JP2010533833A - Plasma ignition burner - Google Patents

Abstract

  The present invention relates to a plasma ignition burner. The plasma generation burner includes at least a two-stage burner cylinder and a plasma generator for igniting pulverized coal with the first-stage burner cylinder of the at least two-stage burner cylinder, and the combustion flame of the previous-stage burner cylinder is the next-stage burner Either ignite the pulverized coal in the cylinder or further combust with the supplementary air in the burner cylinder of the next stage, the direction of the axis of the plasma generator and the direction of flowing into the first stage burner cylinder of the pulverized coal-containing air flow are parallel and simultaneously It is characterized by being parallel to the burner cylinder axis.

Description

  The present invention relates to the technical field of pulverized coal combustion, in particular to a plasma ignition burner.

  Coal-fired power generation is the main power generation method currently used in many countries. Ignition is the main requirement of the boiler combustion process. How quickly and economically the boiler start-up process is achieved when the boiler capacity increases is an important issue to be solved immediately.

  Plasma ignition technology has recently been developed to replace oil ignition methods that consume large amounts of fuel oil.

  Conventional plasma ignition systems employ a so-called “pre-combustion chamber” technique so that poor charcoal can be ignited. This pre-combustion chamber is usually configured to attach a refractory material layer to the inside of the fire chamber to maintain the burner tube temperature. The walls of the pre-combustion chamber become very hot due to the initial heating and help fuel ignition (even independently). The length of the pre-combustion chamber is long (about 2 meters), and the powdered coal is gasified in the air flow containing pulverized coal by the plasma action and flows into the pre-combustion chamber, thereby generating a large amount of combustible gas, mainly carbon monoxide. . The subsequent pulverized coal is then ignited using the thermal energy released by the combustion of the combustible gas. This is a hierarchical ignition method, but because the temperature of the pre-combustion chamber is too high, the pulverized coal is easily clinkered internally, so that it cannot be used any more.

  In order to solve the above problems, a new structure hierarchical burner tube has been proposed. As shown in FIG. 1, the plasma ignition burner includes multi-stage burner cylinders such as a first stage burner cylinder 104, a second stage burner cylinder 106, a third stage burner cylinder 108, a fourth stage burner cylinder 110, etc. Depending on the size of the output and space, it may be more or less than 4 stages). The pulverized coal-containing airflow (indicated by the thick arrows in FIG. 1) flowing in from the pulverized coal-containing airflow inlet 102 is divided into two directions by the spacers 116, and each is divided into the first stage burner cylinder 104 and the second stage burner cylinder 106. enter. The plasma generator is inserted into the first stage burner cylinder 104 along the axial direction of the multistage burner cylinder, and generates the first stage pulverized coal flame A by igniting the pulverized coal-containing air flow flowing into the first stage burner cylinder 104. . The generated flame further ignites the pulverized coal-containing air stream in the second stage burner tube, thereby forming the second stage pulverized coal flame B. At the same time, the airflow (thin arrow in FIG. 1) flowing in from the air intake 114 enters the third stage burner cylinder 108 through the third intake 120 and replenishes oxygen to the second stage pulverized coal flame that did not sufficiently burn. Thus, the third stage pulverized coal flame C is formed. This air may also enter the fourth stage burner tube through the fourth intake 122 and further replenish oxygen. At the same time, this air flow acts to cool the burner cylinder so as to prevent clinkering by flowing into the space between the outer wall of the previous stage burner cylinder and the burner outer cylinder 118 before flowing into the next stage burner cylinder.

  In the above technique, the plasma generator is inserted along the axial direction of the burner cylinder, and both the pulverized coal-containing air flow inlet and the air flow are arranged to be perpendicular to the axis of the burner cylinder. That is, the direction of the plasma flame is perpendicular to the direction of the air flow flowing into the first stage burner cylinder. Therefore, it is necessary to use a guide plate (not shown) that deflects the path so that the air flow is parallel. Similarly, since the direction in which the second stage pulverized coal enters the second stage burner cylinder is also perpendicular to the direction of the flame injected from the first stage burner cylinder, it is necessary to use a guide plate so that the directions are parallel. However, this guide plate cannot completely change the course of the air flow due to space limitations. Since the two air flows are not perfectly parallel, the incoming air flow blows a plasma flame (or pre-flame) and changes its path. This leads to an increase in the cylinder wall temperature and clinkering of the pulverized coal.

