Experimental

Samples of medium- and high-softening-point coal-tar pitches were used under laboratory conditions. The elemental composition and technical characteristics of the pitches are presented in Table 1. Samples of industrial 'dry' anode pastes were used which contained petroleum coke calcined at 1,200°C and 30.5 wt.% MP or 27 wt.% HP. Studhole anode paste was also used, which contained 37 wt.% MP or HP (APMP and APHP).

The experimental techniques for simulating the formation of slow (1°/min) and rapid (70°/min) carbonisation were described by Koptyug et al. (1997) and Anshits et al. (2001). Extraction of industrial dust and carbon residues was described by Kurteeva et al. (2002). Analysis of PAHs in pyrolysis tars and extracts was carried out using the U.S. EPA method number 610, using a micro-capillary quartz column with an SE-54 immobilized silicone phase (12 m x 0.2 mm x 0.3 ^m). The overall content of anthracene and phenanthrene (A+Ph) was determined, as well as the contents of the following individual PAHs: fluoranthene (Fl), pyrene (Py), benz(a)anthracene (BaA), chrysene (Chr), benz(b)fluoranthene (BbF), benz(e)pyrene (BeP), benz(a)pyrene (BaP), dibenz(ah)anthracene (DBA), benz(ghi)perilene (BP). The sum of the PAHs (ZPAH) was determined as a summary content of A+P and 9 individual PAHs.

Table 1. The elemental composition and technical characteristics of the studied pitches.

Parameter

High-softening-point pitch

Medium-softening-point pitch

Softening point, °C

110-113 (Metler)

75-77 (ring-rod)

Content, wt.%:

Insoluble matter:

In toluene

25.6-26.4

26.0-28.0

In quinoline

6.0-7.0

10.0-13.8

Volatiles

56

55-58

Ash

0.16-0.20

0.10-0.20

Content, wt.%:

C

92.46-93.01

91.66-92.48

H

4.00-4.40

3.90-4.10

N

1.00-1.08

1.52-1.75

S

0.27-0.36

0.16-1.27

O (determined by

1.44-1.78

1.46-1.76

difference)

C/H

1.75-1.94

1.80-1.88

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