 4way out of the furnace, a bank -of oil-heating tubes in said heating chamber over which' said gases circulate, and a relatively thin wall between said bank and irebox, said wall being adapted to transmit heat without a substantial drop-in temperature `to those tubes of said bank which are adjacent said wall. i

, 4.. In an oil-heating furnace, the combinationl of a heating chamber and firebox in com# munidcation with each other at ythei-rupper ends whereby hot gases from the firebox must pass through said chamber on their way out of the furnace,-a vbank of oil-heating tubes inL l the firebox for absorbing firebox heat.

i communication with each other at 4their upper ends whereby hot gases from the .fir/ebox must pass through said chamber on their way out of the furnace, a. `bankof oil-heating tubes in said heating chamber over' which said gases circulate, anl imperforate relatively thin wall between `said bankI and ireb'ox whereby said wall being adaptedto transmit heat to those tubes of said bank which' are adjacent said wall at a' comparatively high rate, and a bank ofvbare oil-heating tubes ,overlying the rebox wfor absorbing 1 firebox heat. L e

6. In an oil-heatingfurnace, the combination of a heating chamber and firebox in communication with each other at their upper ends whereby hot gases" fropmthe firebok must pass through said chamber on their way out yof the furnace,` abank of oil-heating tubes 4 in said heating chambercover whichtsaid gases circulate, a relatively thin wall lbe'- tween said bank and firebox, said'wall being adapted to conduct heat to those tubes of 1 said bank which are adjacent said Wall without. a substantial drop intemperatue'nd means for re-introducing into'the rebox controllable amounts of ,combustion gases which have ypassed through said heatingy chamber whereby the heat of the firebox may be tempered. v

y7. In an oil-heating furnace, the combina- Y tion of a heating chamber and frebox in communication with each other at their upper ends whereby hot gases vfrom the" firebox must pass through said 'chamber on their way out of the furnace, a bank of oil-heatin tubes in said heating chamber over which sai gases circulate, an imperforate heat transmittin wall between said bank and firebox,said wal beingadapted to transmit heat at a relative- V ly high temperature to those' tubes of said bank which are adjacent said wal1,'heat absorbing meansI overlying the irebox, and means for re-introducing into the firebox controllable amounts of combustion gases which have' assed through said heating chamber wheie y the heat of the firebox maybe tempere. c 8. In an oil-heating furnace, the combinasoX tion of a heatin chamber andfirebox in com- I munication wit ends whereby hot gases from the; irebox must ass through said vchamber on their Way each other attheir upper out o the furnace, a bank of oil-heating tubes v in saidheating chamber over `which said gases circulate, a heatermeable wall be'- tween said bank and ireliox adapted to conduct substantial quantities of heat from said fireboxvtothose tubes of said bank which are, A

adjacentsaid wall, and means for injecting fluid fuel into the irebox in a direction away from 'said wall.

9. Inv an oil-heating furnace, the combi,

nation of a heatingchamber and firebox n communication with each other at their upper ends whereby hot gases Vfrom the irebox must passv through said chamber, ontheir wayout of the furnace, a bank of oil heating Y tubes in said heating chamber over vwhich said gases circulate, a heat: ermeable wall between said bank 'and fire ox whereby irebox heat may pass therethrough for absorption by those tubes" of said bank which are adjacent said wall, means for vinjecting fluid fuel into theirebox in a direction away from said wall, and means for injecting into the firebox anterior of the injected fuel .a portion of the` combustion gases which have passed through'said heating chamber.

10.l In an oil-heating furnace, the combination of a heating chamber and firebox incommunication with each other at theirrupper v ends whereby hot gases from the irebox must pass through said chamber on their Way out of the furnace, a bank of oil-heating tubes in said heating chamber over which said gases circulate, a heat-permeable wall f' between 'said bank and firebox whereby rebox heat may pass therethrough for absorption by those tubes of said bank which are adjacent said wall, means for injecting fluid fuel into ,the firebox in a direction away' from said 1l. In an oil-heating wall, andA means for injecting into the firebox through the Hoor thereof, a portion of the combustion gases which have passed through said heating chamber. t v

furnace, the combination of a heating chamber and firebox in communication with each other at their upper ends whereby hot gases from the irebox musty pass through said chamber on their Way out of the furnace, afbank of .oil-heating tubes in said heating chamber over which said gases I circulate, a heat-permeable wall between said bank and iirebox' whereby irebox heat may pass therethrough` for absorption by those tubes ofv said bank which are adjacent said wall, means for injecting fluid fuel into the firebox' in a direction away from said wall, means for injecting into the rebox through the floor thereof, a portion of the combustion lying the rebox.

