What Is The Difference Between Structured Packing And Random Packing?

Random packing uses a random distribution of small packing materials to assist in the separation process, while structured packing uses larger, fixed packing structures. These more formal materials guide the liquid materials through complex structural channels into a specific, fixed shape.

Random packing is used in separation columns, such as a distillation column, to increase surface area for vapor/liquid contact so that chemical separation is more efficient.  The small pieces of random packing in a distillation column are designed to form a large surface area where the reactants can interact while minimizing complexity within the column.  Random packing is designed to maximize the surface-to-volume ratio and minimize pressure drop.

 The efficacy of random packaging depends upon a few factors — efficiency, pressure drop and capacity.  Typically, when random packing is large, capacity is increased at the cost of lower efficiency.  Conversely, when random packing is small, efficiency is increased at the cost of lower capacity.  Low pressure drop is ideal because high pressure drop diminishes both performance and efficiency.

 Initially, random packing materials were made of ceramic.  The use of ceramic has declined because of its brittleness, but it still is used in some applications that require strong corrosion resistance.  Today, many random packing materials are made of metal and plastic, with some other materials used in specialized applications.

Sometimes, however, more structure is called for than random packing can provide. In this case, structured packing is necessary.

Structured packing is a type of organized packing used to channel liquid material into a specific shape. It uses discs composed of materials such as metal, plastic or porcelain with their internal structures arranged into different types of honeycombed shapes. These honeycombed shapes are always found within cylindrical columns.

Structured packing cylinders are precisely engineered to provide a large surface area for the liquid to contact without causing resistance that impedes the liquid’s flow.