JP3485453B2 - Desorption method of activated carbon adsorbing dioxin in waste gas treatment equipment of garbage incinerator - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for desorbing dioxin-adsorbed activated carbon in an exhaust gas treating apparatus for a refuse incinerator. More specifically, since the activated carbon that is an adsorbent is circulated and used in the exhaust gas treatment device of a refuse incinerator, the activated carbon that decomposes NOx in the presence of NH ₃ is desorbed from SO ₂ and HCl in the desorption tower, Dioxins provide a way to break down.

[0002]

2. Description of the Related Art In an exhaust gas treatment device for a refuse incinerator,
The conventional one uses lignite or activated carbon as an adsorbent to adsorb dioxin, and used lignite or activated carbon is returned to the furnace and burned. S at exhaust gas temperature of 140 ° C
FIG. 17 shows the gas generation state in the desorption tower when O ₂ is adsorbed at 500 ppm and NH ₃ is adsorbed at 250 ppm. Exhaust gas temperature 1
Desorption situation when adsorbed at 15 ℃ shown in FIG. 18.

As can be seen from the graph of the desorption / regeneration test in FIG. 17 , water (H ₂ O) begins to desorb (release). When the temperature reaches 200 to 230 ° C, SO ₂ is gradually desorbed,
Desorption decreases gradually at a peak of 330 to 340 ° C, and desorption is almost completed at 400 ° C. Therefore, normal SO
It can be said that desorption of the activated carbon having adsorbed ₂ is complete at 400 ° C. or higher.

FIG. 18 shows that since the exhaust gas temperature is 115 ° C., which is low, water (H ₂ O) is adsorbed excessively.
Desorption of ₂ O component reaches a peak at around 200 ° C.
When ℃ the SO ₂ becomes more starts desorbed, it can be seen that in desorption (release) of H _{2 O} in an amount commensurate with the SO _2.

19 and 20 are plots of the generation states of NH3 and N2. 19 corresponds to FIG. 17, and FIG. 20 corresponds to FIG. NH3 reacts with SO2 and NOX in the adsorption tower and is adsorbed on the activated carbon in the form of ammonium salt and ammonia. The ammonium salt and ammonia are finally decomposed into N2 and H2O, but undecomposed NH3 remains as shown in FIGS. 19 and 20. Most of NH3 is decomposed, but the undegraded state is shown in FIGS. If the desorbed gas is washed with the undecomposed NH3, the amount of nitrides in the water increases and the water treatment becomes complicated. Furthermore S
There is a problem such that O2 is dissolved in the water and SO2 is reduced. How to reduce undecomposed NH3 is about 200 to 1,000 pp in SO2 concentration in conventional pulverized coal-fired boilers.
It was a technical problem to be solved for m. As one example, the countercurrent type desorption tower of FIG. 24 is designed to reduce the generation of undecomposed NH3 and prevent NH3 from being emitted from the outlet of the desorption tower.

That is, in the cocurrent desorption column (FIG. 23 ), the NH ₃ concentration in the desorbed gas is 300 to 8000 ppm (Table 1), and the NH ₃ concentration in the countercurrent system is 2 to 10 ppm. The degree is (Table 2). Thus, how to reduce undecomposed NH ₃ has been a problem of the conventional technology.

[0007]

[Table 1]

[0008]

[Table 2]

[0009]

The desorption method according to the present invention consists in decomposing dioxin adsorbed on activated carbon in a desorption tower, and ammonium salt adsorbed on activated carbon.
It is an object of the present invention to provide a method of increasing the concentration of (for example, NH ₄ (H) SO ₄ ) higher than the conventional ammonia concentration with respect to the SO ₂ concentration and conversely increasing the undecomposed ammonia concentration.

[0010]

[Means for Solving the Problems] SO in the flue of the adsorption tower
Corresponds to the total of ₂ and NO concentrations multiplied by the reaction rate
Normal NH ₃ injection concentration than injecting the excess NH _3, the regenerator
SO ₂ by increasing undecomposed ammonia in
Dioxin is decomposed at the same time as desorption
A method for desorption of activated carbon having adsorbed ioxin, which is an airlock device that allows activated carbon to pass through but not air through the desorption tower. The activated carbon is heated at a temperature of 350 ° C or higher for 1 hour or more, and is not decomposed into activated carbon. In the presence of NH ₃ ,
Dioxins were decomposed from the time when SO ₂ desorption was approaching the end. Also, the desorption tower is preferably a parallel flow type,
A countercurrent type may be used, and it can be performed with or without a carrier gas.

[0011]

BEST MODE FOR CARRYING OUT THE INVENTION S
O ₂ is contained at 0 to 50 ppm and NO is contained at 60 to 120 ppm. In the conventional NH ₃ injection concentration, the total amount of SO ₂ concentration + NO concentration × reaction rate (depending on temperature) is usually set as the maximum injection amount. However, in the present invention, since the adsorbed dioxin is decomposed while desorbing SO ₂ in the desorption tower, the dioxin can be decomposed at a low temperature by intentionally increasing the concentration of undecomposed ammonia. Is.

