JPH0639363A - Method and equipment for sintering incineration fly ash of municipal waster - Google Patents

Abstract

PURPOSE:To provide a method and equipment capable of preventing discharge of dioxine to the outside of the system and convenient in environmental protection by adding natural material, binding material and kneading material to the incineration fly ash of municipal waste, kneading the mixture to mold a raw pellet, performing sintering treatment and thermally decomposing dioxine contained in the raw pellet. CONSTITUTION:Carbon not more than 5wt.% is added as natural material from a carbon silo 23 to the incineration fly ash of municipal waste not less than 75wt.% which is discharged from an incineration equipment H of municipal waste. Cement and/or bentonite not more than 10wt.% are added as binding material from a cement silo 24 to the incineration fly ash. Water is added as kneading material from a water tank 21 thereto. The mixture is kneaded by a molding machine 26 and raw pellets P are molded on a curing conveyor 27. The raw pellets P are sintered to sintered pellets P1 by performing sintering treatment for the raw pellets P in a sintering chamber 5. Dioxine contained in the raw pellets P is thermally decomposed by the constitution.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sintering apparatus, and more specifically, it produces a fly ash from an incineration ash of municipal waste discharged from an incinerator of municipal waste as a raw material and granulates and sinters it. TECHNICAL FIELD The present invention relates to a method for sintering municipal solid waste fly ash and a sintering apparatus for producing consolidated pellets.

[0002]

2. Description of the Related Art As is well known, among municipal waste incineration ash,
Fly ash (hereinafter referred to as fly ash) is collected and collected in a dust state by a dust collecting device such as a bag filter.

The recovered fly ash contains various heavy metals and dioxins which are trace harmful substances in a considerable amount. Therefore, for example, before landfilling fly ash at the final disposal site, heavy metal and dioxins contained therein are prevented from scattering and eluting.

As the above-mentioned scattering and elution preventing treatment, for example, a treatment method called cement hardening method is known. This cement solidification method is a method of producing spherical (diameter 10 to 20 mm) pellets with a pan-type pelletizer, a method of forming into a cylinder (diameter 20 mm x length 20 to 30 mm) with a kneading extruder, and vibration granulation. There are three methods, vibrating granulation method, in which agglomerates (diameter: 5 to 50 mm) having different particle diameters are granulated by a machine.

On the other hand, Japanese Patent Laid-Open No. 62-256747 discloses a coal fly ash sintering apparatus for treating fly ash collected from a combustion facility such as a boiler that uses coal as a fuel instead of municipal waste. . This publication proposes a method of producing a lightweight aggregate by granulating and sintering coal fly ash using a sintering apparatus 1 as shown in FIG.

The outline of the sintering apparatus 1 disclosed in the above publication will be described below. The sintering machine 1 comprises a grate 2 arranged such that the horizontal rod circulates in a caterpillar fashion. Above the grate 2, a drying preheating chamber 3 for preheating the raw pellets P loaded and conveyed on the grate 2,
An ignition chamber 4 having an ignition burner (not shown) for igniting the raw pellets P and a firing chamber 5 for sintering the ignited raw pellets P are provided. A cooling zone 6 for cooling the sintered pellets P1 is provided on the downstream side of the firing chamber 5.

Further, on the upstream side of the grate 2, a dust silo 22 and a coal ash silo 25, a kneader 26a for kneading dust and coal supplied from these, and a kneaded material supplied from this kneader 26a. And a pan-type granulator 26 for granulating. Furthermore, the above-mentioned grate 2
A crusher 11 for crushing the sintered pellets P1 and a vibrating screen 12 for sieving the crushed sintered pellets P1 are provided on the downstream side.

The coal ash and dust stored in the coal ash silo 25 are supplied to the kneader 26a for kneading, and then supplied to the next pan-type granulator 26 for granulation. And is supplied to the upstream side of the dry preheating chamber 3 of the grate 2 through the hopper 26b.

Raw pellets P supplied to the grate 2
While being transported by the grate 2, is dried and preheated in the drying preheating chamber 3, ignited in the ignition chamber 4, and sintered in the firing chamber 5 to form the sintered pellet P1. The sintered pellets P1 are cooled in the next cooling zone 6 and, through the disintegrator 11 and the vibrating sieve 12, only the product pellets P2 having a predetermined particle size become lightweight aggregates. The dropped one is returned to the dust silo 22. Further, falling rocks and dust that have dropped downward from the grate 2 are returned to the dust silo 22 together with the dust from the vibrating screen 12.

[0010]

By the way, in the case of incineration fly ash of municipal waste, if the fly ash is molded and solidified by the cement solidification method, the elution of heavy metals can be almost prevented.
However, since fly ash also contains dioxins, even if the fly ash is solidified by the cement solidification method, the most harmful dioxins remain in the molded solidified substance without being decomposed. In addition, as shown in the fly ash component list in Table 1, the fly ash contains a large amount of various salts caused by municipal solid waste, so even if solidified, high-strength pellets can be obtained. However, if the pellets are stored for a long period of time, salts may be eluted, and the pellets may be pulverized due to the phenomenon of pellet collapse caused by the eluted salts, and harmful substances such as dioxins may be scattered again.

[0011]

[Table 1]

As shown in FIG. 6, the toxicity of dioxins in the incineration ash (fly ash) of municipal solid waste increases in proportion to the increase in the concentration of dioxins in the fly ash. .

