JP3358912B2 - Flue gas treatment system - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flue gas treatment system, and more particularly to a flue gas treatment system capable of easily removing and detoxifying dust and selenium (Se) in flue gas containing dust and Se components. About.

[0002]

2. Description of the Related Art Conventionally, a flue gas treatment system installed in a thermal power plant or the like includes a dust collector (usually an electric dust collector) for removing dust such as fly ash from flue gas, and a sulfur dioxide gas in flue gas. Although a flue gas treatment system provided with a flue gas desulfurization device that absorbs gas has become widespread, handling of harmful impurities other than sulfur oxides contained in flue gas has recently become a problem.
In particular, in a flue gas treatment system for a coal-fired boiler, the harmfulness of selenium (Se) contained in coal at a content of up to about 10 mg / kg has recently become a problem, and it has become harmless to treat. Is desired.

[0003] Se is insoluble by a treating agent.
Easy tetravalent Se (main form: SeO2 selenite)_Three ^2-)
And hexavalent Se which is difficult to insolubilize (main form: selenic acid
SeO _Four ^2-), And hexavalent Se in particular has a solubility of
High (soluble at 20 ° C. 95%) and easy to elute. Also,
This Se has toxicity similar to arsenic compound,
There are cases of obstacles and emission regulations.
Environmental standards (0.01 mg / lit.)
), Wastewater standard (0.1mg / liter), landfill disposal
Elution standard (0.3mg / l) has been established
I have.

FIG. 7 shows a conventional example of this type of flue gas treatment system (an example of a flue gas treatment system for a coal-fired boiler). In FIG. 7, the flue gas A emitted from the coal-fired boiler 1 is supplied to a denitration device 2 provided downstream of the boiler 1 in this case.
After removing nitrogen oxides (NOx) and passing through the air heater 3 and the heat recovery unit 4 of the gas gas heater (GGH),
The dust is introduced into the electric dust collector 5 (EP) to remove dust such as fly ash. Next, the flue gas is guided to a wet flue gas desulfurization unit 7 by a fan 6, the sulfur dioxide gas is removed in the desulfurization unit 7, and the gas passes through a reheating unit 8 of a gas gas heater (GGH). The chimney 10 is guided and released into the atmosphere. Then, the dust such as fly ash removed by the electric dust collector 5 is discharged from a plurality of hoppers 5a (dust collecting units) formed in the electric dust collector 5, and is collectively conveyed and collected by the conveyor 11. It has become. The dust B thus collected is reused, for example, as a raw material for cement or the like, or is discarded in an ash dump.

[0005] Here, the desulfurization unit 7 is provided with, for example, an absorption tower into which flue gas is introduced, and in this absorption tower, the flue gas and an absorbent slurry (usually a calcium compound-containing slurry).
Is a wet type that absorbs sulfurous acid gas in flue gas by contacting with gypsum, and usually produces gypsum as a by-product from slurry in an absorption tower. Further, the heat recovery unit 4 of the gas gas heater (GGH) may be disposed immediately before the desulfurization device 7 as shown in FIG.

[0006]

In the above-mentioned conventional flue gas treatment system, Se in coal (Se in flue gas) is used.
Is condensed on the downstream side of the air heater 3 or the like (that is, at a position before being introduced into the electrostatic precipitator 5), is removed by the electric precipitator 5 in a state of being contained in the dust in the smoke exhaust, and remains as it is. It will be mixed in the waste at the dump site or in the cement raw material. Therefore, in order to detoxify Se by observing the elution standard and the like, it is necessary to perform a troublesome and costly post-treatment such as diluting the ash removed by the electrostatic precipitator 5 with, for example, a large amount of water. There was a problem of becoming.

The present invention has been made in view of the above circumstances, and has as its object to provide a flue gas treatment system capable of easily removing and detoxifying Se components contained in flue gas.

[0008]

SUMMARY OF THE INVENTION The present invention relates to (1) a flue gas treatment system for treating flue gas containing dust and Se components, comprising a cooling means for cooling the flue gas to 350 ° C. or less, and a flue gas. A dust collecting means for separating the dust in the dust, and adding water and a treating agent to the dust separated by the dust collecting means to remove S in the dust.
and (2) a flue gas treatment system for treating flue gas containing dust and Se components, which comprises: a Se treatment means for converting an existing form of e into an insoluble compound. A cooling means for cooling the flue gas to 350 ° C. or lower, a dust collecting means for separating dust in the flue gas, and adding water and a treating agent to the dust separated by the dust collecting means to add Se to the dust in the dust. Exhaust gas treatment comprising: Se treatment means for converting an existing form of the compound into an insoluble compound; and solid-liquid separation means for solid-liquid separation of a slurry containing the insoluble Se compound coming out of the Se treatment means. System.

