JP2003117520A - Method for treating incineration ash - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for treating incineration ash using a reactant of slaked lime as a (chlorine and calcium) source of a chlorination volatilization method. SOLUTION: A material which acts as a carbon source and the reactant of the slaked lime with HCl in incineration waste gas (a mixture composed of calcium chloride and calcium hydroxide) are mixed with main ash generated from a municipal refuse incinerator equipped with a dry process waste gas treating equipment or an industrial waste incinerator, flying ash recovered from the waste gas or their mixture. The resulted mixture is heated at 400 to 1,200 deg.C in a gaseous atmosphere containing steam within a chlorination volatilization reactor 22. Hazardous materials in the ash are removed, by which the ash is made non-polluting. Heavy metals-containing waste gas discharged from the above incinerators 22 are cooled and the condensed heavy metals are recovered in the form of solids by a dust collector. The waste gas cooled is thereafter returned from a dust collector to the upstream side of a waste gas treating equipment.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for detoxifying incineration main ash and fly ash generated from an incinerator for municipal solid waste or an incinerator for industrial waste having a dry exhaust gas treatment device. Incinerator ash (referred to as main ash) discharged from municipal waste incinerators or industrial waste incinerators and fly ash collected from exhaust gas usually contain dioxins and heavy metals as harmful substances and are recycled. It is necessary to remove these harmful substances before they can be used. The present invention provides a method for detoxifying such harmful substances.

[0002]

2. Description of the Related Art As one technique for incinerating municipal waste or industrial waste, there is an ash melting furnace technique for melting generated ash at a high temperature. This technology burns or thermally decomposes and removes dioxins contained in ash by heating the ash to a melting temperature, and volatilizes heavy metals that volatilize as chlorides into gas and volatilizes them. What remains without being, is to try to reduce the volume of ash by trapping it in molten slag to prevent elution. Heavy metal chloride volatilized in the gas is cooled by cooling the gas to condense the chloride into solid chloride, which is then collected and collected by a dust collector such as a bag filter. The collected ash thus collected is referred to as molten fly ash, and has a higher concentration of heavy metals than ordinary incinerated fly ash. This molten fly ash is washed with water, and after sulfuric acid burning ore and calcium chloride are added to the residue after washing with water to granulate, the particles are roasted at high temperature to form C
A heavy metal recovery method called a chloride volatilization method has been proposed in which u, Pb, Zn and the like are volatilized and recovered, and the remaining iron oxide is used as an iron-making raw material (Cited document 1: Masakatsu Hiraoka, Shinichi Sakai " Prospects of waste incineration fly ash and treatment technology ", Journal of Japan Society of Waste, vol. 5, No. 1, p. 3-17,
1994).

In this method, the heavy metal chloride recovered as a chlorine source for the volatilization of chloride is subjected to a wet treatment, and the resulting calcium chloride solution is concentrated and recycled.

As described above, it is known to recover heavy metals from fly ash, especially molten fly ash, by a chlorination volatilization method. The chlorine used, the calcium carbonate added to the wet treatment step, and the calcium chloride obtained from calcium oxide are used.

As a chlorine source for removing heavy metals in incinerated ash and fly ash by the chlorination volatilization method, H in exhaust gas from an incinerator is used.
It is conceivable to use HCl in the wash water generated when Cl is wet-washed with water, but in this case, it is necessary to add the latent heat of vaporization of the wash water coexisting with HCl to the chloride volatilization unit, resulting in energy loss. Has a major drawback.

[0006]

As described above, there is a heavy metal chloride volatilization method as one of the methods for detoxifying the main ash, fly ash, or both discharged from the incinerator. What to use as the source of chlorine to do is an important issue.

In the above cited document 1, a calcium chloride solution, which is a reaction product of chlorine circulating in a chloride volatilization section-wet heavy metal recovery section, and a calcium compound newly added to the wet metal recovery section is used as a chlorine source. Used in concentrated form.

