JP2013095605A - Incineration ash treatment method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a method for most efficiently reducing the amount of chlorine in incineration ash with a limited amount of water when the incineration ash is added to water, slurried and subjected to solid-liquid separation, and the resulting solid (filtration residue) is washed to reduce the chlorine content, in order to effectively utilize the incineration ash as a raw material and fuel for cement.SOLUTION: Since an effect of reducing the chlorine concentration of the filtration residue by water washing reaches a ceiling when ≥500 pts.mass of water is used relative to 100 pts.mass of the incineration ash, but lower slurry concentration produces a larger effect of reducing the chlorine concentration, when the total amount of water usable for slurry preparation and washing is assumed to be Y pts.mass, the amount of water used for washing the filtration residue is confined to 500-2,000 pts.mass relative to 100 pts.mass of the incineration ash, and all of the remaining water (Y-500 to Y-2,000 pts.mass) is used for slurry preparation. A filter press is preferably used for the solid-liquid separation in terms of filtration efficiency and the like.

Description

  The present invention relates to a method for treating incinerated ash. More specifically, the present invention relates to a method for treating incinerated ash that can reduce the amount of chlorine, which is a problem when used as a raw material for cement production, and an apparatus therefor.

  Incineration fly ash such as municipal waste is characterized by a large amount of generation, high chlorine content, heavy metals, dioxins, and components that vary greatly depending on the location of generation. Yes.

  One of the utilization methods is a method of using cement as a raw fuel. However, when used as a cement raw fuel, it can not be used without limitation. In particular, in order to keep the chlorine content in the cement, which is the final product, in JIS standards, it is necessary to clean the incineration ash and reduce its chlorine content. (Patent Documents 1 to 3, Non-Patent Document 1, etc.).

JP-A-11-351546 JP 2010-132463 A JP 2003-103231 A

Joichi, Joichi, “Perfect Recycling of Waste Incineration Ashes Using Cement Kilns-Making Waste Incineration Ash as Cement Raw Material”, published by Hi-Tech Information, China Technology Promotion Center, February 28, 2001, vol. 14-19

  However, after filtering the incinerated ash slurry, there is a problem that even if the filtration residue is washed using a large amount of water, the chlorine content of the obtained washed ash may not be sufficiently reduced.

  In view of the above problems, the present inventors have conducted intensive studies. As a result, the chlorine concentration in the incinerated ash after washing hardly changes after the amount of washing water after filtration exceeds a certain level. Rather, it depends on the slurry concentration (ratio of incinerated ash in the slurry) at the time of slurry preparation. It has been found that most of them can be decided, and the present invention has been completed.

That is, the present invention comprises a step of mixing incinerated ash with water in a slurry storage tank to form a slurry, a step of separating the slurry into washing ash and washing water, and a step of washing the filtration residue with water. In the water washing treatment method for making cement raw fuel,
When the total amount of water that can be used for slurry preparation and washing is Y parts by mass,
In order to prepare a slurry of all the remaining water (Y-500 to Y-2000 parts by mass) with respect to 100 parts by mass of incinerated ash, the amount of water used when washing the filtration residue with water is 500 to 2000 parts by mass. It is a water-washing method of incinerated ash characterized by using.

Another invention comprises a step of mixing incineration ash with water in a slurry storage tank to form a slurry, a step of separating the slurry into washing ash and washing water, and a step of washing the filtration residue with water. In the water washing method for making cement raw fuel,
A method for washing incinerated ash with 100 mass parts of incinerated ash, wherein the amount of water used when washing the filtration residue with water is 500 to 2000 parts by mass, and the incinerated ash concentration of the slurry is 10 mass% or less. is there.

  In the incineration ash washing method, the apparatus used in the step of separating the slurry into washing ash and washing water is preferably a filter press.

  According to the present invention, a treated incinerated ash having a low chlorine content can be stably obtained with a relatively small amount of water. As a result, even if the incinerated ash is used as a cement raw fuel, it is possible to suppress the amount of chlorine in the produced cement, and thus it becomes easy to always use a large amount of incinerated ash as the cement raw fuel. .

The figure which shows the amount of washing water and chlorine content when making incineration ash slurry density | concentration constant. The figure which shows a slurry concentration and a chlorine content rate. The figure which shows a slurry density | concentration and chlorine content when changing the distribution ratio of the water for slurry adjustment, and the water for washing | cleaning, making the total amount of water constant.

  The incinerated ash to be treated in the present invention is not particularly limited, but the amount of generated incineration ash is large, the city has no useful use other than the cement raw material, and the city has a relatively large chlorine content. It is preferable to target garbage incineration ash.

  Of the incineration ash discharged from municipal waste incinerators, the main ash is mainly incinerated ash discharged from the lower part of the stalker furnace as burned husks, and because it comes into contact with water after cooling incineration, the water content is 20% to 50%. It is obtained as a lump containing about (mass). The chlorine content ranges from 0.5 to 5.0% (mass). On the other hand, fly ash is fine powder supplemented from exhaust gas from a stalker furnace or exhaust gas from a fluidized bed furnace, and generally contains chlorine at a ratio of about 5 to 30% (mass).

