US2029293A - Heating of fluids - Google Patents

Description

Jfs. ALTHER HEATING OF FLUIDS Filed Aug. 10, 1933 2 Sheets-Sheet 1 Feb. 4, 1936.

Feb. 4, 1936.

J. G. ALTHER HEATING OF FLUIDS Filed Aug. 10, 1933 2 Sheets-Sheet 2 I I l l l I I I I I I I I I I I I II III Patented Feb. 4, 1936 PATENT: oFrlcs HEATING 0F, FLUIDS Joseph G. .Alther, Chicago, 111., assignor to Universal Oil Products Company, Chicago, 111., a corporation of Delaware I Application August 10, 1933, Serial No. 684,507

8 Claims.

This invention refers to an improved method and means for heating fluids, and in one preferred embodiment is particularlyadapted to the heating of hydrocarbon oils to the high temperatures required for their conversion. The invention permits the use of exceptionally high rates of heat input to theoil undergoing treatment by applying direct radiant heat simultaneously and in substantially equal quantities to opposite sides of tubular elements comprising the fluid conduit. By employing substantially equal high rates of heating on opposite sides of the tubes less tube surface is required for the same amount of heating than when one side of the tube is subjected to direct radiation and the opposite side to reflected radiation and also, with this method of heating, the substantially equal heating conditions around the entire periphery of the tube eliminate internal stresses in the tube walls, due to wide differences in temperature at different points in the tube walls.

In the present invention the oil is first passed through fluid conduits comprising tube banks of the conventional convection heating and radiant heating type, while the succeeding portion of the fluid conduit, wherein substantially equal and high rates of heating are employed on opposite sides of each tubular element, is divided into a multiplicity of tube banks and the heating conditions about each of these banks are independently controlled so as to independently control the rate of heating in each section of this portion of the fluid conduit. This practice permits the us of any type of heating curve regulated to suit the requirements of the particular type of oil undergoing treatment. In this manner, for example, progressively increasing, progressively decreasing or substantially the same rate of heating may be employed throughout that portion of the fluid conduit wherein a substantial proportion of the latent heat of vaporization and a major portion of the latent heat of cracking is imparted to the oil, or any other desired type of heating curve may be employed in this portion of the fluid conduit. It is specifically within the scope of the invention to utilize one or more of said separate sections of the fluid conduit as a soaking zone wherein the oil previously heated to the desiredconversion temperature may be maintained at or near this temperature under-the desired pressure conditions for a predetermined time. This type of heating curve has been found particularly desirable in the treatment of light distillates such as straight-run gasoline, naphtha, kerosene or kerosene distillate and the like for the production of high yields of motor fuels of high anti-knock value.

As another special feature of, the invention, each separate section of that portion of the fluid conduit wherein direct radiant heating is employed on opposite sides of the tubes preferably in series, when desired, but'preferably adjacent tubes in the same row are connected in series and the different rows are connected in parallel so that separate and substantially equal streams of the same oil may pass simultaneously through the two parallel rows whereby each stream is subjected to substantially'equal heating conditions. This practice permits high rates of feed through the heating coil, permitting high charging capacities without excessive pressure drop, due to friction through the fluid conduit. The preceding portions of the heating coil may also be arranged for either series or parallel flow, as desired. I

It is within the scope of the invention to utilize conventional methods of heating in conjunction with the improved method above described whereby opposite sides of tubes in adjacent parallel rows are subjected to uniform heating by direct radiation. Such conventional methods may involve the use of separate banks of fluid conduits employing heating by convection, heating by direct application of radiant heat on one side of the tubes and by the application of reflected radiant heat on the opposite side of the tubes, et cetera. The use of such methods are, however, not to be considered a limiting feature of the invention although they are included in the following more detailed description of the inand 8, extending between the end walls 3 and 4 and from the roof 5 to a point somewhat above the floor of the furnace, divide the combustion zone of the furnace, in the case illustrated, into three main combustion and heating sections designated in the drawings as 9, II) and I I. The partitions I and 8 each comprise, in the case illustrated, adjacent parallel walls with space provided therebetween for a supporting steel structure, (not shown). It is also within the scope of the invention to circulate all or any desired portion of the air requiredfor combustion within the furnace through the spaces provided between the adjacent walls of partitions I and 8 to cool the walls and preheat the air, although well known means whereby this may be accomplished are not shownin the drawings.