On the other hand, in Japan, due to the problem of dioxins in the exhaust gas from incinerators, the incinerator exhaust gas is cooled in a gas cooling tower, and then slaked lime is blown into the exhaust gas to remove HCl and collect fly ash with a bag filter. Exhaust gas purification methods are widespread.

This method further comprises a) a method of using one bag filter, in which slaked lime for desalination is blown into the exhaust gas in the upstream of the bag filter, and dust and desalination are simultaneously carried out by the bag filter, and b) two groups. The bag filter of No. 1 is used to collect only fly ash by the first filter, and slaked lime is blown into the exhaust gas in the upstream of the second filter to perform desalting.

The fly ash collected by the method a) contains slaked lime, but in the method b), the collected products are the dust ash collected by the bag filter in the first stage and the ash collected in the second stage. And separated into slaked lime reactant collected by the bag filter of.

Dioxins in the exhaust gas are roughly classified into dioxins in a state of being adsorbed in fly ash called particulates, and dioxins in a gaseous form, but they are contained in the exhaust gas when the method of b) is adopted. Most of the dioxins collected are concentrated in the first-stage collected ash, and dioxins are not included in the second-stage bag filter ash. In order to remove gaseous dioxins in both the method a) and the method b), activated carbon may be blown together with slaked lime in the method a) and upstream of the first stage bag filter in the method b).

Usually, the slaked lime blown in for removing HCl (desalting) in the exhaust gas is used in an excess amount of about 2 times as an equivalent ratio to HCl because of the rate-determining reaction in the reaction product layer on the particle surface. It Therefore, the slaked lime reaction product after reacting with HCl in the exhaust gas is considered to be roughly an equimolar mixture of calcium chloride and calcium hydroxide.

The present invention proposes to use this slaked lime reaction product as a (chlorine and calcium) source for the chlorination volatilization method. According to this method, a new calcium source is not required, and an aqueous HCl solution is used. Energy consumption does not increase unlike when chlorine is used as the chlorine source.

[0014]

A first method for treating incinerated ash according to the present invention is a main ash generated from an incinerator for municipal solid waste or an incinerator for industrial waste equipped with a dry exhaust gas treatment device, and a fly recovered from exhaust gas. The ash, or a mixture thereof, is mixed with a substance serving as a carbon source and a slaked lime reaction product (a mixture of calcium chloride and calcium hydroxide) of HCl in the incineration exhaust gas, and the obtained mixture is placed in a chlorination volatilization reaction furnace. Is a method for detoxifying ash by heating to 400 to 1200 ° C. in a gas atmosphere containing water vapor to remove harmful substances in the ash, and cooling the exhaust gas containing heavy metals discharged from the reactor. After collecting the condensed heavy metals as solids with a dust collector, the cooled exhaust gas is returned from the dust collector to the upstream side of the exhaust gas treatment device.

In the first method for treating incinerated ash, preferably, the exhaust gas treating apparatus is a first stage dust collector for removing fly ash in exhaust gas from an incinerator, and slaked lime is blown into the dust-exhausted exhaust gas to react with HCl. And a second-stage dust collector for collecting the generated slaked lime reaction product. The slaked lime reaction product was recovered by the second-stage dust collector, and the reaction product was subjected to a chloride volatilization reaction. Used as a chlorine source for converting heavy metals in main ash and / or fly ash into chloride in a furnace.

It is preferable to granulate a mixture of main ash, fly ash or a mixture thereof, a substance serving as a carbon source, and a slaked lime reaction product before introducing them into a chloride volatilization reaction furnace.