Incidentally, FIG. 6 is a graph showing the relationship between the concentration of dioxins in municipal waste incineration ash and its toxicity equivalent conversion value. The horizontal axis of the logarithmic graph paper shows the dioxins in fly ash. The concentration is set, and the toxic equivalent conversion value is set on the vertical axis. Then, the toxicity equivalent conversion values corresponding to the actually measured concentrations of dioxins are plotted (Waste Society Journal Vol. 1, No. 1, P20-37,
(Reproduced from FIG. 12 of 1990). The toxicity equivalent conversion value here is the concentration (w) of all dioxins present in fly ash.
t%) is the concentration of toxic dioxin (wt)
%), Which is the highest toxicity among dioxins homologues of which about 210 kinds exist.
7,8 TCDD (Tetra Chlorinated Dibenzo Dioxin)
In comparison with, the toxicity of the other dioxins is expressed as an average value (that is, a weighted average value) of those weighted with a numerical value of 1 or less according to the strength of the toxicity.

Further, the municipal solid waste incineration facility is required to completely burn the municipal solid waste so that the burning loss of the fly ash becomes 3% or less. In fact, since the municipal solid waste is completely burned as such, The fly ash contains almost no residual carbon, and contains a large amount of salts as described above. Further, since properties such as melting point of fly ash itself are different from those of coal ash, the lightweight aggregate cannot be easily manufactured by directly adopting the sintering method and conditions of coal ash.

Further, the coal fly ash sintering apparatus usually has a temperature of 200 to
It is a facility that performs large-scale treatment at 300 t / day (7 to 12 t / h), whereas it is 10 to 50 t / day (0 in the case of a device that treats fly ash discharged from municipal waste incineration facilities. It is possible to fully cover with a small-scale equipment of about 4 to 2 t / h).

Further, the operating time of the fly ash sintering device is in accordance with the general operating mode of municipal waste incineration equipment of 8 to 24 hours / day, and intermittent operation of less than 24 hours or continuous operation of 24 hours / day. Is required, and it must be able to respond flexibly to any of them.

Therefore, a coal fly ash sintering apparatus, which is large in size and is basically operated continuously, cannot be used as a municipal waste fly ash sintering apparatus. Therefore, it is conceivable to use a coal fly ash sinter device that is significantly downsized in scale to make it like municipal waste. However, there is a problem that it cannot be used as a general sintering machine.

In particular, when treating municipal waste incineration ash, high and low treatment costs are important judgment points for equipment adoption, and both capital investment and operating costs are low, and stable molded products are required. There is a need for a sintering machine that can be manufactured.

The present invention has been made in order to solve the above problems and meet the above-mentioned desires, and depending on the operating mode of municipal waste incineration equipment, 8 hours / day or 16 hours / day for less than 24 hours. It is possible to easily switch from intermittent operation of 24h / day to continuous operation of 24h / day, and vice versa.
Moreover, it is an object of the present invention to provide a method for sintering fly ash of municipal solid waste and a sintering apparatus which can manufacture a stable molded product and which is low in capital investment and operating cost.

[0020]

According to the method for incinerating municipal waste incineration fly ash according to claim 1 of the present invention, carbon as a self-combusting material is combined with the municipal waste incineration fly ash discharged from the municipal waste incineration facility. Cement and / or bentonite as a material and water as a kneading material are added and kneaded to form raw pellets, and then the raw pellets are sintered to thermally decompose dioxin in the raw pellets. It is a feature.

[0021] According to the second aspect of the present invention, the method for incinerating municipal waste incineration fly ash according to claim 2, wherein 5% by weight or less of carbon and 10% by weight of carbon incineration fly ash of 75% by weight or more discharged from the municipal waste incineration facility are used. Cement and / or bentonite of less than wt% and an appropriate amount of water are added and kneaded to form raw pellets, and the raw pellets are held at 900 to 1300 ° C. for 1 minute or more to remove dioxin in the raw pellets. It is characterized by thermal decomposition.

The municipal solid waste incineration fly ash sintering apparatus according to claim 3 of the present invention is provided with a grate for loading a material to be sintered and circulatingly driving the material in a horizontal direction. A drying preheating chamber that dries and preheats the material to be sintered, an ignition chamber that ignites the material to be sintered, and a firing chamber that sinters the material to be sintered are provided. In a municipal solid waste incineration fly ash sintering apparatus in which a hot air supply duct for sending hot air to the heating chamber and the firing chamber is provided, any one of the inside of the drying preheating chamber, the ignition chamber and the firing chamber, and the inside of the duct, or It is characterized in that an electric heating element is provided on both sides.

According to a fourth aspect of the present invention, there is provided the municipal waste incineration fly ash sintering apparatus according to the third aspect, wherein the inside of the dry preheating chamber, the ignition chamber and the firing chamber and the duct are provided. A refractory material that covers the inner wall surfaces of these is disposed inside, and an electric heating element is embedded in the refractory material that covers the inner wall surfaces of the drying preheating chamber, the ignition chamber, and the firing chamber. It is characterized in that an electric heating element is provided so as to traverse.

[0024]

According to the method for incinerating municipal waste incineration fly ash according to claim 1, carbon as a self-combusting material, cement and / or bentonite as a binder, and a kneading material in the municipal waste incineration fly ash are used. Water is added and kneaded to form a raw pellet, and the raw pellet is obtained by sintering the raw pellet. Therefore, the self-heating of the raw pellet due to self-combustion of the carbon and the binding action of the binder are As a result, the fly ash becomes good sintered pellets, and the dioxin in the fly ash is effectively thermally decomposed by maintaining the sintering temperature at a considerably high temperature.

According to the method for incinerating municipal waste incineration fly ash according to claim 2, 75 wt% or more of fly ash, 5 wt% or less of carbon, and 10 wt% or less of cement and / or bentonite, Since a proper amount of water is added,
Stable granulation is made possible by the adhesive force of this cement or bentonite at the time of production, and the pellets granulated by the binding force of cement or the like at the time of storage are effectively suppressed from collapsing.

