Environmental Engineering Reference
In-Depth Information
In the Selexol™ process the solvent, which consists of a proprietary
mix of dimethyl ethers of polyethylene glycol (DEPG), absorbs CO 2 from
the fl ue gas at a relatively high pressure. Unlike amine-based gas removal,
Selexol™ uses a physical solvent that does not involve internal chemical
reactions between CO 2 and the liquid. One of the main advantages of
Selexol™ is that it does not use any water. The disadvantage, however,
is that the solvents used have higher viscosities than water, and thus
require more energy to be pumped around, have reduced mass transfer
rates and tray effi ciencies, and increased packing or tray requirements.
Rectisol® is another commercial process that just uses methanol as
the solvent. Methanol binds CO 2 suffi ciently well, but the entire system
must be run at very low temperatures (between -40ºC and -62ºC), which
necessitates expensive stainless steel refrigerated vessels.
Most of these processes were developed in the context of cleaning
natural gas, and were later adopted for fl ue gasses. Much of the current
research is focussed on developing novel solvents or processes to
reduce the costs associated with carbon capture from fl ue gasses. One
such solvent is KS-1™, a sterically hindered amine that was developed
jointly by the Kansai Electric Power Company (KEPCO) and Mitsubishi
Heavy Industry (MHI). KEPCO and MHI report that the regeneration
energy required for KS-1™ solvents is less than that for MEA. KS-1™
solvent has been used commercially since 1999 at a steam reforming
power plant at Kedah Danul Aman in Malaysia, where the process cap-
tures 160 tonnes of CO 2 per day [5.12].
Section 4
Beyond equilibrium
thermodynamics
Up to this point, we have looked at solvents from a purely thermodynamic
point of view. Thermodynamics tells us all about the equilibrium situation.
In practice, however, a reaction never reaches true equilibrium in the froth
Search WWH ::




Custom Search