JP2006118725A - Pilot burner - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To solve problems in a pilot burner for igniting a main burner installed in a heating furnace, a heat treatment furnace or the like, wherein an electrode for electric spark ignition often shorts and does not spark, a nozzle at a a pilot burner tip end portion glows and is thermally damaged, thus a main body is burnt by backfire and misfire occurs. <P>SOLUTION: An outer pipe is concentrically mounted on an outer periphery of an inner pipe at an interval less than a distance of propagation of flame, a swirl vane having an inner diameter smaller than an inner diameter of the inner pipe and an outer diameter smaller than an inner diameter of the outer pipe, is mounted on a tip end portion of the inner pipe, and a gas fuel or a mixture gas of the gas fuel and the air for combustion is allowed to flow between the inner pipe and the outer pipe, thus the short circuit of the electrode for electric spark ignition is prevented, and the glowing or the like of the nozzle at the pilot burner tip end portion is prevented. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a pilot burner that ignites a main burner installed in a heating furnace, a heat treatment furnace, or the like.

  Recently, in the combustion furnaces in the steel industry, as the adoption of auto-ignition pilot burners has increased due to personnel rationalization, etc., pilot burners are required to have ignition reliability, combustion stability, flame detection reliability, life extension, etc. ing.

  However, the conventional pilot burner is mainly a Bremix type, and after mixing gas fuel such as coke oven gas and combustion air with a set of venturi mixers in each zone, about 8 to 12 pilot burners are mixed. Distributing. For this reason, if one burner burns back-fire, the other pilot burners in the zone will burn back.

  An example of a conventional auto-ignition type Bremix pilot burner is shown in FIG. In FIG. 5, a mixture of combustion air and gas fuel mixed in advance is supplied from the connecting portion 10, and a jet flame is formed from a nozzle 14 provided at the tip of the burner body. The flame holding cylinder 15 is attached to the end of the burner body in order to stabilize this flame.

The electric spark ignition electrode rod 2 is held by the insulator 4 at the burner center axis position in an insulated state from the burner body, and between the bent tip of the electric spark ignition electrode rod 2 and the nozzle 14, for example, 6000V. A high voltage is applied to ignite a mixture of combustion air and gas fuel by blowing electric sparks.
JP2003-343815

  However, such a conventional pilot burner has the following problems.

  (1) Since the electrode rod for electric spark ignition is disposed in a narrow space in the pilot burner body, both of them are easily short-circuited and do not spark.

  (2) Since the fuel flows in contact with the electric spark ignition electrode rod, coke oven gas, etc., which is a by-product gas in the steelworks, has tar, naphthalene, moisture, etc. attached to the electric spark ignition electrode rod, causing a short circuit. , Will not spark.

  (3) Since the fuel flows in contact with the electric spark ignition electrode rod, tar, naphthalene, moisture, etc., adhere to the electric spark ignition electrode rod in the coke oven gas that is a by-product gas in the steelworks. The spark is ignited and burned and burned in the pilot burner.

  (4) The pilot burner tip nozzle 14 burns red and burns and burns back to the pilot burner body.

  (5) When exhaust gas is sucked by the heat treatment radiant tube burner, the pilot burner misfires when the pressure in the radiant tube before the burner becomes an extremely negative pressure.

  (6) Like the regenerative burner, when the furnace pressure fluctuates extremely, the pilot burner misfires.

  An object of the present invention is to provide a premix type pilot burner and a nozzle mix type pilot burner that eliminate all the above problems, have excellent durability and combustion stability, have high ignition reliability, and have a wide range of applications.

  As a result of various studies to eliminate all of the above problems, the inventor arranged an inner tube at the center of the burner, and provided an outer tube concentrically at an interval equal to or less than the distance at which the flame propagated around the inner tube, A swirl vane whose inner diameter is smaller than the inner diameter of the inner tube and smaller than the inner diameter of the outer tube is connected to the tip of the inner tube, and gas fuel or gas fuel and combustion air are connected between the inner tube and the outer tube. The present invention was completed by discovering that the above-mentioned object can be achieved by flowing a mixed gas.

In addition, the inventor, in the above configuration,
A configuration in which an electrode rod for electric spark ignition is provided at the center of the inner pipe,
A configuration in which the inner diameter of the swirl vane is 9 mm or more, the electrode rod for grounding is connected to the swirl vane or the outer tube, and the electric spark ignition electrode rod at the center of the burner is installed at an interval of 1.5 mm ± 0.5,
A structure in which the distance of the outer tube from the swirl vane and the distance of the electrode rod for electric spark ignition are extended to a length at which the tip of the electrode rod becomes red hot,
A configuration in which the distance from the swirl blade to the outer tube at the tip and the distance from the electrode rod for electric spark ignition is extended to such a length that an ion current having a strength capable of detecting a flame can be generated between the electrode rod at the center and the electrode rod for grounding,
A configuration that allows air to flow into the inner pipe,
We propose a configuration in which the electric spark ignition electrode rod in the center is straight and a small hole is made in the inner tube near the swirl vane.

