US3721728A

US3721728A - Furnace having cyclically moving flames

Info

Publication number: US3721728A
Application number: US00179706A
Authority: US
Inventors: W Luetzelschwab
Original assignee: Marathon Oil Co
Current assignee: Marathon Oil Co
Priority date: 1971-09-13
Filing date: 1971-09-13
Publication date: 1973-03-20
Anticipated expiration: 1990-03-20
Also published as: DE2230036A1

Abstract

By cycling the pressure of fuel gases which impinge upon an air or other oxygen-containing stream directed at an angle to the fuel gases, the gas jet pattern can be caused to sweep across the combustion zone in a furnace, e.g., a Wulff regenerative furnace. This cyclic motion varies penetration and evens out heat distribution. The cyclic changes in pressure can be accomplished by rotating members presenting varying cross-sectional areas to flow or by other devices all of which may be powered externally or powered by the energy of the flowing stream.

Description

United States Patent 1 Luetzelschwab 1March 20, 1973 [54] FURNACE HAVING CYCLICALLY MOVING FLAMES [75] Inventor: Wayne E. Luetzelschwab, Littleton,

[73] Assignee: Marathon Oil Company, Findlay,

Ohio

[22] Filed: Sept. 13, 1971 [2.1] Appl.No.: 179,706

[52] U.S. Cl ..432/26,431/1,432/31,

432/120, 432/227, 432/266 [51] Int. Cl ..F23n 1/02 [58] Field of Search ..43l/l, 8; 239/101; 263/2, 28

['56] References Cited UNITED STATES PATENTS -1 1/1964 Cremer et al ..43l/1 X FOREIGN PATENTS OR APPLICATIONS 251,742 9/1969 U.S.S.R. ..431/1 Primary Examiner-Charles J. Myhre Assistant ExaminerWilliam C. Anderson Attorney-Joseph C. Herring et al.

57 ABSTRACT By cycling the pressure of fuel gases which impinge upon an air or other oxygen-containing stream directed at an angle to the fuel gases, the gas jet pattern can be caused to sweep across the combustion zone in a furnace, e.g., a Wulff regenerative furnace. This cyclic motion varies penetration and evens out heat distribution. The cyclic changes in pressure can be accomplished by rotating members presenting varying cross-sectional areas to flow or by other devices all of which may be powered externally or powered by the energy of the flowing stream.

11 Claims, 23 Drawing Figures F/GS. 5A 5B PATEI-HEUmmomn 3,721,728 SHIEET 3 0F 4 GENERAL APPARATUS FRONT VIEWS OF VARIOUS VANE SHAPES SOLID VANES FRONT VIEW TOP TOP VIEWS OF VARIOUS VANE ANGLES AND NUMBERS F/GSE 6A 6B 6C 60 6E 6F Pmw m 3,721,728

' SHEEILLDFQA F/G. .7 v

IIJ 11 111/11 1 11111111 1/1/1111 FIG. 8

FURNACE HAVING CYCLICALLY MOVING FLAMES BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to power plants, mixed fluids with pressure activated valve (U.S. Pat. class 60, subclass 39.80; With fuel metering valve (U.S. Pat. class 60, subclass 39.81); and to Combustion Bursts or flare-ups in pulses or serial pattern (U.S. Pat. class 431.1).

2. Description of the Prior Art The following prior art pertains to the general field of the invention: U.S. Pat. No. 2,709,890 (to R.I-I. Goddard), which uses a rotating vaned rotor (FIG. 6) or a vibrating reed FIG. 5, which are actuated by the flowing fuel and which cause a pulsation of the fuel to break up the liquid fuel stream into many fine drops in the combustion chamber; and U.S. Pat. No. 1,616,778 which causes pulsing in a flow line to prevent accumulation of sediment or sludge in the burner nozzle. The pulsation can be caused by a fuel valve 26 which reciprocates (see FIG. 1) or by a vaned rotor 32 which rotates (see FIG. 2).

