Choose the Right Solvent Still

The Hazardous Waste Services Directory lists several vendors for units that distill solvent. The Department of Ecology's Technical Assistance staff cannot make recommendations about particular units.  However, the following are questions that would be good to ask a solvent-still vendor about their product.

Ask Your Vendor:

Do you have a customer user list, referrals, and/or a letter of recommendation?

Can/ should I upgrade my existing still?

Your vendor may be able to repair, modify, or upgrade an older existing distillation unit. Remember that switching to a newer or more efficient piece of equipment may be the most cost-effective solution in the long run.

Does this still have a UL 2208 label rated for the solvents I plan to recycle?

This rating allows you to operate your still inside your facility. Without this rating, fire code requires that you use the still outside your facility.

Are there other costs in setting up this still at my facility? 

To determine this, identify any special requirements of the still such as electrical, water system, or fireproofing, needed for proper installation and operation.

What kind of maintenance is required?

Make sure the maintenance procedures are provided by the vendor in a written manual.

When using the still, do the different types of solvent need to be distilled separately? 

If the answer is yes, make sure employees understand the solvent-separation procedure.

Will you (the vendor) distill a sample of my waste?

This can help you evaluate the quality of the reclaimed product and determine what percentage of the initial waste can be successfully recovered.

Are the still bottoms easily removed from the pot and how will I dispose of them? 

Still liners help remove the sludges left in the bottom of a still. Otherwise you may have to remove them by scooping them out, requiring personal protective equipment. Do not scoop out hot still bottoms, as their vapors could be explosive if ignited.

Will the unit need a vacuum to more efficiently distill the solvent(s) I use? What level of vacuum? 

A vacuum unit lowers the boiling temperature. If you have large volumes of solvent with high boiling points to distill, a vacuum unit can make recovering the solvent more energy efficient. A vacuum unit can make the cost of distilling high boiling solvents more economical. Vacuum units are more expensive than atmospheric units.

What kind of condenser will I need? 

Choosing the right condenser depends on the type of solvent you are distilling. A still boils solvent into vapors by adding heat. The condenser then removes that heat from the vapors to form a liquid again. An inadequate condenser will only condense a portion of the vapors, wasting solvent and allowing the uncondensed vapors to escape to the atmosphere.

Water-cooled equipment delivers a higher, more consistent condensation than air-cooled equipment. Water-cooled condensers are generally more efficient and provide more consistent solvent recovery year-round. Consider reusing the cooling water. In some cases, an air-cooled condenser may be adequate. However, these condensers are not as effective as water-cooled condensers in controlling the solvent vapor temperature.

Will the solvent deteriorate any components of the still with extended use?

Use a still built with components that are compatible with your solvents.

Special Health and Safety Features

Talk to Labor & Industries about necessary versus desirable features.   The following features have been included with some stills with good results.

Look for:

Related information

On-site Distillation is an Ecology publication that details distillation issues.  It includes worksheets and cost-benefit analysis.