  Furthermore, in this technology, both the pulverized coal-containing air flow and the air flow flow in a direction perpendicular to the burner cylinder, and the cross-section perpendicular to the burner cylinder does not have a uniform pulverized coal concentration and air flow velocity. Effect.

  Thereafter, a plasma ignition burner having the configuration shown in FIG. 2 was used to facilitate on-site placement. For the sake of simplicity, the figure shows only the pulverized coal-containing air flow inlet 102, the first stage burner cylinder 104 and the second stage burner cylinder 106, and the air inlet 114, the burner outer cylinder 118, and the third stage burner of FIG. The cylinder and the structure corresponding to the fourth stage burner cylinder are not shown. The pulverized coal-containing air flow flowing in from the intake 102 is divided into two parts by the cylindrical wall of the first-stage burner cylinder, the central part flows into the first-stage burner cylinder 104, and the peripheral part is separated from the first-stage burner cylinder. Proceed along the space between the cylinders 202 (on which the pulverized coal-containing airflow intake 102 is provided) and enter the second stage burner cylinder from the second intake 204 of the second stage burner cylinder. As shown in the figure, the plasma generator is inserted along the radial direction of the burner, and the pulverized coal-containing air flow is blown along the axial direction of the burner cylinder. These two directions remain vertical. Due to the action of the pulverized coal-containing air stream, the plasma flame is blown in a different path, and the temperature on the bent side of the plasma flame is particularly increased, resulting in the formation of a clinker.

  Therefore, there is a need for a new technique that further inhibits pulverized coal from forming clinker on the burner cylinder wall.

  An object of the present invention is to provide a plasma generator that can alleviate the clinkerization problem. From the above description regarding the prior art, it can be seen that the fact that there is an angle between the direction of insertion of the plasma generator (ie, the direction of the plasma flame) and the direction of the flow of air containing the pulverized coal is responsible for the clinkering problem. . Therefore, with regard to the above object, the main point of the present invention is to rearrange the pulverized coal-containing air flow inlet and the plasma generator so that the direction of the flow of the pulverized coal-containing air into the first stage burner cylinder coincides with the direction of the plasma flame. It is.

  In order to further solve the clinkering problem, it is necessary to match the air flow containing pulverized coal or the air flow of the next stage as much as possible with the pulverized coal flame of the previous stage.

  For this purpose, the present invention includes at least a two-stage burner cylinder and a plasma generator for igniting pulverized coal in the first-stage burner cylinder of the at least two-stage burner cylinder, Ignites the pulverized coal in the next stage burner cylinder, or further combusts with supplementary air in the next stage burner cylinder, and the axial direction of the plasma generator is the inflow direction of the pulverized coal-containing air flow into the first stage burner cylinder The plasma ignition burner is characterized in that it is parallel to the axis of the burner cylinder at the same time.

  The present invention will be described in detail with reference to the accompanying drawings. In these drawings, the same reference signs are used for the same or corresponding technical features.

FIG. 1 is a cross-sectional view schematically showing a prior art plasma ignition burner. FIG. 2 is a partial sectional view schematically showing another prior art plasma ignition burner. FIG. 3 is a partial sectional view schematically showing a first embodiment of the plasma ignition burner according to the present invention. 4 is a cross-sectional view taken along line AA in FIG. FIG. 5 is a partial sectional view schematically showing a second embodiment of the plasma ignition burner according to the present invention. FIG. 6 is a sectional view showing the structure of a prior art axially swirling pulverized coal burner.

