JPH109542A - Method for incinerating waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for incinerating waste which makes it possible to generate electric power efficiently, suppress the evolution of dioxin, and reduce the emitted smoke dust in quantity to make chlorides adequately removable. SOLUTION: A fluidized-bed furnace 1 is charged with waste to be disposed of through a waste charging port 11 and incinerates it. To remove chlorine from the exhaust gas, from a nozzle 12 a Ca compound is blown into a region 1a with the temperature in the range of 500 deg.C-800 deg.C in the furnace or heat-absorption part. By the injection of the Ca compound into the region 1a chlorides are almost all removed. Steam of high temperature and high pressure is obtainable by virtue of high temperature and the efficiency of electric power generation is improved and dioxin is not evolved. The matter discharged from the furnace 1 is separated by a high-temperature cyclone into clean exhaust gas having use for electric power generation and materials led into a decomposition furnace 7, where harmful metals and chlorides undergo volatilization separation at temperatures in the range of 900 deg.C to 1,200 deg.C and collected by an exhaust gas disposal device 8. Part of the ash from the decomposition furnace 7, which contains a Ca compound, is put back into the temperature region 1a of the furnace 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a refuse incineration method for incinerating municipal refuse and the like, and more particularly to a refuse incineration method suitable for refuse incineration using a fluidized-bed furnace.

[0002]

2. Description of the Related Art Municipal refuse is incinerated in an incinerator such as a fluidized bed furnace or a stoker. Electric power is generated by using the heat generated at that time. Exhausted exhaust gas contains high concentrations of harmful heavy metals such as chlorides such as hydrogen chloride and cadmium (Cd), lead (Pb), and mercury (Hg), which are significant for local residents, animals and plants. Serious damage. For this reason, regulations on exhaust gas emitted from incinerators are extremely strict, and it is thought that these regulations will become more and more strict in the future.

In order to satisfy the above regulations on exhaust gas, in a conventional incinerator, a calcium (Ca) compound as a chlorine removing agent is blown into a furnace or a flue and a bag filter is interposed for dust removal. Thereby, means for removing chlorides and harmful heavy metals from exhaust gas has been adopted. In particular, the bag filter has the effect that not only the unreacted Ca compound captured on the surface can further react with the chloride in the exhaust gas on the surface to obtain a high chloride removal rate, but also has the following effect. It also has an effect. That is,
Dioxin, which is a harmful substance generated in exhaust gas, is said to be generated in the exhaust gas temperature range of 250 to 500 ° C in the presence of chlorine.
Since the temperature is as low as about ℃, the bag filter will be operated at a low temperature of less than 250 ℃ of dioxin generation temperature.
In combination with the above chloride removing effect (dioxin is generated in the presence of chloride), it has an effect of inhibiting the generation of dioxin. The conventional incinerator employs a flow method in which the residence time of exhaust gas in the temperature range of 250 to 500 ° C., which is the temperature at which dioxin is generated, is made as short as possible.

[0004]

In the above conventional means,
The high-temperature exhaust gas discharged from the incinerator is rapidly cooled in order to guide it to the bag filter operating at a low temperature.However, such rapid cooling cannot recover heat from the high-temperature exhaust gas. Cannot be obtained, and high-efficiency power generation cannot be performed. Further, the removal of chloride by the Ca compound is not always sufficient, and
It is unavoidable that high-temperature corrosion occurs in the heat exchanger due to the chlorides in the exhaust gas, and continuous operation is impossible to cope with this, and high-efficiency power generation cannot be performed from this aspect as well. .

Further, the low temperature operation of the bag filter allows
Although the dioxin concentration in the exhaust gas released into the atmosphere can be reduced, the generation of dioxin in the flue cannot be sufficiently suppressed, and the dioxin concentration collected by the bag filter is extremely high. It is necessary to suppress or decompose dioxin, which complicates the apparatus. In recent years, melting and solidification, which can also decompose dioxin, has been adopted as a method of detoxifying ash. Therefore, there has been a problem that it is difficult to stably operate the melting furnace for a long time.

Furthermore, according to the conventional means, the utilization rate of the Ca compound is extremely low at 30 to 40%, and it is necessary to increase the blowing amount of the Ca compound in order to sufficiently remove chlorine. However, landfill sites for soot and dust from refuse incinerators cannot be sufficiently secured at present, and it is expected that securing them will become increasingly difficult in the future. Therefore, increasing the blowing amount of the Ca compound for improving the chlorine removal rate increases the dust amount, and it is not desirable to increase the blowing amount of the Ca compound due to the problem of landfill.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned problems in the prior art, to enable efficient power generation, to suppress the generation of dioxin, and to reduce the amount of soot and chloride. It is an object of the present invention to provide a refuse incineration method that can be sufficiently removed.

