JP4579178B2 - Methods for removing and recovering heavy metals from the cement manufacturing process - Google Patents

Description

  The present invention relates to a method for removing and recovering heavy metals from a cement manufacturing process, and in particular, a part of combustion gas is extracted from an exhaust gas passage of a cement kiln, and heavy metals such as lead and thallium are efficiently extracted from the extracted combustion gas. It relates to a method of removing or recovering well.

  Conventionally, it has been considered that lead (Pb) in cement is fixed and hardly dissolved or contaminated in soil. However, as the amount of recycled resources used in cement production equipment has increased in recent years, the amount of lead in cement has also increased, so there is concern about the risk of soil contamination, and there is a movement to regulate the upper limit of lead concentration in cement. It has begun.

  In addition to lead, in the cement manufacturing process, a small amount of thallium (Tl) is produced from coal as fuel and waste tires. Since this thallium has a low boiling point, it volatilizes between the kiln and the preheater of the cement baking apparatus, and most of it is concentrated in the preheater. In addition, since heavy metals such as zinc, copper, silver and cadmium are also harmful, attempts have been made to reduce the heavy metal content of cement.

  As a technique for removing the heavy metals, for example, Patent Document 1 discloses a chlorine bypass dust obtained by extracting a part of combustion gas from a kiln exhaust gas passage from a kiln bottom of a cement kiln to a bottom cyclone. A waste processing method is disclosed for the purpose of reducing the amount of chemicals used in separating and recovering lead, chlorine, and calcium from such waste.

  According to this method, waste containing lead, calcium, and chlorine and water for slurrying are mixed to form a slurry, and the slurry is classified into a coarse particle and a fine particle, and water is added to the fine particle. After adding an alkali agent such as sodium oxide, solid-liquid separation is performed to obtain a filtrate containing solid content including calcium hydroxide, lead and chlorine, and a sulfurizing agent such as sodium hydrosulfide is added to the filtrate. After the addition, solid-liquid separation is performed to obtain a filtrate containing lead sulfide and a chlorine content, and the obtained filtrate is used as water for the slurrying.

Further, Patent Document 2 discloses that when waste containing lead content such as chlorine bypass dust and slurry water are mixed and lead content in the waste is eluted in water, the elution rate of lead content in water. A method for treating waste is disclosed. In this method, waste containing lead content and slurry water are mixed to form a slurry, the pH of the slurry is adjusted to 7.0 to 11.5, and the oxidation-reduction potential is adjusted to 400 mV or more. The slurry containing the solid is subjected to solid-liquid separation to obtain a filtrate containing solid content and lead content, and after adding a sulfiding agent to the filtrate containing lead content, solid-liquid separation is performed to obtain lead sulfide and filtrate. A part of the obtained filtrate is used as water for slurrying.
JP 2003-236497 A JP 2003-236503 A

  However, in the prior art described in the above patent document, the slurry containing lead contained in chlorine bypass dust or the like is solid-liquid separated, and the lead is removed or recovered from the filtrate. The proportion of lead removed outside is only about 30% of the total. Even if 100% of lead in chlorine bypass dust is removed, the remaining 70% is still clinker discharged from the cement kiln. Therefore, there is a problem that it is not easy to reduce the lead content of cement. Moreover, there were similar problems with heavy metals other than lead.

  Therefore, the present invention has been made in view of the problems in the above-described conventional technology, and an object thereof is to provide a method for efficiently removing or recovering heavy metals such as lead and thallium from a cement manufacturing process. And

  In order to achieve the above object, the present invention provides a method for removing heavy metals from a cement manufacturing process, wherein a chlorine source is added to a cement raw material (including waste) containing heavy metals to chlorinate the heavy metals. The heavy metals are volatilized in the cement manufacturing process, and a part of the combustion gas of the cement kiln in the cement manufacturing process is extracted to remove the heavy metals.

  And according to the present invention, by adding a chlorine source to form heavy chlorides in the form of chloride, volatilize in the cement manufacturing process, and by extracting a part of the combustion gas of the cement kiln containing the volatilized heavy metals More heavy metals can be efficiently removed from the cement manufacturing process. As a result, the amount of heavy metals taken into the clinker discharged from the cement kiln is reduced, and the heavy metal content of the cement can be reduced.