Externally powered pressure fluctuation devices have been previously used in U.S. Pat. No. 3,044,711 which uses perforated discs 37, 42, and 47, driven by external power to modulate the flow of liquid propellant; U.S. Pat. No. 3,253,784 which uses vane 9 (see Col. 2, lines 34-35) externally powered (a sort of rotating butterfly valve) to cause variations in the volume and pressure of water in a dishwasher; U.S. Pat. No. 3,327,758 which uses rotary valve 24 driven by drive motor 70 in a fuel line; and U.S. Pat. No. 3,449,913 which utilizes programmed valve 24 for introducing separately and sequentially predetermined amounts of a fuel and air into a combustion tube.

Other devices relating to' pulsing of fuel into combustion chambers are taught by U.S. Pat. No. 2,945,459 which accelerates combustion by causing vibrations of controlled frequency in a gaseous combustion supporting media, e.g., to burn granulated coal; and British Pat. 813,563 which uses a rotary slide valve to inject pulses of fuel oil into a burner.

SUMMARY OF THE INVENTION GENERAL STATEMENT OF THE INVENTION According to the invention, in a furnace having a stream of fuel which impinges at an angle on a stream of air or other oxygen-containing gas, to cause a flame or hot gas stream which in turn impinges upon the surface to be heated, there is provided a pulsation or cyclic variation in pressure in the fuel stream and/or the oxygen-containing gas stream. This fluctuation causes the flame or hot gas stream to be moved about so that it successively impinges on a number of different points on the surface to be heated. This cyclic movement reduces hot spots" and under-heated areas as well as providing burn-off of soot or other carbon deposits.

The surface to be heated may be a hot water tank, a tube bundle in a steam generator or water heater, refractories in a regenerative furnace in which the refractories are alternately heated and then used to deliver heat to a stream of gases which alternately flow past the surface, or a simple oven wall, etc.

UTILITY OF THE INVENTION The invention is useful in a wide variety of heating devices including ovens, regenerative furnaces, water heaters, etc. and has the advantage of reducing carbon deposits and improving heat distribution in such heating devices.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a plan section view of a conventional Wulff process furnace which is described in more detail in U.S. Pat. No. 3,366,702, U.S. Pat. application, Ser. No. 888,683 (now allowed) and Miller, S. A., Acetylene, Its Properties, Manufacture and Uses, Vol. I & 11, Academic Press, N .Y. 1965-66).

FIG. 2 is a plot of pressure vs. time for a stream of fuel measured at a point upstream from the point of entry into the combustion zone of the Wulff furnace shown in FIG. 1.

FIGS. 3a through 3d are plan views of combustion zone 18 of FIG. 1, and show the pattern of the hot gases and flame within the combustion chamber under a succession of fuel line pressures which correspond to those marked on FIG. 2.

FIG. 4 shows one general type of device useful for causing pressure fluctuations in fuel or air lines which consists of a rotating element analogous to a butterfly valve.

FIGS. 50 through 5e show substantially two dimensional rotating elements for use in the device of FIG. 4. FIGS. 5f and 5g are a front section and a plan section view of a three dimensional rotating element. Each of the devices of FIGS. 5a-g present successively different cross section views of the path of flow through the conduit of FIG. 4 as they are rotated. FIGS. 6a-6f are views of various alternate elements for use in the device of FIG. 4, said views having been taken in a plane transverse to the axis of rotation of the element.

FIG. 7 shows a bucket meter-type of device for causing pressure fluctuations. This device can be powered by the energy of the gas stream or powered externally.

FIG. 8 shows a rotating vane-type of device for causing pressure fluctuations. This device can be powered by the energy of the gas stream or powered externally.

FIG. 9 shows a surge vessel with a spring-loaded valve or control valve for causing pressure fluctuations.

It should be understood that all of the above figures are schematic and exemplary only.

DESCRIPTION OF THE PREFERRED EMBODIMENTS STARTING MATERIALS Fuels: Fuels for the use of the invention may be hydrocarbons either gaseous or liquid, and powdered solids, e.g., powdered coal slurries may be utilized where desired. The most preferred fuels will be gases, e.g., refinery fuel gas.

