US2177296A - Method and apparatus for heating oils - Google Patents

Description

CL 24, 1939 M. ALEXANDER 2,177,296

Y METHOD .AND APPARATUS FOR HEATING OILS Filed March 26, 1937 Y 2 Sheets-Sheet 1 Oct. 24, 1939. c. M. ALEXANDER METHOD AND APPARATUS FOR HEATING OILS Filed March 26, 1937 2 Sheets-Sheet 2 are undergoing passage through elongated Zones or reforming, are placed in the furnace so as to 30 the convection chamber by way of a flue leading said pasasges has its lower end communicating 30 f4() processing operations, such as the heating of oils furnace gases to the oils passing through the 40 45 trol of viscosity ranges, to heatoils to distillation into the various sections or banks of the fluid 45 50 unsaturated hydrocarbons, or the polymerization certain sections or banks of the heating tubes re- 50 -55 `Vwherein .different processing temperatures are ceives its heat by the forced recirculation of the 55 ratenfed oct. 24, 1939 2,177,296

UNITED STATES PATENT OFFIQE METHOD AND- APPARATUS FOR HEATING OILS Clive M. Alexander, Louisville, Ky.

Application March 26, 1937, Serial No. 133,208

3 Claims. (Cl. 196-116) This invention relates to improvements in demanded by placing the tube banks in different tubular heaters or furnaces of the type utilized in locations within the furnace with respect to the various industrial processes for the heating of heat generating burners. Thus those operations fluids to desired temperatures while such iiuids requiring high temperatures, such as in cracking of restricted cross-sectional area. While tubube located in the Zone or higher temperature lar vheaters of this character are employed in therein, and those requiring lower temperatures, many industrial capacities, they are now quite Such as viscosity breaking or simple distillation, widely used in the heating of hydrocarbon oils in zones of lower furnace temperature. to in processes wherein such oils are subjected to This usual arrangement of heating tubes, howheating for electing the distillation or molecular ever, does not provide for any particular ilexidecompos'ition thereof, the present invention probility in the control of the heat input into any one vviding an improved tubular heater especially of the heat absorbing sections or tube banks of adaptable for the efcient heating of such oils to the furnace independently of and with respect to desired processing temperatures. the remaining sections or tube banks, and it is Tube stills or converters, as ordinarily conone of the important objects of the present in structed for the continuous heating of moving Vention to provide an oil heating furnace of the streams of hydrocarbon oils in the liquid, vapor multiple tube bank type wherein through imor mixed phases, involve a suitable wall structure proved control of the movement of the furnace forming a` heat-confining enclosure in which is gases, better regulation of the heat input into one 20 vsituated a vertical bridge wall so disposed as to Or more selected tube banks is readily obtainable. divided the enclosure internally into a combustion Another object of the invention resides in the or radiant heat chamber, in which combustion is provision of a tubular heater of the character set f actively maintained by the operation of fuel forth wherein the heater walls are so arranged burners or the like, and a spaced convection as to provide a combustion zone and a pair of rel- 25 chamber, the latter receiving heat by the passage atively spaced convection passages containing of furnace gases from the combustion chamber banks of oil heating tubes, one of said passages passing over the top of the bridge wall, the furhaving its lower portion in communication with nace gases being discharged fromithe bottom of a stack outlet or chimney while the other of to the outlet stack or chimney of the heater. In by means of a conduit with the lower portion of such heaters, it is a common expedient to arthe combustion Zone, there being a furnace gas 'range the oil heating tubes in both the combusrecirculating means arranged within said contion and convection chambers, depending upon duit, whereby, through the employment of this the quantity of heat input which it is desired to construction,independent thermal conditions can 35 impart .to each particular bank of tubes through be established within said passages without varywhichthe oil or vapors thereof are passed. Thus ing the setting of the combustion creating devices `inasingle furnace of thetype set forth, it is comdisposed in the combustion Zone to the end of mon to'rcarry out simultaneously several different obtaining the desired transfer of heat from the to high temperatures `wherein rapid molecular heating tubes but without injury to the tubes or decomposition of high boiling oils into lower boiloverheating or underheating of the oils passing ing cils takes place, the heating of heavy oils to therethrough.

incipient conversion temperatures to obtain con- I obtain such improved control of heat input temperatures without molecular change, and heating tubes primarily through the employment other possible operations, such as reforming lowof an improved means for effecting forced recirboiling oils composed mainly of paraffin hydroeulation of the furnace gases within the heater carbons into low boiling oils composed mainly of at Variable and controllable rates of ilow so that 0f normally gaSGOuS hydrOCarbOnS DtO liquid hyceive their normal heat in a conventional mandrocarbons. ner from the operation of the fuel burners and Such a furnace or converter may be designed the furnace gases resulting therefrom, while to carry out two or more of these operations another independent section or tube bank refurnace gases at desired rates of flow through the furnace.