  Further, the present invention is a method for recovering heavy metals from a cement manufacturing process, wherein a chlorine source is added to a cement raw material containing heavy metals to make the heavy metals chloride, and the heavy metals are removed in the cement manufacturing process. It is characterized by volatilizing, extracting a part of the combustion gas of the cement kiln in the cement manufacturing process, and recovering the heavy metals from the extracted gas.

  According to the present invention, heavy metals in the form of chloride by adding a chlorine source are volatilized in the cement manufacturing process, and a portion of the combustion gas of the cement kiln containing the volatilized heavy metals is extracted to remove the heavy metals. Because it is recovered, more heavy metals can be efficiently recovered from the cement manufacturing process.

  In the method for recovering heavy metals from the cement manufacturing process, the heavy metals can be recovered from dust recovered by cooling the extraction gas. In the recovery method, the heavy metals may be recovered from a liquid obtained by treating the extraction gas with a wet scrubber. Furthermore, in the said collection method, after making the dust contained in the said extraction gas into a slurry, you may collect | recover the said heavy metals by a flotation process.

  In the method for removing or recovering heavy metals from the cement manufacturing process, the cement raw material may contain heavy metals circulating in the cement manufacturing process. For example, chlorine bypass dust and kiln EP dust correspond to this cement raw material.

  In the method for removing or recovering heavy metals, the cement raw material may be a cake after washing and desalting the incinerated ash with water. As a result, chlorine can be removed from the incinerated ash by washing, and more heavy metals can be efficiently recovered from the cement manufacturing process.

  Furthermore, in the method for removing or recovering heavy metals, the heavy metals can be lead, thallium, rubidium, zinc, copper, silver or cadmium, and volatilize in the cement manufacturing process by adding a chlorine source. Further, heavy metals that can be recovered from a part of the combustion gas of the cement kiln can be removed or recovered.

  In the method for removing or recovering heavy metals, the chlorine source can be hydrochloric acid, waste hydrochloric acid or chlorine gas.

Furthermore, the present invention is an apparatus for removing heavy metals , wherein a chlorine source is added to a cement raw material containing heavy metals and the heavy metals are used as chlorides, and the heavy metals are converted into chlorides. And a bleeder that bleeds a part of the combustion gas of the cement kiln in the cement manufacturing apparatus in which is volatilized. With this apparatus, as described above, more heavy metals can be efficiently removed from the cement manufacturing process, and the heavy metal content of the cement can be reduced.

The present invention also relates to a heavy metal recovery device , wherein a chlorine source is added to a cement raw material containing heavy metals and the heavy metals are used as chlorides, and the heavy metals are converted into chlorides. And a heavy metal recovery device for recovering the heavy metals from the extracted combustion gas of the cement kiln. . With this apparatus, as described above, more heavy metals can be efficiently recovered from the cement manufacturing process.

  As described above, according to the present invention, heavy metals can be efficiently removed or recovered from the cement manufacturing process, and the content of heavy metals such as lead in the cement can be reduced.

  Next, as an embodiment of the present invention, an example in which incineration ash such as municipal waste incineration ash is used as a cement raw material containing heavy metals, and lead contained in the incineration ash is removed and recovered from the cement manufacturing process is an example. I will explain to you.

  FIG. 1 shows an embodiment of a heavy metal removal / recovery device according to the present invention. This heavy metal removal / recovery device 1 is attached to a cement manufacturing apparatus 11 having a preheater 12 and a cement kiln 13. The incinerated ash A is washed with water, followed by solid-liquid separation, and a first water washing device 2 for separating the cake C1 and the filtrate F1, and a first hydrochloric acid for adding hydrochloric acid (HCl) as a chlorine source to the cake C1. After washing the chlorine bypass dust D recovered by the addition device 3, the chlorine bypass facility 4 that functions as an extraction device for extracting a part of the combustion gas of the cement kiln 13, and the chlorine bypass facility 4, solid-liquid separation is performed. The second water washing device 5 for separating the cake C2 and the filtrate F2 and the second hydrochloric acid addition device 6 for adding hydrochloric acid to the cake C2.

  The first water-washing device 2 includes, for example, a dissolution tank for mixing the received incinerated ash A with warm water to form a slurry, a belt filter for separating the slurry discharged from the dissolution tank into a solid-liquid separation, and the like. The The water-soluble chlorine compound contained in the incineration ash A is dissolved and removed in the filtrate F1 separated by the first water washing device 2, and the cake C1 supplied to the cement manufacturing device 11 is dissolved in the filtrate F1. Contains lead that did not.

