JPH0350924B2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a fluidized bed boiler for fluidized combustion of coal, etc., and particularly to a collision type inertial dust collector as a collection device for particles scattered from a combustion section. This relates to a fluidized bed boiler equipped with a.

[Prior Art] As is well known, in a fluidized bed boiler, a gas distribution plate is installed inside a furnace body, a fluidized combustion section is formed on the upper side of the gas distribution plate, and a fluidized combustion section is formed on the lower side of the gas distribution plate. forms an air chamber. A gas dispersion plate passes through the air chamber and blows up air, which causes particles such as coal to flow together with the fluidizing medium and burn.

In conventional fluidized bed boilers, sand or limestone for desulfurization is used as the fluidized medium, and the fluidized medium extracted from the fluidized bed is discarded after heat recovery. In addition, particles containing debris and unburned carbon in the coal scattered from the fluidized bed are collected by a cyclone, etc., and returned to the combustion fluidized bed for re-burning.
Alternatively, it is introduced into a separately installed reburning furnace and reburned.

Another type of fluidized bed boiler is to form a fluidized bed of desulfurization material such as limestone above the combustion section where solid particles such as coal are burned, and to introduce gas from the combustion fluidized bed into the desulfurization material fluidized bed. Desulfurization products have been developed in recent years.

[Problems to be Solved by the Invention] In a type in which limestone is supplied as a fluidized medium into a combustion fluidized bed of coal, etc., and combustion and desulfurization are performed simultaneously, the temperature conditions for desulfurization and the temperature conditions for combustion are different. It is difficult to overlap each other, making it difficult to perform efficient desulfurization. In addition, when collecting combustion gas from a fluidized bed using a cyclone, it is necessary to increase the flow rate of the combustion gas to separate particles.
The pressure loss was large, for example, about 50 to 100 mmAq. In addition, in order to prevent wear caused by this high-temperature, high-velocity, dust-containing air flow, an expensive wear-resistant heat insulating material must be attached to the inner wall surface of the cyclone, increasing the cost of the device configuration. Furthermore, the size of the cyclone was almost the same as the combustion chamber, and the installation space was unnecessarily large.

Additionally, when desulfurization is generally performed by introducing combustion gas into a fluidized bed of desulfurization material, if the amount of particles (ash) contained in the combustion gas increases, such as when the solid fuel has a high ash content, the desulfurization reaction will be hindered. ,
Desulfurization efficiency may decrease. That is, since CaSO ₄ , which is a product of the desulfurization reaction, has the effect of lowering the melting point of the ash, if the amount of ash becomes excessively large, a large amount of ash will be fused to the surface of the desulfurization material particles, and the desulfurization reaction will be inhibited.

[Means for Solving the Problems] The fluidized bed boiler of the present invention comprises: a combustion section that performs fluidized combustion of fuel; a desulfurization section that forms a desulfurization material fluidized bed provided downstream of the fluidized combustion section; A collision-type inertial dust collector is provided between the combustion section and the desulfurization section and collects scattered particles from the combustion section.

This dust collector is provided with a gutter-like member at the lower end of a buff-full plate that is vertically installed from the upper lid, and the end of the gutter-like member is connected to a part of the dust collector that extends downward along the inner wall surface of the dust collector. It is connected to a conduit for falling.

[Operation] In the fluidized bed boiler of the present invention, fuel such as coal is supplied to the combustion section and is fluidized and combusted. A suitable fluidizing medium, for example sand, is fed into this combustion section. A considerable amount of unburned carbon and debris scattered from the combustion section is collected by the collision-type inertial dust collector. The combustion gas from which the particles have been collected and separated is introduced into the desulfurization section, where it is desulfurized, and then sent to, for example, a waste heat boiler.

In the above-mentioned collision type inertial dust collector, the airflow velocity is much lower than that of a cyclone, so the pressure loss is small. In addition, internal wear is small and the volume is small.

Further, in the desulfurization section, the combustion gas from which the required amount of particles have been collected and separated by the collision-type inertial dust collector is introduced, so that the desulfurization reaction is prevented from being inhibited by ash, and the desulfurization reaction is carried out with high efficiency.

[Example] Examples will be described below with reference to the drawings.

FIG. 1 is a system diagram showing a fluidized bed boiler according to an embodiment of the present invention. Reference numeral 10 is the main body of the fluidized bed boiler, in which a dispersion plate 14 is installed at the bottom of the furnace body 12, the lower side of the dispersion plate 14 is used as an air chamber 16, and the upper side of the dispersion plate 14 is used for fluidized combustion. A combustion section 18 is formed. Reference numeral 20 indicates a pipe for supplying fuel (coal in this embodiment).

A water pipe 22 is installed inside this furnace body 12, and an opening 26 is provided on the side in the upper freeboard section 24, and a chamber 3 of an impact type inertial dust collector 28 is provided.
It is communicated within 0. This collision type inertial dust collector 28 is equipped with a buff-full plate 32, and the combustion gas from the freeboard section 24 is transferred to the buff-full plate 32.
2 and flows downstream.

