JP2714530B2 - Incinerator and incineration method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an incinerator installed in a municipal solid waste incineration plant and the like, and a method for incinerating incinerated materials using the incinerator.

[0002]

2. Description of the Related Art In general, in a municipal solid waste incineration plant, an incinerator is one of the important equipment, and plays a role of completely burning and incinerating input waste and suppressing generation of harmful substances during the combustion. Play.

This incinerator is roughly classified into a stoker type and a fluidized bed type. Here, as an example, a conventional structure of a fluidized bed incinerator is shown in FIG.

[0004] A main body 80 of an incinerator shown in the figure is formed by laminating a refractory material 81, a heat insulating material 82 and a steel shell 83 in this order from the inside, and a sand layer 84 is provided at the bottom. Fluidized air (primary air for combustion) is blown out from below the sand layer 84 through an air diffuser 86 into the sand layer 84, and the sand layer 84 starts flowing by this air. During start-up, the sand layer 84 is heated by the heating burner 87 at the upper part,
When the temperature reaches 700 ° C., dust is charged into the furnace from the dust feeder 88, and a part of the dust is ignited by the heat of the sand layer and gasified. Part of the heat generated by this combustion is
And the sand layer temperature is kept constant at about 700 ° C.
The gasified waste is in the space above the sand layer 84 (free board)
90, where secondary combustion is performed while being mixed with the secondary air (auxiliary combustion air) from the secondary combustion air nozzle 89.
It is discharged outside at an outlet temperature of 900 ° C. The non-burnable refuse circulates in the sand layer 84, and finally, the incombustible discharge pipe 9.
2. The sand (fluid medium) discharged to the outside through the incombustible extractor 94 and the vibrating sieve 96 and separated from the incombustible waste by the vibrating sieve 96 is returned to the sand layer 84 in the incinerator through the fluid medium circulator 98. It is.

[0005]

In recent years, the emission of dioxins from municipal waste incineration plants has become a major social problem. In order to control such dioxin emission, three Ts, namely, the residence time (Time) of the gas in the free board 90, the temperature (Temperature) in the free board 90, and the turbulence of the gas in the free board 90 are described. (Turbulence), that is, the mixing efficiency of gasified waste and air is considered important.

Here, in the conventional incinerator, the time and the temperature among the above three T sufficiently satisfy the conditions, and the improvement of the mixing is a major problem. As means for improving the mixing of air and unburned gas generated from this waste, (A)
Secondary air is blown into the incinerator from the side to bend the main flow (Japanese Patent Laid-Open No. 5-141646, etc.), and (B) the shape of the incinerator itself is constricted or bent to induce gas turbulence. Measures have been taken, but none of them has been sufficiently effective.

[0007] Instead of improving the degree of mixing, dioxin can be reduced by performing combustion control so as to supply an optimal amount of air to the actual amount of waste. It is difficult to perform accurate combustion control as described above because it is difficult to accurately measure the temperature and the combustion state changes depending on the quality of the refuse.

As means for improving the mixing,
Although it has been considered to form irregularities such as a restrictor and a baffle plate in the furnace to disturb the air flow, such irregularities are easily worn, and the production is not easy, so there is an inconvenience that leads to an increase in cost.

In view of such circumstances, the present invention effectively mixes incineration materials such as gasified refuse and auxiliary combustion air with dioxin without providing a throttle or baffle plate in the furnace. It is an object of the present invention to provide an incinerator that can reduce emissions.

[0010]

As a means for solving the above-mentioned problems, the present invention provides a primary combustion region in which a supplied incineration material is burned and gasified at the bottom of an incinerator body. A direction in which a swirling flow is formed on a horizontal plane with respect to the secondary combustion region in an incinerator in which a secondary combustion region for further burning the gas is formed in the incinerator main body space above the primary combustion region. A plurality of first injection sections for injecting auxiliary combustion air in the circumferential direction, and on a horizontal section at a height position higher than the first injection sections, at the center of the secondary combustion area. A plurality of second injection units for injecting auxiliary combustion air in a direction toward the head are arranged side by side in the circumferential direction, and at a height position higher than the second injection units, the first injection unit is disposed on a horizontal plane with respect to the secondary combustion region. Auxiliary fuel in the direction that forms a swirl flow opposite to the swirl flow by the injection unit It is obtained by juxtaposed third ejecting portion of a plurality of injecting air in the circumferential direction (claim 1).

