JPH0531475A - Treatment of ash - Google Patents

Abstract

(57) [Summary] [Purpose] To provide an ash treatment method for decomposing and removing trace organic chlorine compounds in fly ash contained in exhaust gas from an incinerator. [Structure] Fly ash contained in the exhaust gas from the incinerator 11 is collected by a first dust collector 14. The fly ash is caused to flow together with the high-temperature exhaust gas of 400 ° C. or higher from the incinerator 11, and the heat decomposes the trace amount of organic chlorine compounds in the fly ash. The fly ash in the high-temperature exhaust gas is recollected by the second dust collector 19.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ash treatment method for decomposing and removing trace amounts of organic chlorine compounds such as dioxins contained in fly ash discharged from a cleaning plant.

[0002]

2. Description of the Related Art In a refuse incineration plant, ash collected from a gas cooler or a reaction tower (hereinafter collectively referred to as GC ash), ash collected from an electrostatic precipitator or a bag filter (hereinafter collectively referred to as EP) It has recently been revealed that ash) contains a small amount of chlorinated compounds such as dioxin, which is a harmful substance. There is still no method of removing the above-mentioned harmful substances in the refuse incineration plant,
Development of the above-mentioned harmful substance removing device is desired at an early stage.

A conventional technique for removing dioxins and the like contained in EP ash is shown in FIG.
The EP ash 1 is introduced into the processing apparatus from the direction of arrow A in FIG. 2, conveyed by the screw conveyor 3 heated to 400 to 600 ° C. by the heater, and discharged in the direction of arrow B. As a result, polychlorinated dibenzodioxin (hereinafter referred to as PCDD) which is an organic chlorine compound contained in EP ash.
s), polychlorinated dibenzofuran (hereinafter PCDF
s) is decomposed and PCDD
The removal rate of s and PCDFs exceeds 99%. In the figure, reference numeral 5 is a controller, 7 is a motor, and 9 is a recovery unit (for example, canned food). (G. OK. Y. Hanal, Y. La
tou, "Dechlorination Techniques of PCDDs and PCDFs
in Fly Ashfrom Municipal Refuse Incineration Plant
s ", 10th The International Conference on Organohal
ogen Compounds (1990), ps. 393-396.)

[0004]

However, in the above-mentioned prior art, since energy is externally supplied by a heater or the like for the treatment of GC ash and EP ash, the running cost is high. Further, the removal rate of dioxins and the like decreases at a temperature lower than 590 ° C., but it is considered that the cause is that the ash temperature varies and the average ash temperature is lower. Therefore, an object of the present invention is to provide an ash treatment method capable of completely decomposing and removing trace organic chlorine compounds such as dioxins in ash.

[0005]

To achieve the above object, in the treatment method of the present invention, a step of collecting fly ash contained in the exhaust gas from the incinerator by a first dust collector, A step of decomposing trace organic chlorine compounds in the fly ash by the heat of the high temperature exhaust gas while flowing the fly ash together with the high temperature exhaust gas of 400 ° C. or higher from the incinerator; And a step of re-collecting with a second dust collector.

[0006]

The trace amount of organic chlorine compounds such as dioxins in the fly ash collected by the first dust collector is decomposed by the heat of the high temperature exhaust gas at 400 ° C or higher. The fly ash is recollected by the second dust collector for high temperature. Desirably, the hot exhaust gas is returned to the line in front of the first dust collector.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a diagram showing an embodiment of a system to which the ash processing method according to the present invention is applied.

The high-temperature exhaust gas generated in the incinerator 11 is brought into a state where unburned gas is recombusted in the gas mixing chamber and cooled to about 350 ° C. in the boiler 12. Next, HCl and SO ₄ are removed by the harmful gas removing device 13 using the slaked lime slurry, and the dust reaches the dust collector 14. Fly ash is collected here, and a trace amount of organic chlorine compounds such as dioxins is removed by a dust layer (mainly composed of unreacted slaked lime, reaction product with acidic gas, fly ash, etc.) in the dust collector 14. To be done. The exhaust gas that has been cleaned by removing the fly ash passes through the IDF (induction blower) 15 and is discharged into the atmosphere by the chimney 16.

On the other hand, the fly ash containing a trace amount of organic chlorine compounds such as dioxins, which has been collected, reaches the shoe 18 via the screw conveyor 17. Here, high temperature exhaust gas of 800 ° C. or higher is caused to flow from the combustion chamber outlet to the chute 18 by the dust 23, and guides fly ash to the high temperature dust collector 19. Between the chute 18 and the high-temperature dust collector 19, trace organic chlorine compounds such as dioxins are completely decomposed and removed. The fly ash collected by the high temperature dust collector 19 is transferred to the screw conveyor 20.
It is collected in the fly ash hopper 21.

Here, the amount of high temperature exhaust gas introduced from the outlet of the combustion chamber is 800 Nm ³ / H, which is adjusted by the boiler outlet damper 24 and the damper 25 of the duct 22. At this time,
The amount of fly ash discharged is about 150 kg / h.

As the high temperature dust collector 19, a woven metal cloth, a felt, a filter member using a brush wire, a filter member using a ceramic filter, or a cyclone whose inner surface is covered with castable bricks can be used.

Table 1 shows the analysis results of fly ash in the apparatus shown in FIG. As shown in this result, in the system to which the treatment method of the present invention is applied, the PCDDs and PCDFs in the fly ash are almost completely removed in the hopper 21.

[0013]

[Table 1]

[0014]

According to the ash treatment method of the present invention, trace organic chlorine compounds such as dioxins in the exhaust gas from the incinerator are completely decomposed and removed by utilizing the heat of the high temperature exhaust gas of the incinerator itself. Will be able to.

[Brief description of drawings]

FIG. 1 is a diagram showing an embodiment of a system to which an ash processing method according to the present invention is applied.

FIG. 2 is a view showing a conventional technology for removing dioxin contained in ash.

[Explanation of symbols]

11 ... incinerator, 12 ... boiler, 14 ... dust collector, 16 ... chimney, 17 ... screw conveyor, 19 ... high temperature dust collector, 2
0 ... Screw conveyor, 21 ... Hopper.

 ─────────────────────────────────────────────────── (72) Inventor Atsushi Morishige Atsushi Marunouchi 1-2-2 Marunouchi, Chiyoda-ku, Tokyo Japan Steel Pipe Co., Ltd. (72) Kentaro Ito 1-2-1 Marunouchi Chiyoda-ku, Tokyo Inside the steel pipe company

Claims (1)

Claims: 1. A step of collecting fly ash contained in exhaust gas from an incinerator with a first dust collector, and the fly ash together with high-temperature exhaust gas of 400 ° C or higher from the incinerator. While flowing, a step of decomposing a trace amount of organic chlorine compounds in the fly ash by the heat of the high temperature exhaust gas, and a step of re-collecting the fly ash in the high temperature exhaust gas with a second dust collector An ash treatment method characterized by.