Improvement of the Microalgae Harvest by the “Foaming-Scumming” Function of an Airlift Column

The aim of this research work is to valorize the microalgae grown-up in an Airlift column. The system of fluid circulation and mass transfer is based on the principle of interaction between gas bubbles and a liquid. Thus, this study focuses on the phenomenon of the determination of the vacuum rate, the size and the speed of the bubbles including the optimization of microalgae development within the culture process. In addition, this study tries to understand the close relationship between these phenomena, its environment and the microalgae cell. These studies were conducted on the operation of an Airlift column in aquaculture, mainly in freshwater [1]. However, other researchers [2] are interested in studying saline water. In conclusion, a series of experiments were carried out in order to evaluate the profitability of the Microflotation technique, as a method of separation and concentration in microalgae. These results are very interesting since they reveal that the efficiency of the column, for the foaming-skimming function, is greater by working with less significant air injections, which lead to a reduction in energy cost.

Mass Transfer around a Rising CO2 Bubble in an Air Lift Column Applied to Aquaculture

He mentioned in the 18th century the possibility of injecting gas bubbles into a column of liquid to create a displacement of this liquid due to the rise of bubbles. This system takes the name of Air Lift and the first publications around this process appear at the beginning of the 20th century. There are many economic and ecological interests: CO2 from industrial production is valued because it is consumed by algae, which once they reach maturity can be converted into fuel. It is therefore a very good energy balance thanks to a low consumption of gray energy and the system is simple to set up. In this study, we will delve deeper into the description of the bubble column and the theory that accompanies it. We will then describe our experiences and the work done.

Influence of Fresh Water on Microbubble Generation in an Airlift Column Applied to Aquaculture: Extraction Capacity

Bubble flows consist a liquid phase and a gaseous phase dispersed as bubbles. They occur in nature and in many industrial applications, such as oil transportation in pipelines and steam generators for power generation. Due to large difference in density between gas and liquid, the flottability force causes bubbles to rise, which in turn can generate overall motion and agitation in liquid. This use of gravity as a flow driver, which is specific to disperse phase systems, is used in process engineering (bubble columns and gasosiphon) to sparingly promote mixing and exchange between gas and liquid. In many applications, bubbles are used to agitate a liquid in order to promote mixing and transfers. This work is devoted to study of hydrodynamics of a bubble column. Experimentally, we have determined properties fluctuations of velocities inside the aquarium of rising homogeneous bubbles for different bubble sizes and vacuum rates. The interfacial area between gas and liquid phase is a crucial factor for mass transfer in bubble columns. The molecular exchange between a given volume of gas and water can be enhanced by formation of smaller bubbles, leading to a larger gas-liquid interface. This work presents the various physical phenomena that apply to bubbles, as well as associated dimensionless numbers. A state art of Micro-Bubble Generators (MBG) is then presented, presenting systems using various phenomena such as cavitation, electrolysis, or shear.

Freshwater Purification by Vacuum Airlift Column Using Methyl Isobutyl Carbinol and Casein

Water purification by foaming in a bubble column is a major challenge for research. It leads to the development of innovative airlift column operated under depression. Sea water clarification by bubble column is well documented, but for freshwater remains insufficiently studied. Extraction of suspended clay particles in freshwater is carried out in an airlift column. The system used is under depression and operates in a closed circuit, thanks to a recirculation tank. Methyl isobutyl carbinol (MIBC) and soluble casein are used as surfactants to allow extraction. Clay used is fine and ultra-ventilated and a turbidimeter is used to measure turbidity. This study showed that the combined use of methyl isobutyl carbinol and casein in the airlift column makes it possible to completely clarify water loaded with clay particles. A turbidity of less than 1 NTU is obtained after 30 minutes of extraction.