[0008]

As a result of various studies on chlorine removal by blowing a chlorine remover into a furnace, the inventors have found that a chlorine remover, such as CaO, can be used at a temperature of 750 to 800 ° C. or lower, and It has been found that chlorine can be removed by maintaining a sufficient reaction time (1 second or longer). The present invention is based on the results of such research, and in order to achieve the above object, the invention according to claim 1 is directed to a method for incinerating garbage into a furnace and incinerating the same, wherein the furnace or A chlorine remover is blown into the heat absorber at a temperature range of 500 ° C to 800 ° C and in a region where the reaction time with the chloride in the exhaust gas can be secured for 1 second or longer. The exhaust gas is separated into other substances, and the separated exhaust gas is supplied to a steam heating system.

According to a second aspect of the present invention, in the refuse incineration method according to the first aspect, a compound of the chlorine removing agent and chloride separated by the high-temperature separation device, soot, and unreacted chlorine are removed. The agent is introduced into the decomposition furnace,
The harmful metal is volatilized and separated from the soot at a temperature of 900C, preferably 900C to 1100C, and the chloride is volatilized and separated from the compound.

Further, the invention according to claim 3 is the waste incineration method according to claim 2, wherein the harmful metal and the chloride which have been volatilized and separated are collected by an exhaust gas treatment device, and the residual containing the chlorine removing agent. A part of the substance is returned to the temperature range of 500 ° C. to 800 ° C. in the furnace.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to the illustrated embodiments. FIG. 1 is a diagram showing an incineration system used in the incineration method according to the embodiment of the present invention. In this figure, 1 is a fluidized bed furnace, 1a is a predetermined area in the fluidized bed furnace 1, 1
Reference numeral 1 denotes a refuse inlet of the fluidized-bed furnace 1, and reference numeral 12 denotes a Ca compound injection nozzle of the fluidized-bed furnace 1. 2 is a high-temperature cyclone, 3 is a superheater composed of a primary superheater 31 and a secondary superheater 32,
4 is a economizer, 5 is a bag filter, and 6 is a chimney. Reference numeral 7 denotes a cracking furnace, 8 denotes an exhaust gas treatment device for treating exhaust gas from the cracking furnace 7, and 9 denotes ash discharged from the cracking furnace 7.

Next, the incineration method according to the present embodiment will be described. The Ca compound is blown into the region 1a in the furnace using the blowing nozzle 12. The area 1a is 500 to
A region is selected which is 800 ° C., preferably 700 to 750 ° C., and can secure a reaction time of 1 second or more between the introduced Ca compound and the chloride in the exhaust gas.

As described above, by selecting the region 1a to be 500 ° C. or higher, it is possible to prevent the generation of dioxin having a temperature range of 250 to 500 ° C. Also, 80
The reason for selecting the temperature below 0 ° C is as follows. That is, the reaction between Ca and chlorine does not proceed at a very high temperature, and the decomposition reaction of CaCl ₂ produced as a result of the reaction is faster at 750 to 800 ° C. or higher, and therefore 750 to 800 ° C. or lower. Is appropriate. 750 ° C in this temperature range
In order to obtain 500 ° C, which is often used as a suitable steam temperature for high power generation efficiency,
The most desirable temperature range of region 1a is 700-800 ° C., both for 0 ° C. and 700 ° C. being required.
Even if the average gas temperature in the furnace is 800 ° C. or less, the flame portion is hotter and the reacted CaCl ₂ is decomposed, so that it is not blown into the flame portion.

The blown Ca compound reacts with the chloride in the gas to form both compounds CaCl ₂ and removes chlorine. Also, dioxin is not generated because chlorine is removed and the temperature is high. As a result, high temperature (700 ° C. or more) exhaust gas containing neither chlorine nor dioxin, a compound of Ca and chlorine, soot and dust, and an unreacted Ca compound are discharged from the fluidized bed furnace 1. These are introduced into the hot cyclone 2 and separated into exhaust gas and other substances. As described above, the separation means using the high-temperature cyclone 2 can be used because chlorine is not contained in the exhaust gas from the fluidized-bed furnace 1.
If chlorine is contained in the exhaust gas, it will be contained in the exhaust gas obtained as a result of the separation in the high-temperature cyclone, and high-temperature corrosion of the heat exchanger by chlorine will occur, so that the cyclone cannot be used.

The exhaust gas at 700 ° C. obtained in the high-temperature cyclone 2 is supplied to the superheater 3 and the economizer 4 through a pipe 21.
The air is discharged from the chimney 6 to the outside air via the bag filter 5 (removal of a small amount of dust and dioxin). Superheater 3
The heat exchange at, for example, produces a high-temperature steam of 500 ° C,
This steam is supplied to a steam turbine to generate power.
In the economizer 4, the supply water is preheated by heat exchange. Since chlorine is not contained in the exhaust gas from the high-temperature cyclone 2, high-temperature corrosion does not occur in the superheater 3 or the economizer 4,
Continuous operation is possible.

