|Publication number||US3081818 A|
|Publication date||Mar 19, 1963|
|Filing date||Apr 3, 1958|
|Priority date||Apr 20, 1957|
|Publication number||US 3081818 A, US 3081818A, US-A-3081818, US3081818 A, US3081818A|
|Inventors||Frederic F A Braconier, Jean J L E Riga|
|Original Assignee||Belge De L Ayote Et Des Prod C|
|Export Citation||BiBTeX, EndNote, RefMan|
|Patent Citations (8), Referenced by (24), Classifications (27)|
|External Links: USPTO, USPTO Assignment, Espacenet|
United States Patent 3,081,818 GAS MIXING APPARATUS Frederic F. A. Braeonier, Plainevcaux, and Jean J. L. E.
Riga, Liege, Belgium, assignors to Societe Belge dc LAyote et des Produits Chimiques du Marly, Liege,
Belgium Filed Apr. 3, 1958, Ser. No. 726,248 Claims priority, application Austria Apr. 20, 1957 8 Claims. (Cl. 158-99) This invention relates to method and apparatus for mixing fuel and comburent gases for the combustion of hydrocarbons, and more particularly to burners for partial combustion of hydrocarbons in the production of less saturated hydrocarbons.
This invention relates more particularly, but not exclusively, to mixing apparatus of the annular type, in which the gases of a combustible mixture are led separately and then brought into intimate mixture, which is then forced into a combustion chamber through a gas distributing device.
For feeding burners with gases, it has already been proposed to use devices of the type comprising an annular pipe surrounding a central core. A mixture of hydrocarbon and primary air is led into this annular pipe so that its direction and speed are changed therein. It passes through this space with a swirling movement before being brought into contact with secondary air. Then the mixture of hydrocarbon and primary air on one hand and the secondary air on the other hand become in the burner separate and swirling layers (US. Patent No.
In the case of a partial combustion of hydrocarbons for conversion into acetylene and/or olefines and for obtaining the most efficient operation, the mixture should be homogeneous and should have substantially laminar flow before entering the distributor of a burner.
According to this invention, these conditions are obtained with a special arrangement which essentially comprises a vertical annular chamber widening downwards, with a gas-distributor screen at its bottom and surround ing a central inverted conical core, the tip of which is at the center of the distributor, and by a procedure of bringing together the reaction gases in a narrow annular space, passing them along a widening annulus and through said screen to a reaction zone.
To obtain the best conditions regarding the homogeneity of the gaseous reaction mixture, the angle formed with the vertical by the walls of this annular device is advantageously between and and preferably near 7. A substantially cylindrical wall portion near the top of said angle and parallel to the axis of the burner delimits on the distributor a central zone with surface area substantially equal to that of the surrounding annular zone.
FIGURE 1 is a sectional view of one form of themvention.
FIGURE 2 is a sectional view of a modified form of the invent-ion.
The nature of this invention will appear more clearly by the description of a burner schematically represented in vertical section by FIGURE 1, given by way of example.
In such burner, the mixing chamber 1 having a wall 2 of heat-resistant steel, surrounds a central hollow conical core 3, the wall 4- of which is also in refractory steel. The end of said core reaches to the center 0 of the burner screen 5.
As shown, the mixing chamber 1 consists of an annular space widening downwards, until it reaches screen 5 which distributes the gaseous mixture into the combustion chamber 6. The walls 2 and 4 of the mixing chamher are inclined so as to form in the upper part of said chamber an angle of about 7 with the vertical and the projection of said top on the screen 5 (indicated by dot-dash lines on FIGURE 1) defines an annular section AB of the screen 5, surrounding a central portion CD, both portions having substantially equal surfaces.
The central core 3 with its surmounting conical head 7, with tire-resistant steel walls, surrounds an axial pipe 8 for feeding one of the two reaction gases. Pipe 9, feeding the other reaction gas, discharges into an annular chamber 10, leading to an annular space 11 between head 7 and the upper part of wall 2. The upper edge 12 of the wall 2 is inclined, as shown, so as to insure a uniform pressure drop and a homogeneous distribution of the gas in said space 11. The space 11 decreases in cross section in the direction of the flow of the gases.
The space 11 and the interior of mixing chamber 1 are connected by the narrow annular gap in zone 13. This brings the gaseous reagents into contact, the wall 4 of the central core being provided with several perforation rings 14 for injecting into space 11 a fluid from pipe 8. This fluid comes through pipe 8 and the space 7 Within the central core 3. Said spaces 11, 13 and 1 thus form an annular convergent-divergent nozzle of the Venturi type.
