JP2534426B2 - Fuel combustion method in exhaust gas boiler - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fuel combustion method in an exhaust gas boiler, which uses an exhaust gas containing oxygen such as exhaust gas from a diesel engine for power generation or a gas turbine for power generation as an oxygen source for fuel combustion.

[0002]

2. Description of the Related Art An example of a conventional exhaust gas boiler is shown in FIGS. FIG. 4 is a horizontal sectional view (IV-IV sectional view of FIG. 5),
FIG. 5 is a vertical sectional front view (VV cross section in FIG. 4). In these figures, a convection heat transfer surface (06) composed of a heat transfer tube group is adjacent to a boiler furnace (02) composed of a radiant heat transfer surface (01) composed of a water cooling wall. The convection heat transfer surface (06) is a steam drum (0
7), Boiler is formed with water drum (08).

Exhaust gas (09) containing oxygen is sent from a diesel engine, a gas turbine or the like (not shown) and enters a wind box (03) provided at the inlet of the boiler furnace (02). An air register (04) is installed in the air box (03) facing the inside of the furnace, and a burner gun (05) is installed at the center of the air register (04). The oxygen-containing exhaust gas (09) sent to the wind box (03) is blown into the furnace (02) through the air register (04).

On the other hand, the fuel (10) is sent to a burner gun (05) from a fuel supply device (not shown), and the boiler furnace (0
It is blown into the inside of 2), ignited by an ignition source (not shown), and separately mixed and burned with the exhaust gas (09) containing oxygen blown into the boiler furnace (02). The combustion gas (11) generated by the combustion of the fuel (10) passes through the radiant heat transfer surface (01) and the convection heat transfer surface (06), and after heat exchange, is discharged from the combustion gas outlet (12).

[0005]

In such a conventional fuel combustion method for a boiler, since the boiler furnace (02) is generally small for cost reduction, the boiler furnace (02) is often filled with flames, The flame collides with the low temperature radiant heat transfer surface (01) and the convective heat transfer surface (06), and the combustion deteriorates. Also, to prevent this, shorten the flame by using an air register.
It is necessary to increase the ejection speed of the exhaust gas (09) blown from (04) or increase the flow rate to increase the air ratio,
In that case, although the combustibility is improved, there is a drawback that the generation of nitrogen oxides (hereinafter referred to as NO _x ) is increased.

[0006]

In order to solve the above-mentioned conventional problems, the present invention provides a pre-combustion chamber which is covered with a refractory material and whose rear end is narrowed, a throat portion having a constant cross section and a throat portion which follow the narrowed portion. A main combustion chamber that communicates with the pre-combustion chamber through a divergent portion that continues to the throat, a burner gun provided on the front wall of the pre-combustion chamber, and a plurality of primary exhaust gas jets provided around the burner gun. Holes, a plurality of secondary exhaust gas ejection holes provided in the side wall of the pre-combustion chamber, a plurality of tertiary exhaust gas ejection holes provided in the throat, and a plurality of primary air provided in the divergent portion. The jet holes, a plurality of secondary air jet holes provided on the front wall or the side wall of the main combustion chamber, the exhaust gas jet holes, and the flow rates of the exhaust gas or air supplied to the air jet holes are respectively adjusted. Equipped with adjusting means, exhaust gas containing oxygen In an exhaust gas boiler used as an oxygen source for body fuel combustion, the total amount of oxygen contained in the exhaust gas supplied to the primary exhaust gas ejection hole and the secondary exhaust gas ejection hole for the fuel blown into the pre-combustion chamber from the burner gun. With an air ratio of 0.4 to 0.8, and the total amount of oxygen contained in the exhaust gas supplied to the primary exhaust gas ejection hole, the secondary exhaust gas ejection hole and the tertiary exhaust gas ejection hole is The present invention proposes a fuel combustion method in an exhaust gas boiler, which is characterized in that the combustion is completed by oxygen in the air supplied to the secondary air ejection holes and the theoretical oxygen amount required for combustion or less.

[0007]

In the preceding stage where the fuel is burned by the residual oxygen in the exhaust gas, the exhaust gas is supplied to the fuel so that the amount of oxygen is less than the theoretical amount, and the fuel is burned in a reducing atmosphere to generate NO _x and NO _x brought in by exhaust gas
Endeavor to return.

