JPH0561985B2 - - Google Patents

Description

[Detailed description of the invention]

(Field of Industrial Application) The present invention relates to an electrically heated ash processing device attached to a waste incinerator for incinerating municipal waste, industrial waste, etc., for processing fly ash discharged from the waste incinerator. . (Prior Art) In recent years, the problem of acidic rainforests has been attracting attention in Europe and the United States. This is a phenomenon in which sulfuric acid, hydrochloric acid, sulfuric acid, etc. in exhaust gas dissolve into raindrops and fall, 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 Japan, there is no so-called black forest, but recent soil measurements (acidity) by the Environment Agency have shown a pH of 4.5 nationwide, and it is becoming a problem. By the way, in garbage incinerators that incinerate municipal waste, industrial waste, etc., there are incineration ash and fly ash as residue after incineration, and the exhaust gas also contains HCl,
SOx and NOx are included, and the soot and dust also contains Cd and Pb.
Contains heavy metals such as Recently, exhaust gas regulations have been tightened for waste incinerators in Japan, and technology for removing HCl, SOx, and NOx has advanced, and the amount of harmful gases emitted from chimneys has become extremely small. Cd and Pb are collected in the form of soot dust or adsorbed to desalting agents.
It is emitted in the form of coexistence with heavy metals such as. In addition, bug 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 electrostatic precipitators and bag filters is disposed of in a landfill as is, it will not meet the elution test using fresh water (regulated value
Since it does not pass Pb3mg/, Cd0.3mg/),
The reality is that cement is generally disposed of in landfills after it hardens. 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 and hydrochloric acid to simulate acid rain, and acetic acid to simulate decay of organic matter in landfills. are used respectively. 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, sorrel, chelate, coral, and peat moss in various ratios, and an acid elution test was conducted. Table 1 below is an example, and after solidifying the ash by mixing black powder or liquid chelate with a solidifying agent (using Autoset), an elution test with acetic acid (0.67 regulation) and clean water was conducted. be.

[Table] As is clear from Table 1, although it passed the water elution test specified by the Environment Agency, large amounts 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 of melting all of the ash at 1400℃ in a melting furnace and extracting it as vitrified slag. (Problem to be solved by the invention) However, since the above method is a liquid treatment,
Problems with exhaust acid and treatment of heavy metal contamination remain, and as a practical device there are many troublesome aspects, making it difficult to put it into practical use. In addition, this method requires a large amount of fuel such as electricity, oil, and gas, which increases processing costs.In addition, a large amount of heavy metals evaporates from the melting furnace, which requires containment treatment when collected. , various problems arise. The present invention was created 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. It is an object of the present invention to provide an electrically heated ash processing device that can easily and inexpensively separate heavy metals from ash and easily recover and treat 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 ash.
Heating at 200, 400, 600, 800, 1000, 1200℃,
A Cd and Pb volatilization test was conducted. Table 2 below shows the concentrations of Cd and Pb in the ash due to heating.