  According to the configuration of the pilot burner of the present invention, the electric spark is easily generated only at a position of a predetermined narrow interval, the electric spark or the short circuit does not occur in other portions, and the gas fuel and the gas fuel are spaced at an interval equal to or less than the distance through which the flame propagates. Since the mixed gas of combustion air flows, no backfire combustion occurs, and the pilot burner has a wide application range that can be used for both the premix burner and the nozzle mix burner.

  The pilot burner according to the present invention is safe and excellent in durability without causing any flashback trouble in both the bremix type and the nozzle mix type. In addition, the flame of the pilot burner is surely ignited and the flame stability is excellent. Flame detection by an ultraviolet flame detector is also good, and it can also be used as a flame rod flame detector.

  The configuration of the present invention will be described. An inner pipe is arranged in the center of the burner, and an outer pipe is provided concentrically at an interval equal to or less than the distance at which the flame propagates on the outer circumference of the inner pipe. By connecting a swirl vane having an outer diameter smaller than the inner diameter of the gas pipe and flowing gas fuel or a mixed gas of gas fuel and combustion air between the inner pipe and the outer pipe, the flame is prevented from being transmitted into the burner body. (3) While preventing the flashback combustion of (4) from occurring, a stable flame is formed by the effect of the swirling flow.

  B. By providing an electric spark ignition electrode rod at the center of the inner pipe, the gas fuel or a mixed gas of gas fuel and combustion air and the electric spark ignition electrode rod are not in contact with each other. Trouble will not occur.

  C. By setting the inner diameter of the swirl vane to 9 mm or more, connecting the electrode rod for grounding to the swirl vane or the outer tube, and installing it at an interval of 1.5 mm ± 0.5 from the electrode rod for electric spark ignition in the center of the burner Sparks easily occur at this narrow distance of 1.5 mm ± 0.5, and sparks and short circuits do not occur because the distance is wide at other parts. For this reason, the problems (1), (2) and (3) do not occur.

  D. By extending the distance of the outer tube from the swirl vane and the distance of the electrode electrode for electric spark ignition to the length at which the tip of the electrode electrode for electric spark ignition is red-hot, the tip of the electrode rod that is red-hot is used as a flame holder. It plays the role of, and does not misfire even in a misfire-prone atmosphere. For this reason, the troubles (5) and (6) do not occur.

  E. By allowing air to flow into the inner tube, the prevention of adhesion of foreign matter to the electrode electrode for electric spark ignition is strengthened. Or it is set as a nozzle mix burner using this air.

  F. By making the electric spark ignition electrode rod in the center of the burner straight and providing a small hole in the inner tube near the swirl vane, gas fuel and combustion air flow in the center of the burner, and ignition in the center is ensured At the same time, since the electric spark ignition electrode rod is linear, it is easy to replace the electric spark ignition electrode rod. In addition, when an ultraviolet flame detector is attached to the rear end of the pilot burner, a flame concentrated at the center of the burner is formed, so that flame detection is also good.

Example 1
Details of the pilot burner of the present invention will be described below with reference to FIGS. 1-4, 1 is a pilot burner, 2 is an electrode rod and frame rod, 3 is an inner tube, 4 is an insulator, 5 is an outer tube, 6 is a swirl vane, 7 is a spark plug, 8 is a viewing window, 9 Is an electrode rod for grounding, 10 is a connecting portion, 11 is a plug, 12 is a connecting portion, and 13 is a small hole.

  In FIG. 1, an inner tube 3 (outer diameter 19 mm) is arranged at the center of the pilot burner 1, and the outer tube 5 is concentrically spaced at a distance (1.61 mm) less than the distance at which the flame propagates to the outer periphery of the inner tube 3. (Inner diameter 22.2 mm) is provided, and the swirl vane 6 (inner diameter 9.3 mm, gap 3 between the electrode rod and the inner diameter is smaller than the inner diameter of the inner tube and smaller than the inner diameter of the outer tube at the tip of the inner tube 3. 5 mm) and a mixed gas of gaseous fuel and combustion air is allowed to flow between the inner tube 3 and the outer tube 5.

