JP3575958B2 - Apparatus and method for reducing soluble heavy metals in slag water - Google Patents

Description

[0001]
TECHNICAL FIELD OF THE INVENTION
TECHNICAL FIELD The present invention relates to an apparatus and a method for reducing soluble heavy metals in slag granulated water for granulating molten slag that is stored in a pit provided below a combustion chamber of a waste melting furnace and falls from the combustion chamber.
[0002]
[Prior art]
As a waste melting furnace, for example, there is a surface melting furnace as shown in FIG. In this surface melting furnace, waste 21 such as municipal waste incineration residue is uniformly introduced in the circumferential direction between the inner cylinder 22 and the outer cylinder 23 and moved in the core direction by its own weight, and the combustion inside the inner cylinder 22 is performed. In the chamber 24, the inner peripheral surface side is burned and melted by the combustion heat of the combustion device 25 and the self-combustion heat of the waste 21, and the generated molten slag 26 is continuously dropped from the slag port 27 together with the combustion exhaust gas. The slag that has cooled and solidified is taken out.
[0003]
As a device for cooling the molten slag, a slag granulator excellent in operability and ease of maintenance is often used. The slag granulator has a simple structure in which water 29 is stored in a pit 28, and the molten slag 26 falls into the slag granulated water 29, is rapidly cooled, and rapidly undergoes thermal contraction to be granulated. .
[0004]
[Problems to be solved by the invention]
However, in the above-described conventional slag granulator, the pH of the granulated slag water is not adjusted, so that the acidic gas in the exhaust gas is dissolved and the pH is lowered, thereby dissolving heavy metals such as lead in the exhaust gas. There was something to do. If the slag crushed water containing such soluble heavy metals is absorbed by countless cracks in the slag, the heavy metals may be gradually eluted from the slag in the future.
[0005]
The present invention has been made to solve the above problems, and has as its object to reduce soluble heavy metals in crushed slag water.
[0006]
[Means for Solving the Problems]
In order to solve the above-mentioned problem, the apparatus for reducing soluble heavy metals in slag granulated water according to the present invention is capable of granulating molten slag stored in a pit below a combustion chamber of a waste melting furnace and falling from the combustion chamber. A device for reducing soluble heavy metals in crushed slag water, comprising: pH measuring means for continuously measuring the pH of the crushed slag water; alkali injecting means for injecting an aqueous alkali solution into the crushed slag water; and a control means connected to the pH measuring device and the alkali injection means, the control means controls the alkali injection means on the basis of the pH value measured by the pH measuring means, the slag water砕水p H9 ~ A sedimentation tank configured to automatically inject an appropriate amount of an alkaline aqueous solution maintained at 12 and equipped with a coagulant injection means to coagulate and settle the entire amount of slag crushed water taken out of the pit; It is obtained and means for returning to the pit.
[0007]
As the alkaline aqueous solution, various alkaline aqueous solutions such as sodium hydroxide and calcium hydroxide can be used. Further, the method for reducing soluble heavy metals in the crushed slag water of the present invention is characterized in that the slag is stored in a pit below a combustion chamber of a waste melting furnace, and the molten slag that falls from the combustion chamber is granulated into the slag water. a method for reducing sexual heavy metals, which was in order to maintain automatically 1 0.5 the pH of the slag water砕水by the presence of solid magnesium hydroxide over the saturation concentration in said slag water in砕水is there.
[0008]
According to the configuration described above, since the pH of the slag water砕水is maintained automatically 9-12 or 1 0.5, the slag water砕水such as lead may exhaust gas is absorbed in contact Heavy metals form hydroxides to form SS. Therefore, the soluble heavy metal in the slag crushed water has a very low concentration, and the probability that the heavy metal is absorbed by the slag and the probability that the heavy metal is eluted from the slag in the future become extremely low.
[0009]
BEST MODE FOR CARRYING OUT THE INVENTION
Hereinafter, embodiments of the present invention will be described with reference to the drawings.
In FIG. 1, crushed slag water 3 for granulating molten slag 2 falling from the combustion chamber is stored in a pit 1 provided below a combustion chamber (not shown) of the waste melting furnace.
[0010]
Inside and near the pit 1, a pH meter 4 for continuously measuring the pH of the crushed slag water 3, NaOH injection means 5 for injecting an aqueous NaOH solution into the crushed slag water 3, and a pH meter 4 and NaOH injection A control device 6 connected to the means 5 by lines L1 and L2 is provided, and the pH meter 4, the NaOH injection means 5 and the control device 6 constitute a reduction device for reducing soluble heavy metals in the crushed slag water. Have been. The control device 6 controls the NaOH injecting means 5 based on the pH value measured by the pH meter 4 so as to inject an appropriate amount of NaOH so that the pH of the crushed slag water 3 is maintained at about 9 to 12. To do.
[0011]
