Carbonization of coal-tar pitch into lump needle coke in a tube bomb

The carbonization of coal-tar pitches and their QI (quinoline insoluble)-free fractions was studied by evaluating their lump cokes produced in a tube bomb at various temperatures (470 to 550° C) and pressures (0 to 75 kg cm^–2 gauge). The lump coke from QI-free fractions had a comparable anisotropic development and coefficient of thermal expansion (CTE). The carbonization temperature and pressure were found to influence strongly the properties of the cokes. At the highest temperature of 550° C, the most appropriate pressure for the best needle coke was 15 kg cm^–2 G (gauge). Either higher or lower pressure increased the CTE value of coke. In contrast, at a moderate temperature of 500° C, the higher pressure produced the better coke. At the lowest temperature of 470° C, it took 10 h to complete the carbonization, and the lowest pressure allowed the best extent of uniaxial arrangement. Among the cokes prepared under the present conditions, the Carbonization at 500° C under 40 kg cm^–2 G produced the best needle coke with a CTE value as low as 0.1 × 10^–6° C^–1. The carbonization scheme leading into the needle coke is discussed for a better understanding of how the carbonization temperature and pressure cooperatively influence the quality of the resultant coke, in relation to the carbonization reactivity of coal-tar pitch.     

Predicting the strength reduction of particleboard subjected to various climatic conditions in Japan using artificial neural networks

Particleboard specimens were subjected to various climatic conditions in Japan, and the relationships between climatic factors and internal bond strength (IB) were investigated using multiple regression analysis (MRA) or artificial neural networks (ANN). At low- and middle-temperature sites, the IB predicted using MRA (IB_MRA) and ANN (IB_ANN) decreased linearly with increasing exposure time. In addition, at high-temperature sites, with increasing exposure time, IB_MRA decreased linearly, whereas IB_ANN decreased exponentially. The trend of IB_ANN was almost identical to that of the measured IB of the specimens subjected to various climatic conditions. Moreover, IB_MRA and IB_ANN for 1-, 3-, and 5-year exposures were predicted using nationwide climatic factors. The minimum IB is zero when the particleboard is deteriorated; however, negative IB was predicted using MRA when the exposure time increased in the high-temperature area. In addition, the IB for 1-year exposure in the low-temperature area near site 1 was higher than the initial IB of 0.833 MPa. MRA is not always valid because of the assumption of linearity. However, negative IB even for 5-year exposure in the high-temperature area and high IB even for 1-year exposure in the low-temperature area were not predicted using ANN. The IB reduction was predicted correctly using ANN, and the correct IB reduction could be mapped.     

Carbonization of coals to produce anisotropic cokes. 2. Up-grading of modification activities of petroleum process residues and their correlation with structural parameters

Modifying activities of petroleum pitches and up-graded pitches in the co-carbonization with a range of coals have been examined with the object of proposing an effective co-carbonization process for blast-furnace coke production. Up-grading of additives was attempted using thermal, acidic and oxidative reactions. Acidic reactions with aluminium chloride were most effective with lighter petroleum residues of initially poor modifying activity, this being attributed to dealkylation, ring-closure and ring condensation reactions. The relation between modifying activity and structural indices is discussed. The aromaticity (f_a) and the naphthenic ring number in the unit structure T_n,us can be used as appropriate parameters for the activity when the coking yield is taken into account.     

Enhanced reactivity of some lignites by deashing pretreatment in hydrogen-transferring liquefaction under atmospheric pressure

The reactivities of five lignites were studied in the hydrogen-transfer liquefaction process undet atmospheric pressure, using a hydrogenated petroleum pitch (HA240). Although asphaltene yield from Yallourn brown coal was as high as 70%, other lignites showed inferior yields. Pretreatment in boiling 0.4N hydrochloric acid enhanced the liquefaction reactivity significantly to the extent that the asphaltene yield from Berga lignite increased to as much as 70%.     

Carbonization of coals to produce anisotropic cokes: 5. Structural factors of coals influencing carbonization properties

The carbonization properties are studied of two particular coals (Zontag Vlei and Metla coals) which are markedly different despite their similar coalification rank, maceral composition, and oxygen and exinite contents. These coals possess different structural features which influence their carbonization. A demineralizing pretreatment improves the properties of Metla coal. However, this is still inferior to the Zontag Vlei coal. O-alkylation of the Metla coal improves fusibility in single carbonizations and susceptibilities, equalling those of the Zontag Vlei coal. Preheat-treatment differentiates between the coals: Metla coal loses its susceptibility at lower temperatures. The chemical analyses of oxygen functionalities of both the original and preheated coals show that their hydroxyl groups behave differently in carbonizations at lower temperatures, indicating that oxygen functionality may be another influential factor. Hydrogen shuttling within the coal may be a third factor as it may remove the oxygen functionality.     

Carbonization properties of partially hydrogenated aromatic compounds—II: Factors influencing the coke yield in the carbonization of hydrogenated pyrene

Factors influencing the coke yield in the carbonization of hydrogenated pyrenes were investigated from the view of reactivities of their hydrogens. The amount of hydrogen located at 4 ppm in their proton NMR spectrum was found to be intimately related to the coke yield of hydrogenated pyrenes. Oxidative pretreatment at 150°C significantly increased the coke yield. The structural changes of hydrogenated pyrenes by oxidative pretreatment were investigated by means of GPC, IR and NMR. The scheme of oligomerization as the first step of carbonization is discussed in connection with the reactivities of hydrogens in hydrogenated pyrenes.     

A microscopic study on the oxidative stabilization of a coal-tar-based mesophase pitch and its blends with PVC pitch

Coal-tar-based mesophase pitch and its blends with PVC pitch at 5 or 10 wt% were oxidatively stabilized at 230, 270 and 300°C for variable periods to clarify the progress of stabilization and the effects of the blending with PVC pitch on the stabilization reactivity. PVC pitch which was prepared from PVC by heat-treatment at 420°C for 2h enhanced the stabilization reactivity of whole pitch fibres to shorten the stabilization time to a half of that for mesophase pitch alone. PVC pitch carrying considerable amounts of aliphatic components and large molecular weight may initiate, as a trigger, the stabilization reactions of mesophase constituent molecules. Carbonized fibres of 30μm diameter after stabilization at 270 and 300°C exhibited a skin-core structure, while fibres of 10μm diameter showed no skin-core structure, indicating a homogeneous progress of stabilization in the radial direction of the latter fibres. Lower stabilization temperatures provoked no skin-core structure even in the thick fibres. The rate of core diminishing became relatively slower in the later stage of the stabilization, even when the reactivity of the pitch fibres was enhanced by blending with PVC pitch and using a higher stabilization temperature. The diffusion of the oxidant and stabilization reactivity of the pitch fibres are discussed comparatively.