JPS61101709A - Fluidized bed type incinerator - Google Patents

Abstract

PURPOSE:To lower the height of free board and provide an incinerator having high efficiency by a method wherein a wall surface for returning dispersed flowing medium is arranged at the entire circumference of the intermediate part of the free board and at the same time the height of the free board is decreased. CONSTITUTION:An incinerator body 2 is constructed such that the horizontal cross sectional area of a part generating a fluidized bed at the lower part of the fluidized bed 10 is narrower than the horizontal cross sectional area of the lower free board 62. Between the supper and lower free boards 61 and 62 is arranged at the entire circumference of the incinerator body 2 a projection 16 having at its lower surface a wall surface 5 directed below the part for returning the dispersion medium and projected toward the center of the incinerator. The shape of the projection 16 is made such that its lower surface is a horizontal wall surface 5 and its upper surface 17 is directed toward the center part of the incinerator. It is preferable that the extremity end of the wall surface 5 for returning the fluidized medium is projected toward the central part than the part of the incinerator wall 18 forming the fluidized bed. When bumping phenomenon is generated along the incinerator wall 18 contacting with the fluidized medium 1 at the part of the fluidized bed 10, the dispersion fluidized medium 1 is struck against the wall surface 5 below the projection 16 for returning the dispersion fluidized medium, repelled and directed downwardly into the fluidized bed 10.

Description

[Detailed description of the invention] [Purpose of the invention] [Industrial application field] This invention relates to a fluidized bed incinerator.

[Conventional technology]

A fluidized bed incinerator is a fluidized bed incinerator that uses cheap heat-resistant particles such as sand or crushed stone as a fluidized medium, and is used to incinerate sewage sludge, paper sludge, plastic waste, or other industrial waste singly or in combination at the same time. A3
Organic matter is almost completely decomposed due to the liquefaction treatment at a high temperature of 0°C or higher, making it a sanitary waste treatment method.

FIGS. 6 and 7 are vertical sectional views of conventional fluidized bed incinerators, with FIG. 6 showing one without a steam boiler and FIG. 7 showing one with a steam boiler.

In order to cause the fluidized medium/for example, non-flammable sand to flow in the lower part of the furnace body on the air distribution plate J by a perforated plate etc. provided in the furnace body, an air distribution chamber is arranged under the air distribution plate 3, The air distribution room hiro is located below the air distribution plate 3 below the inlet for incineration materials such as municipal waste (not shown), and consists of multiple spaces with partitions (not shown) so that the air flow velocity differs depending on the location. is supplied to the fluidized medium l through the air distribution plate 3 to give a stirring motion to the fluidized medium l to energize it, and to supply secondary air from a secondary air port (not shown) to assist the flow of the fluidized medium l. A fluidized bed 10 is formed. The materials to be incinerated that are input into the furnace from the garbage input port are instantly combusted by the fluidized medium 1 in the fluidized bed io, and the gas space surrounded by the freeboard group (hereinafter, the gas space may be referred to as the freeboard 6). ) is sent to the post-processing equipment from the furnace exit lower.

Furthermore, Fig. 7 shows a radiant heat transfer section surrounded by a water tube wall g, and a steam boiler arranged so that exhaust gas passes between groups of water tubes.
is configured, and the furnace outlet lower of the fluidized bed incinerator is connected to the gas inlet 1 of the steam boiler l/ through the expansion joint /J.
3, and through these, heat exchange between the heat medium and gas in the water tube wall t1 and the gas is carried out, and the exhaust gas outlet/
Gas is exhausted from the plug.

In FIGS. 6 and 7, the horizontal cross-sectional area of the lower part of the furnace body where the fluidized bed 10 is generated is narrower than the horizontal cross-sectional area of the freeboard base part, and the lower furnace wall that generates the freeboard 6 and the fluidized bed lθ. The space is connected by a diagonal furnace wall/3.

