Effect of parent coal rank on the yield and properties of carbonization extracts

The paper describes the study of carbonization of solvent extracts derived from coals of different rank. The solvent was hydrogenated anthacene oil. The characteristics of the parent coals and of their extracts are presented here as well as the mass balance from carbonization of each extract at a final heat-treatment temperature of 803 K, the physicochemical and structural analysis of the cokes obtained, and the chemical analysis of the liquid and gaseous products. The experiments showed that the properties of the carbonization products significantly depend on the physicochemical properties of the parent extracts. Parent coal rank had a slight effect on carbonization yields from extracts, but markedly influences the structure and texture of the solid carbonization products.     

煤种及炭化条件对活性焦表面化学性质的影响

在不同煤种及炭化条件下,于一间歇流化床上制备活性焦(AC)。使用XPS等分析手段考察不同制备条件下制得的活性焦表面化学性质的差异。研究结果表明,煤种不同制得的活性焦的表面性质相差较大;炭化条件(炭化温度400—800℃、炭化时间0—60min)对最终制得的彬县煤活性焦表面化学性质影响很小。     

Carbonization of petroleum binders. 2. Oils from carbonization of petroleum binders

Changes of composition, structure, and contents of some functional groups, of oils from petroleum binders, in relation to temperature of carbonization from about 710 K to 1200 K have been investigated. Oils from carbonization of petroleum binders are of hydrocarbon type, and their elemental compositions are almost independent of carbonization temperature. During the thermal decomposition of these binders, about 75–80 wt % of gaseous and vapour products are emitted. As carbonization temperature increases, molecular weights of the oils increase from about 250 to about 290; their density, index of refraction, and molar refraction increase. Structural analysis of the oils showed that they contained about 30% of cyclic hydrocarbons (aromatic and cycloalkane) as well as alkanes. The number of rings in the average structural unit of oil increases with increase of carbonization temperature, especially the number of aromatic rings. About 60–70 vol % distills before 633 K under atmospheric pressure; the distillate is paraffinic, while the residue after distillation is aromatic-alicyclic. Oils from carbonization of P-70 asphalt have similar compositions and chemical natures, but lower molecular weights, than oils from carbonization of residues after vacuum distillation of crude oil. Oils from carbonization of pitch are decidedly aromatic.     

Gasification studies of cokes from coals. The effects of carbonization pressure on optical texture and porosity

Ten coals were carbonized under various pressures (4 kPa, normal pressure and 10 MPa). Optical textures and physical structures of resultant cokes were monitored. The extent of optical anisotropy increased greatly with increasing carbonization pressure, such a trend being more pronounced with the lower-rank coals. Physical structure was also influenced by carbonization pressure. Gasification reactivities of the cokes with carbon dioxide and steam (1200 °C) were studied with respect to their optical anisotropy and physical structure. Gasification reactivities of optical textures were estimated using both the point-counting technique and regression analysis. The reactivities of cokes with the same optical texture produced from the same parent coal were similar. However, there were considerable differences when compared with cokes from different parent coals. Although the values estimated by regression analyses are consistent with those obtained by point-counting, except for the leaflet and inert textures, the physical locations of respective textures can be important in quantitative discussions of their reactivities.     

Carbonization of aromatic hydrocarbons—VI: Carbonization of heterocyclic compounds catalyzed by aluminum chloride

Carbonization properties of heterocyclic compounds were studied in the presence of aluminum chloride to observe the effects of carbonization reactivity difference due to the kinds of heteroatoms and the ring structures on the structural properties of the carbon. The amount of catalyst was shown to have a significant influence on the properties of cokes. Some of the heterocyclic compounds gave graphitizable needle cokes with a suitable amount of the catalyst, some gave graphitizable mosaic cokes and the others gave non-graphitizable isotropic cokes. The tendency to give a graphitizable needle coke decreased in the order of sulfur, nitrogen and oxygen as for the heteroatom, and did in fluorene, anthracene and phenanthrene types as for the ring structure. Such a tendency is compared with that observed in carbonization under high pressure. A large part of sulfur and nitrogen atoms was left in the coke after carbonization, and no correlation was observed between the remaining amount and the structure of the coke.     

