Title of Invention

"A PROCESS FOR MANUFACTURING SILICA INSULATING REFRACTORY BRICKS AND SHAPES"

Abstract

Production of insulating bricks using rice husk ash has been reported earlier but the processes used expensive materials like hydrated alumina, phosphoric acid, sodium silicate and sodium silicofluoride which stood in the way of making the products cost-effective. The present invention aims at producing refractory bricks and shapes using inexpensive, indigenously available starting materials and provides a process for manufacturing silica insulating refractory bricks and shapes, which comprises mixing of rice husk ash and an inorganic binder of calcium bearing materials selected from the group of calcium hydroxide, milk of lime, calcium carbonate, Plaster of Paris and gypsum or combination thereof and optionally one or more additives like iron oxide, titanium dioxide, copper oxide, sulphite lye or molasses, forming the mix into shapes, drying and firing the product at a temperature varying between 1200°C and 1600O C, wherein the calcium hearing material varies between 2 - 20% by weight and the additive is present in an amount varying between 0.5% and 5% by weight of the mix.

Full Text

2 The present invention relates to a process for manufacturing 3ilica insulating refractory bricks and chapes. More particularly, this invention pertains to the manufacture of 3ilica insulating refractory bricks from an aggregate of rice husk ash and an inorganic binder, optionally in the presence of additives, and water. In an agricultural country like India, rice grow3 abundantly. Rice husk is normally used as a fuel, only a small amount being employee for extraction of oil. The burnt material is thrown away as waste which causes nuisance to the environment. Rico husk servos as a source for pure form of silica and we had boon endeavouring to find a suitable avenue for its effective utilisation. Ash resulting from burning of rice husk has been found to possess very desirable characteristics which can be made into insulating shaped bodies, which will also constitute a viable and profitable use of a waste material. Work in this direction has been done by CSIR, such as reported in Indian Patents Nos.l60l64 and 165436. According to one aspect of the invention, rice husk ash may be used either as such or mixed with some amount of finely divided rice husk ash in an amount ranging from 0 - 70$ by weight of rice husk ash. The finely divided material is obtained by grinding normal rice husk a3heither in a ball mill or vibrating mill so that upto 70$ of the ground ash passes 0.063 mm sieves. According to a further feature of the invention, the minimum silica (SiO2) content in the rice husk ash is 90% on the loss free basis, and maximum loss on ignition at 1000 C is 20%, preferably below 10%. 3 The present invention provides for a process for the manufacture of silica insulating refractory "bricks and shapes, which comprises mixing of rice husk ash and an inorganic "binder of calcium bearing materials selected from the group of calcium hydroxide, milk of lime, calcium carbonate, Plaster of Paris and gypsum or combination thereof and optionally one or more additives like iron oxide, titanium dioxide, copper oxide, sulphite lye or molasses, forming the mix into shapes, drying and firing the product at a temperature varying "between 1200 C and 1600 C, wherein the calcium "bearing material varies between 2 - 20% by weight and the additive is present in an amount varying between 0.5% and 5% by weight of the mix. -4- For obtaining insulating bricks of predetermined shape, size and configuration, the ingredients are mixed with water to attain a mouldable consistency which is then moulded to the desired shape of a brick either in a plaster of paris or other moulds by conventional casting method, such as vibrocasting, hand moulding, slip casting and/or pneumatic ramming or by pressing in a conventional press. Addition of water, which is thin formed into shaped bodies, e.g. bricks, in a manner as discussed hereinbefore. The thus shaped bricks are dried and fired at a temperature not below 1200°C and not exceeding l600°C, preferably between 1300°C and 1500°. The inorganic binder used in this invention comprises at least one calcium bearing material such as calcium hydroxide, milk of lime, calcium carbonate, hydrated lime, piaster of paris and gypsum. Tho aforesaid binder is included in the mix in an amount ranging between 2 and 20% by weight, preferably more than 5% by weight. This invention also envisages use of organic binder(s) along with tho inorganic binder(s). Such organic binders may be selected from the group of sulphite lye, molasses and starch. The refractory mix of this invention may optionally employ fedditive(s), which comprises iron oxide, titanium dioxide and