Carbonization of coals into anisotropic cokes: 7. Copreheat-treatment under short contact-time conditions at high temperature

The copreheat-treatment of non-fusible and slightly fusible coals with A240 and hydrogenated A240 under high temperature-short contact-time conditions around 500 °C has been examined in an attempt to produce a formed coke with better anisotropic development. These conditions shortened the copreheat-treatment time and provided better anisotropic development in the resultant coke after carbonization. Effectiveness of short contact-time has been discussed in terms of the extent of depolymerization of coal molecules suitable for anisotropic development, this being related to coal liquefaction under similar conditions.     

Carbonization of coals to produce anisotropic cokes. 1. Modifying activities of some additives in the co-carbonization of low-rank coals

Using low-rank coals, the modifying activities of some petroleum, coal tar and aromatic hydrocarbon additives have been examined to find procedures for their utilization in the preparation of blast furnace coke. Petroleum pitch, especially after hydrogenation, exhibited excellent modifying activity even with non-fusible coals. In contrast, the activity of coal tar was very limited with such coals. The napththenic component, revealed by n.m.r. of the additives, appears to be important in the co-carbonization by inducing fusibility and anisotropic development in such coals. Co-carbonization to recover the dehydrogenated additives was attempted. However, there was no development of the anisotropy in the resultant coke by dissolution of the coal particles although the coal particles were firmly fixed in the matrix. Acid-refluxing treatment of non-fusible coals was found to enhance their modification susceptibility, indicating that some of the acid-soluble mineral matter is important in the thermal depolymerization or fusion process of the coal.     

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.     

Carbonization of coals into anisotropic cokes: 8. Carbonization of a canadian weathered coal into anisotropic coke

The carbonization properties of a weathered high rank bituminous coal were compared with those of the non-weathered coal. The weathering decreased the fusibility of the coal to leave more basic anisotropy and to diminish the size of the majority of the anisotropy in the resulting coke. On the other hand, more domain and flow domain textures developed. Co-carbonization with a petroleum pitch additive (Ashland A240) was found effective in enhancing the fusibility of the coal and anisotropic development in the coke. Formed coking of the weathered coal by means of copreheat-treatment with the additive, provided an anisotropic, dense and strong coke of uniform size. For the weathered coal, the optimum copreheat-treatment was shorter than that using the non-weathered coal indicating high coking reactivity of the weathered coal. The transferable hydrogens from the additive are rapidly consumed by the oxygen containing groups of the weathered coal.     

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.     

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 of coals to produce anisotropic cokes: 3. Evaluation of low-rank bituminous and subbituminous coals by single and co-carbonizations with pitch

Single carbonizations and co-carbonizations of 17 low-rank bituminous and subbituminous coals have been studied to evaluate their suitability as sources of blast furnace coke in terms of pore-wall profile and anisotropic development within the cokes. Co-carbonizations suggest the possible use of low-rank coals which from single carbonizations would not have been considered suitable. To evaluate semi-quantitatively the coke quality, two structural characteristics of the cokes produced by single and co-carbonizations are graded on a scale of 1 to 5. Overall assessments for each coal are plotted against the atomic H/C and 0/C ratios of the original coals. Although there are a few exceptions, coals with similar assessments are located in the same region of the plot, indicating that, to a first approximation, the H/C and 0/C ratios are suitable indicators of the single and co-carbonization properties of a coal. The presence of cations in the coal appears to be an additional factor influencing the carbonization properties and may explain the exceptional behaviour of some coals. Removal of these cations by pretreatment of the coals improves the carbonization properties.     

Carbonization of coals to produce anisotropic cokes.: 4. Improving co-carbonization behaviour of bituminous and subbituminous coals with pitch by pretreatment coals to remove cations

Several de-ashing pretreatments of selected coals have been examined to establish simple and effective procedures to improve, in terms of anisotropic development, the co-carbonization behaviour of the coals with pitches. Refluxing pretreatments of the coals in 1N HCI containing methanol and in boiling water containing EDTA-2Na (EDTA-2Na/coal = 7/100 byweight) improve the co-carbonization behaviour of Witbank, Miller, Taiheiyo and Wandoan coals, all of which, in their original, untreated form, are modified in terms of anisotropic development only very slightly in co-carbonizations with A240 petroleum pitch. Pretreatment of coals of very low rank appears to be ineffective in co-carbonizations with A240; however, co-carbonization with hydrogenated A240 shows that the pretreatments are effective. Analyses and FT-i.r. spectroscopy of mineral matter suggest that improved behaviour due to the pretreatment is related to the removal of divalent cations and to the modification of the oxygen functionality of the coals.     

