JP2005000757A - Exhaust gas treatment method and exhaust gas treatment system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an exhaust gas treatment method by which a heavy metal and an acidic gas can be removed satisfactorily from the exhaust gas of a cement kiln, or the like, and the solid to be recovered at this removal step can easily be made into a raw material of cement by a simple apparatus. <P>SOLUTION: The treatment method comprises: a step (A) to recover a coarse particle portion from the exhaust gas containing the coarse particle portion, a heavy metal-containing fine particle portion, hydrogen chloride and the acidic gas such as sulfur oxide; a step (B) to recover the fine particle portion from the exhaust gas treated at the step (A); a step (C) to add calcium hydroxide to the exhaust gas treated at the step (B) and obtain the exhaust gas containing solids such as calcium chloride and calcium sulfate; a step (D) to recover the solids from the exhaust gas obtained at the step (C); a step (E) to remove the heavy metal from the fine particle portion obtained at the step (B) and obtain a raw material of cement; and a step (F) to wash the coarse particle portion obtained at the step (A) and the solids obtained at the step (D) with an alkaline aqueous solution and obtain another raw material of cement containing calcium hydroxide. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a treatment method and a treatment system for removing heavy metals and acid gas from a combustion furnace such as a cement kiln using waste incineration ash or the like as part of a raw material, or an exhaust gas from an incinerator.
[0002]
[Prior art]
Conventionally, cement clinker has been fired using waste incineration ash or the like as a part of raw materials. However, in the exhaust gas of cement kiln, trace amounts of heavy metals contained in incineration ash, etc., hydrogen chloride (HCl) derived from chlorine and sulfur, and sulfur oxides (SO _X ) And other acidic gases. Therefore, various techniques for removing these heavy metals have been proposed.
For example, in a method for treating combustion exhaust gas generated with the production of cement or aggregate using waste incineration ash containing heavy metal as a part of the raw material, the combustion exhaust gas containing acid gas generated from the rotary kiln is alkalinized. There has been proposed a method for treating combustion exhaust gas, characterized by adding an absorbent containing at least one selected from the group consisting of metal hydroxides and carbonates (see Patent Document 1).
In this technology, even if the absorbent is added, if it does not meet the emission standards for acid gases (specifically, hydrogen chloride, sulfur oxide, etc.), slaked lime is added before the dust collector. By doing so, it is said that most of the acid gas can be removed.
[0003]
[Patent Document 1]
JP 2002-166125 (Claim 1 of Claim 2 on page 2, Paragraph 0027 on page 4 and FIG. 1 on page 5)
[0004]
[Problems to be solved by the invention]
Generally, in order to treat exhaust gas containing coarse and fine particles, a processing system that combines a cyclone for collecting coarse particles and a bag filter for collecting fine particles is used. It is used.
However, for example, when cement clinker is fired using waste incineration ash as a part of raw materials, trace amounts of heavy metals such as lead (Pb) and zinc (Zn), hydrogen chloride (HCl), and sulfur oxides are used. (SO _X Exhaust gas containing acidic gas such as In order to remove most of the acidic gas contained in the exhaust gas, for example, as described in Patent Document 1 described above, after adding a specific absorbent, slaked lime is added as necessary. Processing such as addition must be performed.
[0005]
Here, slaked lime is an effective drug for removing acid gas. However, when a large amount of slaked lime is used, there is an inconvenience that the amount of collected solids in a dust collecting means such as a bag filter increases. In other words, the solid content collected by the dust collecting means contains harmful heavy metals in addition to calcium-containing substances derived from slaked lime (for example, calcium chloride), so the amount of this solid content is large. As a result, problems such as an increased burden of heavy metal removal processing occur.
[0006]
On the other hand, from the viewpoint of recycling waste, it is desirable to use the solid content obtained after purification of exhaust gas containing heavy metals as cement raw material. In this respect, the solid content recovered by the dust collecting means, etc. can be easily converted into a cement raw material (for example, a form that does not contain heavy metals and can be obtained efficiently with calcium hydroxide as the main component) ), It is considered that cement raw material can be realized without excessively increasing the cost and equipment burden.
