JP3308363B2 - Waste incineration, ash melting method and equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for melting and solidifying ash generated by incineration of refuse and incineration of garbage, and more particularly to a refuse incineration and ash melting system which is simple, low-cost and easy to operate and maintain.

[0002]

2. Description of the Related Art Conventionally, ash generated by incineration of refuse has been used for landfills, but it has become difficult to secure landfill sites due to the recent increase in the amount of refuse. There is a demand for a volume reduction treatment by melting and solidifying ash. FIG. 7 shows an example of a conventional refuse incineration and ash melt-solidification system.
Garbage is put into the garbage incinerator 2 from the garbage chute 1. The air for incineration is divided into primary air via a valve 14 and secondary air via a valve 15 from a blower 13 via an air preheater 4, and is supplied to the refuse incinerator 2. The exhaust gas after incineration is cooled by the gas cooler 3 and the air preheater 4
Gas cooler 5, bag filter 6, gas heater for denitration 7,
The smoke is discharged from the chimney 12 via the denitration device 8.

[0003] From the refuse incinerator 2, about 10 to 10
Ash of about 20% by weight is discharged and collected by the bag filter 6. The collected ash is conveyed to an attached ash melting and solidifying furnace 19 via a relay hopper 17. The ash conveyed to the ash melting and solidifying furnace 19 is melted by the high-temperature flame of the heavy oil burner 20. The molten ash flows down the furnace wall and the slag tap 21 and falls into the slag hopper 22 to be solidified. On the other hand, the ash melting and solidifying furnace 1
The high temperature combustion gas of 1400 to 1600 ° C. from 9 is cooled to 300 to 400 ° C. by the gas cooler 23 so as not to burn the air preheater 26 installed downstream. The cooled combustion gas is discharged through the dust collecting cyclones 24 and 25, the air preheater 26, the denitration device 27, and the induction blower 28. The air for combustion in the ash melting and solidifying furnace 19 is supplied to the blower 3
It is supplied from 0 through an air preheater 26 and a preheated air flow path 31.

[0004] The ash melting and solidifying furnace 19 usually employs a structure capable of efficiently separating and collecting molten particles by centrifugal force using a swirling flow or the like. In addition, since most of the injected refuse incineration ash is easily collected by the fusion and coalescence, most of the ash is collected in the furnace 19 and the amount of ash scattered as dust in the exhaust gas is small. Although very little ash is accompanied by the exhaust gas and scattered, these ashes are also porous, light and easily scattered when they are put into the ash melting and solidifying furnace 19. Since it is coarse and has a high specific gravity, it is possible to sufficiently collect dust using the cyclones 24 and 25 for dust collection. A high temperature flame from a burner is required to melt the ash. However, when high-temperature combustion is performed, a large amount of N
Since Ox is generated, the installation of the denitration device 27 is indispensable, although expensive. As described above, when the ash melting and solidifying furnace 19 is provided in addition to the conventional refuse incinerator 2, a very complicated system and expensive equipment are required. In addition, since the system is complicated, a great deal of labor is required for operation, maintenance and maintenance of the equipment.

[0005]

However, the above-mentioned prior art has problems that the system configuration is very complicated, so that the equipment cost is high and the operation and maintenance require a great deal of labor. An object of the present invention is to provide a simple incineration and ash melting system for waste such as garbage without accumulating harmful substances such as mercury in the system in view of the problems described above.

[0006]

The object of the present invention is attained by the following constitution. In other words, incineration of waste such as garbage in an incinerator and melting of the incinerated ash in a melting furnace.In the ash melting method, part of the high-temperature gas discharged from the ash melting furnace is introduced into the incinerator. And a method for incineration of wastes and ash melting, wherein the volatile harmful substances are removed by a flue gas purifying device after cooling another part of the high-temperature gas.
In the waste incineration and ash melting method of the present invention, the supply amount of high-temperature gas from the ash melting furnace to be introduced to the flue gas purifying device is controlled based on the gas temperature from the ash melting furnace to be introduced to the flue gas purifying device. As a result, the high-temperature gas introduced into the flue gas purifying device can be sufficiently cooled. Also, a part of the combustion air of the incinerator can be branched and used as combustion air for the ash melting furnace.