FIG. 1 shows waste incinerator conditions (SO ₂ = 50 ppm,
The desorption / regeneration test results of SO ₂ adsorbed at NO = 100 ppm and temperature = 140 ° C. are shown. S in the exhaust gas from the refuse incinerator
Since the amount of O ₂ is small, the exothermic heat of the activated carbon is hardly seen.
Therefore, there is a feature that a large amount of water is adsorbed. This is Figure 1
7 is similar to the tendency for SO _{2 at} 500 ppm at 115 ° C.

FIG. 2 shows the result of the desorption / regeneration test at a temperature of 115 ° C. In any case, SO ₂ is released after desorption of water, and two peaks appear. ₃ and 4 show graphs showing desorption of NH ₃ component, and FIGS. 5 and 6 show the relationship between N ₂ and NH ₃ corresponding to SO ₂ . 7 and 8 show the state of undecomposed NH ₃ . Thus, obviously undecomposed NH ₃ appears after the SO ₂ desorption peak has passed.

Decomposition of dioxin occurs from the time when the SO ₂ desorption peak has passed. Since the desorption peak temperature is 330 to 340 ° C. as is clear from FIG. 7 or FIG. 8, it was found that the desorption peak temperature is decomposed after passing 350 ° C. That is, in order to decompose dioxin, it is necessary to add NH ₃ in excess and increase the concentration of undecomposed NH ₃ .

(Function) Excessive NH ₃ is injected into the flue of the adsorption tower to increase the amount of undecomposed ammonia in the desorption tower, thereby decomposing SO ₂ and decomposing dioxin. To do. In addition, an air lock device is used above and below the desorption tower to pass activated carbon but not air. Desorption of SO ₂
Up to a temperature of 350 ° C., physically adsorbed NH ₃ is decomposed to N ₂ , and then ammonium salt is desorbed and decomposed to release SO ₂ , N ₂ and H ₂ O.

Then, the temperature reaches 330 to 340 ° C., and 35
When the temperature becomes 0 ° C. or higher, the desorption decomposition continues, but the desorption tower has a completely reducing atmosphere. That adsorbed _{O 2,} taken CO or CO ₂ or the like, because consumes _{O 2} (Fig.
9 and FIG. 10 ). Further, as a gas other than NH ₃ , H is
₂ , H ₂ S, etc. are several ppm to several tens of ppm, and the surface of activated carbon is -N
The atmosphere is of a basic compound such as H, —NH ₂ .
Since these concentrations and atmosphere correlate with the concentration of excessive NH ₃ , it was decided to decompose dioxin at the same time as desorption of SO ₂ using undecomposed NH ₃ as an index.

FIG. 11 shows the correlation between the NH ₃ concentration in the desorbed gas of the waste incinerator exhaust gas and the H ₂ S, H ₂ concentrations of other components. That is, FIG. 11 shows that the H ₂ S and H ₂ concentrations in the desorbed gas are high during the NH ₃ excess operation. Further, FIG. 12 shows the relationship between the desorption temperature and the H ₂ generation concentration with the injection ratio (NH ₃ injection ratio) at the adsorption tower inlet as a parameter.
It can be seen that the H ₂ generation concentration is high when NH ₃ / SO ₂ = 1. The amount of NH ₃ injection for waste incineration is NH ₃ = C (SO ₂ ) × η (SO ₂ ) + C (NO) × η (NO)
Since + C (HCl) × η (HCl) + physical adsorption amount, NH ₃ / SO ₂ = 1 or more in the above formula. Where C ()
Indicates the concentration, and η () indicates the reaction rate. That is, a large amount of NH ₃ is put in, NH ₃ is decomposed in the desorption tower, a large amount of H ₂ concentration is generated, and dioxin is decomposed by this H ₂ concentration.

FIG. 13 shows the decomposition rate of the dioxin adsorbed at the actually measured concentration as a parameter with the desorption temperature according to the form. That is, in the dioxins and dibenzo furans easily decomposed towards dibenzo furan, also better Cl molecule is large it indicates that tends to decompose. This means that the oxygen bridge is 1 rather than 2
It is shown that K is more likely to be decomposed, and that the decomposition is progressing from the one having a large amount of Cl molecules to the one having a smaller amount of Cl molecules. That is, it indicates that destruction of the oxygen bridge (see FIG. 25 ) and dechlorination (see FIG. 26 ) have occurred. Further, as described above, the desorption temperature is the base of the present invention to make the state of NH ₃ excess → H ₂ concentration high, and the efficiency of dioxin decomposition is 500 ° C.> 400 ° C.> 350 ° C. in this order. Has become.

