Published in Hydrocarbon Processing (February 2021), this DWC Innovations article shows how a light naphtha isomerization unit can earn more margin by producing additional high-value C6 products. In a typical isomerization unit, n-hexane building up in the deisohexanizer (DIH) recycle loop caps how much fresh feed the reactor can process; by drawing that n-hexane off and converting it into marketable food-grade, polymer-grade, pharma-grade and isohexane products, refiners add a new revenue stream and simultaneously debottleneck the unit — freeing capacity for 15–25% more fresh feed with no changes to the reactor. Rather than installing two new columns for this extra product, the article shows how revamping the existing DIH column into a dividing-wall column (DWC) delivers four cuts in a single shell, at half the equipment footprint, 20–50% lower CAPEX/OPEX, and about 30% less energy. A case study of an Asian refinery (39 t/hr feed, isomerate RON 88) puts numbers to it: the DWC revamp lifts net benefit from $14.9 MM/yr to $21.5 MM/yr for a $3.8 MM investment — about a 7-month payback — with isomerate octane unchanged.
>20%More unit capacity
2-12 moRevamp payback
4th cutAdditional C6 products
HPFeb 2021 feature
What the article covers
Highlights
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Revamping the DIH into a DWC Prime column adds a fourth cut of C6 products — food-grade hexane, polymer-grade hexane, isohexane, or special boiling-point solvents
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Enhanced separation efficiency and over 20% more unit capacity
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Improved energy efficiency and product flexibility, using existing infrastructure
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Typical revamp payback of 2 to 12 months, without major capital investment
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The takeaway
Revamping the DIH into a DWC Prime column adds a fourth C6 product cut and over 20% more capacity, with a 2–12 month payback — using existing infrastructure without major capital investment.