According to this invention, the device just described may be operated as follows:
One of the two gases, e.g., the fuel gas, is introduced through pipe 9. It flows upward in the space 11, where, due to the gradual decrease in section, it obtains an increasing yelocity, while its pressure decreases. The remaining gaseous reagent, e.g., oxygen, fed through pipe 8, flows successively through the annular space 3 and openings 14, into the restricted section of the nozzle in which it is injected perpendicularly to the direction of the fuel flow while forming a turbulent mixture. This mixture passes then through mixing chamber 1, i.e., the diver-gent portion of the nozzle, by which it is led to the screen 5 with a substantially laminar movement without any of the gaseous reagents having a preferential dynamic effect.
According to the invention, one can attain a quite uniform oxygen content throughout the gas at the end of the mixing chamber, a uniform throughput in each channel of the screen 5 and a better yield of unsaturated hydrocarbon (e.=g., of acetylene in the case of a partial combustion burner). Backfires from the combustion chamher 6 to the mixing chamber 1 are avoided; and, even if a backfire should occur, its effects would be substantially reduced by the cooling action of the lower end of the conical core 3.
FIGURE 2 shows another device to be used for the process of this invention, in which the gaseous reagents are brought as separate opposite streams into the mixing zone instead of perpendicular flows as in FIGURE 1.
Pipe 9 for feeding the fuel gas enters the annular chamber 10a connected with the annular space 11a, as shown; but, instead of the open annular space continuing at the bottom of space 11a into a Venturi throat, there is a perforated ring 16, the perforations of which are staggered with respect to the oxygen distributing perforations 14a.
Both gaseous reagents thus enter as oppositely directed jets at the top of the annular and divergent mixing chamber 1 having a construction similar to that of FIGURE 1. The resulting combustion mixture passes with substantially laminar flow to the screen 5 which distributes this mixture into the combustion chamber.
Example The burner shown in FIGURE 1 comprises an annular mixing chamber 1 of 350 mm. in height and having a mean diameter of 200 mm., with an angle of 14 at the top, between the walls 2 and 4, said chamber being topped by an annular zone 13 for contacting the reagents, said zone being of 12.5 mm. in radial width at the inlet 13, before the perforations 14, and of 20 mm. in width at the outlet 20. Said annular zone 13 is of 130 mm. in height. The annular distributing space 11 has an average height of 130 mm. The central core 3 has a total height (from the end of 760 mm. and a diameter of 194 mm. at its greatest width. It surrounds pipe 8 having a diameter of 140 mm. The wall 4 is provided with 390 holes having a diameter of 3 mm., and uniformly distributed along 3 rings spaced 15 mm.
The projection of the mean circumference between the ID. of the shell 2 and the OD. of the core 4- delimits on said distributor 5, a surface CD surrounded with an annular surface AB, both said surfaces having approximately the same area. The distributor 5 is of 215 mm. in height While being traversed by 112 pipes having a diameter of 12 mm.
1,125 cubic meters per hour, caluculated to normal temperature and pressure (Nm. /H.) of methane (98% pure and containing 2% of nitrogen) preheated at 600 C. under a pressure of 1.13 atmospheres, absolute (atm., abs.), and fed through pipe 9, are introduced in said mixing device, said methane passing through the dis:
tributing space 11 and then through the annular zone 13, at the inlet of which it has a flow rate of 90 m./sec.
610 Nm. /h. of 97% pure oxygen (97% of oxygen and 3% of nitrogen), also preheated at 600 C. are also introduced through pipe 8, under a pressure of 1.2 atm. abs. After being passed through the central core 3, said oxygen is injected into the methane stream through perforations 14, with a linear flow rate of 163 m./sec.
=Both reagents are thereby rapidly contacted in zone 13 and their mixture is homogenized in chamber 1, before being introduced in the combustion chamber 6, through distributor 5.
The areas of the surfaces AB and CD being the same, the reagent mixture is homogeneously distributed in the pipes of distributor 5, the throughput of the gaseous mixture being substantially the same in each of said pipes.
The mixture is ignited in said combustion chamber 6 and the methane is subjected to a partial combustion, the flames being stabilized by a further addition of oxygen (pilot oxygen) of approximately 80 m. /h.
After a partial combustion and quenching of the combustion gases, 2060 Nm. /h. of gas (dry gas volume) containing 7.6% of C H are obtained.
This mixing device is constructed with refractory nickel, chrome and molybdenum steel, preferably the A.I.S.I. steel of the type No. 321 (as identified by the Steel Products Manual No. 24 of the American Iron and Steel Institute).
As will be evident from the dimensions given above, the tip of the core 4 does not extend entirely through the distributor 5, as indicated in FIGS. 1 and 2. Ohviously such extension is unnecessary and the tip need extend only far enough to support the core accurately in the specified position.
