US2035337A

US2035337A - Tube still or heater and the like

Info

Publication number: US2035337A
Application number: US23331A
Authority: US
Inventors: Ostergaard Povl
Original assignee: Gulf Oil Corp
Current assignee: Gulf Oil Corp
Priority date: 1935-05-24
Filing date: 1935-05-24
Publication date: 1936-03-24
Anticipated expiration: 1953-03-24

Description

Web

24, 13

P. QSTERGAARD TUBE STILL OR HEATER AND THE LIKE Filed May 24, 1955 4 Sheets-Sheet PW flsi'ergaarcl,

24, 1936. P. OSTERGAARD TUBE STILL OR HEATER AND THE LIKE} Filed May 24, 1955 4 Sheets-Sheet 2 9 193.. P. OSTERGAARD TUBE STILL 0R HEATER AND THE LIKE Filed May 24, 1935 4 Sheets-Sheet 5 M WM W 2 7 n w H 5% MM a w j uwlr v fi a w w M a M a m E r N- W M 5 6 5 w 2W L 6%? S 2 \5/ F/ EEE g 6 M? .mu mwmmmvfl flaw W 1 E fi N mm 2 q i A w M a a H936. F. OSTERGAARD TUBE STILL OR HEATER AND THE LIKE Filed May 24, 1955 4 Sheets-Sheet 4 Q \=\S K Patented Mar. 24, 1936 UNITED STATES TUBE STILL OR HEATER AND THE LIKE Povl Ostergaard, Mount Lebanon, Pa., asslgnor,

by mesne assignments, to Gulf Oil Corporation of Pennsylvania, Pittsburgh, Pa., a corporation of Pennsylvania Application May 24, 1935, Serial no. 23.331

11 Claims. (01.122-356) This invention relates to tube stills or heaters and the like and it comprises a tubular heater in the form of a cage of interconnected tubes in banks situated within a furnace and adjacent to a plurality of burners, the latter being so arranged within the fire chamber that radiant heat is uniformly and efllciently applied to the tubes,

elf ctive utilization of radiation is increased, a

greater portion of the generated heat is absorbed,

and a radiant heater of greater capacity can be constructed, all as more fully hereinafter set forth and as claimed.

In small capacity tube heaters the most ellicient construction is that in which one burner,

axially located, radiates heat directly upon vertical tubes lining the Walls of a cylindrical fire chamber, or furnace. As the burner is equidistant from all tubes and the flame radiates heat in every direction, the tubes are uniformly heated and the radiant energy emitted by the flame is efficiently absorbed by the tubes. However, when the capacity of the heater is increased v as by increasing the number of tubes and enlarging the fire chamber, one burner becomes inadequate and a plurality of burners in such a fire chamber cannot be positioned to. give maximum radiation upon the tubes. Unsymmetrical arrangement of burners in a cylindrical furnace gives irregular radiation, and a symmetrical arrangement of more than two burners in the center of a cylindrical furnace gives rise to an excessively hot core of gases leaving the radiation furnace, In prior large capacity heaters of this type three or more burners have been located at uniform intervals on an inner circle concentric with the circle formed by the furnace walls. As the flame of each burner radiates heat in every direction, symmetrical arrangement of several burners about an axial point results in development of a highly heated core of gas at the center of the group. Thus in the case of cylindrical heaters having three burners grouped symmetrically about the axis, the burners are at the points of an equilateral triangle and each flame shields the tubes from radiation from the other flames, to a certain extent. Inthe center of a group of burners, there is a central core of gas which has passed through and out of its luminous or radiant stage without loss of heat content such as hasv so taken place in the case of other portions of the flame. The heated core tends to rise swiftly and thereby carry heat out from the furnace proper. The result is that a large portion of the heat generated in the furnace is recoverable only by 55 convection. The central core of such gas comes into being when three burners are symmetrically positioned about an axis, and this central core represents an increasing proportion of the total generated heat as the number of burners is in-' creased above three. Many advantages, includ- 5 ing very great economy in original construction and subsequent maintenance, are attainable when the radiant heat generated by the burners can be efliciently transferred to the material which is to be heated, but when three burners are sym- 10 metrically arranged only a fraction of the radiant heat of the burner flames can be transferred as radiation. When a. larger number of burners are symmetrically arranged utilization of the flame radiation is even less eflicient. 15

