JPH03267186A - Electric heating type ash treatment apparatus - Google Patents

Abstract

PURPOSE:To simply separate heavy metal from ash at a low cost by heating flown ash with electric heating body in a kiln, volatilizing the heavy metal, separating volatile material from non-volatile material and cooling and collecting the volatile material. CONSTITUTION:In the closed type cylindrical kiln 1 providing the electric heating body 14, the flown ash collected from waste gas in a waste incineration furnace is heated to decompose a dioxin in the ash, and also by volatilizing the heavy metal, this is separated into the volatile material and the non-volatile material. A cooling device 2 set to a waste gas discharging passage in the kiln 1 cools the waste gas containing the volatile material discharged from the kiln 1. A collecting device 3 set to this waste gas discharging passage collects the volatile material from the waste gas through the cooling device 2. Further, a discharging device 4 arranged in the kiln 1 discharges only non- volatile material in the kiln 1. In this result, the heavy metal can be simply separated from the ash at a low cost.

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention is an incinerator that is attached to a garbage incinerator for incinerating municipal waste, industrial waste, etc., and is used to treat fly ash discharged from the garbage incinerator. Related to electric heating type ash processing equipment.

(Prior Art) In recent years, the problem of acidic rainforests has been attracting attention in Europe and America. This is a phenomenon in which sulfuric acid, hydrochloric acid, nitric acid, etc. in exhaust gas dissolve into raindrops and fall down, drying up the forest and creating a dead state called a black forest.In particular, smoke flowing from other countries can cause harm. In addition to becoming an international problem, it is also developing into a global environmental problem.

On the other hand, in our country, the so-called black forest does not exist, but
Recent soil measurements (acidity) by the Environment Agency show that the pH is 4 nationwide.
, 5, and it is becoming a problem.

By the way, in garbage incinerators that incinerate municipal waste, industrial waste, etc., the residue after incineration is incinerated ash and fly ash, and the exhaust gas contains HCQ, SOx, NOx, and more. , soot and dust contain heavy metals such as Cd and PB.

Recently, exhaust gas regulations have been tightened for garbage incinerators in Japan, and the removal technology for HCQ, SOx, and NOx has advanced, and the amount of harmful gases emitted from chimneys has become extremely small. It is collected in the form of soot dust or adsorbed to desalting agents, and is emitted in the form of coexistence with heavy metals such as Cd and PB. In addition, bag filters are increasingly being used to remove dioxins and other substances present in exhaust gas along with heavy metals.

If the fly ash collected by an electrostatic precipitator or bag filter is directly disposed of in a landfill, the elution test using fresh water (regulation value Pb 3 mg/fl,
Since it does not pass the Cd0.3mg/ff) standard, it is generally disposed of in a landfill after solidifying with cement.

On the other hand, in European countries, the method of using acids for elution tests has begun to be carried out, and the acids include sulfuric acid,
Hydrochloric acid is used, and acetic acid is used to prepare for the decay of organic matter in landfills.

In Japan, acid elution tests are also beginning to be considered, and there is a possibility that they will be implemented in the near future.

Therefore, in view of these global trends, the inventor conducted an acid elution test of incinerated ash and fly ash discharged from garbage incinerators.

That is, incineration ash and fly ash were mixed with heavy metal adsorbents such as zeolite, whitebait, blackberry, chelate, coral, and peat moss in various ratios, and an acid elution test was conducted.

Table 1 below is an example of this.After solidifying the ash by mixing black powder or liquid chelate with a solidifying agent (using Autoset), an elution test with acetic acid (0.67N) and clean water was conducted. It is something that

Table 1 As is clear from Table 1, although the water elution test specified by the Environment Agency was passed, a large amount of heavy metals were eluted in the acid elution test, and as a result, even with the use of adsorbents, heavy metals were not collected in landfills. It turned out that it was not possible to stop the elution of .

In particular, fly ash is problematic because it contains much more heavy metals and dioxins than incinerated ash, and because the particles are thinner, heavy metals and the like are easily eluted.

Therefore, in order to prevent the elution of heavy metals, it is necessary to rely on technical treatment within the incinerator.

