Refinery Columns & Vessels - FCCU, CDU, DHT Treatments & Flare Units
No.6 CASESTUDY
TESTIMONIAL " These were some of the cleanest columns seen after decontamination " Shutdown Manager
GRANGEMOUTH REFINERY
OVERVIEW The project was to decontaminate the columns and vessels on the FCCU, CDU, DHT, Treatments and Flare Units during the client 2016 TAR to make them ready for entry and inspection. CHALLENGES The refinery TAR team were under pressure to meet a challenging planned TAR duration and several of the columns & vessels included in the decontamination were considered critical path items. It was imperative that the decontamination processes were completed efficiently, safely and successfully within the allotted time frame and budgeted cost. PAST PROCEDURE Previous FCCU Tar's utilised a combination of steaming, flushing, liquid circulation and nitrogen purging to remove contaminants prior to opening columns and vessels for entry and inspection. This had proved to be time consuming and difficult to predict the duration of these operations making TAR planning a more difficult tasks. It was therefore decided that, as a result of previous success of the Zyme-Flow® products and processes, the decontamination of the units would be best achieved by implementing these processes during this TAR event.
DECON SOLUTION The most efficient means of achieving decontamination was to treat the production units as systems rather than individual vessels where ever possible and a combination of boil out and Vapour Phase processes were employed to achieve this end. Zyme-Flow® UN657 was used as the decontamination chemical. Actual processing time was a maximum of 12 hours per system/vessel, with possible reduction in processing times as indicated by test results obtained by Denholm process monitoring. RESULTS Despite some delays by the client in releasing plant for decontamination and an issue with steam supply which resulted from the client steam supply line suffering a failure the TAR decontamination was completed on time and within budget. The time lost by the delays mentioned was recovered by being able to reduce the processing time on other systems and by taking a flexible approach to the planned decontamination schedule. Actual decontamination processing times were all within the expected 12-hour period with H2S, LEL and Benzene levels being reduced to acceptable levels and no problems experienced due to pyrophoric iron sulphide. CLIENT COMMENTS Client personnel were extremely pleased by this performance as it had out-performed other previous chemical and physical treatments with had not achieved the same levels of success.
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