Title of Invention	A METHOD OF CONVERTING FIRED CERAMIC SCRAP INTO FINE CERAMIC POWDER FOR PREPARING CERAMIC ARTICLES
Abstract	A method of converting fired ceramic scrap into fine ceramic powder for preparing ceramic articles, which comprises heating pre-sized fired ceramic scrap to a temperature in the range of 500° to 850°C for a period in the range of 20 to 30 minutes, subjecting the said heated ceramic scrap to instant water quenching, allowing the ceramic scrap to remain in water for a period in the range of 20 to 30 minutes to obtain quenched ceramic scrap, drying the said quenched ceramic scrap at a temperature in the range of 100 to 120°C, grinding the dried quenched ceramic scrap by known methods into fine ceramic powder.

Title of Invention

A METHOD OF CONVERTING FIRED CERAMIC SCRAP INTO FINE CERAMIC POWDER FOR PREPARING CERAMIC ARTICLES

Abstract

A method of converting fired ceramic scrap into fine ceramic powder for preparing ceramic articles, which comprises heating pre-sized fired ceramic scrap to a temperature in the range of 500° to 850°C for a period in the range of 20 to 30 minutes, subjecting the said heated ceramic scrap to instant water quenching, allowing the ceramic scrap to remain in water for a period in the range of 20 to 30 minutes to obtain quenched ceramic scrap, drying the said quenched ceramic scrap at a temperature in the range of 100 to 120°C, grinding the dried quenched ceramic scrap by known methods into fine ceramic powder.