The following methods are generally known as this technical process.

■ A method in which the ash is washed with acid in advance and the eluted liquid is treated with heavy metals.

■ A method in which all of the ash is melted at 1400°C in a melting furnace and removed as vitrified slag.

(Problem to be solved by the invention) However, method (2) above involves liquid treatment.

Problems with exhaust acid and treatment of heavy metal sludge remain, and as a practical device there are many troublesome aspects, making it difficult to put it into practical use. In addition, method (2) requires a large amount of fuel such as electricity, oil, and gas, which increases processing costs.In addition, large amounts of heavy metals are volatilized from the melting furnace, and when they are collected, containment treatment is required. Various problems arise.

The present invention was made in view of these problems, and uses surplus electricity generated in a waste incineration plant equipped with a power generation device and an electric heating type kiln to heat fly ash. The object of the present invention is to provide an electrically heated ash processing device that can easily and inexpensively separate heavy metals from the inside and easily recover and process the separated volatile and non-volatile materials.

Therefore, the inventor of the present application has repeatedly conducted numerous tests in order to solve these problems.

For example, the inventor of the present application has prepared samples of various pigs at 200.4
It was heated to 00, 600, 800, 1000, and 1200°C, and a volatilization test of Cd and Pb was conducted.

Table 2 below shows the concentrations of Cd and Pb in the ash due to heating.

Table 2 From the results, the volatilization rate at each temperature was determined and graphed, as shown in FIGS. 5 and 6. Incidentally, the reason why the volatilization rate is negative is that the weight loss due to ignition resulted in the heavy metal content being higher than at room temperature.

As is clear from these graphs, both Cd and pb are 1
It was found that when the temperature reached 000°C, the amount of volatilization suddenly increased and the rate of weight loss also increased. It is assumed that the weight loss up to 600°C is due to the volatilization of other chlorides and the combustion of organic substances.

Furthermore, as a result of conducting an elution test using an acid on the ash after the heavy metals had been volatilized, it was found that almost no heavy metals were eluted.

On the other hand, large-scale waste incineration plants usually generate electricity within the plant.For example, a plant that processes 400 tons of waste per day can generate approximately 6,500 KWh of electricity, as the calorie content of waste has increased in recent years. The amount of electricity used within the plant is 1,800 KWh, and 4,700 KWh of surplus electricity is generated, which is actually being generated for the electric power company.

Therefore, the inventor of the present application focused on the surplus power generated in a waste incineration plant equipped with a power generation device, and came up with the idea of using this surplus power to heat fly ash.

In other words, if the temperature at which the heavy metals in the ash can be volatilized is around 1000°C, there is no need to melt the ash in a melting furnace, and the inventor of the present application can melt the fly ash at a temperature of about 1000°C using surplus electricity.
The ash is heated to 0°C to decompose dioxins and at the same time volatilize heavy metals such as Cd and Pb contained in the ash, separating volatile matter and non-volatile matter, and then cooling and collecting the volatile matter. I learned that this is the best way.

(Means for Solving the Problems) In order to achieve the above object, the electric heating type ash processing device of the present invention heats fly ash collected from the exhaust gas of a garbage incinerator, and removes the ash contained in the ash. The kiln is a closed cylindrical kiln equipped with an electric heating element that can decompose dioxins in the air and volatilize heavy metals to separate volatile and non-volatile substances. A cooling device that cools the exhausted exhaust gas containing volatile matter; a collection device that is installed in the exhaust gas exhaust route and that collects the volatile matter from the exhaust gas that has passed through the cooling device; and a collection device that is installed in the kiln and collects the It is equipped with a discharge device capable of discharging only volatile matter.

The kiln is a rotary kiln in which a drum part, an inlet side chain part, and an outlet side mirror part are integrated, and an electric heating element is buried in a wound shape in the drum part, and fly ash is introduced from the center of the inlet side chain part. At the same time, it is preferable to configure the exhaust gas containing volatile matter to be discharged from the center of the outlet side mirror section.

