JP2016031200A - Combustion method of gas burner for low calorie gas, and gas burner for low calorie gas - Google Patents

Abstract

PROBLEM TO BE SOLVED: To stably burn a fuel gas of a low calorific value even when a combustion load is low or a combustion air ratio is high.SOLUTION: A thermal insulation body 12 is provided which has an inner annular part 12i made of a refractory material and outwardly fitted with an outer annular part 12o made of a heat insulation material. A thermal insulation chamber 13 is formed in the inner annular part 12i. A mixed gas MG in which a fuel gas FG with a low calorific value and a combustion air FA are mixed is injected from a mixed gas outlet 26 into the thermal insulation chamber 13. An ignited flame is thermally insulated and combusted in the thermal insulation chamber 13.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a combustion method of a gas burner and a gas burner for stably burning a fuel gas having a low calorific value generated from a metal manufacturing process such as a blast furnace or a chemical plant.

  Prior art related to a gas burner that satisfactorily and stably burns fuel gas with a low calorific value, as disclosed in Patent Document 1, forms an air nozzle in a mouth member having a conical tip surface that extends toward the tip, A gas nozzle is disposed on the same axis of the air nozzle. And a swirl air flow is ejected from the circumference | surroundings of a gas nozzle by arrange | positioning a swirl | wing blade in an air nozzle. The gas nozzle closes the tip portion through a small diameter portion, and has a plurality of gas injection ports for injecting fuel gas into the swirling air flow around the small diameter portion. In these gas injection ports, large-diameter gas injection ports and small-diameter gas injection ports are alternately arranged.

Japanese Utility Model Publication No. 01-025871

  However, in the above configuration, there is a problem that when the fuel gas having a low calorific value is combusted, the combustion load is low, or when combustion is performed at a high air ratio, the combustion is not stable. In addition, the pilot burner used for ignition always ignites, and there is a risk of misfire if it is not supplemented.

  The present invention solves the above problems, and can stably burn a fuel gas with a low calorific value even when the combustion load is low or the combustion air ratio is high, and no auxiliary combustion by a pilot burner or the like is required. It is an object of the present invention to provide a combustion method for a gas burner and a gas burner.

The combustion method of the gas burner for low calorie gas according to the present invention is as follows:
The outer annular portion made of a heat insulating material is externally fitted to the inner annular portion made of a refractory material to form a heat retaining body, and a mixed gas obtained by mixing a low calorific fuel gas and combustion air from the mixed gas outlet, It is characterized by burning the flame which was injected and ignited in the heat retention room formed in the inner annular part inside the heat retention room while being kept warm by the heat retaining body.

The gas burner for low calorie gas according to the present invention is
In the burner body, a combustion air passage provided along the burner axis, a combustion gas passage provided in an outer peripheral portion of the combustion air passage, a closing portion provided in a front end portion of the combustion air passage, A plurality of injection air holes for injecting the combustion air in the combustion air passage into the fuel gas in the combustion gas passage before the closing portion to mix the fuel gas and the combustion air, and mixing of the outer peripheral portion of the closing portion A swirl vane provided at the gas outlet,
The burner body is installed at the base end of the heat retaining body penetrating the wall of the combustion chamber,
The warmer at the tip side of the burner body is connected to the warmer chamber having a larger diameter than the mixed gas outlet and the warmer chamber and the combustion chamber formed to have substantially the same inner diameter as the mixed gas outlet. The guide chamber is formed continuously along the burner axis.

  According to the combustion method of the gas burner for low calorie gas according to the present invention, the heat resistance and the heat insulation against the flame in the thermal insulation by burning the mixed gas in the thermal insulation formed in the thermal insulation body composed of the refractory material and the heat insulating material. This makes it possible to keep the flame of the mixed gas in good condition. By keeping the flame warm, even when the combustion load is low or the combustion air ratio is high, the fuel gas having a low calorific value can be stably burned. Further, by keeping the flame warm, stable combustion is possible even without supplementary combustion by a pilot burner or the like.

