US2029292A - Process of heating fluids and apparatus therefor - Google Patents

Description

Feb. 4, 1936. J. s. ALTHER I 2,029,292.

PnocEss oF 'HEATING FLUIDS .AND APPARATUS Tl-usx'luef'orrv original Filed June 4, 1932 nc. 2 l FIGL 3' /a f IV I4' mmmlzmcnchclm: t)

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V /l\V A77' INVENTOR JOSEPH C. ALTHER ATTOR Patented Feb. 4, A1936 rltoc'uszss or HEATING FLUmsaND Arraaaros 'marcaron Joseph G. Alther, Chicago, Ill., assignor Unlversal Oil Products Company, Chicago, Ill., a

corporation of South Dakota Application June 4, 1932, Serial No. 615,360' Renewed February 7, 1935 18 Claims.

This invention particularly refers to an improved method and means of heating uids, during their passage through a fluid conduit, which comprises subjecting the maximum surface of the iiuid conduit to high rates of heating in order to obtain av high average rate of heat input over the entire surface of the conduit.

More particularly the invention refers to a process for heating fluids wherein radiant and tire surface and periphery of the heating tubes than obtainable by ordinary-methods with the same maximum heat input; (b) Flexibility of control of heat application to obtain any desired rate of heat input by direct control of the firing conditions; (c) High tube eiiiciency, i. e., increased capacity for a given tube surface or, vice versa, decreased tube surface for a given capacity as compared with conventional radiant and convection heating methods; (d) Quick heating of the fluid to relatively. high temperatures with minimum time, With consequent reduction in overheating and overcracking when processing hydrocarbonv oils, thus increasing the yield and octane number or knock rating of the gasoline product and reducing the gas formation and coke deposition in the tubes, Among the further advantages of the present invention are the reduction in the cost of installation, maintenance and operation and increased safety, due to the smaller equipment required, and tothe minimization of internal stress in the tube walls, due to unequal heat distribution.

In heaters employing both radiant and convection heat which provide for the application of direct or nascent radiant heat energy from a source of heat to the uid conduit or heating tubes from one direction only, the opposite sides of the tubes ordinarily receive some indirect radiant heat from adjacent reecting surfaces, while the distribution of convection heat around the tubes is uncontrolled and varies with different furnace structure, and tube arrangements as well as with variations in draft and other ring conditions inl the furnace. Obviously this method gives unequal heating around the tube or uid conduit, the side exposed to direct radiation from the source of heat usually receiving heat at an average rate approximately twice as great as the average rate of heating on the opposite surface vof the tube, which is 'exposed to reected raf5 diant heat, thus greatly decreasing the average rate of heat input, over the entire tube surface, below the maximum rate. Due to unequal 'heat ,intensity at different points around the circumference of the tube, the walls of the tube are sub- A jected to unequal expansion stresses and, in the heating of hydrocarbon oils to the high temperatures required for their conversion, high local heat intensities often cause local overheating of a portion of the oil and the resulting formation of excessive-quantities of coke and gas.

lThe present invention embodies a furnace in` which the iiuid conduit is heated from opposite. sides by both radiant and convection heat in such a manner that the maximum surface of each tube 20 of the uid conduit is subjected toa high rate of heat input and uniform heating conditions are obtained on opposite sides of the tube. In this manner the average rate of heating over the entire tube surface may be greatly increased over that obtainable by other methods without increasing the maximum rate of heating. Thus a much higher tube-efficiency is obtainable and the uid' undergoing heating may be heated to the desired temperature in a minimum of time. The simplicity and compactness of the furnace structure of the present invention, as well as the decreased amount of tube surface required for a given capacity, are obvious advantages. Also, due to more uniform heating of the tube, unequal expansion stresses are minimized, permitting higher maximum rates of heating than may be safely employed when high unequal expansion stresses are present in the tube walls. Uniform heating also eliminates local overheating of the fluid passing through the tube and results in the production of less gas and coke and in a motor fuel product of increased antiknock value, as applied tothe conversion of hydrocarbon oil. The attached diagrammatic drawing illustrates one speciiic'form of apparatus designed to in corporate the features and advantages of the present invention. vIt should be understood that a specific form ,of apparatus is shown only for l the purpose of more clearly illustrating the ease 5o of incorporating the features of the invention in a simple furnace structure and that the invention is not limited to this nor to any other specic form of apparatus.