The second method for treating incinerated ash according to the present invention is
In a method for detoxifying main ash and fly ash generated from an municipal waste incinerator or an industrial waste incinerator equipped with a dry exhaust gas treatment device, the exhaust gas treatment device is a first stage for removing fly ash in an incinerator exhaust gas. An eye dust collector, a slaked lime blowing means that blows slaked lime into the dust removal exhaust gas to react with HCl, and a second-stage dust collector that collects the generated slaked lime reaction product, main ash, and a first-stage dust collector Part of the slaked lime reaction product discharged from the second stage dust collector by supplying the granulated product consisting of fly ash and carbon source to the upstream part of the chlorination volatilization reactor divided into the upper, middle and lower parts. Is granulated, if necessary, and then supplied to the midstream portion, air is supplied from the downstream portion to the upstream portion in a countercurrent flow with the above granulated material, and the combustion exhaust gas for heating and steam are produced from the midstream portion to the upstream portion. It is supplied countercurrently with granules and the exhaust gas after reaction is Taken out from the flow portion, in a gas atmosphere containing water vapor in a chloride volatilization reactor 400-120
The ash is rendered harmless by heating to 0 ° C to remove harmful substances in the ash, the exhaust gas containing heavy metals discharged from the reactor is cooled, and the condensed heavy metals are collected as a solid by a dust collector and then cooled. It is a method characterized in that the exhaust gas is returned from the dust collector to the upstream side of the exhaust gas treatment device.

In the first and second methods for treating incinerated ash according to the present invention, as the carbon source, used activated carbon (for example, activated carbon after used to remove dioxins in incinerator exhaust gas), coal, coke Preference is given to using class and / or waste wood chips. The atmosphere in the chloride volatilization reactor is preferably air containing combustion gas and / or steam. The dust collector that collects the condensed heavy metals as a solid by the dust collector after cooling the exhaust gas containing heavy metals discharged from the chloride volatilization reactor is preferably a bag filter.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION Next, the present invention will be specifically described based on Examples.

Example 1 FIG. 1 is a flow chart showing an example in which the first method for treating incinerated ash according to the present invention is applied to a municipal solid waste incinerator having an incineration amount of 200 t / D.

8,330 kg / h of municipal solid waste is supplied from the hopper (1) to the stoker-type incinerator (3) and 33,070 Nm ³ / h of combustion air is supplied from the pipeline (2) to incinerate the municipal solid waste. To be done. At this time, combustion gas of 40,000 Nm ³ / h containing about 1000 ppm of HCl was generated,
After recovering energy at (4), enter the gas cooling tower (6) through the duct (5). Here, the combustion gas is cooled to 170 ° C with 4,800 kg / h of water blown from the pipe (7),
Enter the first stage bag filter (9) via the duct (8).
Dust and volatilized chloride condensate generated in the combustion process,
That is, the fly ash and the dioxins adsorbed on it are the first
Almost completely captured by the bug filter (9) in the second row.
The flue gas discharged from the bag filter (9) of the first stage further passes through the duct (10) and enters the bag filter (12) of the second stage. The HCl gas circulation path (36) is connected, and the slaked lime injection pipe (11) is provided on the downstream side.
Are connected. From slaked lime blow pipe (11) to duct (1
140 kg / h of desalting slaked lime was blown into (0) and reacted with HCl in the gas in the duct (10) and in the furnace cloth deposition layer of the bag filter (12), and the reaction product calcium chloride 10
The second mixture is 4 kg / h and 70 kg / h of unreacted slaked lime.
It is discharged from the bottom of the bag filter (12) in the first stage. The purified exhaust gas dedusted and desalted is diffused from the chimney (16) to the atmosphere through the duct (13), the induced blower (14) and the duct (15).

