JPH10205734A - Secondary air supply method in stoker type combustion furnace - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the concentration of CO and the production of dioxin in an exhaust gas by making secondary air inject to a combustion chamber at a downward angle from a side of the combustion chamber and from a wall surface on the side facing the above side to form a spiral flow of the secondary air and a combustion gas in an upper space of a stoker. SOLUTION: A secondary air injection port 7a for injecting secondary air B1 at a downward angle θ1 is provided on a wall surface 4a on the side of a fuel supply port 5a of a combustion chamber 4 and a secondary air injection port 7b for injecting secondary air B2 at a downward angle θ2 is provided on a wall surface 4b facing the above wall surface. The secondary air B1 and B2 are injected into a space of a stoker 2 from a secondary air chamber 8. The downward angle θ1 of the secondary air B1 injected from the injection port 7a on the side of the fuel supply port is made larger than the downward angle θ2 of the secondary air B2 injected from the injection port 7b so that a counterclockwise spiral flow D of the air and a combustion gas is formed in an upper space of the stoker 2. Thus, the combustion gas and the secondary air are thoroughly mixed thereby achieving a complete combustion of the combustion gas.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a stoker-type combustion furnace for general industrial boilers, municipal solid waste, industrial waste, sludge, wood chips and the like (hereinafter referred to as "fuel") using solid fuels such as coal and wood chips. ) Relates to the improvement of the stoker type combustion furnace used in the combustion of the stoker type combustion furnace, in which the generation of dioxin and the reduction of the CO concentration in the exhaust gas are enabled by completely and stably burning the fuel with high efficiency. The present invention relates to a method for supplying secondary air.

[0002]

2. Description of the Related Art Municipal solid waste and the like have been mainly subjected to combustion processing, and stoker type combustion furnaces and fluidized bed type combustion furnaces have been widely used. FIG. 6 shows an example of a staircase type stoker type combustion furnace used for the combustion treatment of municipal solid waste and the like. In FIG. 6, 1 is a fuel supply hopper, 2 is a stoker, 2a is a dry stoker, 2b is a burning stoker, 2
c is a post-burning stoker, 3 is an ash outlet, 4 is a combustion chamber, 5
, A fuel supply port, 6 a hopper, 7
Is a secondary air supply port, and 8 is a secondary air chamber.

Fuel C, such as municipal waste, supplied into the fuel supply hopper 1 by an automatic crane (not shown) or the like,
It is sequentially supplied from the supply port 5a to the drying stoker 2a by the constant-quantity supply device 5, and is dried by the radiant heat from the primary air A and the high-temperature combustion section H supplied from below the stoker 2a. CO and C _m H _n, a reducing gas such as NH ₃ is released.

[0004] The dried fuel C is continuously transferred onto the combustion stoker 2b, where the primary air is supplied from below to burn up the flame and burn, and at the tip of the stoker 2b, the burn-off point , And is sent onto the post-combustion stoker 2c. Then, the so-called burning is performed on the post-burning stoker 2c, and here, after almost completely turned into ash,
It is discharged from the ash outlet 3 to the outside of the furnace.

[0005] On the other hand, the reducing gas generated from the dry stoker 2a and the unburned matter in the combustion gas are mixed and agitated with the secondary air B in the lower part of the combustion chamber 4 so that the combustion chamber 4 Then, the so-called secondary combustion is performed, and the combustion is completed by staying in the combustion chamber 4 for a predetermined time.

[0006] The oxygen concentration in the combustion gas reaching the lower part of the combustion chamber depends on the combustion characteristics in the dry stoker 2a, the combustion stoker 2b, and the post-combustion stoker 2c. The oxygen concentration varies greatly depending on each zone through which the gas has passed. Therefore, by mixing the combustion gas having different temperatures, compositions, oxygen concentrations, etc. from the respective zones by a method such as squeezing the inlet portion of the upper portion of the stoker 2 into the combustion chamber 4, the secondary air is introduced into the vicinity thereof. By injecting B to promote mixing and stirring of the combustion gas, good combustion in the combustion chamber 4 is achieved.

