US2223379A - Heating of fluids - Google Patents

Description

Patented Dec. 3, 1940 PATENT OFFICE HEATING F FLUIDS Lev A. Mekler, Chicago, Ill., assigner to Universal Oil Products Company, Chicago, Ill., a corporation of Delaware Application January 20, 1939, Serial No. 251,869

4 Claims.

This is a continuation-in-part of my co-pending application Serial Number 120,013, led January 11, 1937, now Patent No. 2,147,662.

In the aforementioned co-pending application, I disclose an improved fluid heater of the radiant and convection type which is particularly advantageous as applied to heating hydrocarbon oils to the high temperatures required for their pyrolytic conversion. Its advantages result, in part, from its high degree of flexibility with respect to independent control of the rates of heating which may be employed in different portions of the fluid conduit through which the oil undergoing treatment is passed. A further advantage results from its ability to employ high rates of heating in either or both of the separately fired combustion and heating zones provided, wh-erein the fluid conduits disposed therein are heated by direct radiation from llames and hot combustion gases and by direct and reflected radiation from the hot refractory Walls of the heater. It is an upwardly fired heater in which the flames and hot gases resulting from the combustion of fuel are directed over the surface of a substantially vertical refractory wall which is thereby heated to a highly radiant condition and radiates heat to the tubular elements of a fluid conduit located adjacent an opposing wall and disposed outside the main path of travel of said flames and hot com.

bustion gases. The general direction of flow of the flames and combustion gases is upward throughout the entire length of the heater and, after the combustion gases have given up a major portion of their radiant heat to the tubular elements of the fluid conduit disposed opposite the ring wall, they are directly contacted with the tubular elements of another portion of the fluid conduit disposed above said combustion and heating zone and in the direct path of travel of the combustion gases. Due to the firing arrangement, the upward flow of combustion Vgases and the disposition of the fluid conduit, high average rates of heating closely approaching the maximum rate obtained at any point in the iluid conduit may be employed throughout that portion of the fluid conduit in the combustion zone and the danger of excessive localized heating is avoided.

The heater provided in this application is similar in general form to that provided in the copending patent application except that a single is simpler and less expensive to construct and retains all the advantages of the heater abovey described except that, since only a single cornbustion zone is provided, it does not possess the same degree of flexibility with respect to inde- 5 pendent control of the rates of heating about different portions of the fluid conduit. It may, however, be employed to advantage in all cases where flexibility, with respect to the type of heating curve obtained, is not *of paramount importance and is particularly advantageous when substantially uniform heating conditions are desired about the entire length of the fluid conduit disposed Within the combustion zone.

By employing two heaters of the form herein provided with suitable cross connections between the fluid conduits in the two heaters, all of the advantages of the heater provided in the par-ent application may be obtained and, in addition,

greater flexibility with respect to changes in the type of cracking stock employed, are obtainable by simple changes in the outside piping connections to the heaters. Two such heaters disposed back-toback need occupy little if any more ground area than a two-cell heater of the type previously disclosed and will cost approximately the same for a given capacity. With such an arrangement, which is specifically contemplated, one heater may, of course, be utilized without employing the other to accommodate temporary changes in the type of charging stock employed or temporary changes in the charging stock capacity, when desired, whereas, with the heater disclosed in the parent case, both combustion zones must be operated simultaneously. It is also possible to employ two heaters of the type herein provided simultaneously for different classes of service or for the simultaneous processing of two separate streams of the same oil under substantially identical heating conditions.

In the accompanying diagrammatic drawing, which illustrates one specific embodiment of the improved form'of heater herein provided, the

main furnace structure comprises a substantially vertical refractory side wall l, an opposite refractory side wall 2 having a sloping portion 3 and end walls which are not shown in this particular cross-sectional view. I

The space 4 between the lower portion of walls l and 2 comprises a combustion and heating zone, 50 the upper portion of which is narrowed by the sloping section 3 of wall 2. The space 5 between the remaining substantially vertical upper portion 6 of wall 2 and the remaining upper portion of wall l comprises a fluid heating zone.

