JP3317791B2 - Small lump fuel supply device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a small lump fuel (for example,
Supply of solid waste from municipal solid waste and industrial waste, solid fuel such as wood chips, bark and bagasse, or incinerated material such as crushed combustible waste) to combustion furnaces such as solid fuel furnaces and incinerators More particularly, the present invention relates to a device for continuously supplying small-lumped fuel in a hopper at a constant volume ratio per unit time from a fuel supply port of a combustion furnace into the furnace.

[0002]

2. Description of the Related Art In general, when a small-sized fuel such as solid fuel is supplied to a combustion furnace such as a solid fuel furnace, the lower end of a fuel storage hopper is connected to a fuel supply port of the combustion furnace via a chute. Usually, the fuel in the hopper is pushed out to the chute at a constant rate per unit time by a volume feeder such as a screw feeder provided at the lower end.

[0003]

However, small bulk fuels such as solid fuels generally have a low bulk specific gravity (0.1 to 0. 0).
Since 5t / m about ³⁾ also not constant, or not fuel movement in the feeder zone of action which is smoothly caused a so-called bridge phenomenon within the hopper, the fuel layer filled in the feeder zone of action a hopper bottom region There is a possibility that the bulk specific gravity of the portion (hereinafter referred to as “feeder layer portion”) may fluctuate. In addition, the height of the fuel layer in the hopper decreases with the progress of fuel supply by the feeder, or increases or fluctuates when new fuel is supplied to the hopper. Due to the fluctuation of the fuel density, the degree of compression of the fuel layer due to its own weight changes, that is, the bulk specific gravity of the fuel layer changes, and the above-mentioned bridging phenomenon and the bulk density fluctuation phenomenon of the feeder layer portion are further promoted. When such a phenomenon occurs, the quantitative supply of fuel is not performed well,
Stable combustion in the furnace becomes difficult. That is, since the volume feeder pushes out the fuel in the hopper to the chute at a constant volume rate per unit time, not only when the bridging phenomenon occurs but also when the bridging phenomenon does not occur, the volume of the feeder layer portion is increased. When the bulk specific gravity fluctuates, the fuel supply amount fluctuates even if the volume pushed out by the feeder is constant. For example, as the bulk specific gravity decreases, the supply amount also decreases.

[0004] In general, a combustion furnace for burning and incinerating small lump fuel generally has a furnace pressure of -1 for safety measures and the like.
It is operated in a state where it is held between 0 mm water column and -30 mm water column. Therefore, in order to achieve complete combustion at a low excess air ratio, it is important to prevent air intrusion from the fuel supply port as much as possible. However, as described above, when the bridging phenomenon occurs or the bulk specific gravity fluctuates, the filling degree of the fuel in the fuel supply system reaching the fuel supply port becomes unstable, and the material sealing function by the filled fuel decreases. As a result, stable combustion in the furnace becomes difficult. In addition, if the fuel contains flammable materials such as paper that can easily ignite,
There is a possibility that a fire may occur in the fuel supply system due to flashback from the furnace.

Furthermore, aside from the fact that the properties (especially the calorific value) of the fuel newly replenished in the hopper and the fuel already existing in the hopper are the same or similar, when the properties are different (generally different In many cases, even if a fixed amount is supplied into the furnace, the combustion state in the furnace varies and stable combustion cannot be performed. Such a problem is more remarkable not only when the fuel supply amount fluctuates as described above, but also when a plurality of fuel supply ports are provided in the combustion furnace, and when the fuel supply is performed separately from these combustion supply ports. Become.

[0006] The present invention has been made in view of such a point, and it is possible to satisfactorily supply a small lump of fuel to a combustion furnace without causing the above-mentioned problems, and to perform combustion in the furnace. It is an object of the present invention to provide a small lump fuel supply device capable of stably performing the process.

