JP2000346329A - Method and apparatus for treating waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce a concentration of dioxins in an incinerating furnace and to suppress generation of dioxins or the like even in an electric dust collector by multi-fuel burning a sludge in the case of incinerating a waste, and operating the collector at a specific temperature or below. SOLUTION: Not only a waste supply hopper 1a but also a sludge supply hopper 1b are newly provided in an incinerating furnace 1. A temperature sensor 7 for detecting an exhaust gas temperature is installed at an inlet of an electric dust collector 4. Further, a dust collector inlet temperature controller 8 for controlling to operate the collector 4 at 230 deg.C or below by controlling a temperature lowering facility 2 to increase a temperature lowering degree of a high temperature exhaust gas when a detected value of the sensor 7 exceeds 230 deg.C or when a temperature rise is abrupt even at the stage that the value of the sensor 7 does not exceed 230 deg.C is provided. The facility 2 has a temperature lowering tower of the type for passing here the high temperature exhaust gas through a water spraying atmosphere to thereby lower the gas temperature.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste treatment method for efficiently reducing dioxins in a waste treatment system in which waste is incinerated in an incinerator, and the generated exhaust gas is treated and released to the atmosphere. And equipment.

[0002]

2. Description of the Related Art FIG. 3 shows a typical system configuration of an incinerator facility for incinerating waste such as municipal waste and plastic waste (hereinafter, these are simply referred to as waste).
In the figure, reference numeral 1 denotes an incinerator having a waste supply hopper 1a, 2 denotes a temperature-reducing facility composed of, for example, a temperature-reducing tower, a boiler, a heat exchanger, and the like.
Exhaust gas treatment equipment for removing acidic gases such as Cl and SOx, 4 is an electric dust collector, 5 is an induction fan, 6 is a chimney, and these are connected in series via a flue.

[0003] In such a case, the waste put into the incinerator by the crane from the waste pit is dried and burned in the incinerator 1, and the unburned matter is completely burned. After the incineration, the combustion exhaust gas is discharged out of the furnace, and is discharged from the chimney 6 through the temperature reduction equipment 2, the exhaust gas treatment equipment 3, and the electric dust collector 4.

[0004]

As is well known, the electrostatic precipitator 4 is characterized by being able to collect fine particles without being affected by the properties of gas or dust. However, in the case of such a waste treatment system, the exhaust gas discharged from the furnace outlet of the incinerator 1 is introduced into the electric precipitator 4 at about 300 ° C. through the temperature reduction equipment 2 and the exhaust gas treatment equipment 3, Dust collection is often performed. The temperature of about 300 ° C. is a temperature at which dioxin is easily generated. If the flue gas is passed through the electric dust collector 4 at the temperature of about 300 ° C., the dioxin concentration becomes high and the dioxin is discharged from the chimney 6. There is a problem.

The technical problem of the present invention is to maintain a constant combustion state in an incinerator by introducing a relatively simple apparatus,
It is an object of the present invention to reduce the concentration of dioxins in an incinerator and to suppress the generation of dioxins in an electric dust collector.

[0006]

According to the present invention, there is provided a waste disposal method comprising connecting an incinerator, a temperature reduction facility, an exhaust gas treatment facility, an electric dust collector, an induction fan, and a chimney in series via a flue. In the waste treatment system, when incinerating the waste, the sludge is mixed and the electric dust collector is set to 230.
It is characterized in that it is operated at a temperature of not more than ℃.

[0007] The apparatus used in this method is a waste treatment system in which an incinerator, a temperature reduction facility, an exhaust gas treatment facility, an electric dust collector, an induction fan, and a chimney are connected in series via a flue. The incinerator is equipped with a waste supply hopper and a sludge supply hopper, and the
It is provided with a dust collector inlet temperature control device for controlling operation at a temperature of not more than ° C.

Further, the waste disposal method according to the present invention is characterized in that the temperature reducing equipment is controlled so that the temperature of the exhaust gas at the inlet of the electric dust collector is 230 ° C. or less.

