Title of Invention

A PROCESS FOR THE PRODUCTION OF RICE HUSK ASH NODULES USEFUL AS HEAT INSULATING MATERIAL

Abstract

In the present invention, a process has been developed to manufacture rice husk ash nodules useful as heat insulating material. In the present process, surface active agents and binders have been used to modify the behaviour of green nodules during nodulizing and subsequent improvement in plasticity, workability, wetting and green strength. A schedule of air and oven drying has been followed to get the final product. The product obtained from the present invention possess lower bulk density (0.72 - 0.75 gm/cc), higher apparent porosity (58-60%) and a workable crushing strength ( 15-25 Kg/cm2) which are the prime requirement of using as a heat insulating material. The developed rice husk ash nodule product can be directly used in pre-fired state over molten metal in iron and steel industries for insulating purpose.

Full Text

The present invention relates to a process for the production of rice husk ash nodules useful as heat insulating material. The present invention is useful for producing rice husk ash nodules for application as a heat insulating material over molten metal in iron & steel industries. In the present day method for the production of rice husk ash nodules as heat insulating material comprises : pulverizing rice husk ash below 325 mesh BS Sieve ; blending the pulverized ash with surface active agents such as sodium alginate, sodium salt of carbomethoxy cellulose, sodium hexametaphosphate in the range of 0.1 - 1.0 wt% of pulverized ash and binders such as polyvinyl alcohol, molasses, portland cement, sodium silicate, pptd. CaCO3 in the range of 2 - 20 wt% pulverized ash ; nodulizing ; drying of nodules at 110°C; heating of dried nodules in the range of 800°C - 1300°C. Reference may be made to the work of A.K. Roy & G. Banerjee, Indian Patent application No. 1684/DEL/95. 1995, German Patent No. 19731653, 1997, Japanese Patent No. 9272925, 1997 wherein the nodules are finally heated at a temp, of 800°C -1300°C in order to obtain the final product for use as heat insulating material. The main disadvantages of these processes are : (a) The method requires heat treatment of the nodules in the temperature range of 800tol300°C. (b) Higher capital investment due to the requirement of firing. (c) Higher cost of production. (d) Energy intensive. (e) Decrease in productivity due to extra process steps. (f) Higher rejection possibilities during firing. The main object of the present invention is to provide a process for the production of rice husk ash nodules useful as heat insulating material which obviates the drawbacks as detailed above. Another object of the present invention is to provide a process for producing dried rice husk nodules which can be directly used without heating at high temperature thereby reducing process steps and providing energy efficient process. Yet another object of the present invention is to provide a process yielding higher green strength and facilitate the formation of nodules from rice husk ash which is an agro waste. In the present invention, a process has been developed to manufacture rice husk ash nodules useful as heat insulating material. In the present process, surface active agents and binders have been used to modify the behaviour of green nodules during nodulizing and subsequent improvement in plasticity, workability, wetting and green strength. A schedule of air and oven drying has been followed to get the final product. The product obtained from the present invention possess lower bulk density (0.72 - 0.75 gm/cc), higher apparent porosity (58-60%) and a workable crushing strength ( 15-25 Kg/cm ) which are the prime requirement of using as a heat insulating material. The developed rice husk ash nodule product can be directly used in pre-fired state over molten metal in iron and steel industries for insulating purpose. Accordingly, the present invention provides a process for the production of rice husk ash nodules useful as heat insulating material which comprises : pulverizing rice husk ash below 325 mesh BS Sieve by conventional methods to obtain a pulverized ash, blending the pulverized ash with surface active agents in the range of 0.1 - 1.5 wt% of pulverized ash and binder in the range of 2-15 wt% of pulverized ash, nodulizing by conventional methods, air drying nodules for a period of 24-30 hrs followed by drying at a temperature in the range of 120 - 150°C for a period in the range of 24 - 30 hrs. In an embodiment of the present invention, the silica (SiO2)and unburnt carbon content of rice husk ash may be in the range of 88 - 93 wt% and 2-5 wt% respectively. In another embodiment of the present invention, surface active agents used may be selected from sodium di-hydrogen phosphate, Na or Ca lignosulfonate, polyacrylate, sulfite lye or mixture thereof in the range of 0.1-1.5 wt% of pulverized ash. In yet another embodiment of the present invention, the binders used may be selected from prepared silicate of Na or K from rice husk ash and corresponding hydroxides by conventional methods, colloidal silica, calcium aluminate cement, bentonite or mixture thereof in the range of 2-15 wt% of pulverized ash. The detail of the process steps of the present invention are : (1) pulverizing rice husk ash below 325 meshBS Sieve by known methods to obtain a pulverized ash? (2) blending the pulverized ash with surface active agents in the range of 0.1 - 1.5 wt% of pulverized ash and binder in the range of 2-15 wt% of pulverized ash. (3) nodulizing by known methods, (4) air drying of nodules for a period of 24-30 hrs followed by drying at a temperature in the range of 120 - 150°C for a period in the range of 24-30 hrs. The novelty of the present invention resides in obtaining a heat insulating material from rice husk ash which gives a low density (0.72 - 0.75 gm/cc), high