US2928460A - Annulus type burner assembly with face cooling and replaceable inner tip - Google Patents

Description

March 15, 1960 DU BOIS EASTMAN ET AL 2,928,460

ANNULUS TYPE BURNER ASSEMBLY WITH FACE COOLING AND REPLACEABLE INNER TIP 4 Sheets-Sheet 1 Filed July 13, 1956 llllll [I] a"""'l""in iii March 15, 1960 DU BOIS EASTMAN ETAL 2,928,450

ANNULUS TYPE BURNER ASSEMBLY WITH FACE COOLING AND REPLACEABLE INNER TIP 4 Filed July 15, 1956 Sheets Sheet 2 March 15, 1960 DU BOIS EASTMAN ETAL 2,923,460

ANNULUS TYPE BURNER ASSEMBLY WITH FACE COOLING AND REPLACEABLE INNER TIP 4 Sheets-Sheet 3 Filed July 13, 1956 March 15, 1960 DU 501s EASTMA ET AL 2,928,460

ANNULUS TYPE BURNER ASSEMBLY H FACE COOLING AND REPLACEABLE INNER TIP 4 Sheets-Sheet 4 Filed July 15, 1956 ANNULUS TYPE BURNER ASSEMBLY COOLING REPLACEABLE INNER TIP Du Bois Eastman, Charles P. Marion, and William- Leon Slater, Whittier, Calif assignors t Texaco Iuc., a corporation of Delaware Application my 13,1956, Serial Nb. 597,666 f;

2 Claims. (Cl. 158-109) This invention relates generally to an apparatus for synthesis 'gas generation by'partial oxidation and is particu larlyuapp licable to the generation of carbon monoxide and hydrogen by the partial combustion ofa gaseous hydrocarbon fuel with oxygen-enrichedair or substan tially pure oxygen.

Synthesis gas mixtures consisting essentially of carbon 2,928,460 Patented Mar. 15, 1960 requirements and give a maximum yield of the desired product gas. This is further complicated by the fact that the transfer of heat from the high temperature reactant gases to .the cooling structure of the burner elements must bekept to a minimum.

For one or more of the foregoing reasons, failure of the prior art burner elements-is characterized by erosion of metal at the burner tips even where these have been water cooled, and where the reactants are premixed and injected from the burner at rates of flow in excess of the rate of flame propagation, the highly reactive oxygenmonoxide and hydrogen are important commercially as a source of hydrogen for hydrogenation reactions andas a source of feed gas "for the synthesis of hydrocarbons, oxygen-containing organic compounds, or ammonia.

Thepartial combustion of a hydrocarbon fuel with oxygen-enriched air or with-relatively pure: oxygen to produce carbon monoxide and hydrogen presents unique problems not encountered normally in the burner art. Not .only is a very' rapid, and complete mixing of the hydrocarbon fuel mixtures react along a film of gases ever-present on the surface of the conduit or orifice through which they are discharged resulting in overheating and failure.

' 'It is an object of invention to provide a simple and economical burner for synthesis gas generation which corrects the cause of the failures of the prior art burner structures. 7

is another object of invention to provide an improved burner structure which is adaptable for use with various reactants.

And another object of invention is to provide an improved burner construction which is adequate for a variable choice of burner orifices and is capable of cooling the burner tips with a minimum of heat loss from preheated reactants.

reactants required, but also special precautions are necessary to'protect the burner from overheating.

' Because of the'reactivity of oxygen with the metal from which a suitable burner may be fabricated, it is extremelyimportant to prevent the burner elements from reaching those temperatures at which their rapid oxidation takes place. In this connection, it is essential that the reaction between the hydrocarbon fuel and oxygen take place entirely outside the burner proper and that localized concentration of combustible mixtures at or near the surfaces of the burner elements be prevented. Even though the reaction takes place beyond the point of discharge from. the burner, the burner elements are subjected to heating by radiation from it.

