Title of Invention

"A PROCESS FOR THE PRODUCTION OF POROUS CERAMIC TILES USING MARBLE DUST"

Abstract

A PROCESS FOR THE PRODUCTION OF POROUS CERAMIC TILES USING MARBLE DUST In the present invention, a process has been developed for the production of porous ceramic tiles using waste material like marble dust, clay and calcium silicate mineral by hydrothermal treatment. Marble dust fines generated by the marble industries during cutting and polishing processes is used as a source of reactive lime for hydrothermal solidification. The various chemical reactions involved in the process contributed towards the formation of calcium silicate hydrate bond which is responsible for the strength development in the present invention. The product obtained by the present invention possesses 20 to 24% apparent porosity and 84 to 188 kg/cm2 cold modulus of rupture strength. Such type of high strength porous tiles can be used in the floors and walls of residential buildings.

Full Text

The present invention relates to a process for the production of porous ceramic tiles using marble dust. The present invention particularly relates to a process for the production of porous ceramic tiles using waste marble dust by hydrothermal treatment without firing. In the present invention the process for the production of porous ceramic tiles waste marble dust is utilized as a constituent material which is a hazardous by-product generated by the marble cutting and polishing industries in huge quantities. The marble dust fine (90% less than 200 micron size) air borne particles lead to severe dust pollution, contaminate underground water and affect the productivity of the land and vegetation. As detected by x-ray diffraction study marble dust mainly consists of pure marble powder (calcium carbonate) and contaminated with different calcium silicate phases, such as wollastonite (CaO.SiO2), rankinite (3CaO.2SiO2). In the present invention marble dust has been considered as the potential source of reactive lime instead of chemical grade calcium carbonate required for hydrothermal solidification. During this treatment alumino-silicate from clay source reacts with lime and forms calcium silicate hydrate (CaO-SiO2-H2O) and calcium alumino-silicate hydrate (CaO-AI2O3-Si02-H20) bonds. Again calcium silicates present in the marble dust also form calcium silicate hydrate phases in addition to the above. These bond materials are responsible for the strength development. Hence no separate source of silica is essential for the present invention. In cases, where calcium silicate phases, such as wollastonite, rankinite, are present in marble dust, external addition of wollastonite is not necessary. In case marble dust is of high purity and free from silicates wollastonite is to be externally added. Accordingly the present invention provides a process for the production of porous ceramic tiles using marble dust, which comprises: a) Calcination of marble dust to obtain calcined marble dust, b) mixing the said calcined marble dust as obtained from step (a) in the ratio of 15 to 48 wt%, with clay and wollastonite in a ratio of 52 to 64 wt% and 0 to 33 wt% respectively to obtain a mixture, c) slaking the said mixture obtained from step (b) with water to obtain a slaked batch, d) slaked batch as obtained from step (c) followed by air drying for a period of 40 to 48 hours, e) air dried slaked batch as obtained from step (d) is subjected to hydraulic pressing to obtain pressed products of the said mixture, f) drying the pressed products as obtained from step (e) in an oven to obtain dried products of the said mixture, g) dried products as obtained from step (f) are subjected to hydrothermal solidification under saturated vapour pressure of 100 to 160 psi in an autoclave for a time period upto 2 hours. In an embodiment of the present invention the calcination of marble dust is done at a temperature in the range of 900 to 1000°C, with a soaking period in the range of 1 to 2 hours. In another embodiment of the present invention clay used is naturally available china clay or ball clay. In yet another embodiment of the present invention the slaking of the batch is done using water in the range of 46 to 51 wt% of the total mix. In still another embodiment of the present invention the hydraulic compaction of the dried slaked product is done at a pressure in the range of 350 to 400 kg/cm2. In a further embodiment of the present invention the oven drying of the pressed products is done at a temperature in the range of 110 to 120°C for a period in the range of 24 to 30 hours. The novelty of the present invention resides in providing high strength porous ceramic tiles from industrial waste marble dust by hydrothermal treatment of a mixture of calcined marble dust, clay and wollastonite, if required. Presence of combination of lime