[0007]

SUMMARY OF THE INVENTION The small lump fuel supply apparatus of the present invention is particularly provided for a combustion furnace having a plurality of fuel supply ports juxtaposed. Thus, this supply device
A fuel supply port is formed on the upper wall, and a fuel inlet having the same number of fuel supply ports as the number of fuel supply ports is adjustable in the front and rear side and formed in the front and rear side of the lower wall, and arranged behind the last fuel inlet. A fuel distribution case having an excess fuel discharge port, a plurality of hoppers having an upper end connected to each fuel inlet, and a lower end connected to each fuel supply port, and a lower end of each hopper. A volume feeder that continuously feeds the fuel in the hopper to the fuel supply port at a constant volume rate per unit time, a silo as a refueling source arranged in the lower direction of the fuel distribution case, and a group of fuel supply ports. A fuel supply mechanism that continuously transfers and supplies small lump fuel that exceeds the amount of fuel supplied to the combustion furnace from the silo to the fuel supply port of the fuel distribution case, and is provided inside the fuel distribution case and supplied from the fuel supply port Was done A fuel pushing mechanism for sequentially pushing the fuel from the fuel inlets into the hoppers while discharging the fuel over the lower wall of the case to the rear, and discharging excess fuel not supplied to the hopper group from the excess fuel outlet, And a surplus fuel return mechanism for returning surplus fuel discharged from the outlet to the silo and mixing it with the small lump fuel in the silo.

[0008]

According to the fuel supply to the fuel supply port, the hopper is replenished while being pushed in with an amount of fuel corresponding to the fuel amount reduced thereby. Therefore, the inside of the hopper is always kept filled with fuel. That is, the height of the fuel layer in each hopper is always kept constant, and the bulk specific gravity does not change due to the change in the layer height. Moreover, since the replenishment fuel is pushed into the hopper, a substantially constant compression force always acts on the fuel layer in the hopper. From these facts, each hopper 4 is always filled with a fuel layer having a substantially constant bulk specific gravity.

Therefore, in the hopper, even when the small bulk fuel has a small bulk specific gravity and a variation in the bulk specific gravity, a bridging phenomenon does not occur, and the feeder action area is always filled with the fuel. The bulk specific gravity of the feeder layer portion, which is the fuel layer portion that is held and filled in the feeder action region, is always kept substantially constant. As a result, a fixed amount of fuel is supplied from the fuel supply port, and the fuel to be supplied into the furnace can always be maintained at a constant amount.
Moreover, since the hopper is always kept filled with fuel, it is not necessary to make the hopper larger in volume than necessary.

Further, since the inside of the hopper is kept filled with fuel and the bulk density of the filled layer, that is, the compressibility of the layer is kept substantially constant, the fuel reaching the fuel supply port is maintained. The material sealing function in the supply system is sufficiently exhibited, and air intrusion from the fuel supply port can be reliably prevented. Therefore, complete combustion at a low excess air rate in the combustion furnace can be favorably realized. In addition, even when a combustible material such as paper which easily ignites is mixed with the fuel, there is no fear that a fire occurs in the fuel supply system due to a flashback or the like from the furnace.

Further, surplus fuel not supplied to the hopper is returned to the fuel supply source, and a part of the fuel supplied to the combustion furnace is circulated between the fuel supply source and the fuel supply source. Even when the new fuel is different in properties (especially the calorific value) from the existing fuel of the replenishment source, they are mixed and the fuel supplied to the furnace is homogenized, and the combustion state in the furnace Does not fluctuate and stable combustion can be performed.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The construction of the present invention will be specifically described below with reference to the embodiments shown in FIGS. In this embodiment, a lumped fuel (eg, municipal solid waste, industrial waste solidified, solid fuel such as wood chips, bark, bagasse, etc.) The present invention relates to an example in which the present invention is applied to a device for supplying incinerated materials such as combustible waste.

First, the configuration of the fuel supply device 1 according to the present invention will be described. In the following description, front and rear mean left and right in FIG. 1, and left and right mean upper and lower in FIG. 4, respectively.

[0014] The small lump fuel supply device 1 of the present embodiment comprises:
As shown in FIGS. 1 to 3, first to third fuel supply ports 3 ₁ , 3
_{The first} , _second , and third hoppers 4 ₁ , 4 ₂ , 4 ₃ connected to each fuel supply port 3 are attached to a fluidized-bed combustion furnace 2 in which ₂ and 3 ₃ are arranged side by side in the front-rear direction. And hopper 4 ₁ ,
A fuel distribution case 5 in which 4 ₂ and 4 ₃ are suspended in series, a silo 7 as a replenishing source for small bulk fuel 6, a fuel supply mechanism 8 interposed between the silo 7 and the fuel distribution case 5, The fuel supply system includes a fuel push-in mechanism 9 housed in the distribution case 5 and a surplus fuel return mechanism 10 interposed between the fuel distribution case 5 and the silo 7.

