US2212526A - Heater - Google Patents

Description

Aug. 27, 1940. L. A. MEKLER 2,212,526

HEATER Filed June 26, 1939 3 Sheets-Sheet 1 L. A. MEKLER Aug. 27, 1940.

HEATER Filed June 26, 1939 3 Sheets-Sheet 2 Aug. 27, 1940. L. A. MEKLER HEATER Filed June 26, 1939 3 Sheets-Sheet 3 Patented Aug. 27, 1940 UNITED STATES PATENT OFFICE HEATER tion of Delaware Application June 26, 1939, Serial No. 281,073

6 Claims.

The invention particularly refers to an improved form of heater of the type now generally known in the oil refining industry as an equiflux heater the particular form of heater herein provided having three individual cells or compartments each independently fired along opposite side walls of the cell and each provided with a plurality of tubular elements interconnected in such a manner as to simultaneously heat two separate streams of fiuid under substantially identical conditions with definite control of the rate of heating and the temperature curve obtained in different sections of each stream.

This improved form of heater is particularly advantageous as applied to that type of hydrocarbon oil conversion known as reforming, where relatively light hydrocarbon oil distillates such as gasoline or gasoline fractions of inferior antiknock value, naphtha and the like are converted into high yields of good antiknock gasoline. In such service the heater is adaptable to high charging stock capacities, the flow of oil through the various tubular elements and the various cells being such that the total charging stock may be divided into two streams of substantially equal quantity to avoid excessive pressure drop through the heating coil, while each separate stream is simultaneously heated under substantially identical conditions and the heating curve most advantageous for this type of conversion is obtained in both streams. v The advantageous features of the invention will be clearly understood by those familiar with the art with reference to the accompanying drawings. Figure l of the drawings is a cross-sectional elevation of one specific form of heater provided by the invention and illustrates one specific flow which may 'be employed for simultaneously heating two substantially equal streams of the same oil under substantially identical conditions. Figures 2, 3, and 4 each illustrate a different modification of the flow illustrated in Figure 1, the general contour of the heater being shown by broken lines in Figures 2, 3 and 4.

Referring to Figure l, the three individual cells or compartments of the heater are designated as l, 2 and 3, cells I and 3 being disposed on opposite sides of the central cell 2. The two outcrcells are each provided with a side wall 4 and walls 5 and 6 separate cell 2 from cells I and 3, respectively. Walls 5 and 6 may be of the sectionalized double suspended insulated and air-cooled construction shown in the drawings or of any other desired conventional construction, not illustrated. For example, partition walls of solid masonry comprising fire-brick or other refractory shapes laid up in a conventional manner may be employed. The same applies to the outer side walls 4 and end walls (not shown) and other details of the construction illustrated may be 5 modified in any conventional manner, since the invention is concerned with the general arrangement and disposition of the fluid conduits rather than structural details. Each cell is provided with a roof I and end Walls which are now shown 10' in this particular view of the heater.

The lower portion 8 of cell I, which is of reduced cross-sectional area as compared with the upper portion of the cell, is a fluid heating zone containing a plurality of horizontal rows of horizontally disposed tubes 9, which comprise tube bank ill of the heater. The upper portion of cell l s a radiant heating zone containing two vertical rows of horizontally disposed tubes H, which comprise tube bank I2 of the heater, this 80 bank being located centrally between walls 4 and 5 of cell i and adjacent tubes in the two rows being arranged in staggered formation.

The lower portion l3 of cell 3 is substantially the same as the lower portion 8 of cell I and is a fluid heating zone containing tube bank l5 substantially identical with bank IU of cell l and comprising a plurality of horizontal rows of horizontally disposed tubes I4. The upper portion of cell 3, which corresponds to the upper portion 80 of cell I, is a radiant heating zone containing a tube bank I! which, like bank 12 of cell l, is disposed centrally between the side walls of the cell and comprises two vertical rows of horizontally disposed tubes "5, the adjacent tubes in the two rows being arranged in staggered formation.