Full Text	This invention relates to a method of converting fired ceramic scrap into fine ceramic powder useful for the manufacture of ceramic articles. Ceramic scrap is generated in the normal course of production of ceramic articles and also as a result of post-use breakage. The fired ceramic scrap so generated are vitrified and dense and hence hard. These hardened ceramic scrap material may pose environmental hazards of improper disposals and safety. Hence, reuse of the scrap may be an attractive option, if made economically viable. The reuse can be made possible by comminution of fired ceramic scrap into fine ceramic powder. The main use of ceramic powder is as raw material for the manufacture of ceramic articles such as white ware bodies including crockery wares, sanitary wares, ceramic tiles and ceramic insulators. Fired ceramic scrap after being converted to ceramic powder is recycled as raw material for the manufacture of ceramic articles. The present day methods are recycling or reuse of different types of ceramic scrap and include different methods of grinding. Reference may be made to Artemjev V.K; Garcia-Segovia A.J; Standart 90; Cementos Mexicanos, S.A in US Patent 5551639 "Method and apparatus for solid material grinding" wherein a method and an apparatus was devised for crushing and fine grinding of solid particulate materials utilizing a conventional ball mill or jet mill. Reference may also be made to Eminov A.M; Maslennikova G.N; Nabijev H.M. (Tashkent Chemical Technology Institute) in Keram Z 50 (11), 1998 pp 936-938, "Influence of broken crockery on the grinding behaviour of porcelain bodies" wherein biscuit fired and glost fired scraps were used during wet preparation of porcelain tableware bodies. In all the above processes scraps were used although in a limited way but mainly for the purpose of recycling of raw materials and in some cases to improve the properties of the end products. But ceramic fired scraps in most cases, are vitrified and dense and thus, harder than the ceramic raw materials like clays, quartz and feldspar normally used in the triaxial compositions. Grinding of such harder materials by the conventional process is cumbersome, time consuming and requires more energy and therefore the main drawbacks of the above processes are the unsafe handling of scrap and longer duration of grinding leading to consumption of more energy and thus, rendering the recycling process less attractive as well as uneconomical. The other drawbacks are ineffective method for raw material resource saving and ineffective waste management. The main object of the present invention relates to a method of converting fired ceramic scrap into fine ceramic powder useful for the manufacture of ceramic articles, which obviates the above noted drawbacks. Another object of the present invention is to provide a safe and economically viable method of comminution of all types of vitrified and semi-vitrified fired ceramic scraps into fine powder obviating the drawbacks as detailed above. Yet another object of the present invention is the economic use of ceramic waste materials such as fired ceramic scrap through the recycling route in the production of ceramic articles. Still another object of the present invention is to improve the quality of ceramic products by using ceramic powder obtained from pre-reacted or processed ceramic waste materials through enhancement in the fired strength as well as widening of vitrification range of the products. Yet another object of the present invention is to prepare consistent quality ceramic powder from pre-reacted scrap ceramic material for the production of traditional products like grinding media, acid resistant bricks and tiles as well as other ceramic products like crockery, sanitary ware, & ceramic tiles. Another object of the present invention is to provide for raw material resource saving, energy saving as well as abetment of environmental pollution through effective ceramic solid waste management. The present invention provides a novel method of converting fired ceramic scrap into recyclable fine ceramic powder as raw material for the manufacture of ceramic articles. The method of the present invention consists of heating pre-sized fired ceramic scrap followed by instant water quenching to impart thermal shock. This results in increased grindability thus removing the serious problem of hazardous and uneconomical grinding of vitrified and hard ceramic scrap material to obtain fine ceramic powder. Accordingly, the present invention provides a method of converting fired ceramic scrap into fine ceramic powder useful for the manufacture of ceramic articles which comprises heating pre^-sized fired ceramic scrap to a temperature in the range of 500° to 850°C for a period in the range of 20 to 30 mins., subjecting the heated ceramic scrap to instant water quenching, allowing the ceramic scrap to remain in water for about 20 to 30 mins to obtain quenched ceramic scrap, drying the saud quenched ceramic scrap at a temperature in the range of 100 to 120°C, grinding the dried quenched ceramic scrap by known methods into fine ceramic powder. In an embodiment of the present invention, the fired ceramic scrap used is such as white wares, insulators, porcelains, crockery wares, glass, sanitary wares, ceramic tiles, acid resistant bricks and tiles. In another embodiment of the present invention the fired ceramic scrap used is broken by known methods into sizes in the range of 5 to 300 cm3 prior to heating. In still another embodiment of the present invention the instant water quenching of the heated ceramic scrap is effected by immersing in water kept at ambient temperature. In yet another embodiment of the present invention the dried quenched ceramic scrap is ground by known methods such as ball milling into fine ceramic powder of size in the range of 75 to 53 micron. The details of the processing steps of the method of the present invention are given below : 1. Waste ceramic articles i.e. fired ceramic scrap are broken by conventional methods to sizes