The first hydrochloric acid addition device 3 is provided for adding hydrochloric acid to the lead contained in the cake C1 from the first water washing device 2 to change it to lead chloride (PbCl ₂ ) and volatilizing it in the cement production device 11. .

  Similarly to the first water washing apparatus 2, the second water washing apparatus 5 is a dissolution tank for mixing the chlorine bypass dust D from the chlorine bypass equipment 4 with hot water to form a slurry, and the slurry discharged from the dissolution tank. Is constituted by a belt filter or the like for solid-liquid separation. In the filtrate F2 separated by the second water washing device 5, the water-soluble chlorine compound contained in the chlorine bypass dust D is dissolved and removed, and the cake C2 supplied to the cement manufacturing device 11 is transformed into the filtrate F2. Contains lead that did not dissolve.

  The second hydrochloric acid addition device 6 is provided to add hydrochloric acid to the lead contained in the cake C2 from the second water washing device 5 to change it to lead chloride and volatilize it in the cement production device 11.

  Next, the operation of the heavy metal removal / recovery device 1 having the above configuration will be described with reference to FIG.

  Of the incineration ash A received from municipal waste disposal facilities, etc., fly ash contains 10-20% chlorine, so it is necessary to remove the chlorine before recycling it as a cement raw material. Therefore, the water-soluble chlorine compound contained in the incineration ash A is removed by washing with the first water washing device 2. After washing with water, the water-soluble chlorine compound dissolved in the filtrate F1 is treated by a wastewater treatment facility (not shown).

  On the other hand, the cake C1 from which the water-soluble chlorine compound has been removed is supplied to the cement manufacturing apparatus 11, but the cake C1 contains lead that has not been dissolved in the filtrate F1 as described above. Therefore, hydrochloric acid is added to the cake C1 from the first hydrochloric acid addition device 3, and the lead in the cake C1 is changed to lead chloride, and then supplied to the cement manufacturing device 11.

  The cake C1 supplied to the cement manufacturing apparatus 11 is baked together with the normal cement raw material R supplied to the preheater 12 in the cement kiln 13 via the preheater 12. At that time, since lead chloride has a melting point of 501 ° C. and a boiling point of 950 ° C., it volatilizes in the cement kiln 13 and moves to the preheater 12 side together with the combustion gas of the cement kiln 13. Therefore, in the chlorine bypass facility 4, a part of the combustion gas of the cement kiln 13 is extracted, and the chlorine bypass dust D obtained by cooling the extracted gas is washed in the second water-washing device 5, and the chlorine bypass dust D is obtained. The contained lead chloride and water-soluble chlorine compound are removed by washing to the filtrate F2 side, and the separated cake C2 is returned to the cement production apparatus 11.

  Since the cake C2 returned to the cement manufacturing apparatus 11 contains lead that did not dissolve in the filtrate F2 in the second water washing apparatus 5, hydrochloric acid was added to the cake C2 from the second hydrochloric acid addition apparatus 6. Then, after the lead in the cake C2 is changed to lead chloride, the lead is supplied to the cement manufacturing apparatus 11.

  The cake C2 supplied to the cement manufacturing apparatus 11 is volatilized in the cement kiln 13 when burned in the cement kiln 13 via the preheater 12 as in the case of the cake C1, and together with the combustion gas of the cement kiln 13 It moves to the preheater 12 side. Therefore, in the chlorine bypass facility 4, a part of the combustion gas of the cement kiln 13 is extracted, and the chlorine bypass dust D obtained by cooling the extracted gas is washed in the second water-washing device 5, and the chlorine bypass dust D is obtained. The contained lead chloride and water-soluble chlorine compound are removed by washing to the filtrate F2 side, and the separated cake C2 is returned to the cement production apparatus 11. Thereafter, this step is repeated.

  As described above, in the present embodiment, lead contained in the cake C1 and the cake C2 is volatilized in the cement kiln 13 by adding hydrochloric acid by the first hydrochloric acid addition device 3 and the second hydrochloric acid addition device 6. Therefore, more lead can be removed and recovered by the second water-washing device 5 through the chlorine bypass facility 4 in order to change to lead chloride. Thereby, the quantity of the lead taken in into the clinker CL discharged | emitted from the preheater 12 of the cement manufacturing apparatus 11 falls, and the lead content rate of cement can be reduced.

