How to Recover Solvents From a Product Mixture?
RAPID RESPONSE QUESTION: An Oregon client has a high-boiling point substance contaminated with organic solvents. What resources are available to help select the appropriate technology to recover solvents (acetone and toluene) from the mixture?
Request by: Anonymous
An Oregon manufacturer recovers a high-boiling point product material from an industrial process. The material contains residual acetone and toluene which the manufacturer wants to remove and potentially recover for re-use. Information was requested on methods to recover solvent from the product mixture.
Solvent Recovery by Distillation
Both acetone and toluene are fairly volatile solvents. Their boiling points are substantially different (acetone boils at 56 C and toluene at 110.6 C), which would likely lead to an easy separation and recovery by a simple batch “kettle” still. If the initial product mixture contains other volatile components, fractional distillation may be required to achieve desired individual solvent purity.
Distillation for solvent recovery and reuse is widely practiced. Guidance documents on factors to consider in solvent recovery are provided in the Resource section below. Case studies of commercial implementations and vendor links are also listed. Equipment vendors can provide guidance on the scale and type of equipment appropriate for individual applications. Vendors will typically perform test distillations to verify performance.
Other Treatment Options
There are other treatment technologies available depending on the specific contaminant to be reduced.
Ion exchange is a proven technology with effective treatment results for the removal of dissolved metals. For example, Siemens Water Technologies offers permanent, hard-piped ion exchange treatment systems containing contaminant-specific treatment resins, as well as removable systems.
If in-house expertise is not available, expert consultants can help design a system for the specific situation. System components can be selected based upon labor capacity, safety issues, space limitations, access limitation, the contaminant(s), and the specific water quality required. Designs are often flexible enough to accommodate future production growth, compliance limits, or different streams. Exchange vessels are often serviced and exchanged by a DOT-compliant vendor. Service ion exchange minimizes the need for handling and on-site storage of chemicals and wastes for improved safety and compliance.
Microfiltration is another technology that also offers a cost-effective solution for removal of heavy metals in wastewater and for water reuse applications. The membrane provides a barrier to the passage of solids and therefore is capable of removing metals (and other contaminants) to their solubility limits.
Questions to ask when considering in-house solvent recovery:
- On-Site Solvent Recovery Stills: http://dnr.wi.gov/org/caer/cea/publications/pubs/section3/sw150.pdf
- A Guide For Choosing and Operating an On-Site Distillation Unit: http://www.deq.state.ok.us/lpdnew/pollutionprevention/guiddstl.pdf
- Solvent Recovery Systems (includes a simple economic calculation example): http://infohouse.p2ric.org/ref/12/11493.pdf
Case studies on solvent recovery:
- Solvent recovery case study at Bayer Corporation, North Carolina: http://infohouse.p2ric.org/ref/07/06123.pdf
- Solvent recovery case study at Crumrine Company, Nevada: http://unrbep.org/wp-content/uploads/2009/11/Crumrine.pdf
Commercial vendors of systems or distillation services:
- An Oregon vendor with experience in solvent recovery by distillation (includes considerations of Oregon hazardous waste disposal regulations): http://www.orenviro.com/solvent-recovery-systems-lower-your-EPA-classification.htm
- A California provider of distillation systems: http://www.cal-water.com/pdf/products/Lit%20Distillation.pdf
- Vacuum distillation equipment may be required where the mixture to be separated includes large, complex molecules that would be affected by high temperatures. Oregon Environmental mentioned above makes equipment for this purpose: http://www.orenviro.com/products/vacuum-generator-VAC200.htm
- CBG, a large commercial system provider: https://www.cbgtechnologies.com/case-study-new-jersey-manufacturer.aspx
- NexGenEnviro Systems, Inc., a large commercial system provider: http://www.nexgenenviro.com/category/481/solvent_distillation.html
- Commercial services are also available to purify solvents for recycle, even complicated mixtures: http://www.veoliaes.com/en/services/enterprise/recycling/solvents.html
Disclaimer: PPRC does not endorse any particular vendor, material, or process, and provides these commercial links as examples only. Be sure to ask vendors for references and consider looking into competitors in the same market before proceeding with any purchase or commercial contract.