JP2001232150A - Waste material combustion waste gas treating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent the deterioration of the performance of a catalyst for decomposing DXNs in a waste material combustion waste gas before desalting by lightening the load on the catalyst to reduce the cost and to decrease the discharge quantity of DXNs. SOLUTION: In the waste material combustion waste gas treating system, a feeder 31 for feeding powdery activated carbon P to the waste gas in the front stage across a dust collector 32 and the de-DXNs catalyst 33 in the waste gas in the post stage are arranged. The desalting device, a denitration reaction device, or the like, is arranged in the post stage after the de-DXNs catalyst 33. For example, about 90% of DXNs is removed in a de-DXNS catalyst inlet (b) to lighten the load on the de-DXNs catalyst. In a desalting device outlet (d), total discharge quantity of DXNs is remarkably decreased. The load on the catalyst is lightened and the deterioration of the performance of the catalyst is prevented by adding the powdery activated carbon in the waste gas to adsorb DXNs, and after that, passing the waste gas after dust-collected through the de-DXNs catalyst.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a waste combustion exhaust gas treatment apparatus, and more particularly to an organic chlorine compound containing dioxins (DXNs) and the like (hereinafter referred to as dioxins) in exhaust gas generated by burning waste. The present invention relates to a combustion exhaust gas treatment apparatus suitable for removing methane.

[0002] Here, the exhaust gas is intended to be an exhaust gas containing hydrogen chloride, particularly an exhaust gas generated when treating waste. In addition, waste includes combustibles such as general waste such as municipal waste from homes and offices, waste plastic, car shredder dust, waste office equipment, electronic equipment, and industrial waste such as chemical products. .

[0003]

2. Description of the Related Art As a method of treating an exhaust gas containing hydrogen chloride, for example, a method of treating an exhaust gas discharged from a combustion furnace of a waste treatment apparatus for treating waste is known (see, for example, Japanese Patent Application Laid-Open No. 1-49816 (Tokuhei 6)
-56253)).

[0004] In this waste treatment apparatus, dust (also referred to as "combustion fly ash" or "dust dust") in the exhaust gas is filtered by a dust collector or a first bag filter, and then serially connected to the dust collector. Exhaust gas is desalted by a connected exhaust gas purifying device or a second bag filter, and then denitration and dioxin treatment are performed.

[0005] The denitration / deoxin treatment utilizes the fact that dioxins are simultaneously decomposed by the catalyst when exhaust gas is passed through an oxidation catalyst and ammonia is injected to perform denitration treatment.

[0006]

However, in the above-mentioned conventional exhaust gas treatment method, desalting is performed after dust is removed from the exhaust gas. Here, dioxins in the exhaust gas are contained in the desalination residue and are discharged. Therefore, it is not preferable to dispose of such a desalted residue in a conventional landfill from the viewpoint of protection of the natural environment.

Furthermore, the amount of waste is increasing year by year, and the amount of desalination residue is increasing accordingly. Therefore, treatment of the desalination residue containing dioxins has become a serious problem. Was.

Therefore, it is conceivable to decompose dioxins in exhaust gas with a catalyst before desalting, but in this case, durability of the catalyst becomes a problem. That is, since the load on the catalyst is large, there is a possibility that the performance of the catalyst may be reduced at an early stage. Moreover, since the catalyst for removing DXNs is expensive, there is a possibility that initial costs will rise.

An object of the present invention is to reduce dioxins in waste combustion exhaust gas with a catalyst before desalting, to reduce dioxins in the desalination residue, to prevent a decrease in the performance of the catalyst, and to reduce the cost. Control, safety, processing efficiency, and
It is to improve maintenance.

[0010]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a method for decomposing dioxins in exhaust gas by adding a powdered activated carbon to waste combustion exhaust gas and collecting the dust together with the dust. Then, a desalination treatment and a denitration treatment were performed.

