Page 196 - Adsorption Technology & Design, Elsevier (1998)

182 Design procedures

respect, from the full-size design. Kinetic data which is obtained from batch
stirred experiments can only be used in rigorous design models and cannot
be used in any of the short-cut design techniques for packed beds, for
example.
Kinetic data which is obtained from dynamic mini-column experiments
must be treated carefully. The mini-column, or rapid adsorption, experi-
ment is based on the principle of high pressure liquid chromatography
(Rosene and Manes 1976) and was designed particularly for the water
industry in order to provide rapid evaluation of dynamic adsorbent
performance to complement data from isotherm experiments. The appara-
tus typically comprises a high pressure liquid pump and a small diameter
stainless steel column which contains pulverized adsorbent. The effluent
concentration is monitored for breakthrough and the adsorptive capacity
calculated from the known mass of adsorbent in the column and the volume
of liquid passed. Flows are typically in the range 2 to 3 cm3/min with a fine
carbon (200 x 325 mesh range) packed to a depth of about 20 to 25 mm
(Bilello and Beaudet 1983). Direct scale-up of mini-column breakthrough
profiles to full-scale systems is not easy because of the substantial differences
in sizes, flow distribution and wall effects. The technique should not be used
for the ab initio design of large-scale plant. Rather it should be used as a
screening technique for different types of adsorbent or for the effects of
preferential adsorption and desorption in water purification applications.

6.10 ADSORPTION PROCESS DESIGN AND SIMULATION

The design of any adsorption process should be based on sound fundamental
principles, backed up by laboratory- and pilot-scale experimentation and
modelling. A process simulator which incorporates an adsorption module
can be a useful tool to aid optimization of a design. However, a process
simulator is only as good as the adsorption model and associated data it
incorporates. One of the more comprehensive computer packages is
ADSIM TM (available from AspenTech) which is capable of simulating and
designing adsorption processes for the commercial separation and purifica-
tion of gases and liquids. ADSIM TM is a dynamic simulator based on the
equation-solving software known as SPEEDUP TM, and comprises three
components. The Preprocessor is used to generate adsorption bed models
and flowsheets. Here the choice of many different model attributes may be
made, including for example the choice of isothermal, adiabatic or non-
isothermal heat effects, the choice of mass transfer kinetic model, the choice
of equilibrium model, etc. A wide range of both single component and
multicomponent adsorption isotherm models are included. The Library