The details of the structure of this collision type inertial dust collector will be explained with reference to FIGS. 2 to 4. Reference numeral 28A denotes a device casing, one end of which is provided with a combustion gas inlet 28B that communicates with the opening 26, and the other end with an outlet 28C. The baffle plate 32 is installed between the inlet 28B and the outlet 28C, tilting downward from the upper lid part 28D, and a particle outlet 28E is provided below the buffle plate 32. There is.

This baffle plate 32 is shown in FIG.
As shown in FIG. 3, which is a line cross-sectional view, and FIG. 4, which is a cross-sectional view taken along the line - in FIG. A gutter-like member 28F is provided along this bottom portion 32a. The gutter-like member 28F
Both ends of the baffle plate 32 extend to the left and right sides of the buff-full plate 32, and are connected to the particle falling conduit 28G at both the left and right ends. The conduit 28G extends downward along the side wall surface of the casing 28A,
Its lower end reaches near the outlet 28E.

Reference numeral 28H indicates a blanket made of fireproof and heat insulating fibers attached to the inner surface of the casing 28A.

The collision type inertial dust collector 28 is connected to the desulfurization section 34 . This desulfurization section 34 fluidizes limestone as a desulfurization material supplied from a supply pipe 36 on a dispersion plate 38 to form a fluidized bed of limestone to perform desulfurization. On the downstream side of the desulfurization section 34, there is a first
A waste heat boiler 40 and a second waste heat boiler 42 are installed in series. Reference numeral 44 indicates a duct connecting these waste heat boilers 40 and 42, and 46 indicates a duct for guiding gas passing through the waste heat boiler 42 to a bag filter, an electrostatic precipitator, or the like. code 4
8 is a dust collector, and rotary valve 5
It is connected to an ash processing device via a powder discharge device such as 0 and piping 52.

Reference numeral 54 denotes a reburning furnace constituting the reburning section, and a gas distribution plate 56 is installed inside the reburning furnace to partition the air chamber 58 and the fluidized reburning section 60.
An air supply pipe 62 is connected to the air chamber 58. Reference numeral 63 indicates a fluidized medium discharge pipe from the reburning section 60. Reference numeral 63b indicates a separator, and 63a indicates a recycle line.

This reburning furnace 54 and the furnace body 12 are connected by a pipe 64, and the combustion ash of the fluidized medium can be introduced from the combustion section 18 into the fluidized reburning section 60. Further, the reburning furnace 54 is connected to the bottom of the chamber 30 through a pipe 66, so that particles collected by the inertial dust collector 28 can be introduced into the fluidized reburning section 60. Reference numeral 67 indicates a powder discharge device such as a rotary valve. In addition, 63 is a fluidized reburning section 6
0, and is connected to a separator 63b for separating small-diameter particles and large-diameter particles. 63a is a recycling line for small diameter particles.

The combustion exhaust gas from this reburning furnace 54 is passed through the exhaust duct 6.
8, 68a, and 68b, it can be introduced into one or both of the downstream side of the desulfurization section 34 and the duct 44. 68a and 68b indicate ducts branched from the duct 68.

In the fluidized bed boiler configured in this way,
Coal as a fuel is supplied to the combustion section 1 through a supply pipe 20.
8 and is fluidized and combusted by the air blown up from the air chamber 16. The combustion gas rises within the furnace body 12, exchanges heat with the water tube 22, and is then introduced into the inertial dust collector 28 through the opening 26. Then, the particles that collide with the baffle plate 32 fall into the gutter-like member 28F, slide down the gutter-like member 28F, reach the conduit 28G, and further fall to reach the outlet 28E. Further, when the particles go around the lower side of the buff-full plate 32, the particles are separated from the airflow due to their inertia and fall in the direction of the outlet 28E. In this way, the gas with the required amount of scattered particles collected and separated is introduced into the desulfurization section 34, undergoes a desulfurization reaction while passing through the desulfurization fluidized bed of limestone supplied from the supply pipe 36, and then undergoes a desulfurization reaction. After passing through a waste heat boiler 40 and a second waste heat boiler 42 in order to exchange heat, the waste heat is extracted from the fluidized bed boiler through a duct 46.

From the combustion section 18, most of the large-diameter ash together with the fluidized medium is introduced into the re-combustion section 60 via a pipe 64. Furthermore, the particles collected by the collision type inertial dust collector 28 are introduced into the reburning section 60 through a pipe 66. In the fluidized reburning section 60, the unburned components contained in the combustion ash and collected particles are reburned by the air that passes through the dispersion plate 56 and blows up. At this time, the exhaust gas generated by the combustion is supplied from the duct 68 to the upstream side of the desulfurization section 34 or to the duct 44. Further, the fluidized medium and combustion ash extracted from the reburning section through the discharge pipe 63 are separated into large diameter ones and small diameter ones in the combustion ash and fluidized media in the separator 63b. The material passes through the discharge pipe 63c,
Discarded after heat recovery. Moreover, the small-diameter ones are returned to the combustion section 18 of the furnace body 12 through the recycling line 63a, and are reused as a fluidized medium.