Heaters of the type to which this invention relates have a superstructureconsisting of a top arch and a stack or flue, and sometimes either a convection heater and an air preheater, or both. All of these are supported above the tube 20 chamber. This superstructure requires a-supporting frame consisting of vertical columns spanned by suitable structural members. As the tube area ofa cylindrical tube still is increased, the diameter of the cylinder formed by the walls 25 of the fire chamber is necessarily increased proportionally. The vertical columns must be placed on the outside of the walls, and hence the span between the columns is increased with increased diameter of the heater; the result being 0 that the construction of suitable members to span the columns becomes increasingly diflicult and expensive. When a hot core of gases is formed in the fire chamber, a large convection heater is required to absorb the heatconveyed by those 35 gases: the size of this heater further complicates the superstructure. If the convection heater is' omitted the available heat is wasted and operation becomes uneconomical.

A convection heater ordinarily consists of 9.40 rectangular bank of tubes, and, as this shape does not conform to the circular shape of the chambers discussed, the passage connecting the two must necessarily vary in cross section from circular at one end to rectangular at the other. 45 The construction of such a passage is highly involved and the design unwieldy. When such a passage is used the length of the convection heater tubes is limited. It is necessary that the diagonal dimension of the convection heater be less than the diameter of the tube circle of the radiant heater; this to provide access to the ends of the tubes of the radiant heater for purposes of inspection, cleaning, and replacement.

An object of the present invehtion is the provision of a tube still or heater having a large capacity and having a plurality of burners and one or more banks of tubes uniformly and closely spaced from the burners, so that the radiant heat produced by the burners is uniformly absorbed by the tubes, and formation of a heated core of gases is obviated. The banks of tubes are arranged in a sort of cage surrounding the burners. Usually the tubes are arranged vertically; sometimes they are arranged horizontally, or some vertically and some horizontally.

Another object of the invention is the provision of a multi-burner tube still capable of utilizing radiant heat from the burners with maximum efliciency and having a fire chamber of such a shape that the capacity may be increased without increasing the distance between burners and tubes and without increasing the span between columns supporting the superstructure, and whereby such an increase of capacity does not complicate the construction for supporting the superstructure. The length of the furnace is increased without proportional increase of its width.

Another object of the invention is to provide a multi-burner fire chamber, capable of utilizing radiant heat from the burners with greatest efficiency and the shape of which conforms in general to the shape of a rectangular convection heater supported above it so that the passage connecting the two may be of simple design. The tubes in the convection heater may consequently be fully utilized, and they may be of greater length than has been practical with circular fire chambers.

A further object of the invention is the provision of a multi-burner tube still wherein a convection heater may be employed to absorb the nonradiant component of the heat generated by the burning gases within the furnace which has not been completely absorbed by the still tubes, and wherein the convection heater can be kept to minimum size.

In the drawings;

Fig. 1 is a vertical section along the major vertical axial plane of an elongated vertical tube still with air preheater, and shows the arrangement and shape of the various elements according to one embodiment of my invention;

Fig. 2 is a horizontal section taken along the line 2-2 of Fig. 1, and shows the elongated shape of the fire chamber, semi-circular end walls, and the relative position of the burners and tubes;

Fig. 3 is a vertical section of a tube still similar to that shown-in Fig. 1, but this still has straight end walls and has a convection heating section interposed between the preheater and the fire chamber;

Fig. 4 is a horizontal section taken along line 4-4 of Fig. 3 and shows the elongated fire chamber of rectangular shape;

Fig. 5 is a diagrammatical plan and shows one form of tube arrangement in the fire chamber, wherein the tubes are subdivided into separate heating imits, and passage of liquids through separate units is indicated;

Fig. 6 is a diagrammatic view in elevation showing the tube arrangement of Figure 5 surmounted by a convection heater, and also showing one method of connecting the tubes in the convection heater to those in the fire chamber;

Pig. 7 is an elevation taken on line 1-1 of Fig. 6 showing the convection heater of that view, and also showing a manner of dividing the convection heater into separate units for preheating different m;

being of the same length and positioned in a row, 7

parallel to one another, with all of their upper ends in one horizontal plane. The heater 8 is designed to heat fluid circulated through the tubes, the heat emanating from combustion of fluid fuel supplied by a plurality of burners 21. The burners serve as means for producing radiant heat. The flames from the burners rise in the furnace and radiate heat in all directions, but principally laterally by reason of their naturally elongated nature. The heater may consist of one row, or more than one row of tubes, and at least one row of these tubes will completely surround the plurality of burners which furnish the source of heat. Figs. 2 and 4 and 5 depict two complete rows 50 and 5|, each totally surrounding the burners 21. In some respects this appears most clearly in Fig. 5.