The combustion gas containing unburned fuel is oxidized at the outlet of the pre-combustion chamber by the combustion air supplied from the air ejection holes in the latter stage to complete combustion. Thus, the flame length is adjusted and NO _{x is} suppressed.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the method of the present invention will be described with reference to FIGS. FIG. 1 is a horizontal sectional view of the exhaust gas boiler (II cross section of FIG. 2), and FIG. 2 is a vertical sectional front view (II-II cross section of FIG. 1).
Is.

In these figures, (21) is a pre-combustion chamber which is covered with a refractory material and whose rear end is narrowed, and (02) is a throat portion having a constant cross section following the narrowed portion and a divergent portion continuing to the throat portion. It is a boiler furnace as a main combustion chamber, which communicates with the pre-combustion chamber (21) through the boiler furnace in sequence. A primary exhaust gas wind box (22a) is provided on the front wall of the pre-combustion chamber (21). Same primary exhaust gas box
A burner gun (23) was attached to the center of (22a), and the fuel (24) sent from a fuel supply facility (not shown) was attached to the tip of the burner gun together with the atomizing medium (25). Atomizer sprays into the pre-combustion chamber (21).

On the other hand, the exhaust gas (09) containing oxygen sent from a diesel engine, a gas turbine or the like (not shown) is a primary exhaust gas supply line (26a), a secondary exhaust gas supply line (26b) and a tertiary exhaust gas supply. It is sent to the primary exhaust gas wind box (22a), the secondary exhaust gas wind box (22b) and the tertiary exhaust gas wind box (22c) by the line (26c).

The primary exhaust gas (38a) sent into the primary exhaust gas wind box (22a) is passed through the flame stabilizer to the pre-combustion chamber (38a) from the primary exhaust gas ejection hole (34a) around the burner gun (23). 21) It is blown inside. The secondary exhaust gas (38b) sent into the secondary exhaust gas wind box (22b) is discharged from a plurality of secondary exhaust gas ejection holes (34b) formed in the side wall of the main combustion part of the pre-combustion chamber (21), It is blown into the pre-combustion chamber (21).

The fuel (24) sprayed into the pre-combustion chamber (21)
Is ignited by an ignition source (not shown) and burns while consuming oxygen in the primary exhaust gas (38a) and the secondary exhaust gas (38b).

The pre-combustion chamber (21) comprises a main combustion section and an outlet section. In the main combustion section, the atomized fuel (24) is the primary exhaust gas (38).
a) and secondary exhaust gas (38b) burned by oxygen,
The generated combustion gas (11) is NO _x generated by the combustion of the fuel (24) and the primary exhaust gas (38a) and secondary exhaust gas (38b).
The total amount of NO _x carried in is set to a volume that allows a sufficient retention time to be reduced.

Primary exhaust gas blown into the pre-combustion chamber (21)
The amount of oxygen supplied by (38a) and the secondary exhaust gas (38b) is 0.4 to 0.8 of the theoretical amount of oxygen required for combustion of the fuel (24) sprayed into the pre-combustion chamber (21) separately. Double. Therefore, the main combustion part of the pre-combustion chamber (21) is completely in a reducing atmosphere. Further, the temperature in the pre-combustion chamber (21) is maintained as high as possible (for example, 1300 ° C. or higher) in order to increase the reduction rate. The reason why the air ratio is 0.4 to 0.8 is that stable combustion cannot be achieved if the ratio is less than 0.4, and conversely, if it exceeds 0.8, the effect of reducing combustion is small.

FIG. 6 is a diagram showing the results of the relationship between the maximum gas temperature in the pre-combustion chamber and the NO _x concentration at the boiler furnace outlet in the combustion test conducted by the inventors of the present invention, and FIG. FIG. 4 is a diagram showing a relationship between an air ratio and a temperature in a pre-combustion chamber in the combustion test. In Japan of the NO _x emission standards, if the oil-fired utility boiler, but the concentration of NO _x in the exhaust gas is regulated to 150ppm or less, in order to achieve this regulation value, the temperature of the pre-combustion chamber 1300 FIG. 6 shows that the temperature needs to be higher than or equal to ° C. Further, it can be seen from FIG. 7 that the temperature in the pre-combustion chamber is maintained at 1300 ° C. or higher by setting the air ratio to 0.4 to 0.8.

The combustion gas (11) generated in the main combustion part of the pre-combustion chamber (21) is sent to the outlet part of the pre-combustion chamber (21) in a state containing unburned fuel due to insufficient oxygen combustion.

The outlet of the pre-combustion chamber (21) is narrowed down from the end of the main combustion section in consideration of the rectification effect of the combustion gas (11), and after a certain straight section (the throat section) is provided, It has a divergent shape and is connected to the front wall of the boiler furnace (02).

