JPS5812483B2 - Fluidized bed combustion equipment - Google Patents

Description

[Detailed description of the invention] The present invention relates to a fluidized bed combustion apparatus.

A conventional fluidized bed combustion apparatus will be explained based on FIGS. 1 to 3.

The fluidized bed combustion furnace has a wind box 6 at the bottom and an air distribution plate 4 above it.
is provided.

Fuel particles (for example, coal particles) 17 are stored in a hopper 15 and fall through a chute 14 connected below it,
The fuel is scraped down into the chute 12 at a constant speed by a raw cliff feeder 22 composed of a rotor 13 and rotating blades 21, and reaches the fuel supply pipe 9.

The fuel 11 that has reached the fuel supply pipe 9 is blown into the largest part of the fluidized bed 1, directly above the air distribution plate 4, by the conveying air 10.

On the other hand, a part of the air 7 is introduced into the wind box 6 and the air distribution plate 4
It is blown up from a large number of small holes 41 provided in the.

Another part of the air 10 is led into the fuel supply pipe 8 and blows fuel particles into the fluidized bed 3.

A large number of fuel supply pipes 8 are provided in one furnace in order to distribute fuel uniformly, and their jet ports 18 are located approximately 1 m above the air distribution plate 4.
It is common that one is provided for each square.

The difference between the air supply pressure and the pressure of the free board 5 is the sum of the pressure drop when passing through the air distribution plate 4 and the pressure to keep the fluidized bed 1 floating.In a practical furnace, the difference is the pressure inside the wind box 6. 1
000 to 1500 miAq is selected.

The pressure inside the furnace is as shown in Figure 2, which is a graph in which the horizontal axis represents the pressure and the vertical axis represents the vertical position of the furnace. The pressure increases to point 103 (indicated by pressure 108)
do.

Furthermore, the pressure loss 106 at the distribution plate 4 is added, and the pressure inside the wind box 6 reaches the pressure shown by the line 105.

Normally, the pressure of the freeboard 5 is set to be approximately equal to the atmospheric pressure 20 due to the structure of the equipment following the furnace.

On the other hand, the air pressure supplied to the fuel supply pipe 8 must be balanced with the total pressure 105 of the air 42 blown up from the hole 41 of the air distribution plate 4, and the connection point 19 between the chute 12 and the fuel supply pipe 8 The differential pressure above the hopper 20 is the pressure indicated by the approximate line 105.

Due to this pressure difference, air flows back through the fuel supply pipe 8 at the connection point 19.
A flow of air is generated upward through the chute 12, and as shown in FIG.
4 to between two adjacent blades 21, and in extreme cases, air flowing upward through the chute 14 would prevent the fuel from falling in the same area.

The fuel supply pipe 8 is deep inside the furnace, and if the amount of conveying air 10 decreases due to some kind of accident, the temperature inside the pipe will rise, causing the fuel particles 9 stuck in the pipe to ignite and burn out, and the pipe 8 to burn out. It had reached this point.

The number of fuel supply pipes 8 provided in one furnace is large, maintenance control is complicated, and failures occur frequently.

Therefore, the purpose of the present invention is to eliminate the above-mentioned drawbacks, and the fuel particles distributed by the rotary feeder are guided into a cyclone to be separated into coarse particles and fine particles, and the coarse particles are carried by the air flow to the furnace in the free board section. The fuel is guided to a fuel nozzle installed on the wall, and is ejected from the same nozzle along with the air flow.The fine powder is carried along with the air flow and guided from the air distribution plate to the fine powder nozzle that looks into the furnace, and is ejected from the same nozzle along with the air flow. By adjusting the pressure of the air flow appropriately, backflow from inside the furnace is prevented, and furthermore, backflow of air into the rotary leaf feeder is prevented. Since the fuel is ejected with the flow, the nozzle that supplies the fuel is cooled by air, which prevents nozzle burnout, and the coarse particle fuel nozzle has a large dispersion of the air flow and fuel that is distributed within the furnace. Since the amount of fine powder is small compared to coarse particles and fewer fine powder nozzles are required, the total number of nozzles is small and maintenance and inspection is easy. The air ejected together with the particles causes two-stage combustion in the furnace, providing a fluidized bed combustion device that generates fewer nitrogen oxides.