Therefore, the present invention is based on a waste furnace containing a heavy metal and an acid gas discharged from a firing furnace such as a cement kiln that burns clinker using waste incineration ash or the like as a raw material, and an incinerator. It is an object of the present invention to provide an exhaust gas treatment method and a treatment system that can sufficiently remove solids and can easily convert solids recovered in the removal treatment process into a cement raw material.
[0007]
[Means for Solving the Problems]
As a result of intensive investigations to solve the above problems, the present inventors first recovered the coarse particles from the exhaust gas discharged from the firing furnace or incinerator, and then recovered the fine particles containing heavy metals. Then, after adding an alkali source such as slaked lime to produce a solid part containing an acid gas component, if this solid part is recovered, a solid part containing a heavy metal and an acid gas component are contained. The solid content can be obtained separately, and as a result, the burden of heavy metal removal treatment, etc. is reduced, and the present invention has been completed by conceiving that the solid material can be easily made into a cement raw material. .
[0008]
That is, the exhaust gas treatment method of the present invention (Claim 1) separates and collects coarse particles from the exhaust gas containing (A) coarse particles, fine particles containing heavy metals, and acid gas, A coarse particle recovery step for obtaining an exhaust gas containing a fine particle containing heavy metal and an acid gas; and (B) a fine particle containing a heavy metal is separated and recovered from the exhaust gas obtained in step (A). A fine particle fraction collecting step for obtaining an exhaust gas containing the acid gas, and (C) adding an alkali source (for example, calcium hydroxide) to the exhaust gas obtained in the step (B), An alkali source addition step for obtaining an exhaust gas containing a solid content (eg, containing calcium chloride and calcium sulfate) consisting of a reaction product with a gas; and (D) the solid content from the exhaust gas obtained in step (C). And a solid content recovery step for separating and recovering (E) step (B A heavy metal removal step of removing a heavy metal from the fine particle portion containing the heavy metal obtained in step 1 to obtain a solid portion from which the heavy metal has been removed, and (F) the coarse particle portion obtained in step (A), The solid content (for example, cement containing calcium chloride and calcium sulfate) obtained in (D) is washed with an alkaline aqueous solution to remove the component derived from the acid gas (for example, cement And a water washing step for obtaining calcium hydroxide that can be used as a raw material.
According to the treatment method of the present invention, it is possible to efficiently and sufficiently remove heavy metals and acid gas contained in the exhaust gas, and the solid content obtained in the treatment process of the exhaust gas is treated with simple treatment means. It can be suitably used as a cement raw material alone.
[0009]
As a preferred embodiment of the method for treating exhaust gas of the present invention, a method using at least one of the solid content obtained in the step (E) and the solid content obtained in the step (F) as a cement raw material is used. (Claim 2).
In particular, when calcium hydroxide is used as the alkali source added in step (C), the solid content obtained in step (F) is mainly composed of calcium hydroxide. Can be suitably used.
[0010]
The exhaust gas treatment system of the present invention (Claim 3) includes (a) a coarse particle fraction for collecting coarse particles in an exhaust gas containing coarse particles, fine particles containing heavy metals, and acid gas. A first means for collecting fine particles containing the heavy metal in the exhaust gas, disposed on the downstream side of the collecting means (for example, a cyclone) and (b) the coarse particle collecting means (a); And (c) a source of alkali (eg, calcium hydroxide) in the exhaust gas at a point downstream of the first fine particle collection means (b). And (d) an alkali source supply means (c) disposed downstream of the alkali source supply means for collecting the reaction product of the acidic gas in the exhaust gas and the alkali source. To be collected by a second fine particle collecting means (for example, a bag filter) and (e) a first fine particle collecting means (b) A heavy metal removing means for removing the heavy metal from the fine particle containing the heavy metal to obtain a solid part from which the heavy metal has been removed; and (f) the coarse particle fraction obtained by the coarse particle collecting means (a), The reaction product collected by the second fine particle collection means (d) is provided with water washing means for washing with an alkaline solution.
According to the treatment system of the present invention, it is possible to efficiently and sufficiently remove heavy metals and acid gas contained in the exhaust gas, and the solid content obtained in the treatment process of the exhaust gas is treated with simple treatment means. It can be suitably used as a cement raw material alone.
[0011]
As a preferred embodiment of the exhaust gas treatment system of the present invention, an adsorbing means for adsorbing an unreacted acidic gas (for example, an activity) on the downstream side of the second fine particle collecting means (d). A coke tower is provided (claim 4).
