Coal semi-coke

The following natural precursors have been selected for KOH activation coal (C), coal semi-coke (CS), pitch semi-coke (PS) and pitch mesophase (PM). An industrial activated carbon (AC) was also used. Activation was performed at 800°C in KOH with 4 1 (C KOH) weight ratio, for 5 hours, followed by a careful washing of the samples with 10% HC1 and distilled water. The activation process supplied highly microporous carbons with BET specific surface areas from 1900 to 3150 m2/g. The BET surface area together with the micro and the total pore volume of the KOH-activated carbons are presented in Table 1. The mean micropore width calculated from the Dubinin equation is designed as LD. 

Materials used in the activation with KOH include high volatile bituminous coal C, coal semi-coke CS, pitch mesophase PM, pitch semicoke PS and commercial activated carbon AC. The semi-cokes CS and PS were produced by the heat treatment of corresponding parent materials at 520°C with a heating rate of 5°C/min and 2 hours soaking time. The preparation of mesophase PM comprised the soaking of coal-tar pitch at 450°C for 7 h with a continuous stirring. All the treatments were performed under argon in a vertical Pyrex retort of 45 mm diameter. 

Varying KOH ratio in the mixture is a very effective way of controlling porosity development in resultant activated carbons. The trend in the pore volume and BET surface area increase seems to be similar for various precursors (Fig. la). It is interesting to note, however, a sharp widening of pores, resulting in clearly mesoporous texture, when a large excess of KOH is used in reaction with coal semi-coke (Fig. lb). Increase in the reaction temperature within 600-900°C results in a strong development... 

Coals mesophase pitch coal chars coal tar pitch carbon mesocarbon microbeads, carbon fibers semi-coke, calcined coke activated carbons premium cokes, carbon fibers, binder and matrix... 

Solid Anthracite coal bituminous coal lignite peat wood Coke charcoal petroleum coke breeze semi-coke (low-temperature coal distillate) pulverized coal... 

Carbonaceous solids appear as a result of retrogressive reactions, in which organic thermal fragments recombine to produce insoluble semi-cokes (59,65). Coke formation is observed during liquefaction of all coals and its extent can vary widely according to the coal, the reaction solvent, and reaction conditions. The predominant inorganic species produced during the process of coal... 

High porosity carbons ranging from typically microporous solids of narrow pore size distribution to materials with over 30% of mesopore contribution were produced by the treatment of various polymeric-type (coal) and carbonaceous (mesophase, semi-cokes, commercial active carbon) precursors with an excess of KOH. The effects related to parent material nature, KOH/precursor ratio and reaction temperature and time on the porosity characteristics and surface chemistry is described. The results are discussed in terms of suitability of produced carbons as an electrode material in electric double-layer capacitors. 

Innovatory boronated carbons (manufactured in the Institute of Chemistry and Technology of Petroleum and Coal, Wroclaw University of Technology, Poland) were obtained by co-pyrolysis of coal-tar pitch with a pyridine-borane complex. In the first stage of pyrolysis (520°C) the so-called semi-coke is obtained. Further carbonization at 2500°C leads to obtaining boron-doped carbonaceous material (sample labeled 25B2). 

Coals coal chars semi-coke, calcined coke activated carbons... 

It can also identify texture of the semi coke formed as illustrated in Figure 6. If a binder is used with a coal, the Plastofrost technique can determine the coal-binder interaction and the texture of coke formed from the binder phase. Although not considered in studies undertaken at Waterloo, the axial location of the thermocouples in the sample holder makes the Plastofrost procedure capable of measuring coal-coke conductivity as a function of coal, temperature and compaction pressure, with just a modest redesign of the heating slab. 

Carbonization of the oxidized Phalen Seam coal at 550°C resulted in a non-agglomerated char. Dilatation and FSI results for this coal are given in Table II and confirm its non-coking character. The semi-coke obtained from dilatation experiments had an isotropic structure, as shown in Figure 1. 

Oxidized Phalen Seam coal hydrogenated at 450°C for 3 hours at different hydrogen pressures gave the dilatation results presented in Table III. Optical micrographs of the semi-cokes obtained from dilatation experiments are shown in Figures 5 to 8. 

A severely weathered bituminous coal from eastern Canada was treated by thermal hydrogenation under various reactor conditions. The coking properties of this coal were found to be restored under appropriate hydrogenation conditions. The semi-coke of the hydrogenated coal exhibited an anisotropic coke structure. The size of the anisotropic domains in the semi-coke was found to depend on reactor temperature and hydrogen pressure during hydrogenation. 

When a coal/blend is coked in slot-type ovens, two principal layers of plastic coal are formed parallel to the oven walls. They are linked near the sole and the top of the charge by two secondary plastic layers forming an envelope of plastic coal. As carbonization proceeds, the plastic layers move progressively inward, eventually meeting at the oven center. It is within these plastic layers that the processes that result in particulate coal being converted into porous, fused semicoke take place. The semi-coke undergoes further devolatization and contracts, which results in fissures in the final coke. 

ISO. 201 Id. Coal and Coke—Determination of Nitrogen, Semi-Micro Method (ISO 333). International Standards Organization, Geneva, Switzerland. 

The pyrolytic conversion of coal into coke, gas and aromatic liquid products is the oldest and, in quantitative terms, most important coal-refining process. In the absence of air, carbonization processes are considered to occur in stages up to 150 °C, carbon dioxide, water and volatile C2 to C4 hydrocarbons are evolved. At pyrolysis temperatures above 180 °C the volatile components also contain aromatics. At temperatures in excess of 350 °C, rapid degasification occurs, which continues to around 550 °C, leading to semi-coke. The rate of degasification approximately follows a reaction of the 1st order, which can be explained by the rupture of the bonds of the macromolecules in the coal. In the secondary degasification of the semi-coke (600 to 800 °C) hydrogen and methane are the main products. 

During the course of the pyrolysis of a petroleum-derived residue (pyrolysis tar, cat-cracker residue) or a filtered coal tar pitch it is possible to observe, under the polarisation microscope and at a certain temperature, the formation of anisotropic spherules, which grow as the reaction time lengthens and the temperature increases, coalesce and, at around 500 to 600 °C, are transformed into a semi-coke phase with marked anisotropy. Figure 13.2 shows photomicrographs of a filtered coal tar pitch pyrolyzed at 400 °C with the formation of spherulitic mesophases after reaction times of 2, 6,10 and 16 hours. 

Coal tar (pitch) is produced hy the carbonization, or coking, of coal. It s a black viscous liquid (or semi-solid), with a naphthalene-like odor (think moth balls), and reportedly a sharp burning taste. It s obtained by the destructive distillation of bituminous coal in coke ovens. One ton of coal yields 8.8 gallons of coal tar. Since it s a mixture, coal tar has a boiling range — typically from 190 to 400°C. 

Andresen, J.M., Martin, Y., Moinelo, S.R., Maroto-Valer, M.M., and Snape, C.E. Solid-state C NMR and high-temperatnre H NMR determination of bulk structural properties for mesophase-containing semi-cokes prepared from coal-tar pitch. Carbon 1998 36(7-8) 1043-1050. 

Figure 6.5.4 Transformation of coal into blast furnace coke in a coking chamber (a) 600-1100°C coke, (b) 450-500°C semi coke, (c) 350-450°C plastic stage, (d) 100-350°C pre-degassed coal, and (e) 0-100°C coal and water. Adapted from Schmidt and Romey (1984).

---