JPH0677662B2 - Waste incinerator exhaust gas treatment method - Google Patents

Description

TECHNICAL FIELD The present invention relates to a method for treating exhaust gas from a refuse incinerator, and more particularly to a refuse incinerator with reduced emission of harmful organic chlorine compounds, particularly aromatic chlorine compounds. The present invention relates to a method for treating exhaust gas.

[Conventional technology]

Organic chlorine compounds that are harmful to the human body, especially aromatic chlorine compounds, such as highly toxic aromatic chlorine compounds such as PCDD (polychlorinated dibenzodioxin) and PCDF (polychlorinated dibenzofuran), are by-products of agricultural chemicals. It is also known to be produced as a secondary product when incinerating waste and polluting the environment (K.Olie et al, Chemosphere,
6 , 455 (1977), and T. Wakimoto et al, Environme.
ntal Health Perspectives, 59 , 159 (1985)). Among them, as a method of preventing the organic chlorine compounds generated during refuse incineration, conventionally, the structure of the incinerator and the incineration conditions have been studied, and a scrubber removal device has been attached. However, the cause of these harmful substances was not clear, and effective preventive measures could not be taken.

[Problems to be solved by the invention]

It is an object of the present invention to provide a method for treating waste incinerator exhaust gas, which is capable of significantly reducing the amount of organic chlorine compounds, particularly aromatic organic chlorine compounds, contained in the waste incinerator exhaust gas.

[Means for solving problems]

The present invention is a method for treating municipal waste incinerator exhaust gas in which dust is removed with a dust collector after cooling the municipal waste incinerator exhaust gas, and at least exhaust gas is discharged between the incinerator outlet and the dust collector.
It is characterized by rapid cooling to 250 ° C or less so that the cooling rate in the temperature range of 300 to 400 ° C is 30 to 100 ° C / sec.

Next, the background of the present invention and the experimental results will be described.

FIG. 1 is a flow sheet of a conventional typical waste incineration facility. Garbage is incinerated at about 900 ℃ in an incinerator,
The exhaust gas is cooled to 300 ℃ in the gas cooling tower, then enters the electrostatic precipitator, is separated into gas and EP ash, and the gas is discharged from the chimney to the outside of the system. The present inventors collected ash and exhaust gas samples from before and after the electrostatic precipitator of such an incineration facility, and quantitatively analyzed the organic chlorine compounds contained therein. The results are shown in Table 1. Further, Table 2 shows the results of obtaining the amount of the generated organic chlorine compound from the product of the value indicating the concentration of each organic chlorine compound in Table 1 and the emission amount (average value). In Table 2, the values of the cooling tower ash, the electrostatic precipitator (EP) ash, and the EP outlet gas correspond to the discharge amount (mg / H) per unit time from the waste incineration facility.

From the results shown in Table 1, it was confirmed that chlorine compounds in the gas were generally present in the electric precipitator ash from the inlet side to the outlet side, and the organic chlorine compounds in the ash were higher in the electric precipitator ash than in the cooling tower ash. .

Next, from the results in Table 2, comparing the ratio of the ash from the electrostatic precipitator and the chlorine compound contained in the exhaust gas, the chlorine compound with a higher chlorine number, that is, the one with a lower vapor pressure was converted to ash. It was recognized that the adsorbed ratio tended to increase. It was also found that when the temperature of the gas passing through the electrostatic precipitator is low, the chlorine compound becomes mainly ash, and when the gas temperature is high, the abundance ratio of the chlorine compound in the exhaust gas becomes high.

Next, the present inventors conducted a heating test on a total of four types of samples of the cooling tower ash and the EP ash that were treated with hydrochloric acid and not treated with hydrochloric acid in the presence of vacuum and oxygen while changing the heating temperature and time. The results are shown in Table 3.

As is clear from Table 3, both the cooling tower ash and the EP ash treated with hydrochloric acid were heated to 300 ° C. in an oxygen atmosphere (Experiment No. 17,
18, 35 and 36), it is understood that an extremely large amount of chlorine compounds are produced. It was also found that chlorine compounds are produced by heating both the cooling tower ash and EP ash, although not as significantly as hydrochloric acid-treated ash.

From the above experimental results of cooling tower ash and electric dust collection ash from the refuse incineration facility, most of the organic chlorine compounds that were thought to be generated in the incinerator, that is, PCDD, PCDF, chlorinated benzene, and lower chlorine compounds Was found to form during passing through an electrostatic precipitator at around 300 ° C.

Based on the above findings, the present inventors have found that about 75
Exhaust gas of 0 to 900 ℃ is cooled in the cooling tower before entering the dust collector.
By rapidly cooling to ℃ or less, preferably 199 ℃ or less,
They have found that the organic chlorine compounds in the exhaust gas can be significantly reduced, and have reached the present invention.

Margin below In the present invention, incinerator exhaust gas, at least 300 ~ 4
Set the cooling rate in the temperature range of 00 ℃ to 30-100 ℃ / sec. 2
By rapidly cooling to 50 ° C. or less, it rapidly passes through the temperature range (300 to 400 ° C.) where chlorine compounds are likely to be generated, so it is considered that the generation of chlorine compounds in the gas phase is suppressed.

In the present invention, the cooling rate when quenching the exhaust gas is 30
~ 100 ° C / sec is appropriate. If the cooling rate is too slow, the amount of chlorine compounds produced increases and the time for passing through the temperature range of 300 to 400 ° C. becomes long, and the amount of chlorine compounds in the exhaust gas increases. Moreover, unless it is rapidly cooled to 250 ° C. or less, generation of chlorine compounds cannot be sufficiently suppressed.

In the present invention, examples of a device for rapidly cooling high-temperature exhaust gas include a sprinkler type cooling tower, a boiler heat exchanger, and combinations thereof. The cooling rate of 30 to 100 ° C./sec can be easily obtained by adjusting the amount of cooling water, for example. Further, the place of cooling may be anywhere between the incinerator and the dust collector, but it is usually desirable to perform it in the cooling part of the incinerator outlet gas. The dust collector is a dry type, semi-dry type,
In addition to the wet type electric dust collector, dust collectors utilizing gravity, centrifugal force, inertial force, cleaning dust collector, filter dust collector and the like may be used.

〔The invention's effect〕

According to the present invention, it is possible to effectively suppress the generation of harmful organic chlorine compounds by rapidly cooling the exhaust gas from the refuse incinerator.

[Brief description of drawings]

FIG. 1 is a diagram showing a schematic flow of a conventional waste gas incinerator exhaust gas treatment method.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Gentaro Takasuka 4-19 Hamamatsucho, Nishi-ku, Yokohama-shi, Kanagawa (56) References JP 49-27074 (JP, A) JP 60-84131 (JP, A)

Claims (1)

[Claims] 1. A method for treating municipal waste incinerator exhaust gas in which dust is removed by a dust collector after cooling the exhaust gas from the incinerator, and at least 30 exhaust gas is discharged from the outlet of the incinerator to the dust collector.
A method for treating waste gas from a refuse incinerator, which comprises rapidly cooling to 250 ° C or less so that the cooling rate in the temperature range of 0 to 400 ° C is 30 to 100 ° C / sec.