Everyone has a role to play in creating a more sustainable future and circular economy, from engineers designing products and processes to purchasing departments sourcing resources to environmental departments looking for greener treatment and disposal options.
In the case of environmental departments, a major area of focus is better management of waste and byproducts. Companies have been recycling solvents since before 1976 when EPA rules came into effect because of the value of solvents. While regulations for managing waste have evolved since then, recycling has ebbed and flowed as a viable option to manufacturers. Why? Because recycling solvents requires more effort compared to traditional methods. Today, new technologies have simplified the process and are helping manufacturers reduce costs and find new sources of revenue while replenishing and protecting our resources.
Waste Reclamation: Why Solvent Recycling Is Key to Manufacturing
When waste is reused, everyone benefits because of lower energy use, reduced greenhouse gas, natural resource conservation, decreased disposal costs and, often, more efficient production by using recycled materials.
A wide variety of organic and inorganic solvents are used in product manufacturing. Some of these include paints and adhesives, cleaners and degreasers, pharmaceuticals and personal care products. As well, a wide variety of manufacturing industries could benefit from solvent recycling, including the electronics, automotive, pharmaceutical and paint industries.
Jim Reddy, a product line manager for Veolia’s solvent reclamation business line, explains how solvent is recycled and used as a replacement for virgin solvent and why the solvent recovery method is both cost-effective and environmentally friendly - benefits which appeal to manufacturers.
The Complexities of Solvent Recycling Made Easy
Reddy has been in the industry for close to 30 years and with Veolia for almost 20. He supports sales and logistics for 20 U.S. states for all solvent reclamation opportunities as well as national sales of Veolia’s reclaimed solvent products.
“Solvent recovery is highly dependent on the characteristics of the waste stream that produces it,” said Reddy. Waste streams come from a variety of industries, such as the pharmaceutical industry, chemical processing and beyond. Once the waste stream has been classified, the type of equipment appropriate for recycling is identified.
“For example, if the waste stream includes solid materials, the solvent would first be processed with a wiped film evaporator, which basically removes any solids and color,” said Reddy. Depending on whether additional recycling is needed, the solvent could then be placed into one of the solvent distillation columns for fractionation.
This is the phase where solvent reclamation and recovery can become complicated, because it may require more than one step. Traditional linear production models are less concerned with byproduct recovery and maximizing the lifecycle of a resource. Solvent recovery is a critical process, but it doesn’t have to be prohibitively complicated.
In addition to distillation columns, other equipment options can accomplish different outcomes, such as those listed below.
- Wiped film evaporator
The wiped film evaporator is a heated cylinder, similar to a distillation column, but includes a rotor going down the center of the column. Attached to the rotor are paddles, which operate much like a blender.
“When you introduce a liquid or solvent to the system, the solvent is spun up against the heated walls where the solvent is vaporized and the solids are left behind for disposal,” said Reddy.
- Distillation / Fractionation Column
A distillation column is a tall, heated cylinder housing a number of trays at various heights inside. When you heat up the column, there is a temperature difference between the top and bottom of the column. For example, heating from the bottom will make the trays hotter at the bottom than the trays at the top of the column.
“Every chemical has a different boiling point, so the chemicals will reflux, vaporize, and then condense multiple times as they move up the trays,” explains Reddy. “This allows the different solvents to separate based on their boiling point. The higher boilers will stay at the bottom of the column, while the lower boilers will concentrate at the top.”
- Molecular Sieve
A molecular sieve is a piece of equipment that contains media material with microscopic pores, which allow the passage of molecules larger than the pore size while absorbing molecules smaller than the pore size. Larger solvent molecules cannot be absorbed by the pores, while smaller molecules such as water can be, so it’s ideal for removing water from a solvent stream.
“At our facility, we run solvent through the sieve and successfully separate it from any water in its composition,” said Reddy. “This allows us to purify the solvent completely, so we can then return or repurpose it.”
Within this tip sheet, Jim identifies the most commonly recycled solvents and what types of spent solvent streams are processed in which types of equipment.
Viable Options for Organic Solvents
“We can recycle a customer’s solvent and return it to them (tolling), recycle and sell in the solvent market or match one company’s solvent to another company’s for beneficial reuse.”
Tolling returns a company's solvent to reuse in their process without the need for disposal, while fuel blending takes used solvents that are not recyclable and repurposes them into fuel for certain industries, such as making cement.
“We do a lot of tolling for companies that will have a solvent they’re using from a specific manufacturing process that can be recycled and reused,” notes Reddy. “We work with these companies to obtain the product specifications they need, recycle the solvent to those specs and then return it to the customer for reuse in their process.”
With fuel blending, any solvent that isn’t suitable for reclaim would go into fuels. The fuel created from used solvents is ideal for making Portland cement, which is a product manufactured from limestone using large amounts of energy. The cement kiln will replace some or all of their coal fuel with solvent fuels.
Determining Your Best Option for Solvent Recycling and Management
Various analyses will determine which solvent recovery option is best for your business—refine and resell, toll processing, on-site recycling or beneficial reuse. A sample analysis will quantify the content of the waste material and determine yield of recovered product versus contaminants.
A full production trial run on a tanker truck or larger batch size can be conducted with glass lab scale equipment that includes simple distillation and fractional distillation under design and capability conditions that replicate plant equipment. These analyses can help your business decide whether you should sell the resulting product or return it for reuse.
A More Circular Economy for the Benefit of All
Whether you are a large corporation or small to medium enterprise, circular thinking can help you extract value from waste and discover renewable resources in your supply chain. Solvent recycling is one innovative way to help your business achieve sustainability goals, reduce your carbon footprint, and benefit your bottom line as materials are reused or sold. So whether you are already engaged in the circular economy, or starting from scratch, maximizing the value of recyclable materials helps build a more sustainable society so nothing goes to waste.
Learn how a large steel company optimized their recycling and reuse solvent management.
