Patent Application
20080282945
This application claims the benefits of German application No. 10 2007 021 924.7 filed May 10, 2007 and is incorporated by reference herein in its entirety.
The invention relates to a pulverized coal combination burner which is used for oxygen gasification of pulverized fuels (brown coals and/or hard coals or similar pulverized fuels) under high pressures and temperatures in reactors with liquid slag removal.
The subject matter of the application relates to a burner for oxidant gasification of pulverized fuels.
Pulverized coal combination burners for partial oxidation of pulverized fuels, comprising a cylindrical water-cooled housing and internal coaxially disposed annuli for supplying the pulverized fuel and oxidant, are well known.
Located in the center of the burner is another small gas/oxygen burner which serves as an igniter or pilot burner and is equipped with an optical flame monitoring device and a high-voltage ignition device. It is used for starting up the abovementioned pulverized coal burner, as disclosed in documents DE 271038 A3 and DE 4306980 C2.
Outside and inside the burner, the pulverized fuel is supplied through one or more tubes. Inside the burner, the supply tube(s) is(are) run to the burner outlet such that they perform at least one full rotation about the axis and then end set tangentially adjacent to the burner outlet. At the end of the pulverized fuel tube(s) the pulverized fuel dust enters a cylindrical annulus in a tangential manner.
At the transition from the tube surface area to the annulus there is an abrupt increase in area and therefore a reduction in the pulverized fuel dust velocity. Although increasing the number of pulverized fuel tubes inside the annulus can reduce the areal discontinuity, it cannot eliminate it. This results in an uneven distribution of the pulverized fuel stream inside the annulus, which can cause asymmetrical flame spread with unilateral stressing of the reaction chamber.
The known burner has the following disadvantages:
1. complicated design of the tubes inside the cylindrical annulus in the burner
2. after the pulverized coal dust outlet there is an unavoidable areal discontinuity, thereby reducing the dust velocity.
3. this areal discontinuity causes the downstream annulus to be unevenly filled with pulverized coal dust, resulting in differential mixing with the oxidant.
The object of the invention is to create a pulverized coal burner which operates reliably at pressure under pulverized coal gasification conditions. The pulverized coal combination burner shall be designed to ensure reliable operation with uniform flame spread, even for pressurized gasification of pulverized products.
This object is achieved in the case of the subject matter outlined by the features of the preamble in that the individual pulverized fuel feeding elements in the burner are implemented such that there is a systematic (continuous in the direction of flow) transition of the cross-section to a curved, equiareal rectangular duct (6) matched to the annulus, while retaining the essentially circular entry cross-sectional area of the tube.
By means of this inventive embodiment of the feeding elements for the pulverized fuels, it is achieved that fuel feeding ends directly adjacent to the oxidant duct and the flow rate provided in the feeding element is maintained up to the outlet. This measure ensures trouble-free conveying of the pulverized fuel and reduces the amount of inert gas necessary for purging the feeding element in the nonoperational state.
Advantageous developments of the subject matter of the application are detailed in the dependent claims.
The subject matter of the application is explained in greater detail below as an exemplary embodiment to the extent required for understanding and with reference to the accompanying drawings, in which:
In the figures, the same designations are used to denote identical elements.
The inventive pulverized coal combination burner has a centrally disposed pilot burner section 1 with fuel gas and oxidant supply, a flame monitoring device and an electrical high-voltage ignition system. Disposed around this module is an annulus 2 for supplying the oxidant for the pulverized coal combination burner. Swirl blades 3 for swirling the oxygen stream are disposed at the outlet port.
The pulverized fuel is supplied outside and inside the burner through one or more tubes (three in the example). In the burner, the individual tubes are designed such that the cross-section makes a systematic (continuous in the direction of flow) transition to a curved, equiareal rectangular duct matched to the annulus, while retaining the essentially circular entry cross-sectional area of the tube. At the burner mouth the rectangular duct is therefore constituted by two spatially separated e.g. 25 mm arcuate sections with the same angle α (alpha), e.g. 80 degrees about the central axis.
It is advantageous here if the ratio of rectangular width to rectangular or arcuate section length is approximately 1:5.3. To avoid pulverized fuel flow blockages, the rectangular width should be no less than 25 mm. Inside the annular duct (inside the burner in the direction of the burner mouth), the transition from the tubular cross-sectional area to the final rectangular area must be designed such that the final rectangular area is attained at the burner outlet.
In another embodiment of the invention, the extension rays of the walls of the annulus (4) intersect the central axis in the direction of the burner mouth, thereby achieving an advantageous flame geometry.
The unnecessary spaces remaining between the rectangular outlets depending on the number of feeding elements provided can be sealed off directly at the outlet and incorporated in the cooling circuit.
By implementing the oxidant supply using swirl blades 3, strong rotation is imparted to the discharging oxygen stream into which the pulverized fuel jets discharging via the specially designed feeding elements are sucked.
Due to the shaping of the pulverized fuel feeding elements up to the burner mouth and immediate entry into the rotating oxygen stream, there is no longer any areal discontinuity with different dust velocities at the pulverized fuel outlet, thereby achieving an even flame spread and stabilization. At the same time, the width and length of the flame spread can be influenced using different settings of the swirl blades 3.
The invention relates to a pulverized coal combination burner for the gasification of pulverized fuels under high pressures of e.g. 80 bar (8 MPa) and temperatures of e.g. 1200 to 1900° C. in reactors with liquid slag removal for oxygen gasification, comprising a cooled housing (7) for accommodating a centrally disposed pilot burner (1) with a gas and oxidant supply as well as an integrated flame monitoring device and a high-voltage ignition device, said pilot burner being used for starting up the pulverized coal combination burner unit, an annular duct (2) disposed around said pilot burner (1) for supplying the oxidant and another annular duct disposed around the annular oxidant duct and having integrated feeding elements (4) for supplying pulverized fuels, characterized in that a plurality of feeding elements (4) are present and, inside the burner, said feeding elements (4) make a systematic transition, up to the burner outlet, from a circular cross-section (5) to a curved rectangular cross-section (6) matched to the annular duct radius in a width/length ratio of approximately 1:5.3 while retaining the same area, the width of the rectangular cross section being necessarily no less than 25 mm, and end at the outlet immediately adjacent to the annular oxidant supply duct at the outlet of which swirl blades (3) are provided which impart strong rotation to the oxygen stream and therefore, by suitable design, allow the flame geometry to be influenced.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 021 924.7 | May 2007 | DE | national |