As preferred embodiments of the present invention, there are the following (3) to (6) flue gas treatment systems. (3) The dust collecting means is provided with a plurality of collecting sections for separating and collecting the dust from the smoke exhaust inlet side toward the outlet side, and the dust collected from the smoke exhaust inlet side collecting section is provided. And the dust collected from the outlet side are separately separated and collected, and only the dust collected at the outlet side is introduced into the Se processing means. (1)
Or the smoke exhaust treatment system of (2).

(4) Classifying means for classifying the dust separated by the dust collecting means into a large particle size and a small particle size is provided, and only the small particle size dust classified by the classifying device is provided. And (2) the flue gas treatment system according to the above (1) or (2), wherein the gas is introduced into the Se treatment means to perform Se insolubilization treatment.

(5) Mixing means for mixing the dust subjected to the Se insolubilization treatment by the Se treatment means and the remaining dust not subjected to the Se insolubilization treatment at a ratio such that the water content is 20% or less is provided. The flue gas treatment system according to (3) or (4), characterized in that:

(6) The flue gas treatment system according to (5), further comprising an agglomerating means for forming the dust mixed by the mixing means into a lump.

In the flue gas treatment system of the present invention, Se
The method of performing the insolubilization treatment can take various forms, but water is added to the dust containing the Se component separated and collected by the dust collecting means to form a slurry, and a treating agent is added to the slurry to remove Se. A method of solid-liquid separation after insolubilization, or spraying a solution of the treating agent on the dust to uniformly penetrate
A typical example is a method of insolubilizing e.

[0014]

According to the flue gas treatment system of the present invention, Se in the flue gas
Is cooled and condensed by the cooling means, and is removed by the dust collecting means while being contained in the dust. And
A processing agent is added to the dust separated by the dust collecting means in the Se processing means, and the presence form of Se in the dust is converted into an insoluble compound. For this reason, even if the dust is disposed of in the same manner as in the related art, the leaching standard of Se and the like are satisfied, and the detoxification of Se can be easily achieved without complicated post-processing.

Further, only the dust separated and collected from the specific collecting section on the outlet side of the flue gas in the dust collecting means is subjected to Se insolubilization treatment, so that the required amount of the processing agent and the capacity of the Se processing means are reduced. It is possible to make the harmlessness of Se easier and cheaper. That is, according to the inventors' research,
It has been found that a larger amount of Se is contained (attached) to dust (ash) having a smaller particle diameter separated and collected from a specific recovery section on the outlet side. Even if only the insolubilization treatment is applied to the
e can be rendered harmless.

Further, for the same reason, only the small-particle-size dust classified by the classification means is subjected to Se insolubilization treatment, so that the required amount of the processing agent and the capacity of the Se processing means can be reduced, and the harmlessness of Se can be reduced. It becomes easier and more economical.

In the case of an apparatus in which only part of the dust is subjected to the Se insolubilization treatment, a mixing means is further provided so that the Se insolubilized dust and the remaining non-Se insolubilized dust have a water content Can be easily reduced to reduce the water content of the dust without providing large-scale equipment such as a solid-liquid separator which requires drainage (filtrate) treatment or the like. This makes it easier to handle dust in the disposal process.

Further, by providing the agglomerating means for forming the dust mixed by the mixing means into a lump, handling of the dust in disposal processing or the like is further facilitated.

In the flue gas treatment system of the present invention, Se contained in the flue gas is separated from the flue gas together with the dust, and is rendered harmless by further insolubilization. Flue gas which is removed dust containing Se content is rendered harmless by further including removing the SO ₂ is guided to a wet flue gas desulfurization apparatus is subjected to appropriate treatment by conventional methods, released into the atmosphere Is done.

