By Saowanee Wijitkosum and Kanoktat Yolpramote

Year 2013

The 14th TSAE National Conference and the 6th TSAE International Conference : TSAE 2013. p.175-178


The rate limiting mechanism for pineapple juice extraction in the reversing continuous countercurrent extraction system was investigated based on a backmixing diffusion model at steady-state condition. Three parameters namely temperature, Peclet number, and Biot number were studied for yield and yield loss calculation using an experimentally verified steady-state backmixing-diffusion model. For simulation purpose, some parameters/factors based on previous experimental results were specified including equilibrium distribution coefficient, diffusivity, time of cell plasmolysis, characteristics length, draft, and overall mass transfer coefficient. It was found that, in most cases of the experimental range, solid-diffusion was rate limiting step while backmixing phenomenon strongly influenced the concentration profiles, yield and yield loss. Backmixing caused the reduction in driving force and the increasing in mass transfer. The combined effect of finite Biot number ( Bi ) and Peclect number ( R ) influenced the yield and yield loss. In majority of cases, in-solid diffusion was predominantly controlled-limiting step while the backmixing phenomenon caused the loss of concentration gradient of extraction system significantly. In some cases, where the backmixing was too strong, the yield loss could be as high as 40 %.

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