As shown in FIG. 3, the fluidized bed combustion furnace 2 forms a fluidized bed 11 on the bottom of the furnace and burns the fuel 6 supplied from each fuel supply port 3 in the fluidized bed 11. The heat transfer tube 12 arranged in the fluidized bed 11 is heated. The combustion furnace 2 is operated in a state where the pressure in the furnace is maintained at −10 mm water column to −30 mm water column, and the required amount Q per unit time to be supplied into the furnace 2 is appropriately determined according to the combustion conditions and the like. Is set. The fluidized bed 1
1 is formed by ejecting fluidized air from nozzles 13 arranged at the bottom of the furnace. As a fluidized medium constituting the fluidized bed 11, silica sand or the like is generally used. The upper region of the fluidized bed 11 is supplied with secondary combustion air for completely burning fly ash and unburned gas.

Further, although not shown, the flue gas 6 'generated in the furnace 2 is guided to a boiler (not shown),
The boiler steam is generated by heat exchange with the can water, and the exhaust gas 6 ′ passing through the boiler is recovered by the economizer and then discharged to the atmosphere through an exhaust gas treatment device such as a dust collector. It has become.

Each hopper 4 is, as shown in FIGS.
Each of them has the same independent volume and the lower end is connected to each fuel supply port 3 via a chute 14. A screw feeder 15 is provided at the lower end of each hopper 4.
Is decorated. The screw feeder 15 is a volume feeder that feeds the fuel 6 in the hopper 4 to the chute 14 at a constant volume per hour.
4, a continuous fuel supply from the fuel supply port 3 into the furnace 2 is performed. Note that the supply amount by the feeder 15 can be arbitrarily set by changing the number of rotations of the screw. The fuel supply amount per unit time (hereinafter referred to as “consumption amount”) q supplied to the furnace 2 by each feeder 15 is the same, and is set to Q / 3 obtained by dividing the required amount Q by the number of fuel supply ports. You.

As shown in FIGS. 1 to 3, the fuel distribution case 5 has a rectangular cross section. The lower wall 5a has first to third fuel push-in openings 16 ₁ of the same rectangular shape arranged in the front-rear direction. ,
16 ₂ and 16 ₃ are provided, and each fuel inlet 1
6 is connected to the upper end of each hopper 4 in communication. Further, the lower third wall 5a of the fuel distribution case 5 has
With rectangular surplus fuel outlet 18 disposed behind the fuel pushing port 16 ₃ is provided, rectangular fuel supply port 19 is provided at the upper wall portion 5b. The left and right widths of each of the fuel inlet 16, the surplus fuel outlet 18 and the fuel supply port 19 match the left and right widths of the case 5, that is, the left and right widths of the lower wall 5 a and the upper wall 5 b.

By the way, the opening degree, that is, the opening area of each fuel push-in port 16 can be arbitrarily adjusted by moving the slide damper 17 provided at the upper end of the hopper 4 in the left-right direction. In this embodiment, as shown in FIG. 4, the opening area of the fuel pushing port 16 _1, 16 _2, 16 _3, by occupying different damper 17 ... position of, it is set to be smaller as the front ones. That is, the third fuel pushing port 16 ₃ of the last position has been fully opened, the second fuel pushing port 16 ₂ of the intermediate positions are closed degree 1/3 region in the lateral direction by damper 17 1st fuel inlet 1
For 6 _1, it is closed to the extent 2/3 region in the lateral direction in the damper 17.

As shown in FIG. 1, the silo 7 is disposed in the lower direction of the fuel distribution case 5, and a large amount of small
Is to be stored. A fuel inlet 20 and a surplus fuel return port 21 are provided on the ceiling of the silo 7, and a fuel transfer port 22 is provided on the bottom.

As shown in FIG. 1, the fuel supply mechanism 8 is provided at the bottom of the silo 7 and discharges the fuel 6 to the fuel transfer port 22 through a belt conveyor 8a. A transport conveyor 8b for transporting the fuel to the fuel supply port 19 of the case 5; and all the fuel supply ports 3 ₁ , 3 ₂ , 3
_An amount of small lump fuel 6 exceeding the amount Q (= 3q) supplied into the furnace 2 from ₃ is continuously supplied to the fuel distribution case 5. The replenishment amount Q 'per unit time by the fuel supply mechanism 8 is increased by 20% of the required amount Q (Q' = Q
(1 + 0.2)).

