US2853370A - Apparatus for distributing gases within fluid burners - Google Patents

Description

M. L. DowNlNG 2,853,370

3 Sheets-Sheet;

' Sept. 23, 1958 APPARATUS FOR DISTRIBUTING GASES WITHIN FLUIDBURNERS' Filed June 14, 1955 Mason L. Downing Inventor By @Wl/Attorney Sept. 23, 1958 M. L. DOWNING 2,853,370` y APPARATUS FOR DISTRIBUTING G AsIzs WITHIN FLUID BURNERS Filed June 14, 1955 s sheets-sheet-z Mason L. Downing lnven'rc'jr By Attorney Sept. 23,y 1958 M. L. DowNlNG APPARATUS FOR DISTRIBUTING GASES WITHIN FLUID BURNERS Fiied'June 14, 1955 3 Sheets-Sheet 3 Inventor Mason L. Downing By Q/LMJAHorney United States atent APPARATUS FOR DISTRIBUTING GASES WITHIN FLUID BURNERS Mason L. Downing, Scotch Plains, N. J., assigner to Esso Research and Engineering Company, a corporation of Delaware Application .lune 14, 1955, Serial No. 515,506

Claims. (Cl. Zit-288) The present invention relates to apparatus for partially burning and heating particulate carbonaceous solids such as fluid coke produced by Huid coking of heavy hydrocarbon oils. This invention pertains more particularly to an improvement of a vessel wherein finely divided solids, either catalytic or non-catalytic are fluidized and treated or reacted with liquid or gaseous uids, for example, for regenerative and/or heat production purposes.

The invention is particularly applicable to the heating of finely divided heat-carrying inert solid materials such as may be employed in the thermal cracking or coldng of heavy hydrocarbonaceous materials, including reduced crudes.

The present invention proposes a method and apparatus for supplying air to and distributing air uniformly within a fluidized solids combustion or burner vessel in a hydrocarbon oil fluid coking system in such a manner as to eliminate the objectionally high temperatures associated with air distributing grids customarily used in previous fluid bed combustion vessels. Particulate coke of high carbon content produced in the process is the heat carrying solid usually employed in a Huid coking process, although other inert solids may be used.

According to this invention, air or a free oxygen-containing gas is distributed to a dense fluidized bed of particulate coke to insure good fluidization of the bed and to eliminate stagnant zones of burning coke which cause damage to the combustion vessel. This invention eliminates in the fluid bed combustion vessel, the hazards of the coke burning in oxygen-rich areas or settling out and burning on attendant surfaces. The air distributing arrangement of this invention adequately distributes air throughout the fluid bed while preventing backow of the finely divided solids undergoing combustion into the air distributing system.

This invention has particular applicability to large size uid bed burners of over ft. in diameter wherein the air distribution problem assumes much importance.

This invention will become clear by reference to the accompanying drawings in which:

Figure 1 is an elevational view, partly in section, of a combustion or burner vessel designed in accordance with the teaching of this invention. The vessel contains the air distributing device of this invention in the lower portion.

Figure 2 is an enlarged sectional view of an elongated bubble cap member used to distribute the air within the vessel.

Figure 3 is a horizontal section through the apparatus according to Figure l along the indicated section line I--I and shows in greater detail the inter-connecting manifold used to distribute air to the bubble cap members illustrated in Figure 2.

Figure 4 is a vertical sectional view of an alternative means of distributing air to the plurality of bubble cap members of this invention.

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According to this invention, to insure good bed uidization and to prevent concentration of too much air in one area of a uid bed burner, an air distributor or manifold with a plurality of elongated bubble cap air outlets is provided. The bubble caps supply and evenly distribute air to a fluid burner bed while eliminating the possibility of backilow of the carbon-containing solids into the air distributing means. The bubble caps are ofsufficient length to prevent backow of the coke through the air distributing system. The manifold system that supplies the bubble caps is so designed as to take a negligible pressure drop such that almost all, preferably over of the pressure drop is taken in the bubble caps. This insures that each bubble cap will admit to the fluid bed approximately the same amount of air.

Succinctly, this invention comprises apparatus for introducing and uniformly distributing gases within a fluidized solids vessel, particularly when the vessel is over 10 ft. in diameter. The apparatus comprises a vertically disposed conduit of relatively large diameter centrally located in the lower end portion of a fluidized solids vessel, a horizontally disposed manifold system attached to the upper end portion ofthe vertically disposed conduit, the manifold system comprising a plurality of concentric inter-connecting pipes of intermediate diameter, and as a third element, a plurality of vertically disposed, top enclosed, elongated bubble caps of relatively small diameter attached to the manifold system and substantially uniformly spaced thereon.

