US2094912A - Heating of fluids - Google Patents

Description

Original Filed Sept. 2, 1933 w Q0 xxx? 8 M B A INVENTOR MARIN Q BARNES TIME OF FLUID IN FIG. 2

Patented Oct. 5, 1937 UNITED STAS PAT 3:1; ()FFICE HEATING OF FLUIDS Application September 2, 1933, Serial No. 687,956 Renewed January 5, 1935 14 Claims.

This invention refers to improvements in furnaces particularly suitable for heating hydrocarbon oils to the high temperatures required for their pyrolytic conversion and, more specifically, adapted to the conversion of relatively lowboiling hydrocarbon oils of the character requiring extended conversion time at a substantially constant temperature in the final stages of their heat treatment in order to produce maximum yields of desirable low-boiling products such as motor fuel of high antiknock value.

It is well known that many hydrocarbon oils of a relatively low-boiling character, such as kerosene or kerosene distillate, pressure distillate bottoms, naphtha, straight-run gasoline or other motor fuel of inferior antiknock value and the like, may be successfully converted for the production of high yields of motor fuel of good antiknock value by heating the oil to the desired conversion temperature and then maintaining the same at or near the temperature attained for a predetermined length of time in the final stages of the heating coil, without the necessity of employing a high pressure reaction vessel for separation of the vaporous and liquid conversion products and continued conversion of the vapors. The present invention offers a simple and eificient heating means whereby this type of operation may be accomplished.

The present invention is, however, not limited to use in the conversion of hydrocarbon oils but will be found advantageous in any process involving the heating of any fluid wherein a heating curve of the general character obtained by the apparatus of the present invention is desired.

One specific embodiment of the apparatus of the present invention may comprise a main furnace structure having side walls, end walls, a roof and a floor, a combustion zone within said structure, a convection heating zone separated from said combustion zone but in communication therewith, means for supplying combustibles to said combustion zone, means for removing combustion gases from said convection zone, a fluid conduit comprising a plurality of tubular elements in said convection heating zone, a fluid conduit comprising an exposed and a shielded row of tubular elements disposed along the roof of the furnace and adjacent the convection hea 0 ing zone, a fluid conduit comprising a plurality of tubular elements adjacent the floor of the combustion zone and a fluid conduit comprising an exposed and a shielded row of tubular elements adjacent the roof of the combustion zone,

55 means for passing a fluid to be heated through adjacent tubes in each fluid conduit in series and means for passing the fluid in series through the various fluid conduits in the .order above given.

The accompanying diagrammatic drawing and the following description thereof will serve to more clearly illustrate the features and advantages of the present invention.

Fig. 1 of the drawing is a cross-sectional elevation of one specific form of furnace embodying the features of the present invention. 0

Fig. 2 illustrates the general type of heating curve obtainable in the furnace shown.

Referring in detail to the drawing and particularly to Fig. l, the front and rear end walls of the main furnace structure are indicated, respective- 15 ly, by reference numerals I and 2, 3 is the roof and 4 the floor. Side wall 5 is shown in elevation and the similar opposite side wall is not shown, due to the view being taken in section. A bridge Wall ti separates combustion zone 1 from the con- 20 vection heating zone 8.

In the embodiment here illustrated, combustible fuel of any desired form is supplied, together with all or a regulated portion of the air required for combustion, to combustion zone I through one 25 or a plurality of similar firing tunnels 9 by means of a burner or burners of any desired form, not shown. Additional air for combustion or auxiliary air may be supplied to combustion zone I through air ducts IIJ controlled by dampers ll 30 disposed adjacent firing tunnel 9 and Within the same general structure. Preferably a plurality of similar firing tunnels and air ducts are employed, positioned along the lower portion of front wall I of the furnace in order to secure a 35 uniform distribution of combustibles to combustion zone I. Only a single firing tunnel is seen in the particular view of the furnace here illustrated. Combustion gases pass from combustion zone 1 over bridge wall 6, downwardly through the convection heating zone 8 and out of the furnace through flue [2 to a suitable stack, not shown.

A fluid conduit or tube bank I3 is positioned within convection heating zone 8 and comprises, 45 in the embodiment illustrated, a plurality of parallel rows of horizontally disposed tubes l4. Adjacent tubes in the same row and at the ends of adjacent rows are connected at their ends in series by means of suitable headers or return bends, not illustrated in the drawing. The connections between the tubes at their rear ends are indicated diagrammatically by the lines I5.

Another bank of tubes or fluid conduits l6, comprising two parallel rows of horizontally dis- 20 I series, the flow through the shielded row being reverse to that through the exposed row.

