JP2001019426A - Process for recovering barium hydroxide - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a barium hydroxide recovery process capable of recovering recyclable barium hydroxide in a high yield. SOLUTION: This process comprises: adding barium hydroxide to a waste plastic material containing chlorine; subjecting the mixture to pyrolysis to obtain a solid fuel containing barium chloride; combusting the solid fuel to form combustion ash; and recovering barium hydroxide from the combustion ash by using a procedure that involves washing the combustion ash with water to elute barium chloride in the ash into water and subjecting the eluted barium chloride to ion exchange to form barium hydroxide.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for recovering barium as reusable barium hydroxide from ash produced by burning solid fuel obtained from waste plastic to which barium hydroxide has been added.

[0002]

2. Description of the Related Art Waste plastics contained in general and industrial wastes have conventionally been disposed of by landfills. Attention has been focused on the reduction to oil of low molecular weight and low boiling point as chemical recycling, i.e., oil conversion, and the conversion of solid fuel as thermal recycling, and energy recovery by combustion.

[0003] Chemical recycling and thermal recycling require that waste plastics be treated at high temperatures. However, if waste plastics contain chlorine-based polymers such as polyvinyl chloride and polyvinylidene chloride, the waste plastics must be treated. At this time, chlorine-based gas is generated, which causes serious problems such as corrosion of the processing apparatus, deterioration of the quality of the product (oil), reduction of the recovery rate of heat and electric energy, and generation of highly toxic dioxin.

[0004] For this reason, in the method of separating and removing chlorine-based polymers from waste plastics, and when performing chemical recycling or thermal recycling, pretreatment is performed to thermally decompose the chlorine-based polymers in waste plastics to remove chlorine. The removal of chlorine and the fixation of chlorine as a high-boiling chloride in fuel have suppressed the generation of chlorine-based gas and dioxin during high-temperature treatment. Of these, as a method of fixing chlorine as a high-boiling chloride in fuel, a method of previously mixing slaked lime (calcium hydroxide) in waste plastic to form calcium chloride or a method of mixing barium hydroxide in waste plastic is used. There is a method of barium chloride by thermal decomposition. When the waste plastic is thermally recycled, the combustion temperature is usually 850 to 900 ° C., so that it is desirable that the chloride is in a solid state at the combustion temperature. Considering this fact, since barium chloride has a high melting point of 962 ° C., it can be said that the method of fixing barium chloride in the fuel is superior to the method of using calcium chloride and the like.

[0005]

However, the method of adding barium hydroxide and fixing it as barium chloride in the fuel is more effective than the method of adding calcium hydroxide to form calcium chloride. Had to be increased. Incidentally, when the national average waste plastic is treated by the above method, the chlorine concentration is about 3.6% by weight (hereinafter simply referred to as "%"), so calcium hydroxide is required about 3.6%. On the other hand, barium hydroxide requires about 8.4%.

Accordingly, an object of the present invention is to provide a method of recovering barium from combustion ash (combustion residue and the like), regenerating it into barium hydroxide, and reusing it.

[0007]

Means for Solving the Problems In view of such circumstances, the present inventors have conducted intensive studies, and as a result, the combustion ash containing barium chloride was washed with water to elute barium chloride into the water, and the ion-exchange resin The present inventors have found that barium hydroxide can be easily reused if barium chloride is used as barium hydroxide, and the present invention has been completed.

That is, the present invention provides a method for recovering barium hydroxide from combustion ash produced by adding barium hydroxide to waste plastic containing chlorine and pyrolyzing the resulting solid fuel containing barium chloride. A method for recovering barium hydroxide from the combustion ash, comprising washing the combustion ash with water to elute barium chloride into water, and obtaining barium hydroxide by ion-exchanging the barium chloride. To provide.

[0009]

BEST MODE FOR CARRYING OUT THE INVENTION A preferred embodiment of the present invention will be described including production of a solid fuel. The waste plastic is put into a solid fueling device together with barium hydroxide, and is converted into a solid fuel by thermal decomposition (300 to 390 ° C). At this time, the generated chlorine-based gas, for example, hydrogen chloride reacts with barium hydroxide to produce barium chloride as shown in the following formula. Therefore, there is no harm due to chlorine gas.

[0010]

Embedded image 2HCl + Ba (OH) ₂ → BaCl ₂ + 2H ₂ O

The solid fuel obtained in this way is not particularly limited for use, but is usually burned in a combustion furnace to recover its heat. That is, thermal recycling is performed. Since the combustion temperature here is usually 850 to 900 ° C., it does not exceed the melting point of barium chloride (962 ° C.), and no chlorine-based gas is generated from barium chloride. If necessary, a combustion aid may be added.

