JP3437828B2 - Fuel-fired incineration ash treatment equipment - Google Patents

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to treating exhaust gas generated from an ash melting furnace when burning incineration ash produced by incineration of general household waste, industrial waste, etc. and melting and solidifying the ash <br / > it relates to that equipment be.

[0002]

2. Description of the Related Art In recent years, in Japan, general household wastes and wastes have been increasing year by year, and their disposal has become a social problem, and each local government is obliged to dispose of them. Since 1993, major prefectures have been regulated by ordinance to have each municipality have an incineration facility, and as a result, large cities and each municipality have more than one incineration facility. Various problems have come to be highlighted, such as securing a final disposal site for landfills and secondary pollution from the buried incineration ash.

Recently, household waste is also designated as specially controlled general waste, incinerated fly ash is separated from main ash (incinerated ash), and it is impossible to bury it at the final disposal site without intermediate treatment. Therefore, the incineration ash melting and solidifying technology that can prevent the elution of harmful substances such as heavy metals contained in the incineration ash has been attracting attention, and the Ministry of Health and Welfare is planning the construction of an incineration ash melting treatment facility targeting metropolitan prefectures. It has been promoted since 1994.

[0004] At present, the garbage discharged from ordinary households is collected by type and treated according to the quality of the garbage.
For example, some of combustible waste is used as a raw material for compost fertilizer, but most of it is incinerated in an incinerator in a cleaning plant. In this incineration process, incineration ash discharged from the incinerator and fine fly ash collected by a dust collector or the like are generated. The latter fly ash is light and easy to fly,
Since it also contains a large amount of heavy metals, it is usually solidified with concrete or neutralized with carbon dioxide in the exhaust gas to stabilize it as a carbonate and then buried. on the other hand,
The incinerated ash is melted and solidified at a temperature of about 1400 to 1500 ° C., and then effectively used for embedding or covering soil material.

Conventionally, as an incinerator ash melting furnace, an electric melting furnace (arc heating method, plasma heating method, resistance heating method), coke bed melting furnace (coke heating method), surface melting furnace (heavy oil burner heating method), etc. Are known.

Most of the incinerator ash melting furnaces currently in operation are electric melting furnaces, for example, plasma heating and melting furnaces, and the power consumption per ton of incinerated ash is 800 to 100.
Since it is as high as 0 kW, in order to operate economically, it is necessary to attach a power generation facility by heat recovery of exhaust gas from the incinerator, and use the electric power generated by it as a heat source of the melting furnace. However, the maximum incineration scale of this power generation facility is as large as 200 tons of garbage per day, and since it is a continuous furnace, it is unsuitable as a small incinerator with a throughput of less than that. Since it is difficult to cope with the rapid fluctuation of the ash, it is necessary to perform a drying process in advance when treating ash having a high water content or ash containing unburned organic matter.

Further, since the coke bed melting furnace uses solid fossil fuel, which is currently difficult to obtain, it is unavoidable that the cost becomes high, and in addition, 0.3 ton of coke and 0.3 ton of lime are obtained per ton of incinerated ash. It has a drawback that the volume reduction rate is low because it requires a certain degree. Therefore, recently, household waste is also designated as specially controlled general waste, and incineration fly ash is separated from main ash, and it is impossible to bury it at the final disposal site without intermediate treatment. Surface melting furnaces that burn fuel have come to the fore.

By the way, in such a fuel-fired surface melting furnace, there is no problem if the exhaust gas heat is recovered after the molten exhaust gas is once rapidly cooled to around 350 ° C. in the gas cooling tower. Normally, the exhaust gas temperature at the outlet of the gas cooling tower is set to 550 to 650 ° C, and this temperature is the same as the temperature at which the metal volatilized from the furnace precipitates as chlorides, oxides, and silicates, so the wall surface of the processing equipment There is a problem that sticky dust adheres to the inside of the pipe and the pipe and the device is blocked.

