JPH03260504A - Fluidized bed type combustion device and combustion method - Google Patents

Abstract

PURPOSE:To perform a high efficient combustion of not-yet burned particles at a free board under an occurrence of a Rankin type circulation flow at the free board formed within the second reaction chamber by a method wherein a circulating vane fixed at an inlet port of the second reaction chamber and an air supplying pipe for injecting air in the same direction as the circulating direction of the circulating vane are provided. CONSTITUTION:Combustion gas is circulated by a circulating vane 13 mounted at an inlet port of a second reaction chamber B and then fed into the second reaction chamber B. The circulating vane is not connected to the outer wall 15 of the second reaction chamber B, but there is a clearance (d) between them, so that the gas at the outer wall 15 of the second reaction chamber does not receive any circulating force from the circulating vane 13. This clearance (d) and an angle theta between the circulating vane 13 and the center of the shaft may also influence over a formation of Rankine eddy flow within the second reaction chamber B. An air supplying pipe 116 is arranged in the center of the shaft in the second reaction chamber B and then a free board air supplying nozzle 14 is opened. This air supplying nozzle 14 has its blowing port mounted in such a direction as one having an angle phi in respect to a radial direction. Under such an arrangement of the angle phi, circulation of combustion gas 108 within the second reaction chamber B is assisted under an injection of the free board air. Accordingly, mean staying time of particle is extended and combustion efficiency of the particles at the free board within the second reaction chamber B is increased.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an apparatus and method applied to the combustion of solid fuels such as coal and liquid fuels such as CWM and heavy oil.

[Prior Art] Conventionally, fluidized bed combustion apparatuses and methods have been put into practical use that use limestone, dolomite, or the like as a fluidized medium to combust coal or the like and simultaneously perform desulfurization.

A typical example of such a conventional method will be explained based on FIG. 7.

The fluidized bed (11) consists of a dispersion plate (
6) Formed on top. A fluidized bed is a state in which particles are suspended by gas supplied from below the dispersion plate and mixed and stirred by the gas. board(
12) exists. Coal (102) and limestone (103)
are the fluidized bed (
11), and the air (101) is supplied to the air supply nozzle (
1), passes through a wind box (10), and is supplied to a fluidized bed (11) from a distribution plate (6) having a large number of small holes.

Cooling pipes (
4) are supplied with cooling water (105) and (104), respectively, in order to remove the reaction heat in the fluidized bed (11).

Coarse particles in the fluidized bed (11) are discharged from the discharge pipe (9). The combustion gas is separated by gravity classification from unburned particles and desulfurization agent particles entrained in the combustion gas in a freeboard (12), and then is discharged from an exhaust port (7) as a combustion exhaust gas (107) containing dust.

Low No., when combustion is not oriented, the air ratio is 1.1 to 1.
It is 2.

When aiming for low No. combustion, reduce the amount of air (101) to reduce the air ratio of the fluidized bed (ratio of supplied air amount/air amount required for complete combustion) to 1.0 to 1.05. By doing so, the amount of No. (No. No. 2, etc.) generated is kept low. By reducing the air ratio of the fluidized bed, low N
Compared to the case where Ox combustion is not directed, CO in the generated gas and unburned particles accompanying the gas increase. Therefore, air (106) is supplied from the nozzle (16),
CO and unburned particles are combusted in the freeboard (12) to prevent a decrease in combustion efficiency.

[Problem to be solved by the invention]

In conventional fluidized bed combustion equipment, when the air ratio was reduced to achieve low No. combustion, combustion efficiency decreased and SOX increased. Furthermore, even if the air ratio was reduced, the amount of Neo generated could not be reduced. Furthermore, even when unburned particles generated in a fluidized bed are combusted by blowing air into the freeboard, the residence time of the unburned particles in the freeboard is short, so it is difficult to combust the unburned particles with high combustion efficiency. Ta. In addition, since the peripheral wall of the freeboard is constituted by a water-cooled wall, the temperature of the freeboard cannot be easily increased.

[Means to solve the problem]

In order to solve the above-mentioned conventional problems, the present invention provides a first tube whose side wall is composed of a cooling water tube and has an air supply port, a solid fuel or liquid fuel supply port, a desulfurization agent supply port, and a combustion residue discharge port. a second reaction chamber communicating with and disposed above the upper end of the first reaction chamber, the peripheral wall of which is made of a fireproof and insulating material, and having a gas outlet at the top; A cooling water pipe provided inside the first reaction chamber, a swirling vane fixed to the inlet of the second reaction chamber, and a swirling vane opening into the second reaction chamber in the same direction as the swirling direction of the swirling vane. A fluidized bed combustion apparatus characterized by comprising: an air supply pipe that blows air into the fluidized bed; At the same time, the fuel is burned at 800°C to 870°C in the fluidized bed, and the generated gas is then swirled in the second reaction chamber to generate a Rankine vortex, and further in the second reaction chamber. This paper proposes a fluidized bed combustion method characterized by burning unburned particles in gas at 880°C to 1000°C using blown air.