of 5 to 300 cm3. The broken ceramic scrap is heated to a temperature in the range of 500° to 850°C for a period in the range of 20 to 30 mins. 2. Hot scrap after attainment of maximum temperature is subjected to instant quenching by dropping into water kept at ambient temperature and allowed to be cooled for 20 to 30 mins. 3. The cooled scrap (quenched) is dried at a temperature in the range of 100 to 120°C. 4. The dried quenched scrap is comminuted into fine powder of 75 to 53 micron by conventional ball milling. Traditional ceramic products are normally manufactured by the process of heating the products in a high temperature kiln. The phenomenon of hardening of ceramic products takes place through the pyro-chemical reactions of raw materials as well as formation of glassy phase which primarily depends on the degree of mixing of solid ingredients as well as their particle fineness. It is therefore, always advantageous to use partially reacted or fully reacted materials like fired ceramic scrap in the body compositions in order to arrest gas formation, to limit pyro-chemical reactions, to reduce the firing shrinkage of products and thus, arresting warpage, distortion and cracking of products, to widen the vitrification range of products and finally reduce substantially the time required for maturing of products and thus, to attain faster firing of ceramic articles. On the other hand, rejection in the ceramic manufacturing unit is normally quite large and if those rejected materials are recycled as raw materials, the production process becomes more economical. The main problem of such raw materials i.e ceramic wastes is their increased hardness which ultimately enhances the cost of the production as their grindability is poor. In the conventional processes, several attempts were made to make the grinding processes efficient by changing the design of grinding equipments. In the present invention instead of altering the configuration of grinding machines more grindability is imparted into the fired ceramic scrap itself by making them brittle and easily breakable, adopting a new technology which is hither to non-existent for this type of material. A synergy of quenching and grinding makes an integrated process for making the desired material. Thus by using similar grinding equipment, the grinding of the fired ceramic scrap may be effected more easily and more economically. The novelty of the method of the present invention lies in increasing the grindability of the fired ceramic scrap by the inventive step of thermal quenching of the material, thus generating a large number of defects in the form of micro and macro cracks within the micro structure of the vitreous matrix. The non-obvious inventive step thus, lies in the thermal shock treatment i.e. thermal quenching of fired ceramic scrap prior to grinding. The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention. Example — 1 60 kg of crockery ware scraps of size 20 to 100 cm3 were heated at 800°C temperature for 20 mins. The heated mass was dropped into water kept at room temperature. Cooled scrap was dried at 105°C temperature. The dried scrap was ground to 53 micron in a ball mill. Example - 2 60 kg of sanitary ware scraps of size 50 to 300 cm3 were heated at 850°C temperature for 30 mins. The heated mass was dropped into water kept at room temperature. Cooled scrap was dried at 110°C temperature. The dried scrap was ground to 53 micron in a ball mill. Example - 3 50 kg of porcelain insulator scraps of size 5.0 to 50 cm3 was heated at 850°C temperature for 25 mins. The heated mass was dropped into water kept at room temperature. Cooled scrap was dried at 115°C temperature. The dried scrap was ground to 53 micron in a ball mill. Example - 4 50 kg of glass scrap of size 5.0 to 225 cm3 was heated at 500°C temperature for 25 mins. The heated mass was dropped into water kept at room temperature. Cooled scrap was dried at 100°C temperature. The dried scrap was ground to 75 micron in a ball mill. The main advantages of the present invention are: 1. Easy grinding of vitrified and hard ceramic scrap of ceramic industry. 2. A reduction in the grinding time. 3. A saving of energy during grinding. 4. Thermally shocked scrap can be used in milling directly in a ball mill without crushing in a jaw crusher or risky manual crushing as required for untreated scrap. 5. Offers an easy solution to the serious problem of grinding of vitrified and hard ceramic scrap of ceramic industry. 6. The technique is applicable to all types of vitrified and semi-vitrified ceramic scrap of ceramic industry. We Claim: 1. A method of converting fired ceramic scrap into fine ceramic powder for preparing ceramic articles, which comprises heating pre-sized fired ceramic scrap to a temperature in the range of 500° to 850°C for a period in the range of 20 to 30 minutes, subjecting the said heated ceramic scrap to instant water quenching, allowing the ceramic scrap to remain in water for a period in the range of 20 to 30 minutes to obtain quenched ceramic scrap, drying the said quenched ceramic scrap at a temperature in the range of 100 to 120°C, grinding the dried quenched ceramic scrap by known methods into fine ceramic powder. 2. A method as claimed in claim 1 wherein the fired ceramic scrap used is such as white wares, insulators, porcelains, crockery wares, glass, sanitary wares, ceramic tiles, acid resistant bricks and tiles. 3. A method as claimed in claims 1-2 wherein fired ceramic scrap is broken by known methods into sizes in the range of 5 to 300 cm3 prior to heating. 4. A method as claimed in claim 1 wherein the instant water quenching is effected by immersing in water kept at ambient temperature. 5. A method as claimed in claims 1-4 wherein the dried quenched ceramic scrap is ground by known methods such as ball milling into fine ceramic powder of size in the range of 75 to 53 micron. 6. A method of converting fired ceramic scrap into fine ceramic powder for preparing ceramic articles substantially as herein described with reference to the examples.

