Repositori URV

Identifier: TDX:1216

Handle: https://hdl.handle.net/20.500.11797/TDX1216

Authors:
Sirin, Sema

Abstract:
Over the past few decades, microalgae become focus of the researches again as a possible raw material for the production of biodiesel due to the myth of the oil crisis and also Kyoto Protocol which entered into force in 2005. Although microalgae have proven to be very efficient at producing oil-rich lipids, the optimum conditions for algae cultivation and methods for harvesting and oil extraction have not been determined in details yet. In particular, the harvesting process is especially important to the effectiveness of the overall process because of the large volumes of algae-rich water that must be processed. The requirements for downstream also makes complicated the chosen harvesting system. Several solid-liquid separation technologies have shown some potential for achieving microalgae/water separation; however, application of these processes to biofuel production requires an evaluation of treatment effectiveness as a function of water quality, algae particle characteristics and process chemistry. Pre-concentration (bulk harvesting) aims to separate the micro algae from culture medium (bulk solution). Flocculation, flotation or gravity sedimentation are the frequently used methods. Filtration, centrifugation and ultrasonic aggregation are mostly used in thickening. Of these technologies, from chemical and/or biological harvesting, by means of flocculants e.g. auto flocculation, chemical coagulation, inorganic coagulants, organic flocculants, combined flocculation, electro-coagulation and ultrasonic aggregation. Flocculation is used in order to ease the following dewatering steps in this study. Flocculation is also a factor that affects the mechanical properties of the culture. Therefore, it is important to study the flow behaviour of flocculated suspensions by a