Claims:We Claim:

1. Insulation castable comprising low density of less than 1.6 g/cc refractory castable incorporating 1-5 wt% alumino-silicate based ceramic fibre blanket (CFB) waste.

2.Insulation castable as claimed in claim 1 which is hydraulically insulation castable of said refractory castable including 42-50 wt % Al2O3 and includes extracted fibre from CFB waste of steel plant of size less than 5 mm having chemical composition of Al2O3:40-48%; SiO2:54-60%; ZrO2:0-19%

3.Insulation castable as claimed in anyone of claims 1 or 2 comprising:
Low density castable comprising CaO:8-12 wt.%; Al2O3: 42-50 wt%; SiO2:40-45 wt%; MgO: 1-2 wt%; TiO2: <0.5 wt% and K2O + Na2O:<1.0 wt%; and
Said Ceramic Fibre Blanket comprises Alumino-silicate comprising Al2O3: 35-45 wt%; SiO2: 50-56 wt%; Fe2O3:<1.0 wt %; TiO2: 0-2.5 wt% and K2O + Na2O: 0.1 -0.2 wt %.

4. Insulation castable as claimed in anyone of claims 1 to 3 comprises castable having
Parameter Characteristics
Bulk Density (g/cc) 1.4-1.55
Cold Crushing Strength (kg/cm2)
@ 110°C/24h
@ 1200°C/2h
80-110
40-55
Permanent Linear Change (%)
@ 1000°C
@ 1200°C 1.15-1.65 (shrinkage)
0.65-0.85 (shrinkage)
Thermal Conductivity @ 1000°C (W/mK) 0.3-0.88

5. A method for manufacture of insulation castable as claimed in anyone of claims 1 to 4 comprising:
involving extraction of CFB waste fibre, addition of extracted waste fibre to refractory castable, dry mixing of the mixture for 2-5 min and wet mixing for 3-6 min by addition of water.

6. A method claimed in claim 5 wherein said CFB waste is sourced from anyone or more of coke oven, SMS, mills, indurating furnace, etc.

7. A method as claimed in anyone of claims 5 or 6 including step of processing of CFB waste comprising said CFB wasteis soaked for 12-24 h followed by washing in running water for 1-4 h at room temperature using distilled water, deionized water or drinking water, drying the washed blankets in an oven for 12-24 h,subsequently the dried blankets are sheared to small pieces and screened using 5mm sieve followed by washing in running water using distilled water, deionized water or drinking water and drying in air for 12-48 h to obtain CFB waste fibre.

8. A method as claimed in anyone of claims 5 to 7 wherein the quantity of extracted CBF fibre added is 1-5 wt% and the water added during wet mixing is 15-35 wt%.

9. A method as claimed in anyone of claims 5 to 8 wherein the CFB waste fibreis selectively incorporated such that the developed castable have:
a thermal conductivity of 0.30-0.88 W/mK at 1000oC.
a cold crushing strength of 80-110 kg/cm2 at 110oC/24h, and 40-55 kg/cm2 at 1200oC/2h.
permanent linear change of -1.15% to -1.65% at 1000oC/2h and -0.65% to -0.85% at 1200oC/2h
a bulk density of 1.4-1.55 g/cc at 110oC/24h.
10. A method as claimed in anyone of claims 5 to 9 comprising involving steps of casting, vibro-casting, trowelling for installation in the form, selectively of coke oven door cover, oven regenerator walls, heat shields, etc.

