JP2007039296A - Method and system for treating exhaust gas in cement manufacturing plant - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a treating method, by which a residual organic pollutant (dioxins, PCBs or the like), mercury, an acidic gas (a sulfur oxide or the like), a nitrogen oxide and a malodorous substance contained in an exhaust gas discharged from a cement manufacturing plant are efficiently removed. <P>SOLUTION: The method comprises a step (A) to collect dust in the exhaust gas by using a dust collector means 11 and to return the dust collected to a cement manufacturing plant 4, 5, a step (B) to subject a residual organic pollutant, mercury, an acidic gas and a malodorous substance contained in the exhaust gas after dust removal to an adsorption by an adsorbent in an adsorption tower 14 and to subject a nitrogen oxide to a reductive decomposition, a step (C) to heat the adsorbent to 300°C or above in an inert gas in a desorption tower 18 so as to decompose the residual organic pollutant and the malodorous substance and to desorb the mercury and the acidic gas, and a step (D) to treat the obtained inert gas containing the mercury and the acidic gas in a cooling tower 24, an absorptive reaction tower 27, a dry mercury adsorptive tower 29 or the like. The adsorbents in the steps (B) and (C) are used to be continuously circulated between these steps. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention is a treatment for efficiently treating and detoxifying harmful substances such as residual organic pollutants, mercury-containing substances, acid gases, nitrogen oxides, and malodorous substances contained in the exhaust gas of cement production equipment. The present invention relates to a method and a processing system.

In recent years, cement production from the viewpoint of resource recycling, such as municipal waste, dust (fly ash) and burning husk (main ash), sewage sludge, papermaking sludge, foundry sand, coal ash, etc. generated by incineration of municipal waste Opportunities for use as raw materials or fuels are increasing.
Of these wastes, municipal waste, soot (fly ash), sewage sludge, paper sludge, and the like generated by incineration of municipal waste are put into a calcining furnace and a rotary kiln constituting a cement manufacturing apparatus. In this case, the residual organic pollutant contained in the waste is decomposed in a high temperature atmosphere.
In addition, burning husks (main ash), foundry sand, coal ash, and the like generated by incineration of municipal waste are put into the upper part of the suspension preheater together with ordinary cement raw materials. In this case, the residual organic pollutant contained in the waste is not completely decomposed and partly volatilizes and remains in the exhaust gas.
Substances containing heavy metals such as mercury contained in the waste are volatilized in the cement kiln and are discharged in a state of being contained in the exhaust gas as volatile components or solids.
On the other hand, when waste is used as a part of cement raw material or fuel, acid gases such as sulfur dioxide and hydrogen chloride in exhaust gas, and malodorous substances such as acetaldehyde are partly absorbed by the cement raw material. The remainder may remain in the exhaust gas. Since acid gases, malodorous substances, and nitrogen oxides generated by combustion are harmful substances in the exhaust gas, they can be decomposed or removed by an appropriate method and detoxified under the recent circumstances of emphasis on environmental protection. It is desired.

Conventionally, various technologies for removing harmful substances such as persistent organic pollutants and mercury-containing substances contained in the exhaust gas of cement manufacturing apparatuses have been proposed.
For example, after collecting dust containing dioxins from the exhaust gas of a cement manufacturing apparatus using municipal waste as part of the raw material, the collected dust is thrown into a predetermined high temperature part of the cement manufacturing apparatus, A method of decomposing dioxins in dust and finally reducing the concentration of dioxins in exhaust gas has been proposed (Patent Document 1).
In addition, the dust collected from the exhaust gas from the cement manufacturing process is guided to a heating furnace and heated to a temperature higher than the volatilization temperature of the volatile metal component (for example, mercury) contained in the dust collection dust, and the volatile metal component is gasified. There has been proposed a method for treating exhaust gas from cement production, characterized in that dust collection dust that has been converted to a volatile metal component and used to remove a volatile metal component is used as part of the cement raw material (Patent Document 2).
JP 2004-244308 A Japanese Patent Laid-Open No. 2002-355531