  Further, according to the gas burner for low calorie gas, a guide chamber for leading out the flame is continuously formed in front of the thermal storage chamber, and the inner diameter of the guide chamber is smaller than the thermal storage chamber and substantially the same as the mixed gas outlet. By forming, it is possible to stabilize the flame while preventing unstable drift of the combustion gas, to reduce heat radiation, and to improve the heat retaining effect.

  Furthermore, since the burner body was installed in the heat retaining body installed at the wall surface opening of the combustion chamber, and the heat retaining room formed in the heat retaining body with a larger diameter than the mixed gas outlet of the burner body, and the guide chamber, The flame of the mixed gas injected from the mixed gas outlet can be surrounded and sufficiently kept warm, and the gas with a low calorific value can be stably burned even at a low combustion load and a high combustion air ratio. . In addition, auxiliary combustion with a pilot burner or the like can be eliminated. Further, the guide chamber can stabilize the flame while preventing unstable drift of the combustion gas, reduce heat radiation, and improve the heat retaining effect. Furthermore, the installation of the guide chamber can prevent the refractory from being lost and deformed near the exit of the greenhouse, and can increase the directivity of the flame by increasing the flow velocity to achieve stable combustion.

  Moreover, since the heat retaining body has an inner annular portion made of a refractory material and an outer annular portion made of a heat insulating material provided on the outer periphery of the inner annular portion, both heat resistance against heat and heat retaining properties are achieved. It can keep the flame well.

  Furthermore, since the plurality of injection air holes with chamfers formed around the inner surface side are formed in the tapered portion formed in the inner cylinder portion forming the fuel gas passage, the pressure loss of the combustion air can be greatly reduced. The generation of combustion noise and vibration can be suppressed, and the output and running cost of the blower can be reduced.

It is a longitudinal cross-sectional view which shows the use condition of Example 1 of the gas burner which concerns on this invention. It is a longitudinal cross-sectional view of the same gas burner. It is a partial expanded longitudinal cross-sectional view which shows the injection air hole formed in the taper part. It is a longitudinal cross-sectional view which shows Example 2 of the gas burner which concerns on this invention. It is a longitudinal cross-sectional view which shows Example 3 of the gas burner which concerns on this invention. It is a longitudinal cross-sectional view which shows Example 4 of the gas burner which concerns on this invention.

[Example 1]
Embodiments of the present invention will be described below with reference to the drawings.
Low calorie gas burner according to the present invention, for example, a blast furnace gas (BFG) calorific value of about 3.4MJ / Nm 3 ^{(approximately} 800kcalNm ^3), those capable of stable combustion with low load and high air ratio is there. In particular, heating value, maximum 5.02MJ / Nm ³ (1200kcalNm ³⁾ below, suitable 2.42MJ / Nm ³ (580kcalNm ³⁾ or more low heating value of the fuel gas, in addition to the blast furnace gas, chemical plants etc. The fuel gas having a low calorific value generated from the fuel can be burned well.

  As shown in FIG. 1 and FIG. 2, the feature of the present invention is that the mixed gas MG injected from the burner body 11 is injected and burned into a heat retaining chamber 13 formed in the heat retaining body 12, and this flame is retained. 13 and the guide chamber 14, and the combustion gas is led out from the guide chamber 14 to the combustion chamber 31. The warming chamber 13 has a sufficient size to wrap the flame through the combustion gas accommodated in the warming space and to keep warm.

  The combustion chamber 31 is formed of a refractory material 31 a and an outer shell material 31 b, and the heat retaining body 12 is fitted into an opening 32 formed on one wall surface of the combustion chamber 31. A warming chamber 13 and a guide chamber 14 are continuously formed along the center direction (burner axis O). And the burner main body 11 is installed along the burner axial center Oi on the base end side of the warm storage room 13.