  The main ash may contain a large amount of foreign matter such as empty cans and wires, and it is preferable to remove these in advance. Further, since the main ash is a lump, it is necessary to adjust in advance so that the average particle size is 200 μm or less, preferably 150 μm or less, and more preferably 50 to 100 μm. Furthermore, it is preferable to remove the unground product and foreign matter that has not been completely removed before pulverization even after the main ash pulverization.

  On the other hand, since fly ash contains a large amount of dioxins with respect to main ash, it is preferable that the diash is treated in advance.

  The method for dedioxins is not particularly limited, and may be performed under known conditions. For example, fly ash may be treated at a temperature of 300 to 450 ° C., preferably 350 to 450 ° C. in an oxygen-free atmosphere. The oxygen-free atmosphere includes not only the case where oxygen is not completely present, but also includes an aspect in which oxygen that inevitably enters due to the structure of an apparatus or the like, oxygen that accompanies the object to be processed, and the like are contained. As for dedioxins, the aspect which forms an oxygen-free atmosphere with nitrogen gas, and heats with a heater is preferable. Mercury can also be volatilized and removed by heating in the dedioxin treatment, which is effective as a pretreatment for municipal waste incineration ash containing a relatively high concentration of mercury.

  In the present invention, incinerated ash such as main ash and fly ash pretreated as described above is mixed with water, respectively, or slurried. The method of slurrying is not particularly limited, and a known method may be selected as appropriate.

  In the present invention, the incinerated ash as described above is mixed with water to form a slurry. The method of slurrying is not particularly limited, and examples thereof include a method in which incinerated ash and water are placed in a slurry storage tank and stirred.

  In the present invention, incinerated ash such as main ash and fly ash pretreated as described above is mixed with water, respectively, or slurried. The method of slurrying is not particularly limited, and a known method may be selected as appropriate. For example, the method of putting incineration ash and water in a slurry storage tank and stirring it can be mentioned.

  The temperature of water when making the slurry is not particularly limited, but is preferably 10 ° C. or higher, more preferably 15 ° C. or higher, and most preferably 20 ° C. or higher. As the water used at this time, general industrial water, ground water, tap water and the like can be used.

  The stirring time is sufficient if it becomes a uniform slurry as a whole, and depending on the stirring device, about 5 to 60 minutes is generally sufficient.

  The feature of the present invention is that the necessary minimum amount of washing water is secured from the total amount of water that can be used, and all the remaining water is used for preparing the slurry, and the slurry concentration is made as low as possible. This is because, as described above, the chlorine concentration in the incinerated ash after washing hardly depends on the amount of washing water after filtration, and is largely determined by the slurry concentration at the time of slurry preparation. Of course, if water can be used without limitation, a large amount of washing water may be used, but usually there is a limit to the amount of water that can be used. Therefore, in the present invention, in order to obtain the maximum chlorine reduction effect of the limited water, the water is divided into the slurry preparation water and the filtration residual washing water as described above.

  Specifically, as shown in FIG. 1, the amount of washing water for washing the filtered residue after filtration is 500 parts by mass or more with respect to 100 parts by mass of incinerated ash, and the effect of reducing the chlorine concentration of the filtered residue is peak. The tendency to become strong. On the other hand, as shown in FIG. 2, the chlorine concentration tends to decrease as the slurry concentration of the incineration ash slurry decreases.

  Therefore, in the present invention, the amount of the washing water is 500 parts by mass or more, preferably 550 parts by mass or more, more preferably 600 parts by mass or more with respect to 100 parts by mass of the incineration ash. On the other hand, the upper limit is 2000 parts by weight, preferably 1800 parts by weight, more preferably 1500 parts by weight or less, and particularly preferably 1000 parts by weight or less in order to turn the total amount of water that can be used into water for slurry preparation as much as possible. And

  From another point of view of the present invention, in view of the fact that the chlorine concentration decreases as the slurry concentration of the incineration ash slurry decreases, the slurry concentration is 10% by mass or less, preferably 7% by mass or less, The chlorine concentration can be sufficiently reduced with a small amount of washing water of about 500 to 2000 parts by mass with respect to 100 parts by mass of incinerated ash.

  By slurrying and washing as described above, most of the chlorine content in the incinerated ash is dissolved in water. In the present invention, the amount of chlorine in the washing ash can be greatly reduced by separating the slurry into washing ash and washing water.

  Although the said separation method can employ | adopt without specifically limiting the well-known method in which solid-liquid separation is possible, a filter press is preferable at the point which is easy to wash | clean separation efficiency and solid content after isolation | separation.

  Of course, besides the filter press, known things such as Nutsche suction filter, drum filter and belt filter can be used without limitation.

  After separating into water and solids (filter residue) by the above filter press etc., solids are removed to remove chlorine contained in the filter residue that was not separated and separated (mostly contained in the wash water that could not be filtered off). The water is further washed with water, and the total amount of water used can be reduced by setting the amount of water in this range to the above-mentioned range. The water temperature in this washing step is not particularly limited, but is preferably 10 ° C or higher, more preferably 15 ° C or higher, and most preferably 20 ° C or higher.

