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Engineering Design Methods of Adsorption Systems - nehaa - 08-16-2017 Engineering Design Methods of Adsorption Systems [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. |