Oxygen-containing Gas: While pure oxygen or airsupplemented with additional quantities of pure oxygen can be employed, air will, in most cases, be most preferred.

Conditions: Temperature, pressure, and flow rate are not narrowly critical and they vary over a wide range, dependent upon the particular furnace and the effect desired. These conditions may readily be optimized by the use of routine trial runs.

EXAMPLE I Referring to FIG. 1, in the heat cycle of a Wulff furnace, refinery fuel gas enters through inlet 26 and its counterpart on the opposite side of the furnace and air enters through inlets 30, cooling refractory stack 8, then mixes with the fuel in combustion chamber 18, burns, heating refractories of stacks l2 and 14 and off gases exit through outlet 31. Similar quantities of fuel and air later enter combustion chamber through corresponding inlets in the other end of the furnace, but this discussion will be continued with respect to combustion chamber 18, taken alone for purposes of clarity.

The fuel line, feeding fuel inlet 26 with a refinery fuel gas, is fitted with the pressure fluctuating device shown in FIGS. 4 and 5a. As the element shown in FIG. 5a rotates under external power, the pressure at the inlet 26 fluctuates as shown in FIG. 2. The pressure under which the air stream enters the combustion chamber 18 remains constant. Thus, the degree of deflection of the flame and hot gas stream 32 varies as shown in FIGS. 30 through 3d. When the pressure is high (at P-max of FIG. 2), the flame 32 extends out almost transverse to the flow of air as shown in FIG. 3a. When the pressure drops (at P-min in FIG. 2), the flame 32 is greatly deflected by the air stream as shown in FIG. 3d.

This sweeping of the flame across the interior surface of the refractories of the center stack 12 of the Wulff furnace causes a uniformity in the heating of the refractories preventing hot spots and aiding in burning off carbon deposits.

The residence time of the flame at any point on the interior surface of the center stack of refractories can be optimized by employing various shapes of vanes as shown in FIGS. Sb-Sg and 6a-6f. Also, a series of inlet nozzles can be utilized so that the flames vary in a coordinated manner sweeping gradually back and forth across various levels of the interior surface of the refractory center stack.

MODIFICATIONS OF THE INVENTION It should be understood that the invention is capable of a variety of modifications and variations which will be made apparent to those skilled in the art by a reading of the specification and which are to be included within the spirit of the claims appended hereto.

FIG. 7 shows a wet bucket meter-type of pressure fluctuating device which can be installed in the fuel line in lieu of the device of FIG. 4 for operation generally as described above. In FIG. 7, the gas enters housing 39 through the inlet 40 into the bucket 41 in position A. This gas displaces the liquid 42 and causes the bucket to rise to position B, at which point gas begins to exit from the bucket and eventually through outlet 43. By the time the bucket reaches position C the gas has been displaced and the bucket moves to position D completely filled with liquid. This operation results in an interrupted gas flow where both the magnitude and frequency of the cycle can be controlled by proper design. Liquid height, volume of each bucket (not necessarily the same), number of buckets, bucket shapes, and resistance to rotation (hindered by friction,

latches, etc.) are all design variables to obtain the desired frequency and cycle shape.

FIG. 8 shows a rotating vane or gear-type of fluctuation device for use in place of the device of FIG. 4. The vanes (or gears) 51 are rotated by the flow of gas through pipe 53 into housing 55. Vanes 51 may also have bucket attachments 52 to help interrupt flow to a greater degree. To enhance the variation in flow, ad ditional resistance to rotation can be added in the form of friction, catches, etc. The vane spacing (not necessarily equal), number of vanes, vane shape (some could be narrow to bypass some flow), and resistance to rotation (friction, catches, etc.) are all design variables to obtain the desired frequency and cycle shape.

While not narrowly critical, rotation speeds (cycle) will preferably be in the range of 0.01 to 500, more preferably 0.1 to I00, and most preferably 0.3 to 50 seconds per revolution (cycle).

