US2354643A - Heater for fluids - Google Patents

Description

1944- c. H. ANGELL 2,35 4,643

HEATER FOR FLUIDS Filed Jan. 19, 1942 2 Sheets-Sheet l 1 000000000 4 00000000 [AW/Ill mmmm Aug. 1944. c ANGELL 2,354,643

' HEATER FOR FLUIDS Filed Jan. 19, 1942 2 Sheets-Sheet 2 Patented Aug. 1, 1944 HEATER FOR FLUIDS Charles H. Angel], Chicago, Ill., assignor to Universal Oil Products Company, Chicago, 111., a

corporation of Delaware Application January 19, 1942, Serial No. 427,346

(Cl. l22356) angle toward side wall I so that the flames and 12 Claims;

The invention relates to an improved form of heater for fluids which is particularly advantageous as applied to the heating of hydrocarbons to the high temperatures required for their thermal or catalytic conversion.

The features and advantages of the invention will be apparent to one familiar with the art from the accompanying diagrammatic drawings and the following description thereof.

Fig. l of the drawings is a cross-sectional elevation of one specific form of the heater provided by the invention. 4 Fig. 2 is a cross-sectional elevation of another specific 'form of the heater provided by the invention.

Referring to Fig. 1., the form of heater here illustrated comprises the vertical exterior side walls I and 2, a roof 5, a floor 4, and end walls, not shown. I

Interior walls and G, spaced from each other and from the side walls I and 2 and extending from the floor to a point beneath the roof, are provided within the heater and divide the space enclosed by the outer walls into separate vertically extending, inter-communicating, heating zones I, 8 and 9.

A bank of horizontally disposed tubular fluid conduits II is disposed within combustion and heating zone I adjacent that surface of wall 5 which faces wall I. Another vertical bank I2 of horizontally disposed tubes I3 is located in combustion and heating zone 8 adjacent the opposite side of wall 5. Another vertical bank I4 of horizontally disposed tubes I5 is located in combustion and heating zone 9 adjacent that surface of wall 5 facing wall 2 and a fourth vertical bank I5 of tubular fluid conduits I1 is disposed in combustion and heating zone 8 adjacent the opposite side of wall 5. A fifth bank I8 of horizontally disposed tubular fluid conduits I9 is disposed in the lower portion of combustion and heating zone 8, the tubes of this bank being arranged in superimposed horizontally parallel rows which substantially span the distance between walls 5 and 6. Bank I8 extends from adjacent the lower ends of banks I2 and IE to adjacent fiue 20, which is disposed beneath and indirect communication with combustion and heating zone 8 and is also in communication with a suitable stack, not illustrated.

The furnace may be constructed in any suitable conventional manner, employing either built up or suspended shapes of suitable refractory material for the walls, and is mounted upon a suitable foundation 2I.

A horizontal row of burners, one of which is indicated at 22, disposed beneath floor 4 and adjacent the lower end of side wall I, supply combustible fuel and air through firing ports 23, disposed in the floor, to combustion and heating zone I. The burners are preferably directed at an hot combustion gases issuing from the burners impinge against the surface of this wall and travel upwardly thereover. Radiant heat is thus imparted to the tubes of bank II) from the surface of wall I, which is heated to a highly radiant condition, and from said. flames and hot combustion gases. Each of the tubes II of bank I8 thus receives direct radiant heat over one sidethereof, and on the other side, receive radiant heat reflected from the adjacent surface of wall 5-. The tubes of bank I5 are heated in, a similar manner from walls 2 and 6 and from flames and hot. combustion gases supplied to combustion and heating zone 8 by another horizontal row of burners 22 disposed beneath floor 4 and adjacent the lower end of wall 2, which burners supply combustible fuel and air through the adjacent burner ports 23 in the floor to zone 9.

