BURNER FOR THE PRODUCTION OF SYNTHESIS GAS

Abstract

A burner suitable for the over stoichiometric combustion of a hydrocarbon source, comprising a nozzle (2) for the formation of a diffusion flame outside the burner, and said nozzle (2) comprising one (20) or more (21, 22) tubular bodies which define a channel (25) or a plurality of coaxial channels (23, 24) for respective reactant streams, wherein the or each of the tubular bodies forming said nozzle (2) are made of a technical ceramic material.

Claims

1. A process burner suitable for the over stoichiometric combustion of a hydrocarbon source, the burner comprising a body and a nozzle associated to said body, wherein: said nozzle is arranged for the formation of a diffusion flame outside said process burner, said process burner has a feeding side with at least one inlet for a reactant stream, and an opposite end side with an outlet section which defines a boundary between a feeding region and a combustion region, the burner being configured in such a way that combustion take place downstream of said outlet section, said nozzle comprises at least one tubular body to define at least one channel for said reactant stream, ending at said outlet section of said nozzle, and said at least one tubular body is integrally made of a technical ceramic material, and said at least one reactant stream are confined by said at least one ceramic body until the reaching of said outlet section.

2. The burner according to claim 1, said at least one tubular body being made in a single piece.

3. The burner according to claim 1, said nozzle comprising a plurality of tubular bodies to define coaxial channels for respective reactant streams such as for example fuel and oxidant.

4. The burner according to claim 1, said technical ceramic material having a thermal conductivity of at least 10 W/(m K), and an elastic modulus of at least 40 GPa.

5. The burner according to claim 4, said technical ceramic material having at least one of the following properties: a thermal conductivity in the range 10 to 230 W/(m K), preferably in the range 25 to 160 W/(m K); an elastic modulus in the range 40 to 450 GPa, preferably between 200 and 360 GPa.

6. The burner according to claim 1, said technical ceramic material having a porosity between 0 and 50% in volume, preferably between 0 and 10% in volume.

7. The burner according to claim 1, said technical ceramic material having a density between 1000 and 6000 kg/m3, preferably between 2000 and 5000 kg/m3.

8. The burner according to claim 1, said technical ceramic material being any of the following: a silicate ceramic; an oxide ceramic; a mixture of oxide ceramics; a dispersion ceramic; a non-oxide ceramic.

9. The burner according to claim 8, said technical ceramic material being a silicate ceramic including at least one of clay, kaolin, feldspar, soapstone as silicate source(s), and optionally including alumina and/or zircon.

10. The burner according to claim 8, said technical ceramic material being an oxide ceramic selected among: aluminum oxide, silicon oxides, magnesium oxide, zirconium oxide, titanium dioxide, yttrium oxide and boron oxides.

11. The burner according to claim 8, said technical ceramic material being a mixture of oxide ceramics, said mixture being a alumina zirconia and yttrium oxide mixture, aluminium titanate (Al2O3+TiO2) or lead zirconium titanate having the formula Pb[ZrXTi1-X]O3, wherein 0.1toreq.x.1toreq.1.

12. The burner according to claim 8, said technical ceramic material being a dispersion ceramic comprising a ceramic matrix and a dispersed ceramic phase, said material being preferably aluminium oxide reinforced with zirconium oxide.

13. The burner according to claim 8, said technical ceramic material being a non-oxide ceramics based on compounds of boron, carbon, nitrogen and silicon, and more preferably being selected among: silicon carbide, silicon nitride, aluminium nitride, boron carbide and boron nitride.

14. The burner according to claim 1, said technical ceramic material being obtained from a mass of raw material, preferably at room temperature, which is subjected to a sintering process.

15. The burner according to claim 1, wherein the body is made of metal and the burner includes a metal-to-ceramic joint between the body and the nozzle.

16. The burner according to claim 15, said joint being realized with one of the following: a flanged connection or a threaded joint between said metal body and said nozzle of the burner; providing a metalized layer on the ceramic nozzle and brazing said metalized layer to the metal body of the burner; a cemented connection, providing a suitable cement between said metal body and said ceramic nozzle, said cement being preferably based on alumina.

17. A device for over-stoichiometric combustion of a hydrocarbon source, particularly a partial oxidation reformer or an autothermal reformer, comprising a process burner according to claim 1.

18. The device according to claim 17, said process burner being installed within a refractory lining and said ceramic nozzle having an outlet section which substantially correspond to an opening in the refractory lining, in such a way that the ceramic nozzle does not protrude from the refractory lining.

19. A method for revamping a device for over-stoichiometric combustion of a hydrocarbon source, particularly a partial oxidation reformer or an ATR reformer, said device comprising a burner, and the method comprising the replacement of said burner with a burner according to claim 1.

Description

DESCRIPTION OF THE FIGURES

[0060] FIG. 1 is a sectional view of a process burner according to an embodiment of the invention.

[0061] FIG. 2 is a sectional view of a process burner according to another embodiment of the invention.

[0062] FIGS. 3 to 6 are examples of a joint between a metal body and a ceramic nozzle of a burner, according to various embodiments.

