Utilisation of desalination waste

1. A process for producing soda ash from brine waste, utilizing high pressure filtration and ion exchange for regenerating ammonia from a mother liquor generated during production of the soda ash, the process comprising:

reacting brine waste with carbon dioxide and ammonia to produce a reaction mixture containing sodium bicarbonate and ammonium chloride;

separating the sodium bicarbonate from the reaction mixture to produce a first mother liquor containing ammonium chloride;

converting the sodium bicarbonate separated from the reaction mixture to soda ash;

filtering the first mother liquor at high pressure to produce purified water and a concentrated ammonium chloride solution;

treating the concentrated ammonium chloride solution with a base anion exchange resin for regenerating ammonia suitable for use in reacting the brine waste with carbon dioxide and ammonia; and,

using the ammonia regenerated from the concentrated ammonium chloride solution for supplying at least 10% of the ammonia used in reacting the brine waste with carbon dioxide and ammonia to produce the reaction mixture.

2. A process according to claim 1 , further comprising heating the sodium bicarbonate separated from the reaction mixture to produce soda ash.

3. A process according to claim 1 , wherein 20 to 80% of the ammonia used in the reaction is regenerated ammonia.

4. A process according to claim 1 , further comprising providing a brine waste which has a sodium chloride concentration of greater than about 50 g/L and less than about 250 g/L.

5. A process according to claim 1 , wherein the brine waste is a waste stream from a desalination plant, or is derived from a waste stream from a desalination plant.

6. A process according to claim 1 further comprising obtaining at least a majority of the carbon dioxide used in the reaction from a waste gas from a combustion source.

7. A process according to claim 1 further comprising pre-treating the brine waste to remove at least some of any undesired inorganic cations present in the brine waste prior to the treatment with carbon dioxide and ammonia.

8. A process according to claim 7 , wherein undesired inorganic cations are selected from the group consisting of calcium, magnesium, and strontium ions.

9. A process according to claim 7 further comprising removing the undesired inorganic cations present in the brine waste either partially or entirely by selectively binding those ions with a binding agent.

10. A process according to claim 9 , wherein the binding agent is a cation exchange resin.

11. A process according to claim 5 further comprising heating the sodium bicarbonate separated from the reaction mixture to produce soda ash.

12. A process for producing soda ash, utilizing high pressure filtration and ion exchange for regenerating ammonia from a mother liquor generated during production of the soda ash, the process including the steps of:

a) providing brine waste having a sodium chloride concentration of between about 50 g/L and about 250 g/L;

b) treating the brine waste to remove at least some of any undesired inorganic cations present to provide pre-treated brine waste;

c) reacting the pretreated brine waste with carbon dioxide in the presence of ammonia, at least a portion of which is regenerated ammonia;

d) separating sodium bicarbonate produced during the reaction of the brine waste with carbon dioxide from the reaction mixture to provide collected sodium bicarbonate and a first mother liquor containing ammonium chloride;

e) heating the collected sodium bicarbonate to produce soda ash;

f) filtering the first mother liquor using high pressure membrane filtration to produce purified water and a second mother liquor containing concentrated ammonium chloride;

g) treating the second mother liquor with a base anion exchange resin to regenerate ammonia suitable for use in the reaction of step (c); and,

h) using the ammonia regenerated from the second mother liquor for supplying at least 10% of the ammonia used in the reaction of step (c).

13. A process according to claim 12 , wherein the base anion exchange resin is a weak base anion exchange resin.