JPS5896913A - Solid fuel feeding method for fluidized bed combustion device - Google Patents

Abstract

PURPOSE:To improve an efficiency of combustion and reduce some noxious substances by a method wherein combustibles with a low density and some fine particles such as pyrolysis char etc. are applied as a fuel and it is fed in a diversed condition from the lower part of the fluidized bed and almost all of the combustibles are combustioned in the fluidized bed. CONSTITUTION:The fuel contained in a hopper 1 is fed from a screw feeder 2 to a rotary feeder 3 and then fed into a furnace 6 from a fuel feeding pipe 5 along with fuel feeding air 4. In turn, the combustion air 11 is flowed through the lower wind box 9 in the furnace 6 and suctioned up into the furnace at the dispersion plate 10. Due to the arragement of thermal conducting pipes 7, 8 in the fluidized bed 17 and hollow column part 18, the heat generated in the furnace 6 is efficiently transformed into a superheated steam. Combustion gas is flowed from discharging gas outlet 13 to a cyclone 14, the discharged gas having its dusts separated there is discharged from piping 15 to the part out of the system. In turn, the ash generated in the fluidized bed boiler is discharged out of the over-flow pipe 16 and an other ash generated in the furnace 6 is discharged out from the ash removal pipe 12.

Description

[Detailed Description of the Invention] In a fluidized bed combustion device or fluidized bed boiler that uses solid fuel containing low-density, fine-grained combustible substances such as combustible dust, pyrolysis char, and coal dust, The present invention relates to a method of supplying solid fuel for fluidized combustion of most of the solid fuel inside a fluidized bed.

As the use of energy resources has become more popular, methods of burning waste and biomass, and systems for recovering and using energy from them are being studied.

In general, fluidized bed combustion equipment is capable of expanding the types of fuel, can process a relatively large amount of fuel even though it is small, can reduce NOx in exhaust gas to below standards by improving the combustion method, and can eliminate S02 and HCl in the furnace. It has features such as high combustion efficiency, that is, high heat recovery rate.

In a normal fluidized bed combustion device, complete combustion can be carried out within the device. That is, it is considered that combustion should be completed in both the fluidized bed section and the freeboard space above the bed. Therefore, if it is simply a matter of incinerating waste, it is sufficient to completely burn the flammable organic matter in a combustion device including a freeboard, but a combustion boiler can be used to effectively recover heat and maintain a constant temperature inside the furnace. In order to maintain this temperature, in a fluidized bed combustion apparatus, a method must be adopted in which most of the combustion occurs inside the bed rather than in the freeboard section. That is, when most of the combustion occurs in the fluidized bed section, heat transfer is very fast due to the mixing action of the particles, the heat exchange operation is easy, and it is advantageous for constant temperature control. In comparison, when combustion occurs at the top of the bed, it is difficult to maintain a constant temperature in a wide space, so a heat exchanger with a wide heat transfer area must be installed to recover heat.
Even in this case, complete combustion may not occur inside the device, and after-burning may occur in the piping system, cyclone, etc. after leaving the device. Such after-combustion can lead to an explosion, which is not only dangerous, but can also cause damage to valves and piping.

On the other hand, sufficient combustion in the fluidized bed section not only facilitates temperature control of the entire device system, but is also important from the standpoint of device safety. In particular, when using a fluidized bed combustion tower as the medium (sand) particle heating section of a dual circulation type pyrolysis device, it is important to carry out combustion inside the bed rather than at the top of the bed. It is necessary to establish a combustion method inside the layer.

The present invention aims to provide a method for supplying solid fuel to establish such a combustion method, and the present invention aims to provide a solid fuel supply method for establishing such a combustion method. In order to combust materials in a fluidized bed, it was discovered that the supply location and distribution method are most important. it is,
The supply position is preferably as low as possible in the lower part of the layer, and the dispersion method requires instantaneous horizontal diffusion near the supply port.

Alternatively, it can be supplied and dispersed in a fluidized bed along with an air flow. Especially for large equipment, increase the number of supply ports,
It is necessary to improve dispersibility. In addition, it is desirable that the heat exchanger tubes for exchanging heat within the layer be horizontal and arranged in a staggered manner to promote lateral diffusion of particles.

