EP2085696A1

EP2085696A1 - Burner

Info

Publication number: EP2085696A1
Application number: EP08101177A
Authority: EP
Inventors: Johannes Cornelis De Jong
Original assignee: Shell Internationale Research Maatschappij BV
Current assignee: Shell Internationale Research Maatschappij BV
Priority date: 2008-01-31
Filing date: 2008-01-31
Publication date: 2009-08-05

Abstract

Burner (1) comprising an igniter burner (3) downstream a feed for a flow of an oxygen-containing gas, which igniter burner (3) is connected to a first fuel supply line (4), wherein the burner (1) comprises one or more secondary fuel supply lines or spuds (7) each leading to a burner mouth (9) at a distance downstream the igniter burner (3). Preferably, the open burner mouths (9) of the spuds (7) are each surrounded by a conical disk (8) widening in flow direction having within the widening end section one or more nozzle openings (14) directed to guide the fuel outflow along at least a part of the conical disk (8).

Description

The present invention pertains to a gas burner comprising a burner igniter connected to a gas supply line, which is particularly suitable for use as an igniter or heat-up burner in partial oxidation reactors for the manufacture of synthesis gas by partial oxidation of a liquid or gaseous hydrocarbon-containing fuel.
Partial oxidation processes are used for the production of, e.g., pressurized synthesis gas, fuel gas or reducing gas. To this end, gaseous or liquid hydrocarbon fuels and oxygen-containing gas are introduced into a reactor via a main gasification burner as for example described in WO-A-96/03345 . In the reactor a flame is maintained in which the fuel reacts with the oxygen-containing gas to form a gas comprising carbon monoxide and hydrogen.
To start-up a partial oxidation reactor, the temperature of the reactor and its refractory lining should be raised to a level sufficiently high to enable self-ignition of the fuel with the oxygen-containing gas. To this end an auxiliary heat-up burner can be used. The heat-up burner must have sufficiently high capacity to increase the temperature of the reactor and refractory lining to such high level that the mixture of oxygen-containing gas and hydrocarbon fuel spontaneously ignites when these reactants are introduced via the main gasification burner into the reactor.
It is advantageous to insert the heat-up burner into the reactor along the central axis of the main gasification burner as no separate nozzle and refractory plug are required. Because the dimensions of the main gasification burner are limited the heat-up burner must be compact to fit within said main gasification burner.
It is an object of the invention to provide a compact high capacity burner, which can, e.g., be used as a heat-up burner in a partial oxidation reactor.
The object of the invention is achieved with a burner comprising an igniter burner downstream a feed or supply for a flow of an oxygen-containing gas, which igniter burner is connected to a first fuel supply line, wherein the burner comprises one or more secondary fuel supply lines, each leading to a burner mouth at a distance downstream the igniter burner. The fuel supply lines and the burner mouth connected to said supply line is also referred to as a spud. In use, the oxygen-containing gas flows along the igniter burner and the spuds, typically with high flow velocity. When a fuel gas is supplied via the fuel supply line to the igniter burner and the spuds, the igniter burner is ignited and the resulting flame, in turn, ignites the burner mouths of the spuds resulting in an enforced combined stable flame.
The expressions "upstream" and "downstream" as used herein refer to the flow direction of the oxygen containing gas flow in the burner.
Preferably, the burner comprises igniting means such as a spark plug, a hot wire, or combinations thereof, to ignite the combustible mixture of fuel gas and oxygen-containing gas. The igniting means are preferably built-in within the igniter burner.
Furthermore, the igniter burner can be provided with a flame detector. Flame detection can for example take place by scanning ionization or UV.
Gas flow control means can be configured to control the fuel flow and the flow of oxygen-containing gas to create a combustion zone of the igniter burner having the downstream burner mouths of the spuds within its reach.
The burner can comprise a duct encasing the igniter burner and the spuds, the duct comprising an upstream inlet for oxygen-containing gas. The duct can be an openended tube with the igniter burner being disposed along the longitudinal axis of the duct. The igniter burner and the spuds receive oxygen-containing gas from the stream flowing through the duct.
Preferably the burner mouth of one or more of the gas spuds is individually surrounded by a conical disk, widening in flow direction. Preferably, the burner mouth of the gas spud is provided with nozzle openings directed to guide the gas flow along the interior side of the conical disk. The resulting divergent gas flow and the flow of oxygen containing gas creates a vacuum downstream of the gas spud. The hot mixture of combustion flue gases will, as a result of this vacuum, flow back in the direction of the conical disk. This is found to result in a very stable flame.
The cone angle α is the angle between the longitudinal axis of the duct and the conical wall. Preferably, the cone angle α is within the range of 40 and 80 degrees.
Optionally, the burner can comprise a single spud, but generally more spuds will be used, e.g., 3 - 12 spuds, preferably at equal distances and in a symmetrical arrangement relative to the igniter burner and the duct.
The fuel gas flow velocity and the flow velocity of the oxygen-containing gas can be varied within the operating range to meet the required thermal capacity. Excess air can be used to reduce the temperature of the burner exhaust gases. The aerodynamic design of the burner and the distribution of fuel gas to ignition burner and spuds is made such that the spuds are within reach of the flame of the igniter burner such that the separate spuds are ignited by said flame.
The oxygen-containing gas can for example be ambient air, oxygen-enriched air, i.e., more than 21 mole % oxygen, or the like. The fuel to be used is preferably a combustible gas, such as LPG or natural gas.
The duct will generally be a tubular body with a longitudinal axis, e.g. an open cylinder.
The igniter burner will generally be disposed centrally within the duct, e.g., along the longitudinal axis.
The inlet for the supply of oxygen-containing gas is located in the duct upstream the igniter burner. This creates a flow around the igniter burner and the spuds, along the duct wall. The flow of oxygen-containing gas is guided to form an annular layer along the duct wall, which effectively cools the duct wall, the wall of the igniter burner and also the conical disks of the gas spuds.
Optionally, spokes, vanes or eddy plates or the like can be used to influence the flow pattern of the oxygen-containing gas.
The burner according to the invention is particularly useful as a high duty, compact auxiliary burner or heat-up burner for a partial oxidation reactor. Optionally, the burner can be an integral part of such a main gasification burner, e.g. as a retractable part if so desired.
The invention will now be described in more detail, by way of example only, with reference to the accompanying drawings, wherein:

