US2598840A - Heater for hydrocarbon fluid - Google Patents

Description

June 3, 1952 A. H. scHUTTE HEATER FOR HYDROCARBON FLUID v INVENTOR. #Igmjflmrgkiz/fie firm i A -1- EY Filed April 9, 1951 capacity and for heat resistance.

serially through af-bank of the tubes.

Patented June 3, l952 UNITED STATES PATENT OFF ICE HEATER FOR. HYDROCARBON FLUID August Henry Schutte, Hastings on Hudson, N. Y., assignor to The Lummus Company, :New York, N. Y., a corporation of Delaware- Application April 9, 1951, Serial No. 219,910

Claims.

This application is a continuation-impart of my similarly entitled copending application, Serial No. 65,917, filed December 17, 1948, now abandoned.

The invention relates to improvements in tube still heaters such as are "employed in plants for pyrolysis or distillation of hydrocarbon fluids. There are two general types of such heaters and in both types the heaters are usually of quite massive and costly construction, for large charge One of these types is known as the fhorizontal type and has massive tubes horizontally arranged within a furnace chamber and connectedby massive headers. Usually it is required that the charge be passed In that case the headers employed are in the form of return bend constructions connected to the tubes by rolling or by means of mechanical joints. The return bends usually have closures which are removable to aiTord access to'each tube for removal of coke therefrom when the heater is shutdown. There is a return bend'foreach'tube in the usual layout and their weight comprises asubstantial percentage of the total weight of abank of the tubes. For support of the tubes and headers, stout brackets are required. These brackets are mounted within the furnacechamber and must be made of costly metal alloys to withstand the intense heat. The headers and the tube supports render the heater extremely costly.

The other of said types is known as the vertical type heater and has the tubes vertically arranged and spaced apart in a circular layout. There also, massive and costly-headers, usually of the return bend type, are required and stout and costly structure is needed for-support of the combined weight ofthe tubes and-the headers.

Important objects of the invention are, to Provide a hydrocarbon heater designed for more economical construction; to provide 'a-heater design wherein the necessity for headers and for tube-supporting brackets is eliminated; to provide for substantially increased tube surface in a heater of given bulk and given'wallarea; to provide for improved control'of heat input and render a desired time-temperaturecurve readily obtainable; to provide an improvedheater-wherein the tubing is helically-coiled and arranged in an annular bank and wherein there is provision for separate heating of the inner side and the outer side of the bank and ior'maintaining substantial thermal independence betweenaheating zone surrounding the bank and one surrounded by the bank; and to provide an improved heater of 'a vertical type having said advantages.

Further objects and advantages of the invention will appear from the following description embodying the invention, parts being shown in elevation.

Figure 2 is a horizontal section approximately on the line 2-2 of Figure 1, with parts broken away;

Figure 3 is an-enlarge'd detail section on the line 33 01 Figure 2; Figure 4 is an enlarged detailsectionon line 4-4 of Figure 2; and

the

Figure 5 is'a side elevation of a portion of a tion la of the shell also lined with refractory material. It may be square or rectangular in horizontal section. Legs l0 support the shell at a suitable elevation. Between two of the legs, the lower wall 3 has a segmentta which is slidably supported on ledges H for outward removal edgewise. Thereby, access is afiorded to the interior of the shell from the underside thereof.

Within theshell thereis a substantially cylindrical bank 12 of helical tubing disposed with its axis on that of the shell. The bank extends from the bottom wall 3 to a level spaced .a'relatively short distance from the upper wall-2, and its external :diameter is substantially less than the internal diameterof the 'linedshell, to afford liberal spacearound the bank. Aisinglehelically coiled tube may formthe entire bank, .or same may be formed of a plurality of'such tubes with their convolutions arranged in alternation along the bank. In either case, the weight of each convolution is borne by the convolution immediately beneath it and the weightof the entire bank is borne by the bottom wall 3 ofv the shell. For reinforcing said wall, the legs I!) are preferably provided with welded-on; -gussets-l0a.

In the present instance, the tub bank I2 is formed of two helically coiled concurrent tubes Her and [2b with their convolutions arranged in alternation and in direct contact with one another in succession along the height of the bank.

' The bank thus forms a substantially closed cylindrical wall dividing the interior of the shell into two combustion chambers, one of these chambers is within the bank, the other is an annular one surrounding the bank, and both open into the chamber 8 at the top. Two fluid charge pipes l3 and 7 [4 lead to the upper end of the bank and are connected to the tubes I21: and I2b. Two fluid discharge lines l5 and I6 are connected to respective tubes of the bank and lead outwardly from the lower end of the bank to the exterior of the shell. Thereby, two streams of fluid to be heated are circulated through the bank.

Combustion within the zone surrounded by the ing, an annular heat-distributing screen 6a is provided within thelower portion of the zone.

As shown, this screen may be formed of a checker-work of refractory bricks laid up with spaces between the bricks of alternate courses thus providing the screen with numerous ports therearound and therealong, The screen is borne by the bottom wall of the shell and is concentric with the tube bank. It is also of substantially less diameter than the bank to afford material space therebetween.

