Process for preparing chemically modified bicarbonate salt particles

1. A method for chemically modifying particles of a bicarbonate salt in a co-rotating twin-screw extruder, the method comprising:

feeding the particles into an intake zone of the extruder;

processing the fed particles in a heat-treatment zone of the extruder at a temperature in the range of 200° C. to 350° C. for a residence time in the range 3 to 20 seconds to convert 3% to 40% w/w of the bicarbonate salt present in the fed particles into a carbonate salt, thereby chemically modifying the particles; and

collecting the chemically modified particles from the extruder.

2. The method as claimed in claim 1 , wherein a 5% aqueous solution of the collected particles has pH in the range of 8.6 to 9.6.

3. The method as claimed in claim 1 , wherein at a constant temperature selected from the range of 200° C. to 350° C., the method provides the chemically modified particles having uniform pH such that, a relative standard deviation of the pH values of 5% aqueous solutions of equal aliquots of the particles collected from the extruder at regular time intervals is less than 1%.

4. The method as claimed in claim 1 , wherein the collected particles has water activity in the range of 0.05-0.3 a w .

5. The method as claimed in claim 1 , wherein the bicarbonate salt is selected from the group consisting of sodium bicarbonate and potassium bicarbonate.

6. The method as claimed in claim 1 , wherein the method provides conversion of 10% to 40% w/w of the bicarbonate salt into the carbonate salt.

7. The method as claimed in claim 1 , wherein the method provides conversion of 15% to 30% w/w of the bicarbonate salt into the carbonate salt.

8. The method as claimed in claim 1 , wherein the particles of bicarbonate salt are fed into the intake zone at a feed rate in the range of 100 g/min to 700 g/min.

9. A method for controlling an amount of carbonate salt formed during chemical modification of bicarbonate salt particles, the method comprising:

feeding the particles of bicarbonate salt into an intake zone of a co-rotating twin-screw extruder;

processing the fed particles in a heat-treatment zone of the extruder for a residence time in the range 3 to 20 seconds to convert 3% to 40% w/w of the bicarbonate salt present in the fed particles into a carbonate salt, thereby chemically modifying the particles; and

collecting the chemically modified particles from the extruder;

wherein the amount of the bicarbonate salt converted into the carbonate salt is controlled by varying temperature of the heat-treatment zone in the range of 200° C. to 350° C.

10. The method as claimed in claim 9 , wherein 11-14% w/w of the bicarbonate salt is converted into the carbonate salt by maintaining the temperature of the heat-treatment zone at 200° C.

11. The method as claimed in claim 9 , wherein 15-19% w/w of the bicarbonate salt is converted into the carbonate salt by maintaining the temperature of the heat-treatment zone at 225° C.

12. The method as claimed in claim 9 , wherein 26-29% w/w of the bicarbonate salt is converted into the carbonate salt by maintaining the temperature of the heat-treatment zone at 275° C.

13. The method as claimed in claim 9 , wherein 35-39% w/w of the bicarbonate salt is converted into the carbonate salt by maintaining the temperature of the heat-treatment zone at 300° C.