Although the treatment method described in Patent Document 1 described above can reduce the amount of dioxins contained in the exhaust gas, it does not remove mercury, acid gas, malodorous substances, and the like.
In the treatment method described in Patent Document 2, mercury contained in the exhaust gas is removed, but removal of dioxins, acid gas, and the like is not performed. Moreover, since the processing method described in Patent Document 2 heats the entire amount of collected dust and volatilizes and removes mercury, it also heats solids other than mercury as a removal target. In other words, there is room for improvement from the viewpoint of thermal energy utilization efficiency.
Therefore, the present invention provides persistent organic pollutants (dioxins, PCBs, etc.), mercury-containing substances (metal mercury, mercury chloride, etc.), acid gases (sulfur oxides, chlorides) contained in the exhaust gas of cement production equipment. It is an object of the present invention to provide a treatment method and a treatment system capable of efficiently removing all of hydrogen and the like and malodorous substances (acetaldehyde and the like).

As a result of intensive studies to solve the above problems, the present inventor collects dust contained in the exhaust gas of the cement manufacturing apparatus by the dust collecting means and returns the dust to the cement manufacturing apparatus, while the dust collecting means is Persistent organic pollution by heating the adsorbent in an inert gas atmosphere after adsorbing the residual organic pollutant, mercury-containing substance, acid gas and malodorous substance contained in the exhaust gas that has passed through the adsorbent It is possible to decompose substances and malodorous substances, and to remove mercury-containing substances and acid gases. Furthermore, adsorption of residual organic pollutants etc. by the adsorbent and regeneration of adsorbent by heating (residuality) The present inventors have found that an efficient treatment can be achieved if decomposition of organic pollutants and the like is performed under continuous circulation of the adsorbent.
That is, the present invention provides the following [1] to [6].

[1] A method for treating exhaust gas from a cement manufacturing apparatus, including persistent organic pollutants, mercury-containing substances, acid gas, malodorous substances, and dust, and (A) contained in the exhaust gas using dust collection means Collecting the collected dust, returning the collected dust to the cement production apparatus, and contacting the adsorbent with the exhaust gas after the treatment of (B) step (A) and the adsorbent. A step of adsorbing residual organic pollutants, mercury-containing materials, acid gases, and malodorous substances contained in the exhaust gas, and (C) the adsorbent after the treatment of step (B) in an inert gas atmosphere (2) decomposing residual organic pollutants and malodorous substances adsorbed on the adsorbent by heating to 300 ° C. or higher and desorbing mercury-containing substances and acidic gas from the adsorbent; ) Mercury-containing material obtained in step (C) and Treating the inert gas containing acid gas and detoxifying it, and in step (B) and step (C), the adsorbent is continuously used between step (B) and step (C). A method for treating exhaust gas from a cement production apparatus, characterized in that the exhaust gas is circulated in a waste water.
[2] In step (D), neutralization of acid gas by contact with an alkaline solution with respect to the inert gas containing mercury-containing substance and acid gas obtained in step (C), and mercury by an adsorbent The method for treating exhaust gas of a cement production apparatus according to the above [1], wherein the contained substance is adsorbed.
[3] The method for treating exhaust gas in a cement manufacturing apparatus according to [1] or [2], wherein in the step (B), the exhaust gas is brought into contact with the adsorbent at a space velocity of 200 to 1,500 / hour.
[4] The exhaust gas of the cement manufacturing apparatus contains nitrogen oxides, and a reducing agent is added to the exhaust gas after the process (A) between the processes (A) and (B). And the processing method of the waste gas of the cement manufacturing apparatus in any one of said [1]-[3] including the process of reducing the said nitrogen oxide to nitrogen gas.