Thus, by providing an adsorption | suction means, the removal rate of acidic gas etc. from waste gas can further be raised.
In this preferred embodiment, the exhaust gas treatment system of the present invention comprises an adsorbent regeneration means for desorbing the acid gas adsorbed by the adsorbing means, and an acid gas desorbed by the adsorbent regeneration means as an aqueous solution ( Specifically, it can be provided with an acid gas recovery means for absorbing and recovering in water and / or a mist of an alkaline aqueous solution (Claim 5).
In an embodiment provided with these adsorbent regeneration means, acid gas recovery means, and the like, the exhaust gas treatment system of the present invention uses the heavy metal removal means (e) or the water washing means for the aqueous solution obtained by the acid gas recovery means. A supply path for guiding to (f) can be provided (claim 6).
If comprised in this way, the acidic gas adsorb | sucked by the adsorption | suction means can be processed, without adding an additional process equipment.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail.
The exhaust gas treatment method of the present invention includes the following steps (A) to (F).
[(A) Coarse grain collection step]
This step uses a coarse particle collection means such as a cyclone to separate and collect coarse particles from the exhaust gas of a firing furnace, an incinerator, etc., and exhaust gas containing fine particles containing heavy metals and acid gas It is the process of obtaining.
Here, as a firing furnace, for example, a cement kiln (for example, an internal heat type rotary kiln) for producing an eco-cement clinker using waste incineration ash or the like as a part of raw material (sub-material), or waste incineration A kiln or the like for producing an aggregate using ash or the like as a part of the raw material (auxiliary raw material) may be mentioned.
Examples of the incinerator include a garbage incinerator.
[0013]
Exhaust gas, which is an object to be treated of the present invention, is a heavy metal such as lead, zinc, copper, hydrogen chloride (HCl), sulfur oxide (SO _X ) And other acidic gases. For example, in the case of exhaust gas from a firing furnace for producing cement clinker, heavy metals and acid gases are mainly derived from auxiliary materials such as waste incineration ash.
The exhaust gas contains coarse particles that can be collected by a cyclone or the like, fine particles that can be collected by a bag filter or the like, and acid gas.
Of these, the coarse particles contain a part of the cement raw material scattered and flowing into the exhaust gas flow passage together with the exhaust gas, calcium chloride, etc., and are separated and recovered in this step.
The fine particles in the exhaust gas contain chlorides of heavy metals and the like, and are not collected by a cyclone or the like, but are sent to the subsequent process while remaining in the exhaust gas. The acidic gas in the exhaust gas is also sent to the subsequent process together with the fine particles.
[0014]
In addition, the cooling process of the exhaust gas for suppressing the resynthesis of dioxin can be provided before this process. Although dioxin is decomposed at high temperatures, it is known to be re-synthesized at 300 to 400 ° C. In order to avoid that the exhaust gas is kept in this temperature range for a long time and the generation of dioxin is promoted, the temperature of the exhaust gas to a temperature lower than the temperature at which dioxin is re-synthesized (for example, 200 ° C. or less). It is desirable to provide a process for rapidly reducing the.
[0015]
[(B) Fine grain collection step]
In this step, fine particles containing heavy metals are separated and recovered from the exhaust gas from which the coarse particles after step (A) have been removed using a fine particle collection means such as a bag filter, This is a step of obtaining exhaust gas containing gas.
Here, the fine-grained fraction containing heavy metals is, for example, cations such as alkali metals, alkaline earth metals, heavy metals and anions such as chlorine, which existed as volatile components, as solids as the exhaust gas temperature decreases. It contains the generated chloride (specifically, calcium chloride, lead chloride, etc.) and the like.
[0016]
[(C) Alkali source addition step]
In this step, an alkali source is added to the exhaust gas containing the acid gas after the step (B), and the alkali source and the acid gas (HCl, SO _X Etc.) to obtain an exhaust gas containing a solid component consisting of a reaction product.
Here, the alkali source may be any substance that can neutralize the acidic gas contained in the exhaust gas. For example, an alkaline earth metal (such as calcium hydroxide) or an alkali metal (such as sodium hydroxide) In addition to these hydroxides, quick lime, calcium carbonate and the like can be mentioned. Using an alkali source containing calcium (specifically, a so-called CaO source such as calcium hydroxide, quicklime, calcium carbonate, etc.) means that the solid content obtained in this step can be suitably used as a cement raw material. Therefore, it is preferable.
