US2772729A - Apparatus for combustion of hydrocarbons - Google Patents

Description

Dec. 4, 1956 2,772,729

R. L. MAYHEW APPARATUS FOR COMBUSTION OF HYDROCARBONS Filed May 3, 1951 INVEN TOR. Poet-PT; MA YHW 1 1 TTaENEYs' United States Patent APPARATUS FOR COMBUSTION OF HYDROCARBON S Robert L. Mayhew, Great Neck, N. Y., assignor to Hydrocarbon Research, Inc., New York, N. Y., a corporation of New Jersey Application May 3, 1951, Serial No. 224,283 3 Claims. (Cl. 158-109) This invention relates to a burner for combustion of fuel mixtures at high temperature conditions. The burner of this invention is particularly designed to effect combustion of a hydrocarbon gas with high purity oxygen.

Burners, whether employed primarily for the production of a product mixture of desired composition such as synthesis gas or primarly for the production of available heat energy, are generally subjected to severe temperature conditions because of their location in the fur nace. The temperature conditions are particularly se vere when high purity oxygen is employed in the combustion since there are not available large quantities of inert diluent gas to aid in the dissipation of the large amount of heat liberated in the highly exothermic combustion. Prior art burners have failed after short periods of on-stream time. Burner failure manifests itself in a number of different ways. Most frequently burner failure is characterized by melting of the metal burner tip and gradual sloughing off of the metal surrounding the burner discharge ports. Burner failure of this type often results in furnace burnout because of the develop ment of hot spots on the furnace wall. Burner failure is sometimes accompanied or preceded by carbon deposition and build-up within the generator which also may cause complete furnace failure because the combustion flame is deflected onto the furnace wall by the carbon deposit. The deficiencies in the prior art burners which result in carbon deposition and burner or furnace failure are attributable in large part to inadequate cooling of the burner assembly. The novel burner design of this invention remedies the drawbacks of prior art burner and provides adequate cooling by a unique means of cooling chamber construction.

The novel burner of this invention is designed to give a long life by eliminating the causes of burner failure. In addition, the burner of this invention is constructed so as to effect good mixing and to provide smooth burning of the the combustion mixture with the resulting formation of a product gas which is substantially free of carbon. The burner of the invention is particularly well suited for production of synthesis gas by the partial combustion of methane or other hydrocarbon gas with substantially pure oxygen.

Good mixing, smooth burning, elimination of carbon formation and increased burner life are effected by a novel burner construction which provides efiicient cooling of the critical areas of the burner and causes the fuel gas and oxygen-containing gas to thoroughly mix with resulting smooth, controlled combustion. The novel burner assembly of this invention comprises two concentric tubular conduits adapted for feeding two gas streams to a furnace; one gas stream is introduced into the furnace through the smaller inner conduit and the second gas stream is introduced through the annular passage between the outer and inner conduits. Both the outer and inner conduits are provided with circular dis charge ports; the outlet end of the larger conduit extends ice beyond the discharge port of the smaller conduit and is arranged so that the stream of gas discharging from the annular passage is directed into the stream of gas discharging from the inner conduit. Cooling jackets are disposed about the discharge ports of both conduits in direct contact therewith so that cooling chambers are formed which encircle the discharge ports. Inlet and outlet tubes are connected with the cooling chambers so that liquid coolant can be continuously introduced to and removed therefrom. The construction of the inlet tube to the cooling chamber surrounding the larger outer conduit is particularly important; this inlet tube terminates in a spray ring which is disposed in annular relationship to the discharge port of the outer conduit and is located in the portion of the cooling chamber immediately contiguous to the discharge port of the outer conduit. The burner of the type described causes extremely efiicient mixing of the fuel gas and oxygen-containing gas by the impingement of one gas stream upon the other. Moreover, the impingement of one gas stream upon another in an area of constricted diameter increases the velocity of the combustion mixture and effects speedy removal of the combustion mixture from the area of the burner tip. The gas stream discharging from the outer conduit impinges on the gas stream discharging from the inner conduit at an angle between about 30 and 60, and preferably at an angle of approximately 45 Since the mixture of the fuel gas and oxygen-rich gas at the temperature conditions existing within the furnace results in immediate ignition and burning of the fuel mixture, their speedy removal from the burner tip through the burner orifice is highly effective in preventing burner failure.

In the utilization of the burner of this invention for the preparation of synthesis gas by combustion of natural gas with oxygen, the gases are passed through the inner conduit and the annular passage at velocities in the range of to feet per second, and are discharged from the burner orifice at a velocity in the range of 225 to 300 feet per second. It is apparent that the speedy removal of the combustion reactants is effected by the unique burner design of the present invention.