Referring to the drawing. Figure i is a. crosssectional plan view. Figure 2 is a' side elevation, showing a cross-section through the furnace taken along a vertical plane indicated by the line 2 2 in Figure l. Figure 3 is an end elevation taken in cross-section on a plane indicated by the ment 1, which contains the fluid conduit. The.

combustion products pass through the perforations 0, in Walls 5 and 5', into heating zone 1, fromvwhich they pass through the openings 9 in the floor I of the heating zone and through flue II to a suitable stack, not shown, `or to a suitable air preheater, also not shown.

'I'he fluid` conduit, in the particular furnace structure here. illustrated, comprises a single vertical row of horizontal tubes I2, which are connected in series by means of suitable headers or returnbends I3 and have inlet and outlet ports I4 and I4', which are interchangeable so that the oil, or other fluid to be heated, may be passed through the tubes of the heating coil or fluid conduit in either an upward or a downward direction. It will be understood that vertically disposed tubes may be employed when desired, also that in either case the tubes may be connected either in parallel or in series and thatmany other modifications may be employed Without departlng from the spirit and scope of the invention.

T he furnace may be fired with any desired form of fuel by means of suitable burners through firing ports I5 which,'in the case illustrated, are located in the side walls I and I' of the furof course, be fired from either the top, ends or sides, or inany combination of these manners,

.although only side firing ports are illustrated in the drawing.

The perforated distributing or baille walls 5 and 5' are preferably constructed of material of high thermal conductivity, such as fused or molded alumina or silica, artificial or natural mullite etc.,

able to withstand high temperatures and capable of assuming incandescence upon heating, or capa.-

ble of radiating heat applied from combustion zones 6 and 6', into heating compartment 1. Ra-

diant heat-from the walls 5 and 5', as well as from Athe name and/or hot combustion gases through ports 8 in these walls, is supplied to opposite sides of each of the tubes I2 of the fluid conduit and hot combustion gases, directed' into heating compartment I through the perforations 8 lof lthe Walls' 5 and 5', come into contact with opposite 4sides of the tubes I2 and supply additional heat` thereto by convection.

By employing uniform ring conditions in combustion zones Band 6', the opposite sides of any tube I2 are heated equally. By regulating the .in-

tensity of firing through different ring ports in each of the side walls` I and I' of the furnace by means of independently controlled burner I6 of any suitable form, the heatintensity along wall 5 and 5' may be evenly distributed or may be varied along different horizontal portions of the walls, to suit requirements. In this manner the intensity of heating may be maintained .uniform along the entire bank of tubes of the fluid conduit or clif- `ferent heating intensities may be employed in -dierent portions of the fluid conduit, permitting a uniform rate of heating of the fluid undergoing treatmentthrough the entire heatingcoil or pro- 'gressively increasing .or progressively decreasing rates of heating as the vfluid passes through the heating coil or, in fact, any desired type of heating curve may be obtained in the same furnace by 'regulating' the ring conditions. Preferably when theintensity of heating along walls 5 and 5' is varied from top to bottom, as well as'when a uniform intensity isemployedover the whole surface of the walls, the heating conditions imposed 5 and 5 are maintained substantially the same by employing equal firing in horizontally opposite firingv ports in order to maintain uniform heating conditions on opposite sides of each individual tube in the heating coil.

It will be understood that ordinary heating methods ymay be employed in conjunction with the methods of the present invention. For example, an additional bank of tubes of any well known form may be employed to recover additional uid heat from the combustion gases leaving the furnace, especially when high furnace` temperatures are employed around the lower portion of the heating coil in a furnace such as illus-v trated. Such well known expedients, however, do not form an essential or novel part of the present invention. I I

As a specific example of the increased efciency of a furnace such as illustrated andabovey described, as compared with the usual type of radiant and convection heaters, we will assume two cases.

In the first case, wherein the featuresof the present invention are not utilized, a single row of radiant roof and wall tubes is employed in the radiant heating section of the furnace and additional heat is recoveredby convection from the hot combustion gases before they pass from the furnace by means of a separate bank of convection tubes.

' In the second case, wherein the features of the present invention are utilized, the furnace structure is of the type above illustrated and both radiant and convection heating is accomplished inthe same tube bank.