Burner blocks I2 containing firing ports I3,-

located within the roof of the furnace, one set of such blocks adjacent each side wall and on opposite sides of each partition wall, as shown, provide for the admission of combustibles into sections 9, I0 and II of the furnace, fuel of any desired form such as oil, gas or pulverized solid being supplied through burners I 4 of any suitable type equipped with suitable control valves I4. Steam for assisting atomization of the fuel and/or. a portion of the air for combustion may be supplied through burners I4, a major portion of the air for combustion preferably being supplied, however, through ducts i5, as will be later more fully described. In the preferred embodiment of the invention, as illustrated in the drawings, the firing ports I3 and the burner block I2 are inclined slightly from the vertical in order to direct the flames against the side walls I and 2 and opposite sides of the partition walls I and 8 and the drawings also illustrate how the central portion-0f the roof above each of the sections 9, I9 and II may be depressed, as illustrated at points I It in the drawings, providing small combustion zones l7 beneath each row of firing ports to allow mixing and partial combustion of the combustibles, prior to their admission into the combustion and heating zones 9, l0 and II.

Preferably, combustion is substantially completed in sections 9, I0 and I I of the furnace and the hot combustion gases pass from these zones along the floor of thefurnace in the space I81 provided between the floor and the partitions I and 8 and side wall Zemerging therefrom to enter the convection heating section I9 of the furnace, from which the combustion products:

pass through ducts 20 and manifold 2| to an air preheater 22, of any suitable form, whereby air for combustion within the furnace is preheated by indirect contact with the combustion products, and the latter finally pass from preheater 22 through flue 29 toa stack (not shown) Air is supplied to preheater 22 by means of a suitable fan or blower (not shown) through duct 24 and the preheated air, having passed through the preheater in direct contact with the flue gases from the furnace, is discharged therefrom through header duct 25 to the branch ducts 26, controlled by dampers 21 and, by means of ducts 26 and ducts I5, controlled by dampers 28, the preheated air is supplied in regulated quantities to each of the firing ports I3 and, together with the fuel from burners I4, to the combustion 4 zones of the furnace, as already indicated.

- time factor.

the combustion and heating zones ,9, III and II. Adjacent tubes in alternate rows are preferably staggered, as illustrated in the drawings, in order that the horizontally projected surfaces from adjacent sides of the tubes in adjacent rows are not shielded by tubes in the adjacent row, opposite sides of each tube being exposed to direct radiation from the side or partition walls and from the materials undergoing combustion.

Another portion of the fluid conduit, here illustrated, wherein conventional heating methods are employed, comprises a' single horizontal row 32 of horizontally disposed tubes 33 located adjacent the floor 6 in the space I8 provided between the bottom of partitions 'I and 8 and side wall 2 and the floor 6. These tubes are exposed on one side to direct radiation from the materials undergoing combustion in sections 9, I9 and II of the furnace and on the opposite side to reflected radiant heat from the floor 6.

Another bank 34 of tubes 35 located in convection zone I9 of the furnace serves to extract available convection heat from the combustion gases, in a conventional manner, prior to their passage from the furnace to the air preheater 22, as previously described.

The dotted lines passing through the tubes of the various sections 29,, 30, 3| and 32 of the fluid conduit indicate one preferred path of travel for the oil through the fluid conduit and the arrows on these lines indicate the general direction of flow therethrough. It will be noted that, in the case illustrated, the oil enters the convection heating bank 34 and is split into two streams each of which flows through an equal number of tubes in this bank and the general arrangement of .the tubes through which each stream flows is the same so that each stream is subjected to equal heating. The oil combined into one stream then passes through each tube 33 of row 32 in succession in a general direction concurrent to the path of flow of the combustion gases. The stream of heated oil leaving row 32 is again split into two equal streams which pass in parallel through the adjacent rows 29 and30 of tubes 3| in series, passing through each of the combustion and heating sections 9, I0 and I I counter-current to the general direction of the flame and the path of travel of the combustion gases.