In a preferred embodiment of this invention, a minor number of strategically located bubble caps are placed at higher elevation within the vessel in order that proper bed fluidity may be uniformly re-established in the event that the bed becomes deaerated.

In place of a horizontal manifold system, the bubble caps may be supplied with air from the centrally located conduit by a plurality of individual conduits of relatively small diameter.

In the drawings, like parts have been designated by the same numbers. The numeral 1 designates a combustion vessel such as is employed for the partial combustion and heating of particulate coke in a hydrocarbon oil uid coking system. The vessel is designed with a conical bottom and contains a fluid bed of particulate coke undergoing combustion having an upper level L An inlet conduit 2 admits relatively cool coke from a uid coking vessel into vessel 1 at an intermediate point within the uid bed. A heated coke withdrawal conduit 4 extends upwardly through the uidized bed, terminates substantially at the level L, and is notched or slotted at the upper end whereby the solids are made to overow more uniformly into the conduit despite slight variations in the Huid bed level. Conduit means 5 introduces hot gaseous materials, e. g., products of combustion, as required to initiate the reaction taking place within the vessel, and also admits the air required to maintain the combustion reaction. This means 5, as shown, is a refractory lined auxiliary burner unit of substantially conventional form for burning liquid or gaseous fuels. Line 6 admits to conduit 5 the required combustion air, which may or may not be diluted as with steam for control purposes. As the auxiliary burner unit 5 is combined with the combustion vessel as a substantially integral part thereof, the need for separate mounting or support means is largely avoided. Conduit 7 is `provided as a safety feature for the introduction of an inert gaseous material in the event of failure of the air supply.

In the upper portion of the Vessel, a cyclone system 8 removes entrained solids from the combustion gases and returns them to the uid bed. The combustion gases, after having entrained solids removed, may be vented by-linew9ormay befrst passed through a heat exchanger-and/or va-fterburner. In this particular example, the burner is designed to operate at iluidizing gas velocities around 2.5 to 3 ft./sec. and two stages of cyclone recovery are provided.

Cent-rally located conduit extends upwardly Vand terminates within combustion vessel 1. vIn Athel preferred embodimentV of this invention, ythere is attached tothe upper end portion of conduit 5 an inter-connectingdistributing -manifold comprising radial conduits 10 With horizontal concentric' conduits 11 running therebetween, more fully shown in Figure 3. Of necessity, the concentric `distributingmanifoldmembers kare given some vagrancy to permitinclusion ofthe coke inlet 2 and outlet 4- lines.

Connecting-with the upper'portion of this manifold system-,areA a'plurality ofl substantially uniformly spaced vertical bubble cap members 12, some of which are also placed on the top end portion of conduit 5. The bubble cap members comprise (see Figure 2)V a-vertical pipe 14 of relatively small diameter vhaving Va notched upper end portion encased with a downwardly extending cap- 16 of relatively extended length. lA horizontal circular distributing baie 23 is attached to the lower end of cap 16 to aid in the distribution of gases. It is preferred to have the cap member 16 disposed to vertical pipe 14 in a substantially close lradial relation so as to maintain the velocity of the gases passing through the annulus during normal operation between 15 to 50 ft./ sec. I-lowever, even though the gases cease to flow, the length of the bubble cap is suicient to prevent the fluid bed from rising lwithin the bubble cap and overflowing into conduitY 14. For good operation, one bubble cap should be used for every 3-to 10 sq. ft. or burner cross-sectional area.

As previously mentioned, a portion of the bubble caps are placed at a higher elevation so that during times of startup or in the event the bed becomes deuidized, uniformuidization may be re-established. These bubble caps of higher elevation are indicated by the numeral 12a.

"The'lower conical portion of vessel 1 below the distributing manifold may be conveniently filled with crushed or finely divided refractory material 17 to ll up the space that does not contribute to the operation of the vessel. This zone `filled with refractory material may be further sealed as by a horizontal layer 18 of refractory concrete.