Ultimate analysis of coals and cokes using instrumental techniques

This Paper describes instrumental techniques for the rapid determination of carbon, hydrogen, nitrogen, oxygen and sulphur. Two Perkin-Elmer Model 240 elemental micro-analysers were used, one for the direct determination of oxygen and the other for the simultaneous analysis for carbon, hydrogen and nitrogen. The Leco Automatic Sulphur Titrator was used for the sulphur assay. Accuracy and repeatability similar to that obtained by the classical methods described in the relevant British Standards were found, and data are presented to illustrate the comparison. Special aspects of developed procedures are emphasized which are essential for the attainment of good precision and accuracy.     

无烟煤与焦煤复配制备型焦的炭化过程研究

对比研究了无烟煤、焦煤和复配型煤在炭化过程中的化学组成与性质变化;采用热天平(TG)和傅立叶变换红外光谱仪(FTIR)对炭化过程中无烟煤、焦煤和复配型煤的气体释放和热失重情况及表面官能团进行了测试分析;采用X射线光电子能谱仪(XPS)对无烟煤型焦、焦煤型焦和复配型焦的碳、氧元素的化学状态进行了表征。结果表明:在低温阶段复配型煤的炭化是无烟煤和焦煤炭化的线性叠加,在高温阶段无烟煤和焦煤炭化存在协同效应,使得复配型煤释放更多的气体,失重大于两者失重的线性叠加;复配型煤在炭化过程中表面官能团的变化趋势与无烟煤和焦煤单独炭化时表面官能团的变化趋势一致,但由于两者的协同作用,复配型煤的碳元素氧化程度更高,易于生成更多的C—O基团。     

Applications of laser Raman microprobe spectroscopy to the characterization of coals and cokes

Optical microscopy is widely used in the characterization of coals and cokes. This Paper shows that the laser Raman microprobe (MOLE) which combines an optical microscope and a Raman spectrometer can provide useful additional information. Three main areas were investigated: identification of minerals in coal and coke; structural characterization of coals and cokes; and the interaction of inorganic additives and coal. Where possible, the results were compared with conventional optical microscopy measurements whereby it was shown that the optical texture and Raman spectra of cokes are not closely related. The Raman spectra of high temperature cokes were used to estimate the size of microcrystalline regions.     

Aspects of gasification and structure in cokes from coals

Cokes were prepared from nine coals of different rank and characterized by surface area measurement, reactivity to carbon dioxide at 1473K and Raman-laser spectroscopy. Rates of gasification of cokes on a unit surlface area basis (K¹ = g m^?2 min^?1) decreased with increasing rank of parent coal based on maximum oil reflectances. However rates of gasification could not be related to coke structure as measured by Raman-laser spectroscopy.     

焦粉与贫瘦煤配合制备铸造型焦的工艺研究

对以贫瘦煤和焦粉为原料、改性的焦油洗油残渣为黏结剂制备铸造型焦的工艺进行了研究,同时在实验室条件下对影响该工艺的主要因素如成型压力、配煤比、黏结剂用量及粉煤粒度等进行了探讨。结果表明,焦粉与贫瘦煤配合制备型焦的最佳工艺条件为:成型压力30 MPa、贫瘦煤质量分数75%～79%、焦粉质量分数6%～8%、黏结剂质量分数13%～15%、粉煤粒度<3 mm。按该工艺技术条件进行型焦生产,可得到优质的二级铸造型焦     

新型型煤技术的开发与应用

以粘结剂、强度、灰熔点等作为技术难点,通过多年的研究开发出新型煤型生产工艺。该型煤可用于化肥生产、锅炉用煤、民用等。是开发利用煤末、焦末、净化环境及充分利用资源的有效途径。     

Measurement of anisotropic development in a low-rank coal using e.s.r. spectroscopy and optical texture

Anisotropic development in a low-rank coal (Cerrejón coal) has been induced using natural heavy oil or anthracene oil as additives in a cocarbonization system at 500 °C. The heavy oil showed better modifying activity. To monitor the anisotropic development optical microscopy and e.s.r. spectroscopy have been used. The concentration of stabilized free radicals, measured at room temperature (trapped free radicals) increased with anisotropic development. The concentration of stabilized free radicals allows interaction in the carbonization system to be followed even when the microcrystallinity of the anisotropic phase is too small to be observed under the microscope.     

