Handbook of Solvents - George Wypych - ChemTech - Ventech!

22.3 Solvent treatment in a paints and coating plant 1557
Figure 22.3.2. Solvent circuit and treatment.
tomer’s contaminated spent solvents are poured in
through a large sieve by means of a drum tilting device.
Twin diaphragm pumps then convey the contaminated
solvent to the first soiled solvent tank. In
view of the large proportion of paint in the solvent
(5-20 vol.%), the solvent is kept homogeneously in
motion in the tank by means of the stirrer. Another
soiled solvent tank is connected up to the wash circuit
and supplies the solvent for pre-washing.
The ASC-200 model used by Kabe operates entirely
under vacuum. A considerable increase in capacity
is achieved by means of the vacuum
equipment; moreover, distillation is milder and residue
is largely solvent free.
The contaminated product is introduced automatically
by suction into the evaporator by means of
a magnetic valve and the vacuum until it reaches the
height of a capacitive level controller, which keeps
the solvent level constant during continuous opera-
Figure 22.3.3. Wash plant for mixing vessels.
tion. The filling operation is adjusted in such a way
that no excessive cooling or interruption in the distillation process takes place.
The solvent is usually heated by means of a double jacket with its own thermal oil facility.
Kabe, on the other hand, operates a catalytic waste air purification plant. The solvent-air
mixture obtained in the plant is converted catalytically to heat and stored as an
energy store. A small portion of the heat thereby obtained is absorbed in our case by a thermal
oil system and released to the distillation plant.
A stirrer is fitted inside the ASC-200 distillation plant. Its scrapers rotate inside the inner
wall of the vessel. They keep the heat transfer surface free from encrustation and guarantee
uniform heat transfer into the boiling solvent. The stirrer keeps the liquid in motion