JP3502364B2 - Dioxin removal method from collected fly ash - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to dioxin in collected fly ash collected in an exhaust gas treatment facility of a refuse incineration facility for incinerating general waste and industrial waste. The present invention relates to a removing method for removing a kind. 2. Description of the Related Art The most widely used technique for reducing dioxins in collected fly ash is a paddle type electropyrolysis apparatus whose schematic structure is shown in FIG. In FIG. 4, a collected fly ash FA containing dust, chloride, unreacted chemicals and dioxins collected by a dust collecting device (not shown) has a function of sealing a temperature difference and a pressure difference between inside and outside. through the metering feeder R ₁ having, it surrounded the outer periphery by an electric heater EH, is fed to the stainless steel and ceramic ash heating drum HD which is controlled to an internal temperature of about 350 to 400 ° C. by the temperature controller TIC By the heating conveyor HP having a unique paddle shape installed inside the ash heating drum HD, the ash is discharged to the ash cooling drum CD over about one hour while being stirred. [0004] During this time, the ash heating drum HD, since the air or nitrogen gas or a gas mixture is fed from the flange F _1, is maintained at a low oxygen concentration, collected by heating the electric heater EH fly ash dechlorination of dioxins in the FA is accelerated, the exhaust gas containing chlorine gas is discharged to relapse chamber (not shown) from the flange F _2. [0005] The desalted fly ash FB from which the chlorine content has been liberated by the above-mentioned heat treatment is sent to an ash cooling drum CD whose outer periphery is surrounded by a cooling jacket CJ, and is cooled by a cooling conveyor CP controlled by a temperature controller TCA. while it is adjusted the transfer speed, and is discharged to the outside as the processing ash TA from discharger R ₂ having the same function as quantity feeder R ₁ described above. [0006] Desalted fly ash FB by the ash cooling drum CD
Is rapidly cooled in a short time to prevent a re-synthesis phenomenon of dioxins which becomes maximum at around 300 ° C. [0007] However, in the case of the above-mentioned paddle type electro-pyrolysis apparatus, since it is a heating system from the outside only by an electric heater which is often divided and installed at a plurality of locations, The temperature of the fly ash tends to be non-uniform, but if the temperature of the fly ash becomes 350 ° C. or less, the removal rate of dioxins decreases, so it is necessary to maintain the average temperature of the fly ash high, for example, 7 for 200kg / h fly ash processing
The consumption of heating power of about 0 to 80 kw increases the operating cost. Further, since the processing of the collected fly ash FA is a work only during the daytime and the operation is often suspended at night, the electrothermal decomposition apparatus is cooled during the suspension of the operation and is released from the collected fly ash FA. Ash heating drum H
There was a problem that the inside of D, especially the heating conveyor HP corroded severely. Further, since the released chlorine is returned to the reburning chamber side, even during operation, corrosion of the piping due to high-temperature chlorine gas occurs. [0010] The method for removing dioxins from collected fly ash according to the first aspect of the present invention is installed in a refuse incineration facility for incinerating general waste and industrial waste, and treating exhaust gas. The dioxins in the fly ash collected by the facility are heated and quenched under low oxygen conditions by an ash heating device and an ash quenching device connected to the ash heating device, and the dioxins from the collected fly ash are treated. A method of removing
The ash heating device is provided with a heating and transferring means through which a part of the exhaust gas for heating flows through the hollow shaft, an inlet for the collected fly ash and the inert gas surrounding the heating and transferring means, a desalted fly ash, and a separated gas. And a heating outer cylinder surrounding the heating inner cylinder and having an inlet for the remaining exhaust gas for heating and an outlet for cooling gas. The collected fly ash sent into the heating inner cylinder, which has become a low oxygen atmosphere by the injection, is stirred and transferred by the heating transfer means, and the low-temperature gas purified by the bag filter is converted by the high-temperature gas heater. Dioxins contained without adding various