JP6541039B2 - Incineration ash processing apparatus and incineration ash processing method - Google Patents

Description

  The present invention relates to an incineration ash treatment apparatus and an incineration ash treatment method for detoxifying harmful substances in incineration ash discharged from a waste incinerator.

  Most of the incineration residue generated when incinerating wastes such as municipal waste and industrial waste is disposed of in landfills. However, in recent years, it has become difficult to secure a landfill site, and there is a demand for reducing the amount of landfill. For this reason, attempts have been made to effectively use the incineration residue (hereinafter referred to as "incineration ash") discharged from a waste incinerator as a resource to reduce the amount of landfill disposal.

  However, incineration ash contains harmful substances, especially heavy metals. Therefore, when the elution amount of heavy metals from incineration ash is more than a reference value, utilization as a resource as it is is difficult. In order to cope with such a situation, in order to make the incineration ash having the above-mentioned properties available as a resource, the treatment to remove heavy metals from the incineration ash is carried out or the heavy metals are stabilized. It is necessary to carry out a low-solubility treatment that makes the amount of elution from incinerated ash less than the standard value. Among heavy metals contained in incineration ash, the content of lead is particularly high, so the heavy metals to be treated are mainly lead.

  The following is known about the low solubility of lead as heavy metals in incinerated ash.

The incineration ash is basic and the pH (basic) of the eluate is high. Regarding the pH of incineration ash, the pH of incineration ash is obtained by reacting calcium oxide (CaO) or calcium hydroxide (Ca (OH) ₂ ) contained in incineration ash with carbon dioxide to convert it to calcium carbonate (CaCO ₃ ). It is carried out to change into a poorly soluble region where heavy metals are poorly soluble. Among the heavy metals in the incineration ash, lead, which has a particularly high content, is an amphoteric metal, and the incineration ash exhibiting strong basicity is treated to lower the pH to make it a poorly soluble region, whereby lead is eluted. The amount can be reduced.

  Thus, by lowering the pH of the incineration ash and changing it to a poorly soluble region, the heavy metals can be made less soluble, elution of heavy metals from the incineration ash can be suppressed, and the criteria for using incineration ash as civil engineering materials It is possible to satisfy the heavy metal elution standard which is the soil environment standard which becomes the value.

  As a standard value for the elution amount of lead in incinerator ash, it is said that the elution amount of lead is 0.01 mg / l or less when it is used effectively as a resource. For this reason, when incinerated ash is used as a resource, it must be treated to make the incinerated ash be below the standard value.

  As an apparatus and method of processing incineration ash, the technique disclosed by patent document 1 or patent document 2 is known.

  First, in Patent Document 1, incineration ash discharged from the incinerator is brought into a calcining furnace (rotary kiln) provided separately from the incinerator, and the incineration ash is calcined at approximately 800 ° C. or higher in the rotary kiln. Harmful removal of harmful heavy metals is carried out to reduce heavy metal concentration in incineration ash (see Patent Document 1, paragraphs [0059] to [0060]).

Next, even in Patent Document 2, as in Patent Document 1, the incineration ash discharged from the incinerator is treated in a rotary kiln provided separately from the incinerator. In this patent document 2, the silicon-containing substance is added to the incineration ash containing the lead component, and heating is performed to 800 ° C. or more with a rotary kiln, and at that time, the CaO / SiO ₂ mass ratio in the incineration ash to which the silicon-containing substance is added By treating with heat treatment temperature and time according to the target lead elution amount, the lead is stabilized and the elution amount is reduced.

Japanese Patent Application Laid-Open No. 2005-169378 Patent document 1: JP-A 2003-159574

  In such Patent Document 1 and Patent Document 2, it is necessary to heat the incineration ash discharged from the incinerator to 800 ° C. or more with a rotary kiln provided separately from the incinerator. Therefore, as a heating device such as a rotary kiln is required separately from the incinerator, not only the equipment of the treatment system becomes large-scale and complicated but also the equipment cost and operation cost increase. Furthermore, in addition to the need for a fuel supply facility for heating incineration ash in a rotary kiln etc., the cost as fuel cost increases.

