JPS63286602A - Black-liquor recovery boiler - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application Field> The present invention relates to the structure of a black liquor recovery boiler provided with a tertiary air port that reduces the amount of smelt particles carried over to the outside of the boiler.

<Prior Art and its Problems> As a conventional airport using swirling flow, a dual air register that gives swirling to secondary air is known.

FIG. 4 is a diagram showing the concept of a conventional boiler that performs two-stage combustion. The combustion air ratio in the burner zone in the furnace is set to 1 or less to form a reducing atmosphere to suppress the generation of NOx, and the air from the secondary air port causes complete combustion in the upper part.

This secondary air port is used as a fifth air port to improve the mixing with the incompletely combusted exhaust gas generated in the burner zone and to improve combustion.
As shown in the figure, a type with dual air registers has been adopted that strengthens the air swirling force and the horizontal penetration force of the furnace.

In conventional recovery boilers, the damper structure controls the amount of tertiary air, but does not have a structure that strengthens the swirling force. (Fig. 6) Conventional measures to prevent smelt carryover include increasing the size of the furnace and lengthening the residence time of exhaust gas in the furnace to allow smelt particles to fall naturally, and reducing the amount of primary and secondary air to prevent smelt from charpet. The aim was to reduce the amount of carryover.

With such conventional means of enlarging the furnace, the amount of carryover is reduced by increasing the residence time of smelt particles in the furnace, but at the same time, the furnace outlet gas temperature decreases, the required height of the superheater increases, and the cost of the boiler increases. do. Again - next,
Reducing the amount of secondary air will make the chirpette function unstable, and secondly, the air flow velocity of the secondary air port will decrease, creating an opportunity for each air port to become clogged with dust, so the amount of air supplied must be extremely restricted. I can't. Further, as schematically shown in FIG. 7, the momentum of the tertiary air in the horizontal direction is small and it makes a short pass toward the upper part of the furnace as indicated by reference numeral 11, so that the effect of suppressing the scattering of the smelt particles 12 cannot be obtained due to the momentum of the tertiary air itself.

<Object of the Invention> The object of the present invention is to propose a structure of a black liquor recovery boiler that reduces carryover of smelt particles.

Overview of means for achieving this> The present invention provides for the
This paper proposes a structure of a black liquor recovery boiler in which a plurality of swirling air ports each having a plurality of swirling air nozzles and a through air port formed at the central axis thereof are provided as tertiary air ports.

<Example 1> FIG. 8 is a drawing showing the concept of a recovery boiler.

FIG. 6 shows the combustion air supply system. In general, a recovery boiler maintains a good combustion state of the t-Yerbet using secondary air, and achieves complete combustion using upper tertiary air. Some of the smelt from the charpet is carried above the furnace along with the combustion gases. Normally, the amount of tertiary air in a recovery boiler is smaller than the primary and secondary air, but this air (symbol 17
If a swirling force is applied to the smelt (as shown in Figure 2) to push the carried over particles 12 back into the charpet as shown in Fig. 2, the amount of smelt discharged along with the gas outside the furnace will be reduced compared to the conventional method. In addition, the rotating airport of the present invention has a structure shown in FIG. 1 in order to prevent troubles caused by dust clogging compared to the vane type register used in general fossil fuel fired boilers.

The axis of the rotating air nozzle 14 is inclined toward the boiler side wall (water tube wall), and each base is located on one circumference, facing inward from the circumferential cutting line in the front view (Fig. 1), A suitable swirling flow is generated together with the air from the axis of the through air port 15.

<Example 2> Furthermore, in order to prevent molten smelt particles floating in the furnace from adhering to the air port, a cold air supply pipe 18 before preheating was provided as tertiary air to rapidly cool the dust near the throat and prevent its welding. .

(FIG. 3) <Embodiment 6> Furthermore, by making the axial direction of the swirling air 17 downward by an angle α shown in FIG. 6 from the horizontal direction, the effect of pushing back the scattered smelt 12 to the chirpette 6 is improved.

By blowing tertiary air with strong swirling horizontally or diagonally downward into the furnace, the upward (floating) momentum of the smelt particles is reduced, so the amount of smelt that is discharged out of the furnace along with the gas is reduced compared to conventional systems. Decrease. Furthermore, floating smelt that is melted by blowing cold air near the air port is rapidly cooled and solidified, so that welding of smelt to the air port can be suppressed. Furthermore, since dust clogging is a problem with conventional ones with registers, a swirling force is applied to the air by using a structure that is less likely to be clogged with dust other than the register.

Effects> By implementing the present invention, the amount of smelt particles entrained in gas and discharged out of the furnace can be reduced without increasing the size of the furnace. This not only reduces costs by making the furnace more compact, but also reduces the need for a superheater due to an increase in the furnace outlet gas temperature (in the past, the furnace outlet gas temperature was low because the furnace was enlarged due to smelt carryover). can.

By preventing the discharge of smelt particles to the outside of the furnace, it is possible to suppress dust troubles in the superheater and evaporative water tube 1 economizer tube group on the downstream side of the gas, and it is also possible to reduce the consumption of soot blower steam.

[Brief explanation of the drawing]

FIG. 1 is a front view of a rotating airport according to a first embodiment of the present invention, FIG. 2 is an explanatory diagram of the effect of pushing back particles by implementing this invention, and FIG. Figure 4 is a side sectional view of the boiler showing the relationship between the burner and secondary air port of a normal heavy oil-fired boiler, and Figure 5 is a schematic diagram of the dual air register and swirling air. , Figure 6 (A) is a side sectional view of a conventional tertiary air port of a black liquor recovery boiler, (B) is its front view, and Figure 7 shows that the conventional tertiary air port is insufficient in trapping particles in exhaust gas. FIG. 8 is a side sectional view showing the arrangement of air ports in a conventional black liquor recovery boiler. 1... Burner 2... Secondary airport 3...
・Air register 4...Damper 5...Tertiary airport 6...Charpet 7...Air preheater
8...Black liquor burner 9...Tertiary air port 10...-Next, secondary air port 11...Tertiary air 1
2...Carry over smelt 1...-Next, exhaust gas generated by secondary air 14...
Rotating air nozzle 15...through air port 16...
New tertiary airport 17...Swivel tertiary air Figure 1 Figure 2 Figure 3 -LJI-

Claims (1)

[Claims] 1. The black liquor recovery boiler is characterized in that a plurality of swirling air ports each having a plurality of swirling air nozzles and a through air port formed at the central axis thereof are provided as tertiary air ports on the upper side wall of the chirpette of the black liquor recovery boiler. Black liquor recovery boiler. 2. The black liquor recovery boiler according to claim 1, further comprising a cold air supply pipe for supplying the tertiary air port.