Pitch coke

Pitch. The principal outlet for coal-tar pitch is as the binder for the electrodes used in aluminum smelting. These are of two types. Older plants employ Sn derberg furnaces, which incorporate paste electrodes consisting of a mixture of about 70% graded petroleum coke or pitch coke and 30% of a medium-hard coke-oven pitch. This paste is added periodically to the top of the monolithic electrode as it is consumed. The more modem smelters employ prebaked electrodes requiring less binder, about 18%. 

Pitch Coke. The manufacture of pitch coke provides a large toimage oudet for coke-oven pitch in Japan, the CIS and, until more recently, Germany (75,76). Pitch coke is used either alone or mixed with petroleum coke as the carbon component of electrodes, carbon bmshes, and shaped carbon and graphite articles. 

In the CIS pitch coke is made by carbonizing a hard coke-oven pitch in modified coke ovens. The hard pitch has an R-and-B softening point of 140—150°C and is made by air-blowing a mixture of medium-soft pitch and recycled coking oils. This feedstock is charged in the molten state over a period of 5 h and coked for 17—18 h at 1250—1300°C. The coke yield is 70%. Oils, which are recycled, amount to 20% by weight of the pitch fed. The gas yield... 

Coal-Tar Pitch Coke. Coal-tar pitch is used to produce needle coke primarily in Japan. Processes for producing needle coke from pitch have also been developed in Germany (4). The key to producing needle coke from coal tar or coal-tar pitch is the removal of the high concentrations of infusible sohds, or material insoluble in quinoline (QI), which are present in the original tar. The QI inhibits the growth of mesophase and results in an isotropic, high CTE coke from coal-tar pitch. After removal of the QI, very anisotropic and low CTE cokes are obtained from coal-tar-based materials. 

Graphitization. Graphitization is an electrical heat treatment of the product to ca 3000°C. The purpose of this step is to cause the carbon atoms in the petroleum coke filler and pitch coke binder to orient into the graphite lattice configuration. This ordering process produces graphite with intermetaHic properties that make it useful in many appHcations. 

Carbon black from oil is the main competition for the product from coal, which is used in filters. Carbon for electrodes is primarily made from petroleum coke, although pitch coke is used in Germany for this product. The pitch binder used for electrodes and other carbon products is almost always a selected coal tar pitch. 

Coke (coal tar), high temperature pitch Coke (coal tar), mixed coal-high temperature pitch Coke (coal tar), low temperature, high temperature pitch Diaminotoluene o-Dianisidine Salts of o-dianisidine o-Dianisidine-based azodyes Diarsenic trioxide Diazomethane Dibenz(a,/i)anthracene 1,2-Dibromo-3-chloropropane... 

Coke materials are generally made by heat-treatment of petroleum pitch or coal-tar pitch in an N2 atmosphere. Coke made from petroleum is called "petroleum coke" and that from coal is called "pitch coke". These materials have the closest-packed hexagonal structures. The crystallinity of coke materials is not so high as that of graphite. The crystallite size of coke along the c-axis (Lc) is small (about 10-20 A) and the interlayer distance (d value about 3.38-3.80 A) is large. 

Pitch Coke and Petroleum Coke Pitch coke is made from coal-tar pitch, and petroleum coke is made from petroleum residues from petroleum refining. Pitch coke has about 1.0 percent volatile matter, 1.0 percent ash, and less than 0.5 percent sulfur on the as-received basis. There are two kinds of petroleum coke delayed coke and fluid coke. Delayed coke is produced by heating a gas oil or heavier feedstock to... 

Under the optical microscope the texture of products derived from the three coals studied show an anisotropy of the type which already has been described for similar materials (I, 4, 9). The texture of the l.t. pitch coke is entirely isotropic, whereas the h.t. pitch coke is characterized by a pronounced anisotropy in bands. The anisotropy of the carbonization products of mixtures of l.t. and h.t. pitches varies linearly as a function of the composition of the mixture (8). 

Figure 1. Pitch coke 500°C., 75% l.t., optical microscopy by reflection on block from microtome X 900 photomontage (a) polarized light without analyzer (b) optical photos taken between crossed nicols...

Figure 2. Pitch coke 500°C75% l.telectron micros-copy on a section from the block observed by optical microscopy X 1800 photomontage (a) in bright field (b) in dark field...

Ralph J. Gray. Dr. Taylor states that the transformation of plastic vitrinite or coal-tar pitch into low temperature coke has some of the characteristics of a crystallization process. The authors place much emphasis on the development of spherical bodies in lx>th vitrinite and pitch. My question concerns the type of pitch, the method of its production, and the method of pitch coke production. 

It is my contention that the optical and physical properties and the optical structure produced during the destructive distillation or thermal decomposition of vitrinite is closely related to mode of carbonization and, in the case of pitch, is intimately related to the method of pitch preparation. For instance, a pitch may be produced from a high or low temperature tar, from a primary cooler tar, or from a flushing liquor tar. In addition, it may be air blown, thermally or chemically treated, straight distilled, or cut back, just to mention a few. Under similar carbonization conditions almost any one of these pitches will produce a coke which has certain characteristics that are related to the parent pitch. Even pitches similarly processed from the tar can differ in the content of quinoline- and benzene-insoluble material and P-resin, and can contain more than one distinct liquid phase. None of these points of difference has been discussed by Dr. Taylor or even recognized in the preparation. To interpret the structure of pitch coke divorced from a knowledge of the pitch source and/or carbonization conditions can lead to erroneous conclusions. These are pertinent data omitted by the authors. 

Carbon pitch is used for carbon electrodes in electrolytic reduction processes, such as aluminum reduction or the production of electro-steels in arc furnaces. Refractory pitch is used in the manufacture of refractory brick, usually burned magnesite or dolomite, the pores of which are filled with pitch by hot impregnation. Upon firing, the pitch in the brick is converted to carbon by carbonization. The remaining pitch coke within the refractory product retards penetration of molten metals and slags, thus prolonging the life of the brick furnace lining. Coke pitch is used in the production of foundry cores. 

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