Method for recovery of alkali values from trona using two-stage leaching

A method of recovering alkali values from trona ore, the method comprising:

• (a) introducing trona ore in a first aqueous solution to obtain a first feed liquor containing a ratio of sodium bicarbonate to sodium carbonate of less than about 0.8, and undissolved trona ore;
• (b) cooling the first feed liquor, precipitating sodium carbonate decahydrate crystals and collecting the sodium carbonate decahydrate crystals from a resulting first mother liquor;
• (c) heating the first mother liquor and recirculating it as the first aqueous solution in step (a);
• (d) dissolving undissolved trona ore from step (a) in a second aqueous solution to obtain a second feed liquor containing a ratio of sodium bicarbonate to sodium carbonate of more than about 0.8;
• (e) cooling the second feed liquor, precipitating sodium bicarbonate crystals and collecting the sodium bicarbonate crystals from a resulting second mother liquor;
• and
• (f) heating the second mother liquor and recirculating it as the second aqueous solution after recirculating the second mother liquor to step (d).

A method of recovering alkali values from trona ore comprising:

• (a) partially dissolving trona ore in a first aqueous solution substantially saturated with sodium bicarbonate such that there remains undissolved trona ore;
• (b) recovering the undissolved trona ore from the first aqueous solution of step (a);
• (c) dissolving the undissolved trona ore in a second aqueous solution to form a feed liquor;
• (d) carbonating the feed liquor to convert sodium carbonate into sodium bicarbonate;
• (e) cooling the carbonated feed liquor to precipitate sodium bicarbonate and form a mother liquor;
• (f) recovering the sodium bicarbonate crystals from the mother liquor;
• (g) calcining the sodium bicarbonate crystals to form light soda ash and carbon dioxide;
• and
• (h) recycling the carbon dioxide to step (d) as the carbonating medium.