US2542029A - Water-cooled fluid fuel burner - Google Patents

Description

Feb. 20, 1951 F. D. HOFFERT WATER-COOLED FLUID FUEL BURNER Filed Sept. 12, 1946 INVENTOR. F/PA NK D. HOFFE/PT A T TORNE' Y Patented Feb. 20, 1951 ,z,54z,ozb WATER-COOLED mm) r-oEL comma Frank D. Hofl'ert, Downers Grove, IlL, assignor to Hydrocarbon Research, Inc., New York, N. Y., a corporation of New Jersey Application September 12, 1946, swarm. 696,405

6 Claims. (01. 158-99) The present invention relates to a fuel burner, which term is meant to include injectors, nozzles and tuyeres for introducing mixed combustible fluids into a reaction zone. It is more particularly concerned with a burner of the type adapted for use in connection with chemical processes of combustion or exothermic reactions where conditions of high temperature prevail. v

Whether used primarily for the purpose of effecting a chemical reaction or for the recovery of exothermic heat, burners are frequently disposed in locations of severe temperature condition. Thus, for example, where it is desired to operate under conditions of surface combustion,

the burner is often subjected to the direct effect of highly radiant surfaces.

Such conditions are met with, for example, in the generation of so-called synthesis gas from hydrocarbons and oxygen-containing gases for the catalytic manufacture of hydrocarbons and oxygenated hydrocarbons. In accordance with many such processes of which I am aware, the gas generation proceeds desirably at above 2000 F. and frequently much higher, as for example, as high as 3000 F. It is moreover advantageous in the production of synthesis gas to use relatively pure reactants such as methane and oxygen. Also, it is highly advantageous to premix and preheat the reactants to high temperatures, as for example 900 F., prior to their discharge from the burner or nozzle into the reaction or generation zone. A burner used in such an operation must be adapted not only to withstand the high tem-.

peratures of reaction to which it is exposed but also to prevent substantial flow of heat to the combustible stream flowing through the burner in order to avoid dangerous flash-backs through the burner. The temperature of such a burner is desirably controlled by circulating a suitable coolant, e. g., water, through a jacket on the burner body. The construction of a jacketed burner must make provision for high differential expansion and contraction of the several elements of the burner, arising not only from exposure of .the burner to high reaction temperatures but'also from the flow of preheated gases through the burner.

Furthermore, the broad temperature changes to which the burners of the present class are subjected, have been found to be an important contributing factor totheir rapid destruction. While temperature and corrosive influence are normally assumed to be responsible for deterioration, the strains set up as a result of repeated expansion and contraction are frequently the cause of burner failure, particularly failure at points of juncture of the burner parts.

An important object in the present invention is to provide a cooled burner as above which is relatively resistant to the detrimental eflfects of direct radiation and high temperatures and particularly wherein the exposed parts'are more or less completely protected by a cooling jacket. Another object contemplates a burner, as above, which is free from the adverse effects of relative expansion and contraction of the several parts. Other objects will be more clearly apparent from a consideration of the following disclosure.

While it will be obvious that the present invention is applicable broadly to the handling of combustible feed materials, particularly under adverse conditions of heating, nevertheless for purposes of convenience the present burner can be best illustrated by reference to the process of synthesis gas generation referred to above and to this end reference is made to the drawing showing an elevational view, partly in section, of a burner embodying the principles of the present invention in combination with a gas generator illustrated only fragmentarily.

The reference numeral I0 designates the metal wall or shell of a gas generator lined with fire brick, refractory or other suitable insulating and heat resisting material ii. The burner mounted on the generator shell ill by cup-shaped element I2, welded to the burner and the generator shell as at [3, comprises a tubular body M adapted to convey a mixture of combustible gases introduced into the T fitting l5 by way of pipe 3.

In accordance with the preferred embodiment of the invention shown, it is intended that combustible gases be introduced to the burner in premixed and preheated relationship, and to this end there is shown symbolically a preheater and mixer I! having a series of inlet pipes l8, I9, 20'.

and 2! for the several feed gases.

In order to better illustrate the operation of the device, it may be assumed that the pipe i8 supplies hlgh purity oxygen and the pipe l9 supplies a stream of methane, for example, in the approximate molar ratio of 1:2. Alternatively, however, air or other relatively diluted stream of oxygen may be substituted for the oxygen stream and the pipes 20 and 2! may introduce, respectively, small quantities of water vapor and carbon dioxide similarly capable of reacting with the methane to produce synthesis gas of substantially the same character although of different hydrogen to carbon monoxide balance.

The burner tube :4 extends into a receiving aperture in the generator wall and the refractory lining i l. The entire outer surface of the tube M to a point beyond the support I2 is disposed within coaxial tubular jacket 23. This jacket at the burner tip is flanged and welded to the inner tube l4 and at its opposite extremity is welded to an expansion member or bellows comprising a pair of frusto-conical plates 24 and- 25 disposed with their concave faces in opposed, coaxial relationship upon the tubes 23 and I4, respectively. The plate 24, and advantageously also the plate 25, is preferably of suitable flexible metal capable of acting as a flexible diaphragm under stress exerted in the axial direction of the burner tube. To this end, the plates 24 and 25 are provided witlrradially spaced annular corrugations as shown. However, sufficient flexibility may be secured by using plain plates without such corrugations.

