Recently, the need to combine the compliance to increasingly
lower emission limit values with cost optimisation requirements
has led to the development of novel solutions. In particular, dry
treatment systems based on double reaction and filtration stages
are an emerging technology, which has been adopted by several
WtE plants in Northern Italy since 2006 (ISPRA, 2013). These
two-stage systems carry out the removal of acid pollutants by
two consecutive steps of neutralisation with alkali compounds
(usually, calcium hydroxide in the 1st stage and sodium bicarbonate
in the 2nd stage) and subsequent filtration for the capture of
the solid residues produced by the reaction.