With reference to Figure 1, auxiliary burner '5 will be more particularly described. As shown, the burner consists of a cylindrical casing 5, the upper portion of which is suitably lined with refractory material. In addition to the refractory liner material, the burner unit is provided internally with a lateral partition 24 disposed at an intermediate level within the casing and in vertical spaced relation to the lower end wall thereof. Supported on the upper 4surface of the partition 24 is a refractory lined combustion chamber 20 in open communication with the lower end portion of casing 5. The chamber is disposed substantially concentrically of casing 5 in radially spaced relation, an annular space or passageway beingl provided between respective casing walls 20 and l5. Afuel burner element 21 Vextends through the lower Wallinto the combustion chamber and is adapted to supply gases or liquid fuel to the burner. Primary air for combustion of fuel supplied to the burner is admitted by conduitconnection 22. Secondary air land air for combustion of the carbon-containing particles in Vthe uid bed is admitted by way of conduit 6.

p Ipntheoperation of the apparatus described, as' in its embodiment as a heating means for a hydrocarbon oil uid coking system, vesselrl forms part of the coke circulation system, receiving continuously stripped cool cokej'fromthe Vcokingvessel and discharging heated coke thereto. `A portion of the heated coke may be withdrawn from the process as product from the coke circulation system lor from-the fluid bed'by means not shown.

The fluid bed Within the combustion vessel is maintained at a depth sucient to prevent oxygen breakthrough which is uneconomical and results in afterburning and damage to the cyclone system. A minimum` bed height of about 10 ft. should be maintained to avoid oxygen breakthrough. Tests have shown that at temperatures as low as 1095 F. the oxygen concentration of the flue gases emerging from the bed is less than 0.3% at bed of about 10 ft. There is, apparently, no further decrease in oxygen concentration with increasing bed depth.

In initiating operation ofthe system, thefuelburner 21 is ignited and a How of free oxygen-containing gas, e. g., air, is introduced by way of conduit 6. The air, heated in the auxiliary burner by combination with gases from the combustion chamber 20, passesv through vessel 1, heating andffluidizing the solids therein. Operation of the burner is continued-until thetemperature ofthe fluid bed within the vessel is raised suiciently to *ignite and maintain combustion ofthe particular coke supplied tothe vesselby way of conduit 2. Normally the vesselwill operate at a temperature in the range of about 1050 to- 1125" F., although the temperature may go as high as 1600v to 1800 F. Coke supplied to the vessel by conduit 2 will normally have a temperature of about 950 F. @nce burning has been initiated, it proceeds for as long as air is supplied to the vessel in quantities sufcient to support combustion. Normally, about 0.9 standard cu. ft. of air per I1b.V ofcoke circulated to the vessel is used. As soon as the combustion reaction is underway, the fuel burner 21 may be extinguished and only the flow of the air continued. In some instances, however, e. g., where the coke produced by the coking process has greater value than available gases orliquid fuels, the burner maybe used to supply heat'to vessel 1 as such fuels will beburnt in the auxiliary burner in preference to the coke in the combustion vessel. ',The

Whole of the airl distributing system may be suitably braced and strengthened as against vibration by interconnecting horizontal and-angled members, and by members fastened to-vessel 1, not shown.

Figure 4 shows one alternative means of supplying air to the plurality of bubble caps used in the designjof this invention. Similar parts have the same number as in the other gures. vInstead of using an inter-connecting manifold system yto supply the bubble caps, a plurality of pipes 30 is used. The pipes are of relatively small diameter and arearranged in a porcupine fashion on centrally located conduit 5.

As a specific example, with reference to Figure 1,-a

` on the drawing:

4 inches.

31 ft. 6 inches. 6 ft.

18 inches.

melanoom For a vessel having the above dimensions in which there is contained particulate coke of a size range -of about 40 to 500 microns, 200 microns average diameter, and a true particle density of about lbs/cu. ft., the level of the fluid bed will be about l2 ft. above the level of the horizontal distributing manifold. Using a luidizing gas velocity of 2.8 .ft./sec. the bed Will have a fluidized density of about 40 lbs./cu. ft. 92 elongated bubble caps, of which 13 are 1 foot higher than the rest, are used to admit the air. 44,000 lbs. of coke/ min. at a temperature of 950 F. may be circulated to the combustion vessel of Whichapproximately 0.7% .will

be consumed and the remainder may be returned to the coking reactor at a temperature of 1125 F. or removed from the system as product. For such a coke circulation rate, air will be supplied to the combustion vessel through centrally located conduit 5 at a rate of 40,300 s. c. f./min. and temperature of 300 F.

Having described the invention, what is sought to be protected by Letters Patent is succinctly set forth in the following claims.