  In view of such circumstances, the present invention is inexpensive in equipment cost and operation cost without heating the incineration ash only by providing only the incinerator or simple auxiliary equipment, and elution of heavy metals such as lead from the incineration ash It is an object of the present invention to provide an incineration ash treatment apparatus and an incineration ash treatment method which can be suppressed and the efficiency of detoxification treatment of incineration ash can be improved.

  According to the present invention, the above-mentioned problems are solved by the following first or second invention in the incineration ash treatment apparatus and the third or fourth invention in the incineration ash treatment method.

[Incineration ash processing system]
<First invention>
Waste having drying area for drying waste in furnace, main combustion area for burning waste after drying and post-combustion area for post-combustion after burning, and an ash discharge part for discharging incineration ash after post-combustion An incinerator for treating incineration ash generated in a waste incinerator, comprising a reactant supply device for supplying a reaction agent containing silica sand and a flux to the incineration ash in the post-combustion zone Ash processing equipment.

<Second invention>
Waste having drying area for drying waste in furnace, main combustion area for burning waste after drying and post-combustion area for post-combustion after burning, and an ash discharge part for discharging incineration ash after post-combustion In the treatment equipment for incineration ash generated in waste incinerators, a reactive agent supply device for supplying a reaction agent containing silica sand and flux to the incineration ash in the post-combustion zone, and the incineration ash discharged from the ash discharge unit A small particle incineration ash having a particle diameter smaller than a predetermined particle diameter and a classification device for classifying the large particle diameter incineration ash having a large particle diameter equal to or larger than the predetermined particle diameter An incineration ash processing apparatus comprising: small particle size incineration ash conveying apparatus for conveying to the apparatus, wherein the reactive agent supply apparatus supplies small particle size incineration ash to the incineration ash in the post-combustion area together with the reactive agent .

  In the first and second inventions, the flux may be a compound containing at least one of boron oxide, magnesium oxide, sodium chloride, potassium chloride, iron or borax.

[Incineration ash treatment method]
<Third invention>
Waste having drying area for drying waste in furnace, main combustion area for burning waste after drying and post-combustion area for post-combustion after burning, and an ash discharge part for discharging incineration ash after post-combustion In the method of treating incineration ash generated in the waste treatment furnace,
Supply the reaction agent containing silica sand and flux to the incineration ash in the post-combustion zone,
The melting point of each component of incineration ash and silica sand is lowered by flux and the silica sand is reacted with calcium oxide in the incineration ash to form a silicic acid compound to reduce the basicity of the incineration ash, and incineration ash A method for treating incineration ash, characterized by suppressing the elution of lead from the soil.

<Fourth invention>
Waste having drying area for drying waste in furnace, main combustion area for burning waste after drying and post-combustion area for post-combustion after burning, and an ash discharge part for discharging incineration ash after post-combustion Processing equipment for incineration ash generated in waste treatment furnaces,
Classify the incineration ash discharged from the ash discharge part into small particle size incineration ash smaller in particle diameter than a predetermined particle diameter and large particle size incineration ash larger in particle diameter than the predetermined particle diameter,
The classified small particle size incineration ash is supplied to the incineration ash in the post-combustion zone together with the reaction agent containing silica sand and flux agent,
The melting point of each component of incineration ash and silica sand is lowered by flux and the silica sand is reacted with calcium oxide in the incineration ash to form a silicic acid compound to reduce the basicity of the incineration ash, and incineration ash A method for treating incineration ash, characterized by suppressing the elution of lead from the soil.

  In the third and fourth inventions, the flux may be a compound containing at least one of boron oxide, magnesium oxide, sodium chloride, potassium chloride, iron or borax.

In the first and third inventions of such a configuration, the basic components contained in the incineration ash present in the post-combustion zone (mainly by mainly supplying the silica sand and flux to the post-combustion zone of the waste incinerator Calcium oxide (CaO) is converted to Si-containing oxides (silicate compounds such as CaSiO ₃ and Ca ₂ SiO ₄ ) to reduce the basicity of incineration ash (by lowering the pH, thereby suppressing lead elution of incineration ash At that time, the fluxing agent lowers the melting point of each component of incineration ash and silica sand, and is easily melted at a temperature of 600 to 700 ° C., which is the ambient temperature of the post combustion zone in the furnace, Let the reaction proceed.

