US2212002A - Heating of fluids - Google Patents

Description

1940- M. w. BARNES 1 ,002

HEATING 0F FLUIDS Filed May 13, 1937 21 7 1 s/p I 0 0 o o o 030 N o o o Q kl oaooooooooooqpooo Patented Aug. 20, 1940 HEATING OF FLUIDS Marion W. Barnes, Chicago, Ill., assignor to Universal Oil Products Company, Chicago, 11]., a corporation of Delaware Application May 13,1937, Serial No. 142,407

1 Claim.

This invention is directed particularly to an improved form of furnace structure, especially well adapted to heating hydrocarbon oils to the high temperatures required for their pyrolytic 5 conversion. Heaters of the improved form herein provided, however, will be found advantageous as applied to the distillation of hydrocarbon oils and the heat treatment of fluids generally and are, therefore, not limited to any particular class of service.

One of the problems confronting the oil industry is the design of an inexpensive and efficient heater for cracking units of relatively low capacity which are rapidly becoming oneof the most essential units of small independent refineries and are often imperative to the successful operation of such refineries. Although there are many types and specific forms of heaters for cracking service well adapted to process from 35) 600 to 800 barrels and upward of raw oil per day, the structural features of such heaters make their initial cost disproportionately high for small capacity units and in many cases small capacity heaters designed along identical lines are not as eflicient as the larger heaters, particularly with respect to fuel economy.

One of the primary objects is to provide a heater for small capacity cracking units which is inexpensive in initial cost, economical to operate 31) and which retains the advantages with respect to the utilization of radiant and fluid heat which have heretofore been exclusive to large capacity heaters.

In the heater herein provided, the proper thermal treatment of the oil being processed is insured by the advantageous distribution of the heat absorbing surface (fluid conduit) with respect to the burners and the path of travel of the flames and combustion gases through the 40 heater. Furthermore, this is accomplished in a structure which, on account of its simplicity, is inexpensive to construct and maintain. The relatively low height of the heater herein provided makes it possible to employ tubes of practical length in the fluid conduit without an excessive amount of heat absorbing surface, thereby mini- 'mizing expensive return bends or tube headers. I The location of the tubes with respect to the source of heat permits the efficient utilization 59 of both direct and reflected radiant heat without the danger of localized overheating of any portion of the fluid conduit. This feature materially decreases the amount of heat surface required, thereby materially reducing the cost of the heater.

55 Another important structural feature of the heater herein provided resides in the fact that it may be built entirely above grade, thereby eliminating expensive underground flues and ducts. This is accomplished without elevating the tubes of the convection or fluid heating bank 5 but places them where they are readily accessible for cleansing and replacment without the use of platforms. It will be readily apparent that these features decrease both the initial and maintenance cost of the heater. In addition, a large 10 portion of the radiant tube bank is readily accessible from the ground and the remaining tubes of this bank may be reached for inspection, cleaning and replacement by simple and inexpensive portable platforms or the like. 1

Another advantage of the-improved structure of the invention resides in the fact that in proportion to the size of the heater a relatively long path of travel is provided for the flames and hot combustion gases issuing from the burners prior to direct contact between the main stream of such gases and any portion of the fluid conduit. This permits wide variations in the amount of excess air employed, so that combustion and heating conditions may be regulated to suit the 2 requirements of the particular type of oil undergoing treatment. Another advantage closely related to that above mentioned resides in the fact that the flames and hot combustion gases issuing from the burners may be directed over and maintained in intimate contact with refractory walls of the furnace which are disposed directly opposite the tubes of the radiant heat absorbing bank of the fluid conduit. This feature permits extraction of substantially all of the radiant heat from the flames and hot combustion gases prior to contact of the combustion gases with the tubes of the convection or fluid heating bank. A major portion of the heat thus extracted is supplied to the tubes of the radiant heating bank, in part 40 by direct radiation from the flames and hot combustion gases and in part by reflection from the highly heated refractory walls over which the flames and hot combustion gases are passed.

The features and advantages of the invention will be more readily apparent with reference to the accompanying diagrammatic drawing and the following description thereof. The drawing illustrates one specific embodiment of the improved form of heater provided by the invention and represents a cross-sectional elevation hereof.

Referring to the drawing, the outer walls of the furnace comprise side walls I and 2, a roof 3, the interior surface of which is preferably curved, as

' wall into a combustion and radiant heating compartment 6 and a fluid heating compartment I. The bridge wall extends between the end walls of the furnace from the floor to a point substantially beneath the roof, leaving a space above the bridge wall for the free and unrestricted passage of combustion gases from zone 6 to zone 1. The bridge Wall may be built up solid of refractory shapes or, as in the case here illustrated, may comprise two spaced refractory walls 8 and 9, which are preferably of suitable refractory shapes suspended from a steel or other suitable metal structure, not illustrated, disposed within the space I0 provided between walls 8 and 9, the metal framework preferably being cooled by permittin the passage of air through space Ill. The suspended type of bridge wall contruction will ordinarily be somewhat more expensive in first cost than the solid type of construction, but will ordinarily be less expensive to maintain. However, due to the fact that the refractory surfaces of the bridge wall are protected by fluid conduits disposed adjacent thereto, as will be later described, a solid bridge wall may be employed in this type of structure without encountering extensive and frequent repairs such as are common with unprotected solid bridge walls.

