Filtration Challenges in Ethylene Process (Cold Section)

In the purification (cold) section, gases are dried and refrigerated via cold boxes in ethylene plant to separate the various products (methane/hydrogen, ethylene, propylene, butadiene) by fractionation (distillation). 

Below, we’ve listed challenges in the cold section and where our filtration and separation solutions can help. 

• Molecular Sieve Protection: This process involves removing liquid from the feed gas.  By protecting this unit against liquid, the results are less regeneration (rapid ageing prevention) and longer lifetime. Pall’s SepraSol™ L/G Coalescers will help in this application to remove hydrocarbon from the gas phase. 

• Cold Box Protection: Consisting of a series of cryogenic heat exchangers, cold refrigerant is evaporated and cools incoming cracked gas before fractionation. This is highly energy intensive as the entire operation is done at very low temperatures. Product gas from cold box is sent to demethanizer tower(s) where methane/hydrogen are removed. 

Fine micron solid particles can be released from the upstream molecular sieve driers due to abrasion of the beads or to the degradation of the beads if liquid ingression takes place in the driers. This results in fouling of cryogenic heat exchangers and increase in delta P. 

Fine micron solid particles coming from the attrition of the dryer can limit the capacity and productivity of the cold box.  Pall’s Epocel ® filter is just one solution that can help in this application in removing these particles. 

• Green Oil Removal: Green Oil is generated by side reactions of hydrogenating acetylene to ethylene and ethane over the Pd catalyst. Steam generation is required to strip away the deposited green oil. The light-end components of the green oil remain in the gas phase; a portion condenses into fine droplets in the gas stream as it cools while leaving the reactor. The green-oil droplets, carried out with the hydrogenated gas from the reactor, deposit. This causes a fouling of downstream heat exchangers, dehydrator beds and ethylene fractionator internals. This can result in expensive unplanned shutdowns which are required to remove the deposited green oil.  To help remove oil from the gas phase, Pall’s Seprasol™ L/G Coalescer is just one solution that will assist in this application. 

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