At the outer side thereof, the tube bank is heated predominantly by radiant heat from combustion conducted by numerous burners I'I distributed over the cylindrical wall of the shell and facing the bank. Preferably these burners are of atype known as nameless burners because of the fact that they produce little or no flame outside of the confines'of the burner. A burner of this type is disclosed in'U. S. Patent No. 2,215,079. In the form shown in Figures 1, 2, and 3 of the present application the burner structure includes a block is of refractory having a frusto-conical concavity l9 facing the tube bank. Back of said block there is a cup-shaped casing 20 forming a chamber to receive a combustible fuel-and-air mixture. A refractory distributing plug 2| for said mixture is screwed into the forward end of the casing 20 and is formed with slots 2m spaced therearound and leading from said chamber to the concavity in the block l3. At their forward ends said slots are directed laterally to deliver the mixture against the wall of the concavity 19 where the mixture is com.- busted, with the result that said wall becomes incandescent. While a satisfactory form of flameless burner is disclosed any suitable burner of a fiameless type may be employed.

The blocks I8 of the burners I! are set in recesses inthe shell lining 4, and the casings 20 are secured to the outer side of the shell I and project inward through holes in the shell. In the present instance, the burners are arranged in vertically spaced circular rows around the tube bank and in each row the burners are equally spaced so that heat may be radiated from the burner concavities l9 over-substantially the entire outer surface of thebank. 'For supplying and i6.

4 and distributing the fuel mixture to the burners a system of manifolds and pipes is provided. In the present instance, there are nine circular rows of burners, and for each three rows there is a manifold 22 encircling the shell and having branch pipes 23 connected to the individual burners of the three rows. A supply manifold 24 has three branch pipes 25 leading respectively, to the three distributing manifolds 20. Each of the pipes 25 has a valve 26 operable to control delivery of the fuel mixture to the manifolds 22 independently. This distributing system may vary to suit different requirements. For example, each manifold 22 may supply only a single row of burners instead of a pulrality of rows.

For recovery of heat from combustion gases passing to the stack, the chamber 8 is provided with a nest of tubes 21 for steam generation, air preheating, or other useful purpose.

Figure 5 shows a slight modification of the tube bank. Here, the successive convolutions of thetubes I2a and i2 are shown as spaced apart instead of in contact and with spacing elements 28 between the convolutions. In this case also, the weight of each convolution is transmitted by 'the spacing elements and is borne by the convolution immediately beneath it and the Weight ofthe entire bank is borne by the floor of the heater. The spacing elements 28 are preferably welded to the tube convolutions above and below them for good heat conduction and for cooling effect by the fluid within the tubes so that the elements will be able to withstand the heat within the combustion chamber. As shown, the convolutions, while separated, are still closely arranged. Fig. 5 shows a spacing of substantially less than a tube diameter. The tube bank forms a substantial screen between the inside and the outside of the bank for maintaining substantial-thermal independence between the heating zone, surrounding the bank and the one surrounded by the bank. Intermingling of combustion gases of said zones is minimized. The

gases from the combustion at the inside burner 6 tend to rise straight to the outlet 1. The gases from the outside burners IT, due the character 'of the burners, are notgiven position direction so that they tend to risewithin the space between the tube bank and the wall 4 and then past the space at the upper end of the bank to the outlet 1.

In the operation of the heater, separate streams of the charge are introduced through the pipes l3 and M to the upper ends of the respective coils Na and i212 and passed downwardly through the bank and out through the pipes [5 Fuel charge to the burner 6 and tothe burners ll isadjusted to obtain the desired heat input, said adjustment for the burners I! being madethrough the valves 26 which control the supply of the fuel to the wall burners. By adjustment of the fuel supply to the burners selectively any time-temperature curve required for a given process may be readily obtained. The annular refractory wall 60. serves to augment the radiant heating effect. It absorbs heat from the combustion conducted by the burner 6 and reradiates the heat to the bank. All of the convolutions of the bank are within view of said wall so that the heat reradiated therefrom is distributed over the entire inner surface of the bank. In servicing the heater, coke deposit within the tubing may be removed by burning it in situ according to a known method, and there are known means for measuring the thickness of the wall of the tubing from outside of the tub- The heater disclosed. was devised primarily for large capacity service and for a high duty of say, 115,000,000 B. t. u. per hour and is intended more particularly for pyrolysis of hydrocarbons in petroleum refining processes. For such service the body of the shell may be approximately 40 feet in height, the inside diameter 20 feet, the outside diameter of the tube bank 14 feet, and the bank may have 90 convolutions of tubing of 5 inches outside diameter. In effectiveness, the tube bank will be the equivalent of approximately 160 straight tubes in a heater of conventional type. The design of the heater provides for greatly increased tube surface for giving combustion chamber size and wall area over heaters of conventional types. At the same time, the improved heating system provides for adequate heating of the increased tube surface and for flexible control of the heat input. In addition, the need for the usual massive and costly return bends and for tube-supporting brackets is entirely eliminated.

The tube bank may be constructed of tube sections welded together end-to-end to form the coils. Each section may comprise one complete convolution or it may be longer or shorter than that. The bank is shown as circular in plan.