  The heat retaining body 12 includes an inner annular portion 12i made of a refractory material that forms the thermal insulation 13 and the guide chamber 14 on the inner peripheral side, and an outer portion made of a heat insulating material provided between the inner annular portion 12i and the outer shell material 31b. It is comprised with the annular part 12o. And in order to protect from heat, the front-end | tip part of the outer annular part 12o is illustrated in the position retreated by the predetermined distance from the combustion chamber 31, but it is optimal that it surrounds at least the heat insulation body 12 full length, and is enough. If the heat retaining performance is obtained, the heat retaining body 12 may be disposed so as to surround at least a part thereof. In addition, if it is the outer annular part 12o made of a heat insulating material that can obtain heat resistance performance as much as the inner annular part 12i, it can be arranged so as to cover the entire length of the thermal storage room 13 and the guide room 14. The inner annular portion 12i ensures heat resistance, the outer annular portion 12o ensures heat retention, and the outer shell material 31b ensures strength. The heat retaining body 12 is held at a high temperature by the heat retaining body 12 so that a flame with a low calorific value fuel gas is stably combusted.

  In the burner main body 11, an inner cylinder portion 21 that forms a combustion air passage 22 is disposed along the burner axis O, and an outer cylinder portion 23 is disposed on the inner cylinder portion 21 on the same axis (burner axis O). It is fitted. A fuel gas passage 24 for supplying the fuel gas FG is formed between the inner cylinder portion 21 and the outer cylinder portion 23. A spacer 24a allows passage of the fuel gas FG.

  Further, a tapered portion 29 having a diameter reduced toward the distal end side is formed on the distal end side of the inner cylinder portion 21, and a plurality of ejection air holes 28 are formed in the tapered portion 29 at predetermined intervals in the circumferential direction. . A closed portion 25 that closes the combustion air passage 22 is formed at the distal end portion of the inner cylinder portion 21, and a mixed gas outlet 26 having substantially the same inner diameter as the fuel gas passage 24 is formed at the outer peripheral portion of the closed portion 25. ing. A plurality of swirl vanes 27 that swirl and inject the mixed gas MG are provided along the circumferential direction at the mixed gas outlet 26.

  A warming chamber 13 formed in the heat retaining body 12 is formed, for example, in a substantially spherical shape with a radius: r (d1 / 2) centered on the burner axis O. The guide chamber 14 is formed in a cylindrical shape along the burner axis O with substantially the same inner diameter as the mixed gas outlet 26.

  Here, the combustion air FA in the combustion air passage 22 is injected and mixed into the fuel gas FG in the fuel gas passage 24 from the injection air hole 28, and this mixed gas MG is swirled by the swirl vanes 27 to be mixed gas outlet. 26 is injected into the warming chamber 13. Further, the mixed gas MG is ignited and combusted in the warming chamber 13, and the flame is led out from the guide chamber 14 toward the combustion chamber 31. The warming chamber 13 is formed larger than the flame, and a warming space for circulating and holding a high-temperature combustion gas flow is formed in the front portion of the closed portion 25 that does not form a flame and the outer peripheral portion of the warming chamber 13. Therefore, the flame is surrounded and kept at a high temperature by the hot combustion gas flow. As a result, when the fuel gas FG with a low calorific value is used, even if it is burned at a low fuel load or burned at a high air ratio, the flame is kept warm and the combustion state is kept stable. Combustion becomes possible.

  By the way, a pilot burner (not shown) disposed in front of the gas burner and used for ignition is often continuously burned for auxiliary combustion when using a fuel gas having a low calorific value. However, in the gas burner of the present invention, since the temperature-retaining room 13 is sufficiently heated after ignition and the high-temperature state is maintained, no auxiliary combustion by a pilot burner or the like is required, and even if the pilot burner is extinguished, a good combustion state Can hold. The effect of this has been clarified by experiments to be described later.