Inadequate mixing results in such concentrations of oxygenin localized areas that relatively complete combustion of a portion of the fuel takes place in these areas, releasing large quantities of heat. I In addition, regard; less of the type of burnerf construction employed,-; ed dies of the reactants form combustible mixtures near the burner surfaces. Unless these surfaces are maintained These and other objects and advantages of the invention will be apparent from the following description when taken in connection with the accompanying drawings wherein:

Fig. 1 is a general illustration of a burner assemblyinjposition; r

Fig. -2. is a diagrammatic longitudinal cross section through the burner tip taken at line 2-2 of Fig.4 and showing the burner face cooling chamber;

at a temperature below the ignition temperature of the mixtures, they act as flame holders, with the ensuing combustion along the surfaces soon causing overheatingand failure of the burner element. i

' Another problem peculiar to this reaction is the tend,-

ency' for, free carbon. to form either .on the burner or within the reaction zone, due primarily to inadequate mixingof the reactants, leading to burner failure. For-- mation of carbon on theisurface of the burner-interferes With tlielmixing of the reactants and causes localized;

concentrations-of oxygen, with resulting overheating. or burner elements following its combustion. s r j conventional burners, it has been found necessary to usea quantity of oxygen in excessof-the theor et i cal to prevent carbon formation; This. often causes" undesirably high reaction temperatures and increases the problem of cooling the burner. The problem is further aggravated by the fact that in the partial combustion of gases, it is desirable to charge the reactant gases to the burner in a ;hi gh1 y preheated state to reduce the oxygen- Fig. 3 is a partly diagrammatic longitudinal cross section through the expansion joint of the burner assembly of Fig. 1, taken along line 3-3 of Fig. 6.

Fig. 4 is a cross section through the burner tip along the line 4-4 of Fig. 2, without the cooling chamber and showing the replaceable inner conduit inoperative position; H Q Fig. 5 its view similar to Fig. 4, without the cooling chamber. and showing the position of the inner conduit during the assembly of the burner and prior to its being locked in operative position; v fFig'. 6 is an end view of Fig. -1, looking toward theexpan sion joint andshowing the orientation of the innerconduit when in operativeposition;

Fig. 7 is an end view similar to Fig. 6 during assembly, corresponding to the position of the conduits shown in Fig. 5;

Fig. 8 is a view corresponding to Fig. 2 and shows a cross section of the burner tip with the inner conduit in recessed position with respect to the burner face;

Fig. 9 discloses a modification of the burner shown in g 8, with the discharge end of the inner conduit forniedwith a cooling chamber;

Fig. 10 is a section of the inner conduit taken along line 10 1o of Fig. 9, showing the inner conduit cooling 3 i the solution to the problem of the shut-downs of gas generators dueto the failure ofthe burner elementsbc cause of theirinadequate cooling, or the like, I

Referring to the figures in the drawings, in Fig, 1, the burner assembly isindicatt'ed generally 'at A, with, t;lre burner tip M3, the 'expans ionjjoint assembly a-t"C, the mounting flange at D,'the hydrocarbon fuel, eig. natural gas, inlet at E, and the oxygen inlet at F. One of thecoolant connections is disclosedat G, the other being located diametrically opposite. V

In Fig. 2, the burner tip at B is shown in cross section, with the inner conduit, providingthe oxygenor an enriched mixture of oxygen,'indicat'ed "at 10, having an out let-therefor at 11 and with diametrically spaced locking lugs indicated at 12, 12 (see also Figs. 4 and 5). 'An outer conduit 13, ending in an orifice 14, is locked in spaced relationship with the inner conduit to define "an annular passage, indicated at 15, which leads to the orifice at 14. The orifice 14 is surrounded by a face cooling chamber indicated at 16, to which an appropriate coolant is provided by coolant tubes; -T he outer conduit 13 carric's complementary lockinglugs indicatcdat 17, 17, and 18, 18, which coact with locking lugs '12, 12 to restrain extensive longitudinal movement of'fthe inner conduit.

with theirre'spectlve All "the locking lugs-may be integral conduits or welded thereto.

The outer conduit 13 also carries a plurality of spacer pins 19, indicated as four-in number in the drawings. (see Figs. 4 and 5) which servei to locate "the inner conduit in spaced relationship to the outer conduit. These and bolts indicated at 26-, which'are used to fasten the i adjoining locking fiangesto each other. Gasket means merit rod 28, "the (purpose for which will be described 'b'elow.