[0020]

Embodiments of the present invention will be described below with reference to the drawings. (Embodiment 1) FIG. 1 is a schematic explanatory view showing a configuration of a smoke exhaust passage section of a first example of a smoke exhaust treatment system of the present invention, and FIG. 2 is a main configuration of the smoke exhaust treatment system. FIG. As shown in FIG. 1, the flue gas treatment system is provided with a cooling device 21 (cooling means) for cooling the flue gas A emitted from the coal-fired boiler 20 and a flue gas A disposed downstream of the cooling device 21. An electric precipitator 22 (dust collecting means, classifying means) for collecting dust such as fly ash therein and separating it from flue gas, and a wet type for discharging flue gas (with dust removed) discharged from the electric precipitator 22. A fan 23 for supplying to a post-process such as a smoke desulfurization device. As shown in FIG. 2, a dust conveyor 24 and a Se treatment device 25 for performing Se insolubilization treatment are provided on the dust discharge side of the electric dust collector 22.
(Se treatment means) and a solid-liquid separation device 26 for solid-liquid separation of the dust slurry subjected to the Se insolubilization treatment are sequentially provided. This system can be incorporated in, for example, the conventional flue gas treatment system shown in FIGS. 7 and 8 and connected to a desulfurization device that removes sulfur dioxide from the flue gas sent by the fan 23. It goes without saying that a conventional air heater or gas gas heater can also function as the cooling device 21.

The cooling device 21 is provided, for example, to set the outlet gas temperature to 1
It can be set within the range of 50 to 400 ° C.
The temperature may be set so that the exhaust gas is cooled to a temperature at which e is sufficiently condensed. Specifically, the smoke emission is 350 ° C.
Hereinafter, the temperature is set so that the temperature is preferably cooled to 310 ° C. or less. The lower limit of the cooling temperature is not particularly limited, but is practically about 90 ° C. The electric precipitator 22 has a plurality of hoppers 31 to 34 (collection unit) for separating and collecting dust, and these hoppers 31 to 34 move from the smoke smoke inlet side (upstream side) to the outlet side (backstream side). With such a configuration, dust having a larger particle diameter is collected from the hopper on the inlet side, and dust having a smaller particle diameter is collected from the hopper on the outlet side. . Conveyor 24
In this case, the respective dusts B1 to B4 collected and discharged from the hoppers 31 to 34 of the electric dust collector 22 are collectively transported to one place (to the Se processing device 25) in this case.

In this case, the Se treatment device 25 has a function of adding a liquid such as water to the dust to form a slurry, and adding a treating agent C thereto and mixing the slurry. For example, the Se treatment device 25 includes a repulp tank for slurrying, The mixing tank for adding and mixing the agent C may be provided separately, or a single tank structure in which these are performed in one tank may be used. Here, as the treatment agent C, an agent that reacts with Se and is insolubilized is required, and the agent S to be removed is required.
e is at least tetravalent Se (main form: selenite S
eO ₃ ^2- ), for example, FeCl ₃ or Fe
₂ (SO ₄ ) ₃ can be used.

When hexavalent Se (main form: SeO ₄ ²⁻ ) is present in the flue gas and needs to be insolubilized in order to meet the elution standard, etc., A reducing agent (for example, Na ₂ SO ₃ ) for converting this hexavalent Se into tetravalent Se and the above-mentioned agent may be added. In this case, a tank that performs only the reduction reaction for converting hexavalent Se into tetravalent Se as pretreatment may be provided separately from the mixing tank as a configuration of the Se treatment device 25. In the case where it is necessary to repulp dust in the Se treatment device 25, circulating water of a desulfurization device can be used as the solvent. The amount of the treatment agent C to be introduced is determined by the stoichiometric equivalent for insolubilizing the whole amount of Se in the dust by the reaction (reaction formula (1), (2) or (3), (4)) described later. May be set slightly higher.

In the flue gas treatment system configured as described above, the dust removal treatment and the detoxification treatment of Se contained in a large amount in the dust are performed as follows.
That is, the flue gas A leaving the boiler 20 is
At the downstream side of the cooling device 21, at least on the downstream side of the cooling device 21, Se in the flue gas is condensed and most of the Se adheres to the ash constituting the dust in the flue gas. Then, the dust is separated and collected by the electric dust collector 22, and in this case, all the separated and collected dust is conveyed to the conveyor 24.
Are collectively introduced into the Se processing device 25.

