Cryogenics keep VOCs in the cold
By Diane Raine, Air Products business manager for cryogenics in Europe.
Emissions control has long been an issue for companies within the chemical and pharmaceutical industries. But for those using volatile organic solvents (VOCs), pressure is getting more intense as Governments across Europe tighten legislation in this area.
What is the EU Solvents Directive?
The EC Solvents Directive (1999/12/EC) sets out a framework for the reduction of solvent emissions in Europe by 67% by 2007. These regulations require industries to consider a range of emissions control measures, from end of pipe abatement to solvent management.
Hundreds of thousands of solvents users across more than 30 sectors are impacted, including: adhesives, coatings rubber, dry cleaning, printing, vehicle refinishing and, of course, pharmaceutical manufacturers.
Why use solvents at all?
Many modern processes rely on solvents. For example, they are used to dissolve the resins used in the production of surface coatings, inks and adhesives and are also used in cleaning agents for removing paints. The manufacture of pharmaceutical products is reliant on a number of organic solvents.
What can companies do to meet their commitments?
Many solvent-using industries are actively reviewing their emissions control systems to ensure they are capable of meeting the most testing emissions limits imaginable. At the moment, these emissions limits are 20mg/m³ for Class 1 solvents - a benchmark set by TA Luft*, the German Technical Directive for Air Pollution Abatement. But with emissions limits set to go lower still, many users are already focussing on zero emissions, with a view to avoiding regulatory pressure altogether.
What solutions exist?
Cryogenic technology, as a means of solvent abatement, has been in use in industry for many years. The latest developments in this area mean that this liquid nitrogen-based technology is now available and affordable to many smaller solvent using companies.
Cryogenic condensation systems represent the greenest and most effective way to remove VOCs from exhaust gas streams, enabling users to meet the toughest global emissions limits currently specified. Such systems are designed to be flexible to changing on site demands and to recover the most difficult VOCs.
How does it work?
Cryogenic condensation systems work by cooling the exhaust gas stream, containing solvents, to below the solvents' freezing point. Liquid nitrogen, which has a temperature of -196 °C, provides the cooling power to achieve this 'freezing out' of solvents in the gas stream. The solvents condense and are collected, and the cleaned gas stream can be released to atmosphere. The clean gaseous nitrogen may be reused elsewhere on site, which can contribute to lower operating costs.
Such systems are capable of recovering most VOCs, including hexane, methyl chloride, acetone, ethyl acetate, toluene and dichloromethane. Examples such as Air Products' CryoCondap® and CryoCondap® ExStreamTM technologies reduce the environmental emission of VOCs to virtually zero and solvent-testing may be carried out in advance of installation to demonstrate effectiveness.
Planning for tightening legislation
Companies offering abatement systems must work closely with both the industry and companies within it, to ensure that the regulations are both understood and adhered to. As more companies are effected by the impact of the solvent directive and as the threshold for solvent emissions are driven even lower, users need the assurance that they are implementing solutions that will not only meet their immediate needs, but be flexible enough to cope with further changes in the future.
Diane Raine is Air Products business manager for cryogenics in Europe and specialises in finding applications for cryogenic technology in modern industrial processes. She joined the company 12 years ago with a Masters degree in Chemical engineering. For more information email: firstname.lastname@example.org
Air Products has installed more than 80 Cryogenic Condensation systems for solvent abatement and recovery.