Silica removal from water

[Unotec]

During the SAGD operations, steam is injected into a bituminous sandy formation. This steam contains caustic soda to promote flow and preserves the formation integrity, amongst other things. Therefore it is unavoidable.
The blow down water from the boilers end result is something very similar to glass water. Since it will contain some bitumen, salts and other minor contaminants, it needs to be disposed of.
Current regulations do not allow for disposal if it has a pH over 12, therefore an acid addition is required. The result, the silicates precipitate when the pH is lowered.
The disposal is deep well or cavern, the silicates plug them.
Press filtering and reverse osmosis has been tried, but the organic component plugs the filters.
Centrifuging has not proved useful either, and all we have come up with is cry$$$talization.
Has anybody dealt with this type of scenario before?
Oh, PSD is about 0.11 microns

 

[bimr]

Perhaps solar evaporation ponds may work if you are located in the proper climate.

 

[Unotec]

-40ºC winters would make that hard. Good idea, though. Thanks

 

[Unotec]

Well, the centrifuging wizards herefigured out the way to do it. Back to the old spin n floc worked awesome!

 

[shahyar]

As you know, it is very hard to predict silica behaviour in saline waters. Generally we just rely on cartridge filters after neutralization. It is strange, but I have never heard about such problem in SAGD projects in AB.
Also, I do not understand what the meaning of "PSD is about 0.11 microns" is. You mean max diameter or avg.? (Because PSD is a diagram or table, not only ONE number).
By the way, usually particles as big as 1 to 2 microns are ok for disposal wells (if reservoir is sedimentry type).

 

[Unotec]

Thank you Shahyar.
PSD is indeed a table or histogram. The interpretation of "PSD is about 0.11 microns" refers to the median.
Particle sizes of 1-2 microns might indeed be ok for disposal, as you mention, depending on the concentration though.
Unfotunately, due to the high concentration, neither direct disposal or any type of filtering is an option.
The SAGD, per se, does not present the problem, the boiler's blowdown water is the one that has the silicates. It is here where they get concentrated (oh, plus some sand and bitumen in the equation just making a tasty cocktail).
In any case, I think we have solved the problem, the next challenge is implementing it as soon as possible.