' ja'cent'tubes in alternate rows ofthis bank are.

posedtubes I4, is positioned along the roof 3 of the furnace adjacent the convection zone 8. Ad-

connected at their ends in series, as indicated, diagrammatically by the lines l5 'at the rear ends of the tubes.

' Another tube bank or fluid conduit l1 comprising a single row of horizontally disposed tubes I4,

j .crossover line indicated diagrammatically "at I 9:into theend tube in'the lower row of bank I6.

diagrammatically at 20 into the end tube adja-f .centbridge Wall 6 ofbank I 7.

tion of flow of the combustion gases.

is positioned adjacent the floor of the combustion zone and adjacent tubes in this bank are conin the same row of this bank areconnected at their ends in series, as indicated diagrammatically by the lines i5, and, in the embodiment. illustrated, the two rows of tubes are connected in The Various tube banks [3, l6, I1, and i8 are preferably connected in series in the order given when the furnace is employed for the conversion of low-boiling hydrocarbon oils and, in ,the particular 'case'here illustrated, the flow of oil, as

indicated by the arrows, may be as follows: The

oil enters an end tube in the lower row of bank l3, flowing through the adjacent tubes in each row and-through the adjacent rows in series,

the general direction offlo'w 'beingupwardly. through this bank countercurrent to the'fiow of combustion gases. The oil'leaves 'an'end tube ini thetop row of bank l3, passing through a The oil then passes into the end tube'of the upper row of bank l6 and through adjacent tubes 'in alternate rows of this bank in series, emerging from the last tube in the QPDositeend of the bank and passing through cross-over line indicated through adjacent tubes in bank I! in series and thegeneral directionof flow in both banks I 6 and ll is, in the case illustrated, countercurrent to the direction of firing and to the general direc- The oil leaves the end tube of bank 11 adjacent the front of the furnace and is transferred through crossj over line indicated diagrammatically at '2! .into '1 the end tube adjacent the front of the furnace of the exposed row of banklB. Theoil then passes through adjacent tubesin the exposed row of bank 58 in series, concurrent to the direci tionof firing and general direction of flow of the combustion gases, is transferred from' the end tube of banklfl most adjacentbridgewall Sinto thelast tube at thesame end of the shield-v ed row of bank I8, passing through adjacenttubesin this row in series countercurent to the direction of firing'and general direction of flow of .7 .the combustion gases, and finallyemerging from the end tube of this row adjacent the front of the iurnacethrough line 22 tosubsequent cracking or the. like equipment; not pertinenttopthe present invention and not here illustrated. V

' 1 The general'type of heating curve ordinarily obtained; in a furnace such as illustrated with a flowjof the general character described is indicated in F g. 2- of the drawing. It. will be noted with reference to this curve that the temperature or the oil is gradually raised as it passes through bank [3, aslindicatedfby the slope of sectimn The oil flows 7 A of the curve. A more rapid rate of temperature riseis obtained in bank l5 as indicated in section B of the curve and a ,still' more rapid rate is obtained in bank I], as-indicated by the slope of section C of the curve and the oil is maintained at a substantially constant temperature 7 V as it passes through'bank l3, as indicated by section D of the curve. Primarily sensible heat is parted to the oil insection A of the curve, corresponding to the time during which the oil passes through bank l3. Additional sensible heat and a large portion'of the latent heat of vaporization is added 'to the oil in section B, corre spending to the time during which the oil passes through bank It; Some of the latentheat of cracking may also be obtained in this section of the furnace. Substantially all of the rej maining'sensible heat impartedto the oil as well as the'rema'ining latent heat of vaporization'a'nd a substantial proportion of "the latent heat of cracking is imparted to. the'oil in section C of the curve, which represents the timein' tube bank I 7. Very little sensible heat but a large proportion of the latent heat of crackingis imparted to the oil in section D' of the curverepresenting the time in'tube bank I8. Q j r I It will be understood that many'rnodifications 'of the specific form of furnace'illustrate'dand described as well asrm'nor departures from the specific flow illustrated and described maybe employed within the scope of the present inven-' .tion. For example, the general direction of flow through any or all of the various individual tube banks maybe reversed, the sequence of flow through the various banks-Ibeingimaintained.

however. .Also parallel instead of series fiow.