The size and spacing of the -tubes in the second case is the same as or equivalent to the size and spacing of the tubes in the radiantbank of the first case and the firing conditions are so regulated that in each case about 30,000 B. t. us. of radiant energy, per square foot of equivalent heat absorbing surface, is available, theoretically, for absorption by the tubes. In the first case approximately 66 per cent of this total is absorbed by that half of the surface of the tubes exposed to direct radiation and approximately 22 per.- cent is absorbed by the other half of the tube surface, making a total of about 26,400 B. t. us. absorbed in the radiant bank, per projected square foot of tubing or about 8,300 B. t. us., per circumferential square foot of tubing. In additionl about 6,000 B. t.l us. perv circumferential square footof tubing are absorbed by convection tube of the iiuid conduit, aboutr66nper cent of the 30,000 B. t.,us. or thereabouts available per square foot of projected tube surface is absorbed 30 per cent of the total heat input in the second case is by convection, in order to make it comparable to the first case,A an additional 5,400 B. t. us. or thereabouts per square foot of circumferential tube surface is absorbed by convection. 'I'his gives a total' averageheat input of about 18,000 B. t. us. per hour per circumferential square foot of tubing in the second case as compared with about 11,500 as above shown in the ilrst case, which is an increase of approximately 52 per cent in favor of the improved method of heating of the present invention.

With firing conditions such that a greater proportion of radiant'to'convection heating is employed, a=still greater percentage increase of the rate of heat input may be accomplished by use of the features of the present invention.

I claim as my invention:

1. In a process for heating iiuid of the character wherein the uid is passed through a conduit of restricted cross section disposed within a heating zone, the improvement which comprises si-v multaneously subjecting opposite sidesv of said 1 fluid conduit to superimposed radiant and convection heat whereby to obtain a high average rate of heating around the entire periphery of the conduit while independently controlling-the rate of heating at various points along the path of `flow of the iiuid through the conduit.

2. In a process for heating iiuid of the characy terwherein the fluid is passed through a conduit of restricted cross section disposed within a heating zone, the improvement which comprisesV uni- "formly heating opposite sides of said iiuid ccnduit by simultaneously supplying superimposedradiant and convection heat thereto whereby to obtain a high average rate of heating around the entire periphery of the conduit while independently controlling the rateA of heating at various points along the path of flow of the iiuid through the conduit.

3. In a process for heating fluid of the character wherein the fluid is passed through a conduit comprising a plurality of tubular elements of restricted cross section disposed within a heating zone' and forming a continuous fluid passageway, the improvement which comprises simultaneously subjecting opposite sides of each element .to superimposed radiant and convection heat whereby to obtain'a high average rate of heat around the entire circumference of each element while 'l independently `controlling the rate of heating to which different elements of the iiuid 'conduit are subjected.

4. In a process for heating uid of the character wherein the uid is passed through a conduit comprising a plurality of tubular elements of reds tricted cross section disposed within a heating zone and forming a continuous passageway, the improvement which comprises uniformly heating opposite sides of each element by simultaneously supplying superimposed radiant and convection heat thereto whereby to obtain a high average rate of heat around the entire circumference of each element while independently controlling the rate of heating to which different elements of the fluid conduit are subjected.

5. In a process for heating uid of the character wherein the uid is passed through a conduit of restricted cross sectionl disposed within a heating zone, the improvement which4 comprises simultaneously subjecting opposite sides of said fluid conduit to fluid heat from directed streams p of hot products of combustion and superimposed radiant-heat from radiating surfaces whereby ,"o obtain a high average rate of heating around the entire periphery o'f the conduit while independradiating surfaces, whereby to obtain a high av erage' rate of heating around the entire circumference of each element, while independently controlling the rate of heating to which different elements of the uid conduit are subjected.

7. In a process for heating fluid of the charac- 'ter wherein the fluid is passed through a conduit comprising a plurality of tubular elements of restricted cross section disposed within a heating zone and forming a continuous iiuid passageway, the improvement which comprises uniformly heating opposite sides of each element by simultaneously supplying uid heat from directed streams of hot products of combustion and superimposed radiant heat from radiating surfaces to said opposite sides, whereby to obtain a high average rate of heating aroundv the entire circumference of each element, while independently controlling the rate of heatingto which different elements of the uid conduit are' sulg'ected.

8. An apparatus for heating fluids comprising, in combination, a furnace structure containing a heating zone, a. fluid conduit of restricted cross section disposed in said heatingzone, combusing zone, a perforated wall, highly conductive to 'radiant heat, separating each combustion zone.

from the heating zone, means for supplying combustible fuel to each combustion zone, vmeans for removing combustion gases from the heating zone wherebyopposite sides of the iiuid' conduit along its entire length in the heating zone are simultaneously subjected to heating by superimposed radiation and convection and means for independently supplying regulated quantities of combustible vfuel to various portions of each combustion zone whereby to-independently control the rate vof heating in different portions of the uid conduit.