[Effect]

In the present invention, by making the second reaction chamber, which corresponds to the conventional freeboard part, have a fireproof and insulating structure, the amount of sensible heat of the generated gas dissipated from the wall to the outside of the system due to heat transfer can be reduced. The temperature of the gas generated therein can be easily increased.

In addition, a swirl vane provided at the entrance of the second reaction chamber and a second
The gas in the second reaction chamber is swirled by the air blown into the second reaction chamber, and the swirling flow is made into a Rankine vortex where the flow velocity in the swirling direction is constant in the radial direction. A situation arises in which the particles swirl within the space of the reaction chamber, but the speed at which they approach the walls is very slow, and regions with high particle concentration occur in the swirling flow. By making the gas in the second reaction chamber a swirling flow of a Rankine vortex in this way, it becomes possible to make the residence time of the particles longer than that of the gas.

Furthermore, in the present invention, since the temperature in the second reaction chamber is made higher than that in the fluidized bed in the first reaction chamber, the amount of SZO decomposed increases. However, depending on the increased value, the desulfurizing agent containing calcium is re-decomposed due to the temperature increase, resulting in the release of SOz. If the temperature is the same as that of the fluidized bed, the amount of SO2 released from the deflow agent will be greater at normal pressure than when pressurized, so depending on the pressurization situation, N, 0. SO□The temperature of the second reaction chamber is selected according to the amount of unburned matter generated, and the amount of decomposition of N and O is large.802
Select a temperature at which re-emission of is small. 880℃+ at normal pressure
When pressurizing at 16a ta, up to 1000''C is required.

〔Example〕

Fig. 1 is a longitudinal cross-sectional view of a fluidized bed combustion apparatus showing an embodiment of the present invention, Fig. 2 is a cross-sectional view taken along ■-■ in Fig. 1, and Fig. 3 is a cross-sectional view taken along ■-■ in Fig. 2; FIG. 4 is a sectional view taken along line IV-IV in FIG. 1.

First, in FIG. 1, A is a first reaction chamber, the side wall of which is composed of cooling water tubes to form a water-cooled wall (5). An air supply nozzle (1), a coal supply nozzle (2), a limestone supply nozzle (3) and a combustion residue discharge pipe (9) are provided.

Reference numeral B designates a second reaction chamber, which communicates with and is disposed above the upper end of the first reaction chamber A, and has a peripheral wall (15) made of a fireproof heat insulating material, and has an exhaust gas pipe in the upper part. (17) is provided.

A fluidized bed (11) is formed on a distribution plate (6) in the first reaction chamber A surrounded by a water-cooled wall (5).

Coal (102) and limestone (103) are supplied from the coal supply nozzle (2) 1 limestone supply nozzle (3) to the fluidized bed (11), and air (101) is supplied from the air supply nozzle (1) to the wind box (10). The liquid is then supplied to the fluidized bed (11) through a distribution plate (6) having a large number of small holes. Cooling water (104) and (105) are supplied to the cooling pipe (4) and water cooling wall (5) installed in the fluidized bed (11), respectively, in order to remove the reaction heat in the fluidized bed (11). has been done. Coarse particles in the fluidized bed (11) are discharged from the discharge pipe (9).

The combustion gas is given a swirl by a swirl vane (13) installed at the entrance of the second reaction chamber B and is introduced into the second reaction chamber B. The swirl vane has a structure as shown in FIGS. 2 and 3. The swirl vane is not connected to the outer wall (15) of the second reaction chamber B, and there is a gap d, so the gas on the outer wall (15) side of the second reaction chamber flows through the swirl vane (13).
Does not receive turning force from

Therefore, the flow velocity in the swirling direction can be distributed such that the flow velocity is high at the center and slow at the outer circumference. Such a gap d between the swirl vane (13) and the second reaction chamber outer wall (15) shown in FIG. 2 has a great influence on the Rankine vortex formation in the second reaction chamber B. Furthermore, the flow velocity in the swirling direction and the angle θ between the swirling vane (13) and the axis shown in FIG. Therefore, since d and θ are factors that influence the combustion efficiency of unburned particles in the second reaction chamber B, they are determined through experiments so as to have optimal values.

An air supply pipe (116) is arranged in the narrow part of the second reaction chamber B, and a freeboard air supply nozzle (14) is opened. As shown in FIG. 4, this air supply nozzle (14) has an outlet installed in a direction forming an angle φ with respect to the radial direction. With such an angle φ, swirling of the combustion gas (108) in the second reaction chamber B is facilitated by blowing out freeboard air. Therefore, the angle φ is experimentally determined to be the optimum value.

Figures 5 (al and bl are diagrams showing the flow velocity distribution in the swirling direction in the second reaction chamber B. Figure 5 ta) are diagrams showing the flow velocity distribution in the swirling direction in the second reaction chamber B.
Part 1 (81 part (TV-IV chain line part in Figure 1), that is, the distribution of the flow velocity in the swirling direction near the air supply nozzle (14) part, box 5) is the part in Figure 5 (center of C1). , that is, the distribution of the flow velocity in the swirling direction in the upper part of the second reaction chamber B. First, in the 61st part, the flow velocity in the swirling direction is almost uniform in the radial direction, and a Rankine vortex is generated.