As a result, dioxins in the combustion exhaust gas are adsorbed by the activated carbon powder and can be removed together with the dust by a dust collector such as an electric dust collector or a bag filter. The removed activated carbon powder is circulated in the combustion and melting process so that the adsorbed dioxins are thermally decomposed, so that the load on the catalyst and the like downstream of the dust collector can be reduced.

Specifically, a first exhaust gas treatment means for removing dust from waste combustion exhaust gas, a catalyst for decomposing dioxins from exhaust gas after dust removal, and a desalinating agent for the exhaust gas after passing through the catalyst. In a second exhaust gas treatment unit for performing a desalination treatment by charging and further in an exhaust gas treatment system in which a denitration unit is disposed at a subsequent stage, powder activated carbon is added to exhaust gas in front of the first exhaust gas treatment unit. did.

[0013] In this way, the powdered activated carbon adsorbing the dioxins contained in the waste flue gas is collected together with the dust and circulated as circulating fly ash to the combustion melting furnace, where the activated carbon is burned and the dioxins are discharged. Is thermally decomposed and does not remain as a solid. Therefore, the amount of dioxins in the exhaust gas after dust removal is reduced, so that the subsequent load on the catalyst can be reduced. Furthermore, since the dioxins are decomposed by the catalyst, the total emission of dioxins from the waste treatment system can be reduced. There is a remarkable effect.

[0014]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is an example of an apparatus configuration showing an embodiment of the present invention.

As shown in FIG. 1, in this example, in a waste combustion exhaust gas treatment system, a feeder 31 for supplying powdered activated carbon P to exhaust gas is provided at a preceding stage with a dust collector 32 interposed therebetween, and a degassing device for exhaust gas is provided at a subsequent stage. The DXNs catalyst 33 was arranged. De-DXNs
At the subsequent stage of the catalyst 33, a desalination device 34 for adding a desalting agent H to desalinate the exhaust gas is arranged, and at the subsequent stage, a denitration reaction device (not shown) is arranged. Table 1 shows a calculation example of DXNs emission behavior in the above configuration example.

[0016]

[Table 1]

The following can be considered from Table 1. In addition,
Comparison with other examples will be described later. Assuming that the DXNs concentration in the exhaust gas at the dust collector inlet a is 0.6 (ng-TEQ / m3N), this is due to the DXNs removal effect of the powdered activated carbon and the dust bag filter, at the catalyst inlet b for removing DXNs, 0.06 (ng-TEQ /
m3N), and about 90% of the DXNs are removed, so that the load on the downstream DXNs catalyst can be reduced.

Next, DXNs in the exhaust gas are removed from the DN
Decomposed by XNs catalyst to remove about 90%,
0.006 (ng-TEQ / m3N) at the desalination device inlet c. Then, the DXNs amount is 3000 at the entrance a of the dust collector.
From (ng-TEQ / garbage ton), it is slightly 9 (ng-TEQ / garbage ton) at the desalter outlet d.

The concentration of DXNs, 0.1,
The desalted residue e of 0021 (ng-TEQ / g) is 10 (kg
/ Garbage ton) generated, 21 (ng-TEQ / garbage ton) DX
Ns is exhausted.

The total DXNs emissions of the entire plant are:
The total of DXNs amount in exhaust gas, 9 (ng-TEQ / garbage ton) and DXNs amount in desalination residue, 21 (ng-TEQ / garbage ton), is 30 (ng-TEQ / garbage ton). .

Next, another embodiment of the present invention is shown in Table 2. In this example, by controlling the DXNs removal rate,
This is an example in which the initial cost of the catalyst for removing DXNs is reduced. That is, the powder activated carbon is added to the DXN of the dust collector.
In the example of Table 1 where the s removal rate was significantly improved,
DXNs removal rate is 80%, with the amount of Ns catalyst being halved.
This is an example.

[0022]

[Table 2]

From Table 2, the following can be considered. As in the example of Table 1, the concentration of DXNs in the exhaust gas at the dust collector a, 0.6 (ng-TEQ / m3N), was reduced due to the effect of removing the DXNs by the activated carbon powder and the bag filter for dust removal. In b, 0.06 (ng-TEQ / m3
N), and about 90% of DXNs is removed, so that the load on the subsequent DXNs removal catalyst can be reduced.

