JPH0658510A - Fluidized layer combustion apparatus - Google Patents

Abstract

PURPOSE:To prevent a fluidized layer combustion furnace from being interrupted even when the property of a fuel is changed by individually controlling the amount of primary air for fluidization supplied to divided wind boxes, controlling the amount of secondary air, and controlling a supply ratio of the amounts of the primary and secondary airs depending upon the property of the supplied fuel. CONSTITUTION:Combustion air enters wind boxes 17, 18, 19 and is blown into a fluidized layer 6, and a fuel is fed into the fluidized layer 6 after passage through a fuel supply sheet 9. Part of air supplied from a fan 1 is fed into a furnace with a secondary air supplied nozzle 21. When a predetermined fuel is used, fluidization primary air is supplied uniformly into the wind boxes 17-19, Where a ratio of the primary air and secondary air is about 8:2. When volatile fractions in the fuel are increased, a valve 23 is closed and a valve 25 is fully opened to increase the amount of air from the secondary air blow-in nozzle 21. In contrast, when the volatile fractions in the fuel are decreased, the valve 23 is opened and the valve 25 is closed whereby the whole amount of the air is used as the fluidization primary air.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fluidized bed combustor such as a fluidized bed boiler, and more particularly to a fluidized bed combustor which uses a fuel whose combustion properties change drastically.

[0002]

2. Description of the Related Art An example of the structure of a conventional fluidized bed combustion apparatus is shown in FIG. The combustion air leaves the blower 1, passes through the air pipe 3 through the valve 2, and is fed into the wind box 4. The air in the wind box 4 is blown into the fluidized bed 6 through the air dispersion plate 5. The fuel is sent into the fluidized bed 6 through the fuel supply pipe 7, the rotary supplier 8, and the fuel supply chute 9. The combustion gas generated by reacting (combusting) with the fuel is sent through the flue 11 to a flue gas treatment device (not shown) arranged downstream. In this conventional technique, the temperature of the fluidized bed is
Usually, it is often operated at 760 ° C to 900 ° C. For example, low calorific value fuel such as dust has low calories,
The fluidized bed temperature is no more than about 800 ° C. on the other hand,
In the case of a fuel having a high calorific value such as coal, when the heat is not absorbed in the fluidized bed, the fluidized bed temperature rises to a high temperature of 1200 ° C or higher, the fluidized medium in the fluidized bed is melted and fixed, and fluidized. May be disturbed. Therefore, when burning a fuel with a high calorific value, a heat transfer tube having an endothermic surface is embedded in the fluidized bed so that the temperature in the bed is lower than the softening temperature of ash, and normally 1000 ° C or lower. adjust. Furthermore, when limestone is supplied together with coal to perform desulfurization at the same time as burning in a fluidized bed, the appropriate temperature range for desulfurization is 760 ° C.
Since the temperature is up to 860 ° C., the temperature is adjusted by embedding a heat transfer tube in the layer so as to be in this temperature range. As described above, in fluidized bed combustion, it is necessary to maintain the fluidized bed temperature within an appropriate range, but if the properties of the fuel used change significantly from what was originally planned, the in-bed combustion temperature will fluctuate significantly. Will be done. Therefore, in the conventional fluidized bed combustion furnace, if the properties of the fuel change beyond the design range of the furnace and the temperature of the fluidized bed goes out of the proper range, the furnace is stopped and cooled. The temperature of the fluidized bed was adjusted to an appropriate range by replacing the heat transfer tube in the fluidized bed or adding a heat transfer tube. As described above, shutting down and remodeling the furnace not only requires a large amount of repair costs, but also causes an extremely large economic loss due to interruption of the operation of the fluidized bed combustion furnace. Therefore, there has been a strong demand for a means capable of coping with a change in the operation of the fluidized bed combustion furnace without stopping the operation of the furnace even if the properties of the fuel change significantly.
As a conventional fluidized bed combustion apparatus, for example, Japanese Patent Laid-Open No.
No. 12336, No. 59-52106, and No. 5
9-195019, 60-36807,
Many proposals have been made such as JP-A-1-181005.

[0003]

As described above, according to the prior art, when the properties of the fuel change greatly and, as a result, the combustion temperature of the fluidized bed deviates from the proper range, the furnace is stopped and the internal combustion of the fluidized bed is stopped. Since the heat pipes were being modified, a large amount of economic loss was inevitable.

The object of the present invention is to solve the above problems in the prior art, and even if the property of the fuel changes greatly, it can be dealt with only by controlling the operation without stopping the fluidized bed combustion furnace. A fluidized bed combustion apparatus is provided.

