Tube Bomb Research Articles

Formation scheme of needle coke from FCC-decant oil

The carbonization process of FCC-decant oil in a tube bomb has been studied by sequential observation of carbons produced at different carbonization times and pressures to establish the carbonization scheme, leading to a needle coke. The amount of gas evolution was also followed during carbonization. The formation of anisotropic spheres was followed by their growth, coalescence, and precipitation to form bulk mesophase first at the bottom of bomb and gradually to the whole region. The bulk mesophase was rearranged into the flow texture parallel to the bomb axis by the gas evolution just at the solidification of the mesophase into a solid lump of needle coke. This timing was strongly influenced by the carbonization pressure to control the extent of orientation in the resultant coke. Only a range of pressure (around 16 kg/cm 2) could provide an excellent flow texture in the coke of the lowest coefficient of thermal expansion at 500°C. Such a scheme provides the three-dimensional structure of a lump of coke that may define its structural change at the calcination stage and its properties.

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.

Evaluation of several petroleum residues as the needle coke feedstock using a tube bomb

Nine feedstocks were carbonized at 500°C for 4 h in a tube bomb into lump cokes which can be evaluated in terms of their optical anisotropy, CTE and bulk density. The properties of some cokes were found comparable to those of commercial ones. Variable carbonization pressure allows more precise evaluation of feedstocks, since higher pressure was generally preferable for the production of better needle coke. The participation of the lighter fraction which is more emphasized under higher pressure is suggested to be very critical for the formation of needle coke. The reactivity of the feedstock measured by the coke formation in the carbonization for 1 h appears to reflect the quality of the resultant coke. The most reactive fraction may form the porous coke in the initial stage of the carbonization, separating from the matrix which can mediate the carbonization reaction.

Semi-quantitative correlation between optical anisotropy and CTE of needle-like coke grains

Anisotropic development in 9 lumps of needle-like cokes produced in the tube bomb was quantitatively evaluated to correlate it to the CTE of the coke. Distribution of anisotropic units classified according to their size and shape is not enough for quantitative correlation. Since the isochromatic unit is recognized as a vector, its length or component to the CTE axis is measured. The average of the latter values was found to be linearly correlated to the CTE value as for all cokes examined except for one from Taching VR. The last coke showed a skin-core distribution of the vectors in the lump, while other cokes showed very homogeneous development of anisotropic textures.

Carbonization in a tube bomb. 1. Carbonization of petroleum residue into a lump of needle coke

Etude de la formation de coke aciculaire par carbonisation de residus petroliers. Influence de la vitesse de chauffage et de la pression sur les caracteristiques du coke produit