JP3145463B2 - Combustion method of fluidized bed combustion furnace - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to relates to a combustion method for a fluidized bed combustion furnace, and more particularly to combustion process of the fluidized bed combustion furnace which volatiles many wastes such municipal waste can be burned in a low-pollution.

[0002]

2. Description of the Related Art A fluidized bed combustion furnace is used for incineration of municipal waste and the like in addition to a stoker furnace. FIG. 2 shows the structure of a municipal waste incineration fluidized bed combustion furnace according to the prior art. In the figure, the combustion air from the blower 1 is divided into two. One is air flow meter 2, valve 3, fluidizing air pipe 2
It enters the air diffuser 4 via 2. The air that has entered the air diffuser 4 is blown into the fluidized bed 13 from a number of air diffuser nozzles 30. A part of the fluidizing air blown into the fluidized bed 13 forms bubbles 14 and blows over the bed of the fluidized bed 13, and the rest passes between the media (bed particles) in the bed and also exits on the bed. To go.
The other air is blown into the furnace from the above-layer air blowing pipe 7 via the above-layer air pipe 21, the flow meter 5, and the valve 6.

[0003] Urban refuse 12 to be incinerated (hereinafter simply referred to as refuse) is put into a fluidized bed 13 through a trash input hole 10 at the furnace top. The fluidized bed portion is fluidized at an air velocity at least twice the minimum fluidization start velocity of the medium in the bed and is in a vigorous stirring state. The fluidized bed 13 is characterized by having a very high heat transfer coefficient in the bed due to its vigorous mixing and stirring action. When the refuse 12 is supplied into the fluidized bed 13, the refuse 12 is rapidly crushed and heated, evaporates water, then vaporizes volatile components in the refuse 12, and finally solid carbide (so-called char). Remains. Since this char is solid, it mixes with the medium in the formation and burns mainly in the formation. Further, many non-burning foreign substances 15 are mixed in the dust 12, and these are drawn out of the furnace bottom discharge pipe 17 together with the surrounding in-layer medium without burning. The extracted mixture of the in-layer medium and the non-combustible foreign matter 15 is sent to a classifier 16 and classified by a screen 32 into coarse particles not suitable for fluidization and fine particles suitable for fluidization. The coarse particles are discharged from the coarse particle discharge pipe 18 and discarded outside the system. The fine particles are returned from the fine particle discharge pipe 19 through the fine particle transport pipe 20 into the fluidized bed 13 through the in-layer medium input hole 23, and are reused as the in-layer medium.

Volatile components vaporized from the municipal waste 12 are gaseous fuels composed of H ₂ , CO, CH ₄ , C ₃ H _{8 and the} like. The fluidized bed 13 is suitable for mixing and agitation of solid particles, but most of the gas becomes bubbles and blows through the fluidized bed 13 in a short time. Therefore, mixing and burning of volatile components and air in the bed are performed. Can not expect much. For this reason, most of the volatiles in the refuse 12 blow off onto the bed, and are blown into the fluidized bed 13 from the diffuser nozzle 30 of the diffuser pipe 4 to form bubbles 14, and the fluidizing air and the bed air blown over the bed. It mixes with the air from the tube 7 and burns as a diffusion flame on the layer.

A problem with such a conventional fluidized bed combustion furnace, particularly a refuse incinerator, is that the refuse quality fluctuates extremely. Also, as the quality of the garbage changes, the physical properties also change. As a result, the supply amount of the municipal trash 12 also temporarily changes greatly. Garbage is originally a mixture of miscellaneous wastes, and these changes are not regular and it is almost impossible to predict and respond in advance.

A decrease in the amount of combustible components in the dust 12 or a decrease in the amount of dust supplied only increases the excess air ratio, and does not cause a serious problem. The problem is that the calorific value of the dust 12 is temporarily increased or the supply amount is increased. As mentioned earlier, these changes have no regularity and are almost impossible to predict, so it is not possible to increase or decrease the amount of air in advance, and if the amount of garbage increases and calories increase, Extreme air shortages occur. When the supply amount of the dust 12 increases temporarily, the fluidized bed 13 is crushed and heated at a stretch because the mixing and stirring of the fluidized bed 13 is intense and the heat transfer coefficient in the bed is high. As a result, the volatile components in the refuse 12 are released and burned at once. That is, oxygen is consumed rapidly, resulting in a temporary lack of oxygen, resulting in air shortage. as a result,
As shown in FIG. 3, the unburned component represented by CO temporarily increases rapidly.