In the fuel-fired surface melting furnace, 1
Since a high temperature of 350 ° C or higher is required, it is a priori problem to recover the exhaust gas heat as much as possible and effectively use it to maintain an economical thermal energy balance, but this problem cannot be solved until now. Therefore, it was not put to practical use.

[0010]

Under the circumstances, the present invention suppresses the generation of sticky dust in the fuel-burning incineration ash treatment, and improves the efficiency by stopping the operation for periodic cleaning. The purpose of the present invention is to provide a device that prevents a decrease in temperature and utilizes exhaust gas heat as effectively as possible to economically improve the balance of heat energy and protect the heat transfer surface .

[0011]

The inventors of the present invention have conducted various studies on the treatment of fuel-burning incineration ash, and as a result, exhaust gas from an ash melting furnace is first heat-exchanged with room temperature air for fuel combustion, If it is preheated and then the temperature of the molten exhaust gas, which has been cooled to some extent, is poured into the molten furnace under conditions that allow it to be completely evaporated, and then rapidly cooled, the low-melting substance gasified in the melting furnace becomes a solid without viscous properties, and therefore the exhaust gas is recovered. It found that it is possible to recover efficient heat energy by appropriately selecting the temperature range to be quenched and the temperature range, the fuel on the basis of this finding
The present invention has led to the device of the present invention used for the treatment of burning incineration ash .

That is, according to the present invention , ( A) an incineration ash charging port (1) and an air introducing port (3, 3 ') for supplying combustion air through a burner (2, 2'), An ash melting furnace equipped with a combustion exhaust gas discharge port (4) and a slag extraction port (5) for extracting the generated slag, (B) a heat exchange section (6) for heating combustion air, and a fireproofing Linin with things
While mixing and stirring the main body (8) attached with the heat receiving surface (7) that is energized, the inlet (9) for the combustion exhaust gas generated in the melting furnace, and the unburned combustible gas contained in the combustion exhaust gas. an air blowing nozzle (10) for combusting, in the exhaust gas combustor with an outlet cooling combustion exhaust gas (11)
The radiant heat of the combustion exhaust gas that rises in the combustor.
Equipped with the function of a radiant heat exchanger that can be recovered in the exchange section (6)
An exhaust gas combustor, and (C) an inlet (12) for the cooled combustion exhaust gas, a dust outlet (13) for taking out dust that freely settled inside, and an exhaust gas outlet (14), and cooling inside Pipe lines (16, 17) configured by arranging gas cooling towers in which the water spray mechanism (15) is arranged in series and connecting the ash melting furnace, the exhaust gas combustor and the gas cooling tower, respectively.
And a pipe line (18) for supplying the heated combustion air from the heat exchange section (6) of the exhaust gas combustor to the ash melting furnace via the burners (2, 2 '). The present invention provides a fuel-fired incineration ash treatment device that does.

[0013]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention will now be described in more detail with reference to the accompanying drawings. Figure 1 is an explanatory diagram showing an example of the onset AkiraSo location, the apparatus ash melting furnace A, and a gas combustor B and gas cooling tower C. Device of the present invention
When incineration ash is treated using the ash melting furnace A from the incineration ash input port 1
Is supplied to. There are two types of incineration ash: main ash that accumulates under the incinerator and fly ash that is collected by a dust collector. Table 1 shows these compositions.