Combustion gases from zones 1 and 8 pass over the upper ends of the respective walls 5 and 6 and are 1 directed downwardly through heating zone 8. Preferably, a rounded projection or bullnose 24, extending downwardly from roof 3 to an elevation adjacent the upper extremity of walls 5 and 6 and disposed substantially midway between the latter, is provided to impart streamline flow to the combustion gases passing from zones I and 9 into zone 8 so as to avoid excessive turbulence in the combustion gas stream adjacent the upper end of zone 8. However, the combustion gases from zones I and 9 commingle as they enter zone 8 and residual heat in these gases is imparted first to the tubes of banks and I6 as the gases pass downwardly therebetween. The gasesthen pass in direct and intimate contact with the tubes I9 of bank I8,'following which they are discharged from the heater through flue 20. v I

As a special feature of the invention, provision is made for increasing the quantity and adjusting the temperature of the hot gases passing from zones 1 and 9 to zone 8 to any desired value, so as to obtain independent control of the heating conditions in zone 8, as well as in each ofthe zones I and 9.

To accomplish this, a row of burner ports; one of which is indicated at 26, is provided through the rounded projection or bull-nose 24 and a row of burners, one of which is indicated at 25, is pro.- vided and disposed adjacent said ports to project names and hot combustion gases downwardly into heating zone 8 to commingle with the streams of combustion gases being supplied thereto from zones 1 and 9. Fuel is supplied to each of the burners 26 through line 29 and valve 38 in regulated amounts and regulated quantities of air are admitted to and through the burners by the adjustment of a damper 21 which serves to regulate the passage of air. into housing 28 disposed about the burners.

In case it is desired reduce the temperature of the combustion gases passing from zones 1 and 9 into zone 8, rather than to supply additional v heat thereto, the supply of fuel to burners 25 may be discontinued and steam may be admitted through lines 29 and valves 36 and through the burners to commingle with the combustion gases passing through zone 8 and/or air may be admitted through the burners, in the manner previously described, to commingle with and reduce the temperature of the combustion gases passing through zone 8.

It will be apparent from the foregoing that the heater provided possesses a high degree of flexibility with respect to control of the heating conditions in each of the zones 1, 8 and 9. This is highly advantageous when, as is usually the case in heating hydrocarbons to the high temperatures required for their thermal or catalytic conversion, it is desirable to control the heating curve by controlling the rate of heat input to the hydrocarbon fluid at various points along its path of travel through the heating coil. Although it is not intended to limit the invention to any specific sequence of flow for the fluid through the various tube banks, it is worthy of note that a considerable variety of arrangements is possible in the heater provided. Preferably, the adjacent tubes of each bank are connected in series at their ends by means of suit--v able return bends or headers, not illustrated, although it is also within the scope of the invention to connect the adjacent tubes of each bank or the tubes of various sections thereof for the parallel flow of separate streams of fluid therethrough. Also, when desired, each or any of the tube banks It), I2, I4 and I6 may comprise two or more parallel rows of tubes instead of the single row illustrated, although with more than two rows in any given bank, the reradiating effect of the adjacent unflred wall will be materially reduced and such an arrangement is, therefore, not ordinarily preferred.

To mention one of the many possible advantageous flows which may be employed in the heater illustrated and above described, letus assume that the fluid to be heated is a hydrocarbon distillate, such as naphtha, and that the heater is employed in reforming service for converting the naphtha into high yields of good antiknock gasoline. This type of service requires that the distillate be quickly heated to reforming temperature and then maintained for a period of time at or hear the maximum temperature previously attained. High superatmospheric pressures are favorable to this type of operation and, due to the high process pressure, excessive pressure drop through the heating coil, due to friction, should be avoided so as to maintain -a reasonably uniform pressure throughout the heating step and avoid excessive pumping costs.

Under these conditions, employing a heater such as herein provided, the stream of naphtha charging stock is preferably divided into two streams of substantially equal volume and tube bank I8 is divided into two vertical sections, each containing an equal number of tubes. One stream of oil is passed in a general upward direction through the right-hand section of bank I8 and then flows in a general upward'direction in series through the adjacent tubes of bank I6, wherefrom it flows in a general downward direction in series through the adjacent tubes of bank I4. The other stream passes in a general upward direction through the left-hand section of bank I8, thence upwardly in series through the adjacent tubes of bank I2 and thence downwardly in series through the adjacent tubes of bank In.-

The heating conditions in zone 8 are controlled to give the desired reforming temperature in the oil streams adjacent the upper ends of banks I2 and I6, and in banks I0 and I4 the respective streams are maintained at or near the temperature attained in banks I2 and I6.