The kiln is a rolling kiln in which a drum part, an inlet side chain part, and an outlet side mirror part are integrated, and a plurality of rod-shaped electric heating elements are removably inserted into the drum part, and the center of the inlet side chain part is inserted into the drum part. It is preferable that the configuration is such that fly ash is introduced from the mirror part and exhaust gas containing volatile matter is discharged from the center of the mirror part on the outlet side.

Furthermore, the discharge device is provided at the mirror section on the exit side of the kiln, and includes a discharge feeder capable of discharging only non-volatile matter in the kiln, and a sealed damper capable of opening and closing the discharge passage of the discharge feeder, and During operation, the hermetic damper closes the discharge passage and the discharge feeder stops, and when the kiln stops, the hermetic damper opens the discharge passage and the discharge feeder operates to discharge non-volatile matter. It is preferable to configure

(Function) Fly ash collected from the exhaust gas of the waste incinerator is introduced into the kiln from the inlet side chain of the kiln, and is transferred to the outlet side while being stirred by the rotational movement or forward and reverse rotational movement of the kiln. It is heated to about 1000°C by an electric heating element.

As a result, dioxins contained in the ash are decomposed, heavy metals such as Cd and Pb are volatilized, and the ash is separated into volatile matter and non-volatile matter.

Note that during the separation work, the discharge feeder is stopped and the hermetic damper closes the discharge path of the discharge feeder.

The separated volatile matter is discharged together with the exhaust gas from the mirror on the outlet side of the kiln, cooled by a cooling device, and then supplied to a collection device where it is collected.

The collected volatile matter is either contained and disposed of in a landfill or used for heavy metal regeneration. Also, the exhaust gas is discharged into the atmosphere.

On the other hand, non-volatile matter, ie, ash that does not contain heavy metals, accumulated in the kiln is discharged by opening the sealed damper and operating the discharge feeder when the kiln is stopped. This discharged ash is either landfilled or put to effective use.

(Example) Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a schematic vertical sectional view of an electrothermally heated ash processing apparatus according to a first embodiment of the present invention, and the ash processing apparatus includes a rotary kiln 1, a cooling device 2, a collection device 3, and a discharge device 4.
It is attached to the waste incinerator (not shown) of the waste incineration plant.

The rotary kiln 1 heats fly ash collected from the exhaust gas of a garbage incinerator to approximately 1000°C using electric heat to decompose dioxins contained in the ash, volatilize heavy metals, and convert it into volatile matter and non-volatile matter. It is constructed so that it can be separated into volatile matter and is of a closed type.

That is, the rotary kiln 1 is integrally constructed with a main body 8 consisting of a drum part 5, an inlet side chain part 6, and an outlet side mirror part 7. It is formed by lining material 11.

Further, a screw feeder 12 for feeding fly ash is disposed at the center of the inlet side chain part 6 so that fly ash can be fed into the interior from the center of the inlet side chain part 6, and a screw feeder 12 for feeding fly ash is disposed at the center of the outlet side chain part 6. An exhaust port 13 for discharging exhaust gas is formed in.

Furthermore, fly ash is added to the refractory material 11 of the drum portion 5 at a temperature of about 1000°C.
An electric heating element 14 for heating is buried in a spiral shape,
Power is supplied to the electric heating element 14 through a slip ring 16 disposed on the outer peripheral surface of both ends of the drum section 5 via an insulating material 15 (for example, an insulator), and a cabtire cable that contacts the outer peripheral surface of the slip ring 16 and connects to the power source 17. This is done by the brush 18 connected via 31.

The main body 8 includes a tire 1 provided on the outer peripheral surface of the drum portion 5.
9 is placed on the roller 20 so that it is rotatably supported in an inclined state, and is rotated by a cantering motor 21 and a chain transmission mechanism 22 interposed between this and the drum section 5. is being done.

Incidentally, the surplus power generated by the power generator of the waste incineration plant (not shown) is used as the power for heating the fly ash.

The cooling device 2 is disposed in the exhaust gas discharge path of the rotary kiln 1 and cools the exhaust gas containing volatile matter discharged from the exhaust port 13 of the rotary kiln 1. In this embodiment, the cooling device 2 is a cooling bag! A water-cooled jacket type exhaust pipe is used in the rotary kiln 2, and one end thereof is inserted into the exhaust port 13 of the rotary kiln 1.

