JP2001158657A - Method and apparatus for sintering granular aggregate - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method and apparatus for sintering granular aggregate, capable of obtaining granular aggregate having high strength by reduced heat energy. SOLUTION: A straight pipe-like sintering part 4 connected to furnace bottom 8 of a fluidized furnace 1 and a vapor phase combustion part 6 is installed on the outside of lower part of furnace body of the fluidized furnace 1. An unburned granular aggregate is charged into the furnace 1 and introduced into the combustion part 4 together with a flow medium and air for combustion is supplied to the combustion part 4 to classify the aggregate from the flow medium. The flow medium is returned to the vapor phase combustion part 6 and only the granular aggregate is left in the combustion part 4. Then, a fuel is supplied to the sintering part 4 and the fuel is burned at high temperature to sinter the granular aggregate and the sintered granular aggregate is discharged from a discharge valve 9 at the lower end of the sintering part 4. A connecting pipe 7 is sealed with a material seal or a damper during sintering.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for sintering granular aggregate using a fluidized-bed furnace.

[0002]

2. Description of the Related Art In recent years, fluidized-bed furnaces have been widely used for incineration of municipal garbage and sewage sludge, but a large amount of incineration ash is generated by incineration, and the treatment method has become a problem. Therefore, in order to make effective use of the incinerated ash, a method of producing granular aggregates with strength and chemical stability by granulating and sintering the incinerated ash collected by a dust collector provided at the latter stage of the fluidized furnace. Is being developed. Generally, sintering of the granular aggregate requires a temperature higher than the temperature inside the fluidized-bed furnace.

Therefore, a high-temperature aggregate sintering furnace is usually provided separately from a fluidized-bed furnace to sinter granular aggregates. However, in order to maintain the inside of the aggregate sintering furnace at a high temperature, many sintering furnaces are used. Since heat energy is required, there is a problem that running costs are high.

[0004] Further, as disclosed in Japanese Patent No. 2909421 of the present applicant, a method has been developed in which granulated aggregate is charged into a circulating fluidized-bed furnace and sintered. This method has the advantages that the equipment is simpler than installing a separate aggregate sintering furnace and that the heat energy consumption is reduced.

However, as described above, since the sintering of the granular aggregate requires a temperature higher than the furnace temperature of the fluidized-bed furnace, the temperature of the entire furnace is slightly increased to obtain a high-strength granular aggregate. It is necessary to set a higher temperature or at least a slightly higher temperature in the vicinity of the bottom of the furnace. Therefore, it is inevitable that the consumption of heat energy is considerably increased as compared with a general fluidized-bed furnace. In addition, since the granular aggregate is taken out in a state of being mixed with the fluid medium, there is also a problem that it takes time and effort to separate the granular aggregate.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned conventional problems, and sinters the granular aggregate while minimizing the increase in the consumption of heat energy to thereby increase the strength of the granular aggregate. It is intended to provide a method and an apparatus for sintering granular aggregates, which can obtain the above-mentioned method, and hardly need to separate the granular aggregates from the fluid medium.

[0007]

Means for Solving the Problems To solve the above-mentioned problems, the method of sintering granular aggregate according to the first aspect of the present invention comprises:
A sintering section connected to the bottom of the fluidized-bed furnace and the gas-phase combustion section is provided at the lower part of the furnace body of the fluidized-bed furnace, and the granular aggregate put in the furnace is introduced into the sintering section together with the fluidized medium. After that, the air for combustion is supplied to the sintering section, and the fluidized medium is returned to the gas phase combustion section while the granular aggregate is allowed to remain in the sintering section for classification.
Next, the fuel and combustion air are supplied to the sintering section, and high-temperature combustion is performed to sinter the granular aggregate at a high temperature, and then discharge the sintered granular aggregate from the lower end of the sintering section. It is a feature. During sintering of the granular aggregate, it is preferable that the space between the sintered part and the furnace bottom is shut off by a material seal or a damper.

According to a third aspect of the present invention, there is provided a granular aggregate sintering apparatus, wherein a straight tubular sintering section having a combustion air supply pipe and a fuel supply pipe is provided at a lower portion of a furnace body of a fluidized-bed furnace. The sintering section is connected to a gas-phase combustion section of a fluidized-bed furnace by an upper vertical pipe, and is connected to a furnace bottom by a connecting pipe branched obliquely from a lower portion of the vertical pipe. Note that a structure in which a damper is provided in the connecting pipe can be used, and a structure in which a plurality of discharge valves are provided below the sintered portion is preferable.