Further, in the second and fourth inventions of the above configuration, the incineration ash discharged from the incinerator is classified by a classification device, and among the classified incineration ash, lead is larger than the large particle size incineration ash. Si-containing oxides (CaSiO ₃ , Ca ₂ SiO _4, etc.) contained in the incineration ash by supplying the small particle size incineration ash containing the silicon oxide together with the silica sand and flux to the post-combustion zone of the incinerator. Changes the basicity of incineration ash and suppresses lead elution of incineration ash.

  As described above, according to the present invention, by supplying the reaction agent containing silica sand and flux to the post-combustion zone of the waste incinerator, the melting point of each component of incineration ash and silica sand is obtained by the action of flux. The basic component contained in the incineration ash in the post-combustion zone is changed to an oxide containing Si, since the temperature can be lowered to the same level as the temperature of the post-combustion zone atmosphere and the reaction is allowed to proceed easily. By reducing the basicity of the incineration ash, lead elution of the incineration ash can be suppressed, and a separate facility for incineration ash treatment can be dispensed with, making it possible to reduce equipment costs and operating costs.

FIG. 1 is a schematic block diagram of an apparatus according to an embodiment of the present invention. It is a schematic block diagram of the other one Embodiment apparatus of this invention.

  Hereinafter, the first and second embodiments of the present invention will be described based on the attached drawings.

First Embodiment
<Waste incinerator>
FIG. 1 is a schematic block diagram of the incineration ash treatment apparatus according to the present embodiment. The incineration ash treatment apparatus is a reaction for supplying a reaction agent containing silica sand and a flux to a grate type waste incinerator 1 (hereinafter simply referred to as "incinerator 1") for incineration of the above waste. The agent supply device 10 is connected. In the incinerator 1, heat recovery is performed by heat exchange with the exhaust gas discharged from the incinerator 1 as a subsequent device (not shown), and a boiler as a heat recovery system for generating steam and heat recovery by the boiler A bag filter as an exhaust gas treatment system for removing dust and detoxifying the exhaust gas, and a chimney for releasing the gas detoxified with the bag filter to the atmosphere are provided.

  The incinerator 1 is disposed above the main combustion chamber 2 for burning waste such as industrial waste and household waste, and the upstream side (left side in FIG. 1) of the flow direction of waste in the main combustion chamber 2. It is disposed and connected to the waste input port 3 for introducing waste into the main combustion chamber 2 and above the downstream side (right side in FIG. 1) of the main combustion chamber 2 for incineration of waste in the flow direction. The grate incinerator is provided with a secondary combustion chamber 4.

  At the bottom of the main combustion chamber 2, a grate (stalker) 5 for burning waste material while moving it is provided. The grate 5 is a drying grate 5a forming a drying area from the side closer to the waste inlet 3, ie, from the upstream side, a combustion grate 5b forming a main combustion area, and a post-combustion area forming a post-combustion area The waste layer A is formed mainly on the dry grate 5 a and the combustion grate 5 b in the order of the grate 5 c.

  The drying grate 5a mainly performs drying and ignition of waste. In the combustion grate 5b, mainly thermal decomposition and partial oxidation of wastes are performed, combustion of combustible gas and solid matter generated by thermal decomposition is performed, and a flame is formed when the combustible gas is burned. On the post combustion grate 5c, the unburned portion of the solid content in the unburned waste is completely burned. When the solid content in the waste is burned, no flame is generated and the flame burns. As a result, a layer of incineration ash B after being completely burned is formed on the downstream portion (right half in FIG. 1) of the post combustion grate 5c. The incineration ash B is dropped and discharged from the ash discharging unit 6 and stored in the ash pit 7.

