Naphtha Splitter Series Revamped to a Single Dividing Wall Column
A series of conventional naphtha splitters converted to one thermally-coupled DWC Prime — lifting capacity 40%+ and sharpening cuts to debottleneck the downstream Isomerization and CCR units, all within the existing columns.
The challenge
At a major refinery in Mumbai, India, the naphtha splitting section — which prepares feed for the Continuous Catalytic Reforming (CCR) and Isomerization units — ran as a series of conventional splitter columns and had become a capacity bottleneck in the gasoline block. The refinery needed to lift processing capacity by more than 40% while still meeting tight product specifications (benzene, C6 naphthenes, C7+ and D86 cut points).
The conventional answer — two new columns in parallel — was ruled out on two counts: no plot space was available, and the CAPEX was high (~US$15 million). The revamp also had to fit a tight envelope: no new columns, no change to the existing column shells (height or diameter), no change to the fired-heater reboilers or existing condensers, and all new internals installed within a roughly 20-day turnaround.
The solution: a single thermally-coupled DWC
DWC Innovations converted the series of naphtha splitters into a single thermally-coupled Dividing Wall Column (DWC Prime) — reusing the existing column shells, fitted with high-capacity structured packing and a side cut to deliver the required top, middle and bottom cuts. The dividing wall performs the multi-cut separation inside one shell, unlocking capacity without new columns, new plot space, or changes to the reboilers and condensers.
DWCI’s scope included the basic engineering package (BEP) and the supply of its proprietary column internals, installed within the plant’s turnaround window.
Sharper cuts debottleneck the downstream units
The biggest win went beyond the splitter itself. By producing sharper, on-spec cuts, the DWC improved the feed quality to the units it serves — a cleaner C6 cut to the Isomerization unit (lower benzene, C6-naphthene and C7+ carry-over) and a better-quality bottoms to the CCR unit. Higher-quality feed lets those downstream units run harder and more efficiently, so the revamp debottlenecks the Isomerization and CCR units as well — the capacity and margin gains flow right through the naphtha and gasoline block, not just the splitter.
The results
| Metric | Conventional expansion | DWC Prime retrofit |
|---|---|---|
| Configuration | Series of naphtha splitter columns | Single thermally-coupled DWC |
| Processing capacity | Baseline | +40% (to ~6,000 MTPD) |
| Product cut quality | At spec limits | Sharper — debottlenecks ISOM & CCR |
| Revamp CAPEX | ~$15M (new parallel columns) | ~$3M |
| New columns / plot space | Two new columns required | None — within existing shells |
| Reboilers & condensers | — | Unchanged |
The retrofit lifted processing capacity by more than 40% (to ~6,000 MTPD) while meeting all product specifications and improving feed quality to both the Isomerization and CCR units — boosting throughput and revenue across the block. It did so for a revamp CAPEX of about US$3 million — roughly one-fifth of the ~US$15 million a conventional two-column expansion would have cost — with no additional plot space and no changes to the existing reboilers or condensers.
Why it matters
This revamp shows a dividing wall column can unlock major capacity and sharpen product quality inside a refinery’s existing equipment and a tight shutdown window — turning a plot-space- and CAPEX-constrained bottleneck into a fast, low-cost debottleneck that lifts the whole naphtha block. Where a grassroots expansion was impractical, a DWC Prime retrofit delivered the capacity, the specs and the downstream relief at a fraction of the cost.