According to the present invention, since only the inside of the small-volume sintered portion needs to be heated to a high temperature, the consumption of heat energy is smaller than in the conventional method. In addition, since the fluid medium entering the sintering section together with the granular aggregate has a small diameter, it is returned to the gas-phase combustion section of the fluidized-bed furnace together with the crushed pieces of the granular aggregate in the classification step of blowing only combustion air into the sintering section. . For this reason, only the granular aggregates remain in the sintered portion, and there is no need for sorting after sintering. The high-temperature gas generated in the sintering section by the high-temperature combustion is sent to the gas-phase combustion section of the fluidized-bed furnace, so that heat energy is not wasted.

[0010]

Embodiments of the present invention will be described below. 1 to 3 are views showing a first embodiment of the present invention, in which 1 is a fluidized-bed furnace, for example, a fluidized-bed incinerator. Reference numeral 2 denotes a fluidizing medium such as silica sand, which is a furnace for flowing the fluidizing medium 2 by air blown from the dispersion pipe 3 and burning the input waste, as in the related art. The average particle size of the fluid medium 2 is, for example, about 300 μm. Although not shown, the incinerated ash discharged from the fluidized-bed furnace 1 is collected by a dust collector at a later stage, and is turned into granular aggregate having a particle size of about 5 to 15 mm by a granulator.

A straight tubular sintered portion 4 is formed outside the lower part of the furnace body of the fluidized-flow furnace 1. The sintering section 4 is connected to a gas phase combustion section 6 of the fluidized-bed furnace 1 by an upper vertical pipe 5, and a connecting pipe 7 which is diagonally branched from a lower portion of the vertical pipe 5.
To the furnace bottom 8. Discharge valves 9, 9 are provided at the lower end of the sintering section 4 in two stages, upper and lower. Further, a combustion air supply pipe 10 is provided at a position slightly above the discharge valve 9 below the sintering section 4, and a fuel supply pipe 11 for supplying LNG or the like is provided above the combustion air supply pipe 10.

First, unsintered granular aggregate is introduced from the inlet 12 of the fluidized-bed furnace 1, and enters the inside of the sintering unit 4 via the connecting pipe 7 while being mixed with the fluidized medium 2. When combustion air of, for example, 650 ° C. is supplied from the combustion air supply pipe 10 to the sintering unit 4 so that the flow velocity becomes 5 m / s, classification is performed inside the sintering unit 4. The fluidized medium 2 has a much smaller particle size than the granular aggregate and is returned to the gas-phase combustion section 6 of the fluidized-bed furnace 1 as shown in FIG. Remains in Note that, among the granular aggregates, those that have been finely crushed and have lost commercial value are also returned to the gas phase combustion unit 6 together with the fluidized medium 2 and are used as the fluidized medium 2. The supply of combustion air is carried out for 3 to 5 minutes. At that time, a new mixture is introduced from the connecting pipe 7, so that the accumulated amount of the granular aggregate is measured by a pressure gauge provided in the sintering section 4,
When the pressure becomes constant, the combustion air is reduced to a flow velocity of 1.0 m / s, and classification is stopped.

Next, when the fuel is supplied from the fuel supply pipe 11 to the sintering section 4, the fuel is burned in the sintering section 4 to a high temperature of 1000 ° C. or more, and the granular aggregate remaining in the sintering section 4 is removed. Sintered.
At this time, combustion air is also supplied. A large amount of combustion gas generated by this combustion is passed through a vertical pipe 5 to a fluidized furnace 1.
Since the heat is blown into the gas-phase combustion section 6, no waste of heat is generated. Sintering is performed for about 15 minutes. If the superficial velocity of the sintering section 4 at this time is reduced to about 1.0 m / s, the granular aggregate is sintered without flowing.

As described above, according to the present invention, the granular aggregate and the fluid medium 2 can be classified and sintered, and only the sintered portion 4 needs to be heated to a high temperature, so that much heat energy is unnecessary. is there. In addition, since the high-temperature combustion gas is blown into the gas-phase combustion section 6 of the fluidized-bed furnace 1 through the vertical pipe 5, little heat energy is lost.

During the sintering of the granular aggregate, the mixture of the granular aggregate and the fluidized medium 2 is filled in the connecting pipe 7 between the sintering section 4 and the furnace bottom 8, and the material is sealed. No new granular aggregate flows into the sintered part 4. This material seal has an advantage that the structure is simple and does not cause a problem of durability of the damper.

After sintering the granular aggregate in this manner, the fuel supply from the fuel supply pipe 11 is stopped, and the air supply from the combustion air supply pipe 10 is also stopped. Then, as shown in FIG. 3, upper and lower two-stage discharge valves 9, 9 at the lower end of the sintering section 4.
, The sintered granular aggregate in the sintered portion 4 is discharged downward. At the same time, new granular aggregate enters the sintering section 4 together with the fluid medium 2 from the connecting pipe 7,
Hereinafter, the same steps are repeated.

As described above, the sintering of the granular aggregate according to the present invention is performed in a batch system, but the operation of the fluidized-bed furnace 1 is continuous. Therefore, as described above, the discharge valves 9, 9 are provided in a plurality of stages and alternately opened and closed to eliminate fluctuations in the furnace pressure, so that the operation of the fluidized furnace 1 is not affected even when the granular aggregate is discharged. It is preferable to keep it.

