JPH0368288B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improved method of operating a fluidized bed furnace in which solid fuel is mixed with a fluidized medium and burned while fluidized.

First, the outline of a fluidized bed furnace will be explained with reference to FIG.

In FIG. 1, 1 indicates a fluidized bed furnace main body. This fluidized bed furnace 1 has a fluidized bed 2 in the upper part and an air chamber 3 in the lower part, and the fluidized bed 2 side has a fuel inlet 4 having a spreader 4a for dispersing fuel onto the fluidized bed 2 and a fluidized medium. A fluid medium input port 5 is provided to input the fluid medium. The fuel used is lumps or powder of coal, oil coke, wood, etc., and the particle size of these is usually about 25 mm or less. In addition, non-combustible materials such as limestone and sand are used as the fluidizing medium, and the particle size thereof is usually about 4 mm or less.

A blower 6 is connected to the air chamber 3 to supply air. This air is blown out from the air chamber 3 to the fluidized bed 2 side through the nozzle 13 and is used for combustion of the fuel and for mixing and fluidizing the fuel and the fluidized medium. Note that the nozzle 13 may be a dispersion plate.

An ash removal pipe 7 is attached to the lower part of the fluidized bed 2 passing through the air chamber 3, and the pipe 7 is provided with a rotary valve 8. By rotating this rotary valve 8, unburnt materials such as ash and stone blocks accumulated at the bottom of the furnace are discharged to the outside through the ash extraction pipe 7. 9 indicates the direction of ash discharge.

In addition, 10 is a thermometer for measuring the typical temperature of the fluidized bed 2, which is usually 800 to 900°C when burning coal, and about 900 to 1000°C when burning oil coke. The temperature will be .
Further, 11 is a differential pressure gauge that measures the pressure difference between the upper and lower parts of the fluidized bed 2, and the greater the thickness of the fluidized bed 2, the greater the differential pressure. Note that 12 indicates the direction in which the combustion gas is discharged.

Next, a method of operating the fluidized bed furnace as described above will be explained.

In the fluidized bed furnace 1, the fluidized bed 2 is formed of a fluidized medium,
Fuel is supplied into it by a spreader 4a, and air is further supplied thereto for combustion. At this time, fuel is supplied so that the temperature is stabilized and the differential pressure in the fluidized bed 2 is constant.
And the ash is discharged from the ash extraction pipe 7 by the rotary valve 8. Combustion gases 12 are exhausted from the top of the furnace.

By the way, in the conventional operation method, the differential pressure gauge 11 is monitored to keep the differential pressure constant, that is, the height of the fluidized bed 2, by continuously pumping ash from the bottom of the furnace according to the amount of fuel and fluidized medium supplied. I was trying to bring it out. However, if the fuel is flame-retardant and maintains its shape even after combustion, or if the fuel contains rock blocks, etc., if the particle size of these foreign substances is extremely large compared to the fluidized medium, fluidization may occur. Instead, it sinks to the bottom of the furnace, eventually forming a layer that accumulates and stops flowing. This caused the temperature to drop from the bottom of the furnace, and there was a fear that combustion would eventually become impossible.

That is, FIG. 2 shows a normal combustion state in the fluidized bed furnace 1. In this case, there are many small-sized particles 15 in the fluidized bed 2, and a small amount of multi-sized particles 16, such as stone blocks. These unburned materials can be smoothly extracted as ash from the bottom of the furnace.

However, if the fluidized bed 2 contains many large particles 16 and is not burned, the large particles 1
6 will accumulate on the dispersion plate 13, making it difficult to maintain good combustion.

Based on these circumstances, the present invention detects the accumulation of flame-retardant unburnt lumps, stone blocks, etc. in the fluidized bed, and actively discharges these non-burnable lumps, thereby achieving a good condition. The purpose of this invention is to provide a method of operating a fluidized bed furnace that maintains the combustion state.

An embodiment of the present invention will be described in detail below with reference to FIGS. 3 and 4. Note that in these figures, the same parts as in FIG. 1 are designated by the same reference numerals, so the explanation of those parts will be omitted.

FIG. 3 is a sectional view of a main part of a fluidized bed furnace shown for explaining the operating method of the present invention. 11a, 11b, and 11c are installed in advance.