[0007] Of course, in consideration of such characteristics of the municipal garbage, the municipal garbage incinerator supplies the furnace with 50 to 80% more air than the average amount of air required for garbage combustion. They are designed and operated so that they do not run out of air. However, there is a temporary change in the dust quality that greatly exceeds this range, in which case unburned components such as CO temporarily increase.

[0008] Such an increase in CO is a temporary phenomenon, which has been overlooked in the past, but has been highlighted as a non-negligible problem with the recent growing interest in environmental issues. To solve these problems, the structure of the fluidized bed is the same as before, and the amount of fluidized air in a part of the fluidized bed is periodically increased or decreased, or a sudden increase in the amount of dust is detected by a sensor and the fluidized Methods have been devised such as temporarily reducing the formation air. However,
When the amount of fluidized air is periodically increased or decreased, the change in the dust quality does not always coincide with the cycle of the increase or decrease in the amount of air. In the method of temporarily reducing the amount of fluidized air to the entire fluidized bed, the amount of A complicated control system for interlocking with the high-sensitivity sensor and the air amount control is required, and there is a disadvantage that the cost of the apparatus increases.

[0009]

When a fuel having various properties and whose properties fluctuate irregularly, for example, municipal garbage, is burned, the above-mentioned prior art includes the volatile matter contained in the municipal garbage. There is a problem that CO2 and unburned gas typified by CO are generated in large quantities due to a temporary lack of oxygen due to rapid combustion of the components.

[0010] The object of the present invention is to solve the above problems,
The quality of the fuel is that the amount of feed to provide a combustion method of the fluidized bed combustion furnace which is capable of preventing a large amount generation of incomplete combustion and CO due to lack of oxygen even if the varied temporarily large.

[0011]

[0012]

According to a first aspect of the present invention, fluidized air is supplied to a fluidized bed made of a fluidized medium, and an object to be burned is supplied to the fluidized bed and burned. In addition, a non-combustible material is extracted and a fluidized medium having a predetermined particle size is circulated through a fluidized bed. As for the medium, air is supplied by the inclined porous air dispersion plate so as to promote the movement of the flowing medium on the plate to the diffusion pipe portion, and the supply of the burnable material and the circulating supply fluid medium is performed by the inclined porous air dispersion plate. The present invention relates to a combustion method for a fluidized-bed combustion furnace, which performs the above-described fluidized-medium section and injects above-bed supply air downward from a furnace side wall provided with a porous air distribution plate.

According to a second aspect of the present invention, fluidized air is supplied to a fluidized bed made of a fluidized medium, municipal waste is supplied to the fluidized bed and burned, and incombustibles are extracted from the lower part of the fluidized bed together with the fluidized medium. In the combustion method of a fluidized bed combustion furnace in which a fluidized medium having a predetermined particle diameter is circulated and supplied to the fluidized bed, and the remainder is discharged to the outside, a large amount of air is diffused through a diffuser for a part of the fluidized medium in the furnace. To form a vigorous fluidization section, and for the remaining fluid medium, a relatively small amount of air is supplied by an inclined perforated air distribution plate to form a gentle fluidized bed or fixed bed, and municipal waste and circulating fluidized fluid Is supplied to the fluidized medium portion on the inclined porous air dispersion plate, the municipal garbage is gently heated to release volatile components, and the remaining solid char is transferred to the diffuser fluidized bed portion together with the fluidized media for combustion. To make Combustion method for fluidized bed combustion furnace according to claim.

In a third aspect of the present invention, in the second aspect , the air supply amount to the fluid medium by the air diffuser is set to 2 to 9 times the minimum fluidization start speed of the fluid medium, and the inclined porous air dispersion plate is provided. Wherein the amount of air supplied to the fluidized medium by the method is 0.7 to 1.5 times the minimum fluidization start speed of the fluidized medium.

