US2108688A - Furnace - Google Patents

Description

Patented Feb. 1;, 1938 T UNITED STATES PATENT OFFICE i FURNACE -tion of Delaware Application October 13, 1934, Serial No. 748,246

This invention particularly refers to an improved form of furnace for the heating of fluids of the type employing both radiant and convection heat and which is of particular advantage as applied to the heating of hydrocarbon oils to the high temperatures required for their pyrolytic conversion. This application is a continuation inpart of my prior application Ser. No. 365,552, filed May 23, 1929, now Patent No. 1,984,687.

As a special feature of the present invention, the main furnace structure is divided into a combination combustion and heating chamber and a fluid heating chamber. A fluid conduit comprising a plurality of tubular elements dis-. posed .to receive heat predominantly by radiation from the materials undergoing combustion within the furnace and the hot refractory walls of the furnace is located within the combustion and;

heating chamben- Another fluid conduit comprising a plurality of tubular elements is located in flown; the combustion gases passing from the combustion and heating chamber to the stack whereby convection heat is imparted thereto by direct contact with said combustion gases.

As another special. feature of the present invention, one or a plurality of firing tunnels are provided communicating with the combustion and heating chamber of the furnace through which firing tunnels combustible fuel and air are independently supplied in regulated amounts to. the

combustion and heating chamber. Fuel of any suitable form ,is preferably supplied together with a regulated quantity of the air required for its combustion through a centrally located combustion compartment in each firing tunnel. and

additional quantities of air maybe supplied in regulated amounts .direct to the combustion and heating chamber through separate air ducts located adjacent the combustioncompartment in each firing tunnel. Steam may also be supplied in regulated amounts to the combustion and heating chamber either alone or together with regulated quantities of air and is preferably introduced beneath the fiamesin the combustion and heating chamber by supplying the same through an air duct located beneath the combustion com- .partment of. the firing tunnel. ,3

said fluid heating chamber in the direct path of bustion and heating chamber, particularly with respect toits length and luminosity, than is otherwise possible and means are thereby afforded for obtaining a better separation of radiant and convection heat when desired, between the 5 combustion and heating chamber and the fluid heating chamber of the furnace and a better control is thereby exerted over the heating conditions about different portions of the fluid conduit. This is particularly desirable in the heating of hydro- 10 carbon oils to the high temperatures required for their pyrolytic conversion in that better control is obtainable over the type of heating curve obtained which control is important and in many cases essential to the successful conversion of 15 various types of oils. The use of steam in the manner provided by the present invention also serves as a means of obtaining better control over the heating conditions about different'portions of the fluid conduit. 0

I Fig. 1 of the accompanying diagrammatic draw- 2 ring is a sectional elevation of .one specific form of the furnace embodying the features of the present invention.

M Fig. 2 is a fragmentary cross-sectional view of 25 the firing tunnels taken along a vertical plane indicated by the line 22 in Fig. 1.

Referring to the drawing, the main furnace structure comprises side walls I and 2, a roof 3,

a floor and end walls which are not indicated 30 in this particular view of the furnace, all of which are of conventional form and may be constructed, all or in part, of suitable refractory materialsuch as-flrebrick or the like. A bridge wall 5 divides the interior of the furnace into a combustion and heating chamber 6 and a fluid heating chamber 1. I

Firing tunnels 8 communicate, in the particular construction here illustrated, through side wall I of the furnace with combustion and heating 40 chamber 6 and preferably a plurality of firing tunnels, or a continuous structure such as illustrated in Fig. 2, extends across the entire length of the furnace in such a manner that substantially uniform heating conditions may be maintained along the length of the combustion and heating chamber (between the end walls of the furnace). Each firing tunnel or each cell of the firing tunnel, in case a single continuous tunnel structure such as shown in Fig.2 is provided, comprises a combustion compartment 9 and air ducts Ill and ll 10- cated, respectively, above and beneath combustion compartment 9. Preferably, the walls of compartments 9, which are exposed to contact with 1 the materials undergoing combustion therein, are

of suitable super-refractory material such as, for example, silicon carbide or the like, capable of withstanding the high temperatures normally prevailing in the combustion compartment. Each of the air ducts liland l l is provided with a suitable damper 113 and a suitable sliding damper or the like (not shown) may be provided, when desired, at the mouth of combustion compartment 9, although when, as in the case here illustrated, means are provided for controlling the quantity of total air supplied to the combustion chamber a damper will not ordinarily be required at the mouth of combustion compartment 9. Preferably, when a continuous firing tunnel structure such as indicated in Fig. 2 is provided relatively small air ducts 26 are provided between adjacent cells or compartments of the firing tunnels in order to cool the side walls of combustion compartments 9 and prevent rapid destruction of the refractories. No method of controlling the relatively small amount of air supplied through tunnels 24 will ordinarily be required, although suitable dampers or the like (not shown) may be provided, when desired.

