Extractive Dividing Wall Column – EDWC Prime
One shell. One reboiler. An extractive dividing wall column that combines the extractive column and the solvent recovery column.
The problem
Two Columns, Two Reboilers, One Hot Solvent Loop
Extractive distillation separates close-boiling and azeotropic mixtures by adding a high-boiling solvent that shifts relative volatility. A conventional unit needs two columns: an extractive column that takes the raffinate overhead, and a solvent recovery column that strips the extract from the solvent.
The solvent is heated, cooled and reheated as it moves between the two. Each transfer adds duty, exchangers, piping and plot space. An extractive dividing wall column does both jobs in one shell.
How it works
Both Steps in a Single Shell
- Extractive sideFeed and solvent enter on one side of the wall. The solvent carries the extract component down; the raffinate leaves overhead on that side.
- Extract sideThe wall runs up to the top head. On the other side, the extract component is rectified and taken overhead as a high-purity product.
- Common bottomA shared stripping section and a single reboiler release the extract from the solvent. Lean solvent leaves the bottom and is recycled, with a small makeup stream to cover losses.
Applications
Where EDWC Prime Fits
- Aromatics recoveryBenzene, toluene and xylenes from reformate or pyrolysis gasoline, with solvents such as sulfolane, NMP or NFM.
- C4 separationButadiene and butene recovery from mixed C4 streams with NMP, DMF or acetonitrile.
- Azeotrope breakingAlcohol–water, THF–water, acetone–methanol and other solvent recovery duties in chemicals and pharma.
- Close-boiling hydrocarbonsSeparations where relative volatility is too low for plain distillation to be economic.
Why it matters
Benefits of EDWC Prime
- Lower energyOne reboiler replaces two. Published extractive-DWC studies report double-digit energy savings against the two-column scheme, depending on the system.
- Lower capexOne shell, fewer exchangers, less piping and a smaller plot.
- Less solvent stressSmaller solvent inventory and shorter hot residence time, which reduces solvent degradation.
- Revamp potentialAn existing extractive or recovery column can be assessed for conversion where its diameter and hydraulics allow.
Proven in the field
A Proven Track Record
Columns commercialized worldwide
Delivered across refining and petrochemical complexes — and we stay on as a long-term partner through design, delivery and start-up.
World’s first multi-column DWC network
Four DWC Prime columns replaced a full seven-column conventional distillation train at an Indian acetone-derivatives complex.
Questions & Answers
Extractive Dividing Wall Columns, Explained
Can’t find your answer? Ask our engineers →
What is extractive distillation?
A separation in which a high-boiling solvent is added to change the relative volatility of the components. It is used where plain distillation fails or is uneconomic — azeotropes and close-boiling mixtures.
What is an extractive dividing wall column?
A single column that does the work of the extractive column and the solvent recovery column. A top dividing wall separates the extractive section from the extract rectifying section, and both share one stripping section and one reboiler.
Which solvents can be used?
The same solvents used in conventional extractive units — for example sulfolane, NMP, NFM, DMF, acetonitrile and glycols. Solvent choice and solvent-to-feed ratio are set during the feasibility study.
Can an existing extractive unit be revamped?
Often, yes. Whether an existing shell can take a wall depends on its diameter, tray or packing hydraulics and the required product purities. We confirm this in a feasibility study before any commitment.
How do we start?
Send us your feed composition, solvent, product specifications and current energy use. We return a feasibility study with the configuration, savings and payback.
Is EDWC Prime right for your unit?
Start with a feasibility study. We tell you whether it pays back before you commit.