It is to be noted that one extremity of th jacketing tube 23 is welded to the inner margin of frusto-conical plate 24 and that the outer margin of this plate or diaphragm is similarly joined throughout its entire periphery with the outer margin of the plate or diaphragm 25. The inner margin of the plate 25 is welded directly to the surface of the tube l4 and an outlet pipe 26 is secured thereto, as shown, for exhausting circulated coolant.

The coolant is advantageously supplied to the jacket in the vicinity of the burner tip or nozzle by an internal tube 21 coaxial with the burner tube H but curved adjacent the burner tip to pass through tube l4 and communicate with the interior of the jacket.

In order to permit some necessary relative expansion and contraction of the supply tube 21 with relation to the remainder of the assembly. the burner'tube I4 is provided by way of T' IS with a tubular extension 28 having a gentle gradual curve as shown. The supply tube 21 extends through the tubular extension 28, in spaced relation to the inner walls thereof, emerging from its extremity as at 29. The tube 21 is sealed into the extremity of the tubular extension 28 by welding or any other suitable means.

It will be noted that the supply tube 21 is supported at two points, namely at the extremity 28 of tubular extension 28 and at its opposite end where it passes through and is joined to tube l4. As a result it will be apparent that the construction is ideally suited to take up diiferential expansion and contraction of the several parts. Thus, longitudinal expansion of tube 2! results merelv in flexure of its curved portion within the tube 28 without unduly stressing points of juncture of tube 21 with associated parts.

So also the inner and outer tubes l4 and 23 are free to ex and or contract relatively, the strains being readily absorbed by the flexible diaphragm construction shown. While the stream of coolant. such as cooling water, may be sunplied throu h tube 21 and withdrawn from the jacket through outlet 28, the flow may be reversed whereby tube 28 serves as the inlet and tube 21 as the outlet.

In operation. methane may be introducedthrou h pipe l8 and oxygen via pipe l8, in the molar ratio of a proximately 2:1. These gases are thoroughly admixed a d preheated to about 900 F. in the preheater IT, and the mixture is i nited on disch rging from th v tip of the burner into the reaction zone. Water is circulated through the jacket burner, as indicated. Temperatures interiorly of the generator may reach this intense heat. However, the burner assembly is protected by the regular and even flow of cooling water through the jacketing tube 23. The cooling stream not only protects the tip of the burner but also prevents the flow of reaction or combustion heat along the burner body to the incoming stream of combustible gases so as to avoid harzardous flash-backs. Since burners of this type are frequently used with reactors having an internal refractory lining of about one foot or more in thickness, it is obvious that the cooling jacket of the burner prevents troublesome heat leaks from the refractory lining to the gas mixture through the walls of the burner tube extending through the lining. A refractory material in powdered form may be used to fill the space between the exterior surface of the burner jacket and the surrounding refractory employed as lining in the reactor or generator in order to minimize heat leaks into the burner arising from the flow of hot reaction gases into this space. In effect, thus, the powdered refractory serves to form a snug fit between the burner jacket and the refractory lining of the generator without interfering with the movement of the parts caused by differences in thermal expansion and contraction. With the present arrangement, moreover, it will be apparent that expansive and con tractive stresses are readily dissipated by the permissible flexing of the several burner parts.

One advantageous improvement disclosed in the drawing, involves the provision internally of the tube i 4 of a reticulated or screen-like packing 30 preferably near the burner tip, which, in the embodiment shown, comprises a, plurality of layers of wire mesh relatively loosely disposed about the coolant tube 21 to operate as a flashback preventor. This packing may alternatively comprise any suitable relatively loose arrangement of fine wires or particles preferably of good heat conductivity, dividing the cross-section of tube [4 into a multiude of restricted passages to prevent the flame from striking back through the burner. Obviously, disposed in contact with the cooling jacket as shown, the reticulated member 30, at least at points materially spaced from the burner tip, is maintained at a temperature below the ignition point of the gaseous mixture flowing therethrough. Broadly, this element may take any of the conventional forms of the so-called Davy diaphragm, although a reticulated or porous member of good heat conductivity is to b preferred.

-' art. For instance, a plurality ofadditional plates similar to 24 and 25 may be arranged in series, in accordion fashion, or there may be employed a short length of flexible tubing of the corrugated type adapted to expand or contract longitudinally, hermetically sealed to the relatively movable parts of the burner assembly.