Dated this the 10th day of January, 2020
Anjan Sen
Of Anjan Sen & Associates
(Applicant’s Agent)
IN/PA-199
, Description:FIELD OF THE INVENTION
The present invention relates to an insulation castable containing hazardous waste and a process for producing the same. More particularly, the present invention is directed to developing a hydraulically insulation castable from a refractory castable, preferably low density castable and hazardous alumino-silicate ceramic fibre blanket (CFB) waste, having a bulk density of less than 1.6 g/cc and thermal conductivity of less than 0.9 W/mK. The process requires extraction of fibre from CFB waste to a size of less than 5mm, addition of it to the castable in the range of 1-5 wt%, dry mixing for 2-5 minutes and wet mixing for 3-6 minutes by addition of water.The insulation castable so producedis suitable for non-critical applications which can be installed by casting, cast-vibrating, rodding or trowelling using selective mix of refractory castable and CFB waste from steel plant wherein the CFB waste is used as an insulating media. The insulation castable thus can be used as a thermal insulation layer in coke oven door cover, oven regenerator walls, heat shields, etc.
BACKGROUND OF THE INVENTION
Ceramic fibre blankets (CFBs) are vitreous fibres intended for high performance thermal insulation applications at elevated temperatures. They are primarily used in lining furnaces, kilns and other industrial heaters. They also find wide application in automotive, marine, petrochemical, steel, aluminium, ceramic, glass and construction industries as a thermal insulating material.
CFBs are generally long, flexible, interwoven fibres manufactured by 'blown' and 'spun' process using kaolin, a naturally occurring alumino-silicate clay or a synthetic mix of alumina and beach sand as the raw materials. They are lightweight and can be used in a temperature range of 1260oC to 1600oC to achieve the insulation property. The chemical composition of these fibres have Al2O3:40-48%; SiO2:54-60%; ZrO2:0-19%.
The global ceramic fibre market was estimated to be approximately USD 1.73 Billion in 2017 and is predicted to be USD 3.59 Billion by 2026 at a CAGR of 9.55%(https://marketsgazette24.com /2019/11/12 /global-ceramic-fiber-market-industry-analysis-and-forecast-2018-2026/).However, owing to its carcinogenic nature, use of CFBs pose serious concern to human health. Therefore, disposal of these blankets in open environment is undesirable. Furthermore, though CFBs possess cost and thermal efficiency advantages over refractory bricks, they become brittle and friable withina limited period of application, thus making them unusable which are ultimately disposed as waste.
As per disposal protocol, it is recommended to dispose the waste blanket in a covered container at a licensed waste disposal area. Disposing waste blanket in open space will lead to air borne dust, prolonged exposer to fibre dust will lead to irritation in respiratory tract, eye, skin and gastro intestine.
Earlier studies about development of various insulating refractories by recycling different organic and inorganic wastes. However, no work has been reported about recycling of a ceramic fibre / ceramic fibre blanket as an insulating media in developing an insulation refractory.
European Patent No EP 0237609A1 dated 23rd Sep 1987 by Brayet aldescribes development of a light weight castable which was prepared from a mixture of fired clay and ground and sized waste cork, which was then molded and fired in a kiln to burn the cork, leaving a highly porous and light brick.
US patent No 2,419,684 dated 21st July 1943 by Johnson et al report about an insulating castable consisting of 76-82% by volume of insulating grog particles, 16.5-23% by volume of fire clay and hydraulic cement binder, 0.5-1% by volume of inorganic colloidal suspensions and 0.05-0.0125% by volume of wetting agent. They were able to develop an insulating castable with a bulk density of 1.12 g/cc.
Patent No DE102012219236A1 dated 22nd Oct 2012 by Brunk reports about a SiO2 rich lightweight refractory that comprises 60-80 wt% burnout materials, 20-40 wt% fine grained refractory SiO2 raw material, 2-10 wt% SiO2 rich filler, 5-20 wt.% fibrous biogenic SiO2, calcium oxide-containing binder, an organic pressing agent and water. The insulating bricks prepared were fired above 1200°C to obtain lightweight refractory brick having a density less than 0.5 g/cc. The burnout material consisted of fine-ground sawdust or coke, mixed with silicium raw materials such as quartz sands, quartz flours or recycled silica stone, and milk of lime, shaped and heat treated at 1420°C to 1480°C.
Patent Publication No WO 2004/085334A1 dated 26th March 2003 by Panda et al reports about production of a silica refractory from 70-95 wt% of agricultural waste ash such as rice husk ash, 1-10 wt% of CaO-containing binder and 0-3 wt% metal oxide. The shaped refractory was fired above 1200°C. The final product has a bulk density of 0.6-0.75 g/cc and thermal conductivity of 0.3 to 0.36 W/mK at 800°C.
Sutcuet al (DOI: 10.1016/j.ceramint.2011.08.027) report about a process to produce porous anorthite based insulating firebrick refractories from mixtures K244 clay and fireclay, recycled paper processing waste and sawdust. Paper waste and sawdust were used as the pore formers to impart the insulating property to the refractory where the saw dust was used up to 30%. The thermal conductivity of the formulation with paper waste varied between 0.13 to 0.25 W/mK at 1000°C.
The crux of the present invention, in particular, differs from the prior art by way of developing a method for processing the ceramic fibre blanket waste generated in steel plantsand subsequently recycling it as an insulating media to develop an insulation castable, thereby addressing the disposal concern of hazardous process waste and lowering down the environment related concerns.
OBJECTS OF THE INVENTION
The basic object of the present invention is directed to develop an insulation castable by adding alumino-silicate based Ceramic Fibre Blanket(CFB)hazardous waste generated from steel plant.
Another object of the present invention is directed to provide a processfor producing said insulation castable involving cleaning and extracting fibres from the CFB waste discarded after use.
Yet another object of the present invention is directed to develop an insulation castable where extracted CFB waste fibre is added as an insulating media.
A further object of the present invention is directed to develop an insulation castable by adding CFB waste generated from steel plantwhere the castable can be a low density one or dense one.
A still further object of the present invention is directed to develop an insulation castable by adding CFB waste generated from steel plantwhere the processed CFB waste is added to the castable during castable mixing stage.
Another object of the present invention is directed to develop an insulationcastable by adding processed CFB waste from steel plantthat can be applied in non-critical applications requiring thermal insulation applications such as oven doors in coke oven.
A further object of the present invention is directed to develop an insulation castable by adding CFB waste generated from steel plant in order to recycle and utilize steel plant process waste, so as to close the sustainable production loop.
Yet another object of the present invention is directed to develop an insulationcastable by adding CFB waste generated from steel plant, to achieve properties comprising bulk density (BD) maximum 1.6 g/cc., the thermal conductivity of minimum 0.9 W/mK and cold crushing strength (CCS) at 110°C is minimum 100 kg/cm2.