[0005]

In order to achieve the above object of the present invention, the air box of the fluidized bed combustion furnace is divided into a plurality of air boxes, and the air boxes are supplied to the air boxes according to changes in the properties of the fuel. By controlling the amount of primary air for fluidization to suppress an abnormal decrease or increase in the combustion temperature in the fluidized bed, it is controlled so that combustion is always performed in the proper temperature range in the fluidized bed, and there is a surplus. In addition to the secondary air flow supplied to the upper part of the fluidized bed, the air is provided with means for adjusting so as to promote combustion in the empty column portion of the fluidized bed combustion furnace. That is,
Without changing the total amount of air supplied to the fluidized bed combustion furnace,
By freely controlling the distribution (supply ratio) of the amount of primary air supplied into the fluidized bed for fluidization and the amount of secondary air for combustion supplied to the empty column above the fluidized bed, the properties of the fuel can be controlled. Of the fuel, such as a fuel with a low rate of combustion in the fluidized bed or a fuel with a high rate of combustion in the fluidized bed, the combustion temperature in the fluidized bed is always maintained within an appropriate range. A means for controlling so that it is provided is provided. In the fluidized bed combustion furnace of the present invention, a fuel supply port (upper part of the fluidized bed) to the fluidized bed combustion furnace corresponding to a change in the properties of the fuel, for example, a fuel having a large proportion of volatile components and a low proportion burned in the fluidized bed. Secondary air that stops the flow rate of the primary air for fluidization to the wind box provided at a position away from the chamber, supplies the amount of air to the fluidized bed, and burns it in the empty tower section above the fluidized bed. By turning to, it is possible to effectively burn a large amount of volatile components generated from the fuel. In this way, by largely adjusting the distribution of the primary air amount for fluidization and the secondary air amount to be burned in the superficial part without changing the total air amount supplied to the fluidized bed combustion furnace. It is possible to maintain the combustion temperature in the fluidized bed within an appropriate range without stopping the operation of the furnace and remodeling or repairing the heat transfer tubes embedded in the fluidized bed. It is possible to prevent the occurrence of troubles due to the above and to achieve dry desulfurization combustion in an appropriate temperature range. In addition, in the case of fluidized bed combustion of fuel with many volatile components,
The injection position of the secondary air to be supplied to the empty column section above the fluidized bed is preferably provided in the vicinity of the fuel supply port where combustible gas is likely to be concentratedly generated.
The gaseous combustibles generated from the fuel and the combustion air can be rapidly mixed, and efficient combustion can be performed.

[0006]

[Action]

(1) In the case of fuel with a low rate of combustion in the fluidized bed,
In addition to reducing the amount of heat generated in the fluidized bed, the flame temperature decreases due to the increased air ratio. In the case of such a fuel, the supply of the primary air, which had been supplied to the wind box of the fluidized bed located away from the fuel supply port, is stopped and turned into the secondary air. Then, since the air ratio in the fluidized bed approaches the proper air ratio, the flame temperature in the fluidized bed, that is, the fluidized bed temperature rises. Further, by blowing the secondary air downward from the vicinity of the fuel supply port into the empty space inside the reactor on the fluidized bed, a large amount of vaporized gaseous combustible components near the fuel supply port or fine powdery particles blown up. Form a downward flame that burns combustibles. The flame further heats the fluidized medium in the bed to raise the temperature of the fluidized bed.
Further, the heat transfer coefficient of the heat transfer tube embedded in the fluidized bed at the portion where the fluidization is stopped becomes almost 0, and the amount of heat absorbed in the fluidized bed is reduced. Therefore, the fluidized bed temperature can be further increased. (2) When a fuel having a high rate of combustion in the fluidized bed is used, the in-bed temperature rises because the amount of heat generated in the fluidized bed is large. In this case, the amount of secondary air to be combusted in the empty column portion is reduced to 1 for fluidization, which is supplied into the fluidized bed as much as possible.
Increase the amount of secondary air. By doing so, the air ratio in the fluidized bed is increased and the fluidized bed temperature is lowered. Also,
By fluidizing the entire fluidized bed, the heat transfer area of the heat transfer tube embedded in the fluidized bed increases, the amount of heat absorption increases, and an excessive rise in the temperature of the fluidized bed can be suppressed.

[0007]