copper oxide or any mixture thereof. Such additive(a) may be included in the composition in an amount not exceeding % by weight. Tho additive(s) may 'also be inorganic or organic binders or combination thereof. The invention will now be further described with tho help of the following typical examples, which are illustrative in nature t - 5 - Example 1 Example 2 Rice husk ash (as it is)% "by wt. 95 35 Rice husk ash (fines)% by wt.O - 58 Calcium bearing materials % by wt. 5 7 The above composition is intimately mixed with water, moulded to shapes and dried. The dried and the shaped brick is then fired at a temperature ranging between 1350 to 1500°C. The properties of the fired bricks are as follows : Apparent Porosity (%) Bulk density (gm/cc) Cold Crushing Strength (in kg/cm2 ) Pyrometric Cone equivalent Residual quartz (%) SiO2(%) It has surprisingly "been found that during moulding, drying and firing of the insulating-, shaped bodies, pores are developed which reduce thermal conductivity of such bodies, e.g. bricks. As indicated earlier, the description and examples appearing above are given by way of illustration, and not by way of limitation, which includes within its scope variants and equivalents without deviating from the spirit of the invention. Having described the invention by way of illustration, it will be more particularly defined by means of the claims appended hereinbelow. Wo Claim 1o A process for manufacturing silica insulating refractory bricks and shapes, which comprises mixing of rice husk ash and an inorganic binder of calcium bearing materials selected from the group of calcium hydroxide, milk of lime, calcium carbonate, Plaster of Paris and gypsum or combination thereof and optionally one or more additives like iron oxide, titanium dioxide, copper oxide, sulphite lye or molasses, forming the mix into shapes, drying and firing the product at a temperature varying between 1200 C and 1600 C, wherein the calcium bearing material varies between 2 - 20% by weight and the additive is present in an amount varying between 0.5% and 5$ by weight of the mix. 2. A process as claimed in Claim 1, wherein the ingredients are mixed with water to attain a mouldable consistency, which is then moulded to impart the desired shape either in a Plaster of Paris mould or other moulds by conventional casting method such as vibrocasting, slip casting, hand moulding, pneumatic ramming or by pressing in a conventional press, 3, A process as claimed in Claims 1 and 2, wherein at least upto 70% of the rice husk or its mix obtained by grinding the husk either in a ball mill or in a vibrating mill will pass through O.O63 mm sieves, 4. A process as claimed in any of the preceding claims, wherein the minimum SiO2 content in the rice husk ash is 90% by wt. on loss free basis and maximum loss on ignition at 1000 C is about 20$, preferably below 10$ by wt. 5. A process as clnimed in Claims 1 to 4, wherein the shaped products such as bricks are fired at a temperature varying between 1300°C and 15OO°C. 6... A.process as claimed in Claim 1, whorein the amount of additive(s) added to the mix varies between 1 - 3% by wt. of the composition. 7. A process for manufacturing silica insulating refractory bricks and shapes, substantially as hereinbefore described with particular reference to tho Examples. Production of insulating bricks using rice husk ash has been reported earlier but the processes used expensive materials like hydrated alumina, phosphoric acid, sodium silicate and sodium silicofluoride which stood in the way of making the products cost-effective. The present invention aims at producing refractory bricks and shapes using inexpensive, indigenously available starting materials and provides a process for manufacturing silica insulating refractory bricks and shapes, which comprises mixing of rice husk ash and an inorganic binder of calcium bearing materials selected from the group of calcium hydroxide, milk of lime, calcium carbonate, Plaster of Paris and gypsum or combination thereof and optionally one or more additives like iron oxide, titanium dioxide, copper oxide, sulphite lye or molasses, forming the mix into shapes, drying and firing the product at a temperature varying between 1200°C and 1600O C, wherein the calcium hearing material varies between 2 - 20% by weight and the additive is present in an amount varying between 0.5% and 5% by weight of the mix.

Documents:

00356-cal-2000-abstract.pdf

00356-cal-2000-claims.pdf

00356-cal-2000-correspondence.pdf

00356-cal-2000-description(complete).pdf

00356-cal-2000-form-1.pdf

00356-cal-2000-form-18.pdf

00356-cal-2000-form-2.pdf

00356-cal-2000-form-3.pdf

00356-cal-2000-letters patent.pdf

00356-cal-2000-p.a.pdf

356-CAL-2000-CORRESPONDENCE.pdf

356-CAL-2000-FORM 27.pdf

356-CAL-2000-FORM-27.pdf