Fuel of any desired form such as oil, gas or pulverized solid fuel is supplied by means of a plurality of suitable burners, one of which is indicated in Fig. 1 at M, to combustion compart ments 9, the amount of fuel supplied to each compartment being controlled, in the case illustrated, by means of a valve H5 in pipe line I5 while air or steam for atomization of the fuel may be supplied to each burner through a pipe line H and valve l8. Air, preferably in preheated state, is supplied, in the case here illustrated, from a main air duct 19 to compartment 20 communicating with compartments 9, l0 and l l of each of the combustion tunnels and the total quantity of air supplied to the combustion chamber may be regulated by means of damper 2i.

Steam may be admitted to combustion and heating chamber 6 and is preferably supplied to this chamber beneath the flames through compartments H, for example, of each of the firing tunnels, to each of which it may be supplied by means of a pipe line 22, controlled by valve 23. It is also within the scope of the invention to supply steam through ducts 10, for example, above the flames issuing from the mouth of combustion compartments 9 although means for accomplishing this, which may be similar, for example, to pipe line 22 and valve 23, are not shown in the, drawing.

A fluid conduit 25 comprising a plurality of horizontally disposed parallel tubes 26 is located, in the case here illustrated, adjacent the floor 4 of combustion and heating chamber 6. Another fluid conduit 21, comprising a plurality of horizontally disposed parallel tubes 26, is located,

in the case here illustrated, adjacent the roof 3 of the furnace and another fluid conduit 28, comprising a plurality of horizontal rows of horizontally disposed parallel tubes 26, is located, in

. the case here illustrated, within fluid heating chamber 1 of the furnace. I

When the furnace is utilized for the treatment of a single stream of fluid the various tube banks 25, 21 and 28 may be connected in any desired sequence and preferably adjacent tubes in each bank are connected at their ends in series by means of suitable return bends or headers, of any well known form (not shown), which are preferably located outside the furnace. However, when desired, different portions of the same bank or diiferent banks of tubes may be connected in aioaess taneous treatment of two or more streams of the same fluid or of difierent fluids. As applied to the simultaneous treatment of two or more streams of the same fluid any desired flow arrangement may be employed which will permit substantially equal heating of both streams. As applied to the simultaneous treatment of two or more streams of different fluids any desired flow arrangement may be employed which will permit heating of the diiferent fluids each under the conditions most suitable for their treatment. The general direction of flow of the fluid through any tube bank may be either concurrent or countercurrent to the direction of firing and the general direction of flow of the combustion gases or the direction of flow of the fluid being heated may be varied in diiferent portions of the same tube bank. In general, the invention is not limited to any specific flow arrangement and no particular flow arrangement is claimed as a novel feature of the invention.

The invention is also intended to include modiflcations to the specific form of fluid conduits illustrated and described, for example, tube bank 25 or 21 or both may comprise two or three parallel rows of tubes instead of a single row with the different rows arranged either in staggered formation or otherwise. Also, the tubes of either or both of the tube banks 25 and 21 may be disposed parallelto the direction of firing instead of at right angles thereto, as illustrated, or, when desired, the furnace may be fired from one or both sides instead of from the end, as illustrated, flring tunnels of the general type illustrated preferably being employed, however, in any case. Tubes may also be disposed, when desired, along the side walls and/or along the end walls of the furnace without departing from the scope of the present invention.

With the fluid conduits arranged, as illustrated in the drawing, the tubes of bank 25 are heated predominantly by radiation from the materials undergoing combustion in combustion chamber 5 and the hot refractorywalls of the furnace.

-6 and from the hot refractory walls of the furnace and are also subjected to appreciable heating by convection, due to contact of the tubes with the hot combustion gases, particularly in the portion of this bank adjacent bridge wall 5. The tubes of bank 28 are supplied with convection heat by direct contact with the hot combustion gases which pass from combustion chamber 6 over bridge wall 5 downward through fluid heating chamber 1 to flue 29, from which they-may pass to a suitable stack (not shown). Combustion gases and hot refractory walls of the furnace impart appreciable heat to the upper two or three rows of bank 28 by radiation while the succeeding rows are heated predominantly by convection. above fluid heating chamber 1, which portion of bank 21 is designated in the drawing' as 21', may be eliminated, in which case a somewhat greater quantity of radiant heat will ordinarily be imparted to the upper rows of bank 28.

When desired, the tubes of bank 21 By controlling the ratio of fuel and air supplied to the combustion chamber and by independently controlling the amount of the air sup- -plied to the combustion chamber with the fuel through combustion compartments 9 of the firing tunnels, relative to the amount of air separately supplied to the combustion chamber through ducts It and II the length and luminosity of the flames in combustion chamber 6 may be controlled to a degree impossible with conventional firing arrangements. For example, by employing a relatively large amount of excess air and by introducing a major portion of the total air to the combustion chamber through combustion compartment 9, together. with the.fuel, the visible portion of the flame issuing from the mouth of compartment 9 will be very short and the flames in combustion chamber 6 will be substantially of non-luminous character. By reducing the total amount of excess air and supplying a major portion of the air through, combustion compartment 9, together with the fuel, somewhat longer flames of a more luminous character may be obtained. With a small amount of total excess air and a major portion of the air supplied through ducts it and i I to combustion'chamber 6 the length of the visible or luminous portion of the flame may be materially increased and by increasing the total volume of excess air and supplying a major portion thereof through ducts it and it longer flames of somewhat decreased luminosity may be obtained.