In my invention I place the burners 21 in a straight row and the closest row of tubes 50 is positioned symmetrically about the burners 21 at a distance therefrom proper for efiicient combustion and proper for most efiective radiation of heat to said tubes 50. The spacing between burners is approximately the same as the spacing between the row of burners and the tubes. If the inter-burner interval is made much greater than the separation between the burner row and the tube row, tubes directly opposite the burners receive a disproportionately large fraction of the heat from the burner as compared to tubes midway between burners. 0n the other hand, spacing the burners very close together does not provide an increase in heating capacity proportionate to the increase in number of burners. A second row of tubes 5| is preferably positioned in back of row 50. The tubes of this second row are positioned to receive maximum radiation of heat from the burning fuel and to provide a maximum shielding effect for the walls ID of the enclosing furnace.

The burners are substantially equidistant from the tubes which absorb the heat. The end burners in the row are positioned at a distance from the end walls equal to their spacing from the side walls. As the burners are placed in a straight line, mutual screening of radiation by the burners is minimized and the radiant heat produced by each flame is radiated upon and is absorbed by the closely adjacent tubes.

The tubes of the heater 8 are seriately connected to one another to form banks, as

banks

36, 31, 38, and 39 of Fig. 5, and the oil to be heated is circulated through these banks to ab,- sorb the heat radiated thereto. Separate banks, either adjacent or remote, may be seriately connected, or separate streams of liquid to be heated may be circulated through separate banks of tubes. Any number of tubes in any portion of any row may be seriately connected into a bank but ordinarily a bank will consist of a number of adjacent tubes as illustrated by the arrangement of header connection I! in Fig. 5.

As previously stated my invention comprises aosass'r a heater 8 having a plurality of burners 21 and these are positioned in one straight line. These burners serve as sources of heat. In positioning the tubes about the line of burners, to receive radiated heat from burner flames, the row of tubes is arranged in an oblong rectangle or in an oblong having parallel straight sides and substantially semicircular ends. The former of these is shown in Fig. 4 and the latter is shown in Figs. 2 and 5. The spacing of the tubes from the burners has already been described.

The heater 8 is enclosed within a furnace comprising side walls 9, end walls I8, a furnace floor l3, and roof l2. All of these are of refractory material. The burners 21 open into the furnace through refractory cones 28 in the furnace floor l3. A central portion of the furnace roof i2 is developed as upturned section l5 into a passageway i8 for directing the combustion gases from the furnace toward a stack 28. The tubes of the heater 8 project through the furnace roof l2 and floor I3 for a distance suflicient to make the return headers l4 accessible from the outside of the furnace, thereby permitting convenient inspection and cleaning of the tubes.

In all embodiments the tube banks form a. sort of cage surrounding the burner row, the walls of the cage being substantially equally spaced from the burner row.

Positioned in the path of the combustion gases, between the furnace and stack 28 is an air preheater H. such a preheater is shown in Figs. 1 and 3. It comprises a bank of parallel tubes IS, the openings of which providecommunication between passage l6 and stack 20. Com.- munication between l5 and '20 is otherwise obstructed by lower tube sheet 52 and upper tube sheet 53. These

metallic tube sheets

52 and 53 are pierced to receive the tubes l8 and the tubes l8 are fastened into and supported by these tube sheets.

Tube sheets

52 and 53, together with peripheral shell 33 serve to enclose a chamber 54 through which air is directed for preheating before directing it to the burners 21. The air preheater may be provided with bafil es I9, if desired, for the usual purpose of such devices. A

blower 2| is provided to force air through conduit 22 to the preheater l1 and thence by way of conduit 23 to burners 26.