Cooling the discharge ports of both the inner and outer conduits prevents overheating of the parts of the burner which are subjected to the greatest amount of radiant heat from the combustion taking place within the furnace proper. The arrangement of the cooling chamber around the outer conduit and the means whereby coolant is introduced therein are particularly important features in the construction of the novel burners of this invention. The coolant is introduced into the cooling chamber surrounding the outer conduit by means of a cooling tube which terminates in a spray ring which is located in the section of the cooling chamber immediately contiguous to the discharge port; the spray ring is disposed in annular relationship to the discharge port of the outer conduit. Introducton of the coolant by the prescribed means prevents the formation of steam pockets or blankets in the cooling chamber surrounding the outer conduit. The intense radiant heat to which the outer conduit is subjected results in the formation of steam blankets in cooling chambers containing conventional means of coolant introduction and removal. Applicants means of coolant introduction completely eliminates the possibility of steam blanket formation in the cooling chambers and assures a continuous, steady cooling of the discharge port of the outer conduit. Steam which is formed in the cooling chamber does not interfere with coolant introduction in the novel burner of this invention.

It is also feasible to utilize similar means of coolant introduction for the cooling chamber surrounding the inner conduit. Ordinarily it is not necessary to resort to such means for introducing coolant to the inner cooling chamber since the discharge port of the outer conduit bears the brunt of the radiant heat reflected from the furnace walls. However, an inlet tube terminating in a spray ring contiguous to the discharge port of the inner conduit is advantageously used in cornbustions involving very severe temperature conditions in the range of 3000 to 3500" F.

As indicated previously, the burner of this invention is particularly adapted to the production of synthesis gas by reatcion at high pressures, say 300 to 500 p. s. i. g. between methane or natural gas and oxygen-rich gas containing more than 90 mol. percent oxygen. Hereafter, the invention will be exemplified by the utilization of the burners in the production of a 2:1 mol. ratio hydrogencarbon monoxide mixture to be employed in the manufacture of synthetic gasoline. It is to be understood, of course, that the novel burner of this invention is adapted for use in a wide variety of reactions involving combustion of oxygen-containing gases with gaseous fuel wherein the temperature within the furnace ranges from 2000 to 3500 F.

The construction of the novel burner of this invention will be better understood by reference to the accompanying drawing wherein there is set forth a sectional view of the burner. The drawing represents a burner inserted in a furnace aperture.

The furnace wall is designated by the numeral 1. The flanged side walls of the aperture through which the burner is inserted into the furnace, are indicated by the numeral 2. The side walls of the burner extending beyond the aperture are identified by the numeral 4 and the flange on the burner is designated by the numeral 5. The numeral 6 designates the gasket between burner flange and the flanged side walls 2 of the furnace aperture.

The portion of the burner which is inserted in the furnace is surrounded by cast refractory which is indicated by the dotted section denoted by the numeral 10. The side wall of the outer conduit is denoted by the numerals 11. The side wall of the inner concentric conduit is denoted by the numerals 15. The annular passage defined by the side wall 11 of the outer conduit and the side wall 15 of the inner conduit is identified by the number 20. The passageway through the inner conduit is denoted by the numeral 2-1.

The numerals 25 and 26 denote the discharge ports of the inner and outer conduits respectively. The cooling chamber surrounding the discharge port 25 of the inner conduit is marked with the numeral 28. Liquid coolant is introduced into the cooling chamber 23 through the tube 30 and is discharged therefrom through tube 31. The coolant enters the tube 30 and is discharged from the tube 31 through the burner flange 5 by means of pipes which are not shown in the drawing.

The discharge port 26 is surrounded by a coolant chamher which is designated by the numeral 34. Coolant is introduced into the cooling chamber 3 through pipe 35 which terminates in a spray ring 36 located in the portion of the cooling chamber contiguous to the discharge port 26. The spray ring 36 is disposed in annular relationship to the discharge port 26. Coolant is withdrawn from the cooling chamber 34 through a pipe 37 which discharges through the burner flange 5.

it is apparent that introduction of coolant into the cooling chamber 34 through the tube 35 and the spray ring 3 6 results in efficient cooling of the discharge port by placing the incoming coolant in contact with the area of the burner which is subject to the most severe heat conditions. In addition, the possibility of vapor lock is obviated by the cooling means integrated in the novel burner of this invention.

In production of synthesis gas, natural gas is ordinarily passed through the annular passage 20 while substantially pure oxygen of better than 90 percent purity is introduced through the passage 21. It is practicable, however, to reverse the positions of the gaseous streams so that oxygen occupies the annular passage 26 and natural gas flows through the passage 21. It will be observed that the intcrior angle formed by the intersection of vectors representing the directions of flow of the natural gas and oxygen streams is approximately 45. The impingement of natural gas on the oxygen in this manner results in excellent mixing of the gaseous streams. Moreover, the constriction in the discharge port 26 increases the gas velocity and effects speedy removal of the reactants from the burner proper.