12. In a furnace, the combination of a heathot gases from the irebox must pass throug the heating chamber on their way out of the furnace, means for introducing into the firebox at a point remote from the division wall between the irebox and heating chamber a portion of the hot gases'which have passed ythrough said heating chamber, and means for introducing burning ,fuel into the irebox ina direction away from said `division wall and toward the place of reintroduction v of said gases into the irebox. 18. In a furnace, the combination of alleating chamber and'ajiirebox in communication withI each other at their upper ends whereby hot 'gases from the rebox must pass through the heating chamber on their way out of the furnace,

which is opposite the division wall between the firebox and heating chamber, means for introducing into the rebox at a place between said walls a controlled amount of the hot gases which havepass'ed throughs-said heating chamber, and a series of bare tubes 1n the roof of the'firebox through which afluid to be heated may be passed, said tubes adapted to absorb radiantheat from the firebox.

14. In a furnace, the combination of a heating chamber and a irebox` in communicationwith each other at their upper ends whereby hot gases from the rebox must pass through the heating chamber on their way out ofthe A,

means for introducingv burning fuel furnace, s

rebox toward that wallof the reinto the box which isoppositethe division wall lbetween the irebox and heating chamber, means for introducing` into the fireboxat a place between s'aid walls a controlled amount of the hot gases which have passed through said heatingchmber, a'series of bare tubes gases which have passegd through said heating chamber, and heat-absorbing means overmeans for introducing' burning fuel l ,1 into the irebox toward that wall of the flrebox i 15. In a furnace structure, the combination of a fire-.box and a heating chamber communicating with each other over abridge Wall, said wall being adapted to transfer heat from tively high rate, a heat absorbing element in said chamber, mea-ns for jetting burning fuel into said fire-box in a direction away from said wall, and a cooling screen comprising a bank of tubes above said fire-box adapted td `absorb heat radiated from said fire-box, said bank of tubes vbeing substantially entirely out of the path of 'flow of the .combustion gases. v

16; The method of controlling the intensity of heat applied by products of combustion to the tube bank of a furnace in which said bank -is separated from the fire-chamber of said furnace by a bridge wall over which said products of combustion pass, and in which a bare 'tube screen is provided under the roof-of said furnace above said bridge walll and substantially entirely out of the path of flow of the products of combustion, which comprises passing a heat-absorbing fluid through the tubes of saidscreen to ab'- sorb radiant heat from said fire-chamber and thereby prevent substantial radiation of heat to said bank, and tempering the products of Acombustion in said fire chamber byA mixing therew-ithfthe products of combustion which Y have been cooled-by passage over of tubes. f

l17. In an oil heating furnace, which comprises a {ire-box, a heating chamber and a. heat-absorbing tube bank, in' said chamber, the improvement which comprises a relatively thin imperforate bridge wall separa-ting said fire-box and heating chamber and over .which hot products of combustion produced. in said fire-box pass into said chamber, said wall being adapted to transmit substantial quantities of heat from said fire-box to the tube bank in said chamber, and means for 'jetting fuel into said fire-box in a direction said .bank .A

lio,

away from said wall, thereby to direct the Y het gases' of combustion away fromsaid wall;v Y i l 18. In an'oil-heating furnace, which comprises a combustion cham er, a heating chamber and a bank of oil con ucting tubes in said heating chamber, and inwhich hot gases of combustion from said combustion lchamber are passed over the tubes in the heating chamber, the improvement which comprises'a relatively thin .imperforate vbridge wall separating said chambers and around whichtheproducts of 9mbustionpass\from said combustion chamber to said heating chamber, said 75 said fire-box to said chamber at a compara- 4 wall beingA adapted to transmit substantial i l' quantities of heat at a'relatively high tern-4 f perature from said combustion chamber tof' against saidy wall.

