2007_6_Nr6_EEMJ

Lazar et al. /Environmental Engineering and Management Journal 6 (2007), 6, 529-535
Treatment methods are grouped in two
categories: non-destructive (condensation, adsorption,
membrane separation) or destructive (thermal
incinerators, catalytic incinerators, catalytic photodegradation,
and bio-degradation. The nondestructive
techniques allow the recovery of the
solvents for their use as raw material, while the
destructive techniques are utilized for oxidative
treatment of VOC emissions, with recovery of the
heat resulted in the process (EPA, 1995; Dumitriu and
Hulea, 1999). Selection of a certain treatment method
is done considering: the process that generates
pollutant emissions with VOC, the nature and flow of
the emission, the minimum, average and maximum
concentrations of VOC, the costs etc. These criteria
involve a good management of the solvents within the
technological phases of the activities that lead to
VOC emissions (EPA, 1995; Lazaroiu, 2000).
4. The mass balance of the solvents in a plant for
surfaces degreasing
4.1. Solvents management
Within a technological process for surface
covering with decorative-protective purposes, a stage
for chemical degreasing in organic solvents is
foreseen aiming at partially removal of the animal and
soluble vegetal fats. Usually, degreasing occurs in a
cave with a parallelepiped shape, containing a
covering device and manufactured by materials
resistant to the action of the solvents.
Due to degreasing of the metallic surfaces in
organic solvents, result VOC emissions that should be
controlled such as the emission limit value,
concordant to the solvent consumption threshold, not
to be exceeded. The control of these emissions
involves a good management of the solvents,
consisting in establishment of the mass balance for
the degreasing industrial activity. The solvent
consumption for a range of 12 months is determined
through the mass balance, and the proof of fulfilling
certain requirements regarding the limit value of
fugitive and total emissions, respective, in accordance
to the regulation is achieved (Table 1).
For the accomplishment of the solvents mass
balance, all the input and output flows containing
VOC should be considered. In Fig. 5, the input and
output flows that constitute the basis of the solvents
mass balance are presented (HG 699, 2003).
4.2. Calculus of the solvents mass balance
Taking into account the solvents management
plan and the methodology for calculus of solvents
mass balance (HG 699, 2003), the mass balance for
the cases of four solvents frequently used for
degreasing of metallic surfaces, such as carbon
tetrachloride, ethylene trichloride, acetone, butanol,
toluene, is further presented. Considering the yearly
necessary amounts of solvent ranged between 5 and
15 t/year, in Tables 2 and 3, the solvents consumption
and the mass balance are shown.
Fig. 5. The input and output flows needed for calculus of the solvents mass balance
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