JP2014228164A - Design method for gas combustor - Google Patents

Abstract

Disclosed is a method for designing a gas combustor having a required flame existence region corresponding to an allowable maximum NOx concentration and a desired maximum combustion amount. A correlation curve K between a combustion load X corresponding to a fuel gas to be used and a generated NOx concentration Y is obtained, and a desired maximum NOx concentration Ya and a maximum combustion amount Qa in a gas combustor to be obtained are set. The combustion load Xa corresponding to the maximum NOx concentration Ya is obtained using the correlation curve K, and from the combustion load X = combustion amount Q / flame existence region S, the flame existence region S = combustion amount Q / combustion load X. Is used to set the flame existence region S of the gas combustor so as to be the value of the combustion load Xa corresponding to the maximum combustion amount Qa / maximum NOx concentration Ya. Assuming that the interval between the nozzles is A, the number of nozzles per injection tube is B, the interval between the injection tubes is C, and the number of injection tubes is D, the condition of the flame existence area S = A? B? C? D The values of A, B, C, and D are set so as to satisfy. [Selection] Figure 2

Description

  The present invention relates to a method for designing a gas combustor that uses a gas as a fuel.

  Gas combustors that use hydrocarbon-based fuel gas as fuel gas have been widely used, and in recent years, only water is produced even when burned, and greenhouse gases are not generated compared to hydrocarbon-based fuel. Therefore, a gas combustor using hydrogen gas as a fuel gas has also been proposed. Moreover, in these gas combustors, reducing the NOx concentration contained in the combustion exhaust gas is also an issue, and several proposals have been made.

  For example, in Patent Document 1, in a gas combustor using light and dark premixed combustion, a burner group is configured by a plurality of first and second burners, and the amount of combustion with respect to the first or second burner is staged during combustion. And a gas combustor that enables low NOx by allowing the flame of the second burner to function as a seed flame with respect to the flame of the first burner. Yes. Patent Document 2 discloses a method for diffusively burning hydrogen and a method for implementing this method, in which NOx generation can be significantly reduced by significantly increasing the fuel region as compared with a conventional burner for diffusion combustion. A burner has been proposed. Patent Document 3 proposes a hydrogen combustion apparatus in which the NOx concentration is set to a desired value or less by appropriately setting the interval between the flame openings in the diffusion combustion of hydrogen.

JP-A-10-68507 JP-A-9-178128 JP 2012-32084 A

  In conventional gas combustors, proposals have been made and implemented on how to structurally improve the burner and how to set the combustion flame to reduce the concentration of NOx produced. It is effectively used as a low NOx gas combustor.

  On the other hand, depending on the environment in which the gas combustor is used, the maximum NOx concentration allowed at the time of combustion may differ, and generally, the maximum combustion amount required for the gas combustor on the user side also differs. Therefore, if a gas combustor having a flame existence region corresponding to the allowable maximum NOx concentration and the desired maximum combustion amount can be obtained, the gas combustor is more effective from the viewpoint of reducing the generated NOx concentration. However, no design method for the gas combustor from such a viewpoint has been proposed.

  The present invention has been made from the above viewpoint, and can easily design a gas combustor having a flame existence region corresponding to an allowable maximum NOx concentration and a desired maximum combustion amount. It is an object to disclose a design method.

The present inventors have an inherent correlation curve K between the combustion load X (W / cm ² ) and the generated NOx concentration Y (ppm) for each type of fuel gas used in the gas combustor. By using the characteristic correlation curve K, it is possible to easily design a gas combustor having a flame existence region corresponding to the maximum allowable NOx concentration and the desired maximum combustion amount. As a result, they have reached the present invention.

