Rethinking Solvent Recycling

Nov. 19, 2017
Examining the potential for on-site recovery and recycling of solvents promises a substantial ROI for pharmaceutical companies

The return on investment for designing and installing an on-site solvent recovery unit can show an ROI of under two years.

The pharmaceutical industry has largely overlooked the benefits of recovering solvents on-site, preferring instead to rely on the repurchase of virgin solvents, or the offsite recovery of solvents using third-party processors.

Currently, many manufacturers rely on toll processors to perform recovery of solvents off-site. In addition to the transportation hazards, because the toll processor can be dealing with a number of different materials for different customers, the residue that remains in the equipment could cause cross contamination of the recovered solvents.

This practice results in other liabilities. While recovery and recycling of solvents during the manufacturing process on-site is more easily controlled, transporting solvents over public roads and railways can result in hazardous material spills, thereby contaminating the environment and putting the public at risk. The owner bears the risk for such a spill as well.

Other solutions for disposal such as incineration may be less attractive from an environmental standpoint.


According to Tom Schafer, vice president at Koch Modular Process Systems, the payback period for installing a solvent recovery system is often less than two years.

“We built a THF (Tetrahydrofuran) Recovery System for a well-known pharmaceutical company. This system was fed a waste solvent stream that contained water, THF, Dichloromethane, toluene and some salts. There were several azeotropes present, and we needed four small distillation columns to recover the purified, dry THF product.”

Schafer went on to explain that the recovered product purity was greater than 99.9 wt% THF, exceeding the virgin THF purity specifications. The system recovered 94.1% of the THF that was in the feed.

“The cost of the system installed was $3.8 million,” said Schafer. “The annual savings from the recovered solvent was $2.2 million. The operating cost for the system was $200,000 per year in utilities and manpower. The system paid for itself in less than two years.”

The quantities of solvents recovered can be thousands of gallons per week, and when one considers that some pharmaceutical manufacturing processes can require fifteen hundred pounds of solvent per hour, that can be 12,000 pounds over an eight-hour period - which can cost millions of dollars in unnecessary expenditures over a year when virgin solvent must be purchased or offsite solvent recovery services are used.

Koch Modular solvent recovery systems are available as modules, which are typically situated outdoors. The typical footprint size of a module is 12 feet by 12 feet, and can easily be shipped by truck from the manufacturing site to the customer’s plant site. The modular systems are manufactured indoors, off-site, and are ready for installation on a much more expedited timeline than traditional stick-built projects. They are especially appropriate for remote locations where experienced construction crews are not available. Another significant advantage of modular construction is that fabrication of the systems can take place while the customer is waiting for permits, which can save a lot of time in the overall project schedule.

The time required to design and build is typically less than one year, which includes an engineering study that provides the anticipated results and purity of recovered solvent. Furthermore, the systems provided by Koch Modular come with a Process Performance Guarantee, often based on results achieved using a client’s actual feed, during pilot plant testing.

There is also an economic downside. Resorting to disposal of used solvents and repurchase of virgin solvents is an expensive process, and many pharmaceutical companies are leaving significant amounts of money on the table. The return on investment for designing and installing an on-site solvent recovery unit can show an ROI of under two years and often can pay for itself in less than one year. Distillation and Liquid-Liquid Extraction columns, installed on modularly constructed skids, have been the solution of choice for many pharmaceutical companies that, today, are focused on finding savings in ever more remote corners of their facilities.

As concerns over climate change become increasingly pressing, pharmaceutical companies are conducting extensive environmental audits across virtually every aspect of their business. Regulatory demands are also becoming increasingly stringent for both environmental (incineration method) and over-the-roadway hazards (toll processor recovery), both of which affect the way in which solvent disposal/recovery is currently handled.

There is also significant public pressure being brought to bear on pharmaceutical companies to demonstrate their commitment to corporate responsibility in this regard. This is a matter often highlighted in corporate annual reports. As a result, facility-based engineering teams, corporate engineering and public-facing corporate executive teams are pulling together to address these challenges.

Solvent recovery and recycling systems are one way these companies can mitigate their impact on the environment, as well as improve safety standards and produce product more economically.
Another advantage of recovering and recycling solvents on-site is consistency of supply. While sourcing virgin or recycled solvents off-site can be interrupted by scarcity of supply or labor disputes and the like, managing the process in-house assures continuity of supply.

A rigorous methodical approach is critical to developing and pilot-testing a waste stream to design the proper process and unit operations that will work best. It is imperative to lay the groundwork in detail. Then a conceptual design is developed that helps evaluate the proposed recovery processes.

Once a preferred design is proposed, pilot-testing is conducted using both computer models and live pilot plant trials to evaluate solvent recovery viability under a variety of conditions and with a range of outcomes, including evaluation for the tendency for emulsification, foaming and fouling characteristics.

The results of the pilot test are then compared to the initial conceptual design, in order to perform a reality check, and establish whether or not there are mitigating factors that call for a different column design or configuration. These may include corrosion and temperature issues, the cost of utilities and construction materials, and physical observation of the performance of the columns. The result of this process will culminate in the optimization of the system design, and lead to less process risk and a better ROI.

There is no question that examining the potential for on-site recovery and recycling of solvents promises substantial ROI for pharmaceutical companies. For engineering teams looking for additional ways to save their organization money and advance environmental stewardship efforts, on-site recovery and recycling of solvents is a straightforward approach that can be effectively tested prior to project approval, to ensure solvent purity and ROI.


Another example of the benefits of on-site solvent recovery systems is the work Koch Modular Process Systems did for a leading pharmaceutical company in Puerto Rico.

An Acetonitrile Recovery System was designed and started up in 2017. This system was fed a waste stream containing a significant amount of Acetonitrile, along with some other low and high boilers. There was an azeotrope present, and the client needed two small distillation columns to recover the dry Acetonitrile product.

Recovered product purity was > 99.85 (weighted) percent Acetonitrile. Nearly 100 percent of the Acetonitrile that was in the feed, was recycled - actual results were 99.7 percent.The cost of the system installed was $3.7 million. The annual savings from the recovered solvent was $3.9 million. The operating cost for the system was $300,000 per year in utilities and manpower. The system will pay for itself in about a year.

About the Author

Tom Schafer | Vice President