In this part, most of the particle trajectories rotate as shown by the dashed line (109) in FIG. Then, as shown by the dotted line (110), a small percentage of particles move to the wall, ride the downward flow of gas near the wall, and fall back into the fluidized bed.

In addition, as shown in the fifth box (in the upper part of the reaction chamber B in FIG. 2), the swirling flow velocity decreases overall, but the Rankine vortex is still maintained. The average residence time of the main combustion gas (Lo8) in the second reaction chamber B is about 3 seconds, but the particles spend a longer time riding the Rankine vortex and swirling at the same height. Average residence time is 10
By extending the average residence time of zero particles to more than a second, the combustion efficiency of the particles in the friboard in the second reaction chamber B increases. According to the test, the combustion rate of particles increased under a pressurized state of 16ata, so the fluidized bed temperature was 850℃.
, combustion efficiency of 99.5% at freeboard temperature of 900℃,
Sow 40111pm, NOx 40ppm, Nz
We were able to achieve low pollution and high combustion efficiency using O5pp.

In addition, the combustion gas (108) is finally passed through the exhaust gas pipe (17).
It is discharged outside the twine.

In order to generate a Rankine vortex in which the flow velocity in the swirling direction of the swirling gas flow is uniform in the radial direction in the second reaction chamber B, three conditions must be considered to The suction method is selected.

The three conditions are: (1) the axial position of the air supply nozzle (14), (2) the angle φ that the blowing direction of the air supply nozzle (14) makes with respect to the radial direction, and (2) the blowing speed of the air into the freeboard. .

FIG. 6 is a longitudinal sectional view of a fluidized bed combustion apparatus showing a second embodiment of the present invention. In this embodiment, combustion gas is taken out of the system through an exhaust gas pipe (27) provided concentrically with and surrounding the air supply pipe (216). The other configurations, functions, and effects are the same as those of the first embodiment, so detailed explanations will be omitted.

〔Effect of the invention〕

In the present invention, by providing a swirling vane at the entrance of the second reaction chamber B and blowing air in the same direction as the swirling direction, a Rankine vortex is created in the freeboard formed in the second reaction chamber B. By generating a swirling flow, it has become possible to burn unburned particles in the freeboard with higher efficiency than before. Therefore, the air ratio of the fluidized bed is 1.0 to 1.0.
5, the combustion efficiency of the entire device did not decrease, and the combustion efficiency in the freeboard increased, so the gas temperature in the freeboard rose easily, making it possible to decompose N and O.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view of a fluidized bed combustion apparatus showing one embodiment of the present invention, FIG. 2 is a cross-sectional view taken along the line ■-■ in FIG.
FIG. 4 is a sectional view taken along IV-fV in FIG. 1. FIG. 5 is a diagram showing the radial distribution of the flow velocity in the swirling direction in the reaction chamber of FIG. 2. FIG. 6 is a longitudinal sectional view of a fluidized bed combustion apparatus showing a second embodiment of the present invention. FIG. 7 is a longitudinal sectional view showing an example of a conventional fluidized bed combustion apparatus. A...First reaction chamber, B...Second reaction chamber (
1)...Air supply nozzle, (2)...Coal supply nozzle. (3)...Limestone supply nozzle, (4)...Cooling pipe (
5)...Water cooling wall, (6)...Dispersion plate. (7), (17), (27)...Exhaust gas pipe (8)
...Wind box wall, (9)...Exhaust pipe 00)...Wind box,
00...Fluidized bed. 0'! J...Free board, 03)...Swirl blade. 041... Air supply nozzle, 051... Peripheral wall of the second reaction chamber. (16), (116)...Air supply pipe, (101)
···air. (102)...coal, (103)...limestone. (104), (105)...Cooling water, (106
)...Freeboard air (107)...Combustion exhaust gas, (108)...Combustion gas. 1st decoy

Claims (1)

[Claims] 1) The side wall is composed of a cooling water tube, and has an air supply port,
A first reaction chamber having a solid fuel or liquid fuel supply port, a desulfurization agent supply port, and a combustion residue discharge port, the first reaction chamber communicating with and disposed above the upper end of the first reaction chamber, and having a peripheral wall made of fireproof heat insulating material. a second reaction chamber having a gas outlet at the top, a cooling water pipe provided inside the first reaction chamber, and a swirl fixed to the inlet of the second reaction chamber. A fluidized bed combustion apparatus comprising: a blade; and an air supply pipe that opens into the second reaction chamber and blows out air in the same direction as the swirling direction of the swirling blade. 2) In the fluidized bed combustion apparatus according to claim 1, the calcium-containing desulfurizing agent is fluidized with air in the first reaction chamber to form a fluidized bed, and the fuel is heated in the fluidized bed at 800°C to 870°C. ℃ combustion, the generated gas is then swirled in a second reaction chamber to generate a Rankine vortex,
Furthermore, a fluidized bed combustion method characterized in that unburned particles in the gas are combusted at 880°C to 1000°C by air blown into the second reaction chamber.