Properties and potential of formed cokes derived from two Turkish lignites by carbonization of binderless briquettes

Two high-sulphur Turkish lignites were briquetted at room temperature under pressures of 113 or 212 MPa and the briquettes were carbonized to 1158–1173 K over special heating cycles. The lower-rank lignite gave a formed coke of superior mechanical strength, lower porosity and higher sulphur content than typical blast furnace cokes. The formed coke produced from the higher-rank lignite briquettes had slightly poorer mechanical strength, lower porosity and much higher ash yield and sulphur content than conventional cokes. The products were considered attractive for use in non-ferrous metallurgy.     

Carbonization and liquid-crystal (mesophase) development. 22. Micro-strength and optical textures of cokes from coal-pitch co-carbonizations

This study examines the micro-strength and optical textures of a laboratory coke from a base-blend of Freyming and Pocahontas coal (wt ratio, 1:1) and of cokes from the co-carbonization of the blend, with each of five petroleum pitches in various proportions. Coke pieces, 212–600 μm, from the micro-strength test are assessed in terms of origin and propagation of cracks induced by the test. Always, the addition of pitch to the base-blend improves the strength of the resultant cokes, the pitches behaving differently. A qualitative, subjective appraisal of results indicates that increases in coke strength are associated with relative abilities of pitches to interact with the coals to produce a fluid phase, of solution of coal in pitch, which gives an ‘intermediate’ coke with an optical texture of mozaics. This intermediate coke strengthens the bonding at interfaces. Cracks originate predominantly from the shrinkage cracks in the domains of Pocahontas coke. Mozaic structures tend to resist crack propagation. The coal/pitch system may flow around coal particles so containing incipient crack formation in resultant coke particles.     

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.     

Some aspects of the role of coal thermoplasticity and coke structure in coal gasification. 2. The effects of pressure and heating rate on dilatometric parameters and optical anisotropy development

An examination of the influence of pressure and heating rate on the thermoplastic properties of a weakly coking coal and of coal with various pitch-like additives was carried out using a high pressure dilatometer. Pressure up to 4 MPa markedly increased the swelling properties and increased the plastic range by decreasing the softening temperature, but the effects of pressure were strongly influenced by rate of heating with high heating rates enhancing the effects. Additions of tar or pitch also enhanced swelling at low pressure. The solid carbonization residues from the dilatometer were examined by polarized light microscopy to determine the content and composition of optically anisotropic species. The anisotropic content was increased by increases in pressure and heating rate and pitch additives enhanced the anisotropic content, especially at low pressure, without affecting the composition of the anisotropy. No direct correlations exist between the dilatometric parameters and the optical anisotropy but their dependence on the conditions emphasizes that when considering high pressure gasification of coal, it is necessary to obtain data under appropriate conditions.     

Macerals in bituminous coals and the coking process: 2. Coal mass properties and coke mechanical properties

Bituminous coals produced in the Ostrava-Karviná coal basin show considerable variation in their maceral composition, vitrinite reflectance and fluidity. There is a close association of the latter with the $\text{H}\text{O}$ atomic ratio expressing the different chemico-structural properties of vitrinites of lower coalification. These properties of the coal mass all influence the coke mechanical properties; moreover the $\text{H}\text{O}{}_{\mathrm{at}}$ parameter is of principal importance to the course of the coking process. Laboratory, pilot-plant and full-scale experiments show that coals rich in inertinite may give cokes of suitable mechanical properties, providing the $\text{H}\text{O}{}_{\mathrm{at}}$, ratio and the bulk density are high enough. It should be noted, however, that these coals contain finely dispersed inertinite in the vitrinite mass and this may have a positive effect on the coke mechanical properties.