The coolant conduit 21 need not merge with the jacket at only one point as shown, but may be branched at its extremity to supply a flow of coolspaced points.

ant to the jacket at several circumferentially The present invention accordingly provides an improved burner construction whereby reactant fluids may be injected into a zone of severe temperature and corrosive conditions without encountering rapid destruction of the burner. This is accomplished by protecting the burner by a flow of coolant, not only at the burner tip but also along the barrel or tube portion conveying the mixed, preheated reactants, so that they do not become overheated and burn inside the tube. In particular, this is so accomplished that expansive and contractive forces are absorbed without detriment to the several parts of the burner. As indicated above, the burner is not limited to the use of two combustible components.

From the foregoing, it will be appreciated that the provision of a cooling jacket extending along the portion of the burner within the reactor is of considerable advantage, particularly where combustible gases are employed. Coolants such as Dowtherm, mercury or fused salts may be used with the burner of this invention.

Obviously many modifications and variations of the invention as set forth above may be made without departing from the spirit and scope thereof and therefore only such limitations should be imposed as are indicated in the appended claims.

I claim:

1. A burner construction comprising tubular means adapted to extend into a reaction zone and terminating in a tip operative to deliver combustible fluid into said zone, said tubular means connecting with means outside of said reaction zone for delivering combustible fluid to said tubular means, a cooling jacket disposed about said tubular means in spaced relation thereto to form a cooling chamber and joined at one end to said tubular means in the vicinity of said tip, said jacket being connected at the other end with the said tubular means through flexible expansion means adapted to permit relative axial movement between said tubular means and said jacket, a coolant conduit extending axially and internally of said tubular means from a point remote from said tip and communicating with said cooling chamber in the vicinity of said tip, a second coolant conduit communicating with said cooling chamber at a point spaced from said tip, said firstnamed coolant conduit having a section within said tubular means at a point remote from said tip disposed at an angle relative to the tip portion of said tubular means operative to permit tlexure of said first-named coolant conduit within said tubular means to absorb axial movement therebetween resulting from expansion and contraction.

2. A burner construction comprising a burner tube adapted to convey combustible reactants theretbrough and to direct said reactants from the outlet extremity of said tube into a combustion zone, a cooling jacket surrounding said tube in spaced relation thereto to form a cooling chamber and being joined with said tube adjacent said outlet extremity, an expansion means connecting said jacket with said tube at a point spaced from said outlet extremity, said expansion means being flexible in a direction longitudinally of said tube whereby to permit differential axial expaneion of said tube and Jacket and being impermeable to coolant in said jacket, a coolant flow conduit extending longitudinally and interiorly of said tube in spaced relation thereto from a point remote from the outlet extremity of said tube, one extremity of said coolant flow conduit communicating with the interior of said cooling chamber in the vicinity of said outlet extremity, a. second coolant flow conduitcommunicating with said cooling chamber in the vicinity of said expansion means, a longitudinal section of said first named coolant flow conduit within said tube being curved at a point removed from said outlet extremity, said curved section being relatively flexible and operative to yield laterally in response to differential longitudinal expansion with respect to said tube, and means for circulating a coolant fluid through said coolant flow conduits and said cooling chamber.

3. A fuel burner comprising a tube terminating at one extremity in an outlet adapted to discharge combustible reactants into a combustion zone, means for supplying reactants to said tube at a point spaced from said outlet extremity, a

cooling jacket embracing said tube in spaced relation thereto to form a cooling chamber and joined to said tube adjacent said outlet extremity, means for supplying fluid coolant to said cooling chamber comprising a fluid inlet conduit disposed interspatially within said tube and extending lonitudinally thereof, one extremity of said inlet conduit connecting with said cooling chamber in the vicinity of said outlet extremity, said coolant inlet conduit being attached to said tube at a point remote from said outlet extremity and having a section within said tube intermediate said point of attachment and said outlet extremity, the axis of said section describing an arc effective to absorb the longitudinal expansion resulting from differential temperature conditions of operation by lateral flexure of said arcuate axis, and outlet means for continually withdrawing coolant from the cooling chamber at a point removed from said outlet extremity.

4. A fuel burner according to claim 3, wherein a longitudinal section of said tube substantially coextensive with the arcuate section of the said coolant inlet conduit is axially curved in an are substantially equivalent to that of the inlet coolant conduit, and wherein the outer surfaces of the coolant conduit sect on are spaced from the inner surfaces of the tube.

5. A fuel burner according to claim 3, wherein a heat conductive, porous member is disposed within said tube within the vicinity of said outlet extremity in heat conductive relationship with said coolant inlet conduit.

6. A fuel burner according to claim 3, wherein a heat conductive, porous member is disposed within said tube within the vicinity of said outlet extremity in heat conductive relationship with said coolant inlet conduit and with the inner walls of said tube.

FRANK D. HOFFERT.

REFERENCES CITED The following references are of record in the file of this patent: V

UNITED STATES PATENTS Number Name Date 1,218,895 Porter Mar. 13, 1917 1,707,772 Robinson Apr. 2, 1929 1,880,938 Emmet Oct. 4, 1932 1,945,902 Johnson Feb. 6. 1934 3,408,282 Wolf Sept. 24, 1948

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