Since the addition amount of heavy and expensive cement or bentonite is set to 10% by weight or less, it is possible to prevent the obtained sintered pellet from becoming heavy,
The handling such as transportation becomes easy, and the increase in manufacturing cost can be avoided.

Further, since 5% by weight or less of carbon is added to the fly ash, the heat generated by the combustion of this carbon contributes to the production of good sintered pellets.

Since the amount of carbon added is set to 5% by weight or less, it is avoided that a large amount of carbon is burned and the sintered pellets are fused or porous by that much. Large sintered pellets can be obtained.

Further, the granulated raw pellets are 900
Since it is held at ˜1300 ° C. for 1 minute or more and sintered, all dioxins in the fly ash are pyrolyzed and heavy metals are also fixed in the sintered pellets.

According to the municipal waste incineration fly ash sintering apparatus of the third aspect, an electric heating element is provided in either or both of the inside of the drying preheating chamber, the ignition chamber and the firing chamber and the inside of the duct. Since it is provided, it is possible to heat the raw pellets on the grate and the hot air in the duct with the electric heating element, and this heating can compensate for the decrease in heat retention effect due to the miniaturization of the sintering device. it can.

The firing temperature can be controlled easily by adjusting the amount of electricity supplied to the electric heating element.
The temperature control accuracy can be increased.

Further, since the electric heating element is forcibly heated, the temperature rising rate in the initial stage of the operation of the sintering apparatus is increased, and the apparatus can be quickly started up. As a result, operational loss time is reduced and operating efficiency is increased, so that intermittent operation with a large number of rises can be efficiently performed.

Further, as the electric power to be supplied to the electric heating element, private power generation using waste heat provided in the municipal waste incineration facility is used to significantly reduce the fly ash processing cost. Will be possible.

According to the municipal waste incineration fly ash sintering apparatus of the fourth aspect, an electric heating element is embedded in the refractory covering the inner wall surfaces of the drying preheating chamber, the ignition chamber and the firing chamber, and the duct of the duct is used. Since the electric heating element is provided inside the duct, the heat generated by the electric heating element is effectively retained in the drying preheating chamber, the ignition chamber and the firing chamber by the heat insulating effect of the refractory. Good thermal efficiency can be obtained.

[0035]

EXAMPLE FIG. 1 is a schematic explanatory view showing an example of a municipal solid fly ash sintering apparatus according to the present invention, and FIG. 2 is a sectional view taken along line AA. Further, FIG. 3 is a diagram for explaining the use of thermal energy, and FIG. 4 is a graph illustrating the relationship between the treatment conditions (temperature × treatment time) and the amount of dioxins in fly ash. Embodiments of the present invention will be described in detail below with reference to these drawings.

As shown in FIG. 1, the sintering apparatus 1 includes a grate 2 which is circularly driven in a caterpillar shape, a drying preheating chamber 3 disposed on the grate 2, and a downstream of the drying preheating chamber 3. It is basically configured by an ignition chamber 4 provided on the side and a firing chamber 5 further arranged on the downstream side of the ignition chamber 4. A cooling zone 6 is formed on the grate 2 and downstream of the firing chamber 5.

The grate 2 is mounted on a pair of left and right sprockets, and is circulated through the sprockets by the rotational drive of a drive means (not shown). And
The raw pellets P supplied from the pellet forming means 20 to be described later are configured to be transported by the circulation drive.

The drying preheating chamber 3, the ignition chamber 4 and the firing chamber 5 are all formed in a hood shape so as to cover the upper part of the grate 2, and the raw pellets P move under them. ing. The drying preheating chamber 3 dries the raw pellets P moving on the grate 2, the ignition chamber 4 ignites the raw pellets P dried by the drying preheating chamber 3, and the firing chamber 5 the firing chamber. Each of them has a role of sintering the raw pellet P ignited in 4. The raw pellet P that has passed through the firing chamber 5 is sintered to form a sintered pellet P1.

At the ceilings of the drying preheating chamber 3, the ignition chamber 4 and the firing chamber 5, there are provided hot air supply ducts 7 for sending hot air to the respective chambers.

Further, the raw pellets P and the sintered pellets P
On the rear surface of the upper grate 2 to which 1 is transferred, a plurality of wind boxes 8 are arranged in order from the upstream side to the downstream side, and an exhaust duct 9 is provided in the lower part thereof. Communicates with the induction blower 10. Then, the air and combustion exhaust gas in the dry preheating chamber 3, the ignition chamber 4 and the firing chamber 5 pass through the layers of the raw pellets P and the sintered pellets P1 and pass through the grate 2, the wind box 8 and the exhaust duct 9. Induction blower 1
It is designed to be aspirated by 0. It is also possible that a part of the combustion exhaust gas sucked by the induction blower 10 is re-supplied to the drying preheating chamber 3, the ignition chamber 4 and the firing chamber 5 through the hot air supply duct 7 and circulates. The effective use of heat is being further promoted.

A crusher 11 is arranged downstream of the cooling zone 6 of the grate 2, and a vibrating screen 12 is arranged following the crusher 11. Then, the sintered pellets P1 supplied from the cooling zone 6 of the grate 2 are crushed by the crusher 11 as needed, and are sieved by the next vibrating sieve 12. The small-sized pellets dropped downward from the sieve mesh of the vibrating sieve 12 and the fallen ore and dust dropped from the grate 2 are combined to form the pellet forming means 2.
It is returned to No. 0 dust silo 22 and can be reused.