A bank H of radiant heat absorbing tubes is disposed adjacent the top and that side of the bridge wall located in zone 6 of the furnace and, in the particular case here illustrated, comprises a single row of tubes l2, preferably connected at their ends in series by means of suitable return bends, not illustrated, located outside the heated zone of the furnace in suitable header compartments within the end walls, not illustrated,

Another bank l3 comprising, in the case here illustrated, a plurality of superimposed horizontal rows of tubes I4 is located within fluid heating zone I of the furnace and occupies substantially themid-portion of this zone.

Another bank l5, comprising a single horizontal row of tubes I6 is located within zone I of the furnace adjacent the surface of the bridge wall and serves to connect bank II with bank l3.

Tube bank l5 may, however, be eliminated, when desired, or may be replaced by a continuation of bank I3, in either of which cases tube banks II and I3 are preferably interconnected by means of a suitable cross-over of any well known form, not illustrated, preferably located outside the heated zone of the furnace.

The tubes of bank l5 are preferably connected in series, as above mentioned in connection with the tubes of bank H, and the three banks H, I3 and I5 may be connected in any desired sequence to give the desired type of heating curve for the particular oil undergoing treatment.

Fuel, preferably in gaseous or liquid form and, in the latter case, in well atomized or finely divided state is supplied to the lower portion of combustion and heating zone 6 by means of suitable burners 11 through firing ports [8 in the floor 4, Regulated quantities of air for combustion and/or steam for atomization of the fuel may be supplied to combustion zone 6 through the burners and additional quantities of air may be supplied to burner compartment l9, by regulation of a suitable damper or the like 20, and drawn into combustion zone 6 through burner ports IB by the jet action of the burners.

Although only a single burner and burner port areshown in this particular view of the furnace, a plurality of each are preferably provided at intervals so spaced along the length of the furnace as to give a substantially continuous curtain of flame and hot combustion gases a short distance above the burner ports.

The opening through each burner port is preferably at a slight angle from the horizontal, as here illustrated, whereby the flames and hot combustion gases are caused to impinge on the refractory side wall I and flow upwardly thereover, thereby heating the wall to a radiant condition and partially cooling the hot gases by contact therewith. Heat is thereby transmitted from the refractory side wall I, as well as directly from the flames and incandescent gases, to one side of each of the tubular elements of bank II and to refractory wall 9,which latter, in turn, reflects heat to the opposite side of each of the tubular elements of this bank.

After leaving combustion and heating zone 6, the hot combustion gases travel over bridge wall 5 and, due to their heated condition, the main stream of these gases is maintained in intimate contact with the surface of roof 3. The curvature of the roof maintains a relatively streamline flow of gases and helps to eliminate excessive localized cycling of the combustion gases (commonly termed parasitic circulation) in the upper portion of the furnace. The hot gases passing over the surface of roof 3 heat the same to a high temperature and radiant heat is transmitted therefrom, as well as from the hot gases themselves, to the tubular elements of bank H located adjacent the upper portion of the bridge wall, the latter also serving to reflect heat to the opposite side of each of these tubes.

Depending upon the firing conditions employed and particularly upon the proportion of excess air utilized, the combustion gases having passed over bridge wall 5 from-combustion and heating zone 6 to fluid heating zone I will retain a variable amount of radiant heat energy which is transmitted from the gases and from the refractory side wall 2 of furnace over which they pass to one side of each of the tubular elements of bank [5 and to the adjacent surface of the bridge wall, which in turn reflects heat to the opposite side of each of the tubes IS.

The tubes in the uppermost rows of bank l3 may, depending upon the firing conditions employed,.also receive a considerable amount of radiant heat and all of the tubular elements of this bank receive fluid heat from the combustion gases which pass downwardly about the tubes to flue 2|, wherefrom they are directed to stack 22 wherein draft is controlled by means of su table damper 23. i

The entire furnace is mounted upon a suitable foundation indicated at 24 and preferably the entire furnace with the exception of the foundation is disposed above the grade line which is here indicated at 25, whereby underground structure is minimized and underground flues and ducts are entirely eliminated.

It will, of course, be understood that the invention is not limited to all of the specific details of construction above mentioned, since many modifications and minor departures therefrom, which are within the scope of its broader aspects, will be readily apparent to those familiar with the art.

I claim as my invention:

A furnace for the heating of fluids comprising, in combination, substantially vertical side and end walls, a roof having a curved inner surface, a floor, a bridge wall extending upwardly from the floor and spaced from said side walls and dividing the inner portion of the furnace into a combustion and radiant heating zone and a communicating fluid heating zone, a fluid conduit located adjacent the one side of said bridge wall within the combustion and radiant heating zone and disposed to receive radiant heat on one side from the materials undergoing combustion in said combustion and heating zone, as well as reflected radiant heat from the side wall of this zone, and being disposed to receive reflected heat on its opposite side from said bridge wall, a fluid conduit located in said fluid heating zone and in the direct path of travel of the combustion gases having passed over said bridge wall from said combustion zone, a flue communicating with the lower portion of said fluid heating zone and leading to a stack, means for supplying air and fuel to said combustion zone in independently regulated quantities, means for directing the flames and hot combustion gases resulting from the path of flow of the main stream of hot com- 15 through the furnace.

bustion gases passing MARION W. BARNES.

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