  Although not shown, air boxes are provided below the drying grate 5a, the combustion grate 5b and the post combustion grate 5c in the main combustion chamber 2 respectively. The combustion air supplied by the blower is supplied to the respective air boxes through the combustion air supply pipes, and is supplied into the main combustion chamber 2 through the respective grates 5a, 5b, 5c. The combustion air is used for drying and burning the waste on the grate 5a, 5b, 5c, and also has the cooling action of the grate 5a, 5b, 5c and the stirring action of the waste.

  In the secondary combustion chamber 4 connected to the main combustion chamber 2, the unburned portion (unburned gas) of the combustible gas in the combustion gas generated in the main combustion chamber 2 is burned (secondary combustion).

<Reactant supply device>
Reactant supply device 10 mainly stores silica sand and flux as a reactant, mixes both silica sand and flux, or separately but at the same time forms an afterburning zone and burns it on post combustion grate 5c. It is connected to the upper wall of the main combustion chamber 2 to supply ash. Here, the flux is a compound or borax containing at least one of boron oxide, magnesium oxide, sodium chloride, potassium chloride and iron. By supplying such a reactive agent to the incineration ash in the post-combustion zone, the fluxing agent lowers the melting points of the respective components of the incineration ash and silica sand, and the incineration ash in the temperature atmosphere of 600 to 700 ° C. on the post-combustion grate 5c. And the components of the silica sand are easily melted, and the reaction is likely to proceed, and a calcium silicate compound is formed from calcium oxide (CaO) in the incineration ash. The basicity (pH) of incineration ash is lowered by reacting and reducing calcium oxide, and the elution of lead in the incineration ash is suppressed.

  In this embodiment, when the reactant is supplied from the reactant supply device 10 onto the post combustion grate 5c forming the post-combustion zone, the elution of lead in the incineration ash is suppressed, but the behavior is as follows: Based on the principle of the present invention as follows.

<Principle of the present invention>
(A) Lead (Pb) is an amphoteric metal, and the higher the basicity (pH) of incineration ash, the higher the concentration of Pb eluted from incineration ash. Since many basic components of incineration ash are calcium oxide CaO, by making CaO into an insoluble compound, its basicity can be reduced and Pb elution can be suppressed.

(B) As a method for converting CaO in incineration ash into an insoluble compound, calcium oxide CaSiO ₃ or Ca ₂ SiO ₄ is reacted by mixing calcium hydroxide and incineration ash with silica sand and heating. It is conceivable to generate. However, this method has a low reaction rate at low temperatures of 1000 ° C. or less, and the reaction does not proceed sufficiently in several hours.

  (C) Therefore, in the present invention, a reactive agent consisting of silica sand and a flux is used. The fluxing agent lowers the melting point of each component of the incineration ash and the silica sand, and the components of the incineration ash and the silica sand are easily melted in a temperature atmosphere of 600 to 700 ° C., thereby facilitating the reaction.

  (D) Since the reaction temperature of 600 to 700 ° C. is about the same as the temperature atmosphere in the post-combustion zone of the stoker incinerator, the heating reactor is installed separately by using the inside of the incinerator as the reaction site There is an advantage that the cost of equipment and fuel can be reduced compared to

  (E) Incineration ash contains a large amount of CaO in the small particle size. The discharged incineration ash discharged from the incinerator is classified into a large particle size larger than the predetermined particle size and a small particle size smaller than the predetermined particle size, and the small particle size incinerated ash is recovered to be combined with silica sand and flux By further reacting CaO and silica sand in the discharged incineration ash by supplying the incineration ash in the post-combustion zone of the incinerator, the effect of reducing the basicity of the incineration ash and suppressing the elution of lead is further enhanced preferable. In this method, since CaO and silica sand after reaction increase in particle size due to sintering, the incineration ash particles after reaction are not recovered again as small particle size incineration ash particles. Since the content of CaO contained in the incineration ash particles is large in the small particle size having a particle diameter of 1 mm or less, it is preferable to set the standard particle diameter of classification of incineration ash to 1 mm.

<Actuation>
Next, the operation of the waste incinerator according to the present embodiment will be described based on FIG.