What remains on the sieve of the vibrating sieve 12 is
The product is a product pellet P2, which is supplied to a product bunker 13 provided downstream of the vibrating screen 12 and is temporarily stored therein. And once product bunker 13
The product pellets P2 stored in 1 are appropriately cut out by a carrying-out means such as a truck and carried out of the system.

The pellet forming means 20 comprises a water tank 21 for storing water for kneading and a dust silo 2 for storing the small pellets and dust dropped from the grate 2.
2, a carbon silo 23 for storing carbon as a fuel for self-combustion of the raw pellets P, and a cement silo 24 for storing cement or bentonite as a binder,
A fly ash silo 25 for storing fly ash collected by the dust collection equipment of the municipal waste incineration equipment H, a molding machine 26 for molding raw pellets P of a predetermined shape and size, and this molding machine 26.
And a curing conveyor 27 that supplies the raw pellets P molded by the above to the most upstream side of the grate 2.

The water tank 21 is provided with a control valve (not shown), and the amount of water supplied can be adjusted by adjusting the opening of this control valve. In addition, the dust silo 22, the carbon silo 23, the cement silo 24
Further, a table feeder (not shown) is provided at the bottom of the fly ash silo 25, and the cut-out amount of the contents stored therein can be adjusted by controlling the rotation speed of the table feeder. It is like this.

A predetermined amount of water is supplied from the water tank 21 to the molding machine 26, and dust is discharged from the dust silo 22, carbon is discharged from the carbon silo 23, and cement or bentonite is discharged from the cement silo 24. From the fly ash silo 25, fly ash is cut out in a preset amount and supplied to the molding machine 26. The dust, carbon, cement or bentonite, and fly ash supplied to the molding machine 26 are kneaded in the presence of the simultaneously supplied water for kneading to form raw pellets P.

In the present invention, the dry preheating chamber 3, the ignition chamber 4 and the firing chamber 5 provided above the grate 2 are also provided.
An electric heating element 5c is disposed on the inner wall surface of the and the inner wall surface of each hot air supply duct 7.

Since the dry preheating chamber 3, the ignition chamber 4 and the baking chamber 5 have substantially the same structure, the structure of the baking chamber 5 illustrated in FIG. 2 will be described below as a representative. The firing chamber 5 is formed of a refractory material 5b, and the outer peripheral surface thereof is a steel skin 5a.
It is covered with. The refractory 5b hangs down so as to cover both sides of the grate 2, and a side wall is formed, and an electric heating element 5c is embedded in the side wall and the inner wall of the ceiling. A hopper-shaped wind box 8 in which the iron skin 5a is extended is formed in the lower part of the baking chamber 5, and the lower part of the wind box 8 communicates with the exhaust duct 9.

The upper part of the firing chamber 5 is connected to a hot air supply duct 7 made of refractory 7b, and the outer peripheral surface of the hot air supply duct 7 is also covered with a steel shell 7a. The hot air supply duct 7 is provided with a rod-shaped electric heating element 7c which penetrates the duct 7 in the horizontal direction. In this embodiment, a rod-shaped so-called radiant tube is applied as the above. The radiant tube is a heating source applied when it is not possible to burn the fuel inside the heating device, and burns the fuel inside the heat-resistant metal tube or energizes the energization heating element to obtain heat, This heat is supplied to the inside of the heating device as radiant heat from the outer surface of the tube. The shape of the radiator is not limited to a rod, but a radiator type with fins for heat dissipation attached to the outer peripheral surface of the radiant tube or a polyhedron formed by three-dimensionally bending the radiant tube, taking into consideration the heating efficiency of hot air. Types can also be applied.

In the present embodiment, the electric heating element 7c is provided in both the hot air supply duct 7 and each of the chambers 3, 4, 5, but the invention is not limited to this. , Electric heating element 7c for only one of them
May be provided. Further, the hot air supply duct 7 is provided with the electric heating element 7c so as to cross the hot air supply duct 7, but the present invention is not limited to this, and the electric heating element 7c may be embedded in the wall. Furthermore, although the hot air supply duct 7 and the above-mentioned chambers 3, 4, 5 are formed separately,
It is not limited to being formed separately, and the hot air supply duct 7 and each of the chambers 3, 4, and 5 may be integrally formed.

Next, referring to FIG. 3, the utilization of heat energy in the present invention will be described. Conventionally, heavy oil for ignition and carbon for sintering were supplied to the sintering apparatus 1, and the raw pellets were sintered only by their combustion heat. However, in the present invention, in addition to these thermal energies, , The private power generation equipment performs private power generation by the steam generated from the waste heat boiler of the municipal waste incineration equipment H, and the private power generated is supplied to the sintering device 1 by dividing it into power for equipment operation and power for heating. I am trying to do it.

Then, various driving devices in the sintering apparatus 1 are driven by electric power for operating the equipment, and electric power for heating is supplied to each of the electric heating elements 5c and 7c, so that the firing chamber 5 and the hot air shown in FIG. The inside of the supply duct 7 is heated and the sintering device 1
We try to make up for the poor thermal efficiency that accompanies the miniaturization. Particularly, by performing automatic control for adjusting the amount of electric power supplied to the electric heating elements 5c and 7c so that the temperature in the firing chamber 5 reaches a predetermined temperature set in advance, the initial operation of the sintering apparatus 1 is performed. Can be quickly started,
It is also possible to finely adjust the temperature in the firing chamber 5.

Next, the carbon used in the present invention will be described. Carbon is a raw pellet P during the sintering process.
Is mixed in the raw pellet P in order to self-combust inside and effectively sinter, and any one can be used as long as it contains a considerable carbon component. However, in the present embodiment, it is 100 μm with a ball mill.
Coal finely pulverized to m or less is used.