[0014]

[Table 1]

Thus, the main component of the main ash is SiO ₂ ,
Al ₂ O ₃ , CaO and Fe ₂ O ₃ , and the main component of fly ash is CaO. These incinerated ash are supplied from the air inlets 3, 3 ′ in the ash melting furnace A, and the fuel-fired burners 2, 2
1350 to 15 depending on the combustion air heated by
It is heated to 00 ° C., usually about 1400 ° C., and melted and solidified. At this time, volatilization of the metal occurs and mixes in the gas discharged from the discharge port 4. The amount of this metal volatilized depends on the basicity of the ash. That is, since the heavy metal components are all weakly basic and the alkali metal and the alkaline earth metal are strong bases, the basic oxides repel each other in a place with high basicity, that is, in a place with a large amount of CaO. Volatilization becomes easy, and conversely, in a place with low basicity, that is, in a place where there is a large amount of SiO ₂ , it becomes difficult to volatilize and remains as slag, and this slag is taken out from the slag outlet 5. The pipe line 20 represents a fuel supply pipe. Table 2 shows the volatilization rate of each metal at a melting temperature of 1400 ° C.

[0016]

[Table 2]

The metal that is volatilized and contained in the exhaust gas forms chlorides, oxides, and silicates as the temperature of the exhaust gas decreases. That is, the low melting point substance is vaporized during melting, and this is solidified as the temperature drops. Then, this adheres to the wall of the exhaust gas combustor or the heat exchanger as a viscous deposit.

[0018] The ash melting furnace exhaust gas discharge port 4 temperature 1,350-1,500 ° C. of the hot gas discharged from the A of this, introduced from the exhaust gas inlet 9 to the exhaust gas combustor B having a heat exchanging section 6, a combustion The temperature at which the low-melting point substance is gasified by heat exchange with air without causing solidification, that is, 1500 to 110
The temperature is lowered to 0 ° C, preferably 1500 ° C to 790 ° C. Therefore, there is a limit to the temperature of the preheated air that can be recovered by the heat exchange section 6, and the maximum temperature is generally 450 ° C., although it depends on the condition of the inlet air temperature. By this heat exchange, the combustion air is heated to 100 to 450 ° C.
It is sent to the burners 2 and 2 ′ from the air introduction ports 3 and 3 ′ of the ash melting furnace A through 8. Further, if desired, a part of the combustion air can be used as secondary combustion air of the combustion exhaust gas sent to the exhaust gas combustor B through the branch pipe line 19.

The exhaust gas combustor B injects combustion air near the combustion exhaust gas introduction port or near the introduced gas rising start portion, and recovers the radiant heat of the combustion exhaust gas rising in the combustor in the heat exchange section 6. It has the function of one type of radiant heat exchanger. This can be achieved by covering the outside of the combustor B with an outer cylinder and forming a gap between the outer wall of the combustor B, that is, the heat receiving surface 7 and the inner wall of the outer cylinder in the air flow path. The outer wall of the combustor B, that is, the heat receiving surface 7 and the inner wall of the outer cylinder are preferably lined with a refractory material. The thickness of this refractory material is 70 to 150 mm, and its thermal conductivity is 3-1.
It is recommended that the temperature be 0 kcal / mh ° C. If a refractory material with a thermal conductivity lower than this is used, heat cannot be transferred sufficiently, so it does not play the role of a heat exchanger.If a refractory material with a higher thermal conductivity is used, heat transfer cannot be sufficiently suppressed and the heat transfer cannot be performed. Cannot protect hot surface.

In this way, the combustion exhaust gas whose temperature is lowered to 790 to 1100 ° C. is introduced into the gas cooling tower C from the inlet 12 through the inlet pipe 17. Inside the gas cooling tower C, a cooling water spraying mechanism, for example, a cold water sprinkling pipe 15 is arranged, and cold water is injected into the combustion exhaust gas to generate 180
Quench to ~ 300 ° C. As a result, the low-melting-point substance in the exhaust gas cools down instantly, resulting in a non-viscous powder,
It is taken out from the dust outlet 13 and can be easily collected by the subsequent dust collector. On the other hand, the exhaust gas is discharged from the exhaust gas outlet 14 to the outside of the system.

[0021]

EXAMPLES The present invention will be described in more detail with reference to examples.