What is claimed is:

1. Apparatus for burning and heating carboncontain ing particulate solids while prohibiting solids backilow into the oxygen-supplying system comprising, in combination, a combustion vessel adapted to contain a uid bed of said particulate solids and means for supplying gaseous materials thereto, said means including a vertically disposed, centrally located conduit projecting through the bottom end wall of said vessel and terminating within said vessel, said conduit being mounted substantially integrally with said bottom end wall, source means for supplying a free oxygen-containing gasiform medium to said conduit, and distributing conduit means for distributing gases from the upper end portion of said conduit in a uniform pattern of discharge throughout the lower portion of said fluidized bed, said distributing conduit means including a plurality of elongated bubble cap members and a conduit system for passing gases from said centrally located conduit to said elongated bubble cap members, each of the majority of said elongated bubble cap members emanating substantially the same quantity of gasiform medium during normal operations, a minor number of said plurality of elongated bubble cap members being at a higher elevation than the majority of said elongated bubble cap members, the points of gas discharge of said minor number of bubble cap members into the solids bed being at a higher elevation than the points of gas discharge of the majority of said bubble cap members, whereby gases are distributed throughout said fluid bed and proper bed fluidity may be re-established in the event said fluid bed becomes de-iluidized.

2. The apparatus according to claim 1 wherein said conduit system comprises a plurality of concentric interconnecting manifold pipes lying substantially in a horizontal plane.

3. The apparatus according to claim l wherein there is one of said bubble cap membersfor every 3 to l0 sq. ft. of cross-sectional area of said combustion vessel, and wherein said minor number of elongated bubble cap members are strategically uniformly located throughout said fluid bed.

4. The apparatus according to claim l wherein said conduit system comprises a plurality of individual conduits connecting said centrally located conduit with each of said bubble cap members.

5. Apparatus for introducing and uniformly distributing gases within a iluidized solids vessel over 10 ft. in diameter which comprises a vertically disposed conduit of relatively large diameter, a horizontally disposed manifold system attached to the upper end portion of said vvertically disposed conduit, said manifold system comprising a plurality of concentric interconnecting pipes of intermediate diameter, and a plurality of vertically disposed, top enclosed, elongated bubble caps of relatively small diameter attached to said manifold system and substantially uniformly spaced thereon, a minor number of. said elongated bubble caps being at a higher elevation than the remainder of said bubble caps, the point of gas discharge of said minor number of elongated bubble caps being at a higher elevation than the point of gas discharge of the remainder of said elongated bubble caps.

References Cited in the le of this patent UNITED STATES PATENTS 2,421,212 Medlin May 27, 1947 2,631,191 Jones Apr. 7, 1953 2,639,973 Fritz May 26, 1953 2,686,113 Odell Aug, 10, 1954 FOREIGN PATENTS 478,374 Canada Nov. 6, 1951 63,626 Netherlands Feb. 15, 1949

Claims (1)

1. APPARATUS FOR BURNING AND HEATING CARBON-CONTAINING PARTICULATE SOLIDS WHILE PROHIBITING SOLIDS BACKFLOW INTO THE OXYGEN-SUPPLYING SYSTEM COMPRISING, IN COMBINATION, A COMBUSTION VESSEL ADAPTED TO CONTAIN A FLUID BED OF SAID PARTICULATE SOLIDS AND MEANS FOR SUPPLYING GASEOUS MATERIALS THERETO, SAID MEANS INCLUDING A VERTICALLY DISPOSED, CENTRALLY LOCATED CONDUIT PROJECTING THROUGH THE BOTTOM END WALL OF SAID VESSEL AND TERMINATING WITHIN SAID VESSEL, SAID CONDUIT BEING MOUNTED SUBSTANTIALLY INTEGRALLY WITH SAID BOTTOM END WALL, SOURCE MEANS FOR SUPPLYING A FREE OXYGEN-CONTAINING GASIFORM MEDIUM TO SAID CONDUIT, AND DISTRIBUTING CONDUIT MEANS FOR DISTRIBUTING GASES FROM THE UPPER AND PORTION OF SAID CONDUIT IN A UNIFORM PATTERN OF DISCHARGE THROUGHT THE LOWER PORTION OF SAID FLUIDIZED BED, SAID DISTRIBUTING CONDUIT MEANS INCLUDING A PLURALITY OF ELONGATED BUBBLE CAP MEMBERS AND A CONDUIT SYSTEM FOR PASSING GASES FROM SAID CENTRALLY LOCATED CONDUIT TO SAID ELONGATED BUBBLE CAP MEMBERS, EACH OF TH EAJORITY OF SAID ELONGATED BUBLE CAP MEMBERS EMANATING SUBSTANTIALLY THE SAME

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