Due to the construction of the heater and the provisions for controlling heating conditions in the combustion zones 1, 8 and 9, each stream -may-be subjected to substantially identical heating conditions and the separate streams emergpresent invention. Due to splitting of the incoming stream and division of the heating coils into two similar sections, excessive pressure drop through the coil is avoided.

This same type of flow may also be employed for simultaneously subjecting two separate streams of the same fluid or different fluids to substantially identical or to difierent heating conditions. different oils, each to be heated to an independently controlled cracking temperature, with a flow through the heater such as above described, the separate streams may be-substantially uniformly heated to below their desired outlet temperatures when they reach the upper ends of coils I2 and I6 and, byemploying different firing conditions in zone 1 than those employed in zone 9, the two streams may then be each independently heated to a different temperature in the respective'tube banks I0 and I4.

Referring now to Fig. 2, the heater here shown comprises exterior side walls 3| and 32, a roof 33, a floor 34, and end walls not shown.

Interior walls 35 and 36, spaced from each other and from the side walls 3| and 32, are provided within the heater and extend downwardly from the roof to an elevation somewhat above the floor 34. Another interior wall 6I extends upwardly from the floor well into the space between walls 35 and 36 and is disposed substantially midway between the latter. The walls 35, 36 and 6| divide the interior of the heater into separate combustion and heating zones 31, 38, 62 and 63 and the space between walls 35 and 36, above the upper end of wall 6|, comprises a fluid heating Zone 39.

A vertical bank 46 of horizontally disposed tubular fluid conduits 4| is located in combustion and heating zone 31 adjacent that surface of wall 35 facing side wall 3|. Another vertical bank 42 of horizontally disposed tubular fluid conduits 43 is located in combustion and heating zone 38 adjacent. that surface of wall 36 facing the side wall 32. A third vertical bank 44 of horizontally disposed tubes 45 is located in heating zone" 62 adjacent that surface of wall 35 facing wall 6| and still another vertical bank 46 of horizontally disposed tubes 41 is located in heating zone 63 adjacent that surface of wall 36 facing Wall 6|. Tube bank 48, disposed in fluid heating zone 39, comprises a plurality of horizontally parallel rows of horizontally disposed tubes 49, the rows extending across substantially the entire space between walls 35 and 36.

Zones 31 and 38 are each fired by a row of burners, one of which is indicated in each zone at In the case of separate streams of 52, disposed adjacent the upper ends of the respective side walls 3| and 32 and above roof 33. The roof is provided with firing ports 55 through which the burners project flames and hot combustion gases at a slight angle toward the side walls 3| and 32, heating the latter to a highly radiant condition as they pass downwardly thereover. The tubes of bank 4| are thus heated on one side by direct radiation from the flames, hot combustion gases and the hot surface of wall 3| and are heated on their opposite sides by reflected radiation from the adjacent surface of wall 35. Likewise, the tubes of bank 42 are heated on one side by direct radiation from'flames, hot combustion gases and the hot surface of wall 32 and on their opposite side by reflected radiation from the adjacent surface of wall 36.

Combustion gases'from zone 31 which have given up a portion of their heat to the tubes of bank 46 pass beneath the lower extremity of wall 35 into zone 62 and supply heat to the tubes of bank 44 in this zone. Likewise, combustion gases which have given up a portion of their heat to the tubes of bank 42 pass beneath the lower extremity of wall 36 into zone 63 and in flowing upwardly therethrough transmit heat to the tubes of bank 46.

Combustion gases from zones 62 and 63 commingle above the upper extremity of wall 6| and flow through fluid heating zone 39 in intimate contact with the tubes of bank 48 to which they supply residual heat. They pass from zone 39 to stack 56.

Wall 6|, which divideszones 62 and. 63, will be heated to a radiant condition on its opposite sides by the combustion gases passing through these zones and radiant heat will be transmitted from these gases and from the opposite sides of wall 6| to..one side of the tubes 'of the respective banks 44 and 46. The opposite sides of these tubes will be heated by reflected radiation from the adjacent surfaces of the respective walls 35 and 36.

When desired, in order to increase the temperatures and rates of heating in zones 62 and 63, as well as in zone 39, flames and hot combustion gases are projected upwardly over the opposite faces of wall 6| from burners 64 through rows of firing ports 65 disposed in floor 34 on opposite sides of wall 6|.