[0017]
As a form at the time of addition of an alkali source, a dry type, a slurry, etc. are mentioned, for example. Among them, the alkali source having a dry form is different from the slurry, because the reaction product of the alkali source and the acid gas does not aggregate and the particle size does not increase. Therefore, for the convenience of collection in the step (D) described later. Is preferable.
Specific examples of the reaction product of the alkali source and acidic gas include calcium chloride and calcium sulfate.
[0018]
[(D) Solid content recovery step]
This step uses a fine particle collection means such as a bag filter, from the exhaust gas containing the solid product consisting of the reaction product (eg, calcium chloride, calcium sulfate, etc.) obtained in step (C), Is a step of separating and recovering.
[0019]
[Treatment process with adsorbent]
In the present invention, the exhaust gas that has undergone the step (D) can be further treated with an adsorbent for removing acid gases, heavy metals, and the like.
For example, if an adsorbent such as activated coke is used, it is possible to adsorb and remove acid gases, heavy metals, and the like that slightly remain in the exhaust gas that has undergone the step (D). Here, activated coke (also abbreviated as “AC”) is a kind of molded activated carbon made of coal, and is an adsorbent having desulfurization / denitration performance and adsorption performance of heavy metals, dioxins and the like. Nitrogen oxides (NO) remaining in the exhaust gas are allowed to pass through, for example, exhaust gas whose temperature is lowered to 100 to 200 ° C. through the active coke tower (AC tower) filled with active coke. _X ) And hydrogen chloride, sulfur oxide (SO _X ) And heavy metals can be adsorbed to thoroughly purify the exhaust gas.
[0020]
Hydrogen chloride, sulfur oxide (SO _X ) And heavy metals adsorbed heavy metal can be heated, for example, by heating in the absence of oxygen to produce hydrogen chloride, sulfur oxide (SO _X ) And heavy metals can be removed and regenerated. Desorbed hydrogen chloride, sulfur oxide (SO _X ) And heavy metal treatment include removal of hydrogen chloride and heavy metal by a washing tower sprayed with water, and sulfur oxide (SO2) by an alkaline washing tower sprayed with an alkaline aqueous solution (for example, an aqueous solution containing sodium hydroxide). _X ) And water removal by a mist catcher that collects mist contained in the gas after the treatment by the alkali cleaning tower.
[0021]
Among these, an aqueous solution containing chlorine and heavy metals obtained in a washing tower sprayed with water is precipitated by heavy metal recovery means (for example, adding a chelating agent to precipitate solids containing heavy metals, followed by solid-liquid separation) The heavy metal can be removed by the heavy metal treatment aqueous solution in the heavy metal removal step (E) after the heavy metal is removed by an apparatus configured to recover the product. Thereby, when processing the waste liquid after the processing in the washing tower sprayed with water, the solution processing can be unified in a form also used as the processing equipment of the heavy metal removal step (E).
[0022]
Moreover, the aqueous solution containing the sulfur content obtained by the alkaline washing tower which sprays alkaline aqueous solution can be added to the water for slurrying in a water washing process (F), for example. Thereby, when processing the aqueous solution (waste liquid) after the treatment in the alkali washing tower, the solution treatment can be unified in a form also used as the treatment equipment in the water washing step (F).
The mist contained in the gas after the treatment in the alkali cleaning tower may contain a trace amount of heavy metal. This mist is collected by a mist catcher and then supplied as an aqueous solution to the above-described heavy metal recovery means to remove the heavy metal. The aqueous solution after treatment in the metal recovery means is added to the aqueous solution for heavy metal treatment in the heavy metal removal step (E).
The exhaust gas that has been subjected to the solid content recovery step (D) and the above-described treatment using the adsorbent provided as necessary is subjected to other purification treatment as necessary and then discharged into the atmosphere.
[0023]
[(E) Heavy metal removal step]
This step is a step of removing the heavy metal from the fine particles containing the heavy metal obtained in the step (B) (for example, containing a chloride such as heavy metal) to obtain a solid content from which the heavy metal has been removed. .