On the other hand, the main ash of 578 kg / h discharged from the lower part of the incinerator (3) by the chute (17) is 102 kg / h discharged from the first stage bag filter (9) through the pipe line (18). 79 kg / h of the slaked lime reaction product discharged from the second stage bag filter (12) in the pipe (19) and the mixture in the pipe (20). 68 kg / h of coke supplied as a carbon source is added, and the whole is sent to the granulator (21) for granulation. Incidentally, 94 kg / h of the slaked lime reaction product discharged from the bag filter (12) of the second stage, which was not sent to the chloride volatilization section, is taken out through the pipe line (39) and is discarded or recovered as gypsum. . Granulator (2
The mixed ash granulated in 1) enters the chloride volatilization reactor (22). In the reactor (22), 100 kg / h of kerosene from the pipe (23) and 1,900 Nm ³ / h of combustion air from the pipe (24) were used to generate in the high temperature gas generating furnace (25). 1100-1200
The high temperature combustion exhaust gas at ℃ and steam 660 Nm ³ / h generated in the waste heat recovery boiler (30) and sent through the pipe line (26) are supplied. In the reaction furnace (22), a chloride volatilization reaction occurs due to a reaction described in the literature relating to the chloride volatilization method. The following is a conceptual summary of these reactions.

During the process in which the mixed ash is heated up to around 900 ° C., the heavy metal chlorides originally present in the form of chlorides mainly derived from fly ash are vaporized and transferred into the gas.

On the other hand, most of the heavy metals derived from the main ash are in the form of oxides, and in this process, for example, react with HCl (g) generated in the next reaction to change into chloride, and chloride vapor As it moves into the gas.

[0025]

[Chemical 1]

Dioxins brought into the ash are burned and decomposed by being exposed to an oxidizing atmosphere at high temperature.

Near the outlet of the chlorination volatilization reactor (22), clean air is supplied at about 600 Nm ³ / h from the pipe (27) for the purpose of cleaning the recovered material from the conveyor (37) and as a carrier gas. . The recovered material is recovered from the conveyor (37) at a rate of 680 kg / h. The recovery amount by element is shown in the column A recovered product in Table 1.

The exhaust gas leaving the chloride volatilization reactor (22) is a duct
It is sent to the waste heat recovery boiler (30) via (28) and heat is recovered.
530 kg / h of boiler water is supplied here from the pipeline (29). Exhaust gas recovered in the boiler has a temperature level of about 700 ° C, is sent to the gas cooling tower (32) through the duct (31), and is cooled to 170 ° C by the cooling water supplied through the pipe line (33). It By this cooling, the heavy metal chloride vapor volatilized in the chloride volatilization reaction furnace (22) is condensed and changed into a solid.
The gas exiting the gas cooling tower (32) is sent to the third bag filter (35) through the duct (34), and after dust removal, blows slaked lime into the incinerator exhaust gas line (10) through the duct (36). It is returned to the upstream side of the mouth (11). Bag filter (35) to conveyor (38)
The amount of recovered products discharged in is about 64 kg / h. The composition by element is shown in the column of B recovered product in Table 1.

In the present embodiment, the product recovered from the conveyor (38) is chloride, but it can be easily converted into another form such as hydroxide by wet-alkali treatment. FIG. 2 is a flow chart showing an embodiment of the second method for treating incinerated ash according to the present invention. In this embodiment, the exhaust gas leaving the gas cooling tower (6) is sent to the bag filter (9) at the first stage via the pipe (8), fly ash is collected, and then, as in Example 1. Similarly, the reflux exhaust gas line (36) and the slaked lime supply section (1
After passing through the connection point with 1), it enters the second stage bag filter (12) and the desalted exhaust gas is discharged through the duct (13).
In this embodiment, the fly ash discharged from the bottom of the bag filter (9) of the first stage via the conduit (18), the main ash from the chute (17), and the carbon source from the conduit (20) are used. Is mixed with coke and the mixture is granulated by the granulator (21a). On the other hand, of the slaked lime reaction product recovered by the second-stage bag filter (12), the portion to be supplied to the chloride volatilization reaction furnace (22) is from the bottom of the second-stage bag filter (12). Granulator in pipeline (19)
It is sent to (21b) and granulated. Chlorine volatilization reactor (22) has 3
It is divided into two parts (22a) (22b) (22c) and the granulator (2
The material to be treated granulated in 1a) is supplied to the upstream portion (22a), and then moves to the midstream portion (22b) and the downstream portion (22c). The slaked lime reactant granulated by the granulator (21b) is a reaction furnace.
It is supplied to the middle part (22b) of (22). On the other hand, the combustion exhaust gas for heating from the high temperature gas generating furnace (25) and the steam from the pipe (26) are supplied to the midstream portion (22b) of the reaction furnace (22), and the pipe (27)
Clean air from each is supplied to the downstream part (22c),
Countercurrent to the object to be processed, i.e., the downstream part (22c), the middle part (22c)
b), the upstream part (22a) and then the pipe (28).

