Challenges

Challenges With Solvent Recovery

The challenges with solvent recovery are often interconnected and range from the equipment availability and limitations as described in table on the Solvent Recovery Technologies page, stream complexity and the requirements of the recovered solvent itself [1].

Azeotropic mixtures can be more difficult to recover solvents from and may require multi-stage recovery processes, such as pressure swing distillation or a distillation followed by a membrane process. This increases the energy and cost of a recovery process and reduces the benefit.

The complexity of a stream impacts the ability to recover solvent from it.  If a stream contains compounds of concern, a significant amount of solid compounds, or compounds that are incompatible with pieces of recovery equipment (such as membranes), this can make solvent recovery very challenging. To prevent this, it is advised that the waste stream complexity is considered early on when developing a process.

Different industries require different specifications from the recovered solvent due to the regulations and registrations that have been put in place for their processes. It is possible to obtain high purity solvents, however the energy requirement is higher.  In some cases, due to the complexity of the solution, a higher purity solvent requires more recovery steps than would be needed for a lower purity solvent. Another consideration that is critical in industries such as pharmaceuticals, is the impurities that may be present; if a solvent has been recovered from a specific drug manufacturing process, it is likely to contain small amounts of that drug, limiting the use of the recovered solvent to the stage where it was originally used or upstream in the synthesis.

Other challenges to consider when looking to implement solvent recovery include:

• The cost of equipment and implementation alongside the payback period.
• The requirement of additional storage for holding the recovered storage, alongside the campaign schedules to ensure the solvent is used within the registered timeframe.
• The technical resource required for scoping and feasibility studies, including the modelling capabilities and software available.

References

1. A. Aboagye, J. D. Chea and K. M. Yenkie, Systems level roadmap for solvent recovery and reuse in industries, iScience, 24, 2021, 103114.