[5] An exhaust gas treatment system for cement production equipment containing persistent organic pollutants, mercury-containing substances, acid gases, malodorous substances, and dust, (a) capturing dust contained in exhaust gas from cement production equipment A dust collecting device for collecting, (b) a dust returning means for returning the dust collected by the dust collecting device (a) to the cement manufacturing device, and (c) after the dust collecting device (a) An adsorption tower disposed on the flow side, which has an inlet and an outlet for the exhaust gas, and adsorbs residual organic pollutants, mercury-containing substances, acid gases, and malodorous substances contained in the exhaust gas An adsorbing tower having an inlet and an outlet for adsorbing material, and filled with a moving bed so that the adsorbing material is in contact with the exhaust gas, and (d) attached to the adsorbing tower (c) Desorption tower with an inert gas inlet Residual organic pollutants and odorous substances having an inlet and an outlet for introducing the adsorbent supplied from the adsorption tower (c) and adsorbed on the adsorbent In the presence of a heating means so that the adsorbent is allowed to come into contact with the inert gas so that the mercury-containing substance and the acid gas can be released from the adsorbent. The adsorbent discharged from the desorption tower (d) is adsorbed so that the adsorbent can continuously circulate between the tower and (e) the adsorption tower (c) and the desorption tower (d). Conveying means for continuously conveying to the tower (c), and (f) means for detoxifying the inert gas containing mercury-containing material and acid gas discharged from the desorption tower (d). An exhaust gas treatment system for cement production equipment.
[6] A means (f) for adsorbing a mercury-containing substance in the inert gas, and a neutralization tank storing an alkaline solution for neutralizing the acid gas in the inert gas The exhaust gas treatment system for a cement production apparatus according to [5], including an adsorption tower containing an adsorbent.

  According to the treatment method and treatment system of the present invention, persistent organic pollutants (dioxins, PCBs, etc.), mercury-containing substances (metal mercury, mercury chloride, etc.), acid gas contained in the exhaust gas of cement production equipment (Sulfur oxide, hydrogen chloride, etc.), nitrogen oxides, and malodorous substances (acetaldehyde, etc.) can all be efficiently removed.

Hereinafter, an exhaust gas treatment method and treatment system of a cement production apparatus of the present invention will be described with reference to the drawings. FIG. 1 is a diagram schematically showing an example of an exhaust gas treatment system of a cement production apparatus according to the present invention.
In FIG. 1, first, a cement raw material (specifically, limestone, clay, silica stone, iron slag, waste (for example, main ash generated from incineration of municipal waste, foundry sand, etc.), etc.) Then, the mixture is pulverized and mixed by a pulverizer (raw material mill) 2, and coal ash is further added as necessary, and then supplied to the suspension preheater 4 via the raw material supply path 3.
Here, the suspension preheater 4 is for preheating the cement raw material while performing heat exchange, and includes a plurality of cyclones 4a, 4b, 4c, and 4d. The temperature in the lowermost cyclone 4d is usually 800 to 900 ° C.
The cement raw material is preheated while being sequentially moved downward in the suspension preheater 4, and is supplied into the rotary kiln 5. A calcining furnace 6 may be provided between the suspension preheater 4 and the rotary kiln 5 as shown in FIG. The temperature in the calcining furnace 6 is normally kept at 800 to 1,000 ° C.

Waste (for example, municipal waste, incineration fly ash of municipal waste, sewage sludge, paper sludge, etc.) can be put into the rotary kiln 5 or calcining furnace 6 to be part of the cement raw material.
The cement raw material supplied into the rotary kiln 5 is fired at a temperature of 1,000 to 2,000 ° C. by a burner using a fuel such as pulverized coal to become a clinker. The clinker discharged from the rotary kiln 5 is cooled by a cooler 7 and then gypsum is added. Then, the clinker is finely pulverized in a finishing mill 8 to become cement.
The cement manufacturing apparatus includes, for example, a dryer 1, a pulverizer 2, a raw material supply path 3, a suspension preheater 4, a rotary kiln 5, a calciner 6, a cooler 7, and a finishing mill 8 (however, the dryer 1 And the pulverizer 2 may be a dual-purpose machine).

Exhaust gas generated by decarboxylation and firing of the cement raw material in a high temperature atmosphere such as the suspension preheater 4 and the rotary kiln 5 rises in the suspension preheater 4 and is connected to the uppermost cyclone 4a (FIG. 1). The exhaust gas path is indicated by a dotted line.)
The exhaust gas contains persistent organic pollutants, mercury-containing materials, acid gases, malodorous substances, and dust. The exhaust gas may contain nitrogen oxides.
Persistent organic pollutants (English: Persistent Organic Pollutants, abbreviated: POPs) are pollutants that are persistent and remain in the environment and have a negative impact on human health and ecosystems, such as dioxins, PCBs, hexachlorobenzene, furan, DDT, aldrin, dieldrin, endrin, chlordane, heptachlor, mirex, toxaphene and the like.
Examples of mercury-containing materials include metallic mercury (Hg), mercury chloride (HgCl ₂ ), and the like.
Examples of the acid gas include sulfur oxides (such as sulfur dioxide) and hydrogen chloride.
Examples of malodorous substances include aldehydes such as acetaldehyde, benzene, acetone, acetonitrile, and the like.