The amount of the secondary air B supplied into the lower part of the combustion chamber 4 is generally reduced to the theoretical air amount required for the secondary combustion by mixing and agitating the secondary air and supplying the secondary air B to the combustion chamber. Multiplied by the excess air ratio in consideration of the residence time of the unburned matter in the fuel supply port, the secondary air jets provided on the fuel supply port side wall surface 4a below the combustion chamber 4 and the wall surface 4b on the side facing the fuel supply port 4b are provided. Exit 7
a, 7b are ejected in a substantially horizontal manner toward the inside of the lower part of the combustion chamber 4.

The stoker type combustion furnace as shown in FIG. 6 can incinerate a high-moisture content flame-retardant fuel with high efficiency, and has excellent practical utility. But,
This type of stoker type furnace still has many problems to be solved. Among them, a particularly important problem is that it is difficult to quickly and completely mix the unburned matter in the combustion gas from the stoker and the secondary air, and as a result, the unburned matter is completely burned and the CO concentration in the exhaust gas is reduced. Cannot be reduced to a sufficiently low value.

More specifically, for example, when the secondary air B is ejected from the secondary air outlets 7a, 7b of the two wall surfaces 4a, 4b in a substantially horizontal collision, the two airs 2 collide with each other. As shown in FIG. 7, the secondary air is pushed up the center of the combustion chamber, and the gas flow velocity V in the center of the combustion chamber 4 increases. Therefore, the residence time of the gas in the combustion chamber 4 is shortened, and the oxygen distribution Q in the combustion chamber becomes non-uniform. Further, the secondary air B that has collided with each other may be in a so-called hunting state as shown in FIG. 8. In this case, the pressure in the combustion chamber 4 greatly pulsates, and Secondary combustion of the fuel becomes unstable. Further, when the secondary air B is jetted out of the secondary air jets 7a and 7b in a stepwise manner, the FIG.
As shown in (2), the main flow of the combustion gas rises along the wall inside the combustion chamber 4, and it is difficult to form a uniform upward flow. As a result, the space in the combustion chamber 4 cannot be fully utilized for secondary combustion, and it is difficult to reduce the size of the combustion chamber 4 by pulling.

As described above, in the method in which the secondary air B is jetted almost horizontally from the both side walls 4a and 4b as in the conventional stoker type combustion furnace, the oxygen distribution in the combustion chamber 4 is reduced. Is not uniform, and complete mixing of the combustion gas and the secondary air cannot be achieved, so that stable and complete combustion of the unburned material becomes extremely difficult.

[0011]

SUMMARY OF THE INVENTION The present invention relates to a conventional stoker-type combustion furnace in which secondary air B is blown out from both side walls 4a, 4b in a substantially horizontal direction so as to face each other. That is, the residence time of the combustion gas in the combustion chamber is short, and a uniform oxygen distribution cannot be obtained.
Pressure fluctuations in the combustion chamber cause unstable combustion, secondary air and combustion gas are not completely mixed, unburned matter is difficult to completely burn, excess air ratio increases, and exhaust gas increases. That the CO concentration in the combustion chamber cannot be reduced sufficiently, and the rising gas flow in the combustion chamber tends to be uneven,
The purpose of the present invention is to solve the problem that the space in the combustion chamber cannot be sufficiently utilized for the secondary combustion, and to ensure a perfect mixture of the combustion gas and the secondary air and a sufficiently long residence time of the combustion gas in the furnace. It is intended to provide a method for supplying secondary air in a stoker type combustion furnace which enables stable combustion of fuel completely and significantly reduces CO concentration in exhaust gas.

[0012]

According to a first aspect of the present invention, there is provided a stoker type combustion furnace in which primary air is supplied from below a stoker and secondary air is supplied to a lower portion of a combustion chamber. Secondary air is blown out from the wall surface on the fuel supply port side below the combustion chamber and the wall surface on the side opposite thereto at the same or different downward angles toward the inside of the lower part of the combustion chamber, and the upper space of the stoker A basic configuration of the present invention is to form a swirling flow of secondary air and combustion gas.