I am aware that heaters or furnaces for oil heating operations have been used involving a combustion zone, a convection zone, an outlet stack, and means for returning the furnace gases to the combustion zone following passage thereof through the convection Zone. My present invention, however, is distinguished from such earlier heaters by the inclusion therein of an additional and separate convection zone (or Zones) having forced circulation of hot furnace gases therethrough, which gases are withdrawn*l from the combustion Zone by the operation of a variable speed hot gas recirculation fan, or the equivalent thereof, and returned to the combustion zone, whereby to regulate with variable control the rate of heat input into the heaty absorb-` ing structures within said additional convection zone while a substantially fixed rate of fuel combustion is taking place in the combustion Zone.

For a further understanding of the invention, reference is to be had to the following description andthe accompanying drawings, wherein:

Fig. l is a vertical sectional view taken through a tubular heater constructed in accordancev with the present invention, and illustrating conventional oil fractionating apparatuswhich may be used in connection therewith.

Fig. 2 is a similar view showing a slightly modied form of the invention, wherein a steam jet is employed as the motivating means lfor effecting recirculation of furnace gases.

Fig. 3 is a similar view through a further modified form of heater wherein `but a single convection passage is usedfor the oil heating tubes Fig. 4 isa variation of a form of the invention disclosed in Fig. 3 showing the use of Va steam jet for recirculating the furnace gases and a slightly different arrangement of the oil heatng tubes.

Fig. 5 is a further modied form of a tubular.

Referring more particularly to Fig. 1 of the drawings, the numeral I designates a tubular heater or converter which has been especially designed for use in oil conversion systems. In the form of the invention illustrated in Fig. 1, the tubular heater comprises side, end and roof walls 2, 3 and 4, respectively, of suitable refractory materials and embodying customary features for effecting the thermal insulation thereof, the said walls defining an enclosing structure. Also arranged Within the converter are spaced vertical bridge walls 5. These walls define between them a combustion Zone 5, in which may be arranged combustion developing means such as oil or gas burners, as indicated at l. The bridge walls 5 are spaced from the end walls 3 to produce convection passages 8 andS through which the furnace gases, developed within the Zone 6, pass downwardly after first having passed over the upper edges of the bridge walls 5. Y

The lower portion of the passage 8 communiprefer to employ a flexible unit such as a rotary fan II driven by a variable speed motor so that the R. P. M. of the fan rotor-will be subjected to considerable variation. obtained, as shown in Fig. 2, with the use of a steam jet or injector I2 arranged withinV said duct or conduit and so positioned as to effect travel'of furnace gases through said duct or conduit for re-delivery to the combustion Zone. Variation in the operation of the steam jet or inlector I2 may be obtained by regulation of the amount of steam, or other motivating fluid delivered thereto.V V

The lower portion of the convection passage 9 communicates at its lower end, in the form of my invention illustrated in Figs. 1 and 2, with a compartment I3 arranged in the foundation I4 of the heater. Arising from theV foundation I4 immediately over the compartment I3 is a furnace gas outlet stack or chimney I5, provided with a suitable damper I6'. 'I'he furnace gases, after'passing through theY passage 9, are not recirculated to the combustion zone but are delivered to the stack I5 at a low temperature for discharge to the atmosphere.

Arranged within the passage 9 is a Abank of primary oil heating tubes I1 and oil to be heated Similar results may be in these tubes enters the lower portion of the in counter-current rrelation to the downwardV flow ofthe furnace gases through the passage 9, with the result that the stack gases, whenY delivered to the compartment I3, possess a low temperature in order to obtain maximum heat economy, i

Oils leaving the top of the bank of tubes I'I pass by way of a connection I9 through a bank of roof tubes 20, arranged Within the Vconverter adjacent to the roof 4. These tubes are heated mainly by radiant heat derived from the operation of the burners 1. hydrocarbons undergoing heat treatment are passed to a third bank of tubes 2| situated in the passage 8, the oil passing through this lastnamed bank of tubesk generally in concurrent flow with Vthe passage of the furnace gases there- K A through. Y Y

During the passage of the hydrocarbons through the tubes 2I, conversion or reaction temperatures are maintained or slightly increased, providing for the necessary time factor in obtaining a desired rate of conversion of, for instance, higher boiling hydrocarbons to lower boiling hyclrcarbons. The heat input imparted to the hydrocarbons passing through the tubes 2I is susceptible to variation, without altering the setting or rate of combustion produced by the operation of the burner 1, by varying the speed of operation of the hot gas fan II. With the use of this fan, or its equivalent, desired and accurate control of the temperatures of the hydrocarbons leaving the tubes 2i may be readily ob-Y tained.