As an example of one method of operation with the flow of oil through the fluid conduit, as illustrated and above described, the oil is first preheated in tube bank 34 by convection heat recovered from the furnace gases and is then subjected to a progressively increasing rate of heating in tube bank 32, which is supplied primarily with nascent radiant heat on one side and reflected radiant heat on the other, and then passes through tube banks 29 and 30 in sections II, II] and 9 of the furnace in the order named wherein a high rate of heating is obtained on opposite "sides of each tube by direct radiation from the flames and from the refractory walls of the furace. The oil may, for example, be brought to or near the desired maximum conversion tempera- ,ture in section II of the furnace, in which case thatportion of the fluid conduit in sections 9 and It serves as a soaking zone wherein the oil may be maintained at or near the maximum conversion temperature during its passage there-- through in order to give the desired conversion In case of an operation of this nature milder heating conditions may ordinarily be employed in sections 9 and II) of the furnace than in section I l as it is only necessary to maintain the attained temperature of the oil in sections 9 and I0. It will be apparent, however, that it is an inherent feature of the invention to maintain substantially the same heating conditions in sections 9, ill and II or to vary the heating conditions in the respective section to any desired degree.

It will be further understood that the invention is not limited to the specific form of apparatus illustrated nor to the specific flow of fluid through the heating coil which has been illustrated and described. As an example of various modifications of the furnace structure and the flow through the heating coil which may be employed within the scope of the invention, although not illustrated, the furnace may, when desired, be fired from the bottom instead of from the top in which case the tube row 32, if employed, is located adjacent the roof of the furnace and the flow of oil through the tube bank 34, if employed, may be in either an upward or downward direction.

The various sections of the fluid conduit may be connected in any desired sequence and the flow in any portion of the fluid conduit may be in any desired direction. The fluid undergoing treatment may flow through the adjacent rows 29 and 30 of any or all of the tube banks in sections 9, i and II of the furnace either in series or in parallel and this is also true with respect to the tubes in the convection heating bank 34, Tube bank 32 may also be arranged for the passage of two streams therethrough, when desired, so that split flow may be employed in this section as well as in the other portion of the fluid conduit. It will also be understood that one or any number of a plurality of combustion and heating sections such as 9, ill and ii may be employed and that the heating conditions in each of such zones are independently controlled. As another possible modification of the furnace, (not shown) more than a single row of tubes similar to row 32 may be employed adjacent the floor of the furnace and, when desired, this portion of the fluid conduit may be replaced or augmented by a row or rows of tubes placed adjacent the roof and floor of an elongated tunnel or flue connecting zone l8 with zone i9.

I claim as my invention:

1. In a furnace for heating hydrocarbon oils comprising a main furnace structure having side walls, end walls, a roof and a floor, the combination with partition walls extending between said sides from near the floor to the roof of the main furnace structure dividing the same into a plurality of separate combustion and heating zones, means for independently supplying combustibles to each combustion zone, means for removing combustion gases' from each combustion zone and passing the same through a convection heating zone to a stack, a fluid conduit located within said convection heating zone and supplied with available convection heat from said combustion gases, a communicating fluid conduit located adjacent the floor of the furnace directly beneath said combustion zones and comprising heating and combustion zones to direct radiation from flames.

2. In a furnace for heating hydrocarbon oils comprising a main furnace structure having side walls, endwalls, a roof and a floor, the combination with partition walls extending between said sides from near the floor to the roof of the main furnace structure dividing the same into a plurality of separate combustion and heating zones, means for independently supplying combustibles to each combustion zone, means for removing combustion gases from each combustion zone and passing the same through a convection heating zone to a stack, a fluid conduit located within said convection heating zone and supplied with available convection heat from said combustion gases, a communicating fluid conduit located adjacent the floor of the furnace directly beneath said combustion zones and comprising horizontally disposed tubes heated on one side by direct radiation from the combustion gases and on the opposite side by reflected radiation from the floor, another communicating fluid conduit comprising a pair of parallel vertical rows of horizontal tubes in each combustion and heating zone, the tubes of one of said rows being staggered with respect to the tubes of the other row, and means for subjecting opposite sides of each tube in said heating and combustion zones to direct radiation from flames.

3. A process for heating fluid hydrocarbons to conversion temperature comprising passing the fluid hydrocarbons in a restricted stream through a heating coil embracing serially connected tubular elements disposed substantially in a common vertical plane intermediate a pair of parallel heat radiant walls substantially parallel to said plane and forming on each side of the heating coil a combustion zone substantially free of heat absorbing elements intermediate the walls and heating coil, projecting flames into said combustion zones on opposite sides of said coil and directing the flames angularly away from the coil and toward said walls so as to impart a high heat radiating capacity to a substantial portion of each of said walls, and so controlling the generation and projection of flames into said combustion zones as to substantially uniformly heat the opposite sides of any given portion of said heating coil.