[0011] In the incinerator, the first injecting part is provided by the second injecting part.
The distance in the height direction to the injection unit and the third distance from the second injection unit
The distance in the height direction to the jetting unit is set to be equal, and the relative angle of the jetting direction of the third jetting unit with respect to the jetting direction of the second jetting unit is set in the first jetting unit with respect to the jetting direction of the second jetting unit. It is more preferable that the angle is set opposite to and equal to the relative angle of the injection direction of the incinerator (claim 2). By setting the injection flow rate and the injection flow rate from the third injection section to be substantially equal, a more excellent effect as described later can be obtained (claim 3).

Further, in the incinerator, when the supply amount of the incinerator into the incinerator main body decreases, only the injection flow rate from the first injection section and the injection flow rate from the third injection section are reduced. Good (claim 4).

[0013]

According to the above incinerator, pyrolysis gas is generated by burning the incinerated material in the primary combustion area at the bottom of the incinerator body, and this gas rises to the secondary combustion area and mixes with the auxiliary combustion air. By doing so, it burns further.

More specifically, the pyrolysis gas that has risen from the primary combustion region is first mixed with the auxiliary combustion air in a swirl flow formed by the injection of the first injection unit. Thereafter, the gas rises to the injection region of the second injection unit. However, since the injection flow from the second injection unit acts in a direction that hinders the swirling of the swirling flow, a large shear flow is generated here. This shear flow causes locally strong flow turbulence, which promotes the mixing of the pyrolysis gas and auxiliary combustion air. Further, when the gas is subjected to a force in a direction opposite to the swirling direction by the auxiliary combustion air injected from the third injection unit, a shear flow similar to that described above is generated, and the mixing is further increased due to the strong flow turbulence. Promoted. By such mixing promotion, the flammability is finally dramatically improved.

Here, if there is no injection from the second injection part (that is, if there is no injection toward the center of the space inside the incinerator main body, and there is only a contradictory swirling flow), the above-mentioned or more than that Although a shearing force can be expected, in this case, the gas from the primary combustion region easily blows upward through the center of each swirling flow, and if such blow-through occurs, the mixing property is significantly reduced. Will be. When there is no injection from the third injection unit, that is, when there is no upper swirl flow, the auxiliary combustion air injected from the second injection unit is affected by the swirl flow by the injection of the first injection unit. Since the gas is swept in the turning direction, the gas may blow through the center of the turning.

On the other hand, as in the incinerator of the present invention, the second
If the injection flow from the injection unit is sandwiched from above and below by the contradictory swirling flows of the first injection unit and the third injection unit, the components in the swirling direction of both swirl flows are offset in the injection region by the second injection unit. In the injection region, the direction of the flow from each second injection unit toward the center is ensured. The jets from the second injection unit collide with each other at the central part of the incinerator main body, thereby increasing the pressure at the central part. By flowing back toward, gas blow-through at the center is effectively suppressed, and good mixing properties are guaranteed.

Here, in the incinerator according to claim 2, the distance in the height direction from the second injection unit to the first injection unit and the distance in the height direction from the second injection unit to the third injection unit. And the relative angle of the injection direction of the third injection unit to the injection direction of the second injection unit is opposite to the relative angle of the injection direction of the first injection unit to the injection direction of the second injection unit. In addition, since the angles are set to be equal in size, the injection flow rate from the first injection unit and the injection flow rate from the third injection unit are set to be substantially equal as described in claim 3, so that The swirling direction components of the two swirling flows can be more reliably canceled in the injection region of the two injection units.

As described above, in order to ensure good mixing, it is premised that prevention of blow-through at the center is required. As described in 4, if only the injection flow rate from the first injection section and the injection flow rate from the third injection section are reduced, the injection flow of the second injection section is reduced even if the overall injection flow rate is reduced. The blow-through prevention action can be reliably maintained, and thereby good mixing properties can be ensured.

[0019]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIGS. In the fluidized bed incinerator shown here, the layer structure of the side wall of the incinerator main body 10 and the configuration of peripheral devices are the same as those in FIG. 6, and the description thereof will be omitted here.