In the Se processing device 25, the introduced dust is
Slurried repulp (hereinafter referred to as dust slurry)
Containing tetravalent Se (main form: SeO2 selenite)_Three
^2-) Is the treating agent C (FeCl_ThreeOr Fe_Two(S
O_Four)_Three) And the following reaction formula (1), (2) or (3),
By causing the reaction shown in (4), iron selenite (Fe_Two
(SeO _Three)_Three) And become insoluble. The hexavalent Se
(Main form: SeO selenate_Four ^2-) Is present
Has a reducing agent as described above,
Hexavalent Se reacts with the reducing agent to become tetravalent Se
Later, the following reaction formula (1), (2) or (3),
The reaction shown in (4) occurs to insolubilize.

Embedded image FeCl ₃ → Fe ³⁺ + 3Cl ⁻ (1) 2Fe ³⁺ + 3SeO ₃ ^2- → Fe ₂ (SeO ₃ ) ₃ ↓ (2) or Fe ₂ (SO ₄ ) ₃ → 2Fe ³⁺ + 3SO ₄ ^2- (3) 2Fe ³⁺ + 3SeO ₃ ^2- → Fe ₂ (SeO ₃ ) ₃ ↓ (4)

Therefore, in the solid-liquid separation device 26, Se
When the insolubilized dust slurry is subjected to solid-liquid separation, most Se is separated on the solid phase side as iron selenite,
The dust cake D discharged from the solid-liquid separation device 26 is insolubilized and mixed. Therefore, even if the dust cake D is directly discarded in the ash dump, the elution standard and the like can be satisfied. The filtrate E from the solid-liquid separation device 26 is Se
Since the concentration is extremely low, it can be easily treated for wastewater treatment, or can be used as additive water for dust slurry formation or returned to the desulfurization unit as circulating water for absorbent slurry in the desulfurization unit.

Next, the results of a smoke exhaust treatment experiment performed by the experimental apparatus having the configuration shown in FIGS. 1 and 2 will be described. The experiment was 3 mg / k
g of coal containing Se at 25 kg / h to the combustion furnace,
150 m ³ N / h of flue gas discharged from the furnace
After cooling to ℃, it was introduced into an electric precipitator. In this case, 99% or more of the dust is collected by the electric dust collector (S
e collection rate of about 99.4%), and the amount of dust collected by the conveyor (total amount collected from each hopper) is 3.4 kg / h.
Met. Then, the dust (B
As a result of analyzing the Se concentration in 1 to B4) by an elution test according to the Environment Agency Notification No. 13 and an atomic absorption method by a hydrogen compound generation method, the concentration (Se contained in the dust and eluted by the elution test) was determined. Was 0.33 mg / liter, which exceeded the dissolution standard for landfill disposal (0.3 mg / liter). However, after adding the treating agent C (using FeCl ₃ ) in the Se treating device 25 and mixing for 30 minutes, the solid-liquid side (the dust cake D) and the liquid phase Se on the side (filtrate E)
The results of measuring the concentration are as shown in Table 1, which sufficiently satisfied the elution standard (0.3 mg / liter). That is, the concentration of the eluted Se on the solid phase side (the amount of Se contained in the solid phase and eluted by the elution test) is 0.04 to 0.1 mg.
/ L, and the eluted Se concentration on the liquid phase side is 0.0
It was 1 mg / liter or less.

[0028]

[Table 1]

As described above, according to the flue gas treatment system of this embodiment, Se in the flue gas is removed together with the dust without performing complicated post-processing as in the prior art. It can be insolubilized and present in the dust cake D and can be disposed of as it is. Moreover, in this smoke exhaust treatment system, the system of the present invention can be incorporated by adding only the Se treatment device 25 and the solid-liquid separation device 26 to the conventional smoke exhaust treatment system shown in FIGS. A smoke exhaust system can be configured, Se in smoke can be made harmless, existing smoke exhaust systems can be easily modified, and even if this system is newly installed, the conventional design or equipment can be used. There is also an effect that can be used as it is.

(Embodiment 2) FIG. 3 is a schematic explanatory view showing the configuration of a second embodiment of the smoke exhaust treatment system of the present invention. Note that the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted. As shown in FIG. 3, this smoke exhaust treatment system removes only dust B3 and B4 separated and recovered from specific hoppers 33 and 34 on the smoke exhaust outlet side among a plurality of hoppers 31 to 34 in the electrostatic precipitator 22. , Se treatment device 25, and a conveyor 42 for transporting dust B1 and B2 separated and collected from specific hoppers 31 and 32 on the smoke exhaust inlet side separately from dust B3 and B4. Then, it is characterized in that only some of the dusts B3 and B4 are subjected to Se insolubilization treatment, and the remaining dusts B1 and B2 are discarded. In addition, the electric dust collector 22 in the present embodiment functions as dust collecting means and classifying means of the present invention.

