Treatment of OTSG blowdown
A method and system generate steam for SAGD operation wherein steam generator blowdown water is acidified, cooled and clarified before reuse. Acid Clarification Treatment, or “ACT”, mitigates organic fouling in Once-Through Stream Generators. Lab tests quantitatively and qualitatively show that ACT reduces Total organic carbon (TOC) and ‘bad actors’ TOC, respectively, in blowdown streams.
1. A method of treating once through steam generator (OTSG) blowdown water for reuse, said method comprising:
a) providing OTSG blowdown water having acid insoluble organics therein;
b) acidifying said OTSG blowdown water to pH 8 or lower;
c) cooling said OTSG blowdown water to 30-40° C.;
d) settling precipitants out of said OTSG blowdown water for at least 12 hours to produce an acid clarified blowdown water having more than 50% of the acid insoluble organics removed; and
e) reusing said acid clarified blowdown water.
2. The method of claim 1 , wherein the cooling step c) occurs at least partially before the acidifying step b).
3. The method of claim 1 , wherein the settling step d) occurs in a sludge pond.
4. The method of claim 1 , wherein the settling step d) occurs in a clarifier tank.
5. The method of claim 1 , wherein the reusing step e) comprises use as feedwater in a steam generator.
6. The method of claim 1 , wherein the reusing step e) comprises blending with clean feedwater and use as feedwater in a steam generator.
7. The method of claim 1 , wherein reusing step e) comprises blending with clean feedwater and use as feedwater in an OTSG.
8. The method of claim 1 , further comprising a softening step f) to remove calcium, magnesium and silica.
9. The method of claim 1 , further comprising a softening step f) in a warm lime softener to remove calcium, magnesium and silica.
10. The method of claim 5 , further comprising a softening step f) in a warm lime softener to remove calcium, magnesium and silica.
11. The method of claim 7 , further comprising a softening step f) in a warm lime softener to remove calcium, magnesium and silica.
12. The method of claim 1 , further comprising a step d-1) adjusting pH of said acid clarified blowdown water to pH 8 or lower.
13. An improved method of producing steam for oil production, the method comprising heating feedwater in a steam generator to generate steam for downhole use and blowdown water to reuse in said steam generator, the improvement comprising acidifying, cooling to 25-45° C. and passively clarifying said blowdown water by settling to produce an acid clarified water having about 50% of total organic carbon removed, before reuse of said acid clarified water in said steam generator.