Detailed Description of the Invention

  FIG. 3 is a partial sectional view schematically showing the first embodiment of the plasma ignition burner of the present invention. For the sake of simplicity, this figure shows only the pulverized coal-containing air flow inlet 102, the first stage burner cylinder 104, and the second stage burner cylinder 106, as in FIG. The structure of the multistage burner cylinder has been described above and will not be repeated here. It should be noted that as described in the “Background Art” section, there are restrictions on the number of stages of the burner cylinder into which the air flow containing pulverized coal flows, the number of stages of the burner cylinder into which air directly flows, and the total number of stages of this burner cylinder Rather, it is determined by the required output and the size of the space. The total number of stages may be two to three, four or more, and the air flow shown in FIG.

  The main point of the present invention is to make the insertion direction of the plasma generator 302 parallel to the direction in which the pulverized coal-containing air flow flows into the first stage burner cylinder 104 and simultaneously to the axis of the burner cylinder. Thus, the pulverized coal-containing airflow flows into the burner cylinder parallel to the burner cylinder axis without causing the distribution of the pulverized coal to be asymmetric on the burner cylinder cross section due to the inertia of the pulverized coal-containing airflow. Further, the plasma flame injection direction of the plasma generator coincides with the direction in which the pulverized coal-containing air flow flows into the burner cylinder, so that the plasma flame is not blown toward the burner cylinder wall by changing the course.

  In the first embodiment shown in FIG. 3, a curved pipe 308 that guides the pulverized coal-containing air flow is provided, and the plasma generator 302 is passed through the curved pipe to the first stage burner cylinder 104 along the axial direction of the burner cylinder. By inserting, the above technical solution is obtained. When the air flow containing pulverized coal flows into the straight burner cylinder at the position of the cross section AA, the arcing of the curved pipe 308 is as much as possible so that it is distributed as evenly as possible on the cross section without being deflected to one side by centrifugal force. It needs to be relaxed. However, centrifugal force is inevitable as long as the arc is present, and the course of pulverized coal is changed to one side of the burner tube. In order to avoid this problem, in one preferred embodiment, the guide plate 306 is disposed along the axis of the curved tube 308, one end of the guide plate on the burner tube side is parallel to the axis of the plasma generator, and the first stage It extends to the vicinity of the intake 310 of the burner tube 104. At the same time, both the plasma generator 302 and the guide plate 306 end are arranged on the axis of the burner tube (of course, the position of the end of the guide plate 306 may be changed to some extent with respect to the axis of the burner tube). As a result, the guide plate 306 not only changes the flow direction of the pulverized coal-containing air flow so as to be parallel to the plasma flame, but also increases the concentration of the pulverized coal entering the center of the cylinder so as to increase the concentration of the pulverized coal. Concentrate the part around the central axis of the burner tube and near the plasma flame to assist ignition. Compared to the structure shown in FIG. 1, the flow direction of the pulverized coal-containing air flow flowing into the burner cylinders at each stage can be changed simultaneously by using only one guide plate, and the structure is simple and the resistance is relatively small. Since the space inside the curved tip is large, the shape of the curved plate may be a flat surface or various curved surfaces in order to further increase the concentration of pulverized coal entering the center portion of the cylinder (Example 4 in FIG. 4). To show).

  As shown in FIG. 3, most of the plasma generator 302 is exposed to a pulverized coal-containing air stream. In order to prevent the plasma generator from being worn by the pulverized coal-containing air stream, the plasma generator can be protected by using an anti-wear sleeve (for example, a ceramic sleeve). In order to further reduce resistance, the windward sleeve surface may be V-shaped.

  Compared to the burner inserted along the radial direction of FIG. 2, this burner has a higher ignitability in solving the clinkering problem. Specifically, the reason is as follows. Since the plasma flame is located at the center line of the burner and the center part of the cylinder is circular, the ignition ability of the plasma flame is the same in each direction, the flame is uniform, and the propagation ability is high. On the other hand, when the plasma flame is disposed on one side of the central portion of the burner cylinder, the flame temperature on one side of the plasma flame is high and the flame temperature on the opposite side is low. In this case, ignition will fail if the crude charcoal is burned.