That is, the method for designing a gas combustor according to the present invention includes a process for obtaining a correlation curve K between the combustion load X (W / cm ² ) corresponding to the fuel gas used and the NOx concentration Y (ppm) generated. The process of setting the desired maximum NOx concentration Ya (ppm) and the maximum combustion amount Qa (W) in the gas combustor and the combustion load corresponding to the maximum NOx concentration Ya (ppm) using the correlation curve K Xa (W / cm ² ), and a combustion load X (W / cm ² ) = combustion amount Q (W) / flame existence region S, flame existence region S = combustion amount Q (W) / Using the combustion load X (W / cm ² ), the gas is adjusted so that the combustion load Xa (W / cm ² ) corresponds to the maximum combustion amount Qa (W) / maximum NOx concentration Ya (ppm). It sets the flame existence area S of the combustor And

  In the gas combustor having the flame existence region S manufactured by the design method according to the present invention, the NOx concentration contained in the combustion exhaust gas is calculated by operating at a combustion amount equal to or less than the preset maximum combustion amount Qa (W). The maximum NOx concentration Ya (ppm) allowed in the environment where the gas combustor is used is not exceeded, and the gas combustor is friendly to the environment.

  In the present invention, the type of fuel gas to be used is not limited, and may be hydrogen gas or hydrocarbon fuel gas. The combustion method may also be diffusion combustion or premixed combustion.

  In the present invention, the “flame existence area S” refers to an area formed by the outer edge of the flame when the entire flame formed in the flame opening is viewed in plan, and there are a plurality of combustors. In the case where the craters are distributed at an equal density, a region surrounded by an imaginary line connecting the outer edges of the flame located at the most peripheral edge is described.

A more specific aspect of the method for designing a gas combustor according to the present invention is that two or more injection tubes are arranged in parallel and at equal intervals, and each injection tube has two or more flame ports formed at equal intervals. A method of designing a gas combustor, in which the interval between the flame ports is A (cm), the number of flame ports per one injection tube is B, the interval between the injection tubes is C (cm), and the number of injection tubes Is defined as D, and the flame existence region S = A × B × C × D, and (a) the combustion load X (W / cm ² ) corresponding to the fuel gas used and the generated NOx concentration Y (ppm) (B) a step of setting a desired maximum NOx concentration Ya (ppm) and a maximum combustion amount Qa (W) in the gas combustor to be obtained; and (c) the correlation curve. Using K, the combustion load Xa (W / cm ² ) corresponding to the maximum NOx concentration Ya (ppm) is obtained. And from the combustion load X (W / cm ² ) = combustion amount Q (W) / flame existence region S, flame existence region S = combustion amount Q (W) / combustion load X (W / cm ² ) A, B so that the value of the combustion load Xa (W / cm ² ) corresponding to the maximum combustion amount Qa (W) / maximum NOx concentration Ya (ppm) becomes the flame existence region S. , C, D values are set.

  In the gas combustor having the rectangular flame existence region S defined by the A, B, C, and D manufactured by the above design method, the combustion amount is equal to or less than the preset maximum combustion amount Qa (W). If it is operated, the NOx concentration contained in the combustion exhaust gas does not exceed the maximum NOx concentration Ya (ppm) allowed in the environment in which the gas combustor is used, and it becomes an environmentally friendly gas combustor.

  In the gas combustor manufactured by the above design method, when one flame becomes larger than necessary or when flames formed in adjacent flame ports are combined, the NOx concentration in the combustion exhaust gas may be increased. . For that purpose, the flame diameter and the interval between each flame mouth are set so that the flame is made as small as possible, and the flame formed in each flame mouth is independent of the flame formed in the adjacent flame mouth. It is desirable to do. In designing an actual gas combustor, through experiments, the optimum flame interval corresponding to the type of fuel gas and the required flame presence area S: A (cm), the number of flame ports per injection tube: B, the interval between the injection pipes: C (cm), the number of injection pipes: D, the diameter of the flame opening: E, the fuel gas to be used is hydrogen in our experiments, Flame diameter: E is preferably 0.03 cm or less, Flame interval: A is 0.63 cm or more, and injection pipe interval: C is 0.95 cm or more. It was found that NOx generation can be effectively suppressed.

  Therefore, the flame interval is A (cm), the number of flame ports per injection tube is B, the interval between injection tubes is C (cm), the number of injection tubes is D, and the flame existence area S = A × B In the above gas combustor design method defined as xCxD, a small flame is formed, and when the fuel gas used is hydrogen, the flame diameter is 0.03 cm or less. It is preferable to use a value of 0.63 cm or more as the interval A and 0.95 cm or more as the interval C of the injection tube.