reaction auxiliaries because the exhaust gas for heating is adjusted to an appropriate temperature by heat exchange and is heated from both sides by being sent into the hollow shaft and the heating outer cylinder. Dechlorination of most of the ash is carried out, resulting in desalted fly ash. The ash is rapidly quenched in the ash quenching device and is discharged as harmless treated ash from the ash treatment device.On the other hand, a small amount of chlorine liberated by the above-described dechlorination is mostly inert gas. And accumulated in the gas reservoir of the heating inner cylinder, absorbed by the neutralizing agent in the connected chlorine absorption device, and then sent to the ash treatment device.The remaining acidic harmful gas accompanying the desalted fly ash Is neutralized by unreacted neutralizing chemicals remaining in the desalted fly ash in the ash quenching device, and both are converted into harmless treated ash without re-synthesizing with the remaining trace amount of dioxins. After the end of a series of operations, the residue in the apparatus is discharged to the ash quenching apparatus by a heating exhaust gas or an inert gas. Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an explanatory diagram showing a schematic configuration of an apparatus for implementing a method for removing dioxins from collected fly ash according to the present invention and related equipment, and FIG. 2 is a diagram showing a structure of an ash heating apparatus. FIG. 3 is a sectional view showing an example of the structure of the ash quenching apparatus. Note that the same reference numerals are given to the same substances and members as those described with reference to FIG. 4, and detailed description will be omitted. In FIG. 1, a high-temperature exhaust gas discharged from a refuse incinerator passes through a reburning chamber and is supplied to a high-temperature gas heater HH.
After being exchanged with a low-temperature gas LG to be described later, and further cooled by a residual heat utilization facility and a gas cooling facility, a bag filter BF provided with a chemical supply facility such as slaked lime and activated carbon constituting an exhaust gas treatment facility. , Collecting dust and acidic harmful gas and dioxins contained in exhaust gas
The gas is removed to become a clean low-temperature gas LG, which is sucked into the draft fan and released from the chimney into the atmosphere. Here, the collected fly ash FA collected by the bag filter BF includes, as described above, besides dust, chloride obtained by combining acidic harmful gas and slaked lime, and activated carbon adsorbing dioxins, It includes a drug or the like of unreacted fed into the ash heating device AH via the metering feeder R _1. The cold gas LG above is diverted from the flue the hot gas heater HH to sent by heated hot gas HG next after the induced draft fan, cold gas L by mixing damper D ₁
Is fed to the ash heating device AH become heating the exhaust gas G _1, which is adjusted to an appropriate temperature is mixed with G, then heating the collected fly ash FA, through the adjusting damper D ₂ becomes cooling gas G ₂ Refluxed before the gas cooling equipment. Collection fly ash FA heated by ash heating device AH
Is converted into desalted fly ash FB in a state in which dioxins are separated by dechlorination described later, sent to an ash quenching device AC, and treated ash TA rapidly cooled by cooling water CW to an ash treatment device. The chlorine contained in the separated gas SG discharged from the desalted fly ash FB enters the chlorine absorbing device, is absorbed by the chemical, and is similarly discharged to the ash processing device. Next, in FIGS. 2 and 3, AH is an ash heating device, which includes a heating transfer means 1, a heating inner cylinder 2, and a heating outer cylinder 3;
The ash quenching device AC includes a cooling transfer unit 4 and a cooling inner cylinder 5 having a shape similar to that of the ash heating device AH.
And a cooling outer cylinder 6 and a support mechanism. The heating and transferring means 1 includes, for example, a hollow shaft 12 which is rotated via a chain gear 11 by a driving device (not shown).
A screw 13 is provided on the outer periphery of the shaft, and bearings 14 and 14 attached to the hollow shaft 12 and rotary joints 15 and 15 are provided.
If, for example, the heating gas inlet 16 for introducing the heated exhaust gas G ₁ of about half, and a cooling gas outlet 17 for discharging the cooling gas G _2. The heating inner cylinder 2 surrounds the outside of the heating and transferring means 1 and collects fly ash FA which is connected to a not-shown quantitative feeder.
