Mathematical Modelling of Drying of Chlorella sp., Neochloris conjuncta and Botryococcus braunii at Different Drying Conditions

Abstract

Drying is one of the most important process in the cultivation of microalgae. Performance of drying depends on appropriate drying methods. This study aimed (1) to determine the effect of different drying methods on the Chlorella sp., Neochloris conjuncta, and Botryococcus braunii strains and (2) to identify the most suitable model for drying methods.

Chlorella sp., Neochloris conjuncta and Botryococcus braunii cultures were grown in basal medium in raceways at the greenhouse condition in Isparta province. During experiment, air temperature and relative humidity, wind speed, solar irradiance, wet and dry mass and temperature of microalgae biomass were measured. Drying applications continued for approximately 3 days.

Microalgae were dried at solar tunnel, outdoor, and greenhouse conditions. Furthermore, the effect of drying methods such as open sun, solar tunnel, and greenhouse drying on drying time, and drying ratio of microalgae have been investigated. The drying data were applied to ten different mathematical models, namely, Newton, Page, Henderson and Pabis, Logarithmic, Midilli and Kucuk, Wang and Singh, Two Term, Two Term Exponential, Weibull and Logistic Equation Models. The performance of these models were compared according to the coefficient of determination, standard error of estimate and residual sum of squares, between the observed and predicted moisture ratios. Results showed that the Weibull equation gave the best prediction to the drying kinetics evidenced by coefficient of determination ranging from 0.9959 – 0.9992 for all drying methods.  In addition, solar tunnel drying method has been determined to be the most suitable one among tested methods for drying of microalgae.

Key words: Chlorella sp., Neochloris conjuncta, Botryococcus braunii, drying, mathematical modelling, microalgae