The exhaust gas passes through the dryer 1 in order to become a drying heat source for the cement raw material, and then flows into the dust collector 11 through the exhaust gas passage 10. The dust collector 11 performs a process of removing dust in the exhaust gas. The exhaust gas after being treated by the dust collector 11 passes through an adsorption tower 14 described later, and is finally discharged from the chimney 16 into the atmosphere via the exhaust gas passage 15.
The exhaust gas passing through the dryer 1 flows into the dryer 1 at a temperature of 200 to 420 ° C., for example, and is discharged from the dryer 1 at a temperature of 80 to 200 ° C.

The dust collector 11 is for collecting dust in the exhaust gas of the cement manufacturing apparatus. The temperature of the exhaust gas at the point where the dust collector 11 is provided is usually 80 to 200 ° C.
Persistent organic pollutants and mercury-containing substances are present as volatile components in the high temperature exhaust gas, but as the temperature of the exhaust gas decreases, they become present as solids in the exhaust gas. Therefore, in the dust collector 11, a part of persistent organic pollutant and mercury-containing material are also collected as solids together with dust.
In addition, as an example of the mercury containing substance contained as solid content in exhaust gas, compounds, such as mercury chloride, and metallic mercury are mentioned.
As the dust collector 11, an electric dust collector is usually used, but other dust collectors (for example, a gravity dust collector, an inertial dust collector, a centrifugal dust collector, a filtration dust collector, etc.) may be used.
The dust collected by the dust collector 11 is returned to the cement manufacturing apparatus via the dust return means (dust return path) 12 and used as a part of the cement raw material.

The exhaust gas after passing through the dust collector 11 is guided to the adsorption tower 14 via the exhaust gas passage 13 and is brought into contact with an adsorbent that moves in the adsorption tower 14 in one direction. The moving direction of the exhaust gas and the moving direction of the adsorbent in the adsorption tower 14 are desirably a cross flow type from the viewpoint of the efficiency of exhaust gas treatment. The residence time of the adsorbent in the adsorption tower 14 is 70 to 200 hours.
The space velocity of the exhaust gas passing through the adsorption tower 14 is preferably 200 to 1,500 / hour (hour), more preferably 250 to 1,000 / hour, and particularly preferably 300 to 800 / hour. If the space velocity is less than 200 / hour, the adsorption tower becomes large, and the cost of equipment and adsorbent increases. When the space velocity exceeds 1,500 / hour, it is difficult to obtain sufficient adsorption performance because the amount of adsorbent is small with respect to the amount of processing gas.
In addition, it is preferable that the space velocity is 1,000 / hour or less because the removal rate of malodorous substances and nitrogen oxides becomes relatively large.
Here, the space velocity (English name: Space Verocity, abbreviation: SV) refers to the amount of exhaust gas per hour passing through the adsorption tower (unit: m ³ ) and the capacity of the adsorbent in the adsorption tower (unit: m ³ ). : Divided by m ³ ).

The adsorbent is not particularly limited as long as it can adsorb persistent organic pollutants, mercury-containing substances, acid gases, and malodorous substances in exhaust gas, and can reduce and decompose nitrogen oxides. From the viewpoint of effective utilization, one or a combination of two or more selected from granular activated carbon, activated coke, activated char, etc. that can be reused as part of the cement raw material or as a firing fuel is preferable.
For the purpose of removing (denitrating) nitrogen oxides in the exhaust gas in the exhaust gas passage 13 on the upstream side of the adsorption tower 14, a reducing agent such as ammonia (NH ₃ ) or urea may be injected. In the denitration reaction, a part of nitrogen oxide (NOx) in the exhaust gas is reduced to nitrogen (N ₂ ) in the adsorption tower 14 in the presence of an adsorbent and a reducing agent.
In the adsorption tower 14, the adsorbent that has moved to the lower part of the adsorption tower as a moving bed is carried to the desorption tower 18 by the carrier 17. As the transport device 17, a material in which the adsorbent is hardly worn or pulverized during transport, for example, a conveyor or the like is preferable.