Bonding of solid additives in cokes from coals: a microscopy study

Cortonwood Silkstone (NCB class 401) and Betteshanger (NCB class 301 a/204) coals were co-carbonized with solid additives such as anthracite, coke breeze, green and calcined petroleum cokes. The resultant carbonization products (cokes) were examined by optical microscopy and SEM was used to investigate polished surfaces etched by chromic acid and fracture surfaces. For both coals only the anthracite and green petroleum coke become bonded to the coal cokes. This probably results from softening and interaction of interfaces of the anthracite and green coke with the fluid coal via a mechanism of hydrogenating solvolysis during the carbonization process. The coke breeze and calcined petroleum cokes were interlocked into the matrix of coal coke.     

Carbonization and liquid-crystal (mesophase) development. 18. carbonization of coal-extract solutions (non-hydrogenated): influence of digestion conditions upon optical texture of cokes

Coal-extract solutions have been produced by the dissolution of a prime coking coal in anthracene oil followed by the removal of the undissolved solids. A range of coal-extract solutions prepared under different conditions was carbonized and the optical texture of the polished surfaces of the resultant cokes were assessed. The coal-extract solution prepared with the longest digestion time and at the highest temperature produced a coke with the largest anisotropic domains with some flow structure. Removal of the anthracene oil component of the coal-extract solution by extraction with selected solvents modified the carbonization behaviour such that although the coke yield increased substantially there was a significant decrease in the size of the anisotropic domains of the resultant cokes.     

Characterization of carbonization reaction of petroleum residues by means of high-temperature ESR and transferable hydrogen

An attempt has been made to characterize the carbonization reaction of petroleum residues through measurements of high temperature ESR, hydrogen donor ability and optical texture of resultant cokes. Good correlations were found between hydrogen donor ability and change in spin concentration. Residues forming cokes with large sizes of optical texture have a high ability as a hydrogen donor and show a low spin concentration at high temperatures. Similar results were obtained also for some model compounds. A model for the mechanism of carbonization is proposed on the basis of these observations.     

Carbonization and liquid-crystal (mesophase) development. 17. Co-carbonization of a solvent-refined coal with petroleum pitches and hydrogenated coal-extract solution

This study characterizes the optical textures of cokes prepared by the carbonization of Ashland petroleum pitches, of non-hydrogenated and hydrogenated coal-extract solutions (CES) and of blends of non-hydrogenated CES materials with the petroleum pitches and hydrogenated CES materials. At an HTT of 823 K petroleum pitches produce cokes with large sized optical texture of flow-type anisotropy characteristic of needle-cokes. The non-hydrogenated CES materials produce cokes with optical textures of mozaics, 2–10 μm. However, following hydrogenation the CES materials carbonized to cokes all of which possess considerable large sized optical textures which for some materials resemble that of needle-cokes by possessing strong flow-type anisotropy, > 100 μm. Hydrogenation of the CES materials evidently facilitates the physical and chemical requirements for growth and coalescence of lamellar nematic liquid-crystals and mesophase from the fluid phase of carbonization leading to anisotropic carbon. Co-carbonizations of the non-hydrogenated and hydrogenated CES materials exhibit the dominant partner effect and are comparable in behaviour with Ashland petroleum pitches which are known to produce needle-cokes on carbonization.     

Carbonization of polycyclic aromatics. 1. Carbonization of anthracene in carbon tetrachloride

Carbonization of anthracene in carbon tetrachloride has been investigated in the temperature range from 200 to 500 °C using a batch autoclave. Anthracene reacted with carbon tetrachloride above 200 °C and the main products were carbonaceous substances, methane, and hydrogen chloride. The benzene-insoluble carbonaceous substances contained chlorine atoms transferred from the carbon tetrachloride molecule. The reaction was considered to be induced by radicals derived from dissociation of the carbon tetrachloride molecule. The development of an anisotropic structure was observed even in the products prepared at 240 °C for 8 h. Around 400 °C a small amount, and around 250 °C a large amount, of carbon tetrachloride promoted the development of anisotropic structure. The graphitizability of the carbonaceous product paralleled the development of anisotropy. The yields of the cokes, their elemental composition and their anisotropic structure were examined in relation to reaction conditions such as temperature, time and the ratio of carbon tetrachloride to anthracene.     

