Distilling Solvents

Published: September 01, 2009, By By David L. Roey, Max Daetwyler Corp.

One of the oldest crafts devised by mankind is distillation — the art of separating mixtures based on their boiling temperatures. Throughout history distillation processes have been used to produce high alcohol content spirits, pharmaceutical remedies, perfumes, and potable water (such as distilling drinking water from sea water).

These practices eventually led to industrial uses. Distillation has been used in separating crude oil; extracting oxygen, nitrogen, and argon from air; and for the recycling of used chemicals. It offers the generators of waste solvents the ability to recover solvents for re-use within their processes.

Isn't it ironic to think that in these days of seeking “green” and “sustainable” processes to preserve our environment, as well as cut costs, one method has been employed in industry for several decades and originally was developed centuries ago?

How does an old process translate into today's world? Distillation simply makes good on old axioms. Today's “solvent-using printers” generate contaminated or waste solvent within their processes. The waste must be stored and disposed. New solvents must be purchased to replace the used products.

Some of the thoughts behind those deciding not to distill solvents were that it cost the user more money in energy consumption and was too dangerous when considering that flammable liquids were being heated up for the sake of recycling. As the price of virgin solvents rise with the price of petroleum, the manufacturing sector no longer can ignore the benefits of recovering used solvents on its own.

Technological advancements have been further employed to make the processes safer and faster. Modern distillation units utilize temperature controls to regulate the heating process as well as level filling and level controls to automate the processes.

Where thermometers once were used, solid-state devices now are installed. Load cells are being employed to replace simple float switches for volume control. Changes in the heating surfaces have allowed for greater efficiency. The ability to achieve a greater recycled solvent output by using less heating energy has made distillation even more practical to printers.

With technological advancements leading to safer and more efficient solvent recovery, the benefit is faster payback in the investment of a distillation process when compared to the cost of purchasing new solvent and disposing of the waste solvent. Now is the time to explore the benefits and advantages of recovering solvents.

What Does This Mean To the Flexo Printer?

Contaminated solvents are generated either from onboard press washup or by washing components used in the printing process. The used solvent must be stored in suitable containers, moved to an acceptable storage area, and then shipped as hazardous waste. The waste is handled repeatedly, increasing the risk of accidental spills or injury to personnel. New solvent must be purchased to replace the waste. The cycle continues all over again.

Solvent costs range from 60 cents to $1/lb. The approximate price of one 55-gal drum of solvent ranges from $200-$400. Waste disposal costs anywhere from one-quarter to one-half the price of new solvent ($50-$200/drum of waste).

It is important to note that solvent costs have increased by at least 50% in an 18-month period. Solvent prices have stabilized over the past six months, but unlike gasoline, solvent prices did not drop.