Next, DXNs in the exhaust gas are removed from the exhaust gas.
It is decomposed by XNs catalyst and about 80% is further removed.
It becomes 0.012 (ng-TEQ / m3N) at the inlet c of the desalination device. Then, the DXNs amount is 3000 at the entrance a of the dust collector.
From (ng-TEQ / garbage ton), at the desalter outlet d, it is slightly 18 (ng-TEQ / garbage ton).

From the desalination unit 34, the DXNs concentration,
0042 (ng-TEQ / g) of the desalted residue e was 10 (kg
/ Garbage ton) generated and DX of 42 (ng-TEQ / garbage ton)
Ns is exhausted.

The total DXNs emission of the entire plant is:
DXNs amount in exhaust gas, 18 (ng-TEQ / garbage ton)
The total amount of DXNs in the desalting residue and 42 (ng-TEQ / garbage ton) is 60 (ng-TEQ / garbage ton).

Here, as a reference example, an example in which powdered activated carbon is not added is shown in Table 3. This corresponds to the case where the powdered activated carbon is not added in the configuration example of FIG. According to this example, about 810 (ng-TEQ / refuse to
DXNs of n) is decomposed, and the load on the catalyst is large.

[0028]

[Table 3]

The three examples of Tables 1 to 3 above will be compared and considered. (1) The total amount of DXNs discharged can be reduced to 1/3 by adding powdered activated carbon to the exhaust gas at the inlet of the dust collector.

(2) Even when the amount of the catalyst is reduced to half, the total discharge of DXNs can be reduced to 2/3 by adding powdered activated carbon to the exhaust gas at the dust collector inlet.

Next, a waste flue gas treatment system in the waste treatment system will be described. FIG. 2 is a system diagram illustrating an embodiment of the waste treatment system according to the present invention.

In this waste treatment system, for example, waste A such as municipal waste crushed to 150 mm square or less is supplied to the pyrolysis reactor 2 by a supply means such as a screw feeder.

The thermal decomposition reactor 2 employs, for example, a horizontal rotary drum, and its interior is kept in a low oxygen atmosphere by a sealing mechanism (not shown), and is disposed downstream of the combustion melting furnace 6. Heated air heated by the heat exchanger 8 is supplied from a line L1.

The waste A supplied to the pyrolysis reactor 2 by the heated air is heated to 300 to 600 ° C., usually 450 ° C.
Heated to about ° C. As a result, the waste A is thermally decomposed to generate a pyrolysis gas G1 and a mainly non-volatile pyrolysis residue B.

Then, the pyrolysis gas G1 generated in the pyrolysis reactor 2 and the pyrolysis residue B are separated by a discharge device (not shown), and the pyrolysis gas G1 is supplied to a line as a pyrolysis gas pipe. It is supplied to the burner of the combustion melting furnace 6 through L2.

Although the pyrolysis residue B varies depending on the type of the waste A, in the case of municipal solid waste in Japan, according to the knowledge of the present inventors, most of the flammable components are relatively fine particles. 60% Relatively fine ash content 5-40% Coarse metal component 7-50% It was found that it was composed of 10-60% coarse rubble, pottery, concrete, etc.

Pyrolysis residue B having such components
Is discharged at a relatively high temperature of about 450 ° C., is cooled to about 80 ° C. by a cooling device (not shown), and guided to a separation device 4 as separation means, where pyrolytic carbon, which is a combustible component, C and valuables D, which are non-combustible components. As the separation device 4, for example, a known separation device such as a magnetic separation type, a centrifugal type, or a wind separation type is used.

The pyrolytic carbon C from which the non-combustible components have been separated and removed as described above is pulverized by a pulverizer (not shown) such as a roll type, a tube mill type, a rod mill type, and a ball mill type. Supplied to The pulverizer is appropriately selected depending on the type and properties of the waste. In this pulverizer, all the pyrolytic carbon C is preferably pulverized to 1 mm or less, and supplied to the burner of the combustion melting furnace 6 via a line L3. .