The utilization of the novel burner of this invention for the manufacture of a 2 to l hydrogen-carbon monoxide synthesis gas mixture is illustrated in the following example:

Natural gas and oxygen of percent purity are charged to a generator containing four burners of the type described in this invention in such proportions that 9,854 mols. of natural gas and 6,667 mols. of oxygen are fed to the generator per hour. The generator is maintained at 310 lbs. per square inch gauge as are the natural gas and oxygen streams which have been preheated to temperatures of 985 F. and 260 F. respectively prior to introduction into the generator. To each of the four burners in the generator, oxygen is charged at the rate of 10 cubic feet per second through the inner conduit and natural gas at the rate of 32.5 cubic feet per second is charged through the annular passage. The oxygen is passed at a velocity of 146 feet per second through the inner conduit which is a 3 /2 0. D. Schedule 4-0 pipe. Natural gas is passed at a velocity of 79.7 feet per second through the annular passage defined by the inner conduit and the outer conduit which is a 10" O. D. Schedule 40 pipe. The velocity of the natural gas is raised to 113 feet per second prior to discharge from the annular passage because of the constriction in the annular passage effected by the cooling chamber disposed about the discharge port of the inner conduit. On mixing of the reactants by impingement of the natural gas on the oxygen stream a total of 42.5 cubic feet per second of reactants issue from the discharge port 26, which has a diameter of approximately 5.57 inches, at a velocity of approximately 250 feet per second. There is produced as a result of combustion in a generator containing four burners of the prescribed construction, a synthesis gas containing hydrogen and carbon monoxide in approximate ratio of 1.85: 1. The generator operation is characterized by long life and is free from burner failure and side-wall blowout.

Obviously many modifications and variations of the invention, as hereinbefore set forth, 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 assembly for combustion of fuel gas cornprising an inner conduit of uniform circular cross section terminating in a discharge port of the same cross section, an outer conduit disposed coaxially about said inner conduit in spaced relationship therewith to define an annular passage between the conduits, said outer conduit comprising a relatively elongated upstream section of uniform diameter and a downstream section of gradually reduced diameter extending beyond the discharge end of said inner conduit and terminating in a discharge port having a diameter larger than that of said discharge port of said inner conduit, and means for cooling said discharge end of said inner conduit at said discharge port thereof comprising an annular cooling chamber located at and surrounding said discharge end of said inner conduit, said cooling chamber diminishing in diameter downstream toward said discharge end of said inner conduit and forming a sharp edge therewith, said annular passage defined by said outer conduit being restricted by said coolingchamber at said discharge end of said inner conduit thereby providing a high velocity gas flow therethrough without a corresponding large pressure drop due to conduit friction, said outer conduit having an annular cooling chamber in contact with said section of gradually reduced diameter and being located at said discharge end of said outer conduit and spaced opposite said means for cooling said discharge end of said inner conduit.

2. A burner assembly of the type defined in claim 1 wherein the walls of the inner and outer conduits are arranged to direct the stream of gas discharged from said angular passage between said conduits into the stream of gas discharged from said inner conduit at an angle of intersection of between 30 and 60.

3. A burner assembly for combustion of fuel gas comprising an inner tubular conduit of circular cross section for feeding a stream of gas and terminating in a circular discharge port of equal cross sectional area, an outer conduit concentric with and disposed about said inner conduit in spaced relationship therewith to define an annular passage for feeding a second gas stream, said outer conduit comprising a relatively elongated upstream section of uniform diameter and a downstream section of gradually reduced diameter extending beyond said discharge port of said inner conduit and terminating in a discharge port exterior of said inner conduit and of a diameter larger than that of said discharge port of said inner conduit, a first cooling chamber in direct contact with and located at and encircling the discharge end of said inner conduit, said first cooling chamber tapering inwardly toward said inner conduit and forming with said inner conduit a sharp edge at said discharge port of said inner conduit, inlet and outlet coolant tubes connected to said first cooling chamber, a second cooling chamber located at the discharge end of said outer conduit in contact therewith and encircling the discharge port thereof, inlet and outlet coolant tubes connected to said second cooling chamber, the inlet coolant tube for said second cooling chamber terminating in a spray ring disposed within said second cooling chamber adjacent said discharge port of said outer conduit, said first cooling chamber being spaced opposite said second cooling chamber thus restricting said annular passage between the conduits adjacent said discharge end of said outer conduit thereby providing for a high velocity gas flow through said annular passage to insure intimate and efficient mixing of the streams of gases and a short contact time by them with the cooling chambers.

References Cited in the file of this patent UNITED STATES PATENTS 1,145,948 Waern July 13, 1915 1,515,172 Ronstrom Nov. 11, 1924 2,515,158 Turpin et al July 11, 1950 2,582,938 Eastman Jan. 15, 1952

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