Since the fine granule contains a large amount of soluble alkali salts such as potassium chloride and sodium chloride, the fine fraction is washed before this step (E) to dissolve and remove these alkali salts. For example, the chlorine ion concentration in the heavy metal recovered in this step (E) can be lowered, which is preferable. At this time, if the pH at the time of washing is adjusted to 8 to 11, elution of heavy metals together with alkali salts can be suppressed.
The method for removing heavy metals may be appropriately determined according to the type of heavy metal.
For example, when lead, zinc, and copper are included as heavy metals, fine particles containing heavy metals are added to an aqueous solution adjusted to pH 4 or less using sulfuric acid, and then solid-liquid separation such as filtration is performed. As a result, a solid content containing lead and a liquid content containing zinc and copper can be obtained. Among these, if a metal (for example, zinc) having a greater ionization tendency than copper is added to a liquid containing zinc and copper, copper is deposited on the surface of the metal, and a liquid containing only zinc can be obtained. it can.
[0024]
On the other hand, if an aqueous solution adjusted to pH 13.5 or higher using an alkalinizing agent such as sodium hydroxide is charged with the above-mentioned solid containing lead, stirred, and solid-liquid separated by filtration or the like, And a liquid containing lead can be obtained. By mixing this solution and the above-mentioned solution containing zinc and adjusting the pH to about 10, a precipitate of zinc and lead can be obtained.
The solid content separated from the liquid containing lead contains calcium hydroxide and can be used as a cement raw material. The recovered heavy metal is used as a raw material for refining.
[0025]
[(F) water washing step]
In this step, the coarse fraction obtained in the coarse fraction collection step (A) and the solid fraction obtained in the solid fraction collection step (D) (calcium chloride, calcium sulfate, etc.) using an alkaline aqueous solution. Wash with water, acid gas (HCl, SO _X Etc.) is a step of obtaining a solid component from which components (chlorine component, sulfuric acid component, etc.) derived from the component are removed.
That is, since the recovered solid content contains hardly soluble calcium sulfate and the like, the liquid property is made alkaline (preferably pH 13.5 or more), and the sulfuric acid content is eluted from the solid content in the liquid. A solid content containing calcium hydroxide is obtained. This solid content is used as a cement raw material. At this time, it is desirable to wash the solids with water to remove cations such as sodium and anions such as chlorine.
[0026]
As alkaline aqueous solution used by this process (F), the aqueous solution which adjusted pH to 13.5 or more using alkalizing agents, such as sodium hydroxide and potassium hydroxide, is mentioned, for example.
Moreover, as a means of water washing, the water tank with a stirring blade etc. which can store alkaline aqueous solution and can stir and mix with the solid content of a process target object etc. are mentioned, for example.
Examples of the solid-liquid separation means after washing with water include a filter press and a belt filter.
[0027]
Next, an example of the processing system of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an example of the processing system of the present invention. In FIG. 1, the solid line indicates a solid flow, the dotted line indicates a gas flow, and the alternate long and short dash line indicates a liquid flow.
In FIG. 1, the cement raw material supplied from outside the system is supplied into the cement kiln 1, fired, cooled by a clinker cooler 2, and recovered as a cement clinker. The cement clinker is pulverized together with gypsum to become cement. The cement kiln 1 has a high-temperature atmosphere (for example, about 1300 ° C.) by a burner 3 provided in front of the kiln.
[0028]
The high-temperature exhaust gas discharged from the cement kiln 1 is guided to the cooler 4 and rapidly cooled to suppress the resynthesis of dioxins. The exhaust gas that has passed through the cooler 4 is guided to a cyclone 5 where coarse particles (such as scattered cement raw material) are collected. The exhaust gas that has passed through the cyclone 5 is guided to the bag filter 6 and fine particles (such as lead chloride) are collected. The exhaust gas that has passed through the bag filter 6 is guided to the bag filter 8 through the flow path. In the middle of the flow path, an alkali source supply port from a storage tank 7 for storing an alkali source (for example, calcium hydroxide) is provided, and the alkali source is supplied into the flow path.