and reactive calcium silicate phases, such as wollastonite, rankinite, in marble dust made it possible to form hydrate bond materials required for strength development at lower saturated vapor pressure (100 to 160 psi). This novel process enables to eliminate costly chemical grade calcium carbonate and natural resource of quartz that are commonly used to produce products by hydrothermal treatment at saturated vapor pressure of 250 psi. The non-obvious inventive step of the process of present invention resides in providing a mixture of calcined marble dust, clay and wollastonite, if required, to obtain a slaked product. Further the slaked mixture on autoclaving produces hydrated bond phases and results strength if the product. The chemical reaction involved in the process are : CaO + H2O → Ca(OH)2 Ca(OH)2 + CaO SiO2 → CaO - SiO2 - H2O. Ca(OH)2 + Al2O3 2SiO2 2H2O → CaO - Al20\O3 - SiO2 - H2O The details of the process steps of the present invention are; i) calcination of marble dust at a temperature in the range of 900 to 1000°C with a soaking period in the range of 1 to 2 hours, ii) intimate mixing of 15 to 48 wt% of calcned marble dust, 52 to 64 wt% of clay, such as china clay or ball clay and 0 to 33 wt% wollastonite. iii) slaking of the mixed batch with 46 to 51 wt% of water of the total mix, iv) air drying of the slaked batch for a time period of 40 to 48 hours, v) hydraulic pressing of the air dried slaked batch at a specific pressure of 350 to 400 kg/cm2, vi) Oven drying of the pressed products for a period of 24 to 30 hours at a temperature in the range of 110 to 120°C, vii) hydrothermal solidification of the oven dried products under saturated vapor pressure of 100 to 160 psi in an autoclave for a time period of around 2 hours. The following examples are given way of illustration of the process of the present invention in actual practice. However, the examples, which are given here by way of illustration, should not be construed to limit the scope of the present invention. Example 1 Raw marble dust was calcined at 900°C for 1 hr in a laboratory electric furnace. Then 363 gms of calcined marble dust was intimately mixed with 637 gms of clay and the batch was slaked with 460 gms of water. Air-drying of the slaked batch was done for 48 hrs. Dried slake batch was then pressed at 350 kg/cm2 specific pressure and samples of 60 mm length, 6 mm width and 6 mm height were prepared. Pressed samples were then dried at 110°C for 24 hrs and then the samples were hydrothermally treated under a saturated vapor pressure of 100 psi for 2 hrs. Hydrothermally treated samples had the following properties : Bulk Density (gm/cc) : 1.90 Apparent porosity (%) : 23.64 Cold modulus of rupture strength (kg/cm2) : 90 Example 2 Raw marble dust was calcined at 900°C for 2 hr in a laboratory electric furnace. Then 363 gms of calcined marble dust was intimately mixed with 637 gms of clay and the batch was slaked with 470 gms of water. Air-drying of the slaked batch was done for 40 hrs. Dried slake batch was then pressed at 400 kg/cm2 specific pressure and samples of 60 mm length, 6 mm width and 6 mm height were prepared. Pressed samples were then dried at 120°C for 24 hrs and then the samples were hydrothermally treated under a saturated vapor pressure of 160 psi for 2 hrs. Hydrothermally treated samples had the following properties : Bulk Density (gm/cc) : 1.96 Apparent porosity (%) : 21.33 Cold modulus of rupture strength (kg/cm2) : 162 Example 3 Raw marble dust was calcined at 1000°C for 1 hr in a laboratory electric furnace. Then 477 gms of calcined marble dust was intimately mixed with 523 gms of clay and the batch was slaked with 495 gms of water. Air-drying of the slaked batch was done for 48 hrs. Dried slake batch was then pressed at 350 kg/cm2 specific pressure and samples of 60 mm length, 6 mm width and 6 mm height were prepared. Pressed samples were then dried at 110°C for 30 hrs and then the samples were hydrothermally treated under a saturated vapor pressure of 160 psi for 2 hrs. Hydrothermally treated samples had the following properties : Bulk Density (gm/cc) : 1.94 Apparent porosity (%) : 22.46 Cold modulus of rupture strength (kg/cm2) : 103 Example 4 Raw marble dust was calcined at 900°C for 2 hr in a laboratory electric furnace. Then 477 gms of calcined marble dust was intimately mixed with 523 gms of clay and the batch was slaked with 510 gms of water. Air-drying of the slaked batch was done for 48 hrs. Dried slake batch was then pressed at 400 kg/cm2 specific pressure and samples of 60 mm length, 6 mm width and 6 mm height were prepared. Pressed samples were then dried at 110°C for 24 hrs and then the samples were hydrothermally treated under a saturated vapor pressure of 160 psi for 2 hrs. Hydrothermally treated samples had the following properties : Bulk Density (gm/cc) : 