35 barg superheated Steam is generated from a waste heat boiler used for heat recovery of reformed gas. Since past few weeks, the silica content in steam remains to the levels of 0.05 to 0.08 ppm (ideally it should be <0.02 ppm. The reason for such rise in silica concentration is not know yet.
The Silica level in Boiler feed water is also in the same range (0.05 to 0.08 ppm) as that in steam. The boiler feed water is a mixture of fresh DM water and recovered condensate from steam used in reforming process. The silica content in DM water is <0.02 ppm. The recovered condensate (from the steam used in reformer process) contains silica <0.02 ppm.
The levels of silica in steam drum continuous blow down water is in the range of 0.4 to 0.8 ppm. Other parameters of BFW and steam quality are in normal range.
Our worry is the increased content of silica in superheated steam. Even when all the parameters are maintained adequately to avoid silica carryover, what could be other reasons for such increase in silica content?