Full Text

This invention relates to a method of converting fired ceramic scrap into fine ceramic powder useful for the manufacture of ceramic articles.
Ceramic scrap is generated in the normal course of production of ceramic articles and also as a result of post-use breakage. The fired ceramic scrap so generated are vitrified and dense and hence hard. These hardened ceramic scrap material may pose environmental hazards of improper disposals and safety. Hence, reuse of the scrap may be an attractive option, if made economically viable. The reuse can be made possible by comminution of fired ceramic scrap into fine ceramic powder.
The main use of ceramic powder is as raw material for the manufacture of ceramic articles such as white ware bodies including crockery wares, sanitary wares, ceramic tiles and ceramic insulators. Fired ceramic scrap after being converted to ceramic powder is recycled as raw material for the manufacture of ceramic articles.
The present day methods are recycling or reuse of different types of ceramic scrap and include different methods of grinding. Reference may be made to Artemjev V.K; Garcia-Segovia A.J; Standart 90; Cementos Mexicanos, S.A in US Patent 5551639 "Method

and apparatus for solid material grinding" wherein a method and an apparatus was devised for crushing and fine grinding of solid particulate materials utilizing a conventional ball mill or jet mill. Reference may also be made to Eminov A.M; Maslennikova G.N; Nabijev H.M. (Tashkent Chemical Technology Institute) in Keram Z 50 (11), 1998 pp 936-938, "Influence of broken crockery on the grinding behaviour of porcelain bodies" wherein biscuit fired and glost fired scraps were used during wet preparation of porcelain tableware bodies.
In all the above processes scraps were used although in a limited way but mainly for the purpose of recycling of raw materials and in some cases to improve the properties of the end products. But ceramic fired scraps in most cases, are vitrified and dense and thus, harder than the ceramic raw materials like clays, quartz and feldspar normally used in the triaxial compositions. Grinding of such harder materials by the conventional process is cumbersome, time consuming and requires more energy and therefore the main drawbacks of the above processes are the unsafe handling of scrap and longer duration of grinding leading to consumption of more energy and thus, rendering the recycling process less attractive as well as uneconomical. The other drawbacks are ineffective method for raw material resource saving and ineffective waste management.

The main object of the present invention relates to a method of converting fired ceramic scrap into fine ceramic powder useful for the manufacture of ceramic articles, which obviates the above noted drawbacks.
Another object of the present invention is to provide a safe and economically viable method of comminution of all types of vitrified and semi-vitrified fired ceramic scraps into fine powder obviating the drawbacks as detailed above.
Yet another object of the present invention is the economic use of ceramic waste materials such as fired ceramic scrap through the recycling route in the production of ceramic articles.
Still another object of the present invention is to improve the quality of ceramic products by using ceramic powder obtained from pre-reacted or processed ceramic waste materials through enhancement in the fired strength as well as widening of vitrification range of the products.
Yet another object of the present invention is to prepare consistent quality ceramic powder from pre-reacted scrap ceramic material for the production of traditional products like grinding media, acid resistant bricks and tiles as well as other ceramic products like crockery, sanitary ware, & ceramic tiles.