[0015]

The cause of the mass production of CO is a temporary shortage of air. The shortage of air is caused by the fact that a large amount of fuel is temporarily injected, or a fuel with high quality (calorific value) is added, and the fuel is rapidly heated, and volatile components in the fuel are rapidly and greatly increased. Is caused by the release of
In the present invention, as a preventive measure, it has been considered that heat transfer to the fuel is suppressed and rapid heating and temperature rise are avoided. Specifically, a high heat transfer coefficient resulting from good mixing and stirring, which is a characteristic of a fluidized bed, was reduced, and rapid heating and temperature rise of the fuel were prevented. In other words, a part of the furnace is made into a fluidized bed or moving bed with very gentle fluidization. First, fuel is injected into the bed and the volatile components are gently vaporized. And burn it.

The remaining solid char and non-combustible foreign matter are transferred together with the medium in the layer to a portion having good mixing and stirring to complete the combustion. In this way, even if a large amount of fuel enters temporarily by gently heating the fuel, the generation of volatiles from the fuel is slow, so rapid vaporization, lack of oxygen due to combustion, CO Mass outbreaks can be avoided.

Further, when transferring the remaining solid char and non-combustible foreign matter together with the medium in the bed to a portion having good mixing and stirring, the furnace bottom in the gentle fluidized portion is used in order to avoid troubles such as deposition on the furnace bottom. Is composed of an inclined air dispersion plate without protrusions on the surface, and the supply hole of the replenished or recycled in-layer medium is provided on the opposite side of the intense fluidized part, so that the entire in-layer medium of the gentle fluidized part is It is made to flow toward the part of severe fluidization. In addition, the direction of air blowing is also oriented in such a manner as to assist the flow of the in-layer medium. SUMMARY OF THE INVENTION In order to suppress the rapid vaporization of volatile components contained in fuel, there are two parts: a part having a low fluidity and a low heat transfer coefficient, and a violent fluidization part for burning char and separating non-combustible foreign matter 15.
The fluidized bed 13 is divided into two parts, and the fuel is supplied to a part of the fluidization where the heat transfer coefficient is low and the temperature is gradually increased by heating, and the volatile components are removed so as to match the supplied air amount (oxygen amount). Slow release is carried out and the generated volatile components are blown over the bed with air and sent to a section of intense fluidization where they are completely burned with a sufficient amount of oxygen.

Further, the furnace bottom of the gentle fluidizing portion is formed of a flat air distribution plate, and is inclined toward the severe fluidizing portion. In addition, the recirculation or replenishment of the in-bed medium is supplied from the side wall so that the flow of the in-bed medium is directed to the portion of the intense fluidization. The in-layer medium replenished from these side walls acts to flush the entire in-layer medium of the inclined air distribution plate toward the diffuser air distribution plate. The solids such as the char and the non-combustible foreign matter 15 in the bed are transported to the part of the fluidization (diffuser tube type air dispersion plate) which is intensely fluidized by the flow of the medium in the bed, and the char burns. Is settled and extracted from the furnace bottom of the diffuser type fluidized bed.

As described above, the oxygen consumption is made uniform by avoiding the rapid heating and heating of the injected fuel and gently volatilizing and burning in a gentle fluidized portion, thereby preventing the incomplete combustion due to the temporary lack of oxygen. To prevent. At the same time, the non-combustible foreign matter and the solid char that has been carbonized in the gentle fluidized portion (inclined air dispersion plate portion) are carried by the flow of the medium in the bed and sent to the diffuser type fluidized bed portion to perform solid combustion. At this time, since the furnace bottom is formed of a flat air dispersion plate, there is no occurrence of fluidization failure due to the char that has been dry-distilled and the incombustible foreign matter being caught and deposited on the furnace bottom.

[0020]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
FIG. 1 is a side sectional view of a municipal garbage fluidized bed combustion furnace applied to the present invention. FIG. 4 shows the combustion furnace of FIG.
FIG . 5 is a cross-sectional view as viewed from the front of FIG. 1, and FIG. 6 is a cross-sectional view showing the structure of the inclined air distribution plate of FIG.

