US2781756A - Apparatus for submerged combustion of liquid fuels - Google Patents

Description

Feb. 19, 1957 K. ADKOBE 2,781,756

APPARATUS FOR SUBMERGED COMBUSTION 0F LIQUID FUELS Filed April 26, 1952 2 Sheets-Sheet l "I 5 I z A l. 9 4 I 45 5 mm M n 4 E i 4 P V A m m G. 4 m g F A H 4 E m .v/ N s 7/ E w. n 4 B I a. 9M 4 4 n i m fi AIR ATT'YS 2,781,756 APPARATUS FOR SUBMERGED COMBUSTION 0F LIQUII; FUELS Filed April 26. 1952 K. A. KOBE Feb. 19, 1957 2 Sheets-Sheet 2 IN V EN TOR:

KENNETH A. KOBE BY d ATT'YS United States Patent APPARATUS FOR SUBMERGED CQMBUSTION 0F LIQ FUELS Kenneth A. Kobe, Austin, Tex.

Application April 26, 1952, Serial No. 284,492

3 Claims. (Cl. 126-360) This invention relates to submerged combustion of liquid fuels and particularly to a novel burner for obtaining high heat output by the submerged combustion of liquid fuels.

The art of submerged combustion is well known today and is recognized as having several significant advantages which are unobtainable by other combustion methods. While there are certain limitations to the use of submerged combustion, it is recognized that high thermal efiiciency and high heat outputs are available by the practice of this method of combustion. The method is particularly useful in the heating of liquids and solutions in which the presence of exhaust gases are not objectionable. At the present time submerged combustion is practiced commercially only with gaseous fuels because the burning of liquid fuels in this manner raises several special problems which heretofore have not been solved. In particular it has not been commercially feasible to use liquid fuels in submerged combustion because the size of the combustion chamber must necessarily be small and there is great difficulty in obtaining a satisfactory mixture of liquid fuel and air and then vaporizing the mixture and securing complete combustion within the limited space available. The advantages of employing liquid fuels in submerged combustion are apparent because of the availability of liquid fuels at locations remote from supplies of gas and because of the low cost of the liquid fuel.

It is therefore an object of this invention to reduce the cost of heating by submerged combustion with liquid fuels and to obtain highly efficient combustion at high feed rates.

Another object of the invention is to burn liquid fuels in a submerged combustion burner employing low pressure air as the source of oxygen for the combustion.

A further object of the invention is to provide means for burning liquid fuels in submerged combustion apparatus by completely mixing low pressure air and liquid fuel and vaporizing and completely combusting the vapor with-in the burner.

Still another object of the invention is to provide apparatus for efficiently adding low pressure air in a submerged combustion burner in order to achieve complete mixing of the air and the liquid fuel.

The foregoing and numerous other important objects advantages and inherent functions of the invention will become apparent as the same is more fully understood from the following description, which, taken in connec tion with the accompanying drawings, discloses a preferred embodiment of the invention.

In the drawings:

Figure l is a perspective View of a device adapted for the heating of liquids by submerged combustion with parts broken away to show the location of the essential parts in the device; 1

Figure 2 is a sectional view of one embodiment of the low pressure burner of this invention;

Figure 3 is an enlarged view, partly in section, of

one embodiment of a burner according to the invention;

Figure 4 is a fragmentary enlarged sectional view of the fuel nozzle and air distributor of the burner shown in Figure 3;

Figure 5 is a sectional view of another form of distributor suitable for use in the invention; and

Figure 6 is a sectional view taken along the lines 6-6 of Figure 5.

in the accomplishment of the foregoing objects and in accordance with the practice of the invention there is now provided a highly efficient submerged combustion burner which employs low pressure air and atomized liquid fuel under high pressure at extremely high feed rates. The burner comprises essentially an elongated chamber which is lined with a refractory material and contains an atomizing nozzle in one end of the chamber through which the liquid fuel is delivered under high pressure and in the absence of air. The burner has an air delivery means adjacent the fuel nozzle which is adapted to provide low pressure air in more than adequate amounts necessary to support the combustion of all the liquid fuel, the air being delivered to the burner at low pressures of the order of 3-8 pounds per square inch. In a preferred embodiment of the invention the incoming supply of air is given a whirling motion by passing it through a grid or distributor in which at least a portion of the passages or holes are disposed at an angle.