As shown in FIGS. 1 to 3, the fuel push-in mechanism 9 comprises a belt conveyor or a chain conveyor 9a in which rectangular plate-shaped lugs 9b are protruded at regular intervals. 9b advances forward along the case upper wall portion 5b while approaching the inner peripheral surface of the fuel distribution case 5, and then reverses at the front end portion of the case 5;
It travels backward along a. Therefore, according to the fuel pushing mechanism 9, the fuel supply port 19
The fuel 6 replenished into the fuel distribution case 5 can be pushed backward on the case lower wall 5a by the respective lugs 9b. In this pushing section, as shown in FIG.
While distributing fuel 6 hopper 4 _1, 4 _2, 4 ₃ are successively pushing supplied can be discharged from further hoppers 4 _1, 4 _2, 4 ₃ excess fuel 6 ₄ fuel outlet 18 is not supplied to the. That is, the fuel 6 replenished in the fuel distribution case 5 is pushed out by the lug 9a, and the case lower wall 5
a at the front end (FIG. 4A). And
The fuel 6 is supplied to the case lower wall 5 as the lug 9a advances.
a, first, the first fuel inlet 16
Let me pass over _one . In this case, first fuel push port 16 ₁ of the opening is left from being set smaller by the damper 17 in the direction, a part of the fuel 6 brought to the first fuel push port 16 ₁ on the lug 9b 6 only ₁ is to be pushed from the first fuel push port 16 ₁ to the first hopper 4 ₁ (Fig. (B)). Then, fuel 6 residual is passed through a second fuel pushing port 16 ₂ on the lug 9a. At this time, the second fuel inlet 16
₂ opening is from being greater than the first fuel push port 16 ₁ by the damper 17 in the horizontal direction,
And only a part 6 ₂ of the fuel 6 brought on the second fuel pushing port 16 ₂ is pushed from the second fuel pushing port 16 ₂ to the second hopper 4 ₂ (FIG. (C)). Thus, even when passing through the second fuel pushing port 16 ₂ ,
A part of the fuel 6 that can be pushed by the lug 9a remains. Therefore, the lug 9a is connected to the third fuel inlet 16 ₃
When passing over, since the third fuel pushing port 16 ₃ of the opening is set larger than the second fuel pushing port 16 ₃ by the damper 17 in the horizontal direction (entire opening), the fuel 6 ₃ 3 Fuel pushing will be pushed from the mouth 16 ₃ in the third hopper 4 ₃ (FIG. (D)). Moreover, excess fuel 6 ₄ passes through the third fuel pushing port 16 ₃ above still remaining, all of which is discharged from the fuel discharge port 18 by the lug 9a (FIG. (E)). FIG.
Shows the pushing action by one lug 9b, and this action progresses at regular intervals.
Is performed almost continuously. By the way, as described above, the fuels 6 ₁ , 6 ₂ , 6
6 ₃ are formed so that substantially the same amount, they are processed the opening regulation by dampers 17 of each fuel pushing port 16. Note that the fuel supply system from the silo 7 to the fuel supply ports 3 ₁ , 3 ₂ , 3 ₃ is closed.

As shown in FIG. 1, the return mechanism 10 is a chute 10a for connecting the fuel discharge port 18 of the fuel distribution case and the fuel return port 21 of the silo 7 located therebelow.
And an appropriate number of picker rollers 10b disposed in the silo 7
, And each lug 9b has a fuel outlet 18
Has with be refunded to the silo 7, the surplus fuel 6 ₄ which is refunded to the silo 7 to be mixed with fuel 6 to existing silo 7 by excess fuel 6 ₄ chute 10a discharged from. That is, the fuel 6 is transferred to the fuel distribution case 5
And the silo 7 is circulated.

Next, a method for supplying a small lump of fuel using the supply apparatus 1 according to the present invention having the above-described structure will be described in detail.

The fuel 6 is uniformly supplied from the fuel supply ports 3 into the combustion furnace 2. That is, the same quantity q, that is, the quantity Q / 3 obtained by equally dividing the required quantity Q, is continuously supplied from each hopper 4 by the screw feeder 15.

In this case, each hopper 4 has a furnace 2
By replenishing while pushing in the amount of fuel 6 corresponding to the consumption q by the supply to the inside, the inside of each hopper 4 is always kept filled with a fuel layer 6a having a substantially constant bulk specific gravity.

