JPH0251084B2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a combustion method for reducing nitrogen oxides (NO _x ), which is particularly efficient in a compact combustion furnace.
The present invention relates to the above method capable of reducing NO _x .

An example of a conventional combustion method for reducing nitrogen oxides (hereinafter abbreviated as NO _x ) is shown in Figure 1.

In Figure 1, 01 is the combustion furnace, 02 is the combustion air duct, 03 is the main burner, 04 is the auxiliary air compartment, 05 is the afterburner, 06 is the afterburning air compartment, 07 is the combustion air, and 08 is the main Burner combustion air, 09 is auxiliary air, 10 is afterburning air (),
11 is afterburning air (), 12 is fuel, 13 is main burner fuel, 14 is afterburning fuel, 15 is main combustion flame, 16 is auxiliary combustion flame, 17 is A area, 18 is B area, 19 is region C, and 20 is a flue.

In FIG. 1, most of the total amount of fuel 12 sent by a fuel supply facility (not shown) is blown into the combustion furnace 01 from the main burner 03 as main burner fuel 13, and the rest is after-sales service. The burning fuel 14 is blown into the combustion furnace 01 from the afterburner 05 .

On the other hand, combustion air 07 is fed from a blower facility (not shown) and blown into the combustion furnace 01 from the main burner 03, the auxiliary air compartment 04, the afterburner 05, and the afterburning air compartment 06, respectively.

The amount of main burner combustion air 08 blown from the main burner 03 is less than the theoretical air amount of the main burner fuel 13, and the amount of auxiliary air 09 blown from the auxiliary air compartment 04 is the main burner combustion air 08
The sum of the amounts is approximately equal to or slightly larger than the theoretical air amount of the main burner fuel 13.

The amount of afterburning air ( ) 10 blown from afterburner 05 is less than the theoretical air amount of afterburner fuel 14, and in region B 18.
Creates a NO _x reducing atmosphere.

Afterburning air compartment 0
Afterburning air blown from 6 () 1
1 is for completely burning the unburned substances generated in the B region 18 of the NO _x reduction atmosphere, and the amount of injection thereof is an appropriate amount depending on the combustion situation.

NO _x reduction using such conventional combustion methods is carried out as follows.

Main burner fuel 1 blown from main burner 03
3 is combusted by main burner combustion air 08,
A main combustion flame 15 is formed, but due to lack of air, unburned fuel remains, while the flame becomes a low temperature flame and NO _x generation is suppressed. Unburnt fuel is A in combustion furnace 01
In region 17, combustion is completed by auxiliary air 09 blown in from auxiliary air compartment 04 provided in the upper stage on the same central axis as the fuel injection direction of main burner 03. As a result, the amount of NO _x in the exhaust gas decreases at the outlet of region A 17, resulting in a low-oxidation atmosphere. This NO _x reduction method is typically
This is called the fire-air method (OFA method) or the two-stage combustion method.

Main combustion flame 1 that completed combustion in area A 17
5 exhaust gas is a small amount of afterburning air () 10 blown from an afterburner 05 provided downstream of the auxiliary air compartment 04.
(below the theoretical air amount of the afterburning fuel 14) and the afterburning fuel 14 form an incomplete combustion sub-combustion flame 16, and the B area 18 in the combustion furnace 01 is filled with NO _x reducing atmosphere. to reduce NO _x generated from the main combustion flame 15.
At the same time, unburned matter is generated in the B area 18 in the NO _x reduction atmosphere, but it is completely combusted by the afterburning air ( ) 11 blown in from the afterburning air compartment 06 provided downstream of the B area 18. be done.

As a result, NO _x in the exhaust gas in the C region 19
The amount is further significantly reduced compared to the amount of NO _x in the A region 17. Therefore, the exhaust gas is discharged from the flue 20 to the outside of the furnace as clean combustion exhaust gas with low _NOx content and unburned matter.

As mentioned above, the conventional NO _x reduction combustion method is
This is an extremely effective NO _x reduction method that combines the OFA method and in-furnace denitrification method using afterburning.
Among these, in-furnace denitrification by afterburning is more effective as the residence time of exhaust gas in the reduction region is longer, and the NO _x reduction rate tends to be higher.

However, from the test research and actual test results to date, the peak of the NO _x reduction rate due to afterburning is almost constant regardless of the NO _x value level, and in order to increase the overall NO _x reduction effect, By increasing the NO _x reduction by the OFA method as much as possible,
It was found that it was necessary to keep the absolute value of NO _x low.

Figure 5 (described later) shows the experimental results (OFA
The relationship between the NO _x reduction rate (according to the method) and the distance L between the center of the main burner 03 and the auxiliary air compartment 04 (data α in Figure 5) is shown.
In order to increase the NO _x reduction effect by the OFA method, the center of the main burner 03 and the auxiliary air compartment 04 must be
It is necessary to make the distance L large.

However, in the conventional NO _x reduction combustion method, the auxiliary air compartment 04 is located mostly on the same axis as the fuel injection direction of the main burner 03,
It was installed above the top part of 3.
When the distance L between the center of the main burner 03 and the auxiliary air compartment 04 is increased for the purpose of measuring the NO _x reduction effect, there is a drawback that the height of the boiler inevitably increases.

The present invention provides a combustion method for reducing NO _x that can effectively reduce NO _x without increasing the height of the boiler.

