Light olefins and paraffins are commonly separated by cryogenic
distillation. A process based
upon reversible chemical complexation, which employs a mass-separating
agent rather than an
energy-separating agent, presents an attractive alternative to
distillation. Use of such a
facilitated-transport-assisted process could substantially reduce the
capital costs and energy
requirements of olefin/paraffin separations. Copper(I) and
silver(I) have long been known to
form electron donor/acceptor complexes with olefins. Several
chemical systems using these
transition metals as the selective separating agent have been studied.
A review of copper- and
silver-based complexing solutions for olefin/paraffin separations via
gas/liquid contacting is
presented.
The mass-transfer area of nine structured packings was measured in a 0.427 m ID column via absorption of CO 2 from air into 0.1 kmol/m 3 NaOH. The mass-transfer area was most strongly related to the specific area (125-500 m Áh). Surface tension (30-72 mN/m) had a weaker but significant effect. Gas velocity (0.6-2.3 m/s), liquid viscosity (1-15 mPaÁs), and flow channel configuration had essentially no impact on the mass-transfer area. Surface texture (embossing) increased the effective area by 10% at most. The ratio of mass-transfer area to specific area (a e /a p ) was correlated within the limits of AE13% for the entire experimental database a e a p ¼ 1:34
This review paper describes systems used to cultivate microalgae for biofuel production. It addresses general design considerations pertaining to reactors that use natural light and photosynthetic growth mechanisms, with an emphasis on large-scale reactors. Important design aspects include lighting, mixing, water consumption, CO 2 consumption, O 2 removal, nutrient supply, temperature, and pH. Though open pond reactors are the most affordable option, they provide insufficient control of nearly all growth conditions. In contrast, a variety of closed reactors offer substantial control, but few feature the likelihood for levels of productivity that offset their high cost. One of the greatest challenges of closed photobioreactor design is how to increase reactor size in order to benefit from economy of scale and produce meaningful quantities of biofuel. This paper also highlights the concept of combining open and closed systems and concludes with a discussion regarding a possible optimal reactor configuration.
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