Abstract
Absorption is a process in which a substance
(solute) is brought into contact with a solvent normally for a
purpose of separation, which can be either physical or
chemical. pH and concentration of the solvent, temperature of
both the gas and the solvent, and absorbing surface area
influence the absorption process. pH affect the absorption rate
and if an acid or base is added into the system the absorption
rate is lowered. Concentration of carbon dioxide in the gas
stream and the loading rate influence the rate of absorption.
MEA has an optimum absorption rate at liquid temperature of
35 °C. Ammonia has high removal efficiency at ambient
temperature and there exists a direct relationship between
absorption rate and temperature. Absorption of CO2 with
sodium hydroxide is normally done at a temperature range of -
1-16 °C (30-60 °F). Calcium oxide requires high temperature
for absorption ranging from 300-390 °C, while 22-80 °C is used
for H2S absorption with K2CO3. A linear increase results from
heating the CO2 gas stream prior to absorption. The rate of
absorption is influenced by the contact area between the
absorbing fluid and the gas.