[0013] The invention according to claim 2 is the invention in which
In a stoker-type combustion furnace that supplies secondary air to the lower part of the combustion chamber while supplying secondary air, the wall surface on the side of the fuel supply port below the combustion chamber and the wall surface on the side facing the fuel supply port are: Secondary air is jetted at the same or different downward angles into the lower part of the combustion chamber to form a swirling flow of the secondary air and the combustion gas in the upper space of the stoker,
Basically, secondary air is ejected from both wall surfaces into the space above the secondary air ejected from both wall surfaces at the downward angle.

[0014] The invention of claim 3 is claim 1 or claim 2.
According to the invention, the secondary air is ejected at a downward angle from a plurality of secondary air ejection ports having an interval in the upward and downward directions.

According to a fourth aspect of the present invention, in the second aspect of the invention, the secondary air supplied to the upper space of the secondary air ejected at a downward angle is the secondary air ejected horizontally. is there.

The invention according to claim 5 is the invention according to claims 1 to 4.
In the present invention, the positions of the axes of the secondary airflows ejected from the secondary air ejection ports on both wall surfaces are mutually shifted in the horizontal direction and / or the vertical direction.

[0017]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 shows a first embodiment of the present invention, in which the present invention is applied to a staircase type stoker type combustion furnace. In FIG. 1, 1 is a fuel supply hopper, 2 is a stoker, 2a is a dry stoker, 2b is a burning stoker, 2C is a post-burning stoker, 3 is an ash outlet,
4 is a combustion chamber, 5 is a fixed amount supply device, 5a is a fuel supply port, 6
Is a hopper, 7 is a secondary air outlet, and 8 is a secondary air chamber. Fuel C supplied onto the stoker 2 from the quantitative supply device 5 through the fuel supply port 5a is sequentially burned on the stoker 2, and The combustion gas or the like generated by the primary combustion on the stalker 2 is secondarily burned in the combustion chamber 4 by mixing and stirring of the secondary air B.

In the present invention, the wall surface 4a on the side of the fuel supply port 5a below the combustion chamber 4 and the wall surface 4b on the side facing the fuel supply port 5a
The downward angle theta and secondary air injection port 7a _{of 1} in ejecting secondary air B _1, a downward angle theta ₂ in are provided the secondary air jet port 7b Togaotto s for injecting secondary air B _2, The secondary air is blown from the secondary air chamber 8 into the space above the stoker 2 (that is, into the space below the combustion chamber 4) as secondary air B ₁ and B ₂ .

The downward angles θ ₁ and θ ₂ when the secondary air B ₁ and B ₂ are jetted are appropriately selected according to the shape of the stoker type combustion furnace and the capacity (size) of the stoker type combustion furnace. ₁ is between 30 ° and 65 °, and θ ₂ is between 15 ° and 4 °
An angle between 0 ° is chosen respectively. In the present embodiment, θ _{1 is set} to about 45 ° and θ _{2 is set} to about 30 °.

Incidentally, in FIG. 1, the wall surface on the fuel supply port side is shown.
Secondary air B spouted from spout 7a of 4a₁Downward angle
Degree θ₁From the outlet 7b of the facing wall surface 4b 2
Next air B_TwoDownward angle θ_TwoMake it bigger, stalker 2
Swirling flow D of air and combustion gas in the space above
However, conversely, θ_Two> Θ ₁
Secondary air B₁, B_TwoSpout, air and combustion
The direction of the gas swirl can be clockwise.
You.

In FIG. 1, the outlet 7a of the wall 4a on the side of the fuel supply port and the outlet 7b of the wall 4b on the opposite side are provided.
As shown in FIG. 2, they are formed symmetrically at substantially the same height position. However, as shown in FIG. 3, the arrangement position (the number of the ejection ports) of the two ejection ports 7a and 7b is changed, or the height position (shown in FIG. 3) is changed. Needless to say, (omitted) may be changed.

