JPS5941086B2 - Fluidized bed furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in fluidized bed furnaces, and in particular to providing a fluidized bed furnace whose operation can be easily adjusted to changes in load.

In recent years, fluidized bed boilers (furnaces) have attracted attention as boilers that burn fuel in various states, and efforts are being made to put them into practical use. (2) The heat transfer coefficient of the heat transfer tube section provided in the fluidized bed is approximately 160~
(230 Kcal/rn2・Hr・℃), the boiler can be made smaller; (3) Since the temperature inside the combustion chamber is uniform due to the use of a fluidized bed, it can be operated at a relatively low temperature of about 800 to 950℃. This is because the amount of nitrogen oxide NOx produced is small, and by using limestone or the like as a fluidizing medium, SOx produced during combustion can be easily removed from the combustion gas.

However, on the other hand, (1) a fluidized bed requires a fluidized medium, and in order to fluidize it, gas must be introduced into the fluidized bed at a speed higher than the fluidization starting speed of the fluidized medium; There are disadvantages such as the inability to easily change the load of the bed furnace.

To explain a conventional fluidized bed furnace using an example of a fluidized bed boiler, in a fluidized bed boiler A, as shown in FIG. is supplied to the fluidized bed boiler.

Fluidization (combustion) air enters the wind box part 3 provided over the lower part of the fluidized bed 1 to be formed from the duct 2, and is evenly sent to the fluidized bed through an air distribution grid 4 to distribute the fluidized medium. flows and burns fuel.

The combustion gas gives heat to the heat exchanger tubes 6 in the flow section to maintain the temperature of the flow section at an appropriate value.

The combustion gas leaving the fluidized bed 1 gives heat to the heat exchanger tube 7 installed in the freeboard, and after being cooled, the fine ash and unburned phosphorus contained in the gas are collected in a dust collector. 12 and released into the atmosphere from a chimney 13.

In order to separate large diameter solids unsuitable for the formation of a fluidized bed produced by combustion of fuel from the fluidized medium, the fluidized medium is extracted from the fluidized boiler A in appropriate amounts through the extraction port 9 at the bottom of the fluidized bed, and sieved. After that, only the lower part of the screen suitable for fluidization is circulated back to the fluidized bed 1 through the fluidized medium inlet 8.

The partition wall 11 creates a chamber at one end of the fluidized bed in which there is no heat exchanger tube group in the fluidized section, and at the start of combustion in the fluidized bed,
After the fluidized medium is heated by the preheating burner 10, fuel is supplied and ignited.

Next, a heat fluidizing medium is supplied to a portion of the boiler in which heat exchanger tubes are provided in the fluidizing section to expand the boiler.

The heat generated by combustion is absorbed by a group of heat transfer tubes installed in the fluidized section and freeboard section, producing water vapor.

Conventional large fluidized bed boilers have tried to cope with load changes by providing multiple combustion chambers with heat transfer tubes as described above.

However, with a boiler designed like this, the boiler load can only be changed in a few large steps, and the operation to ignite the extinguished combustion chamber and reach a steady state of combustion is complicated and takes a long time. There is.

Therefore, the present invention eliminates the above-mentioned disadvantages of the conventional fluidized bed boiler when the load changes, and provides a fluidized bed boiler that can be easily operated to change the load.

The present invention provides a fluidized bed having a fluidized bed without partition walls for holding and burning fuel, and a wind box section consisting of a large number of independent chambers for delivering gas to the fluidized bed to fluidize the fluidized medium in the fluidized bed. In the bed furnace, at least one of the adjoining arbitrary chambers of the wind box section is provided with a means for adjusting the flow rate of the fluidizing gas, and a fluidized bed is always provided on both side walls spanning all the chambers of the fluidized bed furnace. The gist of the present invention is a fluidized bed furnace characterized by having a wind box formed therein and further comprising an ignition chamber partitioned by a partition wall.

Next, the fluidized bed furnace of the present invention will be explained in more detail with reference to the accompanying FIGS. 2 and 3.

Fig. 2 is a schematic side view of the fluidized bed reactor A of the present invention, and Fig. 3 is a schematic plan view thereof (however, the fluidizing gas supply line outside the fluidized bed reactor is not necessarily shown in the plan view for convenience).
In these figures, 1 is the fluidized bed, 2 is the fluidized bed 1
This is a duct for supplying fluidizing gas to 3A,
3B, 3C, and 3D are independent chambers constituting the wind box section 3 provided at the lower part of the fluidized bed 1, and fluidizing gas is supplied to the fluidized bed via these chambers.

Among these, room 3A is a wind box that is constantly fluidized, room 3B is a wind box in which the introduction of fluidizing gas can be adjusted or stopped by valve 14B according to changes in the boiler load, and room 3C, 3C' is a wind box that constantly forms a fluidized bed on the side wall of the fluidized furnace A, and is designed to create a circulation path between the fluidized bed and the outside of the fluidized bed in order to sieve large-diameter particles in the fluidized medium. gas is supplied.

3D is a wind box in the fluidized bed part divided by partition walls 11 for initial ignition of the boiler, and a valve installed in the line 14 to feed fluidizing gas there once all the fluidized parts have been ignited. By closing 14D, the fluidized state can be stopped only in this part.

Note that 14 is a branch line that sends the fluidizing gas supplied from the duct 2 to each wind box.

No heat transfer tube group is provided in the upper part of this 3B, and the fluid medium in the upper part is initially ignited by the preheating burner 10.

5 is a fuel supply port, from which fuel is supplied, and fluidizing gas (air) is supplied through the gas distribution grid 4.
Burns due to

The combustion gas is passed through heat transfer tubes 6 in the flow section and heat transfer tubes 1 in the freeboard section.
After being cooled, it passes through a dust collector and is released into the atmosphere from the chimney (the dust collector and chimney are omitted here).