  By using the design method of the present invention, it becomes possible to easily design a gas combustor having a required flame existence region corresponding to the allowable maximum NOx concentration and the desired maximum combustion amount.

The graph which shows an example of the correlation curve K of the combustion load X (W / cm < ² >) corresponding to the fuel gas to be used, and the NOx density | concentration Y (ppm) to generate | occur | produce. The figure explaining an example of a combustor and the flame presence area | region. The photograph which shows the state (b) which does not unite the state (a) which the adjacent flame united | combined by the difference in the space | interval of a flame mouth. The photograph which shows the state (b) which does not unite the state (a) which the adjacent flame united | combined by the difference in the space | interval of an injection pipe.

  Hereinafter, a method for designing a gas combustor according to the present invention will be described based on embodiments.

(1) First, a correlation curve K between the combustion load X (W / cm ² ) corresponding to the fuel gas to be used and the generated NOx concentration Y (ppm) is obtained. Specifically, one or a plurality of injection pipes having one or a plurality of flame openings are prepared, and combustion is performed by changing the combustion amount Q (fuel gas injection flow rate) of the fuel gas. The NOx concentration in the exhaust gas is measured, and a graph as shown in FIG. 1 is created using the measured NOx concentration.

Here, the combustion amount Q: the amount of fuel supplied to the combustor, the combustion area S: the area where the combustion flame is formed in the combustor, the combustion load X: X = Q / S (that is, the combustion per unit combustion area) 1), NOx concentration Y: means the amount of NOx contained per unit volume of combustion exhaust gas. In the graph shown in FIG. 1, NOx concentration Y is measured by sampling combustion exhaust gas and analyzing it simultaneously with NOx. The oxygen concentration was calculated by converting O ₂ = 0% by the following conversion formula (Formula 1).
Conversion formula: NOx concentration Y (ppm: O ₂ = 0%) = NOx concentration (ppm) × 21 / (21−O ₂ concentration (%)): Formula 1

(2) Next, the desired maximum NOx concentration Ya (ppm) and the maximum combustion amount Qa (W) in the gas combustor to be obtained are set. As an example, the maximum NOx concentration Ya (ppm) is set to 23 ppm, and the maximum combustion amount Qa (W) is set to 350 W.

(3) Next, the combustion curve Xa (W / cm ² ) corresponding to the maximum NOx concentration Ya (ppm) (23 ppm) is obtained using the correlation curve K. Here, the combustion load Xa (W / cm ² ) is 24.5 (W / cm ² ).

(4) Next, since the combustion load X (W / cm ² ) is the combustion amount Q (W) / flame existence region S, the flame existence region S is the combustion amount Q (W) / combustion load X (W / since it can be expressed as cm ^2), using this equation, the maximum combustion amount Qa (W) (350W) / maximum NOx concentration Ya (ppm) (23ppm) corresponding to the combustion load ^{Xa (W / cm 2) (} 24 The flame existence area S of the gas combustor is set so as to have a value of .5 (W / cm ² ).

(5) If the gas combustor having the flame existence region S set as described above is operated at a combustion amount equal to or less than the maximum combustion amount Qa (W) (350 W), the preset maximum NOx concentration Ya Operation at (23 ppm) or less is possible.

(6) As an example, the gas combustor 1 to be designed has two or more injection tubes (four injection tubes in the figure) 2 arranged in parallel and at equal intervals as shown in FIG. In the case of the gas combustor 1 in which two or more flame ports (10 flame ports in the illustrated example) 3 are formed at equal intervals in each injection pipe 2, the interval between the flame ports 3. Is A (cm), B is the number of flame ports per injection tube 2, C (cm) is the interval between the injection tubes 2, D is the number of injection tubes 2, and the flame existence area S is A × B × When defined as C × D, in the gas combustor 1 of the form shown in FIG. 2, the combustion load Xa (corresponding to the maximum combustion amount Qa (W) (350 W) / maximum NOx concentration Ya (ppm) (23 ppm). W / cm ² ) (24.5 (W / cm ² ) so that the values of A, B, C, and D are appropriately selected. By setting the flame existence area S, the desired gas combustor can be obtained.