9. An apparatus for the heating of iiuids comprising in combination a furnace structure containing a heating zone, a uid ,conduit disposed in said heating zone and comprising a plurality of tubular elements connected in series, combustion zones located on opposite sides of said heating zone, a perforated wall, highly conductive to radiant heat, separating each combustion zone from the heating zone, from which walls andl tions combustion gases are directed from the combustion zones into the heating zone to simultaneously supplyuid'heat to opposite sides of each element of theuid conduit, means for removing combustion gases from the heating z e,

'and .means for independently supplying regulate quantities .of combustible fuel to various portions of each combustion zone whereby to independently control the rate of heating in different elements of the fluid conduit. y

10. In a process for heating iiuid of the character wherein the4 fluid is passed through a conduit of restrictedcrosssection disposed within a heating zone,- the improvement which comprises uniformly heating opposite sides of said fluid conduit by uid heat from directed streams of hot products of combustion and superimposed radiant heat from radiating surfaces whereby to obtain a high average rate of heating around the ventire periphery of the conduit while independently controlling the rate of heating at various points along the path of iiow'of the iiuid through the conduit.

11. In a process for heating fluid of the char- 1acter wherein the fluid is passed through a conduit of restricted cross section disposedwithin a heating zone, the improvement which comprises simultaneously subjecting opposite sides of said uidconduit to heat of substantially equal lin tensity whereby to obtain a high average rate of heating around the entire periphery of the conduit and controlling the'amount of heat applied at various points along the path of-flow of fluid through the conduit.

12. In a processfor heating.fiuid of the character whereinthe fluid is passed through a conduit of restricted cross section vdisposed within a heating zone, the improvement which comprisesuniformly heating opposite sides of the said uld by simultaneously supplying thereto' heat of sub.-

stantially equal intensity to obtain a high average rate of heating around the entire periphery of the conduit, and controlling the rate. of heating at various points Aalong the path of iiow of the fluid'through the conduit. t

13. In a process for heating uid of the character wherein the fluid is passed throughv a. conduit comprising a plurality of tubular elements of restricted cross section disposed within a heatingY zone and forming. a continuous uid passageway,

the improvement which comprises simultaneously subjecting opposite sideslof eachelement to heat of substantially equal intensity whereby' to obtain a high average rate of heating around the entire-circumference of each element, and .independently controlling vthe amount of heat to which certain elements of the fluid conduit arel subjected.

14. In a process for heating uid of the character wherein the uid is passed through a conduit comprising a plurality of tubular elements of restricted cross section disposed within a heat'- ing zone and forming a continuous passageway, the improvement which comprises uniformly heating opposite sides of each element by simultensity and controlling the amount of lheat appliedat various points along the path oi ow of fluid through the conduit to thereby secureany desired predetermined heating curve for the iiuid passing through the heating zone and controlling the heating curve dependent upon the character of the uid being heated.

16. In a process for heating fluid o'f the character wherein the fluid is passed through a conduit of restricted cross-section disposed within a heating zone, the improvement which comprises simultaneously subjecting opposite' sides of said fluid conduit to heat of substantially equal intensity and modifying, at a point along the path of flow of uid through the conduit, the amount of heat applied thereto to thereby secure a predetermined heating curvefor the iiuid flowingv through said conduit and to controllablyyary the rate' of heat input to the fluidas it advances through the conduit. y

17. In a process for heating uidof the character wherein the iiuid is passed through a conduit of restricted cross-section disposed within a heating zone, the improvement which comprises simultaneously subjecting opposite sides of said fluid conduit to heat of substantially equal intensity and modifying, at predetermined points along the path of iiow of iiuid through the c'onduit, the amount 'of heat applied thereto to thereby progressively vary the rate of heat input Y' to the fluid as it advances through the conduit.

to secure a predetermined heating curve for the' vfluid being heated.

18. A process for heating fluid in a heating coil embracing serially-connected tubular elements disposed substantially in a common plane intermediate and in unobstructed heat radiatin" relation to heat radiating' walls substantially parallel :to said plane, comprising generatingame in combustion zones on opposite Asides of said coil 1 at a plurality of' spacedpoints therein and -di-A recting the same toward said walls so as to impart incandescence to la substantial-.portion s thereof, and so controlling the generation of name in said combustion zones that heat of substantially uniform intensity embracing direct heat from combustion gases and heat radiated from said incandescent walls is applied to opposite sides of `any given tubular conduit embracedin said heat ing coil. v

JOSEPH G.

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