US2672191A

US2672191A - Apparatus

Info

Publication number: US2672191A
Application number: US208094A
Authority: US
Inventors: Oliver F Campbell; Decker William Harrison
Original assignee: Sinclair Refining Co
Current assignee: Sinclair Refining Co
Priority date: 1951-01-27
Filing date: 1951-01-27
Publication date: 1954-03-16
Anticipated expiration: 1971-03-16

Description

March'l, 1954 o. F. CAMPBELL ETAL 2,672,191

APPARATUS Filed Jan.l 27, 1951 ATTORNEYS Patented Mar. 16, 1954 APPARATUS Oliver F. Campbell and William Harrison Decker, Whiting, Ind., assignors to Sinclair Reiining Company, New York, N. Y., a corporation of Maine Application January 27, 1951, Serial No. 268,094

1 Claim. l

Our invention relates to improvements in di rectional flame burners of the type useful in Deorez oil renery heaters. In the operation of Deilorez heaters or cylindrical furnaces of the all radiant, vertical tube type, it is of prime importance to provide dame control for proper heat distribution permitting control of heat input and balancing oi heater outlet temperatures for splitcoil or multi-heater operation. For this purpose, down-firing has been developed employing a specially designed directional flame control, oil and gas iired burner. The burner handles ne inery gas, natural gas or heavy fuel oil. Each burner is equipped with 8 to l?. individual air nozzles, depending upon the size of the burner, tatably disposed in a burner plate located at the head of the furnace throat. Space for charging preheated air to the nozzles together with ilow regulating means is provided above the burner plate. The individual air nozzles are equally spaced on a common circle around the burner plate and are so constructed that they can be individually rotated through a complete arc or" 360. The nozzles are provided with a 15 curvature on the lower end so that control of the heat distribution in the furnace may be had as desired by the operator. Each nozzle is supplied with a single gas pipe so that the main burner actually is composed of 8 or l2 small gas burners den pending upon the size of the furnace. The highly preheated air, i. e., 100ll F. or above, is forced through the nozzle under pressure where it is mixed with the fuel gas and the resulting mixture burned. Fuel oil, however, is burned with a single oil gun of the steam atomizing type located in the center of the burner plate. For oil ring, a substantial proportion of the combustion air is supplied through a central air register in which the oil burner is installed while air to the individual nozzles is reduced by dempers.

With directional flame burners of this type, it has been established that the shape and dimension of the air nozzles are critical in terms ci proper heat distribution, maximum heat absorp tion and efficiency of operation.

Thus an overall length of at least l inches has been thought necessary for proper directional control and for good mixing and combustion in view of the high velocities and Volumes of air and gas involved. On the other hand, the nozzles cannot be too long, or serious vibration and disturbing noise result. We have now found that when the diameter of the nozzle is limited to rI inches maximum diameter, the distance of the internal gas pipe tip above the nozzle face is critical with respect to eiiicient mixing and combustion. We have further found that by reducing the length of the nozzle to r11/2 inches maximum while maintaining a distance of 41A; inches between the gas pipe tip and the nozzle face that mixing and furnace eciency actually are improved to a signiicant and commercially valuable extent. At the same time capacities are improved through reduced skin friction resistance and good flame control is retained.

-The nature of our invention and its mode of operation will be further described with reference to the accompanying drawings in which Figure 1 represents an underneath plan View of the burn er plate as it appears from a position looking upward into the burner throat. Figure 2 represents a Vertical section through a portion of the burner assembly cut away in a manner illustrating the structure of the nozzles, fuel and air supply system, and directional control system. Figure 3 represents a detail of the nozzle structure in section.

The burner assembly comprises a circular burner plate lll which in actual construction preferably consists of a plurality of segments l l. Spaced around the burner plate I0 are a number of air-gas nozzles I2, each with a centrally positioned internal gas pipe I3. For ecient air-gas mixing and combustion with the shortened nozzles, the tip or the gas pipe must be 41/4 inches above the lower face or the nozzle tube, a critical position within the slight tolerances of fabrication. In the center of the burner plate is located the master air register and damper means lil and a centrally located steam atomizing oil burner nozzle l5. Referring to Figures 2 and 3, it can be seen that the nozzles l2 are fabricated with a curved section l@ and an upper flanged section Il forming a bearing surface coinciding with seating elements i8 on the upper surface of the burner plate. The nozzles advantageously are fabricated from high chrome heat resistant steel alloys for maximum nozzle life. rlie maximum length of the nozzle tube including the curvature and the 4% inches between gas pipe tip and nozzle face is 'l1/2 inches to obtain the improved operational and economical advantages of our in vention. The minimum length is ixed by the desirability of enough length above the gas pipe tip to establish air velocity while providing bearing surface for the rotatable mounting. The diameter may vary from 7 inches I. D. to about 4. rihe curvature for these conditions is 15. The lower surface of the burner plate It! is protected by a layer of refractory material I9 which by reason or the shortness of the nozzles l2 largely protects them 'from direct exposure to the high temperature of the furnace throat.

