JPH11173528A - Treating method for waste - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent generation of clinker in an incinerating furnace and stabilize the operation of the incinerating furnace for a long period of time by a method wherein industrial waste, containing alkali metals, is neutralized by acid and, thereafter, is incinerated. SOLUTION: Waste, containing alkaline metals, is the residue of distillation, which contains alkali metals such as sodium hydroxide or the like which is added at the time of preparation of imidazoles such as imidazole or 2-methyl imidazole or the like, while the residue is treated as the waste finally through incineration. Hydrochloric acid, sulfuric acid, nitric acid or the like can be recommended as the acid employed for the neutralization of residue of such distillation, however, sulfuric acid is preferably employed from a view point that the melting point of salt produced after neutralization is higher than a temperature in the incinerating furnace. A furnace, used for the incineration of waste generally or a dry distillation gasifying incinerator, a direct combustion type incinerator, a rotary kiln type incinerator, a fluidized bed type incinerator or the like, for example, is utilized, however, the fluidized bed type incinerator is preferably used among these furnaces.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for treating a waste containing an alkali metal, for example, a waste such as a distillation residue generated during the production of imidazoles.

[0002]

2. Description of the Related Art Generally, in the production of imidazoles such as imidazole and 2-methylimidazole, an alkali such as sodium hydroxide or potassium hydroxide is added to decompose by-products. Have been
At the time of such production, waste containing alkali metals such as sodium hydroxide and potassium hydroxide is generated, and at present, such waste is incinerated in an incinerator or the like.

[0003]

However, when the above-mentioned waste is subjected to incineration as it is, the alkali metal in the waste is contained in the heat medium (silica sand) and the furnace material (brick) in the incinerator. Reacts (combines) with the silica (SiO ₂ ) to form a so-called glassy clinker such as Na ₂ SiO ₃ or K ₂ SiO ₃ in the incinerator, which makes the operation of the incinerator difficult or difficult In some cases, continuation is not possible.

[0004]

Accordingly, the present inventor has conducted intensive studies in view of the present situation. As a result, the waste containing alkali metals is neutralized with an acid and then incinerated.
The inventors have found that the above problems can be solved, and have completed the present invention.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail.
The waste containing an alkali metal to which the treatment method of the present invention is applied is sodium hydroxide added during production of imidazoles such as imidazole and 2-methylimidazole, and a distillation residue containing an alkali metal such as potassium hydroxide. Finally, it is incinerated as waste. That is,
The reaction is carried out using ammonia, glyoxal and formalin (in the case of imidazole) or acetaldehyde (in the case of 2-methylimidazole) as the raw materials, and then sodium hydroxide, potassium hydroxide, etc. for the decomposition of the generated by-products. When an imidazole such as imidazole or 2-methylimidazole is obtained by distillation by adding an alkali, it is generated as a distillation residue.

The most characteristic feature of the present invention is that such a distillation residue (waste) is neutralized with an acid before being subjected to incineration. The neutralization will be described in detail. The acid used for neutralization is not particularly limited, and examples thereof include hydrochloric acid, sulfuric acid, nitric acid, and phosphoric acid.
It is preferable to use sulfuric acid from the viewpoint that the melting point of the salt formed after the neutralization is higher than the temperature in the incinerator, and usually, commercially available sulfuric acid can be used. In the neutralization, the same amount of acid as the alkali used before the above-mentioned distillation was added to the waste as 20%.
What is necessary is just to drop at about 50 degreeC so that pH may be set to 9 or less.

[0007] The neutralized waste is then supplied to an incinerator, but there are no particular restrictions on the type of incinerator and various conditions at the time of incineration. Incinerators used are made of furnace materials such as magnesia bricks, silica bricks, and alumina bricks. An incinerator can be used, and when a fluidized bed incinerator is used, the effect of the present invention can be remarkably obtained.

The method of supplying the neutralized waste to the incinerator is not particularly limited, and examples thereof include a method of continuously supplying the waste with a feeder or the like, a method of spraying with a spray or the like, and the like. Although possible, there is no particular limitation.

[0009]

The present invention will be specifically described below with reference to examples. Example 1 25% ammonia water (4527 kg), 40% glyoxal aqueous solution (4387 kg) and 37% formalin aqueous solution (2087 kg) were reacted to obtain imidazole.
After adding 7.2 kg and distilling, 98% sulfuric acid 24.2% was added to 350 kg of the obtained distillation residue (waste).
kg was dropped at 30 ° C. over 120 minutes to perform a neutralization treatment (pH = 8.5).

Next, the treated waste is reduced to 40 kg / h.
Continuously in a fluidized bed incinerator at a rate of r (internal volume 22 m ³ )
And incinerated at a furnace temperature of 750 ° C. The operation of the incinerator was performed for 90 days, and no clinker was generated in the incinerator, and good operation could be performed.

Example 2 In Example 1, 25% aqueous ammonia (1847 k
g), a 40% aqueous glyoxal solution (1824 kg) and a 70% acetaldehyde aqueous solution (877 kg) were reacted to produce 2-methylimidazole in the same manner, and the incinerator was operated for 90 days. There was no clinker inside and good operation was possible.

Example 3 In Example 1, 75% was used instead of 24.2 kg of sulfuric acid.
The incinerator was operated for 60 days in the same manner except that 310 kg of phosphoric acid was used. However, no clinker was generated in the furnace, and good operation could be performed.

Comparative Example 1 In Example 1, the waste was directly incinerated without being neutralized, but after 30 days a large amount of clinker was generated in the furnace, and the operation had to be stopped. I didn't get it.

[0014]

According to the present invention, since industrial waste containing alkali metals is incinerated after neutralization with an acid, clinker does not occur in the incinerator, and the operation of the incinerator can be stabilized for a long period of time. Can be done.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI F23G 5/02 ZAB F23G 7/00 ZABA 7/00 ZAB B09B 3/00 303J

Claims (3)

[Claims] 1. A method for treating waste, comprising: neutralizing waste containing an alkali metal with an acid and then incinerating the waste. 2. The method for treating waste according to claim 1, wherein the alkali metal is potassium hydroxide or sodium hydroxide and the acid is sulfuric acid. 3. The method for treating waste according to claim 1, wherein the incinerator used for incineration is a fluidized bed incinerator.