  The electric spark ignition electrode rod 2 is fixed to the inner surface of the inner tube 3 while being insulated by the insulator 4. The electrode rod 2 is connected to a spark plug 7 in an energized state, and the spark plug 7 is connected to a high voltage transformer (not shown). For example, a bent tip of the electrode rod 2 and a ground electrode rod are applied with a voltage of 6000V. An electric spark is generated at an interval of 1.5 mm ± 0.5 with respect to 9, and a mixture of combustion air and gas fuel is ignited.

  At this time, since the inner diameter of the swirl vane is 9 mm or more, the distance between the electrode rod 2 (inner diameter 2.8 mm) and the inner surface of the swirl vane 6 is 3 mm or more, and the distance between the electrode rod 2 and the ground electrode rod 9 is larger. Is as short as 1.5 mm ± 0.5, so that no spark or short circuit occurs between the electrode rod 2 and the swirl vane 6. A plug 11 is provided on the side of the pilot burner 1 opposite to the mounting position of the spark plug 7 so that furnace gas or the like flows into the inner tube 3 and foreign matter does not adhere to the electrode rod 2.

Example 2
In FIG. 2, purge air is supplied to the inner tube 3 from the connecting portion 12 provided at the rear end of the inner tube 3, thereby enhancing the prevention of adhesion of foreign matter to the electrode rod 2.

Example 3
The fuel gas shown in FIG. 3 is supplied between the inner tube 3 and the outer tube 5 from the connecting portion 10 provided at the rear end of the outer tube 5, and from the connecting portion 12 provided at the rear end of the inner tube 3. Combustion air is supplied to the inner pipe 3 to form a nozzle mix type pilot burner.

Example 4
In the example shown in FIG. 4, the electric spark ignition electrode rod 2 in the center is straight, and a small hole 13 is provided in the inner tube 3 in the vicinity of the swirl vane so that the gas fuel and the combustion air are in the center of the burner. The ignition at the center of the flow is ensured, and since the electric spark ignition electrode rod 2 is linear, the electric spark ignition electrode rod can be easily replaced.

  In the figure, an example in which the observation window 8 is attached to the rear end of the pilot burner 1 is shown, but an ultraviolet flame detector can be attached instead of the observation window 8, and at this time, the flame concentrated at the center of the burner. Therefore, the flame detection by the ultraviolet flame detector is also good.

  The pilot burner of the present invention, as in the embodiment, does not cause backfire combustion troubles in both the bremix type and the nozzle mix type, is safe and excellent in durability, and the ignition of the pilot burner flame is reliable and flame stable. Excellent in properties.

It is a section explanatory view of the 1st example of the pilot burner of the present invention. It is a section explanatory view of the 2nd example of the pilot burner of the present invention. It is a section explanatory view of the 3rd example of the pilot burner of the present invention. It is a section explanatory view of the 4th example of a pilot burner of the present invention. It is explanatory drawing of the conventional automatic ignition type Bremix type pilot burner.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Pilot burner 2 Electrode rod and frame rod 3 Inner tube 4 Insulator 5 Outer tube 6 Swirling blade 7 Spark plug 8 Viewing window 9 Ground electrode rod 10 Connection portion 11 Plug 12 Connection portion 13 Small hole 14 Nozzle 15 Flame holding tube

Claims (7)

An inner pipe is arranged in the center of the burner, an outer pipe is provided concentrically at an interval equal to or shorter than the distance at which the flame propagates on the outer circumference of the inner pipe, and the inner pipe is smaller in diameter than the inner pipe at the tip of the inner pipe. A pilot burner in which a swirl vane having an outer diameter smaller than the inner diameter is connected, and gas fuel or a mixed gas of gas fuel and combustion air flows between the inner pipe and the outer pipe. 2. The pilot burner according to claim 1, wherein an electrode rod for electric spark ignition is provided at the center of the inner pipe. The inner diameter of the swirl vane is 9 mm or more, the electrode rod for grounding is connected to the swirl vane or the outer tube, and it is installed at an interval of 1.5 mm ± 0.5 from the electrode rod for electric spark ignition in the center of the burner The pilot burner according to claim 2, characterized in that: 4. The pilot burner according to claim 3, wherein the distance of the outer tube from the swirl vane and the distance of the electric spark ignition electrode rod are extended to a length at which the tip of the electrode rod is red-hot. The distance between the outer tube at the tip of the swirl vane and the distance between the electrode rod for electric spark ignition and the electrode rod for electric spark ignition have been extended to a length that allows a strong ion current to flow between the center electrode rod and the earth electrode rod. The pilot burner according to claim 3 or 4, characterized by the above. The pilot burner according to any one of claims 1 to 5, wherein air is allowed to flow into the inner pipe. The pilot burner according to any one of claims 2 to 6, wherein the electrode electrode for electric spark ignition in the center is linear, and a small hole is provided in the inner tube near the swirl vane.

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