Letter 20038

Silica contamination of condensate water

+++

Help,

We here at Kelvin Power Station have a problem that arises periodically. The steam/condensate system develops a high silica concentrate, causing plant shutdown to clear the system. We use a Demineralisation Plant to produce the make up water.

Anton Gouws
- Kempton Park, Gauteng, South Africa

Hi Anton,

We had a similar problem at an aluminium anodising plant in central Johannesburg this time last year. The silica content in their sealing bath kept going too high and led to major quality problems. On investigation it would seem that the municipal water supply is supplemented with borehole water during the dry summer months and this leads to abnormally high silica concentrations that were defeating the standard DI water plant. The suppliers of the DI plant were able to make some modifications to their equipment and this led to a reduction in the silica levels in the process water.

Good Luck !

Andrew Farrow
- Midrand, Gauteng, South Africa

Hello Anton,

I have the similar problem as Andrew for our brightening and anodizing of the aluminium. It's 8 years ago, we changed our sealing bath each day due to the silica concentration in demi. water. We had a classic demi water plant with 2 columns cationic and anionic. It was a strong cationic and strong anionic. We have simply modified the configuration of the plant just by addition of one anionic column more. For this time, we use : 1 strong cationic column, the first anionic is normal anionic resin and the second anionic is strong anionic resin. The limit for the demi.water quality is detected at the exhaust of the first anionic column. If the conductivity reach 15µS/cm, the regeneration start and the 3 columns are regenerated. So, the second and strong anionic column is never saturated (always good electric polarized) and in any case, it can retain the low electrical polarized particles as silica. From this time, with a free silica demi.water, I can run more than 1 month with the same bath. (30 m3). It's my experience and the solution for my silica problem.

Good Luck,

Paul Moreau
aluminum reflectors for lighting - Liège, Belgium

+++ I have seen electrocoagulation reduce silica (silicon compounds) 95% in raw sugar cane juice. It would probably work on your water if done BEFORE ion exchange. The conductivity of distilled water is too low for the process. The downside is that you would need to add both EC reaction and solids separation equipment ahead of your DI. Paul Morkovsky - Shiner, Texas, USA +++ Hi Anton, Andrew and the two Pauls ! Please have a look at letter # 21077 (removing lead from waste water) I don't know if this approach or thought pattern can be helpful ... but if it is, please acknowledge. As Paul Morkovsky pointed out, you get solids. Therefore it should work. However, in the Assay field, silicates were supposedly DISSOLVED using HF and Perchloric ... but even so, solids DID occur. Food for thought, anyhow. Freeman Newton - White Rock, B.C. Canada