SUMMARY OF THE INVENTION
The basic aspect of the present invention is directed to Insulation castable comprising low density of less than 1.6 g/cc refractory castable incorporating 1-5 wt% alumino-silicate based ceramic fibre blanket (CFB) waste.

A further aspect of the present invention is directed to said Insulation castable which is hydraulically insulation castable of said refractory castable including 42-50 wt % Al2O3 and includes extracted fibre from CFB waste of steel plant of size less than 5 mm having chemical composition of Al2O3:40-48%; SiO2:54-60%; ZrO2:0-19%

A still further aspect of the present invention is directed to saidInsulation castable comprising:
Low density castables comprising CaO:8-12 wt.%; Al2O3: 42-50 wt%; SiO2:40-45 wt%; MgO: 1-2 wt%; TiO2: <0.5 wt% and K2O + Na2O:<1.0 wt%; and
Said Ceramic Fibre Blanket comprises Alumino-silicate comprising Al2O3: 35-45 wt%; SiO2: 50-56 wt%; Fe2O3:<1.0 wt%; TiO2: 0-2.5 wt% and K2O + Na2O: 0.1 -0.2 wt%.

A still further aspect of the present invention is directed to Insulation castable comprises castable having
Parameter Characteristics
Bulk Density (g/cc) 1.4-1.55
Cold Crushing Strength (kg/cm2)
@ 110°C/24h
@ 1200°C/2h
80-110
40-55
Permanent Linear Change (%)
@ 1000°C
@ 1200°C 1.15-1.65 (shrinkage)
0.65-0.85 (shrinkage)
Thermal Conductivity @ 1000°C (W/mK) 0.3-0.88

Another aspect of the present invention is directed to a method for manufacture of insulation castable comprising:
involving extraction of CFB waste fibre, addition of extracted waste fibre to refractory castable, dry mixing of the mixture for 2-5 min and wet mixing for 3-6 min by addition of water.