The locking flanges 24, 25, carried by the casing 2 3 also include a plurality of lugs, shown as three each in number and indicated respectively as 24b and 25b to receive spacer bolts and nuts indicated at 29 and which are assembled onthe expansion joint by the use of the shim indicated in dotted outline.

In the assembly at this joint, the burners are brought up to operatingtemperature and the spacer bolts 29 are inserted. through openings -in the lugs, with shims'inset-ted between the lugs'and nuts. with the burner at operating temperature; the-nuts are. tightened down on;

the shim by hand and then locked in'place, after which p the shims-are removed. The burner should operate with the "spacing of the shim between 'the nuts and the lugs,

V the assembled bolts serving as a safety device should the locking lugs 12, it: or complementary lugs 17,, 17 "give u addition "to "the "spacer pins "disclosed at 19 n the '1 sinner tip and varried I by the out'er conduit in order to maintainthe inner conduit in spaced relationship therespacer pins also may be integral with the outer conduit or affix'ed thereto in some other suitable manner, as by press fittinglinto bore holes and then plug welded, "as disclosed herein. j I

With particular reference to the disclosures in Figs. 4.:a'nd 5, these show respectively the positions 6f the inner conduit when locked in assembly, and during the pro'ce's's of being locked or unlocked from the cuterconduit, with two of the spacer pins shown in aligned position with the centers of the locking lugs. For clarity of'discl'osure, the face cooling chamber has been omitted from these figures. n j

The apparatus disclosed herein is =subjected to severe temperature operating conditions, not "only being disposed adjacent the reaction zone where the synthesis gas generation proceeds desirably at above 2000 F, and frequently as high as 3000 F., but also conveying reactants which areprehe'ated to relatively high temperatures, e.g. 900? F.',- prior to their dischargeinto there- 'action zone. Consequently, structural provision' must'be' made for the high differential expansion and contraction of the several elements of the 'burnenxarising not only from exposure of the burner to radiation from the temperature reaction zone but also from the flow of preheated gases. t

' It has been determined that the wide 'rang'e of temperatures to which burners of the type disclosed are exposed,

contribute greatly to their rapid deterioration, not only with respect to metal erosion, but because of the "strains set up as a result of repeated expansion and contraction leading to failure at the points of junctureof the burner parts. The disclosed structure is :found' to be free from the adverse eifects of relative expansion and contraction of the several parts because joint.

Fig. 3 is an enlarged and partially sectional view-taken through the line 3-3 of Fig. 6, 'showin'g the expansion joint assembly indicated at C. This assembly comprises locking flanges 20 and 21 fixed respectively to the outer of the use of an expansion conduit 13 and inner conduit 10. 'Iheexpansio'n joint includes the bellows at 22, which is supportedhy casing 23, to which are afiixed locking flanges 24 and 25. The expansion joint, i.e. bellows and casing, is adapted to surround the inner conduit Id-and is joined to both-the inner and outer conduits by locking meanssuchasj nuts with, the inner conduit has fixed to it adjacent the exassion joint, "a spacer ring indicated at which should be upstream of the fuel inlet, to serve as a partial against leakagethrongh the joint.

imFig s. "6 and '7, there are shownftwo positions or the expansion joint assembly, when the inner conduitis in locked and unlocked position, "showing the manner in which the'alignl'hent-rod is to be used, the arrow in Fig.

. 6 -'(also in Fig. 4) indicating the direction or rotation for unlocking. The inner conduit 10 is removed from the assembly "by theremoval of "the fastening means. 26 which hold flanges 21 and 25 in position, and then rotating the conduit (to the position indicated in Fig. '7, 'In the assembly of the burner to attain the locked position shown inFig. 6, the alignment'r'ings are oriented'to receive the alignment rod 2-8, which serves as a preliminary locking means before final assembly-is made with the nuts and bolts "26. Alternatively, the inner conduit 10.maybe 're'' moved together with the expansion-joint assembly at C by removal er "the fastening means 26 holding flanges 20 and '24 in assembled position. g

As shown in Figs/{4 and 5, the locking lugs are proximately es -in circumferential extent and may vary .to a maxinium "of Howeventhe smaller arc is I desirable in order to prevent any shadow direct on the flow of the reactant in the 'outer annularconduit due to the=restriction by the lugs.