Next, the present invention will be explained in detail based on the drawings.

FIG. 1 is a schematic diagram illustrating an apparatus for carrying out the present invention. Reference numeral 1 denotes a hopper, to which solid fuel for a fluidized bed boiler is supplied, and the fuel is supplied from a screw feeder 2 through a rotary feeder 3 together with fuel supply air 4 from a fuel supply pipe 5 into the furnace interior 6. Ru. However, the fuel supply position is installed close to the dispersion plate 10, and the size of the fuel supply pipe is 2 to 3 times larger in diameter than the solid fuel. On the other hand, the combustion air 11 passes through the wind box 9 at the bottom of the combustion furnace and is blown up into the furnace from the distribution plate 10.

In the fluidized bed part 17, the fluidized main part heat exchanger tube 8 is still in the empty column part 1.
A hollow heat exchanger tube 7 is disposed at 8 to efficiently convert the heat generated in the furnace into superheated steam.

The combustion exhaust gas containing dust enters the cyclone 14 from the exhaust gas outlet 13 at the top of the furnace. The scattered dust is separated here, and the exhaust gas is discharged from the exhaust gas pipe 15 to the outside of the thread. On the other hand, the ash produced in the fluidized bed boiler is discharged to the outside of the furnace through an overflow pipe 16. The heavy ash produced in the furnace is discharged from the ash removal pipe 12 at the bottom of the furnace.

Next, the combustion mode of this device will be explained. That is, in the conventional apparatus, for example, the calorific value of the char of municipal waste is 5,500 KCl1t/9, the ash content is 20%, and the particle size is 15.
■When the following fuel is supplied from the top of the layer, the layer temperature can be increased to 8.
Even if it is set to 50'C, the bed temperature is only 820°C, and even under conditions where the residual oxygen concentration is 25-4%, more than 10% of the unburned carbon in the flying ash (collected in the cyclone section) remains. The outlet temperature of the exhaust gas reached 850 °C, and combustion was active in the sky column. However, when fuel is supplied from the bottom of the layer,
In the case of the present invention, the layer temperature can be easily adjusted to 850°C.
It is now possible to set the exhaust gas to approximately 6
00c, the amount of unburned carbon in the flung ash is about 2% or less.

From this, it is clear that the device implementing the present invention, in which the fuel supply port is attached to the bottom of the bed, can burn most of the fuel in the fluidized bed, and remove unburned carbon from the flying ash. can be significantly reduced, improving combustion efficiency,
It was possible to reduce harmful gases such as HCl and SO2.

In addition, in an apparatus having a large combustion hearth area, the fuel supply pipe 5 is branched into multiple or more parts as shown in FIG. 2, and each branch pipe 5a,
It is desirable that fuel is supplied from the lower part of the distribution plate to 5a.

[Brief explanation of the drawing]

Fig. 1 and Fig. 2 show a combustion device implementing the solid fuel supply method of the present invention, Fig. 1 is a side sectional view of the first embodiment, and Fig. 2 is a side sectional view of the second embodiment. . 1... Hopper 2... Screw feeder 3... Rotary feeder 4... Fuel supply air 5... Fuel supply pipe 6... Furnace 7.8 Heat exchanger tube 9 Wind box 10 Dispersion plate 11 Combustion air 12 Ash removal Pipe 13...Exhaust gas outlet 14...Cycle, Ron 17...Fluidized bed section 18...Empty column Patent applicant (114) National Institute of Industrial Science and Technology Director's stone plate Makoto/Shun Sahara: Figure 1

Claims (1)

[Claims] In a fluidized bed combustion device that uses low-density, fine-grained combustible materials such as pyrolysis char, coal dust, wood, grass, and garbage as fuel, these solid fuels are dispersed and supplied from the bottom of the fluidized bed, and most of the solid fuel is fed into the fluidized bed. A method for supplying solid fuel in a fluidized bed combustion device in which combustion is performed in a bed section.