The incinerator body 10 shown here has a cylindrical shape, and as shown in FIG. 1, a gas discharge port 12 is formed in an upper portion of the incinerator body 10. A sand layer (not shown) equivalent to the sand layer 84 shown in FIG. 6 is formed in the primary combustion region at the bottom of the incinerator main body 10, and the free board 16 is formed above the sand layer. The sand layer is the incinerator body 1
Fluidized by the primary combustion air blown up from the bottom,
By injecting incineration material such as dust into the sand layer from an inlet (not shown), the incineration material is burned in the sand layer.

The incinerator is characterized by a first injection port 14A, a second injection port 14B, and a third injection port for injecting secondary combustion air (auxiliary combustion air) into the freeboard 16 over a total of three stages in the vertical direction. An injection port 14C is provided. Each injection port 14A, 14B, 14C has a flow control valve 17A,
The air supply device 15 is connected via 17B and 17C, respectively.

The lowermost first injection ports 14A are provided at a plurality of positions in the circumferential direction, as shown in FIG. 2A, at a height above the sand layer. Each first injection port 14
The direction of injection by A (the direction of the bold line arrow in the figure (a)) is a predetermined angle θ with respect to the direction from each first injection port 14A toward the center of the incinerator main body 10 (radial direction; the direction of the dashed line in the figure). It is set in the direction inclined in the circumferential direction.

The second injection port 14B in the middle stage has a horizontal cross section at a height higher than the first injection port 14A.
As shown in (b), it is provided at a plurality of positions arranged in the circumferential direction. The direction of injection by each of the second injection ports 14B (the direction of the thick line arrow in FIG. 3B) is set to the same direction as the radial direction.

The uppermost third injection port 14C is located at a higher position than the second injection port 14B, as shown in FIG.
As shown in (c), they are provided at a plurality of positions arranged in the circumferential direction. The direction of injection by each third injection port 14C (the direction of the thick arrow in FIG. 3C) is the first direction with respect to the radial direction.
Angle θ of the same magnitude in the opposite direction to the injection direction of injection port 14A
It is set in the direction inclined only in the circumferential direction. The distance d between the third injection port 14C and the second injection port 14B
₂₃ (FIG. 1) is set equal to the distance d ₁₂ between the first injection port 14A and the second injection port 14B.

Next, the operation of the incinerator will be described.

In this incinerator, refuse is thrown into a sand layer (not shown) at the bottom of the incinerator body 10, so that the refuse is burned and gasified, and the pyrolysis gas rises to the upper free board 16.

In the free board 16, the auxiliary combustion air (secondary air) injected from the lowermost first injection port 14A forms a swirling flow in the clockwise direction in FIG. 2A. In the swirling flow, the first-stage mixing of the pyrolysis gas and the auxiliary combustion air is performed. After that, the gas
Although it rises to the injection area by the injection port 14B, the injection flow from each of the second injection ports 14B toward the center of the free board 16 acts in a direction that obstructs the swirling of the swirling flow, thereby generating a large shear flow. I do. This shear flow causes locally strong flow turbulence, which further promotes the mixing of the pyrolysis gas and auxiliary combustion air. This gas rises further to the injection region of the third injection port 14C, but in this case, the auxiliary combustion air injected from each third injection port 14C forms a swirling flow in the direction opposite to the above-described swirling direction. A shear flow similar to that between the first injection port 14A and the second injection port 14B is generated between the swirling flow and the injection flow of the second injection port 14B, and the mixing is also caused by strong flow turbulence. Is further promoted. By promoting such mixing, the generation of dioxin can be significantly suppressed.

Here, if there is no injection from the second injection port 14B (that is, if there is no injection toward the center of the secondary combustion region and only a reciprocal swirl flow exists),
Although a shear force equal to or higher than the above can be expected, in this case, gas from the sand layer may blow upward through the center of each swirling flow, and if such a blow-through occurs, on the contrary Mixability will be significantly reduced. When there is no injection from the third injection port 14C, that is, when there is no upper swirl flow, the auxiliary combustion air injected from the second injection port 14B is supplied to the first injection port 14C.
Since it is swept in the swirling direction under the influence of the swirling flow due to the injection of A, the gas may also blow through the swirling center.

On the other hand, if the injection flow from the second injection port 14B is sandwiched from above and below by the contradictory swirling flows by the first injection port 14A and the third injection port 14C as in the incinerator of this embodiment, The component in the swirling direction of both swirling flows is the second injection port 1
4B, the flow toward the center is secured at the second injection port 14B. The jets from the second injection port 14B collide with each other in the central portion of the incinerator main body, thereby increasing the pressure in the central portion, and a part of the rising gas is repelled at the high pressure portion to the lower sand layer. Backflow toward the center effectively suppresses gas blow-through at the center, and ensures good mixing.