On the other hand, the combustion air supplied by a blower (not shown), the pyrolysis gas G1 and the pyrolysis carbon C are burned in the combustion melting furnace 6 at a high temperature of about 1300 ° C. The combustion ash generated from the relatively fine ash of the decomposed carbon C is melted to form a molten slag E.

At this time, it is preferable that the non-combustible components in the valuables are formed into fine powders of 1 mm or less and heated in order to improve the efficiency of combustion and melting. For this reason, it is preferable that the processing such as crushing, crushing, and heating is performed by a device such as a crusher, a crusher, and a heater provided in the supply line and then supplied to the combustion melting furnace 6. Therefore, heating air heated by a heat exchanger arranged on the downstream side of the combustion melting furnace 6 is supplied to the heater.

The molten slag E is dropped from a slag discharge port of the combustion melting furnace 4 into a water tank (not shown) to form granulated slag. The granulated slag is blocked or granulated in a predetermined shape by a device (not shown), and is reused as a building material or a pavement material.

The combustion exhaust gas G2 generated in the combustion and melting furnace 6 of the waste treatment system is recovered by heat in the heat exchanger 8 to become exhaust gas G3, supplied to the waste heat boiler 10 and recovered by heat to become exhaust gas G4, and further reduced. The temperature is sent to the hot tower 12 to lower the temperature.

In the system of the present invention, the activated carbon powder P is added from the activated carbon powder feeder 31 to the exhaust gas G5 whose temperature has been lowered in the cooling tower 12, and the dioxins in the exhaust gas G5 are adsorbed to form the first bag filter. After collecting the dust together with the dust F1 at 14, the exhaust gas G6 is desalinated by the second bag filter 16 via the DXNs removal catalyst 15.

The inlet temperature of the first bag filter 14 is preferably 150 to 170 ° C. If it is lower than 150 ° C., there is a problem of low-temperature corrosion, and if it is higher than 200 ° C., there is a problem that the dioxin removal performance is lowered.

The activated carbon P1 collected by the first bag filter 14 is separated by the separation facility 4 together with the dust F2, F3, and F1 collected by the waste heat boiler 10, the cooling tower 12, and the first bag filter 14. Along with the pyrolytic carbon C and the like, the mixture is returned to the burner of the combustion and melting furnace 6 via the lines L4 and L3, and is burned and melted in the combustion and melting furnace 6 to form slag.

According to the present embodiment, the powdered activated carbon P1 collected by the first bag filter 14 adsorbs dioxins, and the powdered activated carbon burns and melts together with other dust to form slag, and the adsorbed dioxins Is thermally decomposed.
Dioxins contained in other dusts F1 to F3 are also thermally decomposed.

The waste flue gas G 6 from which dust and powdered activated carbon have been filtered by the first bag filter 14 is subjected to DXN before desalting treatment by the second bag filter 16 as described above.
DXNs remaining in the exhaust gas G6 are decomposed through the s-type decomposition device 15.

Next, the DXNs decomposing device 15
A desalinating agent H is added to the exhaust gas from which the substances are decomposed and removed, and chlorine compounds in the exhaust gas are removed as a desalinating residue J by a second bag filter 16, and then a denitrifying agent N (ammonia: N
H3) is added thereto to cause a denitration reaction in the denitration device 18, and is discharged from the chimney 20 as a clean combustion exhaust gas G7.

[0049]

As described above, according to the present invention, in a waste combustion exhaust gas treatment system in which a catalyst for de-DXNs is disposed immediately after a dust collector, powdered activated carbon is added to exhaust gas at a stage preceding the dust collector. Since the dioxins are adsorbed and then collected together with the dust, the load on the DXNs removal catalyst is reduced, and the performance is prevented from deteriorating.