Next, the invention will be specifically explained based on an embodiment shown in FIGS. 4 and 5.

The fuel nozzle 51 is provided on the furnace wall 2 of the combustion furnace 1,
It is pivotally supported by a pivot 53 at the end of the fuel supply duct 52, and by rotating a rotary lever shaft 54, the injection angle into the combustion furnace 1 can be adjusted.
5 surrounds the fuel nozzle 51, communicates with the air duct 56, and controls the dispersion of fuel particles ejected from the fuel nozzle 51 and the combustion air.
Reference numeral 7 is provided on the air distribution plate 4 provided at the lower part of the combustion furnace 1 so that the nozzle slightly protrudes from the air distribution plate 4, and is in communication with a duct 58 arranged in the wind box 6. A cyclone 59 that separates particles and fine powder has a lower part communicating with a fuel nozzle 51 through a duct 52 through which coarse particles pass, and an upper part communicating with a fine powder nozzle 57 through a duct 58 through which fine powder passes.

A booster fan 60 is provided in the middle of the duct 58 to increase the pressure inside the duct 58.

The blower 62 is connected to the wind box 6 through a duct 63 through which an air preheater 64 is disposed and a part of the discharged air passes, and a part of the remaining discharged air is communicated with the upstream part of the air preheater 64. A damper 65 installed in the middle of passing
The chute 12 of the fuel supply device 20 is connected to the duct 66 adjacent to the cyclone 59, and the fuel particles falling in the chute 12 are transferred to the air in the duct 66. It was then sent to Cyclone 59.

The remainder of the discharged air is transferred to a duct 52 which is connected to a duct 52 via a duct 68 branched from the middle of the duct 66 and a damper 6T, which is connected to a chute 59' of a cyclone 59, and the fuel that has fallen down the chute 59' is coarse particles are fed into the fuel nozzle 51.

A duct 56 communicating with the wind box 55 is connected to the duct 68 .

Fuel particles are placed in each duct 61.59', 52.58
The air when conveyed by the blower 62 is 1000 to 1500
It is pressurized to about mmAq and sent out to the duct 63, and most of it is sent to the wind box 6 through the air preheater 64, and blown into the fluidized bed 3 through the air distribution plate 4.

The remaining air is removed by the damper 65 and the pressure is reduced to 200~300i.
The pressure is reduced to about iAq and guided to the duct 66.

A portion of the air therein reaches the fuel supply machine 20.

The fuel particles 17 are stored in the hopper 15, fall through the chute 14, the rotary feeder 22, and the chute 12, reach the duct 61, and are transported by the above-mentioned air and fed into the cyclone 59.

In the cyclone 59, it is separated into coarse particles and fine powder.

The coarse particles fall into the chute 59', pass through a duct 68 and a damper 67, are conveyed by appropriately pressure-regulated air, pass through a duct 52, and are ejected from the fuel nozzle 51 and burned.

The fine powder passes through a duct 58 and is pumped to a booster fan 60.
After being pressurized to about 0 mmAq, it is blown into the lower part of the fluidized bed through a duct 58 and a fine powder nozzle 57, where it is combusted.

The fuel nozzle 51 is housed in an air box 55, and air is introduced into the air box 55 through a duct 56.

As an example of the structure of the nozzle 51 for spraying coarse particle fuel, a structure as shown in FIGS. It is pivotably supported, and the spraying direction can be changed to the left or right using a rotating lever shaft 54.

Further, since air is supplied from a duct 56 to the wind box 55 surrounding the nozzle 51, it is also used for fuel dispersion and combustion.