  The waste is introduced into the main combustion chamber 2 from the waste inlet 3 of the incinerator 1, and then sent downstream on the drying grate 5a, the combustion grate 5b and the post combustion grate 5c. It is incinerated in the same way. After the unburned gas in the combustion gas is secondarily burned in the secondary combustion chamber 4, the exhaust gas is discharged out of the incinerator 1 as the combustion gas generated by the burning of the waste. The exhaust gas from the incinerator 1 is recovered by heat in a boiler of a subsequent device (not shown), dust is removed by a bag filter, and released from the chimney into the atmosphere. In addition, steam generated by heat recovery in the boiler is sent to the steam turbine and used for power generation.

  In the combustion process in the main combustion chamber 2 as described above, the reaction agent supply device 10 supplies a reaction agent containing silica sand and a flux to incineration ash in the post-combustion area. The incineration ash on the post combustion grate 5c, which forms the post combustion zone, is under an atmosphere of 600 to 700 ° C., and when the above-mentioned reactant is supplied to the incineration ash under this atmosphere, The fluxing agent lowers the melting point of each component of incineration ash and silica sand, and the reaction is carried out in a molten state under the above temperature atmosphere. The calcium oxide in the incineration ash and silica sand react to form a calcium silicate compound to lower the pH of the incineration ash to lower the basicity and suppress the elution of lead in the incineration ash.

  Thus, the incinerated ash subjected to the elution suppression processing of lead is discharged from the ash discharging unit 6, stored in the ash pit 7, transported to the landfill site for landfill disposal, or used effectively as a resource.

Second Embodiment
Next, a second embodiment will be described based on FIG. The present embodiment is characterized in that the classification device 11 is connected to the ash discharge unit 6 of the waste incinerator, and the waste incinerator 1 itself is the same as the first embodiment shown in FIG. In FIG. 2, the same reference numerals as in FIG. 1 denote the same parts as in FIG. 1, and a description thereof will be omitted.

  The classification device 11 receives incinerated ash from the ash discharge unit 6 and classifies it into large particle size incineration ash and small particle size incineration ash based on a predetermined particle size. The incineration ash contains a large amount of CaO in the small particle size. The discharged incineration ash discharged from the incinerator is classified into a large particle size larger than the predetermined particle size and a small particle size smaller than the predetermined particle size, and the small particle size incinerated ash is recovered to be combined with silica sand and flux By further reacting CaO and silica sand in the discharged incineration ash by supplying the incineration ash in the post-combustion zone of the incinerator, the basicity of the incineration ash is lowered and the effect of suppressing the elution of lead is further enhanced. Since the content of CaO contained in the incineration ash particles is high at a small particle size having a particle size of 1 mm or less, the particle size of classifying incineration ash into large particle size incineration ash and small particle size incineration ash should be 1 mm. preferable.

  In the present embodiment, the transportation line 8 is provided to transport small particle size incinerated ash from the classification device 11 to the reactive agent supply device 10, and the ash pit 7 for discharging large particle size incineration ash is provided. . The transfer line 8 is configured by a transfer device such as a transfer conveyor.

  The reaction agent supply device 10 receiving small particle size incineration ash from the classification device 11 supplies silica sand and flux as reaction agents to the incineration ash in the post-combustion zone, and also supplies the small particle size incineration ash. It is supposed to be.

  According to this embodiment, the small particle size incineration ash containing a large amount of calcium oxide is classified and taken out from the incineration ash, and is supplied to the post-combustion zone together with the reaction agent. Furthermore, by making it react, the basicity of incineration ash can be reduced and the effect of suppressing the elution of lead can further be heightened.

  Silica sand and borax as flux are supplied to the incineration ash on the post-combustion grate of the grate type waste incinerator, and the temperature atmosphere of the post-combustion stage in the incinerator is a temperature atmosphere of 600 to 700 ° C. Heat-treated. The leaching test was conducted on the incinerator ash discharged from the incinerator based on the test method according to the environmental standard for pollution on soil of the Ministry of the Environment, and the pH of the eluate and the concentration of the dissolved lead were measured. In the case where nothing is blown into the post-combustion stage as Comparative Example 1, the case where only silica sand is supplied as Comparative Example 2 and the case where only borax is supplied as Comparative Example 3 are similarly heat-treated to conduct a lead dissolution test. The respective results are shown in Table 1.