[0029]
In the flow path on the downstream side of the alkali source supply port, acidic gas (eg, HCl, SO _X Etc.) is neutralized by an alkali source (for example, calcium hydroxide), and becomes a powder containing, for example, calcium chloride and calcium sulfate. This powder is collected by the bag filter 8. The exhaust gas that has passed through the bag filter 8 is guided to an active coke tower (denitration device) 10 via a fan 9 and nitrogen oxide (NO) remaining in the exhaust gas. _X ) And hydrogen chloride (HCl), sulfur oxide (SO _X ), Heavy metals are adsorbed and removed.
The exhaust gas after the adsorption treatment is discharged from the chimney 15 into the atmosphere after passing through another purification device as necessary.
[0030]
Coarse particles (solid content) collected by the cyclone 5 are guided to the cleaning means 16 to remove chlorine and the like. Here, the cleaning means 16 includes, for example, a water tank with stirring blades for slurrying the above-mentioned coarse particles (solid content) in which alkaline cleaning water is stored, a cyclone 5 and a bag filter in the water tank. 8 is combined with solid-liquid separation means such as a filter for solid-liquid separation of the slurry after the solid content introduced from 8 is stirred and mixed. The water tank with a stirring blade is supplied with cleaning water from outside the system, and is supplied with an aqueous solution containing sulfur from an alkali cleaning tower 13 described later via a supply path.
The fine particles collected by the bag filter 6 are used as a cement raw material after passing through the heavy metal removing means 17.
[0031]
For example, in the case of the specific example described in the heavy metal removing step (E), the heavy metal removing means 17 is for slurring the fine particles (solid content) and the like stored in the acidic solution adjusted in pH with sulfuric acid. A solid tank such as a filter for obtaining a solid content containing lead and a liquid content containing zinc and copper by solid-liquid separation of the slurry after stirring and mixing in the water tank Separation means and a liquid containing zinc and copper obtained by the solid-liquid separation means are mixed with a metal having a greater ionization tendency than copper, and copper is deposited on the surface of the metal, so that only zinc is present. A mixing tank for obtaining a liquid containing a liquid, a water tank with an agitating blade storing an alkaline aqueous solution for eluting lead from the solid content containing lead obtained by the solid-liquid separation means, and processing in the water tank The resulting slurry is separated into solid and liquid components that contain lead. Solid-liquid separation means such as a filter for obtaining, and water washing means for washing the solid content obtained by the solid-liquid separation means so that it can be used as a cement raw material (for example, a mixing tank or washing water from above) For example, a belt filter for spraying.
[0032]
The solution after the treatment by the heavy metal removing means 17 is discharged out of the system through the waste water treatment means 19.
Since the heavy metal has already been removed, the collected matter in the bag filter 8 is guided to the cleaning means 16 via the supply path without passing through the heavy metal removal means 17.
Hydrogen chloride and sulfur oxide adsorbed by the active coke tower (denitration equipment) 10 (SO _X ) And heavy metal are heated and desorbed in the activated coke regeneration tower 11 and then introduced into the washing tower 12 as a gas. In the washing tower 12, hydrogen chloride and heavy metal are absorbed into the water by spraying water. .
After absorption, the aqueous solution containing chlorine and heavy metal is guided to the heavy metal recovery means 18, where the heavy metal is recovered and removed as a solid content. The aqueous solution (solution containing chlorine) after the treatment by the heavy metal recovery means 18 is guided to the heavy metal removal means 17 through the supply path and used as part of the water.
In addition, when the heavy metal is not contained in the aqueous solution after washing in the washing tower 12, the processing by the heavy metal recovery means 18 may be omitted.
[0033]
Sulfur oxides (SO _X ) Gas is led to the alkali cleaning tower 13, and in the alkali cleaning tower 13, sulfur oxide (SO _X ) Is absorbed in the alkaline aqueous solution. After absorption, the aqueous solution containing sulfur is guided to the cleaning means 16 via the supply path and used as part of the water for slurrying.
The gas that has passed through the alkali cleaning tower 13 contains mist. The mist is collected by the mist catcher 14 and recovered as a solution, and then supplied to the heavy metal removing means 17 through the heavy metal recovery means 18.
The gas that has passed through the mist catcher 14 is discharged from the chimney 15 into the atmosphere after passing through another purification device as necessary.
[0034]
The solid content finally obtained by the cleaning means 16 is used as a part of the cement raw material. The liquid component obtained by the cleaning means 16 is discharged out of the system through the waste water treatment means 19.