In this case, only the dusts B3 and B4 separated and collected from the specific hoppers 33 and 34 on the outlet side of the flue gas are subjected to the Se insolubilization treatment, so that the required amount of the treatment agent C and the Se
There is an inherent effect that the capacity and the like of the processing device 25 can be reduced, and the detoxification of Se can be made easier and at lower cost. In other words, according to the study of the inventors, it was found that the Se (dust) contained in the dust (ash) having a smaller particle diameter separated and recovered from the specific recovery portion on the outlet side contained a larger amount of (sediment). Even if only the dust having a small particle size is subjected to the insolubilizing treatment, Se can be made harmless as a whole, which has an effect of reducing equipment costs and operating costs.

Next, the results of an exhaust gas treatment experiment performed by the experimental apparatus having the configuration shown in FIG. 3 will be described. In the experiment, coal containing 3 mg / kg of Se was supplied to the combustion furnace at 25 kg / h, and 200 m ³ N / h of flue gas discharged from the combustion furnace was cooled to 150 ° C. and introduced into the electric dust collector. Was. In this case, 99% or more of the dust is collected by the electric dust collector (Se collection rate: about 99.4%), and the amount of dust collected by the conveyor (total amount collected from each hopper) is 3.4 kg /. h. Then, the carry-out amount, the average particle size, and the dissolved Se concentration of the dust (collected ash) conveyed and collected by each of the conveyors 41 and 42 (Se contained in the collected ash and dissolved by the dissolution test described above)
Min) were as shown in Table 2.

[0033]

[Table 2]

That is, the hoppers 33, 3 on the exhaust gas outlet side
Of the dusts B3 and B4 separated and recovered from the sample No. 4 is 1.
It is as low as 14 kg / h, but the eluted Se concentration is 0.49 mg.
Per liter, which was much higher than the standard. However, the dust B collected and separated from the hoppers 31 and 32 on the side of the smoke exhaust
1, B2 had a large carry-out amount of 2.27 kg / h, but the eluted Se concentration was as low as 0.20 mg / liter, lower than the standard. Therefore, it can be seen that the dusts B1 and B2 separated and collected from the hoppers 31 and 32 on the smoke exhaust inlet side can be directly discarded. In other words, since the Se insolubilization of the dust on the inlet side of the flue gas, which is about twice as large, is not required, it is clear that the required amount of the processing agent C and the capacity of the Se processing device 25 can be significantly reduced.

The difference in the concentration of the eluted Se is as follows.
It is thought to be due to the particle size of the dust (ash). That is, when gaseous Se (SeO ₂ ) is condensed and adheres to the surface of the ash constituting the dust, the ash having a small particle diameter has a large specific surface area per unit weight, so that more Se adheres. become. On the other hand, in a dust removing device such as an electric dust collector as described above, coarse ash is easily collected at the smoke exhaust inlet side and fine ash is easily collected at the smoke exhaust outlet side. Therefore, it is considered that the concentration of eluted Se in the dust collected on the outlet side of the flue gas increases.

Then, the hoppers 33 and 34 on the exit side of the smoke exhaust
The dusts B3 and B4 separated and recovered from the conveyor are introduced into the Se treatment device 25 by the conveyor 41, and the treatment agent C (FeCl ₃
Is added and mixed for 30 minutes, and after the solid-liquid separation in the solid-liquid separator 26, the Se concentration on the solid phase side (dust cake D) and the liquid phase side (filtrate E) is measured. As a result, the measured values shown in Table 3 were obtained, and the elution standard (0.3 mg /
Liters). That is, the concentration of the eluted Se on the solid phase side (the amount of Se contained in the solid phase and eluted by the elution test) is 0.05 to 0.09 mg / liter, and the concentration of the eluted Se on the liquid phase side is all 0.1. It was not more than 01 mg / liter. Tables 4 and 5 show a comparison of the amount of the treating agent when the slurry concentration and the treating agent (FeCl ₃ ) concentration were the same for Examples 1 and 2. It can be seen that it has decreased to / 3.