Another object of the present invention is to provide for raw material resource saving, energy saving as well as abetment of environmental pollution through effective ceramic solid waste management.
The present invention provides a novel method of converting fired ceramic scrap into recyclable fine ceramic powder as raw material for the manufacture of ceramic articles. The method of the present invention consists of heating pre-sized fired ceramic scrap followed by instant water quenching to impart thermal shock. This results in increased grindability thus removing the serious problem of hazardous and uneconomical grinding of vitrified and hard ceramic scrap material to obtain fine ceramic powder.
Accordingly, the present invention provides a method of converting fired ceramic scrap into fine ceramic powder useful for the manufacture of ceramic articles which comprises heating pre^-sized fired ceramic scrap to a temperature in the range of 500° to 850°C for a period in the range of 20 to 30 mins., subjecting the heated ceramic scrap to instant water quenching, allowing the ceramic scrap to remain in water for about 20 to 30 mins to obtain quenched ceramic scrap, drying the saud quenched ceramic scrap at a temperature in the range of 100 to 120°C, grinding the dried quenched ceramic scrap by known methods into fine ceramic powder.
In an embodiment of the present invention, the fired ceramic scrap used is such as white wares, insulators, porcelains, crockery wares, glass, sanitary wares, ceramic tiles, acid resistant bricks and tiles.
In another embodiment of the present invention the fired ceramic scrap used is broken by known methods into sizes in the range of 5 to 300 cm3 prior to heating.
In still another embodiment of the present invention the instant water quenching of the heated ceramic scrap is effected by immersing in water kept at ambient temperature.
In yet another embodiment of the present invention the dried quenched ceramic scrap is ground by known methods such as ball milling into fine ceramic powder of size in the range of 75 to 53 micron.
The details of the processing steps of the method of the present invention are given below :
1. Waste ceramic articles i.e. fired ceramic scrap are broken by
conventional methods to sizes of 5 to 300 cm3. The broken
ceramic scrap is heated to a temperature in the range of 500°
to 850°C for a period in the range of 20 to 30 mins.
2. Hot scrap after attainment of maximum temperature is
subjected to instant quenching by dropping into water kept
at ambient temperature and allowed to be cooled for 20 to 30
mins.
3. The cooled scrap (quenched) is dried at a temperature in the
range of 100 to 120°C.
4. The dried quenched scrap is comminuted into fine powder of 75
to 53 micron by conventional ball milling.
Traditional ceramic products are normally manufactured by the process of heating the products in a high temperature kiln. The phenomenon of hardening of ceramic products takes place through the pyro-chemical reactions of raw materials as well as formation of glassy phase which primarily depends on the degree of mixing of solid ingredients as well as their particle fineness. It is therefore, always advantageous to use partially reacted or fully reacted materials like fired ceramic scrap in the body compositions in order to arrest gas formation, to limit pyro-chemical reactions, to reduce the firing shrinkage of products and thus, arresting warpage, distortion and cracking of products, to widen the vitrification range of products and finally reduce substantially the time required for maturing of products and thus, to attain faster firing of ceramic articles. On the other hand, rejection in the ceramic manufacturing unit is normally quite large and if those rejected materials are recycled as raw materials, the production process becomes more economical. The main problem of such raw materials i.e ceramic wastes is their increased hardness which ultimately enhances the cost of the production as their grindability is poor.
In the conventional processes, several attempts were made to make the grinding processes efficient by changing the design of grinding equipments. In the present invention instead of altering the configuration of grinding machines more grindability is imparted into the fired ceramic scrap itself by making them brittle and easily breakable, adopting a new technology which is hither to non-existent for this type of material. A synergy of quenching and grinding makes an integrated process for making the desired material. Thus by using similar grinding equipment, the grinding of the fired ceramic scrap may be effected more easily and more economically.
The novelty of the method of the present invention lies in increasing the grindability of the fired ceramic scrap by the inventive step of thermal quenching of the material, thus generating a large number of defects in the form of micro and macro cracks within the micro structure of the vitreous matrix. The non-obvious inventive step thus, lies in the thermal shock treatment i.e. thermal quenching of fired ceramic scrap prior to grinding.
The following examples are given by way of illustration and therefore should not be construed to limit the scope of the present invention.
Example — 1
60 kg of crockery ware scraps of size 20 to 100 cm3 were heated at 800°C temperature for 20 mins. The heated mass was dropped into water kept at room temperature. Cooled scrap was dried at 105°C temperature. The dried scrap was ground to 53 micron in a ball mill.
Example - 2
60 kg of sanitary ware scraps of size 50 to 300 cm3 were heated at 850°C temperature for 30 mins. The heated mass was dropped into water kept at room temperature. Cooled scrap was dried at 110°C temperature. The dried scrap was ground to 53 micron in a ball mill.
Example - 3
50 kg of porcelain insulator scraps of size 5.0 to 50 cm3 was heated at 850°C temperature for 25 mins. The heated mass was dropped into water kept at room temperature. Cooled scrap was dried at 115°C temperature. The dried scrap was ground to 53 micron in a ball mill.
Example - 4
50 kg of glass scrap of size 5.0 to 225 cm3 was heated at 500°C temperature for 25 mins. The heated mass was dropped into water kept at room temperature. Cooled scrap was dried at 100°C temperature. The dried scrap was ground to 75 micron in a ball mill.
The main advantages of the present invention are:
1. Easy grinding of vitrified and hard ceramic scrap of ceramic
industry.
2. A reduction in the grinding time.
3. A saving of energy during grinding.
4. Thermally shocked scrap can be used in milling directly in a
ball mill without crushing in a jaw crusher or risky manual
crushing as required for untreated scrap.
5. Offers an easy solution to the serious problem of grinding of
vitrified and hard ceramic scrap of ceramic industry.
6. The technique is applicable to all types of vitrified and
semi-vitrified ceramic scrap of ceramic industry.