In the desorption tower 18, the adsorbent having adsorbed the residual organic pollutants and the like is heated to 300 ° C. or higher in an inert gas atmosphere to decompose and detoxify the residual organic pollutants and malodorous substances. Remove mercury-containing substances and acid gases from the adsorbent.
Examples of the inert gas supplied to the desorption tower 18 include nitrogen gas, argon gas, and neon gas. Among these, nitrogen gas (N ₂ ) is preferably used because it is easily available.
When a gas other than an inert gas (for example, an oxygen-containing gas such as air) is supplied into the desorption tower 18, it is difficult to decompose residual organic pollutants and odorous substances, and the adsorbent burns. There is a fear.
The heating temperature in the desorption tower 18 is 300 ° C. or higher, more preferably 350 ° C. or higher, and particularly preferably 400 ° C. or higher. When the heating temperature is less than 300 ° C., decomposition of residual organic pollutants and malodorous substances may be incomplete, and separation of mercury-containing substances and acid gas from the adsorbent may be incomplete. The residence time of the adsorbent in the desorption tower 18 is about 4 hours.
The upper limit value of the heating temperature in the desorption tower 18 is not particularly limited, but is preferably 600 ° C. or less, more preferably 550 ° C. or less, and particularly preferably 500 ° C. or less from the viewpoints of energy cost, equipment cost, safety, and the like. It is.

The adsorbent after the heat treatment in the desorption tower 18 is cooled to 150 ° C. or less in the cooling unit 19 provided at the lower part of the desorption tower 18, and then a part of the adsorbent that is finely divided is selected. In order to separate and remove automatically, sieving is performed by a sieving device 20. The finely divided adsorbent obtained as a fine particle fraction (under the sieve) in the sieving device 20 is reused as a cement raw material or a burning fuel via a fine granular adsorbent conveying path (conveying device) 21, or Discarded. The coarse adsorbent obtained as a coarse fraction (on the sieve) by the sieving device 20 is conveyed to the upper part of the adsorption tower 14 via the conveyance path (conveyance device) 22 and supplied again into the adsorption tower 14. Is done.
Note that a new adsorbent in an amount corresponding to the finely divided adsorbent removed by the sieving device 20 is replenished in the middle of the conveyance path 22.

The carrier gas (inert gas) containing the mercury-containing substance and the acid gas separated by the desorption tower 18 is guided to the cooling tower 24 through the exhaust gas passage 23 and is scrubber sprinkled in the cooling tower 24 at 40 to 100 ° C. To be cooled. This temperature range is an optimum temperature for an absorption reaction in the absorption cooling tower 27 described later.
Note that a part of the water-soluble mercury (for example, mercury chloride) in the carrier gas is dissolved in water by the scrubber watering and moved to the solution in the circulation tank 25. The solution in the circulation tank 25 flows into the water channel 26 by a pump and circulates between the cooling tower 24. In order to adjust the temperature of the solution in the circulation tank 25 and replenish the evaporated part by watering, new water is supplied.
The carrier gas after being cooled in the cooling tower 24 is guided to the absorption reaction tower 27 in order to neutralize the acidic gas with alkali. In the absorption reaction tower 27, the solution in the circulation tank 25 is guided into the water channel 31 by a pump, and the scrubber is sprinkled. The pH of the solution in the circulation tank 25 is adjusted to 8-9 by adding an alkaline solution (for example, sodium hydroxide aqueous solution) in the middle of the water channel 31. Thereby, acidic gas is neutralized and removed.
Note that a part of water-soluble mercury (for example, mercury chloride) in the carrier gas is dissolved by the scrubber watering in the absorption reaction tower 27 and moved to the circulation tank 25.