As shown in Table 2, the quality of coal is appropriate, with volatile matter of 25 to 45%, fixed carbon of 32 to 57%, and calorific value of 6300 to 7,000 kcal / kg.
It is excellent as carbon added to the raw pellets P.
5% by weight or less, preferably 1 to 3% by weight, of such coal as raw carbon is added to the raw pellet P as water. The reason why the content is 5% by weight or less is that if the amount is more than that, the raw pellets P due to combustion of coal become fused or become porous, and therefore the sintered pellet P1 having high strength is produced.
Is not obtained.

[0054]

[Table 2]

Next, the cement and the bentonite, which is a typical clay mineral used in the present invention, will be described. These cements and bentonites are mixed in the raw pellets P to make hard sintered pellets P1 due to their bonding function. Note that only one of cement and bentonite may be added to the raw pellet P, or a mixture thereof may be mixed.

The cement may be a commercially available ordinary so-called Portland cement, and there is no particular brand for bentonite, and it may be sodium type or calcium type. Bentonite is the result of alteration of ores such as volcanic ash deposited on the seabed when a volcano erupted.
It has extremely high water absorption performance and has the property of becoming a paste when it absorbs water and expanding. For reference, Table 3 shows examples of chemical compositions of Portland cement and bentonite.

[0057]

[Table 3]

As shown in Table 3, the composition of Portland cement and bentonite is almost the same, except that the former is rich in calcium while the latter is rich in silica. And
Since both of them have a function as a binder or a binder, they are used as an auxiliary agent for firmly bonding the sintered pellets P1.

An embodiment of the sintering apparatus according to the present invention will be described below in more detail with reference to FIGS. 1 and 2, and its operation will also be described.

In the forming means 20, the fly ash, which is the main raw material recovered from the refuse incinerator H, is used as the fly ash from the fly ash silo 25. Dust from the carbon silo 23, coal (carbon) as a self-burning material finely pulverized to a particle size of 100 μm or less, and cement or bentonite as a binder from the cement silo 24 were provided in each silo. The table feeder (not shown) is operated to cut out to the molding machine 26, and in addition to them, water as a kneading medium is supplied to the molding machine 26 from the water tank 21.

Then, from the carbon silo 23 to the molding machine 2
The amount of coal cut out in 6 is set to 5% by weight or less, preferably 1 to 3% by weight of the total supply amount excluding water to the molding machine 26, and the amount of cement or bentonite cut out from the cement silo 24 is set. The amount is set to 10% by weight or less, preferably 1 to 5% by weight, based on the total amount of the feed except the same water. The amount of water supplied from the water tank 21 is set to an appropriate amount so that the kneading process in the molding machine 26 can be favorably performed.

In this embodiment, as shown in FIG.
As the molding machine 26, a known twin screw type is adopted. The raw material supplied to the molding machine 26 is extruded while being pressurized with high pressure to the outlet side as the screw rotates. A die having a large number of discharge holes with a diameter of about 20 mm is provided on the outlet side of the molding machine 26, and the kneaded raw material passes through these discharge holes to produce a diameter of about 20 m.
The raw pellet P is m and has a length of 30 to 50 mm. When producing raw pellets P of different sizes, the dies may be replaced with dies having discharge holes of other diameters.

In this embodiment, a twin-screw type extrusion molding machine was used as the molding machine 26, but the present invention is not limited to the twin-screw type extrusion molding machine, and in the case of granulating into a spherical shape. A known pan-type granulator may be applied, and a known vibrating granulator may be applied when granulating so that the particle size becomes random. The selection of these molding machine models is
It is determined by the use of the final product pellet.

Then, the raw pellets P molded by the molding machine 26 are discharged onto the curing conveyor 27 and conveyed on the curing conveyor 27 for about 10 to 30 minutes,
Natural drying is performed during this transportation.

The raw pellets P thus shaped and conveyed are supplied so as to be stacked on the grate 2 of the sintering apparatus 1. A pellet silo 28 for bedding is provided on the uppermost stream side of the grate 2, and the sieved product of the vibrating sieve 12 obtained by sieving the sintered pellets is stored in the silo 28. . Then, the bedding floor pellets, which are the above-mentioned sieve products, are supplied before the raw pellets P are stacked on the grate 2. Therefore, as shown in FIG. 2, the placement surface of the grate 2 is in a state in which the raw pellet layer is laminated on the floor pellet layer formed by the floor pellets. The two-layer structure on the grate 2 is to protect the grate 2 from high heat during sintering of the raw pellets P.

The specific specifications of the grate 2 are, for example, 1 t /
In the case of the sintering device 1 having a sintering capacity of about h, the width of the grate 2 is set to 600 mm, and the layer thickness of the raw pellet P is 2
It is suitable to set it to about 00 mm. The sintering device 1
Production capacity is determined by the width of the grate 2 × the layer thickness of the raw pellets P × the moving speed of the grate 2. Under any circumstances, the layer thickness of the raw pellets P is 200-300 mm.
It is preferable to set it to a degree.

Then, the raw pellets P supplied onto the grate 2 are first fed to the electric heating element 5 in the drying preheating chamber 3.
c, 7c, the temperature at which it is dried by hot air and easily ignited in the next ignition chamber 4, that is, 200 to 40
Preheated to 0 ° C. Conventionally, in the drying preheating chamber 3, hot air whose temperature has risen by obtaining heat from the hot pellets P during circulating use is only blown to the drying preheating chamber 3. However, in the present invention, An electric heating element arranged in the firing chamber 5 is supplied with hot air heated by an electric heating element 7c arranged in the hot air supply duct 7 in a state where the temperature can be positively controlled. Since the raw pellet P is directly heated by 5c, it is possible to quickly and appropriately cope with the rising of the sintering apparatus 1 and the intermittent operation.

