11-06-2012, 12:19 PM
Engineering Design Methods of Adsorption Systems
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Introduction
Understanding of engineering design methods of adsorption systems is
an important aspect of process engineering design not only in the
chemical industry but also in the fields of environmental pollution control
and energy utilization. Moreover, adsorption is coming to be regarded as
a practicable separation method for purification or bulk separation in
newly developed material production processes of, for example, high-tech
materials and biochemical and biomedical products.
Advances in chemical engineering principles such as transfer rate
processes and process dynamics and accumulation of quantitative data in
the field of adsorption, together with the development of easily accessible
microcomputers, have combined to enable the development of an
integrated curriculum of adsorption engineering.
Porous Adsorbents
Physical adsorption is caused mainly by van der Waals force and
electrostatic force between adsorbate molecules and the atoms which
compose the adsorbent surface. Thus adsorbents are characterized first
by surface properties such as surface area and polarity.
A large specific surface area is preferable for providing large
adsorption capacity, but the creation of a large internal surface area in a
limited volume inevitably gives rise to large numbers of small sized pores
between adsorption surfaces. The size of micropore determines the
accessibility of adsorbate molecules to the adsorption surface so the pore
size distribution of micropore is another important property for
characterizing adsorptivity of adsorbents.
Also some adsorbents have larger pores in addition to micropores
which result from granulation of fine powders or fine crystals into pellets
or originate in the texture of raw materials. These pores called
macropores are several micrometers in size. Macropores function as
diffusion paths of adsorbate molecules from outside the granule to the
micropores in fine powders and crystals. Adsorbents containing
macropores and micropores are often said to have "bidispersed" pore
structures.
Activated Carbon
Act~vated carbons are the microporous carbonaceous adsorbents
whose history can be traced back to 1600 B.C. when wood chars were
used for medicinal purposes in Egypt. In Japan, a well for underground
water equlpped with a charcoal filter at the bottom was found at an old
shrine (Kashiwara Jingu, Nara) constructed in the 13th century A. D. In
Europe, wood char and later bone char were used for refining beet
sugar, a practice started in France because of the blockade against the
Continent during the Napoleonic era. In the 20th century, during the
World Wars, the need to develop gas masks stimulated rapid growth In
adsorption research. Many books have been published on activated
carbon and ~ tasp plications (Araki, 1932; Bailleul et at!, 1962; Hassler,
1974; Mantell, 1951; Mattson and Mark, 1971; Tanso Zairyo-Gakkai,
1975.
[attachment=851]
Introduction
Understanding of engineering design methods of adsorption systems is
an important aspect of process engineering design not only in the
chemical industry but also in the fields of environmental pollution control
and energy utilization. Moreover, adsorption is coming to be regarded as
a practicable separation method for purification or bulk separation in
newly developed material production processes of, for example, high-tech
materials and biochemical and biomedical products.
Advances in chemical engineering principles such as transfer rate
processes and process dynamics and accumulation of quantitative data in
the field of adsorption, together with the development of easily accessible
microcomputers, have combined to enable the development of an
integrated curriculum of adsorption engineering.
Porous Adsorbents
Physical adsorption is caused mainly by van der Waals force and
electrostatic force between adsorbate molecules and the atoms which
compose the adsorbent surface. Thus adsorbents are characterized first
by surface properties such as surface area and polarity.
A large specific surface area is preferable for providing large
adsorption capacity, but the creation of a large internal surface area in a
limited volume inevitably gives rise to large numbers of small sized pores
between adsorption surfaces. The size of micropore determines the
accessibility of adsorbate molecules to the adsorption surface so the pore
size distribution of micropore is another important property for
characterizing adsorptivity of adsorbents.
Also some adsorbents have larger pores in addition to micropores
which result from granulation of fine powders or fine crystals into pellets
or originate in the texture of raw materials. These pores called
macropores are several micrometers in size. Macropores function as
diffusion paths of adsorbate molecules from outside the granule to the
micropores in fine powders and crystals. Adsorbents containing
macropores and micropores are often said to have "bidispersed" pore
structures.
Activated Carbon
Act~vated carbons are the microporous carbonaceous adsorbents
whose history can be traced back to 1600 B.C. when wood chars were
used for medicinal purposes in Egypt. In Japan, a well for underground
water equlpped with a charcoal filter at the bottom was found at an old
shrine (Kashiwara Jingu, Nara) constructed in the 13th century A. D. In
Europe, wood char and later bone char were used for refining beet
sugar, a practice started in France because of the blockade against the
Continent during the Napoleonic era. In the 20th century, during the
World Wars, the need to develop gas masks stimulated rapid growth In
adsorption research. Many books have been published on activated
carbon and ~ tasp plications (Araki, 1932; Bailleul et at!, 1962; Hassler,
1974; Mantell, 1951; Mattson and Mark, 1971; Tanso Zairyo-Gakkai,
1975.