4. A process for heating fluid hydrocarbons to conversion temperature comprising passing the fluid hydrocarbons in a restricted stream in series through a plurality of tube banks, each tube bank embracing a plurality of series-connected substantially parallel tubular elements disposed in acommon vertical plane intermediate a pair of parallel heat radiating walls substantially parallel to said plane and forming on each side of each tube bank a combustion zone substantially free of heat absorbing elements intermediate the walls and tube banks, projecting flames into said combustion zones on opposite sides of each tube bank and directing the flames angnlarly away from said tube banks and toward said Walls so as to impart a high heat radiating capacity to a substantial portion of each of said walls, and so controlling the generation and projection of flames into said combustion zones as to heat substantially uniformly the opposite sides of any given portion of said tube banks.

5. A process for heating fluid hydrocarbons to conversion temperature comprising passing the fluid hydrocarbons in a restricted stream in series through a plurality of tube banks, each tube bank embracing a plurality of series-connected substantially parallel tubular elements disposed in a common vertical plane intermediate a pair of parallel heat radiating walls substantially parallel to said plane and forming on each side of each tube bank a combustion zone substantially free of heat absorbing elements intermediate the walls and tube banks, projecting flames into said combustion zones on opposite sides of each tube bank and directing the flames angularly away from said tube banks and toward said walls so as to impart a high heat radiating capacity to a substantial portion of each of said walls, and so controlling the generation and projection of flames into said combustion zones as to heat substantially uniformly the opposite sides of any given portion of said tube banks, and varying the heat applied to the respective tube banks to obtain the requisite heating curve for the fluid hydrocarbons being heated.

6. A process for heating fluid hydrocarbons to conversion temperature comprising passing the fluid hydrocarbons through elongated tubes comprised in a tube bank embracing two adjacent parallel rows of substantially parallel tubes, the tubes of one row being staggered in respect to the tubes of the adjacent row, the tubes of each row lying substantially in a common vertical plane, said tube bank being disposed intermediate 3, pair of parallel heat radiant walls substantially parallel to said planes, forming on each side of said tube bank a combustion zone substantially free of heat absorbing elements intermediate the walls and tube bank, projecting flames into said combustion zones on opposite sides of said tube bank and directing the flames angularly away from the tube bank and toward said walls so as to impart a high heat radiating capacity to a substantial portion of each of said walls, and so controlling the generation and projection of flames into said combustion zones as to substantially uniformly heat the opposite sides of any given portion of said tube bank.

7. A process for heating fluid hydrocarbons to 1 conversion temperature comprising passing the fluid hydrocarbons serially through elongated tubes embraced in a plurality of tube banks, each' tube bank comprising two adjacent parallel rows of substantially parallel tubes, the tubes of one row being staggered in respect to the tubes of the adjacent row, the tubes of each row lying substantially in a common vertical plane, each tube bank being disposed intermediate a pair of parallel heat radiant walls substantially parallel to said planes, forming on each side of each tube bank a combustion zone substantially free of heat absorbing elements intermediate the walls and tube bank, projecting flames into said combustion zones on opposite sides of each tube bank, directing the flames angularly away from said tube banks and toward said walls so as to impart a high heat radiating capacity to a substantial portion of each of said walls, and so controlling the generation and projection of flames into said combustion zones as to substantially uniformly heat the opposite sides of any given portion of said tube banks.

8. A process for heating fluid hydrocarbons to conversion temperature comprising passing the fluid hydrocarbons serially through elongated tubes embraced in a plurality of tube banks, each tube bank comprising two adjacent parallel rows of substantially parallel tubes, the tubes of one row being staggered in respect to the tubes of the adjacent row, the tubes of each row lying substantially in a common vertical plane, each tube bank being disposed intermediate a pair of parallel heat radiant walls substantially parallel to said planes, forming on each side of each tube bank a combustion zone substantially free of heat absorbing elements intermediate the walls and tube bank, projecting flames into said combustion zones on opposite sides of each tube bank, directing the flames angularly away from said tube banks and toward said walls so as to impart a high heat radiating capacity to a substantial portion of each of said walls, and so controlling the generation and projection of flames into said combustion zones as to substantially uniformly heat the opposite sides of any given portion of-

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