Pall rings are a type of random packing used in chemical processing and various gas and liquid treatment applications. These rings are typically made of materials like metals, plastics, or ceramics and are characterized by their cylindrical shape with several internal and external structural features. The key design elements of pall rings include a series of internal and external structural elements—inner crossbars or struts and outer cylindrical walls—that provide a high surface area within a relatively small volume. This configuration ensures efficient contact between gas or liquid and the packing material, facilitating processes like gas absorption, distillation, and chemical reactions.

A filter press is a solid-liquid separation device used to dewater sludge, separate solids from liquids, and filter materials in various industries, including wastewater treatment, chemical, pharmaceutical, and food processing. The primary purpose of a filter press is to efficiently remove liquid from a mixture and produce a dry cake material. The device comprises a series of filter plates with recessed chambers and a filter cloth or other filter media between each plate. The plates are typically made from materials such as polypropylene, stainless steel, or cast iron. The filter plates are assembled together, forming a stack with an opening in the centre for the feed to enter the chambers.