[Problem that the invention seeks to solve]

This type of fluidized bed incinerator uses sand, etc., as the fluidized medium l, where ' is less than the average particle size /D, so the fluidized medium / is worn out or cracked during fluidization, resulting in a reduction in particle size. is discharged outside the furnace as dust on the exhaust gas flow rising on the freeboard 6, and due to the bumping phenomenon of the fluidized medium 1 caused by the bursting of large bubbles that coalesced inside the fluidized bed IO, as shown by arrow A in the figure. Some of the fluidized media l, which had a mixture of large and small particle sizes, were scattered and were discharged out of the furnace along with the exhaust gas flow ζ of the furnace exit lower duct. For this reason, the rate of rise of gas from the fluidized bed IO depending on the freeboard basis is generally
~3 m/e.

There has been a tendency to determine the height of the freeboard base based on the volume required for combustion, and to increase the height of the freeboard 6 to take into account scattering due to the bumping phenomenon, making the volume of the freeboard base larger than necessary.

In addition, in the case of a fluidized bed incinerator, the fluidized medium 1 jumps up to the freeboard base due to bumping, is heated by the freeboard 6 and falls down, which has the effect of increasing and maintaining the temperature of the fluidized bed. If the freeboard 6 is high, the cycle of jumping up and then falling will be long, and the heat from the freeboard portion will not be returned quickly. %, this tendency is noticeable at the start-up of the fluidized bed incinerator, which has the disadvantage that it takes time for the temperature of the fluidized bed 10 to stabilize. In addition, if a hot water generator is installed on the top of the freeboard in Figure 6, or if a steam boiler is installed as shown in Figure 7, the heat transfer tubes will be worn out by the flying fluid l, so the heat transfer tubes should be made of wear-resistant high-grade materials. Usually, heat pipes or a separate hot water generator or steam boiler are used, which has the disadvantage of high construction costs.

The present invention focuses on the fact that the bumping phenomenon of the fluidized medium occurs at the interface between the furnace wall and the fluidized medium, and provides a protrusion in the middle of the freeboard that forcibly returns the fluidized medium that is scattered due to bumping, thereby reducing the height of the freeboard. The purpose is to provide a highly efficient incinerator.

[Structure of the invention]

[Means for solving the problem] A wall surface for returning the scattered fluid medium was provided around the entire circumference of the freeboard.

[Operation] When the fluidized bed slides on the boundary between the fluidized bed and the furnace wall and a bumping phenomenon occurs, the fluidized medium explosively rises up the freeboard, collides with the wall for returning the scattered fluidized medium provided on the freeboard, and turns over. The liquid flows toward the bed or toward the center of the furnace and descends toward the fluidized bed.

〔Example〕

Embodiments of the present invention will be described below with reference to the drawings.0 Figure 1 is a longitudinal cross-sectional view of a fluidized bed incinerator. The free board 7 is the furnace outlet, and is as explained in the conventional example. The horizontal cross-sectional area of the lower portion of the furnace body where the fluidized bed 1O is generated is smaller than the horizontal cross-sectional area of the upper freeboard 6/ and the lower freeboard 6. Between the upper and lower freeboards 61 and 6 is a wall that faces downward and extends toward the center of the furnace for returning the fluidized medium for scattering! A protrusion 6 having a bottom surface is provided around the entire circumference of the furnace body. Protrusion/6
The shape of the wall 5 is that the lower surface is horizontal, and the upper surface 17 is a slope that slopes down toward the center. Wall surface for returning fluid medium! It is desirable that the tip of the furnace wall protrudes toward the center of the furnace wall where the fluidized bed is generated.

In FIG. 1, a fluidized bed 10 is generated as in the conventional example. When a bumping phenomenon occurs along the furnace wall l in contact with the fluidized medium l in the fluidized bed io, the scattered fluidized medium progresses like a mouth in FIG. ! The liquid collides with the liquid, rebounds, and heads downward into the fluidized bed 10. A part of the scattered fluid medium 1 rises directly to the upper freeboard 61. Since the fluid medium falling in these upper freeboards 6 slides down the upper surface 7 of the flying projection 6, the fluid medium does not accumulate on the upper surface 7.