The above object of the present invention is also achieved by the following constitution. In other words, incineration of waste including an incinerator for waste such as garbage and a melting furnace for the incineration ash, in a ash melting apparatus, a flue of high-temperature gas from the ash melting furnace is introduced into the furnace of the incinerator. It is divided into a flue and a flue to be introduced into the gas cooler, and furthermore, a waste gas incineration and ash melting device with a flue that leads the cooling gas discharged from the gas cooler to a flue gas purifier that removes volatile harmful substances is provided. is there. Incineration of the waste of the present invention,
In the ash melting device, a gas temperature detector is installed in the flue of the gas from the ash melting furnace to be introduced into the flue gas purifying device, and the high temperature from the ash melting furnace to be introduced into the flue gas purifying device is set based on the detected gas temperature. A configuration may be adopted in which a control device for adjusting the opening / closing degree of the gas flow control valve for controlling the gas supply amount is provided.
Further, the waste incineration and ash melting apparatus may have a configuration in which a preheated combustion air supply pipe of an incinerator is branched and connected to a combustion air pipe for an ash melting furnace. Further, the incinerator and the ash melting furnace may be integrated or installed adjacent to each other.

[0008]

[Action] Taking municipal waste as an example, the amount of ash discharged during incineration is 10 to 20% by weight of the amount of waste. When this ash is melted using heavy oil as a heat source, how many kg per 1 kg of heavy oil
The problem is whether the ash can be melted. FIG. 3 is a graph showing the calculation of the temperature to which the ash can be heated when the incineration ash of refuse is heated using heavy oil having a low calorific value of 10,320 kcal / kg. The temperature at which the ash is heated is determined by how many kilograms of ash can be processed per unit weight of heavy oil or how much heat is lost in the melting furnace. In addition, at least 150 to melt the ash
A temperature of 0 ° C. or higher is desirable. Therefore, it can be seen from FIG. 3 that when the heat loss of the ash melting furnace is estimated to be 10%, the amount of the waste incineration ash must be about 5 kg or less.
FIG. 4 shows the relationship between the amount of exhaust gas discharged from the bag filter 6 of the waste incinerator 2 of the system shown in FIG. 7 and the lower heating value of the treated waste.

FIG. 5 shows the result of calculating the relationship between the amount of combustion exhaust gas from the ash melting and solidifying furnace 19 and the amount of treated ash / the amount of heavy oil under the following conditions. Treated waste amount 10 (t / h) Low calorific value of treated waste 1800 (kcal / kg waste) Ash content in waste 20 (wt%) Exhaust gas amount per ton of waste 8267 (m ³ N / ton waste) Per kg of heavy oil 4 (m ³ N / kg heavy oil) As can be seen from FIG. 4 and FIG.
When 0 kcal / kg and the ratio of the amount of ash treatment / heavy oil in the ash melting and solidifying furnace 19 = 4, the amount of combustion exhaust gas from the ash melting and solidifying furnace 19 is about 1/10 of the amount of combustion exhaust gas from the refuse incinerator 2. is there. Even if such flue gas is mixed into the incinerator 2, the temperature and composition thereof do not significantly change.

However, when this system is adopted,
Volatile harmful substances such as mercury vaporized due to high temperature in the ash fusion solidification furnace 19 shown in FIG. 7 are returned into the refuse incinerator 2, and a relatively low temperature portion downstream of the refuse incinerator 2, for example, the gas cooler 3
There is a possibility that the ash is condensed again into the ash at a downstream portion, collected by the bag filter 6, returned to the ash melting and solidifying furnace 19, and accumulated without being discharged out of the system. Therefore, the present invention extracts a part of the high-temperature gas from the ash fusion solidification furnace, for example,
Cooling down to a temperature required by a very small gas cooler (for example, a gas cooler having a small amount of exhaust gas and having a cooling fin for natural heat radiation in the flue can provide a sufficient cooling effect), for example, to 150 ° C. or less. After that, a line was provided to collect volatile harmful substances through a flue gas purifying device (for example, a very small bag filter or an activated carbon gas purifying device) and discharge the remainder to the outside of the system of the present invention. FIG. 6 shows the relationship between the vapor pressure of mercury or the like and the temperature. It can be seen that the higher the temperature, the greater the amount of mercury that moves into the atmosphere as vapor.