FIG. 9 shows a surge-tank combined with a springloaded release or other control valve for providing a fluctuating pressure in the fuel line in place of the device of FIG. 4. The gas enters inlet 61 and leaves by exit 62. Valve 63 can be any valve that will cycle either on its own such as relief valves or back pressure control valves set up in a cyclic mode of operation or a programmed control valve. Surge volume 64 is required only when the fuel gas delivery capacity at inlet 61 is less than the maximum desired withdrawal rate through exit 62.

What is claimed is:

1. In a furnace having a combustion zone in which a stream of oxygen-containing gas and a stream of fuel impinge at an angle to form a flame or hot gas stream which in turn impinges upon a surface to be heated, the improvement comprising cyclically varying the mass flow rate of at least one of said oxygen-containing stream and said fuel stream so as to vary the point of impingement of said flame or hot gases upon said surface to be heated.

2. A process according to claim 1 wherein said furnace is a regenerative furnace having masses of refractories onto which said flame or stream of hot gas is impinged.

3. The process according to claim 1 wherein at least one of said oxygen-containing stream and said fuel stream enters said combustion zone through a constricted inlet fed by a conduit and wherein the pressure at said constricted inlet is varied by pressure varying means in communication with said conduit.

4. A process according to claim 3 wherein said pressure varying means is a surge tank connected to a down stream valve operated in response to the pressure in said surge tank.

5. A process according to claim 3 wherein said pressure varying means comprises a rotating element located within said conduit and having a configuration which cyclically presents varying cross-sectional areas in the plane transverse to flow through said conduit.

6. A process according to claim 5 wherein said rotating element is powered by external power means.

7. A process according to claim 5 wherein said rotating element is substantially a disc.

8. A process according to claim 5 wherein said rotating element is a solid having various cross-sectional areas in the plane transverse to gas flow.

6 9. A process according to claim 5 wherein said rotatbustion chamber, ing element is powered by power means driven by the d. oxygen-containing gas inlet means communicating energy of the gas Stream flowing through Said conduit with said combustion chamber directed at an angle 10. A process according to claim 9 wherein said to id f l i l means,

rotating element comprises a series of rotatable vanes 5 whose axis of rotation is. spaced a distance from the longitudinal center line of said conduit, and is substantially perpendicular to said longitudinal center line of said conduit.

11. Apparatus for the heating of surfaces by the com- 10 bustion of fluids, said apparatus comprising the come. conduit means communicating with at least one of said fuel inlet means or oxygen-containing gas inlet means,

f. pressure fluctuation means operably located in relation to said conduit so as to cause intermittent pressure variation in said conduit,

binatiow whereby said pressure variation causes a hot gas or a a Su'rface to be heated flame stream produced by the combustion of said fuel a b. a combustion chamber communicating with said m commit wlth sald oxygencomammg gases to move Surface across said surface to be heated. 0. fuel inlet means communicating with said com-

Claims

1. In a furnace having a combustion zone in which a stream of oxygen-containing gas and a stream of fuel impinge at an angle to form a flame or hot gas stream which in turn impinges upon a surface to be heated, the improvement comprising cyclically varying the mass flow rate of at least one of said oxygencontaining stream and said fuel stream so as to vary the point of impingement of said flame or hot gases upon said surface to be heated.

9. A process according to claim 5 wherein said rotating element is powered by power means driven by the energy of the gas stream flowing through said conduit.

10. A process according to claim 9 wherein said rotating element comprises a series of rotatable vanes whose axis of rotation is spaced a distance from the longitudinal center line of said conduit, and is substantially perpendicular to said longitudinal center line of said conduit.

11. Apparatus for the heating of surfaces by the combustion of fluids, said apparatus comprising the combination: a. a surface to be heated, b. a combustion chamber communicating with said surface, c. fuel inlet means communicating with said combustion chamber, d. oxygen-containing gas inlet means communicating with said combustion chamber directed at an angle to said fuel inlet means, e. conduit means communicating with at least one of said fuel inlet means or oxygen-containing gas inlet means, f. pressure fluctuation means operably located in relation to said conduit so as to cause intermittent pressure variation in said conduit, whereby said pressure variation causes a hot gas or flame stream produced by the combustion of said fuel in contact with said oxygen-containing gases to move across said surface to be heated.