The principal heater 8 is designed to receive and absorb a maximum portion of the available heat as radiant heat. Not all the heat of a burner flame is in the form of radiant energy, and in certain cases it is advantageous to incorporate a convection section into my tube still to absorb the remaining available heat of the combustion gases. In such case, as shown in Figs. 3 and 6, I interpose a convection section 24 between the heater 8 and the air preheater l'I.

Referring to Fig. 3, an advantageous form of construction is shown wherein a convection heater 24 is interposed between heater 8 and preheater I'I. The heater 24 comprises a bank of horizontal tubes 25 disposed lengthwise of the elongated fire chamber 8 and connected in such manner that liquid may be circulated through the tubes 25 in heat exchanging relationship with hot gases rising from 8. The tubes 25 may be'connected all in series or connected in separate groups as shown in Fig. 7. This convection section 24 may be used to preheat a stream on its way to radiant heater 8, as shown in Fig. 6 or it may be used as a sort of soaking coil for a stream which has been previously heated in radiant heater 8, or it may be used independrefractory burner cones 26 of conical shape opening outwardly at the top. At the lower, narrow end each cone is provided with a suitable burner 21 of any well known type suitable for the particular fuel to be burned. Each burner receives fuel, from a source not shown, and preheated air from conduit 23 for combustion of said fuel. As-illustrated best in Figs. 1, 2, 3, and. 4, the burner cones are positioned at uniform intervals in a horizontal row along the major vertical axial plane of the space enclosed by heater 8. This places the row of burners centrally with respect to the tubes ll lining the side walls 9 of the furnace, and the end burners are substantially the same distance from the tubes lining the end walls ill of the furnace. The tubes adjacent to the end walls it! may be more uniformly heated by arranging them in a semi-circular row about the end burner as axis. The

walls

9 and 10 of the furnace are supported by vertical columns 28 placed at intervals around the walls adjacent to the outside faces thereof and resting on suitable foundations such as 29. The furnace floor l3 and the burners 21 are shown as supported by upright members 38 resting on foundations 3|. The stack is supported by beams 32 spanning the upright columns 28 both lengthwise and crosswise. The roof members l5 and i2 are braced by irons 34. The upper and lower return couplings M of the tubes are advantageously enclosed within housings 35 to prevent loss of heat through radiation.

When more than one row of tubes II are used in the heater 8, the tubes in each row may be so spaced as to receive a definite desired share of the total heat output from the burners and hence the degree of heating in each row may be con-. trolled. Furthermore, the tubes ll may be subdivided into separate heating units' differing from each other in total tube lengths and-in the manner in which the various tubes in the unit are connected, and in this way different stocks may be concurrently subjected to separate and unlike treatment in the radiant heater 8.

Figs. 5, 6, and 7 illustrate diagrammatically one specific arrangement of the tubes of heater 8-and of convection heater 25. This. particular construction may be employed to advantage in a cracking still for petroleum stocks requiring difierent heat treatments during cracking. According to this arrangement the tubes II are divided into four different banks denoted in Figs. 5 and

6.by reference characters

36, 31, 38, and 39. Tube bank 36 may be used to crack stock which is to be subjected to relatively slight heat treatment, such stock entering inlet 48 and passing first through the outer row of tubes and then the inner row and finally leaving the heater 8 through outlet 4|. The entire bank of tubes 38 is heated mainly by two burners and these burners may be fired at a lower rate than the. other burners to prevent overheating of the stock undergoing treatment in group 36.

Tube banks

31 and 38 are arranged for cracking gas oil and are connected to convection heater 24 by pipes 42 and 43 respectively. The convection heater 24 can be constructed as two separate banks and is so shown in Fig. '7 with separate inlets 44 and 45. Gas oil introduced through inlet 45 of con.-

vection heater 24 passes from that heater through pipe 43 into the inner row of tubes of bank 38 of heater 8 and is there rapidly raised in temperature: it is next passed through a soaking section consisting of the outer row of tubes and is then discharged through outlet 46. Gas oil introduced through inlet 44 is similarly heated in the convection heater 24 and in bank 31, after which it leaves the heater 8 through outlet 41. The soaking action in the outer row of tubes of

banks

31 and 38 permits of cracking to a greater extent than is possible in bank 36. Bank 39 is advantageously used to crack naphtha, the naphtha being introduced to the inner row of tubes through inlet 48 and there brought up to cracking temperature. Subsequently, this naphtha is passed through the outer row of tubes where it soaks for an appreciable time at high temperature, and it is finally discharged through outlet 49.