However, it may be of any desired continuous form in plan. In the claims the words annular and helical as applied to the inner wall of the combustion chamber and to the reradiating wall 6a are intended to comprehend plan or cross sectional continuous shapes other than circular.

While a very desirable form of the improved heater is disclosed, modifications of structural details are possible within the scope of the invention. It is to be understood, therefore, that the present disclosure is merely illustrative and in nowise limiting and that the invention comprehends such modifications as will come within the scope of the claims.

I claim:

1. A heater for a hydrocarbon fluid comprising a chamber having an annular upright inner wall, an annular upright bank of multi-convolution helical tubing within said chamber and spaced inwardly from said wall, said tubing having inlet and outlet means disposed for passage of the fluid to be heated through the tubing, the successive convolutions bearing the weight of those above them, supporting means beneath the bank bearing the weight thereof, burner means disposed to conduct combustion within the space surrounded by the bank and effect heating of the inner side of the bank by radiant heat, flameless burners distributed over said wall, along and around the bank and directlyopposed thereto to heat the bank by radiant heat, means for controlling operation of said flameless burners independently of said burner means for heating the inner side of the bank, and outlet means forcombustion gas at one end of the chamber and communicating at the adjacent end of the bank with the space surrounding the bank and the space surrounded by the bank, the convolutions of the tubing being arranged sufliciently closely to enable the bank to form a substantial screen to maintain substantial thermal independence between the space surrounding the bank and the space surrounded by the bank.

2. The heater of claim 1 wherein the successive convolutions of the tubing are in direct contact.

.3. A heater for a hydrocarbon fluid comprising a chamber having an annular inner wall disposed with its axis substantially upright, an annular bank of multi-convolution helical tubing within said chamber, substantially coaxial with said wall and spaced inwardly therefrom, said tubing having inlet and outlet means disposed for passage of the fluid to be heated through the tubing, burner means disposed to conduct combustion within the space surrounded by the bank and effect heating of the inner side of the bank, flameless burners distributed over said wall, along and around the bank and directly opposed thereto to heat the bank by radiant heat, means for controlling operation of said flameless burners independently of said burner means for heating the inner side of the bank, and outlet means for combustion gas at one end of the chamber and communicating at the adjacent end of the bank with the space surrounding the bank and the space surrounded by the bank, the convolutions of the tubing being arranged sufiiciently closely to enable the bank to form a substantial screen to maintain substantial thermal independence between the space surrounding the bank and the space surrounded by the bank.

4. A heater, as claimed in claim 3, wherein the said flameless burners which are located at different levels are controllable independently.

5. A heater for hydrocarbon fluid comprising a furnace chamber having a substantially cylindrical upright inner wall, a substantially cylindrical bank of multi-convolution helical tubing within said chamber and coaxial with and spaced inwardly from said wall, said tubing have inlet and outlet means disposed for passage of the fluid to be heated through the tubing, the successive convolutions bearing the weight of those above them, supporting means beneath the bank and bearing substantially the entire weight of the bank, upwardly directed burner means at a lower region of the said chamber and disposed to conduct combustion within the space surrounded by the bank and effect heating of the inner side of the bank by radiant heat, flameless burners distributed over said wall, along and around the bank and directly opposed thereto to heat the outer side of the bank by radiant heat, means for controlling operation of said flameless burners independently of said burner means for heating the inner side of the bank, and. outlet means for combustion gas at the top of the chamber and communicating at the top of the bank with the space surrounded by the bank and the space surrounding the bank, the convolutions of the tubing being arranged sumciently closely to enable the bank to form a substantial screen to maintain substantial thermal independence between the space surrounding the bank and the space surrounded by the bank.

AUGUST HENRY SCHUTTE.

No references cited.

Claims (1)

1. A HEATER FOR A HYDROCARBON FLUID COMPRISING A CHAMBER HAVING AN ANNULAR UPRIGHT INNER WALL, AN ANNULAR UPRIGHT BANK OF MULTI-CONVOLUTION HELICAL TUBING WITHIN SAID CHAMBER AND SPACED INWARDLY FROM SAID WALL, SAID TUBING HAVING INLET AND OUTLET MEANS DISPOSED FOR PASSAGE OF THE FLUID TO BE HEATED THROUGH THE TUBING, THE SUCCESIVE CONVOLUTIONS BEARING THE WEIGHT OF THOSE ABOVE THEM, SUPPORTING MEANS BENEATH THE BANK BEARING THE WEIGHT THEREOF, BURNER MEANS DISPOSED TO CONDUCT COMBUSTION WITHIN THE SPACE SURROUNDED BY THE BANK AND EFFECT HEATING OF THE INNER SIDE OF THE BANK BY RADIANT HEAT, FLAMELESS BURNERS DISTRIBUTED OVER SAID WALL, ALONG AND AROUND THE BANK AND DIRECTLY OPPOSED THERETO TO HEAT THE BANK BY RADIANT HEAT, MEANS FOR CONTROLLING OPERATION OF SAID FLAMELESS BURNERS INDEPENDENTLY OF SAID BURNER MEANS FOR HEATING THE

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