[0012] Of the combustion ash generated by the combustion, combustion fly ash is recovered from the bag filter, and combustion residues are recovered from the bottom of the combustion furnace. The collected combustion ash is washed. The water washing is preferably performed by using 50 to 100 times by weight of water with respect to barium chloride and stirring the combustion ash in the water. By washing with water, barium chloride, which is water-soluble, migrates from the combustion ash into water, and can be separated from solids.

Barium chloride eluted into water by washing can be used to obtain barium hydroxide by ion-exchanging chlorine ions into hydroxyl ions using an ion exchange resin as in the following formula.

[0014]

[Formula 2] BaCl ₂ + R · OH → Ba (OH) ₂ + R · Cl

[Wherein, R represents an ion exchanger]

The ion exchanger is not particularly limited as long as it can exchange chlorine ions, and an anion exchanger or an amphoteric ion exchanger is used. Anion exchangers are preferred, especially strongly basic anion exchangers, especially ammonium, phosphonium or sulfonium type anion exchangers. Examples of the form of the ion exchanger include an ion exchange resin and an ion exchange membrane.

The barium hydroxide aqueous solution thus obtained can be converted into a reusable solid by dehydration and drying. The method of dehydration and drying is not particularly limited, but an evaporating separation device is preferred.

The use of the barium hydroxide recovered in this way is not particularly limited, but it is preferable to use it for the production of solid fuel from waste plastic because it can be recycled.

[0019]

EXAMPLES The present invention will be described in more detail with reference to the following Examples, but it should not be construed that the invention is limited thereto.

Example 1 The method of the present invention was carried out according to the flowchart of FIG. First,
1000 kg of waste plastic and 84 kg of barium hydroxide were charged into a solid fuel converter, and pyrolyzed at 370 ° C. to obtain a solid fuel. The chlorine-based gas generated at this time is fixed in the solid fuel as barium chloride.

The obtained solid fuel was supplied to a fluidized bed combustion boiler (CPC) at a rate of 30 kg / h at a rate of 800 kg and burned for about 27 hours. The furnace temperature at this time was 850 to 900 ° C. At this time, sand as a combustion aid was 100 kg /
h.

Fly ash is collected from the bag filter, and combustion ash and combustion aids are collected from the furnace bottom.
/ H. As a result of PIXE analysis of these combustion ash, the barium content in the combustion ash was 32.0%.
Therefore, the barium chloride in the combustion ash obtained per unit time is 2.48 kg.

The above combustion ash is washed in a washing tower with 10 barium chloride.
After washing with water 0 times and completely eluting barium chloride into water, a solid content was filtered and separated.

Next, a barium chloride aqueous solution of about 250 kg / h is applied to an ion exchange column and regenerated to barium hydroxide. Here, Amberlite IRA is used as the ion exchange resin.
-410 was used.

About 370 kg / h of the barium hydroxide aqueous solution discharged from the ion exchange tower was dehydrated in a dehydration drying tower, and was regenerated to octahydrate barium hydroxide. The regenerated barium hydroxide was 3.56 kg / h, which was almost equal to the barium content in the combustion ash. As a result of PIXE analysis of the regenerated barium hydroxide, impurities were 0.5% or less and were sufficiently reusable.

[0026]

According to the present invention, barium remaining for fixing chlorine in solid fuel can be efficiently and easily recovered as barium hydroxide from combustion ash. Moreover, the recovered barium hydroxide has a high purity of 99.5% or more.

[Brief description of the drawings]

FIG. 1 is a flowchart of barium hydroxide recovery, regeneration, and reuse according to an embodiment of the present invention.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Takeshi Hirokawa 1-4-1 Kagamiyama, Higashihiroshima City, Hiroshima Prefecture F-term in Hiroshima University Faculty of Engineering 4D004 AA07 AA37 AB07 BA03 BA06 CA15 CA24 CA34 CC03 DA03 DA06 4G076 AA10 AB04 AB28 BA50 BC04 BC07 BE04 CA02 CA36 DA30

Claims (1)

[Claims] 1. A method of recovering barium hydroxide from combustion ash generated by burning barium hydroxide by adding barium hydroxide to waste plastic containing chlorine and burning the obtained barium chloride-containing solid fuel, A method for recovering barium hydroxide from the combustion ash, comprising washing the combustion ash with water to elute barium chloride into water, and ion-exchanging the barium chloride to obtain barium hydroxide.