In this manner better separation of radiant and convection heat may be obtained, when desired, in the two heating chambers of the furnace and the proportionof available heat imparted to the tubes in combustion and heating chamber t relative to that imparted to the tubes in fluid heating chamber 1 may be varied over a wide range to suit requirements.

It is also possible by varying the amount of air supplied to the combustion chamber through air ducts it above the combustion compartments 9 relative to the volume of air supplied to the combustion chamber through ducts ll beneath combustion compartments 9 to control, within fairly wide limits, theheat supplied to fioor bank 25 relative to that supplied to roof bank ill. A large amount of air introduced through air ducts it will tend to form a protective layer above the flame and concentrate heat along the floor of the furnace while the opposite result may be obtained by introducing a large propertion of the airthrough ducts ll beneath combustion compartments t. The'introduction of steam to the. combustion and heating chber, as pro one disposed above and theother below the central tunnel, means for supplying a controlled mixture of combustible fuel and air through said central firing tunnel to said combustion chamber of the furnace and means for separately sup plying independently controlled amounts of additional air to the combustion chamber through each of said air ducts.

2. A firing device for furnaces comprising a central tunnel, a pair of additional tunnels contiguous to the central tunnel, one disposed above and the other below the central tunnel, means for supplying fuel and air to the central-tunnel, and means for supplying independently controlled amounts of combustion controlling medium to each of said additional tunnels.

3. A firing device for furnaces comprising a central tunnel, a pair of additional tunnels contiguousto the central tunnel, one disposed above thereof in communication with the air compartment.

5. A firing device for furnaces comprising a central tunnel, a pair of additional tunnels contiguous to the central tunnel, one disposed above and the other below the central tunnel, an air compartment communicating with said tunnels at adjacent ends thereof, means for supplying fuel to the central tunnel adjacent the end thereof in communication with the air compartment, and a damper in each of said additional tunnels.

6. A firing device for furnaces comprising a central tunnel, apair of additional tunnels con-- tiguous to the central tunnel, onedisposed above and the other below the central tunnel, an air compartment communicating with said tunnels at adjacent endsthereof, means for supplying fuel. to the central tunnel adjacent the end thereof in communication with the air compartment, and means for introducing steam to at least one of said additional tunnels.

' V '7. A furnace having a fioor, a roof and a vertical side wall, a horizontal firing tunnel projecting through said side wall near the furnace floor, a pair of. additional horizontal tunnels contiguous to the firing tunnel, one disposed above and the other below the tunnel, means for supplying fuel and air 'to the firing tunnel to pass through the latter into the lower portion of the furnace, and means for supplying combustion controllingmedium to said additional tunnels to pass through the latter into the lower portion of the furnace. r

8. A furnace having a fioor, a roof and a vertical side wall, a horizontal firing tunnel projecting through said sidewall near the furnace floor, a pair of additionafhorizontal tunnels contiguous to the firing tunnel, one disposed above and the other below the firing tunnel, means for supplying fuel and air to the firing tunnel to pass through the latter into the lower portion of. the

furnace, means for supplying combustion controlling medium to said additional tunnels to pass through the latter into the lower portion of the furnace, and a damper in each of said additional tunnels.

All

9. A furnace having a floor, a roof and a vertical side wall, a horizontal firing tunnel projecting through said side wall near the furnace floor,

a pair of additional horizontal tunnels contiguous to the firing tunnel, one disposedabove and the other below the firing tunnel; an air compartment communicating with said tunnels at adjacent ends of the latter, and means for supplying fuel to the furnace through the firing tunnel.

10. A furnace having a floor, a roof and a pair of vertical side walls, a bridge wall extending upwardly from the floor between said side walls and terminating short of the roof, thereby forming in the furnace a combustion section and a convection section receiving combustion gases from the combustion section, means for removing combustion gases from the convection section, a horizontal firing tunnel projecting through the side wall of the combustion section near the furnace floor, a pair of additional hori-'- zontal tunnels contiguous to the firing tunnel, one disposed above and the other below the firing tunnel, means for supplying fuel and air to the firing tunnel to pass through the latter into the lower portion of the furnace, and means for supplying combustion controlling medium to said additional tunnels to pass through the latter into the lower portion of the furnace.

11. A furnace having a floor, a roof and a pair of vertical side walls, a bridge wall extending upwardly from the floor between said side walls and terminating short of the roof, thereby forming in the furnace a combustion section and a convection section receiving combustion gases from the combustion section, means for removing combustion gases from the convection section, a horizontal firing tunnel projecting through the side wall of the combustion section near the furnace floor, a pair of additional horizontal tunnels contiguous to the firing tunnel, one disposed above and the other below the firing tunnel, an air compartment communicating with said tunnels at adjacent ends of the latter, and means for supplying fuel to the furnace through the firing tunnel.

I LEV A. WELLER.

Images