In addition, as an example of the waste water treatment means 19, for example, after adding an iron salt such as ferrous chloride, the pH is adjusted to generate iron hydroxide, and heavy metals are reduced, adsorbed, and coprecipitated and removed. The equipment comprised so that it can perform these processes is mentioned. Another example is a chelate tower for capturing heavy metals. It is preferable to pass wastewater through this chelate tower because the removal rate of heavy metals in the wastewater can be further increased.
[0035]
【The invention's effect】
According to the treatment method and treatment system of the present invention, heavy metals and acidic gas contained in exhaust gas from a firing furnace, an incinerator, or the like can be efficiently and sufficiently removed.
Moreover, the solid content obtained in the process of exhaust gas is efficiently converted into a cement raw material with simple equipment.
[Brief description of the drawings]
FIG. 1 is a diagram schematically showing an example of a processing system of the present invention.
[Explanation of symbols]
1 Cement kiln
2 Clinker cooler
3 Burner
4 Cooler
5 Cyclone
6,8 Bug filter
7 Alkali source storage tank
9 fans
10 Active coke tower (denitration equipment)
11 Active coke regeneration tower
12 Washing tower
13 Alkali washing tower
14 Mist Catcher
15 Chimney
16 Cleaning means
17 Heavy metal removal means
18 Heavy metal recovery means
19 Wastewater treatment means

Claims (6)

(A) From the exhaust gas containing coarse particles, fine particles containing heavy metals, and acid gas, the coarse particles are separated and recovered to obtain exhaust gases containing fine particles containing heavy metals and acid gases. Coarse grain collection process,
(B) From the exhaust gas obtained in the step (A), the fine particle containing the heavy metal is separated and recovered, and the fine particle collecting step for obtaining the exhaust gas containing the acid gas;
(C) An alkali source addition step of adding an alkali source to the exhaust gas obtained in the step (B) to obtain an exhaust gas containing a solid content composed of a reaction product of the alkali source and the acid gas;
(D) a solid content recovery step for separating and recovering the solid content from the exhaust gas obtained in step (C);
(E) A heavy metal removal step of removing a heavy metal from the fine particle containing the heavy metal obtained in step (B) to obtain a solid content from which the heavy metal has been removed;
(F) The coarse particles obtained in the step (A) and the solid content obtained in the step (D) were washed with an alkaline aqueous solution to remove the components derived from the acidic gas. And a water washing step for obtaining a solid content. The exhaust gas treatment method according to claim 1, wherein at least one of the solid content obtained in the step (E) and the solid content obtained in the step (F) is used as a cement raw material. (A) Coarse-grain collecting means for collecting coarse-grained fraction, fine-grained fraction containing heavy metal, and coarse-grained fraction in exhaust gas containing acidic gas;
(B) a first fine particle collecting means disposed on the downstream side of the coarse particle collecting means (a) for collecting the fine particle containing the heavy metal in the exhaust gas;
(C) an alkali source supply means for supplying an alkali source to the exhaust gas at a point on the downstream side of the first fine particle collection means (b);
(D) a second fine particle collection means disposed on the downstream side of the alkali source supply means (c) and for collecting a reaction product of the acidic gas in the exhaust gas and the alkali source; ,
(E) Heavy metal removing means for removing the heavy metal from the fine particle containing the heavy metal collected by the first fine particle collecting means (b) to obtain a solid content from which the heavy metal has been removed;
(F) To wash the coarse particles obtained by the coarse particle collection means (a) and the reaction product collected by the second fine particle collection means (d) with an alkaline solution. An exhaust gas treatment system comprising: a water washing means. The exhaust gas treatment system according to claim 3, further comprising an adsorption means for adsorbing unreacted acidic gas on the downstream side of the second fine particle collection means (d). An adsorbent regeneration means for desorbing the acid gas adsorbed by the adsorption means; and an acid gas recovery means for absorbing and recovering the acid gas desorbed by the adsorbent regeneration means in an aqueous solution. The exhaust gas treatment system according to claim 4. The exhaust gas treatment system according to claim 5, further comprising a supply path for guiding the aqueous solution obtained by the acid gas recovery means to the heavy metal removal means (e) or the water washing means (f).

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