That is, the present invention provides main combustion fuel and air,
In the nitrogen oxide reduction combustion method in which auxiliary air, afterburning fuel and air, and afterburning air are blown into the combustion furnace from the peripheral wall of the combustion furnace to combust the fuel, when viewed in the combustion gas flow direction of the combustion furnace, The present invention relates to a combustion method for reducing nitrogen oxides, characterized in that auxiliary air is blown from a position where the main combustion fuel and air injection position and the auxiliary air injection position do not overlap.

More specifically, in the method of the present invention, as shown in FIG. By arranging the main burner at a position on the furnace wall where the height from the center does not impair the NO _x reduction effect, effective NO _x reduction can be achieved without increasing the height of the boiler.

The method of the present invention is such that the fuel injection from the main burner and the auxiliary air injection from the auxiliary air compartment do not coincide in the furnace, as shown by the ← mark in Fig. 3, which will be described later.
The NO _x reduction rate becomes smaller.

The method of the present invention can be applied to boilers, various industrial furnaces, etc.

One embodiment of the method of the present invention is shown in FIGS. 2-4. FIG. 2 is a conceptual diagram, and FIG. 4 is a view taken along the - arrow in FIG.

In FIGS. 3 and 4, 101 is a combustion furnace;
102 is a combustion air duct, 103 is a main burner,
104 is an auxiliary air compartment (equipped with an auxiliary air jet nozzle that can be freely moved up and down);
105 is an afterburner, 106 is an afterburning air compartment, 107 is combustion air, 108 is main burner combustion air, 109 is auxiliary air, 110 is afterburning air (), 111 is afterburning air (),
112 is fuel, 113 is main burner fuel, 114
is the afterburning fuel, 115 is the main combustion flame, 116 is the secondary combustion flame, 117 is the A area, 118
is the B area, 119 is the C area, 120 is the flue, a is the center of the entire main burner 103, b is the center of the uppermost main burner, and L _B is the main burner height.

Note that the members indicated by numerals 101 to 120 above correspond to the members indicated by numerals 1 to 20 in FIG. 1 showing the conventional example, and have substantially the same configuration.

The difference between the above example and the conventional example is that, as shown in FIG.
The auxiliary air compartment 1 is located at a height equal to or lower than the top of the main burner.
The auxiliary air 109 from 04 is blown into a position in the furnace that does not overlap with the main burner fuel injection position,
The aim is to reduce NO _x .

The effect of the NO _x reduction combustion method of the present invention is different from that of the conventional method.
It is the same as the NO _x reduction combustion method, but has the following effects.

An auxiliary air compartment 104 equipped with an auxiliary air jetting nozzle that can be freely moved vertically from outside the combustion furnace 101 is arranged on the furnace wall surface other than the axis of the fuel jetting direction of the main burner 103, and the auxiliary air compartment 104 is injected into the furnace. In order to prevent the blown auxiliary air 109 from promoting _NOx generation from the main combustion flame 115, the direction of the auxiliary air 109 is adjusted by an auxiliary air jetting nozzle as shown by the ← mark in FIG. 4. Therefore, the main burner 103
Even if the distance L between the centers of the auxiliary air compartment 104 and the auxiliary air compartment 104 is set small, the NO _x reduction effect will not be impaired.

Figure 5 shows data obtained from the test furnace combustion test results. In Figure 5, NO _x1 is the amount of NO _x generated (ppm) due to combustion in the main burner only, NO _x2 is OFA
The amount of NO _x generated by the combustion method (ppm), L is the distance between the centers of the main burner and the auxiliary air compartment (m),
L _B indicates the main burner height (m), auxiliary air 09,
109 amount is (auxiliary air amount/total air amount) x 100 = 20 (%)
As mentioned above, α is the data obtained by the conventional method shown in FIG. 1, and β is the data obtained by the method of the present invention shown in FIGS. The NO _x reduction effect of OFA combustion is
It can be seen that the case where the auxiliary air compartment 104 of the conventional method is arranged on the fuel injection axis of the main burner 103 (data α) and the case according to the method of the present invention (data β) are substantially equivalent. Therefore, according to the present invention, in which the auxiliary air compartment 104 is provided on the furnace wall surface other than the fuel injection direction axis of the main burner 103 and the auxiliary air is blown in so as not to overlap with the fuel from the main burner, compared to the conventional method, Since the distance L between the auxiliary air compartment 104 and the center of the main burner 103 can be reduced while the NO _x reduction effect is comparable, the height of the boiler can be reduced without increasing the height.
This results in a reduction in NO _x .

[Brief explanation of the drawing]

Fig. 1 shows the conventional NO _x reduction combustion method, Figs. 2 to 4 show an embodiment of the method of the present invention, and Fig. 5 shows the experimental results to confirm the effectiveness of the method of the present invention. This is a chart showing the data.

Claims (1)

[Claims] 1 Main combustion fuel and air, auxiliary air, afterburning fuel and air, and afterburning
In the nitrogen oxide reduction combustion method in which burning air is blown into the combustion furnace from the peripheral wall of the combustion furnace to combust the fuel, when viewed in the combustion gas flow direction of the combustion furnace,
A combustion method for reducing nitrogen oxides, characterized in that auxiliary air is blown from a position where the main combustion fuel and air injection position and the auxiliary air injection position do not overlap.