Alternative additives to enhance slurry dewatering
The invention provides methods and compositions for improving dewatering of Bayer Process alumina trihydrate slurry. The method comprises adding an R-Succinic Compound (such as octadecenyl succinic acid, hexadecenyl succinic acid, and/or dodecenyl succinic acid) to the slurry. The R-Succinic Compound removes water that would otherwise be trapped within the filtered slurry cake and therefore reduces the energy needed to calcine the resulting solids.
1. A method comprising:
adding a wash fluid to an alumina trihydrate bearing slurry comprising alumina trihydrate and caustic-soluble aluminate liquor;
adding to the alumina trihydrate bearing slurry or to the wash fluid a composition comprising at least one R-succinic compound having a structure selected from formula (I) or formula (II), a conjugate acid-base of the R-succinic compound having a structure selected from formula (I) or formula (II), and combinations thereof; wherein formula (I) is
and formula (II) is
and
wherein R and R′ are independent, distinct, and represent alkyl, alkenyl, or aromatic hydrocarbon groups containing 1-30 carbon atoms.
2. The method of claim 1 , wherein the R-succinic compound is selected from octadecenyl succinic acid, hexadecenyl succinic acid, dodecenyl succinic acid, or any combination thereof.
3. The method of claim 1 wherein the composition further comprises a base.
4. The method of claim 1 , further comprising in order:
preparing an aqueous slurry of pulverized bauxite ore and caustic solution;
digesting, comprising extracting alumina from the bauxite ore as a caustic-soluble aluminate liquor;
clarifying, comprising removing solid particles from the liquor;
precipitating, comprising forming the alumina trihydrate bearing slurry from the liquor, and
classifying, comprising separating alumina trihydrate seeds from the liquor.
5. The method of claim 1 , further comprising:
removing liquor and water from the alumina trihydrate bearing slurry to give alumina trihydrate.
6. The method of claim 5 , further comprising calcining the alumina trihydrate.
7. The method of claim 1 , wherein the R-succinic compound forms in situ within the alumina trihydrate bearing slurry or the wash fluid by opening the ring of an R-succinic anhydride compound.
8. The method of claim 7 in which the R-succinic compound forms from an anhydride added to the alumina trihydrate bearing slurry or the wash fluid.
9. The method of claim 1 , wherein the wash fluid comprises water.
10. The method of claim 1 , wherein the wash fluid consists essentially of water.
11. The method of claim 1 , wherein the composition is added to the slurry alongside the wash fluid, before the wash fluid, after the wash fluid, or combinations thereof.
12. The method of claim 1 , wherein the composition is added to the wash fluid.
13. The method of claim 5 , wherein the removing liquor and water from the alumina trihydrate bearing slurry comprises filtration.
14. The method of claim 5 , wherein the wash fluid is added to the slurry before the removing, during the removing, after the removing, or combinations thereof.
15. The method of claim 5 , wherein the removing liquor and water from the alumina trihydrate bearing slurry comprises gravity separation, pressure separation, vacuum separation, or combinations thereof.