Thin layer drying behavior of microalgae and determination of drying model equation

In this study, mixed culture microalgae samples of Porsuk streamlet were grown and their drying behaviour and drying model equation were determined. For this purpose, the growing experiments of the microalgae samples were carried out in an airlift photo bioreactor. The drying experiments of mixed microalgae biomass (MMB) harvested were performed by a tray drier. The photo bioreactor with a capacity of 30 L is mainly composed of timed lighting and ventilation equipment. Zarrouk broth medium which is widely used in literature was used in MMB growing. The mixed microalgae culture which was added by inoculation to the ready reactor was grown for 15 days. At the end of the growing experimental period, MMB samples harvested from the phot bioreactors were centrifuged and stored at +4 ° C for use in drying experiments. Drying experiments were conducted with various air flow rates (0.5-1.5 m/s), in the temperature range of 30-60 ° C and at atmospheric pressure. A typical drying test was done by measuring the weight of a certain quantity of MMB placed in the dryer chamber with temperature and air flow rate set at certain time intervals. The drying experiments were ended when the last two weight values of MMB samples were the same. In all studied temperature values, it was observed that moisture content values of MMB samples equal to zero by decreasing. From the drying curves, it was concluded that the air flow rate did not significantly affect the drying time compared to the temperature, except for a flow rate of 1.5 m/s. Drying rate curves at low temperatures (30 and 40 ° C) showed that the drying phenomena of MMB took place at a constant rate period with two or more stages due to surface drying. At high temperatures (50 °C and in particular 60 °C.), it was observed that MMB drying was carried out in the falling rate period. Effective diffusion coefficients at the temperatures of 50 and 60 °C were also calculated by using t-lnM graphs obtained from MMB drying data. It was determined that the effective diffusivities were not affected much by air flow rate but increased with increasing temperature. Also, in this study, drying test data were compared statistically with various drying model equations. As a result of the statistical analysis, it was found that the drying phenomena of MMB samples represented the best Modified Page equation. In the last stage of this study, the characteristic analyses of MBM samples dried were performed. It can be said that the characteristics test results such as protein, oil, SEM, and FTIR of MMB samples are similar to the properties of some microalgae samples existed in the literature.