A iuid conduit l which, in the particular case here illustrated, comprises a plurality of superimposed horizontal rows of horizontally disposed tubes 8 is located within uid heating zone 5. Another tube bank 9 which, in this particular case, comprises two substantially parallel vertical rows of horizontally disposed tubes Ill, is located immediately adjacent that portion of the side wall 2 beneath the sloping section 3. An extension II of tube bank 9, which also comprises two substantially parallel rows of horizontally disposed tubes. is located immediately adjacent the sloping section 3 of wall 2.

A plurality of burners for gaseous fuel, one of which is indicated at I 3, is disposed within space It between iioor l5 and foundation I5 of the furnace. These burners are preferably arranged in a single row near side wall l and the combustible materials issuing therefrom are directed upwardly through suitable burner ports, one of which is indicated at Il, over side wall I. Preferably, the burners and burner ports are so disposed, as here illustrated, that lthe flames and hot combustion gases impinge against side Wall l at a slight angle and intimately contact and heat this wall to a highly radiant condition as they pass upwardly through the combustion and heating zone. Fuel is supplied to burner i3 through line I8 and valve I 9 and'air for combustion is admitted to zone It through opening 2li in the outer jacket 2| of the furnace in controlled. amounts, regulated by the adjustment of slidable damper 22. Regulated quantities of the air thus supplied to zone I4 are admixed with the fuel supplied to burner I3 by means of mixing device 23 and additional air from zone i4 is admitted to combustion zone 4 through the space 24 provided between the nozzle ofu the burner and the firing port.

Provision is also made for supplying combustible mixtures of liquid fuel and air to the combustion zone through a plurality of burner ports, one of which is indicated at 25, provided at the lower end of side wall 2 above floor I5. Burner 26 supplies fuel and air for atomization thereof through burner port 25 to the combustion zone and additional air is admitted through port 21,

regulated by damper 28.

The tubes in the opposite 4parallel rows of banks 9 and II are preferably arranged in staggered formation and spaced a suiiicient distance apart that one side of each of the tubes receives heat by direct radiation from the ames and hot combustion gases in zone 4 and from the hot refractory side wall I,- while the opposite side of each of the tubes receives reflected radiant heat from wall 2.

The tubes of bank 9 are located out of the direct path of flow of the iiames and hot combustion gases passing through combustion zone 4, to prevent localized overheating in any portion of this bank. While bank II is not disposed directly in the main 'path of flow of the combustion gases, its position, parallel to sloping wall il, is such that a greater amount of heat is imparted to the tubes of this bank by direct contact with the combustion gases, as compared with that imparted in the same manner to the tubes of bank 9.- This tends to compensate for the decreased temperature and decreased radiant heat emissivity of the combustion gases in the upper portion of zone d. Another factor which tends to better equalize the rates of heating in banks 9 -and I I is the fact that the tubes of bank II are arranged so that, as their distance from the source of nascent flames and hot combustion gases increases, they are progressively closer to the heat radiating wall i. Thus, a greater amount of heat is imparted to these tubes by radiation from wall I and by proper control of E the ring conditions, particularly with respect to the amount of excess air employed, the rate of heat transfer to the tubes of banks 9 and Il may be substantially equalized and the average rate of heat transfer to both banks may thereby 10 be made to more closely approach the maximum rate at any point therein, thus materially increasing the eiciency of the heater for any given size and number of tubes.

Of course, when two rows of radiant heat-ab- 15 sorbing tubes are employed, as in the case here illustrated, the row closest to the side wall is partially shielded by the adjacent outer row and receives heat at a lower rate than the latter. It is, however, entirely Within the scope of the invention to employ a single row of tubes in bank 9 or bank l l, or both.