The gas discharged from the absorption reaction tower 27 is guided to the dry mercury adsorption tower 29 through the exhaust gas passage 28. The dry mercury adsorption tower 29 is filled with special activated carbon for gas, and the remaining water-soluble mercury in the gas and metallic mercury are adsorbed and removed by the special activated carbon. The gas after the adsorption treatment is discharged from the chimney 16 to the atmosphere through the exhaust gas passage 30. As the special activated carbon for gas, a commercial product having the ability to selectively adsorb mercury in a dry manner is used. When the special activated carbon deteriorates with time and loses the adsorption performance, that is, when the breakthrough point is reached, the special activated carbon may be appropriately disposed of by handing it over to a mercury recovery company.
Since the waste liquid in the circulation tank 25 contains a mercury-containing substance (metal mercury, mercury chloride, etc.), an oxidizing agent is added in the decomposition tank 33 to completely decompose the metal mercury and the mercury compound. The oxidizing agent may be any oxidizing agent that oxidizes mercury, and hypochlorite (for example, sodium hypochlorite) is generally used.

The waste liquid after the oxidation treatment includes a product ionized into a stable chloro complex ion ((HgCl ₄ ) ²⁻ ) as a complete decomposition product of the mercury-containing substance. This waste liquid is subjected to a predetermined pH adjustment in the neutralization tank 34 and then guided to a wet mercury adsorption tower 35 filled with a special activated carbon or chelate resin for solution as an adsorbent. Complete decomposition products (specifically, chloro complex ions ((HgCl ₄ ) ²⁻ ), etc.) due to oxidation of mercury-containing substances are adsorbed on the adsorbent and removed from the waste liquid.
As the adsorbent for the solution, a commercial product having the ability to selectively adsorb mercury in a wet state is used. The waste liquid after the adsorption treatment may be discharged to the outside through the drainage channel 36 or may be reused in the cement manufacturing process.

Hereinafter, the present invention will be described by way of examples.
[Example 1]
An exhaust gas treatment experiment was conducted by using a medium-scale test exhaust gas treatment facility having the configuration shown in FIG.
The total amount of exhaust gas from the actual cement manufacturing equipment is 800,000 m ³ N / hour (hour), and the amount of exhaust gas supplied to the test equipment is 200 m ³ N / hour (space velocity: 300 / hour). It was. The size of the adsorbent moving layer was 0.5 m × 1.3 m × 1.0 m, and commercially available activated coke was used as the adsorbent. The adsorbent in the adsorption tower was a moving bed with a residence time of 130 hours.
The size of the desorption tower was 0.5 m (diameter) × 8 m (height), and nitrogen gas was circulated in the desorption tower at a gas amount of 30 m ³ N / hour. The temperature in the desorption tower was adjusted to 390 ° C.
While the exhaust gas is continuously ventilated, the residual properties at the adsorption tower inlet (reference A in FIG. 1), the adsorption tower outlet (reference B in FIG. 1), and the desorption tower outlet (reference C in FIG. 1). The concentrations of organic pollutants (dioxins, PCBs), mercury, acid gases (sulfur dioxide, hydrogen chloride), nitrogen oxides, and odors (bad odor substances) were measured. Moreover, each density | concentration of mercury and acid gas was measured in the exit (code | symbol D in FIG. 1) of a dry-type mercury adsorption tower. Further, the mercury concentration was measured at the outlet of the wet mercury adsorption tower (symbol E in FIG. 1). The measuring method of each concentration is shown in Table 1. The measurement results are shown in Table 2.

[Example 2]
The experiment was performed in the same manner as in Example 1 except that the amount of exhaust gas supplied to the test facility was 520 m ³ N / hour (space velocity: 800 / hour). Table 3 shows the measurement results.
[Example 3]
The experiment was performed in the same manner as in Example 1 except that the amount of exhaust gas supplied to the test facility was changed to 780 m ³ N / hour (space velocity: 1,200 / hour). Table 4 shows the measurement results.

  As shown in Tables 2 to 4, it can be seen that according to the treatment method of the present invention, residual organic pollutants, mercury-containing substances, and acid gases can be efficiently removed. In particular, in Examples 1 and 2 where the space velocity (SV) of the exhaust gas passing through the adsorption tower is 1,000 / hour or less, nitrogen oxides and odorous substances are also removed at a high removal rate.