The height from the air distribution plate 3 to the top /q of the fluidized bed incinerator is 1 (-H): /~, where H is the conventional example in Fig. 6 and ■'' is the height of the example of the present invention. cm, and even if the height is low, the amount of fluidized medium that comes out of the furnace exit lower due to bumping is reduced.

2 and 3 are longitudinal sectional views of other embodiments of the present invention, in which the shape of the wall surface for returning the scattered fluidized medium is such that the cross-sectional area of the exhaust gas flow path is smooth toward the exhaust gas discharge side. This is a slope for returning the scattered fluid medium that gradually decreases. The cross-sectional area of the exhaust gas passage surrounded by the j end of the wall surface on the center side of the furnace, 2/, has an exhaust gas flow rate of 3. ! ; If it can be made below /θ,
It may be smaller than the cross-sectional area of the exhaust gas flow path just above the fluidized bed (same as the part with the symbol /g).

In the embodiment shown in FIG. 2, the wall surface j for returning the scattered fluidized medium in the embodiment shown in FIG. Similarly, a wall surface 5 is provided, and a furnace upper wall 22 is provided in a cylindrical shape having the same cross section as the end of the wall surface 3 on the furnace center side.

Figure 5 is a longitudinal cross-sectional view of still another embodiment, in which a plurality of secondary air ports 23 are provided on the wall surface for returning the scattered fluid medium in which the cross-sectional area of the exhaust gas flow path gradually decreases toward the exhaust gas discharge side. An example is shown below. By supplying secondary air to this part, it is possible to promote combustion in the part where the scattered fluidized medium is forced to fall, and it is possible to increase the rate of heat reduction to the fluidized bed part by the scattered fluidized medium. . The wall surface for returning the scattered fluidized medium where the cross-sectional area of the freeboard 6 starts to gradually decrease from the top of the fluidized bed 10! The height h to the part is 2.0 to l
ljm is desirably 0. This is because if it is too low, the fluidized bed IO will be cooled due to the influence of secondary air and the temperature of the fluidized bed 10 will drop. On the other hand, if it is too high, the scattered fluidized medium 1 cannot be returned properly. According to experiments, it is preferable to attach a plurality of them downward toward the center line of the furnace toward the secondary air vent 3 within an angle range of θ to 1IS0 with respect to the horizontal line.

FIG. 5 is a longitudinal sectional view of an embodiment in which a steam foiler is installed above the freeboard. Top of fluidized bed incinerator/? does not have a furnace wall, and constitutes a radiant heat transfer section 27 which is open and surrounded by a water tube wall g above the furnace top 19, and the exhaust gas passes through the radiation heat transfer section 27 and enters the water tube for convection heat transfer. It passes between the two groups and is discharged from the exhaust gas outlet /lI. The cross section of the boiler body uF gradually decreases toward the bottom, leading to the incineration ash conveyor t. Since there is no wear due to collision with the wall t, there is no need to use high-grade wear-resistant steel pipe material for the water pipe wall. The fine fluid medium and incinerated ash discharged together with the exhaust gas proceed as shown by arrow 2 in the figure, descend while passing through the water pipes, enter the conveyor t from the inlet of the conveyor, 2g, and L5, and are sent to the conveyor exit. -26 and the exhaust gas is discharged from the exhaust gas outlet lII and discharged into the atmosphere through an exhaust gas treatment device (not shown).

In this embodiment, even if the water tube wall g is provided in the upper part of the fluidized bed incinerator, there is a wall surface 3 for returning the scattered fluidized medium, so most of the fluidized medium due to bumping is returned by the wall surface 3, and the water tube wall is Only a very small amount of the scattered fluid medium reaches the water tube wall t, and no wear of the water pipe wall t due to the scattered fluid medium is observed. Since the height of the fluidized bed incinerator can be made low, this example shows that it is suitable for providing a boiler in the upper part of a fluidized bed incinerator that requires a high overall height.