The area ratio of the diffused pipe type fluidized bed section 33 and the inclined type air distribution plate section 26 depends on the city refuse 12 mainly serving as fuel.
Is determined by the properties, particularly the contents of combustibles and volatiles. In the embodiment shown in FIG.
The case where the area ratio of the inclined air distribution plate portion 26 is approximately 1: 1 is shown. In this embodiment, about 50% of the total amount of air is added to the diffuser type fluidized bed section 33, and about 10% to the inclined air distribution plate section 26.
%, And an air distribution of about 40% as layer air was optimal.

The air branches off from the blower 1 and is sent to three locations: a diffused pipe type fluidized bed section 33, an inclined air distribution plate section 26, and a layered air blowing pipe 7. The air blown into the diffuser-type fluidized bed section 33 through the flow meter 2, the valve 3, the fluidizing air pipe 22, and the diffuser pipe 4 vigorously mixes and stirs the medium in the bed and simultaneously scatters from the inclined air dispersion plate section 26. It reacts with the char that has entered the trachea-type fluidized bed portion 33 to completely burn the char. Also,
The non-combustible foreign matter 15 that has entered together with the char sinks through the space between the diffuser tubes 4 and is discharged out of the furnace together with the in-layer medium.

In ordinary municipal refuse 12, the proportion of combustibles that become chars is about 10%, whereas
The amount of air sent to the diffuser type fluidized bed section 33 is 50% of the whole
It is. Therefore, a large amount of surplus oxygen remains in the combustion gas in the layer of the diffuser type fluidized bed portion 33. The combustion gas containing the excess oxygen is used on the layer of the diffused pipe type fluidized bed 33 together with the jet 29 from the air-absorbing pipe 7 to burn volatile components blown into the diffused piped fluidized bed 33. , A high-temperature flame 27 is formed. Most of the combustion gas from the flame 27 is discharged from the furnace outlet 9, but a part of the combustion gas becomes a swirl flow 28 in the furnace and the refuse 1 in the inclined air distribution plate 26.
2 serves as a heat source for heating 2.

The air sent to the inclined air distribution plate section 26 through the flow meter 24 and the valve 25 is blown into the furnace from the blowing nozzle 31 in a substantially horizontal direction, and the medium in the layer near the furnace bottom is diffused into a diffused tube type fluidized bed. After being pushed to the portion 33, it flows upward through the gap in the medium in the layer. As a matter of course, in such an inclined type air distribution plate portion 26, the blowing nozzle 3
If the diameter of the nozzle 1 is designed to be the same, the depth differs depending on the place where the blow nozzle 31 is placed. Therefore, even if the original pressure of air is the same, the air from the blow nozzle 31 depends on the position (depth) where the blow nozzle 31 is placed. Differences in volume occur. Therefore, if the blowing nozzles 31 having the same diameter are arranged, a large amount of air enters from a shallow portion and a small amount of air enters from a deep portion, so that air cannot be uniformly blown over the entire surface of the inclined air distribution plate portion 26. . Therefore, also in this embodiment, the diameter of the blowing nozzle 31 in the shallow part is designed to be small, and the diameter of the blowing nozzle 31 arranged in the deep part is designed to be large.

Since the amount of air sent to the inclined air distribution plate portion 26 is small, the inclined air distribution plate portion 26 is in a state just before fluidization starts or in a state of a moving bed with a slow movement. For this reason, the municipal refuse 12 charged into the inclined air distribution plate portion 26 is not broken down while remaining on the layer surface, and the high-temperature combustion gas 28 entrapped in the jet stream 29 from the on-layer air blowing pipe 7 and the furnace Heated from the surface by radiant heat from the flame 27 inside. In the process of drying by these heats and evaporating volatile components, the municipal waste 12 is carbonized and becomes brittle. In addition, a part of the high-temperature medium in the bed blown up on the bed due to the intense fluidization in the diffuser-type fluidized bed section 33 causes the swirl flow 28 in the furnace.
The dust 12 is deposited on the dust 12 on the inclined air distribution plate portion, and the dust 12 is carbonized and penetrates into the layer.

The force of the jet flow of the blowing nozzle 31, the in-layer medium entered through the in-layer medium input hole 23, and the in-layer medium scattered from the diffuser-type fluidized bed section 33 and deposited on the fluidized bed of the inclined air dispersion plate section 26. As a whole, the in-bed medium moves toward the diffuser-type fluidized bed section 33 due to the weight of. The municipal refuse 12 also moves to the diffuser type fluidized bed 33 while being carbonized by the flow of the medium in the bed.

