PROCESS FOR PARTIAL OXIDATION OF A HYDROCARBON-CONTAINING FUEL

Abstract: Process for the partial oxidation of fuel using a multi-­ orifice burner comprising a central channel and three concentric channels encircling the central channel. Fuel is supplied through the second concentric channel at a specific velocity: oxygen is supplied through the other channels at specific mass flow distribution and velocities.

Description: The invention relates to a process for partial oxidation of a hydrocarbon-containing fuel using a multi-orifice burner. In particular, the invention relates to a process for partial oxidation of a hydrocarbon-containing fuel wherein an oxygen-containing gas and a hydrocarbon-containing fuel are supplied to a gasification zone through a quadruple orifice burner comprising a concentric arrangement of 3 oxygen-passages or channels and 1 fuel passage or channel, and wherein autothermically a gaseous stream containing synthesis gas is produced under appropriate conditions. 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 can be supplied to said zone. In particular, the invention relates to a process as described in the foregoing, wherein a liquid is suitable as a fuel. More in particular, (heavy) residue feedstock is suitable to be used as a fuel. In such processes it is necessary to ensure fine atomization of the fuel and good and rapid contacting or mixing of the fuel and the oxygen-containing gas in order to obtain an excellent gasification process. It is an object of the invention to provide a process for partial oxidation of a hydrocarbon-containing fuel wherein in situ fine atomization of the fuel is obtained. It is another object of the invention to provide a process for partial oxidation of a hydrocarbon-containing fuel wherein a good and rapid mixing or contacting of oxygen and fuel is obtained and pre-ignition or flame-flash-back is prevented. It is another object of the invention to provide a process for (heavy) residue gasification wherein economic process conditions (for example reduction of supply moderator gas and reduction of soot production) are achieved with a sufficiently long burner-lifetime (longer than 8000 operating hours). The invention therefore provides a process for partial oxidation of hydrocarbon-containing fuel comprising the steps of supplying an oxygen-containing gas and hydrocarbon-containing fuel to a gasification zone through concentric arranged circular passages, characterized in that the oxygen-containing gas is supplied through the central channel of the concentric arrangements at a velocity 21 to 42 m/s in an amount 5 to 40 mass per cent of a total amount of oxygen-containing gas, oxygen-containing gas is supplied through the first concentric channel encircling the central channel at a velocity 60-120 m/s; that (heavy) residue feedstock is applied as fuel, said fuel having a specific gravity at 15 °C in the range of 980-1018 kg/m³ and a viscosity at the channel outlet in the range of 0.02-0.2 Pa.s and being supplied through the second concentric channel encircling the first concentric channel at a velocity 3.0-3.8 m/s and remaining oxygen-containing gas is supplied through the third concentric channel encircling the second concentric channel at a velocity 60-120 m/s measured at the outlet of the said respective concentric channels into the gasification zone and wherein the mass flows through the first and third channel are distributed in an even manner. The velocity measurement can be carried out in any way suitable for the purpose and will not be described in detail. In an advantageous embodiment of the invention the oxygen-containing gas contains steam or carbon dioxide as a moderator. In another advantageous embodiment of the invention the gasification process is carried out at a pressure of 0.1-12 MPa. The fuel and the oxygen-containing gas are supplied to the gasification zone through a concentric burner-arrangement of 3 oxygen passages and 1 fuel passage. A central channel for oxygen supply is surrounded by a first annular channel for oxygen supply. The said first annular channel is surrounded by a second annular channel for fuel supply and the said second channel is surrounded by a third annular channel for oxygen 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. Usually such burners comprise hollow wall members with internal cooling fluid passages. However, the burner may for example be provided with a suitable ceramic or refractory lining applied onto or suspended by a means closely adjacent to the outer surface of the burner front wall for resisting the heat load during operation or heat-up/shut down situations of the burner. It is remarked that US patent specification No. 4,525,175 discloses a concentric arrangement of channels in a burner for partial oxidation of slurries of solid carbonaceous fuel in a liquid carrier. However, the specific process of the invention for partial oxidation of (heavy) residue feedstock in order to obtain a fine atomization of the fuel and a good and rapid mixing cannot be derived therefrom. According to the invention the oxygen and the fuel are supplied to the gasification zone through the respective channels at specific velocities in order to obtain a good atomization and mixing. When carrying out the specific process of the invention a typical crude syngas composition having relatively high contents of H₂ and CO and having a relatively low content of N₂ is obtained. The invention will now be described in more detail by reference to the following example. Example Tests have been carried out under the following conditions: a) Feedstock b) oxygen composition O₂ %vol 99.05 N₂%vol 0.01 Ar%vol 0.94 H₂O%vol -- c) Operating conditions feedstock (fuel) mass flow (kg/s) 1.1 - 1.4 supply temperature to channel (degr.C.) 120 - 170 supply pressure (MPa) 3.6 - 3.7 velocity at fuel channel outlet (m/s) 3.0 - 3.8 resulting slot width (mm) 3 oxygen containing gas oxygen to fuel ratio (kg/kg) 1.0 - 1.3 steam to fuel ratio (kg/kg) 0.3 - 0.65 supply temperature of mixture (degr.C) 210 - 220 supply pressure (MPa) 3.6 - 3.7 Distribution of mass flow and velocity central channel, 5-40 mass per cent 21 - 42 m/s first concentric channel 60 - 120 m/s third concentric channel 60 - 120 m/s wherein the mass flows through the first and third channel are distributed in an even manner reactor pressure (MPa) 0.1 - 12 temperature (degr.C.) 1300 - 1450 Typical crude syngas composition %vol dry CO₂ = 5.3 - 9.1 H₂S = 0.1 - 0.3 O₂ = 0.0 - 0.1 H₂ = 44.7 - 47.5 N₂ = 0.1 - 0.4 CO = 43.7 - 48.9 CH₄ = 0.05 - 0.3 unconverted carbon-containing products ca 0.3-4% by weight on fuel, may be added to the feedstock. In an advantageous embodiment of the invention the burner-lifetime can be increased by supplying an inert gas (a gas which does not react exothermically) such as H₂O, CO₂, CH₄ and the like through a fourth concentric annular channel surrounding the third channel. In this manner flame-lifting can occur and the heat flux can decrease.