On the other hand, the remaining substances separated from the exhaust gas by the high-temperature cyclone 2, ie, a compound of Ca and chlorine, soot and dust (including dioxins and harmful metals), and unreacted C
The compound a is introduced into the decomposition furnace 7, where it is thermally decomposed.
As the cracking furnace 7, for example, an external heat type kiln is used. By this thermal decomposition, harmful metals (Pb and Cd) in the dust are volatilized and separated from the dust. In addition, dioxin in dust is decomposed and made harmless. Also, Ca
And chlorine (CaCl ₂ ) are mostly decomposed, and C
Regenerate compound a. As a result of experiments, the temperature at which such volatilization or decomposition is possible is 900 to 1200 ° C, preferably 1000 to 11
The temperature was found to be 00 ° C. This temperature is at least 300 ° C. lower than the temperature used in the conventional treatment of molten exhaust gas, and the amount of exhaust gas is significantly smaller than the amount of exhaust gas in the treatment of molten exhaust gas (approximately 1/20). .

Chloride and harmful metals that are volatilized and separated in the cracking furnace 7 are collected in the exhaust gas treatment device 8. The exhaust gas treatment device 8 includes a bag filter, a wet-type flue gas washer,
Alternatively, a water tube type gas cooler or the like is used, and the weight of the substance collected here is about 15% of the total weight of the substance discharged from the decomposition furnace 7.

On the other hand, substances discharged from the decomposition furnace 7 other than the substances discharged by volatilization and separation are shown as ash 9 in the figure. The ash 9 is made up of harmless soot, pyrolyzed Ca compounds, and unreacted Ca compounds, and a part of the ash 9 passes through the recycle line 91 and enters the area 1 of the fluidized bed furnace 1.
a and returned to the outside through a discharge line 92 as harmless ash. As described above, it is clear that the utilization rate of the Ca compound can be significantly improved from the conventional utilization rate (30%) by using the regenerated Ca compound. Since the Ca particle concentration can be increased without blowing into the furnace, the chlorine removal rate can be improved, and the amount of discharge can be reduced.

In the above embodiment, a fluidized bed furnace has been described as an example, but the same method can be applied to a stoker. In addition, although an example in which a high-temperature cyclone is used as the high-temperature separation device has been described, a high-temperature ceramic filter may be used.

[0020]

As described above, according to the present invention, the temperature range of the furnace or heat absorbing section is 500 ° C. to 800 ° C. and the reaction time with the chloride in the exhaust gas can be secured for 1 second or more. Chlorine remover is blown in, so chlorine can be removed in the furnace, and dioxin is not contained in exhaust gas. Etc. can be separated.
Further, since the temperature of the exhaust gas is high, high-temperature and high-pressure steam can be obtained, and high-efficiency power generation can be performed.

Further, since the cracking furnace is used at the subsequent stage of the separation apparatus, the processing can be performed at a temperature lower than the temperature in the conventionally performed molten exhaust gas treatment by 300 ° C. or more.
Since the amount of exhaust gas is also significantly smaller than the amount of exhaust gas in the treatment of molten exhaust gas, the treatment becomes extremely easy.

Furthermore, since the chlorine remover regenerated in the cracking furnace is returned to the furnace, the utilization rate of the chlorine remover can be greatly improved from the conventional utilization rate, and a large amount of the chlorine remover can be used in the furnace. The particle concentration of the chlorine removing agent can be increased without blowing into the air, the chlorine removal rate can be improved, and the emission can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing an incineration system used in an incineration method according to an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Fluid bed furnace 1a Furnace area 2 High temperature cyclone 3 Superheater 4 Energy saving device 5 Bag filter 7 Decomposition furnace 8 Exhaust gas treatment device 11 Garbage inlet 12 Ca compound injection nozzle

Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical display location B09B 3/00 F23G 7/00 ZAB F23G 5/14 ZAB B09B 3/00 ZAB 7/00 ZAB 303M (72) Invention Person Hiromichi Fujiwara 1-2-10 Isogo-ku, Yokohama-shi, Kanagawa Prefecture Babkotsuk Hitachi, Ltd. Yokohama Engineering Center

Claims (3)

[Claims] 1. A refuse incineration method in which refuse is put into a furnace and incinerated, wherein the refuse is incinerated at 500 ° C.
The chlorine remover is blown into the temperature range of ~ 800 ° C and the area where the reaction time with the chloride in the exhaust gas can be secured for 1 second or more, and the emission from the furnace is separated from the exhaust gas and other substances by the high temperature separator. A waste incineration method characterized in that the separated exhaust gas is supplied to a steam heating system. 2. The waste incineration method according to claim 1,
The compound of the chlorine removing agent and the chloride separated by the high-temperature separation device, the dust, and the unreacted chlorine removing agent are introduced into a decomposition furnace, and 900 ° C. to 1200 ° C., preferably 900 ° C.
A refuse incineration method, wherein harmful metals are volatilized and separated from the dust at a temperature of 1C to 1100C, and the chloride is volatilized and separated from the compound. 3. The waste incineration method according to claim 2,
Collecting the harmful metals and chlorides that have been volatilized and separated by an exhaust gas treatment device, and returning a part of the remaining substances including the chlorine remover to the temperature range of 500 to 800 ° C. in the furnace. Characterized garbage incineration method.