Thus, even though burner. tip deterioration arising from temperature and corrosive influences is present on der normal burner operating conditions, the most rapid deterioration of *burn'ertip metal may 'be confined 'to the discharge opening of the inner conduit by feeding the oxygen or oxygen-enriched air through it, so that easily replaceable "conduits, whichfprotect otherbu'rn'er tip surfaces trum "oxygen 'andfithe primary name, are a;

solution *to the problem; Thelife of the outer conduit of the -burnen-ha's'be'en increased so much by putting? the fuel through the annul'ar passage and cooling discharge end of the outer conduit, that the inner conduit life the controlling factor new in burner operation Therefore, when operating conditions require that the burner-tip be changed, the inner c'onduit may be replaced without the inconvenience andexpense of replac ing an entire new assembly, such as indicated it A. Oneform of'cooling structure usbd-tdlengthbn the life of the burper tinso chat the trequency or replacing" for sealing the casing to the conduits are indicated at asasneo eroded-burner elements is lessened has been disclosed in the copending application, Ser. No. 520,871,- filed by Du B. Eastman and W. L. Slater, on July 8, 1955. While the: cooling chamber disclosed in the aforesaid application is efiicacious, the heat loss by the preheated reactants'to" the cooling chamber is greater than is desirable and the gain anticipated by the preheating of the reactants is reduced. It has been found that the burner tip may be cooled asefficiently as-inthe prior art burners by cooling the face onlyof the burner, with but a relatively slight heat transfer loss from the preheated reactants to the cooling means. This has been achieved by attachment of the coolant tubes only at the inlet to and outlet from the face cooling chamber, and wrapping the tubes about the outer conduit with at most but a surfacecontact therewith.

This structure is clearly disclosed in Figs. 2, 8 and 9, with Fig. 8 disclosing the recessed position of the inner conduit, such that the discharge ends of the inner and outer conduits end at the surface of an imaginary frustum of a cone which has an apex angle of the order of 60, indicated at X, the enumeration in Figs. 8 and 9 being the same as that in Fig. 2, for the identical elements.

In particular, the structure of the face cooling chamber is shown as comprising a pair of upstanding spaced flanges extending normal to the longitudinal axis of the outer conduit to form a channel on the flame exposed part of the burner tip, as disclosed at 30. The cooling chamber is completed by fastening a ring at the exterior periphery of the channel as disclosed at 31, but other means of forming the cooling chamber are not excluded. The inlet and outlet coolant tubes are disclosed at 32 and 33, coiled about and limited to the ending of the outer conduit and adjacent the cooling chamber, the surface contact of the tubes with the outer conduit being clearly disclosed in these three figures.

Referring now to Figs. 12 and 13, the manner in which the coolant is directed about the face ofthe burner tip is disclosed, with the partition member 34 interposed between the openings 35 and 36, for the inlet and outlet coolant tubes, and the direction of flow of the coolant being shown by arrows.

Fig. 9 is a modification of the structure disclosed in Fig. 8, to the extent that the discharge end of the inner conduit is cooled. The cooling chamber 37 at the outlet of the inner conduit is formed by some appropriate means, with the coolant being supplied by the inlet and I outlet passageways indicated respectively at 38 and 39. The manner in which the coolant is made tofiow around the cooling chamber 37 is the same as that for the burner face cooling, viz. a partition as disclosed at 40, Fig. 10.

Fig. 11 is a cross section upstream of the locking lugs, showing the inner conduit in locked position.

The face cooling of the burner as disclosed in Figs. 2, 8 and 9 not only reduces the erosion'at the discharge ends of the inner and outer conduits but results in a considerable saving in the loss of heat from the preheated reactants, while the fabrication costs of the cooling structure have been reduced considerably. In addition, the life of the tubes furnishing the coolant has been increased considerably by the protection from the radiant heat which the upstanding flange structure of the face cooling chamber of the burner provides, without any decrease in the efiiciency of cooling. The disclosed face cooling structure serves as a shield, with the cooling function isolated to the critical part of the burner structure where it is required.

