JPS63690B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the temperature within a fluidized bed of a fluidized bed furnace for incinerating waste containing a large amount of waste plastic.

Many of the waste plastics that are mixed in with waste have a small apparent specific gravity and a very fast burning rate. after-combustion chamber)
tends to burn 50-70%. In comparison, the in-bed combustion rate (rate of combustion in the fluidized bed) of municipal waste and dewatered sewage sludge is high at 60-80%, and compared to the 30-50% in-bed combustion rate of waste plastic, Easy to maintain temperature and easy to operate. In other words, the basis of a fluidized bed incinerator is to increase the combustion rate within the fluidized bed as much as possible. The common method of controlling the temperature inside the fluidized bed is to change the amount of combustion air and the amount of treatment, but for materials that burn at a high rate, such as waste plastics, the air ratio required for combustion, It may be difficult to achieve combustion unless the fluidization speed, hearth load, etc. are varied over a wide range.

On the other hand, when JIS No. 4 silica sand (particle size d = 0.2 to 1.6 mm) was used alone as a fluidizing medium, JIS No. 4 silica sand and JIS No. 5 silica sand (particle size d = 0.02 to 1.6 mm) were used.
0.7) in a 50:50 mixture,
A test was conducted in which waste plastic (100%) was burned in a 200 mm square fluidized bed incinerator. According to this test result, the fluidized bed temperature is as shown in Figure 1 when using a fluidized medium of JIS No. 4 silica sand and when using a fluidized medium that is a 50:50 mixture of JIS No. 4 and JIS No. 5. There was a difference. Note that when JIS No. 5 silica sand was used alone, the results were similar to those when JIS No. 4 silica sand was used alone. The above phenomenon is due to the fact that the particle size distribution becomes larger in mixed fluidized media, which improves the mixing and stirring effects within the fluidized bed, and especially the expansion at the interface of the fluidized bed (it is expected that small particles of fluidized media will flow around this area). Therefore, it is considered that more effective heat transfer (waste plastic combustion heat → fluidized medium) is achieved for processed materials that instantly burn near the fluidized bed interface, such as waste plastics.

The present invention was developed in view of the above points, and instead of controlling the temperature by controlling the main factors such as the air ratio required for combustion, fluidization speed, and hearth load, as in the past, the present invention The present invention aims to provide a method for controlling the temperature in a fluidized bed of a waste incineration fluidized bed furnace, which controls the temperature to the optimum temperature necessary for combustion by controlling the particle size.

That is, in the method of the present invention, fluidized media having different particle sizes are fed to a waste incineration fluidized bed furnace to form a fluidized bed, and the fluidized media containing noncombustibles extracted from the waste incineration fluidized bed furnace is divided into noncombustibles and large particles. Separate into particle size fluidized media and small particle size fluidized media, mix these fluidized media with different particle sizes in appropriate proportions, and supply to the waste incineration fluidized bed furnace to control the temperature inside the fluidized bed to the appropriate combustion temperature. It is characterized by

Hereinafter, the configuration of the present invention will be explained based on the drawings. In Fig. 2, 1 is a fluidized bed furnace, in which silica sand,
Fluid media such as CaO, CaCO ₃ and dolomite are used. In waste such as waste plastic,
It contains non-combustible materials that are unsuitable for combustion (iron pieces, rubble, etc.), and when these are put into the furnace, they accumulate on the bottom of the furnace, which in turn has a negative effect on combustion. In other words, when 10 to 20% of noncombustibles accumulate at the bottom of the furnace, air passes between the noncombustibles and the bubbles become large, causing the air to escape, causing a blow-by phenomenon and preventing the formation of a fluidized bed. Therefore, non-combustible materials must be discharged from the furnace. When this incombustible material is discharged, the fluid medium is also discharged, so a separator 2 such as a vibrating sieve is used to separate each particle size, and the noncombustible material contained in the waste is excluded. 3 is a fluidized medium discharge device, 4 is an air distribution plate, 5 is a fluidized bed, 6 is a wind box, 7
is a free board.

The fluidized medium is stored in a large-particle fluidized medium bunker 8 and a small-particle fluidized medium bunker 9 according to particle size, and depending on the temperature in the fluidized bed, the large-particle fluidized medium alone or the large-particle-sized fluidized medium and the small-particle-sized fluidized medium are stored. A mixture of the medium and the medium at an appropriate ratio (for example, 50:50) is supplied to feeder 1.
0 and 11 to charge the fluidized medium into the furnace 1. Specifically, the temperature inside the fluidized bed 5 is detected, and the temperature recording control and alarm device (TRCA) 1 is activated based on this temperature.
2, if the temperature inside the fluidized bed is lower than the set value, both supply feeders 10 and 11 are opened, and when the temperature inside the fluidized bed is higher than the set value, either supply feeder 10 or 11 is opened. Open.
13 is the intralayer pressure differential indication control alarm device (ΔPICA),
By setting the differential pressure within the fluidized bed to an optimal value depending on the operating conditions and controlling the fluidized medium discharge device 3,
Maintain the static bed height required for combustion. Reference numeral 14 denotes a particle surface control alarm device (LCA), which is interlocked with the supply feeder 17 of the replenishment large particle size fluidized medium storage tank 15 and the supply feeder 18 of the replenishment small particle size fluidized medium storage tank 16. In addition, although the above-mentioned embodiment explained the case where two types of fluid media are used, it is also possible to use three or more types of fluid media.

As explained above, the method of the present invention can control the temperature in the fluidized bed to the optimum temperature required for combustion by controlling the particle size of the fluidized medium, and since waste plastic has a high calorific value, The temperature inside the fluidized bed becomes high, and if some cooling method is not used, clinker will occur in the fluidized bed, causing trouble with the furnace.However, in the present invention, the fluidized medium is forcibly circulated, so the temperature inside the fluidized bed can be reduced. It has the effect of being able to cool the air.

[Brief explanation of the drawing]

Figure 1 shows the results of a waste plastics burning test, and is a graph showing the relationship between the height of the stationary bed and the temperature inside the fluidized bed when the particle size of the fluidized medium is changed, and Figure 2 shows the results of the method of the present invention. It is an explanatory view showing an example of a device. DESCRIPTION OF SYMBOLS 1... Fluidized bed furnace, 2... Separation device, 3... Fluidized medium discharge device, 4... Air distribution plate, 5... Fluidized bed, 6... Wind box, 7... Free board, 8... Large particle size fluidized medium bunker, 9... Small particle size fluidized media bunker, 10, 11
...supply feeder, 12...temperature recording control alarm device,
13...Intralayer pressure differential indication control alarm device, 14...Particle surface control alarm device, 15...Large particle size fluidized medium storage tank for replenishment, 16...Small particle size fluidized medium storage tank for replenishment, 17,1
8...Supply feeder.

Claims (1)

[Claims] 1. Fluidized media with different particle sizes are fed to a waste incineration fluidized bed furnace to form a fluidized bed, and the fluidized media containing noncombustibles extracted from the waste incineration fluidized bed furnace are divided into noncombustibles, large particle size fluidized media, and small particle size fluidized media. Particle size separated into fluidized medium,
A fluidized bed for a waste incineration fluidized bed furnace characterized in that these fluidized media having different particle sizes are mixed in an appropriate ratio and supplied to the waste incineration fluidized bed furnace to control the internal temperature of the fluidized bed to an appropriate combustion temperature. Internal temperature control method.