Similarly to FIG. 3, a steam boiler can be installed using any of the fluidized bed incinerators shown in FIGS. 1 to 4.

The fluidized bed incinerator of each embodiment may be equipped with a hot water generator above the freeboard (not shown).

〔Effect of the invention〕

The present invention eliminates the need to increase the freeboard volume unnecessarily by installing a wall surface for returning the scattered fluidized medium all around the middle part of the freeboard of the fluidized bed incinerator, thereby reducing the height of the fluidized bed incinerator. Since the flying fluid medium is forced to collide and fall, the heat from the freeboard can be quickly returned and a highly efficient combustion state can be created. Sara '
Furthermore, by supplying secondary air to the portion where the cross-sectional area of the exhaust gas flow path gradually decreases, heat can be returned from the freeboard to the fluidized bed part more efficiently. In addition, because the scattering fluidized medium due to the bumping phenomenon is forcibly restricted, it is possible to install a hot water generator or a steam boiler without using heat exchanger tubes made of wear-resistant, high-grade materials on the top of the freeboard, and the heat exchanger tubes do not wear out. becomes less.

If the wall surface for returning the scattered fluid medium is installed obliquely so that the cross-sectional area of the exhaust gas flow path gradually decreases toward the exhaust gas discharge side, the scattered fluid medium that bounces off the wall surface will rise along with the gas flow. Since the rise of the medium is suppressed, the fluidized medium discharged outside the furnace and the incineration pressure are reduced.

As described above, the present invention has the great effect of reducing the construction cost of an incinerator and making it possible to provide a highly efficient incinerator.

[Brief explanation of drawings]

1 to 3 are longitudinal cross-sectional views of embodiments of the present invention, respectively;
6 and 7 are longitudinal sectional views of the conventional example. l... Fluid medium C... Furnace body 3... Air distribution plate D...
・Air distribution room j・・Wall surface 6−・Free board 61
・・Upper freeboard 6a・・Lower freeboard 7・
・Furnace outlet t・・Water tube wall D・・Water tube lO・-Fluidized bed//'-I air boiler /λQ-Expansion joint
lJe・Gas population /4I・・Exhaust gas outlet 13・・Furnace wall 16・・Protrusion /7・・Top surface it・・・Furnace wall 19
・Furnace top, 2/・Fist exhaust gas flow path Here...Furnace upper wall
λ3...Secondary air port Jl...Boiler can body Ko5...Inlet loco 6...Outlet Core...Radiation heat transfer section 2t...Incinerated ash conveyor 0

Claims (1)

[Scope of Claims] 1. A fluidized bed incinerator characterized in that a wall surface for returning a scattered fluidized medium is provided around the entire circumference of the intermediate portion of the freeboard, facing downward and protruding toward the center of the furnace. 2. The fluidized bed incinerator according to claim 1, wherein the wall surface for returning the scattered fluidized medium is formed by providing a protrusion projecting from the freeboard to the center. 3. The fluidized bed incinerator according to claim 1 or 2, wherein the wall surface for returning the scattered fluidized medium is installed obliquely so that the cross-sectional area of the exhaust gas flow path gradually decreases toward the exhaust gas discharge side. 4. A plurality of secondary air ports are provided on the wall for returning the scattered fluidized medium, facing the center line of the furnace and downward in the range of 0 to 45 degrees with respect to the horizontal line.Claim 1 or 2 The fluidized bed incinerator described in item 3 or item 3. 5. The fluidized bed incinerator according to any one of claims 1, 2, 3, and 4, which has a hot water generator on the top of the freeboard. 6. A fluidized bed incinerator according to any one of claims 1, 2, 3, and 4, which has a steam boiler radiant section above the freeboard.