An ignition burner B is provided in the next ignition chamber 4, and the ignition burner B ignites 200 to 200
The raw pellets P that have been preheated to 400 ° C. and moved are ignited and burned. The ignition chamber 4 is also provided with electric heating elements 5c and 7c. Since the raw pellets P are also heated by the electric heating elements 5c and 7c, the raw pellets P are assisted in ignition and combustion, and the raw pellets are also heated. P will be ignited more uniformly than ever before.

Then, in the subsequent firing chamber 5, the raw pellets P ignited in the previous step are self-combusted by the combustion of carbon (pulverized coal) which is a combustible component, and the raw pellets P are burned to about 900-
It reaches 1300 ° C. The raw pellets P are exposed to this temperature for about 1 minute to sinter and become sintered pellets P1. The heating chamber 5 is also provided with electric heating elements 5c and 7c, and the sintering of the raw pellets P proceeds efficiently with the help of these.

The heat generation temperatures of the electric heating elements 5c and 7c can be easily controlled by adjusting the amount of electric power supplied thereto. Therefore, each of the above chambers 3,
The temperature inside each of the chambers 3, 4 and 5 and the duct 7 is set in advance by providing a temperature sensor inside the ducts 4 and 5 and adjusting the power supply amount based on the temperature detected by the temperature sensor. It is easy to control the temperature to a predetermined temperature, and also from this aspect, the attachment of the electric heating elements 5c and 7c is useful.

Sintered pellets P1 thus obtained
In the next cooling zone 6 on the grate 2, the air is cooled by exchanging heat with the atmosphere sucked by the suction force of the induction blower 10. Since the cooled sintered pellets P1 may be fused with each other depending on the properties of fly ash,
It is disintegrated into independent particles by a crusher 11 in the next step of the grate 2. Then, if necessary, it is supplied to the vibrating screen 12 and screened.

That is, when the sintered pellet P1 is used as an aggregate or the like, it is necessary to make the particle diameters uniform. Therefore, the sieve product of the vibrating sieve 12 is separated as the product pellet P2 and sent to the product bunker 13. The small pellets under the sieve are returned to the molding machine 26 through the dust silo 22 and used again as a part of the raw material. However, when the purpose is only to treat a trace amount of harmful substances such as dioxins in fly ash, the entire amount can be a product without sieving with the vibrating sieve 12.

Further, the fallen mine and dust that have fallen from the grate 2 are collected via the wind box 8 and the exhaust duct 9 into the recovery conveyor 9
It is collected in a, is returned to the dust silo 22 together with the small pellets, and is reused as a part of the raw material.

The operating conditions such as residence time and temperature of the raw pellets P and P1 in the drying preheating chamber 3, the ignition chamber 4, the firing chamber 5 and the cooling zone 6 of the sintering apparatus 1 and the control of the production amount are controlled by the grate. The transport speed of 2 and the layer thickness of the raw pellets P are taken into consideration and appropriately set. For example, in the case of the sintering apparatus 1 having the above-mentioned sintering capacity of about 1 t / h, the operation shown in Table 4 is performed. The conditions are adopted as standard.

[0075]

[Table 4]

When a large amount of slaked lime powder or slaked lime slurry is used to remove toxic gases such as hydrochloric acid in the exhaust gas treatment section of the municipal solid waste incineration facility H, a large amount of slaked lime and Since the compound is present, these components act as a substitute for cement or bentonite, and as a result, the amount of cement or the like added can be reduced.

The fly ash obtained from the municipal solid waste incineration facility H contains a large amount of dioxins, but as can be seen from the graph shown in FIG. 4, the content of dioxins in the fly ash is , The amount of heat applied to fly ash, that is, the product of the processing temperature and the processing time, decreases in inverse proportion to, for example, 52
When treated at 5 ° C. for 10 minutes, the dioxin content, which was initially about 7,000 ng / g, is reduced to about 500 ng / g. In the present invention, fly ash is 900 in the ignition chamber 4.
Since it is exposed to a high temperature of ˜1300 ° C., dioxins are surely decomposed, and the sintered pellet P1 or the product pellet P2 does not adversely affect the environment.

Regarding the heavy metals in the fly ash, when the raw pellet P is treated at a high temperature, each heavy metal is melted on the particle surface of the powder and fixed at the sintered portion.
It becomes a state of being confined inside the sintered pellet P1,
The elution is effectively suppressed. Particularly harmful hexavalent Cr
For, by burning the carbon in the raw pellets P,
Since the inside of the pellet is maintained in a reducing atmosphere, various heavy metals can be stabilized in a safer form, such as being reduced to harmless trivalent Cr.

Since the fly ash obtained from the municipal solid waste incinerator H contains a large amount of various salts, the melting temperature (melting point) of the fly ash is lowered together with heavy metals.
Therefore, if the amount of carbon added to the product pellets P2 is increased as in the conventional case, the sintering temperature becomes too high, and the sintered pellets P1 are fused together into a large mass due to the melting of the fly ash. The product pellet P2 cannot be obtained.

Therefore, in the present invention, the raw pellets P
The amount of carbon added therein is set to a small amount of 5% by weight or less, and the temperature rise due to self-combustion of the raw pellets P is suppressed so that fusion between the sintered pellets P1 does not occur.