Vthe tubes in said heating chamber, an means -19. An oil still furnace comprising Yside walls and a roof, a bridger wall extending upwardly, terminating short of the roof'and dividing the oil still furnace into a heating ychamber and a heat absorption chamber,

means for producing combustion in the heating chamber, a first tube group comprising a plurality7 of fluid-conveying tubes in the heat 1 absorption chamber, a second tube group `comprising a plurality of rows of exposed fluid-conveying tubes under the entire roof and arranged above the top of the bridge wall and spaced from said top of the bridge wall,

" sa'id tubes of the second tube group being fluid from thefirst tube `group to the second so spaced relative to each other as to revent reflection of rad1ant heat rays from t e roof into the heat absor tion chamber and soV connectedas to have ow of fluid from Yany rovvl to the next higher row and means to conduct tube group. Y

' 20. An oil still Ifurnace comprising sidei walls and a roof, a bridge wall extending upwardly, :terminating short ofthe roof and chamber and ai heat absorption chamber,I

' means for producing combustion in the heating, chamber, a first tube group comprising a plurality of fluid-'conveying tubes in the ,40. heat absorption chamber, a second tube group,

com rising a plurality of rows of exposed flui -conveying tubes under the roof and arranged abc-ve the top of the bridge wall andy spaced from said top of the bridge wall and extending transversely to the bridge wall, said tubes of the second tube group having a relatively-long path of fluid flow and being so spaced relative to each other as to revent reflection of radiant heat rays from t e roof into the-heat absorption chamber and so con-y nected as to have flow of fluid from any row to the next higher row and means to conduct fluid from the first-tube grou to the second tube group, the arrangement eing such that l t the uppermost tubes of the second tube group '65 are in a. zone of relatively still gas.

421. .An oil still furnace comprising side walls and a roof, a bridge wall extendingupward-ly, terminating short of the roof'and dividing the oil still furnace'finto a heating- :d0 chamber' @and Ya heat l absorption chambersY means for producing combustion in the heating chamber, a first tube group comprising a plurality of fluid-conveying tubes 1n the heat absorption chamber, a second tube group comprising apiurality of rows of exposed fluid-conveying tubes lindenthe 4entire roof and `arranged above the top of thebridge wall and spaced from said top of the bridge "wall, said tubes of thesecond tube group havyond group are inLa zone of relatively7 still gas.

22. An oil still furnacel comprising side walls and aroof, a bridge wall7 extending upwardly, terminating short of the roof and dividing the oil still furnace into a heating chamber and a heat absorption chamber, means for producing combustionin the heating chamber, a first tube group comprising a plurality of fluid-conveying tubes in the heat absorption chamber, l av second tube group comprising a plurality of rows of exposed fluid-conveying tubes under the roof and arranged above the top of the bridge wall and spaced from: said top of the bridge wall and extending transversely to the bridge wall,

said tubes of the secondy tube group being so spaced relative to'each other as to prevent reflection of radiant heat rays from the roof into the heat absorption chamber and so connected as to have flowA of fluid from any row Yto the next higher row and rneansto conduct fluid from the firstltube group to the second wardly; terminating short of the roof andai dividing the oil still furnace into a heating chamberY and a' heatabsorption chamber,

means for producing combustion in the heating chamber, a first tube group Ycomprising a l plurality of fluid-conveying tubes in the heat absorption chamber, a second tube group `comprising a plurality of vertically spaced rows of exposed fluid-conveying tubes under the entire roof and arranged above the top of the bridgewall and spaced fromY said top of theV bridge wall and extending transversely to the bridge walland above the tubes'of the first group, said tubes of the first group being varranged to be heated by convection heat,and

said second tube group arranged to be heated by radiant heat and means to conduct fluid from. the first tube group to the second tube group, the arrangement being such that the uppermost tubes ofthe second group are in a zone of relatively still gas.

2f-'An oil-still furnace comprising side walls-and a roof, a bridge Wall extending up- Wardly, terminating-short yof the roof and dividing the oil stillV furnace into a heating chamber and a heat absorption chamber, means for producing combustion in the heatheat absorption chamber, a second tube group f' ing chamber, a` first tube group comprising a plurality of fluid-conveying tubes in the comprising a plurality of rows of vertically spaced exposed fluid-conveying tubes under s walls forming a setting, meansv for effecting combustion of fuel to provide a source of radiant heat in said setting, a first tube group in said setting exposed to direct radiant heat from said source, a second tube group in said setting, and a wall of thin imperforate tile in said setting between said second tube group and said source, said wall providing communicating chambers in said setting, the

' source of heat being in yone chamber and said secondtube group being in a second chamber, andl said wall serving to transmit Yheat through the material thereof from said source to said second tube group. v

26. An oil-heating furnace comprising walls forming a setting, meansfor eecting combustion of fuel to provide a source of radiant heat in said setting, a first tube group in said settingV exposed to direct radiantrheat from said source, a second tube group in said setting,l and a continuous wall of thin material in said setting between said second tubey group' and said source, said wall providing communicating chambers in said setting, the source of heat being in one chamber and said second tube group being in a second chamber, and said wall serving to transmit heat through the material thereof from" said source to said second tube group.

