PHARMACEUTICALS

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High pressure

Excipient

Re-circulation

In-line heat

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Figure 2 - Temperature shift process

allow lower volumes of less toxic solvents to be used . Spray drying is used on a very large scale in the food industry . Sustainability efforts there in recent years have focused heavily on reducing the amount of energy used in the process . Turning a solution into solids by evaporating the solvent is energy-intensive because of the phase change involved in converting the liquid solvent into a vapour . Lessons already learned there regarding process parameter optimisation and heat recovery to maximise thermal efficiency while maintaining product quality ought to be transferrable to pharmaceutical applications . However , while this should contribute to greater sustainability , organic solvents are still required in the pharmaceutical industry and for many processes other than spray drying . Therefore , careful handling and control is important to minimise their impact . Companies must ensure that all operators within the manufacturing environment are protected from their potential hazards . The potential path of exposure , for example , should be tracked throughout the manufacturing process . Additionally , solvent waste should be recovered from the process as effectively as possible to minimise emissions to air and water .

Figure 1 - Spray drying process

Technology tricks

Additional enabling technologies will be required if the sustainability of the spray drying process is to be improved further . These may reduce the amount of solvent and also allow less toxic , more environmentally friendly solvents to be used in place of those that pose hazards to people and the environment . One option is to heat a less hazardous solvent , such as acetone or methanol , to improve API solubility . For example the solution tank can be warmed to just below the boiling point of the solvent with a heating jacket . Whilst additional energy is required to heat the tank , energy savings will