Adsorptive exhaust air cleaning (ZAR) with
small RTO
Process
The absorption rotor is an integrated system for air pollution
control. By means of the absorbing properties of the zeolith,
this system removes VOCs from exhaust air capturing them inside
the honeycomb structure.
The exhaust air leaving the rotor has a low concentration
of VOCs and is conveyed directly to the clean air stack. Part
of this air is then heated up and used for purging the rotor
itself from the adsorbed VOC. The purging air, with high VOC
concentration, is then conveyed to an oxidizing system (RTO).
The ZAR is a dynamic system: the absorbing zeolith is inserted
in a wheel, continuously and slowly rotating. The wheel has
three sections: adsorption, cooling, desorption. Each section
is separated from one to the other and perfect tight. The
exhaust air passes mainly the adsorbing section where the
VOCs are adsorbed by the zeolith. Part of the exhaust air
(5 % to 10 % depending on the process conditions) is conveyed
through the cooling section. This same air is then heated
up and conveyed back to the desorption section for purging
the rotor from VOCs.
Thus the rotor concentrator continuously passes throughout
the three sections, with continuous cycles of adsorbing and
purging.
The main advantages of this system are the reduction of energy
consumptions for large exhaust air quantities having low solvent
concentration:
The exhaust air flow to be oxidized is reduced (gas consumption
reduction)
The VOCs concentration is increased leading to almost
autothermal operation of the oxidizing system
(gas consumption reduction).
Most of the exhaust air passes only through the rotor
concentrator with very low pressure drop
compared to a post- combustion system (Energy consumption
reduction)
Gas cost are only necessary for heating up of the post
combustion system (Monday in the morning,
or, if lower exhaust air concentrations are coming).
The overall dimensions of the complete plant (ZAR + RTO)
are lower (installation cost reduction).