Further, in FIG. 1, the secondary air B ₁ , B
₂ are jetted from the jet ports 7a and 7b arranged in two stages, respectively, but the jet port 7a and the jet port 7b are arranged in one stage depending on the structure of the stoker type combustion furnace and the supply amount of the secondary air B. And a one-stage (ie, one row) ejection port 7a and ejection port 7
It is also possible to eject secondary air B ₁ and B ₂ from b.

In addition, in the embodiment of FIG. 1, the amount of secondary air B ₁ , B ₂ discharged from the outlets 7a, 7b on both sides is substantially the same, but the secondary air B ₁ , B 2 from both sides, it is also possible to adjust the state of swirling flow D ejection amount of B ₂ respectively adjusted to.

In FIG. 1, the stoker-type combustion furnace has a structure in which the lower part of the combustion chamber 4 is narrowed so that the combustion gas on the stoker and the secondary air B are mixed well.
The present invention can of course be applied to a stoker type combustion furnace having a combustion chamber 4 having the same cross-sectional area without narrowing down the lower part of the combustion chamber 4. Although FIG. 1 shows a stoker-type combustion furnace for municipal solid waste or the like that does not aim at so-called power generation as an example, a stoker furnace provided with a waste heat boiler or a power generation facility may of course be used. That is, the present invention is applicable whether the structure of the combustion chamber 4 is a fire-resistant wall structure or a water-cooled wall structure. In addition to burning furnaces for municipal solid waste and the like, solid industrial fuel such as coal, wood chips, bagasse, etc., and general industrial boilers using chain bed stokers, transfer stokers, fixed grate, etc. The invention is applicable.

FIG. 4 shows a second embodiment of the present invention. In the staircase type stoker type combustion furnace shown in FIG. 1, the secondary air injection ports 7a and 7b are connected to the fuel supply port 5a side wall 4a. And a wall surface 4b on the opposite side thereof, and are provided in three steps. That is, as shown in FIG. 4 and FIG.
Ejection opening 7a in three stages under in the above--to 4b, 7b are arranged, in and from the ejection ports 7a _1, 7b ₁ of the upper horizontal respectively secondary air B _11, B _21, from also middle and lower of each spout _{7a 2, 7a 3, 7b 2} , 7b 3, downward angle _{θ 12, θ 13, θ 22} , with the theta ₂₃ 2 secondary air _{B 12, B 13, B 22} , B 23 Are squirted respectively.

Each of the outlets of the two wall surfaces 4a and 4b is shown in FIG.
As shown in the figure, they are formed in a line at substantially the same height. However, the respective ejection ports 7a ₁ and the ejection port 7b ₁ instead of facing in front, lateral position is Dzura mutually. This is also true for the middle and lower spouts 7
The same applies to the columns a ₂ and 7a ₂ . Further, the interval in the height direction between the rows of the outlets in each stage is appropriately determined according to the shape and capacity of the furnace, but in the present embodiment, the interval between the rows of the upper-stage outlets and the rows of the middle-stage outlets is set. Is the same as the interval between the rows of the spouts in the middle and lower rows.

Downward angle of each of the middle and lower spouts
θ₁₂, Θ₁₃, Θ_{twenty two}, Θ_{twenty three}Is the furnace shape and furnace size, etc.
Is selected as appropriate, but in the present embodiment, the downward angle
Degree θ ₁₂= Θ₁₃= About 45 °, downward angle θ_{twenty two}= Θ_{twenty three}= About 3
0 °.

In this embodiment, as described above, θ₁₂= Θ
₁₃And θ_{twenty two}= Θ_{twenty three}And θ ₁₂≠ θ₁₃And θ_{twenty two}≠
θ_{twenty three}It may be. In the present embodiment, θ₁₂= Θ₁₃>
θ_{twenty two}= Θ_{twenty three}And θ₁₂= Θ₁₃<Θ _{twenty two}= Θ_{twenty three}age
And the circulation direction of combustion gas and air should be opposite to that of Fig. 4.
Is also possible. Further, in the present embodiment, the secondary air ejection port is provided.
It is arranged in three stages, upper, middle, and lower.
In rows, the upper row is a horizontal spout and the lower row is a downward spout.
The outlet may be used, or the upper and middle stages are horizontal outlets
Alternatively, the lower stage may be configured as a downward-shaped jet port.