In the apparatus used in this method, a temperature sensor for detecting the temperature of exhaust gas is installed at the entrance of the electric precipitator, and the temperature control device at the entrance of the precipitator is based on the detected value of the temperature sensor. The structure is such that the temperature reducing equipment is controlled so that the temperature is 230 ° C. or less.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, a waste disposal method according to an embodiment of the present invention and an apparatus used in the method will be described with reference to FIG. FIG. 1 is a diagram showing a system configuration of a waste disposal apparatus according to the present embodiment. In the figure, the same parts as those in the above-described conventional example (FIG. 3) are denoted by the same reference numerals.

The waste treatment apparatus according to the present embodiment includes an incinerator 1
In addition to the waste supply hopper 1a, a sludge supply hopper 1b is newly provided, and a temperature sensor 7 for detecting the temperature of the exhaust gas is installed at the entrance of the electric precipitator 4, and the detected value of the temperature sensor 7 is 230 ° C. If the temperature rises rapidly even when the temperature exceeds the temperature, or even when the detected value of the temperature sensor 7 does not exceed 230 ° C., the temperature reduction equipment 2 is controlled to increase the degree of temperature reduction of the high-temperature exhaust gas. Dust collector inlet temperature control device 8 that controls so that it operates at 230 ° C or less
Is provided.

The temperature reducing equipment 2 here comprises a temperature reducing tower of a type in which a high-temperature exhaust gas is passed through a water spray atmosphere to lower the gas temperature, and a dust spray inlet temperature control device 8 issues a water spray amount increase command. The water spray amount is increased.

The sludge used here is generated when solid-liquid separation is performed on sewage sludge, night soil sludge generated with sewage treatment, sludge generated when organic wastewater is treated with activated sludge, and wastewater containing organic substances. Any type of sludge may be used, such as sludge generated in closed water bodies during river dredging, and sludge generated in the course of sewage treatment.

Next, a method of treating waste using the apparatus according to the present embodiment will be described in further detail. First, waste is conveyed from a refuse pit by a crane, and is put into the incinerator 1 from the supply hopper 1a, and organic sludge generated in, for example, a sewage treatment process is thrown from the sludge supply hopper 1b. The sludge and waste put into the incinerator 1 are dried in the furnace, ignited and co-fired, and the exhaust gas is sent downstream from the furnace outlet. As a result, the dioxin concentration is lower than in the case where only waste is incinerated. This is for the following reason.

That is, the S component in the sludge is present in the incinerator 1 as H2S, CS2, COS, SO2, and SO3 during the combustion process. These substances have a poisoning effect on copper or a similar substance serving as a catalyst for the production of dioxins, and effectively suppress dioxins in an exhaust gas line from the high temperature combustion field in the furnace to the exhaust gas after the furnace outlet.

Further, N in sludge generates ammonia in the combustion process, particularly in a reducing atmosphere in the primary combustion zone,
This reacts with the chlorine compound to suppress the dioxin production reaction of Cl in the process of producing dioxins.

Further, the moisture in the sludge suppresses the combustion reaction rate of combustibles and reduces the generation of soot. If the amount of soot generation is suppressed, the concentration of aromatic organic compounds resulting therefrom decreases, and as a result, the concentration of dioxin-like substances, which are incomplete combustion products, is also reduced.

For the above reasons, the dioxin concentration is reduced by co-firing waste and sludge. However, as a result of extensive studies, the present inventors have found that when co-firing waste and sludge, an electric precipitator 4 is used. It has been found that dioxin concentration decreases when the operating temperature is lowered by using a gas. This is considered to be because the generation of dioxins is suppressed by operating at a low temperature in a region around 300 ° C. where dioxins are easily generated. FIG. 2 is a graph showing this finding obtained by the experimental study of the present inventors. This is a graph showing the relationship between the operating temperature of the electric precipitator 4 and the rate of increase of dioxin between the inlet and the outlet of the electric precipitator 4, where the vertical axis indicates the dioxin increase rate and the horizontal axis indicates the electric precipitator inlet temperature. I have.

