The significance of solvent recovery

An important phase in the life of solvents concerns the processes employed after they have performed their primary role and involves either the recovery or disposal of the solvent. 

However, small scale users of solvents do not have the benefits of large volumes and the cost of operation of an on site recovery system is unjustified. Nevertheless, the solvent remains recoverable and hence retains a value. Under these circumstances, provided the economics are viable, conglomeration of a solvent obtained from a number of small users is required. This role of collection and subsequent bulk recovery is performed by solvent recovery agents . The reclaimed solvent obtained from such agents is generally of good quality and purity and can often be reused for less critical applications than those serviced by the virgin solvent. 

This process can often be quite lucrative as the first user will invariably pay the recovery agent to remove the waste and, following a recycling process, the material can be resold  

In many instances, the implications of regulation and the initial cost of instigating recycling and recovery has resulted in the elimination of solvents from processes and formulations. This is evident in trends such as the use of waterborne paints and coatings, aqueous based adhesives and metal pretreatments (although these changes may result in the need to comply to different legislation). 

Recovery techniques exist for the separation of solvents from solids, residues, liquids, including water, and from gases. These are achieved by such technologies as decanting, distillation, liquid-liquid extraction, condensation, adsorption and absorption. In many instances several processes are used in series to achieve the most efficient recovery, or desired quality, from the recovered solvent. A summary of the principal technologies used in solvent recovery is discussed below. 

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