Usually, if the temperature of the exhaust gas is reduced to 150 ° C. or less, mercury in the exhaust gas is condensed and adhered to the surface of the ash. Therefore, the mercury in the exhaust gas purifying device can be collected together with the ash by, for example, a bag filter. And the diffusion of mercury into the atmosphere can be prevented. As a result, the volatile harmful substances do not circulate and accumulate in the system, and the blower 30, the air preheater 26, and the denitration device 2 for the ash melting and solidifying furnace 19 of the prior art (FIG. 7)
7. The induction blower 28, the gas cooler 23 for the ash melting and solidifying furnace 19, and the cyclones 24 and 25 for dust collection can be omitted.
The simplification of the system according to the present invention is based on the above study results.

[0012]

An embodiment of the present invention will be described with reference to the drawings. FIG.
1 shows a refuse incineration and ash melting system of this embodiment. Garbage is put into the garbage incinerator 2 from the garbage chute 1. The air sucked by the blower 13 is preheated by the air preheater 4 and is divided into primary air supplied via a valve 14 and secondary air supplied via a valve 15 to serve as combustion air for refuse. It is introduced into the refuse incinerator 2. Exhaust gas after refuse combustion in the refuse incinerator 2 is cooled by the gas cooler 3, and is discharged from the chimney 12 through the air preheater 4, the gas cooler 5, the bag filter 6, the denitration gas heater 7, and the denitration device 8 in that order. . Gas cooler 3 is refuse incinerator 2
The high temperature combustion gas of 800 to 950 ° C at the outlet is supplied to the air preheater 4
Gas temperature of 300-400 ° C, which is not damaged by heat
Usually, a method of injecting water into a flue to cool a combustion gas is employed. The gas cooler 5 controls the gas temperature at the outlet of the air preheater 4 to about 300 ° C.
This is a device for cooling the gas to an appropriate gas temperature of about 200 to 150 ° C. or lower, and usually also employs a water injection method. The denitration gas heater 7 is a bag filter 6.
This is for heating the low temperature gas at 140 to 190 ° C. at the outlet to 300 to 400 ° C. necessary for the denitration reaction.

The refuse incinerator 2 supplies a large excess of air which is 1.5 to 2 times the air required for combustion in order to completely burn the refuse. As a result, as much as 7 to 12% of excess oxygen remains in the exhaust gas at the outlet of the bag filter 6.
Therefore, the denitration gas heater 7 only introduces heavy oil as a heat source, and usually does not require addition of new heavy oil combustion air. Atmospheric temperature air is sucked from the air suction duct 11 provided with the valve 10 to cool the gas temperature at the outlet of the denitration device 8 at 300 to 400 ° C. to lower the gas temperature to 200 to 300 ° C. at which the induced blower 9 does not burn out. About 10 to 20% by weight of the ash is discharged from the incinerator 2 and collected by the bag filter 6. According to the experimental results so far, if dust is collected at a low temperature of about 150 ° C. in the bag filter 6, 90% or more of the mercury in the flue gas is collected and removed in a state where it is condensed in the ash. That is, most of the mercury in the refuse or waste is present in the collected ash. The collected ash is transferred to the relay hopper 17 having the valve 16 and the ejector 4.
3 and is conveyed to the ash melting and solidifying furnace 19. A double damper 42 is installed at the entrance of the relay hopper 17 to cut off the pressure of the flue of the incinerator 2.

Ash melting and solidifying furnace 1 via ejector 43
The ash conveyed to 9 is heated and melted by the high-temperature flame of the heavy oil burner 20, and the melted ash flows down the furnace wall and falls into the slag hopper 22. 140 from the ash melting and solidifying furnace 19;
The high-temperature combustion gas of 0 to 1600 ° C. is introduced into the incinerator 2 through a high-temperature flue 39 lined with refractory casters. If the refuse incinerator 2 and the ash melting and solidifying furnace 19 are arranged at adjacent positions or have an integrated structure, the flue 39 for high temperature can be very short. The amount of the combustion gas from the ash melting and solidifying furnace 19 is usually one of the combustion gas amount of the refuse incinerator 2.
Therefore, the gas temperature rise due to the mixing of the high-temperature combustion gas from the ash melting and solidifying furnace 19 with the combustion gas from the refuse incinerator 2 is about several tens of degrees to about one hundred and several tens degrees Celsius. If it rises, it is not necessary to significantly change the specifications of the flue gas treatment equipment such as the downstream gas cooler 3, air preheater 4, and bag filter 6.

