Method for treatment of high pH/silica brines
A method for neutralizing brines that contain high levels of silica accompanied with a high pH. Brine is processed through a reactor in which the pH is lowered and the resultant silica precipitate is adsorbed onto a sacrificial crystal structure. The resultant stream is then processed through a solids removal zone wherein the solids are removed and recovered for reuse. The neutralized solids-free brine is then suitable for down-hole injection in the heavy oil industry or further treatment by common water treatment methods if further adjustment is required for other industries.
1. A process for preparing an effluent stream for down-hole injection from a silica-containing brine, comprising:
Cooling a silica-containing brine below 180° F.;
adding an inert particle to said silica-containing brine, wherein the inert particle is mixed with the silica-containing brine in an amount of at least 2%, by weight, of the total weight of the brine;
reducing the pH of the silica-containing brine to 9 or below;
polymerizing and adsorbing said silica onto the inert particle; and
removing the inert particle and adsorbed silica from the silica-containing brine, thereby creating a solution for down-hole injection.
2. The process of claim 1 , wherein the pH of the silica-containing brine is reduced to below 7.
3. The process of claim 1 , wherein the pH of the silica-containing brine is reduced by addition of concentrated acid.
4. The process of claim 3 , wherein said concentrated acid is selected from the group consisting of sulfuric acid and hydrochloric acid.
5. The process of claim 1 comprising maintaining a reactor vessel a having a seed bed of inert particles of 3-6%, by weight for use during pH reduction and silica polymerization.
6. The process of claim 5 , comprising agitating said reactor vessel sufficiently to maintain the inert seed bed in suspension.
7. The process of claim 5 , comprising recirculating a portion of the reactor vessel contents back to the cooled silica-containing brine.
8. The process of claim 5 , wherein the total time elapsed in the mixing, reducing, and adsorbing steps is about 0.5 hours.
9. The process of claim 1 , wherein said inert particle is selected from the group consisting of gypsum and diatomaceous earth.
10. The process of claim 1 , wherein the silica-containing brine has an initial silica concentration between 500 ppm and 10,000 ppm, and the solution for down-hole injection has a silica concentration below 400 ppm.
11. The process of claim 1 , wherein the pH of the silica-containing brine prior to treatment is between 9 and 13.
12. A process for preparing a solution for down-hole injection from a silica-containing brine, comprising:
mixing a silica-containing brine with an inert particle at a temperature below 180° F., wherein the inert particle is mixed with the silica-containing brine in an amount of at least 2%, by weight, of the total weight of the brine;
reducing the pH of the silica-containing brine to 9 or below;
polymerizing and adsorbing silica onto the inert particle; and
separating adsorbed silica from the silica-containing brine in a first solids separation step, thereby separating said silica-containing brine into a supernatant and first separated solids;
subjecting said supernatant to a second solids separation step, thereby separating said supernatant into second separated solids and a solution for down-hole injection.
13. The process of claim 12 , further comprising subjecting said first separated solids to de-watering wherein a filtrate stream and a final separated solids stream are generated.
14. The process of claim 13 , further comprising recycling said filtrate stream into said silica containing brine.
15. The process of claim 13 , further comprising disposal of said final separated solids to a landfill site.
16. The process of claim 12 , further comprising recycling said second separated solids into said silica-containing brine.