As shown in FIG. 2, if there are many small-sized particles 15 in the fluidized bed 2 and a small amount of large-sized unburned particles 16, the fluidized state is ideally maintained, but usually As shown in FIG. 3, in the upper layer 21 of the fluidized bed 2, there are many small-sized particles 15 and the fluidization is active, and in the middle layer 22 of the fluidized bed 2, there are many medium-sized particles 17, and the fluidization state is It becomes a little slow. Furthermore, fluidized bed 2
In the lower layer 23, many unburnt particles 16 of large particle size accumulate, making it difficult to flow.

When differential pressure gauges 11a, 11b, and 11c were installed in the upper layer 21, middle layer 22, and lower layer 23, respectively, and variations in the differential pressure were monitored, it was found that the changes occurred as shown in FIG. 4. That is, a in FIG. 4 is the output waveform of the differential pressure gauge 11a in the upper layer, and it is seen that the fluidized bed is actively flowing as a waveform with minute fluctuations in a short period. FIG. 4b shows the output waveform of the differential pressure gauge 11b in the middle layer, and it can be seen that the period is a little longer and the flow of the fluidized bed is becoming a little slower. Furthermore, c in FIG. 4 is the output waveform of the differential pressure gauge 11c in the lower layer, and it is a rough waveform with a long period, and it can be seen that the flow condition is deteriorated due to the accumulation of large particles.

Therefore, by monitoring the differential pressure in the fluidized bed 2, it is necessary to monitor the waveform as shown in FIG. 4b (i.e., the fluctuation period of the differential pressure) before it shows the waveform shown in FIG. 4c. When the ash is discharged, open the rotary valve 8 shown in Figure 1 to discharge unburned lumps and ash from the bottom of the furnace, or, if it is continuously discharged, control to increase the discharge amount. Make it. In this way, large particles that inhibit fluidization are discharged from the bottom of the furnace, causing the fluidized bed to fluctuate actively.
It becomes possible to maintain stable combustion by returning to the fluctuation cycle of the differential pressure as shown in FIG. 4a.

In order to perform such control automatically, the period that should be the standard of the output waveform of the differential pressure gauge is stored in a storage device, and the output waveform of the differential pressure gauge is stored continuously or intermittently. A control device may be installed to control the opening/closing or opening/closing amount of the rotary valve by comparing the waveforms.

Although the embodiment has been described in which the differential pressure gauges 11a, 11b, and 11c are installed in the upper layer 21, middle layer 22, and lower layer 23 of the fluidized bed 2, at least the lower layer 2
The object of the present invention can be achieved by installing one differential pressure gauge 11c for monitoring the differential pressure of No. 3.

As described in detail above, according to the present invention, the differential pressure in the vertical direction of the fluidized bed or the differential pressure in the lower layer 23 of the fluidized bed is detected, and the waveform is detected before it becomes a waveform of a slow flow abnormality with a long period. To provide a fluidized bed furnace operating method that enables stable continuous combustion of flame-retardant fuel by extracting large-diameter unburned lumps and stone blocks from a fluidized bed furnace 1 and reducing their density. be able to.

In addition, if many large-diameter unburnt lumps or stone blocks accumulate in the fluidized bed, if a large amount of small limestone or sand is supplied as the fluidizing medium, the average particle size distribution of the fluidized bed can be improved. As the fluidized bed becomes smaller or the thickness of the fluidized bed increases, vertical fluctuations within the fluidized bed become stronger.
There is also the effect that large-diameter particles can be extracted smoothly.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing the outline of a fluidized bed furnace, Figure 2
The figure is an enlarged view of the main parts of a fluidized bed furnace shown to explain the combustion state of the fluidized bed furnace, and FIG. FIG. 4 is a sectional view of a main part of the bed furnace, and is an output waveform diagram of a differential pressure gauge shown for explaining the operation of the present invention. 1... Fluidized bed furnace body, 2... Fluidized bed, 3... Air chamber, 4... Fuel inlet, 15... Fluidized medium inlet, 7... Ash extraction pipe, 8... Rotary valve, 11a, 11b, 11c... Differential pressure gauge.

Claims (1)

[Claims] 1 In a fluidized bed furnace that mixes solid fuel with a fluidized medium, fluidizes it, and burns it, the differential pressure in the vertical direction of the fluidized bed is detected, and when the period of differential pressure fluctuation reaches a predetermined period, the furnace is activated. 1. A method of operating a fluidized bed furnace, characterized in that the extraction of unburned material from the bottom is started or the amount of unburned material to be extracted is increased.