Further, in the present invention, as described above,
Since the heat obtained by supplying the electric heating elements 5c and 7c with the free electric power of private power generation using the waste heat boiler can reduce the self-combustion heat of the raw pellets P, As a result, it is possible to reduce the amount of carbon that is a self-combustion heat generating component in the raw pellets P, and it is also possible to reduce the amount of heavy oil supplied to the ignition burner B. The economic effect of using this self-generated power is enormous and can be reduced to 1/3 to 2/3 of the conventional operating cost. Therefore, by applying the fly ash sintering apparatus of the present invention, it is surely advantageous in terms of operating cost, in particular, compared with the conventional melting and solidifying method of municipal waste incineration fly ash.

Further, also in terms of the operation of the sintering apparatus 1, the electric heating element 5 is produced by using the electric power obtained by the private power generation.
c and 7c are caused to generate heat, and this heat is used together with hot air to heat the raw pellets P. Therefore, it is possible to easily adjust the amount of electric power supplied to the electric heating elements 5c and 7c to an appropriate value. The temperature can be controlled. As a result, the temperature rise at the time of starting the sintering apparatus 1 is 1/2 (about 30 minutes) of the conventional one,
Since the start-up operation of the sintering apparatus 1 is performed quickly, it is possible to efficiently cope with the intermittent operation that requires many start-up operations.

Further, the sintered pellet P1 has about 20 to 4
Uniaxial compressive strength of 0 (kg / pellet) is given,
Since its shape is stably maintained for a long period of time, it can be safely dumped without adversely affecting the final disposal site. Also, concrete aggregate, roadbed material, backfill material,
Alternatively, it can be applied to many uses such as a material for promoting drainage of flower beds.

Test Example In order to investigate the performance of the sintered pellets obtained by the method and apparatus of the present invention, 1 t / h
The firing test was carried out using the full-scale sintering apparatus 1 having the production capacity of. As the main raw material, only the fly ash captured by the dust collector of the municipal waste incineration facility is used, and the dust and falling mine generated in the system of the sintering device 1 are not used.

A plurality of mixtures of fly ash and additive materials were prepared by adding the additive material for binding and the additive material for self-combustion to the above fly ash at different addition ratios. This mixture and water as a kneading aid were supplied to a molding machine to mold spherical raw pellets P. In this test, in order to make the pellet into a spherical shape with a wide range of applications, the above-mentioned twin-screw type molding machine 2
Instead of 6, a pan pelletizer type molding machine is used. The above mixture is set to 84% by weight of the whole raw material, and water is set to 16% by weight of the whole raw material. Bentonite is used as the binding additive, and pulverized coal finely pulverized to 100 μm or less is used as the self-burning additive.

The raw material sample set in this way is 1
It was one type. No. shown in Table 5 1-No. The raw material sample of No. 5 is a comparative example in which no additive is mixed. In addition, No. 6-No. In the raw material sample of No. 8, bentonite was added at 2% by weight based on the raw material excluding water, but pulverized coal was not added. No. 9
The raw material sample of bentonite is 2 per raw material excluding water.
%, Pulverized coal is set to 4.5% by weight, and No. 10
The raw material sample of bentonite is 5 per raw material excluding water.
%, Pulverized coal was set to 3% by weight, and No. In the 11 raw material samples, bentonite was set to a maximum of 10% by weight and pulverized coal was set to 3% by weight per raw material excluding water. The firing conditions (firing time and firing temperature) are set slightly different from each other as shown in Table 5. The firing time is the total time during which the raw pellets P stay in the dry preheating chamber 3, the ignition chamber 4 and the firing chamber 5, and the firing temperature is the temperature in the ignition chamber 4.

The raw material samples as described above were supplied to a molding machine for molding, and the raw pellets P thus obtained were continuously supplied to the grate 2 to produce sintered pellets P1. By the way, the product pellets P2 on the screen of the vibrating screen 12 are sampled and the product properties (24 hr water absorption rate,
The uniaxial compressive strength) was measured.

The above water absorption rate for 24 hours is the product pellet P2.
Is a value obtained by dividing the weight difference between before and after water absorption when immersed in water for 24 hours by the weight after water absorption, and the uniaxial compressive strength is
This is the value of the compressive force when the product pellets P2 are crushed by applying pressure one by one until they break. 24 hr
Multiple product pellets P2 with both water absorption and uniaxial compression strength
The average value of the results of tests conducted on is used as data. The test results are shown in Table 5.

[0089]

[Table 5]

As can be seen from this table, No.
1-No. The raw materials of No. 5 did not reach the target value of 5 (kg / one pellet) in any of the raw materials of No. 5, and at such compressive strength, this product pellet P2 was used as a soil conditioner or agricultural / horticultural plant. When it is used as a lumber, it cannot withstand field laying, burial in the soil, and excavation thereof, and it often breaks, so its commercial value is low. The 24 hr water absorption exceeds the target value of 30% under any firing condition.

On the other hand, No. 1 according to the present invention. 6 to N
o. It can be seen that the raw materials of No. 11 have all cleared the above-mentioned target value of the uniaxial compressive strength, and the above-mentioned compressive strength increases as the amount of the additive material increases. And, the binder typified by bentonite is 2 to 5% by weight based on the raw material excluding water, and the self-combustion material (carbon) typified by pulverized coal.
It is understood that a combination of 0 to 5% by weight based on the raw materials excluding water is suitable. In addition, about 24 hr water absorption, all exceeded the target value of 30%.

[0092]

As described in detail above, according to the method for incinerating municipal waste incineration fly ash according to claim 1 of the present invention, incineration incinerator fly ash, carbon as a self-combusting material, cement as a binder, and / Or Bentonite and water as a kneading material are added and kneaded to form raw pellets, and the raw pellets are obtained by sintering the raw pellets. By the binding action of the binder, the fly ash becomes a good sintered pellet, and by maintaining the sintering temperature at a considerably high temperature, the dioxin in the fly ash is effectively heated at the sintering treatment stage. It decomposes and prevents the emission of dioxins out of the system, which is convenient for environmental protection.

