JP2008093492A - Method and apparatus for treating fly ash - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a fly ash treatment method constituted so as to bring the amount of a heavy metal elution inhibitor to be kneaded with fly ash to a proper amount without excessively adding the heavy metal elution inhibitor by uniformizing the distribution of the heavy metal concentration in the fly ash within a fly ash storage tank by putting existing equipment to practical use only by the minimum increase of equipment when the heavy metal elution inhibitor and the fly ash taken out of the fly ash storage tank are kneaded in order to perform the elution preventing treatment of heavy metals from fly ash, and a fly ash treatment apparatus. <P>SOLUTION: The fly ash treatment method includes a process for feeding the collected fly ash to the fly ash storage tank 1 by a fly ash feed conveyor 2 to store the same in the fly ash storage tank 1, a process for kneading the fly ash quantitatively supplied from the fly ash storage tank 1 with the heavy metal elution inhibitor and a process for taking the fly ash out of the fly ash storage tank 1 in a non-kneading time zone to return the same to the fly ash feed conveyor 2 subjected to feed operation. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is a pretreatment for landfill disposal of fly ash separated from exhaust gas generated in a waste incineration facility, so as to prevent heavy metals contained in the fly ash from eluting after landfill disposal. The present invention relates to a fly ash treatment method and apparatus.

  Fly ash is contained in the exhaust gas generated by incineration of garbage at the garbage incineration facility. The fly ash separated from the exhaust gas is finally landfilled. However, when fly ash contains heavy metals (lead, cadmium, mercury, hexavalent chromium, arsenic, selenium, etc.), heavy metals may be eluted in rainwater after the fly ash is reclaimed. In order to prevent elution of heavy metals, it is necessary to treat fly ash in advance with a heavy metal elution inhibitor to obtain a fly ash treated product in which elution of heavy metals in the fly ash is prevented. In addition, fly ash was collected by waste heat boilers of garbage incineration facilities, "dust" collected in gas cooling chambers (cooling towers), and dust collection ash (dust collection facilities (back filter etc.)). "Baijin") is a general term.

  The conventional fly ash treatment method will be described. First, the collected fly ash is transported to the fly ash storage tank by the fly ash transport conveyor and stored in the fly ash storage tank. After storage, a certain amount of fly ash was cut out from the fly ash storage tank, and this and a certain amount of heavy metal elution inhibitor were kneaded by a kneader. In this case, for example, in a waste incineration facility where the incinerator is operated continuously for 24 hours, the kneader is operated for about 2 hours per time to stabilize the fly ash stored in the fly ash storage tank until then. The next kneading is performed after about 8 hours from the end of the kneading.

  However, the conventional fly ash treatment method has the following problems. The heavy metal concentration in fly ash varies depending on the properties of the incinerated waste (city waste, industrial waste, etc.), so the concentration of heavy metals in the fly ash storage tank is also the bottom of the tank. From the top to the top of the tank is not uniform but non-uniform. Therefore, for the fixed amount of fly ash cut out and supplied from the fly ash storage tank, regardless of the level of heavy metal concentration in the fly ash, as a safe process, heavy metals based on the past accumulated data that has been updated A predetermined amount of heavy metal dissolution inhibitor was added based on the maximum concentration. As a result, although the fly ash treated with chemicals meets the elution standard for heavy metals, it always adds an excessive amount of anti-elution agent for heavy metals, and an appropriate amount without excessive addition to the fly ash. No heavy metal dissolution inhibitor was added.

  The prior art document information related to the present invention includes the following.

JP-A-11-244638 (paragraphs [0007], [0010], [0026], [0033], FIG. 1, FIG. 3, FIG. 4)

  Therefore, the object of the present invention is to prevent the elution of heavy metals from the fly ash, when kneading the heavy metal elution inhibitor and the fly ash cut out from the fly ash storage tank, only existing facilities are required with minimal addition of equipment. By making uniform the distribution of heavy metal concentration in the fly ash in the fly ash storage tank by utilizing equipment, the amount of heavy metal elution inhibitor kneaded with fly ash is adjusted to an appropriate amount without excessive addition. Another object of the present invention is to provide a fly ash treatment method and apparatus that can be used.

