A combined vacuum and temperature swing adsorption process for the recovery of amine from foundry air

The removal and recovery of an amine from waste air of a foundry by adsorption is discussed on the basis of experiments and simulation studies. The results show that activated carbons as well as a hydrophobic Y-zeolite are well suited for the purification. Since parts of the amine are chemically bound to the adsorbents, a decrease in adsorption capacity is found for both adsorbents after the first cycles. For the desorption and recovery, a combined vacuum and temperature swing (VTSA) technique is used. To achieve a sufficient degree of regeneration without using too low pressures, a small amount of purge gas is added during the vacuum desorption. This allows the condensation to be performed at an ambient temperature (10–20°C). In experiments with a single adsorption column as well as in cyclic experiments with a three column setup it was shown that more than 95% of the continuously fed amine can be removed and recovered from the waste air. The further purification down to the required clean gas concentration has to be done in a second purification step, e.g. a bio-filter.