  On the other hand, when silica sand and borax are supplied to the incineration ash on the post-combustion grate as an example, as shown in the table, the incineration ash may be used as civil engineering material such as landfill roadbed material It was possible to make it less than 0.01 mg / l which is the elution standard of lead. In the comparative example, the above elution standard was exceeded.

  In the first embodiment and the second embodiment, the grate waste incinerator has been described as an example, but in the present invention, the type of incinerator is not limited, and the inside of the furnace is a drying area, the main combustion area, and the post-combustion area. The present invention can be applied as long as it is roughly divided into areas.

1 Waste incinerator 5a Drying grate (drying area)
5b Main combustion grate (main combustion area)
5c Post combustion grate (post combustion area)
6 ash discharge unit 10 reactant supply device 11 classification device

Claims (6)

Waste having drying area for drying waste in furnace, main combustion area for burning waste after drying and post-combustion area for post-combustion after burning, and an ash discharge part for discharging incineration ash after post-combustion Processing equipment for incineration ash generated in waste incinerators,
What is claimed is: 1. An incineration ash processing apparatus comprising: a reactive agent supply device for supplying a reactive agent containing silica sand and a flux to incineration ash in a post-combustion zone. Waste having drying area for drying waste in furnace, main combustion area for burning waste after drying and post-combustion area for post-combustion after burning, and an ash discharge part for discharging incineration ash after post-combustion Processing equipment for incineration ash generated in waste incinerators,
A reactive agent supply device for supplying a reactive agent containing silica sand and flux to incineration ash in the post-combustion zone;
A classification device for classifying incineration ash discharged from the ash discharge unit into small particle size incineration ash having a particle diameter smaller than a predetermined particle diameter and large particle size incineration ash having a large particle diameter equal to or larger than the predetermined particle diameter;
And a small particle size incineration ash conveying device for conveying the classified small particle diameter incineration ash to the reactant supply device;
An incineration ash processing apparatus characterized in that the reactant supply device supplies small particle size incineration ash to the incineration ash in the post-combustion zone together with the reactant.   The incineration ash treatment apparatus according to claim 1 or 2, wherein the flux is a compound containing at least one of boron oxide, magnesium oxide, sodium chloride, potassium chloride, iron or borax. Waste having drying area for drying waste in furnace, main combustion area for burning waste after drying and post-combustion area for post-combustion after burning, and an ash discharge part for discharging incineration ash after post-combustion In the method of treating incineration ash generated in the waste treatment furnace,
Supply the reaction agent containing silica sand and flux to the incineration ash in the post-combustion zone,
The melting point of each component of incineration ash and silica sand is lowered by flux and the silica sand is reacted with calcium oxide in the incineration ash to form a silicic acid compound to reduce the basicity of the incineration ash, and incineration ash A method for treating incineration ash, characterized by suppressing the elution of lead from the soil. Waste having drying area for drying waste in furnace, main combustion area for burning waste after drying and post-combustion area for post-combustion after burning, and an ash discharge part for discharging incineration ash after post-combustion Processing equipment for incineration ash generated in waste treatment furnaces,
Classify the incineration ash discharged from the ash discharge part into small particle size incineration ash smaller in particle diameter than a predetermined particle diameter and large particle size incineration ash larger in particle diameter than the predetermined particle diameter,
The classified small particle size incineration ash is supplied to the incineration ash in the post-combustion zone together with the reaction agent containing silica sand and flux agent,
The melting point of each component of incineration ash and silica sand is lowered by flux and the silica sand is reacted with calcium oxide in the incineration ash to form a silicic acid compound to reduce the basicity of the incineration ash, and incineration ash A method for treating incineration ash, characterized by suppressing the elution of lead from the soil.   The incineration ash treatment method according to claim 4 or 5, wherein the flux is a compound containing at least one of boron oxide, magnesium oxide, sodium chloride, potassium chloride, iron or borax.

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