A fixed-bed is a type of reactor or filtration system where solid materials, such as catalysts or adsorbents, are packed in a stationary bed. In this setup, fluids flow through the bed, allowing for chemical reactions or the removal of impurities. The solid particles remain in place, providing a consistent surface for interaction. This design is commonly used in various industrial processes, including catalytic converters in vehicles and water treatment systems. The fixed-bed configuration allows for efficient contact between the fluid and solid materials, optimizing performance and ensuring effective processing.