From these results, it can be seen that if the temperature of the electric dust collector is 230 ° C. or less, preferably 210 ° C. or less, the concentration of dioxins in the electric dust collector 4 does not increase, and the concentration of dioxins can be reduced efficiently.

Therefore, the temperature of the exhaust gas is monitored by the temperature sensor 7 installed at the entrance of the electric precipitator and the temperature control device 8 at the entrance of the precipitator, and when the detected value of the temperature sensor 7 exceeds 230 ° C. If the temperature does not exceed 230 ° C. and the temperature rises sharply, the dust collector inlet temperature control device 8 outputs a water spray amount increase command to the temperature reduction device 2 to increase the water spray amount of the temperature reduction device 2. By increasing the temperature reduction of the high-temperature exhaust gas and thereby controlling the temperature of the electric precipitator 4 during operation to 230 ° C. or less, the concentration of dioxins can be reduced. The synergistic effect with the substance concentration reducing effect allows the dioxin concentration to be reduced more efficiently.

When the entire system is automatically controlled, the detection value of the temperature sensor 7 may be incorporated as one of the operation parameters.

The fine particles are collected and removed by the electric precipitator 4 and the clean air is discharged from the chimney 6 to the atmosphere.

In order to verify the effects of the present invention, municipal solid waste and sludge were incinerated in a grate incinerator, and the temperature of the exhaust gas was reduced to 210 ° C. in a cooling tower, and then collected by an electric dust collector. When the dioxin concentration in the case and the dioxin concentration in the case where only the municipal waste was incinerated and the electric dust collector was operated at 270 ° C. were compared, the former one according to the present invention had a higher dioxin concentration than the latter. Is about 9
It was confirmed that it was reduced relatively.

[0024]

As described above, according to the present invention, a disposal system in which an incinerator, a temperature reducing facility, an exhaust gas treatment facility, an electric dust collector, an induction fan, and a chimney are connected in series via a flue. In the waste disposal system, when incinerating waste, the sludge was mixed and the electric precipitator was operated at 230 ° C or lower, so that the generation of dioxins could be reduced efficiently.

[Brief description of the drawings]

FIG. 1 is a system configuration diagram of a waste disposal apparatus according to an embodiment of the present invention.

FIG. 2 is a graph showing the relationship between the operating temperature of an electrostatic precipitator and the rate of increase in dioxin.

FIG. 3 is a system configuration diagram of a conventional waste disposal apparatus.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Incinerator 1a Waste supply hopper 1b Sludge supply hopper 2 Temperature reduction equipment 3 Exhaust gas treatment equipment 4 Electric dust collector 5 Induction fan 6 Chimney 7 Temperature sensor 8 Dust collector inlet temperature control device

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Yoshinari Fujisawa 1-2-1 Marunouchi, Chiyoda-ku, Tokyo F-term (reference) 3K061 AA24 AB01 AC02 BA05 BA08 DA18

Claims (4)

[Claims] 1. A waste treatment system in which an incinerator, a temperature reducing facility, an exhaust gas treatment facility, an electric dust collector, an induction fan, and a chimney are connected in series via a flue, when incinerating waste. A waste treatment method comprising co-firing sludge and operating an electric dust collector at 230 ° C or lower. 2. The temperature of the exhaust gas at the inlet of the electrostatic precipitator is 23.
The waste treatment method according to claim 1, wherein the temperature reducing equipment is controlled so as to be 0 ° C or less. 3. A waste treatment system in which an incinerator, a temperature-reducing facility, an exhaust gas treatment facility, an electric dust collector, an induction fan, and a chimney are connected in series via a flue, A waste treatment apparatus comprising a supply hopper and a sludge supply hopper, and a dust collector inlet temperature control device for controlling the electric dust collector to operate at 230 ° C. or lower. 4. A temperature sensor for detecting exhaust gas temperature is installed at an entrance of the electric precipitator, and a temperature control device at the entrance of the precipitator detects a temperature of the entrance of the electric precipitator based on a detection value of the temperature sensor.
4. The waste treatment apparatus according to claim 3, wherein the temperature reduction equipment is controlled so as to be 230 ° C. or less.