Ash inlet 21 and desalted ash outlet 2 for desalted fly ash FB
2 and an inert gas inlet 2 using, for example, nitrogen gas NG
3, a gas reservoir 24, and a gas outlet 25 for the separation gas SG. The heating outer cylinder 3 has a cylindrical shape surrounding the outer periphery of the heating inner cylinder 2, and has a heating gas inlet 31 for the remaining heating exhaust gas G ₁ and a cooling gas outlet for the cooling gas G ₂ at both ends. 32
And are respectively attached. Next, the cooling / transporting means 4 includes a hollow shaft 42, a screw 43, and a structure similar to the above-described heating / transporting means 1, which are rotated by a driving device (not shown) via a chain gear 41 and the like.
It comprises bearings 44, 44, rotary joints 45, 45, a cooling water inlet 46 for introducing, for example, about half the amount of cooling water CW, and a heated water outlet 47 for discharging heated water HW. The cooling inner cylinder 5 surrounds the outside of the cooling transfer means 4 and is connected to the desalted ash discharge port 22 to connect the desalted fly ash F.
It is a tubular body provided with a desalted ash inlet 51 for feeding B and a treated ash outlet 52 for discharging treated ash TA. The cooling outer cylinder 6 is a cylinder surrounding the outer periphery of the cooling inner cylinder 5 and having an inlet 61 for cooling outer cylinder cooling water CW and an outlet 62 for heating water HW attached thereto. AC
A cooling water tank 65 and a cooling water cooler 66 are respectively provided with pumps and the like outside (see FIG. 1). The outer surfaces of the ash heating device AH and other high-temperature portions are subjected to heat insulation using a heat insulation material (not shown). Next, an operation method of the thus configured apparatus for removing dioxins from collected fly ash will be described. The collected fly ash FA containing dioxins collected by the bag filter BF is supplied to the quantitative feeder R _1.
Through the trapping ash inlet 21 into the heating inner cylinder 2 and transferred to the desalting ash outlet 22 side for about one hour while being stirred by the heating transfer means 1. [0027] During this time, the collecting fly ash FA is hollow shaft 12 and of the heating outer tube 3 by the regulated exhaust gas G ₁ to 2 in the temperature heating the tube becomes 350 to 400 ° C by the damper D ₁ While being heated indirectly from both sides, the inside of the heating inner cylinder 2 is in a low oxygen state (reducing atmosphere) by an inert gas such as nitrogen gas NG injected into the heating inner cylinder 2 together.
Therefore, the dechlorination proceeds to form a desalted fly ash FB by a reaction in which most of the chlorine constituting the dioxins in the collected fly ash FA is replaced with hydrogen. The liberated chlorine is a small amount, becomes a separation gas SG together with the inert gas, and is discharged from the gas reservoir 24 through the gas discharge port 25 to, for example, a chlorine absorbing device filled with slaked lime to become calcium chloride. It is discharged to an ash treatment device. The above-mentioned desalted fly ash FB is sent to the ash quenching device AC together with the residual gas not discharged to the chlorine absorbing device side, and is cooled by the cooling water CW flowing through the cooling transfer means 4 and the cooling outer cylinder 6. It is rapidly cooled, and the acidic harmful gas in the above-mentioned residual gas is neutralized by unreacted chemicals, and becomes ordinary treated ash TA without resynthesizing with the remaining trace amount of dioxins. After that, it is discharged to the connected ash processing device. The temperature-raised water HW, whose temperature has risen with the cooling of the desalted fly ash FB, enters a cooling water tank 65 and a cooling water cooler 66.
And is reused as cooling water CW. After the end of a series of operations, the exhaust gas G ₁ for heating or the nitrogen gas NG is fed from the trapping ash inlet 21 or the inert gas inlet 23, and the heating transfer means 1 and the heating inner cylinder 2 are fed.
Further, the residue in the cooling transfer means 4 and the cooling inner cylinder 5 is discharged to the ash treatment device via the ash quenching device AC to prevent a corrosion accident during the downtime (see FIG. 1). In FIG. 1, the ash heating device AH and the ash quenching device AC are shown in the vertical position, but may be in the horizontal position.