Since the fuel nozzle 51 opens into the freeboard section 5, the air pressure of the fuel supply system can be selected as low as 100 to 300 mmAq.

Therefore, the fuel particle chute 12, the rotary feeder 2
It is possible to avoid falling failures within 2.

The fine powder system is also equipped with a cyclone 59 and a booster fan 60 in the duct 58, so that the supply pressure can be increased freely, so the air pressure in the duct 66 is also 100~3.
About 00 miAq is sufficient.

The fuel nozzle 51 is attached to the wall 2 of the freeboard section 5, is slightly set back from the wall surface, and is cooled by the air of the wind box 55, so that it is considerably isolated from high-temperature combustion heat.

On the other hand, fine powder can be transported by air more easily than coarse particles, and its supply pipe 58 passes through the bottom air box 6 and is supplied from a nozzle 57 that is slightly above the air distribution plate 4, so this part is also used. Protected from high heat and there is no risk of burnout.

Since the fuel nozzle 51 is attached to the furnace wall 2, the fifth,
A distributed nozzle mechanism as shown in Fig. 6 can be adopted, and the number of installed nozzles may be about 20% of the conventional number.

The amount of fine powder is less than 50% of the total, and the supply nozzle 5
Maintenance and inspection control is facilitated because the number of parts required is also less than 7.

If the air for coarse particle fuel supply and the air in the wind box 55 are set at around 15% of the total air supplied into the combustion furnace 1 required for combustion, the so-called two-stage combustion method (over Fire Air
), it can also be expected to have a nitrogen oxide suppressing effect.

By introducing the fine powder into the furnace bottom, the residence time of the fine powder in the furnace remains the same as in the conventional method, and the unburned loss can also be maintained as in the conventional method.

In this embodiment, the air guided to the cyclone 59 was a part of the air sent from the blower 62, but instead of this, a duct 72 equipped with a damper 71 is used as shown by the parallel dotted line in FIG. A separate low-pressure blower 70 may be provided and connected to the duct 66.

[Brief explanation of drawings]

Figure 1 is a diagram showing a conventional fluidized bed combustion apparatus, Figure 2 is a graph showing the relationship between the position in the combustion furnace and the pressure, and Figure 3 is an enlarged view of section A in Figure 1. FIG. 4 is a diagram showing one embodiment of the present invention, FIG. 5 is an enlarged view of section B in FIG. 4, and FIG. 6 is a view taken along arrows -■ in FIG. 1... Combustion furnace, 2... Furnace wall, 3... Fluidized bed, 4... Air distribution plate, 5... Free board section, 6, 55... Wind box, 1
2,14,59/...Chute, 15...Hopper, 17
... Fuel particle, 20 ... Fuel supply machine, 51 ... Fuel nozzle, 52.56.5B, 6L63, 66, 68, 72 ...
...Duct, 53...Pivot, 54...Rotating Leher shaft,
59...Cyclone, 60...Booster fan, 62.
70...Blower, 64...Air preheater, 65,67,7
1...Damper.

Claims (1)

[Claims] 1. An air distribution plate with a large number of through holes is arranged in the lower part of the combustion furnace, a freeboard part is formed above the air distribution plate, and a wind box is formed below, and solid fuel particles are supplied onto the air distribution plate. In the fluidized bed combustion apparatus, the furnace wall of the freeboard section is provided, in which floating combustion is carried out by air ejected from the wind box to the freeboard section through the through hole of the air distribution plate.
and a plurality of fuel nozzles are each provided facing onto the air distribution plate from below the air distribution plate, and among the solid fuel particles separated by the cyclone, coarse fuel is directed to the fuel nozzle on the furnace wall; A fluidized bed combustion apparatus characterized in that means is provided for transporting the pulverized fuel to the fuel nozzles on the air distribution plate through pipes in air flow.