We Claim:
1. A method of converting fired ceramic scrap into fine ceramic powder for preparing ceramic
articles, which comprises heating pre-sized fired ceramic scrap to a temperature in the range
of 500° to 850°C for a period in the range of 20 to 30 minutes, subjecting the said heated
ceramic scrap to instant water quenching, allowing the ceramic scrap to remain in water for
a period in the range of 20 to 30 minutes to obtain quenched ceramic scrap, drying the said
quenched ceramic scrap at a temperature in the range of 100 to 120°C, grinding the dried
quenched ceramic scrap by known methods into fine ceramic powder.
2. A method as claimed in claim 1 wherein the fired ceramic scrap used is such as white
wares, insulators, porcelains, crockery wares, glass, sanitary wares, ceramic tiles, acid
resistant bricks and tiles.
3. A method as claimed in claims 1-2 wherein fired ceramic scrap is broken by known
methods into sizes in the range of 5 to 300 cm3 prior to heating.
4. A method as claimed in claim 1 wherein the instant water quenching is effected by
immersing in water kept at ambient temperature.
5. A method as claimed in claims 1-4 wherein the dried quenched ceramic scrap is ground by
known methods such as ball milling into fine ceramic powder of size in the range of 75 to
53 micron.
6. A method of converting fired ceramic scrap into fine ceramic powder for preparing ceramic
articles substantially as herein described with reference to the examples.

Documents:

811-del-2001-abstract.pdf

811-del-2001-claims.pdf

811-del-2001-correspondence-others.pdf

811-del-2001-correspondence-po.pdf

811-del-2001-description (complete).pdf

811-del-2001-form-1.pdf

811-del-2001-form-18.pdf

811-del-2001-form-2.pdf

811-del-2001-form-3.pdf

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Patent Number

227059

Indian Patent Application Number

811/DEL/2001

PG Journal Number

04/2009

Publication Date

23-Jan-2009

Grant Date

01-Jan-2009

Date of Filing

30-Jul-2001

Name of Patentee

COUNCIL OF SCIENTIFIC & INDUSTRIAL RESEARCH

Applicant Address

RAFI MARG, NEW DELHI-110001, INDIA.

Inventors:

#	Inventor's Name	Inventor's Address
1	KEDAR NATH MAITI	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, NARODA CENTRE, AHMEDABAD 382 330
2	BHIKHALAL BHAGVANJI MACHHOYA	CENTRAL GLASS & CERAMIC RESEARCH INSTITUTE, NARODA CENTRE, AHMEDABAD 382 330

PCT International Classification Number

C04B 035/00

PCT International Application Number

N/A

PCT International Filing date

PCT Conventions:

#	PCT Application Number	Date of Convention	Priority Country
1			NA