JPH0716667B2 - Smoke washing waste liquid treatment method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) Generally, in a refuse incinerator plant, an alkaline liquid is used to remove hydrogen chloride HCl and sulfur oxide SOx contained in the exhaust gas discharged from the refuse incinerator. However, since the smoke effluent, which is the effluent to be treated, contains fluorine, boron, and various heavy metals, the smoke effluent must be subjected to some treatment to remove such harmful substances. Must be removed.

The present invention relates to a method for removing fluorine, boron and various heavy metals contained in such a smoke washing effluent.

(Prior Art) Conventionally, various methods for removing fluorine and heavy metals in a smoke-washing effluent or methods for removing boron have been proposed.

That is, as a method for removing fluorine and heavy metals in the smoke washing effluent, generally, a calcium salt or an aluminum salt is added to first remove the fluorine, and then high alkali coagulation precipitation is performed, so-called two-stage method. Coagulation sedimentation treatment methods are well known. In addition, a method has also been proposed in which an aluminum salt or an iron salt and a sulfide or a heavy metal fixing agent are added to the smoke washing effluent to simultaneously remove fluorine and heavy metals.

As a method for removing boron, generally, in the presence of an aluminum compound and a calcium compound and under a condition of pH 9 or more, a method of producing an insoluble precipitate and performing solid-liquid separation,
Alternatively, an adsorption method using an ion exchange resin is well known.

(Problems to be solved by the invention) However, in the past, no method has been proposed at the same time for simultaneously removing fluorine, boron, and heavy metals in the smoke washing effluent at the same time. It is the actual situation that the removal of boron and the removal of boron are separately performed by the above-mentioned methods. Therefore, the construction cost and maintenance cost of equipment required for the removal treatment of fluorine, boron, and heavy metals will inevitably rise,
Moreover, there is a problem in that the smoke washing waste liquid cannot be treated efficiently.

The present invention has been made in view of the above circumstances, and in consideration of the fact that heavy metals contained in dust discharged from a refuse incineration plant also need to be treated in terms of dust disposal, the smoke washing waste liquid It is an object of the present invention to provide a smoke-washing effluent treatment method capable of efficiently treating fluorine, boron, heavy metals in dust and heavy metals in dust all together.

(Means for Solving Problems) According to the method of the present invention, fluorine can be satisfactorily removed by an aluminum salt and boron by an aluminum salt and a calcium salt, respectively. It was made paying attention to the fact that it is mixed with the waste incinerator smoke effluent and the dust collected by the electrostatic precipitator, and then the aluminum compound is added to this mixture, which also contains an aluminum salt and a calcium salt. By blowing the waste incinerator exhaust gas into the mixture,
It was adjusted to 10 to 11.5, and then the liquid mixture subjected to the PH adjustment was subjected to solid-liquid separation treatment so that fluorine, boron, heavy metals in the smoke washing effluent and heavy metals in the dust discharged from the electrostatic precipitator were simultaneously removed. It is a thing.

That is, specifically, first, the smoke-washing waste liquid and the dust are mixed, and then the mixed liquid is added with an appropriate amount of aluminum salt and stirred. As the aluminum salt, for example, sulphate earth is added at about 150 mg / l. As the smoke-washing effluent mixed with the dust, a smoke-washing effluent stock solution or its mercury treatment solution is used.

Next, the pH of the mixed stirring liquid is adjusted to 10 to 11.5 by blowing the exhaust gas from the refuse incinerator.

By the way, there are some garbage incineration plants equipped with a dry (or semi-dry) removal treatment device for HCl and SOx that uses slaked lime or calcium carbonate. In some cases, since unreacted calcium is mixed in the dust, the mixed slurry with the smoke washing effluent has a high pH value (12 to 13), so it is The above-mentioned pH adjustment treatment is performed as it is on the mixed stirring liquid with dust. On the other hand, when the refuse incineration plant does not have a dry (or semi-dry) removal treatment device for HCl and SOx as described above, and the dust has not been subjected to hydrogen chloride removal treatment, the above mixed stirring liquid is used. The pH of was adjusted to 11 to 13 by adding an alkaline agent in advance, and then 10 to 11.5 by blowing exhaust gas.
Adjust to

In this way, by adjusting the pH to 10 to 11.5 by blowing the exhaust gas into the smoke washing exhaust liquid / dust mixed liquid, fluorine and boron are simultaneously removed, and the smoke washing exhaust liquid stock solution and the dust are mixed. In this case, heavy metals other than mercury are stabilized, and in the case of mixing the mercury treatment liquid of the smoke washing exhaust liquid with dust, all the heavy metals are stabilized.

Then, by performing solid-liquid separation treatment on the smoke-washing effluent / dust mixed liquid whose pH has been adjusted in this manner, the fluorine,
Boron and heavy metals are simultaneously removed at once. At the same time, the heavy metal is stabilized and the dust is processed well.

(Example) Direct mixing of the smoke effluent stock solution of an municipal refuse incinerator and the dust discharged from a refuse incineration plant having a dry (or semi-dry) removal facility for hydrogen chloride by blowing calcium carbonate,
After adding 150 mg / l of sulphate to this mixed solution, blow the exhaust gas to adjust the mixed solution pH to about 11 and react for 20 minutes, then leave this pH adjusted solution to stand still for 30 minutes for solid-liquid separation. did.

Then, the concentrations of fluorine, boron and heavy metals in the treated solution containing the supernatant and the elution values of T-Hg and Pb from the precipitate were measured. The results are shown in Tables 1 and 2 in comparison with the smoke washing effluent and dust before treatment.

From Tables 1 and 2, it is clearly understood that fluorine, boron, various heavy metals in smoke effluent and Pb in dust are treated very well. In addition, T-Hg in the dust is
It may increase slightly if you use the uncleaned solution of the smoke effluent as a mixture, but by mixing with the smoke effluent treatment solution, you can simultaneously remove fluorine and boron, stabilize the heavy metals, and pass the landfill standard value. It can be a harmless cake.

(Effects of the Invention) As will be easily understood from the above description, the method for treating smoke-washing effluent of the present invention can efficiently treat fluorine, boron, and heavy metals in the smoke-washing effluent simultaneously. In addition, it is possible to perform dust treatment at the same time, and it is a very effective and practical treatment method that can significantly reduce equipment construction costs and maintenance costs required for the treatment.

Claims (4)

[Claims] 1. A waste incinerator exhaust gas is mixed with a dust incinerator flue gas and an electrostatic precipitator exhaust dust, and an aluminum compound is added to the mixture, and the waste incinerator exhaust gas is mixed into a mixture containing an aluminum salt and a calcium salt. By blowing that
By adjusting the pH to 10 to 11.5, and then performing the solid-liquid separation treatment of the pH-adjusted mixed solution, the fluorine in the smoke washing effluent,
A method for treating smoked effluent, characterized in that boron, heavy metal, and heavy metal in dust discharged from an electrostatic precipitator are simultaneously removed. 2. The smoke exhaust according to claim 1, characterized in that as the dust discharged from the electrostatic precipitator, dry dust such as hydrogen chloride with slaked lime or calcium carbonate is used. Liquid treatment method. 3. The smoke wash according to claim 1, wherein as the dust discharged from the electrostatic precipitator, one which has not been subjected to a dry removal treatment of hydrogen chloride or the like with slaked lime or calcium carbonate or the like is used. Drainage treatment method. 4. The pH of the mixed solution is adjusted to 11 to 13 by adding an alkaline agent, and is then adjusted to 10 to 11.5 by blowing waste incinerator exhaust gas. The method for treating smoked effluent according to any one of claims 1, 2 or 3.