Yet another aspect of the present invention is directed to said method wherein said CFB waste is sourced from anyone or more of coke oven, SMS, mills, indurating furnace, etc.
A further aspect of the present invention is directed to said method including step of processing of CFB waste comprising said CFB waste soaked for 12-24h followed by washing in running water for 1-4 h at room temperature using distilled water, deionized water or drinking water, drying the washed blankets in an oven for 12-24 h, subsequently the dried blankets are sheared to small pieces and screened using 5mm sieve followed by washing in running water using distilled water, deionized water or drinking water and drying in air for 12-48 h to obtain CFB waste fibre.
A still further aspect of the present invention is directed to said method wherein the quantity of extracted CBF fibre added is 1-5 wt% and the water added during wet mixing is 15-35 wt%.
A still further aspect of the present invention is directed to said method wherein the CFB waste fibreis selectively incorporated such that the developed castable have:
a thermal conductivity of 0.30-0.88 W/mK at 1000oC;
a cold crushing strength of 80-110 kg/cm2 at 110oC/24h, and 40-55 kg/cm2 at 1200oC/2h;
permanent linear change of -1.15% to -1.65% at 1000oC/2h and -0.65% to -0.85% at 1200oC/2h; and
a bulk density of 1.4-1.55 g/cc at 110oC/24h.
A still further aspect of the present invention is directed to said method comprising involving steps of casting, vibro casting, trowelling for installation in the form selectively of coke oven door cover, oven regenerator walls, heat shields, etc.
Yet another aspect of the present invention is directed to said process wherein a dry insulation castable is prepared by adding required quantity of said CFB waste fibre and dry mixing in a mixer.
Yet another aspect of the present invention is directed to said process to produce an insulation castable using ceramic fibre blanket waste wherein the water added can be drinking water, distilled water, de-ionized water.

The above and other objects and advantages of the present invention are described hereunder with reference to accompanying figures and examples.

BRIEF DESCRIPTION OF THE ACCOMPANYING FIGURES
Fig. 1: Process flow of insulation castable preparation as per the invention.
Fig.2: shows photographs of CFB waste and fibres extracted from the blanket after washing.
Fig.3: shows the photographs of insulation castable blocks prepared using extracted CFB waste fibre.

DETAILED DESCRIPTION OF THE INVENTION WITH REFERENCE TO ACCOMPANYING DRAWINGS

The present invention relates to a process for manufacturing of an insulation castable using ceramic fibre blanket waste from coke oven. More particularly, the present invention is directed to provide an insulation castable comprising low density castable and alumino-silicate based ceramic fibre blanket waste from coke oven 1-5% by wt, wherein the waste blanket is used as the insulating medium to lower the thermal conductivity of castable.

Referring to Fig. 1, a method 100 for obtaining the blanket fibre from CFB waste, is shown at steps S.101-S.108. At step S.101, the ceramic fibre blanket (CFB) is obtained from coke oven after the blanket is discarded as waste post use. Cleaning of the CFB waste is done through steps S.102 and S.103 to remove any dirt, dust, impurities from the blanket. Drying of the washed blanket is done through step S.104. Steps S.105 and S.106 illustrate the process to obtain blanket fibres from the dried CFB. The blanket fibres are washed again in running water and subsequently dried as per steps S.107 and S.108 to remove any remaining dust, dirt or impurities. The proportion of extracted blanket fibre to be added to the castable that will form the dry insulation castable is determined in the step S.110. Step S.110 also ensures homogeneous mixing of the material in dry condition. In step S.111, water is added to the dry insulation castable to obtain the insulation castable.

Fig. 2 shows the CFB waste generated in coke oven and dried CFB waste fibre extracted from the blanket after washing.

Fig. 3 shows photographs of insulation castable blocks produced according to the invention for few batches after drying at 110°C for 24h.
The invention will now be illustrated by means of the following examples. However, the following examples are only for explaining the present invention in more detail, but scope of the present invention is not limited to the particular embodiments only.
The raw materials used were low density castable with 42-50wt% Al2O3, and alumino-silicate ceramic fibre blanket waste from coke oven, SMS, mills, indurating furnace, etc having the chemical composition shown in Table 1.
Table 1: Chemical composition of the raw materials (wt%)
Material CaO Al2O3 SiO2 Fe2O3 MgO TiO2 K2O+Na2O
Castable Low density 8-12 42-50 40-45 < 1.0 1-2 < 0.5 < 1.0

