JP5558253B2 - Hydrogen combustion equipment - Google Patents

Description

The present invention relates to a hydrogen combustion apparatus, and more particularly to a hydrogen combustion apparatus capable of suppressing a nitrogen oxide (NOx) concentration in combustion exhaust gas to a desired value or less.

In recent years, hydrogen that does not emit CO2 due to combustion has attracted attention as clean energy. Conventionally, with respect to the combustion of hydrogen, a premixed combustion system in which hydrogen and an oxidant (oxygen or air) are mixed in advance upstream of the combustion section is mainly used.
However, since the burning rate of hydrogen is extremely high, there is a risk of flashback (backfire) when the premixed combustion method is adopted. Therefore, for a combustion apparatus using hydrogen as a fuel, a diffusion combustion system in which fuel and an oxidant are separately supplied and burned while mixing them in a combustion chamber is suitable.
Conventionally, there is little disclosure regarding diffusion combustion type hydrogen combustion equipment, but for example, Patent Document 1 can be cited. FIG. 7 shows a configuration of a hydrogen combustion burner 100 according to the same document, in which a first perforated plate 101 made of metal and a second perforated plate 102 made of a porous material are arranged at a predetermined interval d. And a number of guide tubes 103 supported by the two perforated plates 101 and 102. An air guide pin 105 made of a cylindrical rotating body is inserted into each guide tube 103. The air guide pin 105 includes a disk 105a at the tip and four guide passages 105b in the axial direction.
With this configuration, in the hydrogen combustion burner 100, hydrogen is introduced into the distribution chamber 106 formed by the perforated plates 101 and 102, and is finely distributed in the local area of the porous perforated plate 102. And enters the combustion chamber 107. On the other hand, the air is introduced into the combustion chamber 107 through the guide passage 105b of the guide tube 103, and an air flow in the shape of a conical outer peripheral wall is generated by turning by the disc 105a. A rotationally symmetric diffusion flame is formed.

JP-A-9-178128

  However, this document does not stipulate the distance between adjacent flame holes, and when the combustion amount (input) is large, the adjacent flame holes are integrated and adjacent flames come into contact with each other locally. There are places where the temperature becomes high, and there are concerns such as an increase in the concentration of nitrogen oxides and a decrease in thermal efficiency. Further, since the burner structure is complicated, there is a problem that the equipment cost is increased.

As a result of diligent research on hydrogen diffusion combustion, the applicants have found that the NOx value can be suppressed to a predetermined value or less by appropriately setting the separation distance between adjacent flame holes and the combustion output per flame hole. The present invention was completed after confirmation.
The gist of the present invention is as follows. That is, the hydrogen combustion apparatus according to the present invention is
(1) A hydrogen combustion apparatus that injects hydrogen gas from a plurality of flame holes and burns hydrogen by a diffusion combustion method,
For the allowable NOx value (X) (where 10 ppm ≦ X ≦ 70 ppm) and the required output Q (kW) , the number of flame holes n, the distance D (mm) between both ends of adjacent flame holes, and the output q per unit flame hole (= Q / n: kW) it is,
q / √D ≦ 0.0036X + 0.22
It is characterized by arranging the flame holes so as to satisfy the relationship .
(2) In the invention of (1) above,
q / √D ≦ 0.29
It is characterized by arranging the flame holes so as to satisfy the relationship .
(3) In the invention of (1) above,
q / √D ≦ 0.37
It is characterized by arranging the flame holes so as to satisfy the relationship .
( 4 ) In the invention of (1) above,
q / √D ≦ 0.44
It is characterized by arranging the flame holes so as to satisfy the relationship .

FIG. 2 shows a relationship between output (flow rate) (kW) and flame length (mm) when a single flame hole is provided at the center of the upper surface of a combustion apparatus (see FIG. 4) described later, and H2 gas is burned. The flame hole diameter is shown as a parameter. From the figure, it can be seen that the flame length increases in proportion to the increase in flow rate. In this case, the flame length increase rate with respect to the increase in the combustion amount is more remarkable as the flame hole diameter is smaller.
FIG. 3 shows the relationship between the output (kW) and the NOx value (ppm) for the H2 or CH4 gas with the flame hole diameter as a parameter. From the figure, it can be seen that the change in NOx value is small for CH4 even when the output is increased, whereas the NOx value is increased in proportion to the increase in output for H2.