  Hereinafter, the present invention will be described by way of examples.

(1) Setting of correlation curve K Using hydrogen as the fuel gas and using an injection pipe formed with six flame outlets with a diameter of 0.03 cm at intervals of 0.63 cm, the combustion amount Q (hydrogen injection flow rate) is low. It was burned by changing from multiple to high fire. The NOx concentration Y (ppm: O ₂ = 0%) is measured for each combustion amount according to the above equation 1, and is connected as a continuous curve, thereby generating the combustion load X (W / cm ² ) shown in FIG. A correlation curve K with NOx concentration Y (ppm) was obtained. Combustion was performed at room temperature and atmospheric pressure, and air was supplied by natural convection. In the experiment, the flame formed was a small flame divided in all combustion amounts, and adjacent flames did not merge.

(2) Setting of maximum NOx concentration Ya (ppm) and maximum combustion amount Qa (W) As shown in Table 1 below, maximum NOx concentration Ya (ppm) and maximum combustion amount Qa (W) were set.

(3) Next, combustion load X (W / cm ² ) = combustion amount Q (W) / flame existence region S, and flame existence region S = combustion amount Q (W) / combustion load X (W / cm ²⁾ Therefore, for each of the examples, the combustion load Xa (W / cm ² ) corresponding to the maximum combustion amount Qa (W) / maximum NOx concentration Ya (ppm) is obtained, and the flame existence region is set to the value. S (cm ² ) was calculated. The results are shown in Table 1.

(4) Gas combustor design As a gas combustor, two or more injection pipes are arranged in parallel and at equal intervals, and each injection pipe has two or more flame ports formed at equal intervals. Assume that the combustor is designed, the interval between the flame ports is A (cm), the number of flame ports per injection tube is B, the interval between the injection tubes is C (cm), the number of injection tubes is D, and the flame existence area S = A × B × C × D. And about Examples 1-3, the flame diameter: E is 0.03 cm, the space | interval of a flame mouth: A is 0.63 cm, and the flame mouth number per injection tube: B as satisfying the flame presence area | region S A combustor was designed with 6 nozzles, spray tube spacing: C of 0.95 cm, and spray tube spacing: D of 4. Further, in Examples 4 to 6, the flame diameter: E is 0.03 cm, the gap between the flame openings: A is 0.63 cm, the number of flame holes per one injection pipe: B is 14, the gap between the injection pipes: C Was designed to be 0.95 cm and the number of injection tubes: D was 24.

(5) Using the gas combustors obtained for Examples 1 to 6, a combustion experiment was performed at the set maximum combustion amount Qa (W), and the amount of NOx actually generated was measured. The results are shown in Table 1.

(6) Consideration As shown in Table 1, even when the gas combustor designed by the design method of the present invention is burned at the set maximum combustion amount Qa (W), the NOx concentration in the combustion exhaust gas is determined in advance. The set maximum NOx concentration Ya (ppm) was never exceeded. The state of the flame at this time was a state where the flame formed in each flame mouth was independent of the flame formed in the adjacent flame mouth as shown in FIG. 3 (b) and FIG. 4 (b). . If the characteristic time of diffusion affected by the flame diameter and the type of fuel is shorter than the characteristic time of the reaction where the length of the flame relative to the flame diameter and the flow rate of the fuel passing through it is shorter than the characteristic time of the reaction, a flame temperature is required due to a small flame. Thus, it is possible to avoid a high temperature and to reduce NOx. This indicates that a gas combustor that complies with the NOx emission regulations required by the usage environment and the like can be easily and reliably designed and manufactured by following the design method according to the present invention.

(7) Other Examples (7-1) About A (cm),
About Examples 1-6, the state of the flame at the time of combustion was observed from the side surface of the injection tube in the long direction. A photograph at the maximum combustion amount is shown in FIG. Each flame was small and independent, and adjacent flames were not observed to coalesce. As a comparison, a combustion experiment was conducted using a flame opening interval A (cm) of 0.63 mm to 0.50 mm without changing the value of the flame existence region S. As shown in FIG. As shown, there was a phenomenon where adjacent flames coalesced. When the flames are combined, it is considered that one flame having a large flame length and a large flame diameter is formed, so that a high temperature part is likely to be formed, and the NOx concentration may increase. From this, in the present Example, it turned out that it is preferable that the space | interval A of a flame mouth shall be 0.63 cm or more from a viewpoint which does not increase a NOx density | concentration.