That is, the swirling flow sandwiching the jet flow from the second injection port 14B from above and below plays the role of promoting the mixing by the formation of the shear flow, and properly maintains the direction of the jet flow from the second injection port 14B. It will play both roles in maintaining the central part blow-through prevention effect.

Further, in the incinerator of this embodiment, the distance d ₁₂ from the second injection port 14B to the first injection port 14A and the distance d ₂₃ from the second injection port 14B to the third injection port 14C.
Are set equal, and the relative angle of the injection direction by the third injection port 14C with respect to the injection direction by the second injection port 14B is changed by the injection direction of the first injection port 14A with respect to the injection direction by the second injection port 14B. Since the angle is set opposite to the relative angle and equal in size, the first injection port 14A is operated by operating the flow control valves 17A and 17C.
By setting the injection flow rate from the third injection port 14C and the injection flow rate from the third injection port 14C to be substantially equal, it is possible to surely cancel out the effects of both swirling flows in the injection area of the second injection port 14B.

As described above, since it is premised to prevent blow-through at the center in order to ensure good mixing, when the amount of dust or the like charged into the incinerator main body decreases, the The injection flow rate from the second injection port 14B is fixed,
If only the flow rate adjusting valves 17A and 17C are operated to reduce only the injection flow rate from the first injection port 14A and the injection flow rate from the third injection port 14C, the overall injection flow rate can be reduced. The blow-through prevention action by the jet flow of the second jet port 14B can be surely maintained, and thereby good mixing properties can be ensured.

FIGS. 3 and 4 show the CO in the conventional incinerator shown in FIG. 6 and the CO in the incinerator of this embodiment shown in FIG.
3 shows the result of calculating the mixed state and the velocity vector of the gas by numerical flow calculation. However, regarding the mixed state of CO, an appropriate amount of tracer is allowed to flow through the sand layer portion, and the calculation is performed by tracking the tracer. Referring to these figures, the recirculation vortex is hardly formed inside the conventional incinerator, and the mixed state of CO is poor. On the other hand, in the incinerator according to the present embodiment, the recirculation vortex clearly appears in the secondary combustion region. It can be understood that backflow is generated at the center and gas blow-through is effectively prevented.

The present invention is not limited to the embodiment described above, but may take the following forms as examples.

(1) In the present invention, each of the injection ports 14A to 14A
Although the specific height position of 4C is not limited, the height position of the lowermost first injection port 14A may be set at least high enough that the injection flow is not affected by the sand layer or the like in the primary combustion area. Extremely desirable.

(2) In the present invention, the air ratio in the secondary combustion region may be set appropriately. However, it is preferable to adjust the air ratio so that a high temperature of about 1000 ° C. can be maintained in this region.

(3) In the present invention, the specific temperature of the auxiliary combustion air does not matter, but if the auxiliary combustion air is preheated before the introduction, the cooling in the incinerator due to the introduction can be avoided. And better combustion can be ensured.

(4) In the present invention, the cross section taken along line AA, line BB, and line CC shown in FIG. 1, for example, is shown in FIG. (B) Even in the case of a rectangular shape as shown in (c), as shown in these figures, the swirling flow is generated in the injection region by the first injection port 14A and the second injection In the same manner as in the previous embodiment, the injection direction is set so as to form the injection flow toward the center in the injection region by the port 14B, and to form the swirl flow in the injection region by the third injection port 14C in the direction opposite to the swirl flow. Can obtain good mixing properties.

In the above embodiment, the swirling flow in the clockwise direction in the injection region of the first injection port 14A is generated by the third injection port 1A.
While the swirl flow in the counterclockwise direction is formed in the injection region by 4C, the swirl flow in the counterclockwise direction in the injection region by the first injection port 14A and the clockwise rotation in the injection region by the third injection port 14C. The swirling flows in the circumferential direction may be respectively formed.