1. The method of forming a combustible mixture of a hydrocarbon gas and oxygen and of homogenizing the distribution of said mixed gases into a reaction chamber which comprises the steps of supplying said gases sep arately at superatmospheric pressures of approximately the same order of magnitude, preheating said separate gases, continually introducing a stream of said preheated gaseous hydrocarbon into one end of an annular distribution chamber of gradually decreasing cross section, homogeneously distributing, and increasing the velocity of, said gas stream in said distribution chamber by passing the said stream through a narrow annular channel,
injecting a plurality of streams of preheated oxygen into the accelerated stream of hydrocarbon in a midportion of said narrow channel so that these streams of hydrocarbon and oxygen impinge, uniformly mixing said streams in a conical annular duct of expanding cross section and passing them through a distributor screen and into a reaction chamber, the flow being maintained in a substantially laminar annular flow and the inner boundary of the annular flow of gases decreasing gradually to a point substantially in center of the distributor while the outer boundary increases correspondingly, and uniformly distributing the mixed gases into the channels of said distributor.
2. An apparatus for mixing reactant gases, such as fuel gas and oxygen, which comprises a mixing chamber having an outer wall which diverges in the direction of gas fiow from a restricted portion of the chamber at which the reactantgases are introduced; a reaction cham ber below the mixing chamber; a distributor screen through which the mixed gases pass from the mixing chamber into the reaction chamber but which serves as a barrier against backfire to confine the reaction to the reaction chamber; a hollow, substantially conical central core enclosing a substantially frusto-conical cavity therein, said conical core having a converged end centrally positioned at the distributor screen and a base portion adjacent the mixing chamber wall at said restricted portion of said mixing chamber at which the reactant gases are introduced, the core wall diverging from the mixing chamber Wall toward said screen, thus forming an annular channel between them, the an le of divergence near the most restricted portion of the mixing chamber being between 5 and 10 from the vertical, said base portion of said conical core being of such diameter that its projection by a perpendicular cylinder dropped from the median line of the most restricted portion of the mixing chamber to the screen defines on said screen a central circular zone and an annular zone, the areas of which are equal; and a pipe extending into said frusto-conical cavity, said pipe feeding a reactant gas, the outer wall of said core in the area of the most restricted portion of the mixing chamber having perforations through which this gas may be led into the mixing chamber.
3. Apparatus according to claim 2, wherein the gas feeding pipe extends axially into said frusto-conical cavity substantially to those portions of said cavity which are of smallest cross-section.
4. Apparatus according to claim 2 wherein the angle is about 7.
'5. Apparatus according to claim 2, wherein the top of the mixing chamber is provided with perforations for introducing the reactant gases, said perforations being radial with respect to the axis of the chamber.
6. The method of forming a combustible mixture of preheated gases having completely uniform composition which comprises supplying said gases separately both at superatmospheric pressures of approximately the same order of magnitude, preheating the separate gases, bringing at least one of said preheated gases to high velocity by passing said gas through a volume of uniformly decreasing cross section culminating in a narrow annulus, separately introducing at least one other of said preheated gases therein by injecting a plurality of jets of said other gas transversely into the accelerated stream of the first gas in said narrow annulus, and then passing the gases through a duct in an expanding conical annular flow, the flow through said narrow annulus and duct being substantially laminar flow in which the inner boundary of the annular gas flow decreased in diameter from said jets through said duct.
7. The method as defined in claim 6 in which the inner boundary of the annular flow of gases decreases gradually to substantially zero.
8. The method as defined in claim 6 in which the inner boundary of the annular flow of gases decreases gradually while the outer boundary increases correspondingly.
References Cited in the file of this patent UNITED STATES PATENTS Hoff Ian. 17, 1911 Dodge June 15, 1926 6 Wolff Jan. 1, 1929 Maxwell July 10, 1934 Oldham May 16, 1944 Campbell et a1. Oct. 3, 1950 Lehrer May 6, 1958 FOREIGN PATENTS Great Britain Jan. 5, 1955
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|U.S. Classification||48/180.1, 431/346, 585/540, 431/353, 585/923, 585/537|
|International Classification||B01F5/06, B01F5/04, C07C2/78, B01F3/02, B01F5/00|
|Cooperative Classification||B01F5/0659, C07C2/78, B01F5/0426, Y10S585/923, B01F5/0682, B01F2005/0022, B01F5/0688, B01F3/02, B01F5/0415|
|European Classification||C07C2/78, B01F5/04C12S2, B01F5/06F4B, B01F3/02, B01F5/06F, B01F5/04C12B, B01F5/06B3H|