World’s First Dual Dividing Wall Deisohexanizer in an Isomerization Unit
At Chennai Petroleum Corporation Limited’s (CPCL) Manali refinery near Chennai, India, DWC Innovations converted the isomerization unit’s deisohexanizer into a four-cut Dual Dividing Wall Column — adding a new pharma / food-grade hexane product and higher throughput, with no impact on isomerate RON.
The challenge
CPCL wanted to extract more value from its light-naphtha (C5–C6) isomerization unit. A conventional deisohexanizer (DIH) column recycles a C6-rich side stream to protect octane, but it yields no saleable specialty product and leaves little room to raise feed rate. The refinery needed to create a new, high-value hexane product, process additional light-naphtha feed, and do so without eroding the RON of the isomerate — all by revamping existing equipment rather than building a new column.
The solution: a four-cut Dual Dividing Wall Column
DWC Innovations converted the existing deisohexanizer into a four-cut Dual Dividing Wall Column (DDWC) using its Dual DWC Prime technology. A single revamped column now delivers four distinct products — light isomerate, heavy isomerate, a C6 recycle stream, and a new pharma / food-grade hexane cut — where a conventional scheme would need several columns. The design was engineered for flexibility: the column can also run in its original configuration with no hexane drawn, so CPCL can switch its product slate with the market. The project scope also included a grassroots Benzene Saturation Unit (BEN Prime), likewise designed and licensed by DWC Innovations, to meet gasoline benzene limits.
What the revamp delivers
The revamped column adds a new pharma / food-grade hexane product to the unit’s slate while continuing to make on-spec isomerate, and it lifts isomerization throughput by processing additional light-naphtha feed — without modifying the isomerization reactors and with no impact on product RON. Because it reuses the existing column shell instead of adding a new tower, the revamp fits within the plant’s footprint.
Why it matters
This is the world’s first application of Dual Dividing Wall Column technology in an isomerization unit. It shows that a deisohexanizer revamp can do more than protect octane — it can turn a recycle column into a source of high-value specialty product and extra throughput at once, from existing equipment. For refiners running C5/C6 isomerization, a four-cut Dual DWC opens a new margin stream without a grassroots column.
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