Ceramic Fibre Blanket Alumino-Silicate -- 35-45 50-56 < 1.0 Nil 0-2.5 0.1-0.2
The physical properties such as bulk density and cold crushing strength were determined after drying at 110oC for 24 h for all compositions.
Example 1: An insulation castable comprising of 2% by weight of extracted CFB waste fibre, and 98% by weight of low density castable, having the fibre size less than 5mm and castable grain size in the range of 0-4 mm.
A method for extracting the fibre using drinking water with soaking for 24h followed by washing in running water for 2h and drying in oven for 12h and subsequently drying of the extracted fibre for 24h in the oven.
A method for the preparation of the insulation castable, comprising the steps of dry mixing of the ingredients for 3 minutes followed by addition of 25% water and mixing for 4 minutes. The physical and chemical indicators: compressive strength (110°C/24h) 106 kg/cm2, compressive strength (1200°C/2h) 448 kg/cm2; bulk density (110°C/24h) 1.54 g/cm3; permanent linear change on heating (1000°C/2h)-1.27%, permanent linear change on heating (1200°C/2h) -0.79%; thermal conductivity (1000°C) 0.88 W/mK.

Example 2: An insulation castable comprising of 3.5% by weight of extracted CFB waste fibre, and 96.5% by weight of low density castable, having the fibre size less than 5mm and castable grain size in the range of 0-4 mm.
A method for extracting the fibre using drinking water with soaking for 24h followed by washing in running water for 2h and drying in oven for 24h and subsequently drying of the extracted fibre for 12h in the oven.
A method for the preparation of the insulation castable, comprising the steps of dry mixing of the ingredients for 3 minutes followed by addition of 25% water and mixing for 4 minutes. The physical and chemical indicators: compressive strength (110°C/24h) 104 kg/cm2, compressive strength (1200°C/2h) 492 kg/cm2 bulk density (110°C/24h) 1.49 g/cm3; permanent linear change on heating (1000°C/2h) -1.53%, permanent linear change on heating (1200°C/2h) -0.81%; thermal conductivity (1000°C) 0.33 W/mK.

Example 3: An insulation castable comprising of 3.5% by weight of extracted CFB waste fibre, and 96.5% by weight of low density castable, having the fibre size less than 5mm and castable grain size in the range of 0-4 mm.
A method for extracting the fibre using drinking water with soaking for 24h followed by washing in running water for 2h and drying in oven for 12h and subsequently drying of the extracted fibre for 24h in the oven.
A method for the preparation of the insulation castable, comprising the steps of dry mixing of the ingredients for 3 minutes followed by addition of 25% water and mixing for 4 minutes. The physical and chemical indicators: compressive strength (110°C/24h) 110 kg/cm2, compressive strength (1200°C/2h) 510 kg/cm2; bulk density (110°C/24h) 1.47 g/cm3; permanent linear change on heating (1000°C/2h) -1.3%, permanent linear change on heating (1200°C/2h) -0.68%; thermal conductivity (1000°C) 0.41 W/mK.

Compressive strength and thermal conductivity of the castable depend on the quantity of fibre added and amount of porosity present. It would be evident from the above results that the insulation castable formulations of the invention have considerable CCS that can withstand the handling strength requirement and substantially low thermal conductivity for applications where thermal insulation is critical.

In the process according to the invention, it was observed, when the fibre content is more than 5% by weight, the cold crushing strength (CCS) of the castable decreases drastically. Very low CCS will lead to poor structural strength after installation.

Typical properties of the developed insulation castable are shown in Table 2. Properties of a standard alumina based insulation castable commercially available (source M/s Totale Refractories) in India is provided for comparison.

Table 2: Typical properties of developed castable
Parameter Commercial Castable Developed Castable
Bulk Density (g/cc) 1.57 1.4-1.55
Cold Crushing Strength (kg/cm2)
@110°C/24h (heated and cooled down to room temperature)
@ 1200°C/2h(heated and cooled down to room temperature)
110
51
80-110
40-55
Permanent Linear Change (%)
@ 1000°C
@ 1200°C
1.18 (shrinkage)
0.76 (shrinkage) 1.15-1.65 (shrinkage)
0.65-0.85 (shrinkage)
Thermal Conductivity @ 1000°C (W/mK) 0.95 0.3-0.88
As described above, the present invention has advantages in that the hazardous ceramic waste generated in a steel plant, which has up till now being disposed as a waste, can be recycled and the insulation castable manufactured therefrom by the present invention can be utilized in the non-critical applications such as coke oven door cover, oven regenerator walls, heat shields, etc.It is thus possible by way of the present invention to provide an insulation castable using appropriate proportion of hazardous process waste comprising 1-5% bywtas an insulating media, thereby reducing the disposal and environmental concerns.