The collection device 3 is connected to a cooling device or an exhaust pipe,
It collects volatile substances from cooled exhaust gas,
In this example, the collection bag! 3 uses a bag filter type filter. Further, an induced draft fan 23 and an exhaust pipe 24 are connected to the outlet side of the collection device 3.

The discharge bag N4 is for discharging non-volatile matter, that is, ash that does not contain heavy metals accumulated in the main body 8 of the rotary kiln 1, and in this embodiment, it is provided in one main body 8 and
It consists of a discharge feeder 25 that rotates together with the discharge feeder 25, a hermetic damper 26 disposed on the discharge feeder 25, and a lower conveyor 27 disposed below the discharge feeder 25.

Specifically, the discharge feeder 25 is provided at the peripheral edge of the outlet side mirror section 7 of the rotary kiln 1 in order to discharge only the non-volatile matter in the main body 8, and is oriented in the radial direction of the outlet side mirror section 7. A discharge chute 28 is provided as a discharge path for non-volatile matter. A water-cooled screw feeder is used as the discharge feeder 25.

Further, the sealing damper 26 is disposed in the discharge chute 28 to open and close the discharge passage of the discharge feeder 25, and is placed in a closed position M (FIG. 2 - dotted chain line position) to prevent passage of non-volatile matter and gas. and an open position II (solid line position in Figure 2) that allows the passage of the valve.

Furthermore, the lower conveyor 27 is disposed at a position below the discharge feeder 25, and has a vertical supply chute 29 that can match the discharge port of the discharge chute 28 of the discharge feeder 25, and a vertical supply chute 29 for discharging non-volatile matter. A discharge port 30 is provided. This lower conveyor 27 is a water-cooled screw conveyor.

Thus, in the rotary kiln 1 and the discharge device 4, when the rotary kiln 1 rotates, the hermetic damper 26 closes the discharge path of the discharge feeder 25, and the discharge feeder 25 and the lower conveyor 27 stop. When the kiln 1 is stopped, the kiln 1 stops at a position where the discharge chute 28 of the discharge feeder 25 and the supply chute 29 of the lower conveyor 27 match, and the sealed damper 26 opens the discharge path and the discharge feeder 2
5 is automatically controlled by an automatic control device (not shown).

Moreover, since the particles of the fly ash to be fed into the rotary kiln 1 are fine, the drum part 5 and each chain part 6, 7 are integrally formed.
In addition, the gaps between the inlet side chain part 6 and the fly ash charging screw feeder and between the outlet side mirror part 7 and the exhaust pipe are sealed with air seals to prevent particle leakage.

Next, the operation of the ash processing device will be explained.

Fly ash collected by an electrostatic precipitator or the like from the exhaust gas of a garbage incinerator is supplied to a screw feeder 12 for feeding fly ash, and is fed into the main body 8 from the inlet side chain 6 of the rotary kiln 1 by the screw feeder 12. .

The fly ash charged into the rotary kiln 1 moves to the outlet side mirror part 7 while being gently stirred by the rotational movement of the rotary kiln 1, and is heated to about 1000° C. by the electric heating element 14.

As a result, dioxins contained in the ash are decomposed and heavy metals such as + Cd and Pb are volatilized and separated into volatile matter and non-volatile matter.

The separated volatile substances are sucked together with the exhaust gas into the cooling device or the exhaust pipe, where they are cooled and then sent to the collection bag [3, where they are collected together with the soot and dust.

Further, the exhaust gas that has passed through the collection device 3 passes through an induced draft fan 23 and is discharged into the atmosphere from an exhaust stack 24.

Note that while the rotary kiln 1 is rotating, the discharge feeder 25 stops, and the sealed damper 26 closes the discharge feeder 25.
The discharge passage is blocked.

When a certain amount of ash that does not contain non-volatile matter, that is, heavy metals, has accumulated in the rotary kiln 1, the rotary kiln 1 is moved to the discharge chute 28 of the discharge feeder 25 and the lower conveyor 2.
It stops at the position where the supply chute 29 of No. 7 matches (the solid line position in Fig. 2), and the sealed damper 26 closes the discharge feeder 25.
At the same time, the discharge feeder 25 and the lower conveyor 27 are operated.