[0037]

[Table 3]

[0038]

[Table 4]

(Embodiment 3) FIG. 4 is a schematic explanatory view showing the configuration of a third example of the smoke exhaust treatment system of the present invention. Note that the same components as those in the first embodiment are denoted by the same reference numerals and description thereof is omitted. As shown in FIG. 4, the smoke exhaust treatment system includes dusts B <b> 1 to B <b> 4 collected by an electric dust collector 22 and conveyed collectively by a conveyor 24.
Classifier 51 (classifying means) for classifying into a large particle size (hereinafter referred to as coarse ash) B5 and a small particle size (hereinafter referred to as fine ash) B6. Only the fine ash B6 collected is collected by the fine particle collecting device 52 and
It is configured to be introduced into the e-processing device 25 to perform the Se insolubilization process. In this case, the dusts B1 to B4 conveyed collectively by the conveyor 24 are conveyed by air F and are classified by the classifier 5
1 is adopted. In addition, the classification device 51
Is convenient if it can be composed of, for example, a cyclone and the classification can be adjusted. Further, in this case, a bag filter is used as the fine particle collecting device 52.

In this case, only the fine ash B6 is subjected to the Se insolubilization treatment, so that the necessary amount of the treatment agent C and the capacity of the Se treatment device 25 can be reduced as in the second embodiment, and the harmlessness of Se can be reduced. There is an inherent effect that can be easily and inexpensively made. In this flue gas treatment system, if only the Se treatment device 25 and the like and the classification device 51 and the like are added to the conventional flue gas treatment system shown in FIGS. In this way, a flue gas treatment apparatus incorporating the system of the present invention can be configured, detoxification of Se in flue gas can be achieved, and the existing flue gas treatment system can be easily modified, and this system can be newly installed. Even in this case, there is an effect that the conventional design or equipment can be used as it is.

Next, the results of a smoke exhaust treatment experiment performed by the experimental apparatus having the configuration shown in FIG. 4 will be described. In the experiment, coal containing 3 mg / kg of Se was supplied to the combustion furnace at 25 kg / h, and 200 m ³ N / h of flue gas discharged from the combustion furnace was cooled to 150 ° C. and introduced into the electric dust collector. Was. In this case, 99% or more of the dust is collected by the electric dust collector and the amount of dust collected by the conveyor (total amount collected from each hopper)
Was 3.4 kg / h. The amounts of coarse ash B5 and fine ash B6 collected, the average particle size, and the dissolved Se concentration (the amount of Se contained in the collected ash and dissolved by the dissolution test) are as shown in Table 5. Was.

[0042]

[Table 5]

That is, the fine ash B6 has an average particle size of 5.
4 μm and the collection amount is as small as 1.30 kg / h.
The eluted Se concentration was 0.36 mg / liter, exceeding the standard. However, the coarse ash B5 had an average particle size of 13 μm and a trapped amount of 2.05 kg / h, but the eluted Se concentration was as low as 0.26 mg / l, which was lower than the standard.
Therefore, it is understood that the coarse ash B5 can be discarded as it is. In other words, the amount of coarse ash B5,
eSince the insolubilization treatment is not required, the necessary amount of the treatment agent C and the amount of S
It is clear that the capacity and the like of the e-processing device 25 can be remarkably reduced.

Then, the fine ash B6 is supplied to the Se treatment device 25.
After adding the treating agent C and mixing for 30 minutes,
The results of measuring the Se concentrations on the solid phase side (dust cake D) and the liquid phase side (filtrate E) after the solid-liquid separation in the solid-liquid separation device 26 are shown in the above-mentioned Table 3 in Example 2. A value equivalent to the value was obtained, which sufficiently satisfied the elution standard (0.3 mg / liter).

(Embodiment 4) FIG. 5 is a schematic explanatory view showing the configuration of a fourth example of the smoke exhaust treatment system of the present invention. Note that the same components as those of the second embodiment shown in FIG. As shown in FIG. 5, the smoke exhaust system includes dust G separated and collected from hoppers 33 and 34 on the outlet side of the exhaust gas, introduced into the Se processing apparatus 25 by the conveyor 41 and subjected to Se insolubilization processing, Dust B1 and B2 separated and recovered from the hoppers 31 and 32 on the inlet side of the
Are mixed at a ratio such that the water content is 20% or less (more preferably, 10% or less). In addition, as a Se treatment means, a liquid containing a treatment agent such as FeCl ₃ or Fe ₂ (SO ₄ ) ₃ (concentration of about 0.5 to 5.0 wt%) is uniformly jetted to the dust, so that Se is treated. Insolubilizing reaction (for example, the reaction formula (1), (2) or (3),
(4) The Se processing device 25a having the configuration that causes the above is used.