In association with the converter, the hydro' carbons dischargedY from the tubes 2| pass soV Voil is forced upwardly through the tube bank II.

From the tubes 20, the

through a pressure reducing valve 22 and may Y enter a flash chamber, or enlarged separating zone, of the type indicated at 23. In this chamber, heavy oils which are not vaporized under the temperatures and reduced pressures existing in the flash chamber, drop to the bottom of said chamber and are withdrawnV from the system as fuel oil. The lighter or vaporous hydrocarbons Dass 'overhead from the chamber 23 and are delivered to a fractionating column 24. The liquid 'condensate or distillate which collects in the bottom of the fractionating column may bereturned to the converter as recycle stock for reheatng, while the vapors which pass overhead from the fractionating column may be condensed as at 25 and thence delivered to a gas separator 26 containing a pressure reducing valve 21 in the top thereof, through which the fixed gas generated by the system is discharged, the liquid condensate being withdrawn from the bottom of the gas separator as a motor fuel spirit.

Another variation of the present invention has been disclosed in Fig. 2, wherein hydrocarbon oils or other fluids to be heat treated enter the converter at 3@ and pass through the roof tubes 20w and are thence transferred to the bank of tubes ll'a in the passage 9, leaving the converter by way of the pipe line 3|. An independent bank of tubes gia is disposed in the passage 8. The heat treated products leaving the tubes Ha and 21a may be delivered to a common point of discharge, such as the flash `chamber 23. As shown in Fig. 2, positive advance of the furnace gases through the duct or conduit l0 may be effected by the employment of the steam jet or injector l2, in lieu of the fan Il.

In the form of the invention depicted in Fig. 3, the converter comprises but a single convection passage 9b and a single bridge wall 5b. The lower end of the passage 9b communicates with the stack compartment |3b and also with a duct or conduit lb leading to the combustion Zone 6b, the said duct or conduit having posi tioned therein a variable speed hot gas fan Hb.

` Control dampers 32 and 33 are arranged in the lower portion of the passage 9b to provide for the deflection` of hot gases as desired either into the compartment i319 and thence to the outlet stack or to the duct or conduit lb and thence back to the combustion zone. If desired, the passage 9b may be provided with seperate banks 34 and of oil heating tubes, the upper bank being connected with the roof tubes 20h by way of the connection 35.

In Fig, 4, a similar construction is used, with the exception that the lower portion of the bridge wall 5c is provided with an opening 31 establishing communication between the convection passage 9c and the lower portion of the combustion zone 6c. In the opening 3l, there is arranged a steam jet or injector I2C.

In Fig. 4, a single bank of tubes 38 has been shown, which bank is independent of the radiant heat tubes 39 and 40 positioned, respectively, adjacent to one of the vertical walls of the ccmbustion Zone and the roof wall 4c thereof.

In View of the foregoing, it will be seen that in tubular heaters of the type illustrated in Figs'. 1 and 2, the use of a hot gas fan or steam jet for furnace gas recirculation permits the heat input applied to the coil of one convection passage to be independently varied with respect to that applied to the heating coil in the other convection passage. Changes in firing will vary the heat input in the coildisposed in the convection passage leading to the stack or chimney, whereas changes in the rate of gas recirculation will vary the heat input in the coil disposed in the convection passage which communicates at its lower end with the combustion chamber of the converter. This improvement in heater operation has a number of advantages: A single combustion zone may be used to supply heat to two separate coils 'with independent control of heat input for each coil and, in addition, controlled convection heat input can be obtained either from mild heating of heavy oils subject to coke formation, or for very high temperature heating of refractory oils without undue tube stress and failures.

With the arrangement of the tubes disclosed in Fig. 2, the tube bank arranged in the'passage 8 may be used for the heating of oils to incipient cracking temperatures providing for Viscosity control, while the tube banks disposed in the roof of the furnace and in the convection passage 9 may be used to effect molecular decomposition of the oils. The tube arrangement disclosed in Fig. l is particularly applicable to the molecular decomposition of oils or to reforming or polymerization operations since after the oil has been brought to desired reaction temperatures, the time period and control of the iinal exiting temperatures may be conveniently regulated by controlling the recirculation of furnace gases through the passage 8. Regardless, however, of the particular operations which may be carried out in the furnace, the present invention provides for flexibility in the control of heat input into one or more of the coils of a multiple coil furnace.