The combustion gases which have given up a substantial portion of their radiant heat to the tubes of banks 9 and II pass upwardly from the combustion zone through zone 5 and impart heat to the tubes of bank 'I by direct contact there with. The lowermost rows of tubes in bank 'l will ordinarily also receive a substantial amount of heat by radiation, while heating by convection will predominate inthe remaining rows of bank l. The combustion gases, after passing through zone 5, are directed therefrom through iiue 29 to a suitable stack, not shown.

I claim as my invention:

1. A heater for fluids comprising, in combination,- side and end walls defining an elongated substantially vertical combustion zone, means for supplying fuel and air to one end of said combustion zone and passing resulting flames and hot combustion gases over and in intimate contact with the inner vertical surface of one of said side walls, fluid conduits disposed to receive heat by direct radiation from the flames and hot combustion gases and from the side wall over which the iiames and hot combustion gases are passed,

4said uid conduits being disposed in a bank adjacent the opposite side Wall and out of the direct path of travel of the flames and hot combustion gases and all of the conduits of said bank being directly opposite said inner vertical surface, that portion of said bank remote from the source of said ames and hot combustion gases being horizontally closer to said inner vertical surface than that portion of the bank disposed adjacent said source, a uid heating zone defined by extensions of said side and end Walls and directly communicating with the combustion zone at that end of the latter opposite the source of said flames and hot combustion gases, means for passing combustion gases from the combustion zone through the fluid heating zone, and uid conduits disposed in the uid heating zone and in the direct path said flames and hot combustion gases and from the side wall over which the flames and hot combustion gases are passed and all of the conduits of said bank being directly opposite ksaid inner vertical surface, the tubular elements in the upper portion of said bank being horizontally closer to said inner vertical surface than the tubes in the lower portion of the bank, a fluid heating zone disposed above and in direct communication with the combustion zone, means for passing combustion gases from the combustion zone upwardly through the fluid heating zone, and a bank of tubular fluid conduits disposed within the iiuid heating zone and in the direct path of travel of the combustion gases passing therethrough.

3. A heater for uids comprising, in combination, side and end walls defining a combustion zone, the upper portion of one of said side walls being inclined at an angle toward the opposite side wall, a fluid heating zone defined by substantially vertical extensions of said side and end walls, means for supplying fuel and air to the lower portion of said combustion zone and passing resulting flames and hot combustion gases over and in intimate contact with the inner surface of said opposite side wall, whereby to heat said surface to a radiant condition, a tube bank having tubular fluid conduits located adjacent the vertical and inclined portions of said one side wall and disposed to receive heat by direct radiation from the opposite side wall and from said flames and hot combustion gases, all of the tubes of said bank being directly opposite said surface and the tubes adjacent said inclined portion being horizontally closer thereto than the tubes adjacent said vertical portion of said one side wall, means for directing combustion gases from the combustion zone upwardly through said iluid heating zone to a flue, and a bank of tubular fluid conduits located in the fluid heating zone in the direct path of travel of the combustion gases passing therethrough.

4. A heater for fluids comprising, in combination, side walls, end walls and a floor, one of said side Walls being substantially vertical throughout its length and a portion of the opposite side wall being inclined at an angle toward the substantially vertical side wall, the lower portion of said side and end walls defining a combustion zone and the upper portion thereof defining a iiuid heating zone, a row of burner ports Within said floor adjacent the substantially vertical side Wall, a burner beneath each of said burner ports for supplying a combustible fuel-air mixture to the combustion zone, said burners and burner ports f being disposed to direct flames and combustion gases resulting from the combustion of said fuel upwardly over and in intimate contact with the surface of the substantially vertical side wall, a separate row of burner ports disposed adjacent said floor opposite the substantially vertical side Awall andV communicating with the combustion zone for supplying air and another type of fuel thereto, a bankof horizontally disposed tubular fluid conduits located adjacent the side wall having said inclined portion, a bank of horizontally disposed tubular fluid conduits in said fluid. heating zone, and means for removing combustion gases resulting from the combustion of said fuels from the upper portionlof the luid heating zone. 35

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