Hydrogen donor and acceptor abilities of pitch: 1H n.m.r. study of hydrogen transfer to anthracene

Petroleum pitches, coal-extract solutions and hydrogenated coal-extract solutions are co-carbonized with anthracene at 673 K. Chloroform-soluble fractions of the system are monitored by ¹H n.m.r. for formation of 9.10 dihydroanthracene (DHA). A hydrogenated coal-extract solution is also co-carbonized at 673 K with anthracene together with thianthrene and sulphur. Ashland A240 petroleum pitch and anthracene are co-carbonized with hydrogenated anthracene oil and resultant ¹H n.m.r. spectra are analysed for DHA. The pitches and coal-extract solutions are carbonized to 823 K and the optical textures of resultant cokes are assessed by optical microscopy. The purpose of the study is to assess if pitches which form cokes with larger optical textures or have greater abilities to modify the carbonization behaviour of coals also have the ability to act as ‘hydrogen shuttles’ in the carbonization system. Results would indicate that such pitches produce the largest amounts of DHA. It is proposed that the most efficient of the modifying pitches operate by extending the zone of temperature of maximum fluidity and by increasing the value of maximum fluidity by removal by proton transfer of radicals which if left in the carbonizing system would interact to form cokes of smaller optical texture.     

Co-carbonization of hard coals and coal extracts 2. The co-carbonization of medium- and high-rank coals with extracts

Studies on the influence of anthracene coal extracts on the carbonization process of medium- and high-rank coals were undertaken. Extracts from flame coal (Int. Class. 900) and gas-coking coal (Int. Class. 632) were used as additives. The blends prepared from the examined coals and the extracts exhibited better coking properties than the parent coals. The addition of extract to the coals gave an increase in the microstrength of the resultant cokes. The effects of co-carbonization of coking coals with extracts were increases in the size of the optical texture as well as in the degree of structural ordering of cokes. In the co-carbonization of semicoking coal with addition of coal extracts, a reduction in the size of the anisotropic units and a decrease in the crystallite height of cokes were observed. No modification of the basic anisotropy of coke from anthracite by coal extract was observed. With increasing extract content in anthracite/extract blends there was an increase in the degree of structural ordering of co-carbonization products. Extract addition was unable to modify the behaviour of fusinite. Based on the results of investigation of the influence of coal extracts on the carbonization of different-rank coals, a division of coals according to the modification of the optical texture of coke is given.     

Carbonization and liquid-crystal (mesophase) development. 7. Optical textures of cokes from acenaphthylene and decacyclene

Optical textures of cokes prepared by carbonizing acenaphthylene, decacyclene and mixtures thereof at selected values of heat-treatment temperatures and soak time have been compared. Optical textures are assessed using polished surfaces and reflected-polarized-light microscopy in conjunction with a half-wave plate. The acenaphthylene is chemically more reactive than the decacyclene which is itself formed during the carbonization of acenaphthylene. Products of carbonization of acenaphthylene can influence rates of carbonization of the decacyclene. Similar optical textures in cokes cannot be formed by compensating low heat-treatment temperatures with long soak periods. In addition to chemical rate-controlling processes, the physical properties of the system must be acknowledged, in particular the viscosity. Very large non-coalesced growth units of mesophase (800 μm diameter) have been observed. Pre-alignment of growth units of mesophase may occur prior to coalescence.     

Development of optical anisotropy in vitrains during carbonization

The purpose of this work was to examine the possible significance in the formation of metallurgical coke of the anisotropic spherical mesophase exemplified by that found during the carbonization of pitch-like materials, and to ascertain if the various types of optical anisotropy found in coke could form a basis for the characterization of cokes produced from different coals. Vitrains from a wide range of coals were carbonized at temperatures from 370 to 1000 °C and the types and amounts of optical anisotropy in the resulting semi-cokes and cokes were determined from microscopic examination, the anisotropic components being classified according to grain size of the granular mosaics and appearance. The anisotropy developed directly from the isotropic phase, appearing initially as a fine-grained mosaic. With increasing carbonization temperature, this fine-grained mosaic was transformed into progressively coarser-grained anisotropy, the extent of this transformation depending on the rank of the vitrain. It is therefore concluded that the formation, growth and coalescence of anisotropic spherical bodies, such as occurs during the carbonization of pitch, is not a necessary precursor of the mosaic anisotropy in coke. The type and amount of anisotropy developed provide a quantitative means of characterising different cokes.     