In Fig. 5, a heater has been disclosed involving heat conning walls so disposed as to produce a combustion chamber 6d, a bridge wall 5d and a convection chamber 8d, the latter being in cornmunication with the combustion chamber at the top thereof. Within the chamber 8d, there is disposed a bank of oil heating tubes 2id and heat is applied to said tubes by the forced passage of the furnace gases downwardly through the chamber 8d. The bottom of this chamber communicates with a conduit ld in which is located a variable speed gas recirculating fan or blower Hd, by which the furnace gases, after passing through the chamber 8d, are returned to the combustion chamber for recirculation through the heater.

Located above the chamber 8d and in substantially vertical registration therewith is a second convection chamber 9a in which is located a bank of oil heating tubes Hd, the latter being connected by a pipe line I9d with a bank of radiant heat tubes 20d located contiguous to the walls of the combustion chamber 6d. A portion of the furnace gases discharged from the combustion chamber 6d passes upwardly under normal draft ow through the chamber 9a and nds eXit as at I3d to an outlet stack ld.

With the construction disclosed in Fig. 5, it will be observed that the tubes 20d in the combustion chamber are mainly heated by radiant heat, and the rate of heat input thereto is only controllable by variations in the operation of the burner or burners 1d. The coil Hd receives mainly convected heat derived from the furnace gases passing upwardly under normal draft flow through the chamber 9a, and variations of heat input into this coil are likewise subject to the setting of the burner or burners ld. The independent convection coil 2Id may have the rate of heat input thereto varied without disturbing the setting of the burner 1d by variations in the speed of operation of the fan Hd, thus providing for independent control of the heating of this particular tube bank.

It will thus be seen that the present invention provides: rst, an improved form of tubular heater construction having an independent convection, zone with forcedhot'furnace gas circulation. Second, a construction of heater with two tubular coils or heating sections therein so located that one of such coils or sections receives its heat input in the greater proportion from radiancy and the other in the greater proportion from convection with means for independently varying their heat inputs. Third, the invention provides a method of controlling independently the heat input to or temperature rise of liquids flowing within multiple coils in a tubular heater of the'type described, the method further providing for independently controlling theheat input to or temperature rise of liquids flowing within separate sections of a continuous coil in such a heater, or separately controlling the heat input to tWo coils located in a furnace having one combustion zone. Moreover,v a method is provided for dispersing the heat of combustion from a single combustion Zone in controlled and variable proportions to two heating coils obtaining their heat from the .single combustion Zone.

It will be understood that the essential features of the invention may be carried out with the use of apparatus other than that disclosed in the several figures of the drawings, and, therefore, my invention is subject to such further variations or modifications, apparent to those skilled in the art, and which may be said to fall fairly within the scope of the following claims.

What is-claimed is: f

1. The method of heating a plurality of streams of hydrocarbon oils of varying boiling ranges which comprises effecting fuel combustion within a single confined combustion zone, divertw ing the resulting furnace gases to form two independent streams, passing said streams through a pair of convection zones, passing one of said streams following travel thereof through one of said convectionrzones :to the atmosphere, returning the furnace gas stream passed through the other of said convection zones to the combustion zone, controlling the rate of flow of the furnace gas stream passing through said lastoils of different boiling ranges through heat absorbing devices arranged in said convection zones. y

Y 2. `A heater comprising a wall structure provided internally with a pair of spaced bridge walls of refractory heat transmission resisting materials, said walls dividing the heaterY internally into a centrally disposed combustion chamber and a pairV of spaced convection chambers, one of the latter being arranged at each side of the combustion chamber, heat absorbing fluid heating means arranged Within each of said convection chambers, an outlet stack in communication with the lower end of one of said convection chambers, a duct uniting the lower end of the other of said convection chambers with said combustion chamber, and means for effecting a forced flow of furnace gases withdrawn from said last-named convection chamber through said duct and into said combustion chamber at variable and controlled rates of flow.

3. The method of simultaneously heating a plurality of hydrocarbon uids of different molecular weights, the improvement which comprises effecting fuel combustion within a confined combustion zone, diverting the furnace gases resulting from such combustion into two separate streams, passing said streams through a pair of spaced convection zones wherein each of said zones contains heat absorbing structures through which hydrocarbon iiuids of different molecular weights are passed, discharging one of the furnace gas streams following passage thereof over the heat absorbing structure in the Zone through which the gas stream is passed to the atmosphere, returning the other of said furnace gas streams following passage thereof over the neat absorbing structure in the convection zone through which it travels to said combustion zone, and controlling the rate of iiow of the lastnamed furnace gas stream through its convection zone to regulate the absorption of heat by the structure in said last-named zone.

' CLIVE M. ALEXANDER.

vnamed convection zone, and passing hydrocarbon y

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