Located above the burner plate l0 is an insulated cover section 20 supported by members 2l forming a cylindrical housing which communicates with the air supply system and functions as a distributing means for the combustion air to the individual air-gas nozzles. Each nozzle l2 is equipped with a slotted cylindrical member 23 which permits access of combustion air to the nozzle. Advantageously, the member 23 is in the form of a vertically adjustable damper controlled by means of sleeve 2S which functions to raise and lower the damping means under control of hand wheel 25. Each air nozzle i2 is rotatable by means of hand wheels 2% operating on the outer portions of sleeves 2li. The oil burner is fitted with steam connection 2l and oil connection 28. The master damper control lll is operated through rod 2S and wheel Elli.

In operation, the burner is lighted off using available refinery by means of lighting ports 3| with the master damper id closed. As the heater is brought up to temperature, the supply through individual. air registers 2S supplemented as necessary through master register it is preheated by exchange with the rlue gases to 1000 il'. and higher. Usually, soon as gas is available from the unit in which the heater is functioning, the fuel supply is charged over and the unit is brought up to full firing rate. Tube temperatures, particularly in the critical regions, are followed and heat distribution adjusted as necessary by rotation of individual nozzles it to develop the proper heat absorption. At least per cent excess air is desirable to handle surges in fuel supply, but it is imp to minimize excess air for furnace efliciency and capacity. When fuel oil is burned through the single oil gun centrally located in burner plate lil, as much of the combustion air is possible is supplied through the center air register ill in which the oil burner is installed with a minimum amount of air through the individual nozzles Since the flame burst temperature for fuel oil is considerably above that of fuel gas, the combination of this condition with the central air supply may result in excessively high nozzle metal temperatures. The very short relationship with respect to dialnet-er of the new air-gas nozzles of our invention is particularly advantageous under these conditions in avoiding oxidation of the lower curved portions or the nozzles. -For if the metal is destroyed by oxidation, of course the control of llame pattern and thus heat distribution in the furnace becomes increasingly dirlicult with resulting poor operation. The nozzles of our invention are protected by the refractory layer attached'to the burner plate and there is no need therefore to resort to the various insulating expediente which are unsatisfactory in function and diflicult and expensive to maintain.

The air-gas nozzle assemblies of our invention are more eflicient in operation because less excess air is required and surprisingly better mixing results in the short fat annulus. Higher capacities are obtained due to reduced frictional resistance in the shortened nozzles. The value of the new type air-gas nozzle assembly is illustrated in a series of tests conducted over a period of seven weeks on the number-1 heater of a typical pressure coil thermal cracking still. The furnace data for the new type nozzle assembly were obtained over a period of seven weeks operation and are compared with operation with the old style nozzle assemblies over the directly preceding seven week period. The heater was the first of 2 serially connected heaters in a split coil 2 heater design. The number-1 heater contained 120 4- inch by 35-foot tubes of 4-6 chrome alloy metal. The total heating surface was 4,050 square feet. During the run, the heater throughput averaged 18,500 barrels gas oil per hour. The oil temperature into the heater typically averaged 585 F. and the outlet temperature was maintained at about 875 F. The average furnace load was 44: million B. t. u.s per hour. The furnace temperature ranged from 1150o to l250 F. and the ilue gas temperature ran about 1130o F. The new type nozzles were quite sensitive to control and it was the opinion of the operators that control was somewhat better with the new type than with the old type.

The unit was brought up to a rate of 41.0 million B. t. u. per hour with a 76 per cent efficiency, using a fuel gas with a heating value of approximately 2200 B. t. u. per cubic foot. `While operating at the level and with a high B. t. u. fuel gas the flame was entirely non-luminous. The flame was quite similar to that which is produced when burning natural gas with a heating value of around G E. t. u. per cubic foot. This would indicate that extremely rapid, highly efcient combustion was tasing place through the burners. riube temperatures showed that the heat distribution throughout the furnace was very uniform. The short nozzles permitted the names to fan out the furnace throat so as to produce excellent firing without sacrifice of control or damage to the furnace throat or nose tile. In addition, the furnace efficiency averaged 1.3% higher, or 76.7% against 'lfl over the test periods. The amount of excess air required was lowered from an average of 29.86% to 35.56%. Thus the air-fuel mixing characteristics were unexpectedly better and valuable heater economies were effected. In addition to these operational advantages, the new type air-gas nozzle assembly is cheaper to fabricate, has an almost indefinite service life, requires no external insulation, materially reduces the labor and repair costs on the heater, and provides better controllability over the entire heater on stream period.

We claim:

in a multiple nozzle, directional flame control, oil and gas fired burner for cylindrical, vertical tube radiant type oil refinery heaters in which each nozzle comprises a tubular air-gas nozzle symmetrically and rotatably mounted in a burner plate and equipped with means for individual rotation through 360, an improved air-gas nozzle assembly which essentially comprises an air duct of about l inches to '7 inches maximum inside diameter by 71/2 inches maximum length having an upper open end forming an air inlet said duct being constructed with an angle of curvature from its inl-et of about 15 at its lower end, a gas pipe coaxially mounted within the inlet with the tip or" the gas pipe l1/x inches above the lower face of the duct, means for supplying air under pressure down through the duct, and means for supplying gas down through the gas pipe.

GLF/'ER F. CAMPBELL. VVILLAM HARRISON DECKER.

References Cited in the le 0I" this patent UNITED STATES PATENTS Number Name Date 2,196,282 Voorheis .Apr. v9, 1940 2,395,276 Jordan Feb. .19, 1946