The entire furnace structure is mounted on a suitable foundation 5| and a space is provided beneath the floor in which burners 64 are disposed. Preferably, these spaces are sealed from the atmosphere, except through openings 60 provided through the outer walls of the foundation, and an adjustable damper 6| at each of these openings regulates the quantity of air admitted to the burners. In case it is desired to decrease rather than increase the temperatures and rates of heating in zones 62, 63 and 39, the supply of fuel to burners 64 may be shut off and regulated quantities of air admitted through the burners and firing ports to zones 62 and 63. Likewise steam for cooling may be admitted through lines 53, valves 54 and burners 64 to heating zone 62 or to heating zone 63 or both.

In the case illustrated, walls 35 and 36 are of hollow construction, permitting suspension of the refractory shapes from. which these v walls are formed on suitable structural steel members, not illustrated, disposed within the spaces provided between opposite sides of the walls 35 and 36. Brackets of any suitable conventional form, not illustrated, for supporting the tubes of banks 40,

42, 44 and 46 may also be anchored through the walls 35 and 36 to the same structural member which carry the refractories of these walls or to separate structural members disposed in the spaces between the opposite sides of walls 35 and 36. Preferably, these structural members are cooled by the admission of air through ducts or ports 56 extending through one or both end walls of the heater adjacent the lower ends of walls 35 and 36 to the spaces provided between the opposite sides of these walls. The air may be suplied, when desired, by a suitable fan or blower not shown, but this will ordinarily not be required since heating of the air by contact with the walls and metal members will cause a natural draft action and give good thermal circulation. Thus, heated air is discharged from the upper end of the spaces provided between the opposite sides of walls 35 and 36 into suitable housings 66 provided above the roof 33 and in which the burners 52 are disposed. Dampers 51 provided in housings 66 are adjustable to regulate the quantity of preheated air admitted through burners 52 to the combustion zones 31 and 38 and any remaining quantity of preheated air, not required for combustion, is discharged through openings 58 in housings 66, which openings are controlled by the same dampers 51.

What has been previously said with respect to the flexibility of control in the heater illustrated in Fig. 1 also applies to the modified form of heater shown in Fig. 2. The chief difference between the two forms of heaters resides in the provision of the wall 6| in the heater shown in Fig. 2, whereby four independently controlled heating zones are provided, rather than three as illustrated in Fig. 1, wall 6| also providing radiant surfaces from which heat is transmitted to the tubes of banks 44 and 46.

In the heater illustrated in Fig. 2, as in that iilustrated in Fig. 1, any or all of the tube banks adjacent the unfired walls may comprise more than one row of tubes, when desired, and the adjacent tubes of each bank may be connected at their ends in series or tubes of the individual banks or sections thereof may be connected for the parallel flow of separate streams of fluid therethrough. Also, any desired sequence of flow through the various banks may be employed within the scope of the invention. 'A flow similar to that described,

side of a vertical plane passing through wall 6|,

may be devoted to cracking relatively heavy oil, while that portion on the opposite side of this vertical plane may-be devoted to cracking relatively light oil under independently controlled conditions.

I claim as my invention:

1. A heater for fluids comprising, in combina-' tion; a radiant heating zone having a fired wall and an opposite unfired wall, a bank of tubular fluid conduits disposed adjacent the unfired wall, means for projectingflames and hot combustion gases into said zone from adjacent one end thereof over the surface of said fired wall in radiant heat-transmitting relation to said fluid conduits, a separate radiant heating zone disposed between said unflred wallof the first named zone and a separate wall spaced therefrom in a direction opposite to that of said fired wall, an additional wall between said unflred wall and said'separate wall, tubular fluid conduits disposed in said separate heating zone adjacent said unflred wall and adjacent said separate wall, means for directing combustion gases from that end of the first named zone remote from the source of said flames and hot combustion gases into and through said separate heating zone in contact with one side of said additional wall and means for firing the opposite side of said additional wall. g

2. A heater for fluids compris ng, in combination, a radiant heating zone disposed between a pair of spaced refractory walls, a second radiant heating zone disposed between another pairof spaced refractory walls, a third radiant heating zone disposed between one of said walls of the first named zone and one of said walls of the second zone, 'a bank of tubular fluid condu ts disposed along opposite sides of each of said walls which are common to two of said zones, means for projecting flames and hot combustion gases independently into said first and second named zones along said walls thereof opposite the fluid conduits disposed therein and in radiant heattransmitting relation to said conduits, a refractory wall disposed in and spaced from the walls of said third zone, and means for directing com- -bustion gases from said first and second zones through said third zone in contact with the opposite sides of the last-named wall.

