Since 1965, the year in which the the first Spanish desalination plant was built, the demand for the construction of such plants has grown exponentially. In parallel an increase has also been observed in the demand for reverse osmosis tubes used to satisfy the needs of these plants. Osmosis is a phenomenon related to the behaviour of water as a solvent of a solution that moves across a membrane that is semi-permeable to the solvent (water) but not to the solutes (e.g. salt).
Such behaviour involves a simple diffusion through the membrane with no energy input. By this procedure desalinated water can be obtained from seawater.
In this context, Bekaert Progressive Composites - a subsidiary located in Mungia (Bizkaia, Spain) of the renown multinational - concentrates on the in-depth study of possible improvements in the functioning and performance of the reverse osmosis tubes that are currently used. The growing demand for tubes has shown the need to invest resources in R&D to develop new materials and manufacturing processes to reduce tube manufacturing costs and weight, thus facilitating their assembly, handling, etc. The R&D project in which GAIKER-IK4 is currently collaborating with Bekaert focuses specifically on identifying the different parts of the reverse osmosis tube. These will be modified in terms of the design and will then be adapted to the composite materials and manufacturing processes.
The advantages of composites
The components we use today are manufactured with metallic materials, thus requiring several surface treatments. These treatments endow these parts of chemical resistance, but render a significantly more expensive final piece. On the other hand, they are relatively heavy materials, which is a disadvantage that the project's composites do not have.
Composite materials are those compounds comprising two or more physically distinct components. Their mechanical properties are superior to the sum of the properties of their components. These materials arise from the need for materials that combine the properties of ceramics, plastics and metals. They are common in the transport industry, which requires lightweight, rigid materials, that at the same time are resistant to impacts, corrosion and wear; properties that rarely come together.
In this particular case, the company's requirements are for a rigid and resistant material, since it must meet high mechanical requirements. They are also interested that the new material for reverse osmosis tubes can support different chemical attacks while being lightweight.
On the contrary, as regards the transformation processes, the processes used today to manufacture metallic components, render a significantly costly final piece and allow a relatively low manufacturing capacity. Hence the feasible transformation processes using composite materials is favourable for both, thus becoming an interesting option.