In addition, in the present embodiment, the amount of the secondary air B ₁₁ , B ₂₁ jetted horizontally is reduced to about 40% of the total secondary air amount,
The amount of the secondary air B ₁₂ , B ₁₃ , B ₂₂ , and B ₂₃ ejected downward is about 60% of the total amount of the secondary air, but the former is 20 to 20 depending on the shape and capacity of the stoker type combustion furnace. It is adjusted in the range of 70% and the latter in the range of 80-30%. Further, in the present embodiment, the amount of secondary air ejected from both wall surfaces is set to be substantially equal. However, the ratio of the amount of ejected air can be adjusted.

Referring to FIG. 4, fuel C on stoker 2
Unburned matter generated by drying, burning and post-burning
The combustion gas containing the gas at the lower portion of the combustion chamber 4 has a downward angle
Degree θ ₁Secondary air B jetted at₁₂, B₁₃And downward angle θ
_TwoSecondary air B jetted at_{twenty two}, B_{twenty three}And the circulation caused by
It is entrained in the reflux D and is uniformly stirred and mixed with the secondary air flow.
But circulates counterclockwise. This allows the combustion gas furnace
The internal residence time is extended considerably, and the combustion gas and secondary
The air is uniformly mixed. Mix uniformly with the secondary air
The burned gas is further ejected horizontally to the secondary gas.
Air B₁₁, B_{twenty one}Are mixed in the combustion chamber 4
So-called complete combustion. As a result, CO
Concentrations will be greatly reduced and need
The amount of excess air can be minimized. Furthermore,
The amount of dioxin generated in the lower part of the combustion chamber is also reduced
Will be.

According to the test results, when municipal solid waste is incinerated in the stoker type combustion furnace (FIG. 1) of the first embodiment, a position approximately 2.5 m above the secondary air injection position of the combustion chamber 4. The maximum value of the O ₂ concentration was about 11.8% and the minimum value was 9.0%, and the difference between the two was about 2.8% or less. On the other hand, the maximum value of the O ₂ concentration in the stoker type combustion furnace shown in FIG. 6 is 13.6%, and the minimum value is 7.0%.
It is confirmed that the O ₂ concentration distribution is greatly uniformed compared to the difference of 6.6%. The average O ₂ concentration at the furnace outlet during each of the tests was about 10.5%. Similarly, in the stoker-type combustion furnace of the first embodiment, the CO concentration at the outlet at the upper part of the combustion chamber was measured, and was found to be about 40 to 65 ppm. On the other hand, the CO concentration at the outlet in the case of FIG.
0 to 150 ppm, compared with C in the exhaust gas.
It has been confirmed that the O concentration is significantly reduced.

In the stoker type combustion furnace of the second embodiment (FIG. 4), a similar test was conducted using municipal solid waste as a fuel. In this case, the amount of secondary air ejected in the horizontal direction was 40% of the total secondary air, and the remaining 60% was ejected downward. According to the test results, the maximum value of the O ₂ concentration distribution was about 11.0%, and the minimum value was about 8.6%, and the difference between the two was about 2.4% or less. As in the case of the first embodiment, it can be seen that the O ₂ concentration distribution is remarkably improved as compared with the case of the conventional stoker type combustion furnace. The CO concentration in the exhaust gas at the exhaust gas outlet at the upper part of the combustion chamber is about 30%.
ppm to 50 ppm, and it has been confirmed that the CO concentration can be significantly reduced as compared with the conventional furnace.

[0033]

According to the present invention, the secondary air is directed toward the lower inside of the combustion chamber at different downward angles from the wall on the side of the fuel supply port below the combustion chamber and the wall on the side opposite thereto. And a circulating flow of combustion gas and secondary air is formed in the upper space of the stoker (that is, the lower space of the combustion chamber). As a result, the agitation and mixing of the combustion gas and the secondary air are promoted and the two are more completely mixed, and the stagnation time of the combustion gas in the lower space of the combustion chamber increases,
Complete combustion of the combustion gas becomes possible. This achieves a reduction in the CO concentration in the exhaust gas, a reduction in the amount of dioxin generated in the lower part of the combustion chamber, a reduction in the amount of excess air, and the like.

