CERAMIC BURNER FOR PARTIAL OXIDATION OF A HYDROCARBON CONTAINING FUEL

Abstract: A protruding lining separates burner internals from the hot gasification environment. The lining is cooled by at least one of the feedstreams. The lining can be made of ceramics such as silicon carbide and/or silicon nitride. In order to lower thermo-mechanical stress the lining is thin-walled.

Description: The invention relates to a reactor-mix burner for the partial oxidation of hydrocarbon-containing fuel and an oxygen-containing gas, said burner comprising a tubular burner head having a feed supply end and a discharge end, said burner head being disposed around an arrangement of plurality of concentric tubular passages for feeding the fuel and oxygen-containing gas and optionally a moderator to a partial oxidation reactor. In such reactor-mix burners the fuel and oxidant are supplied through the burner separately to the reactor through a burner head protruding into the reactor and the fuel and oxidant are not mixed until having entered the reactor. The oxygen-containing gas is usually air or pure oxygen or a mixture thereof. In order to control the temperature in the gasification zone a moderator gas (for example, steam or carbon dioxide) can be supplied to said zone. Further, the gasification process can be carried out at any suitable pressures, for example at 0.1-12 MPa. In particular, the invention relates to a burner as described in the foregoing, wherein a liquid is suitable as a fuel. For example, (heavy) residue feedstock is suitable to be used as a fuel. Further, methane can be used as a fuel. It is already known to apply water-cooled burners in partial oxidation processes of hydrocarbon-containing fuel. However, such water-cooled burners are limited in their scale-up potential. The capital expenditure and maintenance of a fail safe water-cooled system is significant and scale-up is important in order to reduce cost. Further, it has appeared that in large burners problems may arise with respect to withstanding the cooling water pressure when the reactor pressure is at ambient. In conventional reactor-mix burners protruding into the reactor such as described in US-A-4,525,175, it is required to have the burner head internally water-cooled in order to reduce the heat flux to the refractory dome and thus to prevent over-heating. However, such water-cooling has the above disadvantages. It is therefore an object of the invention to provide a non-water-cooled burner which has virtually no scale-up limitations, is relatively cheap and maintenance-free and which can operate at severe reactor conditions and limits the heat flux from the flame in front of the furner to the reactor dome. The burner of the present invention therefore is characterized in that said burner further comprises a thin-walled tubular mantle of impervious ceramics having a high thermal conductivity, said tubular mantle having an inner skin and an outer skin and being mounted at the feed supply end on the burner head and the other, discharge end, disposed to protrude into the reactor, and to separate the said tubular passages from the reactor environment, wherein the outer skin of said mantle is exposed to the reactor environment whereas the inner skin of said mantle, during operation of the burner, is cooled by at least one of the feed streams. The invention will now be described by way of example in more detail by reference to the accompanying drawing, in which the figure represents schematically a sectional view of a part of a burner according to the invention. Referring now to the figure, the burner comprises a burner head 1 which is provided with a ceramic burner lining or thin-walled mantle 2 protruding into the reactor 3 through the refractory dome 4. The lining or mantle is connected at one of its ends to the burner head in any way suitable for the purpose. The protruding lining or mantle separates the burner internals 5 from the reactor environment. The burner internals comprise the arrangement of reactants-channels or passages (only partially shown at the burner mouth 6 for reasons of clarity). The fuel and the oxygen-containing gas are supplied to the gasification zone through the burner-arrangement of oxygen and fuel passages. For example, the burner can comprise a concentric arrangement of oxygen and fuel passages. In such an arrangement a central channel 5a for reactant supply (fuel or oxygen) is surrounded by a first annular channel 5b for reactant supply. The said first annular channel is surrounded by a second annular channel 5c for reactant supply and the said second channel is surrounded by a third annular channel 5d for reactant supply. Multi-orifice burners comprising arrangements of annular concentric channels for supplying oxygen and fuel to gasification zones are known as such and will not be described in detail. However, it will be appreciated that the invention is not restricted thereto. The oxygen-containing gas and the fuel are supplied to the gasification zone through the respective channels at specific velocities and mass distribution in order to obtain a good atomization and mixing. According to the invention the burner internals are confined by a lining or thin-walled mantle of ceramics having a high thermal conductivity. Advantageously, this mantle is cylindrical. Such ceramic burner linings can be used successfully at severe process conditions and their scale-up potential is unlimited. In operation of the burner, the outer skin of the said mantle is exposed to the reactor environment and the inner skin is cooled by at least one of the feed streams (oxygen-containing gas, fuel, moderator). The burner fluid dynamics are selected in such a manner that a slender and short flame is obtained. The burner protrudes in the reactor to reduce direct radiative heat transfer from the flame to the refractory dome surrounding the burner. In operation, the flame is lifted from the burner face and the radiative heat flux to the burner lining, the internals and the refractory dome is low. The connection between ceramic part and metal parts of the burner should allow free thermic expansion, while being gastight. Suitable ceramics having a large heat conductivity are for example silicon carbide and silicon nitride. Such materials are also sufficiently corrosion-resistant. It will be appreciated that in order to reduce thermo-mechanical stress an advantageous wall thickness of the lining is in the range of 2 to 8 mm, advantageously 5 mm. It will further be appreciated that the lining can have any dimensions suitable for the purpose. Advantageously its length and diameter are in the range of 35 to 40 cm and in the range of 12 to 16 cm respectively, whereas its protrusion into the reactor is in the range of 1 to 20 cm.

Claims: 1. A reactor-mix burner for the partial oxidation of hydrocarbon-containing fuel and an oxygen-containing gas, said burner comprising a tubular burner head having a feed supply end and a discharge end, said burner head being disposed around an arrangement of plurality of concentric tubular passages for feeding the fuel and oxygen-containing gas and optionally a moderator to a partial oxidation reactor, characterized in that said burner further comprises a thin-walled tubular mantle of impervious ceramics having a high thermal conductivity, said tubular mantle having an inner skin and an outer skin and being mounted at the feed supply end on the burner head and the other, discharge end, disposed to protrude into the reactor, and to separate the said tubular passages from the reactor environment, wherein the outer skin of said mantle is exposed to the reactor environment whereas the inner skin of said mantle, during operation of the burner, is cooled by at least one of the feed streams. 2. The burner as claimed in claim 1 characterized in that the said ceramics is mainly silicon nitride. 3. The burner as claimed in claim 1 characterized in that the said ceramics is mainly silicon carbide. 4. The burner as claimed in any one of claims 1-3 characterized in that the thickness of the wall of the lining is in the range of 2 to 8 mm. 5. The burner as claimed in any one of claims 1-4 characterized in that the lining has a length in the range of 35 to 40 cm and a diameter in the range of 12 to 16 cm, whereas its protrusion into the reactor is in the range of 1 to 20 cm.

Inventors: MARTENS, FRANCISCUS JOHANNA ARNOLDUS
Applicants: SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1988
Main classification: F23D11
IPC codes: F23D14, C01B3