SEM study of binder coke in electrode carbon

As part of a study on the use of coal-tar pitches as binders in electrode carbons for the aluminium industry, the object of the present work was to attempt to identify textural components in electrode binder cokes. Accordingly, four experimental carbons, made using the same petroleum coke as filler and four coal-tar pitches of differing characteristics as binders, were examined in a scanning electron microscope (SEM) after embedding in resin, polishing and etching in atomic oxygen. Binder cokes could be distinguished from the filler particles and could be characterized in terms of the content of three components, termed lamellar, intermediate and granular. The textural composition of the binder cokes was dependent upon the character of the pitch and the type of quinoline-insoluble components present. Pitch cokes, made by carbonizing the pitches alone, differed markedly from the corresponding binder cokes. The findings are considered in terms of current ideas on pitch carbonization.     

Modifying carbonization properties of pitches. 1. Conversion of benzene-insoluble matter of coal-tar pitch into graphitizable carbon

Reactivities of benzene-insoluble/quinoline-soluble matter (QS—BI) and quinoline insolubles (QI) of coal-tar pitch in reductive alkylation and hydrogenation with the aid of alkali metals were investigated, to obtain basic information on the possibility of changing their graphitizability and the orientation of their cokes. Alkylation increased the solubility in benzene of both components; however only the soluble fraction of QS—BI was fusible. In contrast, the soluble fractions produced by hydrogenation from both QS—BI and QI were fusible giving a flow-pattern structure and graphitizable carbon. Fusibility of pitches in the early stage of carbonization is discussed from the viewpoints of graphitization and orientation of cokes obtained by subsequent heat treatment.     

Activation of brown-coal chars with oxygen

Semicokes and cokes prepared respectively at 773 and 1173 K from brown-coals, xylitic and earthy, from Polish coal seams, were activated with gaseous oxygen (10% oxygen and 90% argon) in a thermogravimetric apparatus to different burn-offs. With increasing temperature of oxygen activation a constant decrease of the sum of micropores and mesopores is observed, but probably as a result of chemisorption of oxygen the micropore volume passes through a maximum at 663 K. There is a strong influence of the temperature of carbonization of the char on the formation of porosity in the products of oxygen activation: activated cokes have better adsorptive properties than activated semicokes. The highest value of surface areas (benzene adsorption) are, for semicokes and cokes respectively, 520 and 700 m² g^?1. These differences can be attributed to the uniform microporosity in the non-activated coke as distinct from the wide range of the micropore diameters in the non-activated semicoke, and also to the lack of ultramicropores in the former sample. The earthy type of brown coal yields products with a less developed porosity than the corresponding products from the xylitic coal. For the xylitic semicoke as well as for the coke, after continuing the process of activation to burn-offs higher than 50%, a lowering of adsorptive properties is observed.     

Carbonization and liquid—crystal (mesophase) development. 19. Co-carbonization of oxidized coals with model organic compounds

This study examines further the phenomena of the modification of coal carbonizations by organic additives. Anthracene, pyrene and chrysene modify the carbonization in a closed system of coking coals as observed from increases in the size of optical textures of resultant cokes. Weakly caking coals are unaffected. Chrysene is the most efficient modifier probably because of its lowest calculated free valence. The co-additives tetralin and hydrogenated anthracene oil further enhance the modification processes so obviating the necessity to use hydrogenated additives. Co-carbonizations of oxidized coking and caking coals with decacyclene are effective in removing the effects of mild oxidation. Increased rates of carbonization enhance the sizes of optical textures of resultant cokes.     

Hydrothermal Carbonization – 1. Influence of Lignin in Lignocelluloses

Hydrothermal carbonization is an attractive process for converting biomass with high water content into different products. The requirements on the products, which may be soil improvement or substitution of lignite or carbon black, are opposed to biomass as a feedstock that has a very complex and variable composition. The goal of this work was to study the influence of an ingredient, here lignin, on carbonization, with the focus being not only on the composition but also on the structure of the product formed.     

Laboratory coal carbonization oven

A laboratory coal carbonization oven has been described which simulates the carbonization of coal in a commercial slot-type oven. Essentially a cylinder of packed, crushed coal is inserted at a controlled rate into a long furnace so that a plastic layer moves progressively along the cylinder. Widely varying coal charges and carbonization conditions can be employed. The tensile strength and pore structural data of the cokes produced under standard conditions lie within the range of values obtained for commercial cokes.