Claims: A process for partial oxidation of hydrocarbon-containing fuel comprising the steps of supplying an oxygen-containing gas and hydrocarbon-containing fuel to a gasification zone through concentric arranged circular passages, characterized in that the oxygen-containing gas is supplied through the central channel of the concentric arrangements at a velocity 21 to 42 m/s in an amount 5 to 40 mass per cent of a total amount of oxygen-containing gas, oxygen-containing gas is supplied through the first concentric channel encircling the central channel at a velocity 60-120 m/s; that (heavy) residue feedstock is applied as fuel, said fuel having a specific gravity at 15 °C in the range of 980-1018 kg/m³ and a viscosity at the channel outlet in the range of 0.02-0.2 Pa.s and being supplied through the second concentric channel encircling the first concentric channel at a velocity 3.0-3.8 m/s and remaining oxygen-containing gas is supplied through the third concentric channel encircling the second concentric channel at a velocity 60-120 m/s, measured at the outlet of the said respective concentric channels into the gasification zone and wherein the mass flows through the first and third channel are distributed in an even manner. The process as claimed in claim 1 characterized in that the oxygen-containing gas contains a moderator. The process as claimed in claim 2 characterized in that the moderator is steam or carbon dioxide. The process as claimed in any one of claims 1-3 characterized in that the process is carried out at a pressure of 0.1-12 MPa. The process as claimed in any one of claims 1-4 characterized by the step of supplying an inert gas (a gas which does not react exothermically) through a fourth concentric channel encircling the said third channel.

Inventors: HASENACK, HENDRIKUS JOHANNES ANTONIUS, MARTENS, FRANCISCUS JOHANNA ARNOLDUS
Applicants: SHELL INTERNATIONALE RESEARCH MAATSCHAPPIJ B.V.
Application year: 1987
Main classification: C01B3
IPC codes: C01B3, C10J3