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Question

  • In a coker with more than one module, for example two, when they have to lower the power supply, do they take one module out of service or do they lower the load on both modules? What would this decision depend on?

    Nov-2021

Answers


  • Jake Gotham, InSite Technical Services, jake.gotham@insitetechnical.com

    Power consumption will be mostly in pumps, blowers and compressors.  The power curve for a centrifugal pump is typically quite flat.  Reducing to 50% throughput on two modules might only save 20% of the power required for pumps, whereas shutting down one module would save half.  It will be a similar story for blowers providing air to furnaces.  The offgas compressor might be shared between the modules, in which case the power saving will be the same regardless of whether you half the capacity of each module or shut one module down.  If each module has its own compressor, the power saving will depend on the compressor type and capacity control mechanism (spillback vs speed control vs variable valve unloading etc).

    In summary, at steady state you will save more power by shutting one module down.  Whether this is the optimum solution will depend on multiple other factors including the duration of the outage.  Whereas you can cut capacity on both modules quite quickly and realise some power savings, to shut one module down in a controlled manner will take a few shifts before pumps, blowers and compressors can be stopped.  Hence for a short slowdown you’ll save more power overall by keeping both modules on-line at low capacity, whereas for a longer slowdown you’ll probably save more energy by shutting one module down.

    Jan-2022