Further according to the invention a means for burning liquid fuels in submerged combustion apparatus is provided in which a lining of refractory material in an elongated chamber is heated to incandescence. A mixture of liquid fuel in a finely atomized condition and air are forced into the chamber separately in such a manner as to secure thorough mixing of the ingredients in a turbulent stream. The mixture is vaporized and ignited by heat radiated from the incandescent material and the fuel is completely burned within the confines of the chamber. All of this is accomplished in a relatively small chamber at exceptionally high rates on the order of several million B. t. 11. per hour per cubic foot of combustion space. This is in contrast to maximum combustion rates obtained in standard industrial oil-fired furnaces of about 100,000 B. t. u. per hour per cubic foot of combustion space. In actual practice burners have been operated according to the invention at rates between two million and 14 million B. t. u. per hour per cubic foot of combustion space. It is, of course, necessary to first raise the refractory material to a high temperature, such as the incandescent temperature previously referred to in order to operate the burner at full efiiciency. This preheating may be done in any suitable manner as by preheating with gas or with a carefully adjusted oil flame. Once the refractory has become incandescent and combustion of liquid fuel at the previously described rates has been initiated, the refractory will remain incandescent due to the heat generated within the chamber by the combustion of the fuel.

In the drawings the invention is illustrated in a simple form as it is applied to the heating of a liquid contained in the tank 1. The tank is made of medium gauge steel and is in the shape of a cylinder having a conical bottom 2. At the bottom of the tank a valve 3 is provided through which the contents of the tank may be drained. An inlet 4 is provided for adding liquid to the tank as needed. The depth of the liquid 5 in the tank is recorded on the gauge 6 which is of conventional design. The tank 1 stands on a supporting member 7 which raises it from the floor. An A-frame 8 or similar structure is mounted above the tank 1 and is provided with the pulley 9 and the rope or cable 10 by means of which the burner structure may be withdrawn from the tank.

A plate 11 is provided at the top of the tank and has an opening through which the burner assembly may be raised or lowered. A second opening is provided for the exhausting of steam and vapors from the tank and the flue 12 carries these vapors away.

The burner assembly consists of a combustion chamber 13 and a burner head 14 which are secured by a conventional flanged arrangement. Air under low pressure is supplied to the burner head 14 through the pipes 15--15 which are connected at the upper end to the air supply line 16. The air may come from any suitable source, such as the compressor 17 and it is ordinarily maintained at a pressure between about 3 and 8 p. s. i., as for example, p. s. i. Liquid fuel is supplied to the burner head 14 through the small conduit 18 and is ordinarily supplied at a high pressure on the order of 80 to 115 p. s. i. from a high pressure pump (not shown).

In one of the simpler versions of the invention the apparatus illustrated in Figure 2 has been shown .to be highly efiicient in the submerged combustion of liquid fuels. The device consists of an elongated tubular metal body 19 which has a layer of refractory material 20 aflixed to the inner surface thereof. At the upper end of the body 19 a burner head is secured by means of the flanged connection 21. In the center of the plate 22 there is located an annular opening which receives a tubular member 23. Near the upper end of the tubular member a plurality of holes 24 are provided which communicate with the space 25 between the tubular member 23 and the casing 26. The casing is provided with a pair of openings which receive the air pipes 15.

In this construction air is led into the space 25 through the pipes 1515 and is distributed thoroughly in the upper part of the tubular member 23 through the holes 24. Liquid fuel under high pressure and in the absence of air is introduced through the conduit 18 at the nozzle 27 from which it is atomized and sprayed into the chamber 28 formed by the refractory material 20. As the oil passes through the nozzle 27 it comes in contact with the air supplied through the holes 24 and begins to mix therewith. As the mixture emerges from the tubular member 23 into the substantially larger chamber 28, a considerable turbulence is set up and the oil and air become thoroughly mixed. Due to the incandescence of the refractory material the mixture of oil and air is rapidly vaporized and is brought to the combustion temperature. Combustion takes place almost immediately and before the mixture emerges from the open end of the chamber .28 the combustion has been completed.

In a more elaborate version of the invention the burner assembly illustrated in Figures 3 and 4 is employed in place of that shown in Figure 2. Air is admitted through the pipes 1S-15 and passes through the space to the openings 24. The air circulates in the chamber 29 and passes through the passages or holes 30-30 in the distributor 31 into the larger chamber 28. Oil is admitted under high pressure through the line 18 into the nozzle assembly 27 in which it is mechanically atomized. The oil is ejected from the nozzle through the opening 32 and forms a cone-shaped or bell-shaped spray as it emerges into the chamber 28. The air which passes through the distributor 31 strikes the cone-shaped oil spray and mixes intimately with the oil.

