Influence of air-blowing conditions on the properties of pitches and microstructure of pitch cokes

Abstract

The influence of the raw materials and the conditions of air-blowing on the properties of the airblown pitches (ABP) produced and the microstructure of the corresponding pitch cokes is investigated. In the production of ABP, variation in the temperature (270–390°C) and duration (1–14 h) of air-blowing and the air flow rate (0–100 L/(kg h)) is investigated. The initial materials considered are coal tar pitch (CTP) and a mixture of CTP with the anthracene fraction from coal tar. The samples of ABP are characterized by a softening point of 87–239°C and contain 27.3–67.7% of the toluene insolubles and 8.8–58.2% of the quinoline insolubles. Although most of the pitch samples obtained exhibit a relatively high degree of condensation, they do not yield coke with uniform isotropic microstructure for the production of high-quality strong and dense structural graphite. The mean microstructure score of the coke obtained is 2.7–4.2; anisotropic structural elements predominate (with scores of 4 and 5); and numerous shrinkage cracks, pores, and other structural defects are observed. Since it is impossible to obtain satisfactory isotropic coke by the air-blowing of CTP, new methods of modifying carbon-bearing materials so as to obtain coke with uniform and isotropic microstructure must be developed.