The client’s process involves the extraction of metal ions from an aqueous feed stream using a mixed solvent of approximately 10% of an aliphatic tertiary amine in a heavy aromatic, naphtha organic.
The client was interested in replacing the mixer settlers used in the process with an extraction column that is durable, corrosion-resistant, and minimizes the amount of acid water entrainment in the organic extract phase.
For this process application, Koch Modular engineers recommended using the SCHEIBEL®Column due to it having highest efficiency of any commercially available column based upon data published in the literature.
This column also complied with the height limitation at the client’s plant. Pilot testing was performed using feed samples provided by the client and a 3” diameter, 20 agitated stage SCHEIBEL®Column.
Variables such as capacity (combined flow of both phases), column height (number of agitated stages), solvent to feed ratio, agitation speed, and temperature were studied and optimized.
Koch Modular provided a 50” inner diameter, 20-stage SCHEIBEL®Column with a 100” diameter expanded chamber at its top.
The expanded chamber was included for minimization of the amount of water entrainment in the organic extract phase.
A 6” thick coalescing element was also included in the expanded zone for removal of fine water droplets.
Reducing the amount of water entrainment resulted in the elimination of the washing step, transforming the client’s three-step process into a two-step process. The elimination of the washing step further resulted in the decreased generation of wastewater.
To provide corrosion resistance, the material of construction for column internals was chosen to be an alloy known as C-276.
The SCHEIBEL®Column installation was successful and it has been running ever since with no reported issues.