[Table] From these results, the volatilization rate at each temperature was determined and graphed, as shown in Figures 5 and 6. The reason why the volatilization rate remains the same is because the weight loss due to ignition resulted in the heavy metal content being higher than at room temperature. As is clear from these graphs, Cd,
When the temperature of both Pb and Pb reaches 1000℃, the amount of volatilization increases rapidly.
It was found that the weight loss rate 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 matter. Furthermore, as a result of performing an elution test using acid on the ash after the heavy metals had been volatilized, it was found that the heavy metals were not eluted at all. 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 650KWh of electricity, as the calorie content of waste has increased in recent years.
The amount of electricity used within the plant is 1800KWh.
The actual situation is that 4,700KWh of surplus electricity was generated and the electricity is sold to the electric power company. Therefore, the inventor of the present application focused on the surplus electricity generated in a waste incineration plant equipped with a power generation device, and came up with the idea of using this surplus electricity to heat fly ash. In other words, the temperature at which heavy metals in the ash are volatilized is 1000℃.
If the ash could be reduced to about 1,000 degrees Celsius, there would be no need to melt the ash in a melting furnace, and the inventor of the present application heated the fly ash to approximately 1000℃ using surplus electricity to decompose the dioxins and at the same time decompose the Cd contained in the ash. We learned that the best method is to volatilize heavy metals such as Pb and separate them into volatile matter and non-volatile matter, and then cool and collect the volatile matter. (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. A closed cylindrical kiln equipped with an electric heating element capable of decomposing tyoxin, volatilizing heavy metals, and separating volatile substances and non-volatile substances; a cooling device that cools the exhaust gas contained in the volatile matter discharged from the kiln; 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; It is equipped with a discharge device capable of discharging only non-volatile matter. The kiln is a rotary kiln in which a drum part, an inlet side mirror part, and an outlet side mirror part are integrated, and an electric heating element is embedded in the drum part in a wound shape, and fly ash is introduced from the center of the inlet side mirror 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 mirror 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 mirror 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 furnace and the discharge feeder stops, and when the kiln stops,
It is preferable that the sealing damper opens the discharge path and the discharge feeder operates to discharge the non-volatile matter. (Function) Fly ash collected from the exhaust gas of a garbage incinerator is
It is poured into the kiln from the mirror part on the inlet side 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, and is heated by an electric heating element to about
Heated to 1000℃. As a result, the dioxins contained in the ash are decomposed, and heavy metals such as Cd and Pb are volatilized.
It is separated into volatile matter and non-volatile matter. Note that during the separation operation, the discharge feeder is stopped and the airtight damper closes the discharge path of the discharge feeder. The separated volatile matter is discharged from the outlet mirror section of the kiln together with the exhaust gas, 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 tamper 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 cross-sectional view of an electrothermal heating type processing device according to a first embodiment of the present invention, and the ash processing device includes a rotary kiln 1, a cooling device 2, a collection device 3, a discharge device 4, etc. It is attached to the waste incineration path (not shown) of the waste incineration plant. The rotary kiln 1 heats the fly ash collected from the exhaust gas of the garbage incineration route to approximately 1000°C using electric heat, decomposes dioxins contained in the ash, and evaporates heavy metals to 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 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 10 and a fireproof material such as refractory brick. It is formed by lining material 11. Further, a fly ash feeding screw feeder 12 is disposed at the center of the entrance side mirror section 6 so that fly ash can be thrown into the interior from the center of the entrance side mirror section 6.
At the center of the exit side mirror part 7 is an exhaust port 1 for exhaust gas discharge.
3 is formed. Furthermore, fly ash is added to the refractory material 11 of the drum portion 5.
An electric heating element 14 for heating to 1000°C is embedded in a spiral shape, and power is supplied to the electric heating element 14 through slips provided on the outer peripheral surface of both ends of the drum part 5 via an insulating material 15 (for example, an insulator). A brush 1 is connected to the ring 16 and the outer peripheral surface of the slip ring 16 and connected to a power source 17 via a cab tire cable 31.
It is carried out by 8. The main body 8 is rotatably supported in an inclined state by placing a tire 19 provided on the outer peripheral surface of the drum part 5 on a roller 20, and the main body 8 is supported in an inclined state and rotatably by a tire 19 provided on the outer peripheral surface of the drum part 5. A chain transmission mechanism 22 interposed therebetween allows rotational movement. Incidentally, surplus power generated by a power generation device (not shown) of the waste incineration plant is used as 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 A water-cooled jacket type exhaust pipe is used, and one end of the exhaust pipe is inserted into the exhaust port 13 of the rotary kiln 1. The collection device 3 is connected to the exhaust pipe, which is the cooling device 2, and collects volatile matter from the cooled exhaust gas.In this embodiment, the collection device 3