). 8 is a fluidized medium input port, and the fluidized medium introduced from here passes through the 3C side and is distributed throughout the fluidized bed.
The solids collected on the ' side are extracted from the extraction port 9, and solids having an inappropriate size for forming a fluidized bed are separated.

Thereafter, the fluid medium is circulated again to the fluid medium inlet 8.

Depending on the operating conditions of the boiler, the 3A room group can be divided into the first half and the second half (for example, the left half or the right half in the figure), so that the amount of air can be adjusted within the range that can be fluidized. It is also possible to provide a valve on the line 14 so as to withstand even smaller changes in the boiler load.

In addition to adjusting the amount of air in each chamber, the amount of fuel supplied to the fluidized bed in that section is also adjusted.

Figure 4 schematically shows the state of the fluidizing section when the supply of fluidizing gas (air) to the 3B chamber is stopped, but the movement of the fluidizing medium in the upper part of the 3B chamber has stopped. , indicating that heat transfer to the heat exchanger tube 6 is restricted.

If fuel and air are started to be fed into chamber 3B, the heat fluid medium will be easily mixed and the chamber can be immediately expanded.

Therefore, load change adaptation is achieved extremely quickly.

Furthermore, according to the device of the present invention, excess air is sent to a certain group of chambers (for example, group 3A) in each compartment to completely burn the fuel, and other chamber groups (for example, group 3B) contain reducing gas. ,
Alternatively, it is also possible to create a region where oxygen-deficient gas is sent for complete combustion and incomplete combustion, thereby reducing NOx in the boiler exhaust gas.

Example 1 A wind box section of a fluidized bed with an inner diameter of 1 m was divided into three approximately equal areas (approximately 0.0 m).
The upper part of the first chamber is used as the ignition part without heat exchanger tubes, and the upper part of the second and third chambers is divided into small chambers with a diameter of 1 inch (the area of the heat exchanger tube is 0.62 m2). m2, third chamber 0.54,112) in a fluidized bed boiler,
It was filled with river sand to a static height of 60 cm.

First, the part of the fluidized bed without heat transfer tubes on the wall side is fluidized,
After preheating to approximately 500°C by LPG gas combustion, coal is supplied and ignited, and when the temperature reaches 850°C, the upper part of the second chamber in the center is fluidized at an air flow rate of 3 m/sec (850°C), and the coal is supplied. started.

The upper part of the second chamber ignited immediately and stabilized after about 10 minutes (
The amount of coal supplied was approximately 63 kg/hr) L, and steam at atmospheric pressure (12.7 kg/hr) was generated.

Next, the air supply to the upper part of the first chamber for ignition was stopped, fluidizing air was supplied to the upper part of the third chamber at 3 m/see (850°C), and coal was supplied at 65 kg/hr. After 4 minutes, the amount of steam generated reached 240 kg/hr.

From this state, when the supply of fluidizing air and coal to the upper part of the third chamber is stopped, the amount of steam generated is 136 kg/h after about 5 minutes.
It decreased to r.

Example 2 The wind box section of a fluidized bed with a width of 300 mm and a length of 1,000 mm is divided into 5 equal chambers in the length direction, and the area of each chamber of the wind box is 0.
．． 06m, excluding the upper part of the small chamber (first chamber) at one end, the second
．． In a fluidized bed boiler with heat transfer tubes with a diameter of 1 inch (heat transfer tube area above each chamber: 0.096r112) placed in the upper part of chambers 3 and 4, olivine sand (mountain sand) was placed at a height of 400 mm at rest.
Filled.

First, the upper part of the first chamber where there is no heat exchanger tube is fluidized and LP
Ignite the G burner (preheating burner), and when the temperature of the fluidized bed reaches approximately 830°C, feed coke powder.9
The temperature was raised to 50°C.

After the combustion in the upper part of the first chamber became stable, the upper part of the adjacent second chamber was fluidized with air at a flow rate of 2.3 m/sec (950°C), and the supply of fine coke powder was started, and after the combustion stabilized, the same process was carried out. As luck would have it, the upper parts of rooms 3, 4, and 5 caught fire.

The coke powder supply speed to the upper part of each chamber is 11~i 2kg
/hr.

After the upper part of the fifth chamber was ignited, the supply of LPG and fluidizing air to the upper part of the first chamber was stopped.

From this state (combustion occurs in the upper part of chambers 2 to 5), the supply of coke powder and fluidized air to the upper part of the second chamber is stopped, and then the supply of coke powder and fluidized air to the upper part of the fourth chamber is stopped. After that, the upper parts of the second and fourth chambers were re-ignited, and the amount of steam generated as shown in the table below was obtained, resulting in extremely stable operation.

From the above results, it can be seen that the fluidized bed boiler of the present invention allows easy operation to change the boiler load.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view of a conventional fluidized bed cellar furnace. FIG. 2 is a schematic side view of a fluidized boiler according to one embodiment of the present invention, and FIG. 3 is a plan view thereof. FIG. 4 is a partially enlarged view of FIG. 2, and is for explaining the situation when a part of the fluidized bed is stopped.

Claims (1)

[Claims] 1. In a fluidized bed furnace that has a fluidized bed without partition walls that holds and burns combustion, and a wind box section that is made up of a number of independent chambers that feed gas that fluidizes the fluidized medium in this fluidized bed to this fluidized bed. , comprising means for adjusting the flow rate of the fluidizing gas in at least one of the arbitrary chambers of the wind box section,
A fluidized bed reactor characterized in that it has a wind box on both side walls spanning all chambers of the reactor to constantly form a fluidized bed, and further includes an ignition chamber partitioned by a partition wall.