The outlet straight portion of the pre-combustion chamber (21) is provided with a plurality of tertiary exhaust gas ejection holes (34c) on its side wall, and a tertiary exhaust gas wind box (34c) is provided through the tertiary exhaust gas supply line (26c). The third exhaust gas (38c) sent to 22c) is blown into the combustion gas (11) to shorten the flame.

Combustion gas at the straight part of the outlet of the pre-combustion chamber (21)
(11) The amount of the tertiary exhaust gas (38c) blown into the primary exhaust gas (38a), the secondary exhaust gas (38b) and the tertiary exhaust gas (38c)
The total amount of oxygen supplied from the device is supplied so as to be equal to or less than the theoretical amount of oxygen required for combustion of the fuel (24) separately sprayed into the pre-combustion chamber (21). Therefore, the combustion reaction in the pre-combustion chamber (21) is a reduction reaction, and the N generated by the combustion of the fuel (24)
_Ox and the primary exhaust gas (38a), the secondary exhaust gas (38b), and the NO _x carried in the tertiary exhaust gas (38c) are reduced.

The combustion gas (11), which has burned a part of the unburned fuel by blowing in the tertiary exhaust gas (38c), still contains unburned fuel due to oxygen-deficient combustion, and remains in the pre-combustion chamber (2
1) It is blown into the boiler furnace (02) through the outlet divergent section.
In this divergent part, there is a primary additional air ejection hole (36a) for blowing the primary additional air (41a) to the combustion gas (11) blown into the boiler furnace (02).
There are multiple perforations. Also, on the front wall of the boiler furnace (02),
2 for blowing secondary additional air (41b) to the combustion exhaust gas (11) blown into the boiler furnace (02)
A plurality of the additional air ejection holes (36b) are formed. (29) is an additional air supply line, (32a)
Is a primary additional air air box, and (32b) is a secondary additional air air box.

Combustion gas (11) containing unburned fuel blown into the boiler furnace (02) from the pre-combustion chamber (21) is a primary additional air (41a) and a secondary additional air (41b).
Is blown in to complete its combustion.

Now, in the main combustion section of the pre-combustion chamber (21), the blow-in momentum of the primary exhaust gas (38a) and the secondary exhaust gas (38b) is increased so that the fuel (24) spray and the primary exhaust gas (38a) and By promoting diffusive mixing with the secondary exhaust gas (38b) and maintaining the temperature in the pre-combustion chamber (21) as high as possible, the NO _x reduction rate is increased and the flame is shortened.

The tertiary exhaust gas (3) blown into the high-temperature high-speed combustion gas (11) from the side wall of the straight part of the outlet of the pre-combustion chamber (21)
8c) is used to oxidize flue gas (11) containing unburned fuel due to oxygen deficiency combustion in the main combustion part. Third exhaust gas
Since the NO _x increases when the blowing speed and the blowing amount of (38c) are increased, it is necessary to gently blow a small amount. However, since the injection of the third exhaust gas (38c) is extremely effective for improving the combustibility and shortening the flame,
It is essential.

The primary additional air (41a) is blown from a plurality of primary additional air ejection holes (36a) drilled in the side wall of the outlet divergent portion of the pre-combustion chamber (21), but the combustion gas (11) The effect of shortening the flame is diminished by setting the mixing into the downstream portion as much as possible, but N
Combustibility can be improved while suppressing the amount of O _x generated. Secondary additional air (41b) is used for boiler furnace (02)
Multiple secondary additional air ejection holes on the front wall
From (36b), it is blown into the combustion gas (11) further downstream than the primary additional air (41a), is gently diffused and mixed, and has the same effect as so-called overfiring air.

Thus, the primary, secondary and tertiary exhaust gas (38
a), (38b), (38c) and the primary and secondary additional air (41a), (41b) are properly adjusted to achieve good combustion and short flame, and NO _x. Can be suppressed to a low level. Therefore, in this embodiment, adjustment means (not shown) for adjusting the flow rates of exhaust gas and air are provided.

Next, FIG. 3 is a horizontal sectional view showing an exhaust gas boiler to which the second embodiment of the present invention is applied. In this embodiment, a plurality of secondary additional air ejection holes (36b ')
However, it is different from the first embodiment in that it is provided not on the front wall but on the side wall of the boiler furnace (02), and the other configurations, functions and effects are the same as those of the first embodiment. . The secondary additional air ejection hole (36b ') may be provided closer to the center of the burner gun than the position shown in FIG. 3, and the inclination angle in the ejection direction may be made small (to face the boiler furnace outlet side). .

