Chemistry of inorganic compounds – Zeolite
Reexamination Certificate
2002-06-28
2004-02-17
Sample, David (Department: 1755)
Chemistry of inorganic compounds
Zeolite
C423S712000
Reexamination Certificate
active
06692722
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method of manufacturing zeolite using waste discharged from an optical fiber manufacturing plant and from an aluminum-related manufacturing plant.
2. Description of the Related Art
In an optical fiber manufacturing plant, various kinds of waste containing silicon which is a component raw material of optical fibers (hereinafter referred to as “silicon-containing waste”) are discharged in the course of manufacturing optical fibers and manufacturing optical fiber products. The thus discharged silicon-containing waste includes, for example, exhaust gas treatment sludge mainly comprising SiO
2
, optical fiber refuse and preform refuse. Most of such silicon-containing waste have conventionally been used for reclamation without being fully used, except for reuse as subbase course materials.
In an aluminum-related manufacturing plant as well, various kinds of waste containing aluminum (hereinafter referred to as “aluminum-containing waste”) are discharged in the course of manufacturing metal aluminum, aluminum alloys or various products thereof. Discharged aluminum-containing waste includes, for example, aluminum dross, aluminum dust collection ash, crystalline aluminum hydroxide sludge, aluminum or aluminum alloy cleaning waste liquid, metal aluminum, metal aluminum scrap, aluminum alloy scrap and alumina scrap. These kinds of aluminum-containing waste have conventionally been used to some extent as a deoxidant or a subbase course material. Most of these refuses have however been disposed of as in the case of silicon-containing waste.
More recently, the United Nations University is urging a project known as the Zero Emission Recycle Initiative for the purpose of working out a new industrial society to eliminate industrial waste. The project is to promote use of waste from an enterprise as a raw material for the other enterprises, with a view to reducing the amount of waste resulting from business activities of the individual enterprises to null in the society as a whole. There is also a demand for achieving zero emission of the silicon-containing waste discharged from optical fiber manufacturing plants and aluminum-containing waste discharged from aluminum-related manufacturing plants.
The present invention was developed to satisfy such a demand, and has an object to effectively use waste discharged from optical fiber manufacturing plants and aluminum-related manufacturing plants as raw materials for manufacturing zeolite to use thus manufactured zeolite in the other industrial sectors.
SUMMARY OF THE INVENTION
The present invention provides a manufacturing method of zeolite from waste, comprising the steps of mixing, with an aqueous alkali solution, a reaction raw material containing at least one of silicon-containing waste discharged from an optical fiber manufacturing plant such as exhaust gas treatment sludge mainly comprising SiO
2
, optical fiber refuse and preform refuse, and at least one of aluminum-containing waste discharged from an aluminum-related manufacturing plant such as aluminum dross, aluminum dust collection ash, crystalline aluminum hydroxide sludge, aluminum or aluminum alloy cleaning waste liquid, metal aluminum scrap, aluminum alloy scrap and alumina scrap, and heating the resultant mixture to cause a reaction.
The invention provides also a manufacturing method of zeolite from waste, comprising the steps of adding one or more crystal minerals having a specific ratio Si/Al to a zeolite manufacturing raw material prepared by mixing a reaction raw material comprising silicon-containing waste and aluminum-containing waste of which the ratio Si/Al is not specified, thereby manufacturing zeolite of a specific kind corresponding to the crystal minerals.
According to the present invention, it is possible to further accelerate the tendency toward zero emission of waste by reusing unreacted substances or waste liquid discharged from a zeolite synthesizing process as all or part of the above-mentioned reaction raw material again for the manufacture of zeolite.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
Manufacture of zeolite by the zero emission type effective use method of waste, discharged from an optical film manufacturing plant and an aluminum-related manufacturing plant, of the present invention will now be described further in detail.
(1) Silicon Source
In the manufacture of zeolite in the present invention, concrete examples of silicon-containing waste discharged from an optical fiber manufacturing plant used as a silicon source include exhaust gas treatment sludge mainly comprising SiO
2
, optical film refuse, and preform waste. Waste containing one or more kinds thereof may also be used.
Apart from the above, as required, coal ashes, natural zeolite, pearlite or diatomaceous earth may be used as a silicon source, or general waste other than the above capable of serving as a silicon source may also be used. Such general waste includes, for example, quartz glass and a silicon wafer.
The above-mentioned kinds of silicon-containing waste serving as a silicon source will now be described.
1) Exhaust gas treatment sludge mainly comprising SiO
2
is waste discharged from an optical fiber manufacturing plant. More specifically, this means a brown dehydrated cake obtained, from among hydrogen chloride gas, chlorine gas, and silicon oxide fine powder occurring when generating cylindrical lumps (called preforms) of silicon oxide, a manufacturing raw material of optical fiber, by catching SiO
2
, Cl
2
and HCl, adding caustic soda and ferric oxide to adjust pH, then, adding a polymer to cause agglomeration and precipitation, and dehydrating the resultant mixture.
This brown dehydrated cake contains Si in an amount of from about 20 to 25 wt. %. In addition to Si, the cake contains from 35 to 40 wt. % Fe, from 1 to 3 wt. % Ca, from 0 to 1 wt. % Mg, from 0 to 1.5 wt. % Al and the balance incidental impurities, and has a water content of from about 68 to 75%.
Another applicable form of cake is a white dehydrated cake obtained by similarly catching SiO
2
and HCl, then, adding caustic soda and polyaluminum chloride to adjust pH, adding a polymer to cause agglomeration and precipitation, and dehydrating the same. The white dehydrated cake contains from about 60 to 70 wt. % Si. In addition to Si, the cake contains from 0 to 1 wt. % Fe, from 0 to 1 wt. % Ca, from 0 to 1 wt. % Mg, from 7 to 12 wt. % Al and the balance incidental impurities, with a water content of from about 65 to 70%.
The white dehydrated cake and the brown dehydrated cake, which are two types of exhaust gas treatment sludge mainly comprising SiO
2
, are very excellent in reactivity, and therefore, satisfactorily applicable as silicon sources serving as materials for zeolite.
Particularly, the brown dehydrated cake, which contains about 30 wt. % Fe, is suitable for the manufacture of Fe-containing zeolite. Fe-containing zeolite contains Fe
2
+ as exchangeable cation, and Fe serving as a buffer. As a result, even when Fe-containing zeolite is ion-exchanged, Fe is supplied from the buffer. It can therefore retain the function as Fe-containing zeolite for a long period of time. The white dehydrated cake, containing from 7 to 12 wt. % Al in addition to Si constituent, can be used as an effective raw material for manufacture of zeolite even with the white dehydrated cake alone. It is thus a very characteristic material.
2) Polishing chips of the above-mentioned preform and optical fiber refuse are applicable as silicon sources. Such preform polishing chips and optical fiber refuse have a very high silicon content and can be used favorably as silicon sources. Particularly, because of the very high purity of silicon, these materials can be used favorably for inductive synthesis of zeolite having a FAU structure.
Silicon contained in waste liquid discharged from a zeolite manufacturing process described later ca be reused as a silicon source, thus permitting achievement of a higher degree of zero emission.
(2) Aluminum Source
Kinds
Ando Takao
Asada Yoshihisa
Henmi Teruo
Furukawa Electric Co. Ltd.
Sample David
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