Raschig ring and alumina ball
Another alternative mode of preparation includes admixing the finely divided refractory-grade alumina and water, but without any iron, to form a thick mixture which is passed through a roll-type briquetting machine, pelleting mill, or tabletingpress. Prior to passing the alumina ball into the cavities of the mill or press, an iron particle such as a burr is inserted into each cavity and can be held in the cavity by such as a cleat or small magnet. The iron-particle containing pellets aresubsequently treated to produce balls in effect with an internal iron piece or burr.
Raschig rings are pieces of tube (approximately equal in length and diameter) used in large numbers as a packed bed within columns for distillations and other chemical engineering processes. They are usually ceramic or metal and provide a large surface area within the volume of the column for interaction between liquid and gas or vapour. Raschig rings are named after their inventor, the German chemist Friedrich Raschig.
They form what is now known as random packing, and enabled Raschig to perform distillations of much greater efficiency than his competitors using fractional distillation columns with trays.