As best available technology in solvent recovery, cryogenic systems are not only capable of ensuring near zero emissions, across a range of processes and solvents, they can also help plants to enhance their sustainability and minimise some of the costs associated with waste disposal.

In 2003, the UK Government announced a programme of progressive increases in landfill tax that will take it from £13 per tonne before April 2003 to £18 by 2006 and the rate is ultimately set for £35 per tonne to be achieved by 2010. These increases are already underway and in April 2004 the cost of 'active waste' disposal at designated UK landfill sites will rise to £15 per tonne.
While acknowledging that the landfill tax has not led to a reduction in the amount of waste being disposed of at UK landfill sites, a report published by the Advisory Committee on Business and the Environment (ACBE) has recommended that the Landfill Tax review is brought forward to this year and that long-term targets for reducing industrial and commercial waste are established, to be achieved between 2005 and 2020. Despite the lack of certainty about the pace of landfill tax increases in the future, it is clear that UK businesses can expect some significant changes.
Clearly such cost increases will impact on many businesses across a range of industry sectors, not least among process industries, which typically produce a higher proportion of 'active waste' by-products and most are expected to review their waste management strategies as a result. For example, the chemical and pharmaceutical processing industries, which frequently operate solvent-using processes, typically invest in sophisticated emissions control systems. These systems are designed to recover solvents or volatile organic compounds (VOCs) from waste gas flows in order to dispose of them and avoid their release into the environment. In the past such manufacturers have relied on traditional emission abatement technologies, such as carbon adsorption, in order to manage the recovery of VOCs. But one drawback of such systems is the need to dispose of the VOC contaminated carbon materials at designated landfill sites.

The cryogenic alternative

There is an alternative abatement solution, which is both highly efficient and does not incur landfill costs. Such systems use cryogenic technology to recover solvents by using liquid nitrogen to literally freeze out VOCs from process gas flows and recover them efficiently and cleanly. Such systems are nothing new, but recent developments mean they are suitable for use across a range of manufacturing processes and are flexible enough to recover even the most complex VOCs at low gas flow rates. The systems can also be adapted quickly and easily on site to allow for changes in gas flows.
In recent years an increasing number of pharmaceutical and chemical manufacturing businesses have adopted new generation cryogenic solvent recovery systems but most have yet to realise the green potential inherent in such systems.
The pharmaceutical and chemical manufacturing industries are such that they often have to react very quickly to get production underway once a contract has been awarded or a new drug has been sponsored. For this reason, it is unusual for manufacturers to give much thought to how unwanted solvents will be disposed of let alone reused and instead the focus is on delivering product on time and ensuring optimum efficiency and quality. After all, processes can change and so can the solvents used.
Another barrier to earlier consideration of how recovered solvents could be reused is the fact that such processes usually require regulatory approval. Clearly, the main focus for managers is to gain approval as quickly as possible and it is not unusual for processes to be approved and up and running before solvent reuse options have even come up for discussion. However, solvent recovery systems do no automatically trigger regulatory approval.

The 'green' potential of cryogenics

As environmental management matters come increasingly to the fore, not least due to the increase in landfill costs and the impact of far-reaching environmental legislation, such as the Integrated Pollution Prevention and Control (IPPC) regulations, many solvent-using manufacturers are becoming increasingly interested in developing sustainable processes.
New generation cryogenic solvent recovery systems represent a major opportunity for processes to operate in a more sustainable way. Not only can manufacturers reuse the recovered solvent within their own processes, they can also choose to sell the recovered solvent elsewhere if they prefer. In addition, the liquid nitrogen used as part of the cryogenic freezing process can itself be recovered and reused elsewhere on site to ensure an inert process environment.
Clearly such systems represent a worthwhile business opportunity, as yet not fully realised, for manufacturers to demonstrate their commitment to green practice as well as delivering efficiencies.
In the meantime, it is important that we continue to work on the research and development of cryogenic solvent recovery technology in order to develop new solutions for industry. These systems are becoming ever more efficient and more flexible and will become a more mainstream solution for a wider range of industrial processes. Cryogenic recovery technology is still relatively new and while much as been achieved, there is likely to be more to come.
In the challenging times that lie ahead it will become ever more important that industry and providers of technological solutions such as Air Products, work closely together to ensure we can develop more efficient, clean and sustainable solutions than ever before. l

Diana Raine is Air Products' business manager for cryogenics in Europe, Walton-on-Thames, Surrey, UK. www.airproducts.com/epm