Handbook of Solvents - George Wypych - ChemTech - Ventech!

1214 Margot Scheithauer
An analysis of the activity requires data on solvent consumption as calculated from the
amount of solvent purchased both as pure solvent and included in solvent containing materials
less the amount of solvent retained and/or contained in waste. The calculated difference
includes all emissions including diffuse emissions such as the solvent loss from drying
racks or solvent initially retained by pained, varnished, printed or dry cleaned articles.
These measurements are essential if the statutes are to be enforced and emissions are to be
effectively reduced.
Emissive limit values are stipulated for plants covered under this directive for exhaust-gases
in mgC/Nm³ as well as limits for diffuse emissions in % solvents input. If these
data are not available, total emission limit values are used.
Definition of “Emission Limit Value”: The “Emission Limit Value” is understood as
the mass of volatile organic compounds, the concentration, the percentage and/or the
amount of emission - ascertained under normal conditions - expressed in certain specific parameters,
which in one or several time periods must not be exceeded
[EU-VOC-Richtlinie]. 1
Plant measurement must be made to provide data for analyzing the actual situation as
well as for being able to prove the emission reduction which business must attain.
18.1.4.2 The determination of the total carbon content in mg C/Nm³
18.1.4.2.1 Flame ionization detector (FID)
The total C/Nm³ is assessed according to the Guideline VDI 3481/page 3 25 by means of a
flame ionization detector (FID). This device is the component of a mobile device for random
sample tests or a continuously measuring device for total carbon concentration measurement
in an exhaust-gas flow. This approach measures the total organic substance in an
exhaust gas. Should the composition of the solvents contained in the exhaust air not be
known, their concentration may be quoted in carbon equivalents as mgC/m³.
Measuring principle:
An FID detects ionized organically compounded C atoms in a hydrogen flame. The
ion flow developed in the induced electrical field is electrically amplified and measured.
The ion flow arising when burning carbon compounds is proportional to the mass of carbon
atoms exposed to the flame per time unit.
The detection of organic compounds with heteroatoms, e.g., N, O, S, Cl, is generally
less sensitive. The calibration of the device is done in most cases with propane as the test
gas. Procedural data (measuring ranges, proof limits, etc.) by FIDs of various types are compiled
in a table in the Guidelines VDI. Figure
18.1.2 shows a measuring arrangement
for assessing emissions from a drying plant
by means of an FID.
18.1.4.2.2 Silica gel approach
The determination of the total carbon concentration
in an exhaust gas by means of the
silica gel approach is effected according to
the Guideline VDI 3481, p. 2. 26 A partial
flow of the exhaust air to be tested is guided
through a sorption pipe filled with silica
Figure 18.1.2. Emission measurement by FID.
gel. The organic compounds are absorbed