(21d) Boost Octane of Light Naphtha Isomerization Units Using Dual Dividing Wall Column Technology

Advancements in distillation can play a key role in minimizing costs of new and revamp projects in a refinery. Dividing wall column technology which had limited acceptance 20 years back is now enhancing our distillation processes. This technology offers varied options when it come to number of cuts that can be taken out from the column by the use of single or multiple walls.

Dual dividing wall columns have multiple walls in a single column shell. These columns have the potential to influence the profitability of most commonly used units in the refinery. One such example of dual DWC application would be a light naphtha isomerization unit. Dual DWC Technology offers the following benefits in an isomerization process:

Boost Octane using existing columns:

DWC’s can boost the octane of isomerization units by 2-4 points. The isomerization process converts low octane straight chain hydrocarbons to high octane branched chain isomers. Since the isomerization reactions are in equilibrium, the product octane is defined by the number of separation units in the process.

A typical light naphtha isomerization unit with a deisohexanizer (DIH) column can produce an isomerate product of RON 87-88. For further increase in RON additional deisopentanizer (DIP) and depentanizer (DP) columns are required. Dividing wall column retrofits in the existing DIH column and provides it with an additional functionality of a DIP or a DP column.

Increase octane barrel and produce C6 products:

Deisohexanizer column (DIH column) separates light and heavy isomerate along with a side cut recycle stream to the isomerization reactor. The DIH column revamp to DWC produces an additional 4th cut of C6 products (Food Grade Hexane/ Polymer grade hexane/ Isohexane / Special boiling point solvents). This revamp not only increases the profitability of Isom unit, but also increases the capacity of Isom unit by more than 20%.