PERFORMANCE EVALUATION OF A CONVENTIONAL NAUTAMIXER APPLIED AS A DIRECT DRYER

This paper describes the experiments which were conducted with the objective to determine the potential of a conventional Nautamixer applied as a direct dryer. This convective Nautamixer-dryer was used for drying the urea nitrate containing around 15% of water, which is converted from a pasteous form into a powder of a moisture lewel below 1%.

The influence of the following variables was studied: increased hot air velocity and temperature, number of revolutions of the agitator, and mass of the drying material. The effect of inlet air distribution to the periphery of the bed of the material was studied with a perforated plate distributor by blanking the holes (17%). which adversely affected the drying rate. The examination of the effect of external heating through the wall indicated that it is not possible to achieve the desired moisture level of the product without the introducing the flowing hot air. As an addition to the convective drying the indirect drying contributed more to the increase of the outlet air temperature than to the increase of the drying rate. As expected, shorter drying time is obtained with higher air flow rates and temperatures as well as with increased number of revolutions of both the orbital arm and the mixing screw.