Modeling of two-stage diffusion in heat pump drying of protein
Advancing the chemical engineering fundamentals
Transport Phenomena in Porous/Granular Media - I (T2-7a)
Keywords: Heat-pump drying, protein, modelling
There is an increase effort to adopt the international GMP standards in the pharmaceutical industry and other fields in Russia. Among the requirements of these standards is the manufacture of the highest quality products. Without conformity to such standards the Russian producers in the field of pharmaceutical industry will not have the needed edge to succeed in this highly competitive international market.
Drying is an essential unit operation in processing and production of pharmaceutical powders. This process has a great impact on the final product quality and energy utilization. The traditional technologies for drying of pharmaceutical are the vacuum freeze-drying, spray drying and fluidized bed drying. These technologies have limitations concerned to powder final quality, product residence time and production cost.
An innovative technology is atmospheric two-stage fluidized bed heat pump drying. This technology allows:
• to obtain the highest quality and predefined structure of the final product;
• to significantly reduce process energy consumptions.
This process includes two stages, the first is fluidized bed freeze drying and the second is fluidized bed drying at medium temperature. The gentle conditions of atmospheric freeze drying allow improvement of product quality as well as preservation of the material structure. It promotes intensive mass and heat transfer during medium temperature drying and reduction in material residence time or production cost.
The main advantages of heat pump drying technology are:
• recovering of the latent heat of the air exhaust in the drying chamber and consequent energy reduction in the order of 35 to 50%;
• the closed drying cycle reduces product contamination and inlet gas filtering is much simpler compared to open cycles;
• there is no environmental pollution by fine dried particles usually transported and discharged into surroundings in open cycles.
Several experiments were carried out on atmospheric two-stage fluidized bed heat pump drying of the protein.
To optimize the process the mathematical modeling of kinetics was made using the experimental data. It was considered that the second Fick’s law describes the moisture removal during freeze drying and medium temperature drying. The effective diffusivities were determined for the first and second drying periods. An implicit difference procedure was used for the numerical solution of the mathematical model. The comparison of calculated and experimental data shows that the second Fick’s law satisfactorily describes the mass transfer in two-stage drying.
Presented Tuesday 18, 11:40 to 12:00, in session Transport Phenomena in Porous/Granular Media - I (T2-7a).