Because of the differences in the velocities required for the satisfactory provision of different fuels to the reaction chamber, the sizes of the inner conduit and the anfor the fuel to be employed, the same burnertip asseni bly can-be used for both liquid and gaseous fuels.

The locking flange indicated at Dis used to position the burner for operation through the structure in which the burner is to operate, but since it is not part of the invention, no further description of the same will be made. 7 r Although modifications and variations of the invention as. set'forth above may be made without departing from the spirit and scope thereof, only such limitations should be imposed as are indicated in the appended claims 1. A cboliti g m cans construction-at the fajce of a bumer assembly exposed to the'elevated'temperature of the heat. ofreaction of synthesis gasgeneration includingan outer conduit ending in an orifice in said face, a removable inner conduit positioned in spaced relationship with said outer conduit and ending in a dischargeopening adjacent said orifice, means for locking said conduit against longitudinal movement in either axial direction with respect to the endings of each other, means between and in contact with said conduits for positioning the same in annular spaced relationship with each other to define an annular passageway therebetween, and means for compensating for the differential expansion of said conduits as said burner assembly passes through its operating cycle, said cooling means construction comprising a cooling chamber carried by said outer conduit at its orifice defined by a pair of relatively closely spaced upstanding flanges extending from said outer conduit normal to the longitudinal axis of said outer conduit and means interconnecting the outer edges of said flanges thereby enclosing a narrow chamber with the lesser dimension thereof adjoining said outer conduit at said orifice and the greater dimension thereof being at the heat exposed face of said burner assembly, said chamber having a dividing partition member, and means for providing to and withdrawing a coolant from said chamber, said chamberhaving inlet and outlet openings for said coolant located adjacent and separated by said partition member, the coolant providing and withdrawing means comprising tubes coiled around said outer conduit adjacent the ending thereof and limited to the vicinity of said cooling chamber and in surface contact with said outer conduit whereby coolant flows through said tubes and said cooling chamber with minimum heat exchange relationship to the preheated reactant provided by said outer conduit and with maximum heat exchange relationship to said heat ofYreaction at said heat exposed face and at the outer conduit ending of said burner assembly.

2. A burner tip structure with a flat planar'heat block face adapted to be exposed to the heat of. a high temperature reaction zone comprising, in combination with an outer conduit ending at an orifice in said face, a removable inner conduit having an opening at its discharge end adjacent said orifice to define an annulus type burner tip and spaced from said outer conduit to define an annular passage therewith, means carried by said conduits by which relative longitudinal movement with respect to each other at said burner tip is prevented in either axial direction when in assembled position, and means joined to said conduits for compensating for the differential expansion between said conduits during operation, said nular passage which it defines with the outer conduit heat block face comprising a pair of relatively closely spaced flanges extending outwardly from said outer conduit at said orifice thereof normal to the longitudinal axis of said outer conduit, and means interconnecting the outer ends of said flanges to define a narrow cooling chamber with its lesser dimension adjoining said outer conduit and its greater dimension being along the face exposed to high reaction zone temperatures, said cooling chamber having a dividing partition therewithin, and means for providing to and withdrawing a coolant from said cooling chamber joined thereto on opposite sides of said partition, said last mentioned means being shielded mam firom zradihnt heat from 'said'reactionzdne :by'said-heat' block faccgand compnising tubcs coil'edfi-arbundesa id outer conduit adjacent @he mendingv :th'ereof and limited to ihe vicinityvbf and behind said cooling chamber and in sur fab: contact with' sflid ,ouier conduit-whereby minimum heat cxchan-ge relalzionship'fis cstabiishcd with the pre heated reactant provided by said outer conduit and max imilm. hoat Exchange 'elationship with thc high icmperature reaction zone atthcheat expcsed Lface-ofsai'dcooiing chambbr and atihc ending -of said outer conduit adjacent saidcooling chamber. 7

References Citediin the file of this pzitcnt PATENTS

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