Cell 2 also has a lower portion l8 similar to the lower portions 8 and i3 of cells'l and 3, respectivelv, and zone i8 is a fluid heating zone containing a, plurality of horizontal rows of hori- 40 zontally disposed tubes l9 comprising tube bank 20. Bank 20 is divided into a right-hand and a left-hand section each containing an equal number of tubes. Provision may be made for passing a single stream of fluid in series through the tubes of each section of bank 20, as illustrated, or, when desired, the sections of this bank may be further divided by well known means, not illustrated, to'permit the passage of any desired number of parallel streams therethrough.

The upper portion of cell 2 is a radiant heating zone containing four vertical rows of horizontally disposed tubes 2| located centrally between the side walls 5 and 6 of this cell and comprising tube bank 22. Bank 22 is divided into a right-hau-rl and a left-hand section each containing an equal number of tubes, the adjacent tubes in adjacent rows of bank 22 being arranged in staggered forma-tion.

In the' particular case here illustrated, each. of the cells I, 2 and 3 is fired in a downward direction through firing ports 23 provided in the roof I adjacent side walls 4, 5 and 6 by means of burners 24. Each of the burners points at an angle toward the adjacent side wall so that the flames and hot combustion gases resulting from the combustion of fuel in the various cells impinge against said adjacent walls and pass downwardly thereover, heating the same to a highly radiant condition. The fuel is supplied through the burners and the air for combustion is supplied, in part, through the burners and, in part, directly through firing ports 23 by the inductor action of the mixture issuing from the burners or, when desired, a forced-draft fan or blower, not illustrated, may be employed for supplying air at atmospheric temperature, air preheated by contact with the walls of the furnace setting or air preheated by heat exchange with flue gases through and around the burners. Preferably, the burners and firing ports are arranged in a row adjacent each of the walls 4 and each side of the walls 5 and 6 within the cells so that there is a substantially continuous sheet of flames and hot combustion gases travelling downward over the fired surface of each of these walls, although this arrangement is not illustrated in the particular view of the heater herein shown.

Heat is imparted to opposite sides of each of the tube banks I2 and I1 by direct radiation, a major portion of the heat transmitted to the oil flowing through the tubes of banks I2 and I! being imparted to the tubes by radiation from the flames, hot combustion gases and highly heated walls of the cells wherein they are disposed at relatively high rates of heat transfer.

The combustion gases, from which a major portion of their radiant heat has been extracted by transmission to banks I2 and Il, pass downwardly through the zones 8 and I3 of the respective cells I and 3 in direct and intimate contact with the tubes of banks II] and I5, respectively, whereby a substantial quantity of fluid heat is extracted from the gases, and they then pass through the respective flues and 26 to a suitable stack, not shown, a single stack being preferably employed for all three of the cells.

Predominantly radiant heat is also imparted to each of the tubular elements of bank 22 from the flames, hot combustion gases and highly heated side walls of cell 2. However, with the particular arrangement here illustrated, the tubes of the-two central rows of bank 22 are each partially shielded on one side by the adjacent tubes of the two outer rows, and vice versa, so that, even if identical firing conditions were employed in all three cells, the tubes of bank 22 would not receive heat at such a high rate as those of banks I2 and IT.

The combustion gases from the upper portion of cell 2, from which a substantial portion of their radiant heat has been extracted, pass downwardly through zone I8 in direct and intimate contact with the tubular elements of bank '20, which receive a large amount of fluid heat heating zone, which is disposed above rather than beneath the radiant heating zone to a flue disposed above the fluid heating zone.

The adjacent tubes of each of the banks are connected in series at their ends by means of suitable return bends which are located outside the heated zone and do not appear in this particular view of the heater. The single lines connecting the adjacent tubes and connecting the various tube banks indicate the flow therethrough in each of the figures of the drawings, the general direction of flow being indicated by arrows.