According to the method for incinerating municipal waste incineration fly ash according to claim 2 of the present invention, the amount of fly ash of 75% by weight or more is 5% by weight.
By adding the following carbon, 10% by weight or less of cement or bentonite, and an appropriate amount of water, it is possible to obtain good sintered pellets which are inexpensive and easy to handle without becoming too heavy, By setting 5% by weight or less of carbon, it is possible to prevent the sintered pellet from becoming porous due to the combustion of carbon which is a combustible component, and to obtain a good quality product.

The raw pellets obtained by molding are
Since it is held at 900 to 1000 ° C for 1 minute or more and sintered, all dioxins in the fly ash are pyrolyzed and the heavy metals are also fixed. Scattering of dioxins,
There is no fear of elution, which has a great effect on environmental protection.

According to the method for incinerating municipal waste incineration fly ash according to claim 3 of the present invention, one or both of the inside of the drying preheating chamber, the ignition chamber and the firing chamber and the inside of the duct are electrically operated. Since the heating element is provided, the above-mentioned electric heating element can heat the raw pellets on the grate and the hot air in the duct, and this heating reduces the heat retention effect due to the downsizing of the sintering device. Can be supplemented.

By controlling the amount of electricity supplied to the electric heating element, the firing temperature can be controlled easily, and the temperature control accuracy can be increased.

Further, since the electric heating element is forcibly heated, the temperature rising rate in the initial stage of operation of the sintering apparatus is increased, and the apparatus can be quickly started up. As a result, operational loss time is reduced and operating efficiency is increased, so that intermittent operation with a large number of rises can be efficiently performed.

Further, as the electric power to be supplied to the electric heating element, the fly ash treatment cost can be greatly reduced by utilizing the private power generation using waste heat provided in the municipal solid waste incineration facility. Will be possible.

In addition, according to the municipal waste incineration fly ash sintering apparatus of claim 4 of the present invention, an electric heating element is embedded in the refractory material covering the inner wall surfaces of the drying preheating chamber, the ignition chamber and the firing chamber. Since the electric heating element is provided inside the duct so as to traverse the duct, the heat generated by the electric heating element is effectively dried by the heat insulating effect of the refractory, and the drying preheating chamber,
It is held in the ignition chamber and the firing chamber, and good thermal efficiency can be obtained.

As described above, in the municipal waste incineration fly ash sintering apparatus of the present invention, the emission of harmful dioxins accompanying fly ash, which has been a problem in the past, is effectively suppressed, and The ash treatment cost can be significantly reduced, and as a result, it contributes to the reduction of the operating cost of the municipal solid waste incineration facility.

[Brief description of drawings]

FIG. 1 is a schematic explanatory view showing an example of the configuration of a municipal solid waste incineration fly ash sintering apparatus of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is an explanatory diagram of utilization of heat energy.

FIG. 4 is a graph showing the relationship between the treatment temperature and the amount of dioxins in fly ash.

FIG. 5 is a schematic configuration explanatory view illustrating a conventional coal fly ash sintering apparatus.

FIG. 6 is an explanatory diagram of the concentration of dioxins in the fly ash of municipal waste incineration.

[Explanation of symbols]

 1 Sintering device 11 Crusher 12 Vibrating screen 13 Product bunker 2 Grate 21 Water tank 22 Dust silo 23 Carbon silo 24 Cement silo 26 Molding machine 27 Curing conveyor 28 Floor pellet pellet silo 3 Drying preheating room 4 Firing room 5 Firing room 5c , 7c Refractory 5c Electric heating element 6 Cooling zone 7 Hot air supply duct 8 Air box P Raw pellets P1 Sintered pellets P2 Product pellets

Claims (4)

[Claims] 1. A municipal waste incineration fly ash discharged from an municipal waste incineration facility is added and kneaded with carbon as a self-combusting material, cement and / or bentonite as a binder, and water as a kneading material. After molding the raw pellets,
A method for incinerating municipal waste incineration fly ash, characterized in that dioxin in the raw pellets is pyrolyzed by sintering the raw pellets. 2. 75% by weight or more of municipal waste incineration fly ash discharged from the municipal waste incineration facility, 5% by weight or less of carbon, 10% by weight or less of cement and / or bentonite, and an appropriate amount of water. A method for incinerating fly ash of municipal solid waste, characterized by pyrolyzing dioxin in raw pellets by adding and kneading to form raw pellets and holding the raw pellets at 900 to 1300 ° C for 1 minute or more. . 3. A grate for loading and sintering the material to be sintered is provided in the horizontal direction, and a drying preheating chamber for drying and preheating the material to be sintered during transportation is provided above the grate. An ignition chamber for igniting the material to be sintered and a firing chamber for sintering the material to be sintered are provided, and a hot air supply duct for sending hot air to these drying preheating chamber, ignition chamber and firing chamber is provided. In the municipal waste incineration fly ash sintering device, an electric heating element is provided in any one or both of the inside of the drying preheating chamber, the ignition chamber and the firing chamber and the inside of the duct. Municipal refuse incineration fly ash sintering equipment. 4. The municipal solid waste incineration fly ash sintering apparatus according to claim 3, wherein a refractory for covering the inner wall surfaces of the drying preheating chamber, the ignition chamber and the firing chamber and the inside of the duct is disposed. The electric heating element is embedded in the refractory covering the inner wall surfaces of the dry preheating chamber, the ignition chamber and the firing chamber, and the electric heating element is provided inside the duct so as to cross the duct. Characteristic municipal waste incineration fly ash sintering equipment.