[0063] FIG. 7 illustrates the burner of FIG. 1 when mounted in a reactor.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0064] FIGS. 1 and 2 show embodiments of a non-cooled process burner comprising essentially a metal body 1 and a ceramic nozzle 2. The metal body 1 is made of stainless steel or of a high temperature alloy, while the nozzle 2 is made of a technical ceramic material.

[0065] The burner is preferably a substantially cylindrical body with axis A-A, as shown. The burner is a non-cooled burner having no internal chambers for the circulation of a cooling medium.

[0066] In use, a diffusion flame is formed outside the process burner, downstream of the exit section 3. For example said flame is formed in the combustion chamber of a PDX or ATR reactor, to which the burner is mounted.

[0067] The nozzle 2 comprises one or more tubular bodies which define a channel, or a plurality of coaxial channels, for a reactant stream or a plurality thereof.

[0068] FIG. 1 shows an embodiment which is particularly suitable for use in an ATR, wherein the nozzle 2 comprises a single tubular body 20, thus delimiting a single channel 25 for a reactant stream. In this particular embodiment, the tubular body 20 has a first cylindrical part, proximal to the metal body 1, and a second cylindrical part proximal to the exit section 3, and said parts are joined by a conical part.

[0069] FIG. 2 shows an embodiment which is particularly suitable for use in a PDX reactor, wherein the nozzle 2 include two tubular bodies 21, 22 which form two coaxial passages 23, 24 and two exit sections 3, 4 for reactant streams, e.g. a fuel gas and an oxidant. Hence the nozzle 2 shall be intended to encompass a single part or a plurality of parts, according to various embodiments of the invention. In FIG. 2 also the body 1 of the burner includes two coaxial parts, to which the ceramic bodies 21, 22 are connected respectively.

[0070] It shall be noted that each tubular bodies of the nozzle 2, namely the tubular body 20 according to FIG. 1 or bodies 21, 22 according to FIG. 2, are made preferably in a single piece and they are integrally made of said technical ceramic material.

[0071] Said technical ceramic material is for example an oxide such as aluminum oxide, silicon oxide, magnesium oxide, zirconium oxide, titanium dioxide, boron oxides, or a non-oxide such as silicon carbide, silicon nitride, aluminium nitride, boron carbide and boron nitride, etc.

[0072] In the shown embodiments, the body 1 of the burner is made of metal, for example stainless steel or a high-temperature alloy. Hence the burner comprises metal-to-ceramic joints 5 between body 1 and a part of the nozzle 2. FIGS. 3 to 6 show some preferred embodiments of said joints 5.

[0073] FIG. 3 discloses a flanged joint. The ceramic nozzle 2 is provided with a lap 6 which is fixed to a flange 7 of the metal body 1 of the burner by means of a floating flange 8 and a number of screws 9. A gasket 10 between the body 1 and the ceramic nozzle 2 prevents leakages of fuel gas or oxygen.

[0074] FIG. 4 discloses a brazed joint. The ceramic nozzle 2 comprises a metalized layer 11 which can be realized with a per se conventional technique, such as vacuum deposition process at high temperature. The metal body 1 forms an enlarged end seat 12 adapted to receive the nozzle 2. The nozzle 2 is made integral with the body 1 by means of a brazing 13 between the edge of the end seat 12 and the metalized layer 11. Said brazing 13 can be made with well-known techniques. Said connection between the body 1 and the nozzle 2 is tight and no gasket is required.

[0075] FIG. 5 shows an embodiment where the ceramic nozzle 2 is connected to the metal body 1 using a suitable cement 14. Preferably said cement 14 is based on alumina. After curing, the cement 14 provides a permanent joint between the ceramic material of nozzle 2 and the metal of the body 1. As in FIG. 4, the connection is tight and no gasket is required.

[0076] FIG. 6 shows an embodiment with a threaded connection 15. Threads can be obtained by machining the ceramic nozzle 2 as well as the body 1, allowing for a simple and effective connection. Since no sealing can be guaranteed through a threaded connection, a gasket 10 (as in FIG. 3) is located between the two elements.

[0077] In other (not shown) embodiments, also the body 1 can be made of a technical ceramic, which means that the body 1 and nozzle 2 are integrally formed in a single piece of a ceramic material. The embodiments with a metal body 1 however can be preferred for saving costs, limiting the use of the technical ceramics only to the most stressed part of the burner, namely the nozzle 2.

[0078] FIG. 7 illustrates a burner according to FIG. 1, when mounted in a device such as a PDX or ATR reactor. In use, a reactant stream R (for example a mixture of fuel and air or oxygen) is delivered via the chamber 25 to a combustion chamber C, where a diffusion flame is formed. The burner is installed within a refractory lining 30 and, preferably, the ceramic nozzle 2 has an outlet section 3 which substantially correspond to an opening in the refractory lining towards the combustion chamber C, in such a way that the ceramic nozzle 2 does not protrude from the refractory lining. The same is applicable to other embodiments, such as the multi-channel embodiment of FIG. 2.

[0079] The process burner has a feeding side opposite to the outlet section 3. A reactant stream or a plurality of reactant streams are fed to the process burner at said feeding side. It can be noted that downstream of the joint 5, and until the outlet section 3, the reactants are confined by the fully ceramic walls of bodies 20, 21, 22 according to the various embodiments of the invention. This is an advantage because ceramic walls offer the best resistance to high temperature and flame, better than conventional refractory materials.