Therefore, the cost of the expensive de-DXNs catalyst can be suppressed, and the de-DXNs treatment with improved safety, processing efficiency and maintenance can be performed. Furthermore, the total amount of dioxins emitted from the waste treatment system can be reduced.

[Brief description of the drawings]

FIG. 1 is an apparatus configuration diagram showing an embodiment of the present invention.

FIG. 2 is a system diagram showing an embodiment of a waste treatment system according to the present invention.

[Explanation of symbols]

 2 Pyrolysis reactor 4 Separation equipment (separation means) 6 Combustion / melting furnace 14 First bag filter 15 DXNs decomposition device 16 Second bag filter 18 Denitration device 20 Chimney 31 Powder activated carbon feeder 32 Dust collector 33 Catalyst for deDXNs removal 34 Desalination equipment A Municipal waste (waste) B Pyrolysis residue C Pyrolytic carbon (combustible component) D Valuable material (non-combustible component) E Molten slag F, F1, F2, F3 dust G1 pyrolysis gas G6 Combustion exhaust gas H Desalting agent J Desalting residue N Denitrifying agent P, P1 Activated carbon powder

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B09B 3/00 B01D 53/36 101A F23G 5/44 ZAB B09B 3/00 303K F23J 15/00 F23J 15/00 A B HJ F term (reference) 3K065 AA24 AC01 BA06 HA01 3K070 DA01 DA02 DA24 DA25 4D002 AA19 AA21 AB01 AC04 BA04 BA05 BA13 BA14 CA11 CA13 DA07 DA41 EA02 EA11 GA01 GB03 HA08 4D004 AA07 AA22 CA12 CA47 CB01 CB09 CB31 4D048 AA06 AA17 AB02 AB03 AC04 CC38 CC61 CD03 CD05 CD08 CD10 DA03 DA13 EA05

Claims (5)

[Claims] 1. A dust collecting means for removing dust from exhaust gas generated by burning waste, a supply means for supplying powdered activated carbon to the exhaust gas in a stage preceding the dust collecting means, and a dust collecting means in a stage subsequent to the dust collecting means. A waste combustion exhaust gas treatment device comprising: a catalyst for decomposing dioxins in the exhaust gas. 2. A step subsequent to the dioxin decomposition catalyst,
The waste combustion exhaust gas treatment apparatus according to claim 1, further comprising a desalting means for removing a chlorine compound in the exhaust gas. 3. The waste combustion exhaust gas treatment apparatus according to claim 2, further comprising a denitration means for removing a nitrogen compound in the exhaust gas by a denitration reaction at a stage subsequent to the desalination means. 4. A powder activated carbon supplying step of supplying powdered activated carbon to exhaust gas generated by burning waste, a dust collecting step of removing dust from the exhaust gas supplied with the powdered activated carbon,
A dioxin decomposition process of decomposing the dioxins in the exhaust gas from which the dust has been removed by a catalyst, and circulating the powdered activated carbon removed together with the dust in the dust collection process in a combustion melting process, and adsorbed on the powdered activated carbon. Waste gas treatment method for pyrolyzing waste dioxins. 5. A pyrolysis reactor which pyrolyzes waste to generate a pyrolysis gas and a pyrolysis residue mainly composed of a non-volatile component, and converts the pyrolysis residue into a combustible component and a non-combustible component. A combustion and melting furnace for supplying and burning the pyrolysis gas and the combustible component to discharge molten slag and exhaust gas, and a first exhaust gas treatment unit for removing dust from the exhaust gas. A second exhaust gas processing unit that performs desalination by adding a desalting agent to the exhaust gas processed by the first exhaust gas processing unit; and the first exhaust gas processing unit and the second exhaust gas processing unit. Means for supplying powdered activated carbon to the exhaust gas from the combustion and melting furnace at a stage prior to the first exhaust gas processing means, and the exhaust gas processing means between the first exhaust gas processing means and the second exhaust gas processing means. Decomposes dioxins in water A waste treatment system including a catalyst for decomposing dioxins.