[0040]

As described above, according to the present invention, as means for injecting auxiliary combustion air into the secondary combustion area, the first injection section for forming a swirling flow on the horizontal plane and the center of the incinerator main body. Since the second injection unit that forms the jet flow in the direction and the third injection unit that forms the swirl flow in the opposite direction to the swirl flow of the first injection unit are provided in order, the flow is generated between the respective injection units. The mixing of the auxiliary combustion air and the pyrolysis gas is promoted by the generated shear flow, and the swirling direction components of the upper and lower swirling flows are canceled in the injection region by the intermediate second injection unit, and the injection toward the center is performed by the second injection unit. By ensuring the flow, the effect of preventing the central gas from being blown through by the jet flow can be favorably maintained, whereby there is an effect that sufficient mixing is obtained and the emission of dioxin can be largely suppressed.

Here, in the incinerator according to the second aspect, the distance in the height direction from the second injection unit to the first injection unit and the distance in the height direction from the second injection unit to the third injection unit. Are set equal, and the relative angle of the injection direction of the third injection unit with respect to the injection direction of the second injection unit is set to the second angle.
Since the angle is opposite to and equal to the angle of the injection direction of the first injection unit with respect to the injection direction of the injection unit, the injection flow rate from the first injection unit is set as described in claim 3. By setting the injection flow rate from the third injection section to be substantially equal to each other, it is possible to more reliably cancel both swirling flows in the second injection section, thereby maintaining a sufficient central part blow-through prevention effect. There is an effect that can be.

Further, when the supply amount of the incinerator into the incinerator main body is reduced, only the injection flow rate from the first injection section and the injection flow rate from the third injection section are determined. By reducing the amount, even if the overall injection flow rate is reduced, the blow-by prevention action by the injection flow of the second injection unit can be reliably maintained, and the effect of ensuring good mixing properties can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional front view showing a main part of an incinerator according to a first embodiment of the present invention.

2A is a cross-sectional view taken along the line AA of FIG. 1, and FIG.
1 is a sectional view taken along line BB of FIG. 1, and FIG. 2C is a sectional view taken along line CC of FIG.

FIG. 3 is a diagram showing a result of calculating a mixed state of CO and a velocity vector of gas in a conventional incinerator.

FIG. 4 is a diagram showing a result of calculating a mixed state of CO and a velocity vector of gas in the incinerator of the embodiment.

5 (a), 5 (b) and 5 (c) are cross-sectional plan views showing modified examples of the planar cross-sectional shape of the incinerator of the present invention.

FIG. 6 is a sectional front view showing an example of a conventional incinerator.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Incinerator main body 14A 1st injection port 14B 2nd injection port 14C 3rd injection port 15 Air supply device 16 Free board

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Kenzo Kokura 1-3-18 Wakihama-cho, Chuo-ku, Kobe Kobe Steel, Ltd. Kobe Head Office (56) References JP-A-5-288305 (JP, A )

Claims (4)

(57) [Claims] A primary combustion region is formed at the bottom of the incinerator main body to burn and gasify the supplied incineration material, and the gas is provided in an incinerator main body space above the primary combustion region. In the incinerator in which a secondary combustion region for further burning the fuel is formed, a plurality of first injection units for injecting auxiliary combustion air in a direction of forming a swirling flow on a horizontal plane with respect to the secondary combustion region are arranged in a circumferential direction. A plurality of second injection units for injecting auxiliary combustion air in a direction toward the center of the secondary combustion region on a horizontal cross section at a height position higher than the first injection units. And at a height position higher than the second injection section, the first combustion section is located on a horizontal plane with respect to the secondary combustion area.
An incinerator characterized in that a plurality of third injection units for injecting auxiliary combustion air in a direction forming a swirl flow in a direction opposite to a swirl flow by an injection unit are arranged in a circumferential direction. 2. The incinerator according to claim 1, wherein a distance in a height direction from the second injection unit to the first injection unit and a distance in a height direction from the second injection unit to the third injection unit are determined. And the relative angle of the injection direction of the third injection unit with respect to the injection direction of the second injection unit is opposite to the relative angle of the injection direction of the first injection unit with respect to the injection direction of the second injection unit. An incinerator characterized in that the angles are set to be equal in size. 3. The incineration method according to claim 2, wherein an injection flow rate from said first injection section and an injection flow rate from said third injection section are set substantially equal. . 4. The incinerator according to claim 1, wherein when the supply amount of the incinerated material into the incinerator main body decreases, the injection flow rate from the first injection unit and the injection flow from the third injection unit. An incineration method using an incinerator characterized by reducing only the flow rate.