Here, the size of the storage room 13 will be described.
When the inner diameter of the mixed gas outlet 26 (fuel gas passage 24) is d,
The outer diameter d0 of the closing part 25 is (1/6) × d or more and (1/2) × d or less. This is because when the outer diameter of the closed portion 25: d0 is less than (1/6) × d, there is less heat insulation space for keeping the flame warm, and when d0 exceeds (1/2) × d, This is because the mixed state of the mixed gas MG is lowered.

  Further, the inner diameter d1 of the thermal storage chamber 13 is (4/3) × d or more and (13/6) × d or less. Further, the length L1 of the warming chamber 13 in the burner axis O direction is formed to be (1/3) × d or more and (3/2) × d or less. This is because if the inner diameter d1 of the thermal insulation chamber 13 is less than (4/3) × d, the thermal insulation space for retaining the flame is reduced and the thermal insulation effect is reduced, and d1 is (13/6) × d. This is because an unstable drift is likely to occur in the combustion gas, resulting in vibration and combustion noise. And when the length: L1 of the thermal insulation 13 is less than (1/3) × d, the thermal insulation space is reduced and the thermal insulation performance is lowered. Further, if L1 is (3/2) × d or more, unstable drift tends to occur in the combustion gas, and the temperature decreases due to heat dissipation.

  Furthermore, the inner diameter d2 of the guide chamber 14 is (5/6) × d or more and (7/6) × d or less. The length L2 of the guide chamber 14 in the burner axis O direction is formed to be (1/6) × d or more and (1/2) × d or less. This is because if the inner diameter d2 of the guide chamber 14 is less than (5/6) × d, the flow velocity of the flame increases, the pressure loss increases, and the combustion noise increases, so that d2 is (1/2). If xd is exceeded, the flame becomes unstable, heat dissipation increases, and the heat retention effect decreases. Further, when the length of the guide chamber 14: L2 is less than (1/6) × d, the refractory material is easily burned out, and when L2 exceeds (1/2) × d, the cost of the refractory material and the heat insulating material is required. This is because of the above.

  Furthermore, the outer diameter d3 of the heat retaining body 12 is formed to be 2.0 × d or more and 3.0 × d or less. This is because if the outer diameter of the heat retaining body 12: d3 is less than 2.0 × d, sufficient heat retaining action cannot be obtained. If d3 exceeds 3.0 × d, the manufacturing cost increases, and the combustion chamber This is because it may be difficult to attach to the camera.

  By the way, if the pressure loss of the combustion air FA is large, an increase in combustion noise and vibration occur, leading to an increase in blower output and an increase in running cost. For this reason, as shown in FIG. 3, in the gas burner of the present invention, chamfered portions 28 a are respectively formed on the inner surfaces of the blast air holes 28 formed through the tapered portion 29. Assuming that each jet air hole 28 has a diameter: D, the thickness of the tapered portion 29: T (the length of the jet air hole 28) is approximately (1/2) × D, and the width of the chamfered portion 28a is C≈ ( 1/10) × D. Therefore, when the diameter of the ejection air hole 28 is D = 8 mm to 27 mm, the width of the chamfered portion 28 a is C = 0.8 mm to 2.7 mm.

Pressure loss: ΔP due to the chamfered portion 28a is as follows: air density: ρ, combustion air average flow velocity: v, loss factor: ζ
ΔP = ζ × (1/2) × ρv ² (Expression 1)

From this (Equation 1), it is understood that when D = 19 mm, C≈2 mm, and the average flow velocity of the injection air hole 28 is 75.8 m / s, the pressure loss of the combustion air FA can be reduced by about 32%.
As described above, the chamfered portion 28a formed on the inner surface of each injection air hole 28 can reduce the pressure loss of the combustion air FA by about 32%, suppress the generation of combustion noise and vibration, and the blower. Output and running cost can be reduced.