The flow illustrated in Figure 1 is as follows: The oil to be treated enters the heater as two separate streams 28 and 28' of substantially equal volume. The left-hand stream flows in a general upward direction through the left-hand section of tube bank 20 and is transferred from the uppermost tube of this bank through line 29 to the lower portion of bank II), through which it flows in a general upward direction and is thence transferred through line 30 to'thelower end of tube bank I2 and flows in series through adjacent tubes in the opposite rows of this bank in a general upward direction. This stream is transferred from the upper end of tube bank I2 through line 3I to the upper end of the lefthand section of tube bank 22 and flows downwardly in series through the adjacent tubes in the two rows of this section to its lower end. The right-hand stream 28 follows a substantially identical course through the right-hand section of bank 20, through line 32, bank I5, line 33, bank I'I, line 34 and the right-hand section of bank 22, in the order given, and the two separately heated streams emerge from the lower ends of the right and left-hand sections of bank 22 to commingle in line 35 through which they are directed to subsequent portions of the system not pertinent to the present invention.

With the particular arrangement and flow illustrated and above described, when reforming gasoline or other light hydrocarbon oil distillate, substantially identical flring conditions are preferably employed in each of the cells I and 3 and on opposite sides of each of the cells, while somewhat milder firing conditions are employed in cell 2, with substantially equal firing on opposite sides of this cell. Thus, the two streams of oil are substantially equally heated and each stream attains a high cracking temperature within the respective banks I2 and I1 and is maintained for a predetermined time in bank 22 at a substantially uniform temperature close to that prevailing at the outlet of banks I2 and II. By thus employing banks 20, I5, I0, I2 and I! as heating and cracking sections and employing bank 22 as a soaking section, a heating curve will be obtained (by plotting the time in the coil against the temperature rise) which rises rather steeply to or near the maximum temperature attained and has a relatively flat end, representing the soaking section, this being the ideal heating curve for reforming.

In Figure 2, the tubes of each of the banks I0, I5 and both sections of bank 20 are. connected as illustrated in Figure 1, the left-hand section of bank 20 being connected with bank l0 and the right-hand section of bank 20 being connected with bank l5, but instead of connecting adjacent tubes in opposite rows of banks l2, I1 and the right or left-hand sections of bank 22 in series. adjacent tubes in the same row are connected in series and parallel flow is employed in the two rows of each bank. 1

In Figure 3, the arrangement of banks l0, I5, 20, I2 and I1 and the flow therethrough is the same as illustrated and described in conjunction with Figure 2, while the flow through the right and left-hand sections of bank 22 is as illustrated in Figure 1, except that the general direction of flow through the two rows of each section of bank 22 is reversed. The left-hand section of bank 20 and banks Ill, I2 and the lefthand section of bank 22 are connected in series in the order named, while the right-hand section of bank 20 and banks l5, l1 and the right-hand section of bank 22 are connected in series in the order named.

In Figure 4, the arrangement and flow through banks l0, l5 and 20 is the same as illustrated in Figure 1, the arrangement and flow through banks l2 and I? also being the same as illustrated in Figure 1 and the arrangement and flow through the right-hand and Tait-hand sections of bank 22 being the same as illustrated in Figure 1.

The flow illustrated in Figures 2, 3 and 4 each give still greater flexibility with respect to control of the heating curve than that illustrated in Figure 1, since firing conditions on opposite sides of each tube bank may be independently controlled and by varying the amount of excess air employed, variations between the rates of heating obtained in the upper and lower portions of each cell may be accomplished. The flow illustrated in Figure 2 provides the greatest degree of flexibility, while that illustrated in Figure 3 provides greater flexibility with respect to banks l2 and H as compared with that illustrated in Figure 1, and the flow illustrated in Figure 4 provides greater flexibility with respect to bank 22 as compared with that illustrated in Figure 1.

