Waste Oil Recycling with Ceramic Membranes

Used engine and lubricating oils – often referred to as used lubricant oils or ULO – are both hazardous waste and a valuable resource. Nearly two million tons of waste oil are collected each year in the EU, around 60 percent of which is already reprocessed. Due to their content of spent additives, contaminants and degradation products, ULOs are more toxic and more harmful to health and the environment than unused oils. Conventionally, ULO recycling involves at least three distillation steps in which water, tar-like compounds and spent additives are removed. Distillation is energy-intensive and difficult to scale, however. The EU project CUMERI (Customized Membranes for Green and Resilient Industries) involves the synthesis, testing and piloting of tailor-made ceramic ultrafiltration membranes with the aim of replacing distillation steps and developing an energy-efficient, easily scalable membrane filtration process.

At Fraunhofer IKTS and project partner VITO, ceramic membranes were synthesized, functionalized and tested. One major challenge is the high viscosity of the waste oils, which makes filtration more difficult. CFD simulations (Fig. 1) were used to study the influence on hydraulic properties within the membranes and during mass transfer. The separation layers of the ceramic membranes were also modified. Pore sizes were adjusted to achieve maximum retention, and surface properties were optimized for suitable wetting behavior.

After extensive and successful laboratory tests, the membranes were examined on a pilot scale in an industrial waste oil reprocessing plant operated by Osilub. For this purpose, a pilot filtration system developed by project partner VITO was adapted and installed at Osilub for a six-month pilot phase (Fig. 2). The delaboratory results were confirmed in pilot operation: water and sulfur content can be significantly reduced using fine ultrafiltration membranes, for example, while metallic impurities from additives or engine wear were almost completely removed. Subsequent membrane filtration steps can refine the processed oils to a quality comparable to that of new base oils (OSIL150).

Services offered
 

• Development and modification of ceramic membranes
• Characterization and testing of membranes, development of membrane systems