\ -27. An oil-heating furnace comprising walls forming av setting, means for eecting combustion of fuel to provide a source of;

radiant heat in said setting, afirst tube group v in said setting yexposed to direct radiant heat from said source, a secondtube group in said setting, a wall of thin imperforate ,tile in said setting between said second tube' group and said source, said walll providing com.- municating chambers in `said setting, the source of heat being in one ehamberand said second tube group being in a second chamber, saidy wall serving to, ltransmit heat through the material thereof from said source to said second tube group, and means to remove products of combustion from said second chamber.

28. An oil-heating furnace comprising walls forming a setting, means for effecting combustion of fuel to .provide a source of radiant heat in said setting, a first tube group in said setting exposed to direct radiant heat from said source, a second tube group in said setting, a continuous wall of thin material in said setting between said second tube group and said source, said wall providing communicating chambers in said setting, the

source of heat being in one chamber and said second tube group being in a second `chamber, said wall serving to transmit heat through the material thereof from said source to said second tube group, and means to remove products of combustion from said second chamber. J n

29. In an oil-heating furnace, wall structure forming a heating chamber and a firebox in communication with each other whereby hot gases from the fire-box pass into said chamber on their way out of the furnace, a

tube group exposed to direct radiant heat A from the ho't gases in the firebox and substantially entirely out of the path of flow of said gases, and a bank of oil-heating tubes in said heating chamber over which said gases circulate, said wall vstructure -includingy a relatively thin imperforate wall between said bank and said lire-box, and said wall being .adapted to transmit a substantial amount of heat through the material thereof to those tubes of said bank in the heating chamber which are adjacent said wall.

.30. An oil still furnace comprising side walls and a roof,a' bridge wall, extending upwardly, terminating short of the roof and dividing said oil still furnace into a heating chamber and a heat absorption chamber, means for eectingcombustion of fuel to develop relatively intense radiant heat in the heating chamber, a first tube group com.-

prising a plurality of superposed rows of fluid conveying tubes in the heat absorption chamber and a second tube group comprising a plurality of vertically spaced rows of bare fluid conveying tubes under and adjacent the yroof and exposed to direct radiant heat produced in the heating chamber,said plurality of rows of the second tube group comprising an upper row immediately adjacent the roof and a lower row immediately Aunder said upper row, thetubesof the lower row and higher row being staggered with respect to each other, said lower row being at` a higher elevation than the top of the bridge wall and at a higher elevation than the uppermost row of tubes in-said heat absorption chamber wherebyv a substantial amount of heating ,gases may pass over the bridge wall and into .the heat absorption chamber` without giving up heat of convection to the second tube group, said second tube group being disposed' under substantially the ent-ire roof portion above the heating chamber.

31. An oil still furnace comprising an enclosure defined by walls arrang l 4 substantially right angles to each other, a thin imperforate bridge Wall extending substantially at right vangles from one of said Aenclosing walls and. terminating short'ofthe Wall opposite said last mentioned Wall,` said bridge Wall dividing Athe oil still furnace into a heating chamber 'and a heat absorption 'chamber communicating with each other, means for effecting combustion of fuel to develop relatively intense radiant heat in the heating chamber, a first tube group comprising a plurality of` rows, of fluid conveying tubes in the heatfabsorption chamber, and a second tube group comprising a plurality of spaced, barefiuid conveying tubes disposed adjacent to and extending entirely across the wall opposite said last mentioned Wall, said second tube group being spaced from the outer end of the bridge Wall whereby direct flow of heating gases may be established over the outer'edge of the bridge Wall and into the heat absorption chamber without said heating gases giving up a substantial amount of -heat of convection to the second tube group, said bridge Wall being adapted to transmit heat through the material thereot` v from the heating chamber to those tubes of the first tube group which are adjacent the bridge Wall, and means to remove products kof combustion from said heat'absorption chamber.`

In testimony whereof I alIiX my signature.

DAVID G. BRANDT.

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