Embodiments of the present invention will be described below in more detail with reference to the drawings. FIG. 1 is a schematic diagram showing an example of the configuration of the fluidized bed boiler of the present invention. In the figure, the combustion air comes out of the blower 1, passes through the valve 2, and partially passes through the air pipes 14, 15 and 16, and the wind boxes 17 and 18, respectively.
Enter 19. Then, it is blown into the fluidized bed 6 through the air dispersion plate 5. The fuel is sent into the fluidized bed 6 through the fuel supply pipe 7, the rotary supplier 8, and the fuel supply chute 9. The combustion gas generated by reacting (combusting) with the fuel is
The flue gas 11 is sent to a flue gas treatment device (not shown) downstream. In addition, a part of the air supplied from the blower 1 is
It is fed into the furnace from the secondary air blowing nozzle 21 through the air pipe 20. When the fuel having the planned combustion property is used, the primary air for fluidization is uniformly supplied to the wind boxes 17, 18, and 19. In a normal case, the ratio of primary air to secondary air is about 8: 2. The properties of the fuel change drastically, for example, the volatile content in the fuel becomes extremely large,
When the proportion of the fuel that vaporizes immediately in the vicinity of the fuel supply port and burns in the fluidized bed decreases, or the fuel dries and changes from a mud form to a powder form, even if it is supplied into the furnace, it immediately becomes empty near the fuel supply port. For example, when it is blown up into the tower and it is difficult for fuel to mix in the fluidized bed. In this case, the valve 23 is closed and the valve 2
5 is fully opened. Then, the fluidization in the fluidized bed zone B shown in FIG. 1 is stopped, and the amount of heat absorbed by the in-bed heat transfer tube 13 in the fluidized bed zone B becomes almost zero. Also, valve 25
Through, the amount of air from the secondary air blowing nozzle 21 installed downward in the empty tower section 10 above the fluidized bed 6 increases,
The ejection speed increases. Therefore, the gas-like combustible component generated near the outlet of the fuel supply chute 9 or the fuel scattered in powder form is rapidly mixed, and a powerful downward flame is formed. This flame heats the fluidized bed in the fluidized bed zone B, and further raises the temperature of the fluidized bed. On the other hand, when the volatile component in the fuel is small and the proportion of char burning solid is increased, the valve 23 is opened and the valve 25 is closed, and the entire amount of air is used as the primary air for fluidization. Then, fluidization becomes active, particle mixing around the in-layer heat transfer tube 13 becomes active, and the heat transfer coefficient of the in-layer heat transfer tube increases. That is,
The amount of heat absorbed in the fluidized bed increases, which lowers the temperature of the fluidized bed. Further, since the air ratio in the fluidized bed increases, this also acts in the direction of lowering the fluidized bed temperature. As described above, since the fluidization range and the distribution of primary and secondary air can be greatly controlled in response to changes in the fuel properties, the fluidized bed temperature is always appropriate despite the significant changes in the fuel properties. It can be maintained in a wide range.

[0008]

As described in detail above, the fluidized bed combustion apparatus of the present invention supplies primary air for fluidization and a secondary air blowing nozzle provided near the fuel supply port above the fluidized bed. Since the ratio with the secondary air can be freely adjusted and controlled, fluidized bed combustion can always be performed within an appropriate temperature range even if the properties of the fuel change significantly, and problems such as melted sticking of the fluidized medium can occur. It is possible to prevent the occurrence of the above, and it is possible to achieve efficient dry desulfurization combustion in an appropriate temperature range.

[Brief description of drawings]

FIG. 1 is a system diagram showing an example of a configuration of a fluidized bed boiler furnace illustrated in an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a system diagram showing a configuration of a conventional fluidized bed boiler furnace.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Blower 2 ... Valve 3 ... Air piping 4 ... Wind box 5 ... Air distribution plate 6 ... Fluidized bed 7 ... Fuel supply pipe 8 ... Rotary supply machine 9 ... Fuel supply chute 10 ... Empty tower part 11 ... Flue 12 ... Furnace Main body 13 ... In-layer heat transfer tubes 14, 15, 16 ... Air piping 17, 18, 19 ... Wind box 20 ... Air piping 21 ... Secondary air blowing nozzles 22, 23, 24, 2
5 ... valve

Claims (3)

[Claims] 1. In a fluidized bed combustor in which a fuel is made to flow together with a fluidized medium for combustion, a plurality of wind boxes for supplying primary air for fluidization to a fluidized bed are divided into a plurality of divided winds. Means for individually controlling the amount of primary air for fluidization supplied to the box, and means for controlling the amount of secondary air supplied to the secondary air blowing nozzle for combustion provided near the fuel supply port above the fluidized bed Is provided, and the above 1 is selected according to the properties of the fuel to be supplied.
A fluidized bed combustion apparatus comprising means for controlling the supply ratio of the secondary air amount and the secondary air amount. 2. The primary air for fluidization of a fluidized bed at a position distant from a fuel supply port is throttled when the fuel having a low rate of combustion in the fluidized bed is combusted in the fluidized bed. A fluidized bed combustion apparatus comprising means for supplying to a secondary air blowing nozzle for combustion provided near a fuel supply port. 3. The amount of secondary air supplied to a secondary air blowing nozzle for combustion provided in the vicinity of a fuel supply port when the fuel having a high rate of combustion in the fluidized bed is combusted in the fluidized bed according to claim 1. A fluidized bed combustion apparatus, characterized in that means for squeezing the same and merging this with the primary air supply part for fluidization are provided.