FIG. 14 shows the total decomposition rate of the measured concentrations,
FIG. 15 shows the decomposition rate at the toxic equivalent concentration. In any case, the dioxin can be decomposed at a low temperature by setting the activated carbon temperature at 350 ° C. or higher for 1 hour or longer by making the desorption column the reducing atmosphere of O ₂ 1% or lower. The results of the decomposition rate in the actual shown in FIG.

[0020]

According to the desorption method of the present invention, since SO ₂ is desorbed and dioxin is decomposed in the desorption tower, the activated carbon is circulated without incineration after treatment as in the conventional case. It is now possible to use.

[Brief description of drawings]

FIG. 1 is a graph showing a desorption retest (SO ₂ = 50 ppm,
NO = 100 ppm, temperature = 140 ° C.).

FIG. 2 is a graph showing the results of a desorption regeneration test at a temperature of 115 °.

FIG. 3 is a desorption regeneration test graph including a graph showing desorption of NH ₃ components.

FIG. 4 is a desorption regeneration test graph including a graph showing desorption of NH ₃ components.

FIG. 5 is a desorption regeneration test graph showing the relationship between N ₂ and NH ₃ corresponding to SO ₂ .

FIG. 6 is a desorption regeneration test graph showing the relationship between N ₂ and NH ₃ corresponding to SO ₂ .

FIG. 7 is a desorption / regeneration test graph showing the relationship between the decomposition of dioxin and NH ₃ .

FIG. 8 is a desorption / regeneration test graph showing the relationship between the decomposition of dioxin and NH ₃ .

FIG. 9 is a desorption regeneration test graph (exhaust gas temperature = 140 ° C.) for explaining that the inside of the desorption tower is in a reducing atmosphere.

FIG. 10 is a desorption regeneration test graph (exhaust gas temperature = 115 ° C.) for explaining that the inside of the desorption tower is in a reducing atmosphere.

FIG. 11 is a correlation diagram showing the relationship between the NH ₃ concentration and the H ₂ S and H ₂ concentrations in the desorbed exhaust gas.

FIG. 12 is a correlation diagram showing the relationship between the desorption temperature and the H ₂ generation concentration with the injection ratio as a parameter.

FIG. 13 is a dioxin desorption decomposition test result graph showing the decomposition rate with the desorption temperature of each dioxin as a parameter.

FIG. 14 is a desorption decomposition test result graph showing the total decomposition rate of measured concentrations.

FIG. 15 is a dioxin desorption decomposition test result graph showing the decomposition rate at a denaturing equivalent concentration.

FIG. 16 is a graph showing the result of decomposition rate in an actual machine.

FIG. 17: SO ₂ of 500 ppm at an exhaust gas temperature of 140 ° C.
Graph showing the gas occurrence of desorption in the column when the NH ₃ adsorbed to 250 ppm.

FIG. 18 is a graph showing a state of desorption when adsorbed at an exhaust gas temperature of 115 ° C.

FIG. 19 is a graph showing a state of generation of NH ₃ and N ₂ corresponding to FIG.

FIG. 20 is a graph showing the generation status of NH ₃ and N ₂ corresponding to FIG.

FIG. 21 is a graph illustrating a place where undecomposed NH ₃ remains.

FIG. 22 is a graph explaining the remaining portion of undecomposed NH ₃ .

FIG. 23 is a block diagram of a parallel flow type desorption tower.

FIG. 24 is a block diagram of a countercurrent desorption tower.

FIG. 25 is a chemical formula describing the destruction of the oxygen bridge.

FIG. 26 is a chemical formula for explaining desalination.

Continuation of front page (51) Int.Cl. ⁷ Identification code FI B01D 53/81

Claims (2)

(57) [Claims] 1. SO ₂ concentration and NO in the flue of the adsorption tower.
Usually NH ₃ Note that correspond to the total amount obtained by multiplying the reaction rate on the concentration
NH ₃ in excess of the input concentration was injected, and undecomposed in the desorption tower.
Simultaneously with SO ₂ desorption by increasing the ammonia
Dioxin that is designed to decompose dioxin
A method for desorbing the adsorbed activated carbon, wherein an air-lock device that allows activated carbon to pass through but not air through the desorption column is used, and at least the activated carbon temperature is heated to 350 ° C. or higher for 1 hour or more, and undecomposed NH in the activated carbon is used. _A method for desorbing dioxin-adsorbed activated carbon in a waste incinerator exhaust gas treatment apparatus, characterized in that ₃ is present, and dioxin is decomposed when SO ₂ desorption approaches the end. 2. The desorption of activated carbon adsorbing dioxin in a waste incinerator exhaust gas treatment apparatus according to claim 1, wherein the desorption tower is a parallel flow type or a counter flow type, and it does not matter whether or not there is a carrier gas. Method.