| dc.description.abstract | Adsorption technologies have been widely used to control the emissions
of volatile organic compounds (VOCs), and it is regarded as an effective way
for VOCs removal. Especially, activated carbon and zeolite are commercially
available for field application. However, they still have some limitations.
Therefore, this study is motivated to improve the performance of adsorption
systems of activated carbon and zeolite. First, methods for inhibiting
butanedione (BDO) formation during activated carbon adsorption-desorption of
methyl ethyl ketone (MEK) were investigated. In total, more than 28 types of
modified activated carbons were extensively examined. The tests included five
types of commercial activated carbons, nine kinds of modifiers, three kinds of
solvents, and a variety of processing time and temperatures. Experimental
results indicated that BDO formation from MEK oxidation could be greatly
inhibited by suitable modifier, high modifier loading, and adopting N2 as
desorption medium. For instance, BDO concentration in the test with raw
activated carbon as adsorbent was 0.123%, and decreased to 0.0115% as
modified activated carbon was applied, indicating that BDO concentration
could be reduced by more than 10 times. Although the capital and running costs
would increase by using modified activated carbon for solvent recovery, the
operational safety can be greatly improved and it is economically feasible. On
the other hand, zeolite adsorption rotor was studied for the enhancement of
mesitylene adsorption. It is found that a rotor with single type of zeolite could
not achieve good removal efficiency due to various VOCs molecular sizes in
the exhausts of spray coating processes. This study hence proposed a possible
engineering solution with the integration of both micropore (H-ZSM-5) and
iii
mesopore (MCM-41) zeolites. Experimental results indicated that the
breakthrough time with H-ZSM-5-25/MCM-41-AS as adsorbent was greatly
extended to 20.5 min. On the other hand, the breakthrough times were 3.5 and
6.5 min, respectively, when H-ZSM-5 and MCM-41-AS were applied as
adsorbent, respectively, for the gas stream containing 50 ppm toluene and
mesitylene. Obviously, the breakthrough time of the combined zeolite
developed can increase by 3.2 - 5.9 times if compared with individual zeolite. It
is proved that combined H-ZSM-5-25/MCM-41-AS zeolite as adsorbent is
suitable for simultaneous and effective removal of VOCs from spray coating
exhaust. | en_US |