No.5 CASESTUDY
Desalters TESTIMONIAL " This is a much better process and is the way forward for future TAR's " Crude Unit Area Specialist
GRANGEMOUTH REFINERY
DECON SOLUTION Denholm recommended a Boil Out procedure using Zyme-Flow® UN657 at 1.5% and Rezyd-X® Z67 at 0.5%. Duration of the process was 12 hours and after 6 hours a reduced Vapour Phase was implemented across the vapour space of the vessels to drive any light end hydrocarbons and H2S to the flare. Once the test results indicated that contaminant levels were acceptable, the desalters were isolated from the flare and vented to atmosphere. On completion of the boil out the desalters were allowed to cool to 60c. Free oil was drawn off to the slops system and the aqueous phase was pumped out into a temporary tank for subsequent disposal. RESULTS Each desalter decontamination was completed within a 24-hour timeframe, including rigging, heat up and processing. On completion of the decontamination, LEL and H2S were zero. Residual solids volume remaining was significantly lower than in previous TAR's and residual solids were essentially oil free and conditioned such that their removal was greatly facilitated. Significant time savings were achieved over previous cleans. The minimal equipment footprint for the decontamination enabled other work to continue unrestricted by the process. CLIENT COMMENTS The client was pleased that the desalter decontamination was completed in a much reduced time frame compared to previous TAR's and also that the results were much better. The residual solids were less than on previous occasions and essentially oil free making their removal and disposal a much quicker operation. Effluent volumes were massively reduced and the aqueous effluent was suitable for discharge to site effluent treatment plant.
OVERVIEW This case study is for the decontamination of 3 off Desalters during the Crude Unit 2019 TAR at a UK oil refinery. The full scope of work also included Crude units 1&2, Hydrotreater unit, Hydrocracker unit Vacuum unit and the Treatments and Sulphur units. CHALLENGES The refinery TAR team were striving to reduce the overall TAR duration and the desalter cleaning was a major factor as, in previous TAR's, this process took a week or more to complete and previous results were only average. The challenge was to improve upon the decontamination performance whilst reducing the duration of the decontamination process and minimising the equipment and manpower footprint. PAST PROCEDURE Previously, decontamination had been by circulation of a hot (80C) aqueous chemical solution for 24 hours. This required the temporary installation of some significant equipment such as circulation pumps, heat exchangers and several temporary storage tanks of 70m3 capacity, all of which was connected using 6" hard piping. Rigging/de-rigging, heat up, circulation and draining result in a duration of several days to complete the decontamination. The large equipment footprint meant that other operations in the vicinity of the desalters were impeded thus impacting adversely on the overall TAR duration. Overall quality of the clean was variable and not completely successful.
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