However, in the ash melting and solidifying furnace 19, almost 100% of volatile harmful substances such as mercury contained in the ash due to high temperature.
Is vaporized again in the high-temperature combustion gas. That is, in the present system, there is a problem that mercury collected as a solid by the bag filter 6 is vaporized again in the ash melting and solidifying furnace 19, and refuse is accumulated and concentrated. In order to solve this point, in this embodiment, a part of the combustion gas of the ash fusion solidification furnace 19, for example, about 3 to 10% of the high temperature combustion gas of the ash fusion solidification furnace 19 is used.
Degree (this is 0.3% for the amount of exhaust gas from refuse incinerator 2)
~ 1.0%. ), And the temperature required for a very small gas cooler 37 (for example, a gas cooler with a small amount of exhaust gas and a cooling fin for natural heat radiation attached to the flue can provide a sufficient cooling effect), for example, 150.
After cooling to about ° C., a line was provided for collecting volatile harmful substances through a flue gas purifying device 38 (for example, a bag filter or an activated carbon gas purifying device) and discharging the same through a duct 34 to the outside of the system.

When the natural heat radiation type is adopted for the gas cooler 37, the outlet gas temperature of the gas cooler 37 (the inlet gas temperature of the exhaust gas purifying device 38) changes when the processing gas amount and the inlet gas temperature change. In the case of this system, the ash fusion solidification furnace 19
Since the ash must melt the ash, the gas is operated in a relatively narrow temperature range around 1500 ° C. in the furnace. Therefore, the temperature of the high-temperature gas discharged from the ash melting and solidifying furnace 19 fluctuates relatively little, and the ash throughput also passes through the relay hopper 17, so that it fluctuates little. However, if the temperature or amount of the high-temperature gas from the ash melting and solidifying furnace 19 changes for some reason, the processing gas amount of the natural heat radiation type gas cooler 37 is adjusted, and the outlet gas temperature of the gas cooler 37 is set to a predetermined temperature. For example, it needs to be kept at 150 ° C. The flow control valve 35 of the duct 34 is provided for that purpose. The flow rate control valve 35 detects the outlet temperature of the gas cooler 37 by using a temperature detector 41 provided in the duct on the outlet side of the gas cooler 37, and a controller 40 is provided in the duct 34 so that the temperature becomes a set temperature. The opening / closing control of the flow control valve 35 is performed to adjust the gas amount.

The pressure loss in the path from the ash melting and solidifying furnace 19 to the inlet of the denitration device 8 via the gas cooler 37 is controlled by the ash melting and solidifying furnace 19 via the refuse combustion furnace 2, the bag filter 6, and the like. Since the pressure loss is lower than the pressure loss of the path leading to the inlet of the exhaust gas purifier, the amount of gas to be processed by the flue gas purifying device 38 is sufficient only by adjusting the opening and closing of the flow control valve 35. Further, in the present system, a part of the combustion air for the refuse incinerator 2 is branched and used as the combustion air for the heavy oil burner 20 for the ash melting and solidifying furnace 19, whereby the conventional technology described in FIG. Blower 30, air preheater 26 for ash melting and solidifying furnace 19,
The denitration device 27, the induction blower 28, the gas cooler 23 for the ash melting and solidifying furnace 19, and the cyclones 24 and 25 for dust collection can also be omitted. In addition, by introducing high-temperature gas discharged from the ash melting and solidifying furnace 19 into the furnace of the refuse incinerator 2, the gas temperature in the refuse incinerator 19 is increased, and harmful unburned components such as CO and dioxin are reduced. It also has an effect. Although the embodiment shown in FIG. 1 shows a case in which the waste heat of the refuse incinerator 2 is not recovered, the same applies when a waste heat boiler 3 'is installed instead of the gas cooler 3 of FIG. 1 as shown in FIG. Effects can be obtained.

