Page 201 - Adsorption Technology & Design, Elsevier (1998)

7

Selected adsorption

processes

7.1 INTRODUCTION

To illustrate some of the features of adsorption processes a number of
examples have been selected which vary in their mode of design and
operation. Purification of gases is by far the oldest type of process and
includes the drying of air and other industrial gases, the sweetening
(removal of acidic gases) of natural gas, air purification and removal of
solvents from air streams. A second category of adsorption process is the
separation of a component gas, or gases, from a mixture of gases. The
production of oxygen and nitrogen from air are two well-known separation
processes as are the separation of n-paraffins from iso-paraffins and the
recovery of hydrogen from industrial gas mixtures. The two most common
adsorbents used for gas separation are activated carbon and zeolites of
various types (see Chapter 2). The adsorbent properties which enable the
separation of gases are the nature of the adsorbate-adsorbent equilibrium
and the rates at which gaseous components diffuse into the pore structure of
the adsorbent. The sieving property of zeolites is prominent in the
separation of n-paraffins from iso-paraffins and in the drying of gaseous
streams. The production of nitrogen from air using a molecular sieve carbon
depends on the difference in rates of diffusion of nitrogen and oxygen within
the adsorbent pore structure.