1.98 Apparent porosity (%) : 20.69 Cold modulus of rupture strength (kg/cm2) : 188 Example 5 High pure raw marble dust, free from silicates, was calcined at 900°C for 2 hr in a laboratory electric furnace. Then 149 gms of calcined high pure marble dust was intimately mixed with 523 gms of clay and 328 gms of wollastonite. The batch was slaked with 510 gms of water. Air-drying of the slaked batch was done for 48 hrs. Dried slake batch was then pressed at 400 kg/cm2 specific pressure and samples of 60 mm length, 6 mm width and 6 mm height were prepared. Pressed samples were then dried at 110°C for 24 hrs and then the samples were hydrothermally treated under a saturated vapor pressure of 100 psi for 2 hrs. Hydrothermally treated samples had the following properties : Bulk Density (gm/cc) : 1.92 Apparent porosity (%) : 21.96 Cold modulus of rupture strength (kg/cm2) : 84 From the above examples it is observed that from a waste material such as marble dust, which causes health hazards and environmental pollution, the present invention provides a process of making low cost porous ceramic tiles possessing properties like bulk density in the range of 1.90 to 1.98 gm/cc, apparent porosity in the range of 20 to 24% and cold modulus of rupture in the range of 84 to 188 kg/cm2. The main advantages of the present invention are : 1) the present process utilizes hazardous waste material marble dust as a potential source of reactive lime by fully replacing the costly chemical grade calcium carbonate, thereby reduces the product cost, 2) the present process does not require natural sources of quartz thereby reserves earth, 3) the present process require lower saturated vapor pressure during hydrothermal processing, 4) the present process can solve the environmental pollution problem created by the marble dust, 5) the product produced by the present process can be used in the floors and walls of residential buildings at a affordable prices for comfortable living. 6) the porous ceramic tiles produced by the present process is a unfired product, which can have a lower cost as it saves the cost of fuel for firing. We claim: 1) A process for the production of porous ceramic tiles using marble dust, which comprises: (a) calcination of marble dust to obtain calcined marble dust, (b) mixing the said calcined marble dust as obtained from step (a) in the ratio of 15 to 48 wt%, with clay and wollastonite in a ratio of 52 to 64 wt% and 0 to 33 wt% respectively to obtain a mixture, (c) slaking the said mixture obtained from step (b) with water to obtain a slaked batch, (d) slaked batch as obtained from step (c) followed by air drying for a period of 40 to 48 hours, (e) air dried slaked batch as obtained from step (d) is subjected to hydraulic pressing to obtain pressed products of the said mixture, (f) drying the pressed products as obtained from step (e) in an oven to obtain dried products of the said mixture, (g) dried products as obtained from step (f) are subjected to hydrothermal solidification under saturated vapour pressure of 100 to 160 psi in an autoclave for a time period upto 2 hours. 2) A process as claimed in claim 1, wherein the calcination of marble dust is done at a temperature in the range of 900 to 1000°C, with a soaking period in the range of 1 to 2 hours. 3) A process as claimed in claim 1-2, wherein the clay used is naturally available china clay or ball clay. 4) A process as claimed in claim 1 - 3, wherein the slaking of the batch is done using water in the range of 46 to 51 wt% of the total mix. 5) A process as claimed in claim 1 - 4, wherein the hydraulic compaction of the dried slaked product is done at a pressure in the range of 350 to 400 kg/cm2. 6) A process as claimed in claim 1-5, wherein the oven drying of the pressed products is done at a temperature in the range of 110 to 120°C for a period in the range of 24 to 30 hours. 7) A process for the production of porous ceramic tiles using marble dust, substantially as herein described with reference to the examples.

Documents:

215-DEL-2003-Abstract-(06-01-2009).pdf

215-del-2003-abstract.pdf

215-DEL-2003-Claims-(06-01-2009).pdf

215-DEL-2003-Claims-(27-01-2009).pdf

215-del-2003-claims.pdf

215-del-2003-complete specification (granted).pdf

215-DEL-2003-Correspondence-Others-(06-01-2009).pdf

215-DEL-2003-Correspondence-Others-(27-01-2009).pdf

215-del-2003-correspondence-others.pdf

215-del-2003-correspondence-po.pdf

215-DEL-2003-Description (Complete)-(06-01-2009).pdf

215-del-2003-description (complete)-(27-01-2009).pdf

215-del-2003-description (complete).pdf

215-DEL-2003-Form-1-(27-01-2009).pdf

215-del-2003-form-1.pdf

215-DEL-2003-Form-18-(27-01-2009).pdf

215-del-2003-form-18.pdf

215-DEL-2003-Form-2-(06-01-2009).pdf

215-del-2003-form-2.pdf

215-DEL-2003-Form-3-(06-01-2009).pdf

215-del-2003-form-3.pdf