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Significance Statement
Freeze-drying is known to produce the highest quality of products among all current drying techniques. However, it is one of the most energy-consuming unit operations. Improving process economic by increasing energy utilization has been a hot topic of research. To save drying time and increase productivity, a novel idea was proposed for freeze-drying of liquid materials by creating an initially unsaturated structure frozen with prebuilt pores. Experimental results show that freeze-drying can be significantly enhanced with the initially unsaturated frozen material and substantial drying time can be saved compared with conventional freeze-drying. Drying time for the initially unsaturated frozen sample (S0 = 0.28 or 0.69 of initial porosity) can be at best 32% shorter than that required for the initially saturated one (S0 = 1.00 or zero porosity). This unique technique would impose an impact on the traditional freeze-drying technology and develop an unprecedented freeze-drying process of liquid materials.
Journal Reference
AICHE Journal, Volume 61, Issue 6, 2015, Pages: 2048–2057,
Wei Wang1,2, Dapeng Hu1, Yanqiu Pan3, Yanqiang Zhao3, Guohua Chen2,4,5
[expand title=”Show Affiliations”]- School of Chemical Machinery, State Key Laboratory of Fine Chemicals, Dalian University of Technology, China
- College of Life Science, Dalian Nationalities University, China
- School of Chemical Engineering, State Key Laboratory of Fine Chemicals, Dalian University of Technology, Dalian, China
- of Chemical and Biomolecular Engineering, The Hong Kong University of Science and Technology, Hong Kong, China
- School of Environmental and Biological Science and Technology, Dalian University of Technology, Dalian, China
Abstract
To save drying time and increase productivity, a novel idea was proposed for freeze-drying of liquid materials by creating an initially unsaturated frozen structure. An experimental investigation was carried out aiming at verifying the idea using a multifunctional freeze-drying apparatus. Mannitol was selected as the primary solute in aqueous solution. Liquid nitrogen ice-cream making method was used to prepare the frozen materials with different initial porosities. Results show that freeze-drying can be significantly enhanced with the initially unsaturated frozen material, and substantial drying time can be saved compared with conventional freeze-drying of the initially saturated one. Drying time was found to decrease with the decrease in the initial saturation. The drying time for the initially unsaturated frozen sample (S0 = 0.28 or 0.69 of initial porosity) can be at best 32% shorter than that required for the saturated one (S0 = 1.00 or zero porosity). This unique technique is easy to implement and improves the freeze-drying performance of liquid materials.
© 2015 American Institute of Chemical Engineers AIChE J, 61: 2048–2057, 2015
Go To AICHE JournalFigure Legend: SEM images of dried products with two freezing methods at different magnifications; (a) and (b) for the initially saturated sample (S0 = 1.00); (c) and (d) for the initially unsaturated one (S0 = 0.28).