In Figure 4 it will be observed that the oil passes from the conduit 18 through the screen 33 and through the openings 3434 in the tubular element 35 of the spray nozzle 27. The oil thereafter passes through the opening 36 into the tubular element 37 and outwardly through the opening 32 into the bottom portion 38 of the burner head 14. The portion 38 is in communication with the chamber 28 and as the mixture of air and oil passes from the portion 38 to the considerably larger chamber 28 a turbulence is created which assists materially in mixing the air and oil into a vaporizable and combustible fuel mixture. A portion of the oil feed passes through the hole 39 in the tubular element 37 and likewise exhausts through the opening 32 to assist in the formation of a cone-shaped or bell-shaped spray of atomized oil. The layer of refractory material 20 (Fig. 3) is ordinarily maintained at high temperature and preferably at incandescent temperature in order to supply radiant heat to the mixture of atomized oil and air which passes from the burner head of the combustion chamber. The heat is so intense as to cause almost instantaneous vaporization of the oil with the result that combustion takes place almost immediately within the chamber 28 and is completed before the vaporous mixture of oil and air passes out of the chamber. The pipe 40 is provided in order to admit gas to the combustion chamber for preheating thereof to incandescent temperature before the oil spray is admitted.

In the preferred form of the invention illustrated in Figures 3 and 4, the distributor 31 has an important function in providing the most efficient operation of the burner. As stated before, one of the principal reasons that liquid fuels are not commercially used in submerged combustion is that there has been a great difiiculty in obtaining a satisfactory mixture of liquid fuel and air. In this invention air in satisfactory amounts is supplied to the burner head at low pressure and is then distributed about the nozzle 27 in a manner to cause complete and efficient mixing of air with the mechanically atomized oil in amount at least suflicient to support complete combustion thereof. In addition to the plurality of axially bored holes 30-30 it has been found desirable to supply a plurality of holes 41-41 at the inner dimension of the distributor 31 which are bored at an angle with the vertical dimension of the distributor. Stated in another Way the inner holes 4141 extend through the distributor disc at an angle with respect to the plane of the face of the disc and in vertical planes, and the holes are thus helically disposed relative to the axis of the disc.

Air passing through the angularly bored holes 4141 is deflected and given a whirling motion which strikes the cone of mechanically atomized oil issuing from the opening 32. This whirling motion breaks up the cone and allows the passage of air from the holes 41-41 and 30--30 to penetrate the cone and mix thoroughly with each individual tiny droplet of atomized oil. The axially bored holes 30-30 serve an additional purpose of preventing the cone from being dispersed too widely so that drops of oil are prevented from impinging upon the sides of the burner head and .upon the sides of the chamber 28 before they are heated to the vaporization and combustion temperature. It will be seen therefore that the preferred arrangement is to have the angularly bored holes immediately surrounding the nozzle 27 and one or more rings of axially bored holes at the outer dimensions of the distributor 31.

Another form of distributor plate similar to that illustrated at 31 in Figures 3 and 4 is shown in Figures 5 and 6. As illustrated, the distributor 42 is comprised of a plate having an inner opening 43 which is adapted to receive the nozzle 27. A plurality of angularly bored holes 44-44 are located around the opening 43 and a plurality of axially bored passages or holes 45-45 are provided in the outer dimensions of the plate 42. The effect is the same as that previously described for the distributor 31 in that the air is given a whirling motion by the angularly bored holes 4444 and tends to break up the cone of atomized oil. The axially bored holes 45-45 tend to restrict the scattering effect of the whirling air in the cone and to prevent unnecessary impingement and condensation of oil droplets on the surfaces of the burner head and combustion chamber. It will be observed from Fig ure 6 that one of the holes 44 is bored at an angle approximating 30 but it will be understood, of course, that the holes may be bored at any suitable angle depending in part upon the size and capacity of the burner.

The layer of refractory material 20 on the interior of the combustion chamber is preferably of a ceramic material which is capable of becoming incandescent and withstanding exceptionally high temperatures without fracture. As examples of this material I may use the materials known commonly as Insulcrete and Insulclad. Insulcrete is a refractory insulating material which sets hydraulically at air temperature and withstands temperatures up to 2500 F. Insulclad is a refractory protective air-setting coating for surfaces directly exposed to high temperatures and for sealing the pores of the surfaces. A chemical analysis of one sample of each of the materials shows the following compositions:

Insulcrete Insulclad Another type of suitable lining is that made from zirconium silicate. Silicon carbide is another refractory material which may be employed in the lining of the combustion chamber.