[0018]

According to the present invention, the incineration of waste such as refuse and the ash melting system are greatly simplified without accumulating harmful substances such as mercury in the system, and the cost and labor required for operation and maintenance of the system are reduced. it can.

[Brief description of the drawings]

FIG. 1 is a diagram showing a refuse incineration and ash melting system according to an embodiment of the present invention.

FIG. 2 is a diagram showing a refuse incineration and ash melting system according to an embodiment of the present invention.

FIG. 3 is a diagram showing a calculation result of a relationship between an amount of treated ash per 1 kg of heavy oil and a heating temperature of the treated ash.

FIG. 4 is a view showing a result of calculating a relationship between a lower heating value of treated waste and an exhaust gas amount at a bag filter outlet in the system of FIG. 7;

FIG. 5 is a diagram showing a calculation result of a relationship between a treated ash amount / heavy oil amount ratio and a combustion exhaust gas amount in an ash fusion solidification furnace.

FIG. 6 is a diagram showing a relationship between a gas temperature and a vapor pressure of mercury.

FIG. 7 is a diagram showing a refuse incineration and ash melting system according to the related art.

[Explanation of Signs] 2… Garbage incinerator, 3, 5, 23, 37… Gas cooler
3 ': waste heat boiler, 4, 26: air preheater, 6: bag filter, 7: gas heater for denitration, 8, 27: denitration device,
17 ... relay hopper, 19 ... ash melting and solidifying furnace, 20 ... heavy oil burner, 21 ... slag tap, 22 ... slag hopper, 2
4, 25: cyclone for dust collection, 35: flow control valve, 38
... Smoke emission control device, 40 ... Controller, 41 ... Temperature detector, 4
2 Double damper 43 Ejector

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Meiji Ito 3-36 Takara-cho, Kure City, Hiroshima Prefecture Inside the Kure Institute (72) Inventor Wakako Matsumi 3-36 Takara-cho Kure City, Hiroshima Prefecture Babcock Date Kure Laboratory Co., Ltd. (56) References JP-A-53-118868 (JP, A) JP-A-5-141633 (JP, A) JP-A-57-210213 (JP, A) JP-A-63-315820 ( JP, A) JP-A-4-302909 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) F23G 7/00 B01D 53/34 B09B 3/00

Claims (7)

(57) [Claims] 1. A waste incineration method in which waste such as refuse is incinerated in an incinerator and the incinerated ash is melted in a melting furnace. In the ash melting method, a part of high-temperature gas discharged from the ash melting furnace is incinerated. Waste incineration and ash melting, characterized in that, after cooling another part of the high-temperature gas, volatile harmful substances are removed by a flue gas purifying device and discharged out of the system. 2. The amount of hot gas supplied from the ash melting furnace to be introduced into the flue gas purifying device is controlled based on the gas temperature from the ash melting furnace to be introduced into the flue gas purifying device. The incineration and ash melting method of the waste described. 3. The method according to claim 1, wherein a part of the combustion air of the incinerator is branched and used as combustion air for an ash melting furnace. 4. A waste incineration and ash melting apparatus provided with an incinerator for waste such as garbage and a melting furnace for the incinerated ash, wherein a flue of high-temperature gas from the ash melting furnace is supplied to an incinerator furnace. Into the flue to be introduced into the gas cooler and the flue to be introduced into the gas cooler,
Further, a waste incineration and ash melting device is provided with a flue that guides a cooling gas discharged from a gas cooler to a flue gas purification device for removing volatile harmful substances. 5. A gas temperature detector is provided in a flue portion of a gas from an ash melting furnace to be introduced into a flue gas purifying device, and a high temperature from the ash melting furnace to be introduced into the flue gas purifying device is determined based on a detected gas temperature value. 5. The waste incineration and ash melting apparatus according to claim 4, further comprising a control device for adjusting a degree of opening and closing of a gas flow control valve for controlling a gas supply amount. 6. The waste incineration and ash according to claim 4, wherein a preheated combustion air supply pipe of the incinerator is branched and connected to a combustion air pipe for an ash melting furnace. Melting equipment. 7. The waste incineration and ash melting apparatus according to claim 4, wherein the incinerator and the ash melting furnace are integrated or installed adjacent to each other.