As mentioned above, particles contained in the combustion gas from the combustion section 18 are separated from the gas flow in the collision type inertial dust collector 28, but this collision type inertial dust collector 28 has a lower gas flow rate than a cyclone. There is no need to increase the pressure, so pressure loss is extremely small. Note that the conduit 28G is provided along the inner wall surface, which is a particularly low flow velocity region, and causes almost no flow resistance. Further, since the gas flow rate is low, there is almost no wear, and the inner lining can be made of fireproof and heat insulating fiber blanket 28H, which is inexpensive and easy to install. Furthermore, the size of the collision-type inertial dust collector 28 is smaller than that of a cyclone, and requires less installation space. In addition, since this collision type inertial dust collector is provided with a gutter-like member 28F and a conduit 28G,
Particle collection efficiency is also high because once collected particles are not scattered again. In particular, in this embodiment, since the buff-full plate 32 is inclined toward the downstream side, turbulence in the gas flow is reduced, thereby making the particle collection efficiency even higher. Since the fluidized medium at a high temperature (for example, 900 to 1000°C) in the combustion section 18 is directly used as a fluidized medium in the reburning section 60, the temperature inside this reburning section 60 becomes high, and it cannot be used as an auxiliary fuel as in the past. There is no need to supply coal, heavy oil, etc. to this reburning section 60.

In addition, a collision type inertial dust collector 28 is provided in the desulfurization section 34.
Since the gas in which the required amount of scattered particles has been collected and separated is introduced, a decrease in desulfurization efficiency due to ash is prevented, and an extremely efficient desulfurization reaction is carried out.

The combustion exhaust gas generated in the reburning section 60 is transferred to a pipe 68.
By increasing or decreasing the reburning section exhaust gas supplied to the upstream side of the desulfurization section 34,
The amount of ash and the amount of sulfur oxides contained in the exhaust gas introduced into the desulfurization section 34 can be controlled, and the desulfurization load on the desulfurization section can be controlled. Therefore, the desulfurization efficiency can be improved by setting the desulfurization load to an appropriate value.

Note that by adjusting the protrusion length of the full plate 32 into the chamber 30, the particle collection efficiency within the collision-type inertial dust collector 28 can be adjusted, thereby reducing the amount of particles sent to the desulfurization section 34. It is possible to control the amount of particles (ash). Furthermore, as shown by the dashed line in FIG. 1, another buff-full plate 70 may be provided on the upper portion of the inner wall of the chamber 30.

In the above embodiment, the particles collected by the collision type inertial dust collector 28 are introduced into the reburning furnace 54, but in the present invention, the collision type inertial dust collector 28 and the furnace body 12 are The collected particles may also be introduced into the combustion section 18 by connecting them.

In addition, in this embodiment described above, if sand is used instead of limestone as the fluidizing medium in the combustion section, the small-diameter particles scattered from the combustion section will not contain CaSO ₄ , a product of the desulfurization reaction by limestone. When the particles are re-burned, CaSO ₄ decomposes and sulfur oxides are generated again, and there is no need to feed more limestone to the combustion zone for desulfurization. And in this case, the products of the desulfurization reaction
When CaSO ₄ and coal ash are mixed, the melting point of the coal ash decreases, making it easier for the coal ash to stick in the dust collector, but this never happens.

In the embodiment described above, a plurality of furnace bodies 12 are installed together, the combustion waste gas from each furnace body 12 is introduced into a common desulfurization section 34, and the fluidized medium and combustion ash from each combustion section 18 are fed into a common reburning furnace. 54, but one desulfurization section and one reburning section may be provided for one furnace body.

Further, although two waste heat boilers are installed in series, this installation method is arbitrary. Separator 63b
may be provided in the middle of the piping 64.

[Effects] As described above, in the fluidized bed boiler of the present invention, particles of combustion gas from the combustion section that performs fluidized combustion of fuel are efficiently collected in the collision type inertial dust collector. This collision-type inertial dust collector has excellent features such as low pressure loss; inexpensive wear-resistant lining material is sufficient; and small installation space; It is possible to significantly reduce costs and operating costs.

Furthermore, desulfurization efficiency can be improved by reducing the amount of scattered particles in the combustion gas introduced into the desulfurization section.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing an embodiment of the present invention, Fig. 2 is a sectional view of a collision type inertial dust collector, Figs.
The figure is a sectional view of the same main part. 18... Combustion part, 28... Collision type inertial dust collector, 28F... Gutter-like member, 28G... Conduit, 32
... Batsuful plate, 34 ... Desulfurization section, 40,
42...waste heat boiler, 60...reburning section.

Claims (1)

[Scope of Claims] 1. A combustion section that performs fluidized combustion of fuel; a desulfurization section that forms a fluidized bed of desulfurization material provided downstream of the fluidized combustion section; and a desulfurization section that is provided between the combustion section and the desulfurization section. and a collision-type inertial dust collector for collecting scattered particles from the combustion section. The end of the gutter-like member is connected to a conduit for dropping particles that extends downward along the inner wall surface of the dust collector.