In this case, by the mixer 61, Se
The dust G subjected to the insolubilization treatment and the remaining dusts B1 and B2 not subjected to the Se insolubilization treatment are mixed to generate a detoxified dust cake H (mixed ash) having a low water content. For this reason, even if large-scale equipment such as a solid-liquid separator that requires drainage (filtrate) treatment is not provided, the water content of the dust is easily reduced, and the detoxified dust is handled in the disposal treatment and the like. There is an inherent effect that can be easily achieved. In the configuration of the present example, an experiment was performed under the same operating conditions as in Example 2 to measure the water content and the eluted Se concentration of the mixed ash H (Se content contained in the mixed ash and eluted by the elution test). Table 6 shows the results.

[0047]

[Table 6]

(Embodiment 5) FIG. 6 is a schematic explanatory view showing the structure of a fifth embodiment of the exhaust gas treatment system of the present invention. Note that the same components as those of the fourth embodiment shown in FIG. As shown in FIG. 6, this smoke exhaust treatment system is provided with a lump device 71 (lumping means) for compacting the dust H mixed by the mixer 61 to form a lump. In this case, since the lump unit 71 forms the lump dust H (lump ash) by lumping the dust H, the volume of the dust H is reduced, and there is an effect that the handling in the disposal processing and the like becomes easier. . The water content of the dust H was set to 20 by the mixer 61.
% Or less (more preferably 10% or less) has the effect of facilitating the operation of compacting with the bulk device 71. As a result of an experiment conducted under the same operating conditions as in Example 4, the dust cake H mixed by the mixer 61 was obtained.
While the bulk density of the (mixed ash) was 0.8 g / cc, the dust (lumped ash) I
Had a bulk density of 1.5 g / cc.

The present invention is not limited to the embodiment described above, but may have various aspects. For example, as a treatment agent for insolubilizing Se, in addition to FeCl ₃ or Fe ₂ (SO ₄ ) ₃ , a chelating agent (for example, Miyoshi resin EPORAS MX)
-7) or a polymer heavy metal collector (for example, Miyoshi resin Epofloc L-1) or the like can be used. Further, the dust collecting means or the classifying means of the present invention is not limited to the above-described electric dust collector or a single cyclone connected thereto, and for example, the dust collecting means and the classifying means of the present invention may be constituted by a multi-cyclone. Can also. Further, the flue gas treatment system of the present invention can be configured to be incorporated in a part of a flue gas treatment system provided with a conventional desulfurization device. For example, in the first embodiment, a desulfurization device for removing sulfur dioxide from flue gas sent by the fan 23 may be provided, for example, as in the conventional example shown in FIGS.
Further, a conventional air heater or gas gas heater can also function as the cooling means of the present invention.

[0050]

According to the flue gas treatment system of the present invention, most of Se in the flue gas is cooled by the cooling means, condensed, and removed by the dust collecting means while being contained in the dust. And, the dust separated by this dust collecting means,
The processing agent is added by the Se processing means, and S in the dust is added.
e is converted to an insoluble compound. For this reason, even if the dust is disposed of in the same manner as in the related art, the leaching standard of Se and the like are satisfied, and the detoxification of Se can be easily performed without performing complicated post-processing.

If only the dust separated and collected from the specific collecting section on the outlet side of the flue gas in the dust collecting means is subjected to Se insolubilization treatment, the required amount of the processing agent and the capacity of the Se processing means can be reduced. Detoxification of Se can be performed more easily and economically.

If only the small-particle-size dust classified by the classifying means is subjected to Se-insolubilizing treatment, the necessary amount of the treating agent and the capacity of the Se treating means can be reduced, and the detoxification of Se is made easier and more economical. Can be done

A mixing means is provided to mix the Se-insolubilized dust with the remaining Se-insolubilized dust.
If the mixing is performed so that the water content is 20% or less, the water content of the dust can be easily determined without providing a large-scale device such as a solid-liquid separator that requires drainage (filtrate) treatment. Can be reduced, and handling in dust disposal processing or the like can be facilitated.

