(193b) Four High Purity Products from Dividing Wall Column

Dividing wall columns typically combine two columns into one, produce three cuts and are known to save 20-30% in OPEX and CAPEX.

After operating successful DWCs many refiners are approaching us to develop and install more complex DWC configurations. These configurations can produce four high purity cuts and can replace three columns.

The case study presented in this paper is from the Isomerization process involving Deisohexanizer column. Many Isom units are lined up to produce a C6 cut, which is used as a commercial solvent in this DIH Column. The production of C6 cut comes at an expense of a decrease in overall RON from the gasoline pool. As of now, usage of DWCs is limited to combining of two columns (DIH Column and C6 cut column) to produce three cuts ( Light Isomerate, Heavy Isomerate and C6 Cut). In absence of a recycle stream of low RON components to the Isomerization reactor, there is a significant penalty of RON. The revamped DWC produces four cuts in additional to light and heavy isomerate products, the column produces C6 cut and a stream of low RON components as a recycle to the ISOM reactor. This four cut DWC fits in existing DIH column revamps. This innovative DWC configuration not only provides additional revenue of C6 product but also minimizes any impact of RON in the gasoline pool.

Thermodynamically, the four cut DWC combines the features of a middle and a top dividing wall column to achieve the required separation.