  In general, the longer the flame length, the more the flame comes into contact with the object to be heated and the like, and there are places where the temperature locally rises, causing inconveniences such as an increase in nitrogen oxide concentration and a decrease in thermal efficiency. Accordingly, it is appropriate to shorten the flame length by reducing the amount of combustion per flame and increasing the area of the flame hole for ejecting hydrogen. In this case, it is a condition that adjacent flames are not in contact with each other and independent flames can be maintained. Based on the above findings, the optimum flame hole arrangement in the case of a plurality of flame holes will be examined for application to an actual combustion apparatus.

Specifically, according to the equation (1) derived from FIG. 6 to be described later, by setting the output per flame (q) and the inter-flame distance (D), the burner suppressed to a desired NOx value or less. Design becomes possible. The set NOx value can be selected as appropriate in consideration of legal restrictions on the type of target combustion device.
Y = 0.0036X + 0.22 (1)
Here, X: NOx value, Y: q / √D
For example, when a NOx value of 20 ppm or less is required, q / √D ≦ 0.29 may be set. Further, when the NOx values are 40 ppm and 60 ppm or less, q / √D ≦ 0.37 and q / √D ≦ 0.44, respectively.

ADVANTAGE OF THE INVENTION According to this invention, the design of the combustion apparatus which can be suppressed below to a predetermined value according to the legal regulation regarding a NOx value etc. according to the type of a combustion apparatus is attained.
Further, according to the present invention, since the burner structure is simple, there is an effect that cost reduction can be easily realized.

1 is a plan view of a hydrogen combustion apparatus 1 according to an embodiment of the present invention. 1 is a side view of a hydrogen combustion apparatus 1. FIG. It is a figure which shows the relationship of the output-flame length in the case of the single flame hole diffusion combustion which used the flame hole diameter as a parameter about H2. It is a figure which shows the relationship of the output-NOx value in the case of single flame hole diffusion combustion about H2 and CH4. It is a figure which shows schematic structure of the combustion test apparatus of an Example. It is a figure which shows the relationship of the output-NOx value in H2 diffusion combustion which made the distance (D) between flame holes a parameter (Example). It is a figure which shows the relationship of NOx value and q / (root) D which made the distance (D) between flame holes a parameter. It is a figure which shows the structure of the conventional diffusion type hydrogen combustion burner 100. FIG.

Hereinafter, embodiments of the hydrogen combustion apparatus according to the present invention will be described in more detail. Needless to say, the scope of the present invention is described in the claims and is not limited to the following embodiments.
Referring to FIGS. 1 (a) and 1 (b), a hydrogen combustion apparatus 1 according to an embodiment of the present invention is formed in three layers, both of which are a ring-shaped outer burner 2a, an intermediate burner 2b, The inner burner 2c, supply pipes 4a to 4c for supplying hydrogen gas to the burners, and flow rate adjusting valves 5a to 5c interposed in the supply pipes are provided as main components. Each of the burners is set to have a ring diameter Ra, Rb, Rc so that an independent flame is maintained without being affected by combustion by the flame holes of the adjacent burners. In addition, although illustration is abbreviate | omitted, the hydrogen combustion apparatus 1 is provided with the support part for hold | maintaining the arrangement | positioning of the figure in a horizontal installation state.
A plurality of flame holes 3a-3c for ejecting hydrogen gas are provided in a row on the circumference of the upper side surface of each burner. The flame diameter, the total number of flame holes, the distance between flame holes (between the center and both ends), the total input, and the output per flame hole of each burner are set as shown in Table 1, respectively. The per-flame output (q) and the inter-flame distance (D) are set so that the relationships of equations (2-1) to (2-3) are established.
For burner 2a, qa / √Da ≦ 0.29 (2−1)
For the burner 2b, qb / √Db ≦ 0.29 (...) (2-2)
For the burner 2c, qc / √Dc ≦ 0.29 (2-3)