  In order to solve the above problems, the present invention takes the following technical means.

  The invention of claim 1 is a fly ash treatment method for preventing elution of heavy metals from fly ash, wherein the collected fly ash is transported to a fly ash storage tank by a fly ash transport conveyor, and the fly ash is stored. The step of storing in the tank, the step of kneading the fly ash quantitatively supplied from the fly ash storage tank and the heavy metal elution inhibitor, and the fly ash from the fly ash storage tank during the time period when the kneading is not performed. A fly ash treatment method comprising: cutting out and returning the fly ash to the fly ash transport conveyor that is transporting the fly ash.

  The invention according to claim 2 is a fly ash treatment apparatus for preventing elution of heavy metals from fly ash, and a fly ash storage tank and a fly ash transport conveyor for transporting the collected fly ash to the fly ash storage tank. A fly ash quantitative supply device that cuts out and supplies the fly ash from the fly ash storage tank, and a kneader that kneads the fly ash and the heavy metal elution inhibitor by supplying the fly ash in a fixed amount by the fly ash quantitative supply device And fly ash circulation return means for returning the fly ash cut out from the fly ash storage tank to the fly ash transfer conveyor that is moving in a time zone during which the kneading is not performed. This is a fly ash treatment apparatus.

  The fly ash treatment method or fly ash treatment apparatus of the present invention cuts out fly ash from the fly ash storage tank in a time zone in which the heavy metal elution inhibitor and the fly ash from the fly ash storage tank are not kneaded, and the fly ash Since the operation of returning the fly ash to the fly ash conveyance conveyor is repeated, the fly ash in the fly ash storage tank is uniformly mixed as a whole, and heavy metals in the fly ash in the fly ash storage tank The concentration distribution can be made uniform. Therefore, when kneading heavy metal dissolution inhibitor and fly ash from the fly ash storage tank, the average amount of heavy metals concentration based on the past accumulated data that has been updated for the amount of heavy metal dissolution inhibitor mixed with fly ash. By setting so as not to cause insufficient addition based on the above, an appropriate amount can be obtained without excessive addition, and an increase in processing cost due to excessive addition can be eliminated. Moreover, as an extension facility, it is only necessary to provide a means for returning the fly ash cut out from the fly ash storage tank onto the fly ash transport conveyor, and the increase in the apparatus cost can be minimized.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a schematic configuration diagram showing a fly ash treatment apparatus according to an embodiment of the present invention.

  In FIG. 1, 1 is a fly ash storage tank, 2 is a fly ash conveyance conveyor, and fly ash collected by a waste heat boiler, a gas cooling chamber (temperature reduction tower), a back filter, etc. in a garbage incineration facility. Is transported to the fly ash storage tank 1. 3 is a table feeder as a fly ash quantitative supply device for quantitatively cutting out and supplying fly ash from the fly ash storage tank 1, and 4 is a fly ash quantitative supply by the table feeder 3 to prevent elution of fly ash and heavy metals. It is a kneader that kneads the agent together with the added water for dilution.

  The heavy metal elution inhibitor is for preventing elution of heavy metals in fly ash, and examples of the heavy metal elution inhibitor include heavy metal stabilizers, pH adjusters and the like. The heavy metal stabilizer is for chemically stabilizing heavy metals in fly ash. Examples of the heavy metal stabilizer include liquid chelating agents and inorganic processing agents.

  A chemical tank 6 stores a liquid heavy metal stabilizer (liquid chelating agent) as a heavy metal elution inhibitor. Reference numeral 7 denotes a chemical pump, which sends a heavy metal elution inhibitor (liquid chelating agent) from the chemical tank 6 to the kneader 4 in a fixed amount in accordance with the amount of fly ash cut out from the fly ash storage tank 1. Further, 8 is an additive water tank, and 9 is a pump for additive water for quantitatively feeding the additive water from the additive water tank 8 to the kneader 4 according to the amount of fly ash cut out from the fly ash storage tank 1. 10 is a carry-out conveyor, and 11 is a fly ash processed product pit. The fly ash processed product after kneading is stored in the fly ash processed product pit 11 after being naturally cured on the carry-out conveyor 10 to prevent the fly ash processed product pit 11 from sticking. In some cases, a fly ash processed product bunker is used instead of the fly ash processed product pit 11.