through all or a portion of the tubes in. bank [3 .may be employed, if desired, in order to decrease pressure drop, due to friction, through the heating coil. Another modification of the specific scribed, whichis specifically within thescope of the present invention, comprises eliminating from the furnace that portion of tube bank [6' directlyabove bank 13, which portion is, indicated byline 24. V V It will be understood thatthe various Qmodifications mentioned arenot to be considered equivalent although they do not alter thegeneral heating method employed nor the general typeof heating'curve obtained. .For example, by elim-.

inating section 23'of tubebank I 6 a somewhat." higher rate of heating than that indicated by.

the curve in Fig. 2 of the drawing will be obtained in bank l3, particularly in fthefupper two: or three rows of. this bank and the slopeof section A of. the curve in Fig. 2 will be somewhat more pronounced, for example as indicated by line A,

4.0 form of furnace and the fiow'illustrated andd 1 4a at.23, inwhich casethe'fiow of oil between tube bank I3 and l6 is as indicated diagrammatically Various other modifications of the specific T '7 form of furnace and the specific flow illustrated and described Will be apparent'to those skilled in the art and it is therefore" not intendedjto limit the broad spirit and scope of the present invention except as defined in the appended. claims.

I claim'as'my invention:

. 1. A furnace for a heating hydrocarbon oils 1 which comprises; in combination, a main furnace structure having side walls,end walls,.a roof 7 and a floor,.a combustionzone within said furi nace structure, a separate convection heating zone 1 in communicationwith said combustion zone, means .for supplying combustibles to said W combustion zone, means for removing combustion gases from said convection zone, a fluid conduit within said convection heating zone, a fluid conduit disposed along the roof'of the furnace adjacent said convection zone, a fluid conduit adjacent the floor of the combustion zone, a fluid conduit positioned adjacent the roof of the combustion zone and means for passing hydrocarbon oil through the various fluid conduits in the sequence above given.

2. A furnace for heating hydrocarbon oils which comprises in combination, a main furnace structure having side walls, end walls, a roof and a floor, a combustion zone within said furnace structure, a separate convection heating zone in communication with said combustion zone, means for supplying combustibles to said combustion zone, means for removing combustion gases from said convection zone, a fluid conduit within said convection heating zone, a fluid conduit disposed along the roof of the furnace adjacent said convection zone, a fluid conduit adjacent the floor of the combustion zone, a fluid conduit positioned adjacent the roof of the combustion zone and means for passing hydrocarbon oil in a continuous stream through the various fluid conduits in the sequence above given.

3. A furnace for heating hydrocarbon oils which comprises in combination, a main furnace structure having side walls, end walls, a roof and a floor, a combustion zone within said furnace structure, a separate convection heating zone in communication with said combustion zone, means for supplying combusti les to said combustion zone, means for removing combustion gases from said convection zone, a fluid conduit comprising a plurality of serially connected, horizontally disposed tubular elements positioned within said convection heating zone, a fluid conduit comprising a plurality of serially connected, horizontally disposed tubular elements disposed along the roof of the furnace adjacent said convection heating zone, a fluid conduit comprising a plurality of serially connected, horizontally disposed tubular elements positioned adjacent the floor oi the combustion zone, a fluid conduit comprising a plurality of serially connected, horizontally disposed tubular elements positioned adjacent the roof of the combustion zone, and means for passing hydrocarbon oil in a continuous stream through the various fluid conduits in the sequence above given.

4. A furnace for heating hydrocarbon oils which comprises, in combination, a main furnace structure having side walls, end walls, a roof and a floor, a combustion zone within said furnace structure, a separate convection heating zone in communication with said combustion zone, means for supplying combustibles to said combustion zone, means for removing combustion gases from said convection zone, a fiuidconduit comprising a plurality of superimposed horizontal rows of horizontally disposed tubular elements connected at their ends in series and positioned within said convection heating zone, a conduit comprising two parallel horizontal rows of horizontally disposed tubular elements positioned along the roof of the furnace adjacent said combustion heating zone, adjacent tubes in alternate rows being connected at their ends in series, a fluid conduit comprising a single horizontal row of horizontally disposed tubular elements connected at their ends in series and positioned adjacent the floor of the combustion zone, a fluid conduit comprising an exposed horizontal row and a shielded horizontal row of horizontally disposed tubular elements positioned adjacent the roof of the combustion zone, adjacent tubes in each row being connected at their ends in series and the two rows connected in series, and means for passing a continuous stream of hydrocarbon oil through the various fluid conduits in the sequence given.