  In the above embodiment, lead is recovered by washing the chlorine bypass dust recovered by the chlorine bypass facility 4 with water, but the bleed gas from the chlorine bypass facility 4 is treated with a wet scrubber to remove lead from the treatment liquid. It can also be recovered. In addition, after the dust contained in the combustion gas extracted by the chlorine bypass facility 4 is slurried, lead can be recovered by a flotation process.

  Moreover, in the said embodiment, although lead was collect | recovered from the chlorine bypass dust collect | recovered with the chlorine bypass equipment 4, from the kiln bottom of the cement kiln 13 to the bottom cyclone of the preheater 12 like the chlorine bypass equipment 4 Instead of extracting a part of the combustion gas from the kiln exhaust gas flow path, a part of the combustion gas may be extracted from another kiln exhaust gas flow path in the preheater 12.

  Furthermore, in the above embodiment, as a cement raw material containing heavy metals, incineration ash such as municipal waste incineration ash was used, and the case where lead contained in incineration ash was removed and recovered from the cement manufacturing process was described. The present invention can also be applied to waste materials other than incinerated ash and raw materials usually used in the cement manufacturing process.

  Further, heavy metals that can be removed and recovered from the cement manufacturing process according to the present invention are not limited to lead, but as shown in Table 1, thallium, rubidium, zinc, copper, silver, cadmium, etc., hydrochloric acid, etc. By adding the chlorine source, it is possible to remove or recover heavy metals that are volatilized as chlorides in the cement manufacturing process and can be recovered from a part of the combustion gas of the cement kiln. In addition, waste hydrochloric acid, chlorine gas, or the like can be used.

It is a flowchart which shows one Embodiment of the heavy metal removal and collection | recovery apparatus concerning this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Heavy metal removal and collection | recovery apparatus 2 1st water washing apparatus 3 1st hydrochloric acid addition apparatus 4 Chlorine bypass equipment 5 2nd water washing apparatus 6 2nd hydrochloric acid addition apparatus 11 Cement manufacturing apparatus 12 Preheater 13 Cement kiln

Claims (11)

  A chlorine source is added to a cement raw material containing heavy metals to convert the heavy metals into chlorides, volatilize the heavy metals in the cement manufacturing process, and extract a part of the combustion gas of the cement kiln in the cement manufacturing process. Removing the heavy metals from the cement manufacturing process.   A chlorine source is added to a cement raw material containing heavy metals to convert the heavy metals into chlorides, volatilize the heavy metals in the cement manufacturing process, and extract a part of the combustion gas of the cement kiln in the cement manufacturing process. A method for recovering heavy metals from a cement manufacturing process, wherein the heavy metals are recovered from the extracted gas.   The method for recovering heavy metals from a cement manufacturing process according to claim 2, wherein the heavy metals are recovered from dust recovered by cooling the extraction gas.   The method for recovering heavy metals from a cement manufacturing process according to claim 2, wherein the heavy metals are recovered from a liquid obtained by treating the extraction gas with a wet scrubber.   3. The method for recovering heavy metals from a cement manufacturing process according to claim 2, wherein the heavy metals are recovered by a flotation process after the dust contained in the extraction gas is slurried.   6. The method for removing or recovering heavy metals from a cement manufacturing process according to claim 1, wherein the cement raw material contains heavy metals circulating in the cement manufacturing process.   6. The method for removing or recovering heavy metals from a cement manufacturing process according to claim 1, wherein the cement raw material is a cake after washing and desalting the incinerated ash with water.   The method for removing or recovering heavy metals from a cement manufacturing process according to any one of claims 1 to 7, wherein the heavy metals are lead, thallium, rubidium, zinc, copper, silver or cadmium.   The method for removing or recovering heavy metals from a cement manufacturing process according to any one of claims 1 to 8, wherein the chlorine source is hydrochloric acid, waste hydrochloric acid or chlorine gas. A chlorine source addition device for adding a chlorine source to a cement raw material containing heavy metals and using the heavy metals as chlorides ;
An apparatus for removing heavy metals, comprising: an extraction device for extracting a part of combustion gas of a cement kiln in a cement manufacturing apparatus in which the heavy metals converted to chloride are volatilized. A chlorine source addition device for adding a chlorine source to a cement raw material containing heavy metals and using the heavy metals as chlorides ;
An extraction device for extracting a part of the combustion gas of the cement kiln in the cement manufacturing apparatus in which the heavy metals converted to chloride are volatilized;
A heavy metal recovery device comprising: a heavy metal recovery device that recovers the heavy metal from the combustion gas of the extracted cement kiln.

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