According to the experience of the inventors who designed and operated a number of fluidized-bed boilers and fluidized-bed incinerators and the results of a fluidized-bed cold model test, the non-combustible foreign matter 15 was removed by such an inclined air dispersion plate section 26. It has been found that the following conditions are necessary for smooth discharge. a) The inclination angle of the inclined air distribution plate part 26 is 10 degrees or more.

B) There are no protrusions on the surface of the inclined air distribution plate portion 26 so that foreign matter can be caught. c) The blowing direction of air is the same as the moving direction of foreign matter. d) The moving direction of the whole medium in the layer is the same as the moving direction of the foreign matter. The municipal refuse 12 as a fuel falls from the refuse input hole 10 on the furnace top onto the layer of the inclined air distribution plate portion 26. The dropped municipal solid waste 12 is radiant heat from the furnace, comes into contact with the high-temperature combustion gas in the furnace entrained in the jet stream 29 from the air-above-bed air blowing pipe 7, and is a high-temperature in-layer medium that accumulates from the diffuser-type fluidized bed 33. The surface is heated and heated by the heat of the surface. Since it is almost in the state close to the fixed layer, the municipal refuse 12 is on the layer without being crushed, and the volatile components gradually evaporate from the surface as a lump. The volatile components vaporized are H ₂ , CO, CH
₄ , a gaseous fuel composed of C ₃ H _{8 and the} like. These gas fuels are sent to the diffuser type fluidized bed section 33 by the jet stream 29 from the above-layer air blow-in pipe 7 and burn to generate a high-temperature flame 27.

The refuse 12 from which volatile components have been removed becomes solid carbide. This is a so-called char. This char and garbage 1
Non-combustible foreign substances 15 such as stones, iron pieces, glass pieces, etc., mixed in with the recirculating fine particles and the replenishing medium introduced from the intra-layer medium input hole 23, are almost discharged from the blowing nozzle 31 of the inclined air dispersion plate section 26. It is sent to the diffuser type fluidized bed part 33 by the force of the air jet blown out in the horizontal direction, where it is vigorously stirred and the char completely burns. It is withdrawn through the furnace bottom extraction tube 17. The extraction medium including the extracted non-combustible foreign matter 15 is sent to the classifier 16, and the large non-combustible foreign matter 15 unsuitable for fluidization is separated and discarded by the screen 32. Fine non-combustible foreign matter 15 that has passed through screen 32
And the medium in the bed is sent to the medium inlet 23 through the fine-grain conveying pipe 20 and returned to the fluidized bed 13 again for use.

As described above, by providing a part that is hardly fluidized in the furnace and charging the dust 12 into the part, a large amount of volatile components can be prevented from being released due to rapid heating of the dust 12, and the volatile component can be moderated. Combustion can be performed. As a result, even if a large amount of garbage 12 or high-calorie garbage 12 enters temporarily, the combustion can be performed slowly.
O mass can be prevented from being generated.

[0031]

[Comparative Example] If the inclined air distribution plate portion 26 is made of another type of air distribution plate, for example, a flat air distribution plate or a bubble cap type air distribution plate which is forced to have a projection on the furnace bottom. However, since solid char and non-combustible foreign matter generated here accumulate on the furnace bottom, they cannot be smoothly transferred to a portion where the fluidization is severe.

As shown in FIG. 7, when the inclined air distribution plate is constituted by a diffuser-type air dispersion portion, solid char and non-combustible foreign matter pass through the space between the diffuser tubes and unburned. There is a problem that the gas is discharged from the furnace bottom extraction pipe 17 as it is. Further, when the diffused-tube type fluidized bed portion in the present invention is constituted by the inclined air distribution plate portion 34 as shown in FIG. 8, the pressure of the fluidizing air is increased so as to resist the pressure of the deepest fluidized bed portion. Therefore, there arises a problem that an air power cost is increased as compared with the present invention.

[0033]

According to the present invention, the generation of incomplete combustion products such as CO in a fluidized bed combustion furnace can be suppressed, and environmental pollution can be prevented.

[Brief description of the drawings]

FIG. 1 is a side sectional view of a fluidized bed combustion furnace according to the present invention.