That is, the fuel supply mechanism 8 replenishes the fuel distribution case 5 with the quantity Q ′ of the quantity Q ′ exceeding the required quantity Q from the silo 7. Then, the fuel 6 supplied to the fuel distribution case 5 is distributed substantially equally by the lugs 9 b of the fuel pushing mechanism 9, and each hopper 4 is inserted through each fuel pushing port 16.
Press

At this time, the supply amount Q to the fuel distribution case 5
Is larger than the consumption 3q which decreases in all the hoppers 4 ₁ , 4 ₂ , 4 ₃ (about 20% increase), the opening degree of each fuel push-in port 3 is adjusted by the damper 17 as described above. Each hopper 4 is supplied with the fuel 6 in an amount corresponding to the consumption amount q, and the inside of each hopper 4 is always kept filled with the fuel 6.
That is, the height of the fuel layer in each hopper 4 is always kept constant, and a change in bulk specific gravity due to a change in the layer height does not occur. Moreover, the fuel 6 is pushed into each hopper 4 by the action of the lug 9b, and a substantially constant compression force always acts on the fuel layer 6a in each hopper 4. From these facts, the inside of each hopper 4 is always filled with the fuel layer 6a having a substantially constant bulk specific gravity.

Therefore, in each hopper 4, even when the small bulk fuel 6 has a small bulk specific gravity and a variation in the bulk specific gravity, the bridging phenomenon does not occur, and the action area of the feeder 15 is always the fuel 6 , And the bulk specific gravity of the feeder layer portion 6b, which is the fuel layer portion filled in the feeder action region, is always kept substantially constant. As a result, the fuel 6 is supplied quantitatively from each fuel supply port 3, and the required amount Q of the fuel 6 to be supplied into the furnace 2 can be always maintained. And feeder 15
By changing the screw rotation speed of the
Can be easily and accurately controlled. Further, since each hopper 4 is always kept filled with the fuel 6, it is not necessary to make the volume larger than necessary. In an extreme case, the volume is slightly larger than the volume of the feeder action area. Is sufficient.

Further, as described above, the fuel 6
In is held in filled state, and the compression of the bulk density, i.e. layer 6a of the filling layer 6a because it is also held substantially constant, the fuel reaching the fuel supply port 3 _1, 3 _2, 3 ₃ from silo 7 material seal function in the supply system is sufficiently exhibited, the air entering from the fuel supply port 3 _1, 3 _2, 3 ₃ can be reliably prevented. Therefore, complete combustion at a low excess air ratio in the combustion furnace 2 can be favorably realized. In addition, even when a combustible material such as paper that easily ignites is mixed in the fuel 6, there is no fear that a fire occurs in the fuel supply system due to a flashback or the like from the furnace 2. In particular, by disposing the silo 7 in the lower direction of the fuel distribution case 5, the fuel supply ports 3 ₁ ,
3 _2, 3 even if a fire occurs in the fuel supply system leading to _3, without effects such as extends to a silo 7 for reserving a large quantity of fuel 6, fear is no become conflagration.

Further, as described above, the replenishment amount Q 'to the fuel distribution case 5 is larger than the consumption amount 3q reduced in all the hoppers 4 ₁ , 4 ₂ , 4 ₃ (about 20% increase). A part of the fuel 6 supplied to the distribution case 5 is discharged from the fuel discharge port 18 by the lugs 9b.
0 returns to silo 7 and picker roll 10b ...
By such an action, it is mixed with the fuel 6 in the silo 7. That is, part of the fuel 6 supplied into the combustion furnace 2 is circulated between the silo 7. Therefore, even if the new fuel 6 ₅ to be supplied to the silo 7 existing fuel 6 and characterization (in particular heating value) in the silo 7 are different,
These are mixed and the fuel 6 supplied to the furnace 2 is homogenized, and the fuel 6 can be supplied quantitatively into the furnace 2 as described above. Does not fluctuate and stable combustion can be performed.

It should be noted that the present invention is not limited to the above embodiment, but can be appropriately changed and improved without departing from the basic principle of the present invention. For example, the number of fuel supply ports is appropriately determined depending on the combustion capacity of the combustion furnace 2 and the like. However, the present invention includes a case in which the fuel 6 is supplied from only one fuel supply port 3 into the furnace 2. Regardless of the degree, it can be applied in the same manner as in the above embodiment.
However, the effect described above becomes more remarkable as the number of combustion supply ports increases. Further, the combustion furnace to which the present invention is applied is not limited to the fluidized bed combustion furnace 2 described above, and any combustion furnace that burns or incinerates a small lump of fuel, such as a boiler combustion furnace using solid fuel, is applied without exception. be able to. Also,
The feeder mounted on the hopper 4 is not limited to the screw feeder 15 described above. Any feeder that continuously feeds the fuel 6 in the hopper 4 to the fuel supply port 3 at a constant volume rate per unit time may be used. The configuration is optional. Of course, the shapes of the hopper 4 and the fuel distribution case 5 and the configurations of the mechanisms 8, 9, and 10 are also arbitrary.