[0028]

According to the fuel combustion method for an exhaust gas boiler of the present invention, good combustion and shortening of flame are realized, and N
Generation of O _x can be suppressed low.

[Brief description of drawings]

FIG. 1 is a horizontal cross-sectional view (cross-section I-I in FIG. 2) showing an exhaust gas boiler to which an embodiment of the method of the present invention is applied.

FIG. 2 is a vertical sectional front view taken along line II-II of FIG.

FIG. 3 is a horizontal sectional view showing an exhaust gas boiler to which another embodiment of the method of the present invention is applied.

FIG. 4 is a horizontal sectional view (IV-IV section in FIG. 5) showing an example of a conventional exhaust gas boiler.

5 is a vertical cross-sectional front view taken along line VV of FIG.

FIG. 6 is a diagram showing the relationship between the maximum gas temperature in the pre-combustion chamber and the NO _x concentration at the boiler furnace outlet.

FIG. 7 is a diagram showing the relationship between the air ratio and the temperature in the pre-combustion chamber.

[Explanation of symbols] (01) Radiant heat transfer surface (water cooling wall) (02) Boiler furnace (main combustion chamber) (03) Wind box (04) Air register (05) Burner gun (06) Convection heat transfer surface (07) Steam drum (08) Water drum (09) Exhaust gas containing oxygen (10) Fuel (11) Combustion gas (12) Combustion gas outlet (21) Pre-combustion chamber (22a) Primary exhaust gas wind box (22b) Secondary exhaust gas wind Box (22c) Third exhaust gas wind box (23) Burner gun (24) Fuel (25) Spray medium (26a) Primary exhaust gas supply line (26b) Secondary exhaust gas supply line (26c) Third exhaust gas supply line (29) Additional Air supply line (32a) Primary additional air box (32b) Secondary additional air box (34a) Primary exhaust gas ejection hole (34b) Secondary exhaust gas ejection hole (34c) Third exhaust gas ejection hole (36a) Primary Additional air outlets (36b), (36b ') Secondary additional air outlets (38a) Primary exhaust gas (38b) Secondary exhaust gas (38c) Tertiary exhaust gas (41a) Primary adder Air (41b) 2-order Adi relational air

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Nobuaki Murakami Inventor No. 1-1 Atsunoura-machi, Nagasaki City Nagasaki Research Institute, Mitsubishi Heavy Industries Ltd. (72) Tsuneo Kobayashi 12 Nishiki-cho, Naka-ku, Yokohama Mitsubishi Heavy Industries Ltd. (56) References JP-A-58-96905 (JP, A) JP-A-51-82434 (JP, A) Actual development Sho-60-43832 (JP, U)

Claims (1)

(57) [Claims] 1. A pre-combustion chamber which is covered with a refractory material and whose rear end is narrowed, and a pre-combustion chamber which is connected to the pre-combustion chamber through a throat portion having a constant cross-section following the narrowed portion and a diverging portion continuing to the throat portion in order. A main combustion chamber, a burner gun provided on the front wall of the pre-combustion chamber, and a plurality of 1s provided around the burner gun.
A secondary exhaust gas ejection hole, a plurality of secondary exhaust gas ejection holes provided in the side wall of the pre-combustion chamber, a plurality of tertiary exhaust gas ejection holes provided in the throat, and a plurality of secondary exhaust gas ejection holes provided in the divergent portion. The primary air ejection holes, a plurality of secondary air ejection holes provided on the front wall or the side wall of the main combustion chamber, the exhaust gas ejection holes and the flow rate of the exhaust gas or air supplied to the air ejection holes are In the exhaust gas boiler, which comprises adjusting means for adjusting each, and uses the exhaust gas containing oxygen as an oxygen source for liquid fuel combustion, for the fuel blown into the pre-combustion chamber from the burner gun, the primary exhaust gas ejection hole and the above The total amount of oxygen contained in the exhaust gas supplied to the secondary exhaust gas ejection holes is set to an air ratio of 0.4 to 0.8, and the primary exhaust gas ejection holes, the secondary exhaust gas ejection holes and the tertiary exhaust gas are exhausted. The oxygen content total amount of exhaust gas supplied to the injection holes and less theoretical amount of oxygen required for combustion of the fuel,
A method of burning fuel in an exhaust gas boiler, characterized in that combustion is completed by oxygen in the air supplied to the secondary air ejection holes.