FIG. 2 is a side sectional view of a fluidized bed combustion furnace according to the prior art.

FIG. 3 is a diagram showing a CO generation record in a fluidized bed combustion furnace according to the prior art.

FIG. 4 is a horizontal sectional view of a fluidized bed combustion furnace according to the present invention.

FIG. 5 is a cross-sectional view of the fluidized bed combustion furnace according to the present invention as viewed from the front.

FIG. 6 is a cross-sectional view of an air nozzle provided on an inclined air distribution plate of a fluidized bed combustion furnace according to the present invention.

FIG. 7 is a diagram showing a comparative example for the present invention.

FIG. 8 is a diagram showing a comparative example for the present invention.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... blower, 2 ... flow meter, 3 ... valve, 4 ... diffuser pipe, 5 ... flow meter, 6 ... valve, 7 ... layered air blowing pipe, 8 ... furnace body, 9 ...
Furnace outlet, 10: Garbage inlet, 11: Empty tower, 12: Garbage, 13: Fluidized bed, 14: Bubbles, 15: Non-combustible foreign matter, 16
... Classifier, 17 ... Bottom extraction tube, 18 ... Coarse particle discharge tube, 1
9: fine-grain discharge pipe, 20: fine-grain transport pipe, 21: air pipe on the bed, 22: air pipe for fluidization, 23: medium input hole in the bed,
24 ... flow meter, 25 ... valve, 26 ... inclined air distribution plate
27 ... flame, 28 ... furnace swirl flow, 29 ... jet flow, 30 ... diffusing tube nozzle, 31 ... blowing nozzle, 32 ... screen,
33 ... diffuser type fluidized bed section

Continuation of the front page (72) Inventor Toru Sente 6-9 Takara-cho, Kure-shi, Hiroshima Babcock Hitachi Ltd. Inside the Kure factory (56) References JP-A-57-108513 (JP, A) JP-A-63- 282404 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F23G 5/30 F23C 11/00

Claims (3)

(57) [Claims] 1. A fluidized medium having a predetermined particle size is supplied with fluidized air to a fluidized bed made of a fluidized medium, supplies and burns a substance to be burned to the fluidized bed, and extracts incombustibles together with the fluidized medium from a lower part of the fluidized bed. In the combustion method of a fluidized bed combustion furnace for circulating and supplying the fluidized bed to a fluidized bed, a part of the in-furnace fluidized medium is supplied with fluidized air by a diffuser tube, and the remaining fluidized medium is supplied to the plate by an inclined porous air dispersion plate Air is supplied so as to promote the movement of the fluidized medium to the diffuser pipe section, and the supply of the burnable material and the circulating supply fluidized medium is performed to the fluidized medium section on the inclined porous air dispersion plate, and the porous air is supplied. A combustion method for a fluidized bed combustion furnace, comprising injecting air above the bed downward from a furnace side wall provided with a dispersion plate. 2. Fluidized air is supplied to a fluidized bed composed of a fluidized medium, municipal waste is supplied to the fluidized bed and burned, and incombustibles are extracted from the lower part of the fluidized bed together with the fluidized medium. Circulating a fluidized medium of a particle size to the fluidized bed,
In the combustion method of a fluidized-bed combustion furnace, the remainder is discharged to the outside.Some of the fluidized media in the furnace is supplied with a large amount of air through a diffuser pipe to form a vigorous fluidized portion, and the remaining fluidized media is inclined porous. A relatively small amount of air is supplied by the air dispersion plate to form a gentle fluidized bed or moving bed, and municipal solid waste and a circulating supply fluidized medium are supplied to the fluidized medium portion on the inclined porous air dispersion plate to heat the municipal solid waste. Gently to release volatile components, and transfer the remaining solid char together with the fluidizing medium to the diffuser fluidized bed to burn it. 3. The air supply amount to the fluid medium by the inclined porous air dispersion plate according to claim 2, wherein the air supply amount to the fluid medium by the diffuser tube is set to 2 to 9 times the minimum fluidization start speed of the fluid medium. With the minimum fluidization start rate of the fluidized medium of 0.7
A combustion method for a fluidized bed combustion furnace, characterized in that the combustion rate is 1.5 to 1.5 times.