  As a cleaning method, a known method may be employed depending on the solid-liquid separation device used. For example, when a filter press is used, a method of performing through-cleaning with a dehydrated cake sandwiched between filters can be used.

  The present invention as described above is particularly effective when the amount of water that can be used is limited, and the total amount of water that can be used for slurry preparation and washing is 5000 parts by mass or less, particularly 3000 parts by mass with respect to 100 parts by mass of incinerated ash. Its effectiveness is high in the following cases.

  In the present invention, the solid content (washed ash) obtained in the above washing step is mainly used as a cement raw material in a cement manufacturing plant because it contains a calcium compound and silica as main components and the chlorine content is greatly reduced. The In this case, since the solid content contains water, it is preferably supplied to the suspension preheater through the dryer together with the cement raw material in the raw material preparation process. Moreover, what is necessary is just to discharge | emit the waste_water | drain obtained by this invention as a treated waste water after performing a known waste water treatment.

  Hereinafter, the present invention will be described in more detail with reference to experimental examples, but the present invention is not limited to these examples.

  The chlorine concentration in the incinerated ash in each experimental example was measured by fluorescent X-ray analysis after drying the incinerated ash of the sample at 100 ° C.

Experimental Examples 1-8
In the slurry reservoir, 1400 parts by mass of water (water temperature 25 ° C.) was added to 100 parts by mass of the garbage incineration ash obtained from the municipal waste incinerator to obtain an incineration ash slurry having a slurry concentration of 6.7% by mass. This slurry was introduced into a filter press for solid-liquid separation. Furthermore, the filtration residue cake (solid content) was subjected to through washing with a water amount corresponding to 0 to 14000 parts by mass with respect to 100 parts by mass of the garbage incineration ash. The results of measuring the chlorine content of the washed cake are shown in Table 1 together with the amount of water used for washing.

Experimental Examples 9-16
In the slurry reservoir, 900 parts by mass of water (water temperature 18 ° C.) was added to 100 parts by mass of garbage incineration ash obtained from a municipal waste incinerator to obtain an incineration ash slurry having a slurry concentration of 10% by mass. This slurry was introduced into a filter press for solid-liquid separation. Further, the filtration residue cake (solid content) was subjected to through washing with a water amount corresponding to 0 to 4000 parts by mass with respect to 100 parts by mass of the dust incineration ash. The results of measuring the chlorine content of the washed cake are shown in Table 2 together with the amount of water used for washing.

  The results of Experimental Examples 1 to 16 are plotted in FIG. 1 as a result of plotting the amount of water used for cleaning (100 parts by mass of incinerated ash) on the horizontal axis and the amount of chlorine in the washed cake after cleaning on the vertical axis.

  As can be seen from FIG. 1 and Tables 1 and 2, the amount of chlorine in the washing cake decreases until the washing water reaches 500 parts by mass with respect to 100 parts by mass of the incinerated ash, but even if the amount of washing water is increased further. There is no decrease in chlorine content.

Experimental Examples 17-20
Slurries were prepared by changing the slurry concentration, and each was subjected to solid-liquid separation with a filter press, and then washed with 500 parts by mass or more of washing water with respect to 100 parts by mass of incinerated ash. The results of measuring the amount of chlorine in the washed cake after washing are shown in Table 3 and FIG. 2 together with the slurry concentration and the like. As shown in this chart, the chlorine content of the washing cake decreases as the slurry concentration decreases.

Experimental Examples 21-27
100 parts by mass of incinerated ash and 2900 parts by mass of water were prepared, 0 to 2750 parts by mass of water were secured as washing water, and slurries with different concentrations were prepared using the remaining water. Each was subjected to solid-liquid separation with a filter press and then washed with washing water. The amount of chlorine in the washed cake after washing was measured. The results are shown in Table 4 and FIG.

Claims (3)

Incineration ash is used as a raw cement fuel, comprising a step of mixing incinerated ash with water in a slurry storage tank to form a slurry, a step of separating the slurry into washing ash and washing water, and a step of washing the filtration residue with water. In the water washing method for
When the total amount of water that can be used for slurry preparation and washing is Y parts by mass,
In order to prepare a slurry of all the remaining water (Y-500 to Y-2000 parts by mass) with respect to 100 parts by mass of incinerated ash, the amount of water used when washing the filtration residue with water is 500 to 2000 parts by mass. A method for washing with water of incinerated ash, characterized by being used. Incineration ash is used as a raw cement fuel, comprising a step of mixing incinerated ash with water in a slurry storage tank to form a slurry, a step of separating the slurry into washing ash and washing water, and a step of washing the filtration residue with water. In the water washing method for
A method for washing incinerated ash with water, wherein the amount of water used for washing the filtration residue with respect to 100 parts by mass of incinerated ash is 500 to 2000 parts by mass, and the incinerated ash concentration of the slurry is 10% by mass or less.   The incineration ash washing method according to claim 1 or 2, wherein the apparatus used in the step of separating the slurry into washing ash and washing water is a filter press.

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