Many modifications of the specific form of heater illustrated are possible within the scope of the invention and will be apparent to those familiar with the art. For example, although each of the figures of the drawings illustrates a separate fluid heating bank communicating with each radiant heating compartment, the invention specifically contemplates a multiple compartment heater having an odd number of radiant heating zones and a single fluid heating zone communicating with each of the radiant heating zones. In' such cases, the tube banks Ill, I5 and 20 may be replaced by a single tube bank divided into a plurality of substantially identical sections equal in number to the number of separate streams supplied to the heater, each stream being passed through one of said separate sections. k

I claim as my invention:

1. A heater for fluids comprising, in combination, an odd number of separately fired heating compartments, a plurality of tubular elements in each compartment disposed to receive heat by direct radiation from flames and hot combustion gases resulting from burning of fuel in said compartments and by radiation from hot refractory walls of the compartments, means for relatively mild firing of one of said compartments and means for more severe substantially uniform firing of the other compartments, means for passing a separate stream of the fluid to be heated through the tubular elements in each of said other compartments and means for thence passing each of said separate streams through separate sections of the tube bank comprising said tubular elements in the mildly heated compartment, the arrangement of said separate sections and of the tubular elements in each compartment and the form of the compartments and arrangement of the means for firing the same being such that each of said separate streams is substantially uniformly heated.

2. The heater defined in claim 1, wherein each of said compartments has substantially vertical side walls and the means for firing each compartment comprises separate sets of burners arranged to direct a separate sheet of flames and hot combustion gases over each of said side walls in a substantially vertical direction, the tubular elements of each compartment comprising a bank having a plurality of substantially parallel vertical rows of horizontally disposed tubes, each of said banks being located centrally between said side walls of the compartment in which it is disposed, the adjacent tubes in each row of the individual. banks in each of said other compartments being connected for the series of flow of fluid therethrough and the adjacent rows of tubes in each of the. last named banks being connected for the series flow of fluid therethrough.

3. The heater defined in claim 1, wherein each of said compartments has substantially vertical side walls and the means for firing each compartment comprises separate sets of burners arranged to direct a separate sheet of flames and hot combustion gases over each of said side walls in a substantially vertical direction, the tubular elements of each compartment comprising a bank having a plurality of substantially parallel vertical rows of horizontally disposed tubes, each of said banks being located centrally between said side walls of the compartment in which it is disposed, the adjacent tubes in each row of the individual banks in each of said other compartments being connected for ti": series flow of fluid therethrough and the adjacent rows of tubes in each of the last mentioned banks being connected for the series flow of fluid therethrough in countercurrent directions.

4. The heater defined in claim 1, wherein each of said compartments has substantially vertical side walls and the means for firing each compartment comprises separate sets of burners arranged to dllGC J a separate sheet of flames and hot combustion gases over each of said side walls in a substantially vertical direction, the tubular elements of each compartment comprising a bank having a plurality of substantially parallel vertical rows of horizontally disposed tubes, each of said banks being located centrally between said side walls of the compartment in which it is disposed, the -djacent tubes in different rows of each bank in said other compartments being connected for the series flow of fluid therethrough.

5. The heater defined in claim 1, wherein each compartment has substantially vertical side walls, the means for firing each compartment comprising separate sets of burners arranged for directing a separate sheet of flames and hot combustion gases over each of said side walls in a substantially vertical direction, the tubular elements in each of said other compartments comprising a single bank having a plurality of vertical rows of horizontally disposed tubes connected for the series flow of fluid through the several tubes of each bank and said separate sections of the tube bank in said one compartment each comprising a plurality of vertical rows of horizontally disposed tubes, the adjacent tubes in each row of said separate sectionsbeing connected for the series flow of fluid therethrough and the adjacent vertical rows in each of said separate sections being connected for the series flow of fluid therethrough, the tube bank in each of said compartments being located centrally between said side walls of the compartment in which they are disposed.

6. The heater defined in claim 1, wherein each compartment has substantially vertical side walls, the means for firing each compartment comprising separate sets of burners arranged for directing a separate sheet of flames and hot combustion gases over each ofsaid side walls in a substantially vertical direction, the tubular elements in each of said other compartments comprising a single bank having a plurality of vertical rows of horizontally disposed tubes connected for the series flow of fluid through the several tubes of each bank and said separate sections of the tube bank in said one compartment each comprising a plurality of vertical rows of horizontally disposed tubes, the adjacent tubes in different rows of said separate sections being connected for the series flow of fluid therethrough and each of said banks being located centrally between said walls of the compartment wherein it is disposed.

LEV A. MEKLER.

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