Figure 1 shows a burner according to the invention in longitudinal cross section;
Figure 2 shows in detail a gas spud of the burner in Figure 1.

Figure 1 shows a burner 1 with a cylindrical tubular duct 2 in cross section encasing an igniter burner 3 shown in side view. A gas supply line 4 is connected to the igniter burner 3 for the supply of a gaseous fuel. An oxygen-containing gas enters the duct 2 via an upstream inlet (not shown). In Figure 1, arrows O indicate the flow direction of the oxygen-containing gas along the longitudinal axis 15 of the burner, whereas the arrows F indicate the flow direction of the fuel gas.
Gas supply line 4 of the igniter burner 3 leads to an open burner end 5 discharging the gas into a combustion zone 6. Six branching lines or spuds 7, of which only two are shown in the Figure for reasons of clarity, branch off from the igniter burner 3. The branching lines 7 are bent to form gas supply lines of equal length parallel with the longitudinal axis of the duct 2. The branching lines 7 have open burner mouths 9 each being provided with a conical disk 8.
A fixed spark plug (not shown) is mounted on the igniter burner 3 sufficiently close to the combustion zone to enable ignition of a flame. A flame detection rod 10 is mounted on igniter burner 3 to detect the presence or absence of a flame.
Oxygen-containing gas, such as ambient air, flows from the inlet along the igniter burner 3, branching supply lines 7 and conical disks 8.
As shown in Figure 2, gas is discharged from the spuds 7 with an outflow direction along the interior wall of the conical disks 8 to form a divergent conical gas outflow. The flow of oxygen containing gas is guided by the conical disks 8. Figure 2 also shows the cone angle α as the angle between the longitudinal axis 15 of the duct (2) and the conical wall 16 of conical disk 8. Preferably, the cone angle α is within the range of 40 and 80 degrees The larger the cone angle α of the conical disk 8, the larger the angle between the fuel gas flow and the flow of oxygen-containing gas passing the branching lines 7, and the better both flows mix. Due to the divergent flow direction of the fuel gas, an area of low pressure is created downstream of the conical disks 8. This causes the hot mixture of fuel gas and oxygen-containing gas to flow back in the direction of the low pressure area, as shown by arrows O (oxygen containing gas) and F (fuel gas) in Figure 2. As a result, the fuel gas mixes intensively with the oxygen-containing gas and the flame stabilizes on the conical disk 8.
The interior wall of the duct 2 is constantly cooled by a stable flow of oxygen-containing gas. This prevents overheating of the duct wall.
When a fuel gas flow exits from the igniter burner 3 and oxygen-containing gas flows along the igniter burner 3, the spark plug can be activated to ignite a flame 11. While the fuel gas flows from the spuds 7 into the flow of oxygen-containing gas, the flame 11 ignites the gas discharged by the spuds 7 to form a front line of flames 12.
Within the conical disk 8, a concave partition 13 points towards the flame zone and abuts the conical disk 8 under right angles. The partition 13 is provided with nozzle openings 14 adjacent the conical disk 8, guiding the fuel gas flow along the wall of the conical disk 8 to create a low pressure along the center line of the gas spud 7.
The described embodiment of the present invention is intended to be illustrative rather than restrictive, and is not intended to represent every embodiment of the present invention. Various modifications and variations can be made without departing from the spirit or scope of the disclosure as set forth in the following claims both literally and in equivalents recognized in law.

Claims

Burner (1) comprising an igniter burner (3) downstream a feed for a flow of an oxygen-containing gas, which igniter burner (3) is connected to a first fuel supply line (4), wherein the burner (1) comprises one or more secondary fuel supply lines (7) each leading to a burner mouth (9) at a distance downstream the igniter burner (3).
Burner according to claim 1 wherein the igniter burner (3) comprises ignition means, such as a spark plug.
Burner according to claim 1 or 2 wherein the igniter burner (3) comprises a flame detection means (10).
Burner according to any one of the preceding claims wherein the burner is positioned within a duct (2) comprising an upstream inlet for the oxygen-containing gas.
Burner according to any one of the preceding claims wherein one or more of the open burner mouths (9) of the secondary fuel supply lines (7) are each surrounded by a conical disk (8) widening in flow direction and within the widening end section one or more nozzle openings (14) directed to guide the fuel outflow along at least a part of the conical disk (8).
Burner according to claim 4 and 5 wherein the angle α between the longitudinal axis (15) of the duct (2) and the wall (16) of conical disk (8) is within the range of 40 and 80 degrees.
Burner according to any one of the preceding claims wherein the secondary fuel supply lines (7) are equidistantly disposed in a circular configuration around the igniter burner (3).
Burner according to any one of claims 1 - 3 wherein the burner (1) comprises 6 secondary fuel supply lines (7) symmetrically arranged in a circular array.