  In the first embodiment described above, the concentration of the powder in the center portion of the cylinder of the burner is due to the concentration action of the guide plate 306 in the bending tube 308. However, due to space limitations, the concentration at the center of the cylinder cannot be increased without limit, which affects the ignition efficiency. For this purpose, a second embodiment according to the present invention as shown in FIG. 5 is provided.

  For simplicity, FIG. 5 shows only the components corresponding to those shown in FIGS. 2 and 3, ie, the first stage burner cylinder 104 and the burner inner cylinder 202. As described in the above embodiment, more stages of burner cylinders can be arranged inside the burner inner cylinder 202 following the first stage burner cylinder 104. Components corresponding to the burner outer cylinder 118 may exist on the outside of the burner inner cylinder 202, and a number of stages of burner cylinders may be provided inside the burner outer cylinder 118 following the burner inner cylinder.

  In this embodiment, the pipe supplying the pulverized coal-containing air stream branches into two pipes, namely a main pipe 508 and a branch pipe 502. The main pipe 508 may be connected to the burner inner cylinder 202 by a known method or using the curved pipe 308 of the first embodiment. At the same time, the central cylinder 510 is guided from the first stage burner cylinder 104 and connected to the branch pipe 502. Similarly, the connection between the branch pipe 502 and the central cylinder 510 may be performed by using a known method or by using the second bending pipe 512 similarly to the bending pipe 308 of the first embodiment. A guide plate 306 (not shown in FIG. 5) can also be used. The arrangement method of the plasma generator 302 may be the same as in the first embodiment.

  In this way, the concentration of pulverized coal entering the center of the cylinder and further entering the first stage burner cylinder can be relatively controlled by directing the pulverized coal-containing air flow directly to the center of the cylinder using a branch pipe to assist ignition. Can be high. In a preferred embodiment, it is necessary to adjust the amount of incoming pulverized coal-containing air stream and / or increase the pulverized coal concentration in the pulverized coal-containing air stream entering the plasma ignition burner as high as possible. For this purpose, an adjusting device may be arranged at the branch point of the main pipe and the branch pipe so as to flexibly adjust the amount of pulverized coal entering the branch pipe.

  As a variant of the above-mentioned solution, if there are more than three stages of burner cylinders that guide the pulverized coal-containing air flow in the burner, each stage of the burner cylinder may be distributed between the central cylinder and the burner inner cylinder. For example, in the case of a three-stage burner cylinder, the first stage burner cylinder and the second stage burner cylinder of the plasma ignition burner are passed through the center cylinder and the branch pipe (in this case, the center cylinder and its internal structure are shown in FIG. The burner inner cylinder of FIG. 2 is changed to the central cylinder of FIG. 5), and the pulverized coal of the third stage burner cylinder can enter from the main pipe. Conversely, the pulverized coal in the first stage burner cylinder of the plasma ignition burner may be guided through the center cylinder and the branch pipe, and the pulverized coal in the second stage burner cylinder and the third stage burner cylinder may enter from the main pipe.

  In a preferred embodiment, the branch pipe may comprise a valve 504, which opens to the burner ignition start phase and the low load and stable combustion phase and closes after ignition is complete and burner combustion is stable. The valve 504 may also be designed to be incorporated into the regulator 506 so that the regulator acts as a regulator and a branch pipe valve simultaneously.

  From the above description of the second embodiment, it can be seen that the main point of this embodiment is to increase the pulverized coal concentration of the first stage burner cylinder using a branch pipe. A plasma generator is not necessarily used for ignition, and the plasma generator is not necessarily provided in the axial direction of the burner cylinder. Accordingly, the details of the various aspects of the second embodiment may or may not be combined with those of the first embodiment. Specifically, the ignition device may be an oil gun in addition to the plasma generator, and the arrangement method is not limited to axial insertion, but can be inserted in an arbitrary direction including insertion in the radial direction and inclined insertion.

  In the above-mentioned solution, since the branch pipe is arranged and the adjusting device is attached, the flow velocity and the pulverized coal concentration of the pulverized coal-containing air flow at the center of the burner cylinder can be adjusted separately, so that the optimum operating condition of ignition can be obtained.