In the case of fuels having particulate combustibles, the fuels carry out floating combustion and remain completely unburned, resulting in an increase in unburned components and CO concentration. However, in the present invention, these unburned components are entrained in the swirling flow and completely burn, and the unburned components and the CO concentration can be greatly reduced. The present invention has excellent practical utility as described above.

[Brief description of the drawings]

FIG. 1 is an explanatory diagram showing a first embodiment of the present invention.

FIG. 2 is an explanatory view showing an arrangement state of secondary air ejection ports in the stoker type combustion furnace of FIG.

FIG. 3 is an explanatory diagram showing another arrangement state of the secondary air ejection ports.

FIG. 4 is an explanatory view showing a second embodiment of the present invention.

FIG. 5 is an explanatory view showing an arrangement state of secondary air injection ports in the stoker type combustion furnace of FIG. 4;

FIG. 6 is a schematic cross-sectional view of a conventional stoker type combustion furnace.

FIG. 7 is an explanatory diagram of an influence of a secondary air on a gas flow velocity in a conventional stoker type combustion furnace.

FIG. 8 is an explanatory diagram of a mechanism for generating hunting due to supply of secondary air.

FIG. 9 is an explanatory diagram showing a state of a gas flow flowing in a combustion chamber when secondary air is discharged from both side wall surfaces in a stepped manner and discharged.

[Explanation of symbols]

A primary air, B is the secondary air, B ₁ is the secondary air supplied from the wall of the fuel supply port side, the secondary air supplying B ₂ from the wall surface of the opposite side, C is the fuel, V is a gas Flow velocity, D: swirling flow of combustion gas / air, H: high temperature combustion section, 1: fuel supply hopper, 2: stoker, 2a: dry stoker, 2b: combustion stoker, 2c: post combustion stoker, 3: ash outlet ,
Reference numeral 4 denotes a combustion chamber, 4a denotes a wall surface on the side of the fuel supply port, 4b denotes a surface opposing the wall surface on the side of the fuel supply port, 5 denotes a fixed-quantity supply device, 5a denotes a fuel supply port, 6 denotes a hopper, and 7 denotes a secondary air outlet. , 8 are secondary air chambers.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F23G 5/16 ZAB F23G 5/16 ZABE F23L 9/02 F23L 9/02

Claims (5)

[Claims] In a stoker type combustion furnace in which primary air is supplied from below a stoker and secondary air is supplied to a lower portion of a combustion chamber, a wall on a fuel supply port side below the combustion chamber is provided. Secondary air is ejected from the opposite wall surface at the same or different downward angles toward the inside of the lower part of the combustion chamber, and the swirling flow of the secondary air and the combustion gas is formed in the upper space of the stoker. A method for supplying secondary air in a stoker type combustion furnace, characterized in that the secondary air is formed. 2. A stoker type combustion furnace in which primary air is supplied from below a stoker and secondary air is supplied to a lower part of a combustion chamber. Secondary air is ejected from the opposite wall surface at the same or different downward angles toward the inside of the lower part of the combustion chamber, and the swirling flow of the secondary air and the combustion gas is formed in the upper space of the stoker. To the upper space of the secondary air ejected from both wall surfaces at the downward angle,
A secondary air supply method in a stoker type combustion furnace, wherein secondary air is ejected from both wall surfaces. 3. The secondary in a stoker type combustion furnace according to claim 1, wherein secondary air is ejected at a downward angle from a plurality of secondary air outlets having an interval in an upward / downward direction. Air supply method. 4. The secondary air in a stoker type combustion furnace according to claim 2, wherein the secondary air supplied to the upper space of the secondary air ejected at a downward angle is the secondary air ejected horizontally. Supply method. 5. A jet 2 ejected from secondary air jets on both wall surfaces.
The secondary air flow in the stoker-type combustion furnace according to claim 1, wherein the axial center position of the secondary air flow is mutually shifted in the horizontal direction and / or the vertical direction. Supply method.