3. A heater for fluids comprising, in combination, a pair of substantially parallel refractory side walls, a pair of substantially parallel refractory interior walls spaced from each other to provide an intermediate heating zone therebetween and spaced from said side walls to provide endheating zones therebetween, a bank of tubular fluid conduits disposed adjacent each side of each of said interior walls, means for projecting flames and hot combustion gases independently into each of said end. heating zones, from adjacent one end thereof, over the inner surface of each of said side wallsin'radiant heat transmitting relation to the fluid conduits disposed in said end zones, a refractory wall disposed in and spaced from the walls of said intermed ate zone, and

means for directing combustion gases from adjacent the opposite end of each of said end zones into and through said intermediate zone in conheating zone in intimate contact with the tube tact with the opposite sides of the last-named wall.

4. A heater for fluids comprising, in combinarefractory interior wall disposed substantially par allel to and between said pair of interior walls to provide another radiant heating zone between the last named wall and each wall of said interior pair, a bank of tubular fluid conduits disposed in each of said heating zones adjacent one of said walls thereof, means for projecting flames and hot combustion gases from adjacent one end of each of said heating zones into the same over the-refractory surface of that wall thereof facing said tube bank disposed therein, and means for directing combustion gases, from adjacent that end of each of the first named heating zones remote from the source of said flames and hot combustion gases, into and through the next adjacent other heating zone over the refractory surface of that wall thereof facing said tube bank disposed therein.

5. A heater for fluids comprising, iii-combination, a pair of substantially parallel refractory side walls, a pair of substantially parallel refractory interior walls disposed substantially parallel to and spaced from said side walls to provide radiant heating zones therebetween and also spaced a substantial distance from each other, another refractory interior wall disposed substanti 11y parallel to and between said pair of interior w lls to provide additional radiant heating zones etween. the last named wall and each wall of s id interior pair, a bank of tubular fluid conduits disposed in each of said heating zones adjacent one of said walls thereof, means for projecting flames and hot combustiongases from adjacent one end of each of the first named heating zones into the same over the refractory surface of that wall thereof facing said tube bank disposed therein, means for directing combustion gases, from adjacent that end of each of the first named heating zones remote from the source of said flames and hot combustion gases, into and through the next adjacent heating zone over the refractory surfaceof that wall thereof facing said tube bank disposed therein, a fluid heating zone common to the second named radiant heating zones and disposed adjacent that end ofthe latter opposite the point of introduction of said combustion gases thereto, another bank of tubular fluid conduits disposed in said fluid heating zone, and means for directing combustion gases from each of the last mentioned radiant heating zones through the fluid bank disposed therein.

6. .A heater such as defined in claim 5, provided with means for increasing the temperature of said combustion gases as they pass from the first named radiant heating zones to said additional radiant heating zones.

7. A heater such as defined in claim 5, provided with independent burner means for increasing the temperature and volume of combustion gases passing through said additional radiant heati'g zones, said burner means being located adjacent the inlet end of each of said additional radia t heating zones and being disposed to direct flamEs and hot combustion gases over the refractory surface of that wall thereof facing said tube bank disposed therein.

8. A heater such as defined in claim 1, provided with means for adjusting the temperature of said combustion gases as they pass from the first named to the second named heating zone.

9. A heater such as defined in claim '1, provided with means for increasing the temperature of said combustion gases as they pass from the first named to the second named heating zone.

10. A heater such as defined in claim 1, provided with means for firing said one side of said additional wall. 11. A heater such as defined in claim 3, provided with means for adjusting the temperature of said combustion gases as they pass from said end zones into said intermediate zone.

12. A heater such as defined in claim 4, provided with means for adjusting the temperature of said combustion gases as they pass from the first named radiant heating zones to the second named'radiant heating zones.

CHARLES H. ANGELL.

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