FIG. 4 is a diagram showing a second embodiment of the present invention. In this embodiment, a damper 13 is provided in the connecting pipe 7, and the damper 13 is opened to introduce a mixture of unsintered granular aggregate and the fluid medium 2 into the sintering unit 4. Next, add combustion air at about 650 ° C for 3 to 5 so that the flow velocity becomes 5 m / s.
Minutes, and the same classification as described above is performed. Thereafter, fuel and combustion air are introduced into the sintering section 4, and the temperature of the sintering section 4 is set to about 1000 ° C., and sintering is performed for 15 minutes. During sintering, the superficial velocity of the sintering section 4 is reduced to about 1.0 m / s to prevent the flow of the granular aggregate. After the sintering is completed in this way, the discharge valves 9 and 9 are opened to discharge the sintered granular aggregate.

[0019]

EXAMPLES Table 1 shows Examples 1 to 3 in which the granular aggregate is sintered according to the present invention, and Table 2 shows Comparative Examples 1 to 6 in which the granular aggregate is sintered by the conventional method. The column of strength shows the force required to crush one sintered granular aggregate, and the column of heavy metal elution shows the amount of heavy metal eluted from the sintered granular aggregate.

[0020]

[Table 1]

[0021]

[Table 2]

From the data of the above Examples and Comparative Examples,
According to the present invention, the strength of the sintered granular aggregate is increased,
The amount of heavy metal eluted from the granular aggregate is the standard value of the Environment Agency (Notification No. 4
No. 6), it was confirmed that the CO concentration in the exhaust gas was reduced and the sand mixing ratio in the sintered granular aggregate was also reduced.

[0023]

As described above, according to the present invention, the granular aggregate is sintered in the straight tubular sintering portion provided outside the lower part of the furnace body of the fluidized-flow furnace, so that only the sintering portion is heated to a high temperature. The hot gas discharged from the sintering section is returned to the fluidized-bed furnace. Therefore, it is possible to obtain a high-strength granular aggregate by sintering the granular aggregate while minimizing an increase in the consumption of heat energy. Also, there is no need to provide a separate aggregate sintering furnace, and the equipment cost is reduced. Further, the granular aggregate and the fluid medium are classified based on the particle size difference before sintering, and the fluid medium is returned to the furnace, so that only the sintered granular aggregate can be taken out. Furthermore, since the transfer of the granular aggregate from the fluidized-bed furnace to the sintering section is naturally performed by gravity, there are many advantages such as no need for trouble.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a step of introducing a granular aggregate into a sintered part in a first embodiment.

FIG. 2 is a sectional view showing a classification step.

FIG. 3 is a sectional view showing a step of discharging sintered granular aggregate.

FIG. 4 is a cross-sectional view illustrating a step of introducing a granular aggregate into a sintered part according to a second embodiment.

[Explanation of symbols]

1 fluidized furnace, 2 fluidized medium, 3 dispersion tube, 4 sintering section,
5 vertical pipe, 6 gas-phase combustion part of fluidized-bed furnace, 7 connecting pipe, 8
Furnace bottom, 9 exhaust valve, 10 air supply pipe for combustion, 11
Fuel supply pipe, 12 inlet, 13 damper

Claims (5)

[Claims] 1. A sintering section connected to a furnace bottom of a fluidized-bed furnace and a gas-phase combustion section is provided at a lower portion of a furnace body of a fluidized-bed furnace, and granular aggregate put into the furnace is mixed with a fluidized medium. After being introduced into the sintering section, the air for combustion is supplied to the sintering section, and while the fluidized medium is returned to the gas phase combustion section, classification is performed in which the granular aggregate remains in the sintering section. A granular aggregate characterized by sintering the granular aggregate at a high temperature by supplying fuel and combustion air to the high temperature and burning the granular aggregate at the lower end of the sintered part. The method of sintering the material. 2. The method for sintering granular aggregate according to claim 1, wherein the sintering section and the furnace bottom are shut off by a material seal or a damper during sintering of the granular aggregate. 3. A straight tubular sintering section having a combustion air supply pipe and a fuel supply pipe is provided at a lower portion of a furnace body of a fluidized-bed furnace, and the sintered section is connected to an upper vertical pipe of the fluidized-bed furnace. A sintering apparatus for granular aggregates, wherein the apparatus is connected to a gas phase combustion section and connected to a furnace bottom by a connecting pipe branched obliquely from a lower part of a vertical pipe. 4. The apparatus for sintering granular aggregate according to claim 3, wherein a damper is provided in the connecting pipe. 5. The apparatus for sintering granular aggregate according to claim 3, wherein a plurality of discharge valves are provided below the sintering section.