A filter type filter is used. In addition, an induced draft fan 23 is installed on the outlet side of the collection device 3.
and an exhaust pipe 24 are connected. The discharge device 4 discharges non-volatile matter, that is, ash that does not contain heavy metals, accumulated in the main body 8 of the rotary kiln 1. It consists of a rotating 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
The rotary kiln 1 is provided with a discharge chute 28 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 therein, and serving as a non-volatile matter discharge path facing in the radial direction of the outlet-side mirror section 7. There is. A water-cooled screw feeder is used as the discharge feeder 25. Further, the sealed damper 26 is connected to the discharge feeder 25.
It is arranged in the exhaust chute 28 to open and close the exhaust passage of the gas, and is located in the closed position (dotted chain line position in Figure 2) that prevents the passage of non-volatile substances and gases and the open position (solid line position in Figure 2) that allows their passage. It is designed so that it can be oscillated between the two positions. Further, 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 outlet of the discharge chute 28 of the discharge feeder 25, and for discharging non-volatile matter. A discharge port 30 is provided. This lower conveyor 27 is a water-cooled screw conveyor. 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 stops, 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 hermetic damper 26 opens the discharge path and the discharge feeder 25 operates. This is automatically controlled by an automatic control device (not shown). In addition, since the rotary e-kiln 1 has fine particles of fly ash, the drum part 5 and each mirror part 6,
7 are integrally formed, and between the inlet side mirror part 6 and the fly ash feeding screw feeder and the outlet side mirror part 7.
An air seal is used between the exhaust pipe and the exhaust pipe 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 the screw feeder 12 for feeding fly ash, and
2 into the rotary kiln 1 from the inlet side mirror section 6 to the main body 8. 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, heavy metals such as Cd and Pb are volatilized, and the ash is separated into volatile matter and non-volatile matter. The separated volatile matter is sent to the cooling device 2 along with the exhaust gas.
After being sucked into the barrel exhaust pipe and cooled there, it is sent to the collection device 3, where it is collected together with soot and dust. Furthermore, 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 is stopped, and the sealing damper 26 closes the discharge path of the discharge feeder 25. When a certain amount of non-volatile ash, that is, ash that does not contain heavy metals, has accumulated in the rotary kiln 1, the rotary kiln 1 is moved to the discharge chute 2 of the discharge feeder 25.
8 and the supply chute 29 of the lower conveyor 27 match (solid line position in Figure 2), the hermetic damper 26 opens the discharge path of the discharge feeder 25, and the discharge feeder 25 and the lower conveyor 27 Operate. Therefore, the non-volatile matter in the rotary kiln 1 is
It is discharged by the discharge feeder 25, and is 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 sealed damper 26 closes the discharge path and the discharge feeder 25 closes.
stops, and rotary kiln 1 starts rotating. 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. That is,
A pool-shaped pit made of reinforced concrete is constructed, volatile matter is poured into it, and when it is full, the upper opening is sealed with concrete. This volatile matter is
It 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 longitudinal 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 collecting device 3, the discharging device 4, etc. have the same structure as in 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 10 and a refractory brick etc. It is formed by lining with a refractory material 11. Further, a fly ash feeding screw feeder 12 is disposed at the center of the entrance side mirror section 6 so that fly ash can be thrown into the interior from the center of the entrance side mirror section 6.
At the center of the exit side mirror part 7 is an exhaust port 1 for exhaust gas discharge.
3 is formed. Furthermore, about 1,000 pieces of fly ash is placed on the ceiling of the drum section 5.
A plurality of rod-shaped electric heating elements 14 for heating to ℃ are removably inserted at regular intervals, and power is supplied to the electric heating elements 14 by connecting a power source 17 and the electric heating elements 14 with a cabtyre cable 31. This is done by The main body 8 is rotatably supported in an inclined state by placing a tire 19 provided on the outer peripheral surface of the drum portion 5 on a roller 20, and is supported by a drive motor 21 and a chain transmission mechanism 22. , during separation work at a certain angle (X in Figure 4,
It rotates forward and backward alternately within the range of X' (between Note that this rolling kiln 1 also has an entrance side mirror section 6.
Air seals are used to seal the space between the feeder and the screw feeder for feeding fly ash, and between the outlet side mirror section 7 and the exhaust pipe to prevent particle leakage. The fly ash put into the rolling kiln 1 is transported while being stirred by the forward and reverse rotating motion of the rolling kiln 1, and is heated by the electric heating element 14.
Heated to 1000℃. 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. The separated volatile matter and non-volatile matter are then processed in the same manner as in the first embodiment. Table 3 below shows the results of an elution test using acetic acid after heating ash to about 1000°C in rotary kiln 1 or rolling kiln 1. As is clear from Table 3, Cd and Pb are hardly eluted from the ash after heat treatment, and as a result, rotary kiln 1 or rolling kiln 1
Even if the ash after heating is disposed of in a landfill as it is, no problems will occur.