Here, the storage room 13 is formed in a spherical shape. However, as shown in FIG. 4, an elliptical rotating body, a right-angled trapezoidal rotating body shape shown in FIG. 5, or a trapezoidal rotating body shape shown in FIG. Good.
Next, using the gas burner shown in FIG. 5 in which the warming chamber 13 is formed into a right-angle trapezoidal rotating body, a combustion test using a blast furnace gas [BFG, calorific value is about 3.4 MJ / Nm ³ (about 800 kcal Nm ³ )] is performed. The results are shown in Table 1. The shape of the heat retaining body of the gas burner used in this experiment is as follows. When the inner diameter of the mixed gas outlet 26 is d, the outer diameter of the closed portion 25 is d0 = 0.21 × d, and the inner diameter of the warming chamber 13 is d1 = 1. .46 × d, inner diameter of the guide chamber 14: d2 = 1.04 × d, outer diameter of the heat insulator 12: d3 = 2.5 × d, length L1 = 0.625 × d of the warming chamber 13, guidance chamber 14 L2 = 0.42 × d.

  According to the above experiment, when the blast furnace gas is used as the fuel gas FG and burned at a combustion air ratio (hereinafter referred to as air ratio) of 1.1 to 1.4, the combustion air temperature is both normal temperature and 200 ° C., and the combustion load Good combustion conditions were obtained at 100% and 75%. A relatively good combustion state was obtained at a combustion load of 50%, and the combustion state could be maintained even at a combustion load of 25%. At an air ratio of 1.6 and 1.8, when the combustion air temperature was 200 ° C. heating, the air ratio could not be ensured due to the capacity of the experimental equipment, but when the combustion air temperature was normal temperature, the air ratio was 1 Good results were obtained as in .1 to 1.4. Therefore, it has been found that the gas burner should be designed so that the combustion load is 75 to 100%. These experiments were performed without igniting the pilot burner used for ignition during the experiment, and it was confirmed that there was no need for auxiliary combustion by the pilot burner. As a result, it was confirmed that no supplementary combustion with a pilot burner was required.

Also by adding nitrogen gas to the blast furnace gas (about 3.4MJ / Nm ^3), it was reduced to the heating value of about 2.93MJ / Nm ³ (approximately 700kcalNm ³⁾ and 2.42MJ / Nm ³ (580kcalNm ³⁾ Using fuel gas FG, combustion ratio no. 6 and no. 7 was performed. As a result, the calorific value was about 2.93 MJ / Nm ³ No. In No. 6, a good combustion state was confirmed when the combustion air temperature was 200 ° C. and the combustion load was 100% and 75%. In addition, a combustion experiment No. 2 having a calorific value of about 2.530 MJ / Nm ³ In No. 7, a good combustion state was confirmed when the combustion air temperature was 200 ° C. and the combustion load was 100%.

  According to the said Examples 1-4, the thermal insulation 13 was formed in the heat insulating body 12 provided with the inner annular part 12i which consists of a refractory material, and the outer annular body 12o which consists of heat insulation materials, and the thermal insulation from the mixed gas exit 26 13 is injected with a mixed gas and burned. It is a case where the flame of the mixed gas MG can be well kept by the heat-retaining room 13 having heat resistance and heat-retaining properties, and by keeping the flame well, the combustion load is low or the combustion air ratio is high. However, the fuel gas FG having a low calorific value can be stably burned. Further, by keeping the flame warm, stable combustion is possible even without the aid of a pilot burner used at the time of ignition.

  In addition, a guide chamber 14 that leads the flame to the combustion chamber 31 is continuously formed in front of the warm chamber 13, and the inner diameter of the guide chamber 14 is smaller than that of the warm chamber 13 and substantially the same inner diameter as the mixed gas outlet. As a result, the flame can be stabilized, and the heat retention effect can be improved by reducing the heat dissipation, and the refractory near the outlet of the warming chamber 13 is prevented from being deformed, and the directivity of the flame is increased by increasing the flow velocity. Stable combustion can be achieved.

  Furthermore, since the heat retaining body 12 is provided with an inner annular portion 12i made of a refractory material and an outer annular portion 12o made of a heat insulating material provided on the outer peripheral portion of the inner annular portion 12i, heat resistance and heat retention against a flame are provided. Both flames can be kept warm well.

