Online Cleaning technology applied to a major European refinery (ERTC)
A major European refinery processing a variety of light, heavy and opportunity crudes, along with slop and gasoline condensate, faced high delta P on their CDU pre-flash tower in excess of 0.35 kg/cm2, while the normal operating delta P was 0.15 kg/cm2. The high delta P prevented the entire crude distillation unit being run at its maximum throughput.
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In particular, the light straight-run naphtha product was coloured and off-spec, so the CDU had to run at a significantly lower capacity or accept non-optimised process conditions, with related losses.
In addition, the delta P was variable and sensitive to both crude quality and flow rate, which forced the refinery to make continuous operating condition adjustments.
Typical mechanical cleaning would have forced the refinery to shut down the CDU for about two weeks, with a severe impact on refinery production and consequent financial losses, not to mention the mechanical cleaning costs and the associated safety and environmental concerns. Instead, they decided to ask ITW to repeat the pre-flash tower Online Cleaning (OLC) method they had successfully performed two years earlier.
ITW’s OLC technology is able to clean an entire production unit or any equipment with the use of patented cleaning methods and chemicals, together with a proprietary monitoring system. The technology is capable of dissolving and stabilising any precipitated asphaltene or coke-like deposits on a closed loop basis in less than 24 hours. The deposits are turned into a stable liquid, which can be fully reused and reprocessed.
The ITW patented chemical was injected into the bottom of the pre-flash tower through a temporary line, and circulated together with a refinery stock used as a carrier on a closed loop basis. In about 24 hours, the OLC cleaning procedure was complete and the unit resumed production straight away. Within about one day, the unit was at its maximum capacity, with all products on-spec and the pre-flash tower delta P back to its normal level of 0.15 kg/cm2. In addition, the achieved delta P was very stable and operating conditions were running smoothly.
The entire OLC procedure was completed without opening any of the equipment involved in the cleaning process, and without any waste generation since all of the washing fluids were fully reprocessed. Based on data collected during the monitoring period, it was estimated that a total of 14 tons of coke-like material was removed during the OLC process.
The refinery is now considering ITW’s OLC technology as an operational excellence tool to postpone or completely avoid any major mechanical cleaning, and maintain the unit at its maximum performance, maximising profitability.
This short article originally appeared in the 2017 ERTC Newspaper, produced by PTQ / DigitalRefining.
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