The distributor and packing define the performance of
this equipment. Their proper selection entails an understanding
of packing operational characteristics, and
the effect on performance of the points of significant
physical difference between the various types.
Good progress has been made in the past decade in
the development of packing types for difficult and wide
ranging process applications (see: Websites in bibliography).
These types include:
1. Random particle packings are discrete, individually
shaped particles designed to provide contactingsurfaces between (normally) down-flowing liquid
and up-flowing vapor/gas. The degree of effectiveness
of the various shapes varies along with the mass
pressure drop through the packed bed. Usually these
particles are ‘‘dumped’’ into the column (tower) and
allowed to float gently to their free-fall resting position
in a column full of water. Some shapes and sizes
are not installed using water, but dumped in using
a special ‘‘sock’’ that allows the particles to be
lowered without a damaging free fall. Sometimes
large particles are hand set ‘‘dry’’ into position to fill
the tower tightly, See Figure 14-1A. The vapor-liquid
performance is different for each method of loading,
and appropriate data must be available to properly
size the tower. The random ‘‘dumped’’ (wet or dry)
method is the technique usually used in most
published data (see Figures 14-6A–X).
2. Structured packing, which is offered by several
manufacturers, is usually composed of pack ‘‘pads’’
fabricated by shaping/crimping, bending, rolling, etc.
sheets of thin gauge metal or wire, (see Figures
14-6Y to 14-6OO). Some ‘‘pads’’ or packs are
formed using various plastics material, selected to be
resistant to the fluid services involved.
3. Grid packing is probably the newest packing type. It
is lower in pressure drop, and has higher capacity, but
lower efficiency than the other types. (See Figures
14-6PP–UU)