(7-2) About the interval C (cm) of the injection pipe,
About Examples 1-6, the state of the flame at the time of combustion was observed seeing from diagonally upward. A photograph at the maximum combustion amount is shown in FIG. The flames of the injection tubes were small and independent from each other, and it was not observed that the flames of the adjacent injection tubes merged. As a comparison, a combustion experiment was conducted using a flame spacing region S of 0.95 mm to 0.63 mm without changing the value of the flame existence region S. As shown in FIG. Thus, a phenomenon was observed in which the flames of adjacent injection pipes merged. When the flames are combined, it is considered that one flame having a large flame length and a large flame diameter is formed, so that a high temperature part is likely to be formed, and the NOx concentration may increase. From this, in the present Example, it turned out that it is preferable that the space | interval C (cm) of an injection pipe shall be 0.95 mm or more from a viewpoint which does not increase a NOx density | concentration.

(7-3) For the flame diameter E,
In Examples 1 to 6, when the flame diameter E is changed without changing the value of the flame existence region S, as described in (6), the diffusion characteristic time is shorter than the reaction characteristic time. It is expected that NOx emission can be suppressed within a range of a proper combustion amount. Therefore, in the present embodiment, it is a more preferable aspect to set the flame diameter E to 0.03 cm or less to form a small flame.

1 ... Gas combustor,
2 ... injection pipe,
3 ... The flame mouth.

Claims (4)

A step of obtaining a correlation curve K between the combustion load X (W / cm ² ) corresponding to the fuel gas used and the generated NOx concentration Y (ppm);
A step of setting a desired maximum NOx concentration Ya (ppm) and a maximum combustion amount Qa (W) in the gas combustor to be obtained;
A step of obtaining a combustion load Xa (W / cm ² ) corresponding to the maximum NOx concentration Ya (ppm) using the correlation curve K,
From combustion load X (W / cm ² ) = combustion amount Q (W) / flame presence region S, flame existence region S = combustion amount Q (W) / combustion load X (W / cm ² ) The flame existence region S of the gas combustor is set so as to be a value of the combustion load Xa (W / cm ² ) corresponding to the maximum combustion amount Qa (W) / maximum NOx concentration Ya (ppm). How to design a gas combustor. A method of designing a gas combustor in which two or more injection tubes are arranged in parallel and at equal intervals, and each injection tube has two or more flame ports formed at equal intervals,
The flame exit area S = A × B × C, where A (cm) is the interval between the flame ports, B is the number of flame ports per injection tube, C (cm) is the interval between the injection tubes, and D is the number of injection tubes. X defined as D,
(A) a step of obtaining a correlation curve K between the combustion load X (W / cm ² ) corresponding to the fuel gas used and the generated NOx concentration Y (ppm);
(B) a step of setting a desired maximum NOx concentration Ya (ppm) and a maximum combustion amount Qa (W) in the gas combustor to be obtained;
(C) using the correlation curve K to obtain a combustion load Xa (W / cm ² ) corresponding to the maximum NOx concentration Ya (ppm),
From combustion load X (W / cm ² ) = combustion amount Q (W) / flame presence region S, flame existence region S = combustion amount Q (W) / combustion load X (W / cm ² ) The values of A, B, C, and D so that the value of the combustion load Xa (W / cm ² ) corresponding to the maximum combustion amount Qa (W) / maximum NOx concentration Ya (ppm) becomes the flame existence region S. A method for designing a gas combustor, characterized in that   3. The gas combustor design according to claim 2, wherein the fuel gas to be used is hydrogen, and a value of 0.63 cm or more is used as the gap A of the crater and a value of 0.95 cm or more is used as the distance C of the injection pipe. Method.   The method for designing a gas combustor according to claim 3, wherein a value having a flame diameter of 0.03 cm or less is used.

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