The heaters so far described employ vertical tubes. This I regard as the most useful construction for general purposes. For some purposes, however, it is advantageous to have part of or all the tubes arranged horizontally. The same advantages of high efficiency and uniformity of heating accrue.

Figs. 8, 9 and 10 illustrate diagrammatically alternative tube arrangements within the scope of the invention, some of the tubes being arranged horizontally. In Figs. 8 and 9 the tube banks comprise a bank 60 of horizontal tubes on "each side of the furnace wall (9). The ends of the tubes extend beyond the wall and are pro- .vided with return bends I4. The end tubes are arranged vertically in banks 6|, extending beyond the furnace roof (l2) and floor (l3) as shown and also provided with return bends 14. This arrangement makes for simple construction and allows easy cleaning of the tubes from the outside of the furnace proper. The four tube 'hanks form a sort of rectangular cage, as shown.

A row of burners 21 in refrmtory burner cones 26 is provided as in the other embodiments. The burners are equally spaced from each other and from the walls of the tube cage, as shown.

Referring to Fig. 9, each bank of tubes on each wall is shown as having separate liquid connections 62. This arrangement aFlows four separate stocks to be simultaneously treated in the heater. The banks can be interconnected in any way desired. It is sometimes convenient to connect the end banks in series, and run a stream through them in series.

Fig. 10 shows a modification analogous to the structure of Fig. 2, having approximately semicircular ends. The end tubes are arranged vertically in banks 62, as shown, and the side tubes are arranged in a horizontal bank. This modification is useful in certain installations.

These modifications work similarly to those in Figs. 1 to '7. If desired the tube banks may be subdivided to provide for separate heating operations.

While the specific embodiments of my invention herein described are advantageous for certain purposes, it is to be understood that the invention is not limited thereto. The tubes may be connected in any desired manner to give the required number of units and the tubes may be so spaced as to yield the desired heating characteristics. The heating of other material than petroleum stock is within the purview of my invention.

In general, the vertical tube arrangement as illustrated in Figs. 1 to 7 has the greatest allaround utility.

The essence of my invention is a tubular heater, heated by a plurality of burners, wherein the tubes of the heater are positioned closely about the 5 plurality of burners to receive radiant heat from the flames thereof, and-wherein the individual burners are so positioned with respect to one another that the flames from the individual burners will shield one another from the tubes of the 10 heater only to a minimum degree. I regard as the best embodiment of my invention a construction in which the individual burners are positioned in one straight row, and in which a majority of the radiant heater tubes are positioned in two planes parallel to one another and to the plane of the burner flames, the heater .tube planes being substantially equally distant from and on opposite sides of the flame plane.

The width of the heater is determined by the 20 effective generation of heat by the burners, that is, by the nature, shape and characteristics of the flame produced thereby. The separation between the burners and the tube bank and accordingly the width of the furnace is approximately the same for burners of the same capacity and kind. Greater heater capacity, when required, is obtained by lengthening the furnace horizontally and providing additional burners arranged as described. In this way the capacity of a furnace may be increased several fold while not increasing the spacing between burners and tubes and not increasing the cross span between the columns which support the superstructure. When a convection heater is used, its shape advantageously conforms substantially to the shape of the fire chamber or radiant section. though the convection heater is not necessarily of equal dimensions. The invention thus permits constructions with fewer dead areas than are present in a cylindrical fire heater surrounded by a rectangular convection section and it also permits a considerable reduction in the amount of refractory material in the furnace roof. The tubes in the convection section may be made longer 45 than with a circular type furnace as they may be positioned along the length of the fire chamber. Also, less tube surface is required as the radiant heat produced by the burners is fully utilized in the furnace proper.

In this specification and in the appended claims, I speak of a plurality of tubes positioned in a symmetrical row about a straight row of burners. In this connection I use the term symmetrica in its customary sense except that two portions of 65 the tube row shall be substantially straight, on opposite sides of the burner row, and substantially parallel thereto and substantially equidistant therefrom.

This application is a continuation in part of 60 my prior application, Serial No. 716,439, filed March 19, 1934.