各バーナの流量調整弁５ａ−５ｃは、それぞれ独立に流量を調整できるように構成されており、必要出力に対応して適宜、燃焼バーナ本数、インプットを調整可能としている。
水素燃焼装置１は以上のように構成されており、これにより最小インプット０から最大インプット（Ｑａ＋Ｑｂ＋Ｑｃ）の範囲で、ＮＯｘ値２０ｐｐｍ以下で燃焼させることができる。

The flow rate adjusting valves 5a-5c of each burner are configured so that the flow rate can be adjusted independently, and the number of combustion burners and the input can be appropriately adjusted according to the required output.
The hydrogen combustion apparatus 1 is configured as described above, and can thereby be combusted at a NOx value of 20 ppm or less in the range from the minimum input 0 to the maximum input (Qa + Qb + Qc).

In this embodiment, the flame hole diameters of the burners are different from each other. However, the output per flame hole (q) and the distance between flame holes (D) satisfy the expressions (2-1) to (2-3). As long as it is within the range, the same flame hole diameter may be used.
In the present embodiment, the burner set value is assumed to be a NOx value of 20 ppm or less, but the set value can be appropriately selected in consideration of legal regulations and the like.
Further, the number of burners is not limited to three, and any number of burners can be selected as long as each burner flame hole diameter, total flame hole number, flame hole distance, and the like satisfy the above formula.

Hereinafter, the contents of the tests conducted to verify the validity of the present invention will be described.
As shown in FIG. 4, using a test apparatus in which three flame holes are arranged in a row at the center of the upper surface of the combustion apparatus, hydrogen was supplied and burned to measure the NOx value. Table 2 shows combinations of flame hole diameter, flame hole interval (between both ends), and output per flame hole.

FIG. 5 shows the relationship between unit output and NOx value at each flame hole interval. Further, from the figure, the output per flame hole when the NOx value was 20, 40, 60 ppm for each flame hole interval was obtained, and the value of q / √D at this time was plotted to obtain FIG. From the figure, it was found that the value of q / √D at the same NOx value was almost the same regardless of the flame hole interval.
In this case, the linear regression equation is X: NOx value, Y: q / √D,
Y = 0.0036X + 0.22 (1)
It is represented by
From the above,
q / √D ≦ 0.0036X + 0.22 (1 ′)
The NOx value (x) can be suppressed to a desired value or less in the range of at least 10-70 ppm by designing the burner for the distance between both ends of the adjacent flame holes and the output per unit flame so as to satisfy the above.

  The present invention can be widely applied to a combustion apparatus equipped with a hydrogen diffusion combustion burner regardless of uses such as home use, business use, and industrial use.

DESCRIPTION OF SYMBOLS 1 ... Hydrogen combustion apparatus 2a, 2b, 2c ... Burner 3a, 3b, 3c ... Flame hole 4a, 4b, 4c ... Hydrogen supply piping 5a, 5b, 5c ... Flow control valve

Claims (4)

A hydrogen combustion apparatus that injects hydrogen gas from a plurality of flame holes and burns hydrogen by a diffusion combustion method,
For the allowable NOx value (X) (where 10 ppm ≦ X ≦ 70 ppm) and the required output Q (kW) , the number of flame holes n, the distance D (mm) between both ends of adjacent flame holes, and the output q per unit flame hole (= Q / n: kW) it is,
q / √D ≦ 0.0036X + 0.22
A hydrogen combustion apparatus comprising flame holes arranged so as to satisfy the above relationship . In claim 1,
q / √D ≦ 0.29
Hydrogen combustion apparatus characterized by comprising by arranging the burner port so as to satisfy the relationship. In claim 1,
q / √D ≦ 0.37
Hydrogen combustion apparatus characterized by comprising by arranging the burner port so as to satisfy the relationship. In claim 1,
q / √D ≦ 0.44
Hydrogen combustion apparatus characterized by comprising by arranging the burner port so as to satisfy the relationship.

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