  Reference numeral 5 denotes a fly ash return conveyor as a fly ash circulation return means, and the fly ash cut out from the fly ash storage tank 1 is transported during a time zone when the kneading machine 4 is not kneaded. It is for returning to the ash conveyance conveyor 2.

  Next, a fly ash treatment method performed using the fly ash treatment apparatus will be described. In a waste incineration facility equipped with the fly ash treatment apparatus of the present embodiment and in which the incinerator is continuously operated for 24 hours, for example, the kneader is operated for about 2 hours per time (per batch processing) until then fly ash The fly ash treatment apparatus is operated so that the fly ash stored in the storage tank is stabilized, and the next kneading is performed about 8 hours after the end of the kneading.

  In such an operation cycle, the heavy metal elution inhibitor and the fly ash from the fly ash storage tank 1 are kneaded by the kneader 4 to produce a fly ash treatment product, for example, about the time until the next kneading. The table feeder 3 and the fly ash return conveyor 5 are operated in addition to the fly ash transport conveyor 2 that is continuously operated for 24 hours for 8 hours. The table feeder 3 is operated following the kneading. That is, fly ash is cut out from the fly ash storage tank 1 by the table feeder 3 from the end of the current kneading to the next kneading, and the cut fly ash is removed from the fly ash return conveyor 5 by the fly ash return conveyor 5. The operation of returning to is repeated. As a result, the fly ash storage tank 1 → the table feeder 3 → the fly ash return conveyor 5 → the fly ash transport conveyor 2 → the fly ash is repeatedly transported through the circulation path returning to the fly ash storage tank 1, so that the fly ash storage tank 1 The fly ash is uniformly mixed as a whole, and the distribution of the heavy metal concentration in the fly ash in the fly ash storage tank 1 is made uniform.

  Therefore, when the heavy metal elution inhibitor and the fly ash from the fly ash storage tank 1 are kneaded, the average value of the heavy metal concentration based on the past accumulated data regularly updated for the fly ash is used. By adding a pre-determined amount of heavy metal elution preventing agent so as not to be insufficiently added, it is possible to achieve an appropriate amount without excessive addition, and unlike the conventional method, the increase in processing cost due to excessive addition is eliminated. be able to. Further, as the additional equipment, only the fly ash return conveyor 5 is required, and the increase in the apparatus cost can be minimized.

It is a schematic block diagram which shows the fly ash processing apparatus by one Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Fly ash storage tank 2 ... Fly ash conveyance conveyor 3 ... Table feeder 4 ... Kneading machine 5 ... Fly ash return conveyor 6 ... Chemical tank 7 ... Chemical pump 8 ... Additive water tank 9 ... Additive water pump 10 ... Unloading conveyor 11 ... Fly ash processed product pit

Claims (2)

  In the fly ash treatment method for preventing elution of heavy metals from fly ash, the step of transporting the collected fly ash to the fly ash storage tank by the fly ash transport conveyor and storing it in the fly ash storage tank; A step of kneading the fly ash quantitatively supplied from the fly ash storage tank and the heavy metal elution inhibitor, and cutting out the fly ash from the fly ash storage tank and transporting the fly ash during the time period when the kneading is not performed And a step of returning the fly ash to the operating fly ash conveyor.   In a fly ash treatment apparatus for preventing elution of heavy metals from fly ash, a fly ash storage tank, a fly ash transport conveyor for transporting the collected fly ash to the fly ash storage tank, and the fly ash storage tank The fly ash is supplied from a fixed amount by the fly ash quantitative supply device, the fly ash is supplied quantitatively by the fly ash quantitative supply device, and the kneading is performed. Fly ash circulation return means for returning the fly ash cut out from the fly ash storage tank to the fly ash transport conveyor that is transporting the fly ash in a non-period of time Processing equipment.

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