JPS60129588A - Method of operating fluidized bed furnace - 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 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 spreading fuel onto the fluidized bed 2 and a fluidized medium. A fluid medium input port 5 is provided to input the fluid medium. Incidentally, lumps or powder of coal, oil coke, wood, etc. are used as the fuel, and the particle size of these is usually about 258 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 tones or smaller.

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.

At the bottom of the fluidized bed 2, an ash extraction pipe 7 is inserted through the air chamber 3.
is attached, 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.

Note that 10 is a thermometer used to measure the typical temperature of the fluidized bed 20, and normally 800 is used when burning coal.
The temperature ranges from about 900 to 900°C, and about 900 to 1000°C when oil coke is burned.

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, we will explain how to operate the fluidized bed furnace as described above.

In the fluidized bed furnace 1, a fluidized bed 2 is formed of a fluidized medium, into which fuel is supplied by a spreader 4a and air is further supplied 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 with the rotary valve 8. Combustion gases 12 are exhausted from the top of the furnace. □By the way, in the conventional operating method, the differential pressure gauge 11 is monitored and the pressure is adjusted from the bottom of the furnace according to the amount of fuel and fluidized medium supplied in order to keep the differential pressure constant, that is, the height of the fluidized bed 2 constant. I was trying to extract them continuously. However, if the fuel is flame retardant and retains its shape even after combustion,
Alternatively, if the fuel contains stone lumps and the like, and the particle size of these foreign substances is extremely large compared to the fluidized medium, the fuel will not fluidize and will sink to the bottom of the furnace, eventually forming a layer that will accumulate and stop flowing. This caused the temperature to drop from the bottom of the furnace, and there was a fear that combustion would eventually become impossible.

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. 2 to 4. Note that in these figures, the same parts as those in FIG. 1 are indicated with figure-numerals, and therefore the explanation of those parts will be omitted.

In the present invention, several thermometers 10a to 10h are installed in order to measure the temperature distribution in the height direction or the lateral direction of the fluidized bed 2. A thermocouple or the like can be used as a temperature sensor for the thermometers 10a to 10h. Note that the thermometers 10a to 10c provided for determining the temperature distribution in the height direction m++ are included in the first thermometer group, and the thermometers 10d to 10f provided for measuring the temperature distribution in the lateral direction are included in the second thermometer group. For convenience, we will refer to this as the thermometer group. Further, in FIG. 2, reference numeral 15 denotes a screw feeder that operates together with the low-burning valve 8 to discharge unburned materials such as ash and stone blocks accumulated at the bottom of the furnace.

First temperature side group 10a to 10c and second thermometer group 10
d to 10f are each connected to a temperature difference determination circuit (not shown), and drive the rotary valve 8 and the row feeder 15 when the temperature difference is larger than a set value.

Now, when the fluidized bed 2 is in a good fluidized state and stable combustion is maintained, there is not much temperature difference in the height direction and the lateral direction of the fluidized bed 2. That is, the temperature distribution is stable and there is no temperature difference of about 20 to 30°C at most. Under such circumstances, the rotary valve 8 and the rotary feeder 15 are operated in a normal operating state, that is, the ash from the bottom of the furnace is continuously extracted quantitatively or in predetermined intermittent operations.

However, if the quality of the fuel is poor, as shown in Figure 3,
The flame-retardant unburnt material 20 remains in the fluidized bed 2 in almost the same shape as the supplied fuel. Since the flame-retardant unburnt material 20 is not crushed in the fluidized bed 2, fine ordinary unburned material 21 flows in the upper part of the fluidized bed 2, but the flame-retardant unburnt material 2
0 is classified and deposited in the lower layer, and over time it is laid out like garden stones (.

Eventually, the fluidized bed 2 ceases to fluidize from the lower layer, and as the combustion does not occur at the bottom of the furnace, the temperature decreases, and eventually the fire is extinguished.

In this state, the temperatures Ta and Tb of the thermometers 10a to IOC are
,' Tc increases in the order of Ta > Tb > Tc, and the temperature difference ranges from 50 to 150°C or more.

Therefore, the vertical temperature Ta%'T'l) of the fluidized bed 2
, Tc is detected, and when the temperature difference becomes 50 to 150°C or more, if ash is being extracted continuously, the rotary valve 8 is activated to increase the amount of ash being extracted.
By driving the rotary valve 8 and the rotary feeder 15, the unburned material is actively discharged by driving the rotary valve 8 and the rotary feeder 15 so as to start removing the unburned material when the removal of ash is intermittent. This prevents fluidization in the fluidized bed furnace 1 from stopping.

Further, as shown in FIG. 4, when the flame-retardant unburned flow line 20 and stone blocks are buried only partially at an early stage, the temperature within the fluidized bed 2 decreases locally. Therefore, when a disturbance in the horizontal temperature distribution of the fluidized bed 2 is detected using a thermometer 1od-1Of arranged in the horizontal direction, and when the temperature difference becomes 50 to 150°C or more, a large amount of unburned material 3O is extracted. (30 unburned items)
Start extraction of the area to prevent the build-up from spreading over the entire area.

When taking the above measures, a large amount of fluidized medium is temporarily supplied into the fluidized bed 2 to reduce the average particle size of the particles of the fluidized bed 20, thereby promoting extraction of the flame-retardant unburned flow line 20. By doing this, the height of the fluidized bed 2 becomes thick, and the vertical flow within the fluidized bed 2 becomes strong, which also has the effect of accelerating the movement of the flame-retardant unburned flow line 31. .

As detailed above, according to the present invention, by detecting the temperature distribution within the fluidized bed, the accumulation of unburned substances is detected and they are actively discharged, so that a good combustion state can be maintained. A method of operating a fluidized bed furnace that can be maintained can be provided.

Note that the present invention is not limited to the above-mentioned example,
It goes without saying that various modifications can be made without departing from the scope of the invention. For example, either the first or second thermometer group may be installed.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an outline of a fluidized bed furnace, FIG. FIG. 4 is a narrow sectional view of a fluidized bed furnace shown for explaining the present invention in detail. 1. Fluidized bed furnace body, 2. Fluidized bed, 3. Air chamber, 4
... Fuel inlet, 7. Ash extraction pipe, 8 fist rotary valve, 10a to 10f-φ thermometer.

Claims (1)

[Claims] In a fluidized bed furnace that mixes solid fuel with a fluidized medium, fluidizes it, and burns it, the temperature difference in the height direction or the lateral direction of the fluidized bed is detected, and the temperature difference in at least either direction is set to a set value. A method for operating a fluidized bed furnace, characterized in that when the above condition occurs, the extraction of unburned material from the bottom of the furnace is started or the amount of unburned material to be extracted is increased.