  Furthermore, since the plurality of injection air holes 28 having chamfered portions 28a formed around the inner surface side are formed in the tapered portion 29 of the inner cylinder portion, the pressure loss of the combustion air can be greatly reduced, and the combustion noise And the occurrence of vibrations can be suppressed, and the output and running cost of the blower can be reduced. As a result, leakage loss can be reduced when there is an opening such as a heat storage heat exchanger in the middle of the piping connected to the combustion air passage.

O Burner shaft center FG Fuel gas FA Combustion air MG Mixed gas 11 Burner body 12 Heat insulator 12i Inner annular portion 12o Outer annular portion 13 Warm-holding chamber 14 Guide chamber 21 Inner cylinder portion 22 Combustion air passage 23 Outer cylinder portion 24 Fuel gas passage 25 Closed portion 26 Mixed gas outlet 27 Swivel blade 28 Injection air hole 28a Chamfered portion 29 Tapered portion 31 Combustion chamber

Claims (7)

The outer annular portion made of a heat insulating material is externally fitted to the inner annular portion made of a refractory material to form a heat retaining body, and a mixed gas obtained by mixing a low calorific fuel gas and combustion air from the mixed gas outlet, A combustion method of a gas burner for low calorie gas, characterized in that a flame that is injected and ignited into a heat retaining chamber formed in an inner annular portion is burned in the heat retaining chamber while being kept warm by the heat retaining body. The combustion method of the gas burner for low-calorie gas according to claim 1, wherein the calorific value of the fuel gas is 2.42 MJ / Nm ³ or more and 5.02 MJ / Nm ³ or less. A guide chamber that leads out the flame is continuously formed in front of the warming chamber in the warming body,
The warming chamber is formed such that its inner diameter is larger than the mixed gas outlet,
The method for burning a low-calorie gas gas burner according to claim 1 or 2, wherein the guide chamber has an inner diameter substantially the same as that of the mixed gas outlet. In the burner body, a combustion air passage provided along the burner axis, a combustion gas passage provided in an outer peripheral portion of the combustion air passage, a closing portion provided in a front end portion of the combustion air passage, A plurality of injection air holes for injecting the combustion air in the combustion air passage into the fuel gas in the combustion gas passage before the closing portion to mix the fuel gas and the combustion air, and mixing of the outer peripheral portion of the closing portion A swirl vane provided at the gas outlet,
The burner body is installed at the base end of the heat retaining body penetrating the wall of the combustion chamber,
The warmer at the tip side of the burner body is connected to the warmer chamber having a larger diameter than the mixed gas outlet and the warmer chamber and the combustion chamber formed to have substantially the same inner diameter as the mixed gas outlet. A gas burner for low-calorie gas, characterized in that a guide chamber is formed continuously along the burner axis. The heat insulator is provided with an inner annular portion made of a refractory material facing the warming chamber and the guide room on the inner peripheral side, and an outer annular portion made of heat insulating material provided on the outer peripheral portion of the inner annular portion. The gas burner for low-calorie gas according to claim 4. If the inner diameter of the mixed gas outlet is d,
The inner diameter of the warm chamber is 4/3 × d or more and 13/6 × d or less, and the length of the warm chamber in the burner axial direction is 1/3 × d or more and 3/2 × d or less,
The inner diameter of the guide chamber is 5/6 × d or more and 7/6 × d or less, and the length of the guide chamber in the axial direction of the burner is 1/6 × d or more and 1/2 × d or less. The gas burner for low-calorie gas according to claim 4 or 5. A tapered portion having a diameter reduced toward the distal end side is formed at the distal end portion of the inner cylinder portion forming the fuel gas passage, and a plurality of air injection holes are formed along the circumferential direction in the tapered portion,
The gas burner for low-calorie gas according to any one of claims 4 to 6, wherein a chamfer is formed around the inner surface side of the inner cylinder portion at the air injection hole.

Images