[Table] (Effects of the invention) As mentioned above, the electric heating type ash processing device of the present invention uses surplus electricity to heat fly ash discharged from a garbage incinerator and decomposes dioxins contained in the ash. At the same time, the heavy metals are volatilized and separated into volatile and non-volatile substances, and the volatile substances can be collected from the exhaust gas containing the separated volatile substances, so unlike conventional methods, the ash is 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. In addition, 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, the kiln is
Since it is a rotary kiln with an electric heating element embedded in the drum part, 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. In the event of a failure, the electric heating element can be replaced simply and easily, and power can be easily supplied 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 when the Kinrun is operated, 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 the drawing]

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 schematic longitudinal cross-sectional view of the electrothermal heating type ash processing equipment, FIG. 4 is a side view similar to FIG. 2 of the rolling kiln, 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 entrance side mirror part, 7
14 is an electric heating element, 25 is a discharge feeder, and 26 is a sealed damper.

Claims (1)

[Claims] 1. Fly ash collected from the exhaust gas of a garbage incinerator is heated to decompose tyoxin contained in the ash, and to volatilize heavy metals to separate volatile matter and non-volatile matter. a closed cylindrical kiln 1 equipped with an electric heating element 14 that can be decomposed to A collection device 3 is disposed in the exhaust gas discharge path and collects volatile matter from the exhaust gas that has passed through the cooling device 2; and a discharge device 4 is disposed in the kiln 1 and is capable of discharging only non-volatile matter from the kiln 1. An electric heating type ash processing device characterized by comprising: 2. The kiln 1 is a rotary kiln in which 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 embedded in a wound shape in the drum part 5, and the inlet side mirror part 6 2. The electrothermal heating type ash processing apparatus according to claim 1, wherein the fly ash is introduced from the center of the mirror part 7 and the exhaust gas containing volatile matter is discharged from the center of the mirror part 7 on the outlet side. 3. The kiln 1 is a load ring kiln in which 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 14.
according to claim 1, characterized in that the fly ash is inserted in a detachable manner so that fly ash is introduced from the center of the inlet side mirror section 6, and exhaust gas containing volatile matter is discharged from the center of the outlet side mirror section 7. Electric heating type ash processing equipment. 4 The discharge device 4 is provided at the outlet side mirror part 7 of the kiln 1, and includes a discharge feeder 25 that can discharge only non-volatile matter in the kiln 1, and a discharge feeder 25
and a sealed damper 26 that can open and close the discharge path of the
When the kiln 1 is in operation, the hermetic damper 26 closes the discharge passage and the discharge feeder 25 stops, and when the kiln 1 is stopped, the hermetic damper 26 closes the discharge passage.
opens the discharge path and the discharge feeder 25
The electric heating type ash processing apparatus according to claim 1, 2 or 3, characterized in that the electric heating type ash processing apparatus is configured to operate to discharge non-volatile matter.