A flocculant injection means 7 is provided outside the pit 1, and a sedimentation tank 8 for coagulating and sedimenting the crushed slag water 3 transferred from the pit 1 and a dehydration for dewatering the sediment 9 transferred from the sedimentation tank 8. An apparatus 10 and a storage tank 12 for temporarily storing the desorbed liquid discharged from the dehydrator 10 and the supernatant water 11 transferred from the sedimentation tank 8 are provided.
[0012]
The operation of the above configuration will be described.
The molten slag 2 discharged from the combustion chamber falls into the crushed slag water 3 in the pit 1, is rapidly cooled, and rapidly shrinks in heat to be refined.
[0013]
A part of the flue gas discharged from the combustion chamber together with the molten slag 2 comes into contact with the crushed slag water 3, and the acid gas in the flue gas is absorbed into the crushed slag water 3.
However, at this time, the pH of the crushed slag water 3 is continuously measured by the pH meter 4, the measured pH value is transmitted to the control device 6, and based on the transmitted pH value, the NaOH injection means is controlled by the control device 6. The pH of the slag crushed water 3 is adjusted to 9 to 12 by controlling 5 and injecting an appropriate amount of NaOH.
[0014]
As a result, most of the heavy metals such as lead in the exhaust gas flow out of the furnace without being dissolved in the crushed slag water 3 without being dissolved in the crushed slag water 3, and are absorbed by the crushed slag water 3. Also forms hydroxide to form SS, and dissolution in slag crushed water 3 is prevented.
[0015]
The finely divided slag 2A is appropriately taken out. However, since the dissolution of heavy metals in the crushed slag water 3 is reduced as described above, the probability of absorption of heavy metals into cracks in the slag 2A is reduced, and in the future, There is almost no risk that heavy metals elute from the slag 2A. Therefore, the slag 2A can be used as a resource.
[0016]
The crushed slag water 3 containing SS such as heavy metal hydroxide in the pit 1 is transferred to the sedimentation tank 8 and then the coagulant is injected by the coagulant injection means 7, whereby the SS in the crushed slag water 3 is removed. Coagulate and precipitate, and are separated into a sediment 9 and a supernatant water 11.
[0017]
The sediment 9 in the sedimentation tank 8 is transferred to a dehydrator 10 to be dehydrated, and the dehydrated cake 14 is carried out of the system. The desorbed liquid discharged from the dehydrator 10 and the supernatant water 11 in the sedimentation tank 8 are transferred to the storage tank 12 and temporarily stored, and the stored water 13 formed by mixing these is returned to the pit 1 for reuse. Is done.
[0018]
Instead of the above-described apparatus for reducing soluble heavy metals, solid magnesium hydroxide having a saturated concentration or more may be present in the crushed slag water 3 in the pit 1. Is automatically maintained at about 10.5, so that most of heavy metals such as lead can be converted to SS similarly to the above, and the dissolution of heavy metals in the crushed slag water 3 can be reduced. This method can be easily carried out with existing equipment since only solid magnesium hydroxide is charged.
[0019]
【The invention's effect】
As described above, according to the present invention, the slag crushed water can be automatically adjusted to pH 9 to 12 even when melting a waste containing a large amount of Cl such as crushed incombustibles. The heavy metals brought into the water can be reduced, and the heavy metals brought into the granulated slag water can be insolubilized as hydroxides, so that the soluble heavy metals in the granulated slag water can be reduced. As a result, water crushed water containing heavy metals is no longer absorbed by the slag as in the past, and slag is obtained without the risk of elution of heavy metals. Gone.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram showing a configuration of an apparatus for reducing soluble heavy metals in crushed slag water in one embodiment of the present invention.
FIG. 2 is a cross-sectional view showing the entire configuration of a conventional waste melting furnace.
[Explanation of symbols]
Reference Signs List 1 pit 2 molten slag 3 slag crushed water 4 pH meter 5 NaOH injection means 6 controller

Claims (2)

A device for reducing soluble heavy metals in slag granulated water which is stored in a pit below a combustion chamber of a waste melting furnace and granulates molten slag falling from the combustion chamber, wherein the pH of the slag granulated water is adjusted. PH measuring means for continuously measuring, alkali injecting means for injecting an aqueous alkali solution into slag crushed water, and control means connected to the pH measuring means and the alkali injecting means, based on the measured pH value by the measuring means to control the alkali injection means, the alkaline aqueous solution in the appropriate amount to maintain the slag water砕水the p H9 to 12 configured to automatically inject, comprising a coagulant injection means Heavy water in the crushed slag water, comprising: a settling tank for coagulating and settling all of the crushed slag water taken out from the pit; and means for returning the supernatant water of the settling tank to the pit. Reduction device. A method for reducing soluble heavy metals in granulated slag water, which granulates molten slag falling from the combustion chamber and stored in a pit below a combustion chamber of a waste melting furnace, wherein the saturated concentration of the slag granulated water is reduced. the method for reducing solubility heavy metal of the slag water in砕水characterized by maintaining the pH of the slag water砕水automatically 1 0.5 the presence of more solid magnesium hydroxide.

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