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Molecular Sieve of the Liquid feed Drier of Isomerization Plant was removed for inspection and it was observed that Molecular sieve is blackish in colour.
Is is possible to ascertain the remaining life of Molecular sieve ?
How do we know that pores are not choked or damaged?
 
Answers
03/08/2014 A: Virendra Kapoor, Petroleum Refining Consultants, vkkapoor9@yahoo.com
Light naphtha is a very clean stock and should not contaminate the sieve. Do you get the feed to Isom directly from the splitter / NHDT or it comes from the tank occasionally. If so, the contaminant material from the tank is causing trouble. For molecular sieve degradation in a dehydration unit, I suggest you to refer to an article on Dehydration unit, namely Use analytical tools to investigate LNG molecular sieve underperformance by N. Herald; Shell Global Solutions International.
30/07/2014 A: Lindsay McRae, Pall Corporation, Lindsay_McRae@pall.com
Best way to know mole sieve condition is to monitor the effluent quality and also monitor the frequency between regeneration required to maintain the feed moisture spec. For fouling due to particulate, monitor the pressure drop. As the cycle time between regeneration gets shorter to maintain feed spec then you know to schedule a changeout soon.
The black colour maybe due to heavy hydrocarbons or possibly corrosion products ( black power). If drier bed is being fouled by heavy hydrocarbons or corrosion products ( black power) then a feed filter and/or a feed liquid liquid coalescer can remove free water down to <15 ppmv and also remove the black power to extend mol sieve life and prevent too frequent regeneration and dp build up which can shorten the mole sieve life expectancy.