In our Hydrogen Generation Unit HP steam silica level is running high at about 0.1 PPM against design value of 0.045 PPM. We maintain BFW Ph-9.5, excess Phosphate - 3 PPM, Hydrazine excess 0.1 PPM and continuous blow down Gestra valve is 100% open. Conductivity and TDS is normal. How can we reduce silica? There are no BFW exchanger leakages
Answers
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01/11/2014
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Rajesh Nandanwar, Bharat Oman Refineries Limited, Bina, rajesh.nandanwar@borl.co.in
Silica in steam can be due to carry over. You have not provided full details but check for blow down silica,it should be much lesser than 0.8 ppm. Maintain silica level of 0.2 to 0.40 ppm by adjusting blow down. From the description it seems that there is water carry over from steam drum. If downstream superheater is sufficient to superheat this extra water, it may not get noticed via temperature indication. Make close balance of water and steam and you would know the problem area. Water carryover from steam drum is looking the most probable reason for your problem. Maintain steam drum level lower about 50% and see the changes. If boiler drum water separating baffle panels, primary driers (cyclone separators) are dislodge you could see water carryover and thus higher silica in steam.
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19/07/2014
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Hubert Mueller, Bayernoil, guhumueller@web.de
Have a look at your ion exchangers, especially at the strong basic bed.
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