World’s First Commercial Dual Dividing Wall Column

The challenge

BPCL’s Mumbai refinery was revamping its Lube Oil Base Stock (LOBS) unit and needed a dearomatized-solvent (DAS) splitter able to produce several distinct solvent grades to tight specifications. The conventional route — a sequence of three separate distillation columns — carries a heavy penalty in equipment count, plot space, energy, and capital. The refinery also needed real operational flexibility: the ability to swing across a wide range of feed properties and switch product slates as demand changed, all within a compact, energy-efficient design.

The solution: the DAS Splitter Dual Dividing Wall Column

DWC Innovations designed and delivered the DAS Splitter as a grassroots Dual Dividing Wall Column (DDWC) — the world’s first commercial application of a multiple-wall dividing wall column. A single integrated column performs the separation duty of three conventional columns, producing multiple dearomatized-solvent grades to specification. The design was built for flexibility: external liquid-split arrangements and an adjustable vapor split (varied through feed preheat) let the column absorb wide feed fluctuations and switch between a three-cut and a four-cut product mode. It runs under vacuum with margin engineered into both the hydraulics and the vacuum system, and it is heat-integrated — a pump-around on the lower mid-product serves as the reboiler for the upper mid-cut — for high energy efficiency. In commissioning, the column handled feed above its design rate while meeting product specifications.

What the revamp delivers

One flexible column now does the work of three, cutting equipment count by roughly half along with the associated plot space, and reducing both capital and operating expenditure by approximately 20–50%. The heat-integrated design keeps energy consumption low — supporting the refinery’s net-zero emissions goals — and the built-in operational flexibility lets BPCL move across feed and product scenarios without new equipment. The result is a compact, efficient solvent-production train delivered in a single tower.

Why it matters

As the world’s first commercial multiple-wall dividing wall column, the DAS Splitter proves that Dual DWC technology can re-architect an entire multi-grade separation train — not just a single split — into one flexible, energy-integrated column. For producers of solvents, lube base stocks, and specialty cuts, it shows that several product grades can be made in one tower, with about half the equipment and materially lower capital and operating cost.

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