ISSN 1070-4272, Russian Journal of Applied Chemistry, 2017, Vol. 90, No. 1, pp. 34−40. © Pleiades Publishing, Ltd., 2017.
Original Russian Text © V.V. Samonin, A.S. Zotov, E.A. Spiridonova, M.L. Podvyaznikov,
2017, published in Zhurnal Prikladnoi Khimii, 2017, Vol. 90, No. 1, pp. 38−44.
AND ION EXCHANGE PROCESSES
Effect of Gas Environment Parameters on Operation
Efﬁ ciency of Chemical Absorbents of Carbon Dioxide
V. V. Samonin*, A. S. Zotov, E. A. Spiridonova, and M. L. Podvyaznikov
St. Petersburg State Technological Institute (Technical University), Moskovskii pr. 26, St. Petersburg, 190013 Russia
Received December 27, 2016
Abstract—Effect of main characteristics of the gas medium on the absorbing properties of alkaline chemical
absorbents is demonstrated. The following gas ﬂ ow parameters were examined as variables: carbon dioxide
content of the gas ﬂ ow within the range 0.2–5.0 vol %, gas humidity of 25–90 rel %, and pressure in the zone of
the chemisorption process in the range from 2 to 6 MPa. As objects of study served mixed chemical absorbents
based on calcium, sodium, and lithium hydroxides.
The problem of puriﬁ cation of gas environments is
exceedingly important for such human activity ﬁ elds as
development of collective and individual life-support
systems, puriﬁ cation of technological gases in industries,
and production of breathing mixtures. At present, this
problem is solved by using sorption methods with
nonregenerative alkaline absorbents .
Most of materials belonging to this class are based
on oxides and hydroxides of alkali metals owing to their
chemical properties . These compounds enter into the
reaction with carbon dioxide to form metal carbonates.
The characteristic features of the majority of reactions
of this kind are the strong exothermic effect and the
signiﬁ cant inﬂ uence exerted by the content of water on
the reaction rate .
The composition and application method of an
absorbent are chosen in accordance with the conditions
in which a gas puriﬁ cation process is to be performed.
By the conditions are primarily meant the initial and
maximum admissible (breakthrough) concentrations of
carbon dioxide after the absorber layer and the humidity
and temperature of the gas at the adsorber inlet .
When considering the specificity of processes in
which a mixed chemical absorbent interacts with carbon
dioxide, we should note that there exist certain differences
in the nature of reaction between active components and
Calcium hydroxide interacts with carbon dioxide by
the following overall reaction:
This reaction occurs in a liquid ﬁ lm in the interaction
of carbonate ions with calcium ions, and its rate is
correlated with the concentration of Ca
ions. There is no published evidence on whether the
formation of hydroxo complexes can affect the mechanism
and extent of the reaction. The total heat effect of the
reaction is 73.2 kJ mol
, and the stoichiometric capacity
of calcium hydroxide for CO
reaches a value of 0.59 g g
The interaction of lithium hydroxide with carbon
dioxide can be described in the general form by the
2LiOH + CO
Here, the change in the Gibbs free energy, which
characterizes the reaction, is ΔG = –90.8 kJ mol
the stoichiometric capacity for CO
, 0.91 g g
This interaction may occur by two main mechanisms,
directly or via formation of a crystal hydrate. The
interaction of lithium hydroxide with carbon dioxide is
described by the stoichiometric equation
O + СO