A transfer means may be separately provided between the desalted ash outlet 22 and the desalted ash inlet 51. Further, although an example nitrogen gas NG as an inert gas, no problem even using a heating exhaust gas G ₁ to the oxygen content is reduced. As described above, according to the method for removing dioxins from collected fly ash according to the present invention, the low-temperature gas cleaned by the bag filter is heated to provide a clean and high-temperature heating. Since the exhaust gas is effectively used as a waste gas, not only the power consumption of the electric heater as in the prior art is not required, but also the operation cost can be greatly reduced because there is no need to use various reaction aids. In addition, since the collected fly ash is uniformly heated from both the hollow shaft and the heated outer cylinder by the heating exhaust gas whose temperature is adjusted, the temperature of the collected fly ash to be transferred is increased. Evenly, complete decomposition of dioxins can be easily performed. Further, in addition to neutralizing chlorine in a small amount of dioxins liberated by heating under low-oxygen conditions with a connected chlorine absorbing device, the exhaust gas for heating is placed in the device after the operation is completed. Alternatively, by purging the residue in the apparatus by supplying an inert gas, corrosion of each apparatus such as a heating and transferring means by hydrochloric acid which is cooled and condensed when the operation is interrupted can be reduced, and the repair cost can be reduced. .

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is an explanatory diagram showing a schematic configuration of an apparatus and related equipment for implementing a method for removing dioxins from collected fly ash according to the present invention. FIG. 2 is a sectional view showing an example of the structure of the ash heating device. FIG. 3 is a sectional view showing an example of the structure of the ash quenching device. FIG. 4 is an explanatory diagram showing a schematic configuration of a paddle type electrothermal decomposition apparatus. [Description of Signs] 1 Heat transfer means 2 Heating inner cylinder 3 Heating outer cylinder 4 Cooling transfer means 5 Cooling inner cylinder 6 Cooling outer cylinder AH Ash heating device AC Ash quenching device FA Collecting fly ash FB Desalting fly ash

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) B09B 3/00 B08B 5/00

Claims (1)

(57) [Claims] [Claim 1] An ash heating device installed in a refuse incineration facility that incinerates general waste and industrial waste and collects dioxins in fly ash collected by an exhaust gas treatment facility more ash quenching equipment which is connected to the ash heating device, a method of removing dioxins from Atsumarihi ashes capturing by heating and quenching treatment in a low oxygen conditions, the ash heating device for heating Part of the exhaust gas flows through the hollow shaft
A heating transfer means that, the collecting fly ash surrounds the heating transfer means
Inlet for inert gas and outlet for desalted fly ash and separated gas
And the remaining heating surrounding the heating inner cylinder
A feed inlet of use the exhaust gas and the heating barrel having a discharge port of the cooling gas mainly is composed of, hypoxia Kiri囲by inert gas fed
The collected fly ash sent into the heated inner cylinder
It is agitated and transported by the transport means,
Of low-temperature gas that has been cleaned by a heat exchanger in a high-temperature gas heater
It becomes the exhaust gas for heating adjusted to the appropriate temperature by the above hollow shaft
Heated from both sides by being sent to the inner and heated outer cylinders
Content without adding various reaction aids
Most of the dioxins are dechlorinated due to dechlorination
It becomes fly ash and is rapidly cooled in the subsequent ash quenching device
From the ash treatment equipment
And a small amount of chlorine released by the above-mentioned dechlorination
Is collected in the gas reservoir of the heated inner cylinder together with most of the inert gas.
Stacked and absorbed by the neutralizing agent with a connected chlorine absorber.
After that, it is sent to the ash treatment device, and
The entrained residual acid harmful gas is removed in the ash quenching device.
Neutralized by unreacted neutralizing agent remaining in salt fly ash
Do not re-synthesize with the remaining traces of dioxins.
Both are converted into harmless treated ash and discharged from the ash treatment equipment.
It is further after a series of operations ends, heating the exhaust gas or inert
Discharge residue in the device to ash quenching device by neutral gas
For removing dioxins from collected fly ash
Law.