It should be pointed out in connection with this invention that a successful and highly elficient combustion of liquid fuel is now available for use in submerged combustion processes and a feature of the invention is the use of low pressure air to supply the necessary oxygen for complete combustion of the liquid fuel. In other processes for the combustion of liquid fuels in submerged combustion apparatus it is known to use air at high pressure and to pass the air through the atomizing nozzle along with the oil. In such a process air of about 20 pounds per square inch is required and the cost of compressing air to this figure adds materially to the expense of operating the burner. According to the present invention, however, it is possible to achieve substantially equal results with the use of low pressure air of about p. s. i. and to admit it alongside the oil vaporizing nozzle rather than through the nozzle. The saving which results from compressing air only to 5 p. s. i. instead of to higher pressures is substantial and contributes to the commercial feasibility of the process, as indicated in the following table.

TABLE Direct operating cost of burning 100 gallons of fuel oil Typical values It has been found necessary to employ excess air above a certain minimum figure in order to achieve satisfactory mixing and combustion of the liquid fuel. By excess air as used herein it is intended to mean that amount of air over and above the theoretical amount required for complete combustion of the liquid fuel. In the practice of this invention it has been found that the amount of excess air must be at least about 26% and of course it may be higher within amounts which are not economically undesirable.

By the term liquid fuel it is intended to include all of the hydrocarbon fuels which are liquid at ordinary as alcohols but these are ordinarily not commercially employed .as fuels for large scale heating.

By mechanical atomized fuel as the term is used herein I mean that atomization is achieved solely by mechanical means such as by forcing oil under high pressure through a jet or nozzle. This is distinguished from air atomization in which air and fuel are forced through a jet or nozzle at the same time.

This application is a continuation-in-part of my copending application Serial No. 563,194, filed November 13, 1944, and now abandoned. Application Serial No. 563,194 was a continuation-in-part of my then copending application Serial No. 399,479, filed June 24, 1941, and now abandoned.

The invention is hereby claimed as follows:

1. A submerged combustion burner for liquid fuels,

comprising a burner head and means forming a tubular combustion chamber, said head including an atomizing fuel nozzle adapted to deliver only liquid fuel therefrom and directed axially of said chamber, means forming a chamber surrounding said nozzle, means for delivering air to said nozzle-surrounding chamber, and a disc having air passages extending therethrough positioned in and extending over the cross-section of said nozzle-surrounding chamber, said disc receiving said nozzle in an opening therein, a portion of said passages extending through said disc obliquely with respect to the plane of its face and being arranged c-ircumferentially around said opening to impart a whirling motion to air discharged from said nozzle-surrounding chamber to said combustion chamber, another portion of said passages extending through said disc with their axis parallel to the axis of the disc and being arranged circumferentially around said opening radially outwardly of the first-named portion of said passages.

2. A submerged combustion burner for liquid fuels comprising a burner head and means forming a tubular combustion chamber, said head including an atomizing fuel nozzle adapted to deliver only liquid fuel therefrom and positioned axially of the head and adapted to discharge axially into said chamber, means forming a tubular chamber surrounding said nozzle, means for delivering air to said nozzle-surrounding chamber, and a disc having air passages extending therethrough positioned in and extending over the cross-section of said nozzle-surrounding chamber, said disc receiving said nozzle in a central opening therein, a portion of said passages extending through said disc obliquely with respect to the plane of its face and being arranged circumferentially around said opening to impart a whirling motion to air discharged from said nozzle-surrounding chamber to said combustion chamber,

another portion of said passages extending through said disc with their axes parallel to the axis of the disc and being arranged circumferentially around said opening radially outwardly of the first-named portion of said passages.

3. Apparatus for heating liquids comprising a container for liquid to be heated, means forming a tubular combustion chamber, a lining of refractory material in said chamber, a burner head mounted at one end of said chamber, an atomizing fuel nozzle included in said head and positioned axially thereof and adapted to deliver only liquid fuel and to discharge axially into said chamber, means forming a tubular chamber included in said head and surrounding said nozzle and having a smaller diameter than that of said combustion chamber, means for delivering air to said nozzle-surrounding chamber, means for delivering oil to said nozzle, and a disc having air we use passages extending therethrough positioned in .said nozzlesurrounding-chamber and extending over its cross-section, said disc receiving said nozzle in a central opening in the disc, a portion of said passages extending through said disc obliquely with respect to the plane of its face and being arranged circumferentially around .said opening to impart a whirling motion to air discharged from said nozzle-surrounding chamber to said combustion chamber, another portion of said passages extending through said disc peipendicularly with respect to the plane of its face and being arranged-circumferentially around said opening radially outwardly of the first-named portion of said passages, the remaining end of said combustion chamber being open and arranged to discharge combustion gases therefrom beneath the surface of a liquid in said eontainer.

References Cited in the file of this patent UNITED STATES PATENTS

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