It is a figure which shows typically an example of the waste gas processing system of the cement manufacturing apparatus of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Dryer 2 Crusher 3 Raw material supply path 4 Suspension preheater 4a, 4b, 4c, 4d Cyclone 5 Rotary kiln 6 Calciner 7 Cooler 8 Finishing mill 9, 10, 13, 15 Exhaust gas path 11 Dust collector 12 Dust return path 14 Adsorption tower 16 Chimney 17 Transporter 18 Desorption tower 19 Cooling unit 20 Sieve device 21 Fine adsorbent transport path 22 Transport path 23, 28, 30 Gas path 24 Cooling tower 25 Circulation tank 26, 31, 32 Water path 27 Absorption reaction tower 29 Dry type Mercury adsorption tower 33 Decomposition tank 34 Neutralization tank 35 Wet mercury adsorption tower 36 Drainage channel A Adsorption tower entrance (measurement point)
B Adsorption tower exit (measurement point)
C Dry mercury adsorption tower outlet (measurement point)
D Wet mercury adsorption tower exit (measurement point)

Claims (6)

A method for treating exhaust gas from a cement manufacturing apparatus, including persistent organic pollutants, mercury-containing substances, acid gases, malodorous substances, and dusts,
(A) collecting dust contained in the exhaust gas using a dust collecting means, and returning the collected dust to a cement manufacturing apparatus;
(B) The exhaust gas after the treatment in the step (A) is brought into contact with an adsorbent, and residual organic pollutants, mercury-containing substances, acid gases, and malodorous substances contained in the exhaust gas are added to the adsorbent. Adsorbing, and
(C) By heating the adsorbent after the treatment in step (B) to 300 ° C. or higher in an inert gas atmosphere, the residual organic pollutants and malodorous substances adsorbed on the adsorbent are decomposed, And a step of releasing the mercury-containing substance and the acid gas from the adsorbent,
(D) treating the inert gas containing the mercury-containing substance and acid gas obtained in step (C) to render them harmless,
In the step (B) and the step (C), the adsorbent is continuously circulated between the step (B) and the step (C).   In step (D), neutralization of acid gas by contact with an alkaline solution with respect to the inert gas containing mercury-containing material and acid gas obtained in step (C), and mercury-containing material by adsorbent The method for treating exhaust gas of a cement production apparatus according to claim 1, wherein adsorption is performed.   The method for treating exhaust gas in a cement manufacturing apparatus according to claim 1 or 2, wherein in the step (B), the exhaust gas is brought into contact with the adsorbent at a space velocity of 200 to 1,500 / hour. The exhaust gas of the cement production apparatus contains nitrogen oxides, and
The step of adding a reducing agent to the exhaust gas after the process (A) and reducing the nitrogen oxide to nitrogen gas between the step (A) and the step (B). The processing method of the waste gas of the cement manufacturing apparatus of any one of Claims 1. An exhaust gas treatment system for cement production equipment, including persistent organic pollutants, mercury-containing substances, acid gases, malodorous substances, and dust,
(A) a dust collector for collecting dust contained in the exhaust gas of the cement manufacturing apparatus;
(B) a dust return means for returning the dust collected by the dust collector (a) to the cement production apparatus;
(C) An adsorption tower disposed on the downstream side of the dust collector (a), having an inlet and an outlet for the exhaust gas, and residual organic pollutants contained in the exhaust gas, mercury An adsorption tower having an inlet and an outlet of an adsorbent for adsorbing contained substances, acid gas, and malodorous substance, and the adsorbent is packed as a moving bed so as to be in contact with the exhaust gas; ,
(D) Desorption tower attached to the adsorption tower (c), having an inert gas inlet and outlet, and an inlet for introducing the adsorbent supplied from the adsorption tower (c) And heating means so as to decompose residual organic pollutants and malodorous substances adsorbed on the adsorbent and to release mercury-containing substances and acid gases from the adsorbent. In the presence of the desorption tower, the adsorbent is flowed down in contact with the inert gas,
(E) The adsorbent discharged from the desorption tower (d) is removed from the adsorption tower (c) so that the adsorbent can continuously circulate between the adsorption tower (c) and the desorption tower (d). Transport means for continuously transporting
And (f) a means for detoxifying the inert gas containing the mercury-containing substance and the acid gas discharged from the desorption tower (d), and an exhaust gas treatment system for a cement production apparatus. Means (f) includes a neutralization tank for storing an alkaline solution for neutralizing the acidic gas in the inert gas, and an adsorbent for adsorbing the mercury-containing substance in the inert gas. The exhaust gas treatment system for a cement production apparatus according to claim 5, comprising an adsorption tower accommodated therein.

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