5. A furnace for heating hydrocarbon oils which comprises in combination, a main furnace structure having side walls, end walls, a roof and a floor, a combustion zone within said furnace structure, a separate convection heating zone in communication with said combustion zone, means for supplying combustibles to said combustion zone, means for removing combustion gases from said convection zone, a fluid conduit comprising a plurality of superimposed horizontal rows of horizontally disposed tubular elements connected at their ends in series and positioned within said convection heating zone, a fluid conduit comprising two parallel horizontal rows of horizontally disposed tubular elements positioned along the roof of the furnace adjacent said com bustion heating zone, adjacent tubes in alternate rows being connected at their ends in series, a fluid conduit comprising a single horizontal row of horizontally disposed tubular elements con nected at their ends in series and positioned adconduit comprising an exposed horizontal roW and a shielded horizontal row of horizontally each row being connected at their ends inseries and the two rows connected in series, means for passing a continuous stream of hydrocarbon oil first through the first mentioned fluid conduit in a general direction countercurrent to the flow of combustion gases, then through the second men tioned fluid conduit in a general direction countercurrent to the flow of combustion gases, then through the third mentioned fluid conduit in a general direction countercurrent to the direction of firing, then through the exposed row of tubes in the last mentioned fluid conduit in a general direction concurrent to the direction of firing and finally through the shielded row of tubes in the last mentioned fluid conduit in a general direction countercurrent to the direction of firing.

6. In combination with a furnace having a combustion zone and a convection heating zone in communication with the combustion. zone, means for firing the combustion zone at the end of the furnace opposite the convection zone, a bank of heating tubes in the convection zone, a second bank of tubes adjacent the furnace roof remote from the firing means and connected to the first named bank, a third bank of tubes adjacent the floor of the combustion zone and connected to said second bank, andanother bank of tubes connected to said third bank and positioned adjacent the furnace roof closer to the firing means than said second bank.

7. The combination as defined in claim 6 further characterized in that said second bank of tubes is positioned partially in the combustion zone and in part directly over the first-named bank.

8. A furnacecomprising a combustion zone, a convection heating zone at one end of the furnace and in communication with the combustion zone, means for firing the combustion zone at the opposite end of the furnace toward the convection zone, a bank of heating tubes in the convection zone,;a secondtube bank adjacent the furnace roof and having .a plurality of tubes positioned in the combustion zone remote fromthe firing means, a thirdtube'bank adjacent theffloor of the combustion zone and anothertube bank adjacent the roof of the combustion zone closer to the firing means than said second bank, I and means for passing fluid tube-heated serially through said banks in the order named.

9. A furnace Comprising a combustion zone 7 having roof tubes and floor tubes, means for ea.

, fllQIn a. furnace for ing the furnace at onecnd of the combustion zo'ne,a convection heating zone, communicating withthe opposite end ofcthe combustion zone,

heating tubes in the convection zone, and means [for passing fluid to be heated first through the 'last named tubes, then through a portion ofthe roof tubes remote from the firing means, then the opposite end thereof, the combination, of

means for passing fluid to be heatedfirst through the convectiontubes, then through a portion of thereof tubes remote from the firing means, then through the fioor tubes and finally through the remaining portion of the roof tubes'closer to the firing means. a 1 f heating fluids, thecom bination of a pair of fluid conduits each comprising two parallel horizontal rows of horizontally disposed heating tubes positioned adjacent "the roof ofthe furnace, adjacent tubes in alternate nected between said conduits.

rows of one of the conduits being connected at their ends in series, and adjacent tubes in each" row of the other conduit being connected at their ends in series and 'thetwo rowsof this conduit being connected inseries; and means for passing Y a fluid to beheated through both rows of'one rows of the other'of said conduits.

12. In a furnace for heating fluids, the com-: ,7 o 10 bination of a fluid conduitcom'prising'two par allel horizontal rows 'of horizontally disposed of said conduits and subsequently through both heating tubes positioned adjacentthe roof of the furnace, adjacent tubes in the alternate rows beingconnected at their ends in series, a second fiuid conduit comprising two rows of'horizontal heating tubes, the last-named rows being 'con-' nected in series with each other and .disposed'in the furnace in horizontal alignment with the-rows V of thefirst-named conduit and adjacent tubes of 7 each of said last-named'rows being connected at their ends in series, and means for passing a fluid to be heated through both rows of one of rows of the other of said'conduits.

1s. The combination as.defined in claim 11 further characterized in that said means comsaid conduits and subsequently through both prises a horizontal row'of heating tubes positioned adjacent the floor of the furnace and'con- "14. The combination asfdefined in further characterized in that said means corn claim 12.

prises a horizontal row of heating tubes positioned adjacent the floor of thefurnace and fcon- I nected between saidconduits.

V ,MARION w. BARNES. w

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