The other structure is the same as that of the first embodiment.

In the system according to this embodiment, the middle temperature portion (22b) of the reaction furnace (22) has the highest temperature and the water vapor concentration is high, and the slaked lime reaction product from the second stage bag filter (12) is contained in the reaction product. Since silica is contained as a filter aid, is an environment in which the reaction formula (1) easily occurs. The generated HCl passes through the midstream portion (22a), which is more likely to react at a lower temperature, and converts the oxide into chloride to be vaporized.

[0032]

The effects of the present invention are as follows.

(1) The main ash discharged from the incinerator is finally recovered as a product recovered from the exhaust gas from the chlorination volatilization reactor, and harmful dioxin and heavy metals are removed. It becomes a resource and the landfill site becomes unnecessary.

(2) Heavy metals discharged from the incinerator are
Concentrated as a recovery product from the exhaust gas of a chloride volatilization reactor,
Since it is not dispersed in the main ash and fly ash, it is effective for recycling such as Yamamoto reduction.

(3) All processes are performed in a dry process, and no waste water is generated.

(4) The greatest effect of the present invention is that the chlorine generated as a result of desalination of HCl existing in the main flow of the incinerator as a chlorine source and a calcium source involved in the heavy metal removal reaction by the chloride volatilization method. It is about using calcium.
Therefore, a new calcium source is not required, and energy consumption does not increase unlike the case where an aqueous HCl solution is used as a chlorine source.

(5) According to the method of the present invention, compared with the conventional ash melting method, energy consumption is low at least for the latent heat of fusion due to the treatment at a temperature lower than the melting point of ash, and heavy metals cannot be contained in slag. Therefore, the content of heavy metals in the ash after the treatment is small.

[0038]

[Table 1]

[Brief description of drawings]

FIG. 1 is a flow chart showing an embodiment of a first method for treating incinerated ash according to the present invention.

FIG. 2 is a flow chart showing an embodiment of a second method for treating incinerated ash according to the present invention.

[Explanation of symbols]

(3): Incinerator (4): Boiler (6): Gas cooling tower (9): First stage bug filter (12): Second stage bug filter (21) (21a): Granulator (22): Chlorination volatilization reactor (22a): Upstream part (22b): Midstream part (22c): Downstream part (25): High temperature gas generation furnace (30): Waste heat recovery boiler (32): Gas cooling tower (35): Third bug filter (36): HCl gas circuit

Continued front page    (72) Inventor Kenji Yasuda             1-89 Minami Kohoku 1-89, Suminoe-ku, Osaka             Standing Shipbuilding Co., Ltd. (72) Inventor Hiroshi Onishi             1-89 Minami Kohoku 1-89, Suminoe-ku, Osaka             Standing Shipbuilding Co., Ltd. (72) Inventor Katsuhisa Tsuji             1-89 Minami Kohoku 1-89, Suminoe-ku, Osaka             Standing Shipbuilding Co., Ltd. (72) Inventor Shigehiro Shibakawa             2-32 Kinrakuji-cho, Amagasaki-shi, Hyogo Stock             In ceremony company Takuma (72) Junichi Uchi             2-32 Kinrakuji-cho, Amagasaki-shi, Hyogo Stock             In ceremony company Takuma F term (reference) 4D002 AA28 AC10 BA13 CA13 EA02                       EA20 FA01 GA03 GB03                 4D004 AA12 AA36 AB07 CA14 CA30                       CA34 CA45 CA47 CC01 CC11                       CC12 CC15 DA02 DA03 DA06                       DA10