Implementation Exceptional diameter of 1068 mm, inner diameter of 850 mm (refractory castable inner diameter), length of 4000 mm (effective length) stainless steel cylinder outside the outer diameter 1104 mm, inner diameter 1088 mm,
An ash with a water content of 1 mass% is melted at 1400 ° C in an exhaust gas combustor that also serves as an air preheater and is covered with an outer cylinder with a length of 4000 mm (effective length) and the gap created between them is formed in the air flow path. The combustion exhaust gas generated at the time of solidification was supplied, and heat exchange between the exhaust gas and air was performed at an excess air ratio of 10%. The results are shown in Table 3.

[0023]

[Table 3]

At this time, the temperature of the combustion air preheated by the exhaust gas combustor also serving as the air preheater is 450 ° C. at the maximum, so the outlet temperature of the exhaust gas combustor also serving as the air preheater for the melting furnace exhaust gas is also 950.
Within the temperature range, that is, in the temperature range in which the low-melting point substance volatilized in the furnace was kept in a gas state, adsorption of dust on the heat exchange heat transfer surface was not observed. On the other hand, the air preheating temperature is set to 550, for example.
When the temperature was raised to ℃, the ash melting furnace exhaust gas temperature dropped to about 700 ° C. in the air preheater / exhaust gas combustor, so that the formation of sticky deposits was observed on the heat transfer surface.

[0025]

According to the invention apparatus according to the present invention, it is possible to perform the recovery of exhaust heat which enables suppression of sticky dust formation due to fuel-burning ash processing, efficient incineration ash melting treatment at a low fuel consumption rate It can be performed.

[Brief description of drawings]

FIG. 1 is a schematic diagram for explaining a device of the present invention.

[Explanation of symbols]

A ash melting furnace B Exhaust gas combustor C gas cooling tower 1 Incineration ash input port 2,2 'burner 5 Slag outlet 6 heat exchange section 9 Exhaust gas inlet 13 Dust outlet 15 Cooling water spray mechanism

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields investigated (Int.Cl. ⁷ , DB name) B09B 3/00-5/00

Claims (3)

(57) [Claims] 1. (A) Incineration ash charging port (1), air introducing port (3, 3 ') for supplying combustion air through burners (2, 2'), and exhaust of combustion exhaust gas Exit (4),
An ash melting furnace provided with a slag outlet (5) for taking out the generated slag, (B) a heat exchange section (6) for heating the combustion air, and a heat receiving surface (7) lined with a refractory material. ) Attached to the main body (8), an inlet (9) for the combustion exhaust gas generated in the melting furnace, and an air injection nozzle () for burning the unburned combustible gas contained in the combustion exhaust gas while mixing and stirring the mixture. 10) and an exhaust gas combustor outlet (11) for cooling the combustion exhaust gas ,
The radiant heat of rising combustion exhaust gas can be recovered by the heat exchange section (6).
Exhaust gas combustor with the function of a radiant heat exchanger,
And (C) an inlet (12) for the cooled exhaust gas
And a gas cooling tower having a dust outlet (13) for taking out dust that freely settled inside and an exhaust gas outlet (14) and having a cooling water spraying mechanism (15) arranged therein in series. , Burners (2, 2 ') for the heated combustion air from the pipes (16, 17) connecting the ash melting furnace, the exhaust gas combustor and the gas cooling tower, respectively, and the heat exchange section (6) of the exhaust gas combustor. A fuel-fired incineration ash processing apparatus, which is provided with a pipe (18) for supplying the ash to the ash melting furnace through the pipe. 2. The function of the radiant heat exchanger is made of refractory material.
Of the heat receiving surface (7) being trained and the outer cylinder that covers the outside
Achieved by forming a gap between the inner wall and the air passage
The fuel-fired incineration ash processing apparatus according to claim 1. 3. The heat receiving surface (7) has a thermal conductivity of 3 to 10 kca.
The fuel-fired incineration ash treatment device according to claim 1 or 2, which is lined with a layer having a thickness of 70 to 150 mm of a refractory material of 1 / mh ° C.