Therefore, the non-volatile matter in the rotary kiln 1 is.

It is discharged by the discharge feeder 25 and discharged from the discharge port 30 while being cooled by the lower conveyor 27.

When the discharge operation is performed for a certain period of time, the hermetic damper 26 closes the discharge path, the discharge feeder 25 stops, and the rotary kiln 1 begins to rotate.

Thereafter, the operation is carried out in the same manner as above, repeating the separation work and the discharge work.

In this way, the volatile matter and soot collected by the collection device 3 are sealed and disposed of in a landfill. In other words, a pool-shaped pit made of reinforced concrete was built, and volatile matter was poured into it.
Once full, seal the top opening with concrete. This volatile matter can also be used as a raw material for regenerating Cd, Pb, etc.

Further, the ash discharged from the lower conveyor 27 is used for landfill or effective utilization.

FIG. 3 is a schematic vertical sectional view of an electric heating type ash processing apparatus according to a second embodiment of the present invention, in which a rolling kiln 1 is used instead of a rotary kiln 1, and a cooling device is used. 2. The collection bag W3, waste disposal device N4, etc. have the same structure as those of the first embodiment.

That is, the rolling kiln 1 is integrally constructed with a main body 8 consisting of a drum part 5, an inlet side mirror part 6, and an outlet side mirror part 7, and the main body 8 has a casing 9 covered with a heat insulating material 1o and firebrick etc. It is formed by lining with a refractory material 11.

Further, a screw feeder 12 for feeding fly ash is disposed at the center of the inlet side mirror part 6 so that fly ash can be fed into the interior from the center of the inlet side mirror part 6. An exhaust port 13 for discharging exhaust gas is formed in.

Further, a plurality of rod-shaped electric heating elements 14 for heating the fly ash to about 1000° C. are removably inserted at regular intervals in the ceiling of the drum section 5, and power is supplied to the electric heating elements 14. This is done by connecting the power source 17 and the electric heating element 14 with a cabtyre cable 31.

The main body 8 includes a tire 1 provided on the outer peripheral surface of the drum portion 5.
9 is placed on the roller 20, it is supported in an inclined state and rotatably, and IF! The drive motor 21 and chain transmission mechanism 22 alternately rotate forward and reverse within a certain angle range (between x and This rolling kiln 1 is designed to stop at a position of It is sealed with a seal to prevent particle leakage.

The fly ash charged into the rolling kiln 1 is transported while being stirred by the forward and reverse rotation of the rolling kiln 1, and is heated to about 1000° C. by the electric heating element 14.

As a result, dioxins contained in the ash are decomposed, heavy metals such as Cd and Pb are volatilized, and the ash is separated into volatile matter and non-volatile matter.

Then, the separated volatile matter and non-volatile matter are processed in the same manner as in the first embodiment.

Table 3 below shows the results of an elution test with acetic acid after heating the ash to about 1000° C. in rotary kiln 1 or rolling kiln 1.

As is clear from Table 3, almost no Cd or Pb is eluted from the ash after heat treatment, and as a result, even if the ash heated in rotary kiln 1 or rolling kiln 1 is directly disposed of in a landfill, there will be no benefit. It does not occur.

Table 3 (Effects of the Invention) As mentioned above, the electric heating type ash processing device of the present invention heats the fly ash discharged from the garbage incinerator using surplus electricity and decomposes dioxins contained in the ash. At the same time, the heavy metals are volatilized and separated into volatile matter and non-volatile matter, and the volatile matter can be collected from the exhaust gas containing the separated volatile matter, so unlike conventional methods, the ash can be treated with acid. Heavy metals can be easily and inexpensively separated from the ash without requiring a large amount of fuel for heating the ash.

Further, the collected volatile matter can be contained and disposed of in a landfill or used as a raw material for regenerating Cd, Pb, etc., which is sanitary and practical.

Furthermore, since heavy metals have been removed from the non-volatile matter, there is no problem in directly disposing of it in a landfill, and the ash can also be used effectively.