If the agglomerated means is provided and the dust mixed by the mixing means is formed into a lump, handling of the dust in disposal processing or the like is further facilitated.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing a configuration of a smoke exhaust passage section of a smoke exhaust treatment system according to a first embodiment.

FIG. 2 is a schematic explanatory view showing a main configuration of the smoke exhaust treatment system of FIG. 1;

FIG. 3 is a schematic explanatory view showing a configuration of a smoke exhaust treatment system according to a second embodiment.

FIG. 4 is a schematic explanatory diagram showing a configuration of a smoke exhaust treatment system according to a third embodiment.

FIG. 5 is a schematic explanatory view showing a configuration of a smoke exhaust treatment system according to a fourth embodiment.

FIG. 6 is a schematic explanatory view showing a configuration of a smoke exhaust treatment system according to a fifth embodiment.

FIG. 7 is a schematic explanatory diagram showing the configuration of an example of a conventional smoke exhaust treatment system.

FIG. 8 is a schematic explanatory diagram showing the configuration of another example of a conventional smoke exhaust treatment system.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 21 Cooling apparatus (cooling means) 22 Electric dust collector (dust collecting means, classification means) 25, 25a Se processing apparatus (Se processing means) 31-34 Hopper (recovery part) 51 Classification apparatus (classification means) 52 Fine powder collection apparatus 61 Mixer (mixing means) 71 Lumping device (lumping means)

Continued on the front page (72) Inventor Takashi Haruki 4-2-2 Kanon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture Mitsubishi Heavy Industries, Ltd. Hiroshima Research Laboratory (72) Inventor Tohru Takashin 4-6-kannon Shinmachi, Nishi-ku, Hiroshima City, Hiroshima Prefecture 22 Hiroshima Research Laboratory, Mitsubishi Heavy Industries, Ltd. (72) Inventor Kiyoshi Okazoe 2-5-1 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Heavy Industries, Ltd. Headquarters (72) Kazuaki Kimura 2-5-2, Marunouchi, Chiyoda-ku, Tokyo 1 Mitsubishi Heavy Industries, Ltd. Head Office (72) Inventor Taku Shimizu 2-5-1 Marunouchi, Chiyoda-ku, Tokyo Mitsubishi Heavy Industries, Ltd. Head Office (72) Atsushi Atani 2-5-1, Marunouchi, Chiyoda-ku, Tokyo No. Mitsubishi Heavy Industries, Ltd. Head Office (56) References JP-A-48-66016 (JP, A) JP-A-48-66015 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B01D 53/34-53/85

Claims (6)

(57) [Claims] 1. A flue gas treatment system for treating flue gas containing dust and Se components, comprising: a cooling means for cooling the flue gas to 350 ° C. or lower; and a dust collecting means for separating the dust in the flue gas. And a Se treatment means for adding water and a treating agent to the dust separated by the dust collection means to convert the form of Se in the dust to an insoluble compound. . 2. A flue gas treatment system for treating flue gas containing dust and Se components, comprising: a cooling means for cooling the flue gas to 350 ° C. or lower; and a dust collecting means for separating the dust in the flue gas. A se treatment means for adding water and a treating agent to the dust separated by the dust collecting means to convert the form of Se in the dust to an insoluble compound, and an insoluble Se compound coming out of the Se treatment means. A flue gas treatment system, comprising: solid-liquid separation means for solid-liquid separation of a slurry. 3. A collection section for separating and collecting dust in the dust collection means, wherein a plurality of collection sections are provided from an inlet side of the flue gas to an outlet side, and the collection section is collected from a collecting section on the inlet side of the flue gas. Separated and collected separately from the dust collected from the outlet side.
3. The flue gas treatment system according to claim 1, wherein the dust collection device is configured to introduce only dust collected at an outlet side into the Se treatment unit. 4. The dust separated by the dust collecting means,
Classification means for classifying into a large particle size and a small particle size is provided, and only the small particle size dust classified by this classification means is introduced into the Se treatment means to perform the Se insolubilization treatment. The smoke exhaust treatment system according to claim 1 or 2, wherein: 5. A mixing means for mixing the dust subjected to the Se insolubilization treatment by the Se treatment means and the remaining dust not subjected to the Se insolubilization treatment at a ratio such that the water content is 20% or less. The smoke exhaust treatment system according to claim 3 or 4, wherein: 6. The flue gas treatment system according to claim 5, further comprising a mass forming means for forming the dust mixed by the mixing means into a mass.