JPS61231314A - Method of feeding pulverized coal and air into boiler furnace - Google Patents

Abstract

PURPOSE:To make the flow of a secondary fuel independent of the influence of the flow of a main burner by feeding a secondary pulverized coal for reduction combustion from a secondary fuel nozzle disposed at the rear stream of the main burner and in a direction rectangularly intersecting the main burner. CONSTITUTION:In a pair of faces 1b and 1b rectangularly intersecting another pair of faces 1a and 1a on which are provided upper stage main burners 4 and 4, secondary fuel burners 5 and 5 are disposed at the upper parts of the upper stage main burners 4 and 4 with a step H2 formed thereon. At the upper parts of the secondary fuel nozzles 5 and 5, overfire air nozzles 6 and 6 are disposed with a step H3 formed thereon and are directed in the same direction. Both main burners 3 and 4 and respective nozzles 5 and 6 are disposed in a plurality in parallel to each other in a lateral direction. The flow of the secondary fuel can be made independent of the influence of the flow of the main burner and a clear reduction zone X2 can be formed. The increase in the NOx reduction effect such as NOx of 150 ppm or less and a remarkable improvement in the unburnt part in ashes such as 5% or less, can be performed with use of work worse charcoal, for example.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a method for supplying pulverized coal and air into a boiler furnace using a pulverized coal three-stage combustion method.

Conventional technology Nitrogen oxides (hereinafter referred to as NOx) are produced in the boiler furnace.
The arrangement of the main burner, secondary fuel nozzle, and overfire air nozzle to specifically carry out the three-stage combustion method that suppresses and burns the It is necessary to decide by considering the volume. The opposed combustion type pulverized coal combustion boiler used in the large boiler shown in Figure 3, which is a conventional example, is a boiler 0.
0, the main burner east and the secondary fuel nozzle A/(2) are arranged vertically, and the main burner α°C and the secondary fuel nozzle (2) are connected to a pair of side walls (10a) (10b). ), the main burner α1) (2
) Opposite combustion takes place on the main axis of the furnace, and the swirling flames (2) violently collide and are disturbed in the center of the furnace, so that the combustion of the main pulverized coal (C1) in the combustion oxidation zone, which is the -fire combustion zone. The properties are extremely good, and the flow inside the furnace is also uniform.

Problems to be Solved by the Invention According to the above-described conventional system, the supply direction of the main burner αυ and the supply direction of the secondary fuel nozzle /'l are the same. Secondary pulverized coal (secondary fuel) (C2) for reduction is sprinkled into the thin flow of the swirling flame (2).

A clear reduction zone could not be formed. Therefore NO
The x suppression effect was small, and the amount of unburned matter generated was large.

That is, for example, Warkworth coal has NOx of 200pp.
m 1' could not be sufficiently reduced, and the unresolved amount in the ash was 10
The impact was significant, with both the percentage and the amount generated increasing.

Means for Solving the Problems In order to solve the above-mentioned problems, the method of supplying pulverized coal and air into a boiler furnace according to the present invention supplies secondary pulverized coal for reduction combustion downstream of the main burner and downstream of the main burner. A secondary fuel nozzle is provided perpendicularly to the burner, and overfire air is supplied from an overfire air nozzle located in the same direction as the secondary fuel nozzle in the wake of the secondary fuel nozzle. are doing.

According to the present invention, a well-defined reduction zone can be formed by making the flow of the secondary fuel independent from the influence of the flow of the main burner.

EXAMPLE A facing combustion type pulverized coal combustion boiler employed in a large-sized boiler, which is an example of the present invention, will be described below with reference to FIGS. 1 and 2. (1) is a square cylindrical boiler, and an exhaust gas outlet (2) is provided at the top. Said boiler (1)
At the bottom of , a pair of opposing surfaces (・la) (
The lower stage main burners (3) (3) are arranged in a manner that they face each other, and the downstream (upper) K' membrane step Hl)
Similarly, a pair of upper stage main burners (4) (4) are provided. In another pair of surfaces (1bX1b) orthogonal to the pair of surfaces (la) (la'), the upper stage main burner (4) (4)
A stingy primary fuel nozzle 1v (5 bars 5) is provided,
Then, an overfire air nozzle /l/ (6) (6) facing in the same direction is provided with a step (n3) t- above (swaft) of the secondary fuel nozzle (5) (5). Amphib burners (3) (4) and each nozzle Iv (5)
A plurality of (6) are arranged in parallel in the horizontal direction. A plurality of tube groups (7) are arranged in the upper part of the boiler (1).

(A1) is main combustion air, (A2) is overfire air, (C1) is main pulverized coal, (C2) is secondary pulverized coal, (
G) indicates combustion exhaust gas.

In the above example, the combustion oxidation zone (Xl) of the main pulverized coal (C1), the blowing reduction zone (X2) of the secondary pulverized coal (C2), and the overfire '2K (
A2) Low temperature oxidation slow combustion zone (x3) by blowing
) can be completely separated. That is, the main burners (3) (4
) Opposite combustion takes place on the main axis of the furnace, and the swirling flames (8) violently collide and are disturbed in the center of the furnace, so that the main pulverized coal (C1)
The combustibility is extremely good, and the flow inside the furnace is uniform.

Then, in the wake, secondary pulverized coal (C2
) is supplied, and in this case, the secondary fuel nozzle (5) is slightly biased to both sides to prevent the secondary pulverized coal (C2) from rushing into the main region at the center of the swirling flame (8). The blow reduction zone (x2) can be divided by Furthermore, overfire air (A2) is also supplied from the same direction as the secondary pulverized coal (C2) to make the flow uniform.

Effects of the Invention According to the method of the present invention having the above configuration, it is possible to form a clear reduction zone by making the flow of the secondary fuel independent from the influence of the flow of the main burner.
150 ppm or less, unresolved content in the ash is 5 parts or less, and NOx
The reduction effect can be increased and the unburned content reduction effect can be significantly improved.

[Brief explanation of the drawing]

Fig. 1 and Fig. 2 show one embodiment of the present invention, Fig. 1 is a longitudinal sectional view, Fig. 2 is a sectional view taken along the line ■-■ in Fig. 1, and Fig. 3 is a main part showing a conventional example. FIG. (1)...boiler, (1a)...pair of surfaces, (l
b)...Another pair of surfaces, (3)...Lower main burner,
(4)...Upper stage main burner, (5)...Secondary fuel nozzle, (6)...Overfire air nozzle, (A
2)...Overfire air, (CI)...Main pulverized coal, (C2)...Secondary pulverized coal, agent Mori
Yoshihiro Moto1'Figure 3.4-12. -1 5. -Secondary culture; Kr. Figure 2 Figure 2

Claims (1)

[Claims] 1. Secondary pulverized coal for reduction combustion is supplied from a secondary fuel nozzle arranged downstream of the main burner and in a direction perpendicular to the main burner. A method for supplying pulverized coal and air into a boiler furnace, characterized by supplying overfire air from an overfire air nozzle arranged in the same direction as a secondary fuel nozzle.