Title of Invention

A PROCESS FOR MANUFACTURING STRONTIUM CARBONATE OF ABOVE 99% PURITY

Abstract

57)Abstract:- This invention relates to a process for preparing strontium carbonate of purity above 99%. Strontium containing ores are admixed with lignite after benefication and heated to reduce sulphates to sulphides. Soluble strontium sulphide is leached with hot water to which sodium carbonate is added to precipitate insoluble strontium carbonate which is washed to remove contaminants and then dried. PRICE: THIRTY RUPEES.

Full Text

This invention relates to a process for manufacturing _ Strontium carbonate of above 99% purity. Strontium occurs in nature as celestite and celestine in the form of strontium sulphate. These ores are found in association with gypsum and rock salt. Strontium carbonate is one of the most important strontium compounds which finds many use in industry. For instance strontium carbonate of high purity is required for manufacturing ceramics, electro magnets, colour television picture tubes, and bulbs. Strontium carbonate of a purity above 99% is —- required by most of the above mentioned industries. At present considerable quantity of strontium carbonate of high purity is imported from Germany to meet the demands of the industry . Rapid growth of industries in the field of electronics and communication has increased the demands for high purity strontium carbonate. Hence one object of this invention is to produce strontium carbonate of a purity above 9936 to meet the growing demand for it. In the hitherto known process, powdered are of strontium is boiled with soda Ash solution to convert strontium sulphate con¬tained therein to strontium carbonate. The sulphate ions form sodium sulphate which is water soluble. Strontium carbonate formed is washed repeatedly with hot water till it is free of sodium sulphate. The mass is then dried and powdered. It is possible to obtain strontium carbonate of purity less than 90% by this method. Impurities like calcium, Barium and iron present in the ore also get converted into insoluble carbonates during soda ash treatment* These carbonates as well as silica which is invariably praaaat in tha ore are not leach ad out by hot water tmetment and remain in the strontium carbonate produced as contaminant*. Xhus tne product obtained by the know process is not suitable for industrial application without further processing and purification. We have successfully developed the process according to this in* vention for manufacturing strontium carbonate of high purity that satisfies the demands of various industries from naturally occuring ores* Strontium containing ores are subjected to initial metallur¬gical processing such as crushing, grinding, sizing and separation of waste and value. The ore thus beneficate ted is mixed with lignite In the range of 350 Kgs to 450 Kga per tonne of powdered ore and tha mixture la heated in a rotary Kiln, the temperature In the Kiln is preferably maintained in the range of 1050°C to 1150 °C and the heating maybe carried out using hot furamec oil and air mixture* The reduced ore is called black ash and la leached with hot water* Before leaching the reduced ore maybe powdered in ball mills and the leaching step maybe carried out In leaching tanks The temperature of the water used is preferably In the range of 80 C to 90°C The slurry la filtered while It la still hot to separate clear hot strontium sulphide solution from the insolubles. Soda Ash (Na2CO3) is added to the leach In stoichiometric ratios to pracipiate strontium carbonate therefrom which la then separated ay filtration. The filtered mass is washed with h t water repea¬tedly till free of any contaminants, dried at 140°C and powdered to the required else. By this process, strontlun carbonate of a purity above 99% is obtained which satisfies the desands of the end users* Impurities like calcium and Iron are reduced to their respective sulphides during the reduction steps end allies content of the ere remains unchanged. Calciua sulphide, Iron sulphide sad ell ice are Insoluble in water and foras a sludge during hot water leeching and water soluble strontium sulphide is leached out* Sodium sulphide which is foraed in the reaction maybe recovered froa the filtrate as a by product* Another advantage of this process is that eervironaentsl pollution is such less coapered to the conventional process as the sludge or the slurry is easy to dispose off* Jfce steps of the new process is scheaatieally represented here* in below .1 of above 99% purity The process for manufacturing —strontium carbonate/ac¬ cording to this invention comprises admixing beneficated strontium ore with lignite, heating the said mixture to reduce the sulphates contained therein to sulphides, leaching the reduced mass with hot water to extract soluble strontium sulphide therefrom and to separate insolubles as sludge, adding sodium carbonate to the hot water leach to precipitate strontium carbonate and separating the said strontium carbonate therefrom which is washed and dried. Various alterations and obvious equivalents known to persons skilled in the art are within the scope and ambit of this invention. WE CLAIM : of above 99%purity 1 A process for manufacturing' strontium carbonate /com¬prising admixing beneficated strontium ore with lignite, heating the said mixture to reduce the sulphates contained therein to sulphides, leaching the reduced mass with hot water to extract soluble sulphides therefrom, and to se¬parate insolubles as sludge, adding sodium carbonate to the hot water leach to precipitate strontium carbonate, and separating the said strontium carbonate therefrom which is washed and dried. 2 The process as claimed in Claim 1 wherein the strontium ore lignite mixture is in the range of 350 Kga to 450 Kgs of lignite to 1 tonne of the said ore. 3 The process as claimed in Claims 1 and 2 wherein the reduction of the ore is carried out in a rotary Kiln at a temperature range of 1050°C to 1150°C. 4 The process as claimed in Claims 1 to 3 wherein the reduced mass is powdered in ball mills and is then leached. 5 The process as claimed in any of the above claims wherein the leaching is carried out in leaching tanks with water in the temperature range of 80°C to 90°C. 6 The process as claimed in Claim 5 wherein the sludge is t removed by filtration. 7. The process as claimed in Claims 1, 5 and 6 wherein sodium carbonate is added to the filtrate in stoichiometric proportion and the precipitated strontium carbonate is separated by filtration. 8 The process as claimed in any of the above claims wherein the precipitated strontium carbonate is washed with water and dried at a temperature of 140°C which is subsequently powdered. of above 99'- purity 9 A process for manufacturing strontium carbonate/sub¬ stantially as herein described.

Documents:

1393-mas-1996 abstract.pdf

1393-mas-1996 claims.pdf

1393-mas-1996 correspondence-others.pdf

1393-mas-1996 correspondence-po.pdf

1393-mas-1996 description (complete).pdf

1393-mas-1996 form-1.pdf

1393-mas-1996 form-26.pdf