What I claim is:

1. In a tube heater, a plurality of means for producing radiant heat and radiating it laterally, 65 said means being positioned substantially equidistant from one another in a straight horizontal row, a plurality of heat absorbing tubes positioned to form a vertical-walled cage about said means for producing radiant heat and receiving radiant 70 heat therefrom, the end walls and side walls of said cage being spaced from the row of means for producing radiant heat by a distance substantially equal to the distance between the means for producing radiant heat.

2. The apparatus of claim 1 wherein the tubes are positioned vertically in the vertical-walled cage.

3. In a tube still of the type described, a closed row of parallel heat absorbing tubes and a row comprising a plurality of burners inside said row of tubes, everywhere substantially equidistant therefrom and closely spaced with respect thereto and directly opposed to the tubes, the burners being everywhere substantially equally spaced from each other and from the tubes.

4. In the apparatus of claim 1, a convection heater positioned above the cage of heat absorbing tubes, the heater being smaller than and of shape generally similar to the cage, and passage means leading from the interior of the tube row to the heater.

5. In a tube heater a plurality of straight heat absorbing tubes positioned vertically at intervals in a row, said row being in the form of a rectangle having two long sides and two short ends, and a plurality of radiant heat producing burners positioned at intervals in a straight horizontal row on a vertical plane coinciding with the major axis of said rectangle, the spacing between burners and the spacing of the row of burners from the sides and ends of the rectangular row of tubes being substantially the same.

6. In a tube still or the like a row of vertical heat absorbing tubes, said row being arranged in the form of an oblong having two straight parallel sides joined at either end by semi-circular ends and a straight horizontal row of burners adapted to produce radiant heat, said burner row being parallel to and equidistant from said parallel sides, and each end burner in the row being located at the approximate center of one semicircular end.

7. In the-fire chamber of a vertical tube still, a floor of refractory material, a plurality of burners positioned in .a straight horizontal row within said floor and adapted to produce radiant heat 'in said chamber by combustion of suitable fuel,

a plurality of vertical heat absorbing tubes positioned in a row in which each tube is spaced from .adjacent tubes, said row of tubes being symmetrically arranged around said row of burners and spaced therefrom by a short substantially equidistant interval, to insure efficient combustion and efiective absorption of heat from said burners and refractory walls forming the side walls of the chamber and enclosing said tubes.

8. In a tube heater, a row of vertical, spaced tubes arranged in the shape of .an oblong having two parallel straight sides and substantially semicircular ends in combination with a plurality of radiant heat producing burners arranged at intervals in a straight horizontal row along the major vertical axial plane of the space enclosed by said tubes, said burner row being substantially the same distance from the tubes forming the respective ends of the oblong as it is from the tubes forming the sides of the oblong.

9. In a tube heater, a plurality of heat absorbing tubes positioned in the form of a verticalwalled cage having two ends and two sides, the tubes being arranged horizontally in the sides and vertically in the ends, a plurality of means for producing radiant heat and radiating it laterally upon the tubes, said means for producing radiant heat being positioned substantially equidistant from one another in a straight horizontal row along the center line of the cage, the end walls and side walls of the cage being spaced from the row of means for producing radiant heat by a distance substantially equal to the distance between the means for producing radiant heat.

10. In a tube heater, a plurality of burners for producing radiant heat and radiating it laterally, said burners being positioned substantially equidistant from one another in a straight horizontal row, a plurality of heat absorbing tubes positioned to form a vertical-walled cage about said burners and receiving radiant heat therefrom, the end walls and side walls of said cage being spaced from the row of burners by a distance substantially equal to the distance between the burners, an air heater positioned above the cage of heat absorbing tubes, and flaring passage means leading from the interior of the cage to the heater, the air heater being heated by waste products from the burners.

11. In a tube heater, a plurality of means for producing radiant heat and radiating it laterally, said means being positioned substantially equidistant from one another in a straight horizontal row, a plurality of heat absorbing tubes positioned to form a vertical walled cage about said means for producing radiant heat and receiving radiant heat therefrom, the cage being divided into separate sections each opposed to a different portion of the burner row so that different fluids can be passed through the sections and be simultaneously heated by the means for producing radiant heat, the end walls and side walls of said cage being spaced from the row of means for producing radiant heat by a distance substantially equal to the distance between the means for producing radiant heat.

POVL OSTERGAARD.