Claims (7)

[Claims] 1. A main ash generated from a municipal solid waste incinerator or an industrial waste incinerator equipped with a dry exhaust gas treatment device, fly ash recovered from exhaust gas, or a mixture thereof, a substance serving as a carbon source, and incinerated exhaust gas. Ash by mixing a slaked lime reaction product with HCl in the mixture and heating the resulting mixture to 400 to 1200 ° C. in a gas atmosphere containing water vapor in a chloride volatilization reaction furnace to remove harmful substances in the ash. Detoxifying the exhaust gas containing heavy metals discharged from the reactor, collecting the condensed heavy metals as solids with a dust collector, and then returning the cooled exhaust gas from the dust collector to the upstream side of the exhaust gas treatment device. A method for treating incinerated ash, which is characterized in that 2. The exhaust gas treating apparatus comprises a first stage dust collector for removing fly ash in incinerator exhaust gas, slaked lime blowing means for blowing slaked lime into the dust-exhausted exhaust gas to react with HCl, and a generated slaked lime reaction product. And a second stage dust collector for collecting slaked lime, wherein the slaked lime reaction product is recovered by the second stage dust collector, and the reaction product is removed from the main ash and / or fly ash in a chloride volatilization reactor. The method for treating incineration ash according to claim 1, wherein the method is used as a chlorine source for converting heavy metals into chloride. 3. The method according to claim 1, wherein a mixture of main ash, fly ash or a mixture thereof, a substance serving as a carbon source, and a slaked lime reaction product is granulated before being put into a chloride volatilization reaction furnace.
Or the method for treating incinerated ash according to 2. 4. A method for detoxifying main ash and fly ash generated from a municipal solid waste incinerator or an industrial waste incinerator equipped with a dry exhaust gas treatment device, wherein the exhaust gas treatment device removes fly ash in the incinerator exhaust gas. A first-stage dust collector for removing dust, a slaked lime blowing means for blowing slaked lime into the dust-exhausted exhaust gas to react with HCl, and a second-stage dust collector for collecting the generated slaked lime reaction product. Granulated material consisting of fly ash from the first stage dust collector and a carbon source is supplied to the upstream part of the chlorination volatilization reactor divided into the upper, middle and lower parts, and the slaked lime discharged from the second stage dust collector. Part of the reaction product is granulated if necessary and then supplied to the midstream part, air is supplied from the downstream part to the upstream part in a countercurrent flow with the above granulated product, and the combustion exhaust gas for heating and steam are supplied from the midstream part. It is supplied countercurrently with the above granules in the upstream part, Removed exhaust gas after the upstream portion 400 in a gas atmosphere containing water vapor chloride volatilization reactor
The ash is rendered harmless by heating to ~ 1200 ° C and removing harmful substances in the ash, and the exhaust gas containing heavy metals discharged from the reactor is cooled.
A method for treating incinerated ash, which comprises collecting the condensed heavy metals as solids with a dust collector and then returning the cooled exhaust gas from the dust collector to the upstream side of the exhaust gas treatment device. 5. The method for treating incinerated ash according to any one of claims 1 to 4, wherein used activated carbon, coal, cokes and / or waste wood chips are used as the carbon source. 6. The incineration ash treatment method according to claim 1, wherein air containing combustion gas and / or steam is used as an atmosphere in the chloride volatilization reaction furnace. 7. The dust collector for collecting the condensed heavy metals as a solid by a dust collector after cooling the heavy metal-containing exhaust gas discharged from the chlorination volatilization reactor is a bag filter. The method for treating incinerated ash described in Crab.