  Furthermore, it is possible to provide a simple and inexpensive reconstruction means using the second embodiment described above for the old burner installed at the site, and the present invention can be applied.

  For example, a swirl type pulverized coal burner employed in many coal-fired thermal power generators has a central cylinder, and sends a mixture of pulverized coal and air to the furnace from the outside of the central cylinder. For example, an LNASB axially swirl type pulverized coal burner (see FIG. 6) developed by Mitsui Babcock Energy Co., Ltd. in the 1980s employs this type of structure. In this structure, the oil gun is inserted into the central cylinder 602, and the pulverized coal sent to the furnace from the outside of the central cylinder is ignited by the flame of the oil gun. To directly rebuild this type of burner with plasma ignition technology, the structure of the central tube 602 needs to be removed. This greatly changes the pulverized coal concentration distribution and air velocity in the burner, which affects the initial performance of the burner. However, this problem can be solved by adopting the second embodiment of the present invention. As shown in FIG. 5, it is necessary to reconstruct the central cylinder 602 into a first stage burner cylinder 104, a central cylinder 510, an ignition device (for example, a plasma generator 302), and a branch pipe 502 connected thereto, as shown in FIG. Just do it. There is no need to reconstruct the initial structure of the pulverized coal-containing airflow burner (ie, the structure from the primary air to the tertiary air tube shown in FIG. 6), so that it can be matched as closely as possible to the performance of the initial burner.

  By the above reconstruction method, a three-stage burner is formed (that is, the first-stage burner cylinder, the center cylinder, and the outer cylinder). In practice, it is possible to form a two-stage burner with only the central cylinder and the outer cylinder without adding a first-stage burner cylinder if possible. Further, a multistage burner cylinder may be added to the central cylinder, and a multistage burner cylinder may be added to the outer cylinder.

  Further, the igniter can be any kind of igniter, whether of the initial burner or of the rebuilt burner, including oil guns, plasma igniters and the like.

  The preferred embodiments of the present invention have been described with reference to the accompanying drawings. Obviously, the present invention is not limited to the above specific description, and various modifications and substitutions are possible, and they are also within the protection scope of the present invention.

Claims (9)

  A plasma ignition burner comprising at least a two-stage burner cylinder and a plasma generator for igniting the pulverized coal in the first-stage burner cylinder of the at least two-stage burner cylinder, wherein the combustion flame of the preceding burner cylinder is the next stage The pulverized coal in the burner cylinder is ignited or further combusted with supplementary air in the next stage burner cylinder, and the axial direction of the plasma generator is parallel to the direction in which the pulverized coal-containing air flow flows into the first stage burner cylinder At the same time, the plasma ignition burner is parallel to the burner cylinder axis.   A curved pipe for guiding the air flow containing pulverized coal to the at least two-stage burner cylinder; one end of the curved pipe on the burner cylinder side is parallel to the axis of the burner cylinder; and the plasma generator The plasma ignition burner according to claim 1, wherein the plasma ignition burner is inserted into the first stage burner cylinder along the axial direction of the burner cylinder.   The plasma ignition burner according to claim 2, further comprising a guide plate disposed along the axis of the curved tube, wherein one end of the guide plate on the burner tube side is parallel to the axis of the plasma generator.   The plasma ignition burner according to claim 3, wherein the guide plate extends to the vicinity of the first stage burner tube intake.   The plasma ignition burner according to claim 4, wherein the plasma generator terminal and the guide plate terminal are disposed on an axis of the burner cylinder, or a path is changed from the axis of the burner cylinder by a predetermined distance. .   The plasma ignition burner according to any one of claims 3 to 5, wherein a cross-sectional shape of the guide plate is a flat surface.   The plasma ignition burner according to any one of claims 3 to 5, wherein a cross-sectional shape of the guide plate is a curved surface.   The plasma ignition burner according to any one of claims 2 to 7, further comprising an anti-wear sleeve for protecting the plasma generator. 9. The plasma ignition burner according to claim 8, wherein the windward surface of the wear-resistant protective sleeve is V-shaped.

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