However, since only a small amount of fly ash collected from the exhaust gas can be treated, the ash treatment device itself can be downsized.

In addition to the above-mentioned effects, the devices according to claims 2 to 4 can provide the following effects.

That is, in the apparatus of claim 2, since the kiln is a rotary kiln in which an electric heating element is embedded in the drum portion, the fly ash can be stirred reliably and well, and the fly ash can be heated uniformly. As a result, heavy metals can be reliably separated from the ash.

In addition, in the apparatus of claim 3, the kiln is a rolling kiln in which a plurality of rod-shaped electric heating elements are removably inserted into the drum portion, so that the amount of electric heat can be adjusted by inserting and removing the electric heating elements, and it is possible to prevent malfunctions. In some cases, the electric heating element can be replaced simply and easily, and it is also easier to supply power to the electric heating element, thereby reducing costs.

Furthermore, in the apparatus of claim 4, the discharge device is constituted by a discharge feeder and a sealed damper capable of opening and closing the discharge passage of the discharge feeder, and the discharge feeder is stopped during operation of the kiln, that is, during separation work. The hermetic damper closes the discharge passage, and when the kiln is stopped, i.e. during discharge work, the hermetic damper opens the discharge passage and the discharge feeder operates, so there is no possibility of harmful substances being released to the outside. , fly ash can be processed extremely safely and hygienically.

[Brief explanation of drawings]

FIG. 1 is a schematic vertical cross-sectional view of an electric heating type ash processing apparatus according to a first embodiment of the present invention, FIG. 2 is a partially cutaway schematic side view of a rotary kiln, and FIG. FIG. 4 is a side view of the rolling kiln similar to FIG. 2, FIG. 5 is a graph showing the volatilization rate of Cd in the ash, and FIG. It is a graph showing the volatilization rate of pb. 1 is a kiln, 2 is a cooling device, 3 is a collection device, 4 is a discharge device, 5 is a drum part, 6 is an inlet side mirror part, 7 is an outlet side sharp part,
14 is an electric heating element, 25 is a bath feeder, and 26 is a sealed damper.

Claims (1)

[Claims] 1. Heating the fly ash collected from the exhaust gas of a garbage incinerator to decompose dioxins contained in the ash,
A closed cylindrical kiln (1) equipped with an electric heating element (14) capable of volatilizing heavy metals and separating them into volatile matter and non-volatile matter; (
a cooling device (2) that cools the exhaust gas containing volatile matter discharged from the exhaust gas discharge path;
2) A collection device (3) that collects volatile matter from the exhaust gas that has passed through
); and a discharge device (4) which is provided in the kiln (1) and is capable of discharging only non-volatile matter in the kiln (1). 2. The kiln (1) has a drum part (5), an inlet side mirror part (6)
) and an outlet side mirror part (7) are integrated, and an electric heating element (14) is buried in a wound shape in the drum part (5), and fly ash is collected from the center of the inlet side mirror part (6). Claim 1 characterized in that the exhaust gas containing volatile matter is discharged from the center of the outlet side mirror part (7) at the same time as the exhaust gas is injected.
The electrically heated ash processing device described. 3. The kiln (1) has a drum part (5), an inlet side mirror part (6)
) and an outlet side mirror part (7) are integrated, and the drum part (5) is equipped with a plurality of rod-shaped electric heating elements (1
4) is inserted in a detachable manner so that fly ash is introduced from the center of the inlet side mirror part (6) and exhaust gas containing volatile matter is discharged from the center of the outlet side mirror part (7). The electric heating type ash processing apparatus according to claim 1. 4. The discharge device (4) is connected to the exit side mirror section (7) of the kiln (1).
) and is capable of discharging only the non-volatile matter in the kiln (1);
25) and a sealed damper (26) capable of opening and closing the discharge passage, and when the kiln (1) is in operation, the sealed damper (26) closes the discharge passage and the discharge feeder (25) stops; When the kiln (1) is stopped, the hermetic damper (2
6) opens the discharge path and the discharge feeder (25
4. The electrothermal heating type ash processing apparatus according to claim 1, 2 or 3, wherein the electric heating type ash processing apparatus is configured to operate to discharge non-volatile matter.