Agota Hegedüs | PubMed Health

PubMed2005

[Monitoring the temperature distribution during dielectric drying].

Microwave assisted vacuum drying offers never questioned advantageous and it is getting more and more popular lately. In spite of its uniqueness there is a rightful resistance and mistrust because the temperature distribution of the workload is far from being homogeneous as a result of the existing inhomogeneous electromagnetic field. The aim of this study is to survey the heat thus field distribution in the workload to prevent local overheating that endangers the quality of the pharmaceutical product. Thermography as a non perturbing thermometrical method was used to map the heat distribution in the workload. To get a 3D information Teflon layers were used to form cross-sectional and photogenic surfaces about the dusty blend and a purpose-developed software to evaluate qualitatively the IR pictures.

Electricity↗

PubMed2003

[Benefit of microwaves in case of heat-sensitive agglomerate drying].

The microwave assisted vacuum drying of heat-sensitive materials is increasing in the pharmaceutical industry since the eighties. This paper deals with results of two experiment series obtained on a laboratory scale single pot dryer (Collette Ultima 251). Firstly water was heated up to the boiling point exclusively by predetermined microwave energy and then by various wall temperatures in order to determine the convection efficiency of the system. The experiments were carried out at fixed pressure level (80 mbar) and with optimum bowl load (15 kg). According to the demonstrated idea each single pot system efficiency can be specified at any type and quantity of load. With the help of the presented results the second experiments were designed to compare the microwave and convection efficiency of the single pot system during granule drying. A placebo granule was dried either by an exclusive convection or microwave method up to the determined LOD (< 0.5%). According to the tests extreme high wall temperature (85 degrees C) had to be used to achieve the same drying time--and efficiency--as with the usage of dielectric heating. Based on the results it can be stated that the shorter drying time under favourable conditions is the advantage of microwave radiation over the conventional technique.

Drug Industry↗