porosity (58-60 %) and workable crushing strength in the range of 15 - 25 Kg/cm after drying and can be directly used without firing. The inventive steps lie in using the specific surface active agents such as sodium di-hydrogen phosphate, Na or Ca lignosulfonate, polyacrylate, sulfite lye or mixture thereof to modify the behaviour of a green nodule during nodulizing & subsequent improvement in plasticity, workability & proper wetting. In the present invention, surface active agents used having a polar structure permits the functional groups to interact with the solid surface for wetting the particles fully by reduction of the free energy in the system through intermixing. Another inventive step lies in using the specific binders such as prepared silicate of Na or K from rice husk ash and corresponding hydroxides by known methods, colloidal silica, calcium aluminate cement, bentonite or mixture thereof to increase the green strength of the nodule product keeping the density and porosity in the desired level. Yet another inventive step is the combined schedule of air drying for 24-30 hours followed by oven drying at a temperature of 120 - 150 °C for 24 - 30 hours. The following examples are given by way of illustration and should not be construed to limit the scope of the present invention. Example - 1 1000 gms of Rice husk ash was pulverized in a pot mill so as to pass through 325 mesh BS Sieve. Then 6 gms aqueous solution of sodium-di-hydrogen phosphate was thoroughly mixed with the pulverized ash. The mixture was then put into nodulizer where 55 gms Na2SiO3 solution was sprayed. Required amount of water was also sprayed till it forms nodules of various sizes ( 2 to 10 mm diameter). Few nodules were also produced in the sizes of around 50 mm diameter in order to determine their crushing strength after cutting into a cube shape. The green nodule products were then allowed for air drying for 30 hrs followed by final drying at 130°C for 25 hrs. The resultant product characteristics were : Bulk density (gm/cc) : 0.72 Percent apparent porosity 60 Crushing Strength (Kg/cm2 15 Example - 2 1000 gm of rice husk ash was pulverized in a pot mill so as to pass through 325 mesh BS sieve. Then 2 gms aqueous solution of sulfite lye & 3 gms aqueous solution of sodium di-hydrogen phosphate were thoroughly mixed with the pulverized ash. The mixture was then put into nodulizer where 50 gms (Na2SiO3 solution was sprayed. Required amount of water was also sprayed till it forms nodules of various sizes ( 2 to 10 mm diameter). Few nodules of 50 mm diameter were also produced in order to determine their crushing strength after cutting into a cube shape. The green nodule products were then allowed for air drying for 24 hrs followed by drying at 120°C for 30 hrs. The resultant product characteristics were : Bulk density (gm/cc) 0.75 Percent apparent porosity : 58 Crushing Strength (Kg/cm2) : 18 Example - 3 1000 gms of rice husk ash was pulverized in a pot mill so as to pass through 325 mesh BS sieve. Then 4 gms aqueous solution of sulfite lye and 3 gms aqueous solution of sodium lignosulfonate were thoroughly mixed with the pulverized ash. The mixture was then put into nodulizer where 50 gms prepared Na or K - silicate, 5 gms bentonite suspension were sprayed. Required amount of water was sprayed till it forms nodules of various sizes ( 2 to 10 mm diameter). Few nodules of 50 mm diameter were also produced in order to determined their crushing strength after cutting into a cube shape. The green nodule products were then allowed for air drying for 30 hrs followed by drying at 140°C for 25 hrs. The resultant product characteristics were : Bulk density (gm/cc) 0.73 Percent apparent porosity 60 Crushing Strength(Kg/cm2) ; 25 The main advantages of the present invention are : 1. The present process produces an insulating material with improved green strength. 2. The present process produces a material that can be directly utilized in prefired state thereby increases the productivity. 3. The present process saves energy. 4. The present process produces the product at lower cost. 5. The present process utilizes an agro waste (rice husk ash) as major raw material thereby reduces environmental pollution. We claim 1. A process for the production of rice husk ash nodules useful as heat insulating material which comprises: pulverizing rice husk ash below 325 mesh BS Sieve by conventional methods to obtain a pulverized ash, blending the pulverized ash with surface active agents such as herein described in the range of 0.1-1.5 wt% of pulverized ash and binder in the range of 2-15 wt% of pulverized ash, nodulizing by conventional methods, air drying nodules as herein described for a period of 24-30 hrs followed by drying characterized in that at a temperature in the range of 120-150°C for a period in the range of 24-30 hrs. 2. A process as claimed in claims 1-2 wherein the surface active agents used are selected from sodium di-hydrogen phosphate, Na or Ca lignosulfonate, polyacrylate, sulfite lye or mixture thereof in the range of 0.1-1.5 wt% of purverized ash. 3. A process as claimed in claims 1-3 wherein the binders used are selected from prepared Na or K-silicate from rice husk ash and corresponding hydroxides by conventional methods, colloidal silica, calcium aluminate cement, bentonite or mixture thereof in the range of 2-15 wt% of pulverized ash. 4. A process for the production of rice husk ash nodules useful as heat insulating material substantially as herein described with reference to the examples.

Documents:

62-del-2002-abstract.pdf

62-del-2002-Claims-(19-11-2010).pdf

62-del-2002-claims.pdf

62-del-2002-Correspondence-Others-(19-11-2010).pdf

62-del-2002-correspondence-others.pdf

62-del-2002-correspondence-po.pdf

62-del-2002-description (complete).pdf

62-del-2002-form-1.pdf

62-DEL-2002-Form-18.pdf

62-del-2002-form-2.pdf

62-del-2002-form-3.pdf