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The following items relate to chemical treatment.
Please be advised that the items are not peer-reviewed, and opinions and suggestions are entirely those of the inquirers and respondents. NACE International does not guarantee the accuracy of the technical solutions discussed. MP welcomes additional responses to these items. They may be edited for clarity.
Preparing for sphere shutdown
Q We are trying to prepare for a Horton sphere shutdown storig ammonium hydroSulfide [(NH^sub 4^)SH]. This sphere is coated internally with pyrophoric iron sulfide (FeS) scale, which has developed over 30 years of operation and has never been inspected or disturbed. We expect hydrogen sulfide (H^sub 2^S) to be present during shutdown also.
Does anyone have any experience with use of chemicals that are designed to neutralize and mitigate the effects of pyrophoric iron sulfides and H^sub 2^S during shutdown or operation? Please share any experience or guidelines on safely removing pyrophoric iron sulfides. VVe are limited to the amount of water flushing we can conduct due to dump pond capacity coupled with downstream processes unwilling to accept diluted water in the process circuit. So, we are looking at all options currently to find the best strategy.
A Wash down with 4% potassium permanganate (KMnO^sub 4^) solution, wash and circulate it for 12 to 24 h before opening the vessel. This will neutralize pyrophoric iron sulfide scale. This is safer than acidizing and quicker than a water sock. When the effluent runs purple instead of brown, the wash is complete.
Antifouling system
Q Can anyone recommend an antifouling system for the traveling screens of a power plant seawater intake basin?
A A number of years ago, I was involved in projects using 90/10 copper-nickel alloy (UNS C70600) for a variety of marine applications where the alloy's ability to resist marine biofouling was used to our advantage. Applications included various types of aquaculture screens such as salmon cages, oyster grow-out trays, pump intake screens, fish diversion screens for power plants, and splash zone sheathing. These projects were technically successful but the economics of some of the applications, at that time,...