[0033]

As can be easily understood from the above description, according to the small lump fuel supply device of the present invention, the inside of the hopper can always be filled with the fuel layer having a substantially constant bulk specific gravity. Therefore, fuel can be stably and satisfactorily supplied into the combustion furnace without causing the problems described at the beginning. In addition, since part of the fuel supplied to the furnace is circulated to the silo, the fuel supplied to the furnace can be homogenized, and in combination with the above, combustion in the furnace can be performed. Can be performed stably. In addition, the material seal function in the fuel supply system can be exhibited well, and the prevention of fire due to complete combustion or flashback at a low excess air rate can be effectively achieved without requiring special equipment. Can be realized.

Further, according to the small lump fuel supply apparatus of the present invention, it is possible to carry out the method more suitably when the fuel is supplied to the combustion furnace from a plurality of fuel supply ports.

[Brief description of the drawings]

FIG. 1 is a vertical sectional side view showing an example of a small lump fuel supply device according to the present invention.

FIG. 2 is an enlarged detail view showing a main part of FIG. 1;

FIG. 3 is a vertical sectional front view taken along the line III-III in FIG. 2;

FIG. 4 is a cross-sectional plan view taken along the line IV-IV in FIG. 2;

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Supply apparatus of small lump fuel, 2 ... Fluidized bed combustion furnace (combustion furnace), 3 ... Fuel supply port, 3 ₁ ... 1st fuel supply port, 3 ₂ ...
Second fuel supply port, 3 ₃ ... third fuel supply port, 4 ... hopper,
4 ₁ ... first hopper, 4 ₂ ... second hopper, 4 ₃ ... third hopper, 5 ... fuel distribution case, the lower wall portion of 5a ... fuel distribution case, the upper wall portion of 5b ... fuel distribution case, 6,6 _1, 6 _2,
6 ₃ : small lump fuel, 6 ₄ : surplus fuel, 6 a: fuel layer in hopper, 6 b: feeder layer portion (fuel layer portion filled in the feeder action area), 7: silo (supply source of small lump fuel) , 8 ... fuel supply mechanism, 9 ... fuel pushing mechanism, 10
... Fuel return mechanism, 14 ... Chute, 15 ... Screw feeder (volume feeder), 16 ... Fuel inlet, 16
₁ ... 1st fuel push-in port, 16 ₂ ... 2nd fuel push-in port, 16 ₃ ... 3rd fuel push-in port, 17 ... damper, 18
... fuel outlet, 19 ... fuel supply port.

Claims (1)

(57) [Claims] 1. A fuel supply device for a small lump of fuel attached to a combustion furnace having a plurality of fuel supply ports arranged side by side, wherein a fuel supply port is formed in an upper wall portion and a fuel supply port is provided in a lower wall portion. A fuel distribution case in which the same number of fuel injection ports as the number of ports can be adjusted and formed in a front-rear side and arranged behind the last fuel injection port to form an excess fuel discharge port, and the upper end of each fuel injection case A plurality of hoppers connected at their lower ends to respective fuel supply ports while being connected to the fuel supply ports, and the hoppers are provided at the lower ends of the hoppers, and the fuel in the hoppers is supplied at a constant volume per unit time. And a silo, which is a fuel supply source located in the lower direction of the fuel distribution case, and a small lump of fuel that exceeds the amount of fuel supplied from the fuel supply ports to the combustion furnace from the silo. Continuous to the refueling port And a fuel supply mechanism that transfers and supplies the fuel to the hopper from each fuel push-in port while pushing the fuel replenished from the fuel supply port backward on the lower wall of the case. A fuel pushing mechanism that pushes excess fuel that is not supplied to the hopper group and discharges excess fuel from the excess fuel outlet, and a surplus that returns excess fuel discharged from the excess fuel outlet to the silo and mixes it with small bulk fuel in the silo. And a fuel returning mechanism.