Incineration, coatings industry, solvent

PCBs are industrial compounds used as industrial, dielectric and heat transfer fluids, organic solvents, flame retardants, plasticizers, sealant and surface coatings. They may also be released to the atmosphere by waste incineration (Fig. 3). The worldwide production of this compound has been 1.3 million tonnes, of which 97% in the northern hemisphere [23]. The amount of chlorine atoms in the biphenyl mixtures is related to the duration and temperature of the chlorination process. The commercial mixtures were distributed under names such as Aroclor (Monsanto, USA) or Clophen (Bayer, EU). The chlorine atoms can substitute the para, meta and/or ortho positions of the biphenyls. There are 209 possible congeners. PCBs can be divided into nine isomeric groups and one decachlorobiphenyl, all with an empirical formula of C Hjo-uCln (n = 1-10) (Fig. 4). 

An example where a mass balance approach would yield inaccurate emissions to the atmosphere would be an industrial resin coating line. This process uses an organic carrier solvent, such as ethanol, which is volatized from the resin solids in a drying oven. The vapors (volatile organic compounds [VOCs]) are then incinerated. The ethanol can be transformed into other organic compounds in the incinerator. The total mass of applied carrier solvent (ethanol) would not be accounted for in the incinerator exhaust gas stream due to its transformation into other organic compounds. 

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